Thermoplastic resin composition

Abstract

Provided is a thermoplastic resin composition which has excellent adhesiveness without providing a coating layer on the surface of a cushioning member, can suppress peeling due to stress deformation, and can form a cushioning member having weather resistance.　A thermoplastic resin composition containing a styrene-based thermoplastic elastomer (A) and a softening agent (B), wherein the styrene-based thermoplastic elastomer (A) contains at least one block copolymer composed of at least a styrene block and a butadiene block, the total content of butadiene that holds the carbon-carbon double bond of the butadiene block in the styrene-based thermoplastic elastomer (A) is 59.0-68.5 mass%, and the blending ratio of the styrene-based thermoplastic elastomer (A) and the softening agent (B) is, in terms of mass ratio, B / (A+B) = greater than 0.410 and less than 0.600.

Description

thermoplastic resin composition

[0001] The present invention relates to a thermoplastic resin composition that can be used for shock-absorbing materials for shoes, such as shoe soles and insoles.

[0002] Cushioning materials with excellent designability are used to provide cushioning to visible components, such as footwear soles, smartphone protective cases, bag grips, and shoulder pads. For example, in shoe design for sports shoes and other products requiring functionality, cushioning materials with excellent cushioning properties are incorporated into sole components made of resin or other materials. This type of cushioning material is required to be lightweight for ease of handling and to avoid interfering with the user's movements. Furthermore, since the cushioning material is incorporated into the sole component in a manner that is visible from the outside, which allows the functionality to be appealing to consumers, it is also required to have a high level of designability, such as a transparent appearance. Therefore, various cushioning materials made of styrene-based thermoplastic elastomers, which have low specific gravity (lightweight) and transparency, have been proposed.

[0003] For example, when this type of cushioning material is applied to footwear, Patent Document 1, filed by the present applicant, proposes a cushioning material for footwear that is made of a styrene-based thermoplastic elastomer and has excellent lightness, transparency, flexibility, and adhesiveness. This cushioning material for footwear is obtained by molding a cushioning composition for footwear that contains a styrene-based thermoplastic elastomer composed of at least a styrene-ethylene-butylene-styrene block copolymer (SEBS), an amine-modified styrene-ethylene-butylene-styrene block copolymer (amine-modified SEBS), and a styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and a softener in a predetermined blending ratio, with the molecular weight, styrene content, and blending ratio of each block copolymer falling within a predetermined range.

[0004] In recent years, in order to further pursue functionality and design of cushioning materials, the lightweight nature of the cushioning materials has been utilized, and the shapes have become more diverse, such as by increasing the size of the cushioning materials or by giving them designs that stand out from the outside. For example, in the design of high-performance shoes, as shown in Figures 1 and 2(a), it has become common to incorporate a cushioning material 10 so that it protrudes from the side of a sole member 20.

[0005] In such shoe designs, more reliable adhesion is required to accommodate not only compressive deformation but also complex stress deformation such as shear deformation, etc. Therefore, in the shock-absorbing member for footwear proposed in the above-mentioned Patent Document 1, a protective layer made of a urethane-based coating agent with excellent adhesiveness is formed on the outermost surface of the shock-absorbing member in order to improve adhesion to the sole member.

[0006] Patent No. 5966110

[0007] However, when providing a protective layer made of the above-mentioned urethane coating agent on the outermost surface of a buffer material, it is necessary to go through the steps of applying a primer agent to the surface of a molded product of the buffer composition, drying the primer agent to form a primer-treated layer, applying a photo-curable urethane coating agent on the primer-treated layer, drying the urethane coating agent, and photo-curing the urethane coating agent to form a protective layer. Because many steps are required, this is time-consuming and labor-intensive.

[0008] To address this issue of adhesiveness, in order to improve the adhesiveness of the buffer material itself without providing the buffer material with a coating layer such as a urethane coating agent, one approach has been considered to use a styrene-butadiene-styrene block copolymer (SBS) as the main component of the styrene-based thermoplastic elastomer that makes up the buffer material, instead of a styrene-ethylene-butylene-styrene block copolymer (SEBS). However, due to the high reactivity of the carbon-carbon double bonds contained in the butadiene blocks that make up SBS, the material is susceptible to degradation due to heat, light, ozone, etc., and has problems with weather resistance, such as the formation of fine cracks that cause the surface of the buffer material to become cloudy or oil bleeding to occur on the resin surface.

[0009] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a thermoplastic resin composition that can form a buffer member that has excellent adhesion, can suppress peeling due to stress deformation, and also has weather resistance, without providing a coating layer that contributes to improving adhesion on the surface of the buffer member.

[0010] The present inventors have discovered that when the main component of a styrene-based thermoplastic elastomer is a block copolymer composed of a styrene block and a butadiene block having a carbon-carbon double bond, adjusting the amount of carbon-carbon double bonds contained in the butadiene block to fall within a specific range makes it possible to obtain a cushioning member that can simultaneously achieve improved adhesion, suppression of peeling due to stress deformation, and improved weather resistance. Based on this finding, the present invention has been completed.

[0011] In order to solve the above problems, the thermoplastic resin composition of the present invention is a thermoplastic resin composition containing a styrene-based thermoplastic elastomer (A) and a softener (B), wherein the styrene-based thermoplastic elastomer (A) contains one or more block copolymers constituted of at least a styrene block and a butadiene block, the total content of butadienes holding carbon-carbon double bonds of the butadiene blocks in the styrene-based thermoplastic elastomer (A) is 59.0 to 68.5 mass%, and the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) is, in mass ratio, B / (A+B) = more than 0.410 and less than 0.600.

[0012] The thermoplastic resin composition of the present invention comprises a styrene-based thermoplastic elastomer (A) and a softener (B), wherein the styrene-based thermoplastic elastomer (A) comprises one or more block copolymers each composed of at least a styrene block and a butadiene block. The total content of butadiene retaining carbon-carbon double bonds in the butadiene blocks in the styrene-based thermoplastic elastomer (A) is 59.0 to 68.5 mass %, and the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) is set to a mass ratio of more than 0.410 and less than 0.600, thereby obtaining a thermoplastic resin composition for forming a buffer member that exhibits excellent adhesion, suppresses peeling due to stress deformation, and also exhibits excellent weather resistance. Therefore, when a buffer member is formed from this thermoplastic resin composition, the buffer member and the adherend can be bonded without the need for a coating layer such as a urethane coating agent, thereby reducing the effort and manufacturing costs associated with preparing and assembling the buffer member. In the present invention, weather resistance means that deterioration due to ozone, light, or heat (including moist heat) does not easily occur.

[0013] In addition, in the thermoplastic resin composition of the present invention, it is also preferable that the total content of styrene blocks in the styrene thermoplastic elastomer (A) is 31.5 to 41.0 mass%. This allows a suitable styrene block content in the styrene thermoplastic elastomer (A) of the present invention to be selected. This allows for the production of a thermoplastic resin composition that forms a cushioning member that has excellent adhesion to other members, is capable of suppressing peeling due to stress deformation, and has improved weather resistance, and is also excellent in appearance transparency and cushioning properties.

[0014] In addition, in the thermoplastic resin composition of the present invention, it is also preferable that the main component of the styrene-based thermoplastic elastomer (A) is a styrene-butadiene-styrene triblock copolymer (A1). This allows suitable components to be selected as constituent components of the styrene-based thermoplastic elastomer (A) of the present invention. By selecting the styrene-butadiene-styrene triblock copolymer (A1), a thermoplastic resin composition can be obtained that can form a cushioning member that has excellent adhesive properties and is excellent in suppressing peeling due to stress deformation.

