Method for producing foamed blow-molded body, and foamed blow-molded body

Abstract

A method for producing a foamed blow-molded body, the method comprising a step for blow-molding a foamed parison obtained by foaming a mixed resin of a polyolefin resin (A) containing a branched homo-polypropylene (a1) and a linear block polypropylene (a2), and an olefin thermoplastic elastomer (B) containing a thermoplastic elastomer (B) and a branched homo-polypropylene (a1) and a linear block polypropylene (a2), the mass ratio [(a1): (a2)] of the branched homo-polypropylene (a1) to the linear block polypropylene (a2) is from 50: 50 to 93: 7, and the olefin thermoplastic elastomer (B) is a hydride of a triblock copolymer comprising a crystalline olefin polymer block and a polymer block of a conjugated diene compound, and the weight ratio of the branched homo-polypropylene (a1) to the linear block polypropylene (a2) is from 50: 50 to 93: 7 in the mixed resin. The blending amount of the olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of the polyolefin-based resin (A) is from 20 parts by mass to 40 parts by mass (inclusive).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a foam blow molded body and the foam blow molded body. Background Art

[0002] The foam blow molded body is obtained by shaping a foamed parison formed from a foamable resin melt containing a base resin. Among the foam blow molded bodies, hollow molded bodies using polyolefin resins as base resins are used in various applications such as air conditioning ducts of automobiles, etc. from the viewpoint of lightness, etc. Hereinafter, air conditioning ducts are sometimes referred to as ducts.

[0003] In recent years, foam blow moldings are required to be lightweight and have cold impact resistance. It should be noted that cold impact resistance refers to the impact resistance of foam blow moldings at low temperatures. In order to improve the cold impact resistance of foam blow moldings, Patent Documents 1 and 2 disclose a technology of adding an elastomer to a polypropylene resin.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2020 / 059112

[0007] Patent Document 2: Japanese Patent Application Publication No. 2018-141031 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The techniques disclosed in Patent Documents 1 and 2 have the problem of further improving the cold impact resistance and rigidity of the foam blow molded body. In addition, the techniques in Patent Documents 1 and 2 have the problem of improving the surface smoothness of the inner side surface of the hollow portion of the hollow foam blow molded body. Hereinafter, unless otherwise specified, the surface smoothness of the inner side surface of the hollow portion of the hollow foam blow molded body is simply referred to as surface smoothness.

[0010] One of the objects of the present invention is to provide a method for producing a foam blow-molded article having excellent cold impact resistance, rigidity and surface smoothness, and a foam blow-molded article having excellent cold impact resistance, rigidity and surface smoothness.

[0011] Solutions for solving problems

[0012] The gist of the present invention lies in the inventions described in the following (1) to (5).

[0013] (1) A method for producing a foam blow molded article, comprising the step of blow-molding a foamed parison formed by foaming a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B), wherein the polyolefin resin (A) comprises a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the mass ratio [(a1):(a2)] of the branched homopolypropylene (a1) to the linear block polypropylene (a2) is 50:50 to 93:7, the olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer comprising a crystalline olefin polymer block and a conjugated diene compound polymer block, and the amount of the olefin thermoplastic elastomer (B) in the mixed resin is 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the polyolefin resin (A).

[0014] (2) The method for producing a foamed blow molded product according to (1) above, wherein the melting point of the olefin-based thermoplastic elastomer (B) is 80° C. or higher and 100° C. or lower.

[0015] (3) The method for producing a foam blow-molded article according to (1) or (2), wherein the linear block polypropylene (a2) has a flexural modulus of 1000 MPa to 1500 MPa.

[0016] (4) A method for producing a foam blow molded product according to any one of (1) to (3) above, wherein the melt flow rate (230°C, load 2.16 kg) of the olefin-based thermoplastic elastomer (B) is greater than or equal to 1 g / 10 min and less than or equal to 10 g / 10 min.

[0017] (5) A foam blow molded product, which is a foam blow molded product of a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B), wherein the polyolefin resin (A) comprises a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the mass ratio [(a1):(a2)] of the branched homopolypropylene (a1) to the linear block polypropylene (a2) is 50:50 to 93:7, and the olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer comprising a crystalline olefin polymer block and a polymer block of a conjugated diene compound, and in the mixed resin, the amount of the olefin thermoplastic elastomer (B) is 20 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of the polyolefin resin (A).

[0018] In addition, the present invention may also be the inventions described in the following (6) to (8).

[0019] (6) The blow-molded foam according to (5) above, wherein the melting point of the olefin-based thermoplastic elastomer (B) is 80° C. or higher and 100° C. or lower.

[0020] (7) The blow-molded foam according to (5) or (6) above, wherein the linear block polypropylene (a2) has a flexural modulus of 1000 MPa to 1500 MPa.

[0021] (8) The foam blow molded product according to any one of (5) to (7) above, wherein the melt flow rate (230°C, load 2.16 kg) of the olefin-based thermoplastic elastomer (B) is 1 g / 10 min or more and 10 g / 10 min or less.

[0022] Effects of the Invention

[0023] According to the present invention, a method for producing a foam blow-molded article having excellent cold impact resistance, rigidity, and surface smoothness, and a foam blow-molded article having excellent cold impact resistance, rigidity, and surface smoothness can be provided. DETAILED DESCRIPTION

[0024] The present invention will be described in order with respect to 1. a method for producing a foam blow molded article and 2. a foam blow molded article. It should be noted that the present invention is not limited to the embodiments described below.

[0025] [1. Method for producing a foam blow molded article]

[0026] The manufacturing method of the present invention is a method for manufacturing a foam blow-molded article including a blow molding step. Next, an embodiment of the manufacturing method of the foam blow-molded article of the present invention will be described.

[0027] [1-1. Contents of the manufacturing method]

[0028] (Extrusion foaming process)

[0029] By kneading the mixed resin and the foaming agent inside the extruder, a foamable resin melt is obtained. The obtained foamable resin melt is extruded from a die head connected to the extruder. As the die head, an annular die head is generally used. A forming die is arranged directly below the die head, and the foamable resin melt is extruded into the inside of the forming die. At this time, the foamable resin melt is foamed to form a foamed parison. It should be noted that the forming die has a desired internal shape corresponding to the desired molded body. The forming die is generally a split type die.

[0030] (Pre-blow molding process)

[0031] Immediately after the extrusion foaming process, the foamed parison is in a softened state. The lower part of the softened foamed parison is sealed using a clamping device, etc., and gas is blown into the interior of the foamed parison, thereby increasing the internal pressure of the foamed parison. At this time, the foamed parison expands. During the pre-blow molding process or after the pre-blow molding process, the foamed parison is clamped by the molding die.

[0032] (Blow molding process)

[0033] The blow molding process is a process of blowing gas into the interior of the foamed parison while the foamed parison is clamped in a forming mold. At this time, the outer surface of the foamed parison is pushed against the inner surface of the forming mold, and the foamed parison is shaped into a hollow shape. Through this process, a foamed blow molded body is obtained. As a foamed blow molded body, for example, a hollow molded body is obtained. It should be noted that in the method for manufacturing a foamed blow molded body, it is preferred that the accumulator is provided between the extruder and the die head or provided at the die head.

[0034] (Composition of mixed resin)

[0035] The mixed resin for forming the foamable resin melt is a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B).

[0036] (Polyolefin resin)

[0037] The polyolefin-based resin (A) is a resin composition comprising a branched homopolypropylene (a1) and a linear block polypropylene (a2).

