A foamed molded article made of a thermoplastic polyester elastomer resin composition, and a sound-absorbing material

Abstract

The present invention relates to a molded foam object obtained from a thermoplastic polyester elastomer resin composition, the molded foam object being thin and lightweight and having comfortable cushioning properties and, despite this, being capable of controlling high sound-absorbing properties over a range of from a low frequency to a high frequency, the thermoplastic polyester elastomer resin composition comprising a thermoplastic polyester elastomer (A) and a thermoplastic elastomer (B) which is not (A), the (A) / (B) proportion by mass being 95 / 5 to 50 / 50. The molded foam object has a 23°C loss tangent (tanδ) of preferably 0.10 or greater.

Description

Technical Field

[0001] The present invention relates to a foamed molded body made of a thermoplastic polyester elastomer resin composition excellent in cushioning properties and sound absorption properties. More specifically, the foamed molded body made of the thermoplastic polyester elastomer resin composition of the present invention is thin and lightweight, excellent in cushioning properties, and capable of controlling high sound absorption from the low-frequency to the high-frequency region.

Background Art

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

[0003] Since thermoplastic polyester elastomers are excellent in heat aging resistance, light resistance, and abrasion resistance, they are adopted for automotive parts, particularly parts used in high-temperature environments and automotive interior parts. Furthermore, in recent years, not only the weight reduction of resin parts but also the imparting of cushioning properties and sound absorption properties have been promoted, and the application of foamed molded products can be cited as one of the means to achieve the purpose.

[0004] In Patent Document 1, high-quality foamed molded bodies are manufactured by controlling the melt tension of the polyester elastomer composition and suppressing gels. However, the density of the foamed molded body is high, and it has not reached the production of a low-density foam that is satisfactory for weight reduction. Furthermore, regarding the cushioning properties and resilience required for foamed molded products, no consideration has been given at all.

[0005] By the way, as the foam suitably used for automotive seats, a soft polyurethane foam having high hysteresis loss as cushioning property and excellent resilience modulus is preferably adopted, and Patent Document 2 has proposed a manufacturing method thereof. However, the manufacturing method is not easy to say is simple, and since cyanide gas and the like are generated during combustion in the urethane foam, there is a problem of environmental pollution.

[0006] Conventionally, sound-absorbing materials have been mainly used in various products such as automobiles, houses, and electrical products in order to reduce noise. However, since the frequencies of the sounds generated in each product are different, it is necessary to apply a sound-absorbing material having a high sound absorption rate at a frequency suitable for each product.

[0007] Conventionally, as sound-absorbing materials, fibrous materials such as glass wool and felt and foamed materials such as urethane foam have been widely used. However, although these materials exhibit sound absorption properties in the high-frequency region, their sound absorption properties in the low-frequency to mid-frequency ranges are poor, and it is necessary to use a thick material to obtain sufficient sound absorption at low frequencies (Patent Document 3).

[0008] In addition, in automotive applications, due to engine downsizing and the like, there is a tendency for higher heat resistance to be required, but no material has yet been developed that is excellent in heat resistance, sound absorption, and further cushioning properties.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a foamed molded body of a thermoplastic polyester elastomer resin composition that is thin and lightweight, has a comfortable cushioning property, and can control high sound absorption properties from the low-frequency to the high-frequency range. [Means for Solving the Problems]

[0011] The present inventors earnestly studied to provide a foamed molded body of a thermoplastic polyester elastomer resin composition that has a comfortable cushioning property and can control sound absorption characteristics in the low-frequency to high-frequency range. As a result, by adding a thermoplastic elastomer having a high loss tangent other than the thermoplastic polyester elastomer to the thermoplastic polyester elastomer and controlling the resilience modulus and surface hardness, it was found that it is possible to produce a foam having a comfortable cushioning property. Furthermore, in the foamed molded body of the above-mentioned thermoplastic polyester elastomer resin composition, by changing the ratio of the hard segment and the soft segment of the thermoplastic polyester elastomer and the addition amount of the thermoplastic elastomer, it is possible to control the peak frequency at which the sound absorption rate becomes a predetermined value or more in the frequency range of 0.4 kHz to 5.0 kHz, and the present invention was completed.

[0012] That is, the present invention comprises the following [1] to

[10] . [1] A foamed molded body comprising a thermoplastic polyester elastomer resin composition, characterized in that a thermoplastic polyester elastomer (A) and a thermoplastic elastomer (B) other than (A) are contained in a mass ratio of (A) / (B) = 95 / 5 to 50 / 50. [2] The foamed molded body according to [1], wherein the loss tangent (tanδ) at 23°C is 0.10 or more. [3] The foamed molded body according to [1] or [2], wherein the thermoplastic polyester elastomer (A) is composed of a hard segment made of a polyester composed of an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol, and at least one soft segment selected from an aliphatic polyether, an aliphatic polyester, and an aliphatic polycarbonate, and the content of the soft segment is 40 to 90% by mass. [4] The foamed molded body according to any one of [1] to [3], wherein the thermoplastic elastomer (B) is at least one selected from a thermoplastic polyolefin-based elastomer and a thermoplastic styrene-based elastomer. [5] The foamed molded body according to any one of [1] to [4], having a resilience modulus of 30 to 60%. [6] The foamed molded body according to any one of [1] to [5], having a surface hardness of 10 to 55C. [7] The foamed molded body according to any one of [1] to [6], having an average cell diameter of 10 to 900 μm. [8] The foamed molded body according to any one of [1] to [7], having a density of 0.1 to 0.35 g / cm 3 ³. [9] The foamed molded body according to any one of [1] to [8], having a non-foamed skin layer with a thickness of 100 to 800 μm on the surface layer and a foamed layer composed of foamed cells with an average cell diameter of 10 to 900 μm independent of the resin continuous phase in the inner layer, and having a sandwich structure of the non-foamed skin layer and the foamed layer in the thickness direction.

