Process for producing phosphazene fire retardant

A process for producing fire retardant phosphonitrilate polymers by reacting phosphonitrilic halide with a hydroxyl compound such as an aliphatic or aromatic alcohol at not more than about 40.degree. C in the presence of an acid acceptor, such as pyridine, under conditions such that a relatively low concentration of the hydroxyl compound is present during the initial 1/2 to 3 hours of the reaction and the reaction conditions are maintained at from 20.degree.-50.degree. C for a period of 1/2 to 120 hours and, optionally, further heating the reaction mixture to a temperature of 40.degree.-80.degree. C for 1/2 to 81/2 hours. The phosphonitrilate polymers are suitable for fire retarding cellulosic materials such as regenerated cellulose, rayon and the like.

BACKGROUND OF THE INVENTION 
The reaction of a phosphonitrilic halide and an alcohol in the presence of 
pyridine is known. According to Dutch Patent Publication 71/06772, 
hexa-alkoxy phosphazene is prepared in a known manner by reacting 
phosphorus pentachloride and ammonium chloride in the presence of a 
solvent and after separation of the solid components the reaction mixture 
is reacted with a univalent alcohol and pyridine. The resultant pyridine 
hydrochloride is treated with lye to produce a pyridine water fraction 
from which the pyridine is regenerated. The organic fraction remaining 
after separation of the aqueous pyridine fraction is separated into the 
alkoxy phosphazene and a solvent-rich liquid phase. The difficulty with 
this process is that in the preparation of the alkoxy phosphazene and the 
purification of pyridine different solvents are used making necessary 
separate regenerations. According to the invention in the Dutch Patent 
Publication, chlorobenzene is used as the reaction medium for producing 
hexachlorophosphazene and the alkoxyphosphazene. The pyridine is recovered 
from the aqueous fraction by extraction with the solvent-rich liquids 
after separation of the alkoxyphosphazene, followed by distillation of the 
resultant extract. Thus, auxiliary agents such as the pyridine acid fixing 
agent and solvents are regenerated and used for recycle. 
In a paper by Dishon, Journal of the American Chemical Society, Volume 71, 
p. 2251 (1949), cyclic trimeric phosphonitrilic chloride in pyridine was 
reacted with butyl alcohol at 0.degree. C with vigorous stirring to 
produce the dibutylester of phosphonitrilic chloride. Further, Audrieth et 
al in a paper in Chemical Review, Volume 32, pp. 129-130 (1943) discloses 
the reaction of phosphonitrilic chlorides with alcohols in the presence of 
pyridine. However, no indication of the method of reaction or the 
conditions of reaction were indicated in this paper. Audrieth et al refers 
to Wissemann who used alcohols with or without pyridine as condensing 
agent at elevated temperatures. However, a number of possible reactions 
were believed to take place in this type of reaction which would lead to 
undesirable side reactions, particularly the reaction of the 
phosphonitrilate ester with HCl to produce P-O-H bonds. These species 
increase water solubility and hence are undesirable in a flame retardant 
incorporated in a material which is subject to numerous launderings. 
From the previously described prior art, the processes disclosed appear to 
produce only the ordinarily expected fully substituted or fully esterified 
phosphonitrilate polymers, e.g., hexapropoxyphosphazene or hexapropoxy 
phosphonitrilate polymers. In contrast, according to the present invention 
there is believed to occur a simultaneous substitution or esterification 
and condensation whereby products are produced having entirely different 
properties, insofar as chemical and physical properties, as well as, 
advantageous, and superior qualities for flame retardant applications, 
from prior art process materials. 
As far as can be determined, the process of the present invention has not 
heretofore been disclosed or recognized for producing products of superior 
efficacy for fire retarding cellulosic materials. According to this 
invention, a phosphonitrilate polymer is produced which exhibits a 
relationship of viscosity to molecular weight which is surprising from a 
knowledge of prior art phosphonitrilate polymer and which is believed to 
provide superior retention and flame retardance in the regenerated 
cellulose or rayon fiber at concentrations lower than previously 
considered practical. 
SUMMARY OF THE INVENTION 
According to the invention a phosphonitrilate polymer suitable for fire 
retarding cellulosic materials, is produced by a process comprising 
reacting, in the presence of an acid acceptor, a phosphonitrilic halide 
with a hydroxyl compound selected from aliphatic alcohols having from one 
to about six carbon atoms and aromatic alcohols having from six to about 
ten carbon atoms according to the steps of 
(a) contacting a mixture of said phosphonitrilic halide and said acid 
acceptor with at least about 85 weight percent of the theoretical amount 
based on said phosphonitrilic halide of said hydroxyl compound at a 
temperature of not more than about 40.degree. C, whereby a relatively low 
concentration of said hydroxyl compound to said phosphonitrilic halide is 
present during the initial 1/2 to about 3 hours of the reaction, allowing 
condensation to occur between intermediate phosphonitrilate, alkoxy or 
aryoxy ester species and phosphonitrilic halides or partially esterified 
phosphonitrilates with the evolution of an alkyl or aryl halide compound, 
and 
(b) thereafter, maintaining the reaction mixture at a temperature of from 
about 20 to about 50.degree. C for a period of from about 1/2 to about 120 
hours. 
In a more preferred embodiment, after the above procedure has been 
completed, the reaction is further heated to a temperature of 
40.degree.-80.degree. C for a period of from 1/2 to about 81/2 hours. 
Preferred acid acceptors are tertiary amines, most preferably, pyridine. 
The hydroxyl compound may be selected from an aliphatic alcohol and 
aromatic alcohol which is independently and preferably propanol or phenol. 
