Moisture-curing hot melt adhesives and adhesive sheets

Abstract

The present invention provides a moisture-curable hot-melt adhesive that has storage stability, and is excellent in low-temperature adhesive strength, adhesive strength to SUS and PP, and heat resistance retention. [Solution] The problem is solved by a moisture-curable hot melt pressure-sensitive adhesive which contains 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) contains a polypropylene glycol (a1), a tri- or higher functional polyether polyol (a2), and a rosin polyol (a3), and wherein, in 100 mass% of the polyol compound (A), the content of the polypropylene glycol (a1) is 30 mass% or more and less than 98 mass%, the content of the tri- or higher functional polyether polyol (a2) is 1 mass% or more and less than 5 mass%, and the content of the rosin polyol (a3) ​​is 1 mass% or more and less than 35 mass%.

Description

[Technical Field]

[0001] The present invention relates to a moisture-curable hot-melt pressure-sensitive adhesive and a pressure-sensitive adhesive sheet. [Background technology]

[0002] Solvent-free hot melt adhesives have a low fire risk and are widely used in food packaging, sanitary materials, textiles, building materials, automobiles, electronic components, etc. In addition, because they do not require drying ovens, their range of use is expanding to save space and energy, and the performance requirements for hot melt adhesives are increasing day by day. For example, assuming use in cold regions, the ability to maintain high adhesive strength even in low-temperature environments (hereinafter referred to as low-temperature adhesive strength) is required. High adhesion to olefin-based substrates, which are difficult to adhere to, such as polypropylene (PP) and polyethylene (PE) is also required. Furthermore, assuming use in automobiles and electronic components, the ability to maintain high adhesive strength even in high-temperature environments (hereinafter referred to as heat-resistant adhesive strength) is required.

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

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-120394 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional moisture-curing hot melt adhesives have a short pot life, which causes the problem of viscosity increasing during storage (hereinafter referred to as storage stability).In addition, there was a demand for hot melt adhesives that have good low-temperature adhesive strength, adhesive strength to SUS and PP, and heat resistance retention.

[0006] The problem to be solved by the present invention is to provide a moisture-curable hot-melt pressure-sensitive adhesive that has storage stability, and is excellent in low-temperature adhesive strength, adhesive strength to SUS and PP, and heat resistance retention. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, an embodiment of the present invention relates to a moisture-curable hot-melt pressure-sensitive adhesive comprising 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 tri- or higher functional polyether polyol (a2), and a rosin polyol (a3), and wherein, relative to 100% by mass of the polyol compound (A), the content of the polypropylene glycol (a1) is 30% by mass or more and less than 98% by mass, the content of the tri- or higher functional polyether polyol (a2) is 1% by mass or more and less than 5% by mass, and the content of the rosin polyol (a3) ​​is 1% by mass or more and 35% by mass or less.

[0008] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 1, wherein the polypropylene glycol (a1) contains a polypropylene glycol having a number average molecular weight of 3,000 to 5,000.

[0009] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 1, wherein the tri- or higher functional polyether polyol (a2) comprises a tri- or higher functional polyether polyol having a number average molecular weight of 200 to 2,000.

[0010] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 1, wherein the polyol compound (A) further contains a polyester polyol (a4).

[0011] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 1, further comprising 5 parts by mass or more and 50 parts by mass or less of a tackifier resin (Y) per 100 parts by mass of the urethane prepolymer (X).

[0012] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 5, wherein the tackifier resin (Y) contains a terpene phenol resin having a hydroxyl value of 20 to 160 mgKOH / g.

[0013] Another embodiment of the present invention relates to the moisture-curable hot-melt pressure-sensitive adhesive according to claim 6, wherein the tackifier resin (Y) further contains a rosin ester that is liquid at 23°C.

