Moisture-curable hot melt adhesive

Abstract

To provide a moisture-curable hot melt adhesive capable of maintaining excellent adhesiveness for a long period of time (long-term durability).SOLUTION: A moisture-curable hot melt adhesive of the present invention contains: urethane prepolymers including a urethane prepolymer (A1) which is a reaction product of a polyester polyol and a polyisocyanate and has isocyanate groups at both molecular ends, and a urethane prepolymer (A2) which is a reaction product of a polyether polyol and a polyisocyanate and has isocyanate groups at both molecular ends; a polymeric isocyanate; and an antioxidant.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Hot melt adhesives that cure upon reaction with moisture have been known for some time. Moisture-curing hot melt adhesives exhibit initial adhesion by being applied to an adherend, laminating another adherend to the coated surface, and then solidifying. The isocyanate groups of the moisture-curing hot melt adhesive then react with moisture in the air or the adherend to form a crosslinked structure, thereby exhibiting high adhesion (normal adhesion).

[0003] Patent Document 1 proposes a moisture-curable hot melt adhesive composition, for example, in which 1 to 20 parts by weight of an organic phosphorus compound and 0.1 to 1 part by weight of a morpholine compound having a predetermined structural formula are added to 100 parts by weight of an isocyanate group-containing compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-262113 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the moisture-curable adhesive composition has a problem in that it does not have sufficient adhesive properties over a long period of time (long-term durability).

[0006] The present invention provides a moisture-curable hot melt adhesive that can maintain excellent adhesive properties over a long period of time. [Means for solving the problem]

[0007] The moisture-curable hot melt adhesive of the present invention comprises a urethane prepolymer which is a reaction product of a polyol including a polyester polyol and / or a polyether polyol with a polyisocyanate and has isocyanate groups at both molecular terminals; Polymeric isocyanate It is characterized by containing an antioxidant. [Effects of the Invention]

[0008] The moisture-curable hot melt adhesive of the present invention can maintain excellent adhesive properties over a long period of time, i.e., the moisture-curable hot melt adhesive of the present invention has excellent long-term durability. DETAILED DESCRIPTION OF THE INVENTION

[0009] The moisture-curable hot melt adhesive of the present invention contains a urethane prepolymer, a polymeric isocyanate, and an antioxidant.

[0010] [Urethane prepolymer] The urethane prepolymer is a reaction product of a polyol including a polyester polyol and / or a polyether polyol with a polyisocyanate, and has isocyanate groups at both ends of the molecule.

[0011] In the production of urethane prepolymers, the reaction between polyol and polyisocyanate may be carried out in a conventional manner. For example, the prepolymer can be obtained by charging a polyisocyanate into a reaction vessel, adding a polyol from which moisture has been removed, either separately or mixed with additives, and then reacting the hydroxyl groups with the isocyanate groups under heating. Alternatively, the polyol and additives may be charged into a reaction vessel, heated to melt and disperse the mixture, followed by removing moisture, and then charging the polyisocyanate to carry out the reaction between the hydroxyl groups and the isocyanate groups. The production of urethane prepolymers can usually be carried out without a solvent, but can also be carried out in a solvent that does not inhibit the reaction. Specific examples of solvents include butyl acetate, methyl ethyl ketone, and toluene. A urethane catalyst can be used, if necessary, in the reaction between the hydroxyl groups of the polyol and the isocyanate groups of the polyisocyanate. The urethanization catalyst is not particularly limited, and examples thereof include triethylamine, triethylenediamine, N-methylmorpholine, potassium acetate, zinc stearate, tin octoate, dibutyltin dilaurate, etc. The urethanization catalysts may be used alone or in combination of two or more.

[0012] In the reaction between the polyol and the polyisocyanate, the ratio of the number of moles of hydroxyl groups in the polyol to the number of moles of isocyanate groups in the polyisocyanate (number of moles of isocyanate groups / number of moles of hydroxyl groups) is preferably 1.5 to 3.0. When the molar ratio is 1.5 or more, the applicability of the moisture-curable hot melt adhesive is improved. When the molar ratio is 3.0 or less, the initial adhesion of the moisture-curable hot melt adhesive is improved.

[0013] The polyol includes a polyester polyol and / or a polyether polyol. The polyol may include either a polyester polyol or a polyether polyol, or may include a polyester polyol and a polyether polyol. The polyester polyol may be used alone or in combination of two or more kinds. The polyether polyol may be used alone or in combination of two or more kinds.

[0014] Polyester polyols are condensation polymers of polycarboxylic acids and polyols. That is, polyester polyols are polymers obtained by condensation polymerization of polycarboxylic acids and polyols through an ester reaction between the carboxyl groups of the polycarboxylic acids and the hydroxyl groups of the polyols. The condensation polymerization reaction of polycarboxylic acids and polyols may be carried out using a commonly used method.

