JP2000038561A - Moisture-curing polyurethane hot-melt adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide moisture-curing polyurethane hot-melt adhesive compositions excellent in initial adhesion and initial heat creep properties. SOLUTION: This moisture-curing polyurethane hot-melt adhesive composition is obtained by reacting an excess of an organic isocyanate compound with a mixed polyol composed of 100 mass parts polyester polyol having a number average molecular weight of 1,000-8,000 and 0.5-20 mass parts tri- or more functional polyamine polyol. It is desirable to use a mixed polyol obtained by further adding 5-20 mass parts polyethylene glycol having a number average molecular weight of 500-5,000 to said mixed polyol and a tri- or more functional polyamine polyol obtained by the addition reaction of an alkylene oxide to an aliphatic or aromatic polyamine as the polyamine polyol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Moisture-curable polyurethane hot-melt adhesives exhibit a certain level of adhesive strength by cooling and solidifying the adhesive itself in a short period of time after bonding.
Due to its excellent adhesion to adherends such as wood and metal, it is widely used in various fields such as packaging materials, automobiles, woodwork, building materials, bookbinding and the like.

[0003] However, also in these fields,
The conventional moisture-curable polyurethane hot-melt adhesive has a slow curing reaction due to moisture absorption, and has a problem of shortening the process time for improving productivity. For example, if the adhesive is applied to the car interior skin, the skin is incorporated into the car shortly after bonding and then the car is moved to an outdoor motor pool about six hours later and left in the sun Is done. For this reason, the inside of the vehicle becomes considerably high in temperature, so that an initial heat-resistant adhesive force that can withstand the temperature is required.

[0004] Conventional moisture-curable polyurethane hot-melt adhesives require a long time of one week or more to completely cure moisture. In this respect, conventional moisture-curable polyurethanes which can be applied at room temperature can be used. There is no difference from the system adhesive.

Therefore, a method has been proposed in which a metal-based catalyst or an amine-based catalyst is added to an adhesive to promote a moisture curing reaction.

[0006] However, although this method promotes the curing reaction, it is not practical because it has a drawback that storage stability and thermal stability are reduced.

As another improvement method, ethylene glycol and an alkylene glycol copolymer having 3 or more carbon atoms (an ethylene oxide content of 50 to 80 mol% and a number average molecular weight of 1000) are added to 100 parts by weight of a specific polyester polyol.
~ 5000) special polyether polyol 5
A moisture-curable polyurethane hot melt adhesive obtained by reacting an excess amount of an organic isocyanate compound with 20 parts by weight is disclosed in JP-A-5-214311. At a temperature of 20 ° C 2
It is still insufficient because it has to be left for 4 hours. In addition, since a special polyether polyol is used in combination, there is a disadvantage that the adhesion of the polyester polyol is impaired.

On the other hand, an amine polyol obtained by adding an alkylene oxide to an aliphatic amine having 2 to 25 carbon atoms is blended in an amount of 2 to 100% by weight in the whole polyol component, and an excess of an organic isocyanate compound is reacted therewith. The moisture-curable polyurethane adhesive obtained by the method described in
No. 2 discloses that the moisture curing reaction of the urethane prepolymer is promoted without impairing the storage stability, and that an adhesive having a good initial adhesive strength can be obtained.

However, the adhesive obtained by this method is a room temperature application type moisture-curable polyurethane adhesive, and the number of functional groups of the amine polyol is limited to two. Therefore, although the storage stability is good, there is no initial adhesive force, and it takes 24 hours to obtain sufficient heat resistance.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to achieve excellent adhesive strength and heat creep resistance at an early stage (within 6 hours) after bonding by accelerating a moisture curing reaction. Another object of the present invention is to provide a moisture-curable polyurethane hot melt adhesive having good storage stability and heat stability.

