Visco-elastic Polyurethane Foam for Ear Canal Noise Minimization

The patent modifies the chemical composition parameters of the polyurethane foam by incorporating polyurethaneurea dispersion (V2) with specific molecular weights and functionalities, along with amino-functional chain extenders (V2C). This changes the viscoelastic parameters of the foam, transforming it from rapid resilience (suitable for wound dressings) to slow recovery behavior (suitable for sound insulation/ear plugs) while maintaining water absorption capabilities.

The patent creates a composite material system by combining polyurethane foam (V1) with polyurethaneurea dispersion (V2) in specific weight ratios (1:4 to 4:1). This composite approach integrates the hydrophilic water-absorbing properties of polyurethane with the viscoelastic slow-recovery properties of polyurethaneurea, achieving both high water absorption and suitable recovery time for ear plug applications.

The patent merges the synthesis of polyurethane foam and polyurethaneurea dispersion into a single one-pot reaction process. The polyisocyanate component reacts simultaneously with both the polyol (forming polyurethane) and the amino-functional chain extender (forming polyurethaneurea), eliminating the need for separate synthesis steps and reducing production complexity despite achieving complex viscoelastic properties.

The reaction system is designed to automatically produce the desired polyurethane-polyurethaneurea composite foam through self-regulating chemistry. The isocyanate groups react with both hydroxyl and amino groups in controlled proportions, and the foam expansion and curing occur autonomously without requiring complex external control systems, enabling simple manufacturing at room temperature and normal pressure.