[0038] (Branched Homopolymer Polypropylene)

[0039] The branched homopolypropylene (a1) is a homopolypropylene having a branched structure in the molecular structure. Examples of the branched structure include a branched structure portion in the molecular structure and a structure portion having a free end in the long chain structure portion. It should be noted that the branched structure can be confirmed using high temperature GPC-MALS measurement or the like.

[0040] The melt flow rate of the branched homopolypropylene (a1) measured at 230°C and a load of 2.16 kg is preferably 0.1 g / 10 min to 15 g / 10 min. If the melt flow rate is within the above range, the resin has excellent fluidity when melted, so the drawdown of the foamed parison is further suppressed. From the above viewpoint, the melt flow rate of the branched homopolypropylene (a1) is more preferably 0.5 g / 10 min to 10 g / 10 min, and further preferably 1 g / 10 min to 5 g / 10 min. It should be noted that the melt flow rate (MFR) of the resin can be measured by a known method, for example, it can be measured based on JIS K7210-1:2014 (test method A method). Each numerical range is shown as the numerical range of the melt flow rate of the branched homopolypropylene (a1), and the upper limit value and the lower limit value in the combination of the respective numerical ranges can be independently combined arbitrarily. In this specification, the combination of the specified numerical range represents the combination of the upper limit and the lower limit. It should be noted that the numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. Therefore, the numerical range of the melt flow rate of the branched homopolypropylene (a1) can be set to a numerical range that combines the numerical values ​​of the upper limit and the lower limit of the preferred numerical range, and a numerical range that combines the numerical values ​​of the upper limit and the lower limit of the further preferred numerical range. Specifically, the numerical range of the melt flow rate of the branched homopolypropylene (a1) can be listed as follows: any one of the group consisting of 0.1g / 10 minutes, 0.5g / 10 minutes and 1g / 10 minutes is set as the lower limit, and any one of the group consisting of 15g / 10 minutes, 10g / 10 minutes and 5g / 10 minutes is set as the upper limit. Therefore, for example, the numerical range of the melt flow rate may be 0.1 g / 10 min to 10 g / 10 min, 0.5 g / 10 min to 5 g / 10 min, or 1 g / 10 min to 15 g / 10 min.

[0041] In addition, from the viewpoint of foamability in foam blow molding, the melt tension of the branched homopolypropylene (a1) at 230°C is preferably 5cN to 50cN, more preferably 10cN to 45cN, and most preferably 25cN to 40cN. As for the numerical range of the melt tension of the branched homopolypropylene (a1), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently combined arbitrarily. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the melt tension of the branched homopolypropylene (a1) at 230°C can be listed, for example, as follows: any one of the group consisting of 5cN, 10cN and 25cN is set as the lower limit, and any one of the group consisting of 50cN, 45cN and 40cN is set as the upper limit. The melt tension (MT) of the branched homopolypropylene (a1) can be measured by a known method, for example, by using Capilograph 1D manufactured by Toyo Seiki Seisaku-sho, Ltd.

[0042] The melting point of the branched homopolypropylene (a1) is preferably 155°C to 165°C, and more preferably 157°C to 162°C. As for the numerical range of the melting point of the branched homopolypropylene (a1), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the melting point of the branched homopolypropylene (a1) can be listed, for example, as a range in which any one of the group consisting of 155°C and 157°C is set as the lower limit, and any one of the group consisting of 165°C and 162°C is set as the upper limit. The melting point can be measured based on JIS K7121:2012 in the same manner as the melting point of the olefin-based thermoplastic elastomer (B) described later.

[0043] Branched homopolypropylene (a1) has excellent foaming properties, so by having branched homopolypropylene (a1) in the polyolefin resin (A), it is easy to obtain a foam blow molded body with excellent lightness and surface smoothness. Specifically, as branched homopolypropylene (a1), substances commercially available as HMS-polypropylene and UMS-polypropylene can be listed. In addition, as branched homopolypropylene (a1), branched homopolypropylene (trade name: WB130, WB135, WB140) manufactured by Borealis, branched homopolypropylene resin (trade name: PF814) manufactured by SunAllomer, etc. can be listed.

[0044] (Linear Block Polypropylene)

[0045] The linear block polypropylene (a2) is a block polypropylene having a linear molecular structure. As a block polypropylene, there can be cited: a polymer mixture obtained by polymerizing ethylene and one or more C3~C10-α olefins (α-olefins having 3 to 10 carbon atoms) in the presence of a propylene polymer. In addition, the linear block polypropylene (a2) includes impact-resistant polypropylene polymers specified in JIS K6921-1, and generally includes substances commercially available as block polypropylene. However, the example of block polypropylene shown here is an example, and other examples are not excluded. Specifically, the block polypropylene can be exemplified by propylene / ethylene block copolymers. More specifically, the propylene / ethylene block copolymer can be cited as a block copolymer containing a crystalline propylene block and an ethylene-propylene random block.

[0046] (Flexural modulus of linear block polypropylene)

[0047] The bending elastic modulus of linear block polypropylene (a2) is preferably more than 1000MPa and less than 1500MPa. By the bending elastic modulus of linear block polypropylene (a2) being more than 1000MPa, the rigidity of the foam blow molding body can be more effectively improved, and the cushioning of the foam blow molding body can be improved. From this viewpoint, the bending elastic modulus of linear block polypropylene (a2) is more preferably more than 1100MPa and less than 1400MPa. With regard to the numerical range of the bending elastic modulus of linear block polypropylene (a2), the upper limit and lower limit shown in the combination of the numerical ranges recorded above can be independently arbitrarily combined. The upper limit, lower limit and the value between the upper limit and the lower limit are included in the numerical range determined by arbitrarily combining the upper limit and the lower limit. The numerical range of the bending modulus of the linear homopolypropylene (a2) includes, for example, a range in which the lower limit is any one of the group consisting of 1000 MPa and 1100 MPa and the upper limit is any one of the group consisting of 1500 MPa and 1400 MPa.

[0048] (Measurement of flexural elastic modulus)

[0049] The flexural modulus of the linear block polypropylene (a2) can be measured in accordance with JIS K7171:2016.

[0050] The bending modulus of the resin of the linear block polypropylene (a2) itself is usually smaller than that of the branched homopolypropylene (a1) in most cases. When the polyolefin resin (A) contains not only the branched homopolypropylene (a1) but also the linear block polypropylene (a2), the rigidity of the foam blow molded product can be improved. In addition, when the polyolefin resin (A) contains the linear block polypropylene (a2), it is easy to obtain a foam blow molded product with good lightness and excellent surface smoothness.

[0051] The melt flow rate of the linear block polypropylene (a2) measured at 230°C and a load of 2.16 kg is preferably 1 g / 10 min to 40 g / 10 min. If the melt flow rate is within the above range, the fluidity of the mixed resin when melted is excellent. From the above viewpoint, the melt flow rate of the linear block polypropylene (a2) is preferably 2 g / 10 min to 38 g / 10 min, more preferably 10 g / 10 min to 35 g / 10 min, and more preferably 20 g / 10 min to 33 g / 10 min. With respect to the numerical range of the melt flow rate of the linear block polypropylene (a2), the upper limit and the lower limit shown in the combination of the numerical ranges recorded above can be independently arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the melt flow rate of the linear block polypropylene (a2) can be, for example, a range in which any one of the group consisting of 1 g / 10 min, 2 g / 10 min, 10 g / 10 min and 20 g / 10 min is set as the lower limit, and any one of the group consisting of 40 g / 10 min, 38 g / 10 min, 35 g / 10 min and 33 g / 10 min is set as the upper limit. It should be noted that the melt flow rate (MFR) of the resin can be measured by a known method, for example, it can be measured based on JIS K7210-1:2014 (test method A method).

