Hot melt composition

Abstract

Provided is a hot-melt composition which is capable of forming a stretchable member having excellent extensibility, resilience to stretching, and stress retention during stretching at high temperatures, and which has excellent coating suitability. The present invention provides a hot melt composition containing a thermoplastic resin (A) and a plasticizer (B), the thermoplastic resin (A) containing a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40-65 mass%, and the hot melt composition having a stress maintenance rate of 50% or more after being held for 1 hour in a 2-fold extended state under a temperature condition of 40 DEG C.

Description

Technical Field

[0001] The present invention relates to hot melt compositions. Background Art

[0002] In recent years, absorbent articles including sanitary materials such as diapers and sanitary napkins have been widely used, and in order to prevent these absorbent articles from slipping off when worn, laminated bodies composed of stretchable members are used.

[0003] Among the stretchable members used in the laminate, rubber cords made of natural rubber or synthetic polymers are known. The rubber cords exhibit good stress when stretched, and thus can effectively prevent the absorbent article from slipping when worn.

[0004] In order to prevent the absorbent article from slipping and to suppress the feeling of pressure or irritation when wearing, a stretch film containing a thermoplastic elastomer composition is used as a stretch member of a laminate used in an absorbent article. As a thermoplastic elastomer composition used in the stretch film, a hot melt stretch adhesive composition has been proposed (see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-88097 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, Patent Document 1 does not fully explore the improvement of stretchability, and there is still room for improvement. When wearing sanitary materials such as diapers, the stretchable member used in the sanitary materials is required to have sufficient stretchability.

[0010] In addition, Patent Document 1 does not fully explore the suppression of the reduction in stretch recovery. When wearing sanitary materials such as diapers, the stretch parts used in the sanitary materials are stretched. Therefore, it is required that the stretch parts be able to suppress the reduction in stretch recovery even when they are kept in an extended state. Patent Document 1 records that a considerable amount of tackifier is added to the hot melt composition (Patent Document 1

[0007] , Table 2 (hydrogenated petroleum resin)), but there is a problem that the stretch parts become hard and cannot show sufficient stretch recovery.

[0011] Furthermore, when wearing sanitary materials such as diapers, the temperature is kept close to body temperature for a long time, so the stretchable parts are required to be able to relax the stress even when stretched and maintained in a heated state, and to have excellent stress maintenance during stretching at high temperatures. As described above, Patent Documents 1 and 2 describe that even when a considerable amount of tackifier is added to the hot melt composition, the stress maintenance during stretching at high temperatures is insufficient.

[0012] In addition, even when the telescopic component has the above-mentioned characteristics, the hot melt composition forming the telescopic component is required to have excellent coating adaptability. When the hot melt composition forming the telescopic component has a high melt viscosity or a high softening point, an extruder is required to mold the telescopic hot melt composition, which leads to a problem of reduced productivity. Therefore, the telescopic hot melt composition is required to have coating adaptability (meltability) that allows coating using a general hot melt coating device.

[0013] In view of the above circumstances, an object of the present invention is to provide a hot-melt composition which can form a telescopic member having excellent elongation, stretch recovery and stress maintenance during elongation at high temperatures and has excellent coating suitability.

[0014] Technical solutions to solve problems

[0015] In order to achieve the above-mentioned object, the inventors of the present invention have repeatedly conducted intensive studies and found that, in a hot-melt composition comprising a thermoplastic resin (A) and a plasticizer (B), the above-mentioned object can be achieved by making the thermoplastic resin (A) contain a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass, and making the stress maintenance rate of the hot-melt composition measured under specific conditions be 50% or more, thereby completing the present invention.

[0016] That is, the present invention relates to the following hot-melt composition.

[0017] 1. A hot-melt composition comprising a thermoplastic resin (A) and a plasticizer (B), wherein the thermoplastic resin (A) contains a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass, and the stress retention rate of the hot-melt composition after being maintained in a 2-fold elongation state at a temperature of 40° C. for 1 hour is 50% or more.

[0018] 2. The hot-melt composition according to item 1, wherein the content of the hydrogenated styrene-based block copolymer (A1) is 25 to 40% by mass based on 100% by mass of the hot-melt composition.

[0019] 3. The hot-melt composition according to item 1 or 2, wherein the hydrogenated styrene-based block copolymer (A1) is a hydrogenated product of a block copolymer containing styrene units and butadiene units.

[0020] 4. The hot-melt composition according to any one of items 1 to 3, wherein the hydrogenated styrene-based block copolymer (A1) is a styrene-ethylene-butylene / styrene-styrene copolymer.

