JP2008094959A - Moisture-curable reactive hot melt adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture-curable hot melt adhesive which gives a hard film, can therefore allow a decorative material to assure sufficient surface hardness when used, for example, for lamination of a decorative sheet, and has workability nearly equivalent to that of a conventional one in respect of initial tack, tack-free time, and others. <P>SOLUTION: The moisture-curable reactive hot melt adhesive essentially consists of an amorphous polyester polyol of a Tg of 30°C or higher, a crystalline polyester polyol of a molecular weight of 1,000 to below 3,000, and a crystalline polyol of a molecular weight of 3,000-5,000 and desirably further contains a urethane prepolymer obtained by reacting a polyol containing a liquid polyol of a molecular weight of 3,000-5,000 with a polyisocyanate compound. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a moisture curable reactive hot melt adhesive. More specifically, the present invention relates to a moisture curable reactive hot melt adhesive suitably used for laminating and bonding a wood base material and a decorative sheet.

  A hot melt adhesive is an adhesive containing a thermoplastic resin as a main component, and is applied to an adherend after being heated and melted, bonded, and solidified by cooling. The disadvantage of conventional hot-melt adhesives is that they have low heat resistance, but they are improved by reactive hot-melt adhesives that incorporate a chemical reaction curing mechanism. The point of being able to improve productivity because of the rapid rise of is being evaluated, and alternatives from other adhesives are being promoted in various fields.

  In the process of manufacturing decorative materials by laminating decorative sheets such as decorative paper or plastic film with a design on woody substrates such as plywood, MDF, particle board, etc., bonding with conventional water-based adhesives Since the wood substrate absorbs the moisture in the agent, there are problems such as expansion of the substrate and deterioration of the surface appearance, warping and twisting of the substrate, etc. Reactive hot melt to solve this Adhesives are being introduced.

As reactive hot-melt adhesives improved for decorative sheet laminates, we investigated adhesiveness, heat resistance, solvent resistance (Patent Document 1) and gas impermeable material bonding methods ( Patent Document 2) and the like exist.
JP 2005-75877 Japanese Patent No. 2769103

  However, in a decorative material laminated with a decorative sheet, since the decorative sheet itself does not have sufficient hardness, it is required to exert hardness in the adhesive layer, but a reactive hot melt adhesive is a thermoplastic resin. Since the coating is soft, problems such as formation of dents when a load is applied to the surface of the decorative material have occurred, and such demands have not been met.

  The present invention has a hard film, can ensure a sufficient surface hardness of a decorative material when used for, for example, a decorative sheet laminate, and has the same level of workability as initial products in terms of initial adhesion performance and tack-free time. A moisture-curing reactive hot melt adhesive is provided.

  As a result of studies by the present inventors, the hardness is increased only by using a hard resin component, but the adhesion with the base material is lowered, the tack-free time is extremely shortened, the workability is bad, It has been found that there are problems such as a decrease in initial adhesion performance. Then, when earnest examination was repeated, amorphous polyester polyol whose Tg (glass transition temperature) is 30 degreeC or more, crystalline polyester polyol whose molecular weight is less than 1000-3000, crystallinity whose molecular weight is 3000-10000. Moisture curable reactive hot melt adhesive characterized by containing a urethane prepolymer obtained by reacting a polyol, preferably a polyol having a molecular weight of 3000 to 5000 as a necessary component with a polyol and a polyvalent isocyanate compound Has found that the above-mentioned problems can be solved.

  The moisture curable reactive hot melt adhesive according to the present invention can form a hard film. Therefore, for example, when used for a decorative sheet laminate, sufficient surface hardness of the decorative material can be secured. In addition, workability such as initial adhesion performance and tack-free time is comparable to that of conventional products, and is particularly useful in the production of a decorative material laminated with a decorative sheet.

  The polyol which comprises the urethane prepolymer used as the main component of the moisture hardening type reactive hot melt adhesive of this invention is demonstrated in detail. In the polyol used in the present invention, the non-crystalline polyester polyol is a polyester polyol having no clear crystal structure by X-ray diffraction and having only Tg, and the crystalline polyester polyol has an order. It is a polyester polyol having a molecular arrangement and having a clear crystal structure confirmed by X-ray diffraction and having a Tg and a melting point.

  Each polyester polyol is composed of dicarboxylic acid such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonamethylene dicarboxylic acid, decamethylene dicarboxylic acid, dodecane dicarboxylic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and ethylene. Glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentylglycol, 2-methyl-1,3-propanediol, cyclohexanedimethanol, 2,4-dimethyl Obtained from diols such as -1,5-pentanediol.

  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. By using an amorphous polyester polyol having a Tg of 30 ° C. or higher, the hardness of the hot melt adhesive can be increased, and the surface hardness of the laminated decorative material bonded using the hot melt adhesive can be obtained.

  The dicarboxylic acid constituting the crystalline polyester polyol is preferably adipic acid, sebacic acid, terephthalic acid, dodecanedioic acid or the like, and the diol is preferably ethylene glycol, butanediol, hexanediol or the like. In addition, since the tack-free time of the non-crystalline polyester polyol described above is extremely short, the crystalline polyester polyol is preferably a combination of adipic acid and hexanediol having a relatively long tack-free time. Further, since the amorphous polyester polyol has a high melt viscosity, it is preferable to use a low-molecular weight (less than 1000 to less than 3000) crystalline polyester polyol having a low melt viscosity. On the other hand, since the low molecular weight crystalline polyol has a long tack-free time, it is preferable to use a crystalline polyester polyol having a slightly higher molecular weight (3,000 to 10,000) for the purpose of adjusting the tack-free time.

