JP2011225636A - Moisture-curable reactive hot-melt adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moisture-curable reactive hot-melt adhesive having a long tack-free period while showing high initial adhesion strength, and having excellent workability.SOLUTION: The moisture-curable reactive hot-melt adhesive contains an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition with a polyfunctional isocyanate compound, and a urethane (meth)acrylate compound.

Description

  The present invention relates to a moisture-curable reactive hot melt adhesive having a high initial adhesive force and a long tack-free time and excellent workability.

  Hot melt adhesives are excellent in work environment and productivity because they do not contain a solvent and are excellent in initial adhesive strength, and are used in various fields. In addition, reactive hot melt adhesives having both reactive curability are excellent not only in excellent initial adhesive strength but also in final adhesive strength after curing reaction, and are used in fields where heat resistance is required.

  In recent years, the level of initial adhesive strength required for reactive hot melt adhesives has been further increased, but when the molecular weight of the resin is increased or the crystallinity is increased in order to improve the cooling and solidification properties, If the melting temperature is increased to increase the workability of the coating and to avoid this, there is a problem that the deterioration of the resin and the curing reaction are promoted. In addition, when the reaction curability is increased, the allowable time from melting the resin to applying and bonding to the adherend is shortened. In addition, there is a problem that even the adherend to which the adhesive is applied has to be discarded, which increases the production cost.

Patent Document 1 discloses a method in which a reactive hot melt adhesive mainly composed of a urethane prepolymer having a (meth) acryloyl group at a molecular end is applied to an adherend, and the applied surface is irradiated with ultraviolet rays before bonding. It is disclosed. According to this method, the problem that the workability of applying the adhesive is reduced can be avoided, but there is a problem that an equipment investment for introducing an ultraviolet irradiation device is required and the manufacturing process of the urethane prepolymer is complicated.
JP 2008-63406 A

  An object of the present invention is to provide a moisture curable reactive hot melt adhesive having a high initial adhesive force and a long tack-free time and excellent workability.

  The present invention is a moisture curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition with a polyfunctional isocyanate compound and a urethane (meth) acrylate compound. is there.

  Since the moisture-curable reactive hot melt adhesive of the present invention has a high initial adhesive force, the curing time until the next process such as transfer and cutting can be shortened after bonding the adherends can be shortened. It can be improved. In addition, the tack-free time is long and there is no restriction in the adhesive application process, so workability does not deteriorate. Furthermore, it does not require expensive equipment investment, and the manufacturing process of the adhesive is not complicated.

  The moisture-curable reactive hot melt adhesive of the present invention contains an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition with a polyfunctional isocyanate compound. A polyol composition consists of polyester polyol, polyether polyol, polycarbonate polyol, and the like. The polyester polyol is further classified into a crystalline polyester polyol, an amorphous polyester polyol, and a liquid polyester polyol.

  The crystalline polyester polyol is a polyester polyol having a clear crystal structure confirmed by X-ray diffraction and having a glass transition point and a melting point. Examples of the dicarboxylic acid constituting the crystalline polyester polyol include adipic acid, sebacic acid, terephthalic acid, and dodecanedioic acid. Examples of the diol include ethylene glycol, butanediol, and hexanediol.

  Amorphous polyester polyol is a polyester polyol having no clear crystal structure by X-ray diffraction and having only a glass transition temperature. Examples of the dicarboxylic acid constituting the amorphous polyester polyol include adipic acid, phthalic anhydride, isophthalic acid, and terephthalic acid. Examples of the diol include neopentyl glycol, ethylene glycol, propylene glycol, and hexane diol.

  The liquid polyester polyol is a polyester polyol that is liquid at room temperature. Examples of the dicarboxylic acid constituting the liquid polyester polyol include adipic acid, sebacic acid, terephthalic acid, and dodecanedioic acid. Examples of the diol include ethylene glycol, butanediol, and hexanediol.

  In order to obtain an isocyanate-terminated urethane prepolymer, 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 4,4′-diphenylmethane diisocyanate (4,4) is used as the polyvalent isocyanate compound used in the reaction with the polyol composition. 4'-MDI), aromatic isocyanates such as tolylene diisocyanate and naphthalene diisocyanate, and aliphatic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate. Of these, 4,4'-MDI and carbodiimide-modified MDI, which is a carbodiimide-modified product thereof, are preferably used from the viewpoints of moisture curability and safety. The equivalent ratio NCO / OH of the isocyanate group contained in the polyisocyanate and the hydroxyl group contained in the polyester polyol is preferably 1.5 to 2.5. Within this range, there is no significant increase in viscosity even in the melting state for a long time in the melting apparatus, and there is little foaming due to carbon dioxide during the curing reaction. Moreover, there is little influence on the work environment by volatilization of the unreacted polyfunctional isocyanate compound.

  The urethane (meth) acrylate compound is a polyurethane having an unreacted (meth) acryloyl group in the molecule. For example, it can be obtained by reacting a compound having a hydroxyl group and a (meth) acryloyl group with an isocyanate compound and, if necessary, a polyol or a diamine. Examples of commercially available products include CN9788 (trade name, manufactured by SARTOMER). It is preferable to add 1 to 100 parts by weight of a urethane (meth) acrylate compound with respect to 100 parts by weight of the isocyanate-terminated urethane prepolymer.

  The moisture curable reactive hot melt adhesive of the present invention contains an isocyanate-terminated urethane prepolymer and a urethane (meth) acrylate compound. After reacting the polyol composition with the polyvalent isocyanate compound to produce an isocyanate-terminated urethane prepolymer, a urethane (meth) acrylate compound may be added, or when producing an isocyanate-terminated urethane prepolymer, urethane (meth) is used in advance. An acrylate compound may be added.

