Reactive hot melt adhesive composition, adhesive body and method for producing the same

Abstract

The present invention discloses a reactive hot melt adhesive composition. This reactive hot melt adhesive composition contains a urethane prepolymer which contains a polymer chain that has a structural unit derived from a polyol including a polyester polyol and a structural unit derived from a polyisocyanate, and an isocyanate group that serves as an end group of the polymer chain. The polyester polyol includes a polyester polyol which has a structural unit derived from a divalent aliphatic carboxylic acid and a structural unit derived from a divalent aliphatic alcohol, wherein at least one of the divalent aliphatic carboxylic acid and the divalent aliphatic alcohol has a tertiary carbon atom or a quaternary carbon atom in each molecule.

Description

[Technical Field]

[0001] The present invention relates to a reactive hot melt adhesive composition, an adhesive body, and a method for producing the same. [Background technology]

[0002] Hot melt adhesives are solvent-free, which means they are gentle on the environment and the human body, and can bond in a short time, making them suitable for improving productivity. Hot melt adhesives can be broadly divided into two types: those that use thermoplastic resins as the main component and those that use reactive resins as the main component. Urethane prepolymers with isocyanate groups at the terminals are mainly used as reactive resins.

[0003] After application, reactive hot melt adhesives containing urethane prepolymers as their primary component cool and solidify, developing a certain level of adhesive strength in a short time. The terminal isocyanate groups of the urethane prepolymers then react with moisture (in the air or on the surface of the adherend) to increase their molecular weight, forming crosslinks and thereby exhibiting heat resistance. Such adhesives are also known as "moisture-curing reactive hot melt adhesives." Reactive hot melt adhesives containing urethane prepolymers as their primary component exhibit good adhesive strength even when heated. Reactive hot melt adhesive compositions containing urethane prepolymers, thermoplastic resins, and tackifiers are also known to improve initial and post-cure adhesive strength (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-122860 [Patent Document 2] Japanese Patent Application Publication No. 64-054089 [Patent Document 3] Japanese Patent Publication No. 52-037936 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, as wearable devices have become smaller, the adhesive surface area between parts has tended to become smaller. To prevent damage to such parts, the adhesive layer formed from reactive hot melt adhesives must have high impact resistance.

[0006] Therefore, a main object of the present invention is to provide a reactive hot melt adhesive composition that can form an adhesive layer having high impact resistance. [Means for solving the problem]

[0007] One aspect of the present invention relates to a reactive hot melt adhesive composition. The reactive hot melt adhesive composition contains a urethane prepolymer having a polymer chain with structural units derived from a polyol, including a polyester polyol, and structural units derived from a polyisocyanate, with an isocyanate group as the terminal group of the polymer chain. The polyester polyol is a polyester polyol having structural units derived from an aliphatic dicarboxylic acid and structural units derived from an aliphatic dihydric alcohol, and includes a polyester polyol having a tertiary or quaternary carbon atom in the molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic dihydric alcohol. Here, the aliphatic dicarboxylic acid refers to a compound in which two carboxyl groups are linked by an aliphatic chain (a saturated aliphatic chain (alkylene chain) or an unsaturated aliphatic chain (alkenylene chain), preferably a saturated aliphatic chain (alkylene chain)). The aliphatic dihydric alcohol refers to a compound in which two hydroxyl groups are linked by an aliphatic chain (a saturated aliphatic chain (alkylene chain) or an unsaturated aliphatic chain (alkenylene chain), preferably a saturated aliphatic chain (alkylene chain)). A tertiary carbon atom refers to a carbon atom bonded to three carbon atoms, and a quaternary carbon atom refers to a carbon atom bonded to four carbon atoms. The tertiary or quaternary carbon atom is present in the aliphatic chain of an aliphatic dicarboxylic acid or the aliphatic chain of an aliphatic dihydric alcohol. That is, the presence of a tertiary or quaternary carbon atom in a molecule means that the aliphatic chain has a branched structure and a side chain. Such a reactive hot melt adhesive composition makes it possible to form an adhesive layer with high impact resistance. The reason for this is not entirely clear, but the present inventors believe that it is because, for example, the presence of a side chain portion disrupts the crystalline structure, resulting in flexibility and, as a result, easier impact absorption.

