Thermoplastic resin composition

Abstract

The present invention provides a thermoplastic resin composition from which it is possible to form a stretch elastic member that has excellent extensibility and expansion / contraction recovery, and excellent in stress maintainability at the time of extension at a high temperature.　The present invention provides a thermoplastic resin composition that contains a thermoplastic elastomer (A) and a plasticizing agent (B), and that is characterized in that the thermoplastic elastomer (A): includes a styrene-based block copolymer; has a melt index of 0.1-100 g / 10 min as measured by method-A in compliance with JIS K7210 under a condition of 190°C and 2.16 kg or under a condition of 230°C and 2.16 kg; has a storage modulus G' of 2.5×105 Pa to 1.0×107 Pa at 25°C as measured by the following measuring condition; has at least one peak, of loss tangent tanδ (loss modulus / storage modulus) obtained through measurement of the storage modulus G', in each of a low temperature range of -50°C to 0°C and a high temperature range of 60-120°C; and results in D1, which is the tanδ peak value in the low temperature range, greater than D2, which is the tanδ peak value in the high temperature range. (Storage modulus G' measuring condition) Starting temperature: -60°C, ending temperature: 190°C, temperature elevation rate: 5°C / min., measurement frequency: 1 Hz, distortion: 0.05%

Description

thermoplastic resin composition

[0001] The present invention relates to a thermoplastic resin composition.

[0002] In recent years, absorbent articles including sanitary materials such as disposable diapers and sanitary napkins have been widely used. These absorbent articles use laminates made of stretchable members to prevent the absorbent articles from slipping off when worn.

[0003] Rubber threads, made from natural rubber or synthetic polymers in the form of threads, are known as elastic materials used in laminates. Because rubber threads exhibit good stress when stretched, they are effective in preventing absorbent articles from slipping down when worn.

[0004] In addition, a stretchable film containing an olefin-based elastomer and an inorganic filler has been proposed as a stretchable film that is used in sanitary products, sports goods, medical products, etc. and exhibits stretchability and breathability (see Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2022-108630

[0006] However, in Patent Document 1, improvement of extensibility is not sufficiently considered, and there is room for improvement. When sanitary materials such as disposable diapers are worn, the elastic members used in the sanitary materials are required to have sufficient extensibility.

[0007] Furthermore, Patent Document 1 does not fully consider the prevention of deterioration in stretch recovery. When sanitary materials such as disposable diapers are worn, the stretchable members used in the sanitary materials are stretched. Therefore, the stretchable members are required to prevent deterioration in stretch recovery even when held in a stretched state.

[0008] Furthermore, when sanitary materials such as disposable diapers are worn, they are kept at a temperature close to body temperature for a long period of time, so the elastic members are required to have reduced stress relaxation even when stretched and kept in a heated state, and therefore excellent stress retention when stretched at high temperatures. Patent Document 1 has the problem of insufficient stress retention when stretched at high temperatures.

[0009] In view of the above circumstances, an object of the present invention is to provide a thermoplastic resin composition that can be used to form an elastic member that has excellent extensibility and stretch recovery, and that has excellent stress retention when stretched at high temperatures.

[0010] As a result of extensive research into achieving the above object, the present inventors have found that the above object can be achieved by configuring a thermoplastic resin composition containing a thermoplastic resin (A) and a plasticizer (B), wherein the thermoplastic elastomer (A) contains a styrene-based block copolymer, the thermoplastic elastomer has a melt index and a storage modulus G' within specific ranges, the loss tangent tan δ (loss modulus / storage modulus) has at least one peak in a low temperature range of -50 to 0°C and at least one peak in a high temperature range of 60 to 120°C, and the tan δ peak value D1 in the low temperature range is greater than the tan δ peak value D2 in the high temperature range, and have completed the present invention.

[0011] That is, the present invention relates to the following thermoplastic resin composition: 1. A thermoplastic resin composition containing a thermoplastic elastomer (A) and a plasticizer (B), wherein the thermoplastic elastomer (A) contains a styrene-based block copolymer, has a melt index of 0.1 to 100 g / 10 min measured under conditions of 190°C and 2.16 kg or 230°C and 2.16 kg according to Method A in accordance with JIS K7210, and has a storage modulus G' at 25°C of 2.5 x 10 measured under the following measurement conditions: ５ ~1.0 x 10 ７Item 1. A thermoplastic resin composition characterized in that: the storage modulus G' has a loss tangent tan δ (loss modulus / storage modulus) obtained by measuring the storage modulus G' has at least one peak in a low-temperature region of -50 to 0°C and a high-temperature region of 60 to 120°C, and D1, which is the tan δ peak value in the low-temperature region, is greater than D2, which is the tan δ peak value in the high-temperature region. (Measurement conditions for storage modulus G'): Starting temperature -60°C, ending temperature 190°C, heating rate 5°C / min, measurement frequency 1 Hz, strain 0.05%. 2. The thermoplastic resin composition according to Item 1, wherein the styrene-based block copolymer is a hydrogenated styrene-based block copolymer. 3. The thermoplastic resin composition according to Item 1 or 2, wherein the amount of styrene derived from the styrene-based block copolymer contained in the thermoplastic resin composition is 30 to 50 mass%, based on 100 mass% of the thermoplastic resin composition. 4. 4. The thermoplastic resin composition according to any one of items 1 to 3, wherein the content of the thermoplastic elastomer (A) is 50 to 85% by mass, with the thermoplastic resin composition being 100% by mass. 5. The thermoplastic resin composition according to any one of items 1 to 4, wherein the ratio (D1 / D2) of D1 to D2 is greater than 1 and not greater than 15. 6. The thermoplastic resin composition according to any one of items 1 to 5, further comprising a hydrocarbon resin (C), wherein the content of the hydrocarbon resin (C) is 0.5 to 30% by mass, with the thermoplastic resin composition being 100%. 7. An elastic member made of the thermoplastic resin composition according to any one of items 1 to 6.

