Foamed molded article and method for producing the same

Abstract

The present invention provides a thermoplastic polyester elastomer resin foamed molded article having excellent lightness, resilience, and surface smoothness. The foamed molded article comprises a thermoplastic polyester elastomer resin component forming a continuous phase, wherein a hard segment composed of a polyester composed of an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol is bonded to a soft segment of at least one selected from an aliphatic polyether, an aliphatic polyester, and an aliphatic polycarbonate. The foamed molded article comprises a surface layer from the surface of the foamed molded article to a depth of 1000 μm, which is composed solely of foamed regions having no non-foamed portions having a cell density of 10% or less, or a surface layer having a mixture of foamed regions having the non-foamed portions and foamed regions having no non-foamed portions, and a density of 0.01 to 0.70 g / cm 3 .

Description

Technical Field

[0001] The present invention relates to a foamed molded article in which a resin component containing a thermoplastic polyester elastomer produced using back pressure forms a continuous phase. More specifically, the foamed molded article of the present invention is a foamed molded article having excellent rebound resilience and surface smoothness, and can provide a foamed molded article having a high expansion of 2 times or more. Background Art

[0002] Thermoplastic polyester elastomers are materials with excellent injection and extrusion moldability, high mechanical strength, rubber properties such as elastic recovery, impact resistance, and flexibility, and excellent cold resistance. They are used in applications such as automotive parts, electrical and electronic components, fibers, films, and moving parts.

[0003] Thermoplastic polyester elastomers are used in automotive parts, particularly those used in high-temperature environments and automotive interior components, due to their excellent heat aging resistance, light resistance, and wear resistance. Furthermore, with the recent advancement in lightweighting of resin parts, the use of foamed molded articles is one of the means to achieve this goal.

[0004] One method for achieving lightweight, high-expansion foaming is core-back injection foaming, in which the mold moves in the mold opening direction during foaming. This method not only enables high-expansion foaming of more than 2 times, but also increases resilience by miniaturizing the bubbles in the foamed layer (Patent Document 1).

[0005] However, the foamed molded body manufactured by the core-backward injection foam molding method has a non-foamed skin layer in the surface layer, the foamed layer in the inner layer, and a sandwich structure of the non-foamed skin layer and the foamed layer in the thickness direction. Due to the presence of the non-foamed skin layer, the resilience of the foamed layer is alleviated. At the same time as the resilience is reduced, unevenness is generated due to defects such as swirl marks and dents on the surface of the molded body, resulting in poor surface smoothness.

[0006] In addition, the short-shot injection foam molding method can produce a foamed molded article with a thin skin layer, but has a problem of low expansion ratio and poor lightweight properties (Patent Document 2).

[0007] Furthermore, as a foam suitable for automobile seats, a high-resilience urethane foam having a rebound rate of 60% or more is suitable. Although Patent Document 3 proposes a production method for this, the urethane foam generates cyanide gas during combustion, which poses an environmental pollution problem.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent No. 6358369

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-68819

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2003-342343 Summary of the Invention

[0013] [Problems to be solved by the invention]

[0014] The present invention has been made in view of the above-mentioned state of the prior art, and an object of the present invention is to provide a thermoplastic polyester elastomer resin foam molded product having excellent lightness, resilience and surface smoothness.

[0015] [Technical means to solve the problem]

[0016] To achieve the above-mentioned purpose, the inventors have conducted in-depth research on the composition of the surface layer in a foamed article of a thermoplastic polyester elastomer. It was found that by controlling the foaming area of ​​the surface layer and controlling the bubbles to a specific size, a resin foamed article having extremely high rebound resilience and excellent surface smoothness can be obtained. It was further found that by applying a back-pressure foaming injection molding method in which gas is injected into the mold cavity of a mold and molten thermoplastic resin is ejected under pressure, the above-mentioned high-quality polyester elastomer foamed article can be easily manufactured and provided. That is, it was found that the properties (melt tension, crystallization temperature, gas retention, etc.) of the thermoplastic polyester elastomer are suitable for the back-pressure foaming molding method, can withstand the back-pressure pressurization and decompression process, and can obtain the target foamed article having high foaming and surface smoothness, thereby completing the present invention.

[0017] That is, the present invention consists of the following (1) to (5).

[0018] (1) A foamed molded article, wherein the continuous phase is formed by a resin component and the density is 0.01 to 0.70 g / cm 3 The resin component comprises a thermoplastic polyester elastomer composed of a hard segment composed of a polyester containing an aromatic dicarboxylic acid, an aliphatic and / or an alicyclic diol as a component and a soft segment composed of at least one selected from an aliphatic polyether, an aliphatic polyester and an aliphatic polycarbonate,

[0019] The present invention relates to a foamed molded body having a surface layer which is formed only of a foamed area in which a non-foamed portion having a bubble density of 10% or less is not present, and a foamed molded body having a surface layer in which foamed areas in which the non-foamed portion is present are mixed with foamed areas in which the non-foamed portion is not present.

[0020] (2) A foamed molded article according to (1), characterized in that a flat cell layer having an average cell aspect ratio of 4.0 to 15.0 is present in the foamed region of the surface layer where no non-foamed portion exists.

[0021] (3) A foamed molded article according to (1) or (2), characterized in that, further, in an inner layer deeper than 1000 μm from the surface, there is a circular bubble layer having an average aspect ratio of bubbles of 1.0 to 2.0.

[0022] (4) A method for manufacturing a foamed molded article, characterized in that a foam injection molding method based on a back pressure method is used, wherein pressurized gas is injected into the mold cavity of the mold from the moment the mold is completely closed, and when the gas pressure in the mold cavity reaches a specific pressure, a resin component containing a molten thermoplastic polyester elastomer is injected together with a chemical foaming agent and / or an inert gas in a supercritical state, and immediately after 10 to 55% of the volume of the mold cavity is filled with the resin component or after a specific period of time, the gas is rapidly exhausted.

[0023] (5) A method for producing a foamed molded article according to (4), characterized in that the inert gas in a supercritical state is nitrogen.

[0024] Effects of the Invention

[0025] The thermoplastic polyester elastomer resin foam molded article of the present invention not only exhibits excellent lightness and extremely high rebound resilience, but also has excellent surface smoothness. Furthermore, due to its high expansion ratio, uniform foaming state, high heat resistance, water resistance, and molding stability, it can provide a foam molded article suitable for parts requiring high reliability. Furthermore, by using a foam injection molding method based on the back pressure method, foam molded articles with the aforementioned excellent properties can be obtained in any desired shape by preparing a corresponding mold, even without post-processing such as cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [ Figure 1 ] A schematic diagram illustrating an example of a method for manufacturing a foamed molded article of the present invention.

