Ethylene history

Some representative backbone stmctures of PQs and PPQs and their T data are given in Table 1. As in other amorphous polymers, the Ts of PQs and PPQs are controlled essentially by the chemical stmcture, molecular weight, and thermal history. Several synthetic routes have been investigated to increase the T and also to improve the processibiUty of PPQ (71). Some properties of PPQ based on 2,3-di(3,4-diaminophenyl)quinoxaline and those of l,l-dichloro-2,2-bis(3,4-diaminophenyl)ethylene are summarized in Table 2. 

Most by-product acetylene from ethylene production is hydrogenated to ethylene in the course of separation and purification of ethylene. In this process, however, acetylene can be recovered economically by solvent absorption instead of hydrogenation. Commercial recovery processes based on acetone, dimetbylform amide, or /V-metby1pyrro1idinone have a long history of successfiil operation. The difficulty in using this relatively low cost acetylene is that each 450, 000 t/yr world-scale ethylene plant only produces from 7000 9000 t/yr of acetylene. This is a small volume for an economically scaled derivatives unit. 

The PVA price has historically reflected the cost of ethylene, acetic acid, and energy. The price history for a medium molecular weight, fully hydrolyzed grade is 0.77/kgin 1970, 2.20/kgin 1980, 2.75/kgin 1988, and 2.65/kgin 1995. 

The U.S. price history for merchant ethylene oxide sales is shown in Figure 4. It can be seen that ethylene oxide pricing generally reflects the cost of ethylene and, of course, supply/demand forces. In the late 1980s, several U.S. producers announced their withdrawal from the merchant ethylene oxide market. 

Britton, L. G., Loss Case Histories in Pressurized Ethylene Systems, Process Safety Progress, V. 13, No. 3, 1994, p. 128. 

With lower-molecular-weight polymers unit cell parameters may also vary with the molecular mass distribution. For poly(ethylene terephthalate) the history of reported unit cell parameters reflects the progress of chemical processing technology [105]. 

From several price histories it is possible to establish caustic soda and chlorine values in different markets and hence calculate the ECU value and with it some measure of profitability. The chlorine value in export EDC can be calculated on the formula assuming the ethylene price is known. The chlorine value using hydrogen chloride is complicated by the extra costs of using HC1 rather than chlorine and the slightly lower yields with oxychlorination, though that too can be calculated to give a chlorine value. 

For most of olefin plant history, there was plenty of propylene around, especially in refineries, so olefin plants didn t really have to be built to make propylene, only ethylene. But a petrochemical product that has... 

Note The following derivatives of ethylene guanidine apparently are capable of being isolated in the isomeric forms indicated, plus A(i) mino-or nitra (i) minoethyl guanidines (non-cyclic) not indicated, depending upon pH, thermal and temporal history of their method of prepn... 

I. Romieu et al., Breast Cancer, Lactation History, and Serum Organochlorines, Am. J. Epidemiol. 152 (2000) 565-70 R. Millikan et al., Dichlorodiphenyldichloroethene, Polychlorinated Biphenyls, and Breast Cancer Among African-American and White Women in North Carolina, Cancer Epidemiol. Biomarkers. Prev. 9 (2000) 1255-40 S. D. Stellman et al., Breast Cancer Risk in Relation to Adipose Concentrations of Organochlorine Pesticides and Polychlorinated Biphenyls in Long Island, New York, Cancer Epidemiol. Biomarkers. Prev. 9 (2000) 1241-49 T. Zheng et al., Risk of Female Breast Cancer Associated with Serum Polychlorinated Biphenyls and l,l-dichloro-2,2 -bis(p-chlorophenyl)ethylene, Cancer Epidemiol. Bio-... 

A retrospective assessment of the potential antifertility influence of ethylene dibromide was conducted by studying the reproductive perfonnance of men exposed to ethylene dibromide in the workplace. Data were obtained from four chemical plants manufacturing ethylene dibromide located in the southern part of the United States (Arkansas and Texas). Exposures in the plants ranged from less than 0.5 ppm to 5 ppm [3.8-38 mg/m- ]. Evaluations were made exclusively on the basis of the men s reproductive histories of live births to their wives, subsequent to their occupational exposure. The mmiber of live births was compared with the expected mmiber derived from national fertility tables. One of the four plants studied showed a significant decrease in fertility however, when data from the four plants were combined, there was no significant effect of ethylene dibroniide exposure on reproductive performance (Wong et al., 1979). 

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