[0008] Among the aliphatic dihydric alcohols and aliphatic dicarboxylic acids, aliphatic dihydric alcohols having a tertiary carbon atom or a quaternary carbon atom in the molecule are preferred because of the ease of availability of raw materials.

[0009] Another aspect of the present invention relates to an adhesive structure comprising a first adherend, a second adherend, and an adhesive layer that bonds the first adherend and the second adherend to each other. The adhesive layer contains a cured product of the reactive hot melt adhesive composition described above.

[0010] Another aspect of the present invention relates to a method for producing an adhesive structure, which includes the steps of melting the reactive hot melt adhesive composition and applying it to a first adherend to form an adhesive layer, placing a second adherend on the adhesive layer and pressing the second adherend to obtain an adhesive structure precursor, and curing the adhesive layer in the adhesive structure precursor. [Effects of the Invention]

[0011] The present invention provides a reactive hot melt adhesive composition capable of forming an adhesive layer having high impact resistance. The present invention also provides an adherend using such a reactive hot melt adhesive composition and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0013] In this specification, the term "polyol" refers to a compound having two or more hydroxyl groups in the molecule.

[0014] In this specification, the term "polyisocyanate" refers to a compound having two or more isocyanate groups in the molecule.

[0015] In this specification, a numerical range indicated with "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range. In numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. In this specification, the content of each component in a composition means the total amount of multiple substances present in the composition if multiple substances corresponding to each component are present in the composition, unless otherwise specified.

[0016] [Reactive hot melt adhesive composition] The reactive hot melt adhesive composition (hereinafter sometimes simply referred to as "adhesive composition") of one embodiment contains a urethane prepolymer. Generally, reactive hot melt adhesive compositions are moisture-curing compositions in which the urethane prepolymer undergoes a high molecular weight reaction upon reaction with moisture in the air or on the surface of an adherend, thereby enabling the adhesive strength and other properties to be exhibited.

[0017] The urethane prepolymer contains a polymer chain containing a structural unit derived from a polyol, including a polyester polyol, and a structural unit derived from a polyisocyanate, and has an isocyanate group as a terminal group of the polymer chain. The polyester polyol contains a specific polyester polyol, as described below. That is, the urethane prepolymer of this embodiment is a reaction product of a polyol, including a polyester polyol (a specific polyester polyol, as described below), and a polyisocyanate, and has an isocyanate group as a terminal group of the reaction product. By containing such a urethane prepolymer, the adhesive composition of this embodiment can exhibit excellent adhesive strength after moisture curing, making it possible to form an adhesive layer with high impact resistance.

[0018] <Urethane prepolymer> (Polyol (A)) The polyol (A) that provides the polyol-derived structural units includes a polyester polyol (A1) that provides the polyester polyol-derived structural units. The polyol (A) may be composed of the polyester polyol (A1) and a polyol (A2) other than the polyester polyol (A1). The polyester polyol (A1) is a polyester polyol having structural units derived from an aliphatic dicarboxylic acid and structural units derived from an aliphatic dihydric alcohol, and may be composed of a polyester polyol (A1a) having a tertiary or quaternary carbon atom in the molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic dihydric alcohol, and a polyester polyol (A1b) other than the polyester polyol (A1a). The content of each structural unit corresponds to the amount of each polyol that provides the corresponding structural unit. In other words, the content of each structural unit can be adjusted by adjusting the amount of each polyol that provides the corresponding structural unit.

[0019] In the following, the polyester polyol (A1) will first be described in general, followed by a description of the polyester polyol (A1a) and the polyester polyol (A1b) other than the polyester polyol (A1a) contained in the polyester polyol (A1).

