WO2024019042A1

WO2024019042A1 - Method for producing foam blow molded body, and foam blow molded body

Info

Publication number: WO2024019042A1
Application number: PCT/JP2023/026245
Authority: WO
Inventors: 正浩五味渕; 仁一朗野呂
Original assignee: 株式会社ジェイエスピー
Priority date: 2022-07-19
Filing date: 2023-07-18
Publication date: 2024-01-25
Also published as: JP2024013089A

Abstract

The present invention provides a method for producing a foam blow molded body, the method comprising a step for blow molding a foamed parison that is obtained by foaming a mixed resin of a polyolefin resin (A) and an olefin-based thermoplastic elastomer (B). With respect to this method for producing a foam blow molded body, the polyolefin resin (A) is composed of a branched homopolypropylene (a1) and a linear block polypropylene (a2); the 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 that is composed of a crystalline olefin polymer block and a polymer block of a conjugated diene compound; and the added amount of the olefin-based thermoplastic elastomer (B) relative to 100 parts by mass of the polyolefin resin (A) is 20 parts by mass to 40 parts by mass in the mixed resin.

Description

Method for producing a foam blow molded product, and foam blow molded product

TECHNICAL FIELD The present invention relates to a method for producing a blow-molded foam and a blow-molded foam.

The foam blow molded article is obtained by shaping a foam parison formed from a foamable resin melt containing a base resin. Among foam blow molded products, hollow molded products using polyolefin resin as a base resin are used in various applications, such as air conditioning ducts in automobiles, etc., from the viewpoint of light weight and the like. Hereinafter, the air conditioning duct may be referred to as a duct.

In recent years, foam blow-molded bodies are required to be lightweight and have cold impact resistance. Note that the cold impact resistance refers to the impact resistance of the foam blow-molded article at low temperatures. In order to improve the cold impact resistance of a foam blow molded article, Patent Document 1 and Patent Document 2 disclose a technique of adding an elastomer to a polypropylene resin.

International Publication 2020/059112 Japanese Patent Application Publication No. 2018-141031

The techniques disclosed in Patent Document 1 and Patent Document 2 had the problem of further improving the cold impact resistance and rigidity of the foam blow-molded product. Moreover, the techniques of Patent Document 1 and Patent Document 2 had a problem in improving the surface smoothness on the inner surface of the hollow portion of the hollow foam blow-molded article. Hereinafter, unless specified otherwise, the surface smoothness on the inner surface of the hollow portion of the hollow foam blow-molded object will be simply referred to as surface smoothness.

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 to provide a foam blow-molded article having excellent cold impact resistance, rigidity, and surface smoothness. may be provided.

The gist of the present invention is the inventions shown in the following (1) to (5).

(1) A method for producing a foamed blow-molded article, which includes the step of blow-molding a foamed parison formed by foaming a mixed resin of a polyolefin resin (A) and an olefinic thermoplastic elastomer (B),
The polyolefin resin (A) consists of a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the branched homopolypropylene (a1) and the linear block polypropylene (a2) The mass ratio [(a1):(a2)] is 50:50 to 93:7,
The olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer consisting of a crystalline olefin polymer block and a conjugated diene compound polymer block,
In the mixed resin, the amount of the olefin thermoplastic elastomer (B) based on 100 parts by mass of the polyolefin resin (A) is 20 parts by mass or more and 40 parts by mass or less.
(2) The melting point of the olefinic thermoplastic elastomer (B) is 80°C or more and 100°C or less,
The method for producing a foam blow-molded article according to (1) above.
(3) The linear block polypropylene (a2) has a flexural modulus of 1000 MPa or more and 1500 MPa or less,
The method for producing a foam blow-molded article according to (1) or (2) above.
(4) The melt flow rate (230° C., load 2.16 kg) of the olefin thermoplastic elastomer (B) is 1 g/10 min or more and 10 g/10 min or less,
The method for producing a foam blow molded article according to any one of (1) to (3) above.
(5) A foam blow-molded product of a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B),
The polyolefin resin (A) consists of a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the branched homopolypropylene (a1) and the linear block polypropylene (a2) The mass ratio [(a1):(a2)] is 50:50 to 93:7,
The olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer consisting of a crystalline olefin polymer block and a conjugated diene compound polymer block,
In the mixed resin, the foamed blow-molded article has a blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A) from 20 parts by mass to 40 parts by mass.

Furthermore, the present invention may be the inventions described in the following (6) to (8).

(6) The melting point of the olefinic thermoplastic elastomer (B) is 80°C or more and 100°C or less,
The foam blow-molded article according to (5) above.
(7) The linear block polypropylene (a2) has a flexural modulus of 1000 MPa or more and 1500 MPa or less,
The foam blow molded article according to (5) or (6) above.
(8) The melt flow rate (230° C., load 2.16 kg) of the olefinic thermoplastic elastomer (B) is 1 g/10 min or more and 10 g/10 min or less,
The foam blow molded article according to any one of (5) to (7) above.

According to the present invention, there is provided 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 done.

About the present invention: 1. A method for producing a foam blow molded article, 2. Explanation will be given in order of the foam blow molded article. Note that the present invention is not limited to the embodiments described below.

[1 Method for producing foam blow molded product]
The manufacturing method according to the present invention is a method for manufacturing a foam blow-molded article including a blow molding step. An embodiment of the method for manufacturing a foam blow-molded article according to the present invention will be explained next.

[1-1 Contents of manufacturing method]
(Extrusion foaming process)
Inside the extruder, the mixed resin and foaming agent are kneaded to obtain a foamable resin melt. The resulting foamable resin melt is extruded from a die connected to an extruder. As the die, an annular die is usually used. A mold is placed directly below the die, and the foamable resin melt is extruded into the mold. At this time, a foamed parison is formed by foaming the foamable resin melt. Note that the mold has a desired internal shape depending on the molded product to be obtained. The mold is usually a split mold.

(Pre-blow process)
Immediately after the extrusion foaming process, the foamed parison is in a softened state. The lower part of the softened foam parison is closed using a pinch device, and gas is blown into the foam parison to increase the internal pressure of the foam parison. At this time, the foam parison widens. During or after the pre-blowing process, the foamed parison is inserted into a mold.

(Blow molding process)
The blow molding process is a process in which gas is blown into the foamed parison while the foamed parison is sandwiched between molds. At this time, the outer surface of the foamed parison is pressed against the inner surface of the mold, and the foamed parison is shaped into a hollow shape. A foam blow-molded article is obtained through this step. As the foam blow molded product, for example, a hollow molded product can be obtained. In addition, in the manufacturing method of a foam blow-molded object, it is preferable that an accumulator is provided between an extruder and a die, or in a die.

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

(Polyolefin resin)
The polyolefin resin (A) is a resin composition consisting of a branched homopolypropylene (a1) and a linear block polypropylene (a2).