[0012] The thermoplastic resin composition of the present invention can be used to form an elastic member that is excellent in stretchability and stretch recovery, and that is excellent in stress retention when stretched at high temperatures.

[0013] 1. Thermoplastic Resin Composition The thermoplastic resin composition of the present invention comprises a thermoplastic elastomer (A) and a plasticizer (B), wherein the thermoplastic elastomer (A) comprises a styrene-based block copolymer, and has a melt index of 0.1 to 100 g / 10 min as measured by Method A under conditions of 190°C and 2.16 kg or Method A under conditions of 230°C and 2.16 kg, and a storage modulus G' at 25°C as measured under specific measurement conditions of 2.5 x 10 ５ ~1.0 x 10７ The thermoplastic resin composition of the present invention has a loss tangent tan δ (loss modulus / storage modulus) obtained by measuring the storage shear modulus G', which has at least one peak in a low temperature range of -50 to 0°C and a high temperature range of 60 to 120°C, and the tan δ peak value D1 in the low temperature range is greater than the tan δ peak value D2 in the high temperature range. By virtue of having the above-mentioned configuration, the thermoplastic resin composition of the present invention is excellent in extensibility and stretch recovery, and in stress maintenance during elongation at high temperatures, and is therefore able to combine all of these properties.

[0014] Furthermore, in recent years, environmental considerations have placed importance on reducing resource consumption, and the above-mentioned elastic members also need to be made thinner. Elastic members are required to have reduced stress relaxation even when stretched and maintained in a thin film of about 50 μm, and to have excellent stress retention when stretched. The thermoplastic resin composition of the present invention can form an elastic member that has excellent stress retention when stretched in a thin film state as described above.

[0015] The thermoplastic resin composition of the present invention will be described below.

[0016] As used herein, "high temperature" means a temperature about the same as human body temperature, i.e., about 35 to 42° C., preferably about 35.5 to 41.5° C., more preferably about 36 to 41° C., and particularly preferably 40° C. Furthermore, "heating" means bringing the temperature to within the above range.

[0017] In this specification, "room temperature" and "normal temperature" mean 23°C.

[0018] The thermoplastic resin composition of the present invention has a melt index of 0.1 to 100 g / 10 min, measured by Method A in accordance with JIS K7210 under conditions of 190°C and 2.16 kg or 230°C and 2.16 kg. If the melt index is less than 0.1 g / 10 min, the stress during extension or the stress maintenance during extension at high temperatures is insufficient. If the melt index is more than 100 g / 10 min, the extensibility and stretch recovery are insufficient. The melt index is preferably 1 to 95 g / 10 min, more preferably 5 to 90 g / 10 min.

[0019] The melt index of the thermoplastic resin composition is measured by the method described in the Examples below. The melt index is measured under either of the conditions of (1) 190°C and 2.16 kg or (2) 230°C and 2.16 kg, and either of the conditions that allows measurement is adopted.

[0020] The thermoplastic resin composition of the present invention has a storage modulus G' of 2.5 × 10 at 25°C measured under the following measurement conditions. ５ ~1.0 x 10 ７ Pa. The storage modulus G' is 2.5 × 10 ５ If the storage modulus G' is less than 1.0 x 10 Pa, the stress during elongation is insufficient. ７ If the storage modulus G' exceeds 3.0 x 10 Pa, the stretch recovery is insufficient. ５ ~9.5 x 10 ６ Pa is preferred, 4.0 × 10 ５ ~9.0 x 10 ６ Pa is more preferred.

[0021] (Measurement conditions for storage modulus G') Starting temperature -60°C, Ending temperature 190°C, Heating rate 5°C / min, Measurement frequency 1Hz, Strain 0.05%

[0022] The storage modulus G' of the thermoplastic resin composition is measured in detail by the method described in the examples below.

[0023] The thermoplastic resin composition of the present invention has a loss tangent tanδ (loss modulus / storage modulus) obtained by measuring the storage modulus G', which has at least one peak in the low-temperature region of -50 to 0°C and one peak in the high-temperature region of 60 to 120°C, and the tanδ peak value D1 in the low-temperature region is greater than the tanδ peak value D2 in the high-temperature region. If the thermoplastic resin composition of the present invention does not have at least one peak in the high-temperature region and one peak in the low-temperature region, or if D1 is equal to or less than D2, the stress retention during elongation at high temperatures or stretch recovery is poor.

