Sinopec Vinyl Acetate Monomer

Polyvinyl acetate emulsion (PVAc), commonly known as white latex, are widely used as a key polymer adhesive due to their ability to be directly modified with a variety of additives, excellent mechanical strength, and resistance to adhesive defects. Furthermore, their environmental friendliness as a water-based adhesive makes them particularly attractive. However, due to different synthesis processes, white latexes also have some drawbacks, such as limited water and heat resistance, generally high viscosity, and high solids content, which increase their cost.   1. Effect of Polyvinyl Alcohol on Emulsion Viscosity Experiments were conducted using fully alcoholyzed PVA1799 and partially alcoholyzed PVA1788. The viscosity of the emulsion prepared with PVA1788 was 3.8 Pa·s, while that of the emulsion prepared with PVA1799 was 3.0 Pa·s. This is primarily due to the grafting effect of the tertiary hydrogen atoms -CH(OCOCH3)- in PVA1788. In addition, different polyvinyl alcohol production methods result in different distributions of residual acetate groups within the molecule, resulting in different viscosities in the resulting polyvinyl acetate emulsions. PVA1788 was selected for this experiment.   2. Effect of Initiator on Emulsion Viscosity and Solids Content Generally, at a specific temperature for polymerization, if you start with very little initiator, both viscosity and solids increase as you add more initiator. The viscosity peaks at 4.2 Pa·s when the initiator is 0.6% of the total monomer, resulting in a 36% solids content. If you keep adding initiator past that point, the emulsion gets less viscous, but the solids stay about the same. During emulsion polymerization, the pH of the medium directly affects the decomposition rate of the initiator. The pH of the emulsion polymerization system is required to be around 6. Due to the presence of a small amount of Acetic Acid Vinyl Ester Monomer and the sulfate groups generated during initiator decomposition, the pH of the system drops to 4-5. Therefore, an appropriate amount of sodium bicarbonate is used to adjust the pH.   3. Effect of Emulsifier Amount on Emulsion Viscosity With other conditions unchanged, the emulsifier dosage was varied. The results are shown in Figure 1. Too little emulsifier results in poor emulsion stability and easy demulsification. Emulsion viscosity increases with increasing emulsifier dosage, reaching its maximum viscosity at 0.15% of the total monomer content. When the emulsifier dosage exceeds the optimal value, the emulsion particles increase in number, their size decreases, and the viscosity decreases.   4. Effect of Reaction Temperature on Emulsion Viscosity and Solids Content Experiments show that when you keep the reactant ratios, addition method, and stirring the same, changing the reaction temperature really does change how thick the polyvinyl acetate emulsion is and how much solid stuff is in it. The results are shown in Table 2. This is because polymerization is endothermic, so higher reaction temperatures favor the reaction. However, when the reaction temperature reaches 80°C, exceeding the boiling point of vinyl acetate monomer (72°C), it increases reflux and consumes energy. Low temperatures also slow the reaction, leading to incomplete reaction and low emulsion viscosity.   5. Effect of Monomer Purity on Emulsion Viscosity and Solids Content Due to storage and transportation requirements, polymerization inhibitors are often added to vinyl acetate before shipment to maintain its stability. To facilitate polymerization, the vinyl acetate was distilled before the experiment. The results are shown in Table 3. Table 3 shows that the properties of vinyl acetate directly affect the emulsion viscosity and solids content. Distillation of the monomer significantly increases the viscosity of the polyvinyl acetate.   6. Conclusions The traits of Vinyl Acetate Monomer (VAM) and polyvinyl alcohol change how thick the emulsion is and how much solid stuff is in it. The viscosity and solid content of an emulsion are affected by the reaction temperature, the amount of reactants, and how you add monomers, emulsifiers, and initiators during the emulsification procedure. We got a milky white polyvinyl acetate emulsion with some great qualities. It has a viscosity of 5.8 Pa•s, a solid content of 42%, a pH between 6 and 8, and a blue tint. The best part is, we achieved this by keeping the reaction temperature at 75 ℃ and carefully adding the emulsifier (0.15%) and initiator (0.6%) drop by drop in batches, based on the total monomer amount.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Polyvinyl alcohol (PVA) is a fundamental raw material for vinylon production and is also used in the production of adhesives, emulsifiers, and other products. In the PVA production process, solution polymerization is used to ensure a narrow degree of polymerization distribution, low branching, and good crystallinity. The VAM polymerization rate is strictly controlled at approximately 60%. Due to the control of the polymerization rate during the VAM polymerization process, approximately 40% of the Vinyl Acetate Monomer (VAM) remains unpolymerized and requires separation, recovery, and reuse. Therefore, research on VAM recovery process is a crucial component of the PVA production process. There is a polymer-monomer relationship between Ethylene Vinyl Acetate (EVA) and vinyl acetate monomer (VAM). Vinyl acetate monomer is one of the basic raw materials for making ethylene vinyl acetate polymer.   