Moisture-curing one-component adhesive composition

Abstract

Provided is a moisture-curable one-component adhesive composition having a balance of both water absorption and adhesive strength. One embodiment of the present invention is a moisture-curable one-component adhesive composition. The moisture-curable one-component adhesive composition includes: a polyurethane prepolymer (A) obtained by reacting a crystalline polyol (Aa) and an amorphous polyol (Ab) with a polyisocyanate (B); and a hydrophilicity imparting agent (C).

Description

[Technical Field]

[0001] The present invention relates to a moisture-curing, one-component adhesive composition. [Background technology]

[0002] Hot melt adhesives are used to bond base materials in sanitary materials such as disposable diapers and sanitary napkins. Hot melt adhesives are commonly based on styrene elastomers or olefin resins and are also used in absorbent parts such as gathers. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2000-514108 [Patent Document 2] Japanese Patent Application Publication No. 6-316689 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventional hot-melt adhesives have poor hydrophilicity in their base polymer. This can hinder water absorption at the adhesive interface between components. When used in applications requiring rapid liquid penetration, particularly in hygiene products such as diapers and incontinence pads, water absorption performance may be compromised. Furthermore, while conventional hot-melt adhesives can achieve a certain level of adhesive strength in the aforementioned applications, they suffer from insufficient water absorption. In view of the above-mentioned problems, the present invention aims to provide a moisture-curing, one-component adhesive composition that has a good balance of water absorption and adhesive strength. [Means for solving the problem]

[0005] One aspect of the present invention is a moisture-curing one-component adhesive composition. This moisture-curing one-component adhesive composition comprises a polyurethane prepolymer (A) obtained by reacting a crystalline polyol (Aa) and an amorphous polyol (Ab) with a polyisocyanate (B), and a hydrophilicity imparting agent (C). In the moisture-curing one-component adhesive composition of the above embodiment, the contact angle obtained under the following contact angle evaluation conditions may be 60° or less. (Contact angle evaluation conditions) The moisture-curing one-component adhesive composition is applied to a slide, left for 24 hours, and the contact angle between the cured resin and water is measured in accordance with JIS K6798:1999. Furthermore, the amorphous polyol (Ab) may also include an amorphous polyol (Ab1) having structural units derived from an aliphatic dicarboxylic acid and / or an amorphous polyol (Ab2) having structural units derived from an aromatic dicarboxylic acid. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a technology relating to a moisture-curing one-component adhesive composition that has a good balance of water absorption and adhesive strength. [Modes for carrying out the invention]

[0007] Embodiments of the present invention will be described in detail below. In this specification, unless otherwise specified, the notation "a~b" in the description of numerical ranges means a or greater and b or less.

[0008] The moisture-curing one-component adhesive composition and its manufacturing method according to the embodiment will be described in detail below according to the following items. 1. Moisture-curing one-component adhesive composition 1-1. Raw materials 1-1-1. Polyurethane prepolymer 1-1-1-1. Polyols 1-1-1-2. Polyisocyanates 1-1-2. Additives 1-1-2-1. Hydrophilicity-enhancing agent 1-1-2-2. Others 2. Method for producing moisture-curable one-component adhesive composition 3. Use of moisture-curable one-component adhesive composition

[0009] 1. Moisture-curable one-component adhesive composition The moisture-curable one-component adhesive composition according to this embodiment contains an isocyanate-terminated polyurethane prepolymer as a base resin. Further, other components may be contained in the adhesive composition as necessary. When such a moisture-curable one-component adhesive composition is used, adhesiveness is exhibited due to the cooling and solidification of the molten polyurethane prepolymer, and further, the unreacted isocyanate terminals react with moisture in the air to form a three-dimensional crosslinked structure, thereby exhibiting stronger adhesiveness.

[0010] 1-1. Raw materials 1-1-1. Polyurethane prepolymer A polyurethane prepolymer can be obtained by reacting a polyisocyanate in a stoichiometric excess amount with a polyol.

[0011] The content of the polyurethane prepolymer is preferably 50 to 95% by mass, more preferably 75 to 90% by mass with respect to the entire composition.

[0012] 1-1-1-1. Polyol The polyol used in this embodiment includes a crystalline polyol (Aa) and an amorphous polyol (Ab).