  The moisture curable reactive hot melt adhesive in the present invention may contain a tackifier resin, a catalyst, a nucleating agent, a colorant, an anti-aging agent, and the like as necessary. Examples of tackifying resins include styrene resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, and rosin esters. Examples of the catalyst include tertiary amine type and tin type catalysts. Examples of the nucleating agent include paraffin wax and microcrystalline wax. In order to improve curability at low temperatures, it is effective to add a catalyst or a nucleating agent.

  Hereinafter, based on an Example and a comparative example, this invention is demonstrated in detail. However, the present invention is not limited to the examples.

Example 1
100 parts by weight of crystalline polyester polyol (molecular weight 4000, adipic acid and 1,6-hexanediol as constituent components), amorphous polyester polyol (molecular weight 2000, isophthalic acid, propylene glycol, ethylene glycol, neopentyl glycol and 1 , 4-butanediol as a constituent) 100 parts by weight, liquid polyester polyol (molecular weight 5500, adipic acid, ethylene glycol, neopentyl glycol and 1,6-hexanediol as constituents) 100 parts by weight, molecular weight 20 parts by weight of polypropylene glycol of 3000, 20 parts by weight of polycaprolactone diol having a molecular weight of 50000, CN9788 which is a urethane acrylate compound (molecular weight 3000, manufactured by SARTOMER) Name) 20 parts by weight and 0.1 part by weight of DMDEE (trade name, manufactured by Mitsui Chemical Fine Co., Ltd.), which is an amine catalyst, are placed in a separable flask equipped with a stirrer, a temperature controller, and a vacuum pump. The mixture was stirred for 2 hours and dehydrated. Next, 67 parts by weight of Millionate MT (4,4′-MDI, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name) is added as a polyfunctional isocyanate compound (NCO / OH = 2.0), and 2 at 100 ° C. in a nitrogen atmosphere. The reaction was conducted by stirring for a time to obtain the moisture-curable reactive hot melt adhesive of Example 1 that was solid at room temperature.

Example 2
In Example 1, a moisture curable reactive hot melt adhesive of Example 2 was obtained in the same manner as in Example 1 except that 20 parts by weight of a molecular weight 5000 and hexafunctional urethane acrylate compound was added instead of CN9788. .

Example 3
In Example 1, a moisture curable reactive hot melt adhesive of Example 3 was obtained in the same manner as in Example 1 except that 20 parts by weight of a 15-functional urethane acrylate compound having a molecular weight of 70,000 was added instead of CN9788. .

Comparative Example 1
In Example 1, except having added CN9788, it carried out similarly to Example 1 and the moisture hardening type reactive hot-melt-adhesive of the comparative example 1 was obtained.

Comparative Example 2
In Example 2, it carried out similarly to Example 1 except having added 20 weight part of 2-hydroxyethyl methacrylate (HEMA) instead of CN9788, and the moisture hardening type reactive hot-melt-adhesive of the comparative example 2 was obtained.

Comparative Example 3
In Example 1, a moisture curable reactive hot melt adhesive of Comparative Example 3 was obtained in the same manner as in Example 1 except that 20 parts by weight of urethane resin having a molecular weight of 1000 was added instead of CN9788.

Comparative Example 4
In Example 1, the same procedure as in Example 1 was performed except that 20 parts by weight of ester gum HD (manufactured by Arakawa Chemical Industry Co., Ltd., molecular weight 1000 or less, product name), which is a rosin resin, was added instead of CN9788. A moisture curable reactive hot melt adhesive was obtained.

Comparative Example 5
In Example 1, except that 20 parts by weight of UP1080 (manufactured by Toagosei Co., Ltd., molecular weight: 6000, trade name), which is an acrylic resin, was used instead of CN9788, the same procedure as in Example 1 was carried out. A hot melt adhesive was obtained.

Tack free time Each moisture-curing reactive hot melt adhesive is melted at 120 ° C., and after applying 80 g / m ^{2 to the} substrate, the presence or absence of tack is confirmed by touch with a finger every minute, and tack is not felt Was tack free time (minutes). This tack-free time is a measure of the workable time after applying the adhesive, and the longer the work-free time, the better the workability.

Initial adhesive strength Each moisture-curing reactive hot melt adhesive is melted at 120 ° C., and applied to two polypropylene plates (length 70 mm × width 25 mm) at 80 g / m ² to provide an open time (OT) of 1 minute. After taking, the widths of the two polypropylenes were aligned, the adhesive application surfaces were bonded together so as to overlap each other by 25 mm in the length direction, and pressed for 30 seconds at 0.5 N / m ² using a micro-pressure press. After curing for 5 minutes in an atmosphere of 5 ° C., a shear test was performed to measure the strength (kN). The test was conducted in the same manner by combining conditions of 1 minute and 5 minutes for the open time and 5 ° C and 23 ° C for the curing temperature.

  When each Example and Comparative Example 1 were compared, the tack-free time was longer and the initial adhesive strength was equal or higher. On the other hand, when Comparative Examples 2 to 5 and Comparative Example 1 were compared, the tack-free time was longer, but the initial adhesive strength was greatly reduced. That is, the moisture-curable reactive hot melt adhesive of the present invention can achieve both initial adhesive strength and workability.

Claims (2)

  A moisture-curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition with a polyfunctional isocyanate compound and a urethane (meth) acrylate compound.   2. The moisture-curable reactive hot melt adhesive according to claim 1, comprising 1 to 100 parts by weight of a urethane (meth) acrylate compound with respect to 100 parts by weight of the isocyanate-terminated urethane prepolymer.