Method for manufacturing foamed blow molded articles

Abstract

To provide a method for manufacturing a foam blow molding which is excellent in cold impact resistance even using a recovery raw material recovered in a foam blow molding manufacturing process, and can manufacture a satisfactorily shaped foam blow molding.SOLUTION: There is provided a method for manufacturing a foam blow molding by blow molding a polypropylene-based resin foam parison, wherein the foam parison is formed by supplying a resin A as branched homopolypropylene A, a resin B as linear block polypropylene B, a resin C as low density polyethylene C and a recovery raw material D to an extruder, and extrusion foaming the mixture from a die. Block polypropylene B1 and block polypropylene B2 having specific melt flow rates are used as the resin B in a specific blending amount ratio, a ratio of the blending amount of the resin A, the blending amount of the resin B, the blending amount of the resin C and the blending amount of the recovery raw material D is in a specific range, and a blending amount of components derived from each of the resin A, the resin B and the resin C is in a specific range.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a foamed blow-molded article. [Background technology]

[0002] A foamed blow-molded article is known, which is formed by extruding and foaming a foamed resin molten material to create a foamed parison. Among foamed blow-molded articles, hollow molded articles using polypropylene resin as the resin raw material are lightweight and have excellent rigidity, and are used in various applications such as air conditioning ducts in automobiles.

[0003] In recent years, there has been a demand for foamed blow-molded articles that maintain or improve lightness while also improving cold shock resistance. Cold shock resistance refers to the durability of a foamed blow-molded article against impact at low temperatures. To improve the cold shock resistance of foamed blow-molded articles, for example, Patent Document 1 discloses a technique for blending specific amounts of propylene block copolymer and low-density polyethylene. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-116804 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] On the other hand, in the manufacturing method of foamed blow molded articles, it is required to use recovered raw materials, such as burrs from the foamed parison generated during the manufacturing process, as part or all of the raw materials for the foamed blow molded articles. However, when attempting to manufacture foamed blow molded articles with good cold shock resistance while using recovered raw materials, the blow moldability of the foamed parison tends to decrease, making it difficult to manufacture foamed blow molded articles with good form.

[0006] The object of the present invention is to provide a method for manufacturing a foamed blow molded article that can produce a foamed blow molded article with excellent cold shock resistance and a well-formed shape, even when using recovered raw materials recovered during the manufacturing process of the foamed blow molded article. [Means for solving the problem]

[0007] The gist of this invention is the invention described in (1) to (6) below.

[0008] (1) A method for producing a foamed blow-molded article by blow-molding a polypropylene resin foam parison, The foamed parison comprises branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and component A, which is recovered during the manufacturing process of the foamed blow molded product and is derived from branched homopolypropylene A. R , component B derived from linear block polypropylene B R and component C derived from low-density polyethylene C R It is formed by melting and kneading a recovered raw material D containing the above and then extruding and foaming the resulting foamed resin molten material from a die. As the linear block polypropylene B, Block polypropylene B1, in which the melt flow rate at 230℃ and a load of 2.16kg is 10g / 10min or more and 16g / 10min or less, Using block polypropylene B2, which has a melt flow rate of more than 16 g / 10 min and 40 g / 10 min or less at 230°C and a load of 2.16 kg, The ratio of the melt flow rate of block polypropylene B2 to the melt flow rate of block polypropylene B1 is 1.5 or more. The ratio of the amount of block polypropylene B2 to the amount of block polypropylene B1 is 0.1 or more and 10 or less. The sum of the amounts of branched homopolypropylene A, linear block polypropylene B, and low-density polyethylene C, W A+B+Cand a blending amount W of the recovered raw material D D ratio W to A+B+C :W D is 40:60 to 5:95, the total blending amount W of the branched homopolypropylene A and the component A R blending amount is A+AR is 10 parts by mass or more and 30 parts by mass or less, and the total blending amount W of the linear block polypropylene B and the component B R blending amount is B+BR is 40 parts by mass or more and 70 parts by mass or less, and the total blending amount W of the low-density polyethylene C and the component C R blending amount is C+CR is 10 parts by mass or more and 30 parts by mass or less (provided that the W A+AR the W B+BR the W C+CR and the total of these is 100 parts by mass), which is a method for producing a foamed blow-molded article. (2) The method for producing a foamed blow-molded article according to (1) above, wherein the melt flow rate of the recovered raw material D at 230°C under a load of 2.16 kg is 10 g / 10 min or more and 25 g / 10 min or less. (3) The method for producing a foamed blow-molded article according to (1) or (2) above, wherein the melt flow rate of the linear block polypropylene B at 230°C under a load of 2.16 kg is 15 g / 10 min or more and 30 g / 10 min or less. (4) The method for producing a foamed blow-molded article according to any one of (1) to (3) above, wherein the melt tension of the block polypropylene B1 at 230°C is 1 mN or more and 30 mN or less, and the melt tension of the block polypropylene B2 at 230°C is 1 mN or more and 30 mN or less. (5) The method for producing a foamed blow-molded article according to any one of (1) to (4) above, wherein the melt flow rate of the low-density polyethylene C at 190°C under a load of 2.16 kg is 0.2 g / 10 min or more and 20 g / 10 min or less. (6) The density of the foamed blow-molded article is 0.1 to 0.5 g / cm 3 , which is the method for producing a foamed blow-molded article according to any one of (1) to (5) above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing a foamed blow molded article that can produce a foamed blow molded article with excellent cold shock resistance and a well-formed shape, even when using recovered raw materials recovered during the manufacturing process of the foamed blow molded article. [Modes for carrying out the invention]

[0010] An example of an embodiment of the present invention is described below. However, the present invention is not limited to the embodiments described below.

[0011] [1. Method for manufacturing foam blow molded articles] The present invention relates to a method for manufacturing a foamed blow-molded article, and more specifically, to a method for manufacturing a foamed blow-molded article by performing a blow molding process on a foamed parison. An embodiment of the method for manufacturing a foamed blow-molded article according to the present invention will be described below.

[0012] [1-1 Contents of the manufacturing method for foam blow molded articles] (Extrusion foaming process) A foamed parison is formed by extruding a foamed resin molten material, which is obtained by melting and kneading resin raw materials, from a die. The foamed resin molten material contains a foaming agent. An apparatus for manufacturing a foamed blow molded article is equipped with an extruder capable of supplying resin raw materials. Various resins constituting the resin raw materials supplied to the extruder are melted and kneaded to form a resin molten material. A foaming agent is then added to this resin molten material and kneaded further to obtain a foamed resin molten material. The obtained foamed resin molten material is extruded from a die connected to the extruder. An accumulator may be provided between the extruder and the die. In this case, the foamed resin molten material is filled into the accumulator before being extruded from the die. The resin raw materials supplied to the extruder are extruded and foamed from the die to form a foamed parison. The foamed parison formed at this time may be, for example, a cylindrical foamed parison or a sheet-shaped foamed parison. When forming a cylindrical foamed parison, for example, an annular die can be used as the die. A mold is positioned directly beneath the die, and the mold is configured to form a molding space (mold cavity) corresponding to the shape of the molded product to be obtained. The mold is usually a pair of divided molds (divided mold).

[0013] (Pre-blowing process) The foamed parison is in a softened state immediately after the extrusion foaming process. The lower part of the softened foamed parison is closed using a pinch or similar device, and gas is blown into the hollow part of the foamed parison to increase the pressure inside the hollow part. At this time, the foamed parison is widened. During or after the pre-blowing process, the mold is clamped, and the foamed parison is sandwiched between the molds. In the pre-blowing process, gas may be blown onto the inner surface of the upper part of the foamed parison to widen it before pinching or after pinching and before the mold is clamped.

[0014] (Blow molding process) The blow molding process is a process of blow molding a foamed parison, or more specifically, a process in which gas is blown into the hollow part of the foamed parison while it is sandwiched between molds (mold cavities) to shape the foamed parison. The outer surface of the foamed parison is pressed against the inner surface of the mold, thereby shaping the foamed parison to the cavity shape of the mold. A hollow foamed blow molded body is formed by this blow molding process. In the manufacturing method of a foamed blow molded body, it is preferable that an accumulator is provided between the extruder and the die, or on the die.

[0015] In the manufacturing of foamed blow molded products, when the foamed parison is sandwiched between the split molds, the portion of the foamed parison that is sandwiched between the periphery of the molding cavity fuses together with its opposing inner surfaces to form a pinch-off portion. The area outside this pinch-off portion becomes an excess portion called a burr, and this burr is eventually removed to produce the foamed blow molded product.

[0016] In the present invention, the foamed parison is a polypropylene resin foamed parison. A polypropylene resin foamed parison refers to a foamed parison mainly composed of a polypropylene resin. A polypropylene resin refers to a polymer having structural units derived from propylene in a ratio of 50% by mass or more. In the present invention, the components of the polypropylene resin constituting the foamed parison include branched homopolypropylene (branched h-PP) A and linear block polypropylene (linear b-PP) B, which will be described later. "Mainly composed of a polypropylene resin" means that the mass ratio of the polypropylene resin in the foamed parison is 50% by mass or more, preferably 60% by mass or more.

[0017] (Composition of resin raw materials) In the extrusion foaming process, the resin raw materials supplied to the extruder to form the resin components of the foamed resin molten material include branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and recovered raw materials D. These resin raw materials supplied to the extruder become the resin components that make up the foamed parison.

[0018] As the recovered raw material D, for example, a polypropylene resin composition containing components derived from branched homopolypropylene A, linear block polypropylene B, and low-density polyethylene C can be used. Note that the polypropylene resin composition refers to a composition in which polypropylene resin is the main component. Specifically, the polypropylene resin composition preferably contains a polypropylene resin of 50% by mass or more, and more preferably 60% by mass or more. Furthermore, in the extrusion foaming process, branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and recovered raw material D are blended in specific proportions to constitute the resin components of the foamed resin molten product.

[0019] In the following, branched homopolypropylene A may be referred to as resin A for the sake of explanation. Similarly, for the sake of explanation, linear block polypropylene B and low-density polyethylene C may be referred to as resin B and resin C, respectively.

[0020] In this specification, resin A, which is newly fed into the extruder as a raw material (sometimes referred to as a newly used raw material) distinct from the components contained in recovered raw material D, may be referred to as resin A, etc. as a newly used raw material, and the same applies to resins B and C. Furthermore, branched homopolypropylene A (resin A) as a newly used raw material may be referred to as branched homopolypropylene A F (Resin A F ) may be referred to as such, and similarly for resin B and resin C, linear block polypropylene B (resin B) as a newly used raw material is sometimes referred to as linear block polypropylene B F (Resin B F) may be referred to as low-density polyethylene C (resin C) as a new raw material, and low-density polyethylene C F (Resin C F ) is sometimes referred to as such.

