US2450903A - Phosphorus acid esters of petroleum phenols - Google Patents

Description

Patented Oct. 12, 1948 OFFICE W PHOSPHOBUS ACID ESTE RS OF PETROLEUM PHENOLS Louis A. Mikeska, Westfleld, N. ;J., am... to

Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 17, 1945,

Serial No. 573,312

2 Claims.

This invention relates to new organic phosphorus compounds, useful as blending agents in organic compositions, and more particuarly to novel phosphate and phosphite esters which function as improved plasticizers.

Alkarayl phosphates and alkaryl phosphite have been prepared 'from simple alkyl phenols for use in plasticizing and similar purposes, but these esters have had restricted application due to limitations in their solubility, stability, and wetting power.

In the past, the alkyl phenols generally employed in preparing alkaryl esters were mainly cresols, xylenols, etc., made available by tar acids commercially known as cresylic acid or by alkylating such phenols to introduce a paramnc side group. Other hydroxyaromatic compounds predominantly aromatic in'character, such as naphthols and phenyl phenols, have also been proposed.

According to the present invention, esters of acids of phosphorus, and particularly phosphate esters, are prepared from phenolic compounds having distinctive properties and compositions which confer upon the esters new and beneficial properties or attributes particularly for use as plasticizers. The phenolic-compounds which now have been found to be adapted for this purpose are those recovered from petroleum fractions and known as petroleum phenols. The petroleum phenols for the purpose oi this invention may be characterized as containing a total of about 9 to 23 carbon atoms per molecule with about 3 to 17 of these carbon atoms present in saturated hydrocarbon groups showing a deficiency of hydrogen for parafiinic or straight chain alkyl groups. This deficiency of hydrogen can be ascribed aptly to the presence of cycloaliphatic hydrocarbon groups. Thus, while the saturated hydrocarbons substituents of petroleum phenols may be considered as paraflinoid, they do not have the parafllnicity of simple alkyl groups.

Petroleum phenols are recovered from crude petroleum and mainly from cracked petroleum naphtha distillates and heating oil stocks. In general, a petroleum fraction such as a heating 011 stock is treated with a strong aqueous or alcoholic caustic solution to extract petroleum phenols in the form of alkali phenolate salts. The

alkali phenolate salts in alkaline solution are washed with petroleum ether or naphtha to remove residual hydrocarbons. The solution oi the salts is then treated with carbon dioxide or a weakwhich they are obtained. With sumcient purification and redistiilation, the phenolic compounds can be substantially freed from hydrocarbons and other impurities such as naphthenic acids.

Although it is difflcult to isolate pure components from the petroleum phenols, compounds in close out fractions of the petroleum phenols, and particularly those of higher molecular weight forming a major proportion of the components cannot be identified with simple alkyl phenols having corresponding molecular weights. To a large degree, the petroleum phenols are indicated to include polycyclic molecules which may be described as polymethylene phenols and in the higher petroleum phenols such parafflnoid groups predominate over the aromatic groups. From analytical data including hydrogen and carbon analyses, acetylation and saponification determinations, iodine absorption, molecular weight determinations by the freezing point method, boiling point, etc., can be derived information regarding the composition and structure of the petroleum phenols. As a rule, the petroleum phenols contain only a trace of cresols, if any, and have a minimum formula weight of about 121.3, which is evidence of the fact that they predominantly correspond in molecular weight to higher homologues of ethyl phenol.

Comparative data is shown in the following table on the calculated composition of butyl phenol and the observed composition of a lower petroleum phenol cut boiling in the range of to C. at 5 mm. Hg absolute pressure and cor- Based on the analysis in Table 1, the average empirical formula of the petroleum phenol cut is represented by CmHas-CsI-ROH. As will be shown later, the phosphate esters formed from this petroleum 'phen-ol out have outstanding differences over the esters of the simple phenol. The petroleum phenols used in preparing the phosphate and phosphite esters may be segregated into close out fractions by distillation, in which greater vacuum is used to avoid decomposition as the distillation temperature rises. The

distillation, for example, may begin at 94 C.