[0021] 5. The hot-melt composition according to any one of items 1 to 4, wherein the melt viscosity at 180° C. measured using a Brookfield RVT viscometer (No. 29 spindle) is 5,000 to 35,000 mPa·s.

[0022] 6. The hot-melt composition according to any one of items 1 to 5, wherein the content of the plasticizer (B) is 30 to 70% by mass based on 100% by mass of the hot-melt composition.

[0023] 7. The hot-melt composition according to any one of items 1 to 6, further comprising a hydrocarbon resin (C), wherein the content of the hydrocarbon resin (C) is 1 to 45% by mass based on 100% of the hot-melt composition.

[0024] 8. The hot-melt composition according to item 7, wherein the hydrocarbon resin (C) is an aromatic hydrocarbon resin.

[0025] 9. The hot-melt composition according to any one of items 1 to 8, which is a hot-melt composition for absorbent articles.

[0026] Effects of the Invention

[0027] The hot-melt composition of the present invention can form a stretchable member having excellent elongation, stretch recovery and stress maintenance during elongation at high temperatures, and has excellent coating suitability. DETAILED DESCRIPTION

[0028] 1. Hot melt composition

[0029] The hot melt composition of the present invention is a hot melt composition comprising a thermoplastic resin (A) and a plasticizer (B), wherein the thermoplastic resin (A) contains a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass, and the stress retention rate of the hot melt composition after being kept in a 2-fold elongation state for 1 hour at a temperature of 40°C is 50% or more. The hot melt composition of the present invention can form a telescopic component by containing the above (A) and (B), and in particular, the thermoplastic resin (A) contains a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass, and the stress retention rate of the hot melt composition is 50% or more, so that a telescopic component with excellent elongation, stretch recovery and stress retention during elongation at high temperature can be formed, and excellent coating suitability can be exhibited. That is, the hot melt composition of the present invention has all the above characteristics, and thus can form a telescopic component with excellent elongation, stretch recovery and stress retention during elongation at high temperature, and excellent coating suitability, and all these characteristics are combined.

[0030] In this specification, "high temperature" means a temperature about human body temperature, which is 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. In addition, "heating" means a temperature in the above range.

[0031] In this specification, "room temperature" means 23°C.

[0032] The hot melt composition of the present invention has a stress maintenance rate of 50% or more after being maintained in a 2-fold elongation state for 1 hour at a temperature of 40°C. If the stress maintenance rate is less than 50%, the stress maintenance property during elongation at high temperature is insufficient. The stress maintenance rate is preferably 60% or more, more preferably 70% or more, and further preferably 75% or more. In addition, the upper limit of the stress maintenance rate is as high as possible, and can be 100% or less, 90% or less, or 85% or less.

[0033] The stress maintenance rate of the hot-melt composition can be evaluated in detail by the method described in the examples below.

[0034] The melt viscosity of the hot melt composition of the present invention at 180° C. is preferably 3,000 to 50,000 mPa·s, more preferably 5,000 to 35,000 mPa·s, and even more preferably 7,000 to 28,000 mPa·s. When the melt viscosity is within the above range, the coating suitability of the hot melt composition is further improved.

[0035] The melt viscosity of the hot-melt composition at 180° C. can be evaluated by the method described in the examples described below.

[0036] (Thermoplastic resin (A))

[0037] The thermoplastic resin (A) contains a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass.

[0038] (Styrene-based block copolymer (A1))

[0039] The styrene block copolymer (A1) is not particularly limited as long as it is a hydrogenated styrene block copolymer having a styrene content of 40 to 65% by mass. As the styrene block copolymer (A1), a hydrogenated product of a block copolymer containing styrene units and butadiene units is preferably used.

[0040] Specific examples of the styrene block copolymer (A1) include styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), styrene-ethylene-butylene-olefin crystalline copolymer (SEBC), etc. Among them, styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS), and styrene-ethylene-propylene-styrene copolymer (SEPS) are preferred from the viewpoint of better elongation, stretch recovery, and stress maintenance during elongation at high temperatures. Styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS), and styrene-ethylene-propylene-styrene copolymer (SEPS) are more preferred, styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS), and styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) are further preferred.

[0041] The styrene-based block copolymer (A1) may be used alone or in combination of two or more.

[0042] The above-mentioned styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) is a copolymer in which styrene is also dispersed in the middle block phase in a styrene-ethylene-butylene-styrene copolymer in which the styrene unit at the terminal is the terminal block phase and the ethylene-butylene unit is the middle block phase. By using a copolymer in which styrene is dispersed in the middle block phase, even if the styrene content of the styrene-based block copolymer as a whole increases, the styrene-based block copolymer will not become too hard and will show good elongation. Therefore, in a hot melt composition containing a styrene-ethylene-butylene / styrene-styrene copolymer, good elongation and good stretch recovery can be achieved. In addition, by using a styrene-ethylene-butylene / styrene-styrene copolymer in which styrene is dispersed in the middle block phase in the hot melt composition, the increase in melt viscosity at low temperatures can be suppressed, and therefore, the coating adaptability of the hot melt composition can be further improved.

