Hot-melt composition

Abstract

To provide a hot-melt composition that exhibits superior adhesiveness and dissociability.SOLUTION: A hot-melt composition comprising a thermoplastic elastomer (A), a tackifier resin (B), and a plasticizer (C), characterized in that the hot-melt composition has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt composition. [Background technology]

[0002] BACKGROUND ART In recent years, absorbent articles including sanitary materials such as disposable diapers and sanitary napkins have come into widespread use.

[0003] Absorbent articles are made up of components such as polyolefin resin films, nonwoven fabrics, tissues, and synthetic rubber, and are assembled by adhering these components together with a hot melt composition. For this reason, hot melt compositions are required to exhibit excellent adhesive strength to the components.

[0004] For example, Patent Document 1 proposes a hot melt composition that exhibits excellent adhesive strength to components of absorbent articles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 132625 Summary of the Invention [Problem to be solved by the invention]

[0006] The hot melt composition described in Patent Document 1 is also an excellent hot melt composition, but its ease of disassembly needs further consideration. As environmentally friendly products are expected to increase, absorbent articles are required to be recyclable. Therefore, absorbent articles are required to be easily disassembled for recycling, and hot melt compositions are required to exhibit easy disassembly (dissociation) properties suitable for recycling. Regarding absorbent articles, efforts are being promoted by government agencies to separate them into high-quality pulp, SAP, nonwoven fabric, etc., and then recycle them. However, existing hot melt compositions have high adhesive strength, and disassembling absorbent articles and separating their components requires excessive energy (electricity, heat) and time for recycling. With the declining birthrate and aging population, the amount of waste from used absorbent articles is increasing, posing a problem of inability to keep up with processing.

[0007] Therefore, there is a need for the development of a hot melt composition that has excellent adhesive and releasability properties.

[0008] The present invention has been made in view of the above, and has an object to provide a hot melt composition having excellent adhesive properties and releasability. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned object can be achieved by a hot-melt composition containing a thermoplastic elastomer (A), a tackifying resin (B), and a plasticizer (C), which has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%, and have thus completed the present invention.

[0010] That is, the present invention relates to the following hot melt composition. 1. A hot melt composition containing a thermoplastic elastomer (A), a tackifying resin (B), and a plasticizer (C), The hot melt composition has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%. A hot melt composition comprising: 2. The hot melt composition according to Item 1, wherein the thermoplastic elastomer (A) comprises a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound. 3. The hot melt composition according to Item 2, wherein the block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound comprises a styrene-based block copolymer, and the styrene-based block copolymer comprises at least one selected from the group consisting of a styrene-butadiene-styrene-based block copolymer and a styrene-isoprene-styrene-based block copolymer. 4. The hot melt composition according to Item 3, wherein the styrene block copolymer comprises a styrene block copolymer (A1) having a styrene content of 35% by mass or more. 5. The hot melt composition according to Item 4, wherein the content of the styrene block copolymer (A1) is 30% by mass or less, with the hot melt composition being 100% by mass. 6. The hot melt composition according to any one of items 1 to 5, wherein the plasticizer (C) contains a fatty acid (C1). 7. The hot melt composition according to any one of items 1 to 6, which is for absorbent articles. [Effects of the Invention]

[0011] The hot melt composition of the present invention can exhibit excellent adhesive and release properties. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a test method for an underwater peel test. [Figure 2] FIG. 1 is a schematic diagram showing a test method for an underwater peel test. [Figure 3] FIG. 1 is a schematic diagram showing a test method for an underwater peel test. [Figure 4] FIG. 1 is a schematic diagram showing a test method for an underwater peel test. [Figure 5] FIG. 1 is a schematic diagram showing a method for preparing a test piece for a peel test. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described in detail below. The following description of the components may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0014] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0015] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "include," "consist essentially of," and "consist only of."

[0016] In this specification, "A and / or B" and "at least one of A and B" mean either one of A and B, or both A and B.

[0017] 1. Hot melt composition The hot melt composition of the present invention is a hot melt composition containing a thermoplastic elastomer (A), a tackifying resin (B), and a plasticizer (C), and the hot melt composition has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%. Because the hot melt composition of the present invention having the above characteristics has a loss tangent of 0.83 or less measured under the above specific conditions, it can achieve both adhesive strength at room temperature (when used in an absorbent article) and the strength (dissociability) required for dissociation during recycling (when sorting the absorbent article), thereby imparting recyclability to absorbent articles.

