Moisture-curing hot melt adhesive and adhesive sheet

Abstract

The objective is to provide a moisture-curing hot-melt adhesive that has storage stability and excellent low-temperature adhesion, adhesion to SUS and PP, and heat retention. [Solution] The problem is solved by a moisture-curing hot-melt adhesive containing a urethane prepolymer (X) having isocyanate groups, which is a reaction product of a polyol compound (A) and a polyisocyanate (B), wherein the polyol compound (A) comprises polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and rosin polyol (a3), with the content of polypropylene glycol (a1) being 30% or more and less than 98% by mass per 100% by mass of polyol compound (A), the content of trifunctional or more polyether polyol (a2) being 1% or more and less than 5% by mass, and the content of rosin polyol (a3) ​​being 1% or more and 35% by mass or less.

Description

Technical Field

[0001] The present invention relates to a moisture-curable hot-melt adhesive and an adhesive sheet.

Background Art

[0002] Hot-melt adhesives that do not use solvents have a low fire risk and are widely used in fields such as food packaging, sanitary materials, fibers, building materials, automobiles, and electronic components. In addition, since a drying oven is not required, the space and energy can be saved, and the scope of utilization is expanding toward space and energy savings, and the required performance of hot-melt adhesives is increasing day by day. For example, assuming use in cold regions, performance to maintain high adhesive strength even in a low-temperature environment (hereinafter referred to as low-temperature adhesive strength) is required. In addition, high adhesiveness to poorly adherent olefin-based adherends such as polypropylene (PP) and polyethylene (PE) is required. Furthermore, assuming applications in automobiles and electronic components, performance to maintain high holding power even in a high-temperature environment (hereinafter abbreviated as heat-resistant holding power) is required.

[0003] Patent Document 1 discloses a moisture-curable hot-melt adhesive containing a urethane polymer having an isocyanate group obtained by reacting a polyol compound (A) and a polyisocyanate (B), wherein the storage elastic modulus E'(-10) at -10°C of a cured product formed by curing the adhesive at 25°C and a relative humidity of 50% for 7 days is 100 MPa or less, and the storage elastic modulus E'(23) at 23°C of the cured product is 3.0 MPa or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventional moisture-curing hot melt adhesives have a short pot life, which leads to a problem of increased viscosity during storage (hereinafter referred to as storage stability). Furthermore, there was a need for a hot melt adhesive with good low-temperature adhesion, adhesion to SUS and PP, and heat retention properties.

[0006] The problem that this invention aims to solve is to provide a moisture-curing hot-melt adhesive that has storage stability and excellent low-temperature adhesion, adhesion to SUS and PP, and heat retention. [Means for solving the problem]

[0007] The inventors of this invention have diligently conducted research to solve the above problems and have now completed this invention. In other words, embodiments of the present invention relate to a moisture-curing hot-melt adhesive containing a urethane prepolymer (X) having an isocyanate group, which is a reaction product of a polyol compound (A) and a polyisocyanate (B), wherein the polyol compound (A) comprises polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and rosin polyol (a3), and the content of polypropylene glycol (a1) is 30% by mass or more and less than 98% by mass, the content of trifunctional or more polyether polyol (a2) is 1% by mass or more and less than 5% by mass, and the content of rosin polyol (a3) ​​is 1% by mass or more and 35% by mass or less.

[0008] Furthermore, embodiments of the present invention relate to the moisture-curing hot-melt adhesive according to claim 1, wherein polypropylene glycol (a1) comprises polypropylene glycol having a number average molecular weight of 3000 to 5000.

[0009] Furthermore, embodiments of the present invention relate to a moisture-curing hot-melt adhesive according to claim 1, wherein the trifunctional or more polyether polyol (a2) comprises a trifunctional or more polyether polyol having a number average molecular weight of 200 to 2000.

[0010] Furthermore, embodiments of the present invention relate to the moisture-curing hot-melt adhesive according to claim 1, wherein the polyol compound (A) further contains a polyester polyol (a4).

[0011] Furthermore, embodiments of the present invention further relate to a moisture-curing hot melt adhesive according to claim 1, wherein the adhesive contains 5 to 50 parts by mass of a tackifying resin (Y) per 100 parts by mass of a urethane prepolymer (X).

[0012] Furthermore, embodiments of the present invention relate to a moisture-curing hot-melt adhesive according to claim 5, wherein the tackifying resin (Y) comprises a terpene phenol resin having a hydroxyl value of 20 to 160 mgKOH / g.

[0013] Furthermore, embodiments of the present invention relate to the moisture-curing hot-melt adhesive according to claim 6, wherein the tackifying resin (Y) further comprises a rosin ester that is liquid at 23°C.

[0014] Furthermore, embodiments of the present invention relate to an adhesive sheet having an adhesive layer formed by curing the above-mentioned moisture-curing hot-melt adhesive. [Effects of the Invention]

[0015] The moisture-curing hot melt adhesive of the present invention has a longer pot life and better storage stability compared to conventional moisture-curing hot melt adhesives, thus eliminating problems during coating. In addition, it provides a moisture-curing hot melt adhesive with excellent low-temperature adhesion, adhesion to SUS and PP, and heat retention. [Modes for carrying out the invention]

[0016] The present invention describes a moisture-curing hot-melt adhesive. In this specification, numerical ranges specified using "~" include the numbers before and after "~" as the lower and upper limits. Furthermore, unless otherwise specified, "molecular weight" refers to the number-average molecular weight (Mn). Note that "Mw" and "Mn" are the weight-average molecular weight and number-average molecular weight, respectively, calculated on a polystyrene basis using gel permeation chromatography (GPC).