[0052] The melting point of the linear block polypropylene (a2) is preferably 155°C to 169°C, preferably 158°C to 168°C. As for the numerical range of the melting point of the linear block polypropylene (a2), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the melting point of the linear block polypropylene (a2) can be listed, for example, as follows: any one of the group consisting of 155°C and 158°C is set as the lower limit, and any one of the group consisting of 169°C and 168°C is set as the upper limit. The melting point can be measured based on JIS K7121:2012 in the same manner as the melting point of the olefin-based thermoplastic elastomer (B) described later.

[0053] (Mass ratio [(a1): (a2)])

[0054] In the mixed resin, the mass ratio [(a1):(a2)] of the branched homopolypropylene (a1) and the linear block polypropylene (a2) is preferably 50:50 to 93:7. When the mass ratio [(a1):(a2)] is in the above numerical range, the following effects are obtained: the foamability of the mixed resin is improved, the surface smoothness is improved, and the rigidity and cold-resistant impact resistance of the foam blow molded product are good. It should be noted that from the viewpoint of further improving this effect, the mass ratio [(a1):(a2)] is preferably 70:30 to 92:8, and more preferably 80:20 to 90:10. With respect to the numerical range of the mass ratio [(a1):(a2)], the ratio of the upper limit and the ratio of the lower limit shown in the combination of the numerical ranges described above can be independently combined arbitrarily. The numerical range determined by arbitrarily combining the ratio of the upper limit and the ratio of the lower limit includes the ratio of the upper limit, the ratio of the lower limit, and the ratio between the ratio of the upper limit and the ratio of the lower limit. However, in the combination of each numerical range of the mass ratio [(a1): (a2)], the case where the mass ratio of the branched homopolypropylene (a1) is the smallest is set as the ratio serving as the lower limit, and the case where the mass ratio of the branched homopolypropylene (a1) is the largest is set as the ratio serving as the upper limit. For example, when the numerical range of the mass ratio [(a1): (a2)] is 50:50 to 93:7, the ratio serving as the lower limit is 50:50, and the ratio serving as the upper limit is 93:7. The numerical range of the mass ratio [(a1): (a2)] can be cited, for example, as a range in which any one of the group consisting of 50:50, 70:30, and 80:20 is set as the ratio serving as the lower limit, and any one of the group consisting of 93:7, 92:8, and 90:10 is set as the value serving as the upper limit.

[0055] (Olefin thermoplastic elastomer)

[0056] The olefin-based thermoplastic elastomer (B) is a hydrogenated triblock copolymer comprising a hard segment of a polymer block of a crystalline olefin and a soft segment of a polymer block of a conjugated diene compound. The triblock copolymer is preferably a block copolymer having a so-called A-B-A structure (sandwich type). At this time, it is preferred that A, which is a block portion at both ends of the block copolymer having an A-B-A structure, is a polymer block of a crystalline olefin, and B, which is a block portion (central block portion) sandwiched by A, is a polymer block of a conjugated diene compound. By making the olefin-based thermoplastic elastomer (B) a hydrogenated block copolymer having a structure as described above, the impact resistance of the foaming blow molding can be improved without hindering the foaming property of the foaming parison. In addition, the effect of improving the surface smoothness of the foaming blow molding can be exerted.

[0057] Examples of crystalline olefin polymers include polymers of ethylene, etc. Examples of conjugated diene compound polymers include polymers of ethylene with butene, as well as polymers of ethylene with 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and the like.

[0058] Specifically, the olefin-based thermoplastic elastomer (B) includes a hydrogenated triblock copolymer, wherein the blocks at both ends are blocks of ethylene polymers and the blocks in the center are blocks of 1,3-butadiene polymers. The olefin-based thermoplastic elastomer (B) includes, for example, a block copolymer of a crystalline olefin / ethylene butene / crystalline olefin in a hydrogenated state. In addition, the olefin-based thermoplastic elastomer (B) does not contain a polypropylene resin such as a branched homopolypropylene (a1) or a linear block polypropylene (a2).

[0059] (Melting point of olefin-based thermoplastic elastomer)

[0060] The melting point of the olefin-based thermoplastic elastomer (B) is preferably 80°C or more and 110°C or less. If the melting point of the olefin-based thermoplastic elastomer (B) is within the above range, the foamability is excellent. From this viewpoint, the melting point of the olefin-based thermoplastic elastomer (B) is more preferably 85°C or more and 105°C or less, and further preferably 90°C or more and 100°C or less. As for the numerical range of the melting point of the olefin-based thermoplastic elastomer (B), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently combined arbitrarily. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the melting point of the olefin-based thermoplastic elastomer (B) can be cited, for example, as follows: any one of the group consisting of 80°C, 85°C and 90°C is set as the lower limit, and any one of the group consisting of 110°C, 105°C and 100°C is set as the upper limit.

[0061] (Method for determining melting point)

[0062] The melting point of the olefin-based thermoplastic elastomer (B) can be determined as the melting peak temperature measured by heat flux differential scanning calorimetry according to JIS K7121: 2012. It should be noted that, as the state adjustment of the test piece used in the heat flux differential scanning calorimetry, "(2) the case where the melting temperature is measured after a certain heat treatment" is adopted, and 10°C / min is adopted as the heating rate and the cooling rate. When the DSC curve shows multiple melting peaks, the top temperature of the melting peak with the largest area is taken as the melting point.

[0063] (Flexural modulus of olefin-based thermoplastic elastomer)

[0064] The upper limit of the bending modulus of olefin-based thermoplastic elastomer (B) is preferably 50MPa. By the bending modulus of olefin-based thermoplastic elastomer (B) being below 50MPa, olefin-based thermoplastic elastomer (B) can effectively exert the physical properties as an elastomer. In addition, the lower limit of the bending modulus of olefin-based thermoplastic elastomer (B) is preferably about 1MPa. That is, the bending modulus of olefin-based thermoplastic elastomer (B) is preferably above 1MPa and below 50MPa. By the bending modulus of olefin-based thermoplastic elastomer (B) being the above-mentioned numerical range, it is easy to obtain the effect of further improving the cold impact resistance as a foam blow molding body. From the viewpoint of further improving this effect, the bending modulus of olefin-based thermoplastic elastomer (B) is more preferably above 3MPa and below 30MPa, and more preferably above 5MPa and below 25MPa. As for the numerical range of the bending modulus of the olefin-based thermoplastic elastomer (B), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the bending modulus of the olefin-based thermoplastic elastomer (B) can be listed, for example, as follows: any one of the group consisting of 1MPa, 3MPa and 5MPa is set as the lower limit, and any one of the group consisting of 50MPa, 30MPa and 25MPa is set as the upper limit.

[0065] (Measurement of flexural elastic modulus)

[0066] The flexural modulus of the olefin-based thermoplastic elastomer (B) can be measured in accordance with JIS K7171:2016.

[0067] (Melt flow rate (MFR) of olefin-based thermoplastic elastomer)

[0068] The MFR (230°C, load 2.16kg) of the olefin-based thermoplastic elastomer (B) is preferably 1 g / 10 min or more and 10 g / 10 min or less, and more preferably 1.5 g / 10 min or more and 5 g / 10 min or less. As for the numerical range of the MFR of the olefin-based thermoplastic elastomer (B), the upper limit and lower limit shown in the combination of the numerical ranges described above can be independently arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the MFR of the olefin-based thermoplastic elastomer (B) can be listed, for example, as follows: any one of the group consisting of 1 g / 10 min and 1.5 g / 10 min is set as the lower limit, and any one of the group consisting of 10 g / 10 min and 5 g / 10 min is set as the upper limit.