[0018] In recent years, biomass properties have been required for environmentally friendly products. The present inventors have investigated the use of raw materials exhibiting biomass properties in the composition of plasticizers, etc., and the use of a plasticizer containing a fatty acid as the biomass property. In the present invention, even when a plasticizer containing a fatty acid is used as the biomass property in a hot melt composition for forming an absorbent article, the above-mentioned adhesiveness and releasability can be exhibited.

[0019] The hot melt composition of the present invention will be described in detail below.

[0020] The hot melt composition of the present invention has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%. If the loss tangent measured under these conditions exceeds 0.83, the strength (dissociability) required for disintegration during recycling (when separating absorbent articles) decreases, making it impossible to achieve both the adhesive strength at room temperature (when using absorbent articles) and the strength (dissociability) required for disintegration during recycling (when separating absorbent articles). The loss tangent is preferably 0.80 or less, more preferably 0.70 or less. The lower limit of the loss tangent is not particularly limited, and may be 0.30, 0.40, or 0.50.

[0021] In this specification, the loss tangent (50° C. frequency sweep) of a hot melt composition is measured by the following method.

[0022] Loss tangent measurement (50°C frequency sweep) The hot-melt composition is heated and melted at 150°C and dripped onto the release layer side of a release-treated polyethylene terephthalate film, taking care not to trap air bubbles. Next, another release-treated polyethylene terephthalate film is laminated onto the hot-melt adhesive, with the release layer side in contact with the hot-melt adhesive. The resulting laminate is then compressed using a heat press to obtain a laminate with a substantially bubble-free structure, with the hot-melt adhesive thickness adjusted to 3 mm. The laminate is then sandwiched between polyethylene terephthalate films and allowed to stand at 23°C for 24 hours, after which a test piece 10 mm long and 10 mm wide is cut to prepare a sample for dynamic viscoelasticity measurement.

[0023] The prepared sample is mounted on a dynamic viscoelasticity measuring device (a rotational rheometer manufactured by TA Instruments, product name "DHR-10"), and dynamic viscoelasticity measurement is carried out under the following measurement conditions to obtain the loss tangent tanδ at a temperature of 50°C, the storage modulus G' (Pa) at a temperature of 50°C, and the loss modulus G'' (Pa) at a temperature of 50°C. The value at 5 Hz is read and used as the measurement data.

[0024] <Measurement conditions for dynamic viscoelasticity measurement at 50°C> Frequency range: 0.1Hz~30.00Hz ·Measurement temperature: 50℃ Distortion: 0.05% Bottom plate: 25mm diameter parallel plate Top plate: 8mm diameter crosshatch plate

[0025] Each component constituting the hot melt composition of the present invention will be described below.

[0026] (Thermoplastic elastomer (A)) The present invention contains a thermoplastic elastomer (A) (hereinafter also referred to as "component (A)") as an essential component. The thermoplastic elastomer (A) is not particularly limited, and examples thereof include styrene-based block copolymers, olefin-based block copolymers, polyurethane-based block copolymers, and polyester-based block copolymers. Among these, styrene-based block copolymers are preferred from the viewpoint of further improving the peel strength of the hot melt adhesive.

[0027] The styrene-based block copolymer is a block copolymer obtained by block copolymerizing a vinyl-based aromatic hydrocarbon and a conjugated diene compound. That is, the thermoplastic elastomer (A) preferably contains a block copolymer of a vinyl-based aromatic hydrocarbon and a conjugated diene compound.

[0028] Vinyl aromatic hydrocarbons are aromatic hydrocarbon compounds having a vinyl group.Specific examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc., and among these, styrene is preferred.The vinyl aromatic hydrocarbons can be used alone or in combination of two or more.

[0029] 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 (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 (isoprene) are preferred. The conjugated diene compounds can be used alone or in combination of two or more.

[0030] The styrene-based block copolymer is preferably an unhydrogenated styrene-based block copolymer, since it can exhibit better peel strength and superior adhesiveness. Examples of the unhydrogenated styrene-based block copolymer include styrene-butadiene block copolymer (SB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene-styrene-butadiene block copolymer (SBSB). These styrene-based block copolymers can be used alone or in combination of two or more. Among these styrene-based block copolymers, styrene-butadiene-styrene block copolymer (SBS) and styrene-isoprene-styrene block copolymer (SIS) are preferred, since they can exhibit even better peel strength, and styrene-butadiene-styrene block copolymer (SBS) is more preferred.