[0020] The polymer chain contains a structural unit derived from a polyester polyol, which allows adjustment of the solidification time and viscosity of the adhesive composition. The polyester polyol (A1) that provides the structural unit derived from the polyester polyol can be a compound produced by a polycondensation reaction between a polyhydric alcohol and a polycarboxylic acid. The polyester polyol (A1) may be, for example, a polycondensate of a polyhydric alcohol having 2 to 15 carbon atoms and 2 or 3 hydroxyl groups with a polycarboxylic acid having 2 to 14 carbon atoms (including the carbon atoms in the carboxy groups) and 2 to 6 carboxy groups. The polyester polyol (A1) may be used singly or in combination of two or more.

[0021] The polyester polyol (A1) may be a linear polyester diol produced from a dihydric alcohol and a dicarboxylic acid, or a branched polyester triol produced from a trihydric alcohol and a dicarboxylic acid. The branched polyester triol can also be obtained by reacting a dihydric alcohol with a tricarboxylic acid.

[0022] Examples of polyhydric alcohols include aliphatic polyhydric alcohols or alicyclic polyhydric alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, isomers of butanediol, isomers of pentanediol, isomers of hexanediol, neopentyl glycol (2,2-dimethyl-1,3-propanediol), 3,3-dimethylpentane-1,5-diol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4,4-trimethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; and aromatic polyhydric alcohols such as 4,4'-dihydroxydiphenylpropane, bisphenol A, bisphenol F, pyrocatechol, resorcinol, and hydroquinone. The polyhydric alcohols may be used alone or in combination of two or more.

[0023] 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, suberic 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.

[0024] Instead of the above polycarboxylic acids, polycarboxylic acid derivatives such as carboxylic acid anhydrides and compounds in which a portion of the carboxyl group is esterified can also be used. Examples of polycarboxylic acid derivatives include dodecyl maleic acid and octadecenyl maleic acid.

[0025] The polyester polyol (A1) may be a crystalline polyester polyol or an amorphous polyester polyol. Here, the crystalline and amorphous nature can be determined based on the state at 25°C. In this specification, the crystalline polyester polyol refers to a polyester polyol that is crystalline at 25°C, and the amorphous polyester polyol refers to a polyester polyol that is amorphous at 25°C.

[0026] From the viewpoint of improving waterproofness and adhesive strength, the number average molecular weight (Mn) of the polyester polyol (A1) may be 500 to 12,000, 800 to 10,000, or 1,000 to 9,000. In this specification, the number average molecular weight is a value measured by gel permeation chromatography (GPC) and converted into a standard polystyrene equivalent. GPC measurement can be performed under the following conditions. Columns: "Gelpack GLA130-S," "Gelpack GLA150-S," and "Gelpack GLA160-S" (Hitachi Chemical Co., Ltd., HPLC packed columns) Eluent: tetrahydrofuran Flow rate: 1.0mL / min Column temperature: 40℃ Detector: RI

[0027] From the viewpoint of further improving adhesive strength, the content of the structural units derived from the polyester polyol (A1) may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, and may be 100% by mass or less, 95% by mass or less, or 90% by mass or less, based on the total amount of the structural units derived from the polyol (A). The structural units derived from the polyol (A) may consist of structural units derived from the polyester polyol (A1).

