Reactive hot melt adhesive composition and bonded body and method of manufacturing the same

Abstract

Disclosed is a reactive hot melt adhesive composition. The reactive hot melt adhesive composition contains a polyurethane prepolymer, the polyurethane prepolymer containing a polymer chain and having an isocyanate group as a terminal group of the polymer chain, the polymer chain having a structural unit from a polyol containing a polyester polyol and a structural unit from a polyisocyanate. The polyester polyol has a structural unit from an aliphatic dicarboxylic acid and a structural unit from an aliphatic diol, and has a tertiary carbon atom or a quaternary carbon atom within the molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic diol.

Description

Technical Field

[0001] This invention relates to a reactive hot melt adhesive composition, an adhesive, and a method for manufacturing the same. Background Technology

[0002] Because hot melt adhesives are solvent-free, they have low environmental and health impacts and can bond quickly, making them suitable for improving productivity. Hot melt adhesives can be broadly classified into two types: those primarily composed of thermoplastic resins and those primarily composed of reactive resins. As reactive resins, polyurethane prepolymers with isocyanate groups at the ends are primarily utilized.

[0003] Reactive hot melt adhesives, primarily composed of polyurethane prepolymers, exhibit a certain degree of adhesive strength within a short period after application and upon cooling and curing. Subsequently, the terminal isocyanate groups of the polyurethane prepolymer are reacted with moisture (in the air or on the surface of the adherends) to increase its molecular weight, and heat resistance is achieved through crosslinking. This type of adhesive is also known as a "moisture-curing reactive hot melt adhesive." Reactive hot melt adhesives primarily composed of polyurethane prepolymers exhibit good adhesive strength even when heated. Furthermore, a reactive hot melt adhesive composition is known to improve initial and cured adhesive strength, comprising a polyurethane prepolymer, a thermoplastic resin, and a tackifier (see, for example, Patent Documents 1-3).

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 06-122860

[0007] Patent Document 2: Japanese Patent Application Publication No. 64-054089

[0008] Patent Document 3: Japanese Patent Application Publication No. 52-037936 Summary of the Invention

[0009] The technical problem to be solved by the invention

[0010] In recent years, with the miniaturization of wearable devices, the area of ​​the adhesive portions between components has become narrower. To prevent damage to these components, the adhesive layer formed by reactive hot melt adhesives is required to have high impact resistance.

[0011] Therefore, the main objective of this invention is to provide a reactive hot melt adhesive composition capable of forming an adhesive layer with high impact resistance.

[0012] means for solving technical problems

[0013] One aspect of the present invention relates to a reactive hot melt adhesive composition. This reactive hot melt adhesive composition contains a polyurethane prepolymer comprising polymer chains and having isocyanate groups as terminal groups of the polymer chains. The polymer chains have structural units derived from a polyol comprising a polyester polyol and structural units derived from polyisocyanates. The polyester polyol has structural units derived from aliphatic dicarboxylic acids and structural units derived from aliphatic diols, and has a tertiary carbon atom or a quaternary carbon atom within the molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic diol. The aliphatic dicarboxylic acid represents a compound consisting of two carboxyl groups linked by an aliphatic chain (saturated aliphatic chain (alkylene chain) or unsaturated aliphatic chain (olefin chain), preferably a saturated aliphatic chain (alkylene chain)), and the aliphatic diol represents a compound consisting of two hydroxyl groups linked by an aliphatic chain (saturated aliphatic chain (alkylene chain) or unsaturated aliphatic chain (olefin chain), preferably a saturated aliphatic chain (alkylene chain)). A tertiary carbon atom represents a carbon atom bonded to three carbon atoms, and a quaternary carbon atom represents a carbon atom bonded to four carbon atoms. Tertiary or quaternary carbon atoms are present on the aliphatic chains of aliphatic dicarboxylic acids or aliphatic diols. That is, the presence of tertiary or quaternary carbon atoms within the molecule indicates a branched structure and side chains on the aliphatic chain. According to this reactive hot-melt adhesive composition, an adhesive layer with high impact resistance can be formed. The reason for this is not necessarily clear, but the inventors believe it is because, for example, the crystal structure breaks down due to the presence of side chain portions, exhibiting flexibility, and as a result, readily absorbing impact.

