| Customization: | Available |
|---|---|
| CAS No.: | 68648-82-8 |
| Formula: | C4h5cl3 |
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Weifang Phoenix New Material Co., Ltd
| PROJECT | Test Standards | HT-112 | HT-120 |
| Appearance | Q/DHXJ 008 | 30±1 | 36±1 |
| Density g/cm³ | GB/T 1033.1 (Eqv ISO 1183) |
1.5 | 2.0 |
| Tensile strength MPa | GB/T 1040.2 (Eqv ISO 527) |
0.30 | 0.30 |
| Tensile elastic modulus MPa | GB/T 1040.2 (Eqv ISO 527) |
40 | 40 |
| Izod notched impact strength kJ/m² | GB/T 1843 (Eqv ISO 180) |
65 | 60 |
| Vicat softening temperature ºC | GB/T 1633 (Eqv ISO 306) |
8.0 | 8.0 |
| Oven test | GB/T 9349 (Eqv ISO 305) |
700 | 1000 |
Chlorinated polyvinyl chloride (PVC) resin, also known as perchloroethylene resin, is a new type of polymer elastic material between rubber and plastic obtained by chlorination of polyvinyl chloride (PVC). It is an important modified product of PVC. It has a wide range of applications in plastics, building materials, electrical, medical, agricultural, rubber, paint, pigment, shipbuilding, papermaking, textile, packaging, coating and steel, and has broad prospects for development and utilization. This article briefly introduces the properties, production methods, uses and development prospects of CPVC (chlorinated polyvinyl chloride). Although CPVC is a polymer made from PVC as a matrix and shares some properties with PVC, it is also a polymer with its own characteristics, which is particularly important for its processing. For example, the melting temperature of CPVC polymer ranges from 400°F to a maximum of 450°F. Chrome-plated or stainless steel die heads are required for extrusion processing. The extrusion die head must be well streamlined to ensure long-term processing and operation. Flat die heads cannot obtain satisfactory extrusion operation time. In order to well control the extrusion size of pipes and profiles, it is best to use vacuum shaping technology. Extrusion equipment should be equipped with a screw drive of at least 40 horsepower. There are several screw designs suitable for extrusion processing of various formulated compounds.
Preparation
Preparation method: Polyvinyl chloride is chlorinated to obtain a high molecular compound. According to the degree of polymerization, it can be made into high viscosity, medium viscosity and low viscosity types. The high viscosity type has good counterfeit resistance, chemical corrosion resistance and elasticity. The low viscosity type is more soluble in vegetable oils. Powdered polyvinyl chloride is swollen with an appropriate solvent and chlorinated in water phase suspension at a temperature below 50°C.
Solvent method
The solvent method is the earliest method used to prepare CPVC. The West German AG method company first used the solvent method to produce it. This process is relatively mature. Its main process is to dissolve the PVC resin in chloroform or carbon tetrachloride solvent and then chlorinate it. In this method, the concentration of PVC is very important. For example, when dichloroethylene is used as a solvent, chlorination of 12% (mass fraction, the same below) of PVC solution will cause more dehydrochlorination and degradation, and the resulting CPVC contains approximately equal amounts of 1, 2-dichloroethylene and 1, 1, 2-trichloroethylene units. However, when 7% dichloroethylene solution of PVC is chlorinated, there is less dehydrochlorination and degradation, and PVC chlorination is more uniform. CPVC is mainly composed of 1, 2-dichloroethylene units. It is reported that a 1:1 (volume ratio) mixed solvent composed of dichloroethylene and trichloroethylene can achieve uniform chlorination. PVC is soluble in chlorobenzene, so in the presence of initiator and promoter, PVC can also be chlorinated by reacting with chlorine gas in chlorobenzene at 110~115ºC. The initiator is usually azobisisobutyronitrile, and the promoter can be p-chlorobenzenesulfonamide dichloride.
