Reactive hot-melt adhesive, structure and method for producing structure

Abstract

To provide a reactive hot-melt adhesive excellent in initial adhesion and workability during application, as well as, a structure obtained by using the reactive hot-melt adhesive excellent in the initial adhesion and the workability during application and a method for producing the structure.SOLUTION: A reactive hot-melt adhesive contains an urethane prepolymer and satisfies the following conditions A, B and C. Condition A: The crystallinity of a cured product measured by the differential scanning calorimeter is 25 J / g or more. Condition B: The ratio (V1 / V2) of the viscosity V1 at 120°C and 20 rpm measured by a B-type rotational viscometer and the viscosity V2 at 120°C and 100 rpm is 1.1 or more. Condition C: The ratio of the viscosity V3 at 20°C measured with a rotary rheometer to the viscosity V3 at 120°C (V3 / V4) is less than or equal to 10000.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a reactive hot melt adhesive, a structure, and a method for making a structure. [Background technology]

[0002] A technology has been proposed for producing clothing such as innerwear and sportswear using hot melt adhesives instead of sewing. Hot melt adhesives are solid at room temperature, and are liquefied by heating when they are brought into contact with an adherend, and develop adhesive strength when cooled and solidified. Hot melt adhesives can be broadly divided into two types: those containing thermoplastic resin as the main component and those containing reactive resin. Hot melt adhesives containing urethane prepolymers are known as hot melt adhesives containing reactive resins (hereinafter also referred to as reactive hot melt adhesives).

[0003] Reactive hot melt adhesives containing urethane prepolymers not only exhibit a certain degree of adhesive strength in a short time by cooling and solidifying, but also cure when the terminal isocyanate groups of the urethane prepolymer react with moisture in the air or on the surface of the adherend (moisture curing). As a result, they exhibit a strong adhesive strength that cannot be achieved with hot melt adhesives containing thermoplastic resins. As a reactive hot melt adhesive containing a urethane prepolymer, Patent Document 1 discloses a reactive hot melt adhesive having excellent elasticity after curing. Patent Document 2 discloses a reactive hot melt adhesive having excellent adhesive strength and excellent elasticity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 217574 [Patent Document 1] International Publication No. 2021 / 199339 Summary of the Invention [Problem to be solved by the invention]

[0005] The reactive hot melt adhesive described in Patent Document 1 leaves room for improvement in terms of initial adhesive strength, and the hot melt adhesive described in Patent Document 2 leaves room for improvement in terms of workability during application. In view of the above circumstances, the present disclosure aims to provide a reactive hot melt adhesive that is excellent in initial adhesion and workability during application, as well as a structure obtained using the reactive hot melt adhesive that is excellent in initial adhesion and workability during application, and a method for manufacturing a structure. [Means for solving the problem]

[0006] Means for solving the above problems include the following embodiments. <1> A reactive hot melt adhesive that contains a urethane prepolymer and satisfies the following conditions A, B, and C. Condition A: The crystallinity of the cured product measured with a differential scanning calorimeter is 25 J / g or more. Condition B: The ratio (V1 / V2) of the viscosity V1 at 120°C and 20 rpm measured with a B-type rotational viscometer to the viscosity V2 at 120°C and 100 rpm is 1.1 or more. Condition C: The ratio (V3 / V4) of the viscosity V3 at 20°C to the viscosity V3 at 120°C measured with a rotational rheometer is 10,000 or less. <2> contacting the substrate with a jet dispenser; <1> 2. The reactive hot melt adhesive according to claim 1 . <3> Contacting the substrate in a dot pattern; <1> or <2> 2. The reactive hot melt adhesive according to claim 1 . <4> For use in bonding stretchable substrates, <1> ~ <3> 13. The reactive hot melt adhesive according to claim 12, <5> For use in the manufacture of clothing, <1> ~ <4> 13. The reactive hot melt adhesive according to claim 12, <6> Two or more substrates are bonded to each other <1> ~ <5> and a cured product of the reactive hot melt adhesive according to any one of the above. <7> Melted <1> ~ <5> contacting a first substrate with the reactive hot melt adhesive described in any one of the above items; and contacting a second substrate with the reactive hot melt adhesive on the first substrate. Effect of the Invention

[0007] According to the present disclosure, there are provided a reactive hot melt adhesive having excellent initial adhesion and workability during application, as well as a structure obtained using the reactive hot melt adhesive having excellent initial adhesion and workability during application, and a method for manufacturing a structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described, however, the present disclosure is not limited to the following embodiments.