[0014] In aliphatic diols and aliphatic dicarboxylic acids, from the viewpoint of the availability of raw materials, aliphatic diols with tertiary carbon atoms or quaternary carbon atoms in the molecule are preferred.

[0015] Another aspect of the present invention relates to an adhesive. The adhesive comprises a first adherend, a second adherend, and an adhesive layer for bonding the first and second adherends together. The adhesive layer contains a cured product of the aforementioned reactive hot-melt adhesive composition.

[0016] Another aspect of the present invention relates to a method for manufacturing an adhesive. The method comprises: a step of melting the aforementioned reactive hot-melt adhesive composition and applying it onto a first substrate to form an adhesive layer; a step of disposing a second substrate on the adhesive layer and obtaining an adhesive precursor by pressing the second substrate together; and a step of curing the adhesive layer in the adhesive precursor.

[0017] Invention Effects

[0018] According to the present invention, a reactive hot melt adhesive composition capable of forming an adhesive layer with high impact resistance is provided. Furthermore, according to the present invention, an adhesive using this reactive hot melt adhesive composition and a method for manufacturing the same are provided. Detailed Implementation

[0019] The following describes in detail the methods for implementing the present invention. However, the present invention is not limited to the following embodiments.

[0020] In this specification, "polyol" refers to a compound having two or more hydroxyl groups in its molecule.

[0021] In this specification, "polyisocyanate" refers to a compound having two or more isocyanate groups in its molecule.

[0022] In this specification, the numerical range indicated by "~" represents the range in which the values ​​described before and after "~" are respectively the minimum and maximum values. Within the numerical range described in stages in this specification, the upper or lower limit of the numerical range for a certain stage can be replaced by the upper or lower limit of the numerical range for other stages. Within the numerical range described in this specification, the upper or lower limit of the numerical range can be replaced by the values ​​shown in the embodiments. "A or B" can include either A or B, or both. Unless otherwise stated, the materials illustrated in this specification can be used alone or in combination of two or more. In this specification, when multiple substances corresponding to each component are present in the composition, unless otherwise stated, the content of each component in the composition represents the total amount of the multiple substances present in the composition.

[0023] [Reactive hot melt adhesive composition]

[0024] One embodiment of the reactive hot melt adhesive composition (hereinafter, sometimes simply referred to as "adhesive composition") contains a polyurethane prepolymer. Furthermore, the reactive hot melt adhesive composition is typically a moisture-curing compound that primarily increases the molecular weight of the polyurethane prepolymer through reaction with moisture in the air or on the surface of the adherends, thereby exhibiting adhesive strength and other properties.

[0025] The polyurethane prepolymer comprises polymer chains and has isocyanate groups as terminal groups of the polymer chains. The polymer chains have structural units derived from a polyol comprising a polyester polyol and structural units derived from polyisocyanate. The polyester polyol comprises the polyester polyol specified later. That is, the polyurethane prepolymer of this embodiment is a reaction product of a polyol comprising a polyester polyol (specified later) and a polyisocyanate, and has isocyanate groups as terminal groups of the reaction product. The adhesive composition of this embodiment, by containing this polyurethane prepolymer, can exhibit excellent adhesive strength after moisture curing, thereby enabling the formation of an adhesive layer with high impact resistance.

[0026] <Polyurethane prepolymer>

[0027] (Polyol (A))

[0028] The polyol (A) providing structural units from polyols includes a polyester polyol (A1) providing structural units from polyester polyols. Polyol (A) can be composed of polyester polyol (A1) and polyols (A2) other than polyester polyol (A1). Polyester polyol (A1) has structural units derived from aliphatic dicarboxylic acids and structural units derived from aliphatic diols, and can be composed of polyester polyols (A1a) having tertiary or quaternary carbon atoms within the molecule of at least one of the aliphatic dicarboxylic acids and aliphatic diols, and polyester polyols (A1b) other than polyester polyol (A1a). Furthermore, the content of each structural unit corresponds to the amount of each polyol providing each structural unit added. That is, adjustments to the content of each structural unit can be made by adjusting the amount of each polyol providing each structural unit added.

[0029] The following sections will first describe polyester polyol (A1) as a whole, and then describe polyester polyol (A1a) included in polyester polyol (A1) and polyester polyol (A1b) other than polyester polyol (A1a).