[0024] The ratio (D1 / D2) of the above D1 to the above D2 is preferably greater than 1 and not greater than 15, more preferably 1.5 to 10. When D1 / D2 is in the above range, the stress retention and stretch recovery properties of the thermoplastic resin composition of the present invention when stretched at high temperatures are further improved.

[0025] The tan δ, D1 and D2 of the thermoplastic resin composition are measured by the method described in the examples below.

[0026] (Thermoplastic elastomer (A)) The thermoplastic elastomer (A) includes a styrene-based block copolymer. The styrene-based block copolymer is not particularly limited as long as it is a styrene-based block copolymer used in a thermoplastic resin composition, and examples thereof include styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), and styrene-ethylene-butylene-olefin crystalline copolymer (SEBC). Among these, in terms of being even more excellent in extensibility and stretch recovery, and even more excellent in stress maintenance during extension at high temperatures, styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), and styrene-ethylene-propylene-styrene copolymer (SEPS) are preferred, styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) and styrene-ethylene-butylene-styrene copolymer (SEBS) are more preferred, and styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) is even more preferred.

[0027] The styrene-based block copolymers may be used alone or in combination of two or more.

[0028] The styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) is a styrene-ethylene-butylene-styrene copolymer in which terminal styrene units form an end block phase and ethylene-butylene units form a midblock phase, and in which styrene is also dispersed in the midblock phase. By using a copolymer in which styrene is dispersed in the midblock phase, even if the overall styrene content of the styrene-based block copolymer is high, the styrene-based block copolymer does not become too hard and exhibits good extensibility, and therefore a thermoplastic resin composition containing the styrene-ethylene-butylene / styrene-styrene copolymer can achieve both good extensibility and good stretch recovery.

[0029] The method for preparing the styrene-ethylene-butylene / styrene-styrene copolymer is not particularly limited, and examples thereof include the method described in US Pat. No. 7,169,848.

[0030] As the styrene-ethylene-butylene / styrene-styrene copolymer, commercially available products can be used, such as A1537, A1536, and A1535 manufactured by Kraton Polymers.

[0031] The styrene-ethylene-butylene-styrene copolymer (SEBS) is a copolymer in which terminal styrene units form an endblock phase and ethylene-butylene units form a midblock phase. Furthermore, when a copolymer in which the midblock phase is hydrogenated ethylene-butylene units is used, the polarity difference between the styrene units in the endblock phase becomes more pronounced, and the styrene units in the endblock phase become stronger than in a copolymer in which the midblock phase is not hydrogenated. As a result, the stretch recovery of the thermoplastic resin composition can be further improved. Furthermore, when the midblock phase is hydrogenated, a thermoplastic resin composition with even better heat stability can be provided.

[0032] The styrene-ethylene-butylene-styrene copolymer may be a commercially available product, such as G1653 manufactured by Kraton Polymers and Tuftec H1043 manufactured by Asahi Kasei Corporation.

[0033] The styrene content of the styrene-based block copolymer is preferably 30 to 75% by mass, more preferably 35 to 70% by mass, and even more preferably 40 to 65% by mass, based on 100% by mass of the styrene-based block copolymer. By setting the lower limit of the styrene content within the above range, the stress retention rate during extension at high temperatures of an elastic member formed using the thermoplastic resin composition is further improved. By setting the upper limit of the styrene content within the above range, hardening of the thermoplastic resin composition is further suppressed, and the extensibility of the elastic member is further improved.

[0034] In this specification, the "styrene content" of a styrene-based block copolymer refers to the content (mass %) of styrene blocks in the styrene-based block copolymer.

[0035] In this specification, the method for calculating the styrene content in the styrene-based block copolymer is not particularly limited, and examples thereof include methods using proton nuclear magnetic resonance spectroscopy or infrared spectroscopy in accordance with JIS K6239.

[0036] The amount of styrene derived from the styrene-based block copolymer contained in the thermoplastic resin composition of the present invention is preferably 25 to 60% by mass, more preferably 30 to 50% by mass, and even more preferably 35 to 45% by mass, based on 100% by mass of the thermoplastic resin composition. By setting the lower limit of the styrene amount within the above range, the stress retention rate of an elastic member formed using the thermoplastic resin composition during extension at high temperatures is further improved. By setting the upper limit of the styrene amount within the above range, hardening of the thermoplastic resin composition is further suppressed, and the extensibility of the elastic member is further improved.

[0037] The styrene-based block copolymer may be used alone or in combination of two or more thereof, for example, a styrene-based block copolymer having a high styrene content and a styrene-based block copolymer having a low styrene content may be used in combination.

[0038] The styrene-based block copolymer is preferably a hydrogenated styrene-based block copolymer. That is, the styrene-based block copolymer is preferably a hydrogenated product of a styrene-based block copolymer, and such a hydrogenated product of a styrene-based block copolymer is also referred to as a hydrogenated styrene-based block copolymer. More specifically, the hydrogenated styrene-based block copolymer is a block copolymer obtained by block copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound, and hydrogenating all or a part of the blocks based on the conjugated diene compound in the resulting block copolymer.

[0039] The vinyl aromatic hydrocarbon is an aromatic hydrocarbon compound having a vinyl group. Specific examples of the vinyl aromatic hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene, with styrene being preferred among these. The vinyl aromatic hydrocarbon may be used alone or in combination of two or more.

