JP7196435B2 - Moisture-curable polyurethane hot-melt resin composition - Google Patents

Description

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

Since moisture-curable polyurethane hot-melt adhesives are solvent-free, they have been widely used in industry as environment-friendly adhesives, mainly for fiber bonding and building material lamination.

The moisture-curable polyurethane adhesive develops its final adhesive strength by moisture-curing the isocyanate group of the urethane prepolymer, which is the main ingredient of the adhesive. High initial adhesive strength is required.

In order to obtain high initial adhesive strength, it is common to use a large amount of crystalline polyester polyol (see, for example, Patent Document 1). However, since the cured film obtained by such a method becomes hard, it is currently not used in fields where flexibility is required, such as fiber applications, for the reason that the texture deteriorates.

JP 2011-190309 A

The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot-melt resin composition which has a low viscosity, is excellent in initial adhesive strength, and is capable of forming a cured film having excellent flexibility.

The present invention is a moisture-curable polyurethane hot-melt resin composition containing a urethane prepolymer (i) having an isocyanate group as raw materials for a polyol (A) and a polyisocyanate (B), wherein the polyol (A) is a poly containing tetramethylene glycol (a1-1) and/or polyethylene glycol (a1-2) and an aromatic polyester polyol (a2), the polytetramethylene glycol (a1-1) and polyethylene glycol (a1-2) Provided is a moisture-curable polyurethane hot-melt resin composition characterized in that the total amount is greater than the amount of the aromatic polyester polyol (a2) used.

The moisture-curable polyurethane hot-melt resin composition of the present invention has a low viscosity, is excellent in initial adhesive strength and final adhesive strength, and can give a cured film excellent in flexibility. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be particularly suitably used for fiber applications.

The moisture-curable polyurethane hot-melt resin composition of the present invention contains a urethane prepolymer (i) having isocyanate groups made from specific polyol (A) and polyisocyanate (B).

The polyol (A) contains polytetramethylene glycol (a1-1) and/or polyethylene glycol (a1-2) and aromatic polyester polyol (a2).

The polytetramethylene glycol (a1-1) and/or polyethylene glycol (a1-2) are essential components for obtaining excellent initial adhesive strength and flexibility.

The mass ratio when the polytetramethylene glycol (a1-1) and polyethylene glycol (a1-2) are used in combination is 10/90 in that order from the viewpoint of obtaining even better initial adhesive strength and flexibility. It is preferably in the range of -90/19, more preferably in the range of 20/80 to 80/20, and even more preferably in the range of 50/50 to 70/30.

The number average molecular weights of the polytetramethylene glycol (a1-1) and the polyethylene glycol (a1-2) are both less than 2,800 from the viewpoint of obtaining even better initial adhesive strength and flexibility. A range of 300 to 2,500 is preferred, and a range of 600 to 2,200 is even more preferred. The number average molecular weights of polytetramethylene glycol and polyethylene glycol are values measured by gel permeation chromatography (GPC).

The aromatic polyester polyol (a2) is an essential component for obtaining excellent initial adhesive strength and flexibility. Examples of the aromatic polyester polyol include, for example, a reaction product of a compound having a hydroxyl group and a polybasic acid containing an aromatic polybasic acid; a reaction product of an aromatic compound having two or more hydroxyl groups and a polybasic acid; A reaction product of an aromatic compound having two or more and a polybasic acid containing an aromatic polybasic acid can be used.

Examples of the compound having a hydroxyl group 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, neopentyl glycol, 1,2-butanediol , 1,3-butanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl -aliphatic compounds such as 1,3-propanediol, 2-methyl-1,8-octanediol, 2,4-diethyl-1,5-pentanediol, trimethylolethane, trimethylolpropane, pentaerythritol; cyclopentane Alicyclic compounds such as diols, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and alkylene oxide adducts thereof can be used. These compounds may be used alone or in combination of two or more.

Examples of the aromatic compound having two or more hydroxyl groups include bisphenol A, bisphenol F, and alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adducts thereof. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use an alkylene oxide adduct of Bispher A in terms of obtaining even better initial adhesive strength and flexibility. is preferred.

Examples of the aromatic polybasic acid include phthalic acid, isophthalic acid, terephthalic acid, and phthalic anhydride. Other polybasic acids that can be used include, for example, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, and 1,12-dodecanedicarboxylic acid. These polybasic acids may be used alone or in combination of two or more. As the aromatic polybasic acid, one or more compounds selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, and phthalic anhydride from the viewpoint of obtaining even better initial adhesive strength and flexibility. It is preferable to use

Other polybasic acids include, for example, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, eicosadioic acid, citraconic acid, itaconic acid, citraconic anhydride, Itaconic anhydride and the like can be used.

