Moisture-curing polyurethane hot melt resin composition and adhesive

Abstract

To provide a moisture-curable polyurethane hot-melt resin composition excellent in initial strength and in peeling strength after moisture curing.SOLUTION: The present invention relates to a moisture-curable polyurethane hot-melt resin composition comprising: a urethane prepolymer (i) having isocyanate groups which is a reaction product of a polyol (A) and a polyisocyanate (B), the polyol (A) containing an aliphatic polyester polyol (a-1), a polycaprolactone polyol (a-2), and a polyether polyol (a-3); and an α- methylstyrene polymer (ii). The present invention also relates to a bookbinding adhesive containing the moisture-curable polyurethane hot-melt resin composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a moisture-curable polyurethane hot melt resin composition.

Background Art

[0002] In the interior building materials industry, for members that bond a decorative sheet to a woody base material such as a molding member or flooring, in order to ensure adhesive reliability, the adhesives used there require the development of high adhesive strength (peeling strength). In addition, in order to cope with a method of attaching a sheet to a three-dimensional base material such as a wrapping process, high initial strength (initial adhesive strength) is also required.

[0003] As a method for improving the initial strength of a moisture-curable polyurethane hot melt resin composition, it is often the case that a crystalline long-chain aliphatic polyester polyol or an aromatic polyester polyol with high cohesive force is used as a raw material. However, when a large amount of these is contained, the hardness and modulus after moisture curing of the moisture-curable polyurethane hot melt resin composition become too high, so there is a limit to the peeling strength.

[0004] On the other hand, in order to lower the hardness and modulus after moisture curing, a liquid-phase component such as a polyether polyol is effective (for example, refer to Patent Document 1), but since the processability extremely decreases, it is not practical.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot melt resin composition excellent in initial strength and peeling strength after moisture curing.

Means for Solving the Problem

[0007] The present invention relates to a moisture-curable polyurethane hot melt resin composition containing a urethane prepolymer (i) having an isocyanate group, which is a reaction product of a polyol (A) containing an aliphatic polyester polyol (a-1), a polycaprolactone polyol (a-2), and a polyether polyol (a-3), and a polyisocyanate (B), and an α-methylstyrene polymer (ii), and a bookbinding adhesive characterized by containing the moisture-curable polyurethane hot melt resin composition.

Effect of the Invention

[0008] The moisture-curable polyurethane hot melt resin composition of the present invention ensures excellent processability and is excellent in initial strength and peeling strength after moisture curing.

Mode for Carrying Out the Invention

[0009] The moisture-curable polyurethane hot melt resin composition of the present invention contains, as essential components, a urethane prepolymer (i) having an isocyanate group, which is a reaction product of a polyol (A) containing an aliphatic polyester polyol (a-1), a polycaprolactone polyol (a-2), and a polyether polyol (a-3), and an α-methylstyrene polymer (ii).

[0010] The aliphatic polyester polyol (a-1) is an essential component for obtaining excellent initial strength. As the aliphatic polyester polyol (a-1), for example, a reaction product of a glycol and a polybasic acid can be used.

[0011] As the glycol, for example, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, trimethylolpropane, trimethylolethane, glycerin, etc. can be used. These compounds may be used alone or in combination of two or more. Among these, from the viewpoint of enhancing crystallinity and further improving the initial strength and peeling strength, it is preferable to use one or more selected from the group consisting of butanediol, hexanediol, octanediol, and decanediol.

[0012] As the polybasic acid, for example, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, etc. can be used. These polybasic acids may be used alone or in combination of two or more. Among these, from the viewpoint of further improving the initial strength and peeling strength, it is preferable to use a polybasic acid in the range of 4 to 20 carbon atoms, and it is preferable to use in combination a polyester polyol made from a polybasic acid in the range of 2 to 7 carbon atoms and a polyester polyol made from a polybasic acid in the range of 8 to 20 carbon atoms.

[0013] The number average molecular weight of the aliphatic polyester polyol (a-1) is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 8,000, from the viewpoint of further improving processability, initial strength, and peeling strength. The number average molecular weight of the aliphatic polyester polyol (a-1) indicates a value measured under the following conditions by the gel permeation chromatography (GPC) method.

[0014] Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were connected in series and used. "TSKgel G5000" (7.8 mm I.D. × 30 cm) × 1 piece "TSKgel G4000" (7.8 mm I.D. × 30 cm) × 1 piece One piece of 「TSKgel G3000」 (7.8 mm I.D. × 30 cm) One piece of 「TSKgel G2000」 (7.8 mm I.D. × 30 cm) Detector: RI (Differential Refractometer) Column Temperature: 40 °C Eluent: Tetrahydrofuran (THF) Flow Rate: 1.0 mL / min Injection Volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 mass%) Standard Sample: A calibration curve was created using the following standard polystyrene.

