JP2011084686A - Moisture-curing type reactive hot-melt adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture-curing type reactive hot-melt adhesive that has excellent initial curability, and can reduce aging time required to e.g. stack adhered articles and until transferring to next working stage. <P>SOLUTION: The moisture-curing type reactive hot-melt adhesive includes an isocyanate-terminated urethane prepolymer obtained by reaction of a polyol composition (A) that includes a polyether polyol (a1) having at least an EO-PO random copolymer structure, a rosin resin polyol (a2) whose hydroxyl value is at least 50, and a polyester polyol (a3), with a polyfunctional isocyanate compound (B). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in the initial curing of a moisture curable reactive hot melt adhesive.

  A hot-melt adhesive is solid at room temperature, and when it is melted and applied to an adherend, it is solidified by cooling, so that the adhesive force is rapidly expressed and used as an adhesive with excellent productivity. In addition to the characteristics of the above hot melt adhesives, reactive hot melt adhesives also have excellent post-curing adhesive properties that are characteristic of chemically reactive adhesives, so building materials, bookbinding, sanitary materials, fibers It is used in the manufacturing process of products.

  On the other hand, a disadvantage of the reactive hot melt adhesive is that the initial adhesive force is lower than that of the non-reactive hot melt. Although it does not take much time to apply and press the adhesive, it is easy to peel off or shift due to the stress on the adhesive layer immediately after bonding, so a certain amount of curing is required when stacking adhesives or moving to the next process. Time was needed.

Patent Document 1 discloses a reactive hot-melt adhesive whose main object is to maintain the length of time during which adhesion is possible after application and to improve the resin strength after solidification. However, since the curing time of several hours to about one day is required, further improvement is required.
JP 2004-307658 A

  An object of the present invention is to provide a moisture curable reactive hot melt adhesive having excellent initial curability and capable of shortening the curing time until the adhesives are stacked or transferred to the next process.

  Polyol composition (A) comprising at least a polyether polyol (a1) having an EO-PO random copolymer structure, a rosin resin polyol (a2) having a hydroxyl value of 50 or more, and a polyester polyol (a3), and a polyfunctional isocyanate compound A moisture-curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer obtained by reacting with (B).

  The moisture-curing hot melt adhesive according to the present invention is excellent in initial curability, and therefore hardly peels off or shifts with respect to stress even when the curing time is shorter than conventional ones. Therefore, since it is possible to stack the bonded bodies in a short time after bonding or to move to the next process, it is possible to shorten the production time or to reduce the work in progress.

  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 composition (A) includes at least a polyether polyol (a1) having an EO-PO random copolymer structure, a rosin resin polyol (a2) having a hydroxyl value of 50 or more, and a polyester polyol (a3).

  The polyether polyol (a1) having an EO-PO random copolymer structure is a polyether polyol having an ethylene oxide structure (EO) and a propylene oxide structure (PO) randomly present in the polymer and having hydroxyl groups at both ends. . When the polyether polyol (a1) having an EO-PO random copolymer structure is not contained, the creep performance is lowered, and therefore, deviation is likely to occur after adhesion.

  The rosin resin polyol (a2) having a hydroxyl value of 50 or more is a polyol having a rosin resin as a skeleton and a hydroxyl value of 50 or more. When the rosin resin polyol (a2) having a hydroxyl value of 50 or more is not contained, dents are easily generated when the adhesives are stacked.

  The polyester polyol (a3) is obtained by reacting a dicarboxylic acid and a diol, and examples thereof include a crystalline polyester polyol, an amorphous polyester polyol, and a liquid polyester polyol. By combining these, it is possible to adjust the melt viscosity of the moisture-curable reactive hot-melt adhesive, the pasting time after application, the adhesive strength after curing, and the like.

  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.

  The polyol composition (A) may further contain other polyol components in addition to the (a1), (a2), and (a3), and examples thereof include polyether polyols. In the polyol composition (A), the ratio of the polyether polyol (a1) having an EO-PO random copolymer structure is 5 to 20% by weight, and the hydroxyl value of the rosin resin polyol (a2) is 50 or more. When the ratio is 5 to 20% by weight (more preferably 5 to 10% by weight) and the ratio of the polyester polyol (a3) is 60 to 90% by weight, not only the initial curability but also the melt viscosity and the application after application This range is preferable because it is excellent in balance such as possible attachment time and adhesive strength after curing.

