Polyester block copolymer composition and molded article

Abstract

The object of the present invention is to provide a polyester block copolymer resin composition that exhibits excellent flexibility and transparency, has excellent abrasion resistance, and can be processed into molded articles such as injection molded articles, extruded articles, films, fibers, nonwoven fabrics, and foams. [Solution] The present invention provides a polyester block copolymer resin composition comprising 100 parts by mass of a polyester block copolymer (A) containing 10 to 50% by mass of a high-melting-point crystalline polymer segment (a) consisting of crystalline aromatic polyester units and 90 to 50% by mass of a low-melting-point polymer segment (b) consisting of aliphatic polyether units and / or aliphatic polyester units, 0.01 to 3.0 parts by mass of an alkali metal salt of an aliphatic carboxylic acid (B), and / or 0.2 to 20 parts by mass of an ethylene copolymer (C) having a carboxylic acid metal base in its side chain, and 0.01 to 5.0 parts by mass of a modified wax (D).

Description

Technical Field

[0001] The present invention relates to a polyester block copolymer resin composition and a molded article.

Background Art

[0002] A polyester block copolymer having a crystalline aromatic polyester unit such as a polybutylene terephthalate unit as a hard segment and an aliphatic polyether unit such as poly(alkylene oxide) glycol as a soft segment is excellent not only in extrusion moldability and injection moldability, but also has high mechanical strength, rubber-like properties such as impact resistance, elastic recovery, flexural fatigue resistance, flexibility, low temperature and high temperature characteristics, water resistance, chemical resistance, etc., and is also thermoplastic and easy to mold. Therefore, its applications are expanding in the fields of automotive parts, electrical and electronic parts, fibers, films, etc.

[0003] Although it is such a useful polyester block copolymer, even though it is transparent when melted, it becomes cloudy and opaque when cooled and solidified, so it could not be used for applications that require light transmittance or transparency.

[0004] Techniques for making polyester block copolymers transparent have been studied so far. For example, a resin composition made transparent by blending a sodium salt of a carboxylic acid with a polyether ester block copolymer (see, for example, Patent Document 1), and for a polyester block copolymer, a polyether ester block copolymer is made to contain an ethylene unit and a carboxylic acid-containing unit, and a copolymer in which this carboxylic acid unit is neutralized with a metal ion is blended alone or together with an alkali metal salt of a carboxylic acid to make a transparent resin composition (see, for example, Patent Document 2) has already been proposed.

[0005] According to Patent Document 3, a method has been proposed for imparting high surface hardness and high transparency to molded articles of polyester block copolymers containing a dicarboxylic acid component and a specific glycol component, an alkali metal salt of an organic carboxylic acid, and a glycidyl group-containing styrene-acrylic polymer.

[0006] On the other hand, a method for imparting abrasion resistance to polyester block copolymers is known, which involves adding abrasion-resistant modifiers such as silicone resins (for example, Patent Document 4). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-306263 [Patent Document 2] Patent No. 4380808 [Patent Document 3] Patent No. 2015-74760 [Patent Document 4] Japanese Patent Publication No. 2009-126906 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the polyester block copolymers that have been given transparency in the technologies described in Patent Documents 1 and 2, the more soft segments there are, the more flexible and transparent they become. However, because of their flexibility, they have low surface hardness, and therefore cannot be used in applications that require abrasion resistance, such as those involving repeated contact with people or objects, as this would result in excessive wear.

[0009] The polyester block copolymer described in Patent Document 3 has high surface hardness, which may result in less wear even with repeated contact from people or objects. However, due to its high surface hardness, its flexibility is reduced. Furthermore, there are limitations, such as the use of specific glycol components.

[0010] While the polyester block copolymer described in Patent Document 4 can improve abrasion resistance while maintaining flexibility, from the viewpoint of compatibility between the abrasion resistance modifier and the polyester block copolymer, a decrease in transparency may occur when applied to a transparent polyester block copolymer.

[0011] The inventors of this invention considered that even if surface hardness is controlled or conventional wear-resistant modifiers are added to improve wear resistance, it is difficult to achieve both transparency and flexibility.