[0027] [ Figure 2 ] A schematic diagram of the foamed molded body (B) of the present invention, (X) is a surface viewing angle diagram, (Y) is a cross-sectional view when cut along the ww' plane, and (Z) is a cross-sectional view when cut along the vv' plane.

[0028] [ Figure 3 ] A schematic diagram of the foamed molded body (A) of the present invention, (X) is a surface viewing angle diagram, (Y) is a cross-sectional view when cut along the ww' plane, and (Z) is a cross-sectional view when cut along the vv' plane.

[0029] [ Figure 4 ] A cross-sectional photograph near the surface of the foaming molded body of Example 1 (the uppermost part of the photograph is the surface).

[0030] [ Figure 5 ] A cross-sectional photograph near the surface of the foamed molded body of Comparative Example 3 (the uppermost part of the photograph is the surface).

[0031] Explanation of symbols

[0032] 1 mold (for fixing)

[0033] 2 molds (for mobile use)

[0034] 3 cavities

[0035] 4Injection molding machine

[0036] 4a Plasticizing area

[0037] 5 gas cylinders

[0038] 6 Booster pump

[0039] 7. Pressure control valve

[0040] 8 Back pressure device

[0041] 9Suction solenoid valve

[0042] 10 Exhaust solenoid valve

[0043] 21 non-foaming part

[0044] 22 surface layer

[0045] 23 inner layer

[0046] 24 There is no foaming area with non-foaming parts

[0047] 25 Foaming area with non-foaming part DETAILED DESCRIPTION

[0048] Hereinafter, the foamed molded article of the present invention will be described in detail.

[0049] [Thermoplastic polyester elastomer]

[0050] The thermoplastic polyester elastomer used in the present invention is composed of a hard segment and a soft segment. The hard segment is composed of polyester. As the aromatic dicarboxylic acid constituting the hard segment polyester, conventional aromatic dicarboxylic acids can be widely used, although there is no particular limitation. As the main aromatic dicarboxylic acid, terephthalic acid or naphthalene dicarboxylic acid (preferably 2,6-naphthalene dicarboxylic acid among isomers) is preferred. Among all the dicarboxylic acids constituting the hard segment polyester, the content of these aromatic dicarboxylic acids is preferably 70 mol% or more, more preferably 80 mol% or more. As other dicarboxylic acid components, aromatic dicarboxylic acids such as diphenyl dicarboxylic acid, isophthalic acid, and 5-sodiosulfoisophthalic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and tetrahydrophthalic anhydride, and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, and hydrogenated dimer acid can be cited. These can be used within a range that does not significantly lower the melting point of the resin, and their content is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total acid components.

[0051] In the thermoplastic polyester elastomer used in the present invention, a wide range of conventional aliphatic or alicyclic diols can be used as the aliphatic or alicyclic diols constituting the hard segment polyester. While not particularly limited, preferred are alkylene glycols having 2 to 8 carbon atoms. Specifically, examples include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. Among these, ethylene glycol and 1,4-butanediol are preferred.

[0052] As the component constituting the hard segment polyester, in terms of physical properties, moldability, and cost-effectiveness, it is preferably composed of butylene terephthalate units (units composed of terephthalic acid and 1,4-butanediol) or butylene naphthalate units (units composed of 2,6-naphthalene dicarboxylic acid and 1,4-butanediol).

[0053] Furthermore, when a suitable aromatic polyester is prepared in advance as the polyester constituting the hard segment of the thermoplastic polyester elastomer used in the present invention and then copolymerized with the soft segment component, the aromatic polyester can be readily obtained by conventional polyester production methods. Furthermore, the polyester preferably has a number average molecular weight of 10,000 to 40,000.

[0054] The soft segment of the thermoplastic polyester elastomer used in the present invention is at least one selected from aliphatic polyethers, aliphatic polyesters, and aliphatic polycarbonates.

[0055] Examples of the aliphatic polyether include poly(oxyethylene) glycol, poly(oxypropylene) glycol, poly(oxytetramethylene) glycol, poly(oxyhexamethylene) glycol, poly(oxytrimethylene) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide adducts of poly(oxypropylene) glycol, and copolymers of ethylene oxide and tetrahydrofuran. Among these, poly(oxytetramethylene) glycol and ethylene oxide adducts of poly(oxypropylene) glycol are preferred in view of elastic properties.

[0056] Examples of the aliphatic polyester include poly(ε-caprolactone), polyenantholactone, polyoctalactone, and polybutylene adipate. Among these, poly(ε-caprolactone) and polybutylene adipate are preferred in terms of elastic properties.

[0057] Aliphatic polycarbonates are preferably composed primarily of aliphatic diol residues having 2 to 12 carbon atoms. Examples of these aliphatic diols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,9-nonanediol, and 2-methyl-1,8-octanediol. In particular, aliphatic diols having 5 to 12 carbon atoms are preferred in view of the flexibility and low-temperature properties of the resulting thermoplastic polyester elastomer. These components may be used alone or in combination of two or more as needed, as described below.

[0058] As the aliphatic polycarbonate diol constituting the soft segment of the thermoplastic polyester elastomer used in the present invention and having good low-temperature properties, a substance having a low melting point (for example, below 70°C) and a low glass transition temperature is preferred. Generally, the aliphatic polycarbonate diol composed of 1,6-hexanediol used to form the soft segment of the thermoplastic polyester elastomer has good low-temperature properties because its glass transition temperature is as low as about -60°C and its melting point is also about 50°C. In addition, among the above-mentioned aliphatic polycarbonate diols, for example, the aliphatic polycarbonate diol obtained by copolymerizing an appropriate amount of 3-methyl-1,5-pentanediol has a slightly higher glass transition point than the original aliphatic polycarbonate diol, but because its melting point is lowered or it becomes amorphous, it is equivalent to an aliphatic polycarbonate diol with good low-temperature properties. For example, an aliphatic polycarbonate diol composed of 1,9-nonanediol and 2-methyl-1,8-octanediol has a sufficiently low melting point of approximately 30°C and a glass transition temperature of approximately -70°C, and therefore corresponds to an aliphatic polycarbonate diol having excellent low-temperature properties.

[0059] From the viewpoint of solving the problems of the present invention, the soft segment of the thermoplastic polyester elastomer used in the present invention is preferably an aliphatic polyether.

