Moisture-curing hot melt adhesive

Abstract

To provide a moisture-curable hot-melt adhesive that keeps excellent adhesion even in use in a high humidity atmosphere (moisture adhesion) and excellent normal-state adhesion.SOLUTION: A moisture-curable hot-melt adhesive comprises a urethane prepolymer that is a reactant between a polyol comprising a microcrystalline polyester polyol with a number average molecular weight of 3000-6000 and a crystalline polyester polyol as a condensed polymer of 1, 6-hexanediol and 1,12-dodecanedioic acid, and a polyisocyanate, and has an isocyanate group at an end.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Conventionally, in order to impart design properties, a decorative sheet having a decoration such as coloring is adhered to the surface of a base material such as furniture, exterior materials, and interior materials using an adhesive. As an adhesive used for adhering the base material and the decorative sheet, an adhesive containing an organic solvent and a moisture-curable hot-melt adhesive are known. Among them, the moisture-curable hot-melt adhesive does not contain volatile organic compounds (VOCs) which are the cause of sick house syndrome, and is widely used as a measure against work hygiene and environmental pollution.

[0003] Patent Document 1 discloses a moisture-curable hot-melt adhesive for IC cards containing a urethane prepolymer having an isocyanate group at the terminal, The urethane prepolymer has a chemical structure derived from a polyester polyol obtained by the reaction of a diol and a dicarboxylic acid having 10 or less carbon atoms, The shear modulus (40 ° C) before moisture curing is (1 × 10 4 ) to (1 × 10 8 ) Pa, The shear modulus (80 ° C) before moisture curing is (1 × 10 0 ) to (1 × 10 4 ) Pa, and a moisture-curable hot-melt adhesive for IC cards is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above-mentioned moisture-curing hot melt adhesive has the problem that its adhesive properties decrease when used in a humid atmosphere, and furthermore, its adhesive properties under normal conditions are also insufficient.

[0006] The present invention provides a moisture-curing hot-melt adhesive that maintains excellent adhesion even when used in a high-humidity atmosphere (moisture-resistant adhesion) and also has excellent adhesion under normal conditions. [Means for solving the problem]

[0007] The moisture-curing hot-melt adhesive of the present invention is a reaction product of a polyol and a polyisocyanate, and includes a urethane prepolymer having isocyanate groups at its terminals, and contains a microcrystalline polyester polyol having a number average molecular weight of 3000 to 6000 and a crystalline polyester polyol which is a condensation polymer of 1,6-hexanediol and 1,12-dodecanediic acid. [Effects of the Invention]

[0008] The moisture-curing hot-melt adhesive of the present invention has excellent normal adhesion and also maintains excellent adhesion stably even when used in a high-humidity atmosphere (moisture-resistant adhesion). [Modes for carrying out the invention]

[0009] The moisture-curing hot-melt adhesive of the present invention is a reaction product of a polyol (A) and a polyisocyanate (B), which includes a crystalline polyester polyol (A1) that is a condensation polymer of 1,6-hexanediol and 1,12-dodecanediic acid, and a microcrystalline polyester polyol (A2) having a number average molecular weight of 3000 to 6000.

[0010] The moisture-curing hot-melt adhesive of the present invention contains a urethane prepolymer which is a reaction product of a polyol (A) containing a predetermined polyol and a polyisocyanate (B), and which has isocyanate groups at its terminals. The urethane prepolymer undergoes a crosslinking reaction and hardens in response to moisture contained in the air and / or substrate.

[0011] The reaction between polyol (A) and polyisocyanate (B) can be carried out in a general manner. For example, the reaction can be obtained by charging the polyisocyanate in a reaction vessel, adding the polyol (which has had its water removed beforehand) separately or mixed together with additives, and then reacting the hydroxyl groups with the isocyanate groups under heating. Alternatively, the polyol and additives can be charged in a reaction vessel, heated, melted, and dispersed, then the water can be removed, and then the polyisocyanate can be charged to carry out the reaction between the hydroxyl groups and the isocyanate groups. The production of urethane prepolymers can usually be carried out without solvents, but it 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. In the reaction between the hydroxyl groups of the polyol and the isocyanate groups of the polyisocyanate, a urethane catalyst can be used as needed. The urethane catalyst is not particularly limited and examples include triethylamine, triethylenediamine, N-methylmorpholine, potassium acetate, zinc stearate, tin octoate, and dibutyltin dilaurate. The urethane catalyst may be used alone or in combination of two or more. Polymeric isocyanates with more than two isocyanate groups per molecule (e.g., polymethylene polyphenyl polyisocyanate, crude toluene polyisocyanate, etc.) are preferably used in combination with diisocyanates to reduce the melt viscosity of the moisture-curing hot-melt adhesive. After producing a urethane prepolymer by reacting a portion of the polyol with diisocyanate in the manner described above, polymeric isocyanates with more than two isocyanate groups per molecule may be added to the reaction system and reacted with the polyol to produce a urethane prepolymer.