[0028] Next, polyester polyol (A1a) and polyester polyol (A1b) other than polyester polyol (A1a) included in polyester polyol (A1) will be described. Polyester polyol (A1a) is a polyester polyol having structural units derived from an aliphatic dicarboxylic acid and structural units derived from an aliphatic dihydric alcohol, and at least one of the aliphatic dicarboxylic acid and the aliphatic dihydric alcohol has a tertiary or quaternary carbon atom in the molecule. Here, aliphatic dicarboxylic acid refers to a compound in which two carboxy groups are linked by an aliphatic chain (a saturated aliphatic chain (alkylene chain) or an unsaturated aliphatic chain (alkenylene chain), preferably a saturated aliphatic chain (alkylene chain)), and aliphatic dihydric alcohol refers to a compound in which two hydroxyl groups are linked by an aliphatic chain (a saturated aliphatic chain (alkylene chain) or an unsaturated aliphatic chain (alkenylene chain), preferably a saturated aliphatic chain (alkylene chain)). A tertiary carbon atom means a carbon atom bonded to three carbon atoms, and a quaternary carbon atom means a carbon atom bonded to four carbon atoms. The tertiary carbon atom or quaternary carbon atom is present in the aliphatic chain of an aliphatic dicarboxylic acid or an aliphatic chain of an aliphatic dihydric alcohol. In other words, the presence of a tertiary carbon atom or a quaternary carbon atom in a molecule means that the aliphatic chain has a branched structure and a side chain. In other words, the polyester polyol (A1a) has a branched structure in the aliphatic chain and a side chain. The side chain may be a saturated aliphatic group (alkyl group) or an unsaturated aliphatic group (alkenyl group), or may be a saturated aliphatic group (alkyl group). The polyester polyol (A1a) may be a crystalline polyester polyol or an amorphous polyester polyol. One type of polyester polyol (A1a) may be used alone, or two or more types may be used in combination.

[0029] Among the aliphatic dihydric alcohols and aliphatic dicarboxylic acids, it is preferable that the aliphatic dihydric alcohol has a tertiary carbon atom or a quaternary carbon atom in the molecule, from the viewpoint of easy availability of raw materials.

[0030] Examples of aliphatic dicarboxylic acids that provide structural units derived from aliphatic dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, as well as dimer acids such as linoleic acid.

[0031] Examples of aliphatic dihydric alcohols that provide structural units derived from aliphatic dihydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, each isomer of butanediol (butanediols having a linear or branched structure), each isomer of pentanediol (pentanediols having a linear or branched structure), each isomer of hexanediol (hexanediols having a linear or branched structure), neopentyl glycol (2,2-dimethyl-1,3-propanediol), 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4,4-trimethyl-1,6-hexanediol, and 2,2,4-trimethyl-1,6-hexanediol.

[0032] Examples of aliphatic dihydric alcohols having a tertiary carbon atom in the molecule include 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,2-hexanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. Examples of aliphatic dihydric alcohols having a quaternary carbon atom in the molecule include neopentyl glycol (2,2-dimethyl-1,3-propanediol) and 3,3-dimethylpentane-1,5-diol. Examples of aliphatic dihydric alcohols having a tertiary carbon atom and a quaternary carbon atom in the molecule include 2,4,4-trimethyl-1,6-hexanediol and 2,2,4-trimethyl-1,6-hexanediol.

[0033] The aliphatic dihydric alcohol having a tertiary carbon atom or a quaternary carbon atom in the molecule is easily available as a raw material and has superior impact resistance, and therefore may be an aliphatic dihydric alcohol having a tertiary carbon atom in the molecule or an aliphatic dihydric alcohol having a quaternary carbon atom in the molecule, or may be neopentyl glycol (2,2-dimethyl-1,3-propanediol) or 3-methyl-1,5-pentanediol.

[0034] The content of the structural units derived from the polyester polyol (A1a) may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total amount of structural units derived from the polyester polyol (A1), since this provides better impact resistance, and may be 100% by mass or less, 97% by mass or less, 95% by mass or less, or 90% by mass or less.

[0035] The polyester polyol (A1) may contain, in addition to the polyester polyol (A1a), a polyester polyol (A1b) other than the polyester polyol (A1a). The polyester polyol (A1b) may be used alone or in combination of two or more.

[0036] The content of the structural units derived from the polyester polyol (A1b) may be 0% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total amount of structural units derived from the polyester polyol (A1), since this provides better impact resistance, and may be 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0037] When the structural units derived from the polyol (A) are composed only of structural units derived from the polyester polyol (A1), the contents of the structural units derived from the polyester polyol (A1a) and the structural units derived from the polyester polyol (A1b) may be determined by replacing the standard of "the total amount of structural units derived from the polyester polyol (A1)" with the standard of "the total amount of structural units derived from the polyol (A)."