[10] A sound-absorbing material containing the foamed molded body according to any one of [1] to [9], characterized in that when measuring the normal incidence sound absorption rate of the foamed molded body in the frequency range of 0.4 kHz to 5.0 kHz according to JIS A1405-2 (2007), it has a peak frequency at which the normal incidence sound absorption rate is 40% or more in the frequency range of 0.4 kHz to 5.0 kHz.

Advantages of the Invention

[0013] The foamed molded body made of the thermoplastic polyester elastomer resin composition of the present invention is not only excellent in thinness and lightness, but also has a comfortable cushioning property and can control extremely high sound absorption from the low-frequency to the high-frequency region. Furthermore, despite a high foaming ratio, it has a uniform foamed state, high heat resistance, water resistance, and molding stability, so it is possible to provide a foamed molded body made of a polyester elastomer resin composition that can also be applied to parts that require high reliability.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the foamed molded body made of the thermoplastic polyester elastomer resin composition of the present invention will be described in detail.

[0016] Regarding the foamed molded body made of the thermoplastic polyester elastomer resin composition of the present embodiment, the normal incidence sound absorption rate at the peak frequency of the foamed molded body in the range of 0.4 kHz to 5.0 kHz, measured by a method conforming to JIS A1405-2 (2007), which is the main frequency range of automobile noise, is 40% or more, preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. By satisfying this characteristic, the foamed molded body made of the thermoplastic polyester elastomer resin composition of the present invention can improve the balance between its lightness and sound absorption characteristics. Also, the upper limit value of the normal incidence sound absorption rate of the foamed molded body in the above 0.4 kHz to 5.0 kHz is not particularly limited, but it is 100% or less in terms of measurement. The above-mentioned normal incidence sound absorption rate can be measured, for example, using a normal incidence sound absorption rate measurement system WinZacMTX manufactured by Nippon Acoustical Engineering Co., Ltd.

[0017] Also, in the foamed molded body made of the thermoplastic polyester elastomer resin composition of the present embodiment, the region of the peak frequency is preferably a frequency region of 0.4 kHz to 4 kHz, more preferably a frequency region of 0.4 kHz to 3.5 kHz, still more preferably a frequency region of 0.4 kHz to 3 kHz, particularly preferably a frequency region of 0.4 kHz or more and 2.5 kHz or less, and most preferably a frequency region of 0.4 kHz or more and 2 kHz or less. The sound-absorbing material of the present invention is characterized in that the peak frequency can be controlled particularly in the low-frequency region (0.4 kHz to 4 kHz).

[0018] The foamed molded body made of the thermoplastic polyester elastomer resin composition of the present invention may form a sound-absorbing material only from this foamed molded body, or this foamed molded body may be combined with other materials to form a sound-absorbing material.

[0019] [Thermoplastic polyester elastomer (A)] The thermoplastic polyester elastomer (A) used in the present invention is formed by combining a hard segment and a soft segment. The hard segment is preferably composed of a polyester composed of an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components. As the aromatic dicarboxylic acid constituting the polyester of the hard segment, ordinary aromatic dicarboxylic acids are widely used and are not particularly limited, but as the main aromatic dicarboxylic acid, terephthalic acid or naphthalenedicarboxylic acid (2,6-naphthalenedicarboxylic acid is preferable among the isomers) is desirable. The content of these aromatic dicarboxylic acids is preferably 70 mol% or more, more preferably 80 mol% or more, in all dicarboxylic acids constituting the polyester of the hard segment. Other dicarboxylic acid components include aromatic dicarboxylic acids such as diphenyldicarboxylic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, 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. These can be used within a range that does not significantly lower the melting point of the resin, and the amount is preferably 30 mol% or less, more preferably 20 mol% or less, of all acid components.

[0020] Also, in the thermoplastic polyester elastomer (A) used in the present invention, as the aliphatic or alicyclic diol constituting the polyester of the hard segment, general aliphatic or alicyclic diols are widely used and are not particularly limited, but it is desirable that they are mainly alkylene glycols having 2 to 8 carbon atoms. Specifically, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, etc. can be mentioned. Among these, it is preferable that it is either ethylene glycol or 1,4-butanediol.

[0021] As components constituting the polyester of the above-mentioned hard segment, those composed of butylene terephthalate units (units composed of terephthalic acid and 1,4-butanediol) or butylene naphthalate units (units composed of 2,6-naphthalenedicarboxylic acid and 1,4-butanediol) are preferable from the viewpoints of physical properties, moldability, and cost performance.

[0022] In addition, when a suitable aromatic polyester as the polyester constituting the hard segment in the thermoplastic polyester elastomer (A) used in the present invention is produced in advance and then copolymerized with the soft segment component, the aromatic polyester can be easily obtained according to the ordinary polyester production method. Further, such a polyester desirably has a number average molecular weight of 10,000 to 40,000.

[0023] The soft segment of the thermoplastic polyester elastomer (A) used in the present invention is at least one selected from aliphatic polyethers, aliphatic polyesters, and aliphatic polycarbonates.

[0024] Examples of the aliphatic polyether include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, poly(trimethylene oxide) glycol, a copolymer of ethylene oxide and propylene oxide, an ethylene oxide adduct of poly(propylene oxide) glycol, and a copolymer of ethylene oxide and tetrahydrofuran. Among these, from the viewpoint of elastic properties, poly(tetramethylene oxide) glycol and an ethylene oxide adduct of poly(propylene oxide) glycol are preferable.

[0025] Examples of the aliphatic polyester include poly(ε-caprolactone), poly(enantholactone), polycaprylactone, and polybutylene adipate. Among these, from the viewpoint of elastic properties, poly(ε-caprolactone) and polybutylene adipate are preferable.

[0026] The aliphatic polycarbonate preferably mainly consists 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, 2 - methyl - 1,8 - octanediol, and the like. In particular, from the viewpoints of the flexibility and low - temperature properties of the resulting thermoplastic polyester elastomer, aliphatic diols having 5 to 12 carbon atoms are preferred. These components may be used alone or, if necessary, two or more of them may be used in combination based on the examples described below.