[0021] In this specification, branched homopolypropylene A, linear block polypropylene B, and low-density polyethylene C used as resin raw materials refer to their contents and properties in the state of newly fed raw materials (sometimes referred to as newly used raw materials) unless explicitly stated that they are components of recovered raw material D. The same applies to block polypropylene B1 and block polypropylene B2 described later.

[0022] (Branched homopolypropylene A) Branched homopolypropylene A (resin A), used as a resin raw material, is a type of polypropylene resin that has a branched structure in its molecular structure. Examples of the branched structure in branched homopolypropylene A include the branched portion of the molecular structure that is also a long-chain structure with free ends. The branched structure can be confirmed using methods such as high-temperature GPC-MALS measurement.

[0023] Specific examples of resin A include branched homopolypropylene manufactured by Borealis (product names: WB130, WB135, WB140) and branched homopolypropylene manufactured by Sun Allomer (product name: PF814).

[0024] (Melting tension) The melt tension of resin A at 230°C is preferably 100 mN or more. Having the melt tension of resin A within this range enhances the extrusion foaming properties of the foamed resin molten material, while also allowing for good widening of the foamed parison and stable suppression of drawdown of the foamed parison, thereby enabling the stable production of a good foamed blow molded product. From this perspective, the melt tension of resin A is preferably 120 mN or more, and more preferably 150 mN or more. The upper limit of the melt tension of resin A is preferably 500 mN, and more preferably 450 mN. The melt tension can be determined, for example, by measuring the load value (tension) applied to the load cell just before the strand breaks, when a strand of molten resin (230°C) extruded under predetermined conditions is taken up via a load cell on a pulley while increasing the take-up speed at a predetermined acceleration, using a capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. More specifically, it can be measured by the method described in the examples below.

[0025] Branched polypropylene typically has a higher melt tension than linear polypropylene. Therefore, a polypropylene resin having a high melt tension, such as 100 mN or more at 230°C, can be determined to have a branched structure.

[0026] In this specification, for the sake of clarity, the melt tension at 230°C will be referred to as melt tension (230°C). Furthermore, in this specification, for the sake of clarity, melt tension may sometimes be referred to as MT.

[0027] (Meltflow rate) The melt flow rate of resin A, measured at 230°C and a load of 2.16 kg, is preferably between 0.1 g / 10 min and 15 g / 10 min. If the melt flow rate is within this range, the fluidity of the resin during melting is moderately increased, improving the expandability of the foamed parison while stably suppressing the drawdown of the foamed parison. From the viewpoint of increasing the fluidity of the resin during melting and stably improving the expandability and shapeability of the foamed parison, the melt flow rate of resin A is preferably 0.5 g / 10 min or more, and more preferably 1 g / 10 min or more. From the viewpoint of stably suppressing the drawdown of the foamed parison, the melt flow rate of resin A is preferably 10 g / 10 min or less, and more preferably 5 g / 10 min or less. The melt flow rate (MFR) of the resin can be measured according to JIS K7210-1:2014 (Test Method A).

[0028] In this specification, the melt flow rate measured under conditions of 230°C and a load of 2.16 kg will be referred to as the melt flow rate (230°C, 2.16 kg load). Furthermore, for convenience of explanation, the melt flow rate may be referred to as MFR in this specification.

[0029] (Melting point) The melting point of resin A is preferably between 150°C and 165°C. Having the melting point of resin A within this range makes it easier to improve the extrusion foaming properties of the foamed resin molten material while simultaneously increasing the rigidity and heat resistance of the resulting blow-molded article.

[0030] The melting point of resin A is defined as the melting peak temperature obtained by differential scanning calorimetry based on JIS K7121-1987. For conditioning the test specimen, "(2) When measuring the melting temperature after performing a certain heat treatment" is adopted, and the cooling rate at this time is set to 10°C per minute. The heating rate when measuring the melting temperature is also set to 10°C per minute. If two or more melting peaks appear, the melting point is defined as the temperature of the peak of the melting peak with the highest peak height from the baseline to the peak of the melting peak.

[0031] Branched homopolypropylene A exhibits excellent extrusion foaming properties, is moderately stretchable when softened, and is resistant to breakage. Therefore, including branched homopolypropylene A in the foaming resin molten material enhances the extrusion foaming properties of the foaming resin molten material during foam parison formation, improves the drawdown resistance of the foam parison, and enhances the widening and shaping properties of the foam parison. Furthermore, including branched homopolypropylene A in the resin raw material makes it easier to obtain a foam blow molded article that is lightweight and has excellent internal surface condition and appearance.

[0032] (Linear block polypropylene B) Linear block polypropylene B (resin B) is a block polypropylene having a linear molecular structure. Examples of block polypropylene include polymerization mixtures obtained by polymerizing ethylene with one or more C3-C10-α-olefins (α-olefins with 3 to 10 carbon atoms) in the presence of a propylene polymer, and include impact-resistant polypropylene polymers as defined in JIS K6921-1, and generally include those commercially available as block polypropylene. However, the examples of block polypropylene shown here are just examples and do not exclude other examples. Specifically, block polypropylene can be exemplified by propylene-ethylene block copolymers. More specifically, propylene-ethylene block copolymers include block copolymers containing crystalline propylene blocks and ethylene-propylene random blocks. As linear block polypropylene, it is preferable to use block polypropylene in which a rubber-like material containing ethylene-propylene rubber is dispersed in a polypropylene resin, which is generally commercially available as block polypropylene. Ethylene-propylene rubber is a rubber-like substance composed of an ethylene-propylene copolymer containing an ethylene component and a propylene component, such as an ethylene-propylene copolymer (EPM). Furthermore, the ethylene-propylene rubber may also be an ethylene-propylene copolymer (e.g., EPDM) containing components derived from monomers other than ethylene and propylene, such as dienes, to the extent that the aforementioned effects are not impaired. The rubber-like substance may also contain a polyethylene resin.

[0033] As resin B used as a resin raw material, block polypropylene B1 and block polypropylene B2, which have at least different melt flow rates from each other, are used. The melt flow rates (MFR) of block polypropylene B1, block polypropylene B2, and resin B can be measured according to JIS K7210-1:2014 (Test Method A), as described in the description of resin A above. In this specification, for the sake of explanation, block polypropylene B1 and block polypropylene B2 may be referred to as resin B1 and resin B2, respectively. Also, as described above for resin A, etc., block polypropylene B1 (resin B1) as a newly used raw material will be referred to as block polypropylene B1 F (Resin B1 F ) may be referred to as Block Polypropylene B2 (Resin B2) as a newly used raw material. F (Resin B2 F ) is sometimes referred to as such.

[0034] (Block Polypropylene B1) Block polypropylene B1 is a block polypropylene having a linear molecular structure, with a melt flow rate of 10 g / 10 min to 16 g / 10 min at 230°C and a load of 2.16 kg.

[0035] (Block Polypropylene B2) Block polypropylene B2 is a block polypropylene with a linear molecular structure whose melt flow rate at 230°C and a load of 2.16 kg is greater than 16 g / 10 min and less than or equal to 40 g / 10 min. The MFR of resin B2 is higher than that of resin B1.

[0036] By including resin B1 in resin B, the impact resistance of the resulting foamed blow-molded article can be enhanced while suppressing the drawdown of the foamed parison. Furthermore, by including resin B2 in resin B, the fluidity of the foamed resin molten material can be moderately increased, improving the expandability of the foamed parison in the pre-blow process and the shapeability of the foamed parison in the blow-molding process.

[0037] (Ratio of MFR of resin B1 to resin B2) In resin B, it is preferable that the ratio of the melt flow rate of block polypropylene B2 (MFR of resin B2) to the melt flow rate of block polypropylene B1 (MFR of resin B1) ((MFR of resin B2) / (MFR of resin B1)) is 1.5 or higher. When the value of (MFR of resin B2) / (MFR of resin B1) is within this range, the expandability of the foamed parison is enhanced, and it becomes easier to shape the foamed parison well. From the viewpoint of these effects, the value of (MFR of resin B2) / (MFR of resin B1) is more preferably 1.6 g / 10 min or higher, and even more preferably 1.8 g / 10 min or higher. The upper limit of (MFR of resin B2) / (MFR of resin B1) is 4 g / 10 min, and more preferably 3 g / 10 min.

[0038] If two or more types of resin are used as resin B1, the MFR of resin B1 shall be the load-average value of the MFRs of each resin supplied to the extruder as resin B1. For example, if resin B1 is a combination of two different resins, a first resin and a second resin, the MFR of resin B1 shall be the load-average value obtained by weighting the MFRs of the first resin and the MFRs of the second resin according to the mass ratio of the first and second resins. Similarly, if two or more types of resin are used as resin B2, the MFR of resin B2 shall be the load-average value of the MFRs of each resin supplied to the extruder as resin B2.

[0039] (Mixing ratio of resin B1 and resin B2) In resin B, the amount of block polypropylene B1 added (W B1Amount of block polypropylene B2 blended with (parts by mass) (W B2 The ratio (W) of (mass parts) B2 / W B1 (W) is preferably 0.1 or more and 10 or less. B2 / W B1 When the value of (W) falls within this numerical range, it becomes easier to obtain a foamed blow molded article with good expandability and shapeability of the foamed parison, as well as excellent impact resistance. From the viewpoint of these effects, (W B2 / W B1 The value of ) is more preferably 0.2 or more and 6 or less.

[0040] Furthermore, if two or more types of resin are used as resin B1, the sum of the amounts of each resin supplied to the extruder as resin B1 shall be considered as the amount of resin B1 (parts by mass). Similarly, if two or more types of resin are used as resin B2, the sum of the amounts of each resin supplied to the extruder as resin B2 shall be considered as the amount of resin B2 (parts by mass).

[0041] (Melt flow rate of resin B) It is preferable that the melt flow rate (MFR of resin B (230°C, 2.16kg load)) of resin B at 230°C and a load of 2.16kg is between 15g / 10min and 30g / 10min. Having the MFR of resin B (230°C, 2.16kg load) within this range allows for stable improvement of the blow moldability of the foamed parison. From this perspective, it is more preferable that the MFR of resin B (230°C, 2.16kg load) is between 16g / 10min and 28g / 10min. The melt flow rate of resin B is calculated as the load-average value of the melt flow rates of resin B1 and resin B2. Therefore, the load-average value obtained by weighting the MFRs of resin B1 and resin B2 according to the mass ratio of resin B1 and resin B2 is identified as the MFR of resin B.