[0015] The polycarboxylic acid is not particularly limited, and examples thereof include polycarboxylic acids such as terephthalic acid, isophthalic acid, 1,5-naphthalic acid, 2,6-naphthalic acid, cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decamethylenedicarboxylic acid, and dodecamethylenedicarboxylic acid. The polycarboxylic acid becomes crystalline and improves the initial adhesion of the moisture-curable hot melt adhesive, so it preferably contains an aliphatic polycarboxylic acid, more preferably contains an aliphatic polycarboxylic acid having 4 to 16 carbon atoms, more preferably contains an aliphatic polycarboxylic acid having 6 to 12 carbon atoms, and particularly preferably contains dodecanedioic acid, sebacic acid, and adipic acid.

[0016] Examples of polyols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, cyclohexanediol, etc. The polyol becomes crystalline and improves the initial adhesion of the moisture-curable hot melt adhesive, so it preferably contains an aliphatic polyol, more preferably contains an aliphatic polyol having 2 to 10 carbon atoms, more preferably contains an aliphatic polyol having 4 to 8 carbon atoms, more preferably contains 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and particularly preferably contains 1,6-hexanediol.

[0017] The hydroxyl value of the polyester polyol is preferably 5 to 200, more preferably 10 to 150. When the hydroxyl value of the polyester polyol is 5 or more, the coating properties of the moisture-curable hot melt adhesive are improved. When the hydroxyl value of the polyester polyol is 200 or less, the moisture-curable hot melt adhesive has excellent initial adhesion.

[0018] In the present invention, the hydroxyl value of a polyol is the number of milligrams of potassium hydroxide required to acetylate the hydroxyl groups contained in 1 g of the polyol, and is a value obtained by acetylating the hydroxyl groups (-OH groups) in the polyol with acetic anhydride and titrating the unused acetic acid with a potassium hydroxide solution.

[0019] The number average molecular weight of the polyester polyol is preferably 1,000 to 20,000, more preferably 1,500 to 10,000, more preferably 2,000 to 8,000, and particularly preferably 2,100 to 6,000. When the number average molecular weight is 1,000 or more, the initial adhesiveness of the moisture-curable hot melt adhesive is improved. When the number average molecular weight is 20,000 or less, the thermal stability of the moisture-curable hot melt adhesive is improved.

[0020] In the present invention, the number-average molecular weight of a polyester polyol refers to a value measured as follows. The number-average molecular weight of a polyester polyol can be measured using gel permeation chromatography (GPC). Specifically, a sample solution is prepared by dissolving a sample in tetrahydrofuran (THF) to a concentration of 1.0 mass %. Using this sample solution, the number-average molecular weight of the polyester polyol is measured by GPC using a refractive index detector with standard polystyrene as the reference.

[0021] The measurement system can be, for example, a system consisting of an LC-9A pump, a RID-6A refractive index detector, a CTO-6A column oven, and a C-R4A data analyzer (all manufactured by Shimadzu Corporation). The GPC columns can be, for example, three GPC-805 (exclusion limit 4,000,000) and one GPC-804 (exclusion limit 400,000) (all manufactured by Shimadzu Corporation) connected in this order. The measurement conditions are: sample injection volume 25 μL (liters), eluent tetrahydrofuran (THF), pump rate 1.0 mL / min, and column temperature 45°C.

[0022] The polyether polyol is not particularly limited. As the polyether polyol, since it has excellent adhesive properties under normal conditions in a moisture-curable hot melt adhesive, it is preferable to use a polyether polyol represented by the general formula: HO-(R 1 -O)nH(wherein, R 1 represents an alkylene group having 1 to 14 carbon atoms, and n is the number of repeating units and is a positive integer. ) and polyether polyols obtained by addition reaction of alkylene oxides (e.g., ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, etc.) with the active hydrogen moieties of the bisphenol A molecular skeleton are preferred. The main chain skeleton of the polyether polyol (A4) may consist of only one type of repeating unit, or may contain two or more types of repeating units, or may contain two or more types of polymer blocks. The polyether polyols may be used alone or in combination of two or more types.

[0023] An alkylene group is a divalent atomic group formed by removing two hydrogen atoms bonded to two different carbon atoms in an aliphatic saturated hydrocarbon, and includes both linear and branched atomic groups. Note that branched includes cases where one carbon (methyl group) is bonded as a side chain.

[0024] Examples of the alkylene group include an ethylene group, a propylene group [-CH2-CH2-CH2-(trimethylene group), -CH(CH3)-CH2-], a butylene group, an amylene group, and a hexylene group.