[0013] Examples of the crystalline polyol (Aa) include crystalline polyester polyol, crystalline polycarbonate polyol, crystalline polyether polyol, etc. The crystalline polyol (Aa) may be used alone or in combination of two or more. In addition, when both a melting peak resulting from the melting of the crystal structure of the polyol and a crystallization peak due to the reorientation (crystallization) of the molecular chains in the cooling process are confirmed in the heating process using a differential scanning calorimeter (DSC), the polyol is determined to have crystallinity. On the other hand, if at least one of the melting peak and the crystallization peak is not confirmed in the above heating process, the polyol is determined to be amorphous.

[0014] Examples of the crystalline polyester polyol include those obtained by the dehydration condensation reaction of an aliphatic dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, dodecanedioic acid, and azelaic acid, an aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, an alicyclic dicarboxylic acid such as hexahydrophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid, or an acid ester or acid anhydride thereof, and ethylene glycol, 1,3 - butanediol, 1,4 - butanediol, 1,5 - pentanediol, 1,6 - hexanediol, etc., or a mixture thereof.

[0015] Examples of the crystalline polycarbonate polyol include those obtained by reacting at least one polyhydric alcohol having 3 to 9 carbon atoms such as 1,2 - propylene glycol, 1,3 - propylene glycol, 1,3 - butanediol, 1,4 - butanediol, 1,5 - pentanediol, 1,6 - hexanediol, 3 - methyl - 1,5 - pentanediol, neopentyl glycol, 1,8 - octanediol, 1,9 - nonanediol, and diethylene glycol with diethylene carbonate, dimethyl carbonate, diethyl carbonate, etc.

[0016] Examples of the amorphous polyol (Ab) include amorphous polyester polyol, amorphous polycarbonate polyol, amorphous polyether polyol, etc. Examples of amorphous polyester polyols include aliphatic dicarboxylic acids, such as succinic acid, adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids, such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids, such as hexahydrophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; or polyester polyols obtained by dehydration condensation reactions of these acid esters or acid anhydrides with diethylene glycol, methylpropanediol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, thiodiethanol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc., or mixtures thereof.

[0017] Examples of amorphous polycarbonate polyols include those obtained by reacting at least one polyhydric alcohol, such as ethylene glycol, with diethylene carbonate, dimethyl carbonate, diethyl carbonate, and the like.

[0018] Examples of amorphous polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and their copolymers, which are obtained by polymerizing cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran, respectively. They can also be obtained by polymerizing the above-mentioned cyclic ethers using polyhydric alcohols such as glycerin and trimethylolethane.

[0019] The amorphous polyol (Ab) preferably contains either an amorphous polyol (Ab1) having structural units derived from an aliphatic dicarboxylic acid or an amorphous polyol (Ab2) having structural units derived from an aromatic dicarboxylic acid, and more preferably contains both amorphous polyol (Ab1) and amorphous polyol (Ab2). By using amorphous polyol (Ab1) and amorphous polyol (Ab2) as the amorphous polyol (Ab), a better balance between water absorption and adhesive strength can be achieved. Examples of amorphous polyols (Ab1) having structural units derived from aliphatic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, and azelaic acid, or polyester polyols obtained by dehydration condensation reactions of these acid esters or acid anhydrides with diethylene glycol, methylpropanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, or mixtures thereof. Examples of amorphous polyols (Ab2) having structural units derived from aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, or polyester polyols obtained by dehydration condensation reactions of these acid esters or acid anhydrides with diethylene glycol, methylpropanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, or mixtures thereof.

[0020] The mass ratio of crystalline polyol (Aa) to amorphous polyol (Ab) (mass of crystalline polyol (Aa) / mass of amorphous polyol (Ab)) is preferably 0.2 to 0.9, more preferably 0.25 to 0.85, and even more preferably 0.3 to 0.8. By setting the mass ratio of crystalline polyol (Aa) to amorphous polyol (Ab) within the above range, a good balance between water absorption and adhesive strength can be achieved.

[0021] The number-average molecular weight of the crystalline polyol (Aa) and amorphous polyol (Ab) is preferably 300 to 10,000, more preferably 500 to 5,000, and even more preferably 1,000 to 3,000, in order to achieve a good balance between water absorption and adhesive strength. The number-average molecular weight of the crystalline polyol (Aa) and amorphous polyol (Ab) can be measured by gel per-emission chromatography and converted to the molecular weight of polystyrene, which is a standard sample.