[0012] The object of the present invention is to provide a polyester block copolymer resin composition that exhibits excellent flexibility and transparency, as well as excellent abrasion resistance. [Means for solving the problem]

[0013] The inventors focused on specific waxes. Specifically, they focused on modified waxes and found that by using modified waxes, specific polyester block copolymers, and alkali metal salts of carboxylic acids and / or ethylene copolymers having carboxylic acid groups in their side chains, it is possible to improve abrasion resistance while maintaining transparency and flexibility.

[0014] As a result of diligent research to achieve the above objective, the inventors have come to propose the following invention. That is, the aspect of the present invention is as follows. (1) A polyester block copolymer resin composition comprising 100 parts by mass of polyester block copolymer (A) containing 10 to 50% by mass of high-melting-point crystalline polymer segments (a) consisting of crystalline aromatic polyester units and 90 to 50% by mass of low-melting-point polymer segments (b) consisting of aliphatic polyether units and / or aliphatic polyester units, with 0.01 to 3.0 parts by mass of alkali metal salt of aliphatic carboxylic acid (B), and / or 0.2 to 20 parts by mass of ethylene copolymer (C) having a carboxylic acid metal base in the side chain, and 0.01 to 5.0 parts by mass of modified wax (D). (2) The polyester block copolymer resin composition according to (1), characterized in that the modified wax (D) is acid-modified. (3) The polyester block copolymer resin composition according to (1), characterized in that the haze value (cloudiness) measured on a sheet with a thickness of 2 mm is 60% or less, and the surface hardness in accordance with JIS K7215:1986 is 20 to 50D. (4) A molded article obtained by processing the polyester block copolymer resin composition described in any of (1) to (3) above. (5) A molded article having the polyester block copolymer resin composition described in any of (1) to (3) above used as the outer covering. [Effects of the Invention]

[0015] According to the present invention, a polyester block copolymer resin composition is obtained that exhibits excellent flexibility and transparency, as well as excellent abrasion resistance and moldability. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below.

[0017] The polyester block copolymer (A) used in the present invention mainly comprises a high-melting-point crystalline polymer segment (a) consisting of crystalline aromatic polyester units and a low-melting-point polymer segment (b) consisting of aliphatic polyether units and / or aliphatic polyester units.

[0018] The high-melting-point crystalline polymer segment (a) of the polyester block copolymer (A) used in the present invention is a polyester formed from an aromatic dicarboxylic acid or its ester-forming derivative and an aliphatic diol, preferably polybutylene terephthalate derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol. In addition, a dicarboxylic acid component such as isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sulfoisophthalic acid, or their ester-forming derivatives, and a diol with a molecular weight of 300 or less, such as aliphatic diols such as ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, decamethylene glycol, etc., and alicyclic diols such as 1,4-cyclohexanedimethanol and tricyclodecanedimethylol. The polyester may be derived from aromatic diols such as formula diols, xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4'-dihydroxy-p-terphenyl, 4,4'-dihydroxy-p-quarterphenyl, or a copolymerized polyester using two or more of these dicarboxylic acid and diol components. It is also possible to copolymerize polyfunctional carboxylic acid components with three or more functions, polyfunctional oxyacid components, and polyfunctional hydroxy components in a range of 5 mol% or less. The polyester formed from aromatic dicarboxylic acids or their ester-forming derivatives and aliphatic diols may be derived from fossil fuel resources or biomass resources.

[0019] The low melting point polymer segment (b) of the polyester block copolymer (A) used in the present invention is an aliphatic polyether and / or an aliphatic polyester, and an aliphatic polycarbonate may be used in combination. Examples of the aliphatic polyether include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene 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.

[0020] Examples of the aliphatic polyester include poly(ε-caprolactone), poly(enantholactone), polycapryllactone, polybutylene adipate, and polyethylene adipate. Among these aliphatic polyethers and / or aliphatic polyesters, poly(tetramethylene oxide) glycol, an ethylene oxide adduct of poly(propylene oxide) glycol, poly(ε-caprolactone), polybutylene adipate, polyethylene adipate, etc. are preferable from the elastic properties of the polyester block copolymer obtained. The number average molecular weight of these low melting point polymer segments is preferably about 300 to 6000 in the copolymerized state. Note that the aliphatic polyether, aliphatic polyester, and aliphatic polycarbonate may be derived from fossil fuel resources or biomass resources.