[0043] The method for producing 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.

[0044] As the styrene-ethylene-butylene / styrene-styrene copolymer, a commercially available product may be used, and examples of the commercially available product include A1537, A1536, and A1535 manufactured by Kraton Polymers.

[0045] Taking the styrene block copolymer (A1) as 100% by mass, the styrene content of the styrene block copolymer (A1) is 40 to 65% by mass. If the styrene content is less than 40% by mass, the stress retention rate of the telescopic component formed using the hot-melt composition during elongation at high temperature is reduced. If the styrene content exceeds 65% by mass, the hot-melt composition becomes hard and the telescopic component cannot show sufficient elongation. The styrene content of the styrene block copolymer (A1) is preferably 40 to 65% by mass, more preferably 40 to 63% by mass.

[0046] In the present specification, the "styrene content" of the styrene block copolymer refers to the content ratio (mass %) of the styrene block in the styrene block copolymer.

[0047] In addition, the calculation method of the styrene content in the styrene-based block copolymer in the present specification is not particularly limited, and examples thereof include a method using a proton nuclear magnetic resonance method or an infrared spectroscopy method in accordance with JIS K 6239.

[0048] As the styrene block copolymer (A1), a polymer having a styrene content of 40 to 65% by mass may be used, and one type may be used alone, or two or more types may be mixed. For example, if the styrene content is within the above range, a styrene block copolymer (A1) having a high styrene content and a styrene block copolymer (A1) having a low styrene content may be mixed for use. That is, when two or more types are mixed for use, in the hot melt composition of the present invention, the styrene content of each styrene block copolymer (A1) is within the above range.

[0049] The styrene block copolymer (A1) is a hydrogenated styrene block copolymer. The styrene block copolymer is a hydrogenated product of a styrene block copolymer, also referred to as a hydrogenated styrene block copolymer. More specifically, the hydrogenated styrene block copolymer is a block copolymer obtained by block copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound, and hydrogenating all or part of the blocks of the conjugated diene compound in the obtained block copolymer.

[0050] 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, vinylanthracene, etc., among which styrene is preferred. The vinyl aromatic hydrocarbon may be used alone or in combination of two or more.

[0051] The conjugated diene compound is a diene compound having at least one pair of conjugated double bonds. As the conjugated diene compound, specific examples include 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., among which 1,3-butadiene and 2-methyl-1,3-butadiene are preferred. The conjugated diene compound can be used alone or in combination of two or more.

[0052] In this specification, the proportion of hydrogenated styrene block copolymer (A1) is expressed as "hydrogenation rate". The "hydrogenation rate" of the styrene block copolymer (A1) refers to the proportion of olefinic unsaturated double bonds that are hydrogenated and converted into saturated hydrocarbon bonds based on all olefinic unsaturated double bonds contained in the chain segment based on the conjugated diene compound. The hydrogenation rate can be measured by an infrared spectrophotometer, a nuclear magnetic resonance device, etc.

[0053] The hydrogenated styrene block copolymer (A1) may be partially hydrogenated or fully hydrogenated. Of these, fully hydrogenated is preferred. The heating stability of the hot melt composition is further improved by using a fully hydrogenated styrene block copolymer. The hydrogenation rate of the styrene block copolymer (A1) is preferably about 100%.

[0054] The content of the styrene block copolymer (A1) in the hot-melt composition of the present invention is preferably 20 to 50% by mass, more preferably 25 to 40% by mass, and further preferably 30 to 35% by mass, based on 100% by mass of the hot-melt composition. When the content of the styrene block copolymer (A1) is within the above range, the telescopic component formed using the hot-melt composition of the present invention has better stress retention during elongation at high temperature, and the coating adaptability of the hot-melt composition is further improved.

[0055] The melt flow rate (MFR) of the styrene-based block copolymer (A1) is preferably less than 10 g / 10 min, more preferably less than 7 g / 10 min. If the upper limit of the melt flow rate is within the above range, the stress maintenance rate of the hot-melt composition of the present invention is further improved. The lower limit of the melt flow rate is not particularly limited, but is preferably a value exceeding 0, more preferably exceeding 1 g / 10 min, and further preferably exceeding 3 g / 10 min. If the lower limit of the melt flow rate is within the above range, the increase in the melt viscosity of the hot-melt composition of the present invention is suppressed, and better coating adaptability can be exhibited.