[0022] 1-1-1-2. Polyisocyanates For example, as bifunctional polyisocyanates, there are 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethanedianate (2,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), hydrogenated MDI, xylylene diisocyanate, and 3,3'-dimethyl Aromatic compounds such as 4,4'-biphenylenediisocyanate, 3,3'-dimethoxy-4,4'-biphenylenediisocyanate, polymethylene polyphenyl polyisocyanate, 1,5-naphthalenediisocyanate, xylylenediisocyanate (XDI), hydrogenated XDI, tetramethylxylenediisocyanate (TMXDI), cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and methylcyclohexanediisocyanate. Alicyclic polyisocyanates such as socianates, alkylene polyisocyanates such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, and lysine diisocyanate, and polyisocyanates with three or more functions include 1-methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzol-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, and diphenylmethane-2,4,4'-triisocyanate. Examples include triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, triphenylmethane-4,4',4"-triisocyanate, polymeric MDI, lysine ester triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, bicycloheptane triisocyanate, 1,8-diisocyanatomethyloctane, and modified versions and derivatives thereof.

[0023] 1-1-2. Additives 1-1-2-1. Hydrophilicity-enhancing agent The hydrophilicity imparting agent is not particularly limited as long as it is a component that imparts hydrophilicity to a polyurethane prepolymer or a moisture-curing one-component adhesive composition. For example, it is a compound having one or more hydrophilic groups in one molecule, and examples of hydrophilic groups include hydroxyl groups, carboxyl groups, amino groups, sulfone groups, and polyoxyethylene groups.

[0024] It is believed that the hydrophilicity imparting agent, during the solidification and reaction process of the moisture-curing one-component adhesive composition, exhibits incompatibility with the polyurethane portion that forms the backbone of the moisture-curing hot-melt adhesive, orients itself to the surface, thereby imparting hydrophilicity to the solidified and reacted adhesive. Of these hydrophilicity imparters, hydrophilicity imparters that are nonionic compounds (nonionic surfactants) that do not contain hydroxyl groups, carboxyl groups, sulfonyl groups, amino groups, epoxy groups, or acid anhydrides of carboxyl groups or sulfonyl groups are preferred, hydrophilicity imparters having polyoxyethylene groups are more preferred, and hydrophilicity imparters selected from the group of polyoxyethylene fatty acid esters, fatty acid ester alkoxylates, and polyethylene glycol dialkyl ethers are even more preferred. Most preferred are hydrophilicity imparters represented by any of the following formulas (1) to (4), in which R1, R2, R3, R4, and R5 are alkyl chains having 8 or more carbon atoms, R6, R7, and R8 are alkyl chains having 20 or fewer carbon atoms, and R9 is an alkyl chain having 20 or fewer carbon atoms, and R1 to R9 do not contain hydroxyl groups, active hydrogen groups such as amino acids, or functional groups (carboxylic acids, acid anhydrides, epoxy groups) that can react with isocyanate groups. [ka]

[0025] 1-1-2-2. Others Polyurethane prepolymers or moisture-curing one-component adhesive compositions may contain various additives in addition to the components described above, as necessary, as long as they do not impair the objectives of the present invention. Examples of additives include fillers, plasticizers, pigments, dyes, antioxidants, antioxidants, antistatic agents, flame retardants, tackifiers, antibacterial agents, light stabilizers, stabilizers, dispersants, solvents, and the like.

[0026] In the moisture-curing one-component adhesive composition of this embodiment, the contact angle obtained under the following contact angle evaluation conditions is preferably 60° or less, more preferably 55° or less, even more preferably 50° or less, and particularly preferably 45° or less. (Contact angle evaluation conditions) A moisture-curing, one-component adhesive composition is applied to a microscope slide, left for 24 hours, and the contact angle between the cured resin and water is measured in accordance with JIS K6798:1999.

[0027] According to this, the water absorption of moisture-curing one-component adhesive compositions can be further enhanced.

[0028] The moisture-curing, one-component adhesive composition described above offers a good balance between water absorption and adhesive strength.

[0029] 2. Method for producing a moisture-curing one-component adhesive composition The method for manufacturing the moisture-curing one-component adhesive can be any known method, and is not particularly limited as long as the manufactured moisture-curing one-component adhesive does not impair the purpose of the present invention. For example, a method for producing a moisture-curing one-component adhesive composition can be described as follows: (1) Adding a predetermined amount of polyol dropwise to a reaction vessel containing a predetermined amount of polyisocyanate, then heating the vessel and reacting the polyisocyanate under conditions in which the isocyanate groups of the polyisocyanate are in excess of the hydroxyl groups of the polyol to prepare a polyurethane prepolymer; or (2) Adding a predetermined amount of hydrophilicity imparting agent dropwise to the polyurethane prepolymer and stirring. The reaction is usually carried out at a temperature of 50 to 120°C, preferably 60 to 100°C. The reaction time is usually 1 to 15 hours.