[0025] The general formula: HO-(R 1 The main chain skeleton of a polymer containing a repeating unit represented by [-(R 1 Examples of the -O)n- group include polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetramethylene oxide, polyethylene oxide-polypropylene oxide copolymer, and polypropylene oxide-polybutylene oxide copolymer. Among these, polypropylene oxide and polyethylene oxide-polypropylene oxide copolymer are preferred, and polypropylene oxide is more preferred, as they improve the normal adhesiveness of the moisture-curable hot melt adhesive.

[0026] As polyether polyols obtained by addition reaction of alkylene oxide with the active hydrogen moieties of the bisphenol A molecular skeleton, polyether polyols obtained by addition reaction of propylene oxide with the active hydrogen moieties of the bisphenol A molecular skeleton and polyether polyols obtained by addition reaction of ethylene oxide with the active hydrogen moieties of the bisphenol A molecular skeleton are preferred, as these improve the normal adhesiveness of moisture-curable hot melt adhesives.

[0027] The hydroxyl value of the polyether polyol is preferably 5 to 200, more preferably 10 to 150. When the hydroxyl value of the polyester polyol is 5 or more, the coating properties of the moisture-curable hot melt adhesive are improved. When the hydroxyl value of the polyester polyol is 200 or less, the moisture-curable hot melt adhesive has excellent initial adhesion.

[0028] The number average molecular weight of the polyether polyol is preferably 400 to 20,000, more preferably 410 to 10,000, and even more preferably 420 to 8,000. When the number average molecular weight of the polyether polyol is 400 or more, the normal adhesiveness of the moisture-curable hot melt adhesive is improved. When the number average molecular weight of the polyether polyol is 20,000 or less, the initial adhesiveness of the moisture-curable hot melt adhesive is improved. The number average molecular weight of the polyether polyol is measured in the same manner as for the polyester polyol.

[0029] Moisture-curing hot melt adhesives contain urethane prepolymers, which are the reaction products of polyols and polyisocyanates (monomeric isocyanates). The urethane prepolymers are products obtained by condensation polymerization of polyols and polyisocyanates, forming urethane bonds between the hydroxyl groups of the polyols and the isocyanate groups of the polyisocyanates.

[0030] Examples of the polyisocyanate (monomeric isocyanate) include diphenylmethane diisocyanate (MDI, 4,4'-, 2,4-, 2,2'-, or a mixture thereof), carbodiimide-modified MDI, carbodiimidized diphenylmethane polyisocyanate, tolylene diisocyanate (TDI, 2,4-, 2,6-, or a mixture thereof), xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate (NDI), tetramethylxylene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate (HDI), dimer acid diisocyanate, and the like. Examples of suitable polyisocyanates include norbornene diisocyanate, lysine diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate. Because the moisture-curing rate of the moisture-curing hot melt adhesive is high, polyisocyanates containing aromatic rings (e.g., benzene rings, naphthalene rings, etc.) are preferred. Among these, diphenylmethane diisocyanate and carbodiimide-modified MDI are preferred from the viewpoint of vapor pressure, and 4,4'-diphenylmethane diisocyanate is more preferred.

[0031] The polyisocyanate (monomeric isocyanate) is preferably a diisocyanate, since this improves the thermal stability of the moisture-curable hot melt adhesive.

[0032] In the urethane prepolymer, the content of polyester polyol units is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. A polyester polyol unit content of 20% by mass or more is preferred because it improves the cohesive strength of the moisture-curable hot melt adhesive and improves the initial adhesiveness.

[0033] In the urethane prepolymer, the content of polyester polyol units is preferably 95% by mass or less, more preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. When the content of polyester polyol units is 95% by mass or less, the normal adhesiveness of the moisture-curable hot melt adhesive is improved.

[0034] In the urethane prepolymer, the content of polyether polyol units is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. When the content of polyether polyol units is 5% by mass or more, the coatability of the moisture-curable hot melt adhesive is improved.

[0035] In the urethane prepolymer, the content of polyether polyol units is preferably 80% by mass or less, more preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. When the content of polyether polyol units is 80% by mass or less, the cohesive strength of the moisture-curable hot melt adhesive is improved, and the initial adhesiveness is improved, which is preferable.

[0036] The urethane prepolymer may contain other urethane prepolymers in addition to the above-mentioned urethane prepolymers, such as a urethane prepolymer that is a reaction product of polycarbonate polyol and polyisocyanate and has isocyanate groups at both molecular terminals.

[0037] [Polymeric isocyanate] The moisture-curable hot melt adhesive contains a polymeric isocyanate. The polymeric isocyanate is a condensed isocyanate obtained by condensing the polyisocyanate (monomeric polyisocyanate or pure polyisocyanate) used in the urethane prepolymer described above, and is a polyisocyanate having an average number of isocyanate groups per molecule of more than two. The polymeric isocyanates may be used alone or in combination of two or more.