[0056] In this specification, the above-mentioned melt flow rate is a value measured by a measurement method based on ISO1133 under the conditions of 260°C and 5 kg weight.

[0057] (Other thermoplastic resins)

[0058] The thermoplastic resin (A) constituting the hot melt composition of the present invention may further contain other thermoplastic resins in addition to the above-mentioned styrene-based block copolymer (A1). As such other thermoplastic resin, thermoplastic resins commonly used in hot melt compositions can be used.

[0059] As the other thermoplastic resin, other styrene block copolymers (A2) other than the above styrene block copolymers (A1) can be used. As the other styrene block copolymers (A2), hydrogenated styrene block copolymers having a styrene content of less than 40% by mass or more than 65% by mass can be cited.

[0060] As the hydrogenated styrene block copolymer having a styrene content of less than 40% by mass or more than 65% by mass used as the other styrene block copolymer (A2), there are no particular limitations, and examples thereof include styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), and styrene-ethylene-butylene-olefin crystalline copolymer (SEBC). Among them, styrene-ethylene-butylene-styrene copolymer and styrene-ethylene-butylene / styrene-styrene copolymer are preferred from the viewpoint of having better recovery of expansion and contraction after heating and keeping, and being able to have both stress and good elongation during elongation.

[0061] The above-mentioned other styrene-based block copolymers (A2) may be used alone or in combination of two or more.

[0062] The above-mentioned styrene-ethylene-butylene-styrene copolymer (SEBS) is a copolymer in which the terminal styrene unit is a terminal block phase and the ethylene-butylene unit is a middle block phase. In addition, if a copolymer in which the middle block phase is a hydrogenated ethylene-butylene unit is used, the polarity difference with the styrene unit of the terminal block phase becomes more significant, and the styrene unit of the terminal block phase is more solid than the copolymer of the unhydrogenated middle block phase. As a result, the expansion and contraction recovery of the hot melt composition can be further improved. In addition, if the middle block phase is hydrogenated, a hot melt composition with better heating stability can be provided.

[0063] As the styrene-ethylene-butylene-styrene copolymer, a commercially available product may be used, and examples of the commercially available product include G1654 manufactured by Kraton Polymers, and TUFTECH1041 and H1043 manufactured by Asahi Kasei Corporation.

[0064] Regarding the styrene content of the other styrene-based block copolymer (A2), the styrene-based block copolymer (A2) is preferably less than 40% by mass or more than 65% by mass, with the styrene-based block copolymer (A2) being 100% by mass. The styrene content may also be less than 35% by mass or less than 30% by mass. In addition, the styrene content may also be more than 67% by mass or more than 70% by mass.

[0065] The content of the other styrene block copolymer (A2) in the hot melt composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.5 to 7.5% by mass, and even more preferably 1 to 5% by mass, based on 100% by mass of the hot melt composition. When the content of the other styrene block copolymer (A2) is within the above range, the telescopic component formed using the hot melt composition of the present invention has better stress retention during elongation at high temperature, and the coating adaptability of the hot melt composition is further improved.

[0066] (Plasticizer (B))

[0067] The hot melt composition of the present invention contains a plasticizer (B). The plasticizer (B) is preferably liquid at 23°C. In this specification, "liquid" means a state showing fluidity. The pour point of the plasticizer (B) is preferably below 23°C, more preferably below 10°C.

[0068] In this specification, the pour point is a value measured by a measurement method in accordance with JIS K2269.

[0069] The plasticizer (B) is not particularly limited, and examples thereof include paraffinic process oils, naphthenic process oils, aromatic process oils, and liquid paraffin. Among them, paraffinic process oils, naphthenic process oils, and liquid paraffin are preferred from the viewpoint of excellent thermal stability, and paraffinic process oils and naphthenic process oils are more preferred. In addition, paraffinic process oils are more preferred from the viewpoint of further improving the stress maintenance of the telescopic component formed using the hot-melt composition during elongation at high temperature.

[0070] As the paraffinic process oil, a commercially available product can be used, and examples of the commercially available product include PW-32 produced by Idemitsu Kosan Co., Ltd. and PS-32 produced by Idemitsu Kosan Co., Ltd.

[0071] As the naphthenic process oil, commercial products can be used, such as CALSOL550 produced by Calumet Speciality Products Partners, DIANA FRESIA N28 produced by Idemitsu Kosan Co., Ltd., DIANA FRESIA U46 produced by Idemitsu Kosan Co., Ltd., and Nyflex222B produced by Nynas Co., Ltd.

[0072] As the liquid paraffin, a commercially available product can be used, and examples of the commercially available product include P-100 produced by MORESCO and Kaydol produced by Sonneborn.

