| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 10.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 24.10.00 |
| PATENT TITLE |
Phosphation reagent |
| PATENT ABSTRACT |
The invention relates to a process for producing a unique phosphation reagent and to a simple, single-stage process utilizing is reagent to produce alkyl phosphate esters having high monoalkyl phosphate content in combination with low dialkyl phosphate, trialkyl phosphate, phosphoric acid and residual alcohol. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 21.01.99 |
| PATENT REFERENCES CITED |
Research Disclosure, vol. 354, p. 671 (1993). G. Imokawa, J. Am. Oil Chem.Soc., 55,839 (1978). G. Imokawa, J. Am. Oil Chem.Soc., 56,604 (1979). A. Nelson & A. Toy, Inorg. Chem., 2,775 (1963). T. Kurosaki et al., Oil Chemistry, 39 (4), 259 (1990). T. Glonek, et al, J. Am.Chem.Soc., 92, 7214 (1970). T. Glonek, et al, Inorg. Chem., 13, 2337 (1974). T. Glonek, et al, Phosphorus 1975, 157. T. Glonek, et al. J. Am. Chem. Soc., 97, 206 (1975). T. Glonek, et al, Phosphorus and Sulfur 3, 137 (1977). M. Watanabe, et al, Mem. Chubu Inst. Tech., 81 (1983). T. Kurosaki, et al, Comun.Jorn.Com.Esp.Deterg., 19, 191 (1988). T. Khwaja, et al, J. Chem. Soc. (C) 1970), 2092. T. Kurosaki, et al, Oil Chemistry, 39 (4), 250 (1990). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
Having set forth the general nature and some examples of the present invention, the embodiments in which an exclusive property or privilege is claimed are defined as follows: 1. A composition produced by intimately mixing and exclusively reacting an effective amount of phosphoric anhydride with from about 75 weight % to about 117 weight % polyphosphoric acid (54 weight % to 85 weight % P.sub.4 O.sub.10) to produce a uniform slurry or paste having an effective equivalent polyphosphoric acid weight percent of from about 118 to 125. 2. The composition of claim 1 wherein the effective equivalent weight percent of polyphosphoric acid is from about 119 to 124. 3. The composition of claim 1 wherein the effective equivalent weight percent of polyphosphoric acid is from about 121 to 123. |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION This invention relates to a unique phosphating agent and to a simple, reliable process utilizing this agent to produce phosphate ester compositions which have high monoalkyl phosphate content in combination with low dialkyl phosphate, trialkyl phosphate, phosphoric acid and residual alcohol. DESCRIPTION OF THE PRIOR ART The superior performance of fatty alcohol based anionic phosphate esters enriched in monoalkyl ester content relative to dialkyl content has been demonstrated, particularly with respect to surfactant esters used in cosmetic and personal hygiene cleansers. These high monoalkyl phosphate surfactants exhibit a unique combination of good detergency and low skin irritancy, especially in comparison to alkyl sulfate or alkyl sulfonate surfactants (G. Imokawa, et al., U.S. Pat. No. 4,139,485, Feb. 13, 1979; G. Inokawa, J. Am. Oil Chem. Soc. 56, 604 (1979)). In a given alkyl phosphate mixture, other important properties such as water miscibility, Krafft point and foam production also are a function of the relative amounts of monoalkyl and dialkyl phosphate. As the dialkyl phosphate content increases, the solubility, foaming ability, and detergency decrease and the Krafft point increases. The desirable range for a "monoalkyl" phosphate composition has been defined to be wherein the ratio of monoalkyl to dialkyl phosphate is at least 80:20 weight percent (U.S. Pat. No. 4,139,485). Acceptable performance was found at 70:30, and relatively little additional improvement was obtained above 90:10. Typical phosphation processes do not produce product mixtures with the high monoalkyl phosphate together with the low dialkyl phosphate, low phosphoric acid and low residual alcohol contents necessary to obtain the above advantages. The two commonly used phosphating agents produce two extremes in the compositional range. In one case, polyphosphoric acid, commercially available as 115% phosphoric acid (also described as 83 weight percent phosphoric anhydride, P.sub.4 O.sub.10) reacts with alcohols to produce a mixture of high monoalkyl phosphate and low dialkyl phosphate but also high phosphoric acid. This is expected since the polyphosphoric acid consists essentially of linear chains varying from one to more than fifteen phosphorus atoms connected by oxygen anhydride linkages. Although the alcoholysis reaction is complex because it involves many intermediates of