[0009] In the present disclosure, a numerical range indicated using "~" includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple types of the corresponding substance. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.

[0010] In the present disclosure, "polyol" refers to a compound having two or more hydroxyl groups in the molecule. In this disclosure, "polyisocyanate" means a compound having two or more isocyanate groups in the molecule. In the present disclosure, the term "urethane prepolymer" refers to a compound that is a reaction product of a polyol and a polyisocyanate and has an isocyanate group at the end of the molecule. That is, the term "urethane prepolymer" refers to a compound that includes a polymer chain that includes a structural unit derived from a polyol and a structural unit derived from a polyisocyanate, and has an isocyanate group as the end group of the polymer chain.

[0011] <Reactive hot melt adhesive> The reactive hot melt adhesive of the present disclosure is a reactive hot melt adhesive that contains a urethane prepolymer and satisfies the following conditions A, B, and C. Condition A: The crystallinity of the cured product measured with a differential scanning calorimeter is 25 J / g or more. Condition B: The ratio (V1 / V2) of the viscosity V1 at 120°C and 20 rpm measured with a B-type rotational viscometer to the viscosity V2 at 120°C and 100 rpm is 1.1 or more. Condition C: The ratio (V3 / V4) of the viscosity V3 at 20° C. to the viscosity V3 at 120° C. measured with a rotational rheometer is 10,000 or less.

[0012] As shown in the examples described below, the reactive hot melt adhesive of the present disclosure exhibits excellent initial adhesive strength (adhesive strength that appears in a short time after contact with the substrate). Therefore, when multiple substrates are bonded using the reactive hot melt adhesive, the substrates are less likely to be displaced from one another. Furthermore, the reactive hot melt adhesive of the present disclosure has excellent workability during application. Specifically, the reactive hot melt adhesive has excellent workability when applied to a substrate using a jet dispenser.

[0013] (Condition A: Crystallinity) The reactive hot melt adhesive of the present disclosure satisfies condition A. That is, the crystallinity of the cured product measured with a differential scanning calorimeter (hereinafter also referred to as crystallinity) is 25 J / g or more. A reactive hot melt adhesive with a crystallinity of 25 J / g or more exhibits excellent initial adhesion. From the standpoint of initial adhesion, the crystallinity of the reactive hot melt adhesive may be 30 J / g or more, 35 J / g or more, or 40 J / g or more. From the viewpoint of ensuring the elasticity of the cured product, the crystallinity of the reactive hot melt adhesive may be 60 J / g or less, 55 J / g or less, or 50 J / g or less.

[0014] In the present disclosure, the crystallinity of the reactive hot melt adhesive is measured by the method described in the Examples.

[0015] (Condition B: TI value) The reactive hot melt adhesive of the present disclosure satisfies condition B. That is, the ratio of the viscosity V1 at 120°C and 20 rpm to the viscosity V2 at 120°C and 100 rpm measured with a B-type rotational viscometer (V1 / V2, hereinafter also referred to as the TI value) is 1.1 or more. When the reactive hot melt adhesive has a TI value of 1.1 or more, stringiness is suppressed when the reactive hot melt adhesive is applied to a substrate. From the standpoint of suppressing stringiness, the TI value of the reactive hot melt adhesive may be 1.15 or more, or 1.2 or more. From the standpoint of preventing phase separation of the adhesive during long-term storage, the TI value of the reactive hot melt adhesive may be 1.45 or less, 1.4 or less, or 1.35 or less.

[0016] In the present disclosure, the TI value of a reactive hot melt adhesive is measured by the method described in the Examples.