[0021] In the polyester block copolymer (A) used in the present invention, the copolymerization amount of the high melting point crystalline polymer segment (a) is 10 to 50% by mass, and the copolymerization amount of the low melting point polymer segment (b) is 90 to 50% by mass. Preferably, the copolymerization amount of the high melting point crystalline polymer segment (a) in the polyester block copolymer (A) is 10 to 40% by mass, and the copolymerization amount of the low melting point polymer segment (b) is 90 to 60% by mass. When the copolymerization amount of the high melting point crystalline polymer segment (a) is less than 10% by mass, the crystallinity becomes insufficient and the moldability and heat resistance deteriorate. On the other hand, when the copolymerization amount of the high melting point crystalline polymer segment (a) exceeds 50% by mass, the transparency aimed at in the present invention is not sufficiently exhibited.

[0022] The polyester block copolymer (A) used in the present invention can be produced by a known method. For example, a method in which a lower alcohol diester of a dicarboxylic acid, an excessive amount of a low molecular weight glycol, and a low melting point polymer segment component are subjected to a transesterification reaction in the presence of a catalyst, and the resulting reaction product is polycondensed. Alternatively, a method in which a dicarboxylic acid, an excessive amount of glycol, and a low melting point polymer segment component are subjected to an esterification reaction in the presence of a catalyst, and the resulting reaction product is polycondensed. Also, a method in which a high melting point crystalline segment is prepared in advance, and a low melting point segment component is added thereto and randomized by a transesterification reaction. A method of connecting a high melting point crystalline segment and a low melting point polymer segment with a chain linking agent. Further, when poly(ε-caprolactone) is used as the low melting point polymer segment, any method such as an addition reaction of an ε-caprolactone monomer to the high melting point crystalline segment may be employed.

[0023] The resin composition of the present invention contains an alkali metal salt (B) of an aliphatic carboxylic acid and / or an ethylene copolymer (C) having a carboxylic acid metal base in the side chain.

[0024] Alkali metal salts of aliphatic carboxylic acids (B) are used as clearing agents that have the effect of making polyester block copolymer resin compositions transparent. Aliphatic carboxylic acids are compounds in which a carboxyl group is attached to a linear or branched aliphatic group, and some of the bonds may have other substituents such as unsaturated groups, alicyclic groups, aromatic groups, hydroxyl groups, or phosphate ester groups. The number of carbon atoms in the carboxylic acid of the alkali metal salt of an aliphatic carboxylic acid is preferably 10 or more. More preferably, it is an aliphatic carboxylic acid with 10 to 20 carbon atoms. Most preferably, it is an aliphatic carboxylic acid with 10 to 15 carbon atoms. Aliphatic carboxylic acid metal salts with 9 or fewer carbon atoms are preferred because they can improve transparency with small amounts, but they may cause bleed-out due to their short carbon chains. The alkali metal salt of an aliphatic carboxylic acid may be derived from fossil fuel resources or biomass resources.

[0025] Among aliphatic carboxylic acids, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid are preferred, and among alkali metal salts, potassium salts, lithium salts, and sodium salts are preferred in terms of solubility in polyester block copolymers and good crystal nucleation properties.

[0026] The amount of aliphatic alkali metal carboxylic acid salt (B) is 0.01 to 3.0 parts by mass per 100 parts by mass of polyester block copolymer (A). More preferably, the amount of aliphatic alkali metal carboxylic acid salt (B) is 0.05 to 2.0 parts by mass, and even more preferably 0.1 to 1.0 parts by mass. If the amount of aliphatic alkali metal carboxylic acid salt (B) exceeds 3 parts by mass, the amount of gas generated during processing will increase, which may affect moldability.

[0027] Ethylene copolymers (C) having a carboxylic acid metal base in the side chain are obtained by neutralizing copolymers of ethylene and ethylene-based unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid with alkali metal ions, alkaline earth metal ions, or zinc ions. These are commercially available, for example, as "Sarlin" from Dow or "Hymiran" from Mitsui Dow Polychemicals. Among these, those neutralized with alkali metal ions such as sodium, potassium, and lithium are preferred. The ethylene copolymer having a carboxylic acid metal base in the side chain may be derived from either fossil fuel resources or biomass resources.