  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. 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.

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.

  Commercially available products having the properties described in Table 1 were used as the polyester polyol and polyether polyol used in Examples and Comparative Examples. For example, polyester polyol 1 has sebacic acid as a constituent component as a dicarboxylic acid, hexanediol as a constituent component as a diol, is crystalline, and has a molecular weight of 10,000.

Manufacture of moisture curing type reactive hot melt adhesive Polyether polyol 1 50 parts by weight, rosin resin polyol having a hydroxyl value of 120 (trade name, manufactured by Arakawa Chemical Industries, Ltd.) 20 parts by weight, polyester polyol 1 40 parts by weight, polyester A polyol composition consisting of 60 parts by weight of polyol 2, 60 parts by weight of polyester polyol 3, 50 parts by weight of polyester polyol 4 and 20 parts by weight of polyester polyol 5 is placed in a separable flask equipped with a stirrer, a temperature controller, and a vacuum pump. The mixture was stirred at 120 ° C. under reduced pressure for 2 hours and dehydrated. Next, 51 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 120 ° C. in a nitrogen atmosphere. The reaction was conducted by stirring for a time to obtain a moisture-curable reactive hot melt adhesive that was solid at room temperature.

  In addition to the polyol used in Example 1, KE-615-3 (trade name, manufactured by Arakawa Chemical Industries, Ltd.) which is a rosin resin polyol having a hydroxyl value of 60, and rosin resin polyol HD having a hydroxyl value of 50 (trade name) Arakawa Chemical Industries, Ltd., trade name) A polyol composition was prepared using the rosin resin polyol D-6250 (Arakawa Chemical Industries, trade name) having a hydroxyl value of 40, with the formulation shown in Table 2, respectively. Was produced in the same manner as in Example 1 to obtain each moisture curable reactive hot melt adhesive. The blending amount of Millionate MT was adjusted so that NCO / OH = 2.0 in each adhesive. Each moisture curing type reactive hot melt adhesive was evaluated as follows.

Melt viscosity
Using a Brookfield RVD V-I + (manufactured by Brookfield), 120 ° C. melt viscosity was measured under the conditions of rotor S29 and 10 rpm.

In an initial creep atmosphere of 40 ° C., a moisture-curable reactive hot melt adhesive melted at 135 ° C. is applied to a 25 mm wide steel plate to a thickness of 125 μm, and after 1 minute, another 25 mm wide steel plate is stacked by a length of 25 mm. Glued. After 40 seconds, the bonded steel sheet was suspended vertically and a load of 500 g was continuously applied downward. The time until the two steel plates were peeled and one fell was recorded.

In an atmosphere with an initial hardness of 40 ° C., four bead coatings of a moisture curable reactive hot melt adhesive melted at 135 ° C. were applied in parallel on a steel plate with a diameter of 1.5 mm. An H-shaped weight (weight 5 g, installation surface thickness 0.7 mm) is placed so as to straddle all four pieces every 5 minutes after application, and the weight is removed after 10 minutes respectively, and the bead-coated adhesive is applied. The time until no dent was seen in the agent was recorded.

  As shown in Table 2, since each of the hot melt adhesives of Examples has good initial creep and initial hardness, they can be stacked in a short time after bonding or can be transferred to the next step. On the other hand, since the initial creep or initial hardness is not sufficient for each hot melt composition of the comparative example, a longer curing time is required than in the examples.

Claims (2)

  Polyol composition (A) comprising at least a polyether polyol (a1) having an EO-PO random copolymer structure, a rosin resin polyol (a2) having a hydroxyl value of 50 or more, and a polyester polyol (a3), and a polyfunctional isocyanate compound A moisture-curable reactive hot melt adhesive comprising an isocyanate-terminated urethane prepolymer obtained by reacting with (B).   In the polyol composition (A), the proportion of the polyether polyol (a1) having an EO-PO random copolymer structure is 5 to 20% by weight, and the proportion of the rosin resin polyol (a2) having a hydroxyl value of 50 or more. The moisture-curable reactive hot melt adhesive according to claim 1, wherein the content of the polyester polyol (a3) is 60 to 90% by weight.