The 20 years of reform and opening up are the 20 years of rapid development of China's plastic industry. In recent years, the output of plastics in China has ranked first in the world, and the consumption level and processing application level of some kinds have also entered the international first stop list. Polyvinyl chloride resin (PVC) is one of them. In 2000, the total output of PVC in China reached 2.64 million tons, accounting for more than 25% of the total output of synthetic resin in China.
Even so, there is still a big gap in PVC resin raw materials in the domestic market, and more than 1 million tons need to be imported every year. It is reported that the output of rigid PVC pipes, doors and windows in China in 1998 was 450000 tons and 200000 tons respectively. It is estimated that plastic pipes and door and window products will account for 60% and 30% of the total pipes, doors and windows required in the building materials market by 2010. Chlorinated polyvinyl chloride resin (CPVC) It is a chlorinated modified product of PVC resin. It has made obvious progress in service temperature, strength and weather resistance than PVC resin. Therefore, accelerating the consumption and application development of CPVC resin is a very important topic in front of us.
When chlorinating PVC resin, chlorine addition occurs first on the double bond at the end of PVC macromolecule, and then the chlorine atom replaces the hydrogen atom on the macromolecule under the action of free radical initiator to produce hydrogen chloride at the same time. Therefore, with the increase of chlorine atoms, PVC macromolecules gradually change with different chlorine content. When CPVC contains 65% chlorine, the ratio of the three is about 40:10:50 (while in PVC, the ratio of the three is 0:0:100). It can be seen that when the PVC resin is chlorinated, the chlorine atom first replaces the hydrogen atom on the macromolecule - CH2 -. When the chlorine content is greater than 65%, the partial dichloro chain link (CCK - CH2 -) will be formed. With the recovery of chlorine content, the - CHCl - CHCl chain links increase, the polarity and rigidity of macromolecules increase, and the heat resistance and tensile strength of materials also improve. Different chlorination methods can obtain different structures. The chlorination of PVC resin in halogenated hydrocarbon medium (such as chlorobenzene, dichloroethane, carbon tetrachloride, etc.) is average chlorination. The chlorinated product is extracted from the solution. It has good solubility, commonly known as perchloroethylene resin. The product is used for advanced anti-corrosion coatings and adhesives. Chlorination of PVC resin in non halogenated hydrocarbon medium is non average chlorination (such as aqueous phase and gaseous phase chlorination). The product is insoluble in general solvents. It has higher heat resistance than PVC and various physical and mechanical properties required by hard materials (see Table 1).
Table 1C performance comparison properties of PVC resin and PVC resin Vicat softening temperature / C shore hardness D tensile strength / MPA bending strength / MPA tensile elongation / linear thermal expansion coefficient / 10 thermal conductivity / specific heat capacity.
~ 40 is also better than ABS and PP, and the products are still not deformed in boiling water for a long time.
83.6~125.4X10―5JAcmY°C）。 Therefore, when CPVC pipe is used to transport hot water, there is no need to keep heat outside the pipe, which can save money and reduce the quality of the pipe.
The physical and mechanical properties such as tensile strength, creep and destruction strength are better than those of PVC resin. After chlorination of PVC, due to the increase of molecular polarity, the mechanical strength of the material is improved. The tensile strength at higher temperature (such as 100 ° C) is still up to 50MPa, and the creep property of CPVC resin is still half lower than that of PP resin at 90 ° C. After 50 years of use at 100 ° C, the circumferential damage stress of CPVC pipe is still 2.2MPa. Excellent weather resistance and corrosion resistance: CPVC is not only resistant to ultraviolet light and atmospheric aging, It is also resistant to various acid and alkali media at room temperature. It is still resistant to sodium hypochlorite solution, lactic acid, dilute alkali and other media even at 100 ° C (see).
Corrosion resistance of CPVC resin the coating made of CPVC resin dissolved in some polar solvents has excellent corrosion resistance and weather resistance.