[0015] (Standard Polystyrene) 「TSKgel Standard Polystyrene A-500」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene A-1000」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene A-2500」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene A-5000」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-1」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-2」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-4」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-10」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-20」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-40」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-80」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-128」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-288」 manufactured by Tosoh Corporation 「TSKgel Standard Polystyrene F-550」 manufactured by Tosoh Corporation

[0016] As for the usage amount of the aliphatic polyester polyol (a-1), from the viewpoint of further improving processability, initial strength, and peeling strength, the range of 20 to 70% by mass in the total mass of the urethane prepolymer (i) and the α-methylstyrene polymer (ii) is preferable, and the range of 40 to 60% by mass is more preferable.

[0017] Moreover, when using in combination a polyester polyol made from a polybasic acid in the range of 2 to 7 carbon atoms and a polyester polyol made from a polybasic acid in the range of 8 to 20 carbon atoms as the aliphatic polyester polyol (a-1), from the viewpoint of further improving processability, initial strength, and peeling strength, the mass ratio [C2~7 / C8~20] thereof is preferably in the range of 90 / 10 to 40 / 60, and more preferably in the range of 80 / 20 to 50 / 50.

[0018] The polycaprolactone polyol (a-2) is an essential component for obtaining excellent initial strength. For example, a reaction product of the aforementioned glycol and ε-caprolactone can be used.

[0019] As for the number average molecular weight of the polycaprolactone polyol (a-2), from the viewpoint of further improving processability and initial strength, it is preferably in the range of 5,000 to 200,000, and more preferably in the range of 10,000 to 100,000. The measurement method of the number average molecular weight of the polycaprolactone polyol (a-2) is the same as that of the aliphatic polyester polyol (a-1).

[0020] As for the usage amount of the polycaprolactone polyol (a-2), from the viewpoint of further improving processability and initial strength, the range of 2 to 15% by mass in the total mass of the urethane prepolymer (i) and the α-methylstyrene polymer (ii) is preferable, and the range of 4 to 9% by mass is more preferable.

[0021] The polyether polyol (a-3) is an essential component for obtaining excellent processability. Examples of the polyether polyol (a-3) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, polyoxypropylene polyoxytetramethylene glycol, and the like. These polyols may be used alone or in combination of two or more. Among these, polypropylene glycol is preferred in terms of further improving processability, initial strength, and peeling strength.

[0022] The number average molecular weight of the polyether polyol (a-3) is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 8,000, from the viewpoint of further improving processability, initial strength, and peeling strength. The measurement method of the number average molecular weight of the polyether polyol (a-3) is the same as that of the aliphatic polyester polyol (a-1).

[0023] The amount of the polyether polyol (a-3) used is preferably in the range of 10 to 30% by mass, more preferably in the range of 15 to 25% by mass, based on the total mass of the urethane prepolymer (i) and the α-methylstyrene polymer (ii), from the viewpoint of further improving processability, initial strength, and peeling strength.

[0024] The polyol (A) contains the aliphatic polyester polyol (a-1), the polycaprolactone polyol (a-2), and the polyether polyol (a-3) as essential components, and may contain other polyols as required.

[0025] Examples of the other polyols include polyester polyols other than the (a-1), polycarbonate polyols, polyacrylic polyols, and the like. These polyols may be used alone or in combination of two or more.

[0026] Examples of the polyisocyanate (B) include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate. These polyisocyanates may be used alone or in combination of two or more. Among these, aromatic polyisocyanates are preferred from the viewpoints of reactivity and peeling strength, and diphenylmethane diisocyanate is more preferred.

[0027] The urethane prepolymer (i) is a reaction product of the polyol (A) and the polyisocyanate (B), and has isocyanate groups that can react with moisture present in the air or in the substrate to which the urethane prepolymer is applied to form a crosslinked structure.

[0028] As a method for producing the urethane prepolymer (i), for example, a mixture of the polyol (A) is dropped into a reaction vessel containing the polyisocyanate (B), followed by heating, and the reaction is carried out under conditions such that the isocyanate groups of the polyisocyanate (B) are in excess with respect to the hydroxyl groups of the polyol (A).

