CHLORINE-CONTAINING

Most chlorine-containing compounds can be converted to give chloride ions, for example covalent chlorides by hydrolysis, chlorates by reduction. The chloride ion is then tested for thus ... 

There is a curious irony in the nomination of hypochlorite as an environmentally benign oxidizing agent It comes at a time of increasing pressure to eliminate chlorine and chlorine containing com pounds from the environment to as great a degree as possible Any all inclusive assault on chlorine needs to... 

This is an indirect method of analysis because the chlorine-containing species do not react with the titrant. Instead the total chlorine residual oxidizes l to l3 , and the amount of 13 is determined by the redox titration with Na282 03. 

This example can be used in reverse to show the usefulness of looking for such isotopes. Suppose there were an unknown sample that had two molecular ion peaks in the ratio of 3 1 that were two mass units apart then it could reasonably be deduced that it was highly likely the unknown contained chlorine. In this case, the isotope ratio has been used to identify a chlorine-containing compound. This use of mass spectrometry is widespread in general analysis of materials, and it... 

Amin ophen o1 has been used as a stabilizer of chlorine-containing thermoplastics (153), although its principal use is as an intermediate in the production of 4-aniino-2-hydroxybenzoic acid [65-49-6] a tuberculostat. This isomer is also employed as a hair colorant and as a coupler molecule in hair dyes (154,155). 

Their performance falls short of most present finishes, particularly in durabiUty, resistance to chlorine-containing bleaches, and formaldehyde release, and they are not used much today. Both urea and formaldehyde are relatively inexpensive, and manufacture is simple ie, 1 —2 mol of formaldehyde as an aqueous solution reacts with 1 mol of urea under mildly alkaline conditions at slightly elevated temperatures. 

Other Accelerators. Amine isophthalate and thiazolidine thione, which are used as alternatives to thioureas for cross-linking polychloroprene (Neoprene) and other chlorine-containing polymers, are also used as accelerators. A few free amines are used as accelerators of sulfur vulcanization these have high molecular weight to minimize volatility and workplace exposure. Several amines and amine salts are used to speed up the dimercapto thiadiazole cure of chlorinated polyethylene and polyacrylates. Phosphonium salts are used as accelerators for the bisphenol cure of fluorocarbon mbbers. 

The misconception that vinyl gives off dioxin when it is incinerated is misleading. A study conducted by ASME in 1995 (162) found that the presence, or absence, of chlorine-containing wastes in incinerators had no effect on the levels of dioxin produced. Rather, it was found that incinerator operating conditions (primarily temperature) were the key to controlling dioxin formation. More recentiy, German officials examined the issue of incinerating vinyl waste and decided there was no cause for concern (180). 

A study of the North American bleaching agent market was completed in June 1988 and includes consumption quantities for the year 1986 (156). Chlorine consumption for 1986 was 1.86 x 10 t. The North American consumption volume of other chlorine-containing bleaching compounds including sodium and calcium hypochlorite, chlorinated isocyanurates, and hydantoins was 286,000 t. The 1986 North American consumption of sodium chlorate was estimated at 5.5 x 10 t. 

A significant use of butylene oxide [26249-20-7] is as an acid scavenger for chlorine-containing materials such as trichloroethylene. Inclusion of about 0.25—0.5% of butylene oxide, based on the solvent weight, during preparation of vinyl chloride and copolymer resin solutions minimizes container corrosion which may be detrimental to resin color and properties. 

Cure-Site Monomers. A large variety of cure-site monomers has been proposed, but only a few have achieved commercial significance. Two of the most important classes are labile chlorine containing monomers and epoxy/carboxyl containing monomers. 

Labile Chlorine Containing Monomers. Chlorine is introduced in the acryhc elastomer chain by analogy to polychloroprene (19). The monomers are characterized by the simultaneous presence of a double bond available for polymerization with acrylates and a chlorine atom ready to react easily during the vulcanization step. The general formula is as follows where R is a group that might enhance the reactivity of the double bond and/or of the vicinal chlorine atom. 

Epoxy/Carboxy Cure Sites. Epoxy/carboxy cure sites probably represent the most important alternative to labile chlorine containing monomers. There has been increasing interest in them due to the discovery of the highly efficient quaternary ammonium salt-based accelerators (29—34). The reaction between the epoxy ring and carboxyUc acid can happen in the following three ways ... 

Because of the different vulcanization chemistry involved in each commercial ACM, a vulcanization system specific to the cure site present has to be adopted. Many cure systems for labile chlorine containing ACM have been proposed (45). Among these the alkali metal carboxylate—sulfur cure system, or soap—sulfur as it is called in the United States, became the mainstay of acryflc elastomer technology in the early 1960s (46), and continues to be widely used. 

New efficient vulcanization systems have been introduced in the market based on quaternary ammonium salts initially developed in Italy (29—33) and later adopted in Japan (34) to vulcanize epoxy/carboxyl cure sites. They have been found effective in chlorine containing ACM dual cure site with carboxyl monomer (43). This accelerator system together with a retarder (or scorch inhibitor) based on stearic acid (43) and/or guanidine (29—33) can eliminate post-curing. More recently (47,48), in the United States a proprietary vulcanization package based on zinc diethyldithiocarbamate [14324-55-1]... 

Acryhc elastomers are normally stable and not reactive with water. The material must be preheated before ignition can occur, and fire conditions offer no hazard beyond that of ordinary combustible material (56). Above 300°C these elastomers may pyrolize to release ethyl acrylate and other alkyl acrylates. Otherwise, thermal decomposition or combustion may produce carbon monoxide, carbon dioxide, and hydrogen chloride, and/or other chloiinated compounds if chlorine containing monomers are present ia the polymer. 

Fig. 8. Distribution of chlorine-containing species in a 1 Af chloride solution. A, CIO3 B, CI2 C, HOCl and D, CIO...

From trifluorotriaminomethane (292) and also from perfluoroguanidine (294) fluorodifluoroaminodiazirine (293) was obtained. The presence of chloride leads to the formation of chlorine-containing diazirines. 

Figure 2.17 Pitting at a free-machining austenitic stainless steel threaded valve throat. The valve controlled flow of a chlorine-containing, low-pH biocide.

Corrosion products contained sulfur up to 5% by weight. Aggressive sulfur- and chlorine-containing species concentrated beneath iron oxide, silt, and sand deposits. Localized areas of attack resulted. 

Organic acids—except formic, oxalic, and some chlorine-containing acids—do not appreciably attack aluminum near room temperature. In most acids, the corrosion rate increases slightly with flow velocity. 

The visual and microscopic appearance of the cracks, coupled with the presence of chlorine-containing corrosion products on the cracked surfaces, identifies this failure as chloride SCC. The circumferential orientation of... 

Whilst such stabilisers have found use in many chlorine-containing polymers their main application has been with polyfvinyl chloride). These additives will be considered in Chapter 12. 

Of these various groups there was extensive interest for some years in polyalkenamers such as frani -polypentenamer which has now abated whilst interest in polynorbomene is steadily increasing. Since the chemistry and technology of the two types is somewhat different each type will be dealt with separately. A third group comprises the chlorine-containing polymers announced by Goodyear in 1980. 

---