[0038] The polyol (A) may contain, in addition to the polyester polyol (A1), a polyol (A2) other than the polyester polyol (A1). Examples of the polyol (A2) include polyether polyols, polyether ester polyols, polyurethane polyols, polycarbonate polyols, and polyolefin polyols. One of these polyols may be used alone, or two or more of them may be used in combination.

[0039] The content of structural units derived from polyol (A2) may be 0% by mass or more, 5% by mass or more, or 10% by mass or more, and may be 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total amount of structural units derived from polyol (A).

[0040] (Polyisocyanate (B)) The polyisocyanate (B) that provides the polyisocyanate-derived structural unit can be any compound having two or more isocyanate groups without any particular limitation. The polyisocyanate (B) may be, for example, a compound having two isocyanate groups (diisocyanate). Examples of polyisocyanates 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 viewpoints of reactivity and adhesiveness, the polyisocyanate (B) may contain an aromatic diisocyanate, and among aromatic diisocyanates, it may contain diphenylmethane diisocyanate. The polyisocyanate (B) may be used singly or in combination of two or more kinds.

[0041] The urethane prepolymer can be synthesized by reacting a polyol (A) with a polyisocyanate (B), where the polyol contains a polyester polyol (A1a).

[0042] The urethane prepolymer contains a polymer chain containing a structural unit derived from a polyol and a structural unit derived from a polyisocyanate, and has an isocyanate group as a terminal group of the polymer chain. When synthesizing such a urethane prepolymer, the ratio of the isocyanate group (NCO) equivalent of the polyisocyanate (B) to the hydroxyl group (OH) equivalent of the polyol (A) (the isocyanate group (NCO) equivalent of the polyisocyanate (B) / the hydroxyl group (OH) equivalent of the polyol (A) (NCO / OH)) is greater than 1, and may be 1.3 to 3.0 or 1.5 to 2.0. An NCO / OH ratio of 1.3 or greater tends to prevent the viscosity of the resulting urethane prepolymer from becoming too high, and to facilitate improved workability. An NCO / OH ratio of 3.0 or less tends to prevent foaming during the moisture curing reaction of the adhesive composition, and to facilitate preventing a decrease in adhesive strength.

[0043] The content of the urethane prepolymer may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of the adhesive composition. The upper limit of the content of the urethane prepolymer may be 100% by mass, based on the total amount of the adhesive composition. The adhesive composition may be composed solely of the urethane prepolymer.

[0044] The adhesive composition may further contain a catalyst to accelerate the curing of the urethane prepolymer and to achieve higher adhesive strength, such as dibutyltin dilaurate, dibutyltin dioctate, dimethylcyclohexylamine, dimethylbenzylamine, or trioctylamine.

[0045] The adhesive composition may further contain a thermoplastic polymer from the viewpoint of increasing the rubber elasticity of the adhesive layer formed and further improving impact resistance. Examples of the thermoplastic polymer include polyurethane, ethylene copolymer, propylene copolymer, vinyl chloride copolymer, acrylic copolymer, and styrene-conjugated diene block copolymer.

[0046] The adhesive composition may further contain a tackifying resin from the viewpoint of imparting stronger adhesiveness to the adhesive layer to be formed. Examples of tackifying resins include rosin resins, rosin ester resins, hydrogenated rosin ester resins, terpene resins, terpene phenol resins, hydrogenated terpene resins, petroleum resins, hydrogenated petroleum resins, coumarone resins, ketone resins, styrene resins, modified styrene resins, xylene resins, and epoxy resins.

[0047] The adhesive composition may contain appropriate amounts of antioxidants, pigments, ultraviolet absorbers, surfactants, flame retardants, fillers, etc., as needed.

[0048] The content of components other than the urethane prepolymer may be 0 to 30 mass %, 0 to 20 mass %, 0 to 10 mass %, or 0 to 5 mass % based on the total amount of the adhesive composition.