[0014] Another embodiment of the present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed by curing the moisture-curable hot-melt pressure-sensitive adhesive. [Effects of the Invention]

[0015] The moisture-curable hot-melt adhesive of the present invention has a longer pot life and better storage stability than conventional moisture-curable hot-melt adhesives, eliminating problems that may arise during application. Additionally, it is possible to provide a moisture-curable hot-melt adhesive that is excellent in low-temperature adhesion, adhesion to SUS and PP, and heat resistance retention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The moisture-curable hot-melt pressure-sensitive adhesive of the present invention will now be described. In this specification, a numerical range specified using "to" is intended to include the numerical values ​​before and after "to" as the range's lower and upper limits. Unless otherwise specified, "molecular weight" refers to the number average molecular weight (Mn). "Mw" and "Mn" are the weight average molecular weight and number average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

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

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

[0019] The weight average molecular weight (Mw) of the urethane prepolymer (X) having an isocyanate group 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 the Mw within the above range, the adhesiveness and heat resistance holding power can be improved.

[0020] <Polyol compound (A)> The polyol compound (A) is a polyol having two or more hydroxyl groups in one molecule, and is classified into polypropylene glycol (a1), tri- or higher functional polyether polyol (a2), rosin polyol (a3), polyester polyol (a4), and other polyols other than (a1), (a2), (a3), and (a4). The polyol compound (A) of the present invention is characterized in that, based on 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 tri- or higher functional 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)> The polypropylene glycol (a1) is a bifunctional polymer compound having oxypropylene repeating units and hydroxyl groups at both ends. It is produced by addition polymerization of propylene oxide using a diol such as propylene glycol or ethylene glycol as a starting material, and is not particularly limited as long as it is a compound commonly used in urethane resins, etc., but examples thereof include the Sannix PP series from Sanyo Chemical Industries and the Uniol series from NOF Corporation.

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

[0023] The polypropylene glycol (a1) is used primarily to impart adhesive strength to moisture-curable hot-melt adhesives, although its effects are not limited thereto. The content of polypropylene glycol (a1) in 100% by mass of the polyol compound (A) is 30% by mass or more and less than 98% by mass, and preferably 40% by mass or more and 95% by mass or less. By making the polypropylene glycol (a1) 30% by mass or more in 100% by mass of the polyol compound (A), good low-temperature adhesive strength is achieved, and by making the polypropylene glycol (a1) less than 98% by mass, better heat resistance retention is achieved.

[0024] <Tri- or higher functional polyether polyol (a2)> The tri- or higher functional polyether polyol (a2) is a polymer compound having oxypropylene or oxyethylene repeating units and three or more hydroxyl groups at its terminals. It is produced by addition polymerization of propylene oxide or ethylene oxide with a tri- or higher functional polyol such as glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, aromatic diamine, diethylenetriamine, sorbitol, or sucrose as the starting material. It is not particularly limited as long as it is one commonly used in urethane resins, etc., but examples include the Sannix GP series from Sanyo Chemical Industry Co., Ltd. and the Adeka Polyether series from Adeka Corporation.

[0025] The number average molecular weight (Mn) of the tri- or higher functional polyether polyol (a2) 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 tri- or higher functional polyether polyol (a2) is 200 or more, the urethane bond content of the urethane prepolymer (X) having an isocyanate group contained in the moisture-curable hot-melt pressure-sensitive adhesive can be appropriately designed, thereby improving low-temperature adhesive strength. On the other hand, when the number average molecular weight of the tri- or higher functional polyether polyol (a2) is 2,000 or less, the cohesive strength of the pressure-sensitive adhesive is improved, resulting in good heat-resistance retention.

[0026] The tri- or higher functional polyether polyol (a2) is used primarily to impart heat resistance holding power to the moisture-curable hot-melt adhesive, although its effects are not limited thereto. The content of the tri- or higher functional 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 making the tri- or higher functional polyether polyol (a2) 1% by mass or more in 100% by mass of the polyol compound (A), the heat resistance holding power can be further improved. Furthermore, by making the tri- or higher functional polyether polyol (a2) less than 5% by mass, the pot life can be extended and storage stability can be improved.