[0042] (Melting tension of resin B1 and resin B2) In resin B, it is preferable that the melt tension (MT of resin B1) of block polypropylene B1 at 230°C is 1 mN or more and 30 mN or less, and that the melt tension (MT of resin B2) of block polypropylene B2 at 230°C is 1 mN or more and 30 mN or less. Having the melt tension values ​​of resin B1 and resin B2 within this range makes it easier to achieve good blow moldability of the foamed parison. From the viewpoint of making it easier to increase the expandability of the foamed parison, the MT values ​​of resin B1 and resin B2 are more preferably 20 mN or less and 10 mN or less, respectively. The MT values ​​of resin B1 and resin B2 can be measured in the same way as for the melt tension of resin A, except that resin B1 or resin B2 is used as the measurement sample.

[0043] (Melting points of resin B1 and resin B2) The melting point (°C) of resin B1 is preferably between 150°C and 165°C, and the melting point (°C) of resin B2 is preferably between 150°C and 165°C. Having the melting points of resins B1 and B2 within this range makes it easier to improve the rigidity and heat resistance of the resulting blow-molded article. The melting points of resins B1 and B2 can be measured in the same way as the melting point of resin A, except that resin B1 or resin B2 is used as the measurement sample.

[0044] (Difference in melting points between resin B1 and resin B2) From the viewpoint of facilitating good mixing of resin B1 and resin B2 during the formation of a foamed resin molten product, it is preferable that the difference between the melting point of resin B1 and the melting point of resin B2 (melting point of resin B1 - melting point of resin B2) be between -5°C and 5°C.

[0045] (Difference in melting points between resin A and resin B1, and difference in melting points between resin A and resin B2) From the viewpoint of being able to stably form a foamed resin molten material having good extrudeability and foaming properties, and from the viewpoint of being able to stably form a foamed parison having good spreadability and shapeability, it is preferable that the difference between the melting point of resin A and the melting point of resin B1 (melting point of resin A - melting point of resin B1) is between -10°C and 0°C. Also, from the same viewpoint, it is preferable that the difference between the melting point of resin A and the melting point of resin B2 (melting point of resin A - melting point of resin B2) is between -10°C and 0°C.

[0046] (The difference in crystallization temperatures between resin A and resin B1, and the difference in crystallization temperatures between resin A and resin B2) From the viewpoint of stably forming foamed parisons with good expandability and shapeability, it is preferable that the difference between the crystallization temperature of resin A and the crystallization temperature of resin B1 (crystallization temperature of resin A - crystallization temperature of resin B1) is between -15°C and 10°C. Similarly, from the same viewpoint, it is preferable that the difference between the crystallization temperature of resin A and the crystallization temperature of resin B2 (crystallization temperature of resin A - crystallization temperature of resin B2) is between -10°C and 15°C.

[0047] The crystallization temperatures (°C) of resins A, B1, and B2 refer to the crystallization peak temperatures determined by differential scanning calorimetry based on JIS K7121-1987. In differential scanning calorimetry, a cooling rate of 10°C per minute is used. If two or more crystallization peaks appear, the crystallization temperature is defined as the temperature at the peak of the crystallization peak with the highest peak height from the baseline to the peak of the crystallization peak.

[0048] (Low-density polyethylene C) Low-density polyethylene C (resin C) has a long-chain branched structure and a density of 910 kg / m³. 3 More than 930kg / m 3 This refers to polyethylene with a density of less than 1.5. In this specification, for convenience of explanation, low-density polyethylene may be referred to as LDPE. By including low-density polyethylene C in the resin raw material supplied to form the foamed parison, the foamed blow molded articles formed from the resulting foamed parison exhibit excellent impact resistance in low-temperature environments.

[0049] (Melt flow rate of resin C) The melt flow rate (MFR of resin C) of resin C at 190°C and a load of 2.16 kg is preferably between 0.2 g / 10 min and 20 g / 10 min. Having the MFR of resin C within this range facilitates good blow moldability of the foamed parison. To enhance this effect and make it easier to obtain a foamed blow-molded article with a higher closed-cell ratio, the MFR of resin C is more preferably between 1 g / 10 min and 18 g / 10 min, and even more preferably between 2 g / 10 min and 16 g / 10 min. The MFR of resin C can be measured according to JIS K7210-1:2014 (Test Method A), as described in the above explanations of resins A and B.

[0050] (Recovered material D) The recovered raw material D is the material recovered during the manufacturing process of the foamed blow-molded product. In other words, the recovered raw material D is the scrap material generated in each step of the manufacturing process of the foamed blow-molded product according to the present invention. Examples of scrap material include excess resin raw material generated in the foaming extrusion process, by-products such as burrs generated in the pre-blow process and blow molding process, and molded products obtained in the blow molding process that are judged to be defective. After recovery, the scrap material may be subjected to appropriate processing selected from crushing, kneading, repelling, and combinations thereof, as needed.

[0051] Therefore, the recovered raw material D is component A derived from branched homopolypropylene A. R , component B derived from linear block polypropylene B R and component C derived from low-density polyethylene C R It includes. Furthermore, when referring to the components constituting the recovered raw material D, component A is derived from branched homopolypropylene A. RThe wording refers to a component derived from branched homopolypropylene A that has been kneaded at least once by an extruder, and in this respect it differs from branched homopolypropylene A as a newly used raw material that is newly fed into the extruder to constitute the resin raw material. The same applies to linear block polypropylene B and low-density polyethylene C when referring to the components that constitute the recovered raw material D, and in both cases, when referring to the components that constitute the recovered raw material D, the component B is derived from linear block polypropylene B that has been kneaded at least once by an extruder. R and component C derived from low-density polyethylene C R This indicates.

[0052] Therefore, as a component of the recovered raw material D, "component A derived from branched homopolypropylene A" R "This refers to a component formed from branched homopolypropylene A that has gone through at least one intermediate step in the manufacturing process of a foamed blow molded product (at least the step of melting and kneading in an extruder). "Component B derived from linear block polypropylene B" as a component constituting the recovered raw material D R Similarly, in the case of branched homopolypropylene A, this refers to a component formed from linear block polypropylene B that has gone through at least one intermediate step in the manufacturing process of a foamed blow molded product. Furthermore, "component C derived from low-density polyethylene C" as a component constituting the recovered raw material D. R Similarly, in the case of branched homopolypropylene A, this refers to a component formed from low-density polyethylene C that has gone through at least one of the manufacturing processes of a foamed blow molded article.

[0053] In this specification, branched homopolypropylene A, which is the origin of the components constituting the recovered raw material D, is referred to as branched homopolypropylene A (non-newly used raw material resin A), which has a history of use (non-newly used raw material) and has been used in the formation of molded articles such as foamed blow molded articles. U (Resin A U) may be written as. Similarly, in this specification, linear block polypropylene B from which the components constituting recovered raw material D are derived will be referred to as linear block polypropylene B of non-newly used raw material (resin B of non-newly used raw material), and linear block polypropylene B U (Resin B U ) is sometimes written as, and the low-density polyethylene C from which the components of recovered raw material D originate is referred to as low-density polyethylene C of non-newly used raw material (resin C of non-newly used raw material), and low-density polyethylene C U (Resin C U ) is sometimes written as ). Furthermore, block polypropylene B1 and block polypropylene B2, which constitute linear block polypropylene B from which the components of recovered raw material D originate, are referred to as non-newly used linear block polypropylene B1 and B2 (non-newly used resin B1 and B2), respectively, and linear block polypropylene B1 U B2 U (Resin B1 U B2 U ) is sometimes written as .

[0054] The recovered raw material D is used again in the production of the foamed blow molded product as at least a portion of the resin raw material used in the production process of the foamed blow molded product. Therefore, in the present invention, the production of the foamed blow molded product is carried out repeatedly multiple times, and a predetermined production run of the foamed blow molded product is designated as the reference run. The foamed parison formed in the reference run is formed by supplying branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and recovered raw material D to an extruder and extruding them from the die. The recovered raw material D used in this process is the branched homopolypropylene A (resin A) that was used in the production of the foamed blow molded product before the reference run. U Component A (derived from branched homopolypropylene as a component) R And, linear block polypropylene B (resin B) U Component B (derived from linear block polypropylene as a component) R And, low-density polyethylene C (resin C) UComponent C derived from low-density polyethylene (as an example) R This will include resin A. U Branched homopolypropylene (branched homopolypropylene A, a non-newly used raw material) is resin A in its state before it is marked with a usage history. F It possesses the same and similar properties (melt flow rate, melting point, etc.) as branched homopolypropylene (newly used raw material, branched homopolypropylene A). This is because resin B U , resin B1 U , resin B2 U , resin C U The same applies to this matter.

[0055] (Melt flow rate of recovered raw material D) It is preferable that the melt flow rate (MFR of recovered material D) of recovered material D at 230°C and a load of 2.16 kg is between 10 g / 10 min and 25 g / 10 min. Having the MFR of recovered material D within this range makes it easier to more stably improve the blow moldability of the foamed parison. From the viewpoint of this effect, it is more preferable that the MFR of recovered material D is between 12 and 22. The melt flow rate (MFR) of recovered material D can be measured based on JIS K7210-1:2014 (Test Method A) as described in the above explanation of resins A and B.

[0056] (Melting tension of recovered raw material D) From the viewpoint of being able to stably form a foamed resin molten material having good extrudeability and foaming properties, and from the viewpoint of being able to stably form a foamed parison having good expandability and shapeability, the melt tension (MT) (mN) of the recovered raw material D is preferably 10 mN or more, and more preferably 15 mN or more. Furthermore, the upper limit is preferably approximately 50 mN or less, more preferably 40 mN or less, and even more preferably 30 mN or less.

[0057] The MT(mN) value of the recovered raw material D can be measured in the same way as the melt tension of resin A described above, except that the recovered raw material D is used as the measurement sample.

[0058] (Melting point of recovered raw material D) The melting point (°C) of the recovered raw material D is preferably between 155°C and 170°C, and more preferably between 160°C and 168°C. Having the melting point of the recovered raw material D within this range makes it easier to improve the rigidity and heat resistance of the resulting blow-molded article. It also facilitates the stable formation of a foamed resin molten material with good extrusion foaming properties. The melting point of the recovered raw material D can be measured using the same method as for the melting point of resin A, except that the recovered raw material D is used as the measurement sample.