[0049] The adhesive composition cures as the isocyanate groups of the urethane prepolymer contained in the adhesive composition react with moisture in the air or moisture on the surface of the substrate, resulting in a high molecular weight. The adhesive composition can be cured, for example, by aging at a temperature of 23°C and a humidity of 50% (relative humidity) for 24 hours or more. By curing under these conditions, a cured product of the adhesive composition can be formed.

[0050] The method for producing the adhesive composition may include a step of reacting a polyol (A) with a polyisocyanate (B) to obtain a urethane prepolymer. The reaction temperature of the polyol (A) with the polyisocyanate (B) may be, for example, 85 to 120° C. In addition, during the mixing, degassing under reduced pressure may be performed.

[0051] The melt viscosity of the adhesive composition at 120°C measured using a rotational viscometer may be 30 Pa·s or less, or may be 25 Pa·s or less, from the viewpoint of improving coatability. The lower limit of the melt viscosity at 120°C is not particularly limited, but may be, for example, 1 Pa·s or more. In this specification, the melt viscosity of the adhesive composition at 120°C refers to the value measured by the method described in the examples.

[0052] The adhesive composition of this embodiment makes it possible to form an adhesive layer having high impact resistance. Furthermore, since the adhesive composition of this embodiment is a solvent-free adhesive, it places less strain on the environment and the human body and allows for short-term bonding. Furthermore, since the adhesive composition of this embodiment is a one-component adhesive, it is easy to handle.

[0053] The adhesive composition of the present embodiment can bond various adherends via an adhesive layer containing a cured product of the adhesive composition, such as metal substrates (e.g., stainless steel, aluminum, etc.) and non-metal substrates (e.g., polycarbonate, polyamide, polyetherimide, glass, etc.).

[0054] [Adhesive body and its manufacturing method] An adhesive structure according to one embodiment includes a first adherend, a second adherend, and an adhesive layer that bonds the first adherend and the second adherend together. The adhesive layer contains a cured product of the reactive hot melt adhesive composition. Examples of adhesive structures according to this embodiment include semiconductor devices, seamless clothing, and electronic devices.

[0055] Examples of the first adherend and the second adherend can be the same as those exemplified above as the adherends.

[0056] The adhesive of this embodiment can be produced by a method comprising the steps of melting the reactive hot melt adhesive composition and applying it to a first adherend to form an adhesive layer, placing a second adherend on the adhesive layer and pressing the second adherend to obtain an adhesive precursor, and curing the adhesive layer in the adhesive precursor.

[0057] The temperature at which the adhesive composition is melted may be, for example, 80 to 180° C. The method for applying the adhesive composition to the first adherend is not particularly limited, and known methods can be applied as appropriate.

[0058] The second adherend may be pressure-bonded, for example, by using a pressure roll or the like.

[0059] The conditions for curing the adhesive layer in the adhesive precursor may be the same as the curing conditions for the adhesive composition described above. [Example]

[0060] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0061] (Examples 1 to 5 and Comparative Examples 1 to 3) The polyol (A), which had been previously dehydrated, was added to the reaction vessel in the amount shown in Table 1 and mixed uniformly. Next, the polyisocyanate (B) was further added to the reaction vessel in the amount shown in Table 1 and mixed uniformly, followed by reaction at 110°C for 1 hour. The mixture was further stirred at 110°C for 1 hour under reduced pressure and degassed, yielding adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 3, each containing a urethane prepolymer having an isocyanate group. The amounts in Table 1 are expressed in parts by mass.