[0040] The conjugated diene compound is a diolefin compound having at least one pair of conjugated double bonds. Specific examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferred. The conjugated diene compounds may be used alone or in combination of two or more.

[0041] In this specification, the hydrogenation ratio in a hydrogenated styrene-based block copolymer is referred to as the "hydrogenation ratio." The "hydrogenation ratio" of a styrene-based block copolymer refers to the ratio of ethylenically unsaturated double bonds that have been hydrogenated and converted to saturated hydrocarbon bonds, based on the total number of ethylenically unsaturated double bonds contained in the block based on the conjugated diene compound. The hydrogenation ratio can be measured using an infrared spectrophotometer, a nuclear magnetic resonance spectrometer, or the like.

[0042] The hydrogenated styrene-based block copolymer may be a partially hydrogenated or fully hydrogenated product. Of these, a fully hydrogenated product is preferred. A fully hydrogenated styrene-based block copolymer further improves the heat stability of the thermoplastic resin composition. The hydrogenation rate of the styrene-based block copolymer is preferably about 100%.

[0043] The content of the styrene-based block copolymer in the thermoplastic resin composition of the present invention is preferably 45 to 85% by mass, more preferably 50 to 85% by mass, and even more preferably 55 to 80% by mass, based on 100% by mass of the thermoplastic resin composition. By having the content of the styrene-based block copolymer in the above range, the stress retention during extension at high temperatures of an elastic member formed using the thermoplastic resin composition of the present invention is further improved.

[0044] (Plasticizer (B)) The thermoplastic resin composition of the present invention contains a plasticizer (B). The plasticizer (B) is preferably liquid at 23°C. In this specification, "liquid" refers to a state exhibiting fluidity. The pour point of such a plasticizer (B) is preferably 23°C or lower, more preferably 10°C or lower.

[0045] In this specification, the pour point is a value measured by a measurement method in accordance with JIS K2269.

[0046] The plasticizer (B) is not particularly limited, and examples thereof include paraffinic process oil, naphthenic process oil, aromatic process oil, liquid paraffin oil, etc. Among these, from the viewpoint of excellent heat stability, paraffinic process oil, naphthenic process oil, and liquid paraffin oil are preferred, and paraffinic process oil and naphthenic process oil are more preferred. Furthermore, from the viewpoint of further improving the stress retention of an elastic member formed using the thermoplastic resin composition during extension at high temperatures, paraffinic process oil is more preferred.

[0047] Commercially available paraffin-based process oils can be used, such as PS-32 and PW-32 manufactured by Idemitsu Kosan Co., Ltd.

[0048] As the naphthenic process oil, commercially available products can be used, such as KN-4010 manufactured by Petro China, CALSOL 550 manufactured by Calumet Specialty Products Partners, Inc., Diana Fresia N28 manufactured by Idemitsu Kosan Co., Ltd., Diana Fresia U46 manufactured by Idemitsu Kosan Co., Ltd., and Nyflex 222B manufactured by Nynas Corporation.

[0049] Commercially available liquid paraffin oils can be used, such as P-100 manufactured by MORESCO and Kaydol manufactured by Sonneborn.

[0050] The plasticizer (B) may be used alone or in combination of two or more.

[0051] The content of plasticizer (B) in the thermoplastic resin composition of the present invention is preferably 10 to 55% by mass, and more preferably 15 to 45% by mass, based on 100% by mass of the thermoplastic resin composition. By setting the upper limit of the content of plasticizer (B) within the above range, the stress retention of an elastic member formed using the thermoplastic resin composition during extension at high temperatures is further improved. By setting the lower limit of the content of plasticizer (B) within the above range, the thermoplastic resin composition becomes even more flexible, and the extensibility of the thermoplastic resin composition is further improved.

[0052] (Hydrocarbon Resin (C)) The thermoplastic resin composition of the present invention preferably further contains a hydrocarbon resin (C). The hydrocarbon resin (C) is a component that acts as a tackifier or an endblock resin. By containing the hydrocarbon resin (C), the stress during extension of the thermoplastic resin composition of the present invention and the stress maintenance during extension at high temperatures are further improved.

[0053] The hydrocarbon resin (C) is a hydrocarbon resin other than the thermoplastic elastomer (A) and the plasticizer (B). The hydrocarbon resin (C) preferably does not contain the styrene-based block copolymer described in the thermoplastic elastomer (A), and more preferably does not contain a polyolefin-based copolymer, a polyacrylic-based copolymer, a polyamide-based copolymer, a polyester-based copolymer, or a polyurethane-based copolymer. More specifically, the hydrocarbon resin (C) may include a tackifier resin, an aromatic hydrocarbon resin, etc.