[0027] <Rosin polyol (a3)> The rosin polyol (a3) ​​is not particularly limited as long as it is a rosin-modified polyol having a rosin skeleton in the molecule. Polyols having a rosin skeleton in the molecule are called rosin polyols, and these include polyether types in which the skeleton excluding the rosin portion is polypropylene glycol, and polyester types such as condensation 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 the rosin component to be reacted with a polyhydric alcohol to obtain a rosin polyol include abietic acid and its derivatives, such as pimaric acid-type resin acids as dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, diabietic acid, neoabietic acid, and levopimaric acid; hydrogenated rosins obtained by hydrogenating these; and disproportionated rosins obtained by disproportionating these.

[0029] Commercially available rosin polyols (a3) ​​include D-6011, D-6240, KE-359, KE-601, KE-615-3, KE-622, KE-623, and KE-624 manufactured by Arakawa Chemical Industries, Ltd. Among these, rosin diols having approximately two rosin skeletons and two hydroxyl groups per molecule are preferred. For example, D-6011, a polyol obtained by reacting a rosin component with a bisphenol A epoxy resin, is suitable for use in the moisture-curable hot-melt pressure-sensitive adhesive of the present invention.

[0030] The rosin polyol (a3) ​​preferably has a hydroxyl value (mgKOH / g) of 20 to 300 mgKOH / g, more preferably 25 to 150 mgKOH / g. When the rosin polyol (a3) ​​has a hydroxyl value of 20 mgKOH / g or more, the moisture-curable hot-melt pressure-sensitive adhesive improves in cohesion and heat resistance retention. On the other hand, when the rosin polyol (a3) ​​has a hydroxyl value of 300 mgKOH / g or less, the moisture-curable hot-melt pressure-sensitive adhesive improves in low-temperature adhesion. In the present invention, the hydroxyl value is a value measured in accordance with JIS K 1557-1.

[0031] The rosin polyol (a3) ​​is primarily used to improve the film strength of the moisture-curable hot-melt pressure-sensitive adhesive and to impart heat-resistance holding power, although the effects are not limited thereto. The content of the rosin polyol (a3) ​​in 100% by mass of the polyol compound (A) is 1% by mass or more and 35% by mass or less, and preferably 2% by mass or more and 10% by mass or less. By making the rosin polyol (a3) ​​1% by mass or more in 100% by mass of the polyol compound (A), the heat-resistance holding power can be further improved, and by making the rosin polyol (a3) ​​35% by mass or less, the low-temperature adhesive power can be improved.

[0032] <Polyester polyol (a4)> The polyol compound (A) preferably contains the polypropylene glycol (a1), a tri- or higher functional polyether polyol (a2), and a rosin polyol (a3), and further contains a polyester polyol (a4). The polyester polyol (a4) is primarily used to improve the PP adhesive strength of moisture-curable hot-melt adhesives, although its effects are not limited thereto. The content of the 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 adjusting the content of the polyester polyol (a4) 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 adjusting the content of the polyester polyol (a4) 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 two or more polycarboxylic acids and at least one or two or more polyols.

[0033] Examples of the polycarboxylic acid raw material constituting the 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, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, and tricarballylic acid, and 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 is preferred because it can further improve the adhesive strength to SUS and PP, and it is more preferred to use at least one or both of adipic acid and terephthalic acid.

[0034] Examples of raw polyols that can be used to form the 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 preferably used, as they can further improve the adhesive strength to SUS and PP, and ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, or 3-methyl-1,5-pentanediol is more preferably used.

[0035] <Other polyols> The polyol compound (A) contains the polypropylene glycol (a1), a tri- or higher functional polyether polyol (a2), and a rosin polyol (a3), and preferably contains a polyester polyol (a4), and may further contain other polyols in addition to (a1), (a2), (a3), and (a4) as necessary.