[0031] In the hot melt composition of the present invention, the styrene block copolymer preferably contains a styrene block copolymer (A1) (hereinafter also referred to as "component (A1)") having a styrene content of 35% by mass or more. When the styrene block copolymer contains component (A1), the dissociation properties of the hot melt composition of the present invention are further improved. The styrene content of component (A1) is preferably 37% by mass or more, more preferably 38% by mass or more, and even more preferably 40% by mass or more. The upper limit of the styrene content of component (A1) is not particularly limited, and may be 60% by mass, 55% by mass, 50% by mass, or 45% by mass. When the upper limit of the styrene content of (A1) is within the above range, the adhesiveness of the hot melt composition of the present invention is further improved.

[0032] The content of the styrene block copolymer (A1) in 100% by mass of the hot melt composition of the present invention is preferably 10 to 35% by mass, more preferably 12 to 30% by mass, even more preferably 15 to 25% by mass, and even more preferably 18 to 25% by mass, in order to achieve even better adhesiveness.

[0033] The content of the thermoplastic block copolymer (A) in 100% by mass of the hot melt composition of the present invention is preferably 10 to 35% by mass, more preferably 12 to 30% by mass, even more preferably 15 to 25% by mass, and even more preferably 18 to 25% by mass, in order to achieve even better adhesiveness.

[0034] Tackifying resin (B) The hot melt composition of the present invention contains a tackifier resin (B) as an essential component. The tackifier resin (B) is not particularly limited as long as it enables the hot melt composition of the present invention to exhibit excellent adhesiveness and releasability.

[0035] Examples of the tackifying resin (B) include petroleum resin-based tackifying resins and / or hydrogenated products of the petroleum resin-based tackifying resins, terpene-based tackifying resins, and rosin-based tackifying resins.

[0036] Examples of the petroleum resin-based tackifying resin include petroleum resins such as C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, and dicyclopentadiene petroleum resins. Hydrogenated versions of the petroleum resin-based tackifying resins include partially hydrogenated petroleum resins and fully hydrogenated petroleum resins obtained by adding hydrogen to these petroleum resins. C5 petroleum resins are petroleum resins made from the C5 fraction of petroleum, C9 petroleum resins are petroleum resins made from the C9 fraction of petroleum, and C5C9 petroleum resins are petroleum resins made from both the C5 and C9 fractions of petroleum. Examples of C5 fractions include cyclopentadiene, isoprene, and pentane. Examples of C9 fractions include styrene, vinyltoluene, and indene.

[0037] Examples of the terpene-based tackifying resin include terpene resins (monoterpenes, diterpenes, triterpenes, polyterpenes, etc.), terpene phenol resins, aromatic modified terpene resins, etc. These terpene-based tackifying resins can be used alone or in combination of two or more.

[0038] A wide variety of commercially available terpene tackifying resins can be used, including, for example, "YS Resin TO-105" (acid value: 0 mg KOH / g) manufactured by Yasuhara Chemical Co., Ltd. and "SYLVARES TRM1115" (acid value: 0 mg KOH / g) manufactured by Kraton Corporation.

[0039] As the rosin-based tackifying resin, it is preferable to use at least one of natural rosin and an esterified product of the natural rosin (rosin ester resin), and it is more preferable to use a rosin ester resin, in order to achieve better adhesion (tack).

[0040] Examples of the natural rosin include tall rosin, gum rosin, wood rosin, etc. These natural rosins can be used alone or in combination of two or more.

[0041] Examples of the rosin ester resin include rosin glycerin ester, rosin pentaerythritol ester, rosin methyl ester, rosin ethyl ester, rosin butyl ester, rosin ethylene glycol ester, etc. These rosin ester resins can be used alone or in combination of two or more.

[0042] A wide variety of commercially available rosin-based tackifying resins can be used. Examples of commercially available products include "Super Ester A100" (acid value: 5 mg KOH / g), "Pine Crystal KE-100" (acid value: 6 mg KOH / g), manufactured by Arakawa Chemical Industries, Ltd., "SYLVALITE 9100" (acid value: 7 mg KOH / g), manufactured by Kraton, and "Super Ester A75" (acid value: 5 mg KOH / g), manufactured by Arakawa Chemical Industries, Ltd. These commercially available products can be used alone or in combination of two or more.