(branched homopolypropylene)
Branched homopolypropylene (a1) is homopolypropylene having a branched structure in its molecular structure. Examples of the branched structure include a branched structural part in a molecular structure and a long chain structural part having a free end. Note that the branched structure can be confirmed using high temperature GPC-MALS measurement or the like.

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 minutes to 15 g/10 minutes. If the melt flow rate is within the above range, the resin will have excellent fluidity during melting, and therefore the drawdown of the foamed parison will be further suppressed. From this viewpoint, the melt flow rate of the branched homopolypropylene (a1) is more preferably 0.5 g/10 minutes to 10 g/10 minutes, and still more preferably 1 g/10 minutes to 5 g/10 minutes. The melt flow rate (MFR) of the resin can be measured by a known method, for example, based on JIS K7210-1:2014 (Test Method A). The upper and lower limits in the combinations defining each numerical range shown as the numerical range of the melt flow rate of the branched homopolypropylene (a1) described above may be independently and arbitrarily combined. In this specification, a combination defining a numerical range refers to a combination of an upper limit value and a lower limit value. Note that the numerical range determined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. Therefore, the numerical range of the melt flow rate of the branched homopolypropylene (a1) is a numerical range that combines the upper and lower limits of the preferable numerical range, and the upper and lower limits of the more preferable numerical range. Good too. Specifically, the numerical range for the melt flow rate of the branched homopolypropylene (a1) is, for example, any one of the group consisting of 0.1 g/10 minutes, 0.5 g/10 minutes, and 1 g/10 minutes. The lower limit is 15 g/10 minutes, 10 g/10 minutes, and 5 g/10 minutes. Therefore, for example, the numerical range of the melt flow rate may be 0.1 g/10 minutes to 10 g/10 minutes, 0.5 g/10 minutes to 5 g/10 minutes, or 1 g/10 minutes. The rate may be 10 minutes to 15 g/10 minutes.

Further, the melt tension at 230°C of the branched homopolypropylene (a1) is preferably 5 cN to 50 cN, more preferably 10 cN to 45 cN, and more preferably 25 cN to 40 cN, from the viewpoint of foamability in foam blow molding. Most preferably. Regarding the numerical range of the melt tension of the branched homopolypropylene (a1), the upper and lower limits shown in the combination of numerical ranges described above can be independently and arbitrarily combined. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the melt tension at 230°C of the branched homopolypropylene (a1) is, for example, the lower limit is any one of the group consisting of 5 cN, 10 cN, and 25 cN, and the lower limit is any one of the group consisting of 50 cN, 45 cN, and 40 cN. A range with one of the upper limits can be listed. The melt tension (MT) of the branched homopolypropylene (a1) can be measured by a known method, for example, by Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd.

The melting point of the branched homopolypropylene (a1) is preferably 155°C to 165°C, more preferably 157°C to 162°C. Regarding the numerical range of the melting point of the branched homopolypropylene (a1), the upper limit and lower limit shown in the combination of numerical ranges described above can be arbitrarily combined independently. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the melting point of the branched homopolypropylene (a1) is, for example, the lower limit is any one of the group consisting of 155°C and 157°C, and the lower limit is any one of the group consisting of 165°C and 162°C. A range with an upper limit of . The melting point can be measured in accordance with JIS K7121:2012 in the same manner as the melting point of the olefin thermoplastic elastomer (B) described below.

Branched homopolypropylene (a1) has excellent foaming properties, so by having branched homopolypropylene (a1) in the polyolefin resin (A), it is possible to obtain a foam blow-molded product that is lightweight and has excellent surface smoothness. It becomes easier. Specifically, examples of the branched homopolypropylene (a1) include those commercially available as HMS-polypropylene and UMS-polypropylene. Further, examples of the branched homopolypropylene (a1) include branched homopolypropylene manufactured by Borealis (product name: WB130, WB135, WB140), branched homopolypropylene resin manufactured by Sun Allomer (product name: PF814), etc. .

(Linear block polypropylene)
The linear block polypropylene (a2) is a block polypropylene having a linear molecular structure. Examples of block polypropylene include polymer mixtures obtained by polymerizing ethylene and one or more types of C3 to C10-α olefins (α-olefins having 3 to 10 carbon atoms) in the presence of a propylene polymer. Furthermore, the linear block polypropylene (a2) includes impact-resistant polypropylene polymers defined by JIS K6921-1, and includes those generally commercially available as block polypropylene. However, the example of block polypropylene shown here is one example, and other examples are not excluded. Specifically, the block polypropylene can be exemplified by a propylene/ethylene block copolymer. More specifically, the propylene/ethylene block copolymer includes a block copolymer containing a crystalline propylene block and an ethylene propylene random block.

(Bending modulus of linear block polypropylene)
The bending elastic modulus of the linear block polypropylene (a2) is preferably 1000 MPa or more and 1500 MPa or less. By having a bending modulus of elasticity of the linear block polypropylene (a2) of 1000 MPa or more, the rigidity of the foam blow-molded article can be more effectively improved, and the cushioning properties of the foam blow-molded article can be improved. From this viewpoint, it is more preferable that the flexural modulus of the linear block polypropylene (a2) is 1100 MPa or more and 1400 MPa or less. Regarding the numerical range of the bending elastic modulus of the linear block polypropylene (a2), the upper and lower limits shown in the combinations of the numerical ranges described above can be independently and arbitrarily combined. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the bending elastic modulus of the linear homopolypropylene (a2) is, for example, the lower limit is any one of the group consisting of 1000 MPa and 1100 MPa, and the lower limit is any one of the group consisting of 1500 MPa and 1400 MPa. A range of upper limit values can be listed.

(Measurement of flexural modulus)
The flexural modulus of linear block polypropylene (a2) can be measured based on JIS K7171:2016.

Generally, the bending modulus of the resin itself of the linear block polypropylene (a2) is often smaller than that of the branched homopolypropylene (a1), but if the polyolefin resin (A) is the branched homopolypropylene (a1) In addition, by including the linear block polypropylene (a2), the rigidity of the foam blow-molded article can be improved. Further, since the polyolefin resin (A) contains the linear block polypropylene (a2), it becomes easy to obtain a foam blow-molded product that is lightweight and has excellent surface smoothness.

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 minutes to 40 g/10 minutes. If the melt flow rate is within the above range, the mixed resin will have excellent fluidity when melted. From this viewpoint, the melt flow rate of the linear block polypropylene (a2) is preferably 2 g/10 minutes to 38 g/10 minutes, more preferably 10 g/10 minutes to 35 g/10 minutes, and even more preferably is 20g/10 minutes to 33g/10 minutes. Regarding the numerical range of the melt flow rate of the linear block polypropylene (a2), the upper and lower limits shown in the combination of numerical ranges described above can be independently and arbitrarily combined. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the melt flow rate of linear block polypropylene (a2) is, for example, the lower limit of any one of the group consisting of 1 g/10 minutes, 2 g/10 minutes, 10 g/10 minutes, and 20 g/10 minutes. , and a range in which the upper limit is any one of the group consisting of 40 g/10 minutes, 38 g/10 minutes, 35 g/10 minutes, and 33 g/10 minutes. The melt flow rate (MFR) of the resin can be measured by a known method, for example, based on JIS K7210-1:2014 (Test Method A).