[0030] Examples of a more preferred manufacturing method include: (1) adding a portion of the hydrophilicity imparting agent (2 to 10% by mass of the hydrophilicity imparting agent relative to the total weight of the moisture-curing one-component adhesive composition) dropwise to a reaction vessel containing a predetermined amount of polyisocyanate, mixing it, then adding a predetermined amount of crystalline polyol (Aa) and amorphous polyol (Ab) (hereinafter simply referred to as polyol) dropwise, heating the mixture, and reacting it under conditions where the isocyanate groups of the polyisocyanate are in excess of the hydroxyl groups of the polyol to prepare a polyurethane prepolymer; and (2) adding the remaining hydrophilicity imparting agent dropwise to the polyurethane prepolymer and stirring to produce a moisture-curing one-component adhesive composition. In this way, the hydrophilicity imparting agent can be uniformly dispersed within the polyurethane prepolymer. The reaction is usually carried out at a temperature of 50 to 120°C, preferably 70 to 95°C. The reaction time is usually 1 to 15 hours.

[0031] In producing the polyurethane prepolymer, the blending of the polyol and polyisocyanate is preferably such that the equivalent ratio of isocyanate groups in the polyisocyanate to hydroxyl groups in the polyol (hereinafter referred to as the [isocyanate group / hydroxyl group] equivalent ratio) is within the range of 1.1 to 1.2, and more preferably within the range of 1.2 to 1.5.

[0032] The aforementioned polyurethane prepolymer can usually be manufactured without solvents, but it may also be manufactured by reacting a polyol with a polyisocyanate in an organic solvent. When reacting in an organic solvent, organic solvents such as ethyl acetate, n-butyl acetate, methyl ethyl ketone, and toluene that do not inhibit the reaction can be used, but it is necessary to remove the organic solvent by methods such as reduced pressure heating during or after the reaction.

[0033] When producing the polyurethane prepolymer, a urethane catalyst may be used as needed. The urethane catalyst can be added at any stage of the reaction as appropriate. Examples of urethane catalysts include nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine; metal salts such as zinc stearate and tin octoate; and organometallic compounds such as dibutyltin dilaurate.

[0034] The number-average molecular weight of the polyurethane prepolymer obtained by the above method is preferably in the range of 1,000 to 50,000, and more preferably in the range of 3,000 to 10,000, in order to achieve a balance between water absorption and adhesive strength. The number-average molecular weight can be measured by gel per-emission chromatography and converted to the molecular weight of polystyrene, which is a standard sample.

[0035] The NCO group content of the above isocyanate-terminated polyurethane prepolymer is preferably 0.01 to 10% by mass, more preferably 0.3 to 5.0% by mass, and even more preferably 1.0 to 3.0% by mass. This allows for a balance between water absorption and adhesive strength. The NCO group content can be measured according to JIS K1603-2007.

[0036] The urethane group concentration (mol / kg) of the above isocyanate-terminated polyurethane prepolymer is preferably 0.01 to 1.0 mol / kg, more preferably 0.02 to 0.5 mol / kg, and even more preferably 0.03 to 0.3 mol / kg. This allows for a good balance between water absorption and adhesive strength.

[0037] 3. Applications of moisture-curing one-component adhesives The moisture-curing one-component adhesive according to this embodiment is suitable for applications such as adhesives, sealants, primers, paints, and coatings, but is more suitable as an adhesive for substrates that require hydrophilicity. In particular, it is suitable for joining substrates that need to absorb water rapidly, such as disposable diapers and sanitary napkins. The adherend is an absorbent that separates and absorbs liquids of appropriate viscosity. For example, in a disposable diaper, the absorbent is constructed by laminating a top sheet, which is a liquid permeable layer, on one surface as an intermediate layer, and a liquid leakage prevention sheet or waterproof back sheet, etc., on the opposite surface. The moisture-curing one-component adhesive is applied to the interface between the top sheet and the intermediate layer, and / or the interface between the liquid leakage prevention sheet, etc., and the intermediate layer. The intermediate layer is provided in a pattern such as dots, spirals, stripes, or fibers to allow water to pass through.