[0043] In the present invention, the acid value of the tackifier resin (B) is preferably 15 mgKOH / g or less, more preferably 12 mgKOH / g or less, even more preferably 10 mgKOH / g or less, and particularly preferably 8 mgKOH / g or less. When the upper limit of the acid value is within the above range, oxidation of the tackifier resin is further suppressed, and the heat stability of the hot melt composition is further improved. Furthermore, the lower limit of the acid value of the tackifier resin (B) is not particularly limited and may be 0 mgKOH / g.

[0044] In this specification, the acid value refers to the number of milligrams of potassium hydroxide (KOH) required to neutralize 1 g of a sample. In this specification, the acid value refers to a value measured in accordance with JIS K 0070.

[0045] The ring and ball softening point of the tackifier resin (B) is preferably 90° C. or higher, more preferably 100° C. or higher. The upper limit of the ring and ball softening point is preferably 140° C. When the tackifier resin (B) has a ring and ball softening point of 90° C. or higher, the hot melt composition of the present invention is more likely to exhibit good peel strength.

[0046] In this specification, the ring and ball softening point of the tackifier resin (B) means the temperature measured in accordance with JIS K 6863.

[0047] The content of the tackifier resin (B) in 100% by mass of the hot melt composition of the present invention is preferably 30 to 80% by mass, more preferably 35 to 75% by mass, even more preferably 40 to 70% by mass, and particularly preferably 45 to 67% by mass, in order to further improve peel strength.

[0048] Plasticizer (C) The hot melt composition of the present invention contains a plasticizer (C) (hereinafter also referred to as "component (C)"). In the present invention, the plasticizer (C) preferably contains a fatty acid (C1) (hereinafter also referred to as "component (C1)").

[0049] The fatty acid (C1) is not particularly limited as long as it is an aliphatic carboxylic acid having at least one carboxy group, and may have a hydroxy group. The fatty acid (C1) may be either a saturated fatty acid, which is an acid having no double bond or triple bond in the carbon chain, or an unsaturated fatty acid, which is an acid having a double bond or triple bond in the carbon chain, or a fatty acid derivative obtained by fatty acid substitution or other chemical reaction.

[0050] The saturated fatty acid is not particularly limited as long as it does not adversely affect the hot melt composition of the present invention, and may be either linear or cyclic. The saturated fatty acid is preferably linear. The linear saturated fatty acid may be linear or branched, with linear saturated fatty acids being preferred. Specific examples of saturated fatty acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, tricosylic acid, and 12-hydroxystearic acid.

[0051] The saturated fatty acid preferably has 1 to 30 carbon atoms, more preferably 3 to 26 carbon atoms, further preferably 8 to 24 carbon atoms, and particularly preferably 12 to 22 carbon atoms.

[0052] The unsaturated fatty acid is not particularly limited as long as it does not adversely affect the hot melt adhesive of the present invention, and examples thereof include crotonic acid, oleic acid, linolenic acid, docosahexaenoic acid, linoleic acid, and ricinoleic acid.

[0053] The unsaturated fatty acid preferably has 3 to 26 carbon atoms, more preferably 4 to 22 carbon atoms, and even more preferably 14 to 22 carbon atoms.

[0054] The unsaturated fatty acid preferably has 1 to 6 unsaturated bonds between carbon atoms, more preferably 1 to 3, and even more preferably 1 or 2.

[0055] Examples of fatty acid derivatives include fats and oils, hardened oils, fatty acid amides, fatty acid alkyl esters, monoglycerides, diglycerides, sorbitan fatty acid esters, diglycerin fatty acid esters, etc., with fats and oils and hardened oils being preferred.

[0056] The content of component (C1) in the hot melt composition is preferably 5 to 50 mass%, more preferably 8 to 40 mass%, even more preferably 10 to 30 mass%, and particularly preferably 12 to 20 mass%, based on 100 mass% of the hot melt composition. By setting the lower limit of the content of component (C1) within the above range, the adhesiveness and releasability of the hot melt composition are further improved. By setting the upper limit of the content of component (C1) within the above range, the wet strength is further improved.