[0017] (Condition C: Temperature viscosity dependence) The reactive hot melt adhesive of the present disclosure satisfies condition C. That is, the ratio of the viscosity V3 at 20°C to the viscosity V3 at 120°C measured with a rotational rheometer (V3 / V4, hereinafter also referred to as temperature viscosity dependency) is 10,000 or less. By having the temperature viscosity dependence of the reactive hot melt adhesive be 10,000 or less, the rate at which the viscosity of the reactive hot melt adhesive increases due to cooling is suppressed, and the molten reactive hot melt adhesive can be ejected satisfactorily from the nozzle of the jet dispenser. From the viewpoint of dischargeability from a dispenser, the temperature viscosity dependency of the reactive hot melt adhesive may be 9000 or less, 8000 or less, 7000 or less, or 6000 or less. From the viewpoint of allowing the adhesive to solidify as the temperature decreases and to exhibit excellent initial adhesiveness, the temperature viscosity dependency of the reactive hot melt adhesive may be 50 or more, 75 or more, or 100 or more.

[0018] In the present disclosure, the temperature dependency of the reactive hot melt adhesive is measured by the method described in the Examples.

[0019] (Urethane prepolymer) The urethane prepolymer contained in the reactive hot melt adhesive is obtained by reacting a polyol with a polyisocyanate. The types of polyol and polyisocyanate used in the synthesis of the urethane prepolymer are not particularly limited, and can be selected depending on the desired characteristics of the reactive hot melt adhesive. The polyol and the polyisocyanate used in the synthesis of the urethane prepolymer may each be one kind or two or more kinds. The reactive hot melt adhesive may contain only one type of urethane prepolymer, or two or more types of urethane prepolymers.

[0020] From the viewpoint of stretchability after curing, the structural units derived from the polyol of the urethane prepolymer preferably contain structural units derived from an amorphous polyol. In the present disclosure, a crystalline polyol refers to a polyol that exhibits an endothermic peak (melting point Tm) associated with melting when subjected to DSC measurement, and an amorphous polyol refers to a polyol that does not exhibit an endothermic peak (melting point Tm) associated with melting when subjected to DSC measurement. The proportion of the structural units derived from the amorphous polyol in the structural units derived from the polyol in the urethane prepolymer may be 30% by mass or more, 35% by mass or more, or 40% by mass or more. The proportion of structural units derived from amorphous polyol in the structural units derived from polyol in the urethane prepolymer may be 70% by mass or less, 65% by mass or less, or 60% by mass or less.

[0021] From the viewpoint of adjusting the solidification time and viscosity of the reactive hot melt adhesive, the urethane prepolymer preferably contains a structural unit derived from a polyester polyol as a structural unit derived from a polyol. That is, the raw material of the urethane prepolymer preferably contains a polyester polyol as a polyol.

[0022] The polyester polyol may be a compound produced by a polycondensation reaction between a polyhydric alcohol and a polycarboxylic acid. The polyester polyol may be, for example, a polycondensation product between a polyhydric alcohol having 2 to 15 carbon atoms and 2 or 3 hydroxyl groups and a polycarboxylic acid having 2 to 14 carbon atoms (including the carbon atoms in the carboxyl groups) and 2 to 6 carboxyl groups.

[0023] The polyester polyol may be a linear polyester diol produced from a diol and a dicarboxylic acid, or a branched polyester triol produced from a triol and a dicarboxylic acid. The branched polyester triol can also be obtained by reacting a diol with a tricarboxylic acid.

[0024] Examples of polyhydric alcohols include aliphatic or alicyclic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, isomers of butanediol, isomers of pentanediol, isomers of hexanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-methylpropanediol, 2,4,4-trimethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; and aromatic diols such as 4,4'-dihydroxydiphenylpropane, bisphenol A, bisphenol F, pyrocatechol, resorcinol, and hydroquinone. The polyhydric alcohol may be used alone or in combination of two or more. Among these, aliphatic diols are preferable, and aliphatic diols having 2 to 6 carbon atoms are more preferable.