[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, and dimethylolbutanoic acid (DMBA).

[0037] <Polyisocyanate (B)> The 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 the polyisocyanate (B) include 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), p-phenylene diisocyanate, toluene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), xylylene diisocyanate (XDI), 1,5-octylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated MDI (hydrogenated MDI), hydrogenated XDI (hydrogenated XDI), and polymeric MDI. Among these, aromatic polyisocyanates are preferably used from the viewpoint of reactivity. Among them, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, toluene diisocyanate, 1,5-naphthalene diisocyanate, 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 urethane prepolymer (X) having isocyanate groups> A method for producing the urethane prepolymer (X) having an isocyanate group will be described below, although the present invention is not limited to the following production method. Urethane prepolymer (X) having isocyanate groups can be obtained by subjecting polyol compound (A) and polyisocyanate (B) to a urethane reaction. During the reaction, polyisocyanate (B) is used in a molar ratio (NCO / OH ratio) such that the isocyanate groups (also called isocyanato groups) are greater than the hydroxyl groups of polyol compound (A), resulting in urethane prepolymer (X) having isocyanate groups at the molecular terminals. These isocyanate groups can react with moisture present in the air or the object to be bonded to form a crosslinked structure.

[0039] The following describes the process for producing a urethane prepolymer (X) having an isocyanate group. However, the present invention is not limited to the following process. In the reaction of the first step, for example, polypropylene glycol (a1), a tri- or higher functional polyether polyol (a2), and a rosin polyol (a3) ​​are placed in a reaction vessel. At this time, polyester polyol (a4), other polyols, a tackifying resin (Y), and other additives may also be added as needed. Polyol (a1), polyol (a2), and polyol (a3) ​​are melted by heating and stirred at 100 to 140°C using a heater capable of controlling the temperature uniformly, and dehydration is thoroughly carried out under reduced pressure. Next, a predetermined amount of polyisocyanate (B) is added, and dry nitrogen is blown into the reaction vessel to prevent moisture from entering, allowing the reaction to proceed for approximately 4 hours at 90 to 140°C. In the second step, polypropylene glycol having a number-average molecular weight of 200 to 500 may be added to the same reaction vessel to chain-extend the urethane prepolymer. In the second step, polypropylene glycol having a number-average molecular weight of 200 to 500 may be added to the same reaction vessel, and the reaction may be continued for approximately 2 hours at 90 to 140°C to produce a urethane prepolymer (X) having an isocyanate group. 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 in the polyisocyanate (B) to the hydroxyl groups in the polyol compound (A) is preferably 1.1 to 2.0, more preferably 1.2 to 1.7, in order to improve the heat resistance retention of the moisture-curable hot-melt pressure-sensitive adhesive and its anchoring ability to the substrate, thereby improving the adhesive strength.

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

[0042] <Moisture-curing hot melt adhesive> The moisture-curable hot melt adhesive of the present invention contains a urethane prepolymer (X) having an isocyanate group. The urethane prepolymer (X) having an isocyanate group itself can be used as the moisture-curable hot melt pressure-sensitive adhesive of the present invention, or a tackifying resin (Y) or other additives can be added as needed to form a moisture-curable hot melt pressure-sensitive adhesive.

[0043] <Tackifying resin (Y)> Examples of the tackifier resin (Y) include phenolic resins, modified phenolic resins, terpene phenolic resins, xylene phenolic resins, xylene resins, cyclopentadiene-phenolic 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 alone or in combination of two or more. Among these, from the viewpoints of good compatibility and improved low-temperature adhesive strength, it is preferable to select from the group consisting of terpene phenolic resins, solid rosin ester resins, liquid rosin ester resins, and aromatic petroleum resins, more preferably from the group consisting of terpene phenolic resins and liquid rosin ester resins, and even more preferably to use a terpene phenolic resin and a liquid rosin ester resin in combination. The terpene phenol resin is not particularly limited as long as it is a commonly used one, and examples thereof include the YS Polyster series from Yasuhara Chemical Co., Ltd. and the Tamanol series from Arakawa Chemical Co., Ltd.