[0057] The hot melt composition of the present invention may contain a plasticizer (C) other than the above component (C1).

[0058] Examples of the plasticizer (C) other than the component (C1) include naphthenic process oil and paraffinic process oil, with naphthenic process oil being preferred from the viewpoint of further improving heat stability and peel strength. These plasticizers can be used alone or in combination of two or more.

[0059] As the plasticizer (C) other than the component (C1), a wide range of known commercially available products can be used.

[0060] Examples of commercially available naphthenic process oils include "KN4010" manufactured by PetroChina, "Diana Fresia N28" manufactured by Idemitsu Kosan, "Diana Fresia U46" manufactured by Idemitsu Kosan, and "Nyflex 222B" manufactured by Nynas.

[0061] Commercially available paraffinic process oils include, for example, "Diana Process Oil PW32," "Diana Process Oil PW90," "Diana Process Oil PS32," and "Diana Process Oil PS90," manufactured by Idemitsu Kosan Co., Ltd.; and "Kaydol," manufactured by Witco Corporation.

[0062] When the hot melt composition of the present invention contains a plasticizer (C) other than component (C1), the upper limit of the content of the plasticizer (C) other than component (C1) in 100% by mass of the hot melt composition is preferably 20% by mass, more preferably 15% by mass, even more preferably 10% by mass, and particularly preferably 5% by mass. When the hot melt composition of the present invention contains a plasticizer (C) other than component (C1), the lower limit of the content of the plasticizer (C) other than component (C1) in 100% by mass of the hot melt composition is not particularly limited and may be 0%, 1%, or 2% by mass.

[0063] Antioxidant (D) The hot melt composition of the present invention may contain an antioxidant (D).

[0064] A wide variety of known antioxidants can be used as the antioxidant (D), including, for example, 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 Examples of antioxidants include phenolic antioxidants such as 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; sulfur-based antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate, and pentaerythritol tetrakis(3-laurylthiopropionate); and phosphorus-based antioxidants such as tris(nonylphenyl)phosphite and tris(2,4-di-t-butylphenyl)phosphite. These antioxidants can be used alone or in combination of two or more. Among these antioxidants, phenolic antioxidants are preferred because they further improve heat stability.

[0065] A wide variety of known commercially available products can be used as the antioxidant (D). Examples of commercially available phenolic antioxidants include "Rianox 1010FF" manufactured by Rianlon and "Evernox 10" manufactured by Everspring Chemical.

[0066] When the hot melt composition of the present invention contains an antioxidant (D), the upper limit of the content of the antioxidant (D) in 100% by mass of the hot melt composition is preferably 5% by mass, more preferably 4% by mass, and even more preferably 3% by mass. When the hot melt composition of the present invention contains an antioxidant (D), the lower limit of the content of the antioxidant (D) in 100% by mass of the hot melt composition is preferably 0.1% by mass, and more preferably 0.5% by mass.

[0067] Various additives The hot melt composition of the present invention may contain various additives as needed, such as ultraviolet absorbers, liquid rubbers, and fine particle fillers, as long as the additives do not substantially impair the object of the present invention.

[0068] As the ultraviolet absorber, a wide variety of known ultraviolet absorbers can be used, including, for example, 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. These ultraviolet absorbers can be used alone or in combination of two or more.

[0069] As the liquid rubber, a wide variety of known liquid rubbers can be used, including, for example, liquid polybutene, liquid polybutadiene, liquid polyisoprene, and hydrogenated resins thereof. These liquid rubbers can be used alone or in combination of two or more.

[0070] As the particulate filler, a wide variety of known particulate fillers can be used, including, for example, calcium carbonate, kaolin, talc, titanium oxide, mica, styrene beads, etc. These particulate fillers can be used alone or in combination of two or more.

[0071] When the present invention contains the above-mentioned various additives, the content of the above-mentioned various additives in 100% by mass of the hot melt composition is preferably 5% by mass or less.

[0072] 2. Method for producing hot melt composition The method for producing the hot melt composition is not particularly limited, and examples thereof include a method in which the thermoplastic elastomer (A), the tackifying resin (B), the plasticizer (C), the antioxidant (D) added as needed, and the various additives are charged into a stirring kneader equipped with a heating device and kneaded while heating.