[0069] (Determination of MFR)

[0070] The MFR (g / 10 min (230° C.)) of the olefin-based thermoplastic elastomer (B) can be determined, for example, based on JIS K7210-1:2014 (test method A). As measurement conditions, conditions of 230° C. and a load of 2.16 kg can be employed.

[0071] (Proportion of each component of the mixed resin)

[0072] In the mixed resin, the amount of the olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of the polyolefin-based resin (A) is 20 parts by mass or more and 40 parts by mass or less. By making the amount of the olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of the polyolefin-based resin (A) within the above range, it is easy to achieve both the impact resistance and surface smoothness required for the foam blow molding. From the above viewpoint, the amount of the olefin-based thermoplastic elastomer (B) is preferably 22 parts by mass or more and 35 parts by mass or less, and more preferably 23 parts by mass or more and 30 parts by mass or less.

[0073] In addition, the mass ratio of the olefin thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin resin (A) is preferably 0.2 to 0.5, and more preferably 0.25 to 0.35. In addition, the mass ratio of the olefin thermoplastic elastomer (B) to the linear block polypropylene (a2) in the polyolefin resin (A) is preferably 1.0 to 2.5, and more preferably 1.2 to 2.3. When the mass ratio of the olefin thermoplastic elastomer (B) to the branched homopolypropylene (a1) is within the above range, impact resistance is easily exhibited. It should be noted that the mass ratio of the olefin thermoplastic elastomer (B) to the branched homopolypropylene (a1) is a value obtained by dividing (the amount (mass parts) of the olefin thermoplastic elastomer (B) used in the mixed resin) by (the amount (mass parts) of the branched homopolypropylene (a1)) (the value obtained by division). The mass ratio of the olefin-based thermoplastic elastomer (B) to the linear block polypropylene (a2) is a value obtained by dividing (the amount (mass parts) of the olefin-based thermoplastic elastomer (B) blended in the mixed resin) by (the amount (mass parts) of the linear block polypropylene (a2) blended).

[0074] In the mixed resin, in addition to the numerical range of the blending amount of the olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of the polyolefin-based resin (A), at least one numerical range selected from the numerical range of the mass ratio of the olefin-based thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin-based resin (A) and the numerical range of the mass ratio of the olefin-based thermoplastic elastomer (B) to the branched homopolypropylene (a2) in the polyolefin-based resin (A) satisfies the above numerical values, and preferably both numerical ranges satisfy the above numerical values.

[0075] It should be noted that, with respect to the numerical range of the amount of olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of polyolefin-based resin (A), the upper limit and lower limit shown in the combination of the numerical ranges described above can be independently and arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the amount of olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of polyolefin-based resin (A) can be listed, for example: any one of the groups consisting of 20 parts by mass, 22 parts by mass, and 23 parts by mass is set as the lower limit, and any one of the groups consisting of 40 parts by mass, 35 parts by mass, and 30 parts by mass is set as the upper limit. For the numerical range of the mass ratio of the olefin-based thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin-based resin (A) and the numerical range of the mass ratio of the olefin-based thermoplastic elastomer (B) to the branched homopolypropylene (a2) in the polyolefin-based resin (A), the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently arbitrarily combined. In this regard, the numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the mass ratio of the olefin-based thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin-based resin (A) can be cited, for example, as follows: any one of the group consisting of 0.2 and 0.25 is set as the lower limit, and any one of the group consisting of 0.5 and 0.35 is set as the upper limit.

[0076] (Other additives to mixed resin)

[0077] When producing a foamed blow molded article, the mixed resin and the foaming agent are kneaded as described above. Examples of the physical foaming agent include the following.

[0078] (foaming agent)

[0079] Examples of the foaming agent include: aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, isohexane, and cyclohexane; chlorinated hydrocarbons such as methyl chloride and ethyl chloride; fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane; aliphatic ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; aliphatic alcohols such as methanol and ethanol; organic physical foaming agents such as dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; inorganic physical foaming agents such as carbon dioxide, nitrogen, air, and water; and chemical foaming agents such as sodium bicarbonate, sodium citrate, and azodicarbonamide. These foaming agents can be used alone or in combination.

[0080] If an inorganic physical foaming agent is used to form a foamed parison, the foaming of the foamable resin melt is completed at an early stage, and there is almost no residual foaming agent or no residual foaming agent in the resin constituting the foamed parison. Therefore, the resin constituting the foamed parison will not plasticize, preventing the foamed parison from stretching. As a result, compared with the foamed parison obtained by using an organic physical foaming agent, a foamed parison with excellent blow molding properties can be obtained. From this viewpoint, among the foaming agents, an inorganic physical foaming agent is preferably used, an inorganic physical foaming agent containing carbon dioxide is more preferably used, and a physical foaming agent consisting only of carbon dioxide is further preferably used.

[0081] In the present invention, when a foaming agent containing carbon dioxide is used as a physical foaming agent, 20 mol% to 100 mol% of carbon dioxide is preferably added relative to 100 mol% of the physical foaming agent, 50 mol% to 100 mol% of carbon dioxide is more preferably added, and 70 mol% to 100 mol% of carbon dioxide is further preferably added. If the content of carbon dioxide is within the above range, a foaming blow molding having a small bubble diameter and a high independent bubble ratio can be easily obtained.

[0082] The amount of the physical foaming agent added is preferably 0.05 mol to 0.8 mol, more preferably 0.1 mol to 0.5 mol, per 1 kg of the mixed resin.

[0083] (Other resins)

[0084] In the mixed resin, other resins different from the polyolefin resin (A) and the olefin thermoplastic elastomer (B) can be added within the range that does not hinder the purpose of the present invention. As other resins, thermoplastic resins such as polystyrene resins, polyolefin resins other than the polyolefin resin (A), and thermoplastic elastomers (TPE) other than the olefin thermoplastic elastomer (B) can be added. In addition, as polyolefin resins other than the polyolefin resin (A), biomass polyolefin resins, polyolefin resins derived from ASR, and mass balance polyolefin resins can also be used. The amount of other resins added is preferably 30 parts by mass or less relative to a total of 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B), more preferably 20 parts by mass or less, further preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0085] (Various additives)

[0086] When manufacturing the foam blow molding, various additives other than the above-mentioned foaming agent can be added to the mixed resin. As additives, examples can be shown: flame retardant, flow regulator, ultraviolet absorber, conductivity imparting agent, antistatic agent, colorant, heat stabilizer, antioxidant, inorganic filler, pigment, etc. The amount of the above-mentioned additive is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and further preferably less than 3 parts by mass relative to a total of 100 parts by mass of polyolefin resin (A) and olefin thermoplastic elastomer (B). In addition, the above-mentioned additive can be added to polyolefin resin (A), olefin thermoplastic elastomer (B), branched homopolypropylene (a1) and linear block polypropylene (a2) within the range of not hindering the effect of the present invention. The amount thereof added is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 3 parts by mass or less, relative to 100 parts by mass of each of the polyolefin resin (A), the olefin thermoplastic elastomer (B), the branched homopolypropylene (a1), and the linear block polypropylene (a2).