The product prepared according to the above process is also a preferred 
embodiment of this invention. It provides an excellent fire retardant for 
cellulosic materials, such as regenerated cellulose or rayon. Another 
preferred embodiment of this invention is regenerated cellulose containing 
a flame retardant amount of the product produced by the process of this 
invention. Also, this invention provides a method for preparing flame 
retardant regenerated cellulose filaments which comprises mixing viscose 
and a flame retardant product of this invention, shaping the mixture into 
a filament and coagulating and regenerating the filament. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to this invention a phosphonitrilate polymer is produced by 
reacting, in the presence of an acid acceptor, a phosphonitrilic halide 
and a hydroxyl compound under conditions which are given in more detail 
below. The phosphonitrilic halide or chlorophosphazene starting material 
generally can be illustrated by the formula 
EQU [PN(X).sub.2 ].sub.n 
where X is a halogen, such as fluorine, chlorine or bromine, preferably 
chlorine, and n is an integer of at least 3. More preferably n is an 
integer from 3 to about 8. The phosphonitrilic halide can be linear, 
cyclic or mixtures of these. In general, processes for producing 
phosphonitrilic halides provide a crude mixture containing from 50 to 
about 95 weight percent cyclic materials, for example cyclic trimer, 
tetramer, pentamer, hexamer, heptamer and so on, and the remainder 
linears. Although pure cyclic phosphonitrilic halides, having the linear 
isomers separated therefrom, can be used as the starting materials of this 
invention, a mixture of cyclic and linear isomers is satisfactory and 
preferred because of their inexpensive and more practical processes of 
production. The mixed cyclic and linear isomers of phosphonitrilic halide 
are generally an oily viscous slurry at room temperature, although many of 
the pure materials are solid under normal conditions. 
The phosphonitrilic halides useful in this invention can be produced 
according to known methods by 
1. reacting phosphorus, ammonia and chlorine according to U.S. Pat. No. 
3,658,487; 
2. reacting phosphorus trichloride, chlorine and ammonium chloride 
according to U.S. Pat. No. 3,359,080; 
3. reacting phosphorus pentachloride and ammonium chloride according to 
U.S. Pat. No. 3,367,750; or 
4. reacting phosphorus pentachloride and ammonia according to U.S. Pat. No. 
3,656,916. 
Other known procedures for producing phosphonitrilic halides are found in 
Am. Chem. J., 19, 728 (1897), Berichte, 57B, 1343 (1924), U.S. Pat. No. 
2,788,286; 3,008,799; 3,249,397; 3,347,643; 3,372,005; 3,378,353; 
3,379,511; 3,407,047; 3,462,247; Netherlands 70/05128; and J. Chem. Soc., 
A, pp. 768-772. Each of the foregoing references is hereby incorporated 
herein as if fully set forth. 
A preferred method for preparing phosphonitrilic halides for use in this 
invention may be described as follows: Phosphorus pentachloride slurried 
in monochlorobenzene is charged to a reactor. The reactor is sealed and 
gaseous HCl introduced with agitation to assist solution of the HCl in 
monochlorobenzene. The reactor is pressurized with from about 10 to about 
40 psig with gaseous HCl. Ammonia is then introduced at a rate not less 
than 0.13 liters per minute per mole of PCl.sub.5 and heat is applied to 
raise the temperature of the reaction mixture to 110.degree. C to 
150.degree. C during this initial ammonia feed. The hydrogen chloride 
pressure will fall at first, and additional hydrogen chloride can be added 
to maintain the desired pressure. However, this is not essential if the 
initial pressure is at least 10 psig at the start of ammonia feed since 
by-product hydrogen chloride will be produced before all of the preadded 
hydrogen chloride is used up. The reaction between ammonium chloride and 
PCl.sub.5, initiates at about 60.degree. C. The temperature rises to about 
110.degree.- 140.degree. C. The feed rate of ammonia is reduced after 
about 1/2 hour and held to a rate of from about 0.05 to about 0.13 liters 
per minute per mole of PCl.sub.5. This rate is continued for about three 
hours, or depending upon the amount fed until at least the stoichiometric 
amount of ammonia is added. After the ammonia has been fed into the 
reaction, the temperature is maintained for about 1 hour at between 
110.degree.-150.degree. C, preferably from 120.degree. C to 130.degree. C 
under pressure from 10-40 psig and preferably about 20 psig. This heating 
period finishes the reaction by allowing traces of unreacted material to 
react. After about 1 hour the pressure is released and heating is 
continued for another 1/2 hour at reaction temperature. This allows any 
remaining hydrogen chloride dissolved in the solvent to be removed. 
The product of this reaction is generally 65-75 percent cyclic 
phosphonitrile chloride polymers and 35-25 percent linear materials. In 
general, the cyclic distribution ranges from 60-75 percent trimer, 18-24 
percent tetramer, and 7-12 percent of pentamer. The product yield ranges 
upward of 90 percent, based on the amount of phosphorus used. Yields 
higher than 92 percent are not uncommon. In contrast, products of prior 
art processes have cyclic products ranging from 80-85 percent cyclic using 
lower feed rates followed by higher feed rates of ammonia. Moreover, the 
traditional process for producing phosphonitrile chloride using a solid 
ammonium chloride of commercial grade and a halogenated aliphatic 
hydrocarbon solvent produces a generally higher molecular weight product 
consisting of about 50 percent cyclics and about 50 percent linears. 
EXAMPLE I 
To a glass reactor equipped with stirrer, a reflux condenser and a means 
for heating the reactor contents was charged 208.3 grams (1.0 mole) of 
phosphorus pentachloride in 312.5 grams of monochlorobenzene. The reactor 
was sealed and anhydrous hydrogen chloride was fed into the reactor with 
stirring until the pressure of the reactor was about 15 psig. A total of 
7.6 grams (0.208 mole) of hydrogen chloride was added to the reactor. 
Gaseous ammonia was then introduced to the reactor at a rate of 0.182 
liters per minute per mole of phosphorus pentachloride while the reactor 
contents were heated at a rate of 2.5.degree. C per minute using a heating 
mantle on the reactor. The ammonia feed rate was dropped to 0.0908 liters 
per minute per mole of phosphorus pentachloride after about 5.46 liters 
(0.241 mole) of ammonia was fed into the reactor over a period of about 30 
minutes. The temperature was controlled at 130.degree. C and pressure at 
20.0 psig. The ammonia feed was stopped when a total of 22 liters (1.0 
mole) was fed into the reactor. The heating and stirring was continued for 
one hour at 20 psig, and for another 30 minutes at atmospheric pressure. 
The total reaction time was 51/2 hours. The reactor contents were then 
cooled to room temperature and discharged from the reactor by nitrogen 
pressure. About 400 grams of clear product solution was obtained. Analysis 
by vapor phase chromatograph showed that the solution contained 26.6 
percent phosphonitrilic chlorides of which 63.3 percent were cyclic 
compounds with the following distribution: trimer -- 73 percent, tetramer 
-- 20 percent and pentamer -- 7 percent. The recovered yield was 92 
percent, based on phosphorus pentachloride. 