The melting point of the linear block polypropylene (a2) is preferably 155°C to 169°C, preferably 158°C to 168°C. Regarding the numerical range of the melting point of the linear block polypropylene (a2), 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 defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the melting point of the linear block polypropylene (a2) is, for example, the lower limit of any one of the group consisting of 155°C and 158°C, and the lower limit of any one of the group consisting of 169°C and 168°C. A range with one upper limit can be listed. The melting point can be measured in accordance with JIS K7121:2012 in the same manner as the melting point of the olefin thermoplastic elastomer (B) described below.

(Mass ratio [(a1):(a2)])
In the mixed resin, the mass ratio [(a1):(a2)] of branched homopolypropylene (a1) and linear block polypropylene (a2) is preferably 50:50 to 93:7. When the mass ratio [(a1):(a2)] is within the above numerical range, the foamability of the mixed resin is improved, the surface smoothness is improved, and the rigidity and cold impact resistance of the foam blow molded product are improved. The effect of this can be obtained. In addition, from the viewpoint of further improving this effect, the mass ratio [(a1):(a2)] is preferably 70:30 to 92:8, more preferably 80:20 to 90:10. preferable. In the numerical range of the mass ratio [(a1):(a2)], the upper limit ratio and lower limit ratio shown in the combination of numerical ranges described above can be independently and arbitrarily combined. The numerical range determined by arbitrarily combining the upper limit ratio and the lower limit ratio includes the upper limit ratio, the lower limit ratio, and the ratio between the upper limit ratio and the lower limit ratio. . However, in the combination of each numerical range of mass ratio [(a1):(a2)], the case where the mass ratio of branched homopolypropylene (a1) is the smallest is taken as the lower limit ratio, and the ratio of branched homopolypropylene (a1) is the lowest. The case where the mass ratio is the largest is taken as the upper limit ratio. For example, if the numerical range of the mass ratio [(a1):(a2)] is 50:50 to 93:7, the lower limit ratio is 50:50 and the upper limit ratio is 93: It is 7. The numerical range of the mass ratio [(a1):(a2)] is, for example, one of the group consisting of 50:50, 70:30, and 80:20 as the lower limit ratio, and 93:7, A range whose upper limit is one of the group consisting of 92:8 and 90:10 can be mentioned.

(Olefin thermoplastic elastomer)
The olefinic thermoplastic elastomer (B) is a hydrogenated triblock copolymer consisting of a hard segment of a crystalline olefin polymer block and a soft segment of a conjugated diene compound polymer block. The triblock copolymer is preferably a block copolymer having a so-called ABA type structure (sandwich type). At this time, A as the block parts at both ends of the block copolymer having an ABA type structure is a polymer block of crystalline olefin, and the block parts sandwiched by A (the central block part) are polymer blocks of crystalline olefin. ) is preferably a polymer block of a conjugated diene compound. Since the olefinic thermoplastic elastomer (B) is a hydrogenated block copolymer having the above-mentioned structure, the impact resistance of the foamed blow-molded product is improved without inhibiting the foamability of the foamed Parisian material. can be done. Moreover, the effect of improving the surface smoothness of the foam blow-molded article can be exhibited.

Examples of crystalline olefin polymers include ethylene polymers. Polymers of conjugated diene compounds include, in addition to polymers of ethylene and butylene, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 1,3-pentadiene, 2,3-dimethyl-1, Examples include polymers such as 3-butadiene.

Specifically, the olefinic thermoplastic elastomer (B) is a triblock copolymer in which the block portions at both ends are blocks of ethylene polymer and the block portion in the center is a block of 1,3-butadiene polymer. Examples include hydrogenated substances. The olefinic thermoplastic elastomer (B) can be exemplified by a block copolymer of crystalline olefin, ethylene butylene, and crystalline olefin in a state after hydrogenation. Further, the olefin thermoplastic elastomer (B) does not contain polypropylene resins such as branched homopolypropylene (a1) and linear block polypropylene (a2).

(Melting point of olefinic thermoplastic elastomer)
The melting point of the olefinic thermoplastic elastomer (B) is preferably 80°C or more and 110°C or less. If the melting point of the olefinic thermoplastic elastomer (B) is within the above range, it will have excellent foamability. From this viewpoint, the melting point of the olefinic thermoplastic elastomer (B) is more preferably 85°C or more and 105°C or less, and even more preferably 90°C or more and 100°C or less. Regarding the numerical range of the melting point of the olefinic thermoplastic elastomer (B), the upper limit and lower limit shown in the combination of numerical ranges described above can be independently and arbitrarily combined. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the melting point of the olefinic thermoplastic elastomer (B) is, for example, a lower limit of one of the group consisting of 80°C, 85°C and 90°C, and a lower limit of the group consisting of 110°C, 105°C and 100°C. A range with an upper limit of any one of the following can be mentioned.

(Method of measuring melting point)
The melting point of the olefinic thermoplastic elastomer (B) can be specified as the melting peak temperature measured based on heat flux differential scanning calorimetry described in JIS K7121:2012. In addition, "(2) When measuring the melting temperature after a certain heat treatment" is adopted as the conditioning of the test piece used for heat flux differential scanning calorimetry, and the heating rate and cooling rate are both 10 Adopt °C/min. When multiple melting peaks appear on the DSC curve, the apex temperature of the melting peak with the largest area is taken as the melting point.

(Flexural modulus of olefinic thermoplastic elastomer)
The upper limit of the flexural modulus of the olefinic thermoplastic elastomer (B) is preferably 50 MPa. When the olefinic thermoplastic elastomer (B) has a flexural modulus of 50 MPa or less, the olefinic thermoplastic elastomer (B) can effectively exhibit its physical properties as an elastomer. Further, the lower limit of the flexural modulus of the olefinic thermoplastic elastomer (B) is preferably approximately 1 Ma. That is, it is preferable that the flexural modulus of the olefinic thermoplastic elastomer (B) is 1 MPa or more and 50 MPa or less. When the flexural modulus of the olefinic thermoplastic elastomer (B) is within the above numerical range, it becomes easy to obtain the effect of further improving cold impact resistance as a foam blow-molded article. From the viewpoint of further enhancing this effect, the flexural modulus of the olefin thermoplastic elastomer (B) is more preferably 3 MPa or more and 30 MPa or less, and even more preferably 5 MPa or more and 25 MPa or less. Regarding the numerical range of the flexural modulus of the olefinic thermoplastic elastomer (B), the upper and lower limits shown in the combinations of the numerical ranges described above can be independently and arbitrarily combined. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the flexural modulus of the olefinic thermoplastic elastomer (B) is, for example, a lower limit of any one of the group consisting of 1 MPa, 3 MPa, and 5 MPa, and one of the group consisting of 50 MPa, 30 MPa, and 25 MPa. A range with one upper limit can be listed.