[0012] In the reaction between polyol (A) and polyisocyanate (B), the ratio of moles of hydroxyl groups in polyol (A) to moles of isocyanate groups in polyisocyanate (B) (moles of isocyanate groups / moles of hydroxyl groups) is preferably 1.3 to 4.0, and more preferably 1.5 to 3.0. A molar ratio of 1.5 or higher improves the coatability of the moisture-curing hot melt adhesive. A molar ratio of 3.0 or lower suppresses foaming during the curing of the moisture-curing hot melt adhesive.

[0013] [Polyol (A)] The urethane prepolymer contained in the moisture-curing hot melt adhesive is a reaction product of a polyol (A) containing a predetermined polyol and a polyisocyanate (B). The urethane prepolymer has isocyanate groups at the molecular ends, and preferably has isocyanate groups at both molecular ends.

[0014] Polyol (A) is a compound having two or more hydroxyl groups in one molecule, and contains crystalline polyester polyol (A1) and microcrystalline polyester polyol (A2), which will be described later.

[0015] [Crystalline polyester polyol (A1)] Crystalline polyester polyol (A1) is a condensation polymer of 1,6-hexanediol and 1,12-dodecanediic acid. The condensation polymerization reaction between 1,6-hexanediol and 1,12-dodecanediic acid can be carried out using a general method.

[0016] Crystalline polyester polyol (A1), that is, the condensation polymer of 1,6-hexanediol and 1,12-dodecanediic acid, is crystalline. Crystalline polyester polyol (A1) is a polyester polyol in which the endothermic amount (hereinafter sometimes simply referred to as "endothermic amount") of the melting curve measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC) measurement as specified in JIS K7121 is 10 cal / g (40 J / g) or more.

[0017] The number average molecular weight of the crystalline polyester polyol (A1) is preferably 1000 or more, more preferably 1500 or more, more preferably 1800 or more, more preferably 2000 or more, more preferably 2500 or more, more preferably 3000 or more, and more preferably 3200 or more. The number average molecular weight of the crystalline polyester polyol (A1) is preferably 20000 or less, more preferably 10000 or less, more preferably 7000 or less, more preferably 6000 or less, more preferably 5000 or less, more preferably 4500 or less, and more preferably 4000 or less. When the number average molecular weight of the crystalline polyester polyol (A1) is 1000 or more, the initial adhesion of the moisture-curing hot melt adhesive is improved. When the number average molecular weight of the crystalline polyester polyol (A1) is 20000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the moisture-curing hot melt adhesive has excellent coating properties.

[0018] In this invention, the number-average molecular weight of a polyol refers to the value measured in the following manner. The number-average molecular weight of a polyol can be measured using gel permeation chromatography (GPC). Specifically, a sample solution is prepared by dissolving the sample in tetrahydrofuran (THF) to a concentration of 1.0 mass%. Using this sample solution, the number-average molecular weight of the polyol is measured using a refractive index detector with standard polystyrene as the reference, by GPC.

[0019] For the measurement system, for example, a system consisting of an LC-9A liquid delivery device, a RID-6A refractive index detector, a CTO-6A column oven, and a C-R4A data analyzer (all manufactured by Shimadzu Corporation) can be used. For the GPC column, for example, three GPC-805 columns (exclusion limit 4 million) and one GPC-804 column (exclusion limit 400,000) (all manufactured by Shimadzu Corporation) can be used connected in this order. The measurement conditions are a sample injection volume of 25 μL (liters), eluent tetrahydrofuran (THF), liquid delivery volume of 1.0 mL / min, and column temperature of 45°C.

[0020] The hydroxyl value of the crystalline polyester polyol (A1) is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, and still more preferably 30 mgKOH / g or more. The hydroxyl value of the crystalline polyester polyol (A1) is preferably 50 mgKOH / g or less, more preferably 45 mgKOH / g or less, and still more preferably 35 mgKOH / g or less. When the hydroxyl value of the crystalline polyester polyol (A1) is 20 mgKOH / g or more, the melt viscosity of the moisture-curable hot melt adhesive can be reduced, and the moisture-curable hot melt adhesive has excellent coating properties. When the hydroxyl value of the crystalline polyester polyol (A1) is 50 mgKOH / g or less, the initial adhesiveness of the moisture-curable hot melt adhesive is improved.