[0060] The thermoplastic polyester elastomer used in the present invention is preferably a copolymer containing terephthalic acid, 1,4-butanediol, and poly(oxytetramethylene) glycol as its main components. Of the dicarboxylic acid components constituting the thermoplastic polyester elastomer, terephthalic acid preferably accounts for 40 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. Of the diol components constituting the thermoplastic polyester elastomer, the combined amount of 1,4-butanediol and poly(oxytetramethylene) glycol preferably accounts for 40 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

[0061] The number average molecular weight of the poly(oxytetramethylene) glycol is preferably 500 to 4000. If the number average molecular weight is less than 500, it may be difficult to exhibit elastomeric properties. On the other hand, if the number average molecular weight is greater than 4000, compatibility with the hard segment component is reduced, making it difficult to copolymerize into a block structure. The number average molecular weight of the poly(oxytetramethylene) glycol is more preferably 800 to 3000, and even more preferably 1000 to 2500.

[0062] The thermoplastic polyester elastomer used in the present invention preferably has a soft segment content of 25 to 90% by mass, more preferably 40 to 90% by mass, even more preferably 55 to 90% by mass, and particularly preferably 65 to 90% by mass. If the soft segment content is less than 25% by mass, the rebound resilience is poor due to high crystallinity, while if it exceeds 90% by mass, the crystallinity is reduced, which tends to result in poor foaming properties.

[0063] The thermoplastic polyester elastomer used in the present invention can be produced by known methods. For example, methods include a method of polycondensing the resulting reaction product by transesterifying a lower alcohol diester of a dicarboxylic acid, an excess of a low-molecular-weight diol, and a soft segment component in the presence of a catalyst; a method of polycondensing the resulting reaction product by transesterifying a dicarboxylic acid, an excess of a diol, and a soft segment component in the presence of a catalyst; a method of pre-preparing a hard segment polyester and then randomizing it by adding a soft segment component to the polyester via transesterification; a method of linking the hard and soft segments with a chain linker; and a method of adding poly(ε-caprolactone) to the hard segment when poly(ε-caprolactone) is used as the soft segment.

[0064] [Resin component containing thermoplastic polyester elastomer]

[0065] In the present invention, the thermoplastic polyester elastomer may be mixed with the crosslinking agent and additives described below. In the present invention, a composition containing a thermoplastic polyester elastomer and any of these optional crosslinking agents and additives is referred to as a "thermoplastic polyester elastomer-containing resin component," sometimes simply referred to as a "thermoplastic polyester elastomer resin." The thermoplastic polyester elastomer is preferably contained in this resin component in an amount of 80% by mass or greater, more preferably 90% by mass or greater, even more preferably 95% by mass or greater, and may even be 100% by mass.

[0066] A crosslinking agent may be mixed with the thermoplastic polyester elastomer as needed, as long as it does not impair the effects of the present invention. Such a crosslinking agent is not particularly limited as long as it is reactive with the hydroxyl or carboxyl groups of the thermoplastic polyester elastomer. Examples thereof include epoxy crosslinking agents, carbodiimide crosslinking agents, isocyanate crosslinking agents, acid anhydride crosslinking agents, silanol crosslinking agents, melamine resin crosslinking agents, metal salt crosslinking agents, metal chelate crosslinking agents, and amino resin crosslinking agents. It should be noted that the crosslinking agents may be used alone or in combination of two or more.

[0067] The amount (content) of the crosslinking agent used can be appropriately adjusted according to the extrusion conditions, the desired expansion ratio, etc., and is, for example, preferably 0.1 to 4.5 parts by mass, more preferably 0.1 to 4 parts by mass, and even more preferably 0.1 to 3 parts by mass relative to 100 parts by mass of the thermoplastic polyester elastomer.

[0068] Furthermore, in addition to the crosslinking agent described above, various additives, fillers, and other types of polymers may be mixed into the thermoplastic polyester elastomer used in the present invention, depending on the intended purpose. The types of additives are not particularly limited, and various additives commonly used in foam molding may be used. Specifically, examples of additives include known hindered phenol-based, sulfur-based, phosphorus-based, and amine-based antioxidants, hindered amine-based antioxidants, benzotriazole-based, phenyl ketone-based, benzoate-based, triazole-based, nickel-based, and salicylic acid-based light stabilizers, ultraviolet light absorbers, lubricants, crystal nucleating agents, fillers, flame retardants, flame retardant aids, mold release agents, antistatic agents, molecular weight regulators such as peroxides, metal deactivators, organic and inorganic nucleating agents, neutralizers, antacids, antibacterial agents, fluorescent whitening agents, organic and inorganic pigments and dyes, and organic and inorganic phosphorus compounds for the purpose of imparting flame retardancy and thermal stability. The compounding amounts (contents) of additives, fillers, and other types of polymers can be appropriately selected within a range that does not impair the formation of cells, and the compounding amounts (contents) generally used for molding of thermoplastic resins can be adopted.

[0069] The composition and composition ratio of the thermoplastic polyester elastomer used in the present invention can be determined by dissolving a sample in a solvent such as deuterated chloroform and measuring the 1The proton integration ratio was calculated from H-NMR.

[0070] The MFR (melt flow rate) of the thermoplastic polyester elastomer resin used in the present invention, when measured at a load of 2,160 g and a measurement temperature of 230°C according to the measurement method described in ASTM D1238, is preferably 5 to 40 g / 10 min in order to suitably obtain the foamed molded article of the present invention. The MFR is more preferably 10 to 30 g / 10 min.

[0071] [Foamed molded article]

[0072] The foamed molded article of the present invention is obtained using the aforementioned polyester elastomer resin and is completely free of post-processing such as cutting. In other words, the molded article has no cut surfaces. The cut surfaces in this context refer to surfaces resulting from cutting away non-foamed surface layers, etc., from the foamed molded article and do not refer to surfaces resulting from the removal of unnecessary portions from the mold, such as the gate.