[0073] The plasticizer (B) may be used alone or in combination of two or more.

[0074] Taking the hot melt composition as 100 mass%, the content of the plasticizer (B) in the hot melt composition of the present invention is preferably 25 to 75 mass%, more preferably 30 to 70 mass%, and further preferably 50 to 65 mass%. When the upper limit of the content of the plasticizer (B) is within the above range, the stress maintenance of the telescopic component formed using the hot melt composition during elongation at high temperature is further improved. When the lower limit of the content of the plasticizer (B) is within the above range, the melt viscosity of the hot melt composition is further reduced, and the coating adaptability of the hot melt composition is further improved.

[0075] (Hydrocarbon resin (C))

[0076] The hot melt composition of the present invention preferably contains a hydrocarbon resin (C). The hydrocarbon resin (C) is a component that acts as a tackifier or a terminal block resin. By containing a hydrocarbon resin (C), the increase in the melt viscosity of the hot melt composition of the present invention can be suppressed, and the stress maintenance rate can be further improved.

[0077] The hydrocarbon resin (C) is a hydrocarbon resin other than the thermoplastic resin (A) and the plasticizer (B). The hydrocarbon resin (C) preferably does not contain the styrene block copolymers, polyolefin copolymers, polyacrylic acid copolymers, polyamide copolymers, polyester copolymers, and polyurethane copolymers described in (A1) and (A2). More specifically, the hydrocarbon resin (C) includes tackifier resins, aromatic hydrocarbon resins, and the like.

[0078] As the tackifying resin, natural rosin, modified rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, copolymers of natural terpenes, three-dimensional polymers of natural terpenes, hydrogenated derivatives of copolymers of natural terpenes, terpene resins, hydrogenated derivatives of phenol-based modified terpene resins; petroleum resins such as C5-based petroleum resins, C9-based petroleum resins, C5C9-based petroleum resins, dicyclopentadiene-based petroleum resins, or partially hydrogenated petroleum resins and fully hydrogenated petroleum resins obtained by hydrogenating these petroleum resins. As the tackifying resin, petroleum resins, partially hydrogenated petroleum resins and fully hydrogenated petroleum resins are preferred from the aspects of excellent odor and thermal stability of the hot melt composition, and partially hydrogenated petroleum resins and fully hydrogenated petroleum resins are more preferred. These tackifying resins can be used alone or in combination of two or more.

[0079] The aromatic hydrocarbon resin is a resin that functions as a terminal block resin of a resin component forming a hot melt composition. The aromatic hydrocarbon resin is not particularly limited, and for example, a vinyl aromatic hydrocarbon can be used. A 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, vinylanthracene, etc., among which styrene and α-methylstyrene are preferred.

[0080] The content of the hydrocarbon resin (C) is preferably 1 to 45% by mass, more preferably 2 to 35% by mass, and even more preferably 5 to 20% by mass, based on 100% of the hot-melt composition.

[0081] (Other additives)

[0082] The hot melt composition of the present invention may contain other additives within the range that does not substantially hinder the purpose of the present invention. Examples of such other additives include antioxidants, ultraviolet absorbers, photopolymerization initiators, liquid rubbers, and fine particle fillers.

[0083] Examples of the antioxidant include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl) propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,4-bis(octylthiomethyl)-o-cresol, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-tert-amyl-6-[1-(3, Hindered phenol antioxidants such as 5-di-tert-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-amylphenyl)]acrylate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane; sulfur antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate, pentaerythritol tetrakis(3-laurylthiopropionate); phosphorus antioxidants such as tris(nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, etc. The antioxidants may be used alone or in combination of two or more.

[0084] The content of the antioxidant in the hot melt composition of the present invention is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and even more preferably 0.1 to 1% by mass, based on 100% by mass of the hot melt composition. If the content of the antioxidant is 0.01% by mass or more, the thermal stability of the hot melt composition is further improved. If the content of the antioxidant is 2% by mass or less, the odor of the hot melt composition is reduced.

[0085] Examples of the ultraviolet absorber include benzotriazole ultraviolet absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-tert-butylphenyl)benzotriazole, and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole; benzophenone ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone; salicylate ultraviolet absorbers; cyanoacrylate ultraviolet absorbers; and hindered amine light stabilizers. The ultraviolet absorbers may be used alone or in combination of two or more.

[0086] The content of the ultraviolet absorber in the hot melt composition of the present invention is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and further preferably 0.1 to 1% by mass, based on 100% by mass of the hot melt composition. If the content of the ultraviolet absorber is 0.01% by mass or more, the weather resistance of the hot melt composition is improved. If the content of the ultraviolet absorber is 2% by mass or less, the odor of the hot melt composition is reduced.