[0028] The ethylene copolymer (C) having a carboxylic acid metal base in its side chains is present in an amount of 0.2 parts by mass or more and 20 parts by mass or less per 100 parts by mass of polyester block copolymer (A). Preferably, 0.5 to 15 parts by mass, and particularly preferably 1 to 10 parts by mass, is added.

[0029] If the amount of ethylene copolymer (C) having a carboxylic acid metal base in the side chain is less than 0.2 parts by mass, light transmission and transparency will be insufficient, and if it is 20 parts by mass or more, phase separation may occur, potentially leading to a decrease in mechanical properties, light transmission, and transparency.

[0030] The resin composition of the present invention contains a modified wax (D). By using the modified wax (D), the abrasion resistance of the polyester block copolymer can be improved without causing it to become cloudy.

[0031] The modified wax (D) used in the present invention is a resin obtained by copolymerizing two or more monomers and is not a polyester block copolymer (A) or an ethylene copolymer (C), and is a resin that is solid or semi-solid at room temperature and has a melting point of 40°C or higher.

[0032] Examples of monomers include combinations of olefin resins such as propylene and ethylene, resins with aromatic rings such as styrene, and polar resins such as maleic anhydride, epoxy, and hydroxyl groups. Of the two or more monomers, at least one is an olefin monomer, and at least one is a monomer with an aromatic ring or a monomer with a polar group.

[0033] Among the modified waxes (D), modified waxes (D) that can react with the carboxyl groups and hydroxyl groups of the terminal groups of polyethylene block copolymers are preferred from the viewpoint of compatibility and abrasion resistance, and more preferably acid-modified modified waxes (D). As acid-modified modified waxes (D), maleic anhydride oxide of ethylene-propylene copolymer or copolymers of α-olefin and maleic anhydride are preferred.

[0034] The modified wax (D) is present in an amount of 0.01 parts by mass or more and 5 parts by mass or less per 100 parts by mass of polyester block copolymer (A). Preferably, it is 0.1 to 4 parts by mass, and particularly preferably 0.5 to 3 parts by mass. If the amount of modified wax (D) is less than 0.01 parts by mass, wear resistance cannot be imparted, and if it is more than 5 parts by mass, a decrease in transparency and bleed-out to the surface of the molded product will occur, resulting in an undesirable appearance. The modified wax may be derived from fossil fuel resources or biomass resources.

[0035] When high-temperature and long-term heat resistance is required for the resin composition of the present invention, it is preferable to contain a hindered phenol-based radical scavenger and a peroxide decomposer. More preferably, a combination of a hindered phenol-based radical scavenger and a peroxide decomposer is preferred.

[0036] The hindered phenol radical scavenger used here is preferably a hindered phenol compound with a molecular weight of 500 or more. The peroxide decomposition agent is preferably a phosphite compound and / or a thioether compound. Among phosphite compounds, those having two or more phosphorus atoms in the molecule are even more preferred. The amount added is preferably 0.1 parts by mass or more and 5 parts by mass or less, based on the mass of the resin composition. If it is less than 0.1 parts by mass, the thermal degradation prevention effect may be poor. If it exceeds 5 parts by mass, it may adversely affect the color tone of the resin composition.

[0037] When weather resistance is required, the resin composition of the present invention preferably contains a light stabilizer. Preferred light stabilizers include UV absorbers such as benzotriazole compounds and benzophenone compounds, and hindered amine compounds. These may be used alone, but it is even more preferable to use a combination of a UV absorber such as a benzotriazole compound or benzophenone compound and a hindered amine compound. The amount of these light stabilizers is preferably 0.1 parts by mass or more and 5 parts by mass or less of the resin composition.

[0038] The resin composition of the present invention may contain a plasticizer. Preferred plasticizers include aromatic ester plasticizers such as phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, and glycol dibenzoate plasticizers, as well as oxy acid ester plasticizers, pentaerythritol plasticizers, aromatic sulfonamide plasticizers, alkylene oxide adduct plasticizers of phenol derivatives, polyester plasticizers, aliphatic ester plasticizers, and phosphate ester plasticizers. Among these, aromatic ester plasticizers are particularly preferred. These plasticizers are preferably present in amounts of 1 part by mass or more and 50 parts by weight or less of the resin composition.