[0054] Examples of tackifying resins include natural rosin, modified rosin, glycerol esters of natural rosin, glycerol esters of modified rosin, pentaerythritol esters of natural rosin, pentaerythritol esters of modified rosin, copolymers of natural terpene, three-dimensional polymers of natural terpene, hydrogenated derivatives of copolymers of natural terpene, terpene resins, hydrogenated derivatives of phenol-based modified terpene resins, petroleum resins such as C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, and dicyclopentadiene petroleum resins, as well as partially hydrogenated petroleum resins and fully hydrogenated petroleum resins obtained by adding hydrogen to these petroleum resins. As tackifying resins, petroleum resins, partially hydrogenated petroleum resins, and fully hydrogenated petroleum resins are preferred, with partially hydrogenated petroleum resins and fully hydrogenated petroleum resins being more preferred, due to their excellent odor and thermal stability of the thermoplastic resin composition. These tackifying resins may be used alone or in combination of two or more.

[0055] The aromatic hydrocarbon resin is a resin that acts as an endblock resin for the resin components that form the thermoplastic resin composition. The aromatic hydrocarbon resin is not particularly limited, and for example, an oligomer of a vinyl aromatic hydrocarbon can be used. Examples of the vinyl aromatic hydrocarbon that forms the oligomer include aromatic hydrocarbon compounds having a vinyl group. Specific examples of the vinyl aromatic hydrocarbon that forms the oligomer include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene, with styrene and α-methylstyrene being preferred among these.

[0056] The content of the hydrocarbon resin (C) is preferably from 0.1 to 35 mass%, more preferably from 0.5 to 30 mass%, and even more preferably from 5 to 30 mass%, based on 100% of the thermoplastic resin composition.

[0057] (Other Additives) The thermoplastic resin composition of the present invention may contain other additives to the extent that the object of the present invention is not essentially hindered. Examples of the other additives include antioxidants, ultraviolet absorbers, photopolymerization initiators, liquid rubbers, and particulate fillers.

[0058] Examples of antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,4-bis(octylthiomethyl)-o-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]-2,4-bis(octylthiomethyl)-o-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]-2,4-bis(octylthiomethyl)-o-cresol. Examples of antioxidants include hindered phenol antioxidants such as 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]phenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, and tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; sulfur antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate, and pentaerythritol tetrakis(3-laurylthiopropionate); and phosphorus antioxidants such as tris(nonylphenyl)phosphite and tris(2,4-di-t-butylphenyl)phosphite. These antioxidants may be used alone or in combination of two or more.

[0059] The content of the antioxidant in the thermoplastic resin composition of the present invention is preferably 0.01 to 2 mass%, more preferably 0.05 to 1.5 mass%, and even more preferably 0.1 to 1 mass%, based on 100 mass% of the thermoplastic resin composition. When the content of the antioxidant is 0.01 mass% or more, the thermal stability of the thermoplastic resin composition is further improved. When the content of the antioxidant is 2 mass% or less, the odor of the thermoplastic resin composition is further reduced.

[0060] Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-t-butylphenyl)benzotriazole, and 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole; benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone; salicylic acid ester-based ultraviolet absorbers; cyanoacrylate-based ultraviolet absorbers; and hindered amine-based light stabilizers. One type of ultraviolet absorber may be used alone, or two or more types may be used in combination.

[0061] The content of the ultraviolet absorber in the thermoplastic resin composition of the present invention is preferably 0.01 to 2 mass%, more preferably 0.05 to 1.5 mass%, and even more preferably 0.1 to 1 mass%, based on 100 mass% of the thermoplastic resin composition. When the content of the ultraviolet absorber is 0.01 mass% or more, the weather resistance of the thermoplastic resin composition is improved. When the content of the ultraviolet absorber is 2 mass% or less, the odor of the thermoplastic resin composition is further reduced.

[0062] Examples of photopolymerization initiators include ultraviolet polymerization initiators. When the thermoplastic resin composition of the present invention contains a styrene-based block copolymer having a reactive polystyrene-based hard block in the molecule as the styrene-based block copolymer (A), by further containing a photopolymerization initiator, the thermoplastic resin composition can be irradiated with light such as ultraviolet light to react with the reactive polystyrene-based hard block and crosslink the molecules, thereby adjusting the properties of the thermoplastic resin composition, such as dynamic viscoelasticity. When the thermoplastic resin composition is irradiated with ultraviolet light, the irradiation intensity of the ultraviolet light is 50 to 1,000 mW / cm. ２The integrated light amount is preferably about 1,000 to 15,000 mJ / cm ２ The photopolymerization initiator may be used alone or in combination of two or more.

[0063] Examples of the liquid rubber include liquid polybutene, liquid polybutadiene, liquid polyisoprene, and hydrogenated resins thereof. The liquid rubber may be used alone or in combination of two or more.

[0064] The content of the liquid rubber in the thermoplastic resin composition of the present invention is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass, based on 100% by mass of the thermoplastic resin composition. When the content of the liquid rubber is 1% by mass or more, the thermoplastic resin composition becomes flexible and the extensibility is further improved. When the content of the liquid rubber is 20% by mass or less, the thermoplastic resin composition does not become too soft, and the stretch recovery of the elastic member is further improved.

[0065] The particulate filler is not particularly limited, and examples thereof include calcium carbonate, kaolin, talc, titanium oxide, mica, styrene beads, etc. The particulate filler may be used alone or in combination of two or more.