[0025] Examples of polycarboxylic acids include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and 1,2,4-benzenetricarboxylic acid, and aliphatic or alicyclic polycarboxylic acids such as maleic acid, fumaric acid, aconitic acid, 1,2,3-propanetricarboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, cyclohexane-1,2-dicarboxylic acid, and 1,4-cyclohexanediene-1,2-dicarboxylic acid. One type of polycarboxylic acid may be used alone, or two or more types may be used in combination.

[0026] Instead of the above-mentioned polycarboxylic acids, polycarboxylic acid derivatives such as carboxylic anhydrides and compounds in which a part of the carboxyl group is esterified can also be used. Examples of the polycarboxylic acid derivatives include dodecyl maleic acid and octadecenyl maleic acid.

[0027] The polyester polyol used as the raw material for the urethane prepolymer may be of one type or of two or more types.

[0028] The number average molecular weight (Mn) of the polyester polyol is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 8,000, and further preferably in the range of 1,500 to 6,000.

[0029] In the present disclosure, the number average molecular weight of a polyol is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene. The GPC measurement can be performed under the following conditions. Column: "Gelpack GLA130-S", "Gelpack GLA150-S" and "Gelpack GLA160-S" (HPLC packed columns manufactured by Showa Denko Materials Co., Ltd.) Eluent: Tetrahydrofuran Flow rate: 1.0mL / min Column temperature: 40℃ Detector: RI

[0030] The amount of polyester polyol used as a raw material for the urethane prepolymer may be within the range of, for example, 70% by mass to 100% by mass of the total polyol. The polyester polyol used as a raw material for the urethane prepolymer may include an amorphous polyester polyol and a crystalline polyester polyol.

[0031] The reactive hot melt adhesive may contain a structural unit derived from a polyether polyol as a structural unit derived from a polyol, that is, the raw material of the urethane prepolymer may contain a polyether polyol as a polyol.

[0032] Examples of polyether polyols include aromatic polyether polyols such as polyether polyols having a bisphenol skeleton, polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, and ethylene oxide-modified polypropylene glycol.

[0033] The polyether polyol used as the raw material for the urethane prepolymer may be of one type only, or of two or more types.

[0034] The Mn of the polyether polyol is preferably in the range of 500 to 2000, more preferably in the range of 700 to 2000, and even more preferably in the range of 1000 to 2000, from the viewpoints of initial adhesive strength, adhesive strength after curing, and appropriate open time after application.

[0035] The amount of polyether polyol used as a raw material for the urethane prepolymer may be within the range of, for example, 0% by mass to 10% by mass of the total polyol.

[0036] The polyisocyanate used as the raw material of the urethane prepolymer is not particularly limited. Examples of the polyisocyanate include aromatic isocyanates such as diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and p-phenylene diisocyanate; alicyclic isocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. From the viewpoint of reactivity and adhesiveness, the polyisocyanate is preferably an aromatic diisocyanate, and more preferably diphenylmethane diisocyanate.

[0037] The polyisocyanate used as the raw material for the urethane prepolymer may be of one type or of two or more types.

[0038] The equivalent ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate to the hydroxyl group (OH) of the polyol used as the raw material of the urethane prepolymer is preferably 2.0 or less. When the NCO / OH ratio is 2.0 or less, the amount of unreacted polyisocyanate remaining during the reaction of the polyol with the polyisocyanate is suppressed, and the elasticity after curing is well maintained.

[0039] The equivalent ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate to the hydroxyl group (OH) of the polyol used as the raw material for the urethane prepolymer is preferably 1.6 or more. When the NCO / OH ratio is 1.6 or more, the viscosity of the resulting urethane prepolymer when melted does not become too high, and good workability is maintained.

[0040] The temperature and time for reacting the polyol with the polyisocyanate may be, for example, 85 to 120° C. and 1 minute to 48 hours. When mixing the polyol with the polyisocyanate, degassing under reduced pressure may be performed.

