During the production of wood grain PVC decorative sheets, volatile organic compound (VOC) emissions primarily originate from the heating and melting of raw materials, molding, and surface treatment processes. These exhaust gases are complex, containing vinyl chloride monomer, plasticizer decomposition products, heat stabilizer volatiles, and organic solvents from inks. If released without effective treatment, they pose a threat to human health and contribute to atmospheric pollution. Therefore, reducing VOC emissions requires a comprehensive, multifaceted approach encompassing source control, process optimization, end-of-pipe treatment, and strengthened management.
Raw material selection is paramount in reducing VOC emissions. Companies should prioritize low-VOC PVC resins, environmentally friendly plasticizers (such as citrate esters), and lead-free heat stabilizers to minimize the volatilization of harmful substances during processing. Furthermore, optimizing formulation design and reducing additive usage can reduce waste gas generation at the source. For example, using high-molecular-weight plasticizers can reduce their migration and, therefore, mitigate the risk of volatilization. Furthermore, strict raw material quality control is crucial, avoiding recycled materials or inferior additives to prevent the generation of additional pollutants from the decomposition of impurities.
Precise control of process parameters during production is crucial for reducing VOC emissions. During the heating and melting stage, temperature and time must be appropriately set to avoid excessive temperatures that could lead to excessive decomposition of additives. For example, PVC processing temperatures are typically controlled between 160-200°C. Exceeding this range accelerates plasticizer volatilization and the release of hydrogen chloride. During molding processes, such as extrusion and calendering, mold design should be optimized to minimize material residence time and reduce the risk of thermal decomposition. Furthermore, the use of advanced heating technologies (such as electromagnetic induction heating) can improve thermal efficiency, reduce energy consumption, and indirectly reduce waste gas generation.
End-of-pipe treatment is crucial for ensuring compliance with waste gas emission standards. Given the unique characteristics of waste gas from wood grain PVC decorative sheet production, a combined "pretreatment + purification" process can be employed. In the pretreatment stage, mechanical filtration and electrostatic precipitation remove particulate matter from the waste gas to prevent subsequent equipment clogging. A packed tower wet scrubbing technique uses an alkaline solution to neutralize acidic gases such as hydrogen chloride. During the purification phase, high-volume, low-concentration exhaust gases are suitable for a combined activated carbon adsorption and concentration system with catalytic combustion. Activated carbon adsorbs and concentrates low-concentration organic matter, which is then decomposed into carbon dioxide and water through catalytic combustion. Medium-concentration exhaust gases can be directly treated with catalytic combustion technology, achieving low-temperature oxidation under the action of a catalyst. For chlorinated organic matter, a specialized catalyst resistant to chlorine poisoning is required to prevent catalyst inactivation.
The surface treatment process for wood grain PVC decorative sheets is another key concern for VOC emissions. If printing or laminating processes are employed, water-based or UV-curable inks should be preferred, minimizing the use of solvent-based inks. Water-based inks use water as a diluent and contain significantly lower VOCs than traditional solvent-based inks. UV-curable inks cure instantly through ultraviolet light, producing virtually no solvent volatilization. Furthermore, optimizing printing process parameters (such as drying temperature and air speed) can shorten solvent volatilization time and reduce exhaust gas concentrations. In the laminating process, using hot melt adhesive instead of solvent-based adhesives can fundamentally eliminate VOCs generated by adhesive volatilization.
The sealing quality and maintenance level of production equipment directly impact exhaust gas collection efficiency. Companies should regularly inspect equipment seals (such as flanges and pipe joints) and promptly replace aging seals to prevent exhaust gas leaks. They should also establish a comprehensive equipment maintenance system and regularly clean scale deposits in heating systems, molds, and exhaust ducts to prevent localized overheating and material decomposition. Exhaust gas treatment equipment should regularly replace consumables such as activated carbon and catalysts to ensure stable purification efficiency.
Companies should establish a strict exhaust gas management system and clearly define emission control requirements for each stage. They should install online monitoring equipment to monitor exhaust gas concentration, flow rate, and other parameters in real time to ensure stable operation of treatment facilities. They should regularly commission third-party exhaust gas testing to evaluate treatment effectiveness and adjust process parameters promptly. Furthermore, they should strengthen employee environmental protection training, improve operational standards, and reduce excessive exhaust gas emissions caused by human error.