[0011]

As a result of intensive studies, the inventors have found that a mixed polyol consisting of 100 parts by mass of a polyester polyol having a number average molecular weight of 1,000 to 8,000 and 0.5 to 20 parts by mass of a triamine or higher polyamine polyol has an excessive amount. The present inventors have found that a moisture-curable polyurethane hot melt adhesive composition obtained by reacting an organic isocyanate compound is an adhesive that can solve the above-mentioned problems, and have completed the present invention.

A first feature of the present invention is to effectively utilize the excellent adhesiveness of an amino group. The second feature of the present invention is not only to promote the moisture curing reaction of the polyurethane prepolymer of the adhesive by using a polyamine polyol having three or more functional groups, but also at the same time, to positively intermolecular the polyurethane prepolymer. Crosslinking is intended to impart excellent adhesive strength and heat resistance at an early stage (within 6 hours) after bonding.

The polyester polyol used in the present invention includes ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Neopentyl glycol, 1,3 butanediol, 1,
One or two polyhydric alcohol compounds such as 4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, pentaerythritol, glycerin, castor oil and derivatives thereof Above and maleic anhydride, fumaric acid, itaconic acid, woodless phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, succinic acid, One kind of polyvalent carboxylic acid such as trimellitic anhydride or 2
A polyester polyol obtained by performing a condensation reaction from more than one kind is used.

The number average molecular weight of the polyester polyol is in the range of 1,000 to 8,000. When the number average molecular weight is 1000 or less, the adhesive strength after moisture curing, water resistance, heat resistance, etc. decrease, which is not preferable. On the other hand, when the number average molecular weight is 8000 or more, the viscosity of the adhesive increases. Therefore, the coatability is poor and not preferable.

The amine polyol used in the present invention is ethylamine, butylamine, octylamine, laurylamine, ethylenediamine, diethylenetrilyamine, triethylenetetramine, tetraethylenepentamine, propylenediamine, methylaminomethylamine, methylaminoethylamine. , Ethylaminoethylamine, 1,2 diaminopropane, 1,3 diaminopropane, methylaminopropylamine, bis (3-aminopropyl) ether, 1,3 bis (3-aminopropyl) ethane, 1,4 diaminobutane, lauryl Aliphatic polyamines such as aminopropylamine, iminobispropylamine and methyliminobispropylamine and aromatic polyamines such as meta-xylenediamine are used alone or in combination. One kind or two or more types of polyamine polyols obtained by addition reaction of alkylene oxide is used, on average, 3 or more functional polyamine down polyol is used. In addition, examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and the like.

The amount of the amine polyol to be used is suitably 0.5 to 20 parts by mass with respect to 100 parts by mass of the polyester polyol. Since the effect of accelerating the reaction is not exerted, the initial adhesive strength and the initial heat-resistant crossability are extremely reduced, and the use amount of 20 parts by weight or more is not preferable because storage stability and heat stability are impaired.

[0017] Polyethylene glycol is suitable for still promoting moisture curability, and has a number average molecular weight of 500 to 5
000 is preferred. This number average molecular weight is 5
When it is less than 00, the initial adhesive strength and initial heat creep resistance decrease, and when the number average molecular weight is 5,000 or more, the viscosity of the adhesive increases and the coatability decreases, which is not preferable.

The amount of the polyethylene glycol used is 5 to 20 parts by mass based on the polyester polyol. The amount of polyethylene glycol used is 5
When the amount is less than 20 parts by mass, the effect is small, and when the amount is more than 20 parts by mass, the water resistance after moisture curing is lowered, which is not preferable.

Examples of the organic isocyanate compound used in the present invention include tolylene diisocyanate, hydrogenated tolylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, memetaxylylene diisocyanate, tetramethyl xylylene diisocyanate, diphenylmetane diisocyanate. One or more of hydrogenated diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylenediisocyanate, isophorone diisocyanate, and derivatives thereof are used.

