JP7400257B2 - Moisture-curable polyurethane hot melt resin composition and cured product thereof - Google Patents

Description

The present invention relates to a moisture-curable polyurethane hot melt resin composition and a cured product thereof.

Moisture-curable polyurethane hot melt resin compositions are widely used as various adhesives. When the moisture-curable polyurethane hot melt resin composition is used as various adhesives, it is required to obtain good adhesive strength (initial strength) immediately after applying the adhesive. However, since moisture-curable polyurethane hot-melt resin compositions develop adhesive strength through moisture curing, it has been difficult to develop excellent initial strength.

As the moisture-curable polyurethane hot melt resin composition having excellent initial strength, for example, a method using a crystalline polyester polyol or a polyester polyol having a high glass transition temperature is known (see, for example, Patent Document 1). ). However, these methods have problems in that the viscosity tends to be high and handling properties are poor, and the resulting cured film becomes hard, so that the applications for which it can be used are extremely limited.

Japanese Patent Application Publication No. 2016-121214

The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot melt resin composition that has excellent initial strength.

The present invention comprises a compound (a1) having a number average molecular weight of less than 500, a branched structure, and 2 to 4 hydroxyl groups in one molecule, and a polyester polyol (a2) made from adipic acid. The present invention provides a moisture-curable polyurethane hot melt resin composition characterized by containing a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol (A) and a polyisocyanate (B). The present invention also provides a cured product characterized by being formed from the moisture-curable polyurethane hot melt resin composition.

The moisture-curable polyurethane hot melt resin composition of the present invention has excellent initial strength.

The moisture-curable polyurethane hot melt resin composition of the present invention has a number average molecular weight of less than 500, has a branched structure, and contains a compound (a1) having 2 to 4 hydroxyl groups in one molecule, and adipic acid. It contains a polyol (A) containing a polyester polyol (a2) as a raw material, and a urethane prepolymer having an isocyanate group, which is a reaction product of a polyisocyanate (B).

The compound (a1) has a number average molecular weight of less than 500, has a branched structure, and has 2 to 4 hydroxyl groups in one molecule. By using this compound (a1), the urethane group concentration of the urethane prepolymer is increased and the initial cohesive force is increased due to steric hindrance due to the branched structure, so that excellent initial strength can be obtained. Furthermore, since it is possible to design a cured film that is soft, the scope of use of the moisture-curable polyurethane hot-melt resin composition can be expanded. Note that the number average molecular weight of the compound (a1) indicates a value calculated from the chemical formula.

Examples of the compound (a1) include 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2,4-pentanediol. -diethyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 2-methyl- 1,3-propanediol, 2-ethyl-1,3-hexanediol, neopentyl glycol, 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2-ethyl- 1,6-hexanediol, 3,5-heptanediol, 2-methyl-1,8-octanediol, trimethylolpropane, etc. can be used. These compounds may be used alone or in combination of two or more. Among these, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3- Pentanediol, 2,4-diethyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propane It is preferable to use one or more compounds selected from the group consisting of diol, 2-methyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, neopentyl glycol, and trimethylolpropane.

The amount of the compound (a1) to be used is determined from the viewpoint of maintaining excellent initial strength, having an appropriate viscosity, and obtaining good flexibility of the cured film. It is preferably in the range of 0.1 to 30% by weight, more preferably in the range of 0.2 to 20% by weight, and even more preferably in the range of 0.3 to 15% by weight, based on the total weight of B).

Further, for the same reason, the amount of the compound (a1) to be used is preferably in the range of 0.1 to 30% by weight, more preferably in the range of 0.2 to 25% by weight, and 0.1 to 30% by weight, more preferably 0.2 to 25% by weight, based on the polyol (A). A range of 5 to 20% by mass is more preferred.

Polyester polyol (a2) made from adipic acid has excellent cohesive force and is an essential component for obtaining excellent initial strength. As the polyester polyol (a2), for example, a reaction product of a polybasic acid including adipic acid and an aliphatic and/or alicyclic compound having two or more hydroxyl groups can be used.

