Hydrocarbon blowing agents

The compositions consist of a heat-plastified mixture of an ethylene homopolymer or copolymer, about 3 to 30 pbw of an elastomer, a stability control agent, which is a partial ester of a long chain fatty acid with a polyol, higher allyl amine, fatty acid amide or olefinically unsaturated carboxylic acid copolymer, and a hydrocarbon blowing agent having from 1 to 6 carbon atoms and a boiling point between -175 and 50C. 

Until the late 1980s trichlorofluoromethane (CFC 11) was also used to blow flexible, open-celled polyurethane foams used in furniture upholstery however, the rapid loss of the blowing agent to the atmosphere meant that this CFC application was one of the first to be eliminated when concern over the possible effects of CFCs on stratospheric ozone increased. Similarly, dichlorodifluoromethane (CFC 12) in the relatively minor application of polystyrene hot-food containers was also rapidly replaced by hydrocarbon-blowing agents. 

Some countries have independently banned CFC use. For example, Sweden banned the use of CFC s in 1991, followed by Switzerland in 1992. In Europe Rigid Foam manufacturers are using hydrocarbon blowing agents, such as cyclopentane as an alternative to CFC. 

Phenolic foams can also be prepared without the use of CFG or hydrocarbon blowing agents. In a typical preparation [37], resol 200, ethoxylated castor oil 8, boric anhydride accelerator 36, and SnCl2.2H20 36 parts are mixed and heated for about 4 minute at 120°C to obtain a foam having density 0.003 g/cm and 29% closed cells. In another method [38], 1 mol phenol, 2.6 mol formaldehyde, and 5% dimethylaminoethanol are heated at 70°C-100°C for 4 h to obtain a liquid (70%-80% solids content) which is mixed with 2%-3% silicone foam regulator and 5 parts NaHCOs. Toluenesulfonic add (20 parts, 80% aq.) is then added to obtain a stable rigid foam. 

Gas At a park under construction site, accumulated hydrocarbon blowing agent from land buried Polystyrene Foam, caught fire due to static electrical spark... 

PPE/SAN with cross-linking and C3-C6 hydrocarbon blowing agents Hahn et al. 1992... 

Honeywell argues that hydrocarbon blown foams can suffer from a fall-off in insulation quality at low temperatures (i.e., below 22 °C) as a result of hydrocarbon gas condensing on the cell walls, and recommends that adding a small amount of 245fa to the hydrocarbon blowing agent is beneficial. HFCs can be blended with pentane, forming flammable azeotropic mixtmes. 

Physical blowing agents are usually either hydrocarbons such as pentane or hydrofluorocarbons (HFC). Hydrocarbon blowing agents are of comparatively low cost, but flame-proof plants are required and liberation of hydrocarbons into the atmosphere is generally unacceptable. 

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