[0027] As the aliphatic polycarbonate diol having good low - temperature properties and constituting the soft segment of the thermoplastic polyester elastomer (A) used in the present invention, those having a low melting point (for example, 70°C or lower) and a low glass transition temperature are preferred. Generally, the aliphatic polycarbonate diol composed of 1,6 - hexanediol used to form the soft segment of the thermoplastic polyester elastomer has a glass transition temperature as low as around - 60°C and a melting point of around 50°C, so it has good low - temperature properties. In addition, for example, an aliphatic polycarbonate diol obtained by copolymerizing an appropriate amount of 3 - methyl - 1,5 - pentanediol with the above - mentioned aliphatic polycarbonate diol has a slightly higher glass transition point than the original aliphatic polycarbonate diol, but its melting point decreases or becomes amorphous, so it corresponds to an aliphatic polycarbonate diol having good low - temperature properties. Also, for example, an aliphatic polycarbonate diol composed of 1,9 - nonanediol and 2 - methyl - 1,8 - octanediol has a melting point of about 30°C and a glass transition temperature as low as around - 70°C, so it corresponds to an aliphatic polycarbonate diol having good low - temperature properties.

[0028] As the soft segment of the thermoplastic polyester elastomer (A) used in the present invention, an aliphatic polyether is preferable from the viewpoint of solving the problems of the present invention.

[0029] The thermoplastic polyester elastomer (A) used in the present invention is preferably a copolymer mainly composed of terephthalic acid, 1,4-butanediol, and poly(tetramethylene oxide) glycol. In the dicarboxylic acid component constituting the thermoplastic polyester elastomer (A), the content of terephthalic acid is preferably 40 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more. In the glycol component constituting the thermoplastic polyester elastomer (A), the total of 1,4-butanediol and poly(tetramethylene oxide) glycol is preferably 40 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

[0030] The number average molecular weight of the poly(tetramethylene oxide) glycol is preferably from 500 to 4000. When the number average molecular weight is less than 500, it may be difficult to exhibit elastomer properties. On the other hand, when the number average molecular weight exceeds 4000, the compatibility with the hard segment component decreases, and it may be difficult to copolymerize in a block form. The number average molecular weight of the poly(tetramethylene oxide) glycol is more preferably from 800 to 3000, and still more preferably from 1000 to 2500.

[0031] In the thermoplastic polyester elastomer (A) used in the present invention, the content of the soft segment is preferably 40 to 90% by mass, more preferably 45 to 90% by mass, still more preferably 55 to 90% by mass, and particularly preferably 65 to 90% by mass. When the content of the soft segment is lower than 40% by mass, the surface hardness increases and the cushioning property deteriorates. Furthermore, the lower the surface hardness, the easier the material vibrates, so the sound absorption performance in the low frequency range improves. When the content of the soft segment is lower than 40% by mass, the surface hardness decreases and the sound absorption peak frequency appears in the high frequency range. When it exceeds 90% by mass, the crystallinity decreases too much, so there is a tendency for the foam moldability to be poor. The surface hardness of the thermoplastic polyester elastomer (A) is preferably 10 to 60 C, more preferably 10 to 50 C, and still more preferably 10 to 40 C. In the present invention, the surface hardness is the measured value using a C-type hardness meter, and for convenience, it is described as 10 C, 60 C, etc.

[0032] By changing the ratio of the hard segment to the soft segment and the expansion ratio of the thermoplastic polyester elastomer (A), it becomes possible to control the sound absorption rate to have a peak frequency of a predetermined value or more. However, if the content of the soft segment is 40 to 90% by mass, this control becomes possible without particularly increasing the expansion ratio.

[0033] The thermoplastic polyester elastomer (A) used in the present invention can be produced by known methods. For example, a method of subjecting a lower alcohol diester of a dicarboxylic acid, an excessive amount of a low molecular weight glycol, and a soft segment component to a transesterification reaction in the presence of a catalyst and then polycondensing the resulting reaction product; a method of subjecting a dicarboxylic acid, an excessive amount of a glycol, and a soft segment component to an esterification reaction in the presence of a catalyst and then polycondensing the resulting reaction product; a method of previously preparing a polyester of a hard segment, adding a soft segment component thereto, and randomizing it by a transesterification reaction; a method of connecting a hard segment and a soft segment with a chain linking agent; and further, when poly(ε-caprolactone) is used as the soft segment, a method of subjecting an ε-caprolactone monomer to an addition reaction to the hard segment, etc., any method may be adopted.

[0034] A crosslinking agent may be blended with the thermoplastic polyester elastomer (A) as necessary within a range that does not inhibit the effects of the present invention. Such a crosslinking agent is not particularly limited as long as it is a crosslinking agent that reacts with the hydroxyl group or carboxyl group possessed by the thermoplastic polyester elastomer. Examples thereof include epoxy-based crosslinking agents, carbodiimide-based crosslinking agents, isocyanate-based crosslinking agents, acid anhydride-based crosslinking agents, silanol-based crosslinking agents, melamine resin-based crosslinking agents, metal salt-based crosslinking agents, metal chelate-based crosslinking agents, amino resin-based crosslinking agents, and the like. The crosslinking agent can be used alone or in combination of two or more.

[0035] The amount (content) of the crosslinking agent used is appropriately adjusted depending on extrusion conditions, the desired foaming ratio, etc. For example, it is preferably 0.1 to 4.5 parts by mass, more preferably 0.1 to 4 parts by mass, and still more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the thermoplastic polyester elastomer (A).