[0041] The reactive hot melt adhesive may further contain a catalyst from the viewpoint of promoting the curing reaction of the urethane prepolymer. Examples of the catalyst include dibutyltin dilaurate, dibutylthione octate, dimethylcyclohexylamine, dimethylbenzylamine, trioctylamine, and dimorpholinodiethyl ether (bis(2-morpholinoethyl)ether). The catalyst content may be, for example, 0% to 0.5% by mass of the entire reactive hot melt adhesive.

[0042] The reactive hot melt adhesive may further contain a thermoplastic polymer in order to increase the rubber elasticity of the cured product and further improve the impact resistance. Examples of the thermoplastic polymer include polyurethane, ethylene copolymer, propylene copolymer, vinyl chloride copolymer, acrylic copolymer, and styrene-conjugated diene block copolymer.

[0043] The reactive hot melt adhesive may further contain a tackifier resin from the viewpoint of imparting stronger adhesiveness to the cured product. Examples of the tackifier resin include rosin resin, rosin ester resin, hydrogenated rosin ester resin, terpene resin, terpene phenol resin, hydrogenated terpene resin, petroleum resin, hydrogenated petroleum resin, coumarone resin, ketone resin, styrene resin, modified styrene resin, xylene resin, and epoxy resin.

[0044] The reactive hot melt adhesive may contain components such as antioxidants, pigments, ultraviolet absorbers, surfactants, flame retardants, silane coupling agents, and fillers, as necessary.

[0045] The method for obtaining a cured product of the reactive hot melt adhesive is not particularly limited. For example, the cured product may be obtained by causing a curing reaction of a urethane prepolymer in an environment at a temperature of 20° C. to 30° C. and a relative humidity of 40% to 60%.

[0046] From the viewpoint of workability during application, the viscosity of the reactive hot melt adhesive at 120°C is preferably 20 Pa·s or less, more preferably 15 Pa·s or less, and even more preferably 10 Pa·s or less. There is no lower limit to the viscosity of the reactive hot melt adhesive at 120°C, but it may be, for example, 1 Pa·s or more. The viscosity is measured using a rotational rheometer as is the measurement of the temperature viscosity dependence.

[0047] The reactive hot melt adhesive of the present disclosure is in a solid state before use. The form of the reactive hot melt adhesive in a solid state is not particularly limited. For example, it may be in the form of a pellet, a block, a powder, a sheet, etc.

[0048] The reactive hot melt adhesive of the present disclosure is solid at room temperature and is liquefied by heating when used. The method of contacting the liquefied reactive hot melt adhesive with the object (substrate) is not particularly limited. For example, the liquefied reactive hot melt adhesive may be contacted with the substrate using a dispenser or the like, or a non-liquefied reactive hot melt adhesive such as an adhesive sheet may be heated in contact with the object to be liquefied. The reactive hot melt adhesives of the present disclosure are preferably contacted with a substrate by dispensing.

[0049] As described below, the reactive hot melt adhesive of the present disclosure has excellent dischargeability from a jet dispenser, and therefore, a method using a jet dispenser is particularly suitable for contacting the reactive hot melt adhesive with a substrate. There are two types of dispensers: contact and non-contact, and a jet dispenser is a non-contact dispenser. A jet dispenser is a machine that dispenses a liquid agent contained in a syringe or tank toward an object to be coated. A jet dispenser is excellent in that it accurately dispenses a small and constant amount of liquid agent, and it is preferable to use a jet dispenser for reactive hot melt adhesives. In a method using a jet dispenser, the reactive hot melt adhesive is discharged onto a substrate located away from the nozzle. For this reason, for example, a dot-shaped pattern made of reactive hot melt adhesive can be formed on a substrate.

[0050] When a reactive hot melt adhesive is used as an adhesive for a stretchable substrate such as a fabric, it is necessary that the adhesive has excellent adhesion to the substrate and that the stretchability of the substrate is sufficiently ensured. When a substrate is bonded using a reactive hot melt adhesive with high adhesive strength, the cured product of the reactive hot melt adhesive may be too hard, impairing the elasticity of the bonded portion. One way to solve this problem is to apply the reactive hot melt adhesive to the substrate in a dot pattern. As described below, the reactive hot melt adhesive of the present disclosure is less likely to cause stringiness when applied to the substrate in a dot pattern, and has excellent workability. For this reason, it is suitable as an adhesive for substrates having elasticity.

