Plant-Based Polyurethane Porous Film for Waterproof Breathable Fabrics

The patent uses a composite polyol system combining plant-based polyols (castor oil-based polyol and sebacic acid-based polyol) with petroleum-based polyols to create a polyurethane resin that achieves both environmental benefits and mechanical performance. This composite approach allows the resin to maintain toughness and flexibility while incorporating renewable resources, resolving the contradiction between environmental load reduction and mechanical strength.

The patent optimizes the molecular weight and hydroxyl value parameters of the plant-based polyols to control the crosslinking density and network structure of the polyurethane resin. By carefully selecting polyols with specific parameters (castor oil-based polyol with number average molecular weight of 500-2,000 and sebacic acid-based polyol with number average molecular weight of 500-5,000), the resin achieves appropriate flexibility and toughness while maintaining water pressure resistance above 1,600 mmH2O.

The patent controls the number average molecular weight of the plant-based polyols within specific ranges (castor oil-based polyol: 500-2,000; sebacic acid-based polyol: 500-5,000) to regulate the degree of crosslinking. By adjusting these molecular weight parameters, the patent achieves a balance between incorporating sufficient plant-based content (5-80% by weight) and maintaining the resin's flexibility and processability.

The patent uses a combination of polyols with different hydroxyl group densities and molecular weights to create localized variations in crosslinking density within the resin network. The castor oil-based polyol provides moderate crosslinking while the sebacic acid-based polyol with longer chain length provides flexibility, creating a heterogeneous network structure that balances hardness and flexibility.

The patent selects castor oil-based polyols with number average molecular weights of 500-2,000, which optimizes the balance between plant-based content and viscosity. This molecular weight range prevents excessive chain entanglement and branched structure formation that would lead to high viscosity, while still incorporating sufficient plant-based content (5-80% by weight) to meet environmental requirements and maintain coating processability.

The patent combines castor oil-based polyol with sebacic acid-based polyol and petroleum-based polyols to create a composite polyol system that dilutes the viscosity-contributing structures. This composite approach maintains the beneficial plant-based content while reducing overall viscosity to levels suitable for coating applications.

The patent combines sebacic acid-based polyol (plant-based) with petroleum-based polyols in a composite polyol system. This composite approach provides the hydrophilic groups necessary for moisture permeability while the petroleum-based components contribute to water resistance and structural stability, preventing excessive water-swellability and strength loss.

The patent creates a heterogeneous polyol system where sebacic acid-based polyol molecules with hydrophilic carboxylic acid groups are distributed within a matrix of hydrophobic petroleum-based polyols. This local distribution of hydrophilic and hydrophobic regions enables moisture permeability through the hydrophilic pathways while the hydrophobic matrix prevents excessive water absorption and swelling.