[0038] The polymeric isocyanate is not particularly limited, and examples thereof include polymethylene polyphenyl polyisocyanate [polymeric MDI (polymeric 4,4'-diphenylmethane diisocyanate)] and condensates of xylylene diisocyanate. Polymethylene polyphenyl polyisocyanate [polymeric MDI (polymeric 4,4'-diphenylmethane diisocyanate)] is preferred because it provides excellent long-term durability for moisture-curable hot melt adhesives.

[0039] In the polymeric isocyanate, the average number of isocyanate groups in one molecule is preferably from 2.1 to 4.0, more preferably from 2.2 to 3.5, and particularly preferably from 2.3 to 3.2.

[0040] Polymeric isocyanates are commercially available, for example, from Dow under the trade names "PAPI27" (average number of isocyanate groups per molecule: 2.7) and "PAPI94" (average number of isocyanate groups per molecule: 2.3).

[0041] The content of the polymeric isocyanate in the moisture-curable hot melt adhesive is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 1 to 8 parts by mass, per 100 parts by mass of the urethane prepolymer. When the content of the polymeric isocyanate is 0.1 part by mass or more, the long-term durability of the moisture-curable hot melt adhesive is improved. When the content of the polymeric isocyanate is 20 parts by mass or less, the thermal stability of the moisture-curable hot melt adhesive is improved.

[0042] [Anti-aging agent] The moisture-curable hot melt adhesive contains an antioxidant. Examples of the antioxidant include an antioxidant and a light stabilizer. The antioxidant may be used alone or in combination of two or more kinds.

[0043] The antioxidant is not particularly limited, and examples thereof include hindered phenol-based antioxidants, monophenol-based antioxidants, bisphenol-based antioxidants, polyphenol-based antioxidants, etc., with hindered phenol-based antioxidants being preferred because they improve the long-term durability of the moisture-curable hot melt adhesive. The antioxidants may be used alone or in combination of two or more.

[0044] The hindered phenol antioxidant is not particularly limited, and examples thereof include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)].

[0045] The monophenol-based antioxidant is not particularly limited, and examples thereof include styrenated phenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, and 2-(α-methylcyclohexyl)-4,6-dimethylphenol. , 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di-tert-butyl-4-methoxymethylphenol, branched nonylphenols (e.g., 2,6-di-nonyl-4-methylphenol), 2,4-dimethyl-6-(1'-methylundec-1'-yl)phenol, 2,4-dimethyl-6-(1'-methylheptadec-1'-yl)phenol, 2,4-dimethyl-6-(1'-methyltridec-1'-yl)phenol, and the like.

[0046] The bisphenol-based antioxidant is not particularly limited, and examples thereof include 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(α-methylcyclohexyl)phenol], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(6-nonyl-4-methylphenol), 2,2'-methylenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(6-tert-butyl-4-isobutylphenol), 2,2'-methylenebis[6-(α-methylbenzyl)phenol], 2,2'-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol], 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-methylenebis(6-tert-butyl-2-methylphenol), 1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol, 1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane, ethylene glycol bis[3,3-bis(3'- tert-butyl-4'-hydroxyphenyl)butyrate], bis(3-tert-butyl-4-hydroxy-5-methylphenyl)dicyclopentadiene, bis[2-(3'-tert-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate, 1,1-bis(3,5-dimethyl-2-hydroxyphenyl)butane, 2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 2,2-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercaptobutane, and 1,1,5,5-tetrakis(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane.

[0047] The polyphenol-based antioxidant is not particularly limited, and examples thereof include 2,5-di-t-butylhydroquinone, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, flavonoids (e.g., catechin, anthocyanin, flavone glycoside, isoflavone glycoside, flavan glycoside, flavanone, rutin glycoside, etc.).

[0048] The light stabilizer is not particularly limited, and for example, a hindered amine light stabilizer is preferred, and a hindered amine light stabilizer in which the amine moiety is a tertiary amine is more preferred. Examples of light stabilizers include N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl)ester, a reaction product of 1,1-dimethylethyl hydroperoxide and octane, bis(1,2,2,6,6, -pentamethyl-4-piperidyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, bis(1-octyloxy-2,2,6,6tetramethyl-4-piperidyl)sebacate, etc. The light stabilizers may be used alone or in combination of two or more.

[0049] In the moisture-curing hot melt adhesive, the content of the antioxidant is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the urethane prepolymer. In the moisture-curing hot melt adhesive, the content of the antioxidant is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of the urethane prepolymer. When the content of the antioxidant is 0.1 parts by mass or more, the long-term durability of the moisture-curing hot melt adhesive is improved. When the content of the antioxidant is 15 parts by mass or less, the normal adhesiveness of the moisture-curing hot melt adhesive is improved, which is preferable.