EXAMPLE II 
The procedure of Example I was repeated, except that a total of 22.8 liters 
(1.047 mole) of ammonia was fed to the reactor and the initial heating 
rate was 1.5.degree. C per minute. The reaction was initiated at 
65.degree. C as observed by a sudden change in the rate of temperature 
increase. The reaction mixture was heated to 130.degree. C over two hours 
period and held at that temperature for three hours. The product slurry, 
about 392.5 grams, was obtained after 51/2 hours reaction time. Vapor 
phase chromatograph analysis of the product showed 67.7 percent cyclic 
phosphonitrilic chloride polymers having the following distribution: 
trimer -- 64 percent, tetramer -- 24 percent, pentamer -- 12 percent. The 
recovered yield of total product was 92 percent, based on phosphorus 
pentachloride. 
The procedure of Example I was repeated with different reaction times and 
temperatures. Ammonia was fed at the same rate with 10 percent excess (1.1 
mole total) (Examples III and IV) to 2 percent short (0.98 mole total) 
(Example V). The results of these experiments are shown in the following 
table. 
TABLE I 
__________________________________________________________________________ 
PREATION OF PHOSPHONITRILIC 
CHLORIDE 
Percent 
Reaction 
Reaction 
Product Distribution 
Percent 
Percent 
Example 
Temp. .degree. C 
Time hrs. 
Trimer 
Tetramer 
Pentamer 
Cyclics 
Yield 
__________________________________________________________________________ 
III 120 71/2 65 20 15 75 85 
IV 140 41/2 73 18 9 77 74 
V 150 4 90 8 2 50 80 
__________________________________________________________________________ 
The hydroxyl compound useful in the process of this invention can be any 
hydroxyl compound capable of reacting with or substituting on or replacing 
halogen on the phosphonitrilic halide. Selection of the desired hydroxyl 
compound is not critical and depends to some extent on the end use of the 
phosphonitrilate polymer produced. Analogs of the hydroxyl function can 
also be employed, for example mercaptan compounds, which react similarly 
to the hydroxyl compound. Preferred hydroxyl compounds are aliphatic 
alcohols having from one to about six carbon atoms and aromatic alcohols 
having from six to about 10 carbon atoms. Typical of these are methanol, 
ethanol, propanol, allyl alcohol, isopropanol, butanol, isobutanol, 
tert-butanol, crotyl alcohol, pentanol, isopentanol, hexanol, phenol, 
cresol, xylenol, naphthanol, benzyl alcohol, tolyl alcohol, phenylethyl 
alcohol, xylyl alcohol, phenylpropyl alcohol, tolylcarbinol, pseudocumene 
alcohol, xylylcarbinol, cumic alcohol, cinnamyl alcohol, xylylene alcohol 
and the like. Halogenated derivatives of the foregoing hydroxyl compounds, 
such as, chlorinated and brominated hydroxyl compounds, and particularly, 
ethylene chlorohydrin, ethylene bromohydrin, 2,3-dibromopropyl alcohol, 
2,3-dichloropropyl alcohol and the like are useful hydroxyl compounds in 
the process of this invention. Mercaptan compounds, which are analogous to 
the hydroxyl compounds useful in the present process, can also be 
employed. Representative of useful mercaptan compounds are methyl 
mercaptan and its homologs ethyl, propyl, butyl, amyl, and hexyl 
mercaptans, thiophenol, thionaphthols, benzyl mercaptan, cyclohexyl 
mercaptan and the like. Thus, aliphatic and aromatic mercaptans having 
from one to about six carbon atoms and from six to about 10 carbon atoms, 
respectively, and their alkylated and halogenated, particularly 
chlorinated and brominated derivatives can also be used. Most preferred 
are propanol and phenol. 
The amount of hydroxyl compound employed in the reaction can vary from less 
than the theoretical amount to a large excess. By theoretical amount is 
meant the stoichiometric amount, that is the number of equivalents of 
hydroxyl groups which replace the halide atoms on the phosphonitrilic 
halide. For example, the cyclic trimeric phosphonitrilic chloride 
containing six chlorine atoms requires 6 equivalents of a mono alcohol, 3 
equivalents of a diol, and 2 equivalents of a triol for stoichiometric or 
theoretical reaction. In the process of this invention, the amount of 
hydroxyl compound used is not less than about 85. Practically, amounts of 
hydroxyl compounds greater than about 180 weight percent of the 
theoretical amount are not employed. Greater or lesser amounts of hydroxyl 
compound can be employed but the lesser amounts leave too great an amount 
of halide atoms in the product for practical subsequent removal and the 
greater amounts require too much reactor volume for practical operations. 
Preferably, the amount of hydroxyl compound employed is from about 98 to 
about 130 weight percent of the theoretical amount. Even though excess 
hydroxyl compound is employed, the reaction process of this invention does 
not replace all of the halide groups. The residual halide can be removed 
according to the processing operations described hereinbelow. 
On reaction of the hydroxyl compound and the phosphonitrilic halide there 
is produced a hydrogen halide. If left in the reaction mixture it would 
further react to produce undesirable by-products and cause rearrangement 
of the phosphonitrilate polymer to water soluble species. Thus, the 
retention properties of the phosphonitrilate polymer in the cellulosic 
fiber during processing and laundering would be adversely affected. By 
carrying out the reaction in the presence of a base or an acid acceptor, 
the hydrogen halide produced is reacted, fixed or complexed and can no 
longer affect the reaction mixture. Therefore, a suitable base or acid 
acceptor is one capable of reacting with or complexing with and 
precipitating out the hydrogen halide produced during the reaction. The 
particular base or acid acceptor employed is not critical and the choice 
of a suitable acid acceptor is within the skill of the art. Typical acid 
acceptor previously employed are alkali and alkaline earth metal 
hydroxides and carbonates or a tertiary organic amine. Typical are sodium, 
potassium or calcium hydroxides or carbonates, trimethylamine, 
triethylamine, tripropylamine, methyldiethylamine, dimethylethylamine, 
propyldimethylamine, propyldiethylamine, methylethylpropylamine, pyridine, 
lutidine, colliline, picoline and the like. Pyridine is preferred. 