In the present invention, a polyurethane prepolymer, which is the adhesive composition of the present invention, is obtained by a urethanization reaction of the above-mentioned organic isocyanate compound and the above-mentioned polyol composed of the polyester polyol, polyamine polyol and polyethylene glycol. Isocyanate groups in this organic isocyanate compound (hereinafter, referred to as
NCO) number and hydroxyl groups in the polyol (hereinafter OH)
NCO number / OH number = 1.3 to 5.0.
It is appropriate that the NCO content in the polytarene prepolymer is 1.0 to 5.0% by mass, and when the NCO number / OH number is 1.3 or less, the crosslink density becomes low, so When the adhesive strength, water resistance and heat resistance after curing are extremely reduced, and the NCO number / OH number is 5.0 or more, the foaming of the adhesive layer is increased during moisture curing. This is not preferable because adverse effects such as a reduction in the properties are caused.

Further, the adhesive of the present invention may contain, if necessary, polyurethane, polyester, acrylic copolymer,
Thermoplastic resin such as polyether, ethylene-vinyl acetate copolymer, various rubbers, and petroleum resin, rosin ester resin, hydrogenated rosin ester resin, phenol resin, terpene resin, cumarone resin, xylene resin, ketone resin,
A tackifier such as a styrene resin, a filler such as calcium carbonate, talc, clay, mica, and silica, a solvent, a plasticizer, an ultraviolet absorber, an antioxidant, a coloring agent, and an antibacterial agent are blended.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to examples. The test method was performed by the method described below.

Softening point: Measured by the ring and ball method.

NCO content: Excess amine is added and NCO
After reacting with CO, the remaining amine was back titrated with hydrochloric acid and measured.

Initial adhesive strength: temperature 23 ° C., humidity 65% RH
100-120 temperature on the vinyl chloride sheet in a constant temperature and humidity room
The adhesive which was heated and melted at a temperature of 45 ° C. was applied to a coating amount of 45 g / m ² , and immediately afterward, using a roller, using a medium. Dengeity. About 2kg / c pressure on fiber board (MDF)
prepared specimen was pressed at m ^2. This is at a temperature of 23 ° C and a humidity of 6
After leaving in a constant temperature and humidity room of 5% RH for a predetermined time, a peeling angle of 180 ° and a peeling speed of 200 mm were used using a tensile tester.
The peel strength was measured at a temperature of 23 ° C./min. Initial adhesion is measured immediately.

Heat creep resistance: A specimen having a width of 25 mm, prepared under the same conditions as the initial adhesive strength, was left in a constant temperature and humidity room at a humidity of 65% RH for a predetermined time, and then a peeling angle of 90 ° and a load of 500 were applied.
g was added and left in a thermostat at a temperature of 80 ° C. for 1 hour, and the peel length was measured.

Storage stability: After sealing the adhesive in a container from which moisture was removed with nitrogen gas, the adhesive was allowed to stand in a constant temperature room at a temperature of 23 ° C. for 6 months, and the appearance and viscosity change were measured and judged.

Thermal stability: After sealing the adhesive in a container from which water was removed with nitrogen gas, the adhesive was allowed to stand in a thermostat at a temperature of 120 ° C. for 24 hours, and the appearance and viscosity change were measured and judged.

[0029]

Example 1 A polyester polyol (number average molecular weight 3000, OH value) obtained by subjecting 1,4-butanediol and adipic acid to a condensation reaction in a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen gas inlet tube. 50mgKO
H / g) of 100 parts by mass and 2 parts by mass of a tetrafunctional polyamine polyol (OH value 220 mgKOH / g) obtained by adding propylene oxide to ethylenediamine, and after reducing the pressure to remove water, diphenylmethane diisocyanate was added thereto. Was charged so that the NCO number / OH number = 2.0, and a urethanization reaction was performed under a nitrogen atmosphere at a temperature of 120 ° C. for 3 hours to obtain a moisture-curable polyurethane hot melt adhesive having an NCO content of 2.3% by mass. .

[0030]

Example 2 100 parts by mass of the same polyester polyol as in Example 1, 5 parts by mass of the same polyamine polyol as in Example 1, and diphenylmethane diisocyanate were charged so that the number of NCO / OH was 2.0. 1
In the same manner as in the above, a urethanization reaction was performed to obtain a moisture-curable polyurethane hot melt adhesive.