under a pressure of 4 mm. Hg absolute and proceed to a temperature of 190 C. under an absolute pressure of 3 mm. Hg, the overhead being collected in approximately 10% cuts. The distlllation ranges under the specified reduced pressures, and the average empirical formula of each cut, as determined by analyses for carbon and hydrogen, are as follows:

Table 2 Average Formula Temperature 0. Per Cent Cut and Pressure ut ggs 33 1 li /4 mm. Hg 10 3. Cums-c.8101! 2 99 mm. H 10.3 3 l02l4 mm. g 10.2.. CMHu'QH OII 4 107l4 mm. Hg 10. 3 6 l10/4 mm. Hg l0.2..... Ca li 11.011 s ll6l4 mm. g. 10.3 7 126l4 mm. 113.. 10.4. CuHu-CJLOH 8 l24l3 mm. Hg.. 10.4 9;" l47l3 mm. Hg 10.4. CLIHIJ'CIHAOH l0 190l3 mm. Hg 6.0

From the average empirical formulae of the petroleum phenols, as shown in Table 2, can be recognized that the substituent groups in the phenol nuclei have a definite deficiency of hydrogen as compared with simple alkyl phenols which necessarily have the following general'formula:

In contrast to this, the lower petroleum phenols, except for the lowest boiling fractions difficult to free from hydrocarbons, have the following general formula:

Petroleum phenols vary somewhat according to v their source and in many instances the hydrogen deficiency is greater than shown in the components illustrated-wheres is less than 1, or even a negative quantity, the total quantity 2n+:c being smaller as the average molecular weight increases. For'instance, in the out having the average formula:

. CmHuCsHeOH the value of 2n+ris 7.5, which makes 'z.s-2-s.s)

4 which is equal to 0.9, and

CuHu CeHeOI-I :c is equal to negative 0.7.

This deficiency of hydrogen becomes progressively greater as the molecular weight of the phenols is greater and varies somewhat with the petroleum fraction source. with this deficiency of hydrogen there is also an occurrence of additional non-phenolic oxygen which can be more accurately determined in the higher petroleum phenols. The diand polycyclic rings in the petroleum phenols are regarded as being analogous to the higher molecular weight petroleum hydrocarbons which are built up of fused rings having one or more carbon atoms shared in common.

The low petroleum phenols have been observed to boil without substantial decomposition in the range of about C'. to C. under a pressure of 1 to 6 mm, H absolute pressure. The higher petroleum phenols, which are generally extracted from petroleum heating oil fractions boiling above 150 C., are characterized by compounds boiling in the range of 150 C. to about 350 C. under about 1 to 6 mm. Hg absolute pressure. Although the high phenols, which have more than about 10 carbon atoms per molecule, tend to darken in color, they are very valuable for producing phosphate and phosphite esters which serve very well as addition agents in hydrocarbon products such as lubricants, heavy fuels, hydrocarbon resins, etc., on account of the high miscibility of these esters with such materials.

Further, considering the higher petroleum phenols having more than 10 carbon atoms per molecule, i. e., where n indicates about 5 to 17 carbon atoms, and possibly more, per molecule in thesubstituent group, the average empirical formula may be represented by:

wherein :1: lies in the range of about -1 to 5, and 1! indicates an average of 0 to +1 nonphenolic oxygen atoms in the molecule. This same average empirical formula applies, in general, to all petroleum phenols when a: is, an a1ge-' bralo quantity ranging from below +1 to -5.

As demonstrated in the following examples, phosphate and phosphite esters have been prepared from petroleum phenol cuts similar to those illustrated in Table 2.

Example 1: Preparation of phosphate esters where R represents saturated hydrocarbon substituents having a carbon to hydrogen atomic ratio of about 33:7.5. The reaction product was dissolved in toluene, then washed with dilute hydrochloric acid, followed by dilute alcohol, and finally water. After the washing steps, the toluene solvent was evaporated oil. and the residual product was distilled'under reduced pressure. In the distillation, a fraction was collected at 230 C. to 265 C. under an absolute pressure of 1.5

mm. Hg, and this fraction on analysis showed a molecular weight corresponding to that of tri- (propyl phenyl) phosphate, (CaHr-CsHeOhPO. The yield was 51% based on the phosphorus oxychloride employed, and the product was a pale yellow liquid having a viscosity of 480 Baybolt seconds at 100 F. as compared to 132 seconds for tricresyl phosphate.