[0066] 2. Method for Producing Thermoplastic Resin Composition The thermoplastic resin composition of the present invention can be produced by a known method, for example, by charging the thermoplastic elastomer (A), the plasticizer (B), and, if necessary, various additives such as the hydrocarbon resin (C) into a kneader heated to a temperature of 160 to 260°C, preferably 180 to 230°C, and melt-kneading them while heating.

[0067] The kneading machine is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw extruder, a Banbury mixer, a Brabender mixer, and a kneader.

[0068] The melt-kneading may be carried out, for example, by (1) dry-blending all of the components constituting the thermoplastic resin composition in advance using a mixer such as a Dalton mixer, a tumbler, or a V-blender, and then kneading them all at once; or (2) kneading all of the components except for the plasticizer (B) in advance, and then adding a predetermined amount of the plasticizer (B) to the kneader using a side feeder or the like. Either method may be employed.

[0069] The thermoplastic resin composition of the present invention is generally solid in a temperature range of 0 to 60°C, particularly at room temperature of 23°C, and exhibits stretchability, and therefore, stretchable members formed using the thermoplastic resin composition of the present invention can be used for a variety of applications.

[0070] The uses of the thermoplastic resin composition of the present invention are not particularly limited, and examples thereof include absorbent articles including sanitary materials, hospital gowns, masks, etc. Specific examples of the sanitary materials include disposable diapers and sanitary napkins.

[0071] 3. Elastic Member The elastic member of the present invention is an elastic member made from the above-mentioned thermoplastic resin composition. By configuring the elastic member of the present invention to consist of the above-mentioned thermoplastic resin composition of the present invention, the elastic member formed using the thermoplastic resin composition of the present invention becomes an elastic member that is excellent in extensibility and elastic recovery, and excellent in stress maintenance when stretched at high temperatures.

[0072] The stress when the elastic member is stretched twice is 0.4 N / mm ２ More than 0.8N / mm is preferable. ２ The above is more preferable. When the lower limit of the stress when the elastic member is stretched twice is within the above range, the sanitary material is further prevented from slipping down when worn. Furthermore, there is no particular limitation on the upper limit of the stress when the elastic member is stretched twice, and it may be, for example, 3.0 N / mm ２ Below, 2.0N / mm ２ It may be the following:

[0073] The stress when the elastic member is stretched twice is 0.4 N / mm ２ The stress at double elongation of the elastic member may be less than 0.4 N / mm ２In this case, the stress at double elongation of the elastic member is 0.4 N / mm ２ Preferably less than 0.3 N / mm ２ More preferably, 0.2 N / mm ２ In this case, the lower limit of the stress at double elongation of the elastic member is not particularly limited, and is preferably 1.0×10 －３ N / mm ２ That's about it.

[0074] The stress of the elastic member at two times elongation is measured by the method described in the Examples below.

[0075] The permanent set (stretch recovery) of the elastic member is preferably 55% or more, more preferably 70% or more, and even more preferably 80% or more. When the lower limit of the permanent set of the elastic member is in the above range, the elastic member's stretch recovery after elongation is further improved. Furthermore, the upper limit of the permanent set of the elastic member is not particularly limited and may be 99%, 98%, etc.

[0076] The permanent set of the elastic member is measured by the method described in the Examples below.

[0077] The thickness of the elastic member is not particularly limited, but is preferably 1 to 100 μm, more preferably 10 to 80 μm, and even more preferably 30 to 70 μm. When the lower limit of the thickness of the elastic member is within the above range, the stress and stretch recovery rate of the elastic member are further improved. When the upper limit of the thickness of the elastic member is within the above range, the texture of the elastic member is further improved.

[0078] The elastic member of the present invention can be produced from the thermoplastic resin composition of the present invention described above. The elastic member of the present invention can be formed into a suitable form depending on the intended use, such as a film, strand, nonwoven fabric, strip, fiber, or the like.

[0079] There are no particular limitations on the method for producing an elastic member from a thermoplastic polymer composition, and general molding methods suitable for various shapes can be suitably used.

[0080] When the elastic member of the present invention is, for example, a film, a strand, or a strip, it can be molded using a single-screw extruder or a twin-screw extruder.

[0081] The temperature of the thermoplastic resin composition when producing the elastic member of the present invention is not particularly limited, but is generally preferably 160 to 300°C, more preferably 170 to 290°C.

[0082] The uses of the elastic member of the present invention are not particularly limited, and can be used, for example, in absorbent articles including sanitary materials, hospital gowns, masks, etc. Specific examples of the sanitary materials include disposable diapers and sanitary napkins.

[0083] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0084] The raw materials used in the examples and comparative examples are as follows:

[0085] Thermoplastic resin (A) [Hydrogenated styrene-based block copolymers] A1537 Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) manufactured by Kraton Polymers, Inc. A1537 (styrene content 60% by mass) A1535 Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) manufactured by Kraton Polymers, Inc. A1535 (styrene content 57% by mass) A1536 Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) manufactured by Kraton Polymers, Inc. A1536 (styrene content 41% by mass) G1653 Styrene-ethylene-butylene-styrene (SEBS) manufactured by Kraton Polymers, Inc. G1653 (styrene content 30% by mass) MD6951 Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / S-S) manufactured by Kraton Polymers, Inc. MD6951 (styrene content: 34% by mass) H1043 Styrene-ethylene-butylene-styrene (SEBS) copolymer manufactured by Asahi Kasei Corporation Tuftec H1043 (styrene content: 67% by mass)

[0086] Plasticizer (B) PS-32 Paraffin Oil (Idemitsu Kosan Co., Ltd.)