[0015] In the thermoplastic resin composition of the present invention, the styrene-based thermoplastic elastomer (A) preferably comprises a styrene-butadiene-styrene triblock copolymer (A1) and a styrene-butadiene diblock copolymer (A2), and the blending ratio of the styrene-butadiene-styrene triblock copolymer (A1) to the styrene-butadiene diblock copolymer (A2) is preferably (A1):(A2)=more than 1:0 and less than 0.3 by mass. By configuring the styrene-based thermoplastic elastomer (A) from the styrene-butadiene-styrene triblock copolymer (A1) and the styrene-butadiene diblock copolymer (A2), it becomes easy to adjust the total content of butadiene retaining the carbon-carbon double bonds of the butadiene blocks in the styrene-based thermoplastic elastomer (A) to a specific range, and the melt fluidity of the thermoplastic resin composition of the present invention can be adjusted to a range that is easy to handle.

[0016] In addition, it is also preferable that the butadiene blocks in the one or more block copolymers of the thermoplastic resin composition of the present invention are not substantially hydrogenated. This results in the total content of butadiene blocks in the styrenic thermoplastic elastomer (A) being the same as the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks. This makes it easy to adjust the amount of carbon-carbon double bonds contained in the butadiene blocks to a specific range while maintaining the total content of styrene blocks within an appropriate range, allowing for the selection of a suitable block copolymer constituting the styrenic thermoplastic elastomer (A) of the present invention. Furthermore, even if the butadiene blocks are not hydrogenated, the thermoplastic resin composition of the present invention has sufficient weather resistance by adjusting the amount of carbon-carbon double bonds contained in the butadiene blocks to a specific range.

[0017] In the thermoplastic resin composition of the present invention, the softener (B) is preferably a paraffinic oil or naphthenic oil having a molecular weight of 300 to 1200. This makes it possible to obtain a thermoplastic resin composition that can be used to form a cushioning member having excellent flexibility.

[0018] The thermoplastic resin composition of the present invention preferably further contains an antioxidant, thereby obtaining a thermoplastic resin composition for forming a buffer member having further improved weather resistance, such as moist heat resistance.

[0019] The thermoplastic resin composition of the present invention preferably further contains a light stabilizer, thereby obtaining a thermoplastic resin composition for forming a buffer member having further improved weather resistance, such as light resistance.

[0020] Furthermore, it is also preferable that the hardness of a molded article of the thermoplastic resin composition of the present invention is ASKER C30 to 50 (SRIS 0101 standard, 23±2°C) and the haze value (in accordance with JIS K7136:2000) is 15% or less. A molded article of the thermoplastic resin composition having such physical properties is excellent in flexibility and transparency, and can therefore be suitably used as a cushioning material applied to a portion visible from the outside.

[0021] The shock-absorbing material of the present invention is formed from a molded article of the thermoplastic resin composition described above. The shock-absorbing material of the present invention is also preferably used for footwear. Such a thermoplastic resin composition has excellent weather resistance and design properties, and is therefore suitable for use as a shock-absorbing material for footwear.

[0022] The thermoplastic resin composition of the present invention is also preferably a composition for 3D printers. The thermoplastic resin composition of the present invention is suitably used as a composition for 3D printers that has adhesiveness and transparency. Therefore, a buffer member made of a molded article of the thermoplastic resin composition of the present invention can be formed by molding using a 3D printer.

[0023] According to the present invention, a thermoplastic resin composition and a buffer member having the following excellent effects can be provided. (1) A thermoplastic resin composition can be obtained that can form a buffer member that has excellent adhesion, can suppress peeling due to stress deformation, and is also weather-resistant. (2) Since the surface of the buffer member can be bonded with sufficient strength without providing a coating layer that contributes to improving adhesion, a coating step after forming the buffer member is not required, which shortens the production time and reduces production costs. Furthermore, because a coating layer is not provided, the thermoplastic resin composition can be easily recycled, improving sustainability.

[0024] FIG. 3 is a diagram schematically illustrating a sports shoe in which a cushioning member is incorporated into the side surface of a sole member. FIG. 4 is a diagram illustrating (a) a partial cross-sectional view and (b) a view illustrating a state when a load is applied, which schematically illustrate the configuration of a conventional cushioning member and sole portion. FIG. 5 is a diagram illustrating (a) a plan view and (b) a front view, which schematically illustrate the configuration of a test piece prepared for a creep test and a peel strength measurement test in Examples and Comparative Examples. FIG. 6 is a diagram illustrating a method for a creep test performed using the test piece of FIG. 3. FIG. 7 is a diagram illustrating a method for a peel strength measurement test performed using the test piece of FIG. 3. FIG. 8 is a diagram illustrating a method for an ozone exposure test to evaluate ozone resistance.

[0025] The thermoplastic resin composition according to the present invention comprises a styrene-based thermoplastic elastomer (A) and a softener (B), the styrene-based thermoplastic elastomer (A) comprising one or more block copolymers each composed of at least a styrene block and a butadiene block, the total content of butadiene retaining the carbon-carbon double bonds of the butadiene blocks in the styrene-based thermoplastic elastomer (A) being 59.0 to 68.5 mass %, and the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) being, in mass ratio, B / (A+B) = more than 0.410 and less than 0.600.

[0026] First, the styrene-based thermoplastic elastomer (A) constituting the thermoplastic resin composition will be described. The styrene-based thermoplastic elastomer (A) according to the present invention contains one or more block copolymers composed of at least a styrene block and a butadiene block. Examples of block copolymers composed of at least a styrene block and a butadiene block include a styrene-butadiene diblock copolymer (hereinafter also referred to as SB), a styrene-butadiene-styrene triblock copolymer (hereinafter also referred to as SBS), and a styrene-butadiene-styrene-butadiene tetrablock copolymer. Of these, from the viewpoint of the effects according to the present invention, a styrene-butadiene-styrene triblock copolymer (SBS), a styrene-butadiene diblock copolymer (SB), or a combination thereof can be preferably used as the styrene-based thermoplastic elastomer (A). Furthermore, a styrene-butadiene-styrene triblock copolymer (SBS) is preferably used as the main component of the styrene-based thermoplastic elastomer (A). The block copolymer used in the present invention is preferably not substantially hydrogenated in order to retain the carbon-carbon double bonds of the butadiene blocks. However, the block copolymer may be partially hydrogenated as long as the total content of butadienes retaining the carbon-carbon double bonds of the butadiene blocks can be within a predetermined range described below.

[0027] In the present invention, it is important to adjust the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks of the block copolymer constituting the styrene-based thermoplastic elastomer (A) to a range of 59.0 to 68.5 mass%. In other words, the carbon-carbon double bonds in the butadiene blocks are highly reactive and can react with ozone, light, and heat, causing degradation. However, their high reactivity improves adhesion and suppresses peeling due to stress deformation. In the present invention, by adjusting the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks to a range of 59.0 to 68.5 mass%, a thermoplastic resin composition can be obtained that forms a buffer member with excellent adhesion, suppresses peeling due to stress deformation, and also has excellent weather resistance that can withstand ozone, light, heat, and the like. Note that, in this specification, the content of butadienes retaining carbon-carbon double bonds in the butadiene blocks refers to the content of the butadiene blocks when the block copolymer has not been substantially hydrogenated. When the block copolymer is partially hydrogenated, the content of the butadiene block can be determined by multiplying the proportion of the portion that has not been hydrogenated by the content of the butadiene block.

