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Where do VOCs in plastic processing come from and where do they 'remove'?
In the production process of plastic products, the wastes that may be generated can be divided into three categories: solid, liquid and gas. Among them, there are many sources of gaseous waste, which are more harmful. It mainly includes two categories: organic volatile gas (VOC) and inorganic volatile gas. Among them, organic volatile gas VOC has a huge impact on human health. For example, when the VOC in the environment reaches a certain concentration, people will feel headache, nausea, etc. in a short period of time. 1. What is VOC gas? VOC is short for Volatile Organic Compounds, which are highly volatile in the temperature range of 50-260°C. Common volatile organic compounds include: (1) benzenes (such as benzene, toluene, xylene, ethylbenzene); (2) alkanes (tetradecane); (3) aldehydes (formaldehyde); (4) Alcohols (ethanol); (5) ethers, esters (ethyl acetate); (6) ketones (acetone). These VOC gases are generally invisible to us, and some of the smells you smell are not all the smells of these gases themselves. The main sources of the taste of these organic substances include: (1) formaldehyde odor produced by decomposition in POM production; (2) sour taste of HCl produced by decomposition in PVC production when it meets water; (3) monomer in ethylene-vinyl acetate copolymer processing Vinegar smell, etc. released by vinyl acetate residues. 2. Where does VOC gas come from? 1. Printing inks (1) Solvent-based inks will produce VOC pollution such as benzene, ketones, and ethyl acetate during printing and drying. But the printing effect is better, especially for plastic substrates. (2) The organic solvent content in the water-based ink is low (about 20%), so less VOC is generated during use (drying). 2. Acrylic and polyurethane adhesives commonly used in adhesives are still dominated by ethyl acetate organic solvents. 3. Surface coating can eliminate various defects on the surface of plastic products, and endow the products with functions such as electrical conductivity, anti-static, wear resistance, etc., and can also turn dark plastic products into light-colored products. Commonly used acrylic or polyurethane coatings. 4. Mold release agents commonly used in mold release machines contain organic solvents such as CH2Cl2 and CH3CHCl. 3. How to get rid of VOC gas? 1. Resin with low residual monomer content should be selected as far as possible. For example, the content of VC monomer in medical PVC resin is very low, and the VC content can reach 1ppm (mg/kg) (the normal value is 5); PP for automotive interior panels must choose resins with low content of small molecular volatiles. 2. Use additives with larger molecular weights. Use additives with large molecular weights as much as possible, preferably polymer additives, to ensure that they will not volatilize and externally migrate at the processing temperature. (1) If the coupling agent is changed to a compatibilizer, such as a graft polymer or a branched polymer, but the maleic anhydride graft part has a certain odor. (2) Polypentaerythritol stearate (PETS), etc. for lubricant; polyethylene wax (PE-WAX) with molecular weight greater than 5000 for dispersant. (3) The flame retardant should be of polymer type as much as possible, such as brominated polystyrene, brominated epoxy resin, PVC resin, etc. 3. Increase the adsorption of inorganic substances to adsorb the small molecule volatiles that may be produced with high adsorption materials, so that they will not be released under normal conditions. Commonly used inorganic adsorbents are activated carbon, molecular sieve, diatomaceous earth, synthetic calcium silicate, etc. 4. Controlling processing conditions (1) Low temperature production: On the premise of ensuring the full plasticization of the product, lower the processing temperature, thereby reducing the generation of small molecular decomposition substances. (2) Multi-stage vacuuming: increase the number of vacuuming, which can reach level 3 or even level 4, and remove the generated small molecule volatiles in time. 5. Reduce the use of organic solvent-based materials (1) Water-based coatings: use water as the dispersion medium to replace organic volatile solvents, the current technology still needs to contain about 20% ether and alcohol solvents, which can only be regarded as low-VOC coatings, not VOC-free coatings. (2) Solid powder coating: without any organic solvent, zero VOC emission. (3) Light-curing coating: The film-forming material is formed by light-curing reaction, which can reduce the use of organic solvents, but often needs to contain about 30% of organic solvents. (4) Water-based adhesives and water-based mold release agents: products with low content of organic solvents are currently available. At present, consumers are more and more strict with the VOC requirements of plastics used in automotive interiors. How to reduce the release of VOCs during the processing and use of modified plastics is the research focus of various modification companies. Now there is a new type of VOC solvent recovery device. This device uses activated carbon fiber (ACF) as an absorbent to treat waste gas containing organic solvents ( ( VOC ) discharged from various factories or equipment, and convert the VOC into liquid for separation, and Recycle and reuse. VOC is the English abbreviation of volatile organic compounds, a class of carbon compounds that can participate in atmospheric photochemical reactions. Such substances are often used in raw materials and solvents.In the production process, it enters the atmosphere through different means, and then pollutes the atmosphere. Using activated carbon fiber as an adsorbent, it undertakes the design, processing and manufacturing of VOC waste gas adsorption and recovery devices. More VOC solvent recovery devices http://www.standard-groups.cn/chanpin/glcljcy/qkxfjwkfxy/3681.html
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