EP-4494863-B1 - RESIN COMPOSITION, POLYURETHANE ADHESIVE AGENT, AND LAYERED PRODUCT

Inventors

• FUKAI, MASAKI
• SATOU, HARUMASA

Dates

Publication Date

20260506

Application Date

20230313

Claims (10)

1. A resin composition to be used as a base resin of an adhesive together with a curing agent, the resin composition being a resin composition for a polyurethane-based adhesive and comprising a polyol (A) that comprises 80% by mass or more of a polyurethane resin (c) having a hydroxy group at each molecular terminal of the polyurethane resin (c), the polyurethane resin (c) having a constituent unit derived from a polyol comprising a polyester polyol (a) and a constituent unit derived from a polyisocyanate (b), wherein the polyester polyol (a) has a constituent unit derived from a dicarboxylic acid component and a constituent unit derived from a diol component, the total content of benzene-o-dicarboxylic acid and benzene-m-dicarboxylic acid in the dicarboxylic acid component is 50 mol% or more, the content of benzene-o-dicarboxylic acid in the dicarboxylic acid component is 40 mol% or more, the content of a hydroxy group present at each molecular terminal of the polyester polyol (a) is 0.1 to 2 mol/kg, the content of the polyester polyol (a) in the polyol is 80% by mass or more, and the content of the hydroxy group present at each molecular terminal of the polyurethane resin (c) is 0.04 to 0.4 mol/kg.
2. The resin composition according to claim 1, wherein the content of the hydroxy group present at each molecular terminal of the polyurethane resin (c) is 0.05 to 0.4 mol/kg.
3. The resin composition according to claim 1, wherein the content of benzenedicarboxylic acid other than benzene-o-dicarboxylic acid in the dicarboxylic acid component is 20 mol% or more.
4. The resin composition according to claim 1, wherein the diol component comprises a dialcohol having, in the molecule thereof, two or three C≤8 alkylene groups bonded through an ether bond, and the content of the dialcohol in the diol component is 50 mol% or more.
5. The resin composition according to claim 1, further comprising 2% by mass or more of at least one organic solvent selected from the group consisting of ethyl acetate, methyl acetate, methyl ethyl ketone, and dimethyl carbonate.
6. A polyurethane-based adhesive comprising: a base resin; and a curing agent, wherein the base resin is the resin composition according to any one of claims 1 to 5, the curing agent is a polyisocyanate (B), and the stoichiometric ratio of a terminal isocyanate group (NCO group) of the polyisocyanate (B) to the terminal hydroxy group (OH group) of the polyol (A), (NCO group/OH group), is 2.0 to 50.0.
7. A laminate comprising: two or more adherend layers; and an adhesive layer provided between the adherend layers and formed with the polyurethane-based adhesive according to claim 6.
8. The laminate according to claim 7, wherein the adherend layers comprises a metal layer.
9. The laminate according to claim 7, having a shaped portion shaped into a depression.
10. The laminate according to claim 7, having a sealed portion subjected to heat sealing.

Description

Technical Field The present invention relates to a resin composition to be used as a base resin of a polyurethane-based adhesive together with a curing agent; a polyurethane-based adhesive; and a laminate. Background Art Examples of the applications of laminates such as soft packaging materials include applications in which a laminate is deep-drawn to form a shaped body such as a packaging material; the shaped body is subsequently filled with the contents; and then the shaped body is subjected to heat sealing (for example, an application in food packaging, such as ham or bacon packaging). A hot plate at a high temperature is brought into contact with the laminate during the heat sealing, and on that occasion, so-called "floating" in which air bubbles are mixed between the layers may occur at a part where heat or stress is concentrated. When such "floating" conspicuously occurs, the molding depth (the filling volume of the contents) is limited. A polyester polyol is one of the raw materials for a polyurethane which is used as the base resin of a polyurethane-based adhesive. Generally, the use of a polyurethane obtained by using a polyester polyol as a raw material whose phthalic acid content is larger makes it possible to prepare an adhesive whose heat resistance and adhesion to a metal or the like is improved. However, as the phthalic acid content in the polyester polyol is larger, there is a tendency that the viscosity of the polyurethane increases to lower the fluidity. Therefore, in producing a laminate using an adhesive whose base resin is such a polyurethane as just described above, inclusion of air bubbles due to poor wetting is likely to occur, so that floating is likely to occur in a resultant laminate. For example, there has been proposed an adhesive which instantly exhibits the adhesion to a substrate, such as a metal and a film made of a resin, by irradiation with an active energy ray (Patent Literature 1). In addition, there have been proposed: a shaped packaging material having NY/AL/PP layers; and an adhesive to be used therefor (Patent Literature 2). Note that there have been proposed: a polyester polyol whose phthalic acid content is large; and a technique for decreasing the viscosity of a polyurethane using the same (Patent Literatures 3 and 4), but these do not give an influence on the shapeability of laminates. Further, there has been proposed an adhesive composition containing a polyester urethane compound that contains a particular amount of a trifunctional or higher functional hydroxyl group (Patent Literature 5). Also, a solvent-free adhesive for applying a thin coating which is based on a polyester polyurethane polyol obtained from polyester polyol and hexamethylene diisocyanate and having a hydroxyl-group density/concentration of 1 mol/kg, and a polyisocyanate crosslinker is disclosed. The corresponding polyester polyol is obtained from phthalic anhydride and diethylene glycol (Patent Literature 4). Citation List Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2015-13935Patent Literature 2: Japanese Patent Laid-Open No. 2015-24862Patent Literature 3: Japanese Patent Laid-Open No. 2007-8999Patent Literature 4: Japanese Patent Laid-Open No. 2008-45101Patent Literature 5: Japanese Patent Laid-Open No. 2017-25287 Summary of Invention Technical Problem The floating caused by, for example, inclusion of air bubbles due to poor wetting is per se a defect that impairs the aesthetic value of a laminate. In addition, even an inconspicuous small air bubble causes a problem that when the laminate is drawn for form, the bubble is extended to become large. Further, a small air bubble is expanded by heat during heat sealing, which is likely to cause more conspicuous floating or peeling. Therefore, even a small air bubble cannot be neglected. It cannot be said that the fluidity and the wettability to a substrate of the adhesive proposed in Patent Literature 1 are very good. Particularly under roll-to-roll processing conditions taking productivity into consideration, thermocompression bonding is instantaneous, and therefore a fault caused by inclusion of air bubbles due to insufficient wettability may be likely to occur. In addition, with regard to the adhesive proposed in Patent Literature 2, the temperature during aging is relatively high, and therefore poor wetting is likely to occur under an aging condition of around 40°C, which is a temperature generally employed in soft packaging materials. For this reason, a fault caused by inclusion of air bubbles is likely to occur, and when aging is conducted at a high temperature, the adhesive proposed in Patent Literature 2 is disadvantageous in terms of energy costs. Further, when a laminate obtained using the adhesive composition proposed in Patent Literature 5 is subjected to drawing, a fault, such as floating or peeling, may occur, and therefore there is room for improvements in appearances of finished products. The present invent