[0087] In addition, carbon black can be added as an additive in the mixed resin. The content of carbon black in the mixed resin is preferably 0.1 mass parts or more and 2 mass parts or less relative to a total of 100 mass parts of polyolefin resin (A) and olefin thermoplastic elastomer (B), and more preferably 0.3 mass parts or more and 1 mass part or less. As carbon black, gas furnace carbon black, oil furnace carbon black, acetylene black, channel carbon black, roller carbon black (roller black), thermal cracking carbon black, Ketjen black, etc. can be listed. It should be noted that when manufacturing a foam blow molded body, when a recycled raw material containing carbon black is used as a part of the raw material, the total content of carbon black in the mixed resin is the value of the carbon black contained in the recycled raw material. With respect to the numerical range of the physical foaming agent mentioned above about the mixed resin, the numerical range of various additives such as carbon black, the upper limit and lower limit shown in the combination of the numerical ranges recorded above can be independently arbitrarily combined. The upper limit, the lower limit, and the value between the upper limit and the lower limit are included in the numerical range determined by arbitrarily combining the upper limit and the lower limit.

[0088] (Use of recycled materials (recycled raw materials))

[0089] When manufacturing the foam blow molding of the present invention, it may cause flash, the generation of defective molded products such as dimensional deviation, etc. These flash and defective molded products can be used as recycled raw materials. The recycled raw materials preferably include polyolefin resin (A) and olefin thermoplastic elastomer (B). In addition, in the manufacturing method of the foam blow molding of the present invention, a foamable resin melt containing recycled raw materials can be formed, and the foamed parison formed by foaming the foamable resin melt is formed into a foam blow molding. It should be noted that, when the recycled raw materials including polyolefin resin (A) and olefin thermoplastic elastomer (B) are used as a part of the raw materials when forming the foamable resin melt, the amount of polyolefin resin (A) and olefin thermoplastic elastomer (B) in the mixed resin constituting the foam blow molding is determined to be the value of the polyolefin resin (A) and olefin thermoplastic elastomer (B) contained in the recycled raw materials. The numerical ranges related to the physical properties of the polyolefin resin (A) and the olefin thermoplastic elastomer (B) contained in the recycled raw materials and the numerical ranges of the blending amounts of the polyolefin resin (A) and the olefin thermoplastic elastomer (B) are the same as the numerical ranges mentioned above for the polyolefin resin (A) and the olefin thermoplastic elastomer (B) constituting the mixed resin, wherein the mixed resin constitutes a foam blow molded product.

[0090] [1-2. Effects of the method for producing a foamed blow molded article]

[0091] The use of polypropylene resin in the foam blow molded body is particularly excellent in terms of heat resistance and lightness, and can be appropriately adopted in the use of pipes mounted on vehicles such as automobiles. Regarding the foam blow molded body appropriately used in such uses, in recent years, the foam blow molded body with improved cold impact resistance has been further required.

[0092] However, if an elastomer is added to the polypropylene resin in order to improve the cold impact resistance of the foam blow molded body, the possibility of reducing the rigidity of the foam blow molded body increases. In the case where the foam blow molded body is used as a pipe, if the rigidity of the foam blow molded body is reduced, negative pressure is formed in the pipe when gas such as air passes through the pipe, thereby generating the possibility that the surface portion of the foam blow molded body forming the pipe is slightly bent inward.

[0093] Furthermore, when a blow-foamed body is formed into a hollow shape and used as a duct, it is required to improve the surface smoothness of the inner surface of the hollow portion of the blow-foamed body from the viewpoint of suppressing the air resistance of the duct and suppressing ventilation sound (wind noise).

[0094] According to the method for producing a foam blow molded article of the present invention, a foam blow molded article having excellent cold impact resistance and rigidity can be obtained by using a specific polypropylene resin (polyolefin resin (A)) and a specific elastomer (olefin thermoplastic elastomer (B)) within a specific range. In addition, by using the specific elastomer as described above in the method for producing a foam blow molded article, the foaming property of the polyolefin resin (A) constituting the foamable resin melt is not greatly hindered, thereby suppressing the possibility of deterioration of the surface smoothness of the foam blow molded article.

[0095] Furthermore, by using a branched homopolypropylene and a linear polypropylene block in combination within a specific range as the polyolefin resin, the possibility of a decrease in the rigidity of the foam blow molded article due to the use of an elastomer can be suppressed, and a foam blow molded article having excellent rigidity can be obtained.

[0096] In addition, as a foam blow molded article, foam blow molded articles of various apparent densities are required depending on various conditions such as the purpose. According to the method for manufacturing a foam blow molded article of the present invention, by using a specific polypropylene resin and a specific elastomer within a specific mixing ratio range, a foam blow molded article with excellent surface smoothness (excellent inner surface smoothness) can be obtained even under the condition of obtaining various apparent densities. The properties such as the apparent density, independent bubble ratio, and bending elastic modulus related to the foam blow molded article obtained by applying the method for manufacturing a foam blow molded article of the present invention will be described in [2. Foam blow molded article].

[0097] Next, the foamed blow-molded article of the present invention will be described.

[0098] [2. Foam blow molding]

[0099] [2-1. Structure of foam blow molded article]

[0100] The foamed blow-molded article of the present invention is a foamed molded article of a mixed resin of a polyolefin-based resin (A) and an olefin-based thermoplastic elastomer (B).

[0101] The foam blow molded article of the present invention can be obtained by the above-mentioned method for producing a foam blow molded article. That is, the foam blow molded article can be obtained by performing an extrusion foaming step, a pre-blow molding step, and a blow molding step in the same manner as described in [1. Method for producing a foam blow molded article]. It should be noted that each step is the same as that described in [1. Method for producing a foam blow molded article], so the description is omitted.

[0102] The polyolefin resin (A) blended in the mixed resin used in the foam blow molded article of the present invention contains branched homopolypropylene (a1) and linear block polypropylene (a2) in a specified mass ratio [(a1): (a2)]. The structure, physical properties (melt flow rate, melting point, bending modulus, etc.) and mass ratio [(a1): (a2)] of the branched homopolypropylene (a1) and the linear block polypropylene (a2) are the same as those described in [1. Method for producing a foam blow molded article], so the description is omitted. It should be noted that as the polyolefin resin (A), polypropylene derived from biomass and polypropylene in a mass balance method can be used.

[0103] In addition, the structure, physical properties (melt flow rate, melting point, etc.) of the olefin-based thermoplastic elastomer (B) blended in the mixed resin used in the foam blow molding, and the amount of the olefin-based thermoplastic elastomer (B) in the mixed resin relative to 100 parts by mass of the polyolefin-based resin (A) are the same as those described in [1. Method for producing foam blow molding], so the description is omitted.

[0104] (Shape of foam blow molded product)

[0105] The shape of the foam blow molded article is not particularly limited. If the foam blow molded article is a hollow molded article, the foam blow molded article can be easily used as a duct for an air conditioner provided in a vehicle or the like, for example.

[0106] (Independent bubble rate)

[0107] From the viewpoint of improving the appearance, the closed cell ratio of the foamed blow-molded article is preferably 65% ​​or more, more preferably 70% or more.

[0108] (Determination of independent bubble ratio)

[0109] Prepare a test piece cut from the roughly flat part of the foam blow molded body into a wall thickness of 25 mm × 25 mm × the flat part. Overlap multiple test pieces in such a way that the total thickness is closest to 20 mm, and use them as test pieces for measurement. Next, according to sequence C of ASTM-D2856-70, use an air comparison type specific gravity meter 930 type of Toshiba Beckman Co., Ltd. to measure the true volume Vx of the test piece for measurement, and calculate the independent bubble rate S (%) by the following formula (formula (1)). Use 5 test pieces for measurement to carry out the above measurement, and use the arithmetic mean value as the independent bubble rate of the foam blow molded body.

