| 摘要 |
PROBLEM TO BE SOLVED: To provide a rigid polyurethane foam by increasing fluidity of an urethane raw material (premix polyol), and regulating reactivity of the urethane raw material so that the rigid polyurethane foam is thoroughly filled even in a narrow part of an insulated door or inside boxes of a refrigerator, so as to improve thermal insulating properties of the insulated door and the box of the refrigerator; and reducing shrinkage of the formed urethane foam.SOLUTION: A rigid polyurethane foam using a premix polyol including a polyol, a catalyst, water, cyclopentane and a foam stabilizer, and polymethylene diisocyanate, in which 30-80 wt.% of the polyol is a polyol compound added of a polyhydric alcohol with 4-8 pieces of active hydrogen groups and/or polyamine added with an alkylene oxide; when a peak intensity of IR absorption spectrum at 1,700-1,720 cmis defined as A1, and a peak intensity of IR absorption spectrum at 1,590-1,610 cmis defined as A2, A1/A2 is 1.7 to 2.0. |