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

When the total amount of the polytetramethylene glycol (a1-1) and polyethylene glycol (a1-2) is greater than the amount of the aromatic polyester polyol (a2) used, excellent initial adhesive strength and flexibility are obtained. It is essential from the viewpoint that it is obtained and has a low viscosity. The mass ratio of the total amount of the polytetramethylene glycol (a1-1) and polyethylene glycol (a1-2) (hereinafter abbreviated as "(a1) total amount") to the aromatic polyester polyol (a2) [( a1) total amount/(a2)] is preferably in the range of 99/1 to 51/49 from the viewpoint of obtaining even better initial adhesive strength, flexibility and low viscosity, and 95/5 A range of ∼53/47 is more preferred, and a range of 90/10 to 55/45 is even more preferred.

As the polyol (A), in addition to the polytetramethylene glycol, polyethylene glycol and the aromatic polyester polyol (a2), other polyols can be used as necessary.

Examples of other polyols that can be used include polyester polyols other than (a2), polypropylene glycol, polycarbonate polyols, polyacrylic polyols, butadiene polyols, and hydrogenated polybutadiene polyols. These polyols may be used alone or in combination of two or more.

The total amount of the polytetramethylene glycol (a1-1), polyethylene glycol (a1-2) and the aromatic polyester polyol (a2) is preferably 50% by mass or more in the polyol (A), It is more preferably at least 80% by mass, particularly preferably at least 90% by mass.

Examples of the polyisocyanate (B) include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, Aliphatic or alicyclic polyisocyanates such as cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate can be used. Among these, aromatic polyisocyanate is preferably used, and diphenylmethane diisocyanate is more preferable, from the viewpoint of obtaining even more excellent reactivity and final adhesive strength.

In addition, the amount of the polyisocyanate (B) used is preferably in the range of 5 to 60% by mass, more preferably 15 to 50% by mass, in the raw material of the urethane prepolymer (i), from the viewpoint of obtaining even better adhesive strength. is more preferred.

The urethane prepolymer (i) is obtained by reacting the polyol (A) and the polyisocyanate (B). It has an isocyanate group at the polymer terminal or in the molecule that can react with existing moisture to form a crosslinked structure.

As a method for producing the urethane prepolymer (i), for example, the polyol (A) is added dropwise to a reaction vessel containing the polyisocyanate (B), followed by heating to obtain the isocyanate groups of the polyisocyanate (B). can be produced by reacting under conditions that are excessive with respect to the hydroxyl groups of the polyol (A).

The amount of urethane bonds in the urethane prepolymer (i) is preferably in the range of 0.5 to 3 mol/kg from the viewpoint of obtaining even better initial adhesive strength, flexibility and low viscosity. The range of .9 to 2.7 mol/kg is more preferred, and the range of 1.1 to 2.4 mol/kg is even more preferred.

The equivalent ratio ([isocyanate group/hydroxyl group]) of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) when producing the urethane prepolymer (i) was even more excellent. It is preferably in the range of 1.1 to 1.5, more preferably in the range of 1.15 to 1.45, from the viewpoint of obtaining initial adhesive strength, flexibility and low viscosity.

The isocyanate group content (hereinafter abbreviated as "NCO %") of the urethane prepolymer (i) is 1 to 4 from the viewpoint of obtaining even better initial adhesive strength, flexibility and low viscosity. A range of % by weight is preferred, and a range of 1.2 to 3.5% by weight is more preferred. The NCO% of the urethane prepolymer (i) is a value measured by potentiometric titration in accordance with JISK1603-1:2007.

The moisture-curable polyurethane hot-melt resin composition of the present invention may optionally contain other additives in addition to the urethane prepolymer (i).

Examples of other additives that can be used include antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent whitening agents, silane coupling agents, and waxes. These additives may be used alone or in combination of two or more.

As a method for obtaining a cured film of the moisture-curable polyurethane hot-melt resin composition, for example, the moisture-curable polyurethane hot-melt resin composition is melted at 50 to 130° C., coated on a substrate, and moisture-cured. method.

Examples of the base material include acrylic resins, urethane resins, silicone resins, epoxy resins, fluorine resins, polystyrene resins, polyester resins, polysulfone resins, polyarylate resins, polyvinyl chloride resins, Polyvinylidene chloride, cycloolefin resin, polyolefin resin, polyimide resin, alicyclic polyimide resin, cellulose resin, PC (polycarbonate), PBT (polybutylene terephthalate), modified PPE (polyphenylene ether), PEN (polyethylene) naphthalate), PET (polyethylene terephthalate), lactic acid polymer, ABS resin, AS resin, etc.; wood substrates such as MDF, plywood, particle board; fiber substrates such as non-woven fabrics, woven fabrics, knitted fabrics, etc. can be done. The base material may be subjected to corona treatment, plasma treatment, primer treatment, or the like, if necessary.