[0087] As the photopolymerization initiator, there can be mentioned an ultraviolet polymerization initiator and the like. In the hot melt composition of the present invention, when the styrene block copolymer (A) contains a styrene block copolymer having a reactive polystyrene hard block in the molecule, by also containing a photopolymerization initiator, the reactive polystyrene hard block can be reacted by irradiating the hot melt composition with light such as ultraviolet rays, so that the molecules are cross-linked, thereby adjusting the properties such as dynamic viscoelasticity of the hot melt composition. When irradiating the hot melt composition with ultraviolet rays, the irradiation intensity of the ultraviolet rays is preferably 50 to 1000 mW / cm 2 In addition, the cumulative light intensity is preferably 1000 to 15000 mJ / cm 2 The photopolymerization initiator may be used alone or in combination of two or more.

[0088] 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.

[0089] Taking the hot melt composition as 100 mass%, the content of the liquid rubber in the hot melt composition of the present invention is preferably 1 to 20 mass%, more preferably 2 to 15 mass%, and further preferably 3 to 10 mass%. If the content of the liquid rubber is 1 mass% or more, the melt viscosity of the hot melt composition is reduced, and the coating adaptability is further improved. If the content of the liquid rubber is 20 mass% or less, the hot melt composition does not become too soft, and the telescopic recovery of the telescopic component is further improved.

[0090] The fine particle filler is not particularly limited, and examples thereof include calcium carbonate, kaolin, talc, titanium oxide, mica, styrene beads, etc. The fine particle filler may be used alone or in combination of two or more.

[0091] (Method for producing hot-melt composition)

[0092] The hot melt composition of the present invention can be produced by a known method, for example, by placing a thermoplastic resin (A), a plasticizer (B), and various additives such as a hydrocarbon resin (C) as required in a double-arm kneading machine heated to 150 to 170° C., and melting and kneading the mixture while heating.

[0093] The hot melt composition of the present invention is usually solid in the temperature range of 0 to 60°C, particularly at room temperature of 23°C, and exhibits stretchability. Therefore, the stretchable member formed using the hot melt composition of the present invention can be used in various applications.

[0094] The application of the hot melt composition of the present invention is not particularly limited, and examples thereof include absorbent articles including sanitary materials, hospital gowns, masks, etc. Specific examples of the sanitary materials include diapers and sanitary napkins.

[0095] By bonding porous substrates using the hot-melt composition of the present invention, a laminate can be produced. The laminate is suitable for use in absorbent articles and the like.

[0096] As the porous substrate, nonwoven fabric, paper, etc. can be cited. As the nonwoven fabric, there is no particular limitation, and spunbond nonwoven fabric, spunlace nonwoven fabric, needle punched nonwoven fabric, etc. can be cited. For example, by using the hot melt composition of the present invention and laminating the hot melt composition in a stretched state, a stretchable laminate with good texture can be produced. As the nonwoven fabric, an extensible nonwoven fabric can also be used. For example, the hot melt composition of the present invention is applied in a state where the extensible nonwoven fabric is not stretched, and the hot melt composition of the present invention is laminated between the extensible nonwoven fabrics, so that a stretchable laminate can be produced.

[0097] The above-mentioned stretchable nonwoven fabric stretches a certain amount by stretching in a certain direction, but it is difficult to restore to the original length when the stretching force is removed. By coating the hot melt composition of the present invention on a porous substrate such as a stretchable nonwoven fabric to form a laminate, it can function as a stretch reinforcing material and can give the laminate a function of restoring to the original length.

[0098] The stretchable nonwoven fabric is not particularly limited, and examples thereof include spunlace nonwoven fabrics and needle punched nonwoven fabrics. The coating method for coating the hot melt composition on the porous substrate is not particularly limited, and examples thereof include slit coating, curtain spray coating, spiral spray coating, and film coating. When the hot melt composition is coated by slit coating, the stress of the laminate is further increased because the hot melt composition easily penetrates into the porous substrate. In addition, when the hot melt composition is coated by spray coating, the penetration of the hot melt composition into the porous substrate can be suppressed, and thus the texture and air permeability are further improved.

[0099] The amount of the hot melt composition applied to the porous substrate is not particularly limited, but is preferably 1 to 200 g / m 2 , more preferably 5 to 150 g / m 2 , more preferably 10 to 100 g / m 2 If the lower limit of the coating amount is within the above range, the stress and expansion recovery rate of the laminate are further improved. If the upper limit of the coating amount is within the above range, the texture of the laminate is further improved.

[0100] Example

[0101] Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[0102] The raw materials used in Examples and Comparative Examples are as follows.