[0038] The moisture-curing one-component adhesive according to this embodiment can be applied by known methods by heating and melting. For example, it can be applied using a brush, spatula, syringe, sealing gun, dispenser, spray, etc. Of these, application by spraying is a more suitable method for obtaining a water-permeable adhesive interface. In order to facilitate application by spraying, the viscosity of the moisture-curing one-component adhesive composition is preferably such that the melt viscosity at 120°C is 40,000 mPa·s or less, more preferably 30,000 mPa·s or less, and even more preferably 20,000 Pa·s or less, in order to balance water absorption and adhesive strength. The melt viscosity at 120°C can be measured using a B-type viscometer in accordance with JIS Z8803-2011.

[0039] The aforementioned moisture-curing one-component adhesive solidifies upon application and subsequent curing and bonding through crosslinking caused by the reaction of isocyanate groups with moisture (water) in the atmosphere.

[0040] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0041] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0042] The polyols used in the preparation of the moisture-curing one-component adhesive composition are as follows: (Crystalline polyol) A polyester polyol composed of adipic acid-1,4-butanediol (number average molecular weight 2,000). A polyester polyol composed of adipic acid-1,6-hexanediol (number average molecular weight 2,000). A polyester polyol composed of 1,6-hexanediol sebacate (number average molecular weight 2,000). (Amorphous polyol) A polyester polyol composed of adipic acid and diethylene glycol (number average molecular weight 2,000) A polyester polyol composed of adipic acid and diethylene glycol (number average molecular weight 1,000) A polyester polyol composed of phthalate-diethylene glycol (number average molecular weight 2,000). A polyester polyol composed of phthalate-diethylene glycol (number average molecular weight 1,000). A polyester polyol composed of phthalate-diethylene glycol (number average molecular weight 500). A polyester polyol composed of phthalate-methylpropanediol (number average molecular weight 1,000). A polyester polyol composed of phthalate-neopentyl glycol (number average molecular weight 1,000). A polyester polyol composed of phthalic acid-1,4-cyclohexanedimethanol (number average molecular weight 1,000). The crystalline or amorphous nature of each of the polyols mentioned above was confirmed using the following method. <<Equipment used>> • Equipment used: Hitachi, Ltd., DSC7020 • Sample pan: Made of aluminum (for blanks and sample filling) <<Instructions>> (1) Measure out a predetermined amount of polyol into an aluminum pan. (2) Place the empty aluminum pan (blank) and the aluminum pan filled with polyol (test specimen) in the designated positions on the DSC apparatus. (3) Measurements shall be taken under the following measurement program and conditions. <Measurement (Temperature Conditions) Program> "Room temperature (25°C)", "Cool to -80°C, hold at -80°C (5 minutes)", "Raise temperature to 150°C", "Hold at 150°C (5 minutes)", "Cool to -80°C", "Hold at -80°C (measurement ends after holding for 5 minutes)", "Return to room temperature" <Measurement conditions> Sample size: 10 mg ± 0.5 mg Temperature range: -80°C to 150°C (under nitrogen atmosphere, gas flow rate: 100 mL / min) • Heating / cooling rate: 5°C / min • Refrigerant (used in the cooling process): Liquid nitrogen (4) Check the presence or absence of melting peaks (heating process, negative peaks) and crystallization peaks (cooling process, positive peaks) in the obtained DSC curve, which are caused by the melting point. (5) If both a melting peak and a crystallization peak are observed, the polyol is judged to be crystalline. On the other hand, if at least one of the melting peak and crystallization peak is not observed, the polyol is judged to be amorphous.

[0043] (Preparation of moisture-curing one-component adhesive composition) The preparation methods for each moisture-curing one-component adhesive composition from Examples 1 to 16 and Comparative Examples 1 and 2 are shown below. The amounts of each composition are shown in Table 1. A predetermined amount of isocyanate shown in Table 1 was placed in a reaction vessel, a predetermined amount of polyol was added dropwise, the mixture was heated to 60°C and reacted for 5 hours, then a predetermined amount of hydrophilicity imparting agent was added and the mixture was stirred to prepare the adhesive.

[0044] (Evaluation method) The measurement results obtained using the evaluation method described below are shown in Table 1.