[0051] The type of substrate to be bonded using the reactive hot melt adhesive of the present disclosure is not particularly limited. For the reasons described above, the reactive hot melt adhesive of the present disclosure is also suitable as an adhesive for bonding substrates having elasticity, or as an adhesive for use in the manufacture of clothing. The material of the stretchable substrate is not particularly limited, and may be, for example, natural fiber, synthetic fiber, plastic, or the like. In one embodiment, the stretchable substrate may be a fabric such as a knitted fabric or a woven fabric, and may be a fabric for apparel.

[0052] <Structure> The structure of the present disclosure is a structure comprising two or more substrates and a cured product of the reactive hot melt adhesive of the present disclosure bonding the two or more substrates together.

[0053] The material of the two or more base materials included in the structure is not particularly limited. For example, it may be natural fiber, synthetic fiber, plastic, etc. The material of the two or more base materials may be the same or different. In an embodiment, the substrate may be stretchable, and the stretchable substrate may be a fabric such as a knitted fabric, a woven fabric, a nonwoven fabric, etc. The substrate may be a fabric for clothing.

[0054] <Method of manufacturing the structure> A method for producing a structure of the present disclosure includes contacting a molten reactive hot melt adhesive of the present disclosure with a first substrate, and contacting the reactive hot melt adhesive on the first substrate with a second substrate.

[0055] In the above method, the reactive hot melt adhesive in contact with the first and second substrates is cooled and solidified, and then a curing reaction of the urethane prepolymer contained in the reactive hot melt adhesive occurs, thereby obtaining a structure in which the first and second substrates are bonded together with the cured product of the reactive hot melt adhesive.

[0056] In the above method, the method for contacting the molten reactive hot melt adhesive with the first substrate is not particularly limited. In the methods of the present disclosure, the reactive hot melt adhesive is preferably contacted with the first substrate by dispensing. As described above, the reactive hot melt adhesive of the present disclosure has excellent workability when applied using a jet dispenser. Therefore, the reactive hot melt adhesive may be contacted using a jet dispenser. As shown in the examples described below, the reactive hot melt adhesive of the present disclosure is less likely to form strings between the dots when applied in dots, so the reactive hot melt adhesive may be brought into contact with the first substrate in dots.

[0057] The material of the first substrate and the second substrate is not particularly limited. For example, the material may be natural fiber, synthetic fiber, plastic, etc. The material of the first substrate and the second substrate may be the same or different. In an embodiment, the first substrate and the second substrate may be stretchable, and the stretchable substrate may be a fabric such as a knitted fabric, a woven fabric, a nonwoven fabric, etc. The first substrate and the second substrate may be a fabric for clothing. EXAMPLES

[0058] The present disclosure will be specifically described below based on examples, but the present invention is not limited to these.

[0059] <Preparation of reactive hot melt adhesive> A urethane prepolymer was prepared using the types and parts by mass of polyol and polyisocyanate shown in Table 1. More specifically, the polyol and polyisocyanate, which had been dehydrated in advance using a vacuum dryer, were added to a reaction vessel and mixed at 110°C for 1 hour until uniform. Next, the mixture was stirred at 110°C for 1 hour under reduced pressure and degassed to obtain a urethane prepolymer. As shown in Table 1, since the NCO equivalent / OH equivalent is greater than 1, it is presumed that the obtained urethane prepolymer has a polymer chain containing a structural unit derived from a polyol and a structural unit derived from a polyisocyanate, and an isocyanate group bonded to the end of the polymer chain. In the test, the urethane prepolymer obtained above was used as it is as a reactive hot melt adhesive.