[0059] (Difference between the melting point and crystallization temperature of recovered raw material D) From the viewpoint of stably forming foamed parisons with good expandability and shapeability, it is preferable that the difference between the melting point (°C) of the recovered raw material D and the crystallization temperature (°C) of the recovered raw material D is 30°C or more and 36°C or less. The crystallization temperature of the recovered raw material D can be measured in the same way as the crystallization temperature of resin A, except that the recovered raw material D is used as the measurement sample.

[0060] (The proportion of components derived from resins A, B, and C in the recovered raw material D) Component A derived from resin A in recovered raw material D R The blending ratio is 10% by mass or more and 30% by mass or less, and component B derived from resin B. R The blending ratio is 40% by mass or more and 70% by mass or less, and component C derived from resin C. R The blending ratio of is preferably 10% by mass or more and 30% by mass or less. However, component A derived from resin A is also preferable. R The proportion of the mixture and component B derived from resin B R The proportion of the compound and component C derived from resin C RThe sum of the blending ratios of resins A, B, and C in the recovered raw material is set to 100% by mass. By ensuring that the blending ratios of the components derived from resins A, B, and C in the recovered raw material are within the above numerical range, it is possible to improve the blow moldability of the foamed parison and stably obtain a foamed blow molded article with excellent impact resistance at low temperatures. From this viewpoint, in the recovered raw material D, component A derived from resin A is more preferably included. R The blending ratio is 15% by mass or more and 30% by mass or less, and component B derived from resin B. R The blending ratio is 50% by mass or more and 70% by mass or less, and component C derived from resin C. R The proportion of this ingredient is between 10% by mass and 20% by mass.

[0061] (Mixing ratio of resin A, resin B, resin C, and recovered raw material D in the resin raw material) In the method for producing a foamed blow molded article according to the present invention, the amount of branched homopolypropylene A blended (amount of resin A blended W) A )(parts by mass) and the amount of linear block polypropylene B (amount of resin B W) B ) (parts by mass) and the amount of low-density polyethylene C (amount of resin C W) C )(mass part) and total amount (W A +W B +W C The value) is W A+B+C The amount (parts by mass) of the recovered raw material D is set to W D (Containing amount W D If we consider them as such, then their ratio (W A+B+C :W D The ratio is 40:60 to 5:95. However, the total amount of resin A, resin B, resin C, and recovered raw material D is 100 (parts by mass). Thus, the ratio of recovered raw material D to the mixed resin of resin A, resin B, resin C, and recovered raw material D is large, but according to the method for manufacturing a foamed blow molded article of the present invention, even with such a high ratio of recovered raw material D, a well-formed foamed blow molded article can be obtained, and a foamed blow molded article with excellent impact resistance at low temperatures can be stably obtained.

[0062] (Mixing ratio of resin A and resin B in resin raw materials) Blending amount W of resin A A , relative to which, the blending amount W of resin B B ratio (W B / W A ) is preferably 1 or more and 5 or less. W B / W A falling within this range makes it possible to stably improve the impact resistance of the foamed blow molded article while ensuring the blow moldability of the foamed parison. From this point of view, W B / W A is more preferably 2 or more and 4 or less.

[0063] (Blending amount of resin and blending amount of resin-derived components) The expandable resin melt for forming a foamed parison includes branched homopolypropylene A (resin A F branched homopolypropylene as), component A derived from branched homopolypropylene A (resin A U branched homopolypropylene as) R , linear block polypropylene B (resin B F linear block polypropylene as), component B derived from linear block polypropylene B (resin B U linear block polypropylene as) R and low density polyethylene C (resin C F low density polyethylene as), component C derived from low density polyethylene C (resin C U low density polyethylene as) R are melt-kneaded. In addition, resin B F includes resin B1 F and resin B2 F , and resin B U includes resin B1 U and resin B2 U .

[0064] Branched homopolypropylene A (resin A F ) blending amount W A and the blending amount W of the component A R (parts by mass) the value of the total amount (W AR +W A value) is W AR ​A+AR (Parts by mass) and linear block polypropylene B (resin B F ) Amount of W B and the aforementioned component B R Amount of ingredients W BR (Mass part) and the value of the total amount (W) B +W BR The value) is W B+BR (Parts by mass) and low-density polyethylene C (resin C F ) Amount of W C and the aforementioned component C R Amount of ingredients W CR The value of the sum of (W) C +W CR The value) is W C+CR (Mass part) A+AR , W B+BR and W C+CR The (mass portion) satisfies the following range. Note that linear block polypropylene B (resin B F ) Amount of W B The amount of block polypropylene B1 is W B1 and the amount of block polypropylene B2 W B2 It is determined by the sum of the above components B R Amount of ingredients W BR is component B R Of these, component B1 derived from block polypropylene B1 R Amount of ingredients W B1R and component B R Of these, component B2 is derived from block polypropylene B2. R Amount of ingredients W B2R It is determined by the sum of the amounts. Therefore, W B+BR is, W B1 and W B2 and W B1R and W B2R The sum of (or W B1 and W B1R The total W B1+B1R And, W B2 and W B2R The total W B2+B2R It is determined by the sum of the two values.

[0065] In other words, W A+AR The value of is 10 parts by mass or more and 30 parts by mass or less, WB+BR The value of is 40 parts by mass or more and 70 parts by mass or less, and W C+CR The value of is 10 parts by mass or more and 30 parts by mass or less. However, W A+AR Value and W B+BR Value and W C+CR The sum of this value and the other value is 100 parts by mass.

[0066] Resin A supplied to form the foamed resin molten product described above. F , resin B F , resin C F , component A R , component B R , and component C R By determining the amount of the compound to satisfy the above-mentioned range, it becomes possible to mold the foamed blow molded article well and to obtain a foamed blow molded article with improved impact resistance in low-temperature environments. From this viewpoint, in a foamed parison, W is more preferably used. A+AR The value of is 15 parts by mass or more and 30 parts by mass or less, W B+BR The value of is 50 parts by mass or more and 70 parts by mass or less, and W C+CR The value is between 10 parts by mass and 20 parts by mass.

[0067] Furthermore, the foamed blow-molded article contains a component derived from branched homopolypropylene A (component A T ) and a component derived from linear block polypropylene B (component B T ) and components derived from low-density polyethylene C (component C T ) is included. Component A derived from branched homopolypropylene A in foamed blow molded articles. T The blending ratio is as follows: Resin A as a newly used raw material (Resin A F The amount of ) blended and resin A as a non-newly used raw material (resin A U ) component A derived from R It is determined according to the total amount of the blended components. Similarly, component B derived from linear block polypropylene B in foamed blow molded articles. T The proportions of the blend consist of the amount of resin B used as a new raw material and component B derived from resin B, which is not a new raw material. RIt is determined according to the total amount of the blended components. In addition, component C derived from low-density polyethylene C in foamed blow molded articles. T The blending ratio is determined by the amount of resin C used as a new raw material and the amount of component C derived from resin C, which is not a new raw material. R It is determined according to the total amount of each component. The same applies to foamed parisons.

[0068] The above W A+AR The value (parts by mass) is usually derived from the resin A contained in the foamed parison formed in the manufacturing method of the present invention and the foamed blow molded article obtained by the manufacturing method of the present invention. T This is the same as the value of W. B+BR and W C+CR The same applies to the value (parts by mass) of the component (component B) derived from resins B and C contained in the foamed parison formed in the manufacturing method of the present invention and the foamed blow molded article obtained by the manufacturing method of the present invention. T , component C T It will be the same as the value of ).

[0069] (Foaming agent) As a blowing agent, chemical blowing agents and physical blowing agents can be used, but from the viewpoint of ease of application, physical blowing agents are preferably used. Examples of physical blowing agents include organic physical blowing agents and inorganic physical blowing agents. Examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, chloride hydrocarbons such as methyl chloride and ethyl chloride, and fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane. Examples of inorganic physical blowing agents include nitrogen, carbon dioxide, air, and water. The physical blowing agent used for foaming resin molten material may consist of one type of compound or may contain two or more types of compounds.

[0070] From the viewpoint of compatibility between polypropylene resins and low-density polyethylene and physical blowing agents, and the foaming properties of foamed resin molten products, inorganic physical blowing agents are preferred as physical blowing agents used for foamed resin molten products, and among inorganic physical blowing agents, carbon dioxide is more preferred.

[0071] The amount of blowing agent can be appropriately set according to the type of blowing agent and the desired apparent density. For example, if the blowing agent is carbon dioxide, the amount of blowing agent is preferably 0.05 mol to 0.4 mol per 1 kg of resin component contained in the foamed resin molten product, more preferably 0.07 mol to 0.3 mol, and even more preferably 0.1 mol to 0.2 mol.

[0072] (Other polymers) The foamed resin molten material may contain other polymers besides resins A, B, and C, as long as the effects of the present invention are not impaired. Examples of other polymers include polypropylene resins other than resins A and B, thermoplastic resins such as linear low-density polyethylene (PE-LLD), high-density polyethylene (PE-HD), and ethylene-vinyl acetate copolymer (EVA), and elastomers such as styrene-butadiene-styrene block copolymer. When other polymers are included, the total amount of branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and recovered raw material D is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, based on a total of 100 parts by mass.

[0073] (Additives) The foamed resin molten material may contain additives. Examples of additives include foam regulators, colorants, antioxidants, heat stabilizers, weathering agents, UV absorbers, flame retardants, fillers, and antibacterial agents. As foam regulators, inorganic or organic foam regulators can be used. Examples of inorganic foam regulators include metal borate salts such as zinc borate, magnesium borate, and borax, as well as sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, and sodium bicarbonate. Examples of organic foam regulators include sodium 2,2-methylenebis(4,6-tert-butylphenyl) phosphate, sodium benzoate, aluminum benzoate, and sodium stearate. The foam regulator added to the foamed resin molten material may be one compound or two or more compounds.

[0074] [1-2 Action and Effects] Conventional methods for manufacturing foamed blow molded articles require the use of recycled raw materials, such as burrs from the foamed parison generated during the manufacturing process, as part or all of the raw materials for the foamed blow molded article.