[0021] In the present invention, the hydroxyl value of the polyol means the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group when 1 g of the polyol is acetylated (JIS K0070:1992 2.1(5)). Specifically, it can be measured by acetylating the hydroxyl groups in the polyol with acetic anhydride and then titrating the unused acetic anhydride with potassium hydroxide (JIS K0070:1992 3.1 (neutral titration method)).

[0022] In the polyol (A), the content of the crystalline polyester polyol (A1) is preferably 15% by mass or more, more preferably 18% by mass or more, still more preferably 20% by mass or more, still more preferably 23% by mass or more, and still more preferably 28% by mass or more. In the polyol (A), the content of the crystalline polyester polyol (A1) is preferably 45% by mass or less, more preferably 42% by mass or less, and still more preferably 40% by mass or less. When the content of the crystalline polyester polyol (A1) is 15% by mass or more, the initial adhesiveness of the moisture-curable hot melt adhesive is improved. When the content of the crystalline polyester polyol (A1) is 45% by mass or less, the normal-state adhesiveness of the moisture-curable hot melt adhesive is improved.

[0023] [Microcrystalline polyester polyol (A2)] Polyol (A) contains microcrystalline polyester polyol (A2). Microcrystalline polyester polyol (A2) is a condensation polymer of polycarboxylic acid and polyol. That is, microcrystalline polyester polyol (A2) is a polymer obtained by condensation polymerization in which polycarboxylic acid and polyol undergo an ester reaction at the carboxyl group of the polycarboxylic acid and the hydroxyl group of the polyol.

[0024] The polycarboxylic acid is not particularly limited, and examples include 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. Adipic acid and terephthalic acid are preferred, and it is preferable that a polycarboxylic acid contains both adipic acid and terephthalic acid. The polycarboxylic acid may be used alone or in combination of two or more types.

[0025] The polyol is not particularly limited and includes, for example, 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, and cyclohexanediol. 1,6-hexanediol and ethylene glycol are preferred, and 1,6-hexanediol is more preferred. The polyol may be used alone or in combination of two or more.

[0026] Microcrystalline polyester polyol (A2) is a polyester polyol whose melting curve measured by differential scanning calorimetry (DSC) as specified in JIS K7121, at a heating rate of 10°C / min, has an endothermic value of 2.5 cal / g (10 J / g) or more and less than 10 cal / g (40 J / g).

[0027] The number-average molecular weight of the microcrystalline polyester polyol (A2) is 2000 or more, more preferably 3000 or more, and even more preferably 4000 or more. The number-average molecular weight of the microcrystalline polyester polyol (A2) is 6000 or less, more preferably 5000 or less, and even more preferably 4800 or less. When the number-average molecular weight of the microcrystalline polyester polyol (A2) is 2000 or more, the normal adhesion of the moisture-curing hot melt adhesive is improved. When the number-average molecular weight of the microcrystalline polyester polyol (A2) is 6000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the moisture-curing hot melt adhesive has excellent coating properties.

[0028] The hydroxyl value of microcrystalline polyester polyol (A2) is preferably 20 mg KOH / g or higher, more preferably 21 mg KOH / g or higher, and even more preferably 22 mg KOH / g or higher. The hydroxyl value of microcrystalline polyester polyol (A2) is preferably 60 mg KOH / g or lower, more preferably 40 mg KOH / g or lower, and even more preferably 30 mg KOH / g or lower. When the hydroxyl value of microcrystalline polyester polyol (A2) is 20 mg KOH / g or higher, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the moisture-curing hot melt adhesive has excellent coating properties. When the hydroxyl value of microcrystalline polyester polyol (A2) is 60 mg KOH / g or lower, the normal adhesion of the moisture-curing hot melt adhesive is improved.

[0029] In polyol (A), the content of microcrystalline polyester polyol (A2) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. In polyol (A), the content of microcrystalline polyester polyol (A2) is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content of microcrystalline polyester polyol (A2) is 20% by mass or more, the normal adhesion of the moisture-curing hot melt adhesive is improved. When the content of microcrystalline polyester polyol (A2) is 50% by mass or less, the initial adhesion of the moisture-curing hot melt adhesive is improved.

[0030] In polyol (A), the mass ratio of microcrystalline polyester polyol to crystalline polyester polyol (microcrystalline polyester polyol / crystalline polyester polyol) is preferably 0.3 or higher, more preferably 0.5 or higher, and even more preferably 0.6 or higher. In polyol (A), the mass ratio of microcrystalline polyester polyol to crystalline polyester polyol (microcrystalline polyester polyol / crystalline polyester polyol) is preferably 3.3 or lower, more preferably 2.1 or lower, more preferably 1.5 or lower, even more preferably 1.3 or lower, and even more preferably 1.2 or lower. When the mass ratio of microcrystalline polyester polyol to crystalline polyester polyol (microcrystalline polyester polyol / crystalline polyester polyol) is 0.3 or higher, the normal adhesion is improved. When the mass ratio of microcrystalline polyester polyol to crystalline polyester polyol (microcrystalline polyester polyol / crystalline polyester polyol) is 3.3 or lower, the initial adhesion is improved.

