Phosphate Esters

Abstract

A novel group of compounds, the reaction product of an amine and a phosphate ester that are useful as dispersing agents for the finely divided metal oxides used in preparing magnetic tape coatings. The compound having the formula: where R is a hydrocarbon radical; A is an alkylene radical; R' is an amine; and the sum of x, y and z is 3.

Description

The use of a moving magnetic wire as a means for reproducing audio signals was first demonstrated in 1898. However, it is only since the late 1940's that theories, techniques, and materials have been developed which make possible the reproduction of audio signals with a satisfactory performance from the standpoint of frequency range, signal-to-noise ratio, and distortion. Although satisfactory performances have heretofore been obtained with magnetic wire, magnetic tape consisting of a paper or plastic-base tape coated with a thin layer of magnetized ferromagnetic powder such as iron oxide, is now almost universally used in magnetic sound-reproduction.

Such oxide coated tapes are generally employed in widths such as one-quarter or one-half inch and utilized in rolls of up to about 2,500 feet. Information is recorded on a series of parallel tracks extending the length of the tape. As this type of equipment has become more sophisticated, the characteristics of the oxide coating have become more critical. Thus, an accurate dispersion of the metal oxide in the coating is now essential to uniformity of reproduction. Various dispersing agents have heretofore been employed to assist in providing such a uniform iron oxide coating over the base tape; see for example U.S. Pat. No. 3,144,352 where surfactants such as lecithin have been utilized for this purpose.

The present invention is directed to a novel group of amine salts of complex phosphate esters that have been found to be particularly advantageous when employed for dispersing finely divided ferromagnetic oxide particles, such as acicular gamma ferric oxide, in tape-coating systems. These novel compounds are broadly described by the following formula:

wherein x and z are integers from 1 to 2, y is an integer of 0 to 1 and the sum of x, y and z is always 3; R is a hydrocarbon radical of up to 30 carbons that is selected from aliphatic, cyclic, aromatic and combinations thereof; n is an integer from 3 to 25; A is an alkylene radical of from two to three carbon atoms; R' is a monovalent radical of from 0-20 carbons (preferably 0-12 carbons) selected from aliphatic amines of the formula --NH(A'NH).sub.m H and monocyclic heterocyclic compounds containing from one to three nitrogen atoms and from zero to one oxygen atoms as the only annular hetero atoms. The term aliphatic amines is intended to include alkylene polyamines such as triethylene tetraamine, diethylene triamine as well as ammonia. The term heterocyclic compounds is intended to include morpholine, piperazine, pyridine, triazine, pyrrole, pyrrolidine, and the like with and without substituents.

IN the preferred embodiment the phosphate esters are of the formula:

wherein R is an alkylaromatic radical of from 10 to 20 carbons such as octyl- or nonylphenyl; A and A' are ethylene radicals; m is an integer of from 2 to 3; n is an integer of from 6 to 15, more preferably an average of 8 to 10; and y is 0 and x and z total 3. Depending upon the extent of the reaction, any combination of up to a total of three alkoxy and/or amino groups may be attached to the pentavalent phosphorous atom, it being understood of course that at least one alkoxy and at least one amino radical are always present in the resulting composition.

The novel products of this invention are produced by a carefully controlled two-step process wherein a long chain organic alcohol such as alkylphenoxypoly(alkyleneoxy)alkanol is first reacted (esterified) with, preferably, phosphorous pentoxide to form at least a partial phosphate ester. Thereafter, the resulting mono- or di- phosphate ester is reacted with the above-described amine either through partial neutralization, or displacement of the ester by the amine.

Briefly, in the 2-step reaction of this invention, a pentavalent phosphorous such as phosphorous pentoxide (P.sub.2 O.sub.5), the acid anhydride of phosphoric acid, or phosphorous oxychloride, in an amount in excess of that theoretically required, is combined with a high molecular weight nonionic surface active agent having the general formula:

R (OA).sub.n OH (2)

wherein R, A, and n have the definitions set forth for formula (1), above. The excess of pentavalent phosphorous is necessary to ensure that no free surface active agent remains.