More than theoretical amounts of base or acid acceptor necessary to complex 
with the hydrogen halide formed are required. In general, from about 2 to 
about 3 times the weight of the phosphonitrilic halide is employed. 
Theoretically, one mole of base or acid acceptor for each mole of hydrogen 
halide formed would be sufficient. However, practical considerations 
require at least twice the molar amount of base or acid acceptor 
determined by the number of moles of hydrogen halide formed. This amount 
provides enough base or acid acceptor to quickly react or complex with the 
hydrogen halide and enough free acid acceptor serving as a solvent to 
suspend the reacted or complexed salt so that the system is stirrable. 
According to this invention, it has been found that phosphonitrilate 
polymers having advantageous properties are produced when the reaction of 
the phosphonitrilic halide and the hydroxyl compound is carried out in the 
presence of an acid acceptor by adding the hydroxyl compound to the 
phosphonitrilic halide such that a relatively low concentration of the 
hydroxyl compound is present during the initial portion of the reaction, 
for example, during the first 1/2 to about 3 hours of addition and by 
maintaining the reaction mixture at a temperature which does not exceed 
about 40.degree. C. Preferably the temperature is controlled within the 
range of about 20.degree. to about 40.degree. C, although lower 
temperatures can also be used, for example, down to about 15.degree. C. 
However, at much lower temperatures the reaction does not proceed at a 
sufficiently practical rate. Accordingly, a preferred temperature range 
for the reaction would be from about 15.degree. to about 40.degree. C, 
with reaction temperatures from 20.degree. to about 30.degree. C being 
more preferred. It appears that the reaction temperature during the 
addition of hydroxyl compound, especially at an early stage of reaction is 
important because side reaction competition, especially thermal 
rearrangement to phosphazanes, occurs more readily at higher temperatures. 
Also, the concentration of hydroxyl compound during the initial portion of 
reaction is important. Without limiting the invention to any particular 
reaction mechanism or mode of operation, it is believed that the 
concentration of hydroxyl compound is important because two competing and 
beneficial reactions take place in the process of this invention. 
In reacting the phosphonitrilic halide, for example, cyclic trimeric 
phosphonitrilic chloride, with a hydroxyl compound, for example, propanol, 
the major expected reaction is the substitution of chlorine with a propoxy 
group on a phosphorus atom with the resultant release of hydrogen chloride 
which is reacted or complexed with the base or acid acceptor. A second and 
important reaction is the interaction of intermediate phosphonitrilic 
species such as two incompletely substituted cyclic trimer species, one of 
which contains a phosphorus-propoxy group, or any equivalent residue of 
the above described aliphatic and aromatic hydroxyl compounds, and the 
other containing a phosphorus-chloride group or other suitable halide 
depending on the starting phosphonitrilic halide material, such that 
condensation occurs resulting in the formation of propyl chloride, or 
other alkyl or aryl halide as appropriate to the actual materials employed 
whereby the two phosphonitrilic trimer rings are cross-linked by a P-O-P 
linkage or bridge. Of course, the briding by P-O-P bond links can occur 
between various species of phosphonitriliate polymers such that two or 
more cyclic, linear or cyclic-linear molecules are linked together by one 
or more P-O-P bond linkages. Because of the complexity of the product and 
the competition of the reactions for substitution on phosphorus with the 
hydroxyl compound and for condensation forming P-O-P bond bridges between 
phosphonitrilate molecules, it is difficult to predict exactly the 
concentration of hydroxyl compound required at any given point in the 
reaction. It has been found that addition of the hydroxyl compound over a 
period of time instead of all at once or at a very high rate provides the 
relatively low concentration of the hydroxyl compound to the 
phosphonitrilic halide required to effect both desired reactions, e.g., 
replacement and condensation as indicated above. Accordingly, it has been 
found that addition or feed times of from about 1/2 to about 6 hours or 
more for the total amount of hydroxyl compound can be used to produce 
phosphonitrilate polymers having certain advantageous properties. Longer 
feed times are required in larger reaction equipment in order to handle 
efficiently the heat load from the exothermic reaction. Also, in equipment 
of any given size, feeding or addition of hydroxyl compound can be 
conveniently carried out in a shorter period when reaction temperature is 
is controlled at the higher end of the temperature range, say about 
40.degree. C, and conversely, at lower temperatures, e.g., 
15.degree.-20.degree. C, a longer feed time is employed in order to give 
the desired reactions sufficient time for completion. 
After the hydroxyl compound addition is complete, the reaction mixture is 
maintained at substantially the same conditions for a period of time 
sufficient to allow residual chloride to react and be removed from the 
reaction mixture by complexing with the acid acceptor and precipitating. 
Preferably the reaction mixture is held at a temperature of from about 
20.degree. to about 50.degree. C for a period of from about 1/2 hour to 
about 120 hours. More preferably, the reaction mixture is maintained at a 
temperature of from about 20.degree. to about 40.degree. C for a period of 
from about 1/2 to about 24 hours. 
On completion of this holding step it is sometimes desirable to slightly 
increase the temperature for a period to insure that the reaction is 
completed and remove additional residual chloride, thus finishing the 
reaction. This step is optional and need not be carried out in all 
instances. Usually analysis of a sample of the product will indicate 
whether a finish step is required. When used, it is preferred to further 
heat the reaction mixture to a temperature of from about 40.degree. to 
about 80.degree. C for a period of from about 1/2 to about 81/2 hours. 
In each of the above reaction stages, feeding, holding and finishing, the 
reaction mixture can be agitated to assure good contact of the reactants. 
Any suitable agitation means can be employed, such as stirring, as is well 
known in conventional practice. 
Upon completion of the reaction, the reactor contents are filtered to 
remove the hydrogen halide salt complex or reaction product with base and 
the excess base or acid acceptor, e.g., pyridine, and hydroxyl compound, 
if any, are removed. To insure substantially complete removal of base or 
acid acceptor from the phosphonitrilate polymer, a solvent can be added, 
the solution filtered to remove any remaining salts, and the solvent 
containing base or acid acceptor, such as pyridine, evaporated off again. 
