Studies of the solid-state thermal degradation of PVC. I. Autocatalysis by hydrogen chloride

The thermal degradation of virgin and HCI-treated PVC in powder form, as well as of PVC films of different thicknesses, has been studied as a function of time and temperature. The rate of dehydrochlorination was determined conductimetrically and from the polyene sequence distributions as obtained by UV spectroscopy. Increases in the rate of dehydrochlorination, ranging between 30 and 45%, were observed at all temperatures for the samples pretreated with HCI, while the corresponding activation energies were found to be lower by about 20%. For the PVC films, the rate increased with thickness, i.e., with longer residence time of evolved HCI within the sample. The results offer insight regarding the autocatalytic role of evolved HCI.     

Effects of fillers on and the role of hydrogen chloride in the behaviour of PVC in fires

Calcium carbonate fillers react with hydrogen chloride liberated during pyrolysis of PVC to an extent depending on their particle sizes and concentrations. The effects of these and other fillers on the critical oxygen index is more complex and depends on a number of factors additional to the extent of hydrogen chloride retention, of which char formation in particular is not readily assessed numerically. Differential thermal analyses suggest that the reaction of hydrogen chloride with calcium carbonate or calcium oxide fillers proceeds rapidly upon liberation. Hydrogen chloride added to the gas stream raises the critical oxygen index to a considerably greater extent than do carbon dioxide or nitrogen. It is concluded that the exotherm due to reaction between calcium carbonate fillers and pyrolysis hydrogen chloride contributes only slightly to flammability, and that the involvement of hydrogen chloride in reducing flammability is chemical rather than physical.     

降低聚氯乙烯电缆料在燃烧时氯化氢释放量的方法探讨

详细介绍了聚氯乙烯电缆料在燃烧时降低氯化氢释放量的方法 :(1)加入酸吸收剂 ;(2 )提高酸吸收剂的吸收效率 ,减少颗粒度或改善其表面活性 ;(3)降低聚氯乙烯燃烧时氯化氢的释放速度 ;(4)减少氯化氢的产生源。并从理论上逐个进行了分析 ,并进行了相应的实验室验证     

Prediction of vinyl chloride monomer migration from rigid PVC pipe

Data on the solubility and diffusion of vinyl chloride monomer (VCM) in PVC resin powders have been combined with published solutions of Fick's diffusion equation to yield predictions of the amount and rate of loss of residual VCM (RVCM) from rigid PVC pipe under storage and service conditions. The principal factors controlling VCM migration are the initial VCM content, thickness of the PVC section, temperature and the age of the PVC product. Analysis Solutions are presented for RVCM loss from freshly exturded pipe (uniform VCM concentration) into either the storage environment or the pipe contents. From these solutions, estimates are made for the real-world situation of closed-system service following variable storage periods. The validity of this approach for rigid PVC pipe in water-service is supported by reasonable agreement between its predictions and experimental laboratory data on the VCM content of water stored in PVC pipes. Both the predictive model and experimental data indicate that PVC pipe containing ≤ mg/kg (1 part per million) residual VCM will result in VCM concentrations in water of less than 0.002 mg/kg - under any expected service conditions.     

Diffusion characteristics of vinyl chloride from PVC in slurry phase

The porous nature of poly(vinyl chloride) (PVC) brings along the problem of residual vinyl chloride in the final product. Stripping techniques are developed to eliminate vinyl chloride to the desired levels. After a certain extent of monomer removal, the stripping rate of vinyl chloride is limited by diffusion. Therefore, the diffusion characteristics of vinyl chloride from PVC slurries was investigated. Stripping was carried out at the boiling point of water where the generated steam was used as a carrier substance. The boiling point of water was changed by elevating the pressures. The dependence of diffusion on concentration is put forward and the activation energy of diffusion was calculated.     

PVC生产中氯化氢合成的能源利用分析

针对PVC生产中氯化氢合成工艺过程进行了合成反应热、水能源利用分析。介绍了空气冷却式、水冷夹套式和余热锅炉式3种合成炉的结构及工艺流程。给出了余热回收的数学模型及水耗量数学模型。指出水冷夹套合成炉、水循环利用工艺为最佳能源利用方式。     

Uptake of tridodecylmethylammonium chloride by PVC

The uptake of tridodecylmethylammonium chloride (TDMAC) by poly(vinyl chloride) has been investigated to provide a more quantitative basis for the preparation of blood-compatible surfaces based on TDMAC–heparin coatings. Sorption isotherms of TDMAC from toluene–cyclohexane and toluene–methanol mixtures have been measured. In toluene–cyclohexane mixtures, the TDMAC uptake is proportional to the degree of swelling of the polymer. From ion-exchange experiments with ³⁶Cl^?, it appears that only a small fraction of the TDMAC remains near the PVC surface to provide the heparin binding capacity. Methanol forms a strong H-bonded complex with TDMAC in toluence and prevents its sorption by PVC.     

