HEAT-EXPANDABLE MICROSPHERES AND USE THEREOF

Patentradars sammanfattning

Matsumoto Yushi-Seiyaku discloses heat-expandable microspheres comprising a thermoplastic resin (A) shell encapsulating a vaporizable blowing agent, characterized by a key condition: the glass transition temperature of the shell resin before expansion (Tg of A1) must exceed that of the shell resin recovered after heating 20°C above the maximum expansion temperature for 10 minutes (Tg of A2), i.e., Tg(A1) − Tg(A2) > 0°C. This positive Tg differential indicates elevated intermolecular cohesive energy in the shell polymer, enabling the shell to resist internal pressure increases over a broad temperature range and thus maintain stable expansion characteristics. The preferred shell composition includes carboxyl group-containing monomers (20–70 wt%) and monomers bearing carboxyl-reactive groups (0.1–10 wt%), with nitrile monomer content limited to ≤40 wt% to suppress yellowing.

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