[0017] In this specification, a urethane prepolymer (X) having an isocyanate group may be referred to as urethane prepolymer (X), polypropylene glycol (a1) as polyol (a1), a trifunctional or more polyether polyol (a2) as polyol (a2), rosin polyol (a3) ​​as polyol (a3), and polyester polyol (a4) as polyol (a4).

[0018] <Urethane prepolymer (X) having isocyanate groups> The urethane prepolymer (X) having isocyanate groups is a reaction product of a polyol compound (A) and polyisocyanate (B). The urethane prepolymer (X) having isocyanate groups can be used alone or in combination of two or more types.

[0019] The weight-average molecular weight (Mw) of the urethane prepolymer (X) having isocyanate groups is preferably 10,000 to 100,000, more preferably 20,000 to 80,000, and even more preferably 20,000 to 60,000. By adjusting Mw to the above range, the tackiness and heat retention can be improved.

[0020] <Polyol compound (A)> Polyol compounds (A) are polyols having two or more hydroxyl groups in one molecule, and are classified into polypropylene glycol (a1), trifunctional or more polyether polyols (a2), rosin polyols (a3), polyester polyols (a4), and other polyols other than (a1), (a2), (a3), and (a4). The polyol compound (A) of the present invention is characterized in that, in 100% by mass of the polyol compound (A), the content of polypropylene glycol (a1) is 30% by mass or more and less than 98% by mass, the content of trifunctional or higher polyether polyol (a2) is 1% by mass or more and less than 5% by mass, and the content of rosin polyol (a3) is 1% by mass or more and 35% by mass or less.

[0021] <Polypropylene glycol (a1)> Polypropylene glycol (a1) is a bifunctional polymer compound having oxypropylene as a repeating unit and hydroxyl groups at both ends. It is produced by addition polymerization of propylene oxide using diols such as propylene glycol and ethylene glycol as starting materials, and is not particularly limited as long as it is generally used in urethane resins and the like. Examples include Sannix PP series of Sanyo Chemical Industries, Ltd. and Union series of NOF Corporation.

[0022] The number average molecular weight (Mn) of polypropylene glycol (a1) is preferably 3,000 to 5,000, more preferably 3,500 to 4,500. When the number average molecular weight of polypropylene glycol (a1) is 3,000 or more, the urethane bond content of the urethane prepolymer (X) having isocyanate groups contained in the moisture-curable hot melt adhesive can be appropriately designed, and the low-temperature adhesiveness can be improved. On the other hand, when the number average molecular weight of polypropylene glycol (a1) is 5,000 or less, the cohesive force of the adhesive is improved and the heat resistance retention is good.

[0023] Polypropylene glycol (a1) is mainly used to impart adhesiveness to moisture-curing hot-melt adhesives, although its effects are not limited thereto. In 100% by mass of the polyol compound (A), the content of polypropylene glycol (a1) is 30% by mass or more and less than 98% by mass, preferably 40% by mass or more and 95% by mass or less. By setting the content of polypropylene glycol (a1) in the polyol compound (A) to 30% by mass or more, the low-temperature adhesiveness becomes good, and by setting the content of polypropylene glycol (a1) to less than 98% by mass, the heat resistance retention becomes better.

[0024] <Polyether polyol (a2) having three or more functional groups> The polyether polyol (a2) having three or more functional groups is a polymer compound having oxypropylene or oxyethylene as a repeating unit and having three or more hydroxyl groups at its terminals. It is produced by addition polymerization of propylene oxide or ethylene oxide using a polyol having three or more functional groups such as glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, aromatic diamine, diethylenetriamine, sorbitol, sucrose, etc. as a starting material. It is not particularly limited as long as it is generally used for urethane resins, etc., and examples thereof include Sannix GP series of Sanyo Chemical Industries, Ltd. and Adeka Polyether series of ADEKA Corporation.

[0025] The number average molecular weight (Mn) of the polyether polyol (a2) having three or more functional groups is preferably 200 to 2,000, more preferably 250 to 1,000, and even more preferably 300 to 400. When the number average molecular weight of the polyether polyol (a2) having three or more functional groups is 200 or more, the urethane bond content of the urethane prepolymer (X) having an isocyanate group contained in the moisture-curing hot-melt adhesive can be appropriately designed, and the low-temperature adhesiveness can be improved. On the other hand, when the number average molecular weight of the polyether polyol (a2) having three or more functional groups is 2,000 or less, the cohesive force of the adhesive is improved and the heat resistance retention becomes good.

[0026] The trifunctional or more polyether polyol (a2) is used primarily to impart heat retention to moisture-curing hot-melt adhesives, although its effects are not limited to those of the polyol compound (A). The content of the trifunctional or more polyether polyol (a2) in 100% by mass of the polyol compound (A) is 1% by mass or more and less than 5% by mass, preferably 2% by mass or more and less than 4% by mass. By setting the content of the trifunctional or more polyether polyol (a2) in 100% by mass of the polyol compound (A) to 1% by mass or more, the heat retention can be further improved. Furthermore, by setting the content of the trifunctional or more polyether polyol (a2) to less than 5% by mass, the pot life can be extended and storage stability can be improved.