differing chain lengths and even cyclic structures, ultimately one molecule of phosphoric acid would theoretically be produced from the "tail-end" of each chain or alternatively, the amount of phosphorus remaining as H.sub.3 PO.sub.4 would be equal to 1/n wherein n equals the average polymer chain length (F. Clarke and J. Lyons, J. Am. Chem. Soc. 88, 4401, (1966)). On this premise, the amount of phosphoric acid which would be produced from the chain ends by complete alcoholysis of a sample of an approximately 117% polyphosphoric acid was calculated to be 23.2 mole percent. Reaction of simple alcohols with an equimolar amount of 117% polyphosphoric acid was reported to produce from 21.0 to 23.8% orthophosphoric acid (F. Clarke and J. Lyons, op. cit.). An excess of alcohol was necessary to drive the reaction to completion. Similarly, reaction of an excess of lauryl alcohol with 115% polyphosphoric acid at 70-83.degree. C. for 15 hours, then to 94.degree. C. for four hours, produced a very viscous oil which solidified upon standing, (m.p. about 80.degree. C.), with no residual pyrophosphates and an orthophosphate composition of 23 mole percent phosphoric acid, 73% monolauryl phosphate and 4% dilauryl phosphate. Expressed as weight percent of total phosphorus products, this would be 9.6% phosphoric acid, 83.0% monolauryl phosphate and 7.4% dilauryl phosphate, to note how the numbers are changed by the molecular weight differences. To produce a monoalkyl phosphate without dialkyl phosphate contamination theoretically could be done from pyrophosphoric acid (A. Nelson and A. Toy, Inorg. Chem., 2, 775, (1963)). Alcoholysis would yield one mole of phosphoric acid and one mole of monoalkyl phosphate (also F. Clarke and J. Lyons, op. cit.). Reaction of lauryl alcohol in a molar amount equal to the pyrophosphoric acid plus tripolyphosphoric acid in 105% polyphosphoric acid at room temperature to 65.degree. C. over a two hour period followed by fourteen hours at 71-72.degree. C. produced a creamy, very viscous mass which contained about 69 mole % phosphoric acid, 20 mole % monolauryl phosphate and 11% pyrophosphate intermediates. Addition of excess alcohol to the mass at room temperature followed by heating to 52.degree. C. over three hours to complete the conversion of the pyrophosphates gave a solution in which the molar ratios were 76% phosphoric acid, almost 24% monolauryl phosphate, and only a trace of dilauryl phosphate. The theoretical distribution based on the original 105% polyphosphoric acid composition was 73% phosphoric acid and 27% lauryl phosphate. Because of the relatively low reactivity of the pyrophosphate intermediates with the alcohols, an excess of one of the reactants is usually used. U.S. Pat. No. 3,235,627 discloses that an equivalent ratio of 1.2-4.0 polyphosphoric acid per mole alcohol produces a mixture of 85-100% monoalkyl phosphates. In this patent, the optimum ratio per mole alcohol is 1.0 to 1.3 moles polyphosphoric acid, expressed as 82-84% (by weight) P.sub.2 O.sub.5 (or P.sub.4 O.sub.10 ; also equivalent to about 115% weight percent polyphosphoric acid). This '627 patent notes however that a large percentage of unreacted alcohol will remain, i.e. incomplete phosphation will occur, if an excess of this polyphosphoric acid is not used. For instance, an equivalent amount (0.5 "mole" expressed as P.sub.2 O.sub.5 or 0.25 P.sub.4 O.sub.10 per mole alcohol) produced only a 56% conversion; hence 44% residual alcohol. This patent provides references to the art which practice the use of excess alcohol, claiming that undesirable dialkyl phosphates are produced. Additionally, T. Kurosaki et al., Comun. Jorn. Com. Esp. Deterg. 19, 191 (1988) states that monoalkyl phosphate can be formed with little formation of dialkyl phosphate, but also that polyphosphoric acid was required in excess to complete the reaction. In the graphical representation of his data, FIG. 14, p. 204, which covers the range of 100 to 115% polyphosphoric acid, he shows that the most concentrated acid evaluated, about 113%, produces only 60% alcohol conversion and requires a two-fold molar excess to achieve about 95% conversion. He concludes that in order to manufacture high purity monoalkyl phosphate, the removal of the resulting excess phosphoric acid coproduct from the mixture is required. It is clear that the "polyphosphoric acid" reagents used by this reference were of lower effective equivalent polyphosphoric acid weight percent than that of the reagents of the instant invention which have a minimum of 118 weight percent. A more recent, comprehensive