[0039] The resin composition of the present invention may contain various other additives. These additives may include resins other than those of the present invention, flame retardants, inorganic fillers, stabilizers, and antioxidants widely used as additives to thermoplastic elastomers, provided they do not impair the characteristics of the present invention. Other additives that may be added include coloring pigments, inorganic and organic fillers, coupling agents, tack enhancers, quenchers, metal deactivators and other stabilizers, and polyfunctional glycidyl group-containing styrene polymers.

[0040] The resin composition of the present invention preferably comprises a total of 80% by mass or more of a polyester block copolymer (A), an aliphatic carboxylic acid alkali metal salt (B), and / or an ethylene copolymer (C) having a carboxylic acid metal base in its side chain, and a modified wax (D). More preferably, the total of (A), (B), (D), or (A), (C), (D), or (A), (B), (C), (D), is 90% by mass or more, and even more preferably 95% by mass or more.

[0041] The method for producing the resin composition of the present invention is not particularly limited, but can be appropriately employed, for example, by supplying a raw material mixture containing a polyester block copolymer (A), an alkali metal aliphatic carboxylic acid salt (B), an ethylene copolymer (C) having a metal carboxylic acid base in its side chain, a modified wax (D), and other additives to a screw-type extruder and melting and kneading it, or by first supplying the polyester block copolymer (A) to the screw-type extruder and melting it, and then supplying the alkali metal aliphatic carboxylic acid salt (B), an ethylene copolymer (C) having a metal carboxylic acid base in its side chain, a modified wax (D), and other additives from another supply port and kneading them.

[0042] The resin composition of the present invention is molded by conventional melt molding methods, such as injection molding, extrusion molding, and foam molding, and used in various applications. It can also be used as fibers, films, sheets, tubes, etc. Furthermore, due to its excellent transparency and colorfastness, it can be used in automotive interior parts, electrical appliances, and other applications. [Examples]

[0043] The effects of the present invention will be explained below with reference to examples. In the examples, percentages and parts are all based on mass unless otherwise specified. Furthermore, the physical properties shown in the examples were measured as follows.

[0044] • Melting point A differential scanning calorimeter (TA Instruments DSC Q1000) was used to measure the peak temperature of the melting point when heated at a heating rate of 10°C / min under a nitrogen gas atmosphere.

[0045] • Surface hardness (Shore D scale) Measurements were taken in accordance with JIS K-7215:1986.

[0046] • Total light transmittance (%) and haze value (cloudiness) (%) Using an electric injection molding machine (NEX-1000) manufactured by Nissei Plastic Industrial Co., Ltd., test specimens measuring 125 mm × 75 mm and 2 mm thick were prepared from a polyester block copolymer resin composition at a temperature of 220°C (mold temperature: 40°C). The surface roughness of the test specimens was measured using a VK-9700 manufactured by Keyence and was found to be 0.46 μm. Using these test specimens, measurements were taken using a DIRECT READING HAZEMETER manufactured by Toyo Seiki Seisakusho Co., Ltd. in accordance with JIS K7105:2010.

[0047] • Abrasion resistance test Using injection-molded specimens with a thickness of 2 mm, and with S45C steel as the mating material, the amount of wear was evaluated by sliding them for 1 hour using a thrust abrasion tester in accordance with JIS K-7218:1986 at a test speed of 100 mm / s and a load of 100 N. Abrasion resistance was judged by the amount of wear, as shown below. Wear rate: 100 mg / cm 2 • Less than h: ○, wear amount 100 mg / cm 2 ·More than h:× Manufacturing example Production of polyester block copolymer (A-1) 270 parts by mass of terephthalic acid, which forms a high-melting-point crystalline polymer segment consisting of crystalline aromatic polyester, 686 parts by mass of poly(tetramethylene oxide) glycol with a number-average molecular weight of approximately 1400, which forms a low-melting-point polymer segment consisting of aliphatic polyether units, 311 parts by mass of 1,4-butanediol, and 1.8 parts by mass of titanium tetrabutoxide were charged together in a reaction vessel equipped with a helical ribbon-type stirring blade, and the esterification reaction was carried out by heating at 190-225°C for 3 hours while distilling off the reaction water from the system. After adding 1.0 part by mass of "Irganox" 1330 (a hindered phenol-based radical scavenger manufactured by BASF) to the reaction mixture, the temperature was raised to 245°C, and then the pressure in the system was reduced to 0.2 mmHg over 50 minutes, and polymerization was carried out under these conditions for 2 hours and 45 minutes. The obtained polymer was discharged in strand form into water and cut to form pellets.