The product obtained from this esterification reaction is thought to be primarily a mixture of the mono- and di-ester. The excess of pentavalent phosphorous ensures that little, if any, tri-ester will be formed. Thus the resulting compounds appear to be defined by the formula:

wherein R, A, x and n have the definitions set forth with respect to formula (1), supra.

Thereafter, and following the removal of the excess pentavalent phosphorous, such as by filtering, the phosphate ester of formula (3) is reacted with an amine having at least one nitrogen and including from 0 to 20 carbon atoms. As previously discussed with respect to formula (1) and (1a), the amine can be either aliphatic or heterocyclic. Sufficient of the amine is introduced to adjust the pH of the resulting amine salt to about 5 to 7. In the preferred embodiment, the amine is aliphatic and an alkylene polyamine defined by the following formula:

H NH(A' NH).sub.m H (4)

wherein A' and m have the definitions set forth for formulas (1) and (1a), above.

The nonionic surface-active alcohols useful for reaction with the acid anhydride of phosphoric acid include the ethylene oxide adducts of the alkanols and alkylphenols. Such substances are commercially available under trademarks such as Neodol, from Shell Oil Company and Igepal, from General Analine and Film Corporation. For purposes of convenience, reference will frequently be made in the remainder of this specification to the use of Igepal CO-630, a nonylphenoxypoly(ethyleneoxy)ethanol, as the surface active alcohol. However other long chain alkylphenoxylpoly(alkyleneoxy)alkanols such as Igepal CO-430, Igepal CA-630 and the like, as well as alkylpoly(alkyleneoxy)-alkanols containing up to about 25 alkyleneoxy units, are suitable.

Although the reaction conditions during formation of the phosphate esters in the initial step are not particularly critical, it has been found to be critical for the amount of amine employed to be sufficient to adjust the pH of the resulting complex salt to the range of about 5-7, and preferably 5-6. When the pH of the resulting amine salt is substantially in excess of about 6, the reactants become solid and hard to handle when introduced into the ferromagnetic oxide coating composition. Furthermore, a pH lower than about 5 inhibits subsequent dispersion of the metal oxide in the coating system. During formation of the novel compounds of this invention, the temperature conditions may vary over a wide range, but it is desirable that the reaction temperature at no time greatly exceed the boiling point of water at atmospheric pressure. The reaction pressure employed can be either sub-atmospheric or super-atmospheric, in addition to ambient.

The novel dispersing agents of this invention can be incorporated with any of the iron oxide-containing systems presently employed in the magnetic tape production industry. Such systems have heretofore been prepared with iron oxide as well as various other components normally incorporated in the binder system, including resin materials, lubricants, and solvents, such as set forth in U.S. Pat. No. 3,144,352, supra. For this reason, the present invention is not intended to be limited to any particular metal oxide system, but is useful whenever uniform dispersion of the metal oxide is desirable. The amount of dispersing agent employed can vary widely, as little as about 1 percent by weight being suitable, while amounts up to 10 percent can be advantageous. It is preferable to use from about 2-5 percent based on the total weight of the coating composition.

The resulting coating incorporating the novel dispersing agent of this invention can be employed with a wide variety of known tape bases. However, it will be appreciated by those skilled in the art that tapes formed of polyesters such as polyethylene terephthalate, and available under the trade name Mylar, are particularly suitable as they have an extremely long life.

The organophosphorous compounds, resulting from the reaction of the long chain alcohol with the pentavalent phosphorous oxides, depend upon both the extent to which the esterification reaction is allowed to continue and the relative concentration of the reactants. Subsequently, the amount of amine displacement (or neutralization) will again depend upon the amount of reactants present as well as upon the actual reaction conditions. As previously set forth it is only critical that at least one alkoxy and one amino radical remain complexed with each pentavalent phosphorous. Suitable solvents include toluene and tetrahydrofuran among the many others that could be utilized.