study of alcohol phosphation by ortho- and polyphosphoric acids similarly shows the limitations of this approach, but considering the value of the high monoalkyl phosphate compositions, commercial processes have been developed based upon 115% polyphosphoric acid alone as the phosphation reagent (T. Kurosaki et al. Oil Chemistry, 39(4),259, (1990)). The large amount of phosphoric acid thus unavoidably produced in processes based on the common, approximately 115% polyphosphoric acids, is an undesirable coproduct which is particularly troublesome in cosmetic products, electrolyte solutions, emulsions and in the spinning of synthetic fibers. Purification methods have therefore necessarily been developed to partition the acid and the organophosphate into layers which can then be separated (K. Aimono et al. Japan Kokai Tokyo Koho JP 03,188,089, Aug. 16, 1991; T. Kurosaki et al., U.S. Pat. No. 4,670,575, Jun. 2, 1987; G. Uphues et al. U.S. Pat. No. 4,874,883, Oct. 17, 1989)). The other extreme of the product composition is produced by the use of phosphoric anhydride, P.sub.4 O.sub.10. In contrast to 115% polyphosphoric acid, a viscous liquid, P.sub.4 O.sub.10 is a white powder which is highly reactive with alcohols even at room temperature. It is a powerful dehydrating agent and relatively insoluble in most common organic solvents except those with which it reacts. If in excess or not adequately dispersed in the reaction liquor, it forms undesirable by-products, e.g. i) trialkyl phosphates from the primary alcohol and its dialkyl phosphate by dehydration and/or ii) darkly colored products resulting from the charring of the alcohol that was absorbed into the slowly dissolving, large chunks formed by agglomeration of the powder. Under favorable conditions of good mixing and cooling with precise control of adventitious moisture and reactant ratios, the reaction of P.sub.4 O.sub.10 with alcohols still proceeds through a complex series of intermediates. Possible structures for these condensed phosphates have been prepared and characterized (T. Glonek et al., J. Am. Chem. Soc. 92, 7214 (1970); Inorg. Chem. 13, 2337 (1974); Phosphorus 1975, 157; J. Am. Chem. Soc. 97, 206 (1975); and Phosphorus and Sulfur 3, 137 (1977)). A theoretical sequence is outlined in FIG. 1. The problems with any attempt to control selectivity arise from the fact that each polyphosphate intermediate has its characteristic solubility and reaction rate. Branched phosphates, with three P--O--P bonds to the central phosphorus, are considerably more reactive than linear ones having two P--O--P bonds. The simple pyrophosphate, having only one P--O--P bond, is the least reactive polyphosphate. In addition, hydrolysis studies of the simple acids have shown that the acyclic tetra- and tripolyphosphates are more reactive than their monocyclic precursors, (M. Watanabe et al., Mem. Chubu Inst. Tech., 81 (1983)). In the presence of other hydroxy functional species such as adventitious water or a mixture of alcohols, the product distribution is a function of the concentration, (which is related to solubility), and the competitive reaction rates of each phosphate intermediate with each hydroxy compound. These conditions change throughout the course of the reaction as the more reactive species are preferentially consumed and their relative concentrations decrease. The sequence in FIG. 1 predicts that an equimolar mixture of monoalkyl phosphate (MAP) and dialkyl phosphate (DAP) would be formed under ideal conditions and, in fact, reaction of P.sub.4 O.sub.10 with a two fold stoichiometric excess of lauryl alcohol, i.e. 12 moles per P.sub.4 O.sub.10, under standard laboratory conditions produced a mixture of phosphates in a molar ratio of about 0.509 MAP:0.485 DAP:0.007 H.sub.3 PO.sub.4. A third option, which is the direct esterification of phosphoric acid, is not practical because of its low reactivity, and the difficulty realized in removing water from the polar and increasingly viscous product mixture. The high temperatures of at least 120.degree. C., reduced pressure of 300 torr or less, preferably less than 50 torr, and/or the use of azeotropic solvents which are used to drive the reaction to completion also produce the undesirable dialkyl phosphates and still leave undesirable levels of unreacted phosphoric acid (T. Kurosaki, et al., Oil Chemistry 39(4)259, (1990)). Combination of an orthophosphoric acid with an alcohol under less than anhydrous conditions (specifically as 85% orthophosphoric acid) without less than atmospheric pressure, an azeotropic agent or