[0087] Hydrocarbon resin (C) C-100L C5 hydrocarbon resin manufactured by Synthomer Co., Ltd. Eastotac C-100L SA120 α-methylstyrene resin manufactured by Kraton Co., Ltd. SYLVARES SA120

[0088] Additives [Antioxidant] Phenolic antioxidant Evernox 10 manufactured by Japan Specialty Chemicals

[0089] (Examples and Comparative Examples) The above-mentioned raw materials were charged into a Dalton mixer in the amounts shown in Table 1 and dry-blended. Then, the mixture was melt-kneaded at 190°C in a twin-screw extruder to prepare a strand-shaped thermoplastic resin composition.

[0090] (Preparation of Test Specimen (Elastic Member)) 5 g of the thermoplastic resin composition was dissolved in 15 g of methylcyclohexane to prepare a methylcyclohexane solution containing 25% by mass of the thermoplastic resin composition. The methylcyclohexane solution was then applied to a release-treated PET film using an applicator with a width of 70 mm and a gap of 400 μm. The film was then placed in an explosion-proof oven at 80°C for 2 minutes to thoroughly dry the methylcyclohexane. The test specimen (film) was then removed from the oven and thoroughly cooled to room temperature, and the film thickness was confirmed. If the desired film thickness was not achieved, the solution concentration and / or the applicator gap were adjusted appropriately to adjust the film thickness to 50 μm. A separately prepared release-treated PET film was then laminated and pressure-bonded at room temperature to create a laminate. The resulting laminate was stored at 23°C and 50% relative humidity for 24 hours to prepare a test specimen.

[0091] The properties and characteristics of the prepared thermoplastic resin compositions and test pieces were evaluated by the following methods.

[0092] Properties (Melt Index (MI)) The melt index was measured by Method A in accordance with JIS K 7210. The measurement was performed under the conditions of (1) 190°C and 2.16 kg, or (2) 230°C and 2.16 kg, and either condition that allowed measurement was adopted.

[0093] (Storage Modulus G' and tan δ Peak Value at 25°C) 1 g of a thermoplastic resin composition was dissolved in 20 to 30 g of methylcyclohexane to prepare a methylcyclohexane solution of the thermoplastic resin composition with sufficient fluidity to be handled using a dropper or the like. The methylcyclohexane solution was then poured into a shallow polyethylene cup and dried in a vacuum drying oven set at 50°C to obtain a sheet-like solid of the thermoplastic resin composition with a thickness of approximately 1 to 2 mm. The resulting thermoplastic resin composition was removed from the polyethylene cup and allowed to stand at 23°C for 24 hours to prepare a sample for dynamic viscoelasticity measurement. The sample was subjected to dynamic viscoelasticity measurement (heating process) using a dynamic viscoelasticity measuring device in rotational shear mode at a frequency of 1 Hz, with the temperature rising from -60 to 190°C at a rate of 5°C / min and a strain of 0.05%. The storage modulus G' measured at 25°C was taken as the storage modulus G' at 25°C. Furthermore, the loss tangent tanδ (loss modulus G" / storage modulus G') was calculated from the measured storage modulus G' and loss modulus G". The value of tanδ at a temperature where tanδ was maximum between the low temperature range of -50 to 0°C and the high temperature range of 60 to 120°C was recorded and used as the maximum tanδ value. Note that, as a dynamic viscoelasticity measuring device, for example, a rotational rheometer (trade name "DHR10") manufactured by TA Instruments Co., Ltd. can be mentioned.

[0094] Evaluation (Elongation at Break (Extensibility)) A test piece (width (MD direction) 50 mm, length (CD direction) 70 mm, thickness 50 μm) was placed in a tensile tester with a jig distance of 50 mm, and both ends of the test piece in the application direction were fixed with jigs so that the direction (CD direction) perpendicular to the longitudinal direction (coating direction (MD direction) of the thermoplastic resin composition) was positioned above and below. The test piece was pulled in the vertical direction at a pulling speed of 500 mm / min until it broke. The travel distance of the jig until the test piece broke was measured, and the value of the elongation at break was calculated based on the following formula, and the extensibility was evaluated according to the following evaluation criteria. Note that if the evaluation was △ or higher, it was evaluated as having no problems in practical use. [Fracture elongation (%)] = (distance traveled by the jig until the test piece breaks (mm) / initial jig distance (mm)) × 100. ◯: The fracture elongation is 600% or more. △: The fracture elongation is 500% or more but less than 600%. ×: The fracture elongation is less than 500%.