[0030] The curing time and viscosity of an adhesive composition can be adjusted by incorporating structural units derived from polyester polyols into the polymer chain. Regarding the polyester polyol (A1) providing structural units derived from polyester polyols, compounds generated through the polycondensation reaction of a polyol and a polycarboxylic acid can be used. For example, the polyester polyol (A1) can be a polyol 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. One polyester polyol (A1) can be used alone, or two or more can be used in combination.

[0031] Polyester polyols (A1) can be linear polyester diols formed from diols and dicarboxylic acids, or branched polyester triols formed from triols and dicarboxylic acids. Furthermore, branched polyester triols can also be obtained through the reaction of diols with tricarboxylic acids.

[0032] Examples of polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, various isomers of butanediol, various isomers of pentanediol, various isomers of hexanediol, neopentanediol (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-cyclohexanediethanol, as well as aliphatic or alicyclic polyols; and aromatic polyols such as 4,4'-dihydroxydiphenylpropane, bisphenol A, bisphenol F, catechol, resorcinol, and hydroquinone. A single polyol can be used, or two or more can be used in combination.

[0033] Examples of polycarboxylic acids include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and 1,2,4-benzenetricarboxylic acid; aliphatic or alicyclic polycarboxylic acids such as maleic acid, fumaric acid, arbutinic acid, 1,2,3-propanetricarboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, cyclohexane-1,2-dicarboxylic acid, and 1,4-cyclohexadiene-1,2-dicarboxylic acid. A polycarboxylic acid can be used alone or in combination of two or more.

[0034] Alternatively, polycarboxylic acid derivatives, such as carboxylic anhydrides or compounds obtained by esterification of a portion of the carboxyl group, can be used instead of the aforementioned polycarboxylic acids. Examples of polycarboxylic acid derivatives include dodecyl maleic acid and octadecenyl maleic acid.

[0035] Polyester polyols (A1) can be either crystalline or amorphous. The determination of crystalline or amorphous properties can be made at 25°C. In this specification, crystalline polyester polyol refers to polyester polyol that is crystalline at 25°C, and amorphous polyester polyol refers to polyester polyol that is amorphous at 25°C.

[0036] From the viewpoint of improving water resistance and adhesive strength, the number-average molecular weight (Mn) of the polyester polyol (Al) can be 500–12000, 800–10000, or 1000–9000. Furthermore, in this specification, the number-average molecular weight is a value obtained by gel permeation chromatography (GPC) and conversion to standard polystyrene. GPC determination can be performed under the following conditions.

[0037] Columns: “Gelpack GLA130-S”, “Gelpack GLA150-S” and “Gelpack GLA160-S” (Hitachi Chemical Co., Ltd., HPLC packed columns)

[0038] Eluent: Tetrahydrofuran

[0039] Flow rate: 1.0 mL / min

[0040] Column temperature: 40℃

[0041] Detector: RI

[0042] From the perspective of further improving adhesive strength, the content of structural units derived from polyester polyol (A1) can be 50% or more, 60% or more, 70% or more, or 80% or more, based on the total amount of structural units derived from polyol (A), or it can be less than 100% or less, 95% or less, or 90% or less. The structural units derived from polyol (A) can be formed from structural units derived from polyester polyol (A1).

[0043] Next, the polyester polyol (A1a) included in polyester polyol (A1) and the polyester polyol (A1b) other than polyester polyol (A1a) will be described. Polyester polyol (A1a) has structural units derived from aliphatic dicarboxylic acids and structural units derived from aliphatic diols, and has a tertiary carbon atom or a quaternary carbon atom within the molecule of at least one of the aliphatic dicarboxylic acid and aliphatic diol. Specifically, an aliphatic dicarboxylic acid is a compound in which two carboxyl groups are linked by an aliphatic chain (saturated aliphatic chain (alkylene chain) or unsaturated aliphatic chain (alkenyl chain), preferably a saturated aliphatic chain (alkylene chain)), and an aliphatic diol is a compound in which two hydroxyl groups are linked by an aliphatic chain (saturated aliphatic chain (alkylene chain) or unsaturated aliphatic chain (alkenyl chain), preferably a saturated aliphatic chain (alkylene chain)). A tertiary carbon atom is a carbon atom bonded to three carbon atoms, and a quaternary carbon atom is a carbon atom bonded to four carbon atoms. Tertiary or quaternary carbon atoms are present on the aliphatic chain of aliphatic dicarboxylic acids or the aliphatic chain of aliphatic diols. That is, the presence of tertiary or quaternary carbon atoms within the molecule indicates a branched structure and side chains on the aliphatic chain. Specifically, polyester polyol (A1a) has a branched structure and side chains on its aliphatic chain. The side chains can be saturated aliphatic groups (alkyl) or unsaturated aliphatic groups (alkenyl), or saturated aliphatic groups (alkyl). Polyester polyol (A1a) can be crystalline or amorphous. Polyester polyol (A1a) can be used alone or in combination of two or more types.