Examples of the polybasic acids other than adipic acid include succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, eicosadiic acid, citraconic acid, itaconic acid, and anhydride. Aliphatic polybasic acids such as citraconic acid and itaconic anhydride; alicyclic polybasic acids such as 1,4-cyclohexanedicarboxylic acid and the like can be used. These polybasic acids may be used alone or in combination of two or more. The amount of adipic acid used is preferably 40% by mass or more in the polybasic acid, more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 70% by mass or more.

Examples of the aliphatic or alicyclic compounds having two or more hydroxyl groups include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, triethylene glycol, tetraethylene glycol, neo Pentyl glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentane Diol, 2-ethyl-2-butyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,4-diethyl-1,5-pentanediol, trimethylolethane, trimethylolpropane, penta Aliphatic compounds such as erythritol; alicyclic compounds such as cyclopentanediol, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and alkylene oxide adducts thereof, and the like can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use aliphatic compounds because they provide even better initial adhesive strength, low viscosity, and flexibility, and include ethylene glycol, diethylene glycol, 1,4-butanediol, and neopentyl glycol. , 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propane It is more preferable to use one or more compounds selected from the group consisting of diol and 2,4-diethyl-1,5-pentanediol.

The number average molecular weight of the polyester polyol (a2) is preferably less than 2,800, and from 300 to 2,500, from the viewpoint of obtaining even better initial adhesive strength, low viscosity, and flexibility. The range is more preferable, and the range of 600 to 2,200 is even more preferable. The number average molecular weight of the polyester polyol (a2) is a value measured by gel permeation chromatography (GPC).

The amount of the polyester polyol (a2) to be used is determined from the viewpoint that while maintaining excellent initial strength, it has an appropriate viscosity and good flexibility of the cured film is obtained. It is preferably in the range of 15 to 85% by weight, more preferably in the range of 20 to 80% by weight, even more preferably in the range of 25 to 75% by weight, based on the total weight of (B).

Further, for the same reason, the amount of the polyester polyol (a2) to be used is preferably in the range of 20 to 99.5% by mass, more preferably 30 to 98% by mass in the polyol (A). % range is more preferred.

As the polyol (A), in addition to the compound (a1) and the polyester polyol (a2), other polyols may be used in combination as necessary.

As the other polyols, for example, polyester polyols other than the polyester polyol (a2), polyether polyols, polycarbonate polyols, acrylic polyols, dimer diols, isoprene polyols, polybutadiene polyols, etc. can be used. These polyols may be used alone or in combination of two or more.

The number average molecular weight of the other polyol is preferably less than 2,800, more preferably in the range of 300 to 2,500, from the viewpoint of obtaining even better low viscosity and flexibility. A range of 600 to 2,200 is more preferred, and a range of 700 to 1,500 is particularly preferred. The number average molecular weights of the other polyols are values measured by gel permeation chromatography (GPC).

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

The urethane prepolymer is obtained by reacting the polyol (A) and the polyisocyanate (B), and reacts with moisture present in the air or in the substrate to which the urethane prepolymer is applied. It has an isocyanate group that can form a crosslinked structure.

As a method for producing the urethane prepolymer, for example, the mixture of the polyols (A) is dropped into a reaction vessel containing the polyisocyanate (B), and then heated, so that the isocyanate groups of the polyisocyanate (B) are dissolved. , can be produced by reacting the polyol (A) under conditions in which the polyol (A) has an excess of hydroxyl groups.

When producing the urethane prepolymer, the equivalent ratio of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) (isocyanate group/hydroxyl group) is determined by the adhesive strength, low viscosity, and From the standpoint of further improving flexibility, the range is preferably from 1.1 to 5, more preferably from 1.12 to 3, and even more preferably from 1.15 to 1.45.