[0095] (Permanent set (stretch recovery)) A test piece (width (MD direction) 50 mm, length (CD direction) 70 mm, thickness 50 μm) was fixed with a jig to a tensile tester set at a jig distance of 50 mm so that the direction (CD direction) perpendicular to the longitudinal direction (coating direction (MD direction) of the thermoplastic resin composition) was positioned up and down, and the test piece was pulled in the vertical direction at a tensile speed of 500 mm / min until the strain displacement of the test piece reached 200%. Then, it was returned to its initial position at a speed of 500 mm / min. The process of pulling to a strain displacement of 200% and then returning to the initial position was defined as one cycle, and two cycles were repeated for the same test piece. The permanent set value was calculated based on the integral value during the first cycle of tension and the integral value during the second cycle of tension according to the following formula, and the stretch recovery was evaluated according to the following evaluation criteria. Note that if the evaluation was △ or higher, it was evaluated as having no problems in actual use. [Permanent set (%)] = [(Integrated value (J) at second cycle) / (Integrated value (J) at first cycle)] x 100 ◎: Permanent set is 90% or more. ○: Permanent set is 80% or more and less than 90%. △: Permanent set is 70% or more and less than 80%. ×: Permanent set is less than 70%.

[0096] (Stress Retention Rate (Stress Retention Ability During Elongation at High Temperatures)) In an environment of 40°C, a test piece (width (MD direction) 25 mm, length (CD direction) 50 mm, thickness 50 μm) was fixed with a jig to a tensile tester with a jig distance set to 25 mm so that the direction (CD direction) perpendicular to the longitudinal direction (coating direction (MD direction) of the thermoplastic resin composition) was positioned above and below, and the test piece was pulled in the vertical direction at a tensile speed of 100 mm / min until the displacement of the test piece reached 100%. This state was maintained for 1 hour, and the change in test force was measured. The maximum value of the test force was defined as the initial test force, and the stress retention rate was calculated based on the following formula from the measured test force after 1 hour. The stress retention ability during elongation at high temperatures was evaluated according to the following evaluation criteria. Note that an evaluation of △ or higher was deemed to be satisfactory for practical use. [Stress retention rate (%)] = (Test force after 1 hour (N) / Initial test force (N)) x 100 ◎: Stress retention rate is 80% or more. ○: Stress retention rate is 60% or more and less than 80%. △: Stress retention rate is 50% or more and less than 60%. ×: Stress retention rate is less than 50%.

[0097] (Stress at 2x Elongation) A test piece (width (MD direction) 50 mm, length (CD direction) 70 mm, thickness 50 μm) was fixed with a jig to a tensile tester set at a jig distance of 50 mm so that the direction (CD direction) perpendicular to the longitudinal direction (coating direction (MD direction) of the thermoplastic resin composition) was positioned above and below, and the test piece was pulled in the vertical direction at a pulling speed of 500 mm / min until the strain displacement of the test piece reached 200%. Then, the test piece was returned to its initial position at a speed of 500 mm / min. The process of pulling to the point where the strain displacement reached 200% and returning to the initial position was defined as one cycle, and two cycles were repeated for the same test piece. The stress value at the point where the strain displacement reached 100% during the first pulling cycle was recorded, and the stress at 2x elongation (N / mm ２ If the evaluation was △ or better, it was evaluated as having no problem in practical use. ◯: Stress at 2-fold elongation was 0.8 N / mm ２ △: Stress at 2 times elongation is 0.4 N / mm or more ２ 0.8N / mm or more ２ x: Stress at 2 times elongation is less than 0.4 N / mm ２ is less than

[0098] The results are shown in Table 1.

[0099]

Claims

1. A thermoplastic resin composition comprising a thermoplastic elastomer (A) and a plasticizer (B), wherein the thermoplastic elastomer (A) comprises a styrene-based block copolymer, and has a melt index of 0.1 to 100 g / 10 min measured under conditions of 190°C and 2.16 kg or 230°C and 2.16 kg according to Method A of JIS K7210, and a storage modulus G' at 25°C measured under the following measurement conditions is 2.5 x 10 ５ ~1.0 x 10 ７ Pa, the loss tangent tan δ (loss modulus / storage modulus) obtained by measuring the storage modulus G' has at least one peak each in a low temperature range of -50 to 0°C and a high temperature range of 60 to 120°C, and D1, which is the tan δ peak value in the low temperature range, is greater than D2, which is the tan δ peak value in the high temperature range. (Measurement conditions for storage modulus G') Starting temperature -60°C, ending temperature 190°C, heating rate 5°C / min, measurement frequency 1 Hz, strain 0.05% 2. The thermoplastic resin composition according to claim 1, wherein the styrene-based block copolymer is a hydrogenated styrene-based block copolymer.

3. The thermoplastic resin composition according to claim 1, wherein the amount of styrene derived from the styrene-based block copolymer contained in the thermoplastic resin composition is 30 to 50 mass % relative to 100 mass % of the thermoplastic resin composition.

4. The thermoplastic resin composition according to claim 1, wherein the content of the thermoplastic elastomer (A) is 50 to 85 mass % relative to 100 mass % of the thermoplastic resin composition.

5. The thermoplastic resin composition according to claim 1, wherein the ratio of D1 to D2 (D1 / D2) is greater than 1 and less than or equal to 15.

6. The thermoplastic resin composition according to claim 1, further comprising a hydrocarbon resin (C), the content of said hydrocarbon resin (C) being 0.5 to 30 mass % relative to the thermoplastic resin composition as 100%.

7. An elastic member made of the thermoplastic resin composition according to any one of claims 1 to 6.

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