The solvent method chlorination is relatively uniform, and the product has good solubility, which is very suitable for use as coatings, adhesives, etc. However, the products produced by this method have poor thermal stability and mechanical properties, and cannot be used to make hard products including pipes; at the same time, due to the use of organic solvents such as chloroform or carbon tetrachloride, which are highly toxic and difficult to recycle, it causes environmental pollution. This method is gradually being eliminated.
Suspension method
In the early 1960s, Goodrich Company in the United States first used the aqueous suspension method to produce CPVC. The process is to suspend powdered PVC resin in hydrogen chloride solution and pass chlorine in the presence of additives. The chlorination reaction proceeds according to the free radical reaction mechanism. At this time, the chlorination conversion rate is controlled by diffusion. In order to facilitate the diffusion of chlorine in the polymer phase and improve the uniformity of chlorination, the early process requires the addition of swelling agents, such as chloroform or CCl4, in the aqueous phase to increase the contact area between chlorine and PVC. Other researchers have found that when the raw material PVC is polymerized by vinyl chloride monomer in the presence of a special modifier, the uniformity of CPVC chlorination can be improved without adding swelling agents, and the reaction rate can also be increased to enhance the processing performance of the product. After the preparation of CPVC is completed, an inert gas is introduced into the reaction system in time and a reducing agent is added. The reducing agent can prevent the hypochlorous acid generated by the reaction of Cl2 and H2O from reacting with CPVC to generate organic matter containing carbonyl groups and double bonds.
The suspension method has a simple production process, a short production process, good heat resistance and mechanical properties, and a low production cost. It is a method commonly used at home and abroad. Its disadvantage is that the acidic waste gas generated during the production process needs to be treated, and the post-processing of the product is cumbersome.
Gas-solid phase method
The gas-solid phase chlorination method was first reported by the West German Laurent Company in 1958. The gas-solid phase chlorination method is to put the PVC resin in a dry state into a reactor or fluidized bed at normal pressure and directly carry out the chlorination reaction. The loose particles can be chlorinated by treating with diluted oxygen in a 55°C boiling bed. The gas flow can be composed of a mixed gas containing 50% chlorine (volume fraction), 0.75% fluorine (volume fraction) and 49.25% nitrogen (volume fraction). After 100 minutes of reaction, CPVC containing 64% chlorine (volume fraction) and 0.6% fluorine (volume fraction) can be obtained. Light energy catalyzes chlorination, but trace oxygen also has a catalytic effect when there is no light.
The process has the advantages of short production flow, easy continuous operation, low investment, no waste acid and wastewater in the production process, basically no equipment corrosion, greatly simplified post-treatment and light environmental pollution. The uneven chlorination and difficulty in heat removal of the reaction in the gas-solid phase chlorination method limit the industrialization of the process. The exploration and research on the type of solid phase chlorination equipment, reactor, and reaction process conditions in the United States, Japan, Israel, Germany, and China mainly focus on solving these two problems. The process is still in the development stage.
Processing
Although CPVC is a polymer made from PVC as a matrix and shares some properties with PVC, it is also a polymer with its own characteristics, which is particularly important for its processing. For example, the melting temperature of CPVC polymer ranges from 400°F to a maximum of 450°F. Chrome-plated or stainless steel die heads are required for extrusion processing. The extrusion die head must be well streamlined to ensure long-term processing and operation. Flat die heads cannot obtain satisfactory extrusion operation time. In order to well control the extrusion size of pipes and profiles, it is best to use vacuum shaping technology. Extrusion equipment should be equipped with a screw drive of at least 40 horsepower. Several screw designs are available to suit various formulated compounds.
Injection molding requires a low compression screw with a suitable lead-out length. Pipe materials require a pointed plasticizing screw. Low viscosity, high output materials require a processing screw with the sliding check ring removed, not a ball check screw. Injection molds should be made of stainless steel or at least chrome or nickel plated.
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