[0036] Furthermore, in addition to the above crosslinking agent, various additives can be compounded into the thermoplastic polyester elastomer (A) used in the present invention according to the purpose. The types of such additives are not particularly limited, and various additives commonly used in foam molding can be used. Specifically, as additives, known hindered phenol-based, sulfur-based, phosphorus-based, amine-based antioxidants, hindered amine-based, benzotriazole-based, benzophenone-based, benzoate-based, triazole-based, nickel-based, salicylic-based, etc. light stabilizers, lubricants, fillers, flame retardants, flame retardant aids, mold release agents, antistatic agents, molecular regulators such as peroxides, metal deactivators, organic and inorganic nucleating agents, neutralizing agents, antacids, antibacterial agents, fluorescent brighteners, organic and inorganic pigments, and organic and inorganic phosphorus compounds used for the purpose of imparting flame retardancy and thermal stability, etc. can be mentioned. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles, etc., and the addition amount used in the molding of ordinary thermoplastic resins can be adopted.

[0037] The MFR value of the thermoplastic polyester elastomer (A) used in the present invention at 230 °C is preferably 10 to 20 g / 10 min. When the MFR is within this range, the fluidity and foam characteristics can be optimally maintained.

[0038] As a method for determining the composition and composition ratio of the thermoplastic polyester elastomer (A) used in the present invention, a sample is dissolved in a solvent such as deuterated chloroform and measured. 1 It is also possible to calculate from the proton integration ratio of 1H-NMR.

[0039] [Thermoplastic elastomer (B)] The thermoplastic elastomer (B) in the present invention may be a thermoplastic elastomer other than the thermoplastic polyester elastomer (A), but is preferably an elastomer other than a polyester-based elastomer. For example, thermoplastic polyolefin-based elastomers, thermoplastic styrene-based elastomers, etc. can be mentioned. The thermoplastic elastomer (B) is preferably at least one selected from thermoplastic polyolefin-based elastomers and thermoplastic styrene-based elastomers. As the thermoplastic polyolefin - based elastomer, an α - olefin copolymer is preferably used. Specific examples of the α - olefin copolymer include ethylene - propylene copolymer, ethylene - butene - 1 copolymer, ethylene - hexene - 1 copolymer, ethylene - octene - 1 copolymer, ethylene - ethyl acrylate copolymer, ethylene - methacrylate copolymer, ethylene - propylene - diene terpolymer, isoprene rubber, nitrile rubber, polybutene rubber, and the like. As the thermoplastic styrene - based elastomer, a styrene - based block copolymer composed of a polystyrene block and an elastomer block having a polyolefin structure is preferably used. Specific examples of the styrene - based block copolymer include styrene - isoprene - styrene block copolymer (SIS), styrene - ethylene·propylene - styrene block copolymer (SEPS), styrene - ethylene·butylene - styrene block copolymer (SEBS), styrene - ethylene·ethylene / propylene - styrene block copolymer (SEEPS), and the like. From the viewpoint of obtaining a flexible cushioning property, it is particularly desirable that the thermoplastic elastomer (B) is a thermoplastic styrene - based elastomer.

[0040] The thermoplastic elastomer (B) in the present invention is preferably one having a high loss tangent tanδ (where δ is the loss angle) at 23°C near room temperature. The impact absorption characteristics of the foamed molded body can be evaluated by dynamic viscoelasticity measurement. The loss tangent (tanδ) indicates a measure of the conversion of external vibration energy into thermal energy due to internal friction, and can be used for evaluating impact absorbability. It is known that tanδ shows a maximum value near the glass transition temperature (Tg) of each resin, and the most excellent impact absorption characteristics are exhibited in the vicinity of this maximum peak temperature. By increasing the value of tanδ and widening the temperature range, impact absorbability can be exhibited over a wide temperature range. By dispersing a thermoplastic elastomer (B) having a high loss tangent (tanδ) in the thermoplastic polyester elastomer (A) and expressing impact absorbability, the resilience modulus can be lowered and the repulsive force can be suppressed, thereby obtaining flexibility as a cushion. The loss tangent (tanδ) of the thermoplastic elastomer (B) at 23°C near room temperature is preferably 0.20 or more, more preferably 0.30 or more, still more preferably 0.40 or more, and particularly preferably 0.50 or more.

[0041] By dispersing a thermoplastic elastomer (B) having a high loss tangent (tanδ) in the thermoplastic polyester elastomer (A), the sound absorption characteristics in the low frequency range can be improved. When sound is incident on the foamed molded body, the sound transmits through the skeleton portion of the foamed molded body and diffuses as solid-borne sound. If the loss tangent tanδ of the skeleton portion composed of the thermoplastic polyester elastomer resin composition is high, external sound energy can be converted into thermal energy due to internal friction, so that low-frequency sound that easily travels through solids can be absorbed.

[0042] [Thermoplastic Polyester Elastomer Resin Composition] In the present invention, the thermoplastic polyester elastomer resin composition contains a thermoplastic polyester elastomer (A) and a thermoplastic elastomer (B) in a mass ratio of (A) / (B) = 95 / 5 to 50 / 50. The mass ratio is preferably (A) / (B) = 90 / 10 to 60 / 40. When the mass ratio of the thermoplastic elastomer (B) is less than 5, the elastic modulus at low temperature is high, the use environment is restricted, and the vibration damping performance is poor. If more than 50 is blended, crystallization may be delayed and moldability may decrease, or mechanical strength may decrease, which is not preferable.

[0043] The thermoplastic polyester elastomer resin composition may contain, if necessary, the above-mentioned cross-linking agent and various additives. In the thermoplastic polyester elastomer resin composition of the present invention, the proportion occupied by the total of the thermoplastic polyester elastomer (A) and the thermoplastic elastomer (B) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0044] [Foamed molded article] The foamed molded article of the present invention is obtained by using the above-mentioned thermoplastic polyester elastomer resin composition. The foamed molded article of the present invention preferably has a non-foamed skin layer present on the surface layer and a foamed layer present on the inner layer. Since these non-foamed skin layer and foamed layer are formed of the above-mentioned thermoplastic polyester elastomer resin composition, they have a foamed structure with a uniform cell state and can exhibit excellent lightness, cushioning property, and sound absorption property.