[0044] In aliphatic diols and aliphatic dicarboxylic acids, from the viewpoint of the availability of raw materials, aliphatic diols with tertiary carbon atoms or quaternary carbon atoms in the molecule are preferred.

[0045] 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, octanoic acid, azelaic acid, sebacic acid, and dimer acids such as linoleic acid.

[0046] Examples of aliphatic diols that provide structural units derived from aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, various isomers of butanediol (butanediol with a straight-chain or branched structure), various isomers of pentanediol (pentanediol with a straight-chain or branched structure), various isomers of hexanediol (hexanediol with a straight-chain or branched structure), neopentanediol (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.

[0047] Examples of aliphatic diols that have a tertiary carbon atom in their 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 diols that have a quaternary carbon atom in their molecule include neopentanediol (2,2-dimethyl-1,3-propanediol) and 3,3-dimethylpentane-1,5-diol. Examples of aliphatic diols that have both tertiary and quaternary carbon atoms in their molecule include 2,4,4-trimethyl-1,6-hexanediol and 2,2,4-trimethyl-1,6-hexanediol.

[0048] From the perspective of readily available raw materials and superior impact resistance, aliphatic diols with tertiary or quaternary carbon atoms in the molecule can be aliphatic diols with tertiary carbon atoms in the molecule or aliphatic diols with quaternary carbon atoms in the molecule, or neopentyl glycol (2,2-dimethyl-1,3-propanediol) or 3-methyl-1,5-pentanediol.

[0049] From the perspective of superior impact resistance, the content of structural units derived from polyester polyol (A1a) can be based on the total amount of structural units derived from polyester polyol (A1), and can be 5% or more by mass, 10% or more by mass, 20% or more by mass, 30% or more by mass, 40% or more by mass, or 50% or more by mass, or it can be less than 100% by mass, less than 97% by mass, less than 95% by mass, or less than 90% by mass.

[0050] In addition to polyester polyol (A1a), polyester polyol (A1) may also contain polyester polyol (A1b) other than polyester polyol (A1a). Polyester polyol (A1b) can be used alone or in combination of two or more types.

[0051] From the perspective of superior impact resistance, the content of structural units derived from polyester polyol (A1b) can be based on the total amount of structural units derived from polyester polyol (A1), and can be 0% or more by mass, 3% or more by mass, 5% or more by mass, or 10% or more by mass, or it can be less than 95% by mass, less than 90% by mass, less than 80% by mass, less than 70% by mass, less than 60% by mass, or less than 50% by mass.

[0052] When the structural units derived from polyol (A) consist only of structural units derived from polyester polyol (A1), the content of structural units derived from polyester polyol (A1a) and structural units derived from polyester polyol (A1b) can be the content based on replacing the reference of "total amount of structural units derived from polyester polyol (A1)" with the reference of "total amount of structural units derived from polyol (A)".

[0053] In addition to polyester polyols (A1), polyols (A2) may also include polyols other than polyester polyols (A1). Examples of polyols (A2) include polyether polyols, polyether ester polyols, polyurethane polyols, polycarbonate polyols, and polyolefin polyols. One type of polyol may be used alone, or two or more may be used simultaneously.

[0054] The content of structural units derived from polyol (A2) can be more than 0% by mass, more than 5% by mass, or more than 10% by mass, or less than 50% by mass, less than 40% by mass, less than 30% by mass, or less than 20% by mass, based on the total amount of structural units derived from polyol (A).