temperatures considerably above the 100.degree. C. water boiling point would not result in an esterification reaction. Similar product compositions may be obtained more conveniently by use of the aforedescribed use of polyphosphoric acid or phosphoric anhydride. Several attempts to reduce the tendency of phosphoric anhydride to produce dialkyl phosphate coproduct have been reported. Early work postulated that in the optimum case, substitution of two moles of water for two of the six moles of alcohol required to completely convert P.sub.4 O.sub.10 to orthophosphates would produce essentially four moles of the monoalkyl phosphate. (Sanyo Kasei Kogyo K. K., Japanese Patent Publication 41-14416 (1966)). As mentioned above, the reaction sequence is complex. Although high monoalkyl to dialkyl molar ratios of up to 94:6 were reported, substantial conversion of phosphoric anhydride to phosphoric acid also occurred, 60 mole percent, in this example, at the upper end of the "suitable range" of water content, and generally, excessively high levels of phosphoric acid throughout the series. The unreacted alcohol content was not reported, but under the stated conditions of stoichiometry, it could be presumed to be equal to the moles of phosphoric acid minus the moles of dialkyl phosphate or about 58 mole percent. The author clearly stated that the addition of water to the phosphoric anhydride followed by reaction with the alcohol was an unsuitable alternative. Almost simultaneously, another case (Daiichi Kogyz Seiyaku Co., Ltd., Japanese Patent Publication 42-6730 (1967)) reported the similar use of 85% phosphoric acid (0.960 mole water per mole H.sub.3 PO.sub.4). This strategy, however, was to react the orthophosphoric acid and the phosphoric anhydride separately with the alcohol apparently in the presence of the water introduced with the 85% phosphoric acid. The details are limited, but duplication of the examples clearly showed that the 85% phosphoric acid did not react with the alcohol under the stated conditions. Complete analysis of the reaction mixtures during and at the completion of the experimental sequence farther revealed that the conversion was not complete at the end of the stated reaction period, but rather was finished in the subsequent, apparently necessary work up procedures for separation and characterization of the monoalkyl ester product. Other products were not quantified. The quantities of monoalkyl phosphate found upon duplication of the examples in the laboratory were significantly lower than the high yields of monoalkyl phosphate reported. A more recent study more precisely determined the affect of the ratios between water, alcohol and phosphoric anhydride on the phosphate product composition, again with particular emphasis upon the monoalkyl and dialkyl phosphate ratio (T. Kurosaki, et al. Comun. Jorn. Com. Esp. Deterg. 19, 191 (1988)). High resolution phosphorus-31 nuclear magnetic resonance spectroscopy was used to quantify the phosphorus species during the later stages of the reaction, after the phosphoric anhydride had all dissolved, and in the final mixtures. The 85% and 105% phosphoric acids (separated into their percent "water" and "P.sub.4 O.sub.10 " content for calculation purposes) were also evaluated. The 105% acid, the lowest concentration of phosphoric acid which is free of residual water (i.e. anhydrous), was found to generally produce less favorable results than the use of water as a diluent in the acid or alone. Even under what appeared to be the most favorable ratios and method, the residual phosphoric acid content was still over 15 mole percent of the total phosphorus species and the monoalkyl phosphate leveled off at about 60 mole percent. The residual alcohol level was not reported. The use of phosphorus oxychloride is not a good option because it is not selective; it produces three moles of hydrogen chloride per mole of phosphate, which is highly corrosive and must be scrubbed from the reactor emissions to prevent environmental pollution; and it produces an undesirable alkyl chloride by-product (T. Kurosaki et al., U.S. Pat. No. 4,350,645, Sep. 21, 1982). Even within the limitations of the above phosphation agents, it is possible to obtain desirable intermediate product mixtures by judicious combinations of selected phosphation agents, alcohol and water in staged reaction sequences. For example, the addition of one mole of P.sub.4 O.sub.10 to four moles of an unsaturated alcohol followed by a digestion period, then addition of two moles water and continued heating to completion was reported