(Measurement of flexural modulus)
The flexural modulus of the olefinic thermoplastic elastomer (B) can be measured based on JIS K7171:2016.

(Melt flow rate (MFR) of olefinic thermoplastic elastomer)
The MFR (230°C, load 2.16 kg) of the olefin thermoplastic elastomer (B) is preferably 1 g/10 minutes or more and 10 g/10 minutes or less, and 1.5 g/10 minutes or more and 5 g/10 minutes or less. It is even more preferable that there be. Regarding the numerical range of MFR of the olefinic thermoplastic elastomer (B), 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 defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of MFR of the olefin thermoplastic elastomer (B) is, for example, the lower limit is any one of the group consisting of 1 g/10 minutes and 1.5 g/10 minutes, and 10 g/10 minutes and 5 g/10 minutes. A range having an upper limit of any one of the group consisting of 10 minutes can be mentioned.

(Measurement of MFR)
The MFR (g/10 min (230° C.)) of the olefinic thermoplastic elastomer (B) is determined based on, for example, JIS K7210-1:2014 (Test Method A). As the measurement conditions, conditions of 230° C. and a load of 2.16 kg may be adopted.

(Blending ratio of each component of mixed resin)
In the mixed resin, the blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A) is 20 parts by mass or more and 40 parts by mass or less. By setting the blending amount of the olefin thermoplastic elastomer (B) to 100 parts by mass of the polyolefin resin (A) within the above range, it is possible to achieve both the impact resistance and surface smoothness required for a foam blow molded article. It becomes easier. From the above viewpoint, the blending amount of the olefinic thermoplastic elastomer (B) is preferably 22 parts by mass or more and 35 parts by mass or less, more preferably 23 parts by mass or more and 30 parts by mass or less.

Further, 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, more preferably 0.25 to 0. More preferably, it is 35. Furthermore, 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, preferably 1.2 to 2. More preferably, it is .3. When the mass ratio of the olefinic thermoplastic elastomer (B) to the branched homopolypropylene (a1) is within the above range, it becomes easy to exhibit impact resistance. The mass ratio of the olefinic thermoplastic elastomer (B) to the branched homopolypropylene (a1) is calculated from It is the value (divided value) divided by the blending amount (parts by mass) of homopolypropylene (a1). The mass ratio of the olefinic thermoplastic elastomer (B) to the branched linear block polypropylene (a2) is determined by (the amount (parts by mass) of the olefinic thermoplastic elastomer (B) used in the mixed resin) This is the value divided by the blending amount (parts by mass) of the chain block polypropylene (a2).

In the mixed resin, in addition to the numerical range of the blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A), the olefin with respect to the branched homopolypropylene (a1) in the polyolefin resin (A) At least one numerical range selected from the numerical range of the mass ratio of the thermoplastic elastomer (B) and the numerical range of the mass ratio of the olefinic thermoplastic elastomer (B) to the branched homopolypropylene (a2) is as described above. However, it is preferable that the numerical ranges of both types satisfy the above-mentioned numerical values.

In addition, the numerical range of the blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A) is such that the upper limit and lower limit shown in the combination of the numerical ranges described above are independently arbitrary. It is possible to combine The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A) is, for example, the lower limit of any one of the group consisting of 20 parts by mass, 22 parts by mass, and 23 parts by mass. and the upper limit is any one of the group consisting of 40 parts by mass, 35 parts by mass, and 30 parts by mass. The numerical range of the mass ratio of the olefin thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin resin (A), and the mass ratio of the olefin thermoplastic elastomer (B) to the branched homopolypropylene (a2) Regarding the numerical range of the mass ratio, the upper and lower limits shown in the combinations of numerical ranges described above can be independently and arbitrarily combined. Also in this case, 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 thermoplastic elastomer (B) to the branched homopolypropylene (a1) in the polyolefin resin (A) is, for example, any one of the group consisting of 0.2 and 0.25. A range can be mentioned in which the lower limit is 0.5 and the upper limit is one of the group consisting of 0.5 and 0.35.

(Other additives in mixed resin)
When producing a foam blow-molded article, the mixed resin and the blowing agent are kneaded as described above. Examples of the physical foaming agent include those shown below.

(foaming agent)
Examples of the blowing agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, and cyclohexane; chlorinated hydrocarbons such as methyl chloride and ethyl chloride; - Fluorinated hydrocarbons such as tetrafluoroethane and 1,1-difluoroethane; aliphatic ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; aliphatic alcohols such as methyl alcohol and ethyl alcohol; and dialkyl such as dimethyl carbonate and diethyl carbonate. Examples include organic physical blowing agents such as carbonate, inorganic physical blowing agents such as carbon dioxide, nitrogen, air, and water, and chemical blowing agents such as sodium bicarbonate, sodium citrate, and azodicarbonamide. These blowing agents may be used alone or in combination.

When a foamed parison is formed using an inorganic physical foaming agent, foaming of the foamable resin melt is completed early, and little or no foaming agent remains in the resin constituting the foamed parison. Therefore, the resin constituting the foamed parison is not plasticized, and drawdown of the foamed parison is prevented. As a result, a foamed parison with excellent blow moldability can be obtained compared to that obtained using an organic physical foaming agent. From this point of view, it is preferable to use an inorganic physical blowing agent among the above-mentioned blowing agents, it is more preferable to use an inorganic physical blowing agent containing carbon dioxide, and it is even more preferable to use a physical blowing agent consisting only of carbon dioxide. preferable.

In the present invention, when a blowing agent containing carbon dioxide is used as a physical blowing agent, it is preferable to blend carbon dioxide in an amount of 20 mol% to 100 mol% with respect to 100 mol% of the physical blowing agent, and preferably 50 mol% to 100 mol%. %, more preferably 70 mol% to 100 mol%. When the carbon dioxide content is within the above range, it is possible to easily obtain a foam blow-molded article with a small cell diameter and a high closed cell ratio.

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

(Other resins)
Other resins different from the polyolefin resin (A) and the olefin thermoplastic elastomer (B) can be blended into the mixed resin within a range that does not impede the objective effects of the present invention. As other resins, thermoplastic resins such as polystyrene resins and polyolefin resins other than the polyolefin resin (A), and thermoplastic elastomers (TPE) other than the olefin thermoplastic elastomer (B) can be blended. . Furthermore, as polyolefin resins other than the polyolefin resin (A), biomass polyolefin resins, ASR-derived polyolefin resins, and mass balance polyolefin resins can also be used. The amount of other resins is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B). More preferably, it is 10 parts by mass or less, particularly preferably 5 parts by mass or less.