[0050] The moisture-curable hot melt adhesive may contain tackifiers, oils, plasticizers, thermoplastic resins, catalysts, heat stabilizers, fillers, colorants, flame retardants, fragrances, pigments, dyes, etc., to the extent that the effects of the adhesive are not impaired.

[0051] The tackifier is not particularly limited, and examples thereof include rosin-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, etc. The tackifiers may be used alone or in combination of two or more.

[0052] The ring and ball softening point of the tackifier is preferably 90 to 150°C, as this improves the heat resistance of the moisture-curing hot melt adhesive. The ring and ball softening point of the tackifier is a temperature measured in accordance with JIS K6863 (the measurement method involves supporting a ring filled with a sample horizontally in a glycerin bath, and measuring the temperature when a ball placed in the center of the sample touches the bottom plate).

[0053] The oil is not particularly limited, and examples thereof include aromatic components contained in known oils generally referred to as process oils, extender oils, softeners, etc., which are used as rubber softeners, naphthenic oils, paraffinic oils, etc. The oils may be used alone or in combination of two or more.

[0054] The plasticizer is not particularly limited, and examples thereof include phosphate esters such as tributyl phosphate and tricresyl phosphate, phthalate esters such as dioctyl phthalate, fatty acid-basic acid esters such as glycerin monooleate, fatty acid dibasic acid esters such as dioctyl adipate, aliphatic esters such as butyl oleate and methyl acetyl ricinoleate, trimellitic acid esters, chlorinated paraffins, hydrocarbon plasticizers such as alkyl diphenyls and partially hydrogenated terphenyls, process oils, epoxidized soybean oil, epoxy plasticizers such as benzyl epoxy stearate, vinyl polymers obtained by polymerizing vinyl monomers, and polyalkylene glycol esters such as diethylene glycol dibenzoate, triethylene glycol dibenzoate, and pentaerythritol esters. The plasticizers may be used alone or in combination.

[0055] The thermoplastic resin is not particularly limited, and examples thereof include acrylic resins, methacrylic resins, polyvinyl acetate, polystyrene derivatives, polyisobutene, polyolefins, polyalkylene oxides, polyamides, natural rubber, polybutadiene, polyisoprene, nitrobutadiene rubber (NBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (SEBS), hydrogenated nitrobutadiene rubber (hydrogenated NBR), hydrogenated styrene-butadiene-styrene block copolymer (hydrogenated SBS), hydrogenated styrene-isoprene-styrene block copolymer (hydrogenated SIS), and hydrogenated polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (hydrogenated SEBS). The thermoplastic resin may be functionally modified. The thermoplastic resins may be used alone or in combination of two or more.

[0056] The catalyst is used to improve the curing properties of the moisture-curable hot melt adhesive. The catalyst is not particularly limited, and examples thereof include amine-based catalysts and tin-based catalysts. The catalyst may be used alone or in combination of two or more.

[0057] The amine catalyst is preferably a morpholine compound, and specific examples thereof include 2,2'-dimorpholinodiethyl ether, bis(2,6-dimethylmorpholinoethyl)ether, bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(4-morpholino)ethyl)amine, bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(2,6-diethyl-4-morpholino)ethyl)amine, tris(2-(4 -morpholino)ethyl)amine, tris(2-(4-morpholino)propyl)amine, tris(2-(4-morpholino)butyl)amine, tris(2-(2,6-dimethyl-4-morpholino)ethyl)amine, tris(2-(2,6-diethyl-4-morpholino)ethyl)amine, tris(2-(2-ethyl-4-morpholino)ethyl)amine, tris(2-(2-ethyl-4-morpholino)ethylamine, and the like.

[0058] The tin-based catalyst is not particularly limited, and examples thereof include stannous acetate, dibutyltin dilaurate, dibutyltin dioctate, dibutyltin diacetate, dioctyltin dilaurate, dioctyltin dioctate, dioctyltin diacetate, stannous dioctoate, etc. These may be used alone or in combination of two or more.

[0059] The heat stabilizer is preferably an organic phosphorus stabilizer. Examples of the organic stabilizer include tricresyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-ethylhexyl)phosphate, tributoxyethyl phosphate, triphenyl phosphate, octyldiphenyl phosphate, tris(isopropylphenyl)phosphate, cresyldiphenyl phosphate, triphenyl phosphite, triphenylphosphine, triphenylphosphine oxide, and aromatic phosphoric acid condensed esters.

[0060] The heat stabilizer is preferably solid at room temperature (25° C.) Preferred heat stabilizers are triphenyl phosphate, triphenyl phosphine, triphenyl phosphine oxide, and aromatic phosphoric acid condensed esters.