[0062] <Polyol (A)> Polyester polyol (A1) (A1a-1): Amorphous polyester polyol (number of hydroxyl groups: 2, Mn: 2000) which is a reaction product of adipic acid (aliphatic dicarboxylic acid) and neopentyl glycol (aliphatic dihydric alcohol having a quaternary carbon atom in the molecule). (A1a-2): Amorphous polyester polyol (number of hydroxyl groups: 2, Mn: 5000) which is a reaction product of adipic acid (aliphatic dicarboxylic acid) and neopentyl glycol (aliphatic dihydric alcohol having a quaternary carbon atom in the molecule). (A1b-1): A crystalline polyester polyol (number of hydroxyl groups: 2, Mn: 5000) which is a reaction product of sebacic acid (aliphatic dicarboxylic acid) and 1,6-hexanediol (aliphatic dihydric alcohol). (A1b-2): A crystalline polyester polyol (number of hydroxyl groups: 2, Mn: 5000) which is a reaction product of adipic acid (aliphatic dicarboxylic acid) and 1,6-hexanediol (aliphatic dihydric alcohol). (A1b-3): Amorphous polyester polyol (number of hydroxyl groups: 2, Mn: 2000) which is a reaction product of isophthalic acid (aromatic carboxylic acid) and neopentyl glycol (aliphatic dihydric alcohol having a quaternary carbon atom in the molecule).

[0063] <Polyisocyanate (B)> (B-1): Diphenylmethane diisocyanate (number of isocyanate groups: 2)

[0064] The properties of the adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Table 1.

[0065] (Melt viscosity measurement) The melt viscosity of the adhesive composition (sample amount: 15 g) was measured at 120° C. with a No. 4 rotor using a TVB-25H viscometer (manufactured by Toki Sangyo Co., Ltd.) at a rotor rotation speed of 50 rpm.

[0066] (Evaluation of impact absorption) The adhesive composition was melted at 100°C to form a film with a thickness of 0.15 mm. The resulting film was left to cure for 24 hours at 23°C and 50% relative humidity to obtain a cured film. Impact absorption was evaluated using a digital accelerometer 1340A-01H (manufactured by Showa Sokki Co., Ltd.). A dropping jig was fixed on the cured film, and a dropping object was dropped from above the cured film to measure the impact acceleration of the dropping object. The dropping height of the dropping object was set to 2000 m / s when the impact acceleration without the cured film was 2000 m / s. 2 (200×10 m / s 2 The smaller the impact acceleration value, the better the cured film absorbs the impact, and therefore the better the impact absorption properties.

[0067] [Table 1]

[0068] As shown in Table 1, the impact acceleration values ​​of the reactive hot melt adhesive compositions of Examples 1 to 5 were smaller than the impact acceleration values ​​of the reactive hot melt adhesive compositions of Comparative Examples 1 to 3. These results confirmed that the reactive hot melt adhesive composition of the present invention can form an adhesive layer having high impact resistance.

Claims

1. The composition contains a urethane prepolymer containing a polymer chain having a structural unit derived from a polyol (A) containing a polyester polyol (A1) and a structural unit derived from a polyisocyanate, the polymer chain having an isocyanate group as a terminal group, the polyester polyol (A1) is a polyester polyol having a structural unit derived from an aliphatic dicarboxylic acid and a structural unit derived from an aliphatic dihydric alcohol, and includes a polyester polyol (A1a) having a tertiary carbon atom or a quaternary carbon atom in the molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic dihydric alcohol; the content of structural units derived from the polyester polyol (A1a) is 50 mass% or more based on the total amount of structural units derived from the polyol (A); Reactive hot melt adhesive compositions.

2. The aliphatic dihydric alcohol has a tertiary carbon atom or a quaternary carbon atom in the molecule. The reactive hot melt adhesive composition of claim 1.

3. a first adherend; and a second adherend; and an adhesive layer that bonds the first adherend and the second adherend to each other; Equipped with The adhesive layer contains a cured product of the reactive hot melt adhesive composition according to claim 1 or 2. Adhesive body.

4. a step of melting the reactive hot melt adhesive composition according to claim 1 or 2 and applying it to a first adherend to form an adhesive layer; a step of placing a second adherend on the adhesive layer and pressing the second adherend to obtain an adhesive precursor; curing the adhesive layer in the adhesive precursor; Equipped with Method for manufacturing an adhesive body.

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