(Various additives)
When producing a foam blow-molded article, various additives may be added to the mixed resin in addition to the above-described foaming agent. Examples of additives include flame retardants, fluidity regulators, ultraviolet absorbers, conductivity imparting agents, antistatic agents, colorants, heat stabilizers, antioxidants, inorganic fillers, and pigments. The amount of the additive added is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on a total of 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B), More preferably, it is 3 parts by mass or less. In addition, the above additives inhibit the effects of the present invention on polyolefin resin (A), olefin thermoplastic elastomer (B), branched homopolypropylene (a1), and linear block polypropylene (a2). It can be added to the extent that it does not. The amount added is preferably based on 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). , preferably 10 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less.

Additionally, carbon black may be added to the mixed resin as an additive. The content of carbon black in the mixed resin is preferably 0.1 parts by mass or more and 2 parts by mass or less, based on a total of 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B), and more preferably Preferably it is 0.3 parts by mass or more and 1 part by mass or less. Examples of carbon black include gas furnace black, oil furnace black, acetylene black, channel black, roller black, thermal black, Ketjen black, and the like. Note that when a recovered raw material containing carbon black is used as part of the raw material when producing a foam blow-molded article, the total carbon black content of the mixed resin is a value that includes carbon black in the recovered raw material. Regarding the numerical range of the physical foaming agent mentioned above for the mixed resin and the numerical range of various additives such as carbon black, the upper and lower limits shown in the combination of the numerical ranges described above can be independently combined arbitrarily. Is possible. The numerical range defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value.

(Use of recovered materials (recovered raw materials))
When producing the foam blow-molded article of the present invention, defective molded articles with burrs, dimensional deviations, etc. may occur. These burrs and defective molded products can be used as recovered raw materials. The recovered raw material preferably contains a polyolefin resin (A) and an olefin thermoplastic elastomer (B). In the method for producing a foam blow-molded article according to the present invention, a foamable resin melt containing recovered raw materials is formed, and a foamed blow-molded article may be formed from a foam parison made by foaming the foamable resin melt. . In addition, when the recovered raw material containing the polyolefin resin (A) and the olefin thermoplastic elastomer (B) is used as part of the raw materials for forming a foamable resin melt, the mixed resin constituting the foam blow-molded product The blending amount of polyolefin resin (A) and olefin thermoplastic elastomer (B) inside is determined as a value including the polyolefin resin (A) and olefin thermoplastic elastomer (B) contained in the recovered raw material. . Numerical ranges regarding attributes such as physical properties of the polyolefin resin (A) and the olefin thermoplastic elastomer (B) contained in the recovered raw materials, and the blending amount of the polyolefin resin (A) and the olefin thermoplastic elastomer (B). The numerical range is the same as that described above for the polyolefin resin (A) and the olefin thermoplastic elastomer (B) that constitute the mixed resin that constitutes the foam blow molded article.

[1-2 Effects of the manufacturing method of foam blow molded product]
Foam blow-molded articles using polypropylene resins are particularly excellent in terms of heat resistance and light weight, and can be suitably employed, for example, in ducts installed in vehicles such as automobiles. In recent years, there has been a growing demand for foam blow-molded articles that are preferably used in such applications to have improved cold impact resistance.

However, when an elastomer is added to the polypropylene resin in order to improve the cold impact resistance of the foam blow-molded product, there is an increased possibility that the rigidity of the foam blow-molded product will decrease. When a foam blow molded product is used as a duct, if the rigidity of the foam blow molded product decreases, the duct will be formed due to negative pressure inside the duct when gas such as air passes through the duct. There is a possibility that the surface portion of the foam blow-molded product may curve slightly inward.

In addition, when forming a foam blow molded product into a hollow shape and using it as a duct, from the viewpoint of suppressing the air resistance of the duct and suppressing ventilation noise (wind noise), it is necessary to improve the surface smoothness of the inner surface of the hollow part of the foam blow molding. Improvement is required.

According to the method for producing a foam blow molded article according to the present invention, a specific polypropylene resin (polyolefin resin (A)) and a specific elastomer (olefin thermoplastic elastomer (B)) are used within a specific range. By doing so, it is possible to obtain a foam blow-molded article having excellent both cold impact resistance and rigidity. In addition, by using the specific elastomer as described above in the method for producing a foam blow molded product, the foamability of the polyolefin resin (A) constituting the foamable resin melt is not significantly inhibited, so the foam blow molded product The possibility of deterioration of the surface smoothness can be suppressed.

In addition, not only branched homopolypropylene but also linear polypropylene blocks are used in a specific range as the polyolefin resin, thereby suppressing the possibility of a decrease in rigidity of the foam blow-molded product due to the use of an elastomer. A foam blow-molded product with excellent rigidity can be obtained.

Additionally, foam blow-molded products are required to have various apparent densities depending on various conditions such as usage. According to the method for producing a foam blow molded article according to the present invention, a specific polypropylene resin and a specific elastomer are used in a specific blending ratio, so that surface smoothness can be maintained even under conditions for obtaining various apparent densities. It is possible to obtain an excellent foam blow-molded article (excellent inner surface smoothness). Regarding the attributes such as the apparent density, closed cell ratio, and flexural modulus of the foam blow molded product obtained by applying the method for producing a foam blow molded product according to the present invention, see [2. Foamed blow-molded article].

Next, the foam blow molded article according to the present invention will be described.

[2. Foam blow molded product]
[2-1 Configuration of foam blow molded product]
The foam blow molded article according to the present invention is a foam molded article of a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B).

The foam blow-molded article according to the present invention can be obtained by the above-described method for producing a foam blow-molded article. That is, the foam blow-molded article is produced by the above-mentioned [1. [Method for producing a foamed blow-molded article]], it can be obtained by performing an extrusion foaming process, a blow molding process, a blow molding process, etc. In addition, each process is described above [1. Since it is the same as that described in [Method for producing foam blow-molded article], the explanation will be omitted.

The polyolefin resin (A) blended into the mixed resin used in the foam blow-molded article according to the present invention is composed of branched homopolypropylene (a1) and linear block polypropylene (a2) in a predetermined mass ratio [(a1) :(a2)]. The structure and physical properties (melt flow rate, melting point, flexural modulus, etc.) of the branched homopolypropylene (a1) and the linear block polypropylene (a2) and the mass ratio [(a1):(a2)] are [1 ．． Since it is the same as that described in [Method for producing foam blow-molded article], the explanation will be omitted. Note that as the polyolefin resin (A), biomass-derived polypropylene or polypropylene produced by a mass balance method can be used.

In addition, the structure and physical properties (melt flow rate, melting point, etc.) of the olefin thermoplastic elastomer (B) blended into the mixed resin used in the foam blow molded article, and the 100 mass of the polyolefin resin (A) in the mixed resin. Regarding the amount of the olefinic thermoplastic elastomer (B) based on [1. Since it is the same as that described in [Method for producing foam blow-molded article], the explanation will be omitted.

(Shape of foam blow molded product)
The shape of the foam blow molded product is not particularly limited, but if it is a hollow molded product, the foam blow molded product can be easily used, for example, as an air conditioning duct provided in a vehicle or the like.

(closed cell ratio)
From the viewpoint of improving the appearance, the closed cell ratio of the foam blow-molded product is preferably 65% or more, and more preferably 70% or more.

