Sodium Calcium Phosphate Fibers

The first preparations of calcium polyphosphate fibers were orchestrated following a preplanned approach that was altered as results demanded. Conversely, sodium calcium polyphosphate fibers were discovered. Rather than following a calculated scientific logic we were exploring. We were prospecting a phase diagram around calcium metaphosphate compositions. This discovery was blind luck and it was not obvious that these crystals contained fibers until they were milled for analyses. 

Once the fibrous nature of this system was obvious, work was then initiated to improve the properties of these fibers. The procedure for making laboratory samples is outlined below as described in the patent. 

When laboratory work demonstrated that it was possible to prepare [NaCa(P03)3]n consistently, with uniform properties, work was turned to other venues. Platinum dishes were reasonably good containers in which to prepare laboratory samples, but it was obvious that an industrial process could never withstand the expense of platinum-plated equipment. 

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If the calcium phosphate fibers grown from ultraphosphate melts are slurried with a solution of sodium ethylene diamine tartaric acid the calcium crystals can be converted to a sodium phosphate glass that dissolves very slowly yielding very long chains. 

Three possibilities exist when a salt with a polyphosphate x-ray pattern crystallizes from a melt containing an excess of phosphorus pentoxide. 1. The phosphorus pentoxide is incorporated into the polyphosphate chains converting the chains to crystalline ultraphosphates. 2. The excess phosphorus pentoxide does not enter the polyphosphate crystal structure, but forms an amorphous phase between the crystals of polyphosphate. The amorphous phase is not detected by x-ray. 3. The excess phosphorus pentoxide does not enter the crystal structure of the polyphosphate, but forms as an ultraphosphate between the crystalline polyphosphate crystals as a eutectic phase. (This latter case is precisely what happens in the calcium sodium ultraphosphate system from which calcium phosphate fibers are grown (21) and the phase diagram of Hill et. al. is obeyed as it should be.)... 

The measured values for phosphate fibers compare very favorably with other fiber systems of common use. It is interesting that sodium calcium polyphosphate fibers have a higher tensile strength than calcium polyphosphate fibers. Fiber diameter could account for this difference, or that anions of calcium polyphosphate are more linearly packed in the crystals. Kevlar is a fiber that has been extensively used in nonasbestos brakes for automobiles and it performs well. 

I had hardly demonstrated that useful sodium and calcium phosphate fibers could be made before their safety was questioned. The first to question their safety was a business school type, vice president. He was in the audience when I made the first public disclosure of phosphate fibers within our company. 

Calcium polyphosphates, [Ca(P03)2] , crystals grown in sodium ultraphosphate melts in the preparation of fibers, were grown in a manner similar to how [KPOaln is grown in melts of ultraphosphoric acid. These systems yield salts referred to as cross-linked Kunol s salts. Since potassium Kurrol s salts can be easily and quickly solubilized in water containing some diverse ions, such as sodium, potassium phosphates are much more easily studied. Potassium Kurrol s... 

The future of phosphate fibers should be very bright when the patents on the composition expire in 1999. In the author s mind there has never been a safety issue with phosphate fibers or any other inorganic phosphate that does not contain a toxic cationic or anionic function. Phosphates such as sodium, potassium, calcium, magnesium, ammonium, and hydrogen have never caused a problem of any type with perhaps the exception of renal stones. In this case it may be more of a condition than the cause of a condition. Urine is known to be saturated with respect to calcium phosphates. Some threshold agent or other mechanism that is poorly understood keeps kidneys from becoming completely calcified even in the healthiest of persons. 

Binding of iron by dietary fiber is strongly inhibited by ascorbic acid, citrate, cysteine, EDTA or phytate in concentrations as lew as 100 >uMols/Liter (A3). The inhibitors have the common property of being able to form soluble complexes with iron. The decarbox-ylic amino acids and their amides inhibit binding moderately as do lysine and histidine. Other amino acids either do not interfere with binding of iron fiber or do so only weakly. Calcium (as acetate) and phosphate act as moderate inhibitors. The detergents sodium lauryl sulfonate or cetyltrimethylammonium bromide had no effect on iron binding by fiber (A2). 

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