Additionally, a water wash or basic water wash can be employed to 
neutralize any hydrogen halide remaining uncomplexed and the solution 
refiltered and the organic layer containing the phosphonitrilate polymer 
separated and recovered. 
The reaction sequence described above allows the phosphonitrilic halide and 
hydroxyl compound to react in a manner such that only at the end of the 
feeding stage is there any appreciably high concentration of hydroxyl 
compound. Thus, during the reaction sequence phosphonitrilate ester and 
chloride intermediates having halide and alkyl oxide and/or aryloxide 
groups, as appropriate for the starting materials, condense to evolve 
alkyl or aryl halide, thus linking the intermediate phosphonitrilate 
esters together causing an increase of molecular weight of the final 
phosphonitrilate polymer. The reaction mixture is a highly complex mixture 
and complete analysis of the intermediates or final products would be 
impractically complex. Therefore, it is not known with certainty what 
individual components appear in the reaction intermediates or final 
product. However, using the reaction procedure described above of the 
present invention, it is observed that products with relatively high 
molecular weights and comparatively low viscosities can be made as 
desired. 
The products of the present invention can be characterized as follows: 
______________________________________ 
P, wt % 20-26 
N, wt % 9-12 
Total C1, wt % 0.5-6.5 
Water soluble C1, wt % 
&lt;1 
Viscosity at 25.degree. C, cp. 
900-20,000 
Molecular weight 900-1700 
Specific gravity 1.14-1.20 
Gardner color 2-11 
Water solubility (wt % P) 
0.01-0.1 
0.5 wt % NaOH solubility 
(wt % P) 0.1-0.8 
______________________________________

By reference to the following examples the invention will be more easily 
understood. In addition, several examples of processes not in accordance 
with this invention are given for comparison. 
EXAMPLE 1 
To a suitable glass reaction vessel was charged 316.4 grams of pyridine and 
116 grams of phosphonitrilic chloride having the following analysis: 
______________________________________ 
Total cyclics 71.2 wt % 
Cyclic distribution 
Trimer 71.9 
Tetrameter 22.3 
Pentameter 5.8 
______________________________________ 
The reactor contents were maintained at 20.degree. C with stirring and 100 
grams of propanol at room temperature were added over a period of 2 hours. 
Cooling was used to maintain the reaction mixture at 20.degree.-25.degree. 
C during the addition of propanol because of the exothermic nature of the 
reaction. 
After completing the propanol feed, the reaction mixture was held at 
20.degree.-25.degree. C for 24 hours with continued stirring. The reaction 
mixture was then cooled and filtered. The filtrate, 307.5 grams was 
divided into two samples. The first, 150 grams, was heated further to 
100.degree. C for 21/2 hours and resulted in a solid product. The second 
part of the filtrate, 61.5 grams, was evaporated at 50.degree. C, 
filtered, washed with 20 cc of saturated aqueous sodium bicarbonate 
solution, and evaporated again. The product, 50.7 grams, analyzed as 
follows: 
______________________________________ 
P. wt % 22.2 
N, wt % 9.95 
Total C1, wt % 5.80 
Viscosity at 
25.degree. C, cp. 3574 
Molecular wt 1333 
______________________________________ 
The following table shows the procedure and results of similar examples in 
which the amount of propanol, temperature and time of feeding, holding and 
finishing, if used, and method of recovery were varied to study the effect 
of these variables on the resultant product. 
TABLE II 
__________________________________________________________________________ 
PREATION OF PHOSPHONITRILATE POLYMER 
__________________________________________________________________________ 
Example No. 1 2 3 4 5 6 7 8 
__________________________________________________________________________ 
PrOH, % Theo. 
85 98 98 98 98 110 110 110 
Temp.-Time, .degree. C-hrs. 
Feeding 22- 2 22- 2 22- 2 22- 2 22- 2 22- 2 22- 2 22- 2 
Holding 22-24 22-24 22-48 22-120 22-120 22-24 22-24 22-48 
Heating 50- 0.5 
50- 0.5 
50- 0.5 
50- 0.5 
50- 0.5 
50- 0.5 
-- 50- 1 
__________________________________________________________________________ 
Total Time 26.5 26.5 
50.5 
122.5 
122.5 
26.5 
26 51 
Recovery Method* 
A A A A A A B B 
Product 
Viscosity at 
25.degree. C, cp 
3574 2034 2673 3632 3255 1007 1025 1400 
Molecular Wt. 
1333 1381 1377 1453 1441 1239 1261 1256 
C1, Wt % 5.8 4.13 2.86 1.77 1.53 3.12 3.11 1.7 
P, Wt % 22.2 22.0 22.1 -- 21.8 21.3 21.1 -- 
Yield, % -- -- -- -- -- -- -- -- 
Comments Heptane 
wash 
__________________________________________________________________________ 
Example No. 9 10 11 12 13 14 15 16 
__________________________________________________________________________ 
PrOH, % Theo, 
110 98 98 98 98 98 98 100 
Temp.-Time, .degree. C-hrs. 
Feeding 22- 2 22- 2 22- 2 22- 2 22-2 30-2 22-2 22- 2 
Holding 22-48 22-24 22-24 22-48 30-0.5 30-0.5 
22-16 22-17.5 
Heating -- -- 60- 1 -- 50-2 50-2 60- 2 -- 
__________________________________________________________________________ 
Total Time 50 26 27 50 0 4.5 4.5 20 19.5 
Recovery Method* 
B B B B B B B C 
Product 
Viscosity at 
25.degree. C, cp 
1280 2760 19,900 
648 1670 4500 1714 2993 
Molecular Wt. 
1284 1013 1084 975 1345 1602 1378 1388 
C1, Wt % 1.88 5.79 1.82 -- 7.38 7.74 4.46 4.88 
P, Wt % -- -- 22.8 -- -- -- -- 21.6 
Yield, % -- -- -- -- 64 48 79 92 
Comments 70% Mono- 70% Mono- pH =14 0.32% Water 
chloro- chloro- soluble C1, 
benzene benzene 2% trimer 
__________________________________________________________________________ 
Example No. 17 18 19 20 21 22 23 
__________________________________________________________________________ 
PrOH, % Theo. 
100 100 100 100 100 100 110 
+30 +20 
Temp.-Time, .degree. C-hrs. 