[0055] (Polyisocyanate (B))

[0056] Polyisocyanate (B), which provides structural units derived from polyisocyanates, can be used without particular restriction as long as it is a compound having two or more isocyanate groups. Polyisocyanate (B) can be, for example, a compound having two isocyanate groups (diisocyanate). Examples of polyisocyanates include aromatic isocyanates such as diphenylmethane diisocyanate, dimethyl diphenylmethane diisocyanate, toluene diisocyanate, phenyl dimethyl diisocyanate, and terephthalic diisocyanate; alicyclic isocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. From the viewpoint of reactivity and adhesion, polyisocyanate (B) can contain aromatic diisocyanates, or diphenylmethane diisocyanate can be included within aromatic diisocyanates. Polyisocyanate (B) can be used alone or in combination of two or more.

[0057] Polyurethane prepolymers can be synthesized by reacting a polyol (A) with a polyisocyanate (B). In this case, the polyol comprises a polyester polyol (A1a).

[0058] The polyurethane prepolymer comprises polymer chains with isocyanate groups as end groups of the polymer chains, the polymer chains having structural units derived from polyols and structural units derived from polyisocyanates. In the synthesis of such a polyurethane prepolymer, the ratio of the isocyanate group (NCO) equivalent of polyisocyanate (B) to the hydroxyl group (OH) equivalent of polyol (A) (NCO / OH) equivalent of polyisocyanate (B) / hydroxyl group (OH) equivalent of polyol (A) (NCO / OH)) is greater than 1, and can be 1.3 to 3.0 or 1.5 to 2.0. If the NCO / OH ratio is 1.3 or higher, the viscosity of the obtained polyurethane prepolymer is prevented from becoming excessively high, and there is a tendency to easily improve workability. If the NCO / OH ratio is 3.0 or lower, foaming is less likely to occur during the moisture curing reaction of the adhesive composition, and there is a tendency to easily suppress the decrease in adhesive strength.

[0059] The content of polyurethane prepolymer, based on the total amount of the adhesive composition, can be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The upper limit of the polyurethane prepolymer content, based on the total amount of the adhesive composition, can be 100% by mass. The adhesive composition may consist solely of polyurethane prepolymer.

[0060] From the viewpoint of promoting the curing of polyurethane prepolymers and exhibiting higher adhesive strength, the adhesive composition may further contain a catalyst. Examples of catalysts include dibutyltin dilaurate, dibutyltin dioctanoate, dimethylcyclohexylamine, dimethylbenzylamine, and trioctylamine.

[0061] From the viewpoint of improving the rubber elasticity of the formed adhesive layer and further enhancing its impact resistance, the adhesive composition may further contain a thermoplastic polymer. Examples of thermoplastic polymers include polyurethanes, vinyl copolymers, propylene copolymers, vinyl chloride copolymers, acrylic copolymers, and styrene-conjugated diene block copolymers.

[0062] From the viewpoint of imparting stronger adhesion to the formed adhesive layer, the adhesive composition may further contain a tackifying resin. Examples of tackifying resins include rosin resin, rosin ester resin, hydrogenated rosin ester resin, terpene resin, terpene phenolic resin, hydrogenated terpene resin, petroleum resin, hydrogenated petroleum resin, coumarone resin, ketone resin, styrene resin, modified styrene resin, xylene resin, epoxy resin, etc.

[0063] The adhesive composition may contain appropriate amounts of antioxidants, pigments, ultraviolet absorbers, surfactants, flame retardants, fillers, etc., as needed.

[0064] The content of components other than polyurethane prepolymer can be 0–30% by mass, 0–20% by mass, 0–10% by mass, or 0–5% by mass, based on the total amount of the adhesive composition.

[0065] The adhesive composition is cured by reacting the isocyanate groups of the polyurethane prepolymer contained in the adhesive composition with moisture in the air or on the surface of the substrate to increase its molecular weight. The adhesive composition can be cured, for example, by curing at a temperature of 23°C and a humidity of 50% (relative humidity) for more than 24 hours. Curing under these conditions forms a cured product of the adhesive composition.