[0075] In the manufacturing method of foamed blow molded articles, the recovered raw material D, which is recovered during the manufacturing process of the foamed blow molded article, is again included in the resin raw material. As a result, the recovered raw material contains resin components that have been used repeatedly. Therefore, the recovered raw material contains polypropylene resins that have been subjected to many thermal histories, such as kneading in an extruder. As the number of thermal histories increases, the molecular chains of the polypropylene resin contained in the recovered raw material are broken down, leading to a decrease in the melt tension of the recovered raw material and an increase in the melt flow rate. When such recovered raw material is included in the resin raw material, the drawdown resistance and formability of the foamed parison decrease, making it difficult to obtain a well-formed foamed blow molded article. In particular, when obtaining large foamed blow molded articles, such as those with an extrusion length (longitudinal length of the foamed blow molded article) of 1 m or more, it becomes even more difficult to obtain a good foamed blow molded article. Furthermore, when the ratio of recovered raw material to newly used raw material in the composition ratio of the resin constituting the resin raw material is increased, the problem of the blow moldability of the foamed parison decreasing even more becomes more significant.

[0076] According to the manufacturing method of the present invention, the resin raw material includes resin A, resin B, and resin C, and resin B is used in combination with specific resins B1 and resin B2, which have different melt flow rates. Furthermore, according to the manufacturing method of the present invention, the ratio of the total amount of resins A, B, and C as newly used raw materials to the amount of recovered raw material D is set to a specific range, and furthermore, the total amount of resin A and resin A as a non-newly used raw material, the total amount of resin B and resin B as a non-newly used raw material, and the total amount of resin C and resin C as a non-newly used raw material are set to a specific range. Regarding resins B1 and B2, the MFR of resin B1 is smaller than that of resin B2, and resin B1 tends to have a relatively larger amount of components with larger molecular weights compared to resin B2. Therefore, by including resin B1 in resin B, the drawdown resistance of the foamed parison can be improved, and it becomes easier to ensure physical properties such as impact resistance in low-temperature environments for the foamed blow molded article. Furthermore, resin B tends to have a higher proportion of components with relatively smaller molecular weights in resin B2 compared to resin B1. The inclusion of resin B2 in resin B makes the foamed parison more easily stretchable during the pre-blow and blow molding processes, thus facilitating improvements in the expandability and shapeability of the foamed parison. Thus, from the perspective of the broadening of the molecular weight distribution of the resin components constituting the foamed parison, it is considered that the combined use of resin B1 and resin B2 can improve the blow moldability of the foamed parison. In addition, the components derived from resin B contained in the recovered raw material D include components derived from resin B1 and resin B2. This allows for improved blow moldability of the foamed parison while ensuring impact resistance in low-temperature environments as a foamed blow molded product, even when using a larger amount of recovered raw material D. As a result, even large foamed blow molded products can be molded successfully.

[0077] [2. Foam blow molded body] A foamed blow-molded article can be obtained by the manufacturing method described in [1. Method for Manufacturing a Foamed Blow-Molded Article] above. The shape of the foamed blow-molded article may be appropriately determined according to the shape of the mold used in the blow-molding process, and may also be formed in a hollow shape.

[0078] As a foamed blow-molded article obtained by the manufacturing method of the present invention described above, for example, a foamed blow-molded article having "Configuration 1" described later can be obtained. It is preferable that the foamed blow-molded article obtained by the manufacturing method described above further comprises "Configuration 2" described later in addition to "Configuration 1".

[0079] "Configuration 1": The foamed blow-molded article consists of a polypropylene resin composition comprising branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and recovered raw materials D recovered during the manufacturing process of the foamed blow-molded article.

[0080] "Configuration 2": In the polypropylene resin composition shown in Configuration 1 above, component A is derived from branched homopolypropylene A. T The blending ratio is 10% by mass or more and 30% by mass or less, and component B derived from linear block polypropylene B. T The blending ratio is 40% by mass or more and 70% by mass or less, and component C derived from low-density polyethylene C. T The proportion of this ingredient is between 10% by mass and 30% by mass.

[0081] However, in configuration 2, component A derived from branched homopolypropylene A is T The proportion of the blend and component B derived from linear block polypropylene B T The proportion of the blend and component C derived from low-density polyethylene C T The sum of the proportions of the ingredients is set to 100% by mass.

[0082] From the viewpoint of stably obtaining a foamed blow-molded article that has good internal condition and appearance, as well as good impact resistance in low-temperature environments, it is more preferable that the numerical range shown in Configuration 2 be within the following range. That is, in the polypropylene resin composition shown in Configuration 1, it is more preferable that component A derived from branched homopolypropylene A T The blending ratio is 15% by mass or more and 30% by mass or less, and component B derived from linear block polypropylene B. TThe blending ratio is 50% by mass or more and 70% by mass or less, and component C derived from low-density polyethylene C. T The proportion of this ingredient is between 10% by mass and 20% by mass.

[0083] Furthermore, as mentioned above, component A derived from branched homopolypropylene A in the foamed blow molded article. T The blending ratio is determined by the amount of resin A used as a new raw material and component A derived from resin A as a non-new raw material. R Determined based on the total value of the blending amount of the component B derived from linear block polypropylene B. T The proportion of the mixture is the amount of resin B used as a new raw material and component B derived from resin B as a non-new raw material. R It is determined based on the total value of the blending amount of [component C]. Furthermore, component C derived from low-density polyethylene C T The proportion of the blend is the amount of resin C used as a new raw material and component C derived from resin C as a non-new raw material. R It is determined based on the total value of the combined amount of each ingredient.

[0084] (Density of foamed blow molded product) By the manufacturing method of the present invention, a foamed blow-molded article is produced with a density (apparent density) of 0.1 to 0.5 g / cm³. 3 A foamed molded article can be obtained that has the following characteristics: When the density of the foamed blow molded article is within this numerical range, the foamed blow molded article is lightweight and has appropriate rigidity, making it suitable for various applications such as ducts. In particular, according to the manufacturing method of the present invention, the density is 0.1 to 0.35 g / cm³. 3 Even when seeking to obtain a foamed blow-molded article with a low apparent density, it is possible to stably manufacture the foamed blow-molded article.

[0085] The density of a blow-molded foamed body is calculated by multiplying the mass (W) (g) of the blow-molded foamed body by the volume (V) (cm³). 3The volume of the foamed blow molded body can be calculated as the value obtained by dividing by ( ). The volume of the foamed blow molded body can be measured, for example, by submerging the foamed blow molded body in a container with water markings and measuring the rise in water level (submersion method).

[0086] (Closed-cell ratio of foamed blow molded products) From the viewpoint of improving the appearance and increasing the rigidity of the foamed blow molded article, the closed-cell ratio is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more.

[0087] (Measurement of closed-cell ratio) Test specimens are prepared by cutting a 25mm x 25mm x flat section thickness from the generally flat section of the foamed blow molded body. Multiple test specimens are stacked so that the sum of their thicknesses is as close to 20mm as possible to create a measurement specimen. Next, the true volume Vx of the measurement specimen is measured using a Toshiba Beckman Corporation air-comparative hydrometer 930 or similar device, according to procedure C of ASTM-D2856-70, and the closed-cell ratio (S(%)) is calculated using the following formula (Equation (1)). The above measurement is performed using five measurement specimens, and the arithmetic mean is taken as the closed-cell ratio of the foamed blow molded body.

[0088]

number

[0089] however, Vx: True volume of the test specimen measured by the above method (cm³) 3 ) is equivalent to the sum of the volume of the resin constituting the foamed blow molded body and the total volume of the closed-cell portion of the test piece. Va: The apparent volume (cm³) of the test specimen calculated from the external dimensions of the test specimen used for measurement. 3 ), W: Total mass (g) of the test specimen used for measurement, and ρ: Density of the resin constituting the foamed blow molded product (g / cm³) 3 ), That is the case.

[0090] The foamed blow-molded articles produced using the manufacturing method according to the present invention can be used in a wide range of applications such as ducts, tanks, and containers. 3 In the case of a foamed molded body, a foamed blow molded body can be suitably used as a foamed duct that offers an excellent balance between lightness and rigidity.

[0091] Next, we will explain in more detail using specific examples. [Examples]

[0092] (Preparation of resin) Two types of block polypropylene (resins B1 and B2) that make up branched polypropylene (resin A) and linear block polypropylene (resin B) were prepared as shown in Table 1. Table 1 also shows the MFR (g / 10min (230℃, load 2.16kg)), melt tension (mN), melting point (℃), and crystallization temperature (℃) of the prepared resins A, B1, and B2.

[0093] The MFR (g / 10min (230℃, load 2.16kg)) of resins A, B1, and B2 was measured according to JIS K7210-1:2014 (Test Method A). The melting points of resins A, B1, and B2 were determined by differential scanning calorimetry according to JIS K7121-1987. For conditioning the test specimens, "(2) When measuring the melting temperature after performing a certain heat treatment" was adopted, and the cooling rate was set at 10℃ per minute. The heating rate when measuring the melting temperature was also set at 10℃ per minute. The crystallization temperatures of resins A, B1, and B2 were determined by differential scanning calorimetry according to JIS K7121-1987. The cooling rate was set at 10℃ per minute.

[0094] The melt tension (mN) of resins A, B1, and B2 was measured as follows. First, the method for measuring the melt tension of resin A will be explained. An orifice with a nozzle diameter of 2.095 mm and a length of 8.0 mm was set in a cylinder with a diameter of 9.55 mm and a length of 350 mm. The temperature of the cylinder and orifice was set to 230°C, and the required amount of the sample was placed in the cylinder using resin A. It was left for 4 minutes to form the molten resin of the sample (resin A sample). Next, the molten resin was extruded from the orifice in a string-like manner at a piston speed of 10 mm / min. This string-like material (strand) was placed on a tension-detecting pulley with a diameter of 45 mm, and the string-like material was taken up by a take-up roller while increasing the take-up speed at a constant rate so that the take-up speed reached 200 m / min from 0 m / min in 4 minutes. This operation caused the string-like material to break, and the maximum value of the tension just before the string-like material broke was obtained. The reason for setting the time required for the pull-up speed to increase from 0 m / min to 200 m / min to 4 minutes was to suppress thermal degradation of the resin used as a sample and to improve the reproducibility of the obtained values. By performing the above procedure (the procedure to obtain the maximum value of melt tension using one sample) with different samples, a total of 10 measurements were taken. The three largest and three smallest maximum values ​​obtained from the 10 measurements were excluded, and the arithmetic mean of the remaining four intermediate maximum values ​​was taken to calculate the melt tension (mN).