[0073] The foamed molded article of the present invention is a foamed molded article (A) which is a surface layer from the surface of the foamed molded article to a depth of 1000 μm, and is composed only of a foamed area without a non-foamed portion having a bubble density of less than 10% (hereinafter, sometimes referred to as the surface layer (A)), or a foamed molded article (B) which has a surface layer in which foamed areas with the non-foamed portion and foamed areas without the non-foamed portion are mixed (hereinafter, sometimes referred to as the surface layer (B)). It should be noted that the surface layer here refers to a surface layer composed of a single surface. For example, in the case of a rectangular parallelepiped foamed molded article, it has 6 surface layers, and this refers to one of them. In the case of a rectangular parallelepiped foamed molded article, all 6 sides of the foamed molded article (A) are composed of the surface layer (A), and at least one side of the foamed molded article (B) is composed of the surface layer (B). Therefore, a foamed body in which the top and bottom of a rectangular parallelepiped foamed body are composed only of foamed areas with non-foamed parts, and the side is composed only of foamed areas without non-foamed parts (i.e., a foamed body manufactured by core-back injection foaming molding method and having a non-foamed skin layer) does not belong to the above-mentioned foamed body (B). In the foamed body (B), the area of ​​the foamed area with non-foamed parts in the area of ​​a single surface is preferably 60% or less, more preferably 50% or less, and further preferably 30% or less. If the area of ​​the foamed area with non-foamed parts is 0%, it becomes the above-mentioned foamed body (A). In addition, in the foamed body (B), the area of ​​the foamed area with non-foamed parts is preferably 50% or less, more preferably 40% or less, and further preferably 25% or less relative to the total surface area of ​​the foamed body. In the above-mentioned foamed body (A), the rebound resilience is improved by making the non-foamed parts without bubbles absent in the surface layer of the foamed body. In the above-mentioned foaming molded article (B), since there are few bubbles in the foaming area of ​​the non-foaming part, the rebound resilience is low, and the rebound resilience of the foaming area without the non-foaming part becomes high. In one foaming molded article, different rebound resilience can be present in different areas. It should be noted that the surface of the molded article of the present invention is not necessarily a plane, but can also be a curved surface, a surface with protrusions, etc. An inventive point of the present invention is that a foaming molded article with any desired shape can be obtained by preparing a corresponding mold.

[0074] The non-foamed portion is a phase formed by a thermoplastic polyester elastomer resin having almost no bubbles, and is a portion having a bubble density of 10% or less. Here, the bubble density is calculated by image processing a cross-sectional photograph of a sample observed in a cross-sectional area of ​​the surface layer of the foamed molded body taken by a scanning electron microscope. The details are as described in the various descriptions of the embodiments. In the foamed body of the present invention, the portion that does not belong to the non-foamed portion is referred to as a foamed portion or a foamed layer. The surface of the foamed portion is formed by contacting the molten resin before foaming or the foamed molten resin with the mold surface to form an extremely thin resin layer (i.e., a thin skin), and its thickness is 50 μm or less. In the present invention, since the non-foamed portion having a bubble density of less than 10% is measured in an area of ​​200 μm × 200 μm, the thin resin layer on the surface of the foamed portion does not belong to the "non-foamed portion having a bubble density of less than 10%".

[0075] The foaming molded article of the present invention does not have a sandwich structure in which non-foaming layers are provided on both sides of the foaming layer as a whole (in other words, a structure in which the foaming layer is sandwiched by non-foaming layers on both sides). The foaming molded article of the present invention is a foaming molded article (A) or a foaming molded article (B) as described above. In other words, the foaming molded article (A) is a foaming molded article that does not have a non-foaming layer and is composed solely of a foaming layer. In other words, the foaming molded article (B) is a foaming molded article in which a non-foaming portion (non-foaming skin layer) exists only on part of the surface of the foaming molded article. There is no particular limitation on the size of the foaming molded article of the present invention. As long as the mold can be manufactured, a foaming molded article of the desired size can be obtained.

[0076] In the present invention, bubbles with an aspect ratio of 2.0 or less are defined as round bubbles, and bubbles with an aspect ratio greater than 2.0 are defined as flat bubbles. The foamed molded article of the present invention preferably has a flat bubble layer with a large average aspect ratio of bubbles in the foamed area of ​​the surface layer where no non-foamed part exists. The flat bubbles in the surface layer have a larger aspect ratio, and the surface of the foamed molded article becomes smoother and has an excellent appearance. The average aspect ratio of the flat bubble layer is preferably 4.0 to 15.0. If it is less than 4.0, the surface of the molded article becomes uneven and the surface smoothness is impaired. If it is greater than 15.0, the bubbles are stretched and cause bubble breakage, resulting in unevenness on the surface of the molded article, and there is a tendency for the surface smoothness to be impaired. In order to have excellent surface smoothness, the average aspect ratio of the flat bubble layer is more preferably 4.0 to 10.0. Furthermore, it is preferred that a round bubble layer with a small average aspect ratio of bubbles exists in the inner layer deeper than 1000 μm from the surface. The circular bubbles in the inner layer have a smaller aspect ratio, which improves the rebound resilience. The average aspect ratio of the circular bubble layer is preferably 1.0 to 2.0. If it is greater than 2.0, the rebound resilience tends to decrease. The bubbles in the surface layer are flat bubbles because the resin component flows along the surface of the mold during foaming. As the foamed molded article of the present invention, it is preferred to have a flat bubble layer with an average aspect ratio of 4.0 to 15.0 in the foaming area of ​​the surface layer where there is no non-foamed part. Furthermore, it is preferred to have a circular bubble layer with an average aspect ratio of 1.0 to 2.0 in the inner layer deeper than 1000 μm from the surface.

[0077] The foamed layer is composed of a resin continuous phase and independent bubbles. Here, the resin continuous phase refers to a portion that does not have cavities formed by a resin component containing a cured thermoplastic polyester elastomer. The diameter of the bubbles (cell diameter) only needs to be uniform and without variations, and the characteristics vary depending on the size. For exhibiting high resilience, a small cell diameter is advantageous. Specifically, the average cell diameter is preferably 10 to 400 μm. When the average cell diameter is less than 10 μm, the internal pressure of the molded body is low, and there is a tendency for the appearance to deteriorate due to sink marks. On the other hand, when the average cell diameter is greater than 400 μm, the load resistance decreases and the rebound rate tends to decrease. The average cell diameter is more preferably 100 to 400 μm, and further preferably 200 to 400 μm.

[0078] The density of the foamed molded article of the present invention is preferably 0.01 to 0.70 g / cm 3 Since the density of general polyester elastomer is about 1.0~1.4g / cm 3 Therefore, the foamed molded article of the present invention can be said to be sufficiently lightweight. More preferably, it is 0.1 to 0.60 g / cm 3 , more preferably 0.1 to 0.45 g / cm 3 , particularly preferably 0.1 to 0.35 g / cm 3If the density is less than 0.01g / cm 3 Sufficient strength cannot be obtained and mechanical properties tend to deteriorate. If the strength exceeds 0.70 g / cm 3 , there is a tendency for the resilience to deteriorate.

[0079] Foam molding of the present invention is not only lightweight, can also show high rebound rate, and surface smoothness is also excellent. Further, can provide a kind of not only expansion ratio height, and foamed state uniformly has high heat resistance, water resistance, forming stability, also can be applicable to the polyester foam molding of the parts that needs high reliability. Therefore, for example, can be used for following these purposes. But the purposes of foam molding of the present invention, is not limited only to following purposes.