[0027] <Rosin polyol (a3)> Rosin polyol (a3) ​​is not particularly limited as long as it is a rosin-modified polyol having a rosin skeleton in its molecule. Polyols having a rosin skeleton in their molecule are called rosin polyols, and these include polyether types, where the skeleton excluding the rosin portion is such as polypropylene glycol, and polyester types, such as condensed polyester polyols, lactone polyester polyols, and polycarbonate diols. Examples of rosin polyols include rosin esters obtained by reacting a rosin component with a polyhydric alcohol, epoxy-modified rosin esters obtained by reacting rosin with an epoxy compound, and modified rosins having hydroxyl groups, such as polyethers having a rosin skeleton.

[0028] Examples of rosin components to be reacted with polyhydric alcohols to obtain rosin polyols include abietic acid and its derivatives such as pimaric acid-type resin acids including dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, diabietic acid, neoabietic acid, and levopimalic acid, hydrogenated rosins obtained by hydrogenating these, and disproportionated rosins obtained by disproportionating these.

[0029] Examples of commercially available rosin polyols (a3) ​​include D-6011, D-6240, KE-359, KE-601, KE-615-3, KE-622, KE-623, and KE-624 from Arakawa Chemical Industries. Among these, rosin diols having approximately two rosin skeletons and two hydroxyl groups in the molecule are preferred. For example, D-6011, a polyol obtained by reacting a rosin component with a bisphenol A type epoxy resin, can be suitably used in the moisture-curing hot-melt adhesive of the present invention.

[0030] The hydroxyl value (mgKOH / g) of rosin polyol (a3) ​​is preferably 20 to 300 mgKOH / g, and more preferably 25 to 150 mgKOH / g. When the hydroxyl value of rosin polyol (a3) ​​is 20 mgKOH / g or higher, the cohesive strength of the moisture-curing hot-melt adhesive is improved, resulting in good heat resistance. On the other hand, when the hydroxyl value of rosin polyol (a3) ​​is 300 mgKOH / g or lower, the low-temperature adhesive strength of the moisture-curing hot-melt adhesive is further improved. In this invention, the hydroxyl value is the value measured in accordance with JIS K 1557-1.

[0031] Rosin polyol (a3) ​​is used primarily to improve the film strength of moisture-curing hot-melt adhesives and to impart heat-resistant retention, although its effects are not limited to those mentioned above. The content of rosin polyol (a3) ​​in 100% by mass of polyol compound (A) is 1% by mass or more and 35% by mass or less, preferably 2% by mass or more and 10% by mass or less. By setting the content of rosin polyol (a3) ​​to 1% by mass or more in 100% by mass of polyol compound (A), the heat-resistant retention can be further improved, and by setting the content of rosin polyol (a3) ​​to 35% by mass or less, the low-temperature adhesion can be improved.

[0032] <Polyester polyol (a4)> The polyol compound (A) comprises the polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and rosin polyol (a3), and more preferably contains polyester polyol (a4). The polyester polyol (a4) is used, although not limited to its effects, mainly to improve the PP adhesive strength of moisture-curing hot-melt adhesives. The content of polyester polyol (a4) in 100% by mass of the polyol compound (A) is preferably 0.5% by mass or more and 60% by mass or less. By setting the polyester polyol (a4) content to 0.5% by mass or more in 100% by mass of the polyol compound (A), the PP adhesive strength can be further improved, and by setting the polyester polyol (a4) content to 60% by mass or less, the low-temperature adhesive strength can be improved. The polyester polyol (a4) is a reaction product of at least one or more polycarboxylic acids and at least one or more polyols.

[0033] Examples of polycarboxylic acids used as raw materials for polyester polyol (a4) include aliphatic polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, dodecanediic acid, tetradecanediic acid, hexadecanedioic acid, and tricarbaryl acid, as well as aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, and pyromellitic acid. Among these, adipic acid, terephthalic acid, isophthalic acid, or phthalic acid are preferred because they can further improve the adhesion between SUS and PP, and it is more preferable to use at least one or both of adipic acid and terephthalic acid.

[0034] Examples of polyols used as raw materials for polyester polyol (a4) include linear polyols such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol, and branched polyols such as neopentyl glycol, 3-methyl-1,5-pentanediol, trimethylolpropane, trimethylolethane, and glycerin. Among these, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, trimethylolpropane, and trimethylolethane are preferred because they can further improve the adhesion between SUS and PP. More preferably, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, or 3-methyl-1,5-pentanediol are preferred.

[0035] <Other polyols> The polyol compound (A) comprises the polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and a rosin polyol (a3), preferably containing a polyester polyol (a4), and may further contain other polyols other than (a1), (a2), (a3), and (a4) as needed.

[0036] Other polyols include, for example, polyethylene glycol, polyoxyethylene polyoxypropylene glycol, polytetramethylene glycol, polybutadiene diol, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, glycerin, trimethylolpropane, trimethylolethane, dimethylolpropionic acid, or dimethylolbutanoic acid (DMBA).

[0037] <Polyisocyanate (B)> Polyisocyanate (B) is a polyisocyanate having two or more isocyanate groups in one molecule, and is preferably a bifunctional isocyanate (also called a diisocyanate) having two isocyanate groups in one molecule. Examples of polyisocyanates (B) include 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), p-phenylenediisocyanate, toluene diisocyanate (TDI), 1,5-naphthalenediisocyanate (NDI), xylylene diisocyanate (XDI), 1,5-octylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated MDI, hydrogenated XDI, polymeric MDI, and the like. Among these, aromatic polyisocyanates are preferred from the viewpoint of reactivity. In particular, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, p-phenylenediisocyanate, toluene diisocyanate, 1,5-naphthalenediisocyanate, xylylene diisocyanate, or polymeric MDI are preferred, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, or polymeric MDI are more preferred, and 4,4'-diphenylmethane diisocyanate or 2,4'-diphenylmethane diisocyanate are even more preferred.