[0060] [Table 1]

[0061] Details of the polyols and polyisocyanates shown in Table 1 are as follows. (Amorphous polyester polyol A) Amorphous polyester polyol with aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 2000) mainly composed of dicarboxylic acids (terephthalic acid, isophthalic acid, and adipic acid) and diols (ethylene glycol and neopentyl glycol)

[0062] (Amorphous polyester polyol B) Amorphous polyester polyol with aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 2000) mainly composed of dicarboxylic acids (isophthalic acid and adipic acid) and diols (ethylene glycol and neopentyl glycol)

[0063] (Amorphous polyester polyol C) Amorphous polyester polyol with aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 2000) whose main components are dicarboxylic acid (phthalic anhydride) and diol (ethylene glycol and diethylene glycol)

[0064] (Amorphous polyester polyol D) Amorphous polyester polyol with aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 2000) mainly composed of dicarboxylic acid (phthalic anhydride) and diol (ethylene glycol and neopentyl glycol)

[0065] (Amorphous polyester polyol E) Amorphous polyester polyol having an aromatic ring (manufactured by Toyokuni Oil Mills, product name: HS 2F-306P, number of hydroxyl groups: 2, melting point (Tm): none)

[0066] (Amorphous polyester polyol F) A non-crystalline polyester polyol without aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 2000) whose main components are dicarboxylic acid (adipic acid) and diol (propylene glycol and neopentyl glycol)

[0067] (Crystalline polyester polyol A) A crystalline polyester polyol without aromatic rings (number of hydroxyl groups: 2, number average molecular weight: 4800) whose main components are dicarboxylic acid (sebacic acid) and diol (1,6-hexanediol)

[0068] (Crystalline polyester polyol B) Crystalline polyester polyol without aromatic ring (manufactured by Ito Oil Mills, product name: SE-2606, number of hydroxyl groups: 2, melting point (Tm): 66°C)

[0069] (Crystalline polyester polyol C) Crystalline polyester polyol without aromatic ring (manufactured by Evonik Industries, product name: DYNACOLL7380, number of hydroxyl groups: 2, melting point (Tm): 73°C)

[0070] (Polyisocyanate) Diphenylmethane diisocyanate (manufactured by Tosoh Corporation, product name: Millionate MT, number of isocyanate groups: 2)

[0071] (Crystallization degree) The crystallinity of the reactive hot melt adhesive was measured using an automatic differential scanning calorimeter (DSC). The measuring device used was Shimadzu Corporation's DSC-60A plus (product name). The heat of fusion was calculated from the endothermic peak area obtained when the temperature was raised from -100°C to 100°C at a heating rate of 10°C / min, and the value divided by the sample weight (10 mg) was defined as the crystallinity (J / g).

[0072] (TI value) The TI value of the reactive hot melt adhesive was determined from the viscosity measured at 20 rpm and 100 rpm using a B-type rotational viscometer. The measurement device used was a BH-HH type small volume rotational viscometer manufactured by Toki Sangyo Co., Ltd. The rotor used was a No. 4 rotor, the sample weight was 15 g, and the measurement temperature was 120°C.

[0073] (Temperature viscosity dependence) The temperature viscosity dependency of the reactive hot melt adhesive was obtained from the viscosity at 20°C and 120°C measured using a rotational rheometer. The measurement device used was DISCOVERY HR (product name) manufactured by TA Instruments Japan Co., Ltd. The measurement conditions were: geometry diameter: 20 mm (2° cone plate), gap: 57 μm, shear rate: 33.0 (1 / s), temperature condition: 120°C to 80°C (cooling rate: -5°C / min). The viscosity value at 20°C was calculated by approximating the measurement results from 120°C to 80°C. Note that since reactive hot melt adhesives before moisture curing have viscoelasticity in a solid state, it is possible to calculate the viscosity at 20°C.