[0028] In the present invention, the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks of the block copolymer constituting the styrene-based thermoplastic elastomer (A) is preferably in the range of 59.0 to 68.5 mass%, more preferably in the range of 62.0 to 68.0 mass%, and even more preferably in the range of 64.0 to 66.0 mass%, from the viewpoints of improving adhesion, suppressing peeling due to stress deformation, and improving weather resistance. Here, the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks is determined in accordance with JIS K 6239-1:2017 Raw rubber - Determination of microstructure of solution polymerized SBR (quantitative) - Part 1: １ According to H-NMR and IR (cast film) methods １ The value is determined by the H-NMR method (absolute method).

[0029] On the other hand, the total content of styrene blocks in the block copolymer constituting the styrene-based thermoplastic elastomer (A) is preferably in the range of 31.5 to 41.0 mass%, more preferably in the range of 32.0 to 38.0 mass%, and even more preferably in the range of 34.0 to 36.0 mass%. This results in a thermoplastic resin composition that forms a buffer member that has excellent adhesion to other members, suppresses peeling due to stress deformation, and improves weather resistance, as well as excellent appearance transparency and cushioning properties. Here, the total content of styrene blocks is determined in accordance with JIS K 6239-1:2017 Raw rubber - Determination of microstructure of solution-polymerized SBR (quantitative) - Part 1: １ According to H-NMR and IR (cast film) methods １ The value is determined by the H-NMR method (absolute method).

[0030] In one embodiment of the present invention, the styrene-based thermoplastic elastomer (A) is formed by combining a styrene-butadiene-styrene triblock copolymer (A1) and a styrene-butadiene diblock copolymer (A2). This makes it easier to adjust the total content of butadiene having carbon-carbon double bonds in the butadiene blocks within a specific range. Furthermore, the melt fluidity of the thermoplastic resin composition of the present invention can be adjusted to a range that is easy to handle. From the viewpoint of the effects of the present invention, the blending ratio of the styrene-butadiene-styrene triblock copolymer (A1) to the styrene-butadiene diblock copolymer (A2) is preferably (A1):(A2)=more than 1:0 and less than 0.3, more preferably (A1):(A2)=1:0.03 or more and 0.2 or less.

[0031] The molecular weight of the block copolymer constituting the styrene-based thermoplastic elastomer (A) is not particularly limited. For example, the average molecular weight of the block copolymer may be 100,000 to 400,000. From the viewpoint of mechanical strength, it is preferably 104,000 or more, and from the viewpoint of adhesiveness and fluidity during molding, it is preferably 360,000 or less. That is, the average molecular weight of the block copolymer is preferably 105,000 to 350,000. By setting the average molecular weight of the block copolymer within this range, excellent adhesiveness can be obtained, molded articles that are less susceptible to peeling due to stress deformation such as flow deformation can be formed, and good fluidity can be achieved during molding. In the present invention, the molecular weight refers to the weight-average molecular weight Mw, measured by gel permeation chromatography (GPC).

[0032] The block copolymer constituting the styrene-based thermoplastic elastomer (A) in the present invention is not particularly limited, but examples thereof include Kraton (registered trademark) D1155, DX408, and DX405 (SBS; all products of Kraton Polymer Japan Co., Ltd.), Kraton (registered trademark) D1101, D1118, and DX423 (a mixture of SBS and SB; all products of Kraton Polymer Japan Co., Ltd.), and the like.

[0033] In the block copolymer constituting the styrene-based thermoplastic elastomer (A) of the present invention, the total content of butadienes retaining the carbon-carbon double bonds of the butadiene blocks is adjusted to be within a predetermined range, and within this range, other styrene-based block copolymers may be included in addition to the styrene-butadiene-styrene triblock copolymer (A1) and the styrene-butadiene diblock copolymer (A2). The other styrene-based block copolymer is not particularly limited, and examples thereof include a styrene-ethylenebutylene-styrene triblock copolymer (SEBS), a styrene-isoprene-styrene triblock copolymer (SIS), a styrene-ethylenepropylene-styrene triblock copolymer (SEPS), a styrene-isobutylene-styrene triblock copolymer (SIBS), a styrene-ethylene / ethylene-propylene-styrene block copolymer (SEEPS), and a styrene-ethylenepropylene diblock copolymer (SEP).

[0034] Next, the softener (B) constituting the thermoplastic resin composition will be described. The softener (B) is added mainly for the purpose of imparting flexibility to the composition. With regard to the blending ratio of the softener (B), from the viewpoint of increasing flexibility and achieving the effects of the present invention, the blending ratio of the softener (B) to the sum of the styrene-based thermoplastic elastomer (A) and the softener (B) is preferably more than 0.410 and less than 0.600, more preferably 0.416 or more and 0.550 or less, and particularly preferably 0.420 or more and 0.500 or less. By setting the blending ratio of the softener (B) within the above range, a thermoplastic resin composition can be obtained that imparts flexibility to the styrene-based thermoplastic elastomer (A), while forming a buffer member that has excellent adhesion, suppresses peeling due to stress deformation, and is also excellent in weather resistance.

[0035] Examples of softeners that can be used in the present invention include process oils such as paraffinic oil, naphthenic oil, and aromatic oil; synthetic resin softeners such as liquid polybutene and low-molecular-weight polybutadiene; and rosin. Of these, paraffinic oil is preferably used among process oils from the viewpoint of transparency in appearance, and paraffinic oil or naphthenic oil having a weight-average molecular weight of 300 to 1200 is particularly preferably used from the viewpoint of excellent adhesiveness and mechanical strength. The softener may be used alone, or multiple softeners with different physical properties such as components and viscosity (molecular weight) may be used in combination.

[0036] The thermoplastic resin composition of the present invention may further contain an antioxidant from the viewpoint of further improving weather resistance. By containing an antioxidant, oxidation of the thermoplastic resin composition and its molded article (buffer material) can be prevented, thereby imparting a function of further improving weather resistance. Examples of antioxidants include hindered amine-based antioxidants and hindered phenol-based antioxidants that function as chain terminators, and phosphite-based antioxidants and thioether-based antioxidants that function as peroxide decomposers.The hindered amine antioxidant can be appropriately selected from known antioxidants, and examples thereof include N,N',N",N'"-tetrakis-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine / 1,3,5-triazine / N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine / N-(2,2,6,6-tetramethyl-4 polycondensation polymer of {6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, [bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidine)decanedioate] lysyl) ester, reaction products of 1,1-dimethylethyl hydroperoxide with octane (70%)]-polypropylene (30%), bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, and the like.

[0037] The hindered phenol-based antioxidant may be appropriately selected from known ones, and examples thereof include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide], 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphate, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a' , a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di- tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate, and the like.

[0038] The phosphite antioxidant can be appropriately selected from known ones, and examples thereof include triphenyl phosphite, tris(nonylphenyl) phosphite, dilauryl hydrogen phosphite, triethyl phosphite, tridecyl phosphite, tris(2-ethylhexyl) phosphite, tris(tridecyl) phosphite, tristearyl phosphite, diphenyl monodecyl phosphite, monophenyl didecyl phosphite, diphenyl mono(tridecyl) phosphite, tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra(tridecyl) pentaerythritol tetraphosphite, and hydrogenated bisphenol A. Phenol phosphite polymer, diphenyl hydrogen phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenyl di(tridecyl)phosphite)tetra(tridecyl)4,4'-isopropylidene diphenyl diphosphite, bis(tridecyl)pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, dilauryl pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tris(4-tert-butylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, hydrogenated bisphenol A Examples of the diphosphite include pentaerythritol phosphite polymer, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0039] The thioether-based antioxidant can be appropriately selected from known ones, and examples thereof include pentaerythritol tetrakis(3-dodecylthiopropionate), didodecylthiodipropionate, ditridecylthiodipropionate, ditetradecylthiodipropionate, dioctadecylthiodipropionate, 2-mercaptobenzimidazole, and 2,4-bis[(dodecylthio)methyl]-6-methylphenol.