In 1942, German faben company first prepared CPVC resin by solution method. In 1958, Goodrich's aqueous phase process was successfully developed. In 1962, the industrial plant was put into operation, and the products were put on the market with geonht brand. Subsequently, consumer devices were also built in Britain, France, Japan, Belgium, Yugoslavia, the former Soviet Union and other countries. Goodrich company of the United States changed the consumption of PVC resin to CPVC in 1993, supplying domestic and foreign markets with a scale of 20000 t / A. the scale of other companies is 3 ~ 5kt / a (see Table 2 for details). Since many countries include the output of CPVC resin in the output of PVC resin, it is difficult to accurately count the output of CPVC resin. It is estimated that the world output in 2000 was 50000 ~ 60000 tons, of which hard materials accounted for more than 80%, and the rest were coatings.
Table 3 consumption status of CPVC resin in China company name consumption process scale 8 kt / a) in the late 1950s, Jinxi Chemical Research Institute began to study solution CPVC resin. In the 1970s, Anhui Chemical Research Institute succeeded in studying CPVC by water phase method, and achieved batch consumption on an industrial scale after tackling key problems in the eighth five year plan with a scale of 500t / A. In the late 1980s, Hubei Institute of chemical industry stopped studying the process of gas-phase CPVC resin and built a small consumption unit in Xiangfan chemical plant. According to statistics, the total consumption capacity of CPVC resin in China is more than 10000 tons, and the output is about 3kt / A, See Table 3 for the main consumer plants. Table 2 consumption of CPVC in foreign countries. Main process brands of national consumer manufacturers remarks: American aqueous phase method is put into operation. American aqueous phase method British aqueous phase method has a total of 6 brands. German aqueous phase method German solution method French aqueous phase method French aqueous phase method Belgian aqueous phase method Yugoslav aqueous phase method former Soviet Union physicochemical drilling and Research Institute aqueous phase method Mitsubishi aqueous phase method bendeshan ponding aqueous phase method Carbide aqueous phase method put into operation: benzhong Yuan Chemical aqueous phase method put into operation: benji'ang chemical aqueous phase method put into operation: benji'ang chemical solution method put into operation: Bendong synthetic aqueous phase method put into operation: solution method of Jihua Co., Ltd. solution method of Shanghai Chlor Alkali Chemical Co., Ltd. solution method of Yixing Shanli high temperature coating plant solution method of Luancheng Chemical Co., Ltd. aqueous phase method Jinhua Chemical (Group) Limited liability company solution method Jiaxing pesticide factory solution method Wuxi Chemical Group Co., Ltd. water phase method Changzhou Liaoyuan Chemical plant water phase method Yibin Tianyuan Group Co., Ltd. solution method Wuhan Gehua Group Co., Ltd. gas phase method Qingdao Haijing Chemical Group water phase method Weifang Yaxing chemical group water phase method Xiangfan No. 2 chemical plant gas phase method 1 consumption method CPVC resin mainly has three consumption methods, Solvent method, aqueous phase method and gas phase method. CPVC resins consumed by different methods have great differences in structure and performance, and CPVC resins consumed by different methods have different applications. Solvent chlorination is to stop chlorination of PVC resin in halogenated hydrocarbon solution. The product is a homogeneous random product, which is easily soluble in solvents such as tetrahydrofuran, dichloroethane and chlorobenzene. Therefore, solvent CPVC resin products are mainly used for paint, fiber and adhesive. CPVC resin consumed by water phase method and gas phase method is a heterogeneous and random product. It has low solubility in solvent and high heat resistance and physical and mechanical properties. Therefore, its products are mainly used for hard materials such as pipes and plates. Due to environmental reasons, especially the provisions of the Montreal Protocol, substances that consume the atmospheric ozone layer have been restricted and banned. Therefore, the original solvent consumption process has been limited. In addition to using solvent substitutes to continue to use solvent consumption of CPVC resin for coatings, the chlorination processes of aqueous phase method and gas phase method have been popularized.
1.1 solvent method the process mainly includes chlorination, chlorination solution filtration, CPVC resin sedimentation, drying, solvent recovery and other processes. The consumption process with this method has long process flow, high cost and easy to form environmental pollution. See for the consumption process.