Feeding 22-2 10-2 10-2 10-2 20-2 20-2 30-0.5 
Holding 22-17.5 
25-17 25-17+3 
25-17+3 
30-15 30-15 30-1 
Heating 60-2 -- -- -- -- 52.5 40-3 
__________________________________________________________________________ 
Total Time 21.5 19 22 22 17 22 4.5 
Recovery Method* 
C C C D D D D 
Product 
Viscosity at 
25.degree. C, cp 
4039 446 622 550 1637 1576 446 
Mol. Wt. 1398 945 963 968 1310 1323 1030 
C1, Wt. % 3.63 4.37 2.77 2.57 3.46 2.05 5.25 
P, Wt. % 21.8 21.3 -- 21.3 22.15 21.5,21.3 
21.6 
Yield, % 89 -- -- -- -- -- 90 
Comments 0.43% (1) (2) Wash w/ 
Water 
Water water, soluble 
soluble no water 
C1 &lt; 0.05% 
C1, 0.45% soluble 
Na, 9.87% N C1 
__________________________________________________________________________ 
Example No. 24 25 26 27 28 29 30 
__________________________________________________________________________ 
PrOH, % Theo. 
110 110 110 110 110 130 150 
Temp.-Time, .degree. C-hrs. 
Feeding 30-0.5 25-2 25-2 30-3 40-2 30-2.5 
30-3 
Holding 30-1 24-18 24-18 48-18 40-1 30-1 30-1.5 
Heating 40-22.5 
-- 80-3 -- 70-4 50-3 50-2 
__________________________________________________________________________ 
Total Time 24 20 23 21 7 6.5 6.5 
Recovery Method* 
D D D D D D D 
Product 
Viscosity at 
25.degree. C, cp 
421 928 6044 V.H. Solid 10,170 
16,190 
Mol. Wt. 940 1105 1226 1723 -- 1689 1706 
C1, Wt.% 1.51 3.70 1.62 3.16 5.03 4.67 5.04 
P, Wt. % 21.0 21.8 21.43 21.97 22.55 22.8 22.4 
Yield, % 90 -- 94 -- -- -- -- 
__________________________________________________________________________ 
Example No. 31 32 33 34 35 36 
__________________________________________________________________________ 
PrOH, % Theo. 
130 130 130 130 130 130 
Temp.-Time, .degree. C-hrs. 
Feeding 30-2 
30-2 30-1.67 
30-1.67 
30-1 30-1.67 
Holding 30-2 30-2 30-2.33 
30-2.33 
25-20 30-2.33 
Heating 50-2.5 50-8 50-2.5 
50-.85 -- 50-8 
__________________________________________________________________________ 
Total Time 6.5 12 6.5 12.5 21 12 
Recovery Method* 
D E D D D D 
Product 
Viscosity at 
25.degree. C, cp 
6538 16,912 
3162 6102 1452 3807 
Mol. Wt. 1476 1680 1427 1380 1287 1371 
Cl, Wt. % 4.46 2.26 3.99 1.48 4.53 1.91 
P, Wt. % 22.55 21.8 22.5 22.0 21.6 22.0 
Yield, % 95 70 93 -- 84 -- 
Comments Water Water Water 
soluble soluble soluble 
C1 0.51% C1 0.021%, C1 0.07%, 
N 9.90% Na 0.26% 
__________________________________________________________________________ 
Example No. 37 38 39 40 41 42 
__________________________________________________________________________ 
PrOH, % Theo. 
130 130 130 130 130 130 
Temp.-Time, .degree. C-hrs. 
Feeding 30-1.67 
30-1.67 
30-2 30-2 30-1.83 
30-1.83 
Holding 30-2.33 
30-2.33 
30-2 30-2 30-2.17 
30-2.17 
Heating 50.8 50-2.5 
50-8 50-8 50-8 50-8 
__________________________________________________________________________ 
Total Time 12 6.5 12 12 12 12 
Recovery Method* 
F D D F D G 
Product 
Viscosity at 
25.degree. C, cp 
5230 423 12,500 
20,400 13,831 15,582 
Mol. Wt. 1374 965 1606 1553 1595 1567 
Cl, Wt. % 1.61 4.53 1.36 1.75 2.26 1.86 
P. Wt. % 22.2 22.4 21.4 22.2 22.0 22.3 
Yield, % -- 83 85 -- -- -- 
Comments Water Water 
soluble soluble 
Cl 0.05% Cl 0.05% 
__________________________________________________________________________ 
*A Filter off pyridine . HC1, evaporate pyridine, wash with 
MCB/NaHCO.sub.3 solution, evaporate. 
*B Neutralize pyridine . HC1 with 10% NaOH/heptane, separate phases, 
evaporate. 
*C Neutralize pyridine . HC1 with 16% NaOH/monochlorobenzene, separate 
phases, evaporate. 
*D Neutralize pyridine . HC1 with 16% NaOH/monochlorobenzene, wash with 
water, separate phases, evaporate. 
(1) 4% Monochloropentapropoxyphosphazene, 6% trimer, 1% tetramer. 
(2) 9% Trimer, 1% tetramer, no water soluble Cl. 
*E Neutralize pyridine . HC1 with 16% NaOH, wash with water, separate 
phases, evaporate. 
*F Neutralize pyridine . HCl with 16% NaOH/monochlorobenzene, stand 
overnight, wash with water, separate phases, evaporate. 
*G Neutralize pyridine . HCl with 16% NaOH/monochlorobenzene, wash with 
water, stand overnight, separate phases, evaporate. 
In Examples 10 and 11, a large amount of monochlorobenzene was left in the 
phosphonitrilic chloride. The products had higher viscosity compared to 
molecular weight indicating a rearranged product. In Example 12, the 
neutralization went too far to a pH of 14 and the product which should 
have been similar to Example 9 was apparently degraded into lower 
viscosity and molecular weight material. 