to yield a high monoalkyl phosphate containing a polymerizable vinyl group for applications in which the presence of any dialkyl phosphate would promote crosslinking of the polymer, and thus be very detrimental (T. Hasegawa, U.S. Pat. No. 3,686,371, Aug. 22, 1972). A more complicated example involves preparation of a phosphate ester mixture by a standard reaction sequence, and then use of the resulting mixture as the reaction medium to which additional phosphoric anhydride, alcohol, and water are added. The intent is to produce the symmetrical dialkyl pyrophosphate as the major product, then to hydrolyze it to the monoalkyl phosphate in the final step (F. Via et al., U.S. Pat. No. 4,126,650,Nov. 21, 1978). ##STR1## The best results were obtained by multiply staging the reagent addition and heel production events. That is, to the initially formed heel, the remaining phosphoric anhydride and alcohol are alternately added in four equal aliquots at the reaction temperature of 75-90.degree. C. The mixture is then digested at 85.degree. C. for two hours; water and 30% hydrogen peroxide added; and the reaction completed at 80.degree. C. to yield a final product containing over 80 weight % monoalkyl acid phosphate (based on analysis by titration; phosphorus-31 nuclear magnetic resonance spectroscopy is now more accurate and precise). The primary study (T. Kurosaki et al., U.S. Pat. No. 4,350,645, Sep. 21, 1982) also utilized a two stage process but in direct opposition to the above two examples. The '371 process, in fact, is the same as the Method 2 reported to be inferior by this principal author in his 1988 publication (vide supra). The purpose of the first stage in '645 is to combine an equimolar mixture of water and alcohol with phosphoric anhydride (two moles each, per mole of P.sub.4 O.sub.10) to prepare an intermediate composition, i.e. a heel. This monoalkyl pyrophosphate heel is then reacted with the remaining two ##STR2## moles of alcohol to convert the pyrophosphate intermediates to orthophosphates. The best product ratios realized for lauryl phosphate, about 0.821:0.081:0.099 MAP:DAP:H.sub.3 PO.sub.4 (molar) and 0.829:0.134:0.037 (weight) (MAP:DAP weight ratio, 86.1:13.9) for this simplified two step process are comparable to the multiply staged addition process, considering the accuracy of the titrimetric analysis, (U.S. Pat. No. 4,126,650) and are superior to the extant single stage processes. Further specific evidence was provided by Comparative Example 1 in this case. The lauryl alcohol phosphation by 85% phosphoric acid and P.sub.4 O.sub.10 is essentially the same as the Example 1 in 42-6730. This more completely defined composition, however, is reported as 66.2 mole % monoalkyl phosphate, 18.9% dialkyl phosphate and 14.9% phosphoric acid in contrast to the "yield of dodecyl monophosphate: 94.7%" reported in 42-6730. The above summary essentially describes the state of the existing technology for the preparation of enriched monoalkyl phosphate compositions by direct phosphation and the desirable properties of these compositions, especially for mixtures with MAP:DAP weight ratios of 80:20 or greater. Other, even more sophisticated methods are known which involve the preparation of intermediates in multiple-step processes which have blocking groups that must be removed after the intermediates are used to phosphate the alcohol substrate. The more selective blocking groups would be derived from phenol, substituted phenols, catechol, or substituted triazoles (H. Mori et al., U.S. Pat. No. 5,254,691, Oct. 19, 1993; T. Khwaja et al. J. Chem. Soc. (C) 1970, 2092; and the references cited therein). However, these processes are too expensive to be viable for most commercial product applications. SUMMARY OF THE INVENTION The present invention relates to the discovery of a unique phosphating agent which can be used to produce in a single step, solventless process, phosphate ester compositions wherein the weight ratio of monoalkyl acid phosphate to dialkyl acid phosphate is greater than 80:20, concomitant with low levels of free phosphoric acid and residual alcohol. The optimum phosphation reagent composition is from about 121-123%, expressed as an effective equivalent percent of polyphosphoric acid. The reagent is prepared by the intimate blending and exclusively reacting phosphoric anhydride (P.sub.4 O.sub.10) with phosphoric acid (H.sub.3 PO.sub.4) to produce a uniform slurry or paste. The phosphate esters are formed by contacting the reagent paste or slurry with the organic alcohol (ROH) with sufficient stirring and temperature control to dissolve the reagent in the alcohol and carry the reaction to completion. The primary phosphate ester products of the present invention have the general formula: ##STR3## wherein R is as defined herein. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 describes the theoretical step-wise reaction of an alcohol with phosphoric anhydride (P.sub.4 O.sub.10). DETAILED DESCRIPTION OF THE INVENTION A new process has been discovered which produces enriched monoalkyl phosphate compositions in a single step which avoids the disadvantages associated with the processes of the prior art. A unique phosphating agent is utilized which is a direct derivative of phosphoric anhydride in which phosphoric acid is used as a blocking group. The new agent may be prepared quantitatively under a wide range of times and temperatures and is stable to storage under anhydrous conditions. It dissolves more readily than phosphoric anhydride, is pumpable when warmed to reduce its viscosity, and can be added more rapidly to the alcohol without the highly exothermic heat of reaction problems characteristic of phosphoric anhydride. In contrast to the use of the commercially available 115-117% polyphosphoric acids, it is not necessary to use an excess of this phosphation reagent relative to the alcohol in order to achieve good conversion rates and low residual alcohol content. In fact, stoichiometrically equal amounts of alcohol and the phosphating reagent are most desirable. The phosphoric acid used as the blocking group is consumed in the process, hence does not contribute excessively to the residual amount. Consequently, the residual phosphoric acid concentration is comparable to that obtained by the most preferable, multi-staged processes previously described. With the process of the instant invention, in which monoalkyl to dialkyl phosphate weight ratios greater than 80:20 are achieved, the weight percents of the residual alcohol and phosphoric acid are individually each less than 6%. The action of this reagent is postulated to be as follows, for the simplest case of orthophosphoric acid as the blocking group. ##STR4## These initial reactions are similar to those already shown in the theoretical P.sub.4 O.sub.10 reactions with alcohol in FIG. 1 in which the R group would represent H.sub.2 PO.sub.3 --. The same principles apply but with important limitations. The above series of reactions could continue, particularly if sufficient phosphoric acid were available, or by further reaction of the --OH functionalities on the blocking phosphate groups, until the more reactive branched phosphates ultimately have been converted to linear P--O--P structures. A very complex mixture of intermediates is likely formed. It is, therefore, important to limit the amount of phosphoric acid to a molar ratio of two per P.sub.4 O.sub.10 molecule (or two phosphorus equivalents of phosphoric acid to the four phosphorus equivalents in P.sub.4 O.sub.10). Substantially more phosphoric acid would convert the reactive branched intermediates to components of simple polyphosphoric acid, and substantially less would allow an undesirably high level of the highly reactive tetrahedral P.sub.4 O.sub.10 and its first reaction product, the bicyclic phosphate, to remain. In essence, the latter two highly reactive phosphate species are converted to more controllably reactive intermediates, of which B and C are proposed as examples, and the relatively unreactive (under simple alcohol phosphation conditions) phosphoric acid is converted to more reactive polyphosphate intermediates. Since the phosphorus-oxygen-phosphorus anhydride bonds being broken are being compensated by formation of new phosphorus-oxygen-phosphorus bonds, the energy released in these transformations is primarily that from opening the strained P.sub.4 O.sub.10 and structure A polycyclic rings. These reactive intermediates are also converted in a stable, inorganic, phosphoric acid medium. Importantly, there are no organic compounds present, hence no opportunity for their P.sub.4 O.sub.10 induced decomposition products to be produced. This new phosphation reagent, represented empirically, but not exclusively as structures B and C, is in the form of a suspension of small, "fluffy", white particles in a viscous, clear matrix. It is stirrable above room temperature and therefore pumpable. It dissolves much more readily than P.sub.4 O.sub.10, even though the particle size is much larger, and does not produce the hard, slowly soluble, black chunks which are encountered when P.sub.4 O.sub.10 itself is mixed