  Furthermore, a liquid polyol can be used as the polyol constituting the urethane prepolymer. Examples of the dicarboxylic acid include adipic acid, sebacic acid, isophthalic acid, terephthalic acid, and phthalic anhydride. Examples of the diol include ethylene glycol, pentanediol, Hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, cyclohexanedimethanol, 2,4-dimethyl-1,5-pentanediol and the like are preferable. The molecular weight of the liquid polyol is preferably 3000 to 5000.

  As the polyvalent isocyanate compound used in the present invention, 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI), tolylene diisocyanate, naphthalene diisocyanate In addition to aromatic polyisocyanates such as aliphatic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, 4,4′-MDI is preferably used from the viewpoint of moisture curability and safety. The equivalent ratio NCO / OH between the isocyanate group contained in the polyvalent isocyanate compound and the hydroxyl group contained in the polyester polyol is preferably 1.5 to 2.5. If the NCO / OH is less than 1.5, the viscosity of the urethane prepolymer to be produced increases when melted, and the stability of the viscosity also deteriorates. As a moisture-curable reactive hot melt adhesive, When used, workability is reduced. When NCO / OH exceeds 2.5, a large amount of unreacted polyvalent isocyanate compound remains in the moisture-curable reactive hot melt adhesive, and when used in a hot roll coater or the like, the polyvalent isocyanate compound As a result, a large amount of vapor is diffused in the air as a vapor, which causes a problem in work environment sanitation.

  In addition to the urethane prepolymer obtained by reacting the polyester polyol and the polyvalent isocyanate compound, the moisture curable reactive hot melt adhesive in the present invention adds a tackifier resin, a catalyst, or the like as necessary. be able to. Examples of tackifying resins include styrene resins, terpene resins, and rosin esters. Examples of the catalyst include tertiary amine compounds and tin compounds.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to an Example at all.

Example 1
HS 2F-237P (manufactured by Toyokuni Oil Co., Ltd., molecular weight 2000, Tg 50 ° C.) 70 parts by weight as an amorphous polyester polyol, and HS 2H-201AP (manufactured by Toyokuni Oil Co., Ltd., molecular weight 2000, melting point 55 ° C.) as a crystalline polyester polyol. ) 50 parts by weight and HS 2H-451A (manufactured by Toyokuni Oil Co., Ltd., molecular weight 4500, melting point 57 ° C.), as a liquid polyesterol, HS polyol 2000 (manufactured by Toyokuni Oil Co., Ltd., molecular weight 3500, Tg-31 ° C.) 30 parts by weight was placed in a flask and dehydrated under reduced pressure at 120 ° C. for 2 hours. Next, by adding 35.7 parts by weight of Millionate MT (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) as 4,4′-MDI, the mixture was stirred for 1 hour under a nitrogen atmosphere, and further stirred for 1 hour under reduced pressure. A hot melt adhesive of Example 1 was prepared.

Example 2, Comparative Examples 1 and 2
Except having changed the polyester polyol into the composition shown in Table 1, it was carried out in the same manner as in Example 1, and hot melt adhesives in Example 2 and Comparative Examples 1 and 2 were obtained. In addition to the material described in Example 1, HS polyol 1000 (manufactured by Toyokuni Oil Co., Ltd., molecular weight 3000, Tg 20 ° C.) was used as the amorphous polyester polyol.

Each hot melt adhesive was evaluated according to the following method.
<Melt viscosity>
Using a viscometer (Brookfield viscometer RVDV-I +), a hot melt adhesive preliminarily adjusted to 120 ° C. was set in a 120 ° C. chamber, allowed to stand for 20 minutes, and then measured at 10 rpm.
<Tack-free time>
Each hot melt adhesive is heated to 120 ° C. and melted, and is applied to a particle board (50 mm × 70 mm × 9 mm thickness) to a thickness of 125 μm using a doctor blade. It was confirmed whether it lifted up, and the time from when the adhesive was applied until it could not lift up was measured.
<Surface hardness>
Each adhesive composition was heated to 120 ° C. and melted, and a 100 μm-thick film was prepared with a doctor blade. After curing for 24 hours, the pencil hardness of the film surface was measured according to JISK5600-5-4 (1999). . However, the load was 1 kg.

実施例１及び２においては十分な表面硬度が得られ、タックフリータイムも実用的なものであった。比較例１及び２はＴｇが低い非晶性ポリエステルポリオールを使用したものであり、表面硬度が低かった。

In Examples 1 and 2, sufficient surface hardness was obtained, and tack-free time was also practical. In Comparative Examples 1 and 2, an amorphous polyester polyol having a low Tg was used, and the surface hardness was low.

Claims (2)

  (A) An amorphous polyester polyol having a Tg of 30 ° C. or higher, (b) a crystalline polyester polyol having a molecular weight of less than 1000 to less than 3000, and (c) a crystalline polyol having a molecular weight of 3000 to 10,000 are essential components. A moisture-curing reactive hot melt adhesive comprising a urethane prepolymer obtained by reacting a polyol and a polyvalent isocyanate compound.   The polyol is (a) an amorphous polyester polyol having a Tg of 30 ° C. or higher, (b) a crystalline polyester polyol having a molecular weight of less than 1000 to less than 3000, and (c) a crystalline polyol having a molecular weight of 3000 to 10,000. In addition, the moisture-curable reactive hot melt adhesive according to claim 1, further comprising (d) a liquid polyol having a molecular weight of 3000 to 5000 as an essential component.