Chlorinated Fire Retardants

A major concern with respect to the use of chlorinated FRs is their potential to form known hazardous materials, particularly dioxins or dioxin-like materials. As in the case of the brominated analogues, the most likely product of combustion of chlorinated FRs is HCl. However, the potential for formation of other potentially hazardous materials is real and has to be considered carefully [99]. 

Some countries (e.g., Germany) have developed rules for the maximum content of some 2,3,7,8-substituted polychlorinated dibenzo-para-dioxins and dibenzofurans 

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Chlorinated fire retardants (CFRs) are utilised in polyamides, epoxies and PBT. The use of mixed synergists, that is antimony oxide plus another synergist, can lower the total loading of FR additives to the formulation. With glass-filled polyamide compounds where a higher processing temperature is sometimes required, the elimination of antimony oxide greatly improves the thermal stability of the formulations. 

The majority of secondary plasticizers ia use are chlotinated paraffins, which are hydrocarbons chlotinated to a level of 30—70%. Eor a given hydrocarbon chain, viscosity iacreases with chlorine content, as does the fire retardancy imparted to the formulation. These materials aid fire retardancy due to thein chlorine content. Chlotinated paraffins of the same chlorine content may, however, have different volatiHties and viscosities if they are based on different hydrocarbon chaias (see Cm OROCARBONS and cm OROHYDROCARBONS, cm.ORiNATDD paraffins). 

Some of the chemicals mentioned above and others, such as chlorinated mbber or paraffin, antimony trioxide, calcium carbonate, calcium borate, pentaerythrithol, alumina trihydrate, titanium dioxide, and urea—melamine—formaldehyde resin, may be used to formulate fire retardant coatings. Many of these coatings are formulated in such a way that the films intumesce (expand) when exposed to fire, thus insulating the wood surface from further thermal exposure. Fire retardant coatings are mostly used for existing constmction. 

A key property associated with chlorinated paraffins, particularly the high chlorine grades, is nonflammability, which has led to their use as fire-retardant additives and plasticizers in a wide range of polymeric materials. The fire-retardant properties are considerably enhanced by the inclusion of antimony trioxide. 

Chlorinated paraffins are versatile materials and are used in widely differing appHcations. As cost-effective plasticizers, they are employed in plastics particularly PVC, mbbers, surface coatings, adhesives, and sealants. Where required they impart the additional features of fire retardance, and chemical and water resistance. In conjunction with antimony trioxide, they constitute one of the most cost-effective fire-retardant systems for polymeric materials, textiles, surface coatings, and paper products. Chlorinated paraffins are also employed as components in fat Hquors used in the leather industry, as extreme pressure additives in metal-working lubricants, and as solvents in carbonless copying paper. 

Plasticized PVC. Chlorinated paraffins are employed as secondary plasticizers with fire-retardant properties in PVC and can be used as partial replacements for primary plasticizers (qv) such as phthalates (1) and phosphate esters (2). 

Adhesives and Sealants. Various grades of chloriaated paraffins are used as nonvolatile iaert fire-retardant plasticizers and modifying resias ia adhesives and sealants (3). They find wide appHcation ia polysulfide, polyurethane, acryUc, and butyl sealants for use ia building and constmction. The low volatihty high chlorine types are also employed ia sealants for double- and triple-glazed wiadows. 

Flame Retardants. Although the use of chlorinated derivatives of DCPD has been restricted in the pesticide area, some are widely used in flame and fire retardant chemicals (see Flame retardants). The starting material is the fliUy chlorinated DCPD cracked to monomeric hexachlorocyclopentadiene, which is then converted via a Diels-Alder reaction with maleic anhydride to a reactive bicycHc anhydride (9), known as chlorendic anhydride [115-27-5]. 

The chlorine atom has two further useful influences on the properties of the polymer. Firstly the polymer shows improved resistance to oil compared with all-hydrocarbon rubbers. The rubbers also have a measure of resistance to burning which may be further improved by use of fire retardants. These features together with a somewhat better heat resistance than the diene hydrocarbon rubbers have resulted in the extensive use of these rubbers over many years. 

The self-extinguishing characteristics of the chlorine-containing resins are improved by incorporation of antimony oxide but this approach is not possible where translucent sheet is required. As an alternative to chlorine-based systems a number of bromine-containing resins have been prepared and, whilst claimed to be more effective, are not currently widely used. It is probably true to say that fire-retarding additives are used more commonly than polymers containing halogen groupings. 