[0095] Furthermore, if the molten tension was measured using the method described above and the string-like material did not break even when the draw speed reached 200 m / min, the value of the molten tension (mN) obtained by maintaining a constant draw speed of 200 m / min was adopted. Specifically, in the same manner as the measurement described above, molten resin was extruded from the orifice in the form of a string, and this string-like material was placed on a tension detection pulley. The draw speed was increased at a constant rate so that it reached 200 m / min from 0 m / min in 4 minutes. Data acquisition of the molten tension was started after the rotation speed reached 200 m / min and stopped after 30 seconds. The average value (Tave) of the maximum tension (Tmax) and minimum tension (Tmin) obtained from the tension load curve obtained during these 30 seconds was taken as the molten tension in the method of the present invention. Here, Tmax is the value obtained by dividing the sum of the detected peak (mountain) values ​​in the tension load curve by the number of detected peaks, and Tmin is the value obtained by dividing the sum of the detected dip (valley) values ​​in the tension load curve by the number of detected dips.

[0096] The melt tension (mN) of resins B1 and B2 was measured using the same method as the method for measuring the melt tension of resin A described above.

[0097] Two types of resin A were prepared, as shown in type names a1 and a2 in Table 1. The contents of resin A for type names a1 and a2 are as follows. The MFR (g / 10min (230℃, load 2.16kg)), melting point, and crystallization temperature of resin A for type names a1 and a2 are shown in Table 1, respectively.

[0098] Resin A, identified by type name a1, is the product name "WB140" manufactured by Borealis. Resin A, identified by type name a2, is product name "HEX17112" manufactured by Saudi Basic Industries Corporation (SABIC).

[0099] Four types of resin B were prepared, as shown in the type names b1, b2, b3, and b4 in Table 1. Resin B of type names b1 and b2 corresponds to block polypropylene B1 (resin B1), and resin B of type names b3 and b4 corresponds to block polypropylene B2 (resin B2). The contents of resin B of type names b1, b2, b3, and b4 are as follows. The MFR (g / 10min (230℃, load 2.16kg)) of each resin B of type names b1, b2, b3, and b4 are shown in Table 1.

[0100] Resin B, identified by type name b1 (also corresponds to resin B1): Block polypropylene (manufactured by Prime Polymer Co., Ltd., product name "Prime Polymer (model number J-750HP)"). Resin B identified by type name b2 (also corresponds to resin B1): Block polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec PP (model number BC3BRF)"). Resin B, identified by type name b3 (also corresponds to resin B2): Block polypropylene (manufactured by Prime Polymer Co., Ltd., product name "Prime Polymer (model number J707G)"). Resin B, identified by type name b4 (also corresponds to resin B2): Block polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec (trademark) PP (model number BC03GS)").

[0101] Furthermore, three types of low-density polyethylene (resin C), indicated by the following type names c1, c2, and c3, were prepared. The contents of resin C for type names c1, c2, and c3 are as follows. The MFR (g / 10min (190℃, load 2.16kg)) of resin C was measured in accordance with JIS K7210-1:2014 (Test method A). The melting point of resin C was determined by differential scanning calorimetry in accordance with JIS K7121-1987. For conditioning the test specimens, "(2) When measuring the melting temperature after performing a certain heat treatment" was adopted, and the cooling rate at this time was 10℃ per minute. The heating rate when measuring the melting temperature was also 10℃ per minute.

[0102] Resin C, identified by type name c1, is manufactured by NUC Corporation and is product name "NUC (model number 8351)" (MFR: 14g / 10min (190℃, load 2.16kg), melting point: 108℃). Resin C, identified by type name c2, is manufactured by NUC Corporation and is product name "NUC (model number 8008)" (MFR: 5g / 10min (190℃, load 2.16kg), melting point: 108℃). Resin C, identified by type name c3, is manufactured by Sumitomo Chemical Co., Ltd., and its product name is "Sumikasen (model number F102-0)" (MFR: 0.4g / 10min (190℃, load 2.16kg), melting point: 110℃).

[0103] [Table 1]

[0104] Example 1 (Preparation of recovered materials) The recovered raw material D was composed of recovered material obtained after repeating the foam blow molding process multiple times. In Example 1, the recovered material was composed of recovered material obtained after repeating the foam blow molding process four times as shown below. The resin raw materials used in the first to fourth foam blow molding processes when obtaining the recovered raw material D are referred to as the first to fourth resin raw materials, respectively. However, when explaining the preparation of the recovered raw material, if the first to fourth resin raw materials are not distinguished, they may simply be referred to as resin raw materials.

[0105] The first (initial) manufacturing process for the foamed blow molded body was carried out. In the first iteration, the manufacturing process for the foamed blow molded body was carried out using a first resin raw material that did not contain any recovered raw materials, and a foamed blow molded body was produced as the first molded body. At this time, the manufacturing conditions for the foamed blow molded body were the same as the manufacturing conditions when using recovered raw material D as shown in Example 1. Furthermore, the resins A, B1, B2, and C in the first resin raw material were blended in the same amounts as the resins A, B1, B2, and C in the resin raw material shown in the column for Example 1 in Table 3 (however, each resin was a newly used raw material). Furthermore, during the initial production of the foamed blow-molded product, 5 parts by mass of talc masterbatch: product name "High Filler #12" (manufactured by Matsumura Sangyo, talc concentration 20% by mass, talc median diameter 7.5 μm) was added as a bubble regulator per 100 parts by mass of resin raw material, and 0.5 parts by mass of carbon black masterbatch: product name "PP Black Master Batch, BT920F-JSJ" (manufactured by B&Tech Corporation, CB concentration 45% by mass) was added as a black pigment per 100 parts by mass of resin raw material.

[0106] The resulting first molded body was crushed. The resulting crushed material was fed into an extruder and kneaded at 230°C to obtain molten resin. The molten resin was then extruded and repelled. The resin pellets thus repelled were used as the first recovered material.

[0107] The second foam blow molding process was carried out using the first recovered material. The foam blow molding process was carried out using a second resin raw material containing the first recovered material to produce a second molded product. The second molded product was made into resin pellets, similar to the case in obtaining the first recovered material. The resin pellets were used as the second recovered material.

[0108] For the second batch of foamed blow-molded articles, the same conditions were used as for the first batch of foamed blow-molded articles, specifically the same conditions as when using recovered raw material D as shown in Example 1. Furthermore, the amounts of resins A, B, and C in the second resin raw material were the same as those used for newly used resins A, B, and C in the resin raw material shown in the Example 1 column of Table 3 (the amounts of resins A, B, and C listed separately from recovered raw material D in Table 3). The amount of primary recovered material in the second resin raw material was the same as that used for recovered raw material D shown in the Example 1 column of Table 3. In Example 1, when the total of resins A, B, C, and recovered raw material D was 100 parts by mass, recovered raw material D amounted to 80 parts by mass. Similarly, for the second resin raw material, the first recovered material was used such that when the total of resins A, B, C, and primary recovered material was 100 parts by mass, the primary recovered material amounted to 80 parts by mass.

[0109] The third manufacturing process for the foamed blow-molded product was carried out using the second batch of recovered material. The third manufacturing process for the foamed blow-molded product was carried out in the same manner as the second manufacturing process, except that the second batch of recovered material was used instead of the first batch of recovered material. This resulted in the third batch of recovered material being obtained.

[0110] The fourth manufacturing process for the foamed blow-molded product was carried out using the third recovered raw material. The fourth manufacturing process for the foamed blow-molded product was carried out in the same manner as the third manufacturing process for the foamed blow-molded product, except that the third recovered material was used instead of the second recovered material. As a result, the fourth recovered material was obtained. The fourth recovered material was used as the recovered raw material D. As shown in Table 2, the type name of the recovered raw material D obtained in Example 1 was designated as d1.

[0111] The physical properties of the recovered raw material D were measured using the method described above, including MFR (g / 10min (230℃, load 2.16kg)), melt tension (mN), melting point (℃), and crystallization temperature (℃). The results are shown in Table 2. The same applies to Examples 2 to 8. The same also applies to Comparative Examples 1 to 6 described in Table 4.

[0112] Regarding the recovered raw material D obtained in Example 1, component A is derived from resin A. R , component B1 derived from resin B1 of resin B R , component B2 derived from resin B2 R and component C derived from resin C R The proportions (mass%) of each component are shown in the "Components derived from A," "Components derived from B1," "Components derived from B2," and "Components derived from C" columns in Table 2, respectively. Component A derived from resin A R , component B1 derived from resin B1 of resin B R , component B2 derived from resin B2 R and component C derived from resin C R The blending ratio can be calculated from the resin composition of the resin raw materials (first to third resin raw materials) used in the manufacturing process of the foamed blow molded product from the first to the fourth time. The same applies to Examples 2 to 8. The same also applies to Comparative Examples 1 to 6 listed in Table 4.

[0113] Note that in Table 2, the "Mixing Ratio: B2 / B1" column shows the ratio of resin B2 to resin B1 in the resin constituting the recovered raw material D (amount of resin B2 (W) B2 )) / (Amount of resin B1 (W B1 The table also lists the amount of resin B (mass %) in the "Total percentage of components derived from B" column. In addition, the "Mixing ratio: B / A" column lists the ratio of resin B to resin A in the resins that make up the recovered raw material D (amount of resin B (W B )) / (Amount of resin A (W A )), In the "Mixing Ratio: C / B" column, enter the ratio of resin C to resin B in the resin that makes up the recovered raw material D (amount of resin C (W C)) / (Amount of resin B (W B The following points are also mentioned. These points also apply to Examples 2 to 8. Furthermore, the same applies to Comparative Examples 1 to 6 listed in Table 4.

[0114] (Manufacturing of foamed blow molded products) (Extrusion foaming process) The resin raw material used was a mixture of resins A, B (resins B1 and B2), C, and recovered raw material D, specified by the type names shown in the column for Example 1 in Table 3, in the amounts shown in Table 3. Resins A, B (resins B1 and B2), and C, as shown in the composition of the resin raw material in Table 3, are used separately from the resins contained in recovered raw material D. In addition, 1 part by mass of the talc masterbatch was added to the extruder as a foam regulator per 100 parts by mass of the resin raw material, and 0.1 parts by mass of the carbon black masterbatch was added as a black pigment per 100 parts by mass of the resin raw material. The resin raw material was kneaded at 230°C in the extruder to form a resin molten product, and carbon dioxide was injected into the extruder midway through as a foaming agent. The amount of foaming agent per 1 kg of resin raw material (mol / kg) is as shown in Table 3. A foamy resin molten product was obtained by further kneading the resin raw material with the foaming agent injected into it.