[0045] <Urethane group concentration> The urethane group concentration (mol / kg) of the polyurethane prepolymer contained in each prepared moisture-curing one-component adhesive composition was calculated using the following method. To ensure that the NCO% of the urethane prepolymer reaches the desired value, the blending amounts (masses) of all polyol compounds and polyisocyanate compounds used as raw materials for the urethane prepolymer are determined for a total mass of 1 kg of urethane prepolymer. The blending amount (mass) of each polyol compound is divided by the molecular weight of each polyol compound, and then multiplied by the number of functional groups in each polyol compound to calculate the number of moles of hydroxyl groups contained in all polyol compounds. This number of moles of hydroxyl groups is then used as the urethane group concentration (mol / kg) of the urethane prepolymer, assuming that all of these hydroxyl groups react with the isocyanate groups of the polyisocyanate compounds to form urethane bonds.

[0046] <NCO% of prepolymer> The NCO group content of the polyurethane prepolymer contained in each prepared moisture-curing one-component adhesive composition was measured according to Method A / dibutylamine-hydrochloric acid method of JIS K1603-2007. The measurement conditions for the NCO group content were as follows. • Sample quantity: 10±2g • Dibutylamine toluene solution: 0.1 mol / L • Hydrochloric acid concentration: 0.1 mol / L • Indicator: Bromophenol blue (color change point: purple to yellow)

[0047] <Melting viscosity> The melt viscosity of each prepared moisture-curing one-component adhesive composition was measured using a rheometer (Anton Paar "MCR-302"). The measurement conditions for melt viscosity were as follows: ·Measurement temperature: 120℃ • Strain: 5-20% (1 / 12 second intervals) Angular frequency: 0.1~100 rad / sec (1 / 12 second intervals) • Uses parallel plates

[0048] <Difference in stress from the first normal> The first normal stress difference of each prepared moisture-curing one-component adhesive composition was measured simultaneously with the measurement of the melt viscosity using a rheometer (Anton Paar "MCR-302"). The measurement conditions for the first normal stress difference were as follows. ·Measurement temperature: 120℃ • Strain: 5-20% (1 / 12 second intervals) Angular frequency: 0.1~100 rad / sec (1 / 12 second intervals) • Uses parallel plates The "first normal stress difference" is a parameter that indicates the viscosity of a polymer (resin) liquid. When shear deformation is applied to a polymer (resin) liquid, normal stress (tension) is generated in the flow direction. The "first normal stress difference" is a parameter used as a measure of this normal stress. Its definition is the difference between the normal stress in the flow direction and the normal stress in the velocity gradient direction. When the "first normal stress difference" increases, the melt tension increases, making it easier to form fibers. As a result, fibers are formed between the substrates (foam / nonwoven fabric), improving liquid absorption and diffusion due to capillary action. From this viewpoint, the lower limit of the first normal stress difference of each prepared moisture-curable one-component adhesive composition is preferably 1000 mPa or more, more preferably 2000 mPa or more, and even more preferably 3000 mPa or more. On the other hand, the upper limit of the first normal stress difference is preferably 10000 mPa or less, more preferably 8000 mPa or less, and even more preferably 6000 mPa or less.

[0049] <Fiber retention time> Each prepared moisture-curing one-component adhesive composition was heated to 120°C and applied to a substrate (size: 100mm x 100mm, material: polypropylene (PP) nonwoven fabric) using a coating apparatus under the following application conditions to prepare measurement samples. Application conditions • Application amount: 10g / m² 2 ·Heating temperature: 120℃ • Nozzle diameter: 1mm • Discharge pressure: 0.01 MPa ·Application environment temperature: 25℃ For the obtained sample, the structure was observed using a microscope, and the time during which the fibrous structure was maintained (the time from application until the fibrous structure broke down) was measured with a stopwatch and defined as the fiber retention time. A fiber retention time of 5 minutes or more was scored as 2 points, 2 minutes or more but less than 5 minutes was scored as 1 point, and less than 2 minutes was scored as 0 points. "Fiber retention time" refers to the maximum time that a moisture-curing one-component adhesive composition can maintain its fibrous shape on the substrate surface after application. The longer this time, the longer the fibrous shape can be maintained, and the more effectively the fibrous shape can be preserved even after the substrates are bonded together. On the other hand, if this time is short, the fibrous shape cannot be maintained on the substrate surface, resulting in droplets or aggregates, making it difficult to use in applications requiring fibrous coating, such as disposable diapers.

