PVC Bags Polyvinyl chloride in English abbreviation PVC, can be made by substitution reaction of ethylene, chlorine and catalyst. Because of its fireproof and heat-resisting effect, polyvinyl chloride is widely used in a wide range of products in all walks of life: wire skin, fiber skin, shoes, handbags, bags, ornaments, signs and billboards, building decoration supplies, furniture, ornaments, rollers, pipes, PVC Bags toys (such as the famous Italian "Rody" jump vault), curtains, roll doors, auxiliary medical supplies, gloves, some food preservation paper, some fashion and so on.
Polyvinyl chloride is formed by polymerization of vinyl chloride monomer (VCM). Because the mass of 57% of its molecules is the chlorine element. So it has less oil in the same mass than other plastics, however, because the plastic is relatively dense and consumes other energy in the process of producing chlorine, it loses its edge in many applications.
Using more PVC production process is the suspension polymerization production process. The pure water, liquefied VCM monomer and dispersant are added to the reaction kettle, PVC Bags then the initiator and other auxiliaries are added, and the free radical polymerization of VCM monomer takes place after a certain temperature is heated to produce PVC granules. Continuous agitation makes the particle size evenly, and the resulting particles are suspended in the water. Suspension polymerization method, emulsion polymerization method and bulk polymerization method were mainly composed of suspension polymerization, which accounted for about 80% of PVC total production. PVC Bags In addition, the use of micro-suspension process PVC paste resin, product performance and Gelatinization properties are good.
The Shan suspension polymerization method makes the monomer droplets suspension disperse in the water phase, and the oil soluble initiator is dissolved in monomer. The polymerization reaction is carried out in these droplets, the polymerization reaction heat is absorbed by water in time, in order to ensure that these droplets in the water in a bead-like dispersion, need to join the suspension stabilizer, such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose and so on. The initiator used organic peroxide and azo compounds, PVC Bags such as diisopropyl carbonate, two cyclohexyl peroxide, peroxide, diethyl carbonate and azo dimethyl cyanide, Azo nitrile, and so on, for the most part. Polymerization is carried out in a polymerization kettle with a blender. After polymerization, the material flows into the monomer recovery tank or the stripping tower. Then into the mixing kettle, washed and then centrifugal dehydration, drying is the resin finished product. Vinyl chloride monomer should be removed from the resin as far as possible. For food packaging PVC, free monomer content should be controlled under 1ppm. In order to obtain the specified molecular weight and molecular weight distribution of the resin and prevent detonation, it is necessary to control the polymerization process temperature and pressure. The particle size and particle size distribution of the resin are controlled by the agitation speed and the selection and dosage of the suspension stabilizer. The quality of the resin is characterized by particle size and particle size distribution, molecular weight and molecular weight distribution, apparent density, porosity, PVC Bags fish eye, thermal stability, color, impurity content and free flow of powder. Polymerization reactor is the main equipment, from the steel kettle lined with stainless steel or enamel, equipped with agitator and control temperature of heat transfer jacket, or internal cooling pipe, reflux condenser. In order to reduce production costs, the reactor volume has been a few cubic meters, more than 10 cubic meters gradually to large-scale development, the largest has reached 200m (see Kettle Reactor). After repeated use of the polymerization kettle to remove dirt. PVC, which is made of polyvinyl alcohol and cellulose ether as suspension stabilizer, is generally more loose, porous, and has a large surface area, which is easy to absorb plasticizer and plasticizing.
Shan emulsion Polymerization method of the earliest industrial production of PVC. In emulsion polymerization, except water and vinyl chloride monomer, also need to add alkyl sulfonate and other surfactants as emulsifier, so that the monomer dispersed in the water phase and milk liquid, PVC Bags to water-soluble potassium sulfate or ammonium persulfate as initiator, can also be used "oxidation-reduction" initiation system, polymerization process and suspension method is different. Also have added polyvinyl alcohol as emulsifying stabilizer, 12 alkyl mercaptan as the regulator, sodium bicarbonate as buffer agent. The polymerization method has three kinds of intermittent method, semi-continuous method and continuous method. The polymerization product is latex-like, PVC Bags emulsion particle size 0.05, can be directly applied or spray-dried into powdered resin. Emulsion polymerization period is short, easy to control, the resin molecular weight is high, the polymerization degree is homogeneous, suitable for making PVC paste, PVC Bags making artificial leather or impregnated products. The formula of emulsion polymerization is complex and the impurity content of the product is high.
Shan Bulk polymerization polymerization device is more special, mainly composed of vertical pre-polymerization kettle and horizontal polymerization kettle with frame agitator. The polymerization is divided into two segments (Fig. 3). Monomer and initiator first in the pre-polymerization kettle 1h, the formation of seed particles, then the conversion rate of $number, and then into the second stage polymerization kettle, add and prepolymer equal to the monomer, continue to polymerization. Until the conversion rate reaches $number, the residual monomer is discharged, PVC Bags then the finished product is crushed and sifted. The particle size and particle shape of the resin are controlled by the stirring speed, and the reaction heat is produced by the monomer reflux condensation. PVC Bags This method has simple production process, good product quality and low production cost.