[0031] [Other polyols (A)] Polyol (A) may contain polyols other than crystalline polyester polyol (A1) and microcrystalline polyester polyol (A2). Polyol (A) other than crystalline polyester polyol (A1) and microcrystalline polyester polyol (A2) is not particularly limited, and preferred examples include amorphous polyester polyol (A3), polycaprolactone polyol, polyether polyol, polyalkylene polyol, and polycarbonate polyol, with amorphous polyester polyol (A3) being preferred. These polyols may be used individually or in combination of two or more.

[0032] Since polyol (A) improves the heat creep resistance and normal adhesion of moisture-curing hot-melt adhesives, it is preferable that the polyol (A) includes crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3).

[0033] When polyol (A) contains crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3), the content of crystalline polyester polyol (A1) in polyol (A) is preferably 15% by mass or more, more preferably 18% by mass or more, more preferably 20% by mass or more, more preferably 23% by mass or more, and more preferably 28% by mass or more, when the total amount of crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3) is taken as 100% by mass. The content of crystalline polyester polyol (A1) in polyol (A) is preferably 45% by mass or less, more preferably 42% by mass or less, and more preferably 40% by mass or less. When the content of crystalline polyester polyol (A1) is 15% by mass or more, the initial adhesion of the moisture-curing hot melt adhesive is improved. When the content of crystalline polyester polyol (A1) is 45% by mass or less, the normal adhesion of the moisture-curing hot melt adhesive is improved.

[0034] When polyol (A) contains crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3), the content of microcrystalline polyester polyol (A2) in polyol (A) is preferably 20% by mass or more, more preferably 25% by mass or more, and more preferably 30% by mass or more, when the total amount of crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3) is taken as 100% by mass. The content of microcrystalline polyester polyol (A2) in polyol (A) is preferably 50% by mass or less, more preferably 45% by mass or less, and more preferably 40% by mass or less. When the content of microcrystalline polyester polyol (A2) is 20% by mass or more, the normal adhesion of the moisture-curing hot melt adhesive is improved. When the content of microcrystalline polyester polyol (A2) is 50% by mass or less, the initial adhesion of the moisture-curing hot melt adhesive is improved.

[0035] When polyol (A) contains crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3), the content of amorphous polyester polyol (A3) in polyol (A) is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 20% by mass or more, and more preferably 25% by mass or more, when the total amount of crystalline polyester polyol (A1), microcrystalline polyester polyol (A2), and amorphous polyester polyol (A3) is taken as 100% by mass. The content of amorphous polyester polyol (A3) in polyol (A) is preferably 50% by mass or less, more preferably 45% by mass or less, more preferably 40% by mass or less, and more preferably 38% by mass or less. When the content of amorphous polyester polyol (A3) is 10% by mass or more, the normal adhesion of the moisture-curing hot melt adhesive is improved. When the content of amorphous polyester polyol (A3) is 50% by mass or less, the initial adhesion of moisture-curing hot melt adhesives is improved.

[0036] [Amorphous polyester polyol (A3)] The amorphous polyester polyol (A3) is preferably a condensation polymer of a polycarboxylic acid and a polyol. That is, the amorphous polyester polyol (A3) is preferably a polymer obtained by condensation polymerization in which a polycarboxylic acid and a polyol undergo an ester reaction at the carboxyl group of the polycarboxylic acid and the hydroxyl group of the polyol.

[0037] The polycarboxylic acid is not particularly limited, and examples include terephthalic acid, isophthalic acid, phthalic anhydride, 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. Adipic acid, terephthalic acid, phthalic anhydride, and isophthalic acid are preferred, adipic acid, terephthalic acid, and phthalic anhydride are more preferred, and it is preferable that a polycarboxylic acid contains adipic acid, terephthalic acid, and phthalic anhydride. The polycarboxylic acid may be used alone or in combination of two or more types.

[0038] The polyol is not particularly limited and includes, for example, 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, and cyclohexanediol. Ethylene glycol and 1,6-hexanediol are preferred, and ethylene glycol is more preferred. The polyol may be used alone or in combination of two or more.

[0039] Amorphous polyester polyol (A3) is a polyester polyol in which the endothermic value of the melting curve measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC) measurement as specified in JIS K7121 is less than 2.5 cal / g (10 J / g).

[0040] Amorphous polyester polyols also include liquid polyester polyols (A3). Liquid polyester polyols are concentrated at 1 atmosphere (1.013 × 10⁻¹⁰). 5 It is a liquid at Pa and 20°C.