[0080] Examples of the applications include automotive materials, civil engineering products, building supplies, home appliances, office automation equipment, sporting goods, stationery, toys, medical supplies, food containers, and agricultural materials. Specific examples include automotive mechanical parts, engine components, automotive exterior materials, automotive interior parts, cushioning materials, sealing materials, automotive seats, sound insulation materials, door trims, sun visors, automotive shock-absorbing, sound-absorbing, and heat-insulating materials, earthquake-proof materials, cushioning materials, civil engineering joints, icicle prevention panels, protective materials, lightweight soil, embankments, artificial soil, tatami core materials, building insulation materials, building joint materials, door panels, building maintenance materials, reflective materials, industrial pallets, pipes, pipeline covering materials, air conditioning insulation ducts, valve core materials, concrete formwork, televisions, freezers, cooking equipment, washing machines, air conditioners, lighting fixtures, computers, magnetic optical disks, copiers, fax machines, printers, shoes, protectors, gloves, and sporting goods.

[0081] [Method for producing foamed molded article]

[0082] The foaming method of the foamed molded article of the present invention is not particularly limited, but is preferably a method of impregnating a thermoplastic polyester elastomer resin with high-pressure gas and then reducing the pressure (releasing the pressure) to foam. Among them, as a molding method that can achieve uniform foaming in terms of molding periodicity and cost, a foaming injection molding method based on a back pressure method is preferably used, in which a foaming agent and a thermoplastic polyester elastomer resin are melt-mixed and injection-molded, a gas is injected into the mold cavity of the mold, and the molten thermoplastic polyester elastomer resin is injected under pressure. Specifically, Figure 1As shown, a back pressure device 8 is used to inject pressurized nitrogen gas into the mold cavity 3 formed by the clamped molds 1 and 2. Under the pressurized state with a specific pressure, a molten thermoplastic polyester elastomer resin and a chemical foaming agent and / or a supercritical inert gas (hereinafter collectively referred to as the "foaming agent") are initially injected. Immediately after the resin filling is completed, or after a specific time has passed, the gas applied to the mold cavity is rapidly discharged through a solenoid valve 10 using back pressure, thereby foaming the thermoplastic polyester elastomer resin. The specific pressure is preferably 0.01 MPa to 29.0 MPa. The pressure referred to here is gauge pressure. The specific time is preferably 1 to 60 seconds. Here, by moving a mold 2 in the mold opening direction and expanding the volume of the mold cavity 3 before the gas applied to the mold cavity is rapidly and quickly discharged by back pressure, or at the same time as the gas is discharged, or after the gas is discharged, or after a specific time has passed after the gas is discharged, it can also be combined with the core retreat injection foam molding method for obtaining a foamed molded body.

[0083] It should be noted that the thermoplastic polyester elastomer resin and the foaming agent can be mixed in advance in the plasticizing area 4a of the injection molding machine 4 before filling them into the mold cavity 3. When performing the above-mentioned foam molding, by appropriately adjusting the back pressure gas pressure and the resin filling amount according to the material, a foamed molded body with the target foaming ratio and rebound resilience can be obtained. The back pressure gas pressure affects the smallness of the bubbles and the foaming ratio. Even if a low pressure is applied to the mold cavity, the decompression speed is increased, making high-multiple foaming possible. In addition, if a high pressure is applied, the bubbles tend to become smaller by suppressing the gas generated by the foaming agent from being discharged from the resin. However, if the gas pressure becomes too high, the foaming moldability tends to deteriorate. For this reason, the back pressure is preferably 0.01MPa to 29.0MPa, more preferably 0.05MPa to 15.0MPa, and even more preferably 0.5MPa to 10.0MPa. The pressure described here is gauge pressure. Too much resin filling reduces the expansion ratio, while too little not only increases the expansion ratio but also the resilience. Therefore, the resin filling amount is preferably 10% to 55% of the cavity volume, more preferably 10% to 50%, even more preferably 10% to 40%, and particularly preferably 10% to 30%. Under these conditions, foam molding can produce a lightweight foamed molded article with a high resilience.

[0084] The reason why the foamed molded article of the present invention is the foamed molded article (A) or the foamed molded article (B) described above will be described. Figure 2The schematic structure of a foamed molded article (B) is shown. Foamed molded article (A) has no foamed regions 25, which contain non-foamed portions 21, as in foamed molded article (B), and consists solely of foamed regions 24, which do not contain non-foamed portions 21. As described above, a molten thermoplastic polyester elastomer resin, along with a blowing agent, is filled into a mold cavity pressurized by back pressure in an amount ranging from 10% to 55% of the cavity volume. At this point, a portion of the molten resin contacts the mold and cools, forming non-foamed portions. Subsequently, the pressure in the cavity is released, inducing foaming of the thermoplastic polyester elastomer resin. While a foamed molded article is obtained, the non-foamed portions remain in a portion of the surface layer of the foamed molded article (B). Alternatively, by preventing the molten resin from contacting the mold during filling, or by only contacting a very small area, or by releasing the pressure in the cavity before sufficient cooling is achieved, a foamed molded article (A) can be obtained in which the surface layer does not contain non-foamed portions. Note that, near the surface of the foamed region of the surface layer where no non-foamed portion exists, the thermoplastic polyester elastomer resin flows along the surface of the mold during foaming, so that the cells become flat cells.

[0085] The chemical foaming agent that can be used to obtain the foamed molded article of the present invention is a substance added to the resin melted in the resin melting zone of the molding machine as a gas component that becomes a foaming nucleus or a generation source thereof.

[0086] Specifically, as chemical foaming agents, inorganic compounds such as ammonium carbonate, sodium bicarbonate, and azide compounds, as well as organic compounds such as azo compounds, sulfonylhydrazide compounds, and nitroso compounds can be used. Examples of the azide compounds include terephthalazide and p-tert-butylbenzene azide compounds. Further examples of the azo compounds include azodicarbonamide (ADCA), 2,2-azoisobutyronitrile, azohexahydrobenzonitrile, and diazoaminobenzene, among which ADCA is preferably used. Examples of the sulfonylhydrazide compounds include benzenesulfonylhydrazide, 1,3-disulfonylhydrazide benzene, 3,3-disulfonylhydrazide diphenyl sulfone, and 4,4-oxybisbenzenesulfonylhydrazide, and examples of the nitroso compounds include N,N-dinitrosopentaethylenetetramine (DNPT).