into a polyethoxylated alcohol. Since much of the ring strain energy has been released, the heat of reaction is primarily that resulting from conversion of the phosphorus-oxygen-phosphorus anhydride bonds to the carbon- oxygen-phosphorus ester and the hydrogen-oxygen-phosphorus acid bonds. This staged release of energy is much easier to control on a commercial process scale and the better control allows minimization of undesirable by-products. The sequence of reactant addition to the reaction is not critical. For example, the alcohol can be added to the reactor containing the phosphation reagent or the phosphation reagent can be added directly to the alcohol. As is well known in the art, addition of alcohol to P.sub.4 O.sub.10 powder can result in a vigorous, potentially uncontrollable and hazardous reaction. Because of the transient nature of the initially formed phosphation reagent intermediates and the heterogenous nature of the sample, characterization is very difficult (T. Kurosaki et al., Oil Chemistry 39 (4), 250 (1990)). The branched (trisubstituted) phosphorus centers, even in the non-bicyclic intermediates, would be expected to be of such reactivity that some might be converted to linear, disubstituted species by reaction with terminal --OPO.sub.3 H.sub.2 groups in the process of dissolving the sample in an inert solvent for analysis. However, an indication of the nature of this unique phosphation reagent is given by its phosphorus --31 nuclear magnetic resonance spectrum. For comparison, the principal component in 105 weight % polyphosphoric acid is phosphoric acid itself, 50 mole %, followed by pyrophosphoric acid, 40 mole %, and finally tripolyphosphoric acid, 10 mole % (including the end groups in the pyrophosphoric acid region). The spectrum for 115 weight % polyphosphoric acid still shows some orthophosphoric acid, 8 mole % at -0.5 ppm (relative to external 85% phosphoric acid); a more complex pattern at -13 to -14 ppm comprised of pyrophosphoric acid and the phosphates at the ends of the higher molecular weight chains, accounting for 46 mole % of the phosphorus species; and a similar pattern at -26 to -29 ppm, for the remaining 46 mole % internal chain phosphate groups. The spectrum of the novel reagent of this invention, in contrast, for a composition equivalent to 122.5 weight % phosphoric acid, shows only a trace of orthophosphoric acid; 11 mole % chain end and pyrophosphoric acid groups, at -13 to -14 ppm (only one P--O--P anhydride bond on the phosphorus); 87% internal chain and/or cyclic phosphate groups at -26 to -29 ppm (two P--O--P anhydride bonds on the phosphorus); and a small amount, 2 mole %, of branched phosphate groups (three P--O--P anhydride bonds on each phosphorus), at -37 to -39 ppm. Exhaustive interpretation would be difficult because of the wide range of possible structures. However, it is clear that signals characteristic of P.sub.4 O.sub.10 (-60 ppm) and phosphoric acid are essentially absent, signals for branched and pyrophosphates are minimal, and the bulk of the phosphorus species are of the most desired cyclic or linear anhydride type. The above comments and idealized reaction schemes are the inventor's attempt to theoretically explain the unusual and unexpected characteristics and properties of the reagents of this invention and are not meant to limit his discovery; the metes and bounds of which are determined by the scope of the claims. The process by which the phosphation reagent may be prepared is by contacting and exclusively reacting phosphoric anhydride (P.sub.4 O.sub.10) with phosphoric acid (H.sub.3 PO.sub.4) in a manner such that the two components may be blended into a uniform slurry or paste. The composition of the reagent of this invention is critical and exists within a narrow range. The phosphoric acid component used may be in a concentration range of from about 75% to about 117% (about 54% to about 85% P.sub.4 O.sub.10) and is conveniently available commercially in the range of from about 85% to about 115%. The phosphoric anhydride component used is of high purity and essentially anhydrous. The narrow phosphation reagent composition range is from about 118% to about 125% (expressed as an effective equivalent percent polyphosphoric acid) preferably from about 119%-124% and most preferably from about 121%-123%. Neither the time nor the temperature of the process for the manufacture of the phosphation reagent is critical. The time may range from the minimum required to obtain a uniform mixture in which the P.sub.4 O.sub.10 powder is thoroughly wetted by and blended