[0041] The number average molecular weight of the amorphous polyester polyol (A3) is preferably 2000 or more, more preferably 2200 or more, more preferably 2700 or more, more preferably 2800 or more, more preferably 3000 or more, more preferably 3100 or more, more preferably 3200 or more, and more preferably 3300 or more. The number average molecular weight of the amorphous polyester polyol (A3) is preferably 6000 or less, more preferably 5000 or less, more preferably 4000 or less, and more preferably 3800 or less. When the number average molecular weight of the amorphous polyester polyol (A3) is 2000 or more, the initial adhesion of the moisture-curing hot melt adhesive is improved. When the number average molecular weight of the amorphous polyester polyol (A3) is 6000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the moisture-curing hot melt adhesive has excellent coating properties.

[0042] The hydroxyl value of amorphous polyester polyol (A3) is preferably 20 mg KOH / g or higher, more preferably 25 mg KOH / g or higher, and even more preferably 30 mg KOH / g or higher. The hydroxyl value of amorphous polyester polyol (A3) is preferably 90 mg KOH / g or lower, more preferably 60 mg KOH / g or lower, and even more preferably 38 mg KOH / g or lower. When the hydroxyl value of amorphous polyester polyol (A3) is 20 mg KOH / g or higher, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the moisture-curing hot melt adhesive has excellent coating properties. When the hydroxyl value of amorphous polyester polyol (A3) is 90 mg KOH / g or lower, the normal adhesion of the moisture-curing hot melt adhesive is improved.

[0043] In polyol (A), the content of amorphous polyester polyol (A3) is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 20% by mass or more, and more preferably 25% by mass or more. In polyol (A), the content of amorphous polyester polyol (A3) is preferably 50% by mass or less, more preferably 45% by mass or less, more preferably 40% by mass or less, and more preferably 38% by mass or less. When the content of amorphous polyester polyol (A3) is 10% by mass or more, the initial adhesion of the moisture-curing hot melt adhesive is improved. When the content of amorphous polyester polyol (A3) is 50% by mass or less, the normal adhesion of the moisture-curing hot melt adhesive is improved.

[0044] [Polycaprolactone polyol] Examples of polycaprolactone polyols include those obtained by ring-opening addition polymerization of a lactone compound to a polyol. Examples of polyols include those similar to those mentioned above for polyester polyols. Examples of lactone compounds include β-propiolactone, pivalolactone, δ-valerolactone, ε-caprolactone, methyl-ε-caprolactone, dimethyl-ε-caprolactone, and trimethyl-ε-caprolactone.

[0045] [Polyisocyanate (B)] Moisture-curing hot-melt adhesives contain a urethane prepolymer, which is a reaction product of the polyol (A) and polyisocyanate (B) described above. The urethane prepolymer is a product obtained by condensation polymerization in which polyol (A) and polyisocyanate (B) form urethane bonds between the hydroxyl groups of polyol (A) and the isocyanate groups of polyisocyanate (B).

[0046] Examples of the above polyisocyanate (B) include diphenylmethane diisocyanate (MDI, 4,4'-isomer, 2,4-isomer, 2,2'-isomer, or mixtures thereof), carbodiimide-modified MDI, carbodiimide-modified diphenylmethane polyisocyanate, tolylene diisocyanate (TDI, 2,4-isomer, 2,6-isomer, or mixtures thereof), xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate (NDI), tetramethylxylene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate (HDI), Examples include dimer acid diisocyanate, norbornene diisocyanate, lysine diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate, with polyisocyanates containing aromatic rings (e.g., benzene rings, naphthalene rings, etc.) being preferred. Among these, diphenylmethane diisocyanate and carbodiimide-modified MDI are preferred, and 4,4'-diphenylmethane diisocyanate is more preferred, as they improve the normal adhesion of moisture-curing hot-melt adhesives.

[0047] [Additives] Moisture-curing hot melt adhesives may contain tackifiers, oils, plasticizers, curing catalysts, stabilizers, fillers, antioxidants, light stabilizers, UV absorbers, colorants, flame retardants, fragrances, pigments, dyes, etc., to the extent that they do not impair their effects.

[0048] The tackifier is not particularly limited and examples include rosin resins, terpene resins, aliphatic petroleum resins, and aromatic petroleum resins. The tackifier may be used alone or in combination of two or more types.

[0049] The preferred ring-spherical softening point of the tackifier is 90-150°C, as this prevents elution from moisture-curing hot-melt adhesives at room temperature and allows for sufficient melting during the melting of the moisture-curing hot-melt adhesive. The ring-spherical softening point of the tackifier is the temperature measured in accordance with JIS K6863 (the measurement method involves horizontally supporting a ring filled with the sample in a glycerin bath and measuring the temperature when a sphere placed in the center of the sample touches the bottom plate).