[0038] <Method for producing a urethane prepolymer (X) having an isocyanate group> A method for producing a urethane prepolymer (X) having an isocyanate group is described below. However, the present invention is not limited to the following method. A urethane prepolymer (X) having isocyanate groups is obtained by urethane reaction between a polyol compound (A) and polyisocyanate (B). During the reaction, by using polyisocyanate (B) in a molar ratio (NCO / OH ratio) such that the isocyanate groups (also called isocyanate groups) are more numerous than the hydroxyl groups of polyol compound (A), a urethane prepolymer (X) having isocyanate groups at the molecular ends is obtained. These isocyanate groups can react with moisture present in the air or in the object to be bonded to form a crosslinked structure.

[0039] The manufacturing process for a urethane prepolymer (X) having an isocyanate group is described below. However, the present invention is not limited to the following manufacturing process. In the first step, for example, polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and rosin polyol (a3) ​​are placed in a reaction vessel. At this time, polyester polyol (a4), other polyols, tackifying resins (Y), and other additives may be added as needed. Polyols (a1), (a2), and (a3) ​​are heated and melted, and the mixture is heated to 100-140°C in a heater capable of controlling a uniform temperature distribution while stirring, and thoroughly dehydrated under reduced pressure. Next, a predetermined amount of polyisocyanate (B) is added, dry nitrogen is blown into the reaction vessel to prevent moisture from entering, and the reaction is carried out at 90-140°C for about 4 hours to produce the product. Furthermore, as a second step, polypropylene glycol with a number average molecular weight of 200-500 may be added to extend the chain of the urethane prepolymer. In the second step, polypropylene glycol with a number average molecular weight of 200-500 is added to the same reaction vessel, and the reaction is carried out for a further 2 hours at 90-140°C to produce a urethane prepolymer (X) having isocyanate groups. This reaction does not require a solvent, but a solvent may be used. In this case, the reaction temperature must be below the boiling point of the solvent.

[0040] When producing the urethane prepolymer (X), the equivalent ratio (NCO / OH ratio) of the isocyanate groups of the polyisocyanate (B) and the hydroxyl groups of the polyol compound (A) is preferably 1.1 to 2.0, more preferably 1.2 to 1.7, in order to enhance the heat resistance and anchoring ability to the substrate of the moisture-curing hot melt adhesive and improve the adhesive strength.

[0041] The isocyanate group content (hereinafter abbreviated as "NCO%") of the urethane prepolymer (X) is preferably 0.2 to 3.5%, and more preferably 0.5 to 2.0%. When the isocyanate group content of the urethane prepolymer (X) having isocyanate groups is 0.2% or more, the heat resistance of the moisture-curing hot-melt adhesive is improved, and when the isocyanate group content of the urethane prepolymer (X) having isocyanate groups is 3.5% or less, the storage stability can be improved. The NCO% of the urethane prepolymer (X) is the value measured by potentiometric titration in accordance with JIS K1603-1. NCO% = 4.202 × (V1 - V2) × c / m V1: Amount of hydrochloric acid used for the blank test (mL) V2: The measured amount of hydrochloric acid used for titration of the sample (mL) c: Hydrochloric acid concentration (mol / L) m: Mass of the sample (g) 4.202: The constant for NCO equivalent (42.02 mg / milliequivalent) used to convert 1000 mg to grams and then to a percentage.

[0042] ≪Moisture-curing hot melt adhesive≫ The moisture-curing hot-melt adhesive of the present invention comprises a urethane prepolymer (X) having isocyanate groups. The urethane prepolymer (X) having isocyanate groups itself can be used as the moisture-curing hot-melt adhesive of the present invention, or, if necessary, a tackifying resin (Y) and other additives can be added to form the moisture-curing hot-melt adhesive.

[0043] <Adhesion-enhancing resin (Y)> Examples of tackifying resins (Y) include phenol resins, modified phenol resins, terpene phenol resins, xylene phenol resins, xylene resins, cyclopentadiene-phenol resins, aliphatic, alicyclic, and aromatic petroleum resins, hydrogenated aliphatic, alicyclic, and aromatic petroleum resins, phenol-modified petroleum resins, rosin ester resins that are solid at 23°C (hereinafter referred to as solid rosin ester resins), rosin ester resins that are liquid at 23°C (hereinafter referred to as liquid rosin ester resins), low molecular weight polystyrene resins, terpene resins, and hydrogenated terpene resins. These can be used individually or in combination of two or more. Among these, it is preferable to select from the group consisting of terpene phenol resins, solid rosin ester resins, liquid rosin ester resins, and aromatic petroleum resins, more preferably from the group consisting of terpene phenol resins and liquid rosin ester resins, and even more preferably to use terpene phenol resins and liquid rosin ester resins in combination, in terms of good compatibility and the ability to improve low-temperature tackiness. Terpene phenol resins are not particularly limited as long as they are commonly used, but examples include the YS Polystar series from Yasuhara Chemical Co., Ltd. and the Tamano series from Arakawa Chemical Co., Ltd.

[0044] The hydroxyl value of the terpene phenol resin is preferably 20 to 160 mgKOH / g, and more preferably 60 to 120 mgKOH / g. Setting the hydroxyl value of the terpene phenol resin to 20 mgKOH / g or higher improves the PP adhesive strength of the moisture-curing hot-melt adhesive. On the other hand, setting the hydroxyl value of the terpene phenol resin to 160 mgKOH / g or lower improves the heat-resistant retention of the moisture-curing hot-melt adhesive. In this invention, the hydroxyl value is the value measured in accordance with JIS K 1557-1.