[0074] (Initial adhesive strength) Using a jet dispenser (Marco piezo-type JET dispenser: MV JET), the reactive hot melt adhesive was heated to 100°C and melted, and applied to the substrate to form an adhesive layer (application area 8 mm x 8 cm). Another substrate was placed on the formed adhesive layer and pressed at 100° C. to produce a laminate. The adhesive strength of the adhesive layer 5 minutes after compression was measured by a T-peel strength test using a tensile tester (Shimadzu Corporation: EZ-test) at a measurement temperature of 25°C and a tensile speed of 100 mm / min. The higher the measured value, the better the initial adhesive strength can be evaluated. The base material used was a stretchable fabric (spandex, manufactured by Toray Oprontex Co., Ltd., Lycra (registered trademark), fabric size: 2 cm width x 12 cm length).

[0075] (Dischargeability) Using a jet dispenser (Marco piezo type JET dispenser: MV JET), the reactive hot melt adhesive was heated to 100°C and melted, and then applied in the form of dots to the substrate used in the evaluation of initial adhesive strength. Specifically, a pattern consisting of 300 dots with a diameter of 1 mm (distance between dots: 2 mm, number of dots per row: 30, number of rows: 10) was formed using the reactive hot melt adhesive. During application, it was confirmed whether stable application was possible without interruption, and it was evaluated according to the following criteria. The results are shown in Table 2. ◯: 300 perfectly circular dots were applied without interruption. x: Dots were broken, or the dot diameter or shape was defective.

[0076] (Whether or not stringiness occurs) Using the same method as in the evaluation of the dischargeability, a dot pattern was formed on the substrate using the reactive hot melt adhesive. Then, the presence or absence of stringiness between adjacent dots was visually observed. The results are shown in Table 2.

[0077] [Table 2]

[0078] (Viscosity at 120℃) The viscosity of the reactive hot melt adhesive at 120°C was measured using a B-type rotational viscometer. The measuring device used was a BH-HH type small volume rotational viscometer manufactured by Toki Sangyo Co., Ltd., and the rotor was a No. 4 rotor. The sample weight was 15g, the measurement temperature was 120°C, and the rotation speed was 100 rpm.

[0079] As shown in Table 2, the reactive hot melt adhesives of Examples 1 to 4, in which the cured product had a crystallinity of 25 J / g or more, a TI value of 1.1 or more, and a temperature viscosity dependency of 10,000 or less, exhibited excellent initial adhesive strength and dischargeability, and no stringiness between dots was observed. In the reactive hot melt adhesive of Comparative Example 1, which had a TI value of less than 1.1, stringing was observed between the dots. The reactive hot melt adhesive of Comparative Example 2, which had a temperature viscosity dependency of more than 10,000, had inferior discharge properties to those of the Examples. The reactive hot melt adhesive of Comparative Example 3, in which the degree of crystallinity of the cured product was lower than 25 J / g, had an initial adhesive strength inferior to that of the Examples.

Claims

1. A reactive hot melt adhesive comprising a urethane prepolymer and satisfying the following conditions A, B, and C. Condition A: The crystallinity of the cured product measured by a differential scanning calorimeter is 25 J / g or more. Condition B: The ratio (V1 / V2) of the viscosity V1 at 120° C. and 20 rpm to the viscosity V2 at 120° C. and 100 rpm measured with a B-type rotational viscometer is 1.1 or more. Condition C: The ratio (V3 / V4) of the viscosity V3 at 20° C. to the viscosity V3 at 120° C. measured with a rotational rheometer is 10,000 or less.

2. 10. The reactive hot melt adhesive of claim 1 , wherein the adhesive is contacted with the substrate using a jet dispenser.

3. 10. The reactive hot melt adhesive of claim 1 which is contacted to a substrate in the form of a dot.

4. 2. The reactive hot melt adhesive of claim 1 for use in bonding stretchable substrates.

5. 10. The reactive hot melt adhesive of claim 1 for use in the manufacture of apparel.

6. A structure comprising two or more substrates and a cured product of the reactive hot melt adhesive according to any one of claims 1 to 5, which bonds the two or more substrates.

7. A method for producing a structure comprising: contacting a first substrate with the molten reactive hot melt adhesive according to any one of claims 1 to 5; and contacting a second substrate with the reactive hot melt adhesive on the first substrate.

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