[0048] Production of polyester block copolymer (A-2) 420 parts by mass of terephthalic acid, which forms a high-melting-point crystalline polymer segment consisting of crystalline aromatic polyester, 354 parts by mass of poly(tetramethylene oxide) glycol with a number-average molecular weight of approximately 1400, which forms a low-melting-point polymer segment consisting of aliphatic polyether units and / or aliphatic polyester units, 251 parts by mass of 1,4-butanediol, and 0.3 parts by mass of titanium tetrabutoxide were charged together in a reaction vessel equipped with helical ribbon-type stirring blades, and the esterification reaction was carried out by heating at 190-225°C for 3 hours while distilling off the reaction water from the system. 2.0 parts by mass of titanium tetrabutoxide were added to the reaction mixture, and 0.5 parts by mass of "Irganox" 1098 (a hindered phenol antioxidant manufactured by Ciba-Geigy) was added. The temperature was then raised to 245°C, and the pressure in the system was reduced to 0.2 mmHg over 50 minutes. Under these conditions, melt polycondensation was carried out for 2 hours and 45 minutes. The obtained polyester elastomer was extruded into water in strand form and cut to form pellets.

[0049] Table 1 shows the composition and properties of A-1 and A-2. In the table, PTMG represents poly(tetramethylene oxide) glycol, and the number indicates the number-average molecular weight. BD represents 1,4-butanediol, and TPA represents terephthalic acid.

[0050] [Table 1]

[0051] Table 2 also shows the main components of polymers D-1 to D-4, which will be discussed later, as well as whether copolymerization occurred and whether acid modification occurred.

[0052] [Table 2]

[0053] Examples 1-4 The polyester block copolymer (A-1) obtained in the reference example was dry-blended with an alkali metal salt of carboxylic acid (NS-3A (sodium laurate) manufactured by Nitto Chemical Industries, Ltd.) (B-1), an ethylene copolymer having a sodium carboxylate base in the side chain ("Hymiran" 1707 manufactured by Mitsui Dow Polychemicals) (C-1), and a modified wax ("Hywax" 1105A manufactured by Mitsui Chemicals, Inc.) (D-1) or ("Diacarna" 30M manufactured by Mitsubishi Chemical Corporation) (D-2) in the proportions shown in Table 3. The mixture was then melt-kneaded and pelletized using a twin-screw extruder with a cylinder diameter of 45 mmφ. After drying these pellets at 80°C for 3 hours, test specimens measuring 125 mm × 75 mm and 2 mm thick were prepared using an electric injection molding machine (NEX-1000) manufactured by Nissei Plastic Industrial Co., Ltd. at 220°C (mold temperature: 40°C). The obtained 2mm thick sheet was used to measure total light transmittance and haze value (cloudiness). Surface hardness was also measured according to JIS K-7215:1986.

[0054] Comparative Examples 1-4 The polyester block copolymer (A-1) or (A-2) obtained in the reference example was dry-blended with an alkali metal salt of a carboxylic acid (NS-3A (sodium laurate) manufactured by Nitto Chemical Industries, Ltd.) (B-1), an ethylene copolymer having a sodium carboxylate base in the side chain ("Hymiran" 1707 manufactured by Mitsui Dow Polychemicals) (C-1), a polyethylene resin wax without copolymerization ("Hywax" 400P manufactured by Mitsui Chemicals, Inc.) (D-3), or a silicone resin ("MULTIBASE" BY27-219 manufactured by DuPont) (D-4) in the proportions shown in Table 3. The mixture was then melt-kneaded and pelletized using a twin-screw extruder with a cylinder diameter of 45 mmφ. After drying the pellets at 80°C for 3 hours, test specimens measuring 125 mm x 75 mm and 2 mm thick were fabricated using a Nissei Plastic Industrial Co., Ltd. electric injection molding machine (NEX-1000) at 220°C (mold temperature: 40°C). The total light transmittance, haze value (cloudiness), and surface hardness were measured using the resulting 2 mm thick sheets. Abrasion resistance was also evaluated.

