Copolyamide Hot-Melt Yarn Elasticity and Melting Point Control

The patent creates a composite polymer system by reacting polyamide precursor polymers with cyclic carbonates to form copolyamide resin containing both polyamide segments and cyclic carbonate segments. This composite structure at the molecular level allows the material to simultaneously achieve low melting point (from cyclic carbonate segments) and high elasticity (from the flexible chain structure introduced by the cyclic carbonate groups), resolving the contradiction between melting point and elasticity.

The patent changes the chemical composition parameters of the copolyamide resin by controlling the molar ratio of cyclic carbonate to polyamide precursor polymer (1:4 to 1:20), and by selecting different polyamide types (PA6, PA66, PA11, PA12) and cyclic carbonates (trimethylene carbonate, ethylene carbonate). This parameter optimization enables precise control over both melting point and elasticity, achieving the desired balance between these two properties.

The patent divides the polymerization process into two distinct stages: first synthesizing polyamide precursor polymers with specific molecular weights and end groups, then reacting these precursors with cyclic carbonates in a separate step. This segmentation allows each stage to be optimized independently, simplifying process control and reducing overall production complexity despite the multi-step nature of the process.

The patent uses polyamide precursor polymers as intermediaries that contain reactive end groups (carboxyl or amino groups) which then react with cyclic carbonates. This intermediary approach enables the controlled introduction of cyclic carbonate segments into the polyamide chain, making the complex copolymerization process more manageable and easier to control compared to direct copolymerization.