JP2009242514A - Moisture-curing type reactive hot-melt adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture-curing reactive hot-melt adhesive having a good close adhesion to an aromatic group-containing substrate material e.g. a polyester sheet even in a severe winter period, and useful for the laminate-processing etc. of a decorated polyester sheet. <P>SOLUTION: This moisture-curing type reactive hot-melt adhesive contains an isocyanate terminal urethane prepolymer obtained by reacting a polyol composition (A) with a polyfunctional isocyanate compound (B), and the isocyanate terminal urethane prepolymer contains a 50 to 95 wt.% polyesterpolyol (a1) having an aromatic dicarboxylic acid based on the whole polyols and a 5 to 20 wt.% polypropylene glycol (a2) based on the whole polyols as constituting units. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a moisture curable reactive hot melt adhesive that has good adhesion to an aromatic group-containing substrate, such as a polyester sheet, even in severe winter, and is useful for laminating a decorative polyester sheet.

  Cosmetic materials manufactured by attaching decorative sheets to woody base materials such as plywood, MDF, particle board, and inorganic base materials such as calcium plates are used for wall panels, doors, window frames, furniture, etc. Conventionally, ethylene-vinyl acetate copolymer resin emulsions have been mainly used. In recent years, reactive hot melt adhesives have been evaluated to be excellent in productivity, and since the resin content is 100%, the base material absorbs moisture in the adhesive and there is no risk of warping, etc. It is also used in the laminating process.

  Up until now, PVC sheets have been mainly used as decorative sheets, but as is well known, since PVC may generate harmful substances during incineration, cosmetic materials using PVC sheets are declining. Cosmetic materials using polyolefin sheets and polyester sheets are increasing. In addition, since polyolefin has no polarity, it is extremely difficult to bond, and a surface to which the primer is treated with a urethane resin or the like is used. On the other hand, since polyester has a certain degree of polarity, primer treatment may be performed, but in many cases, it is limited to simple treatment such as corona discharge treatment. However, the primer-untreated polyester sheet has particularly poor low-temperature adhesiveness, and the present situation is that no investigation has been made on an adhesive that can cope with this.

Patent Document 1 describes a moisture-curable hot melt adhesive composition having excellent adhesion to an adherend such as a polycarbonate having an aromatic ring in the molecule. However, as is clear from the fact that only the room temperature adhesiveness is studied in the examples, the adhesiveness under low temperature at which the adhesiveness is remarkably lowered was not taken into consideration. Moreover, although this applicant has proposed the adhesive agent excellent in the adhesiveness with respect to a polyester sheet in patent document 2, there was still room for improvement about the adhesiveness in the severe winter season.
Japanese Laid-Open Patent Publication No.5-194929 Japanese Patent Application No. 2007-097401

  An object of the present invention is to provide a moisture-curable reactive hot melt adhesive that has good adhesion to an aromatic group-containing substrate, such as a polyester sheet, even in severe winter, and is useful for laminating a decorative polyester sheet. Is to provide.

  The present invention is an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition (A) with a polyfunctional isocyanate compound (B), and comprises a polyester polyol (a1) having an aromatic dicarboxylic acid as a structural unit. Moisture curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer containing 50 to 95% by weight based on the total polyol and 5 to 20% by weight of polypropylene glycol (a2) based on the total polyol It is an agent.

  The moisture-curable hot-melt adhesive according to the present invention has good adhesion to a polyester sheet or the like even in the severe winter season, so that it can be laminated without preheating the substrate even at low temperatures. Is possible. In addition, a decorative material produced using the moisture-curable hot-melt adhesive does not easily peel off the base material and the sheet even at low temperatures, and has high cold resistance and is useful.

  The moisture-curable reactive hot melt adhesive of the present invention contains an isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition (A) with a polyfunctional isocyanate compound (B). The polyol composition (A) contains a polyester polyol (a1) having an aromatic dicarboxylic acid as a structural unit and polypropylene glycol (a2), and the content of (a1) with respect to the total polyol is 50 to 95% by weight, The content of polypropylene glycol (a2) with respect to the total polyol is 5 to 20% by weight. With such a composition, good adhesion can be obtained even in the severe winter season with respect to an aromatic group-containing substrate such as a polyester sheet.