[0061] The filler is not particularly limited, and examples thereof include silica, talc, clay, calcium carbonate, magnesium carbonate, anhydrous silicon, hydrated silicon, calcium silicate, titanium dioxide, carbon black, bentonite, organic bentonite, shirasu balloons, glass microballoons, organic microballoons such as phenolic resins and vinylidene chloride resins, polyvinyl chloride (PVC) powder, polymethyl methacrylate powder, and other resin powders. The fillers may be used alone or in combination of two or more.

[0062] The moisture-curable hot melt adhesive may contain a polymer having a hydrolyzable silyl group. The polymer having a hydrolyzable silyl group has at least one crosslinkable hydrolyzable silyl group in one molecule.

[0063] The hydrolyzable silyl group is a group in which a hydrolyzable group is bonded to a silicon atom, and examples of the hydrolyzable group include a hydrogen atom, a halogen atom, an alkoxy group, an acyloxide group, a ketoximate group, an amino group, an amide group, an acid amide group, an aminooxy group, a mercapto group, and an alkenyloxide group.

[0064] The hydrolyzable silyl group is preferably an alkoxysilyl group in which an alkoxy group is bonded to a silicon atom, since no harmful by-products are produced after the reaction. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, a tert-butoxy group, a phenoxy group, and a benzyloxy group, with a methoxy group and an ethoxy group being preferred.

[0065] Examples of alkoxysilyl groups in which an alkoxy group is bonded to a silicon atom include trialkoxysilyl groups such as trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, and triphenoxysilyl; dialkoxysilyl groups such as methyldimethoxysilyl and methyldiethoxysilyl; and monoalkoxysilyl groups such as dimethylmethoxysilyl and dimethylethoxysilyl. The polymers having hydrolyzable silyl groups may be used alone or in combination of two or more.

[0066] Preferred examples of the main chain of the polymer having a hydrolyzable silyl group include polyalkylene oxide, polyether polyol, (meth)acrylate polymer, polyolefin, and polyester. Examples of polyalkylene oxide include polyethylene oxide, polypropylene oxide, and polybutylene oxide. Examples of polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, random copolymers and block copolymers thereof, and polyoxyalkylene-modified bisphenol A.

[0067] Examples of the monomer that constitutes the (meth)acrylate polymer include alkyl(meth)acrylates in which the alkyl group has 1 to 12 carbon atoms. The alkyl group more preferably has 2 to 8 carbon atoms. In the present invention, (meth)acrylate means methacrylate or acrylate.

[0068] Examples of polyolefins include homopolymers and copolymers of α-olefins such as ethylene and propylene. Examples of polyolefins include polyethylene (e.g., low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed polyethylene, and high-density polyethylene (HDPE)), polypropylene (PP), and ethylene-α-olefin copolymers (e.g., ethylene-propylene copolymers).

[0069] The polyester is preferably a polyester polyol, such as a polyester polyol obtained by condensation polymerization of a glycol such as ethylene glycol, propylene glycol, neopentyl glycol, or tetramethylene glycol with a dicarboxylic acid such as terephthalic acid, isophthalic acid, sebacic acid, succinic acid, phthalic acid, or adipic acid.

[0070] The melt viscosity (initial viscosity) of the moisture-curable hot melt adhesive at 120°C before curing is preferably 3000 to 100,000 mPa·s, more preferably 5,000 to 60,000 mPa·s, more preferably 7,000 to 50,000 mPa·s, and even more preferably 8,000 to 40,000 mPa·s. When the melt viscosity at 120°C is 3,000 mPa·s or more, the initial adhesiveness of the moisture-curable hot melt adhesive is improved. When the melt viscosity at 120°C is 100,000 mPa·s or less, the coatability of the moisture-curable hot melt adhesive is improved.

[0071] For moisture-curing hot melt adhesives, the melt viscosity at 120°C before curing (initial viscosity) refers to the melt viscosity measured at 120°C using a Brookfield viscometer in accordance with the Japan Adhesives Industry Association standard JAI-7-1999. Specifically, the moisture-curing hot melt adhesive is heated to 120°C in a nitrogen atmosphere and melted. The viscosity of the moisture-curing hot melt adhesive is measured using a Brookfield viscometer with rotor No. 29. The rotation speed during measurement is 20 rpm for viscosities less than 20,000 mPa·s and 10 rpm for viscosities 20,000 mPa·s or greater. The obtained viscosity is the initial viscosity of the moisture-curing hot melt adhesive. An example of a Brookfield viscometer is the Brookfield Digital Rheometer DVII (Rotor No. 29).