[0045] The foamed molded article of the present invention usually has a sandwich structure in which non-foamed skin layers are provided on both sides of the foamed layer (in other words, a structure in which the foamed layer is sandwiched between non-foamed skin layers on both sides). Regarding the size of the foamed molded article, there is no particular limitation, but the thickness direction of the sandwich structure is assumed to be about 1 to 30 mm.

[0046] The foamed layer is composed of a resin continuous phase and independent foam cells. Here, the resin continuous phase means a portion without cavities formed by a cured thermoplastic polyester elastomer resin composition. The average cell diameter of the foam cells is preferably 10 to 900 μm. When the average cell diameter is less than 10 μm, the internal pressure of the foamed molded body is low and the pressure during the formation of the non-foamed skin layer is insufficient, and the appearance such as sink marks tends to deteriorate. On the other hand, when the average cell diameter exceeds 900 μm, the load-bearing property decreases. As the foaming ratio increases, the diameter (cell diameter) of the foam cells becomes coarser, and the surface hardness of the material decreases. Therefore, the cushioning property is improved, and furthermore, the sound absorption peak frequency appears in the low-frequency region. To further improve the cushioning property and make the sound absorption peak frequency appear in the low-frequency region, the average cell diameter is more preferably 100 to 900 μm, and even more preferably 200 to 900 μm. By applying an appropriate pressure from the inside of the foamed molded body to the non-foamed skin layer, a foamed molded body having an average cell diameter within the above range can be obtained.

[0047] The resilience modulus of the foamed molded body of the present invention is preferably 30 to 60%. When the resilience modulus exceeds 60%, the resilience force is too strong, and it is difficult to obtain flexibility as a cushion. When the resilience modulus is less than 30%, when a high load is applied, bottoming may occur when a high load is applied, or bottoming may occur when the foamed molded body is thinned. The resilience modulus of the foamed molded body is preferably 30 to 60%, more preferably 35 to 55%, and even more preferably 35 to 50%.

[0048] The surface hardness of the foamed molded body of the present invention is preferably 10 to 55 C. Similar to the resilience modulus described above, when the surface hardness exceeds 55 C, it is difficult to obtain flexibility as a cushion. When the surface hardness is less than 10 C, when a high load is applied, bottoming may occur when a high load is applied, or bottoming may occur when the foamed molded body is thinned. The surface hardness of the foamed molded body is preferably 10 to 55 C, more preferably 15 to 50 C, and even more preferably 20 to 45 C. The description of the surface hardness is the same as above.

[0049] The flexibility, resistance to sagging, and lack of a feeling of sticking to the surface of the foamed molded body of the present invention are determined by the balance between the resilience ratio and the surface hardness described above.

[0050] The non-foamed skin layer is laminated on the foamed layer, and preferably has a thickness of 100 to 800 μm. When the thickness of the non-foamed skin layer is less than 100 μm, it tends to be difficult to obtain a good appearance. On the other hand, when it exceeds 800 μm, the specific gravity of the foamed layer becomes too low, so that the foamed structure having a density of 0.01 to 0.35 g / cm 3 described later cannot be obtained in a uniform cell state for the entire foamed molded body.

[0051] The foamed molded body of the thermoplastic polyester elastomer resin composition has a plate vibration type sound absorption mechanism because the non-foamed skin layer is laminated on the foamed layer. Here, in order to perform low-frequency sound absorption with a material of limited thickness, a low-frequency sound absorption effect can be obtained by resonance. Examples of the method include plate vibration type sound absorption using a plate or a film, and Helmholtz resonator type sound absorption using a slit or a perforated plate. The foamed molded body of the thermoplastic polyester elastomer resin composition shows a plate vibration type by having a non-foamed layer, and it is possible to exhibit high sound absorption characteristics even in the low-frequency region. When the non-foamed skin layer is removed and the sound absorption rate of only the foamed layer is measured, the sound absorption peak frequency shifts to a high frequency, so having a non-foamed skin layer is advantageous for low-frequency sound absorption. However, even when the non-foamed skin layer is removed, only the sound absorption peak frequency changes, and the sound absorption characteristics such as the sound absorption rate do not decrease. The thickness of the non-foamed skin layer is more preferably 200 to 600 μm, still more preferably 200 to 400 μm, and particularly preferably 300 to 400 μm.

[0052] Since the foamed molded article of the thermoplastic polyester elastomer resin composition has a high loss tangent (tanδ) at 23°C near room temperature, the sound absorption characteristics in the low frequency range can be improved. When sound is incident on the foamed molded article, the sound is transmitted through the skeleton portion of the foamed molded article and diffused as solid-borne sound. When the loss tangent (tanδ) of the skeleton portion composed of the thermoplastic polyester elastomer resin composition is high, external sound energy can be converted into thermal energy by internal friction, so that low-frequency sound that is easily transmitted through solids can be absorbed. The loss tangent (tanδ) of the foamed molded article at 23°C near room temperature is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. The upper limit of the loss tangent (tanδ) is about 0.50.

[0053] The density of the foamed molded article of the present invention is preferably 0.01 to 0.35 g / cm 3 Generally, the density of a common polyester elastomer is approximately 1.0 to 1.4 g / cm 3 So, it can be said that the foamed molded article of the present invention is sufficiently lightweight. More preferably, it is 0.1 to 0.35 g / cm 3 Even more preferably, it is 0.1 to 0.25 g / cm 3 If the density is less than 0.01 g / cm 3 , sufficient strength cannot be obtained and the mechanical properties tend to be inferior. If it exceeds 0.35 g / cm 3 , the sound absorption peak frequency appears in the high frequency range. To achieve both excellent strength and high sound absorption characteristics, the density of the foamed molded article is more preferably 0.01 to 0.25 g / cm 3 and even more preferably 0.1 to 0.25 g / cm 3 . The density is the apparent density, and the measurement method is shown in the Examples section.

[0054] Since the foamed molded article of the present invention has an average cell diameter within a specific range, a density within a specific range, and a non-foamed skin layer thickness within a specific range, it has a uniform and fine cell structure. As a result, it is possible to control high sound absorption characteristics in a wide frequency range.

