Polyol flame-retardant

A reactive liquid epoxide used as an organic solvent and surfactant intermediate its polymers can be used for polyester, polyurethane, and polyacrylic resins, polyether polyols, flame-retardants, etc. 

Phosphorus-Containing Diols and Polyols. The commercial development of several phosphoms-contaiuing diols occurred in response to the need to flame retard rigid urethane foam insulation used in transportation and constmction. There are a large number of references to phosphoms polyols (111) but only a few of these have been used commercially. 

Nonreactive additive flame retardants dominate the flexible urethane foam field. However, auto seating appHcations exist, particularly in Europe, for a reactive polyol for flexible foams, Hoechst-Celanese ExoHt 413, a polyol mixture containing 13% P and 19.5% Cl. The patent beHeved to describe it (114) shows a reaction of ethylene oxide and a prereacted product of tris(2-chloroethyl) phosphate and polyphosphoric acid. An advantage of the reactive flame retardant is avoidance of windshield fogging, which can be caused by vapors from the more volatile additive flame retardants. 

One noteworthy neurotoxic response was demonstrated in laboratory pyrolysis studies using various types of phosphoms flame retardants in rigid urethane foam, but the response was traced to a highly specific interaction of trimethylolpropane polyols, producing a toxic bicycHc trimethylolpropane phosphate [1005-93-2] (152). Formulations with the same phosphoms flame retardants but other polyols avoided this neurotoxic effect completely. 

Propylene oxide has found use in the preparation of polyether polyols from recycled poly(ethylene terephthalate) (264), haUde removal from amine salts via halohydrin formation (265), preparation of flame retardants (266), alkoxylation of amines (267,268), modification of catalysts (269), and preparation of cellulose ethers (270,271). 

In the 1990s novel polyols included polyether-esters, which provided good prerequisites for flame retardancy in rigid foams and polyether carbonates with improved hydrolysis stability. 

Wang, T. L., Cho, Y. L., and Kuo, P. L., Flame-retarding materials II. Synthesis and flame-retarding properties of phosphorus-on-pendent and phosphorus-on-skeleton polyols and the corresponding polyurethanes, J. Appl. Polym. Sci., 2001, 82, 343-357. 

The main components of intumescent compositions are most often a polyacid, a carbon source, and an expansion agent. In some cases, the carbon source is the host polymer itself and the expansion process is generated by the decomposition products of the polymer or the acid source, e.g., melamine pyrophosphate (MPP). The most frequent polyacid used is APP. Polymers such as those mentioned above are generally preferred rather than polyols due to exudation, water solubility, and difficulties with processing for the filled polymer. Several studies mention the use of OMMT as a nanofiller introduced in the polymer playing the role of carbon source. In other studies, the silicate is blended with all the components of the flame-retarded polymer. 

With regard to reactive flame-retardants, two routes can be followed to improve thermal stability and fire behavior of PU foams use of brominated or phosphorus-containing polyol or, for rigid foams, the introduction inside polymer backbone of more thermally stable structure than urethane, mainly isocyanurate, but also uretidione rings or carbodiimide.19... 

Also phosphorus- and nitrogen-containing polyols are shown to be effective in flame retardancy of PU foams24 such as polyols based on phosphonic acid ester or obtained by partial or full substitution of methylol groups of tetrakis(hydroxymethyl)phosphonium chloride with amine several examples of such polyols were reported by Levchik and Weil.15 Rigid PU foam modified with these polyols showed improved oxygen index values moreover better results were achieved with higher functionality polyols. 

Since melamine is not soluble in the polyol or MDI, it should be very fine dispersed so that it does not interfere with the foaming process. The effect of melamine particle size on properties of flexible PU foams was studied by Kageoka et al.69 They reported that the foam with the finer particles showed higher hardness, better tensile properties, and less flammability than that with the larger ones. A flame-retarded foam with better physical properties can be manufactured by a polyol including melamine particles smaller than the strut thickness of the resultant foam. 

Sivriev, C. Zabski, L. Flame retarded rigid polyurethane foams by chemical modification with phosphorus-and nitrogen-containing polyols. Fur. Polym. J. 1994, 30, 509-514. 

The major raw materials for making isocyanate-based foams include the following compounds polyisocyanates, polyols, catalysts, blowing agents, surfactants, epoxides, and flame retardants. 

Another route to flame-retardant rigid foams is the use of flame-retardant polyether polyols which contain phosphorous and halogen (reactive type). In recent years, due to the fire-gas toxicity caused by halogen-, phosphorous- or nitrogen-containing flame retardants, other types of flame-retardants which do not produce toxic gases are being developed. 

This method, however, did not result in improved flame retardance because the isocyanurate content was too low. In recent years, however, high-functionality and low-viscosity polyether polyols have become available, and therefore the above method has become less important. Even so, the method was sometimes used to make foams having increased crosslink density to improve dimensional stability or chemical resistance. Therefore, a higher isocyanate index, e.g., 150 to 200, was used to incorporate isocyanurate linkages in rigid urethane foams. 

The addition of flame retardants, either additive or reactive types, can provide flame-retardant foams having low flame spread or surface flammability, but flame retardants do not improve the temperature resistance of these foams because the thermal stability or the dissociation temperature of the urethane linkage is relatively low and unchanged by the addition of flame retardants, i.e., the linkage dissociates at about 200°C to form the original components in polyol and polyisocyanate. The dissociation can result in further decomposition of polyol and polyisocyanate into low-molecular-weight compounds at elevated temperatures. For these reasons urethane foams are not temperature-resistant nor thermally stable. 

The advantages of these aromatic polyesters are lower cost than conventional polyether polyols, better flame retardance, and high-temperature resistence. However, their disadvantages include compatibility problems with chlorofluorocarbons and quality deviations in viscosity and hydroxyl values. In order to improve the compatibility problems, amine-based polyether polyols have been blended. 

Reactive polyols which contain halogen groups, phosphorus, or both, are offered by a number of suppliers for flame-netardant urethane-foam applications. These materials can be used alone, or with other flame retardants as synergists. Although reactive flame retardants may appear to be more costly initially, in the long run they may be found to be less expensive than the additive types (31). 

Buszard and Dellar in the UK compared three polyurethane foams using the BS4735 horizontal bum test and the DIN 4102-B2 vertical bum test covering a wide range of polyol types. The flame retardants used were as follows (39) ... 

There are two main types of flexible foam slabstock polyester-based foams, used for technical and high elongation grade laminates or textiles and polyether-based foams used for upholstery, HR, and flame retardance. By varying the type of polyester or polyether, the length of the polyol chain, the structure and size of the hard segment, and the amount of blowing, the foam can be tailored to meet the required specifications. ... 

A special group of polyols for rigid PU foams is the group of reactive flame retardant polyols containing phosphorus, chlorine or bromine, which confer fire resistance to the resulting PU (Chapter 18). 

All the triazinic polyols discussed here, have a high thermostable triazinic structure and a high nitrogen content, which gives inherently flame retardant, rigid PU foams [24]. 

The reactive flame retardants are generally polyols containing halogens and/or phosphorus [1-11], The presence of nitrogen in the structure of reactive flame retardants always improves the flame retardancy, as mentioned previously [1, 4, 14, 16]. 

These polyols called flame retardant polyols, have terminal hydroxyl groups, react with polyisocyanates in the process of PU synthesis and are chemically inserted in the PU structure. The reactive flame retardants being chemically linked in the PU chains assure a permanency of flame retardancy [5, 6, 11]. 

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