[0072] [Moisture-curing hot melt adhesive] The method for producing the moisture-curing hot melt adhesive is not particularly limited. Examples of the method for producing the moisture-curing hot melt adhesive include (1) a method for producing a moisture-curing hot melt adhesive in which a urethane prepolymer produced as described above, a polymeric isocyanate, and an antioxidant are mixed uniformly while heating, with the addition of additives as necessary, (2) a method for producing a moisture-curing hot melt adhesive in which a polyisocyanate and an antioxidant are added to a polyol containing a polyester polyol and / or a polyether polyol, the mixture is heated, the polyester polyol and / or the polyether polyol is reacted with the polyisocyanate to produce a urethane prepolymer, and the polymeric isocyanate is then added to the resulting urethane prepolymer, and (3) a method for producing a moisture-curing hot melt adhesive in which a polyisocyanate is added to a polyol containing a polyester polyol and / or a polyether polyol, the mixture is heated, the polyol is reacted with the polyisocyanate to produce a urethane prepolymer, and the polymeric isocyanate and the antioxidant are then added to the resulting urethane prepolymer.

[0073] The following explains how to use a moisture-curing hot melt adhesive. To use a moisture-curing hot melt adhesive, the adhesive is heated to melt it and then applied to the surface of the adherend. At this time, moisture-curing hot melt adhesives have excellent thermal stability, and viscosity increases due to heat applied during melting are suppressed, making it possible to easily and stably apply the moisture-curing hot melt adhesive to the surface of the adherend.

[0074] Thereafter, another adherend is bonded to the coated surface of the adherend, and the moisture-curing hot melt adhesive is left to stand for 120 to 200 hours, preferably in an environment at 20 to 25°C and a relative humidity of 50 to 60%, thereby hardening the moisture-curing hot melt adhesive due to the moisture in the air or the adherend, and bonding the adherends together.

[0075] The cured product obtained by curing the moisture-curable hot melt adhesive has excellent durability and exhibits excellent long-term durability, so that the adhesive state between adherends is maintained stably over a long period of time. [Example]

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0077] [Polyester polyol] Polyester polyol 1 (manufactured by Toyokuni Oil Mills, trade name "HS 2H-350S", hydroxyl value: 32, number average molecular weight: 3500, condensation polymer of sebacic acid and 1,6-hexanediol) Polyester polyol 2 (manufactured by Toyokuni Oil Mills, trade name "HS 2H-451A", hydroxyl value: 25, number average molecular weight: 4500, condensation polymer of adipic acid and 1,6-hexanediol) Polyester polyol 3 (Arakawa Chemical Industries, Ltd., product name "HM-204", hydroxyl value: 52, number average molecular weight: 2500)

[0078] [Polyether polyol] Polyether polyol 1 (manufactured by Asahi Glass Co., Ltd., trade name "Exenol 3020", polypropylene oxide, HO-[CH(CH3)-CH2-O]nH, hydroxyl value: 35, number average molecular weight: 3000) Polyether polyol 2 (manufactured by Asahi Glass Co., Ltd., trade name "Exenol 510", polyethylene oxide-polypropylene oxide copolymer, polyethylene oxide is attached to both ends of polypropylene oxide (HO-[CH(CH3)-CH2-O]nH), hydroxyl value: 28, number average molecular weight: 4000) Polyether polyol 3 (manufactured by Asahi Glass Co., Ltd., trade name "Preminol 4015", polyethylene oxide-polypropylene oxide copolymer, polyethylene oxide is attached to both ends of polypropylene oxide (HO-[CH(CH3)-CH2-O]nH), hydroxyl value: 7.5, number average molecular weight: 15,000)

[0079] [Polyisocyanate (monomeric isocyanate)] 4,4'-Diphenylmethane diisocyanate

[0080] [Polymeric isocyanate] Polymethylene polyphenyl polyisocyanate (Dow product name "PAPI27", Polymeric MDI (Polymeric 4,4'-diphenylmethane diisocyanate), average number of isocyanate groups per molecule: 2.7)

[0081] [Anti-aging agent] Hindered phenolic antioxidant (BASF product name "Irganox 1010")

[0082] (Examples 1 to 10, Comparative Examples 1 to 3) Polyester polyols 1 to 3, polyether polyols 1 to 3, and a hindered phenol-based antioxidant were each fed in the prescribed amounts shown in Table 1 into a 1-liter four-neck flask equipped with a stirring blade, and were then heated to 120°C to melt and mix. Next, the pressure inside the flask was reduced to 1 mmHg or less to dehydrate the compounds inside the flask.

[0083] Thereafter, the atmosphere inside the flask was replaced with nitrogen and purged with nitrogen, and then the compounds inside the flask were heated to 80° C. 4,4′-diphenylmethane diisocyanate was fed into the flask in the predetermined amounts shown in Table 1, and under a nitrogen atmosphere, polyester polyols 1 to 3 and polyether polyols 1 to 3 were reacted with 4,4′-diphenylmethane diisocyanate to produce urethane prepolymers.

[0084] Furthermore, a predetermined amount of polymethylene polyphenyl polyisocyanate shown in Table 2 was added to the flask and mixed at 80°C for 30 minutes under a nitrogen atmosphere to obtain a moisture-curable hot melt adhesive. The composition of the obtained moisture-curable hot melt adhesive is shown in Table 2.