In Examples 18, 19 and 20, the feed temperature was too low for the times 
normally employed at higher temperatures and resulted in product with low 
molecular weights and viscosities. In Examples 23 and 24, although the 
feed temperature was high enough, the feed time was relatively short, 
giving materials with lower viscosities. In Example 27, the relatively 
long feed time at the temperature employed significantly increased the 
viscosity indicating a thermally rearranged product. In Example 28, the 
feed temperature was too high for the time of reaction producing a solid 
product. Comparison of Examples 10-12, 18, 19, 20, 23, 24, 27 and 28 with 
the other examples indicates the relationship of viscosity and molecular 
weight to the feed temperature and as hydroxyl concentration expressed as 
feed time. It is therefore clear that the proper control of these 
variables can produce products which have advantageous properties of 
viscosity and molecular weight and which can be controlled for best 
advantage as desired. 
The following examples illustrate large scale runs of the process of this 
invention. 
EXAMPLE 43 
Into a glass-lined 30-gallon reactor was charged 148 pounds of 
monochlorobenzene and 65 pounds of phosphorus trichloride. The reactor 
stirrer was started and the reactor contents heated to about 27.degree. C 
and the pressure was atmospheric. To the reactor was charged 36 pounds of 
gaseous chlorine over a period of one hour and ten minutes. The reactor 
temperature increased to about 55.degree. C and was maintained during 
chlorine feed at from 55.degree. to about 60.degree. C. The reactor 
pressure was controlled at from about 2 to about 3.8 psig. 
The reactor was pressurized with HCl up to about 13 psig. Gaseous ammonia, 
8.4 pounds, was added over a period of 4 hours and 10 minutes. The 
temperature was maintained at about 140.degree. C and the pressure at 20 
psig by venting HCl to a water scrubber. The ammonia feed was stopped and 
the reactor pressure and temperature were maintained for 30 minutes. Then 
the reactor was vented for 20 minutes to remove HCl and the pressure was 
decreased to 20 psig during the venting period. The reactor contents were 
then cooled. The unfiltered product phosphonitrilic chloride weighed 201.5 
pounds. The product was then filtered to remove NH.sub.4 Cl and the 
monochlorobenzene solvent was stripped from the phosphonitrilic chloride 
and 128 pounds of solvent were recovered. Stripping was carried out for 2 
hours and 25 minutes at temperatures from about 24.degree. C up to 
77.degree. C and pressure of from 50 mm Hg to 1 mm Hg. 
Then 160 pounds of pyridine was added to the reactor. The reactor contents 
were heated to 22.degree. C and 42.5 pounds of propanol was fed into the 
reactor with stirring over a period of 1 hour and 47 minutes. The 
temperature varied from about 17.degree. to about 22.degree. C during the 
feed period. The propanol feed was completed and the reaction mixture held 
at 22.degree. to about 30.degree. C for 15 hours. At this point, another 8 
pounds of propanol was fed into the reaction mixture during 10 minutes at 
30.degree. C. This amounted to about 10 weight percent over theoretical 
amount of propanol. The reaction mixture was further heated at about 
57.degree. to about 63.degree. C for 41/2 hours to finish off the 
reaction. The reactor contents were cooled to about 22.degree. C and left 
with stirring for 64 hours. Temperature ranged from 22.degree. to about 
27.degree. C during this period. 
Then the reactor contents were cooled to ambient temperature and 140 pounds 
of monochlorobenzene was added. After stirring, there was added 168 pounds 
of 16 weight percent sodium hydroxide solution to neutralize the reaction 
mixture. The final mixture had a pH of 7.6 after neutralization. The 
bottom brine solution was drained and weighed 204 pounds containing water, 
salts and rag layer. A second wash using 25 pounds of water was conducted 
and 48 pounds of pyridine and water were recovered from the top layer. 
The product solution was heated to 101.degree. C under vacuum of 10 to 1 mm 
Hg for 3 hours. Recovery of pyridine and monochlorobenzene from the 
condenser was 272.5 pounds. The product weighing 46.8 pounds is recovered 
from the reactor. 
Analysis of the phosphonitrilate polymer product gave the following 
results: 
______________________________________ 
P, wt % 21.4 
N, wt % 9.75 
Total C1, wt % 0.57 
Water soluble C1, wt % 0.14 
Na, wt % 0.21 
Viscosity at 25.degree. C, cp 
2232 
Molecular weight 1190 
Specific gravity, g/cm.sup.3 
1.16 
Gardner color 11-12 
Acid No. (mg. KOH/g) 23 
Water solubility (wt % P) 0.10 
0.5% NaOH solubility (wt % P) 
0.47 
______________________________________ 
EXAMPLE 44 
To a 30-gallon jacketed glass-lined reactor was charged 65 pounds of 
PCl.sub.3 and 148 pounds of monochlorobenzene. The reactor contents were 
cooled to 17.degree. C, the stirrer was started and chlorine was fed into 
the reactor contents. The temperature increased to about 57.degree. C 
during chlorine feed and a total of 37.5 pounds of chlorine was charged. 
Pressure of the reactor went from atmospheric to 3 psig. 
The reactor was pressurized with HCl to about 19.0 psig and 8 pounds of 
gaseous ammonia was fed into the reactor. The temperature went from 
18.degree. C to about 106.degree. C during the first feeding of ammonia 
and then was controlled at from 127.degree. C to about 137.degree. C. The 
ammonia was fed over a period of 3 hours and 40 minutes. The ammonia feed 
was stopped and the temperature was maintained for 1 hour while the 
pressure was decreased and the HCl vented. HCl was vented during the 
reaction to maintain the reactor pressure at about 17 psig. After the 
ammonia feed was stopped and the HCl vented for 1 hour the reactor 
contents were cooled to ambient temperature. The unfiltered 
phosphonitrilic chloride solution weighed 198.5 pounds. The ammonium 
chloride was filtered off. Stripping of the monochlorobenzene was begun, 
but a leak in the overhead condenser prevented accurate determination of 
the amount of monochlorobenzene stripped. Stripping was conducted at 
140.degree.-142.degree. C for two and one-half hours and then the reactor 
contents were cooled. 
To the reactor was added 150 pounds of pyridine. The stirrer was started 
and 66 pounds of propanol was added to the stirred reaction mixture at 
about 20.degree. C. The reactor temperature was then controlled at 
27.degree. C to about 32.degree. C during propanol feed over a period of 1 
hour and 40 minutes. The amount of propanol fed was about 130 weight 
percent of the theoretical amount. The reactor was maintained at from 
27.degree. to about 34.degree. for 2 hours after propanol feed was 
completed and then heated to 49.degree. to about 55.degree. C for about 8 
hours. The reaction mixture was then cooled. 