(Measurement of closed cell ratio)
A test piece is prepared by cutting a roughly flat part of the foam blow-molded article into a 25 mm x 25 mm x flat part wall thickness. A plurality of test pieces are stacked so that the total thickness is closest to 20 mm to form a test piece for measurement. Next, in accordance with Procedure C of ASTM-D2856-70, the true volume Vx of the measurement specimen was measured using an air comparison hydrometer model 930 manufactured by Toshiba Beckman Corporation, and the following formula (Equation (1)) ) to calculate the closed cell ratio S (%). The above measurement is performed using five test pieces for measurement, and the arithmetic mean value thereof is taken as the closed cell ratio of the foam blow-molded article.

however,
Vx: The true volume (cm ³ ) of the test piece measured by the above method, which corresponds to the sum of the volume of the resin constituting the foam blow-molded product and the total volume of the cells in the closed cell portion within the test piece. ,
Va: apparent volume of the test piece (cm ³ ) calculated from the outer dimensions of the test piece used for measurement,
W: total mass (g) of the test piece used in the measurement, and ρ: density (g/cm ³ ) of the resin constituting the foam blow-molded product.
It is.

(apparent density)
It is preferable that the foam blow-molded article has an apparent density of 100 kg/m ³ or more and 450 kg/m ³ or less. By having the above apparent density, it is possible to stably obtain a molded article that is lightweight and has appropriate rigidity. From the viewpoint of balance between lightness, rigidity, and cushioning properties, the apparent density of the foam blow-molded product is preferably 120 kg/m ³ or more and 400 kg/m ³ or less, and 130 kg/m ^{3 or more and 350 kg/m 3} or less. It is more preferably ³ or less, and even more preferably 150 kg/m ³ or more and 250 kg/m ³ or less. Regarding the numerical range of the apparent density of the foam blow-molded article, 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 defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the apparent density of the foam blow-molded product is, for example, a lower limit of any one of the group consisting of 100 kg/m ³ , 120 kg/m ³ , 130 kg/m ³ and 150 kg/m ³ , and 450 kg/m 3 ³ , 400 kg/m ³ , 350 kg/m ³ and 250 kg/m ³ as the upper limit.

(Measurement of apparent density)
For a total of three vertical cross sections in the longitudinal direction near the longitudinal center and both longitudinal ends of the foam blow molded article, four equally spaced points were selected in the circumferential flat part of each vertical cross section, and Cut out a test piece with an area ^of about 10 cm ² at Vi) was determined, and the arithmetic mean value of these values was taken as the apparent density (D).

(Bending elastic modulus of foam blow molded product)
The flexural modulus (MPa) of the foam blow-molded product is preferably 140 MPa or more and 250 MPa or less. When the flexural modulus of the foam blow-molded article is within the above numerical range, it becomes easy to ensure sufficient rigidity. From the viewpoint of further enhancing this effect, the flexural modulus of the foam blow-molded product is more preferably 150 MPa or more and 200 MPa or less. Regarding the numerical range of the flexural modulus of the foam blow-molded article, 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 defined by arbitrarily combining the upper limit value and the lower limit value includes the upper limit value, the lower limit value, and the value between the upper limit value and the lower limit value. The numerical range of the flexural modulus of the foam blow-molded product is, for example, the lower limit is any one of the group consisting of 140 MPa and 150 MPa, and the upper limit is any one of the group consisting of 250 MPa and 200 MPa. I can list a range.

(Measurement of flexural modulus of foam blow molded product)
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 based on JIS K7171:2016.

[2-2 Effects of foam blow molded product]
The foam blow-molded article according to the present invention can be obtained from the above-mentioned [1. Similar to what was explained in [Method for producing foam blow molded article], a specific polypropylene resin (polyolefin resin (A)) and a specific elastomer (olefin thermoplastic elastomer (B)) are blended in a specific range. Because it is a foamed molded product made from a mixed resin, it has excellent cold impact resistance and rigidity. In addition, the foam blow-molded article is made of a specific elastomer and has excellent surface smoothness.

In addition, as polyolefin resin (A), not only branched homopolypropylene but also linear polypropylene blocks are used in a specific range, thereby suppressing the decrease in rigidity of the foam blow-molded product due to the use of elastomer. It is being Therefore, the foam blow molded article according to the present invention has excellent rigidity.

Additionally, foam blow-molded products are required to have various apparent densities depending on various conditions such as usage. In the foam blow molded article according to the present invention, a specific polypropylene resin and a specific elastomer are used in a specific range, and the foam blow molded article has excellent surface smoothness even when the apparent density of the foam blow molded article is varied. can be obtained.

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

(-10℃ falling ball test (1.5m, 1kg))
Conditioning of the foamed blow-molded product is performed by placing the foamed blow-molded product in an atmosphere of -10°C for 24 hours, and the flat part of the foamed blow-molded product that has been conditioned is placed on a test stand. A 1 kg iron ball is dropped onto a flat surface from 1.5 m above. At this time, the state of damage to the foam blow molded article is observed. It can be evaluated that the smaller the degree of damage to the foam blow-molded article (including cases where there is no damage), the better the cold impact resistance of the foam blow-molded article.

In addition, if the iron ball collides with the foam blow-molded product and the foam blow-molded product is damaged due to force being applied to a place that is off the flat part, the above-mentioned -10°C falling ball test may be performed again. preferable.

Next, the present invention will be explained in more detail using examples.

(Preparation of resin)
Polyolefin resins and elastomers shown in Table 1 were prepared. However, regarding the polyolefin resins, branched homopolypropylene (a1), linear block polypropylene (a2), and linear homopolypropylene were prepared. Table 1 also shows the physical properties (MFR (g/10 min (230°C, load 2.16 kg)) and flexural modulus (MPa)) of the prepared polyolefin resin and elastomer.

The MFR (g/10 min (230°C, load 2.16 kg)) and flexural modulus (MPa) of the polyolefin resin and elastomer are as described above for the polyolefin resin (A) and the olefin thermoplastic elastomer (B). It can be identified by applying a method similar to the method described above. Regarding the melting points (° C.) of the branched homopolypropylene (a1) and the elastomer described later, the method described above for the olefinic thermoplastic elastomer (B) is used to specify the respective melting points. Further, the crystallization temperature (° C.) of the branched homopolypropylene (a1) and the elastomer is measured using a heat flux differential scanning calorimeter based on JIS K 7121:1987. In addition, when a plurality of crystallization peaks appear 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.

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

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

L-PP1 is a copolymer of propylene and ethylene (propylene-ethylene copolymer) (manufactured by Nippon Polypro Co., Ltd., trade name "Novatec (trademark) PP (model number BC03GS)"). The propylene-ethylene copolymer of L-PP1 is a Ziegler-catalyzed copolymer (MFR is 30 g/10 min).