[0087] When using a chemical foaming agent as the foaming agent, a foaming agent masterbatch based on a thermoplastic resin with a melting point lower than the decomposition temperature of the chemical foaming agent can be used to uniformly disperse the chemical foaming agent in the thermoplastic polyester elastomer resin. The thermoplastic resin used as the base material is not particularly limited as long as its melting point is lower than the decomposition temperature of the chemical foaming agent. Examples include polystyrene (PS), polyethylene (PE), and polypropylene (PP). In this case, the mixing ratio of the chemical foaming agent to the thermoplastic resin is preferably 10 to 100 parts by mass of the chemical foaming agent per 100 parts by mass of the thermoplastic resin. If the chemical foaming agent is less than 10 parts by mass, the amount of masterbatch relative to the thermoplastic polyester elastomer resin is too high, which may cause a decrease in physical properties. If the amount exceeds 100 parts by mass, masterbatch formation becomes difficult due to dispersibility issues with the chemical foaming agent.

[0088] When using a supercritical inert gas as a foaming agent, carbon dioxide and / or nitrogen can be used as the inert gas. When using supercritical carbon dioxide and / or nitrogen as the foaming agent, the content is preferably 0.05 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin. If the content of supercritical carbon dioxide and / or nitrogen is less than 0.05 parts by mass, uniform and fine bubbles may be difficult to obtain. If it exceeds 30 parts by mass, the surface appearance of the molded article may be impaired.

[0089] It should be noted that supercritical carbon dioxide or nitrogen can be used alone as the blowing agent, or a mixture of carbon dioxide and nitrogen can be used. Compared to thermoplastic polyester elastomer resins, nitrogen tends to form finer bubbles, while carbon dioxide can be injected in a relatively larger amount, which is suitable for achieving a higher expansion ratio. Therefore, the two gases can be mixed arbitrarily to adjust the state of the foamed structure. The mixing ratio during mixing is preferably within the range of a molar ratio of 1:9 to 9:1.

[0090] As the foaming agent used in the present invention, nitrogen in a supercritical state is more preferred from the viewpoint of uniform fine foaming.

[0091] When injecting the molten thermoplastic polyester elastomer resin and the foaming agent together into the mold cavity 3, the molten thermoplastic polyester elastomer resin and the foaming agent may be mixed in the plasticizing area 4a of the injection molding machine 4. In particular, when using supercritical carbon dioxide and / or nitrogen as the foaming agent, for example, the following can be used: Figure 1As shown, there is a method of injecting gaseous carbon dioxide and / or nitrogen directly from a gas cylinder 5 into the injection molding machine 4 or by pressurizing it with a booster pump 6. From the viewpoint of solubility, permeability, and diffusibility in the molten polyester elastomer resin composition, it is necessary for the carbon dioxide and / or nitrogen to be in a supercritical state inside the molding machine.

[0092] Here, a supercritical state refers to a state in which, when the temperature and pressure of a substance producing gas and liquid phases are raised, the gas and liquid phases cease to be distinguishable within a certain temperature and pressure range. These temperatures and pressures are referred to as the critical temperature and critical pressure, respectively. In other words, a substance in a supercritical state possesses the properties of both gas and liquid, and the fluid produced in this state is called a critical fluid. Because such a critical fluid has a higher density than a gas and a lower viscosity than a liquid, it diffuses easily within the substance.

[0093] Example

[0094] The following examples are given to demonstrate the effects of the present invention, but the present invention is not limited to these examples.

[0095] The following raw materials were used in the following Examples and Comparative Examples.

[0096] Thermoplastic polyester elastomer;

[0097] (Polyester elastomer A)

[0098] According to the method described in Japanese Patent Application Laid-Open No. 9-59491, a thermoplastic polyester elastomer having a soft segment content of 76% by mass was prepared using dimethyl terephthalate, 1,4-butanediol, and poly(oxytetramethylene) glycol with a number average molecular weight of 2000 as raw materials. This was referred to as polyester elastomer A.

[0099] (Polyester elastomer B)

[0100] According to the method described in Japanese Patent Application Laid-Open No. 9-59491, a thermoplastic polyester elastomer having a soft segment content of 83% by mass was prepared using dimethyl terephthalate, 1,4-butanediol, and poly(oxytetramethylene) glycol with a number average molecular weight of 2000 as raw materials. This was referred to as polyester elastomer B.

[0101] (Polyester elastomer C)

[0102] According to the method described in Japanese Patent Application Laid-Open No. 9-59491, a thermoplastic polyester elastomer having a soft segment content of 67% by mass was prepared using dimethyl terephthalate, 1,4-butanediol, and poly(oxytetramethylene) glycol having a number average molecular weight of 1000 as raw materials. This was referred to as polyester elastomer C.

[0103] (Polyester elastomer D)

[0104] According to the method described in Japanese Patent Application Laid-Open No. 9-59491, a thermoplastic polyester elastomer having a soft segment content of 55% by mass was prepared using dimethyl terephthalate, 1,4-butanediol, and poly(oxytetramethylene) glycol with a number average molecular weight of 1000 as raw materials. This was referred to as polyester elastomer D.

[0105] (Polyester elastomer E)

[0106] According to the method described in Japanese Patent Application Laid-Open No. 9-59491, a thermoplastic polyester elastomer having a soft segment content of 28% by mass was prepared using dimethyl terephthalate, 1,4-butanediol, and poly(oxytetramethylene) glycol having a number average molecular weight of 1000 as raw materials. This was referred to as polyester elastomer E.

[0107] cross-linking agent;

[0108] (Styrene copolymer): Epoxy crosslinker

[0109] The oil jacket temperature of a 1-liter pressurized stirred tank reactor with an oil jacket was maintained at 200°C. Meanwhile, a monomer mixture consisting of 89 parts by mass of styrene (St), 11 parts by mass of glycidyl methacrylate (GMA), 15 parts by mass of xylene (Xy), and 0.5 parts by mass of di-tert-butyl peroxide (DTBP) as a polymerization initiator was added to a raw material tank. This mixture was continuously supplied from the raw material tank to the reactor at a constant feed rate (48 g / min, residence time: 12 minutes) to maintain the reactor's liquid mass at approximately 580 g. The reaction liquid was continuously withdrawn from the reactor outlet. The internal temperature of the reactor was maintained at approximately 210°C. After 36 minutes from the time the internal temperature of the reactor stabilized, the withdrawn reaction liquid was introduced into a thin-film evaporator maintained at a reduced pressure of 30 kPa and a temperature of 250°C, where volatile components were continuously removed to obtain a styrene-based copolymer. GPC analysis (polystyrene conversion) revealed a mass average molecular weight of 8500 and a number average molecular weight of 3300 for the styrene-based copolymer. In addition, the epoxy value is 670 equivalents / 1×10 6 The g and epoxy value (average number of epoxy groups per molecule) were 2.2, indicating that the polyol had two or more glycidyl groups in one molecule.

[0110] [Resin component containing thermoplastic polyester elastomer (thermoplastic polyester elastomer resin)]

[0111] The polyester elastomers A, B, C, D, and E obtained above were used as they were.