[0066] A method for manufacturing an adhesive composition may include a step of reacting a polyol (A) with a polyisocyanate (B) to obtain a polyurethane prepolymer. The reaction temperature of the polyol (A) and the polyisocyanate (B) may, for example, be 85–120°C. Furthermore, defoaming under reduced pressure may be performed during this mixing process.

[0067] From the viewpoint of improving coatability, the melt viscosity of the adhesive composition at 120°C, as measured using a rotational viscometer, can be 30 Pa·s or less, or 25 Pa·s or less. There is no particular limitation on the lower limit of the melt viscosity at 120°C, but it can be, for example, 1 Pa·s or more. Furthermore, in this specification, the melt viscosity of the adhesive composition at 120°C represents a value measured using the methods described in the examples.

[0068] The adhesive composition according to this embodiment can form an adhesive layer with high impact resistance. Furthermore, since the adhesive composition of this embodiment is a solvent-free adhesive, it has low environmental and human health impact and can bond quickly. Moreover, since the adhesive composition of this embodiment is a one-component adhesive, it is easy to handle.

[0069] The adhesive composition of this embodiment can bond various substrates via an adhesive layer containing a cured adhesive composition. Examples of substrates include metal substrates such as SUS and aluminum, and non-metallic substrates such as polycarbonate, polyamide, polyetherimide, and glass.

[0070] [Adhesives and their manufacturing methods]

[0071] One embodiment of the adhesive includes 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 aforementioned reactive hot-melt adhesive composition. Examples of adhesives according to this embodiment include semiconductor devices, seamless garments, and electronic devices.

[0072] The first and second adherends can be exemplified as the same adherends exemplified in the above-described adherends.

[0073] The adhesive of this embodiment can be manufactured by the following method, which includes: a step of melting the above-mentioned reactive hot melt adhesive composition and applying it to a first substrate to form an adhesive layer; a step of placing a second substrate on the adhesive layer and obtaining an adhesive precursor by pressing the second substrate; and a step of curing the adhesive layer in the adhesive precursor.

[0074] The temperature at which the adhesive composition is melted can be, for example, 80–180°C. There are no particular limitations on the method of applying the adhesive composition to the first substrate; known methods can be appropriately used.

[0075] As a method of pressing a second bonded object, one example is the method of pressing using a pressure roller or the like.

[0076] The conditions for curing the adhesive layer in the adhesive precursor can be the same as the curing conditions for the adhesive composition described above.

[0077] Example

[0078] The present invention will now be described in detail with reference to embodiments, but the present invention is not limited thereto.

[0079] (Examples 1 to 5 and Comparative Examples 1 to 3)

[0080] Pre-dehydrated polyol (A) was added to the reaction vessel in the amounts shown in Table 1 and mixed uniformly. Next, polyisocyanate (B) was further added to the reaction vessel in the amounts shown in Table 1 and mixed uniformly. The mixture was reacted at 110°C for 1 hour. Then, the mixture was stirred under reduced pressure at 110°C for 1 hour to remove foam, thereby obtaining the adhesive compositions of Examples 1-5 and Comparative Examples 1-3, which contain polyurethane prepolymers having isocyanate groups. Note that the amounts in Table 1 are parts by mass.

[0081] <Polyol (A)>

[0082] • Polyester polyol (A1)

[0083] (A1a-1): An amorphous polyester polyol (2 hydroxyl groups, Mn: 2000) that is the product of the reaction between adipic acid (an aliphatic dicarboxylic acid) and neopentyl glycol (an aliphatic diol with quaternary carbon atoms in the molecule).

[0084] (A1a-2): An amorphous polyester polyol (2 hydroxyl groups, Mn: 5000) that is the product of the reaction between adipic acid (an aliphatic dicarboxylic acid) and neopentyl glycol (an aliphatic diol with quaternary carbon atoms in the molecule).

[0085] (A1b-1): A crystalline polyester polyol (number of hydroxyl groups: 2, Mn: 5000) that is the product of the reaction between sebacic acid (an aliphatic dicarboxylic acid) and 1,6-hexanediol (an aliphatic diol).

[0086] (A1b-2): A crystalline polyester polyol (2 hydroxyl groups, Mn: 5000) that is the product of the reaction between adipic acid (an aliphatic dicarboxylic acid) and 1,6-hexanediol (an aliphatic diol).