Examples of the method for applying the moisture-curable polyurethane hot-melt resin composition include methods using a roll coater, a spray coater, a T-die coater, a knife coater, a comma coater, and the like.

After the coating, the final adhesive strength can be obtained by aging for 0.5 to 3 days at a temperature of 20 to 80° C. and a relative humidity of 50 to 90%.

For the moisture-curable polyurethane hot-melt resin composition of the present invention, the storage elastic modulus (G') of the melt viscoelasticity at 20°C before curing should be 0.00% in order to obtain even more excellent initial adhesive strength. It is preferably 1 MPa or more, preferably in the range of 0.2 to 1,000 MPa, more preferably in the range of 0.3 to 500 MPa.

The storage elastic modulus (G') was measured 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 (manufactured by Anton Paar "MCR-302 ”) is placed on a parallel plate, and melt viscoelasticity measurement is performed from 110° C. to 10° C. at a cooling rate of 1° C./min at a frequency of 1 Hz.

In addition, the Young's modulus of the cured film of the present invention is preferably 20 MPa or less, more preferably 0.5 to 15 MPa, and more preferably 1 to 10 MPa, from the viewpoint of obtaining even better flexibility. More preferred.

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

As described above, the moisture-curable polyurethane hot-melt resin composition of the present invention has a low viscosity, excellent initial adhesive strength and final adhesive strength, and can provide a cured film having excellent flexibility. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be particularly suitably used for fiber applications.

The present invention will be described in more detail below with reference to examples.

[Example 1]
A four-necked flask equipped with a thermometer, stirrer, inert gas inlet and reflux condenser was charged with 70 parts by mass of polytetramethylene glycol (number average molecular weight: 1,000, hereinafter abbreviated as "PTMG1000"), aromatic Group polyester polyol (reacted with neopentyl glycol and phthalic anhydride, number average molecular weight: 1,000, hereinafter abbreviated as “NPG/oPA1000”) is charged and heated under reduced pressure at 90 ° C. Dehydration was carried out until the moisture content became 0.05% by mass or less.
Next, after cooling to a container temperature of 60° C., 33 parts by mass of 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) is added, and the temperature is raised to 110° C. until the isocyanate group content becomes constant. The mixture was reacted for about 3 hours to obtain a urethane prepolymer (i-1) having an isocyanate group and a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-1) had an NCO % of 1.7% by mass, an amount of urethane bonds of 1.50 mol/kg, and a [NCO/OH] of 1.32 at the time of synthesis.

[Method for measuring number average molecular weight]
In the above Examples, the number average molecular weight of the polyol is a value measured under the following conditions by a gel permeation chromatography (GPC) method.

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" (7.8mm 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" (7.8 mm I.D. x 30 cm) x 1 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% 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

[Example 2]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 70 parts by mass of polyethylene glycol (number average molecular weight: 1,000, hereinafter abbreviated as “PEG1000”), an aromatic 30 parts by mass of polyester polyol (6 mol adduct of propylene oxide of bisphenol A and reaction product of sebacic acid, number average molecular weight: 1,000, hereinafter abbreviated as "SEBA/BisA6PO1000") is charged and heated under reduced pressure at 90°C. Dehydration was carried out until the moisture content became 0.05% by mass or less.
Next, after cooling to a temperature in the container of 60° C., 33 parts by mass of MDI is added, the temperature is raised to 110° C., and the reaction is allowed to occur for about 3 hours until the isocyanate group content becomes constant, and the urethane prepolymer having an isocyanate group (i- 2) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-2) had an NCO % of 1.7% by mass, an amount of urethane bonds of 1.50 mol/kg, and a [NCO/OH] of 1.32 at the time of synthesis.

[Example 3]
85 parts by mass of polytetramethylene glycol (number average molecular weight: 650, hereinafter abbreviated as "PTMG650") and SEBA/BisA6PO1000 were added to a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser. and dehydrated by heating under reduced pressure at 90° C. until the moisture content became 0.05% by mass or less.
Next, after cooling to a temperature in the container of 60° C., 46 parts by mass of MDI was added, the temperature was raised to 110° C., and the reaction was allowed to proceed for about 3 hours until the isocyanate group content became constant, and the urethane prepolymer having an isocyanate group (i- 3) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-3) had an NCO % of 1.9% by mass, an amount of urethane bonds of 2.00 mol/kg, and an [NCO/OH] of 1.26 at the time of synthesis.