L-PP2 is a polypropylene block copolymer manufactured by Nippon Polypropylene Co., Ltd. under the trade name "Novatec PP (model number BC6DRF)" (MFR is 2.5 g/10 minutes).

L-PP3 is a propylene block copolymer (manufactured by Sun Allomer Co., Ltd., trade name "Qualia (trademark) (model number CM688A)") containing an ethylene-α-olefin copolymer (MFR is 15 g/10 minutes). The MFR of the propylene block copolymer of L-PP3 is 9.5 g/10 minutes.

In Tables 2, 3, and 4, the linear block polypropylenes shown in L-PP1, L-PP2, and L-PP3 are abbreviated as BC03GS, BC6DRF, and CM688A, respectively.

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 abbreviated as J106G.

As the elastomers, olefin elastomers shown in EL1 to EL4 and styrene elastomers shown in EL5 were prepared.

EL1 is a hydrogenated triblock copolymer consisting of a crystalline olefin polymer block and a conjugated diene compound polymer block. EL1 is a hydrogenated block copolymer in which the block portions at both ends are ethylene polymer blocks and the central block portion is a polymer block of a conjugated diene compound (manufactured by JSR Corporation, product name: Dynalon (trademark)). 6200P'') (30% by mass of ethylene-derived components in the block copolymer, 70% by mass of 1,3-butadiene-derived components, hydrogenation rate (hydrogenation rate) of 98% or more, melting point 97°C, crystallization A temperature of 64° C.) was prepared. EL1 corresponds to the olefin thermoplastic elastomer (B).

EL2 is a metallocene propylene-ethylene copolymer (manufactured by ExxonMobil, trade name "Vistamax (trademark) 6202, melting point 102°C"). EL3 is RPTO (Reactor TPO (Thermoplastic Olefinic Elastomer)) (manufactured by Basell Corporation, trade name "Cataroy (model number Q100F)", melting point 143°C, crystallization temperature 96°C). RPTO is a propylene-based random block copolymer that is sequentially polymerized using a Ziegler catalyst. EL4 is an ethylene butene block copolymer (manufactured by Mitsui Chemicals, Inc., trade name "Tafmer (trademark) (model number DF605)", melting point 50° C. or lower).

EL5 is a hydrogenated styrenic thermoplastic elastomer obtained by hydrogenating the double bonds of a block copolymer made of styrene and butadiene (manufactured by Asahi Kasei Corporation, product name: "Tuftec (trademark) (model number H1041)")

In Tables 2, 3, and 4, the elastomers shown in EL1, EL2, EL3, EL4, and EL5 are abbreviated as 6200P, 6202, Q100F, DF605, and H1041, respectively.

Examples 1 to 5, Comparative Examples 1 to 9
(Extrusion foaming process)
Polyolefin resins and elastomers of the types and amounts (mass%) shown in Table 2 (Examples 1 to 5), Table 3 (Comparative Examples 1 to 4), and Table 4 (Comparative Examples 5 to 9), and additions described below. The agent was supplied to an extruder with a diameter of 65 mm, and melted and kneaded in the extruder to obtain a resin melt. Furthermore, carbon dioxide (CO ₂ ) was pressurized as a foaming agent into the extruder and kneaded with the resin melt to obtain a foamable resin melt. The foamable resin melt was charged into an accumulator connected to an extruder. Then, at a foaming temperature of 170° C., the foamable resin melt was extruded into a normal pressure region through an annular die placed at the tip of an accumulator and foamed, thereby forming a cylindrical foamed parison.

(Pre-blow process)
A two-part mold was placed directly below the annular die, and a cylindrical foam parison formed in the extrusion foaming process was placed between the molds. Furthermore, after the opening of the foamed parison is closed below the mold using a pinch, pre-blow air is blown into the foamed parison, and the two-part mold is further closed, allowing foaming to occur in the mold. The parison was pinched.

(Blow molding process)
Blow air is blown from a blow pin into the inside of the foamed parison sandwiched between the molds, and the air is sucked through holes provided in the mold to reduce the pressure in the space between the outer surface of the foamed parison and the inner surface of the mold. This pressed the outer surface of the foamed parison against the inner surface of the mold. The foamed parison was then shaped to correspond to the inner surface of the mold. After shaping and cooling, the mold, which is a mold, was opened, the molded product was taken out, and burrs and pockets were removed. As a result, a foam blow-molded article was obtained. The obtained foam blow molded article was formed into a hollow shape, and was formed into a shape corresponding to a duct having a generally rectangular cylindrical cross section and a maximum length of 650 mm and a maximum width of 180 mm. Note that the hollow portion of the foam blow-molded product may be particularly referred to as the hollow portion.

Note that the descriptions (description of abbreviations) of the types of polyolefin resins and elastomers (in the "Type" column) shown in Tables 2, 3, and 4 correspond to the types of polyolefin resins and elastomers shown in Table 1. . In Table 2, Table 3, and Table 4, the numerical values shown in the column immediately below the description of the type of polyolefin resin are branched polypropylene and linear polypropylene when the sum of branched polypropylene and linear polypropylene in the polyolefin resin is 100. This corresponds to the blending ratio (mass%) of each type of polypropylene. Further, the numerical value shown in the column immediately below the description of the type of elastomer corresponds to the amount (parts by mass) of the elastomer to be blended with respect to 100 parts by mass of the polyolefin resin.

In addition, the mixed resin contains 0.9 parts by mass of carbon black and 2 parts by mass of talc as additives for a total of 100 parts by mass of the polyolefin resin (A) and the olefin thermoplastic elastomer (B). They were added as carbon black masterbatch (45% masterbatch (MB)) and talc masterbatch (20% masterbatch (MB)). The carbon black masterbatch is manufactured by B&Tech Corporation and has a trade name of "PP Black Master Batch, BT920F-JSJ". The talc masterbatch is manufactured by Matsumura Sangyo and has the trade name "High Filler #12" (talc concentration 20% by mass, median diameter 7.5 μm). Note that talc can function as a bubble regulator.

The amount of blowing agent injected (mol/kg) is as shown in Table 2, Table 3, and Table 4. Note that the amount of blowing agent injected shown in Tables 2, 3, and 4 is the amount (mol/kg) per 1 kg of the mixed resin of polyolefin resin and elastomer.

(Physical properties of foam blow molded product)
The physical properties of each foam blow molded article obtained in Examples 1 to 5 and Comparative Examples 1 to 9 include apparent density (kg/m ³ ), thickness (mm), closed cell ratio (%), and flexural modulus. (MPa) was measured. The results are shown in Tables 2, 3 and 4.

The apparent density, closed cell ratio, and flexural modulus of the foam blow-molded product were measured by the methods described above.

(Thickness of foam blow molded product)
The thickness of the foam blow-molded article indicates the average thickness of the foam blow-molded article, and is a value measured by the following method. Vertical cross sections with respect to the longitudinal direction of the foam blow-molded article are obtained at five parts in total, including the longitudinal center portion, the vicinity of both longitudinal end portions, and the intermediate portion between the center portion and both end portions. The thickness (wall thickness) of the foam blow-molded product was measured at 6 points equally spaced in the circumferential direction of each vertical cross section, and the maximum and minimum values were excluded from the obtained thickness measurements at 30 points. The arithmetic mean value of was taken as the average thickness of the foam blow-molded product.