Example 2: Preparationof phosphate esters Example 3: Preparation of phosphate esters A petroleum phenol fraction boiling from 75 C. under. absolute pressure of 6 mm. Hg to 110 C. under an absolute pressure of 1.5 mm. Hg was reacted with phosphorus oxychloride by the method described in Example 2. The product which distilled in the range of 215 C. to 305 C.

under an absolute pressure of 2.5 mm. Hg had the average empirical formula (C4.2H8.8C8I'I40)3Pl.1 Example 4: Preparation oj phosphite esters A 183- gram fraction of petroleum phenols boiling from 75 C. under an absolute pressure of 6 mm. Hg to 110 C. under an absolute pressure of 1.5 nun. Hg was reacted with 50.7 grams of phosphorus trichloride by heating up to 190 C. in the course of about 9 hours. be represented by the general equation:

'where R represents hydrocarbon substituent groups, e. g., a polymethylene group, and Ar represents a cyclic nucleus, e. g., a phenyl group. A 70% yield of phosphite esters was obtained.

' The ester product distilled at 220 C. to 275 C.

under an absolute pressure of 2.5 mm. Hg.

The temperature of reaction, of course, is controlled to suit the particular reactants, their relative proportions, and, specific catalytic activity, if a catalyst is used. Usually, a temperature be- The reaction may the simple phenol may-be employed for each mol of-petroleum-phenola' v.

Thus, it 'canbe observed that the esters of lower petroleum phenols and phosphorus acids boil approximately in the. range of 200 to 300 C. at 1.5 to 2.5 mm. mercury absolute pressure and have average empirical formulae represented by (R-CaHrO): P=O anld (RCsHlO): P, wherein R, representing saturated hydrocarbon substituents of carbo-cyclic groups linked to phosphorus through oxygen atoms, contains carbon and hydrogen in an average atomic ratio which is less than n:2n+1, n being the number of the saturated substituent carbon atoms. The minimum of this atomic ratio of carbon to hydrogen in the saturated hydro-carbon substituent groups, R is about 0.44, but usually it is higher. ranging up to about 0.55, or more. V

The petroleum phenol phosphate and phosphite esters, thus prepared, have physical properties decidedly diilerent from those of the simple phenol phosphate and phosphite esters having similar molecular weights. This is plainly demonstrated by a comparison between tri(para-tertiary butyl-phenyl) phosphate and the phosphate esters of petroleum phenols having approximately the same molecular weights.

l Calculatrd content is 6.28% for QCEh-CdhO); P-O. 'At room temperature (22 to 25 C.) in parafilnic petroleum oil having a viscosity of 315 Saybolt seconds at 100 F.

The very good oil solubility of this petroleum phenol phosphate at low temperatures is representative and has proved to be a valuable property I in the utilization of these esters. The phosphate low 200 C. is convenient for effecting the esteriflcation or condensation at a suitable rate without excessive formation of objectionable by-products. The use of phosphorus pentachloride in may be employed as the solvent when chlorides and oxychlorides of phosphorus 'are used. High- 4 er boilingsolvents such as alkyl halides are useful for higher temperature reactions. The esterification of the petroleum phenols with the phosphorus acids may also be. carried out with admixed simple phenols or halogenated phenols to obtain desirable products of modified solubility and viscosity. For example, phenol, itself, or cresol may be admixed with the petroleum phenols prior to the esteriflcation or be used to complete the esterification, about one or two mols of esters of the petroleum phenols dissolve in both aromatic and paraflinic naphthas very readily. even without application of heat. and are soluble in'all proportions. Thlsis an important advantage over the known sters of simple alkyl phenols and phosphoric acid, which do not dissolve without heatinfl. because the heating tends to cause decomposition and discoloration.

It is to be noted that the petroleum phenol phosphate esters undernormal conditions exist as a viscous liquid, whereas. the simple phenol phosphate ester is a solid and this solid is miscible with the same oil solvent, only above the melting point of the solid. The combination of excellent I solubility in organic solvents, clear transparency and light color makes the esters of lower petroleum phenols very valuable as plasticizers or gelatinizers of various cellulose derivatives including cellulose acetate, nitrocellulose, and cellulose ethers. In this respect, it is important to note that the petroleum phenol phosphates are soluble in cellulose acetate to a practical degree, even though this cellulose derivative has been one of the most diflicult to provide with a soluble plasticizer. The phosphates of petroleum phenols are compatible with benzyl cellulose in-substantlally all proportions.