[0050] <Contact angle> Each prepared moisture-curing one-component adhesive composition was applied to a glass slide and left for 24 hours to allow it to fully cure, which was used as the evaluation sample. The contact angle with water of the evaluation sample was measured using a contact angle meter (Kyowa Interface Science Co., Ltd.: CA-D). The measurement method was in accordance with JIS K6768:1999. We assigned points to three for contact angles of 34° or less, one for angles between 34° and 60°, and zero for angles greater than 60°.

[0051] <Initial adhesive strength> Each prepared moisture-curing one-component adhesive composition was heated to 120°C and applied to a substrate (material: polypropylene (PP) nonwoven fabric) using a coating apparatus under the following application conditions. Then, the urethane foam and the PP nonwoven fabric were bonded together via the coating film to prepare the measurement samples. Application conditions • Application amount: 10g / m² 2 ·Heating temperature: 120℃ • Nozzle diameter: 1mm • Discharge pressure: 0.01 MPa ·Application environment temperature: 25℃ • Base material dimensions: 25mm wide x 200mm long (coating area: 25mm wide x 150mm long, gripping area: 25mm on each end) One end of the urethane foam sample was clipped and fixed to a force gauge (IMADA Corporation, digital force gauge, maximum load: 500N) via a hook-shaped probe. Thirty seconds after bonding, the nonwoven fabric was peeled off at a 180° angle, and the peel strength at this time was defined as the initial adhesive strength. An initial adhesive strength of 50 cN or higher was scored as 2 points, 41 cN or higher but less than 50 cN was scored as 1 point, and less than 41 cN was scored as 0 points.

[0052] <Final adhesive strength> The final adhesive strength of each prepared moisture-curing one-component adhesive composition was measured using a material testing machine (Tensilon RAC-1150A, manufactured by A&D Corporation) in accordance with JIS K6854-3:1999. For measurement, the adhesive composition was sprayed onto a polypropylene nonwoven fabric measuring 100 mm in length, 25 mm in width, and 100 μm in thickness in a 25 mm width (coating temperature 120°C, coating amount 10 g / m²). 2 The cotton cloths of the same size were glued together and left in a 25°C atmosphere for 24 hours before being used. A final adhesive strength of 1.5N or higher was scored as 2 points, 1.0N or higher but less than 1.5N was scored as 1 point, and less than 1.0N was scored as 0 points.

[0053] <Melting Tack> A moisture-curing, one-component adhesive composition was melted at 120°C. After the moisture-curing, one-component adhesive composition was completely melted, and then a film with a thickness of 50 μm was formed using a bar coater. When the surface temperature of the molten material constituting the film reached 80 ± 2°C, the tack of the molten moisture-curing, one-component adhesive composition was measured using a force gauge equipped with a disc-shaped probe. "Molten tack" is an indicator of the tackiness (adhesion) of a moisture-curing one-component adhesive composition in its molten state. Before application, the moisture-curing one-component adhesive composition is a heated and melted liquid, and remains liquid even immediately after application by spraying, etc. If the tackiness in the liquid state is strong, the substrates will be less likely to separate after being bonded together with the moisture-curing one-component adhesive composition (temporary bonding). On the other hand, if the melt tack is low, the substrates will be more prone to peeling after being bonded together with the moisture-curing one-component adhesive composition, which can easily lead to product defects in the production process.

[0054] <Tack Free Time> A moisture-curing one-component adhesive composition was melted at 120°C. After the moisture-curing one-component adhesive composition was completely melted, a film with a thickness of 300 μm was deposited using a bar coater. The time until the tack disappeared from the obtained film by touch was measured, and the obtained time was defined as the tack-free time. "Tack-free time" refers to the maximum time that a moisture-curing, one-component adhesive composition can maintain its tackiness after application. By increasing the tack-free time, tackiness can be achieved even at temperatures lower than the application temperature, thus preventing peeling after bonding the substrates.

[0055] <Sprayability> A moisture-curing, one-component adhesive composition, melted at 120°C, is applied to a PET film measuring 210mm x 297mm (A4 size) at a rate of 10g / m². 2 The coating was applied, the shape after application was checked with a microscope, and the sprayability was judged according to the following criteria. <<Judgment criteria>> • Can be applied uniformly in a fibrous manner: 2 points • Some aggregates were observed: 1 point • Cannot be applied in a fibrous manner: 0 points