[0044] The hydroxyl value of the terpene phenol resin is preferably 20 to 160 mgKOH / g, more preferably 60 to 120 mgKOH / g. When the hydroxyl value of the terpene phenol resin is 20 mgKOH / g or more, the PP adhesive strength of the moisture-curable hot-melt pressure-sensitive adhesive can be improved. On the other hand, when the hydroxyl value of the terpene phenol resin is 160 mgKOH / g or less, the heat resistance retention strength of the moisture-curable hot-melt pressure-sensitive adhesive can be improved. In the present invention, the hydroxyl value is a 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, which can improve storage stability.

[0046] The softening point of the tackifier resin (Y) is preferably 80 to 160°C, more preferably 100 to 150°C. When the softening point of the tackifier resin (Y) is 80°C or higher, the heat resistance retention of the moisture-curable hot-melt adhesive can be improved. On the other hand, when the softening point of the tackifier resin (Y) is 160°C or lower, compatibility with the urethane prepolymer (X) is good and it can be used preferably. In the present invention, the softening point is measured by the ring and ball method in accordance with JIS K5601-2-2.

[0047] Although the effects of the tackifier resin (Y) are not limited, its use in combination with the urethane prepolymer (X) can improve the PP adhesive strength of the moisture-curable hot-melt adhesive. The content of the tackifier resin (Y) 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, per 100 parts by mass of the urethane prepolymer (X). By using 5 parts by mass or more of the tackifier resin (Y) per 100 parts by mass of the urethane prepolymer (X), the PP adhesive strength is excellent, and by using 50 parts by mass or less of the tackifier resin (Y), the heat resistance retention can be maintained.

[0048] The content of the terpene phenol resin relative to 100 parts by mass of the urethane prepolymer (X) is preferably 5 parts by mass or more and 50 parts by mass or less, 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 terpene phenol resin relative to 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 the terpene phenol resin, heat resistance retention can be maintained.

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

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

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

[0052] <Adhesive sheet> The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed by curing a moisture-curable hot-melt pressure-sensitive adhesive. The pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet, a single-sided pressure-sensitive adhesive sheet having a laminated structure of pressure-sensitive adhesive layer / substrate, or a double-sided pressure-sensitive adhesive sheet having a laminated structure of pressure-sensitive adhesive layer / substrate / pressure-sensitive adhesive layer.

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

[0054] The thickness of the adhesive layer formed by curing the moisture-curable hot-melt adhesive that constitutes 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, desired adhesive properties can be obtained.

[0055] <Method of manufacturing adhesive sheet> The method for producing a pressure-sensitive adhesive sheet is described below. The moisture-curable hot-melt pressure-sensitive 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 attached to protect the coating layer. The moisture-curable hot-melt pressure-sensitive adhesive is then cured under the conditions described below to form a pressure-sensitive adhesive layer.

[0056] Curing for curing the moisture-curable hot melt adhesive may be performed with the substrate and cover film laminated together, or with the substrate and adherend laminated together, but from the viewpoint of improving adhesion to the adherend, curing is preferably performed with the substrate and adherend in contact with each other. Curing conditions are preferably 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-curable hot-melt adhesive include roll coating, gravure coating, reverse coating, blade coating, spray coating, air knife coating, curtain coating, die coating, and comma coating.