[0040] The antioxidants listed above can be used alone or in combination of two or more. When combining two or more types, the same or different components may be combined. Preferred combinations of different components include a hindered phenol-based antioxidant, a phosphite-based antioxidant, and a thioether-based antioxidant. More specifically, a more preferred combination is 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite as the phosphite-based antioxidant, 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate as the hindered phenol-based antioxidant, and 2,4-bis[(dodecylthio)methyl]-6-methylphenol as the thioether-based antioxidant. The antioxidant is preferably added in an amount of 0.1 to 2 parts by mass, more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the styrene-based thermoplastic elastomer (A). When a plurality of antioxidants are combined, the total addition ratio of the antioxidants is preferably within the above-mentioned range, and the addition ratio of each antioxidant is set within that range.

[0041] The thermoplastic resin composition of the present invention may further contain a light stabilizer from the viewpoint of further improving weather resistance. By including a light stabilizer, photo-oxidative degradation of the thermoplastic resin composition and its molded article (buffer material) can be prevented, thereby further improving weather resistance. Examples of light stabilizers include hindered amine light stabilizers (HALS) that have the effect of capturing and detoxifying radicals generated by photodegradation, and benzotriazole ultraviolet absorbers that function as light resistance stabilizers by absorbing ultraviolet light to suppress photoinduced reactions that lead to photodegradation of polymers. These may be used alone or in combination. As the hindered amine light stabilizer, it is preferable to use a tertiary amine-containing hindered amine light stabilizer in order to improve the storage stability of the composition. Examples of the tertiary amine-containing hindered amine light stabilizer include TINUVIN 622LD, TINUVIN 144, TINUVIN 765, and CHIMASSORC119FL (all manufactured by BASF); MARK LA-57, LA-62, LA-67, and LA-63 (all manufactured by Asahi Denka Kogyo Co., Ltd.); and SANOL LS-765, LS-292, LS-2626, LS-1114, and LS-744 (all manufactured by Sankyo Co., Ltd.). Examples of the ultraviolet absorber include ultraviolet absorbers such as benzotriazole-based, triazine-based, benzophenone-based, and benzoate-based compounds.The ultraviolet absorber may be appropriately selected from known ones, and examples thereof include 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, the reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300, and the like. Examples of suitable hindered amine light stabilizers include benzotriazole-based ultraviolet absorbers such as 2-(2H-benzotriazol-2-yl)-6-(linear and branched chain dodecyl)-4-methylphenol, triazine-based ultraviolet absorbers such as 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, benzophenone-based ultraviolet absorbers such as octabenzone, and benzoate-based ultraviolet absorbers that also have a radical scavenging function such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate. The hindered amine light stabilizer and ultraviolet absorber may be used alone or in combination. When a hindered amine light stabilizer and an ultraviolet absorber are used in combination, a combination of a hindered amine light stabilizer and a benzophenone-based ultraviolet absorber is preferred. The addition ratio of the light stabilizer is preferably 0.1 to 1.0 part by mass, more preferably 0.3 to 0.7 part by mass, per 100 parts by mass of the styrene-based thermoplastic elastomer (A). When a hindered amine-based light stabilizer and an ultraviolet absorber are used in combination, they may be combined in an appropriate ratio within the above range.

[0042] Furthermore, as one embodiment of the present invention, other additives may be added to the thermoplastic resin composition as long as the effects of the present invention are not impaired. Examples of additives include pigments, colorants, fillers, lubricants, and mold release agents. These may be used alone or in combination.

[0043] The thermoplastic resin composition of the present invention is required to have flexibility that allows it to fully exert its cushioning effect, and specifically, the hardness of the molded product (SRIS 0101 standard, 23±2°C) is preferably ASKER C15 to 70, more preferably ASKER C25 to 60, and particularly preferably ASKER C30 to 50. This provides a thermoplastic resin composition that forms a cushioning member that has sufficient flexibility to contribute to cushioning properties, excellent adhesion, is resistant to peeling due to stress deformation such as flow deformation, and is also weather resistant.

[0044] Furthermore, the thermoplastic resin composition of the present invention is required to have transparency from the viewpoint of enhancing the designability of the appearance, and specifically, the haze value (based on JIS K7136:2000) is preferably 40% or less, more preferably 30% or less, and particularly preferably 15% or less, thereby obtaining a thermoplastic resin composition that forms a buffer member having high transparency in appearance, excellent adhesion, resistance to peeling due to stress deformation such as flow deformation, and weather resistance.

[0045] The thermoplastic resin composition of this embodiment is produced by a known method for producing a resin composition. Specifically, for example, a melt kneader such as a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, or a heated roll is used to add blending components such as a styrene-based thermoplastic elastomer (A) and a softener (B), or blending components such as a styrene-based thermoplastic elastomer (A), a softener (B), an antioxidant and / or a light stabilizer, and various other components added as needed, in predetermined proportions, and the blending components are heated and kneaded uniformly in a molten state. Alternatively, to improve the dispersibility of the styrene-based thermoplastic elastomer (A) and the softener (B), at least a portion of the softener (B) may be absorbed into the styrene-based thermoplastic elastomer (A) before melt kneading.

[0046] The thermoplastic resin composition obtained as described above may be pelletized or filamentized as necessary, and then molded into a predetermined shape by a known method such as injection molding, extrusion molding, blow molding, compression molding, calendar molding, or 3D modeling using a 3D printer, to obtain a molded article of the thermoplastic resin composition according to the present invention. The haze value (based on JIS K7136:2000) of the molded article of the thermoplastic resin composition of this embodiment is particularly preferably 15% or less. Furthermore, the hardness is particularly preferably 30 to 50 (Asker C standard, SRIS 0101). Therefore, the molded article, which is made of a thermoplastic resin composition having high transparency in appearance and sufficient flexibility to contribute to cushioning properties, can be suitably used as a cushioning material.

[0047] A cushioning member made of a molded article of the thermoplastic resin composition of the present invention will now be described. As shown in FIG. 1 , one embodiment of the cushioning member can be suitably used as a cushioning member 10 for footwear such as sports shoes. The footwear cushioning member 10 of this embodiment can be easily bonded to a sole member 20, such as an EVA resin (ethylene-vinyl acetate copolymer resin) that forms the sole of the shoe 1, directly or via a primer-treated layer with an adhesive, eliminating the need for a coating layer such as a urethane coating agent. In other words, the footwear cushioning member 10 itself has high adhesive properties, allowing it to be firmly bonded to the sole member 20 with known adhesives and reducing the risk of peeling due to flow deformation (creep). Therefore, the footwear cushioning member 10 of the present invention can reduce footwear manufacturing costs and produce durable footwear. Furthermore, as described above, the footwear cushioning member 10 is weather-resistant, meaning it is resistant to deterioration due to light, ozone, heat, etc., and also has excellent appearance transparency (designability) and cushioning properties.