[0029] When producing the urethane prepolymer (i), the equivalent ratio of the isocyanate groups of the polyisocyanate (B) to the hydroxyl groups of the polyol (A) (isocyanate groups / hydroxyl groups) is preferably in the range of 1.1 to 5, more preferably in the range of 1.5 to 3, from the viewpoint of further improving the initial strength and peeling strength.

[0030] The isocyanate group content of the urethane prepolymer (i) (hereinafter abbreviated as "NCO%") is preferably in the range of 1.7 to 5% by mass, more preferably in the range of 1.8 to 3% by mass, from the viewpoint of further improving the initial strength and peeling strength. The NCO% of the urethane prepolymer (i) indicates the value measured by the potentiometric titration method in accordance with JIS K1603-1:2007.

[0031] The α-methylstyrene polymer (ii) is an essential component for obtaining excellent initial strength and peeling strength while ensuring excellent processability. Since the α-methylstyrene polymer (ii) has high cohesive force, it exhibits high initial strength. After moisture curing, it is not incorporated into the cross-linking of urethane, so it is considered that high peeling strength can be exhibited because low modulus can be maintained as a whole film.

[0032] As the α-methylstyrene polymer (ii), for example, a homopolymer of α-methylstyrene, a copolymer of α-methylstyrene and other polymerization components, etc. can be used.

[0033] As the other polymerization components, for example, indene, aromatic vinyl monomers, etc. can be used. These compounds may be used alone or in combination of two or more.

[0034] As the α-methylstyrene polymer (ii), an α-methylstyrene homopolymer is preferable from the viewpoint of further improving processability, initial strength, and peeling strength.

[0035] The softening point of the α-methylstyrene polymer (ii) is preferably in the range of 80 to 120°C, more preferably in the range of 90 to 110°C, from the viewpoint of further improving processability, initial strength, and peeling strength. The softening point of the α-methylstyrene copolymer (ii) indicates the value measured by DSC (differential scanning calorimeter) measurement (heating rate 5°C / min) in accordance with JIS K6924-2-1997.

[0036] As for the number average molecular weight of the α-methylstyrene polymer (ii), from the viewpoint of further improving processability, initial strength, and peeling strength, the range of 500 to 2000 is preferable, and the range of 800 to 1500 is more preferable. The method for measuring the number average molecular weight of the α-methylstyrene polymer (ii) is the same as that of the aliphatic polyester polyol (a-1).

[0037] As for the amount of the α-methylstyrene polymer (ii) used, from the viewpoint of further improving processability, initial strength, and peeling strength, the range of 2 to 30% by mass in the total mass of the urethane prepolymer (i) and the α-methylstyrene polymer (ii) is preferable, and the range of 5 to 20% by mass is more preferable.

[0038] The moisture-curable polyurethane hot melt resin composition of the present invention contains the urethane prepolymer (i) and the α-methylstyrene polymer (ii) as essential components, and may contain other additives as necessary.

[0039] Examples of the other additives include curing catalysts, antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent whitening agents, silane coupling agents, waxes, thermoplastic resins, and the like. These additives may be used alone or in combination of two or more.

[0040] The moisture-curable polyurethane hot melt resin composition of the present invention ensures excellent processability and is excellent in initial strength and peeling strength after moisture curing.

[0041] As a method for adhering an adherend with the moisture-curable polyurethane hot melt resin composition of the present invention, for example, a method of applying the resin composition to the surface of a substrate and laminating it with another substrate can be mentioned.

[0042] Examples of the substrate include fiber substrates, glass substrates, wooden substrates, metal substrates, plastic substrates, and the like.

[0043] As a method for applying the moisture-curing polyurethane hot-melt resin composition to the base material, for example, after melting the moisture-curing polyurethane hot-melt resin composition at 100 to 140°C, coating methods such as a roll coater, a spray coater, a T-die coater, a knife coater, a comma coater, etc.; precision methods such as a dispenser, inkjet printing, screen printing, offset printing, etc.; methods using nozzle coating, etc. can be mentioned.

[0044] Also, after bonding two base materials together, it is preferable to dry and cure the adhesive by a known method as necessary.

Example

[0045] Hereinafter, the present invention will be described in more detail using examples.