[0110] S(%)=(Vx-W / ρ)×100 / (Va-W / ρ) (1)

[0111] Wherein, Vx: the actual volume (cm2) of the test piece measured by the above method. 3 ), which is equivalent to the sum of the volume of the resin constituting the foam blow molded body and the total volume of the bubbles in the independent bubble part of the test piece; Va: the apparent volume of the test piece calculated based on the outer dimensions of the test piece used for measurement (cm 3 ); W: total mass of the test piece used for measurement (g); and ρ: density of the resin constituting the foam blow molded body (g / cm 3 ).

[0112] (Apparent density)

[0113] The apparent density of the foam blow molded article is preferably 100 kg / m 3 Above and 450kg / m 3 By having the above apparent density, a lightweight and moderately rigid molded body can be stably obtained. From the perspective of balancing lightness, rigidity, and cushioning properties, the apparent density of the foam blow molded body is preferably 120 kg / m 3 Above and 400kg / m 3 Below, more preferably 130kg / m 3 Above and 350kg / m 3 Below, more preferably 150kg / m 3 Above and 250kg / m 3 As for the numerical range of the apparent density of the foam blow molded article, the upper limit and the lower limit shown in the combination of the numerical ranges described above can be independently combined arbitrarily. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the apparent density of the foam blow molded article can be listed, for example: 100 kg / m 3 , 120kg / m3 , 130kg / m 3 and 150kg / m 3 Any one of the groups constituted is set as the lower limit value, and 450kg / m 3 , 400kg / m 3 、350kg / m 3 and 250kg / m 3 Any one of the configured groups is set as the upper limit value of the range.

[0114] (Determination of apparent density)

[0115] For the vertical cross-sections of the foam blow molded body at a total of three locations in the longitudinal direction of the center and both ends of the longitudinal direction, four locations with equal intervals on the flat part in the circumferential direction of each vertical cross-section were selected and cut out with an area of ​​about 10 cm in top view. 2 Then, for each test piece, divide its mass Wi [g] by its volume Vi [cm 3 ], the units were converted to obtain the apparent density (Wi / Vi) of each test piece, and the arithmetic mean of these values ​​was taken as the apparent density (D).

[0116] (Flexural modulus of foam blow molded article)

[0117] The bending elastic modulus (MPa) of the foam blow molding is preferably more than 140MPa and less than 250MPa. By the bending elastic modulus of the foam blow molding being the above-mentioned numerical range, it is easy to ensure sufficient rigidity. From the viewpoint of further improving this effect, the bending elastic modulus of the foam blow molding is more preferably more than 150MPa and less than 200MPa. With regard to the numerical range of the bending elastic modulus of the foam blow molding, the upper limit and lower limit shown in the combination of the numerical ranges recorded above can be independently combined arbitrarily. The numerical range determined by arbitrarily combining the upper limit and the lower limit includes the upper limit, the lower limit, and the value between the upper limit and the lower limit. The numerical range of the bending elastic modulus of the foam blow molding, for example, can be listed as: any one of the group consisting of 140MPa and 150MPa is set to the lower limit, and any one of the group consisting of 250MPa and 200MPa is set to the range of the upper limit.

[0118] (Measurement of Flexural Modulus of Foam Blow Molded Article)

[0119] The flexural modulus of the blow-molded foam can be determined by cutting out a sample from a flat portion of the blow-molded foam and measuring the flexural modulus of the sample piece in accordance with JIS K7171:2016.

[0120] [2-2. Effects of foam blow molded article]

[0121] The foam blow molded article of the present invention is a foam molded article of a mixed resin obtained by blending a specific polypropylene resin (polyolefin resin (A)) and a specific elastomer (olefin thermoplastic elastomer (B)) in a specific range, as described in [1. Method for producing a foam blow molded article] above, and thus has excellent cold impact resistance and rigidity. In addition, the foam blow molded article is composed of a specific elastomer, and thus has excellent surface smoothness.

[0122] Furthermore, by using a branched homopolypropylene and a linear polypropylene block in combination within a specific range as the polyolefin resin (A), a decrease in the rigidity of the foam blow molded article due to the use of an elastomer can be suppressed. Therefore, the foam blow molded article of the present invention has excellent rigidity.

[0123] In addition, the foam blow molded article requires various apparent densities depending on various conditions such as the application. In the foam blow molded article of the present invention, a specific polypropylene resin and a specific elastomer are used in a specific range, and even if the apparent density of the foam blow molded article is set to various values, a foam blow molded article with excellent surface smoothness can be obtained.

[0124] The cold-resistance impact resistance of the blow-molded foam can be determined by the following (-10°C falling ball test).

[0125] (-10℃ drop ball test (1.5m, 1kg))

[0126] The foam blow molded body is placed in an atmosphere of -10°C for 24 hours, the state of the foam blow molded body is adjusted, the flat part of the state-adjusted foam blow molded body is placed on the test bench facing upward, and a 1kg iron ball is dropped from 1.5m above the flat part. At this time, the damage state of the foam blow molded body is observed. It can be evaluated that the smaller the degree of damage to the foam blow molded body (including the case of no damage), the better the cold impact resistance of the foam blow molded body.

[0127] When the iron ball collides with the blow-molded foam, if a force is applied to a portion deviated from the flat portion and the blow-molded foam is damaged, it is preferred to perform the above-mentioned -10°C drop ball test again.

[0128] Next, the invention will be described in more detail using examples.

[0129] Example

[0130] (Resin preparation)

[0131] The polyolefin resins and elastomers shown in Table 1 were prepared. Among them, as for the polyolefin resins, branched homopolypropylene (a1), linear block polypropylene (a2), and linear homopolypropylene were prepared. In Table 1, the physical properties (MFR (g / 10min (230°C, load 2.16kg)) and bending modulus (MPa)) of the prepared polyolefin resins and elastomers are also shown.

[0132] The MFR (g / 10 min (230°C, load 2.16 kg)) and flexural modulus (MPa) of the polyolefin resin and the elastomer can be determined by the same method as that described above for the polyolefin resin (A) and the olefin thermoplastic elastomer (B). It should be noted that, with respect to the melting points (°C) of the branched homopolypropylene (a1) and the elastomer described later, the method for determining each melting point uses the method described above for the olefin thermoplastic elastomer (B). In addition, with respect to the crystallization temperatures (°C) of the branched homopolypropylene (a1) and the elastomer, they are measured using a heat flux differential scanning calorimeter based on JIS K7121:1987. It should be noted that, when multiple crystallization peaks are shown in the differential scanning calorimetry (DSC) curve, the peak temperature of the crystallization peak with the highest peak height is taken as the crystallization temperature.

[0133] As branched homopolypropylene (a1), trade name "WB140" (melt tension (230°C): 36 cN, melting point: 159°C, crystallization temperature: 129°C) manufactured by Borealis was prepared. In Tables 2, 3, and 4, the prepared branched homopolypropylene is referred to as WB140.

[0134] As the linear block polypropylene (a2), those shown in L-PP1 to L-PP3 in Table 1 were prepared.

[0135] L-PP1 is a copolymer of propylene and ethylene (propylene-ethylene copolymer) (manufactured by Japan Polypropylene Co., Ltd., trade name "NOVATEC (trademark) PP (model BC03GS)"). The propylene-ethylene copolymer of L-PP1 is a copolymer based on a Ziegler catalyst (MFR is 30 g / 10 minutes).

[0136] L-PP2 is a polypropylene block copolymer manufactured by Japan Polypropylene Co., Ltd. under the trade name “NOVATEC PP (Model BC6DRF)” (MFR: 2.5 g / 10 min).