In the process flow of PVC homogeneous chlorination consumption, anhydrous solvents such as chlorobenzene, dichloroethane and carbon tetrachloride are mixed with PVC resin powder in the enamel feedback kettle to prepare a suspension of 10% ~ 15%, stir and raise the temperature to 70 ~ 90 ° C, so as to gradually dissolve PVC. Then, participate in nitrile initiator under stirring, and inject chlorine into the kettle liquid to start chlorination. The tail gas discharged from the chlorination kettle enters the water absorption tower after passing through the reflux condenser to remove the by-product hydrogen chloride. The end point of chlorination is determined according to the solubility of CPVC resin sample in acetone. After chlorination feedback, the feedback liquid is cooled, degassed and filtered to remove impurities. The filtrate is separated out of CPVC resin with boiling water in the glue spraying tower. The resin slurry is separated from the filter. Then the product is made by boring and screening. The chlorine content of the product is 61% ~ 65%. 1.2 the process flow of heterogeneous chlorination of PVC by aqueous suspension method is to participate in the quantitative water (or dilute hydrochloric acid) PVC resin powder, dispersant and initiator in enamel or titanium feedback kettle to prepare 15% ~ 20% PVC suspension, heat up to 50 ~ 70 ° Q under stirring, and feed back chlorine to the qualified chlorine content. After the chlorination feedback is completed, the acid solution and materials are respectively put into the solution kettle for washing and neutralization, and then CPVC resin with chlorine content of 65% ~ 67% is prepared by centrifugation and drying. The common initiator is azodiisobutyronitrile, which can also be initiated by UV. The consumption quota of 1tcpvc consumed by aqueous phase method is: 0.52t PVC resin, 30t process water and electricity), in which HCl and a small amount of chlorine are mixed with lime water or dilute alkali water.
The by-product dilute hydrochloric acid (230kgarcpvc) with a mass fraction of 6% ~ 8% in the feedback solution can be used for further absorption to make acid. The amount of dilute acid wastewater produced by water washing is 8 ~ 9V (t ° CPVC), in which the mass fraction of HCl is less than 2%. It is proposed to neutralize with hydrated lime. There is a small amount of dust in the dry tail gas, which can be discharged up to the standard after being captured by cloth bags.
The aqueous phase process has been greatly developed in recent years. In order to prepare CPVC resin with better processing performance, Goodrich company and Japan Zhongyuan company have issued a large number of patents on the vinyl chloride polymerization process and copolymerization improvement method of chlorinated raw PVC resin. For example, with DCPD as initiator and polyvinyl alcohol as dispersant, when the VCM conversion reaches 70% - 90%, chlorinate the resin with chlorine in the same kettle under the illumination of high-pressure mercury lamp, and chlorinate the resin to a chlorine content of 66.5%. The product has good stability (70min at 200 ° C). As another example, the dispersion agents such as polystyrene sulfonate, alkaline earth metal chloride and polyacrylamide are involved in the PVC resin suspension, and the chlorinated product has good thermochromism. Another example is that CPVC resin with good impact resistance is prepared by chlorinating pvc-pe (or PP) admixture after participating in polyethylene resin powder (or PP resin powder) with a total amount of 0.5% ~ 2.0% and a participation rate of 0.1 ~ 10.0g/min in VCM suspension polymerization. In terms of post solution process improvement, such as PKA<7柠檬酸盐替代碳酸盐解决氯化后CPVC树月旨的稳定性有较大进步；再如含CPVC的酸性料液加二氧化硫与氢氧化钠中和，而后水洗枯燥，产品的黄色指数仅为31.有报道后解决时参与马来酸二丁基锡能够改善CPVC树脂的枯燥效率。后解决中参与肼、NaOH洗涤能够进步产品的白度。光氯化的CPVC树脂加工性能不如引发剂制得的CPVC树脂。用两步法氯化还能制得高含氯量（70%选择适当的原料，水相法也能制得涂料用的CPVC树脂，如用低聚合度（如300以下）的PVC树脂水相法氯化，能够制得溶解度甚好的产品替代溶剂法过氯乙烯应用于涂料。安徽省化工钻研院近年开发成功水相法工艺的过氯乙烯树脂，该技术不用溶剂，本钱低、产品质量抵达溶剂法水平。
1.3 CPVC resin is obtained by chlorination of PVC resin powder by gas phase method in drum type or fluidized bed feedback reactor under ultraviolet light. Due to complex facilities, difficult heat transfer during chlorination and easy yellowing of products, the scale of industrial consumption of this method is small. In recent years, a large number of patents have disclosed the improvement of the process: such as fluidized chlorination in multi chamber fluidized bed; Staged chlorination (first stage - 20 ~ 50 ° C, second stage 70 ~ 120 ° C); Chlorination under y-ray irradiation; Fluidized bed chlorination in fluorine and chlorine containing gas to improve the thermal stability of tree moon.