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

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

[0060] Specific uses and adherends of the moisture-curable hot melt pressure sensitive adhesive of the present invention are not particularly limited, and examples thereof include adhesion between various substrates and polyolefin foams used in cushioning, sound insulation, and heat insulation materials used in automobiles, building materials, electrical appliances, etc.; adhesion between core and surface materials of door panels and ceiling materials for automobile interiors, door panels, partitions, furniture, office equipment, etc.; adhesion of nonwoven fabrics, cloth, leather, etc. used in textiles and clothing; adhesion of components constituting image display devices (organic electroluminescence (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 the above components. [Example]

[0061] The following examples are provided for a more detailed explanation. However, the present invention is not limited to the following examples. The amounts of raw materials (excluding solvents) listed in the following examples and tables are calculated on a non-volatile basis. In this specification, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively, and RH represents relative humidity.

[0062] [Molecular weight measurement] The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions. Both Mw and Mn are polystyrene equivalent values.

[0063] Measurement equipment: GPC equipment "SHODEX GPC-101" manufactured by Shoko Science Co., Ltd. Column: KF-G 4A / KF-805 / KF-803 / KF-802 Temperature: 40℃ Eluent: tetrahydrofuran (THF) Flow rate: 1.0mL / min Detector: RI (differential refractometer)

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

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

[0066] (Examples 2 to 13, 18 to 20, Comparative Examples 1, 2, 5, and 6) A urethane prepolymer was produced in the same manner as in Example 1, except that the materials and blending amounts shown in Tables 1 to 3 were used, and the resulting urethane prepolymer itself was used as a moisture-curable hot-melt pressure-sensitive adhesive.

[0067] Example 14 For the first step reaction, a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a pressure reducing device was charged with 92 parts of Sannix PP-4000 (Sanyo Chemical Industries, Ltd., number average molecular weight 4000) as polypropylene glycol (a1), 3 parts of Sannix GP-4000 (Sanyo Chemical Industries, Ltd., number average molecular weight 4000) as tri- or higher functional polyether polyol (a2), and 2 parts of Pine Crystal D-6011 (Arakawa Chemical Industries, Ltd., hydroxyl value 125 mg KOH / g, softening point 90°C) as rosin polyol (a3), which were heated to melt and then heated at 120°C under reduced pressure for 2 hours. Under a nitrogen atmosphere, 12 parts of Millionate NM was added as polyisocyanate (B) which had been heated and melted at 70°C, and the mixture was allowed to react at 120°C for 4 hours. Then, in the second step, 3 parts of Sannix PP-400, a polypropylene glycol (a1), was added and the mixture was allowed to react at 120°C for 2 hours, causing the urethane prepolymer to undergo chain extension, producing a urethane prepolymer having isocyanate groups. The resulting urethane prepolymer itself was used as a moisture-curing hot-melt adhesive.

[0068] (Examples 15 to 17) As shown in Table 1, urethane prepolymers were produced 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 resulting urethane prepolymers themselves were used as moisture-curable hot-melt adhesives.

[0069] Example 21 A reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a pressure reducing device was charged with 92 parts of Sannix PP-4000 (Sanyo Chemical Industries, Ltd., number average molecular weight 4000) as polypropylene glycol (a1), 3 parts of Sannix GP-400 (Sanyo Chemical Industries, Ltd., number average molecular weight 400) as trifunctional or higher polyether polyol (a2), 2 parts of Pine Crystal D-6011 (Arakawa Chemical Industries, Ltd., 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 tackifier resin (Y), and the mixture was heated to melt and 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) was added as polyisocyanate (B) heated and melted at 70°C, and the mixture was allowed to react at 120°C for 4 hours. After that, in the second step, 3 parts of Sannix PP-400, a polypropylene glycol (a1), was added and the mixture was allowed to react at 120°C for 2 hours to chain-extend the urethane prepolymer, thereby obtaining a moisture-curable hot-melt adhesive containing a urethane prepolymer (X) having an isocyanate group and a tackifying resin (Y).