[0087] (A1b-3): An amorphous polyester polyol (2 hydroxyl groups, Mn: 2000) that is a reaction product of isophthalic acid (an aromatic carboxylic acid) and neopentyl glycol (an aliphatic diol with quaternary carbon atoms in the molecule).

[0088] <Polyisocyanate (B)>

[0089] (B-1): Diphenylmethane diisocyanate (isocyanate group: 2)

[0090] 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.

[0091] (Determination of melt viscosity)

[0092] The melt viscosity of an adhesive composition (sample weight: 15 g) at a rotor speed of 50 rpm and 120 °C was determined using a TVB-25H viscometer (manufactured by TOKI SANGYO CO.,LTD) with rotor No. 4.

[0093] (Evaluation of impact absorption)

[0094] The adhesive composition was melted at 100°C to form a film with a thickness of 0.15 mm. The obtained film was cured by standing at 23°C and 50% relative humidity for 24 hours, thus obtaining a cured film. Impact absorption was evaluated using a digital accelerometer 1340A-01H (manufactured by Showa Sokki Corporation). A drop jig was fixed to the cured film, and a drop object was dropped from above the cured film, and the impact acceleration of the drop object was measured. The impact acceleration was set at a drop height of 2000 m / s² with the cured film not in use. 2 (200×10m / s 2 The position of the impact acceleration. It can be said that the smaller the value of the impact acceleration, the more the cured film absorbs the impact, so it can be said that the impact absorption is excellent.

[0095] [Table 1]

[0096]

[0097] As shown in Table 1, the impact acceleration values ​​of the reactive hot melt adhesive compositions of Examples 1 to 5 are lower than those of the reactive hot melt adhesive compositions of Comparative Examples 1 to 3. Based on these results, it is confirmed that the reactive hot melt adhesive compositions of the present invention can form an adhesive layer with high impact resistance.

Claims

1. A reactive hot melt adhesive composition containing a polyurethane prepolymer, the polyurethane prepolymer comprising a polymer chain, and having isocyanate groups as terminal groups of the polymer chain, the polymer chain having structural units from a polyol containing a polyester polyol and structural units from a polyisocyanate, the polyester polyol having structural units from an aliphatic dicarboxylic acid and structural units from an aliphatic diol, and being composed of a polyester polyol Al a having a tertiary carbon atom or a quaternary carbon atom within a molecule of at least one of the aliphatic dicarboxylic acid and the aliphatic diol, and a polyester polyol Al b other than the polyester polyol Al a, the polyester polyol Al a having only structural units from an aliphatic dicarboxylic acid and structural units from an aliphatic diol having a tertiary carbon atom or a quaternary carbon atom, the content of the structural units from the polyester polyol Al a being 50 mass% or more based on the total amount of the structural units from the polyol.

2. An adhesive body comprising: a first adherend; a second adherend; and an adhesive layer that adheres the first adherend and the second adherend to each other, the adhesive layer containing a cured product of the reactive hot melt adhesive composition according to claim 1.

3. A method for producing an adhesive body, comprising: a step of melting the reactive hot melt adhesive composition according to claim 1 and applying it to a first adherend to form an adhesive layer; a step of disposing a second adherend on the adhesive layer and obtaining an adhesive body precursor by pressure bonding the second adherend; and a step of curing the adhesive layer in the adhesive body precursor.

4. The method according to claim 3, wherein the polyester polyol Al a has a content of the structural units from the aliphatic diol having a tertiary carbon atom or a quaternary carbon atom of 50 mass% or more based on the total amount of the structural units from the aliphatic diol.

5. The method according to claim 3 or 4, wherein the polyester polyol Al a has a content of the structural units from the aliphatic dicarboxylic acid of 50 mass% or more based on the total amount of the structural units from the aliphatic dicarboxylic acid.

6. The method according to any one of claims 3 to 5, wherein the polyester polyol Al b has a content of the structural units from the aliphatic diol of 50 mass% or more based on the total amount of the structural units from the aliphatic diol.

7. The method according to any one of claims 3 to 6, wherein the polyester polyol Al b has a content of the structural units from the aliphatic dicarboxylic acid of 50 mass% or more based on the total amount of the structural units from the aliphatic dicarboxylic acid.

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