[0045] The hydroxyl value of the solid rosin ester resin is preferably less than 20 mgKOH / g. Reducing the hydroxyl value of the solid rosin ester to less than 20 mgKOH / g improves its storage stability.

[0046] The softening point of the tackifying resin (Y) is preferably 80 to 160°C, and more preferably 100 to 150°C. Setting the softening point of the tackifying resin (Y) to 80°C or higher improves the heat resistance of the moisture-curing hot melt adhesive. On the other hand, setting the softening point of the tackifying resin (Y) to 160°C or lower allows for good compatibility with the urethane prepolymer (X) and is suitable for use. In this invention, the softening point is determined by the ring-and-ball method, and the values ​​shown are those measured in accordance with JIS K5601-2-2.

[0047] The tackifying resin (Y), while not limited to its effects, can improve the PP adhesion strength of a moisture-curing hot-melt adhesive when used in combination with the urethane prepolymer (X). The content of the tackifying resin (Y) per 100 parts by mass of the urethane prepolymer (X) is preferably 5 parts by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 35 parts by mass or less. By using 5 parts by mass or more of the tackifying resin (Y) per 100 parts by mass of the urethane prepolymer (X), excellent PP adhesion strength is achieved, and by using 50 parts by mass or less of the tackifying resin (Y), heat resistance can be maintained.

[0048] The content of terpene phenol resin per 100 parts by mass of the urethane prepolymer (X) is preferably 5 parts by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 35 parts by mass or less. By using 5 parts by mass or more of terpene phenol resin per 100 parts by mass of the urethane prepolymer (X), excellent PP adhesive strength is achieved, and by using 50 parts by mass or less of terpene phenol resin, heat resistance can be maintained.

[0049] The liquid rosin ester resin content is preferably 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the urethane prepolymer (X), and more preferably 0.1 parts by mass or more and 2 parts by mass or less. By using 0.1 parts by mass or more of liquid rosin ester resin per 100 parts by mass of the urethane prepolymer (X), excellent low-temperature adhesion is achieved, and by using 5 parts by mass or less of liquid rosin ester resin, heat resistance can be maintained.

[0050] <Other additives> Other additives that can be used include, for example, chain extenders, curing catalysts, water removers, antioxidants, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent whitening agents, silane coupling agents, waxes, thermoplastic resins, and the like.

[0051] <Properties of moisture-curing hot melt adhesive> The melt viscosity of the moisture-curing hot melt adhesive of the present invention at 120°C is preferably 1,000 to 25,000 mPa·s, more preferably 3,000 to 15,000 mPa·s, from the viewpoint of improving anchorage to the substrate and enhancing adhesive strength. The melt viscosity of the moisture-curing hot melt adhesive of the present invention at 120°C is shown as the value measured using a B-type viscometer (rotor #3, rotation speed 12 rpm) after heating and dissolving the moisture-curing hot melt adhesive at 120°C for 1 hour, sampling 100 mL in a mayonnaise bottle.

[0052] Adhesive Sheets The adhesive sheet of the present invention has an adhesive layer formed by curing a moisture-curing hot-melt adhesive. The adhesive sheet may be a single-layer adhesive sheet, a single-sided adhesive sheet with an adhesive layer / substrate laminated structure, or a double-sided adhesive sheet with an adhesive layer / substrate / adhesive layer laminated structure.

[0053] The thickness of the adhesive sheet is preferably 1 μm to 2 cm, and more preferably 5 μm to 0.4 cm, for single-layer adhesive sheets. For single-sided or double-sided adhesive sheets, the thickness is preferably 2 μm to 3 cm, and more preferably 10 μm to 0.5 cm. By setting the thickness of the adhesive sheet within the above range, good adhesive strength is achieved, and adhesive residue on the adherend can be prevented.

[0054] The thickness of the adhesive layer formed by curing the moisture-curing hot-melt adhesive constituting the adhesive sheet is preferably 1 μm to 1000 μm, and more preferably 5 μm to 500 μm. By setting the thickness of the adhesive layer within the above range, the desired adhesive properties can be obtained.

[0055] <Method for manufacturing adhesive sheets> The method for manufacturing the adhesive sheet is described below. The moisture-curing hot melt adhesive of the present invention, melted at a temperature of 80 to 140°C, preferably 90 to 120°C, is applied to the bonding surface of the substrate. If necessary, a cover film is bonded to protect the coating layer. Furthermore, the moisture-curing hot melt adhesive is cured by curing under the conditions described later to form an adhesive layer.

[0056] For curing moisture-curing hot melt adhesives, the substrate and cover film may be bonded together, or the substrate and adherend may be bonded together. However, from the viewpoint of improving adhesion to the adherend, it is preferable to cure the substrate and adherend in contact. The preferred curing conditions are 25°C and 50% relative humidity for 7 days or more, or 40°C and 80% relative humidity for 1 day or more.

[0057] Examples of methods for applying the moisture-curing hot melt adhesive include the roll coating method, gravure coating method, reverse coating method, blade coating method, spray coating method, air knife coating method, curtain coating method, die coating method, and comma coating method.

[0058] Examples of substrates include plastic films or foams such as polyester (polyethylene terephthalate, polyethylene naphthalate), polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, cyclic olefins, polyvinyl chloride, polyurethane, polyamide, and ethylene-vinyl acetate copolymer, as well as inorganic materials such as glass plates, nonwoven fabrics, and paper. The substrate may have its surface treated with a release agent such as silicone, or it may be corona treated.