[0050] The oil is not particularly limited and includes, for example, aromatic components, naphthenic oils, and paraffinic oils found in known oils commonly used as rubber softeners, such as process oils, extender oils, and softeners. The oil may be used alone or in combination of two or more types.

[0051] The plasticizer is not particularly limited and includes, for example, phthalate esters such as diisononyl phthalate and 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 acetylricylinoleate, trimellitic acid esters, chlorinated paraffins, hydrocarbon plasticizers such as alkyldiphenyl and partially hydrogenated terphenyl, process oils, epoxy plasticizers such as epoxidized soybean oil and benzyl epoxy stearate, vinyl polymers obtained by polymerizing vinyl monomers, and esters of polyalkylene glycols such as diethylene glycol dibenzoate, triethylene glycol dibenzoate, and pentaerythritol ester. The plasticizer may be used alone or in combination of two or more types.

[0052] Curing catalysts are used to improve the curability of moisture-curing hot-melt adhesives. The curing catalyst is not particularly limited and examples include amine-based curing catalysts and tin-based curing catalysts. The curing catalyst may be used alone or in combination of two or more types.

[0053] As amine-based curing catalysts, morpholine-based compounds are preferred, specifically 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-( Examples include 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, and tris(2-(2-ethyl-4-morpholino)ethylamine).

[0054] The tin-based curing catalyst is not particularly limited and examples include stannous acetate, dibutyltin dilaurate, dibutyltin dioctate, dibutyltin diacetate, dioctyltin dilaurate, dioctyltin dioctate, dioctyltin diacetate, and stannous dioctanoate. These may be used individually or in combination of two or more.

[0055] The filler material is not particularly limited and includes, for example, 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 resin and vinylidene chloride resin, polyvinyl chloride (PVC) powder, polymethyl methacrylate powder, and other resin powders. The filler material may be used alone or in combination of two or more types.

[0056] The antioxidant is not particularly limited and examples include hindered phenol antioxidants, monophenol antioxidants, bisphenol antioxidants, and polyphenol antioxidants. The antioxidant may be used alone or in combination of two or more types.

[0057] The light stabilizer is not particularly limited, but for example, a hindered amine light stabilizer is preferred, and a hindered amine light stabilizer in which the amine portion 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-tetramethylpiperidine-4-yl)amino)-triazine-2-yl)-4,7-diazadecane-1,10-diamine, bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl) ester of decandioate, reaction product of 1,1-dimethylethyl hydroperoxide and octane, bis(1,2,2,6,6, Examples include 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-piperidyl sebacate, and bis(1-octyroxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate. The light stabilizer may be used alone or in combination of two or more types.

[0058] The ultraviolet absorber is not particularly limited and examples include benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers. The ultraviolet absorber may be used alone or in combination of two or more types.

[0059] [Moisture-curing hot melt adhesive] The method for manufacturing moisture-curing hot melt adhesives is not particularly limited. For example, a moisture-curing hot melt adhesive can be manufactured by adding additives as needed to a urethane prepolymer manufactured in the manner described above, then heating, melting, and uniformly mixing the mixture.

[0060] The melt viscosity of a moisture-curing hot melt adhesive at 120°C is preferably 2,000 to 60,000 mPa·s, more preferably 3,000 to 55,000 mPa·s, and even more preferably 4,000 to 50,000 mPa·s. A melt viscosity of 2,000 mPa·s or higher at 120°C improves the applicability of the moisture-curing hot melt adhesive. A melt viscosity of 60,000 mPa·s or lower at 120°C also improves the applicability of the moisture-curing hot melt adhesive. Note that the melt viscosity of a moisture-curing hot melt adhesive at 120°C refers to the melt viscosity obtained by measuring it using a B-type viscometer in accordance with the Japan Adhesive Industry Association standard JAI-7-1999, under conditions of a temperature of 120°C and a rotation speed of 20 rpm. As an example of a Type B viscometer, Brookfield Corporation sells one under the product name "Type B Viscometer Digital Rheometer DVII (Rotor No. 29)".

[0061] The normal adhesive strength of the moisture-curing hot melt adhesive is preferably 30 N / inch or higher, more preferably 40 N / inch or higher, and even more preferably 45 N / inch or higher. The normal adhesive strength of the moisture-curing hot melt adhesive is preferably 200 N / inch or lower. The normal adhesive strength of the moisture-curing hot melt adhesive refers to the value measured according to the following procedure.