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

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

[0072] (Storage stability) The melt viscosity of the obtained moisture-curable hot melt adhesive at 120°C and the melt viscosity of the moisture-curable hot melt adhesive at 120°C after storing it at 40°C for 3 months were measured using a B-type viscometer (rotor #3, rotation speed 1.5 to 12 rpm). The viscosity change value (V) was calculated using the following formula to evaluate the storage stability. (V) = (melt viscosity at 120°C after 3 months at 40°C) / (initial melt viscosity at 120°C (before storage)) [Evaluation criteria] 〇 (Excellent): 1.0 or above, less than 1.4. 〇△(Good): 1.4 or more, less than 1.7. △ (Practical): 1.7 or more, less than 2.0. × (Not practical): 2.0 or above.

[0073] (SUS and PP adhesive strength) The moisture-curing hot-melt adhesive was heated to 120°C and applied to a 50µm-thick PET (polyethylene terephthalate) film using an applicator. The film was then cut to a width of 25mm and a length of 80mm. The film was then heat-sealed to a SUS plate and a PP plate at 120°C, 0.1 MPa, and pressure-bonded for 10 seconds to obtain a test specimen. The specimen was then left at 23°C and 50% RH for 7 days to obtain a test specimen with the adhesive layer. The test piece was left to stand in a thermostatic chamber at 23°C for 1 hour, and then the 180° angle peel strength (peel speed: 300 mm / min) of the test piece was measured in the thermostatic chamber at 23°C and used as the adhesive strength of SUS and PP. [Evaluation criteria] 〇(Excellent): 20N / 25mm or more 〇△(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 adhesive strength) The same test piece with the adhesive layer as used to evaluate the SUS adhesive strength was prepared. The test piece was left to stand for 1 hour in a thermostatic chamber at -10°C, and then the 180° angle peel strength (peel speed: 300 mm / min) of the test piece was measured in the thermostatic chamber at -10°C, and this was taken as the low-temperature adhesive strength. [Evaluation criteria] 〇(Excellent): 20N / 25mm or more 〇△(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) Test pieces for the heat-resistance holding power test were prepared in the same manner as the test pieces with adhesive layers used to evaluate the SUS adhesive strength, except that the bonding area was 25 mm × 25 mm. The test pieces were left to stand in an oven at 80°C for 1 hour, and then a 1 kg load was applied parallel to the adhesive layer surface in the oven at 80°C. 24 hours after the start of load application, the displacement (mm) from the original position was measured to evaluate the heat-resistance holding power. [Evaluation criteria] 〇 (Excellent): 0mm (No deviation) 〇△(Good): Over 0mm and less than 3mm △ (Practical): 3mm or more, less than 25mm × (Not practical): 25mm or more

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] Details of the materials in Tables 1 to 3 are as follows: (Polyol (A)) <(a1); Polypropylene glycol> D-4000: "Uniol D-4000" (NOF Corporation, number average molecular weight 4600) PP-4000: "Sannyx PP-4000" (Sanyo Chemical Industry, number average molecular weight 4000) PP-3000: "Sannyx PP-3000" (Sanyo Chemical Industry, number average molecular weight 3000) PP-1000: "Sannyx PP-1000" (Sanyo Chemical Industry, number average molecular weight 1000) PP-400: "Sannyx PP-400" (Sanyo Chemical Industry, number average molecular weight 400) (a2): Tri- or higher functional polyether polyol GP-4000: "Sannyx GP-4000" (Sanyo Chemical Industry Co., Ltd., number average molecular weight 4000, polyoxypropylene triol, trifunctional) GP-2000: "Sannyx GP-2000" (Sanyo Chemical Industry, number average molecular weight 2000, polyoxypropylene triol, trifunctional) GP-400: "Sannyx GP-400" (Sanyo Chemical Industry Co., Ltd., number average molecular weight 400, polyoxypropylene triol, trifunctional) GP-250: "Sannyx GP-250" (Sanyo Chemical Industry, number average molecular weight 250, polyoxypropylene triol, trifunctional) <(a3); Rosin polyol> D-6011: "Pine Crystal D-6011" (Arakawa Chemical Industries, hydroxyl value 125 mg KOH / g, softening point 90°C) <(a4); Polyester polyol> P-2013: "Kuraray Polyol P-2013" (Kuraray Co., Ltd., 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., 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] (Tackifier resin (Y)) U-115: "YS Polyster U-115" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 20 mg KOH / g, softening point 115°C) T-145: "YS Polyster T-145" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 60 mg KOH / g, softening point 145°C) G-125: "YS Polyster G-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 120 mg KOH / g, softening point 125°C) N-125: "YS Polyster N-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 160 mg KOH / g, softening point 125°C) K-125: "YS Polyster K-125" (Yasuhara Chemical Co., Ltd., terpene phenol resin, hydroxyl value 200 mg KOH / g, softening point 125°C) A-100: "Super Ester A-100" (Arakawa Chemical Industries, solid rosin ester resin, hydroxyl value 16 mg KOH / g, softening point 100°C) Ester Gum AT (Arakawa Chemical Industries, liquid rosin ester resin)