[0059] Examples of cover films include plastic films such as polyester (polyethylene terephthalate, polyethylene naphthalate), polycarbonate, polymethyl methacrylate, polyethylene, polypropylene, cyclic olefin, polyvinyl chloride, polyurethane, polyamide, and ethylene-vinyl acetate copolymer. The cover film may have its surface treated with a release agent such as silicone.

[0060] The specific uses and adherends of the moisture-curing hot melt adhesive of the present invention are not particularly limited, and examples include bonding polyolefin foam used as cushioning material, sound insulation material, and heat insulation material in automobiles, building materials, electrical products, etc., to various substrates; bonding core materials to surface materials in door panels, ceiling materials, door panels, partitions, furniture, office equipment, etc. for automotive interior materials; bonding nonwoven fabrics, cloths, leather, etc. used in textiles and clothing applications; bonding of components constituting image display devices (organic electroluminescent (EL) displays, liquid crystal displays, quantum dot displays), light-emitting devices (organic EL lighting, quantum dot lighting), various electronic components (organic thin-film solar cells, thin-film transistors), and input / output devices including touch panels, and sealing of said components. [Examples]

[0061] The present invention will be further described below with reference to examples. However, the present invention is not limited to the following examples. In addition, the amounts of raw materials (excluding solvents) listed in the following examples and tables are calculated on a non-volatile content basis. In this specification, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "percent mass," respectively. RH represents relative humidity.

[0062] [Measurement of molecular weight] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured by gel permeation chromatography (GPC). The measurement conditions were as follows. Note that both Mw and Mn are polystyrene equivalent values.

[0063] Measurement device: GPC system "SHODEX GPC-101" manufactured by Shoko Science Co., Ltd. Columns: KF-G 4A / KF-805 / KF-803 / KF-802 Temperature: 40℃ Eluent: Tetrahydrofuran (THF) Flow rate: 1.0mL / min Detector: RI (Differential Refractometer)

[0064] [Measurement of hydroxyl value] The hydroxyl value of the present invention was measured in accordance with JIS K 1557-1.

[0065] (Example 1) In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube, and vacuum device, 30 parts of Sannix PP-4000 (Sanyo Chemical Industries, number average molecular weight 4000) as polypropylene glycol (a1), 3 parts of Sannix GP-400 (Sanyo Chemical Industries, number average molecular weight 400) as trifunctional or more polyether polyol (a2), 20 parts of Pine Crystal D-6011 (Arakawa Chemical Industries, hydroxyl value 125 mg KOH / g, softening point 90°C) as rosin polyol (a3), and 53 parts of Kuraray Polyol P-2013 (Kuraray, polyester diol obtained by reacting 3-methyl-1,5-pentanediol with adipic acid, number average molecular weight 2000) as polyester polyol (a4) were charged and heated to melt, and then heated under reduced pressure at 120°C for 2 hours. Under a nitrogen atmosphere, 23 parts of myrionate NM (a mixture of 2,4'-MDI and 4,4'-MDI, manufactured by Tosoh Corporation) were added as polyisocyanate (B), and the mixture was reacted at 120°C for 4 hours to obtain a urethane prepolymer having isocyanate groups. The obtained urethane prepolymer itself was used as the moisture-curing hot-melt adhesive of Example 1.

[0066] (Examples 2-13, 18-20, Comparative Examples 1, 2, 5, 6) A urethane prepolymer was manufactured in the same manner as in Example 1, except for the materials and proportions shown in Tables 1-3, and the obtained urethane prepolymer itself was used as a moisture-curing hot-melt adhesive.

[0067] (Example 14) In the first step of the reaction, 92 parts of Sannix PP-4000 (Sanyo Chemical Industries, number average molecular weight 4000) as polypropylene glycol (a1), 3 parts of Sannix GP-4000 (Sanyo Chemical Industries, number average molecular weight 4000) as trifunctional or more polyether polyol (a2), and 2 parts of Pine Crystal D-6011 (Arakawa Chemical Industries, hydroxyl value 125 mg KOH / g, softening point 90°C) as rosin polyol were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube, and vacuum device, and heated and melted, and then heated under reduced pressure at 120°C for 2 hours. Under a nitrogen atmosphere, 12 parts of myrionate NM was added as polyisocyanate (B) heated and melted at 70°C, and the mixture was reacted at 120°C for 4 hours. In the second step, 3 parts of Sannix PP-400, which is polypropylene glycol (a1), were added and the mixture was reacted at 120°C for 2 hours to extend the chain of the urethane prepolymer, thereby producing a urethane prepolymer having isocyanate groups. The resulting urethane prepolymer itself was used as a moisture-curing hot-melt adhesive.

[0068] (Examples 15-17) As shown in Table 1, a urethane prepolymer was manufactured in the same manner as in Example 14, except that Sannix GP-2000, Sannix GP-400, and Sannix GP-250 were used as the trifunctional or higher polyether polyol (a2), and the obtained urethane prepolymer itself was used as a moisture-curing hot-melt adhesive.