[0062] The moisture-resistant adhesive strength of a moisture-curing hot melt adhesive is preferably 20 N / inch or higher, preferably 30 N / inch or higher, and more preferably 35 N / inch or higher. The moisture-resistant adhesive strength of a moisture-curing hot melt adhesive is preferably 200 N / inch or lower. The moisture-resistant adhesive strength of a moisture-curing hot melt adhesive refers to the value measured according to the following procedure.

[0063] The procedure for using moisture-curing hot melt adhesive is described below. To use moisture-curing hot melt adhesive, heat the adhesive to 70-160°C to melt it, and then apply the molten moisture-curing hot melt adhesive to the substrate (adhesion object) or surface sheet (preferably the surface sheet) using a general method. The surface sheet is then bonded to the substrate via the moisture-curing hot melt adhesive. Examples of application tools for applying the molten moisture-curing hot melt adhesive to the substrate (adhesion object) or surface sheet (preferably the surface sheet) include roll coaters, spray coaters, T-die coaters, and knife coaters.

[0064] Subsequently, by leaving the moisture-curing hot melt adhesive in an environment preferably at 20-25°C and 50-60% relative humidity for 120-200 hours, the moisture-curing hot melt adhesive is cured by the moisture (humidity) contained in the air, substrate (adhesion), or surface sheet, thereby bonding and integrating the surface sheet onto the substrate.

[0065] The materials constituting the base material are not particularly limited and include, for example, polyvinyl chloride, polyvinylidene chloride, SPC, polyethylene, polypropylene, polystyrene, ABS, polyamide, polyester, polyurethane, polyvinyl alcohol, ethylene-vinyl acetate copolymer resin, chlorinated polypropylene, melamine resin, and other synthetic resins.

[0066] Examples of surface sheets include decorative sheets. Decorative sheets are not particularly limited and include synthetic resin sheets containing synthetic resins such as polyester, nylon, polystyrene, polycarbonate, polyvinyl chloride, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyethylene, and polypropylene, as well as paper, veneer, and metal foil. The decorative sheet may have its decorative properties enhanced by applying color or patterns to its surface.

[0067] A decorative material obtained by integrally bonding a decorative sheet to the surface of a base material using a moisture-curing hot-melt adhesive is preferably used, for example, as an exterior material for flooring, door frames and panels for wooden doors, window frames, thresholds, handrails, baseboards, moldings, kitchens, closets, and as an interior material and furniture. [Examples]

[0068] The present invention will be described more specifically below with reference to examples, but the present invention is not limited thereto.

[0069] The polyols and polyisocyanates used in the examples and comparative examples are shown below.

[0070] [Polyol (A)] • Crystalline polyester polyol (A11) (manufactured by Evonik Degussa, trade name "Dynacol 7380", endothermic value: 25 cal / g, hydroxyl value: 30 mg KOH / g, number average molecular weight: 3500, condensation polymer of 1,12-dodecanedic acid and 1,6-hexanediol)

[0071] • Crystalline polyester polyol (A12) (manufactured by Toyokuni Oil Co., Ltd., product name "HS 2H-350S", endothermic value: 25 cal / g, hydroxyl value: 32 mg KOH / g, number average molecular weight: 3500, condensation polymer of sebaciic acid and 1,6-hexanediol)

[0072] • Crystalline polyester polyol (A13) (manufactured by Toyokuni Oil Co., Ltd., product name "HS 2H-351A", endothermic value: 18 cal / g, hydroxyl value: 32 mg KOH / g, number average molecular weight: 3500, condensation polymer of adipic acid and 1,6-hexanediol)

[0073] • Crystalline polyester polyol (A14) (manufactured by Ube Industries, Ltd., product name "Ethanacol 3010", endothermic value: 25 cal / g, hydroxyl value: 30 mg KOH / g, number average molecular weight: 3500, condensation polymer of 1,12-dodecanediic acid and 1,6-hexanediol)

[0074] • Microcrystalline polyester polyol (A2) (manufactured by Toyokuni Oil Co., Ltd., product name "HS 2H-458T", endothermic value: 6 cal / g, hydroxyl value: 25 mg KOH / g, number average molecular weight: 4500, condensation polymer of adipic acid and terephthalic acid with 1,6-hexanediol)

[0075] • Amorphous polyester polyol (A31) (manufactured by Toyokuni Oil Co., Ltd., product name "HS 2F-305S", liquid (1 atm and 20°C), hydroxyl value: 36 mg KOH / g, number average molecular weight: 3100, condensation polymer of ethylene glycol, neopentyl glycol and 1,6-hexanediol with adipic acid, sebaciic acid and isophthalic acid)

[0076] • Amorphous polyester polyol (A32) (manufactured by Toyokuni Oil Co., Ltd., product name "Polyol 2000", endothermic value: 2 cal / g, hydroxyl value: 32 mg KOH / g, number average molecular weight: 3500, condensation polymer of adipic acid, terephthalic acid, and phthalic anhydride with ethylene glycol)

[0077] [Polyisocyanate (B)] · 4,4'-diphenylmethane diisocyanate

[0078] (Examples 1-10, Comparative Examples 1-3) Polyol (A) was placed in 1-liter four-necked flasks equipped with stirring blades in the predetermined amounts shown in Tables 1 and 2, respectively. The mixture was heated and melted at 120°C to produce a molten mixture, and the mixture was dehydrated by reducing the pressure to 1 mmHg or less. After that, the flask was purged with nitrogen gas and the temperature of the mixture was cooled to 80°C.