[0112] According to the mixing composition shown in Table 1, the styrene copolymer was melt-kneaded using a twin-screw extruder with respect to 100 parts by mass of polyester elastomer A, and pelletized to obtain pellets A'. The physical properties of each thermoplastic polyester elastomer resin were measured by the methods described below and are shown in Table 1.

[0113] [MFR]

[0114] The MFR (melt flow rate) of the thermoplastic polyester elastomer resin is measured in accordance with the measurement method described in ASTM D1238 at a load of 2160 g and a measurement temperature of 230°C.

[0115] [Table 1]

[0116]

[0117] Examples 1 to 10, Comparative Examples 1 to 2

[0118] The thermoplastic polyester elastomer resin obtained above was then used to produce a foamed molded article using the back pressure method described above. A mold with a clamping force of 10,000 kN and a cavity of 360 mm wide, 190 mm long, and 15.0 mm thick was used. Nitrogen gas at the pressure (back pressure) listed in Table 2 was injected into the cavity of this mold using back pressure. Supercritical nitrogen gas was injected into the molten thermoplastic polyester elastomer resin in the plasticizing zone of an electric injection molding machine equipped with a screw diameter of 60 mm and a screw stroke of 300 mm. The amount of resin listed in Table 2 (resin filling amount relative to the cavity volume) was injected into the cavity of the mold, which had its surface temperature adjusted to 50°C, through the gate (center of the 360 ​​mm wide, 190 mm long surface) in a short shot. Immediately after injection, the back pressure-pressurized nitrogen gas was rapidly discharged, causing the thermoplastic polyester elastomer resin to foam and produce a foamed molded article.

[0119] Comparative Example 1 is a short shot injection foam molding method with a back pressure of 0.

[0120] Comparative Example 3

[0121] The foamed article is produced using the mold expansion method (core-backward injection foam molding). A flat plate mold is used, consisting of a fixed mold and a movable mold. The mold has a cavity width of 360 mm, a length of 190 mm, and a thickness of 3.0 mm when the mold is closed. By withdrawing the core in the mold opening direction, a cavity with the same width and length, but a thickness of 3.0 mm plus the core withdrawal amount (mm), is formed. Specifically, supercritical nitrogen is injected into the plasticizing zone of an electric injection molding machine with a clamping force of 10,000 kN, a screw diameter of 60 mm, and a screw stroke of 300 mm. After the mold, which has been regulated to a surface temperature of 50°C, is completely filled with injection molding, the movable mold is moved 12.0 mm in the mold opening direction to expand the cavity volume, producing the foamed article.

[0122] The foamed molded articles obtained in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Table 2.

[0123] [Composition of Foam]

[0124] The surface of the foamed molded article is visually observed to infer the presence of non-foamed parts by looking at the presence of convexo-concave parts (sink marks) and indentations caused by molding shrinkage. In the case of a foamed molded article where convexo-concave parts and / or indentations are present and it is inferred that there is a non-foamed part, the surface with the non-foamed part facing the center ( Figure 2 The foamed body is cut into pieces as a cross-sectional observation sample. Further, the foamed body is cut into pieces from a surface perpendicular to the cut surface ( Figure 2 The foamed molded body is cut into pieces (the v-v' plane) as a sample for cross-sectional observation. When there are no convexo-concave parts and indentations and it is inferred that there is no foamed molded body with a non-foamed part, the center plane of the foamed molded body ( Figure 3 The foamed body is cut into pieces as a sample for cross-sectional observation. Figure 3 The foamed molded body was cut in half along the v-v' plane to prepare a sample for cross-sectional observation.

[0125] A cross-sectional photograph of a sample for cross-sectional observation in the surface layer of a foamed molded article was taken using a Hitachi High-Technologies SU1510 scanning electron microscope. The cross-sectional photograph was processed, and the cell density was calculated using the following formula within a 200 μm x 200 μm region of the surface layer from the surface of the foamed molded article to a depth of 1000 μm. Portions with a cell density of 10% or less were considered non-foamed areas.

[0126] Bubble density (%) = [total area of ​​bubbles (μm 2 ) / 40,000(μm 2 )]×100

[0127] When it is estimated that the observation area of ​​200 μm×200 μm is a foamed molded body with a non-foamed portion, in the surface layer from the surface to a depth of 1000 μm, there are ( Figure 2 The depth of the white square in the surface layer 22 of the foaming molded body was measured at 5 locations. When it was estimated that there was no non-foamed part in the foaming molded body, in the surface layer from the surface to a depth of 1000 μm, the white square near the surface, near the depth of 500 μm, and near the depth of 1000 μm ( Figure 3 The depth of the white square in the surface layer 22 is measured at 5 locations. If it can be determined from this measurement that there are no non-foamed parts at all three locations from the surface to the depth direction, the area is determined to be an area consisting only of foamed areas with no non-foamed parts.

[0128] Thus, the presence or absence of non-foamed parts is judged, and the products are divided into three categories: a foamed molded body (A) having a surface layer formed only by foamed areas where no non-foamed parts exist, a foamed molded body (B) having a surface layer mixed with foamed areas where non-foamed parts exist and foamed areas where no non-foamed parts exist, and a foamed molded body (C) having a surface layer formed only by foamed areas where non-foamed parts exist (non-foamed skin layer).

[0129] [Ratio of the area of ​​the foamed region to the area of ​​the non-foamed portion]

[0130] In the surface layer (B) of the foamed molded article (B), the area of ​​the foamed region containing the non-foamed portion within the surface area of ​​the foamed molded article is determined by visual observation and from the cross-sectional photographs described above, and its area ratio is calculated using the following formula. If the foamed molded article (B) contains multiple surfaces corresponding to the surface layer (B), the larger ratio is used.

[0131] The ratio of the area of ​​the foamed region with the non-foamed portion (%) = [the area of ​​the foamed region with the non-foamed portion (mm 2 ) / surface area of ​​foamed molded body (mm 2 )]×100

[0132] [Ratio of the area of ​​the foamed region with non-foamed parts to the total surface area]

[0133] The "area of ​​the foamed region with non-foamed portions" is determined in the same manner as the "ratio of the area of ​​the foamed region with non-foamed portions" described above. When there are multiple surfaces corresponding to the surface layer (B) in the foamed molded article (B), the sum of the "areas of the foamed region with non-foamed portions" of all surfaces is calculated. The ratio of the area of ​​the foamed region with non-foamed portions relative to the total surface area of ​​the foamed molded article (B) is calculated using the following formula.