with the phosphoric acid. The order of addition is not critical and can be adapted to the available equipment. The initial temperature may begin at ambient room temperature and range to 180.degree. C. as dictated by temperature control, stirring and pumping capabilities of the reactor and associated equipment. However, prolonged periods at elevated temperatures should be avoided. The phosphation reagent is stable to storage under reasonable conditions as long as anhydrous conditions are maintained in the storage container. Like all condensed (dehydrated) phosphoric acid materials, the phosphation reagent is hygroscopic and absorption of air moisture will result in a change in the composition. With respect to the use of the phosphation reagent in a phosphation esterification reaction, the alcohol may be added to the phosphation reagent or the reagent may be added to the alcohol within the mixing and temperature constraints of the reactor in accordance with standard practices well known in the art. It is not necessary to stage the reaction. Simple combination of the organic alcohol and the phosphation reagent in the proper stoichiometric molar ratio of four alcohols per equivalent mole of P.sub.4 O.sub.10, i.e. equimolar alcohol-phosphorus, is all that is required. A moderate excess of alcohol does not significantly change the MAP:DAP ratio and will contribute to a higher residual alcohol content in the final ester product. Use of significantly less than the stoichiometric amount of alcohol retards the dissolution rate and leaves an undesirably high level of pyrophosphate intermediates which would have to be converted by addition of additional alcohol and/or water. The organic hydroxy compounds which can be phosphated by the phosphation reagent of this invention are of the formula RO{C.sub.n H.sub.2n O}.sub.x H wherein R is selected from the group consisting of a saturated or unsaturated aliphatic C.sub.1 -C.sub.30 straight or branched carbon chain, a phenyl, a mono-,di-,or tri-substituted phenyl, a phenyl C.sub.1 -C.sub.6 alkyl and a mono-,di-,or tri-substituted phenyl C.sub.1 -C.sub.6 alkyl, wherein the phenyl substituent group(s) each have a total of 1 to 30 carbon atoms, and wherein each substitution can be a saturated or unsaturated straight or branched carbon chain, a phenyl, an alkyl phenyl, a phenyl alkyl, or an alkyl phenyl alkyl group; wherein n is from 2 to 4 and may be the same or different for each alkylene oxide unit; and wherein x if from 0 to 100. Examples of preferred alcohols are lauryl, myristol and cetyl alcohols and their ethoxylates; blends thereof; and tristyryl phenol ethoxylates. As noted above, the times and temperatures required for reacting the phosphation reagent with the alcohol can be easily determined by those skilled in the art and are principally a function of the mixing, pumping, and temperature control capabilities of the reactor and associated equipment. During the initial blending step, preferably, the initial temperature would be high enough to promote easy mixing and dissolution, i.e. from about ambient room temperature to about 80.degree. C., but could be the same as the cook temperature. Similarly, the cook temperature would be dictated by the need to obtain reasonably short cycle times without excessive discoloration of the product; typically from about 75.degree. C. to about 100.degree. C. Typical reaction times are from about greater than 3 to about 12 hours. Times from about 4 to about 7 hours are preferred, however, depending upon temperature, to prevent product degradation and color formation. During the reaction process, a point is reached at which the principal remaining phosphate intermediates are the relatively unreactive pyrophosphates, which together with the alcohol are at low concentration. Since little additional beneficial change in the composition can be achieved by prolonged heating, it is expedient to add a small amount of water to complete the conversion of the pyrophosphates to orthophosphates. Upon completion of this step, the liquor is customarily cooled slightly and hydrogen peroxide is added to reduce the color. The characteristics of the above processes for the formation of the phosphation reagent and its reaction with an alcohol to produce a phosphate ester product mixture, suggest that both processes would be adaptable to continuous processes run either concurrently or consecutively. The present invention will be explained in more detail with reference to the following non-limiting working examples. |
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