[0073] The heating temperature during kneading is not particularly limited, and is preferably 100 to 200° C., more preferably 120 to 180° C. The kneading time is not particularly limited, and is preferably 40 to 140 minutes, more preferably 60 to 120 minutes.

[0074] 3. Coating method and uses of hot melt composition

[0075] As a coating method for applying the hot melt composition of the present invention, a wide variety of known coating methods can be used, including, for example, spiral spray coating, slot coater coating, curtain spray coating, roll coater coating, omega coating, dot coating, and bead coating.

[0076] A wide variety of known coating devices can be used as the coating device for applying the hot melt composition of the present invention to the adhesive portion, including, for example, a hot melt applicator such as "REKA Hand Gun TR80LCD (Spray)" manufactured by Suntool Co., Ltd.

[0077] The hot melt composition of the present invention is heated and melted, applied to the bonding portion of an adherend, brought into contact with another adherend while still in the molten state, and then cooled and solidified to bond the adherends. Adherends that can be bonded with the hot melt composition of the present invention include air-through nonwoven fabrics, spunbond nonwoven fabrics, point-bond nonwoven fabrics, tissues, elastic members, polyolefin resin films, and the like. The hot melt composition of the present invention is preferably a hot melt composition for spunbond nonwoven fabrics, a hot melt composition for point-bond nonwoven fabrics, or a hot melt composition for air-through nonwoven fabrics. Of these, a hot melt composition for air-through nonwoven fabrics is more preferred.

[0078] The type of fiber used in the air-through nonwoven fabric is not limited. For example, polyethylene, polypropylene, polyester, etc. can be used as the fiber. Furthermore, the fabric is not limited to a single fiber type, and may be made of two or more types of fibers. Furthermore, the fabric is not limited to fibers made of a single composition, and core-sheath fibers containing two or more types of compositions can also be used.

[0079] The air-through nonwoven fabric may be commercially available, such as "S-Soft" manufactured by JNC Corporation and "NBF" manufactured by Daiwabo Co., Ltd.

[0080] The hot melt composition of the present invention can exhibit excellent adhesive properties to air-through nonwoven fabrics, and is therefore suitable for use in bonding adherends together in the manufacture of absorbent articles. That is, the hot melt composition of the present invention is preferably used for absorbent articles.

[0081] Absorbent articles are intended to absorb bodily fluids such as blood, urine, sweat, pus, gastric juice, saliva, and nasal mucus. Examples of absorbent articles include disposable diapers, sanitary napkins, panty liners, incontinence pads, portable toilets, portable waste disposal bags, animal waste disposal sheets, hospital gowns, surgical gowns, wound dressings, first-aid adhesive bandages, and materials for preserving the freshness of meat, fish, etc. Among these, the hot melt composition of the present invention is suitably used for disposable diapers, sanitary napkins, panty liners, incontinence pads, etc.

[0082] Disposable diapers are basically composed of a liquid-impermeable backsheet made of a polyolefin resin film or the like, a liquid-permeable topsheet made of a nonwoven fabric or the like, and an absorbent body placed between them. To prevent the absorbent body from becoming sticky after absorbing urine or the like, the absorbent body is used with its surface covered with absorbent paper such as tissue. In addition, absorbent articles employ a structure in which elastic members such as rubber are attached in a stretchable manner to fit around the wearer's legs and waist and prevent leakage of excrement.

[0083] The method for bonding and integrating adherends together using the hot melt composition of the present invention is not particularly limited, and any known method can be used. For example, a method can be used in which the hot melt composition of the present invention that has been heated and melted is applied to one adherend, and then the other adherend is placed on the applied hot melt composition, and then they are pressure-bonded. [Example]

[0084] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0085] The raw materials used in the examples and comparative examples are as follows.