Liquid chlorine chlorination is a new process proposed by Goodrich company in the 1980s. It is reported that the process can realize intermittent chlorination.
2cpvc resin processing according to the different needs of market users for CPVC materials, processing manufacturers can provide different types of CPVC products such as hard materials, coatings and adhesives, synthetic fibers and so on.
2.1 hard materials in PVC resin, hard materials account for more than 40% of the total output, such as pipes, pipe fittings, doors and windows, plates, etc. of different specifications. Since the heat resistance of CPVC is 35 ~ 40 higher than that of PVC, it can be predicted that CPVC hard materials will have wider applications. One million residential units in the United States have been laid with CPVC cold and hot water pipes. The application results show that:长期输送0.1MPa、82°c以上热水。与PVC―样，CPVC树脂具有180~200°C的分解温度，但CPVC树脂熔融时的活动性不迭PVC，熔融粘度是PVC的3倍。因此，CPVC硬质材料加工时必需满足两方面要求：（1）参与一定助剂使活动温度下降，进步热稳定性，并且尽可才干口大加工温度和分解温度的差距；（2）参与助剂改善树脂加工时的活动性，如参与CPE、MBS、ABS、EVA等高分子助剂。只有满足以上两点，使用PVC树脂的加工设施（如助塑机、挤出机、压板机等）便能够成功地完成CPVC树脂的加工。2.1.1挤出加工管材及异型材单、双螺杆挤出机均能够使用，机头最好有水冷却，以防过热。腔壁最好镀络，以减轻粘壁。管材配方为：CPVC树脂100份、MBS 50份、加工助剂3份、金属类稳定剂1份、抗氧剂0.份、光滑剂3.5份。使用挤出机加工时，加工条件如表4.表4CPVC管材加工条件项目单螺杆挤出机双螺杆挤出机挤出机类型转速为201/min料筒温度/模具温度/多孔板CPVC树脂的加工中需参与抗冲击、加工活动改性剂。通常能够使用含氯量为25%~40%的CPE或MBS30~40份。MBS等其它抗冲改性剂参与后能够与树脂及其它助剂掺合，也能够在CPVC树脂颗粒上接枝成合金。由于热稳定性和粘度的因素，小口径CPVC管比PVC管难于加工，应对挤出机的工艺参数仔细调试。
为了保障材料能充斥模腔，选用的CPVC树脂聚合度较低或含氯量较低，如T281、H408等。典型的配方为：CPVC树脂100份、马来酸二丁基锡2份、二盐2份、硬钙0.5份、石蜡0. 5~1份、抗氧齐|J（BHT）0.5~1份、MBS2~4份、EVA4份。加工条件：料筒温度Ci ~65MPa；热扭变温度95~105°C；冲击强度（简支梁）14kJ/m2. CPVC树脂吸水性强。因此，在加工前树脂2.2其它加工办法与PVC硬质材料一样，CPVC管材能够用焊接、粘接办法联接。焊接加工时，用CPVC本体材料或PVCHT焊条，焊接速度要比PVC焊接慢50%，热空气温度要控制好，当喷嘴为4mm，热空气温度为290°C.焊面要预先打毛，通常不能用超声波焊接。粘合以前，预先将粘合外表去月旨打毛，使用含CPVC树脂的四氢呋喃溶液。CPVC树脂还能够制造发泡材料。