[0134] The ratio of the area of ​​the foamed region with non-foamed parts to the total surface area (%) = [the area of ​​the foamed region with non-foamed parts (mm 2 ) / surface area of ​​foamed body (mm 2 )]×100

[0135] [Average aspect ratio of bubbles in the flat bubble layer and the round bubble layer]

[0136] By Hitachi High-Tech's scanning electron microscope SU1510, a cross-sectional photograph of a cross-sectional observation sample of the foaming molded body was taken. Confirm that there is a layer consisting of flat bubbles in the surface layer from the surface to a depth of 1000 μm, and there is a layer consisting of round bubbles in the inner layer deeper than 1000 μm from the surface. The cross-sectional photograph is subjected to image processing, and the major axis and minor axis of at least 100 adjacent flat bubbles and round bubbles are measured with a vernier caliper. Thus, 100 average aspect ratios (length of major axis / length of minor axis) are obtained, and these are carried out at any three places in each layer. The 3 average values ​​obtained at the three places are averaged to obtain the value obtained, which is used as the average aspect ratio of the flat bubble layer and the round bubble layer, respectively.

[0137] [Density (apparent density)]

[0138] The dimensions of the foamed molded article were measured with a vernier caliper, and its mass was measured with an electronic balance and calculated according to the following formula.

[0139] Density (g / cm 3 ) = mass of foamed molded body / volume of foamed molded body

[0140] [Average cell diameter]

[0141] When measuring the average aspect ratio of the bubbles in the circular bubble layer, the equivalent circle diameter of the circular bubbles is used as the cell diameter, and the average value of these 100 values ​​is calculated. This is performed at any three locations in the circular bubble layer, and the average value of the three average values ​​obtained at the three locations is used as the average cell diameter.

[0142] [Rebound rate]

[0143] The measurement was performed according to the method described in JIS K 6400. Using a manual measuring tester, a steel ball was dropped from a predetermined drop height (H) onto the foamed molded article, and the maximum rebound height (h) was read. The rebound rate was calculated using the following formula.

[0144] Rebound rate (%) = (maximum rebound height (h) / drop height (H)) × 100

[0145] The rebound rate was calculated by taking the average of three measurements within one minute. The rebound rate was defined as the rebound rate (A) for the foamed area without any non-foamed area, and the rebound rate (B) for the foamed area with any non-foamed area.

[0146] [Surface smoothness]

[0147] The surface smoothness of the foamed molded article was visually inspected and evaluated in the following three stages.

[0148] ○: No unevenness was observed on the surface of the molded article

[0149] △: Concave and convex parts of the surface of the molded body are confirmed

[0150] ×: Concavities and convexities are confirmed on the entire surface of the molded article

[0151] [Table 2]

[0152]

[0153] As shown in Table 2, Examples 1 to 10, all within the scope of the present invention, are foamed molded articles (A) consisting solely of foamed regions without non-foamed portions, or foamed molded articles (B) having a surface layer with a mixture of foamed regions with non-foamed portions and foamed regions without non-foamed portions, exhibiting both lightness and high resilience. The foamed molded articles (B) of Examples 2, 3, 5, 6, 8 to 10, and Comparative Examples 1 and 2, all have the largest non-foamed portion on the surface opposite the surface with the gate, and also have non-foamed portions of approximately the same area on the surface with the gate. Furthermore, Examples 2, 3, 5, 6, 8 to 10 show that the foamed regions without non-foamed portions have a higher rebound rate than the foamed regions with non-foamed portions. Furthermore, the foamed molded articles of Examples 1, 4, and 7, consisting solely of foamed regions without non-foamed portions, exhibit excellent surface smoothness because the surface of the entire foamed molded article is composed of flat bubbles. In contrast, in Comparative Example 1, the foaming was performed by the short shot method without using back pressure, and the density of the foamed body was 0.90 g / cm 3 Not only is the weight reduction insufficient, but the flat cells near the surface layer of the foamed molded article are lower than the specified average aspect ratio, resulting in poor surface smoothness. Comparative Example 2 is a foamed molded article using back pressure foaming, but due to the excessively high back pressure, the foaming moldability is poor, and the density of the foamed molded article is 0.76 g / cm 3 Comparative Example 3 was foamed using the core-backward injection foaming method. Although it was sufficiently lightweight, the foamed body as a whole was not only composed of a sandwich structure of non-foamed layers and foamed layers, but also had unevenness on the surface of the molded body as a whole, resulting in poor surface smoothness.

[0154] The cross-sectional photo of the foaming molding of Example 1 is as follows: Figure 4 As shown. It can be confirmed that the surface layer is composed of flat bubbles. The cross-sectional photo of the foaming molded body of Comparative Example 3 is as shown. Figure 5 The surface layer is a non-foamed skin layer.

[0155] Availability in industry

[0156] The foaming molded article of the present invention is not only lightweight but also exhibits an extremely high rebound rate and excellent surface smoothness. Furthermore, a polyester foaming molded article can be provided that is suitable for parts requiring high reliability because it not only has a high expansion ratio but also has a uniform foaming state and high heat resistance, water resistance, and molding stability.

Claims

1. A foamed molded article, wherein the continuous phase is formed by a resin component and the density is 0.01 to 0.70 g / cm 3 The resin component comprises a thermoplastic polyester elastomer composed of a hard segment composed of a polyester containing an aromatic dicarboxylic acid, an aliphatic and / or an alicyclic diol as a component and a soft segment composed of at least one selected from the group consisting of an aliphatic polyether, an aliphatic polyester and an aliphatic polycarbonate, A foamed molded article having a surface layer consisting solely of a foamed region having no non-foamed portion having a cell density of 10% or less as a surface layer from the surface of the foamed molded article to a depth of 1000 μm, or a foamed molded article having a surface layer in which foamed regions having the non-foamed portion and foamed regions having no non-foamed portion are mixed, In the foamed region of the surface layer where no non-foamed portion exists, there is a flat cell layer having an average cell aspect ratio of 4.0 to 15.

0. In the inner layer deeper than 1000 μm from the surface, there is a circular bubble layer with an average aspect ratio of 1.0 to 2.

0.

2. A method for manufacturing a foamed molded article according to claim 1, characterized in that: A foam injection molding method based on a back pressure method is used. Pressurized gas is injected into the mold cavity from the moment the mold is completely closed. When the gas pressure in the mold cavity reaches a specific pressure, a resin component containing a molten thermoplastic polyester elastomer is injected together with a chemical foaming agent and / or a supercritical inert gas. After the mold cavity volume is filled with the resin component to 10-55%, the mold is quickly vented immediately or after a specific period of time. The back pressure is 0.01MPa to 29.0MPa.

3. The method for producing a foamed molded article according to claim 2, wherein: The inert gas in the supercritical state is nitrogen.

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