[0103] Thermoplastic resin (A):

[0104] [Hydrogenated styrene block copolymer (A1)]

[0105] ·Hydrogenated styrene block copolymer (A1-1)

[0106] Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) A1537 manufactured by Kraton Polymers (styrene content 60 mass%)

[0107] ·Hydrogenated styrene block copolymer (A1-2)

[0108] Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) A1536 manufactured by Kraton Polymers (styrene content 42 mass%)

[0109] ·Hydrogenated styrene block copolymer (A1-3)

[0110] Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) A1535 manufactured by Kraton Polymers (styrene content 57 mass%)

[0111] [Other styrene-based block copolymers (A2)]

[0112] ·Hydrogenated styrene block copolymer (A2-1)

[0113] Styrene-ethylene-butylene / styrene-styrene copolymer (SEB / SS) MD6951 manufactured by Kraton Polymers (styrene content 35 mass%)

[0114] ·Hydrogenated styrene block copolymer (A2-2)

[0115] Styrene-ethylene-butylene-styrene (SEBS) copolymer, TUFTECH 1043 manufactured by Asahi Kasei Corporation (styrene content 67% by mass)

[0116] ·Hydrogenated styrene block copolymer (A2-3)

[0117] Styrene-ethylene-butylene-styrene (SEBS copolymer, TUFTECH 1041 manufactured by Asahi Kasei Corporation (styrene content 30 mass%)

[0118] ·Hydrogenated styrene block copolymer (A2-4)

[0119] Styrene-ethylene-butylene-styrene (SEBS): G1654 manufactured by Kraton Polymers (styrene content: 30% by mass)

[0120] Plasticizer (B):

[0121] · Naphthenic oil (B1) CALSOL550 produced by Calumet Speciality Products Partners

[0122] · Paraffin oil (B2) PS32 manufactured by Idemitsu Kosan Co., Ltd.

[0123] Hydrocarbon resin (C):

[0124] Hydrocarbon resin (C1)

[0125] C5 hydrocarbon resin Eastman Chemical Company produces C100L

[0126] Hydrocarbon resin (C2)

[0127] Styrene resin Eastman Chemical Company produced Piccolastic A75

[0128] Hydrocarbon resin (C3)

[0129] α-Methylstyrene resin, produced by Mitsui Chemicals, Inc. FTR-0120

[0130] Antioxidants:

[0131] Phenolic antioxidants Evernox10 produced by Japan Specialty Chemicals

[0132] (Examples and Comparative Examples)

[0133] The above raw materials were charged into a stirring kneading machine equipped with a heating device in the amounts shown in Table 1. The mixture was kneaded for 90 minutes while being heated at 160° C. to produce a hot melt composition.

[0134] The properties of the obtained hot melt composition and the stretchable member produced using the hot melt composition were measured under the following measurement conditions to evaluate the characteristics.

[0135] Determination of traits

[0136] (180℃ melt viscosity)

[0137] The hot-melt composition was heated and melted, and the viscosity of the molten state at 180° C. was measured using a Brookfield RVT viscometer (No. 29 rotor) while adjusting the rotation speed within a measurable range.

[0138] (Ring and Ball Softening Point)

[0139] The softening point (ring and ball softening point) of the hot melt composition was measured by a measuring method based on JIS K 6863-1994.

[0140] evaluate

[0141] (Preparation of test piece (telescopic member))

[0142] The hot melt composition is applied to the release layer side of the release-treated PET film at a coating temperature of 160 to 180°C to a thickness of 50 μm or 150 μm. The coating width is 100 mm. Next, a release paper with a release treatment applied to one side is laminated to produce a laminate. The obtained laminate is cut into a size of 25 mm in the width direction and 50 mm in the coating direction, or a size of 50 mm in the width direction and 100 mm in the coating direction. The PET film and release paper of the laminate are peeled off to prepare a test piece with a width of 25 mm and a length of 50 mm and a test piece (telescopic component) with a width of 50 mm and a length of 100 mm composed of the hot melt composition.

[0143] (Elongation at break (elongation))

[0144] The test piece (width (MD direction) 50 mm, length (CD direction) 100 mm, thickness 50 μm) was fixed with both ends of the coating direction of the test piece (width (MD direction) 50 mm, length (CD direction) 100 mm, thickness 50 μm) in a tensile tester (manufactured by Shimadzu Corporation, product name: AGS-X) with a clamp spacing of 50 mm so that the direction (CD direction) perpendicular to the long side direction (coating direction (MD direction) of the hot melt composition) is located vertically, and the test piece was stretched in the vertical direction at a tensile speed of 500 mm / min until it broke. The moving distance of the clamp until the test piece broke was measured, and the value of the elongation at break was calculated based on the following formula to evaluate the elongation.