The isocyanate group content (hereinafter abbreviated as "NCO%") of the urethane prepolymer is in the range of 1 to 10% by mass from the viewpoint of further improving adhesive strength, low viscosity, and flexibility. is preferable, the range of 1 to 8% by weight is more preferable, the range of 1.1 to 5% by weight is even more preferable, and the range of 1.2 to 4.5% by weight is particularly preferable. Note that the NCO% of the urethane prepolymer is a value measured by potentiometric titration in accordance with JIS K1603-1:2007.

Further, the content of urethane bonds in the urethane prepolymer should be in the range of 0.2 to 3.5 mol/kg in order to obtain even better initial strength, low viscosity, and flexibility. is preferable, the range of 0.6 to 3.2 mol/kg is more preferable, and the range of 1.1 to 2.9 mol/kg is particularly preferable. The content of urethane bonds in the urethane prepolymer is a value calculated from the amounts of the polyol (A) and polyisocyanate (B).

The moisture-curable polyurethane hot melt resin composition contains the urethane prepolymer, but may contain other additives as necessary.

Examples of the other additives include curing catalysts, antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, optical brighteners, silane coupling agents, waxes, thermoplastic resins, etc. can be used. These additives may be used alone or in combination of two or more.

Examples of a method for obtaining a cured product using the moisture-curable polyurethane hot-melt resin composition of the present invention include a method of coating the moisture-curing polyurethane hot-melt resin composition on a substrate and moisture-curing it.

Examples of the base material include resin base materials such as polyethylene terephthalate and polycarbonate, rubber base materials, fiber base materials, glass base materials, and wood.

Examples of methods for applying the moisture-curable polyurethane hot melt resin composition to the substrate include coater methods such as a roll coater, spray coater, T-die coater, knife coater, and comma coater; dispenser, inkjet printing, and screen coating. Precision methods such as printing and offset printing; examples include nozzle coating.

Furthermore, before applying the moisture-curable polyurethane hot-melt resin composition to the base material, it is preferable to heat and melt the moisture-curable polyurethane hot-melt resin composition at 100 to 140°C.

After the application, drying and curing are preferably performed as appropriate using known methods.

The thickness of the cured layer of the moisture-curable polyurethane hot melt resin composition can be appropriately determined depending on the intended use, and is, for example, in the range of 0.001 to 0.5 cm.

The moisture-curable polyurethane hot melt resin composition of the present invention has a storage modulus (G') of melt viscoelasticity of 0.1 MPa at 20° C. before curing, in order to obtain even better initial strength. It is preferably in the range of 0.2 to 1,000 MPa, more preferably in the range of 0.3 to 500 MPa.

The storage modulus (G') was determined by melting the moisture-curable polyurethane hot-melt resin composition at 110°C for 1 hour, sampling 10 ml, and using a melt viscoelasticity measuring device (MCR-302 manufactured by Anton Paar). The storage modulus (G') at 20°C is shown when melt viscoelasticity was measured at a cooling rate of 1°C/min from 110°C to 10°C and a frequency of 1 Hz.

In addition, the Young's modulus of the cured film of the moisture-curable polyurethane hot melt resin composition of the present invention is preferably 20 MPa or less, and in the range of 0.5 to 15 MPa, from the viewpoint of obtaining even better flexibility. is more preferable, and a range of 1 to 10 MPa is even more preferable.

The Young's modulus is determined by melting a moisture-curable polyurethane hot melt resin composition at 110° C. for 1 hour, then applying it on a polyethylene terephthalate base material that has been subjected to a mold release treatment so that the film thickness after curing is 100 μm. A hardened film was obtained by applying the coating using a knife coater and leaving it for 3 days.The hardened film was peeled off from the release PET and punched out using a No. 2 dumbbell to obtain a test piece. The origin of the chart and the elongation rate when a tensile test was conducted using a tensile tester (“RTM-100” manufactured by Orientec Co., Ltd.) in an atmosphere of 25°C at a crosshead speed of 200 mm/min. shows the value measured from the stress when 2.5%.