[0085] The initial viscosity and viscosity after aging of the obtained moisture-curable hot melt adhesive were measured as described above, and the initial dumbbell strength and dumbbell strength after aging were measured as described below. The results are shown in Table 2.

[0086] (Thickening rate) The viscosity retention rate was calculated based on the following formula and is shown in the "Thickening rate" column of Table 2. Viscosity increase rate (%) = 100 x viscosity after deterioration / initial viscosity

[0087] The initial viscosity of the moisture-curing hot melt adhesive was measured as described above. The viscosity of the moisture-curing hot melt adhesive after aging was measured as follows. The moisture-curing hot melt adhesive was left in a nitrogen atmosphere at 120°C for 24 hours. After that, the viscosity of the moisture-curing hot melt adhesive was measured using a Brookfield viscometer with rotor number 29. The rotation speed during measurement was 20 rpm when the viscosity was less than 20,000 mPa·s, and 10 rpm when the viscosity was 20,000 mPa·s or greater. The viscosity obtained was taken as the viscosity of the moisture-curing hot melt adhesive after aging.

[0088] (Initial dumbbell strength) The initial dumbbell strength of moisture-curing hot melt adhesives is measured as follows: The moisture-curing hot melt adhesive is heated to 120°C in air to melt it. A 200μm thick sheet-shaped test piece is prepared using the molten moisture-curing hot melt adhesive. The test piece is aged for two weeks in air at 23°C and 50% relative humidity. After aging, the test piece is punched out into a No. 3 dumbbell, and the dumbbell strength is measured at a tensile speed of 100mm / min. The obtained dumbbell strength is the initial dumbbell strength.

[0089] (Dumbbell strength after deterioration) The dumbbell strength after aging of moisture-curing hot melt adhesives is measured as follows. A sheet-shaped test piece, cured in the same manner as when measuring the initial dumbbell strength of the moisture-curing hot melt adhesive, is left in air at 70°C and a relative humidity of 90% for two weeks. After that, the test piece is punched out into a No. 3 dumbbell, and the dumbbell strength is measured at a tensile speed of 100 mm / min. The obtained dumbbell strength is the dumbbell strength after aging. The higher the dumbbell strength after aging, the higher the long-term durability can be determined to be.

[0090] (Dumbbell strength retention rate) The dumbbell strength retention rate was calculated based on the following formula and is shown in the "Dumbbell Strength Retention Rate" column in Table 2. Dumbbell strength retention rate (%) = 100 x dumbbell strength after deterioration / initial dumbbell strength

[0091] (Initial adhesion) The moisture-curable hot melt adhesive was heated to 120°C to melt it, and then the molten moisture-curable hot melt adhesive was applied to one side of an olefin sheet (thickness 180 µm) to a coating thickness of 40 µm.

[0092] Next, the above-mentioned olefin sheet was superimposed on a medium-density fiber substrate [medium density fiberboard (MDF)] whose surface temperature had been adjusted to 35°C, via a moisture-curing hot melt adhesive, and then the olefin sheet was pressed onto the medium-density fiber substrate using a rubber roll, thereby laminating the olefin sheet onto the medium-density fiber substrate to prepare a test specimen.

[0093] The test piece was left in an environment of 23°C and 55% relative humidity for 10 minutes to cool and solidify the moisture-curable hot melt adhesive. After that, the olefin sheet was peeled off from the medium-density fiber substrate at a peel angle of 180° and a peel speed of 250 mm / min, and the maximum peel strength during this peeling was measured as the "initial peel strength (N / 25 mm)."

[0094] (normal adhesion) Test pieces were prepared in the same manner as in the measurement of initial adhesion. The test pieces were then left for one week in an environment of 23°C and 55% relative humidity to allow the moisture-curing hot melt adhesive to moisture cure. The olefin sheet was then peeled from the medium-density fiber substrate at a peel angle of 180° and a peel speed of 250 mm / min, and the maximum peel strength during this peeling was measured as the "normal peel strength (N / 25 mm)."

[0095] [Table 1]

[0096] [Table 2]

Claims

1. a urethane prepolymer having isocyanate groups at both molecular terminals, the urethane prepolymer being a reaction product of a polyol containing a polyester polyol and / or a polyether polyol with a polyisocyanate; polymeric isocyanate, A moisture-curing hot melt adhesive characterized by containing an antioxidant.

2. 2. The moisture-curable hot melt adhesive according to claim 1, wherein the antioxidant contains a hindered phenol-based antioxidant and / or a hindered amine-based light stabilizer.

3. The moisture-curable hot melt adhesive according to claim 1 or 2, characterized in that the melt viscosity at 120°C is 3000 to 100,000 mPa·s.

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