[0145] [Elongation at break (%)] = (distance of movement of the jig until the test piece breaks (mm) / initial distance between jigs (mm) × 100

[0146] (Permanent strain (stretch recovery))

[0147] The test piece (width (MD direction) 50 mm, length (CD direction) 100 mm, thickness 50 μm) was fixed on a tensile testing machine (manufactured by Shimadzu Corporation, product name: AGS-X) with a clamp spacing set to 50 mm in a direction (CD direction) perpendicular to the long side direction (coating direction of the hot melt composition (MD direction)) and stretched in the vertical direction at a stretching speed of 500 mm / min to a point where the strain displacement of the test piece reaches 300%. Then, it was returned to the initial position at a speed of 500 mm / min. The process of stretching to a strain displacement of 300% and then returning to the initial position was regarded as one cycle, and two cycles were repeated for the same test piece. Based on the integral value of the stretching in the first cycle and the integral value of the stretching in the second cycle, the value of the permanent strain was calculated based on the following formula to evaluate the stretch recovery.

[0148] [Permanent strain (%)] = [(integrated value of the second cycle (J)) / (integrated value of the first cycle (J))] × 100

[0149] (Stress maintenance rate (stress maintenance during elongation at high temperature))

[0150] The stress maintenance rate after being maintained in a 2-fold elongation state for 1 hour at a temperature of 40°C was measured. Specifically, under a 40°C environment, a test piece (width (MD direction) 25 mm, length (CD direction) 50 mm, thickness 150 μm) was fixed with a clamp in a direction (CD direction) perpendicular to the long side direction (coating direction of the hot melt composition (MD direction)) on a tensile testing machine (manufactured by Shimadzu Corporation, product name: EZ-LX) with a clamp spacing set to 25 mm, and stretched 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 the test force was measured. The maximum value of the test force was taken as the initial test force, and the stress maintenance rate was calculated based on the measured value of the test force after 1 hour based on the following formula to evaluate the stress maintenance during elongation at high temperature.

[0151] [Stress retention rate (%)] = (test force after 1 hour (N) / initial test force (N)) × 100

[0152] (Coating adaptability)

[0153] The hot melt composition was placed in a melting tank heated to 180°C and discharged from a slot nozzle heated to 180°C to coat at a coating amount of 50 g / m 2 The coating was applied to the release-treated PET film under the conditions of 100 mm coating width. The coating condition was visually observed and evaluated according to the following evaluation criteria.

[0154] A: Can be applied evenly.

[0155] B: Slight uneven coating is observed, but there is no problem in practical use.

[0156] C: Uneven coating was observed, but there was no problem in practical use.

[0157] D: Uneven coating is clearly observed, or a predetermined amount of the hot-melt composition cannot be discharged.

[0158] The results are shown in Table 1.

[0159]

[0160] Among them, the hot melt composition of Comparative Example 1 was not sufficiently cured and failed to form a film.

Claims

1. A hot melt composition, characterized in that Containing a thermoplastic resin (A) and a plasticizer (B), The thermoplastic resin (A) contains a hydrogenated styrene-based block copolymer (A1) having a styrene content of 40 to 65% by mass, The hot-melt composition has a stress maintenance rate of more than 50% after being kept in a 2-fold elongation state at a temperature of 40° C. for 1 hour.

2. The hot melt composition according to claim 1, characterized in that The content of the hydrogenated styrene-based block copolymer (A1) is 25 to 40% by mass based on 100% by mass of the hot-melt composition.

3. The hot melt composition according to claim 1 or 2, characterized in that The hydrogenated styrene-based block copolymer (A1) is a hydrogenated product of a block copolymer containing styrene units and butadiene units.

4. The hot melt composition according to claim 1 or 2, characterized in that The hydrogenated styrene-based block copolymer (A1) is a styrene-ethylene-butylene / styrene-styrene copolymer.

5. The hot melt composition according to claim 1 or 2, characterized in that: The melt viscosity at 180° C. measured using a Brookfield RVT viscometer (No. 29 rotor) is 5,000 to 35,000 mPa·s.

6. The hot melt composition according to claim 1 or 2, characterized in that: The content of the plasticizer (B) is 30 to 70% by mass based on 100% by mass of the hot melt composition.

7. The hot melt composition according to claim 1 or 2, characterized in that: The hot melt composition further contains a hydrocarbon resin (C), wherein the content of the hydrocarbon resin (C) is 1 to 45% by mass based on 100% of the hot melt composition.

8. The hot melt composition according to claim 7, characterized in that The hydrocarbon resin (C) is an aromatic hydrocarbon resin.

9. The hot melt composition according to claim 1 or 2, characterized in that: It is a hot melt composition for absorbent articles.

Images