[0082] The moisture-curable hot-melt pressure-sensitive adhesives of the present invention shown in Examples 1 to 32 in Tables 1 and 2 had storage stability and were excellent in low-temperature adhesive strength, adhesive strength to SUS and PP, and heat resistance retention.

[0083] On the other hand, the moisture-curable hot melt adhesives shown in Comparative Examples 1 and 2 in Table 3 had a 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 had poor low-temperature adhesive strength and heat resistance retention.

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

[0085] The moisture-curable hot-melt adhesives shown in Comparative Examples 5 and 6 in Table 3 had a rosin polyol (a3) ​​content of less than 1 mass% and more than 35 mass% relative to 100 mass% of polyol compound (A), and exhibited poor heat resistance and low-temperature adhesive strength. [Industrial Applicability]

[0086] The moisture-curable hot melt adhesive of the present invention can be suitably used for bonding polyolefin foams used in cushioning, soundproofing, and heat insulating materials to various substrates, which are used in automobiles, building materials, electrical appliances, etc.; bonding core materials and surface materials for automobile interiors, such as door panels and ceiling materials, door panels, partitions, furniture, and office equipment; bonding nonwoven fabrics, cloth, leather, etc. used in textiles and clothing; and bonding components that make up image display devices (organic electroluminescence (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. The composition 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) contains polypropylene glycol (a1), a tri- or higher functional polyether polyol (a2), and a rosin polyol (a3); A moisture-curable hot melt pressure-sensitive adhesive, wherein, based on 100 mass% of the polyol compound (A), the content of polypropylene glycol (a1) is 30 mass% or more and less than 98 mass%, the content of tri- or higher functional polyether polyol (a2) is 1 mass% or more and less than 5 mass%, and the content of rosin polyol (a3) ​​is 1 mass% or more and 35 mass% or less.

2. The moisture-curable hot melt pressure-sensitive adhesive according to claim 1, wherein the polypropylene glycol (a1) comprises a polypropylene glycol having a number average molecular weight of 3000 to 5000.

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

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

5. The moisture-curable hot-melt pressure-sensitive adhesive according to claim 1, further comprising 5 parts by mass or more and 50 parts by mass or less of a tackifier resin (Y) per 100 parts by mass of the urethane prepolymer (X).

6. The moisture-curable hot melt pressure-sensitive adhesive according to claim 5, wherein the tackifier resin (Y) comprises a terpene phenol resin having a hydroxyl value of 20 to 160 mg KOH / g.

7. The moisture-curable hot-melt pressure-sensitive adhesive according to claim 6, wherein the tackifier resin (Y) further contains a rosin ester that is liquid at 23°C.

8. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed by curing the moisture-curable hot-melt pressure-sensitive adhesive according to any one of claims 1 to 7.

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