This paper uses the chemical simulation software Aspen Plus to simulate and optimize the VAM recovery process. We studied how process settings in the first, second, and third polymerization towers affect the production unit. We found the best settings to save water used for extraction and lower energy consumption. These parameters provide an important theoretical basis for the design and operation of VAM recovery.   1 Vinyl Acetate Monomer Recovery Process 1.1 Simulation Process This process includes the first, second, and third polymerization towers in the vinyl acetate monomer recovery process. The detailed flow diagram is shown in Figure 1.   1.2 Thermodynamic Model and Module Selection The vinyl acetate monomer recovery unit of the polyvinyl alcohol plant primarily processes a polar system consisting of vinyl acetate, methanol, water, methyl acetate, acetone, and acetaldehyde, with liquid-liquid separation between vinyl acetate and water. The main equipment in the vinyl acetate monomer recovery unit of the polyvinyl alcohol plant was simulated using Aspen Plus software. The RadFrac module was employed for the distillation tower, and the Decanter module for the phase separator.   2 Simulation Results We ran a process simulation on the vinyl acetate monomer recovery unit in the polyvinyl alcohol plant. Table 3 shows a comparison of the simulation results and actual values for the main logistics. As shown in Table 3, the simulation results are in good agreement with the actual values, so this model can be used to further optimize the process parameters and process flow.     3 Process Parameter Optimization 3.1 Determination of the Amount of Stripping Methanol Polymerization Tower 1 takes out vinyl acetate monomer (VAM) from the stream that remains after polymerization. It uses methanol vapor at the bottom for heat. The right amount of methanol is important for how well the tower works. This study looks at how different amounts of methanol affect the mass fraction of PVA at the tower's bottom and the mass fraction of VAM at the top, assuming the feed stays the same and the tower's design is constant.   As shown in Figure 2, when the heat capacity needed for separation in Polymerization Tower 1 is satisfied, raising the stripping methanol amount lowers the PVA mass fraction at the bottom and the VAM mass fraction at the top. The stripping methanol amount has a linear relationship with the PVA mass fraction at the bottom and the VAM mass fraction at the top.   3.2 Optimization of the Feed Position in Polymerization Tower 2 In Polymerization Tower 2, an extractive distillation tower, the locations where the solvent and feed enter greatly affect how well the separation works. This column uses extractive distillation. Based on the physical properties of the extractant and the mixed feed, the extractant should be added from the top of the column. Figure 3 shows how the mixture feed position affects the methanol mass fraction at the top and the reboiler load at the bottom, keeping other simulation settings the same.   3.3 Optimizing the Extraction Water Amount in Polymerization Column 2 In Polymerization Column 2, extractive distillation is used to separate vinyl acetate and methanol azeotrope. By adding water to the top of the column, the azeotrope is disrupted, allowing for the separation of the two substances. The extract water flow rate has a big impact on how well Polymerization Column 2 separates these materials. With consistent simulation settings, I looked at how the amount of extract water affected the methanol mass fraction at the top and the reboiler load at the bottom of the column. The results are shown in Figure 4.   3.4 Optimizing the Reflux Ratio in Polymerization Column 3 In Polymerization Column 3, the reflux ratio is important for separating vinyl acetate from lighter substances like methyl acetate and trace water. This boosts the quality of vinyl acetate obtained from the side stream. We kept the simulation settings constant and studied how the reflux ratio affects both the mass fraction of vinyl acetate from the side stream and the reboiler load. The calculation results are shown in Figure 6. Maintaining the polymerization tower's reflux ratio around 4 helps ensure the vinyl acetate from the side line meets quality standards and keeps the reboiler load low.     4. Conclusion (1) Using AspenPlus software, a suitable thermodynamic model is selected to simulate the entire process of vinyl acetate monomer recovery of the polyvinyl alcohol plant. The simulation results are in good agreement with the actual values and can be used to guide the process design and production optimization of the plant. (2) Based on the establishment of a correct process simulation, the influence of the process parameters of the polymerization tower 1, polymerization tower 2, and polymerization tower 3 on the plant is investigated, and the optimal process parameters are determined. When vinyl acetate meets the needed separation standards, we can save on extraction water and lower energy use.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com