The moisture-curable polyurethane hot melt resin composition of the present invention has excellent initial strength.

Hereinafter, the present invention will be explained in more detail using Examples.

[Example 1]
In a 4-necked flask equipped with a stirrer, a thermometer, an inert gas inlet, and a reflux condenser, a polyester polyol (reacted with adipic acid and diethylene glycol, number average molecular weight: 1,000, hereinafter referred to as "DEG/ (abbreviated as "AA") was charged, and dehydrated by heating under reduced pressure at 90° C. until the moisture content became 0.05% by mass or less. Next, 7 parts by mass of 1,3-butanediol (hereinafter abbreviated as "1,3BG") was charged.
Next, after cooling the temperature inside the reaction vessel to 60°C, 54 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI (1)") was added, and the temperature was raised to 110°C to form an isocyanate. The reaction was continued for about 3 hours until the group content became constant, thereby obtaining a urethane prepolymer having isocyanate groups and a moisture-curable polyurethane hot melt resin composition. The content of urethane bonds in the obtained urethane prepolymer was 2.22 mol/kg.

[Example 2]
In a 4-necked flask equipped with a stirrer, thermometer, inert gas inlet, and reflux condenser, polyester polyol (reacted with adipic acid and 1,4-butanediol, number average molecular weight: 1,000) , hereinafter abbreviated as "BG/AA") and 46.5 parts by mass of polypropylene glycol (number average molecular weight: 1,000, hereinafter abbreviated as "PPG"), and reduced pressure at 90 ° C. Dehydration was performed by heating until the water content became 0.05% by mass or less. Next, 7 parts by mass of 1,3BG was charged.
Next, after cooling the temperature inside the reaction vessel to 60°C, 54 parts by mass of MDI (1) was added, the temperature was raised to 110°C, and the reaction was carried out for about 3 hours until the isocyanate group content became constant. A moisture-curable polyurethane hot melt resin composition was obtained. The content of urethane bonds in the obtained urethane prepolymer was 2.22 mol/kg.

[Example 3]
In a 4-necked flask equipped with a stirrer, a thermometer, an inert gas inlet, and a reflux condenser, a polyester polyol (reacted with adipic acid and neopentyl glycol, number average molecular weight: 1,000, hereinafter referred to as " 97.5 parts by mass (abbreviated as "NPG/AA") was charged and heated under reduced pressure at 90°C to dehydrate until the water content became 0.05% by mass or less. Next, 2.5 parts by mass of 2-butyl-2-ethyl-1,3-propanediol (hereinafter abbreviated as "BEP") was charged.
Next, after cooling the temperature inside the reaction vessel to 60°C, 38 parts by mass of MDI (1) was added, the temperature was raised to 110°C, and the reaction was carried out for about 3 hours until the isocyanate group content became constant. A moisture-curable polyurethane hot melt resin composition was obtained. The content of urethane bonds in the obtained urethane prepolymer was 1.64 mol/kg.

[Example 4]
A moisture-curable polyurethane hot melt resin composition was obtained in the same manner as in Example 1, except that neopentyl glycol (hereinafter abbreviated as "NPG") was used in place of 1,3BG. The content of urethane bonds in the obtained urethane prepolymer was 2.08 mol/kg.

[Example 5]
In Example 1, 2-methyl-1,3-propanediol (hereinafter abbreviated as "2MP") was used instead of 1,3BG, and 2,4'-diphenylmethane diisocyanate and 4 were used instead of MDI (1). , 4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI (2)") was used in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt resin composition. The content of urethane bonds in the obtained urethane prepolymer was 2.22 mol/kg.

[Comparative example 1]
A moisture-curable polyurethane hot melt was prepared in the same manner as in Example 1, except that 1,4-butanediol (hereinafter abbreviated as "1,4BG") was used instead of 1,3BG. A resin composition was obtained. The content of urethane bonds in the obtained urethane prepolymer was 2.22 mol/kg.