[0055] [Table 3]

[0056] As is clear from Examples 1 to 4 in Table 3, a polyester block copolymer resin composition containing 100 parts by mass of polyester block copolymer (A) comprising 10 to 50% by mass of a high-melting-point crystalline polymer segment (a) consisting of crystalline aromatic polyester units and 90 to 50% by mass of a low-melting-point polymer segment (b) consisting of aliphatic polyether units and / or aliphatic polyester units, along with 0.01 to 3.0 parts by mass of alkali metal salt of an aliphatic carboxylic acid (B), 0.2 to 20 parts by mass of ethylene copolymer (C) having a carboxylic acid metal base in the side chain, and 0.01 to 5.0 parts by mass of modified wax (D), is flexible, highly transparent, and has excellent abrasion resistance.

[0057] Comparative Example 1 shows that a polyester block copolymer resin composition containing only a polyester block copolymer (A), an alkali metal salt of an aliphatic carboxylic acid (B), and an ethylene copolymer (C) having a carboxylic acid metal base in its side chain exhibits poor abrasion resistance.

[0058] Comparative Example 2 shows that when the low-melting-point polymer segment consisting of aliphatic polyether units and / or aliphatic polyester units of the polyester block copolymer (A) is greater than 50% by mass, it exhibits excellent abrasion resistance but high surface hardness and poor flexibility.

[0059] Comparative Example 3 shows that when a non-polymerized wax is added to a polyester block copolymer (A), an alkali metal salt of an aliphatic carboxylic acid (B), and an ethylene copolymer (C) having a carboxylic acid metal base in its side chain, the transparency is excellent, but the abrasion resistance is poor. Comparative Example 4 shows that when a silicone resin is added to a polyester block copolymer (A), an alkali metal salt of an aliphatic carboxylic acid (B), or an ethylene copolymer (C) having a carboxylic acid metal base in its side chain, the abrasion resistance improves, but the compatibility is poor and the transparency decreases. [Industrial applicability]

[0060] The polyester block copolymer resin composition of the present invention is useful as a thermoplastic elastomer material that is more flexible, transparent, and has superior abrasion resistance compared to conventional polyester block copolymer resin compositions. For example, it is expected to be used in automotive interiors, electronic and electrical applications, writing instruments, tools, cameras, bicycle grips, cushions, and surfaces.

Claims

1. A polyester block copolymer resin composition comprising 100 parts by mass of a polyester block copolymer (A) containing 10 to 50% by mass of a high-melting-point crystalline polymer segment (a) consisting of crystalline aromatic polyester units and 90 to 50% by mass of a low-melting-point polymer segment (b) consisting of aliphatic polyether units and / or aliphatic polyester units, the composition containing 0.01 to 3.0 parts by mass of an alkali metal salt of an aliphatic carboxylic acid (B), and / or 0.2 to 20 parts by mass of an ethylene copolymer (C) having a carboxylic acid metal base in its side chain, and 0.01 to 5.0 parts by mass of a modified wax (D).

2. The polyester block copolymer resin composition according to claim 1, characterized in that the modified wax (D) is acid-modified.

3. The polyester block copolymer resin composition according to claim 1, characterized in that the haze value (cloudiness) obtained by measuring the polyester block copolymer resin composition as an injection-molded test piece with a thickness of 2 mm is 60% or less, and the surface hardness in accordance with JIS K7215:1986 is 20 to 50 D.

4. A molded article obtained by processing the polyester block copolymer resin composition according to any one of claims 1 to 3.

5. A molded article having the polyester block copolymer resin composition according to any one of claims 1 to 3 used as the outer casing.

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