[0055] Depending on the foaming ratio, foamed molded articles with different thicknesses, weights, and even densities can be obtained. Although the sound absorption peak frequency changes depending on the foaming ratio, the sound absorption characteristics such as the sound absorption rate are hardly affected.

[0056] The foaming method of the foamed molded article of the present invention is not particularly limited, but a foaming method in which a resin is impregnated with high-pressure gas and then depressurized (the pressure is released) is preferable. Among them, as a molding method capable of obtaining molding cycle properties, cost, and homogeneous foaming, a method of obtaining a foamed molded article by expanding the volume of a cavity when a foaming agent and a thermoplastic polyester elastomer resin composition are melt-mixed and injection-molded is preferable. Specifically, as shown in FIG. 1, a molten thermoplastic polyester elastomer resin composition is injected and filled into a cavity 3 formed by a plurality of molds 1 and 2 that are clamped together, together with a chemical foaming agent and / or an inert gas in a supercritical state (hereinafter, sometimes collectively referred to as a "foaming agent"). At the stage where a non-foamed skin layer with a thickness of 100 to 800 μm is formed on the surface layer, at least one mold 2 is moved in the mold-opening direction to expand the volume of the cavity 3, thereby obtaining a foamed molded article. Specifically, after filling the cavity 3 with the thermoplastic polyester elastomer resin composition and the foaming agent, cooling at a predetermined temperature forms a non-foamed skin layer on the surface layer of the thermoplastic polyester elastomer resin composition filled in the cavity 3. When this non-foamed skin layer reaches a predetermined thickness (100 to 800 μm), the mold 2 is moved in the mold-opening direction to expand the volume of the cavity 3. Incidentally, the thermoplastic polyester elastomer resin composition and the foaming agent can be mixed in the plasticizing region 4a of the injection molding machine 4 before being filled into the cavity 3.

[0057] The chemical foaming agent that can be used when obtaining the foamed molded article of the present invention is added to the resin melted in the resin melting zone of the molding machine as a gas component serving as a foaming nucleus or its source of generation. Specifically, as the chemical blowing agent, ammonium carbonate, sodium bicarbonate, inorganic compounds such as azide compounds, and organic compounds such as azo compounds, sulfohydrazide compounds, and nitroso compounds can be used. Examples of the azide compounds include terephthalic azide and P-tert-butylbenzene azide. Further, examples of the azo compounds include diazocarboxamide (ADCA), 2,2-azoisobutyronitrile, azohexahydrobenzonitrile, and diazoaminobenzene, among which ADCA is preferably utilized. Examples of the sulfohydrazide compounds include benzenesulfohydrazide, benzene 1,3-disulfohydrazide, diphenylsulfone-3,3-disulfohydrazide, and diphenyloxide-4,4-disulfohydrazide, etc. Examples of the nitroso compounds include N,N-dinitrosopentamethylenetetramine (DNPT), etc.

[0058] When a chemical blowing agent is used as the blowing agent, in order to uniformly disperse the chemical blowing agent in the thermoplastic polyester elastomer resin composition, it can also be used as a blowing agent masterbatch based on a thermoplastic resin having a melting point lower than the decomposition temperature of the chemical blowing agent. The base thermoplastic resin is not particularly limited as long as it has a melting point lower than the decomposition temperature of the chemical blowing agent. For example, polystyrene (PS), polyethylene (PE), polypropylene (PP), etc. can be mentioned. In this case, the blending ratio of the chemical blowing agent and the thermoplastic resin is preferably 10 to 100 parts by mass of the chemical blowing agent with respect to 100 parts by mass of the thermoplastic resin. When the amount of the chemical blowing agent is less than 10 parts by mass, the amount of the masterbatch with respect to the thermoplastic polyester elastomer resin composition may become too large, leading to a possible deterioration in physical properties. When it exceeds 100 parts by mass, it becomes difficult to form a masterbatch due to the problem of the dispersibility of the chemical blowing agent.

[0059] When using an inert gas in a supercritical state 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, their amount is preferably 0.05 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, based on 100 parts by mass of the thermoplastic polyester elastomer resin composition. If the amount of supercritical carbon dioxide and / or nitrogen is less than 0.05 parts by mass, it becomes difficult to obtain uniform and fine foam cells, and if it exceeds 30 parts by mass, the appearance of the surface of the molded body tends to be impaired.

[0060] In addition, the supercritical carbon dioxide or nitrogen used as the foaming agent can be used alone, or carbon dioxide and nitrogen may be mixed and used. Nitrogen tends to be more suitable for forming finer cells with respect to the thermoplastic polyester elastomer resin composition, and carbon dioxide can relatively increase the injection amount of the gas and is more suitable for obtaining a higher foaming ratio. Therefore, they may be arbitrarily mixed to adjust the state of the foamed structure, and when mixing, the mixing ratio is preferably in the range of 1:9 to 9:1 in terms of molar ratio.

[0061] From the viewpoint of uniform fine foaming, supercritical nitrogen is more preferable as the foaming agent used in the present invention.

[0062] To inject the molten thermoplastic polyester elastomer resin composition into the cavity 3 together with the foaming agent, the molten thermoplastic polyester elastomer resin composition and the foaming agent may be mixed in the plasticizing region 4a of the injection molding machine 4. In particular, when using supercritical carbon dioxide and / or nitrogen as the foaming agent, for example, as shown in FIG. 1, a method of directly injecting gaseous carbon dioxide and / or nitrogen from the gas cylinder 5 or pressurizing it with a booster pump 6 and injecting it into the injection molding machine 4 can be adopted. These carbon dioxide and / or nitrogen need to be in a supercritical state inside the molding machine from the viewpoints of solubility, permeability, and diffusibility into the molten thermoplastic polyester elastomer resin composition.