Secondly, whereas 26-30% chlorine is required to make the resin effectively fire retardant, only 13-15% of bromine is required. It is therfore possible to achieve a greater flexibility in formulation with the bromine resins, which may be blended with other resins and yet remain effectively fire retardant. 

Of major concern are the health and environmental impacts of the abundant chlorinated and brominated hydrocarbons (ref. 2). These materials have numerous industrial applications as pesticides, solvents, propellants, refrigerants, plastics, fire retardants and extinguishers, disinfectants for drinking water, pharmaceuticals and electronic chemicals. Many chemical manufacturers utilize chlorinated and brominated organics as intermediates. It is estimated, for instance, that almost 85 % of the pharmaceuticals produced in the world require chlorine at some stage of synthesis. 

The diaminobenzenes are made from benzene by a combination chlorination-nitration route although para-phenylene diamine is also made directly from aniline. orr/to-Phenylene diamine is widely used for the preparation of biologically active compounds such as fungicides and veterinarian medicines. The mera-diamine is used in fire-retardant textile fibers ( Nomex ) while the / ara-diamine finds use in high-strength textile fibers used for bullet-proof vests, sails, army helmets, and other types of fiber-reinforced plastics ( Kevlar ). 

Chlorinated compounds PCP, PCBs, PCDD/Fs Manufacture of pesticide and herbicide (D) Wood preservation sites (P) Pulp and paper production (P) Municipal waste incineration (P,D) Plastics, fire-retardants manufacture (P,D) Chlorinated phenols -3.6 Chlorinated hydrocarbons - 2.4 [43, 44]... 

Antimony trioxide and chlorinated paraffinic derivatives are common materials used as fire retardants, as are intumescent zinc (or calcium) borate, aluminium hydroxide and magnesium hydroxide. These inorganic materials, used as bulk fillers, act to reduce the fire hazard. Halogenated materials release chlorine, which then combines with the antimony trioxide to form the trichloride, which is a flame suppressant. 

CHLORINATED PARAFFIN AND ANTIMONY OXIDE. The demands Of the armed forces in World War II for a fire retardant, waterproof treatment for canvas tenting led to the development of a combination treatment containing a chlorinated paraffin (CP), antimony oxide and a binder... 

Used industrially for the manufacture of organophosphorus compounds (Insecticides, dyes, pharmaceuticals, defoliants) as well as esters for plasticizers, gasoline additives, and hydraulic fluids used in industry as a chlorinating agent, catalyst, dopant for semiconductor grade silicon, fire retarding agent, and solvent in cryoscopy. 

Flame retardants, 11 447-454, 459-479. See also Fire retardant entries Halogenated flame retardants Phosphorus flame retardants antimony compounds in, 3 54 brominated and chlorinated additive, 11 461-470... 

Due to the chlorine content, oxygen indices are higher than those of the polyethylenes, for example 23 to 25 without fire-retardant additives, but they will act as a combustible material in the event of fire. Combustion products include hydrochloric acid and carbon monoxide, both toxic gases. 

Molybdenum pentachloride is used as a catalyst in chlorination reactions. It also is used in fire-retardant resins for soldering of flux for deposition of molybdenum coating and to prepare several other molybdenum compounds, including molybdenum oxychlorides and hexacarbonyl. 

Fire-retardant coatings currently in use contain a number of ingredients that are either considered to be toxic heavy metals or on the hazardous air pollutants (HAPs) list. In addition, there is concern that the use of halogenated chemicals in these coatings and other products will be banned in the future. A recent paper contains the details of two reformulations programs. The first is a reformulation of a low VOC chlorinated alkyd coating and the second is a reformulation of a chlorinated emulsion system. Both programs successfully reduced the heavy metals and lowered the HAPs to an acceptable level (Dahm, 1996). 

Fire Retardent Paints. Fire retardant paints are based on chlorinated rubber and chlorinated plasticizers with added SbO. These reduce the rate of spread of flames. Addn of NH4H2PO4, PE, or dicyandiamide produces an intumescent or swelling paint that forms a thick insulating layer over the surface to which it is applied when exposed to flames Fire retardant paints do not control fires and are no substitute for an automatic sprinkler system. They are best used where the only hazard is exposed, combustible, interior finish materials or in isolated buildings where sprinklers will not be installed. The paint must be applied at the rate specified on the container if spread thinner the proper... 

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