Polyphosphoric Acid Removal from Polymer Fibers

The patent applies preliminary action by treating the fiber with a catalyst (such as metal salts like zinc chloride, aluminum chloride, or iron chloride) before the washing step. This catalytic treatment activates and accelerates the hydrolysis of polyphosphoric acid, breaking it down into more water-soluble forms that can be rapidly removed. By performing this chemical activation in advance, the subsequent washing process becomes much more efficient, reducing washing time from hours to minutes while effectively removing phosphorous content.

The patent employs parameter changes by modifying the chemical environment through catalyst addition and adjusting pH levels. The catalyst changes the reaction kinetics of polyphosphoric acid hydrolysis, while pH adjustment (typically to acidic conditions) optimizes the hydrolysis rate. These parameter modifications transform the removal process from a slow physical washing operation to a fast chemically-enhanced process, dramatically reducing the time required to achieve effective phosphorous removal.

The patent replaces the thermal mechanism (heating) with a chemical mechanism (catalysis). Instead of relying on high temperature to accelerate hydrolysis and improve removal efficiency, the invention uses catalysts (metal salts or enzymes) to lower the activation energy of the hydrolysis reaction. This substitution allows the same or better removal efficiency to be achieved at lower temperatures, significantly reducing energy consumption and eliminating the risk of thermal degradation to the polymer fiber.

The patent changes the kinetic parameters of the hydrolysis reaction by introducing catalysts. The catalyst provides an alternative reaction pathway with lower activation energy, allowing the reaction to proceed rapidly at ambient or mildly elevated temperatures. This parameter change (from thermal activation to catalytic activation) decouples removal efficiency from temperature, enabling effective polyphosphoric acid removal without the energy costs and degradation risks associated with high-temperature processing.

The patent applies preliminary action by implementing a catalytic pre-treatment step that rapidly converts polyphosphoric acid into water-soluble hydrolysis products. This preliminary chemical action creates a state where the majority of phosphorous is already in a removable form before washing begins. As a result, the subsequent washing step requires minimal time to achieve thorough phosphorous removal, thereby maintaining high production rates without compromising removal effectiveness.

The patent replaces slow mechanical washing with fast chemical catalysis. The catalyst-driven hydrolysis reaction occurs rapidly (within seconds or minutes) compared to conventional prolonged washing. This substitution transforms the rate-limiting step from mass transfer during washing to a fast chemical reaction, dramatically reducing the overall process time and increasing production productivity while achieving the same or better phosphorous removal.