(Evaluation of foam blow molded product)
The foam blow molded articles obtained in Examples 1 to 5 and Comparative Examples 1 to 9 were evaluated for cold impact resistance and surface smoothness. The results are shown in Tables 2, 3 and 4.

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

(-10℃ falling ball test (1.5m, 1kg))
The foam blow molded article was placed in an atmosphere of -10° C. for 24 hours to condition it. The conditioned foam blow-molded product was placed on a test stand with the flat part facing upward, and a 1 kg iron ball was dropped from 1.5 meters above the flat part to test the foam blow-molded product. Observe for damage. The falling ball test was conducted five times. In addition, if the flat part (flat part) of the foam blow-molded body that the falling ball collided with is bent, and the foam blow-molded body is damaged due to force being applied to areas other than the flat part (places that are off the flat part), The falling ball test was performed again without counting the number of falling ball tests. Based on the results of the falling ball test, the cold impact resistance of the foam blow-molded product was evaluated based on the following criteria.

A (very good): The foam blow-molded product does not crack.
B (Good): Cracks are observed in the foam blow-molded product, but no scattering of fragments is observed.
C (Poor): The blow-molded foam was cracked, and the broken pieces of the blow-molded foam were scattered.

For each Example and Comparative Example, 10 samples were prepared as foam blow-molded bodies for conducting a -10°C falling ball test, and each sample was used to evaluate the cold impact resistance of the foam blow-molded bodies. The number of samples with a result of A or B (number of good samples) was counted. The results are shown in Tables 2, 3 and 4.

(Evaluation of surface smoothness)
The surface smoothness of the foam blow-molded article refers to the smoothness of the inner surface of the hollow portion of the foam blow-molded article. The surface smoothness of the foam blow-molded article was measured by cutting out a flat part of the hollow part of the hollow foam blow-molding article and visually observing the inner surface of the foam blow-molded article in the flat part. The surface smoothness of the foam blow-molded product was measured according to the following criteria.

A (good): When the inner surface of the hollow part of the foam blow-molded product is visually observed, the difference in height between adjacent irregularities (difference between the bottom position of the concave part and the tip position of the convex part) is 1 mm or more. The number of formation points is one or less per 100 cm ² of the inner surface (including cases where no unevenness is observed on the inner surface of the hollow part).
B (Poor): When the inner surface of the hollow part of the foam blow-molded product is visually observed, the difference in height between adjacent asperities (difference between the bottom position of the concave part and the tip position of the convex part) is 1 mm or more. There are two or more formation locations per 100 cm ² area on the inner surface of the hollow part.

In Tables 2, 3, and 4, the column for surface smoothness includes the number of recognized unevenness formation locations in addition to the above evaluation results. For example, in the foam blow molded articles obtained in Examples 1 to 5, the number of unevenness formation locations was 0 (that is, no unevenness was observed on the inner surface).

In Examples 1 to 5, as shown in Table 2, it was confirmed that foam blow-molded products with excellent cold impact resistance and surface smoothness were obtained. It was also confirmed that the flexural modulus of the foam blow-molded product had a value corresponding to the rigidity generally required for applications such as ducts.

In Comparative Examples 1 and 2, the blending ratio of polyolefin resin and elastomer in the mixed resin was changed compared to Example 2, and as shown in Table 3, the impact resistance and surface required for the foam blow-molded product were improved. It was not possible to achieve both smoothness and smoothness.

In Comparative Examples 3 to 6, the type of elastomer was changed compared to Example 1, etc., and as shown in Tables 3 and 4, the impact resistance and surface smoothness required for foam blow-molded products were improved. It was not possible to achieve both.

In Comparative Example 7 and Comparative Example 8, the blending amount of linear block polypropylene (a) was changed compared to Example 1, etc., and as shown in Table 4, the impact resistance required for the foam blow molded product was improved. It was not possible to achieve both surface smoothness and surface smoothness. Furthermore, in Comparative Examples 7 and 8, as shown in Table 4, the values of the flexural modulus were lower than those of Examples 1 to 5, and the rigidity of the foam blow-molded products was insufficient.

In Comparative Example 9, linear homopolypropylene was used instead of the linear block polypropylene used in Example 1, etc., and as shown in Table 4, it achieved the impact resistance and surface smoothness required for a foam blow-molded product. I was unable to achieve sexual compatibility.

The manufacturing method and examples of the present invention described above are merely examples, and the present invention is not limited thereto. In the technology disclosed as the present invention, for example, various attributes of the branched homopolypropylene (a1) may be combined. In the technology disclosed as the present invention, for example, the branched homopolypropylene (a1) may have a specific melt tension and a specific melting point. The same applies not only to the branched homopolypropylene (a1) but also to the linear block polypropylene (a2), the olefin thermoplastic elastomer (B), and the recovered raw material. However, the combinations listed here are just examples and are not limited thereto.

Claims

A method for producing a foamed 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 olefinic thermoplastic elastomer (B),
The polyolefin resin (A) consists of a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the branched homopolypropylene (a1) and the linear block polypropylene (a2) The mass ratio [(a1):(a2)] is 50:50 to 93:7,
The olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer consisting of a crystalline olefin polymer block and a conjugated diene compound polymer block,
In the mixed resin, the amount of the olefin thermoplastic elastomer (B) based on 100 parts by mass of the polyolefin resin (A) is 20 parts by mass or more and 40 parts by mass or less.
The melting point of the olefinic thermoplastic elastomer (B) is 80°C or more and 100°C or less,
A method for producing a foam blow-molded article according to claim 1.
The linear block polypropylene (a2) has a flexural modulus of 1000 MPa or more and 1500 MPa or less,
The method for producing a foam blow-molded article according to claim 1 or 2.
The melt flow rate (230° C., load 2.16 kg) of the olefinic thermoplastic elastomer (B) is 1 g/10 min or more and 10 g/10 min or less,
A method for producing a foam blow-molded article according to any one of claims 1 to 3.
A foam blow-molded product of a mixed resin of a polyolefin resin (A) and an olefin thermoplastic elastomer (B),
The polyolefin resin (A) consists of a branched homopolypropylene (a1) and a linear block polypropylene (a2), and the branched homopolypropylene (a1) and the linear block polypropylene (a2) The mass ratio [(a1):(a2)] is 50:50 to 93:7,
The olefin thermoplastic elastomer (B) is a hydrogenated product of a triblock copolymer consisting of a crystalline olefin polymer block and a conjugated diene compound polymer block,
In the mixed resin, the foamed blow-molded article has a blending amount of the olefin thermoplastic elastomer (B) with respect to 100 parts by mass of the polyolefin resin (A) from 20 parts by mass to 40 parts by mass.