[0086] <Thermoplastic block copolymer (A)> (A1) Styrene-butadiene-styrene block copolymer (SBS): LCY GRIT product name "Globalprene 3545", styrene content 45% by mass Styrene-butadiene-styrene block copolymer (SIS): LCY GRIT, product name "Globalprene 5562U", styrene content 45% by mass Styrene-butadiene-styrene block copolymer (SBS): LCY GRIT product name "Globalprene 3542", styrene content 40% by mass Styrene-butadiene-styrene block copolymer (SBS): Product name "Kibton PB-5502" manufactured by CHIMEI Co., Ltd., styrene content 36.5% by mass Styrene-butadiene-styrene block copolymer (SBS): Asahi Kasei Corporation, product name "Asaprene T-438", styrene content 35% by mass

[0087] (Other than A1) Styrene-butadiene-styrene block copolymer (SBS): LCY GRIT product name "Globalprene 3501", styrene content 31% by mass

[0088] <(B) Tackifying resin> Partially hydrogenated tackifying resin: ENEOS Corporation, product name "HB-103" (acid value: 0 mgKOH / g) Fully hydrogenated tackifying resin: Idemitsu Kosan Co., Ltd. product name "ImarvP100" (acid value: 0 mgKOH / g) Rosin-based tackifying resin: Kraton Sylvalite 9100 (acid value: 7 mg KOH / g)

[0089] <(C) Plasticizer> (C1) Fatty acid Sunflower seed oil: Nisshin Oillio Group, product name: "Hi-Ole Himawari (S)" Refined palm oil: Nisshin Oillio Group Co., Ltd. Product name: "Refined palm oil" Palm olein oil: Nisshin Oillio Group, product name "Delica Ace HOL(S)" Rapeseed oil: Nisshin Oillio Group Co., Ltd. Product name: "Rapeseed oil" Linseed oil: Nisshin Oillio Group, product name "N / B Linseed Oil"

[0090] (other than C1) Naphthenic oil: PetroChina product name "KN-4010" Naphthenic oil: Idemitsu Kosan Co., Ltd. Product name "N-90" Non-phthalate oil: BASF product name "Dinch"

[0091] <(D) Antioxidants> Phenolic antioxidant: Rianlon, product name "Rianox 1010FF"

[0092] Examples and Comparative Examples The above-mentioned raw materials were charged into a stirring kneader equipped with a heating device in the amounts shown in Tables 1 to 3, and then kneaded while heating at 145°C for 90 minutes, and then cooled until solid to produce hot melt compositions. Note that the numerical values ​​for each raw material in Tables 1 to 3 all mean "% by mass."

[0093] The loss tangent of each of the hot melt compositions obtained in the Examples and Comparative Examples was measured under the following measurement conditions, and the properties were evaluated.

[0094] Loss tangent measurement (50°C frequency sweep) The hot-melt composition was heated and melted at 150°C and dripped onto the release layer side of a release-treated polyethylene terephthalate film, taking care not to trap air bubbles. Next, another release-treated polyethylene terephthalate film was laminated onto the hot-melt adhesive, with the release layer side in contact with the hot-melt adhesive. The resulting laminate was then compressed using a heat press to obtain a laminate with a substantially bubble-free structure, with the hot-melt adhesive thickness adjusted to 3 mm. The laminate was then sandwiched between polyethylene terephthalate films and allowed to stand at 23°C for 24 hours. After this, test pieces measuring 10 mm in length and 10 mm in width were cut to prepare samples for dynamic viscoelasticity measurement.

[0095] The prepared sample was attached to a dynamic viscoelasticity measuring device (a rotational rheometer manufactured by TA Instruments, product name "DHR-10"), and dynamic viscoelasticity measurements were performed under the following measurement conditions to obtain the loss tangent tanδ at a temperature of 50°C, the storage modulus G' (Pa) at a temperature of 50°C, and the loss modulus G'' (Pa) at a temperature of 50°C. The values ​​read at 5 Hz were used as the measurement data.

[0096] <Measurement conditions for dynamic viscoelasticity measurement at 50°C> Frequency range: 0.1Hz~30.00Hz ·Measurement temperature: 50℃ Distortion: 0.05% Bottom plate: 25mm diameter parallel plate Top plate: 8mm diameter crosshatch plate

[0097] Underwater peel test (Preparation of test specimens) (1) The hot melt composition was heated to 160°C to melt it, and then coated onto a 50 μm-thick release-treated polyethylene terephthalate film by slot coating at a thickness of 45 μm and a coating width of 60 mm. A 60 μm-thick release paper was then laminated to produce a laminate. A point-bonded nonwoven fabric (basis weight: 18 g / m) was then applied. 2) was cut to a size of 35 mm in the machine direction and 25 mm in the width direction, and the release paper side of the hot melt composition laminate was peeled off and pasted together at a position 10 mm from the edge, and a 2 kg roller was rolled back and forth at a speed of 5 mm / sec to prepare Laminate 1 (Figure 1).