[0115] The obtained foamed molten resin was filled into an accumulator located downstream of the extruder and adjusted to 170°C. The foamed molten resin was extruded into a cylindrical shape under atmospheric pressure from the lip (90 mm in diameter) of an annular die attached downstream of the accumulator at a discharge speed of 1500 kg / hr, thereby foaming and forming a foamed parison.

[0116] (Pre-blowing process) After pinching the bottom of the foam parison, pre-blow air was supplied to the hollow part inside the foam parison to inflate it, and the foam parison was then sandwiched between two parts of a mold located directly below the die.

[0117] (Blow molding process) After the mold clamping was complete, blow air at a pressure of 0.1 MPa (G) was blown into the hollow portion of the foam parison, and at the same time, air between the foam parison and the molding surface was sucked out through holes in the mold to perform blow molding. This formed the foam parison into a shape corresponding to the mold shape. After the mold was cooled, the mold was opened and the foamed molded body with molding burrs was removed. By removing the burrs from the foamed molded body with molding burrs, a hollow foamed blow molded body was obtained. The obtained foamed blow molded body was formed with a longitudinal length of 1500 mm and a maximum circumference of 900 mm.

[0118] The density of the resulting foamed blow molded product is (g / cm³). 3 The following were measured: ), average thickness (mm), and closed-cell percentage (%).

[0119] Density (g / cm 3 ) is the mass (W) (g) of the foamed blow molded body, and the volume (V) (cm³) of the foamed blow molded body measured by the immersion method. 3 It was calculated by dividing by ).

[0120] The average thickness (mm) was measured as follows: First, perpendicular cross-sections were obtained from five locations: the longitudinal center of the foam blow molded body, near both longitudinal ends, and midway between the center and both ends. The thickness (wall thickness) of the foam blow molded body was measured at six equally spaced points in the circumferential direction of each perpendicular cross-section. From the 30 thickness measurements obtained, the arithmetic mean of the 28 thicknesses (excluding the maximum and minimum values) was taken as the average thickness of the foam blow molded body.

[0121] The closed-cell ratio (%) was measured as follows. First, a test specimen was prepared by cutting a 25mm × 25mm × the thickness of the flat section from the flat section of the foamed blow molded body. Multiple test specimens were stacked so that the sum of their thicknesses was closest to 20mm to create the measurement specimen. Next, following procedure C of ASTM-D2856-70, the true volume Vx of the measurement specimen was measured using a Toshiba Beckmann Corporation air-comparative hydrometer 930, and the closed-cell ratio (S(%)) was calculated using the above formula (Equation (1)). The above measurement was performed five times using different measurement specimens, and the arithmetic mean was taken as the closed-cell ratio of the foamed blow molded body.

[0122] Table 3 shows the resin raw materials used in the extrusion foaming process, with the "Mixing Ratio: B2 / B1" column indicating the ratio of resin B2 to resin B1 in the resin raw materials (amount of resin B2 (W) B2 )) / (Amount of resin B1 (W B1 The following is stated: )) and in the "Mixing ratio: ([A+B+C]:[D])" column, the total amount of resin A, resin B, and resin C (W A+B+C ) (total amount of blended material) and the amount of recovered raw material D (W D ) ratio ((W A+B+C ):(W D Table 3 contains the following information. Unless otherwise specified, the values ​​for each ratio in Table 3 refer to resins A, B (resins B1 and B2), and C, which are used separately from the resins contained in the recovered raw material D. In Table 3, the "MFR of B" column shows the MFR value of resin B, which was used separately from the recovered raw material D. As mentioned above, the MFR value of resin B is determined as a weighted average value using the relationship between the blending amounts of resin B1 and resin B2, and the MFRs of resin B1 and resin B2. Also, the "MFR ratio: B2 / B1" column in Table 3 shows the ratio of the MFR of resin B2 to the MFR of resin B1, which was used separately from the recovered raw material D. The same applies to Examples 2 to 10. The same also applies to Comparative Examples 1 to 6 described in Table 5.

[0123] Furthermore, in Table 3, the "Mixing Ratio: B / A" column shows the ratio of resin A to resin B in the resin raw material (amount of resin A (W)A )) / (Amount of resin B (W B )), In the "Mixing Ratio: C / B" column, enter the ratio of resin C to resin B in the resin raw material (amount of resin C (W C )) / (Amount of resin B (W B )) is also listed. Furthermore, Table 3 states, "Resin A + Component A R In the column, enter the amount of resin A (W A ) and component A derived from resin A R Amount of ingredients (W AR ) and the sum (W A+AR The (mass) is listed as "Resin B1 + Component B1 R In the column, enter the amount of resin B1 (W B1 ) and component B1 derived from resin B1 R Amount of ingredients (W B1R ) and the sum (W B1+B1R The (mass) is listed as "Resin B2 + Component B2 R In the column, enter the amount of resin B2 (W B2 ) and component B2 derived from resin B2 R Amount of ingredients (W B2R ) and the sum (W B2+B2R The (mass) is listed as "Resin C + Component C R In the column, enter the amount of resin C (W C ) and component C derived from resin C R Amount of ingredients (W CR ) and the sum (W C+CR The (mass parts) is listed. Also, "Resin B + Component B" R In the column, enter the amount of resin B1 (W B1 ) and component B1 derived from resin B1 R Amount of ingredients (W B1R ) and the amount of resin B2 (W B2 ) and component B2 derived from resin B2 R Amount of ingredients (W B2R ) and the sum of (W B+BR ) is listed. Note that "Component A R ”, “Ingredient B1 R ”, “Ingredient B2 R ”, “Component B R " and "Component C RThese are the components derived from resin A, resin B1, resin B2, resin B, and resin C, respectively, contained in the recovered raw material D. The same applies to Examples 2 to 10. The same also applies to Comparative Examples 1 to 6 listed in Table 5.

[0124] The resulting foamed blow-molded articles were subjected to moldability evaluation and ball drop tests.

[0125] (Moldability evaluation) The moldability evaluation was performed by visually observing the foamed parison and the foamed blow molded product to determine whether the foamed parison was sufficiently widened during the pre-blow process (widening ability) and whether any molding defects were observed on the upper part of the foamed blow molded product (presence or absence of molding defects on the upper part of the molded product), as described below. The results are shown in Table 3.

[0126] (Expandability) ○ (Good): In the pre-blowing process, the maximum length of the foamed parison in the mold width direction (the direction perpendicular to the extrusion direction of the foamed parison and the mold clamping direction) can be increased to exceed the maximum length between the peripheral edges of the molding cavity in the mold width direction, without damaging the foamed parison. × (Defective): In the pre-blowing process, it is not possible to widen the maximum length of the foamed parison in the width direction of the mold to a length greater than the maximum length between the peripheral edges of the molding cavity in the width direction of the mold without damaging the foamed parison.

[0127] (Presence or absence of molding defects in the upper part of the molded body) None: The mold cavity shape is formed up to the top of the foamed blow molded body, and no holes or other defects are observed in the foamed blow molded body. Yes: The upper part of the foamed blow molded body is not molded to the shape of the mold cavity, or holes or other defects are observed in the foamed blow molded body.

[0128] (Ball drop test) The ball drop test was conducted as follows. First, the foamed blow molded body was conditioned by placing it in a -10°C atmosphere for 24 hours. The conditioned foamed blow molded body was placed on a test stand with its flat side facing upwards, so that its longitudinal direction was approximately horizontal. A 500g steel ball was dropped onto the flat side of the foamed blow molded body from a position where the distance from the top of the flat side of the foamed blow molded body to the bottom of the steel ball was 40cm, and the damage to the foamed blow molded body was observed. The ball drop test was performed five times. Based on the results of the ball drop test, the cold impact resistance of the foamed blow molded body was evaluated according to the following criteria. The results are shown in Table 3.

[0129] ○ (Good): In five tests, the foam blow molded body did not crack, or cracks were observed in the foam blow molded body, but no fragments were scattered. × (Defective): In at least one test, the foam blow molded body cracked, and fragments of the cracked foam blow molded body were observed to scatter.

[0130] Examples 2 to 8 (Preparation of recovered materials) In Examples 2 to 8, the types and amounts of resins A, B1, B2, and C were those listed in Table 3, corresponding to Examples 2 to 8, respectively. Otherwise, the recovered raw material D was obtained in the same manner as in Example 1.

[0131] Using the recovered raw material D, foamed blow molded articles were produced for each of Examples 2 to 8, under the conditions of the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D, as shown in Table 3.

[0132] The resulting foamed blow-molded body was subjected to the same procedure as in Example 1, and its density (g / cm³) was measured. 3 The average thickness (mm) and closed-cell ratio (%) were measured. The results are shown in Table 3. Furthermore, the obtained foamed blow-molded articles were subjected to moldability evaluation and a ball drop test in the same manner as in Example 1. The results are shown in Table 3.

[0133] Examples 9 and 10 For Examples 9 and 10, the recovered raw material D identified by type name d1 obtained in Example 1, along with resins A, B1, B2, and C2, were used in the proportions shown in Table 3. In Example 9, 1.5 parts by mass of talc masterbatch and 0.15 parts by mass of carbon black masterbatch were added per 100 parts by mass of resin raw material. In Example 10, 0.5 parts by mass of talc masterbatch and 0.05 parts by mass of carbon black masterbatch were added per 100 parts by mass of resin raw material. Otherwise, a foamed blow molded article was obtained using the same method as in Example 1. Note that in Example 9, the proportion of recovered raw material D was smaller than in Example 1, and in Example 10, the proportion of recovered raw material D was larger than in Example 1.

[0134] The foamed blow-molded articles obtained in Examples 9 and 10 were subjected to the same procedure as in Example 1, and their density (g / cm³) was measured. 3 The average thickness (mm) and closed-cell ratio (%) were measured. The results are shown in Table 3. Furthermore, the obtained foamed blow-molded articles were subjected to moldability evaluation and a ball drop test in the same manner as in Example 1. The results are shown in Table 3.

[0135] According to Examples 1 to 10, as shown in the "Mixing Ratio: ([A+B+C]:[D])" column, the total amount of resin A, resin B, and resin C (W A+B+C ) and the amount of recovered raw material D (W D ) ratio ((W A+B+C ):(W D It was confirmed that even with a high proportion of recovered raw material D, foamed blow molded articles with good moldability and good results in the ball drop test were obtained. Furthermore, in Examples 1 to 10, the good results in the ball drop test for the foamed blow molded articles confirmed that they have excellent impact resistance in low-temperature environments.