[0048] Furthermore, a buffer member formed from a molded article of the thermoplastic resin composition of the present invention is bonded to an adherend via an adhesive appropriate for the intended use. Known adhesives compatible with styrene-based elastomers can be appropriately selected depending on the material of the adherend. For example, in footwear applications, shoemaking adhesives such as polyurethane adhesives and chloroprene rubber adhesives can be used. Furthermore, to enhance adhesion between the buffer member and an adherend, such as a sole member, and ensure more reliable adhesion, it is also preferable for the buffer member and the adherend to be bonded via a primer-treated layer. Here, the primer-treated layer refers to a layer formed by previously treating the surface of the adherend or the molded article (buffer member) of the thermoplastic resin composition with a primer such as a surface treatment agent. This allows for even higher adhesion reliability with the adherend through the primer-treated layer. For example, when the adherend is made of urethane rubber, an acrylic primer or a chlorine-based primer is preferably used as the primer. The chlorine-based primer may be, for example, a composition in which chlorinated isocyanuric acid is dissolved in a solvent, and the concentration of chlorinated isocyanuric acid is preferably 0.5 to 5% by weight in terms of ease of application and adhesion. As the chlorinated isocyanuric acid, chlorinated isocyanuric acid and its salts may be used, and examples thereof include trichloroisocyanuric acid, dichloroisocyanuric acid, sodium dichloroisocyanurate and its hydrate, potassium dichloroisocyanurate, calcium dichloroisocyanurate, and magnesium dichloroisocyanurate.

[0049] In another embodiment, the cushioning material made of the molded article of the thermoplastic resin composition of the present invention can be used in sports equipment, bags, cushioning materials for automobiles, building materials, etc., by bonding with an adhesive either directly or via a primer-treated layer.

[0050] Furthermore, in order to further improve the ozone resistance of a buffer member made of a molded product of the thermoplastic resin composition of the present invention, a wax layer or a surface coating layer may be formed on the surface portion of the molded product (buffer member) that is exposed to the atmosphere and light, or the surface portion may be subjected to a surface treatment in which a surface layer is formed by irradiating the surface portion with energy rays that reach a predetermined depth region near the surface.

[0051] A wax layer for improving ozone resistance can be formed by applying a wax component to the surface of the molded article (buffer member). Examples of wax components include petroleum-based waxes and natural waxes. Synthetic waxes obtained by refining or chemically processing multiple waxes can also be used. These waxes may be used alone or in combination of two or more types. Petroleum-based waxes include paraffin wax and microcrystalline wax. Petroleum-based waxes, which are mixtures of hydrocarbons having approximately 20 to 80 carbon atoms, are preferred, with paraffin wax being even more preferred. Natural waxes are not particularly limited as long as they are derived from non-petroleum resources, and examples include plant-based waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and spermaceti; mineral-based waxes such as ozokerite, ceresin, and petrolactam, and refined versions of these waxes. Alternatively, a wax component may be added to the thermoplastic resin composition to the extent that the adhesiveness of the molded article (buffer material) of the thermoplastic resin composition is not impaired, and the wax may be allowed to seep out little by little onto the surface of the molded article (buffer material) to form a thin wax film. When wax is added to the thermoplastic resin composition, the amount of wax added is preferably in the range of 0.1 to 5 parts by weight per 100 parts by weight of the thermoplastic resin composition, from the viewpoint of the balance between ozone resistance and adhesiveness.

[0052] Furthermore, the surface coating layer for improving ozone resistance can be formed by a known method, such as by applying an ozone-resistant resin composition to the surface of a molded article (buffer member). The ozone-resistant resin composition is not particularly limited as long as it has excellent adhesion to the surface of a molded article of a thermoplastic resin composition, but if the surface of the molded article is to be visually recognized as a design, a resin composition having optical transparency is preferred.

[0053] Furthermore, surface treatment by energy ray irradiation to improve ozone resistance crosslinks the double bonds of the butadiene blocks in a predetermined depth region near the surface of the surface portion of the molded article of the thermoplastic resin composition with the energy ray, thereby reducing the double bond content and forming a surface-treated layer with excellent ozone resistance. Examples of energy ray that can be used include radioactive rays and electron beams. The irradiation conditions for the energy ray can be appropriately set depending on the desired ozone resistance.

[0054] A cushioning member made of a molded article of the thermoplastic resin composition of the present invention may further have a decorative layer formed on its surface. When the above-mentioned surface coating layer or wax layer is formed, the decorative layer is formed between the surface coating layer or wax layer and the molded article. The decorative layer can be formed by a known method such as coating or printing using a conventional paint or ink. The thermoplastic resin composition of the present invention has excellent adhesion to paint, ink, etc., and therefore has the effect of facilitating the formation of a beautiful decorative layer.

[0055] The present invention will be described in detail below with reference to examples. The methods for evaluating physical properties such as adhesiveness, weather resistance, and transparency of the thermoplastic resin compositions in the following examples and comparative examples are as follows.

[0056] (1) Adhesion 1: Creep Test (Flow Deformation) A specific creep test method will be described with reference to FIGS. 3 and 4 . FIG. 3 schematically illustrates the configuration of a test piece 50, and FIG. 4 illustrates the creep test method for the test piece. The test piece 50 shown in FIG. 3 was prepared as follows. Molded articles of each thermoplastic resin composition in the Examples and Comparative Examples were each molded into a strip (20 mm wide x 60 mm long x 3 mm thick) to form test piece 51. A urethane piece 52 (Kuramilon U2195, manufactured by Kuraray Co., Ltd., 20 mm wide x 60 mm long x 3 mm thick) similar to test piece 51 was bonded to test piece 51 with adhesive 53 to obtain test piece 50. More specifically, the surface of test piece 51 was wiped with a Kimwipe® soaked in ethanol, and the surface of urethane piece 52 was wiped with a Kimwipe® soaked in acetone, followed by drying at 60°C for 5 minutes. An adhesive primer (a product of No Tape Kogyo Co., Ltd., P-66 (thinner): P-66 (granular) mixed and dissolved at a ratio of 100:2) was applied to one side of the test piece 51 and dried at 60 ° C. for 5 minutes. An adhesive mixture of adhesive 1 (a product of Daito Resin Co., Ltd., GE6602) and adhesive 2 (a product of Daito Resin Co., Ltd., GE366S) in a ratio of adhesive 1:adhesive 2 = 100:5 was applied thereon and dried at 60 ° C. for 5 minutes. The same adhesive was further applied thereon and dried at 60 ° C. for 5 minutes. In addition, an adhesive mixture of adhesive 3 (manufactured by Henkel, 812TF) and adhesive 4 (manufactured by Bayer, Desmodur RFE) in a ratio of adhesive 3:adhesive 4 = 100:5 was applied to one side of the urethane piece 52 and dried at 60 ° C. for 5 minutes. The same adhesive was further applied thereon and dried at 60°C for 5 minutes. Once the adhesive applied to the test piece 51 and the urethane piece 52 had dried, the test piece 51 and the urethane piece 52 were quickly bonded together. The test piece 51 was placed with the side facing up and rolled with a hand roller at 2 to 3 kgf / cm. ２The test piece 50 was obtained by applying a pressure of 0.05 MPa to bond the test piece 51 and the urethane piece 52 together with the adhesive 53. As shown in FIG. 3( b), one longitudinal end of the test piece 51 was left unbonded, extending 15 mm from the distal end toward the other longitudinal end. The test piece 50 was cured at 40°C for at least two hours before being used in a creep test. Before the test, if there was any adhesive pool at the end Q0 of the bonded portion of the test piece 50, an apparent increase in strength would occur. Therefore, a notch was formed by cutting approximately 1 mm along the adhesive layer with a utility knife from the end Q0 of the bonded portion of the test piece 50 shown in FIG. 3( b) toward the bonded portion, before the test. As shown in Figure 4(a), test piece 50 was fixed horizontally to a jig with urethane piece 52 facing up, and a 200g weight W was fixed with vinyl tape to the end of the unbonded portion of test piece 51, applying a tensile load in the direction of gravity. The test piece was then left in a hot air oven (Tokyo Rikakikai Co., Ltd., model number: WFO-520W) at 40°C for 24 hours. After 24 hours, the distance (Q0) from the position Q0 at the end of the bonded joint before the test to the position Q1 at which creep-induced peeling occurred and became the end of the bonded joint after the test (the distance between Q0 and Q1) was measured, as shown in Figure 4(b).