To further illustrate the invention, the following examples are provided. It should be understood that the particular details of the examples are not to be regarded as limitations as they may be varied, as will be understood by one skilled in this art.

EXAMPLE I

Igepal CO-630, a nonylphenoxypoly(ethyleneoxy)ethanol, in an amount of about 1,000 grams was heated with agitation to about 150.degree. F. Phosphorous pentoxide in an amount of about 96 grams was slowly added while the reaction temperature was allowed to rise to about 180.degree. F. The phosphorous pentoxide was added at a rate sufficient to maintain the temperature in the range of 170.degree. to 190.degree. F during the addition which took about 1 hour. The rate of addition was decreased as the reaction neared completion. The reaction temperature was retained at about 180.degree. F for about 1 hour after the addition of the phosphorous pentoxide. Some phosphorous pentoxide remained unreacted in the clear liquid portion. The resulting ester was filtered through diatomaceous earth. Other filters having a 50-75 micron porosity are also suitable for this filtering operation. Care was taken to dispose of the filtering medium as the free phosphorous pentoxide presented a fire hazard.

500 grams of the resulting phosphate ester were combined with 550 grams of toluene and heated to approximately 200.degree. F. Triethylene tetraamine, in an amount of 50 grams was added slowly to avoid raising the temperature of the reaction to above 225.degree. F. The resulting amine salt of the complex phosphate ester was filtered and found to have the following characteristics: The viscosity was found to be about 100-200 centapoise and the composition had a weight of about 8.2 pounds per gallon. The acid number was found to be in the range of 50-60 and the pH of a 1 percent aqueous solution of the complex ester was found to be between about 5 and 7.

EXAMPLE II

Utilizing 30 parts of the complex ester formed in example I, above, in lieu of 30 parts of lecithin, the coating composition set forth in example I of U.S. Pat. No. 3,144,352 is prepared. The coating is applied to a Mylar tape, and the dispersion characteristics of the iron oxide in the coating are found to be excellent.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be appreciated that certain changes and modifications may be practiced within the scope of the invention as limited only by the scope of the appended claims.

Claims

What is claimed is:

1. A composition of matter having the following formula:

wherein x and z are whole number integers of from 1 to 2, y is a whole number integer of from 0 to 1, with the proviso that the sum of x, y and z is 3;

R is a hydrocarbon radical of up to 30 carbon atoms, which is aliphatic, alicyclic, aromatic or combinations thereof;

n is an integer of from 3 to 35;

A is an alkylene radical of from two to three carbon atoms;

R' is a monovalent radical of the formula:

-- NH(A'NH).sub.m H,

wherein A' is an alkylene radical of from two to three carbon atoms; and

m is a whole number integer of from 0 to 5.

2. A composition according to claim 1 wherein A and A' are ethylene, m is 0-3, n is 6-15 and R is an alkyl radical of from 10 to 20 carbons.

3. A composition according to claim 1, wherein m is 2, n is about 4 and R is dodecyl.

4. A composition according to claim 1, wherein m is 3, n is about 8 and R is pentadecyl.

5. A composition according to claim 1, wherein R is an alkylaromatic radical of from 10 to 20 carbons, n is an integer of from 6-15, and A and A' are ethylene radicals.

6. A composition according to claim 5, wherein m is 3, n is about 10 and R is nonylphenyl.

7. A composition according to claim 5, wherein m is 2, n is about 10 and R is nonylphenyl.

8. A composition according to claim 5, wherein m is 3, n is about 11 and R is octylphenyl.

9. A composition according to claim 5, wherein m is 0, n is about 10 and R is nonylphenyl.

10. A composition according to claim 5, wherein m is an integer of from 2 to 3.

11. A composition according to claim 5, wherein m is 0.