The migration of vinyl chloride monomer from PVC pipe into water

A study was undertaken to determine the extent of residual vinyl chloride monomer (VCM) migration from PVC pipe into water. Methods were developed to analyze VCM in water at low levels. Test samples of PVC pipe were exposed to water under static and flowing conditions for varying time intervals. The results indicate that the level of VCM extracted into water is directly proportional to the level of residual monomer in the pipe. Pipe containing <1.0 mg/kg(<1.0 ppm) residual VCM showed no VCM extracted into water with a test sensitive to 0.002 mg/kg (2 ppb).     

光化副产氯化氢用于合成氯乙烯的探讨

分析和评估了光化副产氯化氢的质量状况,讨论了处理方法,认为通过净化技术可使光化副产氯化氢用于合成氯乙烯的原料。     

氯化氢废酸回收装置

介绍了氯化氢废酸回收装置的流程、运行情况和效果。     

小型DCS在PVC生产中氯化氢合成控制系统的应用

叙述了沈阳化工股份有限公司采用西门子慕尔公司小型DCS控制系统PROCIDIA 对PVC生产中合成氯化氢生产过程的控制,介绍了控制方案、控制系统的构成、控制站ICONFIG与操作站WINCC的连接、遇到的问题及解决方法等。     

PTFE生产中副产氯化氢的处理

简要介绍PTFE生产中副产氯化氢的处理方法,设计了安全技术措施,保证生产的安全稳定进行。     

Diffusion of vinyl chloride from PVC packaging material into food simulating solvents

Two models are used to describe vinyl chloride monomer (VCM) diffusion from poly(vinyl chloride) (PVC) packages to food simulating solvents. It was found that when the initial solid concentration in a PVC package is 0,35 ppm: (a) For poor solvents such as water and oils, VCM concentration in the solvent, C_l, theoretically will not exceed 20 ppb. (b) For strong solvents, the volume ratio of package solid/solvent should not exceed 0.1 in order to keep (C_l)_max below 20 ppb. (c) It was demonstrated that thickness can be adjusted to give a C_l = 20 ppb at the time equal to the shelf-life of the package. The method can also be used to calculate the initial concentration of VCM in a package which will give a proposed level of maximum C_l when the solvent and package geometry are fixed. VCM diffusion from PVC pressure pipe to pipe fluids was similarly analyzed.     

高纯氯化氢对电石法PVC失活低固汞催化剂的原位再生

以电石法乙炔氢氯化失活低固汞催化剂为基础,在等温固定床反应器中模拟实际生产转换器单管装置,对失活催化剂通入高纯无水氯化氢气体,研究在氯化氢气体作用下,失活低固汞催化剂的再生效果,并考察再生温度、再生压力、空速以及再生时间对低固汞催化剂再生后汞含量、碘吸附值、四氯化碳吸附值、载体BET比表面积以及催化性能的影响。结果表明,在再生温度220℃、再生压力100 k Pa、空速500 h~(-1)和再生时间60 h条件下,失活低固汞催化剂再生性能最好,再生后乙炔转化率达到99.8%。     

浅析氯化氢合成余热利用

介绍了采用热水型溴化锂机组对氯化氢合成中产生的余热的利用,通过计算,对比分析了节能效果。     

Non-migration level of vinyl chloride monomer in PVC

Recent evidence confirms previous findings that VCM in levels of 1 ppb in PVC bottle resins are nonmigratory and that such resins can be produced in commercial quantities.     

氯化汞触媒在聚氯乙烯行业中的应用

对低汞触媒和高汞触媒在PVC行业的实际应用情况进行了对比,低汞触媒颗粒形态大,转化器填装量少,使用寿命长,可降低汞消耗量,节约了成本,减少了环境污染。     

以丙三醇和氯化氢为原料制备环氧氯丙烷的工艺研究

介绍了以丙三醇和氯化氢为原料制备环氧氯丙烷的工艺,以己二酸为催化剂进行丙三醇的氯化反应,生成的二氯丙醇再和碱反应生成环氧氯丙烷。对影响反应的因素进行了研究,得出了最佳工艺条件：氯化反应温度120℃,氯化氢的通气量326．4mL／min,反应时间20h,催化剂物质的量为丙三醇的16％,环化反应采用1．9mol／L的氢氧化钠在30℃下进行较为合适。在此条件下得到的环氧氯丙烷收率为91．79％。     

聚氯乙烯树脂及其复合物中氯乙烯单体含量测定的不确定度评定

采用自动顶空气相色谱-质谱法测定聚氯乙烯树脂及其复合物中氯乙烯单体的含量,研究了测量过程对不确定度的影响因素。通过建立数学模型,对测试中不确定度的各个分量进行了评定和计算。结果表明:由标准工作曲线得到的样品溶液浓度是影响氯乙烯单体含量测定不确定度的主要因素。