[Example 4]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 60 parts by mass of PTMG1000, an aromatic polyester polyol (a reaction product of neopentyl glycol and phthalic anhydride, number average molecular weight: 2 ,000, hereinafter abbreviated as “NPG/oPA2000”) was charged and dehydrated by heating under reduced pressure at 90° C. until the moisture content became 0.05% by mass or less.
Next, after cooling to a temperature in the container of 60° C., 28 parts by mass of MDI was added, the temperature was raised to 110° C., and the reaction was allowed to occur for about 3 hours until the isocyanate group content became constant, and the urethane prepolymer (i- 4) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-4) had an NCO % of 1.8% by mass, an amount of urethane bonds of 1.25 mol/kg, and an [NCO/OH] of 1.40 at the time of synthesis.

[Comparative Example 1]
20 parts by mass of PTMG1000 and 80 parts by mass of NPG/oPA1000 were charged in a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser, and heated under reduced pressure at 90°C to reduce the water content. It was dehydrated until it became 0.05% by mass or less.
Next, after cooling the temperature inside the container to 60° C., 33 parts by mass of MDI was added, the temperature was raised to 110° C., and the reaction was continued for about 3 hours until the isocyanate group content became constant, resulting in a urethane prepolymer having an isocyanate group ( i-R1) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-R1) had an NCO % of 1.7% by mass, an amount of urethane bonds of 1.50 mol/kg, and a [NCO/OH] of 1.32 at the time of synthesis.

[Comparative Example 2]
30 parts by mass of PEG1000 and 70 parts by mass of NPG/oPA1000 were charged in a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser, and heated under reduced pressure at 90°C to reduce the water content. It was dehydrated until it became 0.05% by mass or less.
Next, after cooling the temperature inside the container to 60°C, 33 parts by mass of MDI was added, the temperature was raised to 110°C, and the reaction was allowed to proceed for about 3 hours until the isocyanate group content became constant, resulting in a urethane prepolymer having an isocyanate group ( iR2) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The urethane prepolymer (i-R2) had an NCO % of 1.7% by mass, an amount of urethane bonds of 1.50 mol/kg, and an [NCO/OH] of 1.32 during synthesis.

[Method for measuring viscosity]
After melting the moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples at 120° C. for 1 hour, 1 ml of the composition was sampled and melted with a cone-plate viscometer (40P cone, rotor speed: 50 rpm). Viscosity was measured and low viscosity was evaluated as follows.
“○”; less than 30,000 mPa s “×”; 30,000 mPa s or more

[Method for measuring initial adhesive strength]
The moisture-curable polyurethane hot-melt resin 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 so as to have a thickness of 100 μm. A polyethylene terephthalate sheet was laminated on the coating layer and pressed with a pressing roller. Five minutes after pressure bonding, the adhesive strength (N/25 mm) was measured using a precision universal tester "AG-10NX" manufactured by Shimadzu Corporation, and the initial strength was evaluated as follows.
"◯": The adhesive strength is 15 (N/25 mm) or more.
"x": The adhesive strength is less than 15 (N/25 mm).

[Evaluation method for flexibility]
The moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples were melted at 110° C. for 1 hour, and then coated on a polyester nonwoven fabric using a knife coater so that the film thickness after curing was 100 μm. A hardened film was obtained by processing and leaving for 3 days. The tactile sensation was used to evaluate the flexibility as follows.
"○": Highly flexible.
"X": Hard impression is received.

The moisture-curable polyurethane hot-melt resin compositions of Examples 1 to 4 of the present invention had low viscosity and were excellent in initial adhesive strength and flexibility.

On the other hand, Comparative Examples 1 and 2, in which the amount of polytetramethylene glycol or polyethylene glycol used was less than the amount of aromatic polyester polyol used, were poor in low viscosity and flexibility.

Claims (3)

A moisture-curable polyurethane hot-melt resin composition containing a urethane prepolymer (i) having an isocyanate group (excluding one having a (meth)acryloyl group) made from a polyol (A) and a polyisocyanate (B) as raw materials can be,
The polyol (A) contains polytetramethylene glycol (a1-1) or polyethylene glycol (a1-2) and an aromatic polyester polyol (a2),
The amount of the polytetramethylene glycol (a1-1) or polyethylene glycol (a1-2) used is greater than the amount of the aromatic polyester polyol (a2) used,
The urethane bond amount of the urethane prepolymer (i) is in the range of 1.1 to 3 mol/kg when the polytetramethylene glycol (a1-1) is contained as the polyol (A),
A moisture-curable polyurethane hot-melt resin composition characterized in that when polyethylene glycol (a1-2) is contained as the polyol (A), the content is in the range of 1.5 to 3 mol/kg. 2. The moisture-curable polyurethane hot-melt resin composition according to claim 1, wherein the molar ratio [NCO/OH] between the polyol (A) and the polyisocyanate (B) is in the range of 1.1 to 1.5. 2. The moisture-curable polyurethane hot-melt resin composition according to claim 1, wherein the urethane prepolymer (i) has an isocyanate group content in the range of 1 to 4% by mass.