[0056] <Water absorption rate> Each prepared moisture-curing one-component adhesive composition was sprayed onto the entire surface of a 100mm x 100mm x 5mm thick urethane foam (application temperature: 120°C, application amount: 10g / m²). 2, nozzle diameter: 1 mm, discharge pressure: 0.01 Pa), 100 mm × 100 mm × 100 μm polypropylene non-woven fabrics were overlapped and left to stand for 24 hours in an atmosphere of 25°C, and the one with the substrates completely adhered to each other was used as the measurement sample. With the non-woven fabric of the measurement sample on the top, a cylindrical tube with an inner diameter of 50 mm was fixed perpendicular to the surface of the non-woven fabric of the sample. 20 mL of water colored with blue ink was weighed and poured into the inside of the cylindrical tube, and the time (until the colored water could no longer be seen from the surface of the non-woven fabric) for the colored water to be completely absorbed by the test sample from above the cylindrical tube was measured. In addition, those with a water absorption time of 15 seconds or less were evaluated as 3 points, those with a time exceeding 15 seconds and less than 20 seconds were evaluated as 1 point, and those with a time of 20 seconds or more were evaluated as 0 point.

[0057] <Diffusion area> The prepared moisture-curable one-component adhesive composition was spray-coated (coating temperature: 120°C, coating amount: 10 g / m 2 , nozzle diameter: 1 mm, discharge pressure: 0.01 Pa), 100 mm × 100 mm × 100 μm polypropylene non-woven fabrics were overlapped and left to stand for 24 hours in an atmosphere of 25°C, and the one with the substrates completely adhered to each other was used as the measurement sample. With the non-woven fabric of the measurement sample on the top, a cylindrical tube with an inner diameter of 50 mm was fixed perpendicular to the surface of the non-woven fabric of the sample. 20 mL of water colored with blue ink was weighed and poured into the inside of the cylindrical tube. After the colored water was completely absorbed by the test sample from above the cylindrical tube, a still image was taken in order to measure the area of the part where the non-woven fabric was dyed blue, and it was read and measured with image analysis software (product name: Hakuto Co., Ltd., Image-Pro 6.2). In addition, those with a diffusion area of 50 cm 2 or more were evaluated as 3 points, those with 41 cm 2 or more and less than 50 cm 2 were evaluated as 1 point, and those with less than 41 cm 2 were evaluated as 0 point.

[0058] <Overall evaluation> The total of each evaluation point was calculated, and those with a total score of 14 points or more were rated as A (excellent), those with 10 - 13 points were rated as B (good), and those with 9 points or less were rated as C (poor).

[0059] [Table 1]

[0060] As shown in Table 1, each of the moisture-curing one-component adhesive compositions in Examples 1 to 16 was found to have good water absorption rate and diffusion area, which are indicators of water absorption, as well as good initial and final adhesive strength. In contrast, Comparative Example 1 had insufficient initial and final adhesive strength, and Comparative Example 2 also had insufficient initial adhesive strength.

Claims

1. A polyurethane prepolymer (A) obtained by reacting a crystalline polyol (Aa) and an amorphous polyol (Ab) with a polyisocyanate (B), Hydrophilicity-imparting agent (C), Includes, The crystalline polyol (Aa) is a crystalline polyester polyol having structural units derived from an aliphatic dicarboxylic acid selected from succinic acid, adipic acid, sebacic acid, dodecanediic acid, and azelaic acid. The amorphous polyol (Ab) is an amorphous polyol having structural units derived from an aliphatic dicarboxylic acid selected from succinic acid, adipic acid, sebacic acid, and azelaic acid, and / or an amorphous polyol having structural units derived from an aromatic dicarboxylic acid selected from phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. The mass ratio of the crystalline polyol (Aa) to the amorphous polyol (Ab) is 0.2 to 0.

9. A moisture-curing, one-component adhesive composition that satisfies at least one of the following conditions (1) to (4). (1) The amount of the hydrophilicity imparting agent (C) added to the total weight of the moisture-curing one-component adhesive composition In contrast, it is 2% by mass or more. (2) The hydrophilic agent (C) has a polyoxyethylene group (3) The hydrophilicity-imparting agent (C) does not contain an amino group. (4) The contact angle obtained under the following contact angle evaluation conditions is 60° or less. (Contact angle evaluation conditions) The moisture-curing one-component adhesive composition is applied to a slide and left for 24 hours to cure. The contact angle between the resin and water is measured in accordance with JIS K6798:1999.

2. The moisture-curing one-component adhesive composition according to claim 1, wherein the hydrophilicity imparting agent (C) is a nonionic surfactant.

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