[0063] Here, the supercritical state refers to a state in which, when increasing the temperature and pressure of a substance that has a gas phase and a liquid phase, the distinction between the gas phase and the liquid phase can be eliminated in a certain temperature range and pressure range. The temperature and pressure at this time are called the critical temperature and the critical pressure, respectively. That is, in the supercritical state, the substance has both the characteristics of a gas and a liquid, so the fluid generated in this state is called a critical fluid. Such a critical fluid has a higher density than a gas and a lower viscosity than a liquid, and thus has the characteristic of being extremely easy to diffuse through a substance.

Examples

[0064] Examples are given below to demonstrate the effects of the present invention, but the present invention is not limited in any way by these examples.

[0065] In the following examples and comparative examples, the following raw materials were used. [Thermoplastic polyester elastomer (A)] (Polyester elastomer A-1) According to the method described in JP-A-9-59491, using dimethyl terephthalate, 1,4-butanediol, and poly(tetramethylene oxide) glycol with a number average molecular weight of 2000 as raw materials, a thermoplastic polyester elastomer with a soft segment content of 83% by mass was produced, and this was designated as polyester elastomer A-1. (Polyester elastomer A-2) According to the method described in JP-A-9-59491, using dimethyl terephthalate, 1,4-butanediol, and poly(tetramethylene oxide) glycol with a number average molecular weight of 2000 as raw materials, a thermoplastic polyester elastomer with a soft segment content of 76% by mass was produced, and this was designated as polyester elastomer A-2. (Polyester elastomer A-3) According to the method described in Japanese Patent Application Laid-Open No. 9-59491, using dimethyl terephthalate, 1,4-butanediol, and poly(tetramethylene oxide) glycol with a number average molecular weight of 1000 as raw materials, a thermoplastic polyester elastomer with a soft segment content of 55% by mass was produced, and this was designated as polyester elastomer A-3. (Polyester elastomer A-4) According to the method described in Japanese Patent Application Laid-Open No. 9-59491, using dimethyl terephthalate, 1,4-butanediol, and poly(tetramethylene oxide) glycol with a number average molecular weight of 1000 as raw materials, a thermoplastic polyester elastomer with a soft segment content of 49% by mass was produced, and this was designated as polyester elastomer A-4. [Thermoplastic elastomer (B)] (Styrene-based elastomer B-1) The thermoplastic styrene-based elastomer "Tuftec H1221" manufactured by Asahi Kasei Corporation was used. (Olefin-based elastomer B-2) The α-olefin copolymer "Absortomer EP1001" manufactured by Mitsui Chemicals, Inc. was used.

[0066] Using (A) and (B) having the loss tangent (tanδ) described in Table 1, various components were melt-kneaded using a twin-screw extruder according to the compounding composition described in Table 2, and then pelletized to obtain the pellets of Examples 1 to 8 and Comparative Examples 1 to 6.

[0067]

Table 1

[0068] [Examples 1 to 8 (Example 7 is a reference example) , Comparative Examples 1 to 6] Next, a foamed molded body was produced by the mold expansion method described above using the above resin component (thermoplastic polyester elastomer resin composition). As the mold, a cavity with a width of 100 mm, a length of 100 mm, and a thickness of 3.0 mm can be formed when the mold is clamped, and a cavity with the same width, the same length, and a thickness of 3.0 mm + core-back amount (mm) can be formed when the mold is core-backed in the mold opening direction. A mold for producing a flat plate composed of a fixed mold and an operating mold was used. Specifically, in the plasticizing region of an electric injection molding machine having a screw with a mold clamping force of 1800 kN, a screw diameter of 40 mm, and a screw stroke of 180 mm, nitrogen in a supercritical state was injected. After injection filling into a mold temperature-controlled to 50°C, when a non-foamed skin layer of 100 to 800 μm was formed by the injection external pressure and the foaming pressure from the inside, the operating mold was moved in the mold opening direction by the length shown as the core-back amount (mm) in Table 2 to expand the volume of the cavity and obtain a foamed molded body.

[0069] Regarding the foamed molded bodies obtained from the thermoplastic polyester elastomer resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 6, the following evaluations were performed. The results are shown in Table 2.

[0070] [Density (apparent density)] The dimensions of the foamed molded body were measured with a vernier caliper, and its mass was measured with an electronic balance, and calculated by the following formula. Density (g / cm 3 ) = mass of test piece / volume of test piece

[0071] [Average cell diameter] Photographs of the foamed cross-section of the cross-section observation sample taken by a scanning electron microscope SU1510 manufactured by Hitachi High-Technologies Corporation were image-processed. The equivalent circle diameters of at least 100 adjacent cells were taken as the cell diameters and measured with a vernier caliper. The average value of these 100 was obtained, and this was done at three arbitrary locations, and the average value of the three average values obtained at the three locations was taken as the average cell diameter.

[0072] [Skin layer thickness] The cross-sectional observation sample's foamed cross-section photo taken by the scanning electron microscope SU1510 manufactured by Hitachi High-Technologies was image-processed, and the thickness of the integrated non-foamed layer observed in the surface layer was measured as the skin layer thickness.

[0073] [Rebound resilience] The measurement was carried out according to the method described in JIS K 6400. Using a manual measurement testing machine, a steel ball was dropped onto the test piece from a specified height, and the maximum height of the bounce was read. Three measurements were taken within one minute, and the median value was obtained to calculate the rebound resilience.

[0074] [Surface hardness] The center of the foamed molded body (the foamed molded body obtained above) with a length of 100 mm and a width of 100 mm was measured using a C-type hardness tester (manufactured by Kobunshi Keiki Co., Ltd., Asker rubber hardness tester C-type) in accordance with JIS K 7312:1996.