[0137] L-PP3 is a propylene block copolymer (manufactured by SunAllomer Co., Ltd., trade name "QUALEAR (trademark) (Model CM688A)") containing an ethylene-α-olefin copolymer (MFR: 15 g / 10 min). The MFR of the propylene block copolymer of L-PP3 is 9.5 g / 10 min.

[0138] In Tables 2, 3, and 4, the linear block polypropylenes represented by L-PP1, L-PP2, and L-PP3 are abbreviated as BC03GS, BC6DRF, and CM688A, respectively.

[0139] The linear homopolypropylene was prepared under the trade name "Prime Polypro (trademark) (model number J106G)" manufactured by Prime Polymer Co., Ltd. In Table 4, the prepared linear homopolypropylene is referred to as J106G.

[0140] As the elastomer, olefin-based elastomers shown in EL1 to EL4 and a styrene-based elastomer shown in EL5 were prepared.

[0141] EL1 is a hydrogenated product of the following triblock copolymer, the triblock copolymer comprising a crystalline olefin polymer block and a polymer block of a conjugated diene compound. As EL1, a hydrogenated product of the following block copolymer is prepared: the block portions at both ends are set to ethylene polymer blocks and the central block portion is set to a polymer block of a conjugated diene compound (manufactured by JSR Corporation, trade name "DYNARON (trademark) 6200P") (the component derived from ethylene in the block copolymer is 30% by mass, the component derived from 1,3-butadiene is 70% by mass, the hydrogenation rate (hydrogenation rate) is 98% or more, the melting point is 97°C, and the crystallization temperature is 64°C). EL1 corresponds to the olefin-based thermoplastic elastomer (B).

[0142] EL2 is a metallocene propylene-ethylene copolymer (manufactured by ExxonMobil Corporation, trade name "Vistamaxx (trademark) 6202, melting point 102°C"). EL3 is RPTO (reactor TPO (Thermoplastic Olefinic Elastomer: thermoplastic olefin elastomer)) (manufactured by Basell Corporation, trade name "Catalloy (Model Q100F)", melting point 143°C, crystallization temperature 96°C). RPTO is a propylene random block copolymer polymerized sequentially using a Ziegler catalyst. EL4 is an ethylene-butene block copolymer (manufactured by Mitsui Chemicals, Inc., trade name "TAFMER (trademark) (Model DF605)", melting point below 50°C).

[0143] EL5 is a hydrogenated product of a styrene-based thermoplastic elastomer obtained by partially hydrogenating double bonds of a block copolymer containing styrene and butadiene (manufactured by Asahi Kasei Corporation, trade name “TUFTEC (trademark) (Model H1041)”).

[0144] In Table 2, Table 3 and Table 4, the elastomers indicated by EL1, EL2, EL3, EL4 and EL5 are respectively abbreviated as 6200P, 6202, Q100F, DF605 and H1041.

[0145] [Table 1]

[0146]

[0147] Examples 1 to 5, Comparative Examples 1 to 9

[0148] (Extrusion foaming process)

[0149] The types and amounts (mass %) of polyolefin resins, elastomers and additives described later shown in Table 2 (Examples 1 to 5), Table 3 (Comparative Examples 1 to 4) and Table 4 (Comparative Examples 5 to 9) are supplied to an extruder with a diameter of 65 mm, and melt-kneaded in the extruder to form a resin melt. Furthermore, carbon dioxide (CO2) as a foaming agent is pressed into the extruder and kneaded with the resin melt to form a foamable resin melt. The foamable resin melt is filled in an accumulator connected to the extruder. Then, at a foaming temperature of 170°C, the foamable resin melt is extruded into the normal pressure area by an annular die head arranged at the top of the accumulator and foamed, thereby forming a cylindrical foamed parison.

[0150] (Pre-blow molding process)

[0151] A two-part mold as a molding mold is arranged directly below the annular die head, and a cylindrical foamed parison formed by the extrusion foaming process is arranged between the molds. Furthermore, after the opening of the foamed parison is closed at the lower side of the mold using a clamp, pre-blowing air is blown into the foamed parison, and the two-part mold is further closed, so that the foamed parison is clamped by the molding mold.

[0152] (Blow molding process)

[0153] Blowing air is blown into the interior of the foamed parison clamped by the forming mold from the blow needle, and the space between the outer side of the foamed parison and the inner surface of the mold is decompressed by suction from the hole provided in the mold, thereby pushing the outer surface of the foamed parison to the inner surface of the forming mold. Then, the foamed parison is shaped into a shape corresponding to the inner surface of the mold. After shaping and cooling, the mold as the forming mold is opened, the molded body is taken out, and the flash and concave portion are removed. Thus, a foamed blow molded body is obtained. The obtained foamed blow molded body is formed into a hollow shape, which is formed into a cylindrical shape with a roughly rectangular cross-section and a maximum length of 650mm and a maximum width of 180mm corresponding to the shape of the pipeline. It should be noted that sometimes the part of the foamed blow molded body formed into a hollow shape is particularly referred to as a hollow portion.

[0154] It should be noted that the description (abbreviation) of the types of polyolefin resins and elastomers ("category" column) shown in Tables 2, 3 and 4 corresponds to the types of polyolefin resins and elastomers shown in Table 1. The numerical values ​​shown in the columns immediately below the description of the types of polyolefin resins in Tables 2, 3 and 4 correspond to the blending ratios (mass %) of the branched polypropylene and the linear polypropylene, respectively, when the sum of the branched polypropylene and the linear polypropylene in the polyolefin resin is 100. In addition, the numerical values ​​shown in the columns immediately below the description of the types of elastomers correspond to the blending amount (mass parts) of the elastomer relative to 100 parts by mass of the polyolefin resin.

[0155] In addition, in the mixed resin, 0.9 parts by mass of carbon black and 2 parts by mass of talc as additives are added in the form of carbon black masterbatch (45% masterbatch (MB)) and talc masterbatch (20% masterbatch (MB)) relative to a total of 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B). The carbon black masterbatch is manufactured by B&Tech Corporation, with the trade name "PP Black Master Batch, BT920F-JSJ". The talc masterbatch is manufactured by Matsumura Industries, with the trade name "HI-FILLER#12" (talc concentration 20% by mass, median particle size 7.5 μm). It should be noted that talc can function as a bubble regulator.

[0156] The injection amount (mol / kg) of the foaming agent is shown in Tables 2, 3 and 4. The injection amount of the foaming agent shown in Tables 2, 3 and 4 is the amount (mol / kg) per 1 kg of the mixed resin of the polyolefin resin and the elastomer.

[0157] (Physical properties of foam blow molded product)

[0158] As the physical properties of each foam blow molded article obtained in Examples 1 to 5 and Comparative Examples 1 to 9, the apparent density (kg / m3 ), thickness (mm), closed cell ratio (%) and bending elastic modulus (MPa). The results are shown in Tables 2, 3 and 4.

[0159] The apparent density, closed cell ratio and flexural modulus of the foam blow-molded article were measured by the above-mentioned methods.

[0160] (Thickness of foam blow molded product)

[0161] The thickness of the foam blow molded body represents the average thickness of the foam blow molded body and is a value measured by the following method. A total of five vertical sections with respect to the long dimension direction are obtained, namely, the central part of the foam blow molded body in the long dimension direction, the vicinity of the two ends in the long dimension direction, and the middle part between the central part and the two ends. The thickness (wall thickness) of the foam blow molded body at 6 locations with equal intervals in the circumferential direction of each vertical section is measured, and the arithmetic mean of the thickness of 28 locations excluding the maximum and minimum values ​​from the obtained 30 thickness measurement values ​​is taken as the average thickness of the foam blow molded body.

