Polyphenylene sulfide (PPS) resin is a high-performance engineering plastic prized for exceptional heat resistance and chemical stability, extensively used across aerospace, electronics, automotive, and petrochemical industries. Traditional synthesis methods, however, struggle with efficiency flaws, including low yield due to material loss during high-temperature loading, extended purification times, and equipment corrosion. Many existing patents, such as those citing stepwise polymerization techniques, fail to address core inefficiencies like vaporization escape of key reactants or inconsistent molecular weight control. This innovation introduces a novel multi-step process that fundamentally overcomes these limitations, setting a new standard for PPS production.

The prior art in PPS synthesis often relied on problematic one-time loading of reactants like para-dichlorobenzene (p-DCB) at reduced temperatures to prevent vaporization and pressure buildup in reaction vessels. For instance, common approaches required lowering the system temperature below 160°C for each addition, disrupting kinetics and escalating energy consumption. Such methods frequently necessitate pressure venting, risking mass loss and imbalanced stoichiometry that can sabotage reaction yields or produce undersized molecules. Alternative attempts, like adding costly reducing agents or sodium acetate as a co-solvent, introduced new issues such as complex crystal formation impeding resin molding or high expense, as seen in various patents. Moreover, solvents like N-methyl-2-pyrrolidone (NMP) were inadequately managed, resulting in poor particle uniformity and prolonged washing cycles, ultimately affecting industrial scalability. This underscores the urgent need for optimized protocols that enhance resin quality without amplifying costs.

The inventive synthesis revolutionizes PPS production by redefining reagent preparation and integration. Key innovations include separating sodium hydrosulfide and sodium hydroxide solutions in distinct reactors under nitrogen atmosphere before controlled mixing to generate sodium sulfide, minimizing impurities and eliminating dedicated purification steps for sulfide sources. Crucially, acetate compounds are injected post-polymerization to stabilize particle growth, accelerating cooling and mitigating apparatus fouling. This multi-phase approach ensures consistent molecular weight distribution, improves solvent recovery, and simplifies scale-up. As described in the invention, PPS synthesis begins with forming sodium hydrosulfide (as 45-60% wt solution) and sodium hydroxide (as 45-60% wt solution) in separate vats heated to 80-100°C. These solutions combine under inert gas flow, with brief thermal maintenance around 120-130°C to yield sodium sulfide. Subsequently, NMP solvent is added in precise proportions for rapid dehydration to 200-204°C to remove water effectively.

Following dehydration, p-DCB joins the reactor to initiate polymerization under pressure-regulated phases: a low-temperature stage at 200-210°C for chain elongation, then gradual heat ramping to 260-270°C for final condensation. A pivotal step involves pumping acetic acid salt (sodium or lithium acetate), NMP, and water into the system during high-pressure hold, which coaxes uniform micro-particles (500-1000 μm) formation by dissolving sodium chloride byproducts and enhancing resin porosity. This acetate-mediated phase is vital in refining viscosity control and solidifying particle size post-reaction. The mixture then cools rapidly to 160-180°C, undergoing hot filtration and progressive purification—multiple NMP washes to strip away solvents, succeeded by deionized water rinses to eliminate residual salts, culminating in drying for low-moisture finished resin. Sodium acetate emerges as optimal for its role in reducing chloride content and fostering resin looseness.

Beneficial impacts span multiple dimensions. First, the segregated solution preparation and acetate addition cut metal ion levels, improving resin properties like thermal stability and ease of molding. Second, optimized particle formation, with acetate acting as a spacer, boosts yield by up to 15% compared to conventional methods, slashing purification timelines by hours as detailed in contrast studies. For example, experiments reveal resin with a molecular weight exceeding 15,000 and reduced solvent residues to 0.1-0.6% wt. Third, equal molar amounts of sodium hydroxide mitigate pH extremes during dehydration, extending reactor lifespan by weakening corrosion. Solvent efficiency gains—due to fewer dissolved byproducts—simplify NMP recycling, amplifying cost-effectiveness. Fourth, the acetate step accelerates cooling rates by 30%, preventing material adhesion to equipment and ensuring batch-to-batch consistency. Overall, this holistic approach renders PPS synthesis greener and scalable, vital for sectors demanding high-purity polymers.

In practical validation, embodiments demonstrate stark superiority over controls. Trials with sodium acetate achieved well-formed resin granules in hours, whereas untreated systems yielded fine powders with washing delays and reduced molecular weights below 13,000. For instance, a comparative batch omitting acetate took 4 extra hours for washing and showed erratic particle sizes. This new method's efficiency and robustness make it a game-changer for mass-producing PPS.