[0069] (Example 21) In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube, and vacuum device, 92 parts of Sannix PP-4000 (Sanyo Chemical Industries, number average molecular weight 4000) as polypropylene glycol (a1), 3 parts of Sannix GP-400 (Sanyo Chemical Industries, number average molecular weight 400) as trifunctional or higher polyether polyol (a2), 2 parts of Pine Crystal D-6011 (Arakawa Chemical Industries, hydroxyl value 125 mg KOH / g, softening point 90°C) as rosin polyol (a3), and 2 parts of YS Polystar T-145 (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 60 mg KOH / g, softening point 145°C) as tackifying resin (Y) were charged and heated to melt, and then heated under reduced pressure at 140°C for 2 hours. Under a nitrogen atmosphere, 16 parts of 4,4'-MDI (Millionate NM, manufactured by Tosoh Corporation) as polyisocyanate (B), which was heated and melted at 70°C, were added and reacted at 120°C for 4 hours. Then, as the second step of the reaction, 3 parts of Sannix PP-400, which is polypropylene glycol (a1), were added and reacted at 120°C for 2 hours to extend the chain of the urethane prepolymer, thereby obtaining a moisture-curing hot-melt adhesive containing a urethane prepolymer (X) having isocyanate groups and a tackifying resin (Y).

[0070] (Examples 22-32, Comparative Examples 3 and 4) A moisture-curing hot-melt adhesive containing an isocyanate group-containing urethane prepolymer (X) and a tackifying resin (Y) was obtained in the same manner as in Example 21, except that the materials and proportions were as shown in Tables 2-3.

[0071] <Physical properties and evaluation of moisture-curing hot melt adhesives> The storage stability, low-temperature adhesive strength, adhesive strength to SUS and PP, and heat retention strength of the obtained moisture-curing hot melt adhesive were evaluated by the following methods.

[0072] (Storage stability) The melt viscosity of the obtained moisture-curing hot melt adhesive at 120°C and the melt viscosity at 120°C after storing the moisture-curing hot melt adhesive at 40°C for 3 months were measured using a B-type viscometer (rotor #3, rotation speed 1.5-12 rpm). The viscosity change value (V) was calculated using the following formula, and the storage stability was evaluated. (V) = (Melting viscosity at 120°C after 3 months at 40°C) / (Initial melting viscosity at 120°C (before storage)) [Evaluation Criteria] ○ (Excellent): 1.0 or higher, less than 1.4. ○△ (Good): 1.4 or higher, less than 1.7. △ (Practical): 1.7 or higher, less than 2.0. × (Not practical): 2.0 or higher.

[0073] (Adhesion strength of SUS and PP) A moisture-curing hot melt adhesive was heated and melted at 120°C, and applied to a 50 μm thick PET (polyethylene terephthalate) film using an applicator, so that the thickness of the moisture-curing hot melt adhesive was 50 μm. The film was then cut to a width of 25 mm and a length of 80 mm, and test specimens were obtained by heat sealing them onto SUS and PP plates at 120°C, 0.1 MPa, and 10 seconds. After being left at 23°C and 50% RH for 7 days, test specimens with an adhesive layer were obtained. After the test specimens were left standing in a constant temperature room at 23°C for 1 hour, the 180-degree peel strength (peel speed: 300 mm / min) of the test specimens was measured in the same constant temperature room at 23°C and was used as the adhesive strength between SUS and PP. [Evaluation Criteria] 〇(Excellent): 20N / 25mm or more ○△ (Good): 5N / 25mm or more, less than 20N / 25mm △ (Practical): 0.1N / 25mm or more, less than 5N / 25mm × (Not practical): Less than 0.1N / 25mm

[0074] (Low-temperature adhesion) The same type of test specimen with an adhesive layer used for evaluating the adhesion strength of SUS was prepared. After the test specimen was left to stand in a -10°C constant temperature chamber for 1 hour, the 180-degree angle peel strength (peel speed: 300 mm / min) of the test specimen was measured in the -10°C constant temperature chamber and was defined as the low-temperature adhesion strength. [Evaluation Criteria] 〇(Excellent): 20N / 25mm or more ○△ (Good): 5N / 25mm or more, less than 20N / 25mm △ (Practical): 0.1N / 25mm or more, less than 5N / 25mm × (Not practical): Less than 0.1N / 25mm

[0075] (Heat resistance holding power) Except for a bonding area of ​​25 mm x 25 mm, a test specimen for the heat retention strength test was prepared in the same manner as the adhesive-layered test specimen used for evaluating the SUS adhesive strength. The test specimen was left standing in an 80°C oven for 1 hour, and then a 1 kg load was applied parallel to the adhesive layer surface in an 80°C oven. After 24 hours from the start of load application, the displacement length (mm) from the original position was measured to evaluate the heat retention strength. [Evaluation Criteria] ○ (Excellent): 0mm (No misalignment) ○△ (Good): Greater than 0mm and less than 3mm △ (Usable): 3mm or more, less than 25mm × (Not practical): 25mm or larger

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] The details of the materials in Tables 1-3 are as follows: (Polyol (A)) <(a1); polypropylene glycol> • D-4000; "Uniol D-4000" (NOF Corporation, number average molecular weight 4600) • PP-4000; "Sannix PP-4000" (Sanyo Chemical Co., Ltd., number-average molecular weight 4000) • PP-3000; "Sannix PP-3000" (Sanyo Chemical Co., Ltd., number-average molecular weight 3000) • PP-1000; "Sannix PP-1000" (Sanyo Chemical Co., Ltd., number average molecular weight 1000) • PP-400; "Sannix PP-400" (Sanyo Chemical Co., Ltd., number-average molecular weight 400) <(a2); Trifunctional or more polyether polyols> • GP-4000; "Sannix GP-4000" (Sanyo Chemical Co., Ltd., number average molecular weight 4000, polyoxypropylene triol, trifunctional) • GP-2000; "Sannix GP-2000" (Sanyo Chemical Co., Ltd., number average molecular weight 2000, polyoxypropylene triol, trifunctional) • GP-400; "Sannix GP-400" (Sanyo Chemical Co., Ltd., number average molecular weight 400, polyoxypropylene triol, trifunctional) • GP-250; "Sannix GP-250" (Sanyo Chemical Co., Ltd., number average molecular weight 250, polyoxypropylene triol, trifunctional) <(a3); rosin polyol> • D-6011; "Pine Crystal D-6011" (Arakawa Chemical Industries, Ltd., hydroxyl value 125 mg KOH / g, softening point 90℃) <(a4); polyester polyol> • P-2013; "Kuraray Polyol P-2013" (Kuraray Co., Ltd., a polyester diol obtained by reacting 3-methyl-1,5-pentanediol with adipic acid, number average molecular weight 2000) • P-2020; "Kuraray Polyol P-2020" (Kuraray Co., Ltd., a polyester diol obtained by reacting 3-methyl-1,5-pentanediol with terephthalic acid, number average molecular weight 2000)