[0136] For Examples 1 to 10, it was confirmed that foam blow molded articles with good moldability evaluation results could be produced in all manufacturing processes from the first to the final batch. Good moldability evaluation results indicate good expandability and the absence of molding defects on the upper part of the molded article. Furthermore, the upper part of the foamed blow-molded body is susceptible to the effects of drawdown of the foamed parison, making it a difficult area to shape. This tendency becomes more pronounced as the size of the blow-molded body increases, but in this invention, we were able to obtain a foamed blow-molded body that was sufficiently shaped all the way to the top.

[0137] [Table 2]

[0138] [Table 3]

[0139] Comparative Example 1 (Preparation of recovered materials) In Comparative Example 1, only resin B1 was used as resin B, and resin B2 was omitted, except that the recovered raw material D was obtained in the same manner as in Example 1. The type name of the recovered raw material D in Comparative Example 1 is d1(ct). The composition of the obtained recovered raw material D is shown in Table 4. As shown in Table 2, the type names of the recovered raw material D in Comparative Examples 2 to 6 are d2(ct), d3(ct), d4(ct), d5(ct), and d6(ct), respectively.

[0140] Furthermore, for Comparative Example 1 and Comparative Examples 2 through 5 described later, foam blow molded articles were manufactured for use as recovered material (from the first to the fourth recovery stage) in the manufacturing process of foam blow molded articles from the first to the fourth stage. However, for Comparative Example 1, Comparative Example 3 described later, and Comparative Example 5, it was not possible to manufacture foam blow molded articles that showed good moldability evaluation results in any of the manufacturing processes of foam blow molded articles from the first stage onward. Also, for Comparative Examples 2 and 4 described later, it was possible to manufacture foam blow molded articles that showed good moldability evaluation in the first (initial) manufacturing process of foam blow molded articles, but it was not possible to manufacture foam blow molded articles that showed good moldability evaluation in the manufacturing processes of foam blow molded articles from the second stage onward.

[0141] (Manufacturing of foamed blow molded products) Using the recovered raw material D obtained in Comparative Example 1, a foamed blow-molded article was attempted to be obtained in the same manner as in Example 1, except that the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D were as shown in Table 5. However, when the moldability of the foamed blow-molded article obtained in Comparative Example 1 was evaluated in the same manner as in Example 1, the expandability was found to be × (poor), as shown in Table 5, and the foamed parison could not be sufficiently expanded in the pre-blow process, making it impossible to obtain a good foamed blow-molded article. Since the expandability was ×, the judgment of whether there were any molding defects on the upper part of the molded article and the ball drop test were omitted. For reference, the density (g / cm³) of the foamed blow-molded article obtained in Comparative Example 1 was evaluated in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0142] Comparative Example 2 (Preparation of recovered materials) In Comparative Example 2, only resin B2 was used as resin B, and resin B1 was omitted, except that the recovered raw material D was obtained in the same manner as in Example 1. The composition of the obtained recovered raw material D is shown in Table 4.

[0143] (Manufacturing of foamed blow molded products) Using the recovered raw material D obtained in Comparative Example 2, an attempt was made to obtain a foamed blow-molded article in the same manner as in Example 1, except that the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D were as shown in Table 5. However, when the foamed blow-molded article obtained in Comparative Example 2 was evaluated for moldability in the same manner as in Example 1, as shown in Table 5, there was a molding defect in the upper part of the molded article, resulting in a poorly molded article and preventing the acquisition of a good foamed blow-molded article. Note that the ball drop test was omitted because there was a molding defect in the upper part of the molded article. For reference, the foamed blow-molded article obtained in Comparative Example 2 was evaluated for density (g / cm³) in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0144] Comparative Example 3 In Comparative Example 3, the same procedure as in Comparative Example 1 was used to obtain the recovered raw material D, except that the resin with type name b2 was used instead of the resin with type name b1 as resin B1. Then, using the recovered raw material D, an attempt was made to obtain a foamed blow molded article in the same procedure as in Example 1, except that the conditions for the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D, as shown in Table 5, were met. However, when the moldability of the foamed blow molded article obtained in Comparative Example 3 was evaluated in the same manner as in Example 1, the expandability was found to be ×, as shown in Table 5. The foamed parison could not be sufficiently expanded in the pre-blow process, and a good foamed blow molded article could not be obtained. Since the expandability was ×, the judgment of whether there were any molding defects on the upper part of the molded article and the ball drop test were omitted. For reference, the density (g / cm³) of the foamed blow molded article obtained in Comparative Example 3 was evaluated in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0145] Comparative Example 4 In Comparative Example 4, the same procedure as in Comparative Example 2 was used to obtain the recovered raw material D, except that the resin with type name b4 was used as resin B2 instead of resin with type name b3. Then, using the recovered raw material D, an attempt was made to obtain a foamed blow molded article in the same procedure as in Example 1, except that the conditions for the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D, as shown in Table 5, were met. However, when the foamed blow molded article obtained in Comparative Example 4 was evaluated for moldability in the same manner as in Example 1, as shown in Table 5, there was a molding defect in the upper part of the molded article, and a good foamed blow molded article could not be obtained. Note that the ball drop test was omitted because there was a molding defect in the upper part of the molded article. For reference, the density (g / cm³) of the foamed blow molded article obtained in Comparative Example 4 was evaluated in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0146] Comparative Example 5 (Preparation of recovered materials) In Comparative Example 5, the amount of resin A, resin B1, resin B2, and resin C was set to the amounts shown in Table 5, respectively, except that the recovered raw material D was obtained in the same manner as in Example 1. The composition of the obtained recovered raw material D is shown in Table 4.

[0147] (Manufacturing of foamed blow molded products) Using the recovered raw material D obtained in Comparative Example 5, an attempt was made to obtain a foamed blow-molded article in the same manner as in Example 1, except that the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D were as shown in Table 5. However, when the moldability of the foamed blow-molded article obtained in Comparative Example 5 was evaluated in the same manner as in Example 1, as shown in Table 5, the expandability was negative, and the foamed parison could not be sufficiently expanded in the pre-blow process, making it impossible to obtain a good foamed blow-molded article. Since the expandability was negative, the judgment of whether there were any molding defects on the upper part of the molded article and the ball drop test were omitted. For reference, the density (g / cm³) of the foamed blow-molded article obtained in Comparative Example 5 was evaluated in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0148] Comparative Example 6 (Preparation of recovered materials) In Comparative Example 6, the amount of resin A, resin B1, resin B2, and resin C was set to the amounts shown in Table 5, respectively, to obtain the recovered raw material D in the same manner as in Example 1. The composition of the obtained recovered raw material D is shown in Table 4.

[0149] (Manufacturing of foamed blow molded products) Using the recovered raw material D obtained in Comparative Example 6, foamed blow molded articles were obtained in the same manner as in Example 1, except that the types and amounts of resins A, B1, B2, and C, and the amount of recovered raw material D were as shown in Table 5. The density (g / cm³) of the obtained foamed blow molded articles was determined in the same manner as in Example 1. 3 The average thickness (mm) and closed-cell percentage (%) were measured. The results are shown in Table 5.

[0150] The foamed blow-molded article obtained in Comparative Example 6 was evaluated for moldability and ball drop test in the same manner as in Example 1. As shown in Table 5, the widening property was good (○) and there were no molding defects on the upper part of the article, but the ball drop test result was poor (×).

[0151] [Table 4]

[0152] [Table 5]

Claims

1. A method for producing a foamed blow-molded article by blow-molding a polypropylene resin foam parison, The foamed parison consists of branched homopolypropylene A, linear block polypropylene B, low-density polyethylene C, and component A, which is recovered during the manufacturing process of the foamed blow molded product and is derived from branched homopolypropylene A. Ｒ , component B derived from linear block polypropylene B Ｒ and component C derived from low-density polyethylene C Ｒ It is formed by melting and kneading a recovered raw material D containing the above and then extruding and foaming the resulting foamed resin molten material from a die. As the linear block polypropylene B, Block polypropylene B1 having a melt flow rate of 10 g / 10 min or more and 16 g / 10 min or less at 230°C and a load of 2.16 kg, Using block polypropylene B2, which has a melt flow rate of more than 16 g / 10 min and 40 g / 10 min or less at 230°C and a load of 2.16 kg, The ratio of the melt flow rate of block polypropylene B2 to the melt flow rate of block polypropylene B1 is 1.5 or more. The ratio of the amount of block polypropylene B2 to the amount of block polypropylene B1 is 0.1 or more and 10 or less. The sum of the amounts of branched homopolypropylene A, linear block polypropylene B, and low-density polyethylene C, W Ａ＋Ｂ＋Ｃ The amount of the recovered raw material D added to the mixture W Ｄ W Ａ＋Ｂ＋Ｃ :W Ｄ The time interval is 40:60 to 5:

95. A total W of the blending amount of said branched homopolypropylene A and the blending amount of said component A Ｒ is 10 parts by mass or more and 30 parts by mass or less, and a total W of the blending amount of said linear block polypropylene B and the blending amount of said component B Ａ＋ＡＲ is 40 parts by mass or more and 70 parts by mass or less, and a total W of the blending amount of said low-density polyethylene C and the blending amount of said component C Ｒ is 10 parts by mass or more and 30 parts by mass or less Ｂ＋ＢＲ (provided that the total of said W Ｒ , said W Ｃ＋ＣＲ and said W Ａ＋ＡＲ is 100 parts by mass), which is a method for producing a foamed blow-molded article. Ｂ＋ＢＲ Ｃ＋ＣＲ Ｃ＋ＣＲ ​

2. The method for producing a foamed blow molded article according to claim 1, wherein the melt flow rate of the recovered raw material D at 230°C and a load of 2.16 kg is 10 g / 10 min or more and 25 g / 10 min or less.

3. A method for producing a foamed blow-molded article according to claim 1 or 2, wherein the melt flow rate of the linear block polypropylene B at 230°C and a load of 2.16 kg is 15 g / 10 min or more and 30 g / 10 min or less.

4. A method for manufacturing a foamed blow molded article according to claim 1 or 2, wherein the melt tension of block polypropylene B1 at 230°C is 1 mN or more and 30 mN or less, and the melt tension of block polypropylene B2 at 230°C is 1 mN or more and 30 mN or less.

5. A method for producing a foamed blow-molded article according to claim 1 or 2, wherein the melt flow rate of the low-density polyethylene C at 190°C and a load of 2.16 kg is 0.2 g / 10 min or more and 20 g / 10 min or less.

6. The density of the aforementioned foamed blow molded article is 0.1 to 0.5 g / cm³. ３ The method for manufacturing a foamed blow-molded article according to claim 1 or 2.

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