[0057] The adhesiveness in the creep test was evaluated as excellent (◯) when the measured distance at which peeling occurred (the length between Q0 and Q1) was 0 mm (no peeling), and as poor (×) when the measured value was over 0 mm (peeling occurred).

[0058] (2) Adhesion 2: Peel Strength The peel strength of each test piece was measured in accordance with JIS K6854-3. The test piece was prepared in the same manner as the test piece 50 used in the creep test described above. This test piece 50 was cured at 40°C for at least 2 hours before being used in the peel strength test. To prevent the apparent increase in strength due to the presence of adhesive pools at the end Q0 of the adhesive joint of the test piece 50, a notch of approximately 1 mm was formed using a cutter knife along the adhesive layer from the end Q0 of the adhesive joint of the test piece 50 shown in Figure 3(b) toward the adhesive joint, as in the creep test. As shown in Figures 5(A) and (B) , the test piece 51 and the urethane piece 52 of the test piece 50 were peeled off using a tensile tester (Shimadzu Corporation, Autograph (registered trademark), AT-100N), and the peel strength was measured. In Figure 5, 54 denotes a fixed-side tensile jig, and 55 denotes a movable-side tensile jig. The load cell was 1 kN (100 kgf), the test speed was 50 mm / min, and the initial gap between the fixed tensile jig 54 and the movable tensile jig 55 was 20 mm. (Note that the adhesive 53 constituting the test piece 50 is not shown in FIGS. 5A and 5B.)

[0059] After measuring the peel strength, the peeling state (peel mode) of the interface of the molded body in each test piece 51 was evaluated as follows: The peeled surface on the urethane piece 52 side of each sample piece 50 and the peeled surface on the test piece 51 side were each measured using an FT-IR device (PerkinElmer, infrared microscope system Spotlight 200) at 380 to 4000 cm －１The specimens were analyzed by attenuated total reflectance (ATR) in the wavenumber range of 100 Hz to 100 Hz. When the analysis revealed no SBS spectrum, a component of the molded body of each specimen 51, on the peeled surface on the side of the test piece 51 or the peeled surface on the side of the urethane piece 52, it was deemed "interfacial delamination." On the other hand, cases that did not fall under "interfacial delamination" were primarily fractures within the molded body, and when the SBS spectrum was detected on both the peeled surface on the side of the test piece 51 and the peeled surface on the side of the urethane piece 52, it was deemed "molded body fracture." Here, the SBS spectrum was obtained by measuring the surface of the molded body constituting each specimen 51 with FT-IR. The presence or absence of SBS was determined by comparing the characteristic absorption bands of the SBS spectrum with the spectra obtained by measuring the peeled surface on the side of the urethane piece 52 and the peeled surface on the side of the test piece 51 of the specimen 50. The spectral identification method conformed to JIS K6230.

[0060] Regarding the evaluation of adhesiveness related to peel strength, for test pieces in which material failure occurred inside the molded body, a measurement value of 4 kgf / 20 mm or more was evaluated as excellent (○), and a measurement value of less than 4 kgf / 20 mm was evaluated as poor (×). Furthermore, test pieces in which interfacial peeling occurred were evaluated as poor (×) regardless of the measurement value.

[0061] (3) Ozone Resistance The ozone exposure test method for evaluating ozone resistance will be specifically described using Figure 6. Molded articles of each thermoplastic resin composition in the Examples and Comparative Examples were each molded into a strip (20 mm wide x 60 mm long x 3 mm thick) to prepare test specimens 61. Test specimens 61 were attached to a curved surface 63 (40 mm radius) of a semi-cylindrical fixture 62, and a warping load was applied to the test specimens 61. The fixture 62 was fixed to a mounting base 64 of a box-shaped test chamber 60 so that the distance from the test specimen 61 to the ceiling of the test chamber 60 was 210 mm. A water tank 65 containing water 66 was placed below the mounting base 64 in the test chamber 60. An inlet pipe 67 and an outlet pipe 68 were provided at the top of the test chamber 60. Ozone gas generated by an ozone gas generator (ED-OG-7TC, manufactured by Ecodesign) was introduced into the test chamber 60 through the inlet pipe 67. The gas in the test chamber 60 was extracted through the outlet pipe 68, and the ozone gas concentration contained in the gas in the test chamber 60 was measured with an ozone gas concentration meter (OZM-7000G2, manufactured by Ecodesign). The ozone exposure test was performed by perfusing ozone gas into the test chamber 60 so that the ozone gas concentration in the test chamber 60 was 0.5 ppm, placing the test piece 61 in the test chamber 60 for 16 hours or more, and photographing the changes in the appearance of the test piece 61 during that time. The photographed images were confirmed, and the time at which cracks due to ozone exposure were observed in the test piece 61 was determined. In this test, the ozone gas concentration of 0.5 ppm in the test tank 60 corresponds to a concentration 100 times higher than the ozone gas concentration in the atmosphere.

[0062] In the evaluation of ozone resistance in the ozone exposure test, test pieces 61 for which cracks due to ozone exposure were observed for more than 16 hours (16<) from the start of the test were evaluated as excellent (○), and those for which cracks were observed for 16 hours or less were evaluated as poor (×).

[0063] (4) Light resistance Each thermoplastic resin composition shown in the examples and comparative examples was molded into an angle shape (dumbbell No. 3, thickness 3 mm) without any notches to prepare test specimens. Three test specimens each were held and hung in the chamber of a light resistance tester (Q-SUN Xe-3 xenon arc tester manufactured by Q-LAB Co.), and the temperature inside the chamber was kept at 40°C, and xenon arc lamp light (wavelength 340 nm) was irradiated at an irradiation dose of 0.35 W / m. ２The condition of each test piece before and after the test was observed visually and by hand to check for discoloration such as yellowing and the occurrence of oil bleeding.

[0064] The lightfastness was evaluated as follows: a test piece in which neither "discoloration such as yellowing" nor "bleeding" was observed and there was no change in appearance before and after the test was rated A; a test piece in which only either "discoloration such as yellowing" or "bleeding" was observed was rated B; and a test piece in which both "discoloration such as yellowing" and "bleeding" were observed was rated C. When all test pieces were rated A, the test piece was evaluated as excellent (◎); when there were no test pieces rated C but some test pieces rated B, the test piece was evaluated as good (○); and when there were some test pieces rated C, the test piece was evaluated as poor (×).

[0065] (5) Moisture and Heat Resistance According to JIS K6252-1 Method B, ten test pieces were molded into an unscored angle shape (dumbbell type B) from each thermoplastic resin composition shown in the Examples and Comparative Examples. Five of the test pieces were exposed to a humid and hot environment of 95% humidity and 80°C for four weeks, and the remaining five were stored in a room temperature environment for four weeks. After drying at 40°C for one day, the maximum load F [N] at break was measured at a pulling rate of 500 mm / min using a tensile tester (Shimadzu Corporation, Autograph (registered trademark), AT-100N), and the tensile strength at break (MPa) was calculated by dividing the value by the thickness t [m] of the test piece. The tensile strength at break (MPa) was calculated by averaging the two values ​​flanking the median tensile strength of the five test pieces.

