Sealant resin composition, and use thereof

A sealant resin composition (X) comprising a 1-butene/ethylene copolymer (A) satisfying the following requirements (A1), (A2) and (A5), and a propylene-based polymer (B), the resin composition satisfying the following requirements (X1) and (X1-2):

• requirement (A1):
• having a content of constituent units (i) derived from 1-butene being in a range of 70 to 99.9 mol %, and a content of constituent units (ii) derived from ethylene being in a range of 0.1 to 30 mol %, provided that a total of the constituent units (i) and the constituent units (ii) is 100 mol %;
• requirement (A2):
• having an isotactic pentad fraction (mmmm) calculated by 13C-NMR being in a range of 80 to 99.9%;
• requirement (A5):
• having no observed melting peak during second temperature raising when, using a differential scanning calorimeter (DSC), the temperature is first lowered from 30° C. to −70° C. at a cooling rate of 20° C./min (first temperature lowering), then maintained at −70° C. for 5 minutes, raised from −70° C. to 200° C. at a heating rate of 20° C./min (first temperature raising), maintained at 200° C. for 10 minutes, then lowered to −70° C. at a cooling rate of 20° C./min (second temperature lowering), maintained at −70° C. for 1 minute, and then raised again from −70° C. to 200° C. at a heating rate of 20° C./min (the second temperature raising);
• requirement (X1):
• having a Shore D hardness measured in accordance with ASTM D2240 being in a range of 44 to 80;
• and
• requirement (X1-2):
• having a melt flow rate (MFR) measured at 230° C. and a load of 2.16 kg in accordance with ASTM D1238 being in a range of 0.1 to 100 g/10 min.