[0075] [Loss tangent (tanδ)] The foamed molded body was cut into pieces with a width of 5 mm, a length of 25 mm, and a thickness of 0.1 - 0.5 mm. Using Rheogel-E4000 manufactured by UBM with a distance of 15 mm between the clamps, the dynamic viscoelasticity was measured under the following conditions, and the tanδ at 23°C was read. Note that the non-foamed skin layer of the foamed molded body was cut for sampling. Measurement temperature range: -100~150°C Temperature rising condition: 2°C / min Here, tanδ refers to the loss angle in the relationship expressed by the following formula when a periodic stimulus of 11 Hz is applied to the test piece and the strain (or stress) is observed as the response. tanδ = E’’ (dynamic loss elastic modulus) / E’ (dynamic storage elastic modulus)

[0076] [Moldability] The moldability of the foam molded body was evaluated from the thickness of the foam molded body produced by the mold expansion method described above. In Examples 1 to 8 and Comparative Examples 1 to 6, in a mold that forms a cavity with a width of 100 mm, a length of 100 mm, and a thickness of 3.0 mm when clamped, the cavity volume was expanded by causing a core back of 12.0 mm in the mold opening direction to obtain a foam molded body. At this time, although a foam molded body with a final thickness of 15.0 mm was obtained, if the moldability of the resin was poor, the thickness would become small. The evaluation of the moldability was carried out according to the following. ○: The thickness of the foam molded body is 14.0 mm or more △: The thickness of the foam molded body is 10.0 mm or more and less than 14.0 mm ×: The thickness of the foam molded body is less than 10.0 mm

[0077] [Sound absorption characteristics] Using a normal incidence sound absorption rate measurement system WinZacMTX manufactured by Nippon Acoustical Engineering Co., Ltd., the normal incidence sound absorption rate was measured in the frequency range of 0.4 kHz to 5.0 kHz, which is the main frequency of automobile noise as defined in JIS A1405-2(2007), for each of Examples 1 to 8 and Comparative Examples 1 to 6. At this time, the peak that first appears when looking from the low frequency where the sound absorption rate is 40% or more was read as the sound absorption peak frequency.

[0078]

Table 2

[0079] As is clear from Table 2, all of Examples 1 to 8 within the scope of the present invention are thin and lightweight, have a resilience modulus of 30 to 60%, a surface hardness of 10C to 55C, a highly flexible cushioning property, and show a sound absorption peak frequency with a high sound absorption rate in the frequency range of 0.4 kHz to 5.0 kHz. From the comparison of Examples 1 to 4 and Comparative Examples 1 and 2, and the comparison of Example 8 and Comparative Example 1, it can be seen that as the content of the thermoplastic elastomer (B) increases, the resilience modulus and surface hardness decrease, showing a flexible cushioning property. Furthermore, as the loss tangent tanδ increases, the sound absorption peak frequency appears in the low-frequency region. However, in Comparative Example 3 where the content of the thermoplastic elastomer (B) is 65 parts by mass, the resin does not follow during foam molding, resulting in poor moldability. Even in Examples 5 to 7 and Comparative Examples 4 to 6 where the content of the soft segment of the thermoplastic polyester elastomer (A) is small, the above-mentioned tendencies of the cushioning property and sound absorption characteristics are shown. From the comparison of Example 2 and Example 8, from the viewpoint of flexible cushioning property, it can be said that the styrene-based elastomer is desirable as the thermoplastic elastomer (B). Industrial applicability

[0080] The foam molded body made of the thermoplastic polyester elastomer resin composition of the present invention is not only excellent in thinness and light weight, but also has a comfortable cushioning property, and can control extremely high sound absorption from the low-frequency to the high-frequency region. Furthermore, despite a high foaming ratio, it has a uniform foaming state, high heat resistance, water resistance, and molding stability, so it is possible to provide a foam molded body made of a polyester elastomer resin composition that can be applied to parts that require high reliability.

Explanation of symbols

[0081] 1 Mold (for fixing) 2 Mold (for operation) 3 Cavity 4 Injection molding machine 4a Plasticizing region 5 Gas cylinder 6 Booster pump 7 Pressure control valve

Claims

1. A thermoplastic polyester elastomer (A) and a thermoplastic elastomer (B) other than (A) are contained in a mass ratio of (A) / (B) = 95 / 5 to 50 / 50, The content of the soft segment of the thermoplastic polyester elastomer (A) is 55 to 90% by mass, and it is a foamed molded body made of a thermoplastic polyester elastomer resin composition, It has a non-foamed skin layer with a thickness of 100 to 800 μm on the surface layer, and a foamed layer composed of foamed cells with an average cell diameter of 10 to 900 μm independent of the resin continuous phase in the inner layer, and has a sandwich structure of the non-foamed skin layer and the foamed layer in the thickness direction.

2. The foamed molded body according to claim 1, wherein the loss tangent (tanδ) at 23°C is 0.10 or more.

3. The thermoplastic polyester elastomer (A) is composed of a hard segment made of a polyester having an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components, and at least one soft segment selected from an aliphatic polyether, an aliphatic polyester, and an aliphatic polycarbonate. The foamed molded body according to claim 1 or 2, which is a thermoplastic polyester elastomer in which the content of the soft segment is 55 to 90% by mass.

4. The foamed molded body according to any one of claims 1 to 3, wherein the thermoplastic elastomer (B) is at least one selected from a thermoplastic polyolefin-based elastomer and a thermoplastic styrene-based elastomer.

5. The foamed molded body according to any one of claims 1 to 4, wherein the rebound resilience is 30 to 60%.

6. The foamed molded body according to any one of claims 1 to 5, wherein the surface hardness is 10 to 55 C.

7. The foamed molded body according to any one of claims 1 to 6, wherein the average cell diameter is 10 to 900 μm.

8. The foamed molded article according to any one of claims 1 to 7, having a density of 0.1 to 0.35 g / cm ３ .

9. A sound-absorbing material containing the foamed molded body according to any one of claims 1 to 8, when measuring the normal incidence sound absorption rate of the foamed molded body in the frequency range of 0.4 kHz to 5.0 kHz according to JIS A1405-2 (2007), the sound-absorbing material is characterized in that it has a peak frequency at which the normal incidence sound absorption rate is 40% or more in the frequency range of 0.4 kHz to 5.0 kHz.

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