[0162] (Evaluation of Foam Blow Molded Articles)

[0163] Cold-temperature impact resistance and surface smoothness were evaluated for each of the foamed blow molded products obtained in Examples 1 to 5 and Comparative Examples 1 to 9. The results are shown in Tables 2, 3, and 4.

[0164] (Cold impact resistance)

[0165] The cold-shock resistance of the blow-molded foam was evaluated by performing a -10°C falling ball test (1.5 m, 1 kg).

[0166] (-10℃ drop ball test (1.5m, 1kg))

[0167] Place the foam blow molded body in an atmosphere of -10°C for 24 hours for state adjustment. Place the flat part of the state-adjusted foam blow molded body on the test bench facing upward, drop a 1kg iron ball from 1.5m above the flat part, and observe the damage to the foam blow molded body. The drop ball test was carried out 5 times. It should be noted that in the case where the flat part (flat part) hit by the falling ball in the foam blow molded body is bent, and force is applied to the part other than the flat part (the part deviating from the flat part) to damage the foam blow molded body, the number of drop ball tests is not counted, and the drop ball test is carried out again. Based on the results of the drop ball test, the cold impact resistance of the foam blow molded body is evaluated according to the following criteria.

[0168] A (very good): The foam blow molded article is not broken.

[0169] B (good): Cracks were observed in the foam blow-molded article, but scattering of fragments was not observed.

[0170] C (poor): The foamed blow-molded article was broken, and scattering of broken fragments of the foamed blow-molded article was observed.

[0171] For each Example and Comparative Example, 10 samples were prepared as foam blow molded products for a -10°C drop ball test, and the cold impact resistance of the foam blow molded products was evaluated using each sample, and the number of samples with evaluation results of A or B (number of good samples) was counted. The results are shown in Tables 2, 3, and 4.

[0172] (Evaluation of surface smoothness)

[0173] The surface smoothness of the foam blow molded article indicates the smoothness of the inner surface side surface of the hollow portion of the foam blow molded article. The surface smoothness of the foam blow molded article is measured by cutting out a flat portion of the hollow portion of the hollow foam blow molded article and visually observing the inner surface of the foam blow molded article of the flat portion. The surface smoothness of the foam blow molded article is measured according to the following criteria.

[0174] A (good): When visually observing the inner surface of the hollow portion of the foam blow molded article, the height difference between adjacent concave and convex portions (the difference between the bottom position of the concave portion and the top position of the convex portion) is 1 mm or more. The number of concave and convex portions formed is 1 mm or more per 100 cm of the inner surface. 2 The area is less than 1 (including the case where no unevenness is observed on the inner surface of the hollow portion).

[0175] B (bad): When visually observing the inner surface of the hollow portion of the foam blow molded article, the height difference between adjacent concave and convex portions (the difference between the bottom position of the concave portion and the top position of the convex portion) is 1 mm or more. The number of concave and convex portions formed is 1 mm or more per 100 cm of the inner surface of the hollow portion. 2 The area is 2 or more.

[0176] In Tables 2, 3, and 4, the above evaluation results and the number of identified locations of the concavoconvex formation locations are recorded in the column of surface smoothness. For example, in the foam blow molded products obtained in Examples 1 to 5, the number of locations of the concavoconvex formation locations is 0 (i.e., no concavoconvex is observed on the inner surface).

[0177] In Examples 1 to 5, it was confirmed that foam blow molded products excellent in cold-weather impact resistance and surface smoothness were obtained as shown in Table 2. In addition, it was confirmed that the flexural modulus of the foam blow molded products also had a value corresponding to the rigidity required for general pipe applications.

[0178] In Comparative Examples 1 and 2, the mixing ratio of the polyolefin resin and the elastomer in the mixed resin was changed compared with Example 2. As shown in Table 3, both the impact resistance and the surface smoothness required for the foam blow molded product were not obtained.

[0179] In Comparative Examples 3 to 6, the type of the elastomer was changed compared to Example 1, etc., but as shown in Tables 3 and 4, both the impact resistance and the surface smoothness required for the foam blow molded product were not obtained.

[0180] In Comparative Examples 7 and 8, the amount of the linear block polypropylene (a) was changed compared to Example 1, etc., but the impact resistance and surface smoothness required for the foam blow molded product were not achieved as shown in Table 4. In addition, in Comparative Examples 7 and 8, as shown in Table 4, the values ​​of the bending elastic modulus were low compared to Examples 1 to 5, and the rigidity of the foam blow molded product was insufficient.

[0181] In Comparative Example 9, linear homopolypropylene was used instead of the linear block polypropylene used in Example 1, etc. As shown in Table 4, both the impact resistance and the surface smoothness required for the foam blow molded product could not be obtained.

[0182] [Table 2]

[0183]

[0184] [Table 3]

[0185]

[0186] [Table 4]

[0187]

[0188] The above-mentioned manufacturing method and embodiment of the present invention are an example, and the present invention is not limited thereto. In the technology disclosed as the present invention, for example, various properties of branched homopolypropylene (a1) can be combined. In the technology disclosed as the present invention, for example, branched homopolypropylene (a1) can have a specific melt tension and a specific melting point. These contents are not only for branched homopolypropylene (a1), but also for linear block polypropylene (a2), olefin-based thermoplastic elastomer (B) and recycled raw materials. However, the combination listed here is an example and is not limited thereto.

Claims

1. A method for producing a foam blow molded article, wherein: The method comprises the following steps: blow molding a foamed parison formed by foaming a mixed resin of a polyolefin resin A and an olefin thermoplastic elastomer B, wherein: The polyolefin resin A comprises a branched homopolypropylene a1 and a linear block polypropylene a2, and a mass ratio a1:a2 of the branched homopolypropylene a1 to the linear block polypropylene a2 is 50:50 to 93:7, The olefin-based thermoplastic elastomer B is a hydrogenated product of a triblock copolymer comprising a crystalline olefin polymer block and a conjugated diene compound polymer block, In the mixed resin, the blending amount of the olefin-based thermoplastic elastomer B relative to 100 parts by mass of the polyolefin-based resin A is 20 parts by mass or more and 40 parts by mass or less.

2. The method for producing a foamed blow molded article according to claim 1, wherein: The melting point of the olefin-based thermoplastic elastomer B is 80° C. or higher and 100° C. or lower.

3. The method for producing a foamed blow molded product according to claim 1 or 2, wherein: The linear block polypropylene a2 has a flexural modulus of 1000 MPa or more and 1500 MPa or less.

4. The method for producing a foamed blow molded article according to any one of claims 1 to 3, wherein: The melt flow rate of the olefin-based thermoplastic elastomer B is 1 g / 10 min or more and 10 g / 10 min or less at 230° C. and a load of 2.16 kg.

5. A foam blow molded product, which is a foam blow molded product of a mixed resin of a polyolefin resin A and an olefin thermoplastic elastomer B, The polyolefin resin A comprises a branched homopolypropylene a1 and a linear block polypropylene a2, and a mass ratio a1:a2 of the branched homopolypropylene a1 to the linear block polypropylene a2 is 50:50 to 93:7, The olefin-based thermoplastic elastomer B is a hydrogenated product of a triblock copolymer comprising a crystalline olefin polymer block and a conjugated diene compound polymer block, In the mixed resin, the blending amount of the olefin-based thermoplastic elastomer B relative to 100 parts by mass of the polyolefin-based resin A is 20 parts by mass or more and 40 parts by mass or less.

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