[0066] The evaluation of moist heat resistance based on tensile break strength evaluates the degree of deterioration of a molded article of a thermoplastic resin composition exposed to moist heat. First, the rate of change in tensile break strength due to moist heat exposure was calculated using the formula: "rate of change (%) = (absolute value of the difference obtained by subtracting the measured value of the tensile break strength of the test piece after storage in a moist heat environment from the measured value of the tensile break strength of the test piece after storage in a room temperature environment) / (measured value of the tensile break strength of the test piece after storage in a room temperature environment)." When the rate of change was 10% or less, the specimen was evaluated as excellent (◎); when the rate of change was more than 10% but not more than 20%, the specimen was evaluated as good (◯); and when the rate of change was more than 20%, the specimen was evaluated as poor (×).

[0067] (6) Haze Value (Transparency) According to JIS K7136:2000, the haze of each test piece was measured using a haze meter (Spectroscopic Haze Meter SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.). Test pieces were prepared by molding each thermoplastic resin composition in the Examples and Comparative Examples into a sheet (50 mm long x 50 mm wide x 3 mm thick). A haze value of 15% or less was evaluated as excellent (○), and a haze value of more than 15% was evaluated as poor (×). Note that even if the haze value was 15% or less, if bubbles were present, the test piece was evaluated as poor (×).

[0068] (7) Hardness (Asker C) The hardness of each test piece was measured using an Asker C durometer (SRIS 0101 standard) conforming to JIS K6253. Test pieces were prepared by molding each thermoplastic resin composition in the Examples and Comparative Examples into a size of 60 mm length x 60 mm width x 3 mm thickness, and laminating four of these in the thickness direction to a layer thickness of 12 mm. An Asker C score of 30 to 50 was evaluated as excellent (○), 25 to less than 30 or more than 50 to 60 as fair (△), and less than 25 or more than 60 as poor (×).

[0069] (8) MFR: Melt Mass Flow Rate (Flowability) The melt mass flow rate of each thermoplastic resin composition was measured at a temperature of 190° C. under a load of 2.16 kg in accordance with JIS K7210-1B.

[0070] Tables 1 and 2 show the specifications of the components of the thermoplastic resin compositions prepared in the following Examples and Comparative Examples. Among the components, the butadiene block in each block copolymer constituting the styrene-based thermoplastic elastomer (A) was not hydrogenated. The molecular weight of SBS of component A21 constituting the styrene-based thermoplastic elastomer (A) is an actual measured value. Component A23 contains 31% oil in addition to component (A) (SBS and SB). Furthermore, the molecular weight of naphthene of component B3 of the softener (B) is an actual measured value.

[0071] The butadiene content and styrene content of each component in Table 1 are determined in accordance with JIS K 6239-1:2017 Raw rubber - Determination of microstructure of solution polymerized SBR (quantitative) - Part 1:１ According to H-NMR and IR (cast film) methods １ Measurements were performed by H-NMR (absolute method) using deuterated chloroform as the measurement solvent at a measurement concentration of 10 mg / 0.7 mL using a Bruker AVANCE NEO 700 nuclear magnetic resonance (NMR) spectrometer.

[0072]

[0073]

[0074] [Example 1] A thermoplastic resin composition of this example was prepared according to the following procedure, and various physical properties and effects were evaluated by the tests described above. The blending ratios of the components of the styrene-based thermoplastic elastomer (A) in this example and each of the examples and comparative examples described below are shown in Table 3 below. Using the components shown in Table 1, 27 parts by mass of SBS (styrene-butylene-styrene triblock copolymer) (A11) having a butadiene block content of 60% by mass and 28 parts by mass of a mixture (A21) of SBS and SB (styrene-butadiene diblock copolymer) having a total butadiene block content of 70% by mass were separately weighed as the styrene-based thermoplastic elastomer (A). Next, using the components shown in Table 2, 45 parts by mass of paraffin oil (B1) having a molecular weight of 400 was used as the softener (B), 0.63 parts by mass of a mixture of a sulfide-based antioxidant (C1), a hindered phenol-based antioxidant (C2), and a phosphite-based antioxidant (C3) mixed in a weight ratio of C1:C2:C3 = 26.7:26.7:46.6 was used as the antioxidant (C), and 0.5 parts by mass of a mixture of a benzotriazole-based light stabilizer (D1) and a hindered amine-based light stabilizer (D2) mixed in a weight ratio of D1:D2 = 1:1 was separately prepared. Each block copolymer was mixed with paraffin oil at room temperature, followed by dry blending with antioxidant (C) and light stabilizer (D) by hand stirring. The mixture was heated at 100°C for 12 hours to allow the paraffin oil to be absorbed and dispersed in the styrene-based thermoplastic elastomer (A). The mixture was kneaded for 15 minutes in a batch-type twin-screw kneader (TD3-10MDX, manufactured by Toshin Corporation) at 130-170°C and 40 rpm to obtain the thermoplastic resin composition of Example 1. This composition was injection molded at 170-190°C or press molded at 130-150°C to obtain a sheet molded product. The molded product was then cut into the desired test piece shape to obtain molded products of the desired test piece shape used in the various evaluation tests described above.

[0075]

[0076] The thermoplastic resin composition and the molded article thereof were subjected to the various evaluation tests described above to evaluate various physical properties. The results of Example 1 are shown in Table 4.

[0077] [Examples 2 to 12] Thermoplastic resin compositions of each Example were obtained in the same manner as in Example 1, except that the constituent components and blending ratios of the styrene-based thermoplastic elastomer (A) were changed as shown in Table 3, and the constituent components and blending ratios of the softener (B) and the blending ratios of the antioxidant (C) and light stabilizer (D) were changed as shown in Tables 4 and 5 below. As in Example 1, the obtained thermoplastic resin compositions and molded articles thereof were subjected to the various evaluation tests described above, and various physical properties were evaluated. The results of Examples 2 to 6 are shown in Table 4, and the results of Examples 7 to 12 are shown in Table 5. Furthermore, the results of the moist heat resistance test of the molded articles of the thermoplastic resin compositions obtained in Examples 9 and 10 are shown in Table 7.

[0078] [Comparative Examples 1 to 4] Thermoplastic resin compositions of each comparative example were obtained in the same manner as in Example 1, except that the constituent components and blending ratios of the styrene-based thermoplastic elastomer (A) were changed as shown in Table 3, and the blending ratios of the softener (B), antioxidant (C), and light stabilizer (D) were changed as shown in Table 6 below. As in Example 1, the obtained thermoplastic resin compositions and molded articles thereof were subjected to the various evaluation tests described above, and various physical properties were evaluated. The results of Comparative Examples 1 to 4 are shown in Table 6.

[0079]

[0080]

[0081]

[0082] Comparative Example 5 A thermoplastic resin composition of Comparative Example 5 was obtained in the same manner as in Example 1, except that the components and blending ratios of the styrene-based thermoplastic elastomer (A) were changed as shown in Table 3, and the blending ratios of the softener (B), antioxidant (C), and light stabilizer (D) were changed as shown in Table 7 below. Since A23, used as a component of the styrene-based thermoplastic elastomer (A), contains 31% by mass of an oil component in addition to SBS and SB, the total amount of component (A) was calculated excluding the amount of the oil component. Molded articles of the obtained thermoplastic resin composition were subjected to moist heat resistance and light resistance tests, and various physical properties were evaluated. The results of Comparative Example 5 and Examples 9 and 10 are shown in Table 7.

[0083]

[0084] The results of Examples 1 to 12 shown in Tables 4, 5, and 7 and Comparative Examples 1 to 5 shown in Tables 6 and 7 demonstrate that by using the configuration according to the present invention, it is possible to obtain a thermoplastic resin composition that not only has excellent adhesiveness and peel strength, but also can suppress peeling due to flow deformation (creep) that reproduces severe stress deformation conditions, and is capable of forming a buffer member that also has weather resistance.