[0046] [Example 1] Into a four-necked flask equipped with a stirrer and a thermometer, 20 parts by mass of an α-methylstyrene homopolymer (“FTR0100” manufactured by Mitsui Chemicals, Inc., number average molecular weight: 990, softening point: 100°C, hereinafter abbreviated as “X-1”), 34 parts by mass of an aliphatic polyester polyol (reaction product of 1,6-hexanediol and adipic acid, number average molecular weight: 4,500, hereinafter abbreviated as “HG / AA”), 9 parts by mass of an aliphatic polyester polyol (reaction product of 1,6-hexanediol and dodecanedioic acid, number average molecular weight: 3,500, hereinafter abbreviated as “HG / DDA”), 5 parts by mass of a polycaprolactone polyol (number average molecular weight: 80,000, hereinafter abbreviated as “PCL”), and 21 parts by mass of a polypropylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as “PPG”) were charged, and dehydration was carried out under reduced pressure conditions until the water content rate became 0.05% by mass or less. Next, after cooling the temperature inside the container to 70°C, 11 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) was added, the temperature was raised to 100°C, and the reaction was carried out for about 3 hours until the NCO content rate became constant to obtain a urethane prepolymer having an isocyanate group and a moisture-curing polyurethane hot-melt resin composition containing the (X-1).

[0047] [Examples 2 to 4, Comparative Example 1] A moisture-curing type polyurethane hot melt resin composition was obtained in the same manner as in Example 1, except that the raw materials used were changed as shown in Table 1.

[0048] [Evaluation method for initial strength] After melting the moisture-curing type polyurethane hot melt adhesives obtained in the examples and comparative examples at 120 °C, they were applied onto a primer-treated olefin decorative sheet to a thickness of 50 μm. Then, MDF (Medium Density Fiberboard) was placed on the applied adhesive layer and bonded. Five minutes after bonding the test pieces, a load of 75 g was applied in the 90° direction to a width of 25 mm in an atmosphere at 35 °C, and the peel length of the sheet was measured after 15 minutes and evaluated as follows. "〇": The peel length is less than 5 mm. "×": The peel length is 5 mm or more.

[0049] [Evaluation method for peeling strength] After melting the moisture-curing type polyurethane hot melt adhesives obtained in the examples and comparative examples at 120 °C, they were applied onto a primer-treated olefin decorative sheet to a thickness of 50 μm. Then, MDF (Medium Density Fiberboard) was placed on the applied adhesive layer and bonded. After curing the test pieces for 1 hour in an atmosphere at a temperature of 30 °C and a relative humidity of 50%, the sheet of the test piece was peeled in the 180° direction, and the peeling strength per 25 mm width was measured using "AGS-X" manufactured by Shimadzu Corporation and evaluated as follows. "〇": The peak strength when peeled by 100 mm is 30 N / 25 mm or more. "×": The peak strength when peeled by 100 mm is less than 30 N / 25 mm.

[0050]

Table 1

[0051] It has been found that the moisture-curing polyurethane hot melt resin composition of the present invention has excellent initial strength and peeling strength without any problem in processability.

[0052] On the other hand, Comparative Example 1 is a mode in which α-methylstyrene polymer (ii) is not used, but the initial strength and peeling strength are poor.

Claims

1. A moisture-curing polyurethane hot-melt resin composition containing a urethane prepolymer (i) having isocyanate groups, which is a reaction product of a polyol (A) and a polyisocyanate (B), and an α-methylstyrene polymer (ii), wherein the polyol (A) contains an aliphatic polyester polyol (a-1), a polycaprolactone polyol (a-2), and a polyether polyol (a-3), and the amount of the α-methylstyrene polymer (ii) used is in the range of 2 to 30% by mass in the total mass of the urethane prepolymer (i) and the α-methylstyrene polymer (ii).

2. The moisture-curing polyurethane hot-melt resin composition according to Claim 1, wherein the aliphatic polyester polyol (a-1) is made from a polybasic acid having 4 to 20 carbon atoms.

3. The moisture-curing polyurethane hot-melt resin composition according to Claim 2, wherein the aliphatic polyester polyol (a-1) uses in combination a polyester polyol made from a polybasic acid having 2 to 7 carbon atoms and a polyester polyol made from a polybasic acid having 8 to 20 carbon atoms.

4. The moisture-curing polyurethane hot-melt resin composition according to any one of Claims 1 to 3, wherein the α-methylstyrene polymer (ii) is a homopolymer of α-methylstyrene.

5. The moisture-curing polyurethane hot-melt resin composition according to any one of Claims 1 to 4, wherein the softening point of the α-methylstyrene polymer (ii) is in the range of 80 to 120°C.

6. The moisture-curing polyurethane hot-melt resin composition according to any one of Claims 1 to 5, wherein the number average molecular weight of the α-methylstyrene polymer (ii) is in the range of 500 to 2,000.

7. An adhesive characterized by containing the moisture-curing polyurethane hot-melt resin composition according to any one of Claims 1 to 6.

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