[0079] Next, 4,4'-diphenylmethane diisocyanate was added to the flask as polyisocyanate (B) in the amounts shown in Tables 1 and 2, and the mixture was stirred under a nitrogen gas atmosphere for 3 hours. This caused the hydroxyl groups of polyol (A) and the isocyanate groups of polyisocyanate (B) to react and undergo condensation polymerization, producing a urethane prepolymer that is a reaction product of polyol (A) and polyisocyanate (B) and has isocyanate groups at both ends, thus obtaining a moisture-curing hot-melt adhesive containing the urethane prepolymer.

[0080] The obtained moisture-curing hot melt adhesives were measured for normal adhesion, initial adhesion, and moisture resistance according to the following procedure, and the results are shown in Tables 1 and 2.

[0081] (normal adhesion) A moisture-curing hot melt adhesive was heated to 120°C to melt it, and then the molten moisture-curing hot melt adhesive was applied to one surface of a polyolefin sheet (thickness 180 μm) to a coating thickness of 50 μm.

[0082] Subsequently, a polyolefin sheet was superimposed onto an SPC substrate (polyvinyl chloride containing calcium carbonate), whose surface temperature was adjusted to 40°C, via a coated moisture-curing hot-melt adhesive. Then, a rubber roll was rolled over the polyolefin sheet to press the polyolefin sheet and the SPC substrate together, thereby obtaining a test specimen.

[0083] Next, the moisture-curing hot melt adhesive was cured by leaving the test specimens in an environment of 23°C and 55% relative humidity for one week. Then, the polyolefin sheet was peeled from the SPC substrate at a peel angle of 180 degrees and a peel speed of 200 mm / min, and the average peel strength at this time was measured as the "normal adhesive strength (N / inch)".

[0084] (Initial adhesion) A moisture-curing hot melt adhesive was heated to 120°C and melted. The molten moisture-curing hot melt adhesive was applied to one entire surface of a rectangular polyolefin resin sheet (150 cm long x 50 cm wide) with a thickness of 180 μm, to a coating thickness of 50 μm.

[0085] Next, a polyolefin resin sheet was completely superimposed on the surface of an SPC substrate (a substrate made of polyvinyl chloride containing calcium carbonate), which had been maintained at a surface temperature of 40°C, with the moisture-curing hot-melt adhesive facing the SPC substrate. Then, a rubber roll was rolled over the polyolefin resin sheet to press the polyolefin resin sheet and the SPC substrate together, thereby obtaining a test specimen. After 30 minutes in an environment of 23°C and 55% relative humidity, the polyolefin resin sheet was peeled off the surface of the SPC substrate, and the peeling state was visually observed. When peeling occurred at the interface between the surface of the SPC substrate and the moisture-curing hot-melt adhesive, it was described as "interfacial failure," and when cohesive failure occurred in the moisture-curing hot-melt adhesive, it was described as "cohesive failure."

[0086] (Moisture-resistant adhesion) Test specimens were prepared in the same manner as when measuring normal adhesion. The test specimens were left in an environment of 80°C and 90% relative humidity for 21 days. Next, the test specimens were left in an environment of 23°C and 55% relative humidity for 24 hours. After that, the polyolefin sheet was peeled from the SPC substrate at a peel angle of 180 degrees and a peel speed of 200 mm / min, and the average peel strength at this time was measured as "moisture-resistant adhesive strength (N / inch)".

[0087] [Table 1]

[0088] [Table 2]

Claims

1. A moisture-curable hot melt adhesive comprising a urethane prepolymer having an isocyanate group at its terminal, which is a reaction product of a polyol containing a crystalline polyester polyol, which is a condensation polymer of 1,6-hexanediol and 1,12-dodecanedioic acid, and a microcrystalline polyester polyol having a number average molecular weight of 3,000 to 6,000, and a polyisocyanate.

2. The moisture-curing hot melt adhesive according to claim 1, characterized in that the mass ratio of the microcrystalline polyester polyol to the crystalline polyester polyol (microcrystalline polyester polyol content / crystalline polyester polyol content) in the polyol is 0.3 to 3.3.