[0085] Specifically, the results of Examples 1 to 12 revealed that thermoplastic resin compositions in which the total content of butadienes retaining carbon-carbon double bonds in the butadiene blocks in the styrene-based thermoplastic elastomer (A) was in the range of 62.0 to 67.9 mass% and the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) was in the range of B / (A+B) = 0.416 to 0.550 by mass exhibited excellent peel strength accompanied by material fracture in the peel test, suppressed flow deformation in the creep test, and exhibited excellent adhesion to other components, transparency in appearance, flexibility, ozone resistance, and light resistance. Furthermore, thermoplastic resin compositions in which the total content of styrene blocks in the styrene-based thermoplastic elastomer (A) was in the range of 32.1 to 38.0 mass% exhibited excellent peel strength accompanied by material fracture in the peel test, suppressed flow deformation in the creep test, and exhibited excellent adhesion to other components, transparency in appearance, flexibility, ozone resistance, and light resistance.

[0086] Furthermore, in the thermoplastic resin compositions of Examples 1 to 12, when the blending ratio of the styrene-butadiene-styrene triblock copolymer (A1) to the styrene-butadiene diblock copolymer (A2) was in the range of a mass ratio of (A1):(A2) = 1:0.00 to 0.20, it was found that the resulting molded article had excellent peel strength accompanied by material failure in a peel test, and flow deformation was suppressed in a creep test, resulting in a buffer member with excellent adhesion to other components, external transparency, flexibility, ozone resistance, and light resistance. Furthermore, it was found that by adjusting the mass ratio (A1):(A2) to a range of greater than 0 and 0.20, the melt flow rate (MFR) of the thermoplastic resin composition could be adjusted to a range that was easy to handle. It was also confirmed that the softener (B) had flexibility suitable for a buffer material and good physical properties, even when it was a paraffinic oil with a molecular weight of 400 or 700 or a naphthenic oil with a molecular weight of 300.

[0087] Comparing the results of Comparative Example 1 and Example 6, in which the styrene-based thermoplastic elastomer (A) was composed of SBS, it was found that the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 58.5% by mass and the total styrene content was 41.5% by mass was inferior in adhesiveness, whereas the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 65.6% by mass and the total styrene content was 34.4% by mass was improved in adhesiveness.

[0088] Furthermore, when the results of Comparative Example 2 and Example 8, in which the styrene-based thermoplastic elastomer (A) was a combination of SBS and SB, were compared, it was found that the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 69.1% by mass and the total styrene content was 30.9% by mass was inferior in ozone resistance. On the other hand, it was found that the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 65.0% by mass and the total styrene content was 35.0% by mass was improved in ozone resistance.

[0089]

[0049] Furthermore, the results of Comparative Example 3 and Example 4 show that a thermoplastic resin composition in which the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) was B / (A+B) = 0.410 by mass was poor in ozone resistance, while a thermoplastic resin composition in which the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) was B / (A+B) = 0.416 had sufficient ozone resistance. The results of Comparative Example 4 and Example 5 show that a thermoplastic resin composition in which the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) was B / (A+B) = 0.600 by mass was poor in adhesiveness, while a thermoplastic resin composition in which the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) was B / (A+B) = 0.550 had improved adhesiveness.

[0090] Furthermore, from the results of Examples 8 to 10, it was confirmed that the thermoplastic resin composition according to the present invention has ozone resistance, light resistance, and moist heat resistance, and exhibits excellent weather resistance, even without containing an antioxidant and / or a light stabilizer.

[0091] Furthermore, from the results of Comparative Example 5 and Example 10 shown in Table 7, it was found that the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 68.8% by mass had insufficient moist heat resistance and light fastness, whereas the thermoplastic resin composition in which the total butadiene content in the styrene-based thermoplastic elastomer (A) was 65.0% by mass had improved moist heat resistance and light fastness.

[0092] The present invention is not limited to the above-described embodiments or examples, and various modified design forms are also included in the technical scope within the scope that does not deviate from the gist of the invention described in the claims.

[0093] The thermoplastic resin composition of the present invention is mainly used for shock-absorbing materials for shoes such as shoe soles and insoles, and is also useful in a wide range of fields including footwear, bag accessories, etc., such as grips and shoulder pads for bags.

[0094] DESCRIPTION OF SYMBOLS 1 Shoes 10, 10a Footwear cushioning member 11a Molded body 12 Primer layer 13 Protective coating layer 20 Sole member 21 Bonding surface between footwear cushioning member and sole member 50 Sample piece 51 Test piece (cushioning member of Example or Comparative Example) 52 Urethane piece 53 Adhesive 54 Fixed-side pulling jig 55 Movable-side pulling jig Q0 End of adhesive part Q1 End of adhesive part after test W Weight 60 Test tank 61 Test piece (cushioning member of Example or Comparative Example) 62 Fixing jig 63 Curved surface 64 Installation stand 65 Water tank 66 Water 67 Inlet pipe 68 Outlet pipe

Claims

1. A thermoplastic resin composition containing a styrene-based thermoplastic elastomer (A) and a softener (B), wherein the styrene-based thermoplastic elastomer (A) comprises one or more block copolymers composed of at least a styrene block and a butadiene block, the total content of butadiene retaining carbon-carbon double bonds of the butadiene blocks in the styrene-based thermoplastic elastomer (A) is 59.0 to 68.5 mass%, and the blending ratio of the styrene-based thermoplastic elastomer (A) to the softener (B) is, in mass ratio, B / (A+B) = more than 0.410 and less than 0.

600.

2. The thermoplastic resin composition according to claim 1, characterized in that the total content of the styrene blocks in the styrene-based thermoplastic elastomer (A) is 31.5 to 41.0 mass %.

3. The thermoplastic resin composition according to claim 2, characterized in that the main component of the styrene-based thermoplastic elastomer (A) is a styrene-butadiene-styrene triblock copolymer (A1).

4. The thermoplastic resin composition according to claim 3, characterized in that the styrene-based thermoplastic elastomer (A) comprises the styrene-butadiene-styrene triblock copolymer (A1) and a styrene-butadiene diblock copolymer (A2), and the blending ratio of the styrene-butadiene-styrene triblock copolymer (A1) to the styrene-butadiene diblock copolymer (A2) is (A1):(A2)=1:0 or more and less than 0.3, in terms of mass ratio.

5. A thermoplastic resin composition according to any one of claims 1 to 4, characterized in that the butadiene block in the one or more block copolymers is not substantially hydrogenated.

6. A thermoplastic resin composition according to any one of claims 1 to 4, characterized in that the softener (B) is a paraffinic oil or naphthenic oil having a molecular weight of 300 to 1,200.

7. The thermoplastic resin composition according to any one of claims 1 to 4, further comprising an antioxidant.

8. The thermoplastic resin composition according to any one of claims 1 to 4, further comprising a light stabilizer.

9. The thermoplastic resin composition according to any one of claims 1 to 4, characterized in that a molded product of the thermoplastic resin composition has a hardness of ASKER C30 to 50 (SRIS 0101 standard, 23±2°C) and a haze value (in accordance with JIS K7136:2000) of 15% or less.

10. A cushioning material comprising a molded article of the thermoplastic resin composition according to any one of claims 1 to 4.

11. The cushioning material according to claim 10, which is for footwear.

12. A composition for 3D printers comprising the thermoplastic resin composition according to any one of claims 1 to 4.

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