To the reactor was added 140 pounds of monochlorobenzene. The reaction 
mixture was then neutralized with 176 pounds of 16 percent NaOH solution. 
After neutralization, the reaction mixture had a pH of 7.6. From the 
reactor was recovered 195 pounds of brine containing water and salt and 20 
pounds of rag. A second wash with 50 pounds of water allowed recovery of 
108.5 pounds of pyridine-water solution from the top layer. 
The reactor was then heated to 96.degree. C over a period of about 3 hours 
at pressure of from 10 to 15 mm Hg to strip the pyridine and 
monochlorobenzene from the product. About 248.5 pounds of pyridine and 
monochlorobenzene were recovered. Product phosphonitrilate polymer was 
47.2 pounds. 
Analysis of the product gave the following results: 
______________________________________ 
P, wt % 21.5 
N, wt % 9.70 
Total C1, wt % 1.12 
Water soluble C1, wt % 0.07 
Na, wt % 0.09 
Viscosity at 25.degree. C, cp 
2069 
Molecular weight 1223 
Specific gravity, g/cm.sup.3 
1.16 
Gardner color 6 
Acid No. (mg. KOH/g) 24.1 
Water solubility (wt % P) 0.02 
0.5% NaOH solubility (wt % P) 
0.37 
______________________________________ 
Accordingly, from the foregoing examples, it can be seen that the product 
phosphonitrilate polymer can be produced having a viscosity from about 900 
to about 20,000 cp at 25.degree. C, preferably from 1000 to about 7000, 
and a molecular weight of from about 900 to about 1700 and preferably from 
1000 to about 1600. 
A particularly preferred embodiment is a process according to this 
invention comprising reacting, in the presence of pyridine, a 
phosphonitrilic chloride with propanol according to the steps of adding 
from about 98 to about 130 weight percent of the theoretical amount of 
propanol to the phosphonitrilic halide at a temperature of about 
20.degree. to about 30.degree. C over a period of from about 1 to about 3 
hours, maintaining the reaction mixture at about 20.degree. to about 
30.degree. C for a period of about 1 to about 2 hours and then further 
heating the reaction mixture to from about 50.degree. to about 55.degree. 
C for a period of from about 1/2 to about 8 hours. 
A most highly preferred embodiment of this invention is a product produced 
by the process of this invention. Also, phosphonitrilate polymers prepared 
by the process as described and exemplified above can be used as flame 
retardants for cellulosic materials, including fiber, filament, staple 
yarn, fabrics and films. The phosphonitrilate polymers can be added by 
dipping, spraying, or other means utilized for treating the surface. 
Preferably, for rayon and other regenerated cellulosics, the fire 
retardants may be impregnated or added to the product by incorporating 
into the viscose prior to spinning. The amount of fire retardant used can 
be from 1 to about 30 weight percent, and preferably from 2 to about 20 
weight percent. 
For impreganation prior to spinning and the finished materials, reference 
is made to U.S. Pat. No. 3,455,713 to Godfrey. That patent is incorporated 
by reference herein as if fully set forth. Thus, one method of flame 
retarding cellulose filaments is to use the phosphonitrilate polymers 
produced according to this invention in the method of Godfrey supra. 
Likewise, the instant invention provides regenerated cellulose fibers, 
filaments, filamentary articles and fabrics prepared from the 
phosphonitrilate polymeric flame retardants herein provided utilizing the 
techniques of Godfrey. 
In obtaining satisfactory fire retardance, an extremely important criteria 
is how well the fire retardant material is retained in the fiber or 
filament during processing. If the fire retardant agent is lost during 
processing, it has no chance to pass the strigent U.S. Government test 
standards, such as the Children's Sleepwear Standard, DOC FF 3-71, which 
requires testing of the finished end product in new condition and after 50 
washings in household machines. 
To illustrate the superior retention of the products produced by the 
process of this invention, the phosphonitrilate polymer of Example 43 was 
added to viscose at several concentrations, spun into filament and 
processed conventionally. The viscose mixture was spun into aqueous 
coagulating and regenerating bath containing aqueous sulfuric acid and 
other conventional components, for example, metal sulfates. Further 
processing includes washing, desulfurizing, bleaching, etc. The following 
results were obtained during processing of the filament: 
______________________________________ 
Retention of Phosphonitrilate Polymer 
in Rayon Filament During Processing 
Loading of 
Phosphonitrilate 
Wt % P Retained 
Polymer of in Rayon 
Example 43 in Acid Free Washed 
Viscose, wt % Yarn Yarn 
______________________________________ 
13.1 98.5 91.0 
16.7 100 96.7 
20.0 98.4 92.2 
______________________________________ 
The extremely good retention of the phosphonitrilate polymer at such low 
concentrations indicates that the phosphonitrilate polymer will provide 
excellent flame retardance for the rayon fabric woven or knit therefrom. 
The flame retardant effectiveness of products made in Examples 43 and 44 
was evaluated by the Children's Sleepwear Test, DOC FF 3-71, in both 
filament-knit fabric and staple yarnwoven fabric. The char lengths are 
recorded below: 
______________________________________ 
Avg..sup.C Char 
Viscose Length (in.) 
Product 
Loading Fab. Wt. After 50 
From (wt %) (oz/yd.sup.2) 
Type Fabric 
Launderings 
______________________________________ 
Ex. 43 13.1 6-7.sup.a 
Filament-Knit 
3.8 
16.7 6-7.sup.a 
Filament-Knit 
0.6 
20.0 6-7.sup.a 
Filament-Knit 
1.0 
20.0 4.0 Filament-Knit 
2.9 
Ex. 44 25.sup.b 3.5 Staple Yarn- 
2.7 W.sup.d 
woven 5.5 F.sup.d (2 Failures) 
______________________________________ 
NOTES:? 
.sup.1 Actual weight of fabric no reported, believed to be in 6-7 
oz/yd.sup.2 range. 
.sup.b Based on cellulose. 
.sup.c Average of 5 samples. 
.sup.d Tested in warp direction, tested in fill direction. 
Accordingly, the products produced by the process of this invention have 
excellent effectiveness even after 50 launderings.