Abstract:
Alkylene-bridged diphosphate compounds can be used to modify, namely, reduce, the viscosity of fluid flame retardants (polybrominated aryl oxides, oligomeric phosphate esters, etc.) which are useful in flame retarding polyurethane and thermoplastic compositions.

Description:
This application is a continuation of Ser. No. 08/322,879 filed Oct. 13, 1994 now abandoned, which is a continuation-in-part of Ser. No. 07/436,285 filed Nov. 14, 1989 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Polyurethane foams, engineering thermoplastics coatings and elastomers are commonly admixed with flame retardants to achieve the desired degree of flame retardancy for the final material desired. Pumpable fluid (or liquid) flame retardant compositions are a preferred class since such pumpable formulations are needed in environments where automation and machine mixing of the various components are used. Examples of the chemical classes for such fluid or liquid flame retardants include brominated aryl flame retardants, such as polybromodiphenyl oxide, and various viscous organophosphorus flame retardants such as the oligomeric phosphate esters, such as the chlorinated oligomeric phosphate esters (e.g. FYROL 99 brand) and the reaction product of 2-chloro-1-propanol phosphate (3:1) with ethylene oxide and phosphorus pentoxide (FYROL PCF brand), and the aromatic oligomeric phosphate esters such as those containing an arylene bridging group derived from a diol such as bisphenol A, hydroquinone or resorcinol. 
     High viscosity in such fluid or liquid flame retardant compositions can be disadvantageous since it makes the pumping and movement of such compositions more difficult thereby complicating manufacturing operations. It can also hinder the flow of thermoplastic polymers containing such a viscous flame retardant. For example, it is known that polybrominated diphenyl oxide flame retardants are very viscous. U.S. Pat. No. 4,746,682 to J. Green indicates that either alkyl diphenyl phosphates or alkylated triaryl phosphates can be used to achieve blends having acceptably low viscosity as compared to the polybrominated aryl flame retardant itself. Copending U.S. Ser. No. 215,406, filed Mar. 14, 1994, describes the use of triphenyl phosphate as a viscosity reduction additive for viscous flame retardants. However, the relatively low volatility of the triaryl phosphates makes them unsuitable for certain applications where high processing temperatures may cause juicing. 
     SUMMARY OF THE INVENTION 
     It has now been found that an alkylene-bridged diphosphate compound is an effective viscosity modifying, namely, reducing agent in the aforementioned types of liquid, but viscous, flame retardant compositions. This type of material is less volatile than a triaryl phosphate compound. It also has a higher phosphorus content resulting in an increased flame retardancy efficacy as compared to a triaryl phosphate compound. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The terminology “alkylene-bridged diphosphate compound” is to be understood to encompass monomeric and low oligomeric species of the formula 
                        
 
Where R is aryl, such as unsubstituted phenyl, n is a number ranging from 0 to about 5, and R 1  is alkylene of from 1 to 8 carbon atoms.
 
     The level of use of the diphosphate viscosity modification additive of the present invention with a particular flame retardant will depend upon its initial compatibility or miscibility with the flame retardant component whose viscosity is initially high and in need of reduction. The level of diphosphate to use is also dependent upon the ultimate viscosity that is desired for the composition containing it. Generally, the amount of diphosphate that needs to be added will range from about 5% to about 80%, by weight of the fluid or liquid flame retardant whose viscosity is to be reduced, preferably from about 5% to about 50%, more preferably from about 5% to about 30%. 
     The liquid flame retardants to which the instant invention can be added include polybrominated diphenyl oxide and aromatic oligomeric phosphates (e.g., resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), poly(resorcinol phenylphosphate), and high molecular weight chloroalkyl phosphates. 
     The aromatic bisphosphates to which the above-described alkylene-bridged diphosphate species can be added are of the same formula given above with the exception that R 1  is derived from an arylene diol, such as resorcinol, bisphenol A, or hydroquinone, and n is generally from 0 to about 15. The diphosphate viscosity reducing additive of the instant invention can also be used in similar amount with flame retardant compositions which contain oligomeric phosphate esters as the sole or predominant component. Generally speaking, it has been found that up to about 50%, by weight of the alkylene-bridged diphosphate compound, based on the weight of the entire composition, can be used in such systems in preferred embodiments. 
     The instant invention allows for the obtaining of low enough viscosities to achieve pumpable flame retardant compositions which are required to satisfactorily process flexible and rigid polyurethane foams, for example. Easier machine mixing and miscibility are achieved by bringing the viscosities of the components closer and preferably lower. Coating and elastomers also require low viscosities for better flowability and processing. 
     The present invention is illustrated by the Examples which follow. 
     EXAMPLES 
     A series of compositions were tested in regard to their viscosity at 23° C.±0.5° C. in a Brookfield viscometer. The Table given below shows the results which were obtained. (The viscosity of the additives responsible for viscosity reduction were as follows: neopentyl glycol bis(diphenylphosphate)-549; ethylene glycol bis(diphenylphosphate)-319; and propylene glycol bis(diphenylphosphate)-367.5. 
     
       
         
               
               
             
               
               
               
             
           
               
                 TABLE 
               
               
                   
               
               
                 Composition - Amount (wt %) 
                 Viscosity (cps) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Bisphenol A bis(diphenyl phosphate) 
                 100% 
                 20,900 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 90% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 10% 
                 12,000 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 80% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 20% 
                 8,292 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 50% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 50% 
                 2,616 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 90% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 10% 
                 11,700 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 80% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 20% 
                 6,548 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 50% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 50% 
                 1,752 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 80% 
               
               
                 Propylene glycol bis(diphenylphosphate) 
                 20% 
                 7,380 
               
               
                 Bisphenol A bis(diphenylphosphate) 
                 50% 
               
               
                 Propylene glycol bis(diphenylphosphate) 
                 50% 
                 2,052 
               
               
                 Resorcinol bis(diphenyl phosphate) 
                 100% 
                 691 
               
               
                 Resorcinol A bis(diphenylphosphate) 
                 90% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 10% 
                 670.5 
               
               
                 Resorcinol A bis(diphenylphosphate) 
                 90% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 10% 
                 636 
               
               
                 Resorcinol A bis(diphenylphosphate) 
                 90% 
               
               
                 Propylene glycol bis(diphenylphosphate) 
                 10% 
                 666 
               
               
                 Pentabromo Diphenyloxide 
                 70% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 30% 
                 8,670 
               
               
                 Pentabromo Diphenyloxide 
                 50% 
               
               
                 Neopentyl glycol bis(diphenylphosphate) 
                 50% 
                 2,090 
               
               
                 Pentabromo Diphenyloxide 
                 70% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 30% 
                 5,090 
               
               
                 Pentabromo Diphenyloxide 
                 50% 
               
               
                 Ethylene glycol bis(diphenylphosphate) 
                 50% 
                 1,225 
               
               
                 Pentabromo Diphenyloxide 
                 70% 
               
               
                 Propylene glycol bis(diphenylphosphate) 
                 30% 
                 5,590 
               
               
                 Pentabromo Diphenyloxide 
                 50% 
               
               
                 Propylene glycol bis(diphenylphosphate) 
                 50% 
                 1,395 
               
               
                   
               
             
          
         
       
     
     The foregoing data is presented for purposes of illustrating certain embodiments of the present invention and, for that reason, should not be construed in a limiting sense. The scope of protection sought is set forth in the claims which follow.