[Method for measuring number average molecular weight]
The number average molecular weights of the polyols used in Examples and Comparative Examples are values measured by gel permeation chromatography (GPC) under the following conditions.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were used by connecting them in series.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 Book "TSKgel G2000" (7.8mm I.D. x 30cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40℃
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (Tetrahydrofuran solution with sample concentration 0.4% by mass)
Standard sample: A calibration curve was created using the following standard polystyrene.

(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

[Evaluation method of initial strength]
The moisture-curable polyurethane hot melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 120° C. for 1 hour. The adhesive was applied onto a polyethylene terephthalate sheet using an applicator to a thickness of 100 μm. A polyethylene terephthalate sheet was laminated onto the coating layer and pressed with a pressure roller. Five minutes after crimping, the adhesive strength (N/25 mm) was measured using a precision universal testing machine "AG-10NX" manufactured by Shimadzu Corporation, and the initial strength was evaluated as follows.
"T": Adhesive strength is 20 (N/25 mm) or more.
"F": Adhesive strength is less than 20 (N/25 mm).

[Viscosity evaluation method]
The moisture-curable polyurethane hot melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 120°C for 1 hour, and then the viscosity was measured using a cone-plate viscometer (40P cone, rotor rotation speed: 50 rpm). The low viscosity was evaluated as follows.
“T”; less than 30,000 mPa·s.
“F”: 30,000 mPa·s or more.

[Flexibility evaluation method]
The moisture-curable polyurethane hot melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 110° C. for 1 hour, and then coated on a polyester nonwoven fabric using a knife coater to give a film thickness of 100 μm after curing. A cured film was obtained by applying the coating as described above and leaving it for 3 days. This was evaluated by touch as follows.
"T": Highly flexible.
"F": Gives a hard impression.

It was found that the moisture-curable polyurethane hot melt resin composition of the present invention has excellent initial strength. It was also found to be excellent in low viscosity and flexibility.

On the other hand, in Comparative Example 1, a linear compound was used instead of compound (a1), but the initial strength was poor. Furthermore, low viscosity and flexibility were also poor.

Claims (4)

A polyol (A) containing a compound (a1) having a number average molecular weight of less than 500, having a branched structure and having 2 to 4 hydroxyl groups in one molecule, and a polyester polyol (a2) made from adipic acid. ), and a moisture-curable polyurethane hot melt resin composition containing a urethane prepolymer having an isocyanate group that is a reaction product of polyisocyanate (B),
As the polyol (A),
When neopentyl glycol is used as the compound (a1), the polyester polyol (a2) is a combination of polyester polyols made from adipic acid and diethylene glycol,
When 1,3-butanediol is used as the compound (a1), the polyester polyol (a2) is a polyester polyol made from adipic acid and diethylene glycol, or adipic acid and 1,4-butanediol. Those using a combination of
When 2-methyl-1,3-propanediol is used as the compound (a1), the polyester polyol (a2) is a combination of polyester polyols made from adipic acid and neopentyl glycol,
When 2-butyl-2-ethyl-1,3-propanediol was used as the compound (a1), a combination of polyester polyols made from adipic acid and diethylene glycol as raw materials was used as the polyester polyol (a2). any of the things
A moisture-curable polyurethane hot melt resin composition. The moisture-curable polyurethane hot according to claim 1 or 2, wherein the amount of the compound (a1) used is in the range of 0.1 to 30% by mass based on the total mass of the polyol (A) and the polyisocyanate (B). Melt resin composition. The moisture-curable polyurethane hot melt resin composition according to claim 1 or 2 , wherein the urethane bond content of the urethane prepolymer is in the range of 0.2 to 3.5 mol/kg. A cured product formed from the moisture-curable polyurethane hot melt resin composition according to any one of claims 1 to 3 .