[0098] (2) Peel off the release-treated polyethylene terephthalate film from the laminate and apply an air-through nonwoven fabric (basis weight: 21 g / m 2 A piece of nonwoven fabric cut to 20 mm in the machine direction and 25 mm in the width direction was attached to the point-bonded nonwoven fabric 5 mm from the edge (Figure 2).

[0099] (3) Next, a 2 kg roller was run back and forth at a speed of 5 mm / sec to prepare Laminate 2. Next, Laminate 2 was fixed to a 2 mm thick PP fixing material (25 mm wide x 130 mm long) at the front and rear edges in the flow direction of the point bond to prevent sagging of the laminate, and a test specimen was prepared. The test specimen was fixed so that the edge of the PP fixing material and the edge of the hot melt composition of Laminate 2 were aligned (Figure 3).

[0100] (Underwater peeling test) (4) 500 ml of tap water was placed in a 500 ml beaker and heated to 50°C using a hot plate stirrer (RSH-4DN, manufactured by ASONE) with an octagonal rotor (size: Φ8 mm x 38 mm) while stirring at 1000 rpm. The rotor was positioned so that it was in the center of the stirrer and beaker. Stirring was performed for a maximum of 8 minutes, and samples that did not peel within 8 minutes were deemed unsuitable for underwater peeling. The test was performed three times, and the average time was taken as the peel time. Evaluation was performed according to the following evaluation criteria (Figure 4). Note that, according to the evaluation criteria below, a rating of ⊚, meaning peeling within 2 to 8 minutes, indicates that the absorbent article has both adhesiveness during use and releasability during recycling, making it optimal. ◎◎: Peeled off within 2 to 8 minutes ◎: Peeled off in 50 seconds or more but less than 2 minutes ○: Peeled off in less than 50 seconds ×: Not peeled within 8 minutes

[0101] Peel test (Preparation of test specimens) The hot-melt composition was heated to 160°C to melt it. The hot-melt composition was then applied to a 25 μm-thick polyethylene terephthalate film by slot coating to a thickness of 45 μm and a coating width of 25 mm, and a 25 μm-thick polyethylene terephthalate film was then laminated to produce a laminate. This resulted in a sample piece of the hot-melt composition measuring 25 mm in the slot coating flow direction and 50 mm in the width direction. A 25 mm width from the edge of the surface not coated with the hot-melt composition was secured with tape to serve as a chuck for the measuring device. The resulting test piece was then left to cool and solidify in an atmosphere of 23°C and 50% relative humidity for 24 hours, preparing a test piece (Figure 5).

[0102] (peel test) The prepared test pieces were subjected to a T-peel test using a tensile testing machine (Shimadzu Corporation, product name "AGS-X") at a tension speed of 100 mm / min in the plane direction of the polyethylene film in an atmosphere of 23°C. The T-peel test was performed using the maximum convex average test force (average test force at the seven maximum convex points in a measurement area of ​​25 mm length x 25 mm width) as the initial peel strength (N / 25 mm).

[0103] The results are shown in Tables 1 to 3.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

Claims

1. A hot melt composition comprising a thermoplastic elastomer (A), a tackifier resin (B), and a plasticizer (C), The hot melt composition has a loss tangent of 0.83 or less at a temperature of 50°C, a frequency of 5.0 Hz, and a strain of 0.05%. A hot melt composition comprising:

2. The hot melt composition according to claim 1 , wherein the thermoplastic elastomer (A) comprises a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound.

3. 3. The hot melt composition according to claim 2, wherein the block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound comprises a styrene-based block copolymer, and the styrene-based block copolymer comprises at least one selected from the group consisting of a styrene-butadiene-styrene-based block copolymer and a styrene-isoprene-styrene-based block copolymer.

4. The hot melt composition according to claim 3 , wherein the styrene-based block copolymer comprises a styrene-based block copolymer (A1) having a styrene content of 35% by mass or more.

5. The hot melt composition according to claim 4, wherein the content of the styrene-based block copolymer (A1) is 30% by mass or less, based on 100% by mass of the hot melt composition.

6. The hot melt composition of claim 1 , wherein the plasticizer (C) comprises a fatty acid (C1).

7. 10. The hot melt composition of claim 1 for use in absorbent articles.

Images