[0031]

Example 3 100 parts by mass of the same polyester polyol as in Example 1, 10 parts by mass of the same polyamine polyol as in Example 1, and a bifunctional amine polyol (OH number 1) obtained by adding propylene oxide to ethylamine.
5 parts by mass (00 mg KOH / g) and diphenylmethane diisocyanate were charged so that the number of NCO / OH was 2.0, and the urethane reaction was carried out in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

[0032]

Example 4 100 parts by mass of the same polyester polyol as in Example 1, 10 parts by mass of the same polyamine polyol as in Example 1, 5 parts by mass of polyethylene glycol having a number average molecular weight of 4000, and diphenylmethane diisocyanate were obtained by adding NCO number / OH number. = 2.0, and urethanization reaction was carried out in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

[0033]

Comparative Example 1 The same polyester posaol (100 parts by mass) and diphenylmethane diisocyanate
It was charged so that the number of CO / OH was 2.0, and the urethane reaction was performed in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

[0034]

Comparative Example 2 100 parts by mass of the same polyester polyol as in Example 1, 20 parts by mass of the same polyethylene glycol as in Example 4, and diphenylmethane diisocyanate were charged so that the number of NCO / OH was 2.0. A urethane-forming reaction was performed in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

[0035]

Comparative Example 3 100 parts by mass of the same polyester polyol as in the actual noodle example 1 and the same amine polyol 1 as in Example 3
0 parts by mass and diphenylmethane diisocyanate
It was charged so that the number of CO / OH was 2.0, and the urethane reaction was performed in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

[0036]

Comparative Example 4 100 parts by weight of the same polyester polyol as in Example 1, 25 parts by weight of the same polyamine polyol as in Example 1, and diphenylmethane diisocyanate were charged so that the number of NCO / OH number = 2,0. A urethane-forming reaction was performed in the same manner as in Example 1 to obtain a moisture-curable polyurethane hot melt adhesive.

Formulation (parts by mass) of moisture-curable polyurethane hot melt adhesives of Examples 1-4 and Comparative Examples 1-4
Table 1 shows the results of the initial adhesion performance test.

[0038]

[Table 1]

As described above, the adhesives obtained from Examples 1 to 4 had a softening point of 39 to 45 ° C. and a viscosity of 19,000 at 120 ° C.
Has a coatable viscosity of ~ 23,500 centipoise,
Each of them has excellent creep characteristics showing almost no peeling in a creep test after 6 hours from bonding.
The heat stability after the test at 24 ° C. for 24 hours is also a good moisture-curable polyurethane adhesive.

[0040]

According to the moisture-curable polyurethane hot melt adhesive of the present invention, a polyamine polyol having three or more functions as a moisture-curing catalyst and a crosslinking agent, the moisture-curing reaction of the adhesive proceeds smoothly, and the initial adhesive strength is improved. And excellent initial heat creep resistance (adhesive strength within 6 hours and heat creep resistance). Further, the adhesive of the present invention has excellent heat stability.

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Claims (3)

[Claims] 1. A moisture-curing type obtained by reacting an excess organic isocyanate compound with a mixed polyol comprising 100 parts by mass of a polyester polyol having a number average molecular weight of 1,000 to 8,000 and 0.5 to 20 parts by mass of a triamine or higher polyamine polyol. Polyurethane hot melt adhesive composition. 2. A mixed polyol according to claim 1, wherein said mixed polyol has a polyethylene glycol having a number average molecular weight of 500 to 5,000.
A moisture-curable polyurethane hot melt adhesive composition further mixed with parts by mass. 3. A moisture-curable polyurethane hot melt adhesive composition comprising a triamine or higher polyamine polyol obtained by subjecting the polyamine polyol according to the above item 1 to an addition reaction of an aliphatic or aromatic polyamine with an alkylene oxide. .