  Examples of the aromatic dicarboxylic acid constituting the polyester polyol (a1) having an aromatic dicarboxylic acid as a structural unit include phthalic anhydride, isophthalic acid, terephthalic acid and the like. Moreover, the dicarboxylic acid which is not aromatic may be included, for example, adipic acid is mentioned. Examples of the diol to be reacted with the dicarboxylic acid include neopentyl glycol, ethylene glycol, propylene glycol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, cyclohexanedimethanol, and 2,4-dimethyl-1 , 5-pentanediol and the like.

  The polyol composition (A) may further contain other polyol components in addition to the above (a1) and (a2). For example, a polyester polyol or polyether polyol that does not have an aromatic dicarboxylic acid as a structural unit can be used. However, it is limited to use within the range where (a1) and (a2) satisfy the above-mentioned content ratio.

  In order to obtain an isocyanate-terminated urethane prepolymer, the polyvalent isocyanate compound (B) used in the reaction with the polyol composition (A) is 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 4,4. Examples include aromatic isocyanates such as' -diphenylmethane diisocyanate (4,4'-MDI), tolylene diisocyanate and naphthalene diisocyanate, and aliphatic polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate. Among 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 between the isocyanate group contained in the polyisocyanate and the hydroxyl group contained in the polyester polyol is desirably 1.5 to 2.5. Within this range, there is no noticeable thickening even in the melted 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.

  In addition to the isocyanate-terminated urethane prepolymer, the moisture curable reactive hot melt adhesive in the present invention may be added with a tackifier resin, a catalyst, a nucleating agent, a colorant, an anti-aging agent, etc. as necessary. it can. 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.

  As the polyester polyol (a1) used in Examples and Comparative Examples, commercially available products having the properties described in Table 1 were used. For example, polyester polyol 1 has adipic acid and terephthalic acid as dicarboxylic acids as constituents, hexanediol as a constituent as diol, is crystalline, and has a molecular weight of 4500.

Manufacture of moisture curable reactive hot melt adhesive Polyester polyol 1 150 parts by weight, polyester polyol 2 100 parts by weight, polyesterol 3 100 parts by weight, (a2) as polypropylene glycol (average molecular weight 700) 50 parts by weight, as catalyst JEFFCAT DMDEE (manufactured by Huntsman, trade name) 0.2 parts by weight, 2.5 parts by weight of synthetic wax FT105 (Nippon Seiwa Co., Ltd.) as a nucleating agent, a separator equipped with a stirrer, temperature controller, and vacuum pump The mixture was placed in a bull flask, stirred at 120 ° C. under reduced pressure for 2 hours, and dehydrated. Next, 62.4 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 = 1.8), at 120 ° C. under a nitrogen atmosphere. And stirred for 3 hours to obtain a moisture-curable reactive hot melt adhesive solid at room temperature. Moreover, it manufactured similarly to Example 1 by the mixing | blending of Table 2, and obtained each moisture hardening type reactive hot-melt-adhesive. Each moisture curing type reactive hot melt adhesive was evaluated as follows.

Test Evaluation Method A moisture curable reactive hot melt adhesive melted at 120 ° C. was applied to a polyester decorative sheet (50 μm thickness, no primer treatment) at 50 g / m ² , bonded to a particle board, and then heated to 120 ° C. A specimen was prepared by pressing with a heat roll. Each specimen was cured for 1 day in an atmosphere of 2 ° C. (low temperature) or 23 ° C. (room temperature), and then forcibly destroyed to observe the destruction state. The case where the entire surface was fractured was evaluated as ◯, the case where material failure and interfacial debonding were mixed together was evaluated as Δ, and the case where the entire surface was debonded or cohesive fracture was evaluated as x.

  As shown in Table 2, each moisture-curing type of Example in which the content of (a1) with respect to the total polyol is 50 to 95% by weight and the content of (a2) with respect to the total polyol is 5 to 20% by weight. It can be seen that the reactive hot melt adhesive has excellent adhesion to the polyester sheet even at low temperatures. On the other hand, each moisture curable reactive hot melt adhesive of Comparative Example in which the content of (a2) with respect to the total polyol is less than 5% by weight or more than 20% by weight has insufficient adhesion at low temperatures.

Claims (1)

  An isocyanate-terminated urethane prepolymer obtained by reacting a polyol composition (A) with a polyfunctional isocyanate compound (B), wherein a polyester polyol (a1) having an aromatic dicarboxylic acid as a structural unit is added to all polyols A moisture-curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer containing 50 to 95% by weight and polypropylene glycol (a2) in an amount of 5 to 20% by weight based on the total polyol.