[0080] (Polyisocyanate (B)) • Millionate NM (Tosoh Corporation, a mixture of 2,4'-MDI and 4,4'-MDI)

[0081] (Adhesion-enhancing resin (Y)) • U-115; "YS Polystar U-115" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 20 mg KOH / g, softening point 115℃) • T-145; "YS Polystar T-145" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 60 mg KOH / g, softening point 145℃) • G-125; "YS Polystar G-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 120 mg KOH / g, softening point 125℃) • N-125; "YS Polystar N-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 160 mg KOH / g, softening point 125℃) • K-125; "YS Polystar K-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 200 mg KOH / g, softening point 125℃) • A-100; "Super Ester A-100" (Arakawa Chemical Industries, Ltd., solid rosin ester resin, hydroxyl value 16 mg KOH / g, softening point 100℃) • Ester gum AT (Arakawa Chemical Industries, Ltd., liquid rosin ester resin)

[0082] The moisture-curing hot-melt adhesives of the present invention, as shown in Examples 1 to 32 of Tables 1 and 2, exhibited storage stability and excellent low-temperature adhesion, adhesion to SUS and PP, and heat retention.

[0083] On the other hand, the moisture-curing hot-melt adhesives shown in Comparative Examples 1 and 2 of Table 3 had polypropylene glycol (a1) content of less than 30% by mass and 98% by mass or more in 100% by mass of polyol compound (A), and their low-temperature adhesive strength and heat-holding strength were unsatisfactory.

[0084] The moisture-curing hot-melt adhesives shown in Comparative Examples 3 and 4 of Table 3 had a content of less than 1% by mass and 5% or more by mass of trifunctional or higher polyether polyol (a2) in 100% by mass of polyol compound (A), respectively, and exhibited poor heat retention and storage stability.

[0085] The moisture-curing hot-melt adhesives shown in Comparative Examples 5 and 6 of Table 3 had a rosin polyol (a3) ​​content of less than 1% by mass and greater than 35% by mass in 100% by mass of polyol compound (A), resulting in poor heat retention and low-temperature adhesion. [Industrial applicability]

[0086] The moisture-curing hot-melt adhesive of the present invention can be suitably used for bonding polyolefin foam used as cushioning material, sound insulation material, and heat insulation material in automobiles, building materials, electrical products, etc., to various substrates; bonding core materials to surface materials in automotive interior materials such as door panels and ceiling materials, door panels, partitions, furniture, and office equipment; bonding nonwoven fabrics, cloths, leather, etc. used in textiles and apparel applications; bonding components constituting image display devices (organic electroluminescent (EL) displays, liquid crystal displays, quantum dot displays), light-emitting devices (organic EL lighting, quantum dot lighting), various electronic components (organic thin-film solar cells, thin-film transistors), and input / output devices including touch panels.

Claims

1. It contains a urethane prepolymer (X) having an isocyanate group, which is a reaction product of a polyol compound (A) and a polyisocyanate (B). The polyol compound (A) comprises polypropylene glycol (a1), a trifunctional or more polyether polyol (a2), and rosin polyol (a3). A moisture-curing hot melt adhesive comprising 100% by mass of polyol compound (A), wherein the content of polypropylene glycol (a1) is 30% by mass or more and less than 98% by mass, the content of trifunctional or higher polyether polyol (a2) is 1% by mass or more and less than 5% by mass, and the content of rosin polyol (a3) ​​is 1% by mass or more and 35% by mass or less.

2. The moisture-curing hot melt adhesive according to claim 1, wherein the polypropylene glycol (a1) comprises polypropylene glycol having a number average molecular weight of 3,000 to 5,000.

3. The moisture-curing hot-melt adhesive according to claim 1, wherein the trifunctional or more polyether polyol (a2) comprises a trifunctional or more polyether polyol having a number average molecular weight of 200 to 2000.

4. The moisture-curing hot melt adhesive according to claim 1, wherein the polyol compound (A) further contains a polyester polyol (a4).

5. Furthermore, the moisture-curing hot melt adhesive according to claim 1 contains 5 parts by mass or more and 50 parts by mass or less of tackifying resin (Y) per 100 parts by mass of urethane prepolymer (X).

6. The moisture-curing hot melt adhesive according to claim 5, wherein the tackifying resin (Y) contains a terpene phenol resin with a hydroxyl value of 20 to 160 mg KOH / g.

7. The moisture-curing hot melt adhesive according to claim 6, wherein the tackifying resin (Y) further comprises a rosin ester that is liquid at 23°C.

8. An adhesive sheet having an adhesive layer formed by curing a moisture-curing hot melt adhesive according to any one of claims 1 to 7.

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