A comparison of viscosities oipetroleum phenol phosphate and phosphite esters produced according to methods in the foregoing examples with the viscosity of triorthocresyl phosphate is given in the following table:

' Table 4 Viscosity in Baybolt Universal Seconds at 100 F. at 210 F.

Trl-o-cres l hos hate 132 89. 4 Phosphatg e ters zii petroleum phenols..- 4.30 to 892 49. 9 to 60. l Phosphite esters oi petroleum phenols..- 517 B0. 2

' The exceedingly higher viscosities of the petroleumphenol esters is quite significant with regard to their complex structure and their properties.

Very favorable results were obtained in using phosphates of petroleum phenols having a molecular weight corresponding to that or propylphenol as a. plasticizer and according to the following formula:

In using the liquid phosphorus acid esters of petroleum phenols as plasticizers for organic solids which are normally too hard or brittle or for any other reason normally require plasticizing, the amount oi th'ese esters to be used will normally range from about 1% to 30% and generally from about to by weight on the basis or the substance being plasticized, i. e. not including any volatile solvent.

As the higher petroleum phenols tend to be somewhat darker than the lower ones, the phosph'ate or phosphite esters or the higher petroleum phenols are most advantageously used for plasticlzing either substances which inherently have a substantial amount or a color ranging from red through brown to black, as for instance high melting point normally brittle asphalt, cracking oil tar, etc. or for normally light colored or colorless Compositions 01' such formulae were tested with the same technique which had been used in testing other known plasticizers such as tricresyl phosphate. Films of these compositions 0.003 inch in thickness were cast. On drying, the composition containing 10% of the plasticizer tormed a clear film. This denotes that the petroleum phenol phosphate plasticizers are compatible with cellulose acetate in as high as a 10% concentration.

Owing to their greater molecular weight, viscosity. and complexity, the petroleum phenol ester plasticizers are able to impart exceedingly better flexibility, tenacity, and durability to cellulose derivatives used in films, lacquers, or molding compositions than simpler compound hitherto recommended as plasticizers. Their desirable high stability. as shown by their marked resistance to water, alkalies, and acids, and low volatility may also be accredited to their relatively high molecular weights and complexity. Another generally useful property of these improved esters is their highwetting power for increasing spread-. ing of compositions and for dispersing added ingradients, such as filler, pigments, and diluents. A valuable property belonging particularly to the phosphite esters is their oxidation inhibiting action.

Although the petroleum phenol phosphates and phosphites have been shown tobe especially useful as plasticizers with cellulose derivatives, their valuable properties make them also useful in various other compositions, as in various other resins andplastics, in lubricating compositions, greases, fuels, insecticides, fungicides, dust collecting agents. cable oils, insulating oils and compounds. textile oils, process oils, finishes, adhesives, polishes, and inks. They are sumciently non-nammable and water resistant to be used as lireprooflng and water-proofing agents;

The present application is a continuation in part oi co-pending application Serial No. 248,901, died December 31, 1938, now abandoned substances such as clear yellow or pale natural red or even colorless synthetic plastics such as cellulose acetates and the like with which has been blended a pigment or soluble dye or other insoluble fillers with which it would not be ob- Jectionable to use a minor proportion 01 plasticizer having a tendency to impart a reddish brown coloration to the plasticized composition.

To illustrate the invention as applied particularly to the preparation of a, phosphate ester of the higher petroleum phenols, the following additional example is given.

Example 5: Tripetroleum phenolphosphates 0! higher phenols the above phenols into a tri-ester, the following procedure was used.

A 3-way flask equipped with a stirrer, a return condenser and a dropping tunnel, was charged with 50 cc. absolute alcohol. To this was then gradually added 3.45 gms. (===O.15 mole) of metallic sodium. When all the sodium had dissolved, 40 gms. (=0.15 mole) of the above described petroleum phenols and 200 cc. of toluene were added as solvent. The mixture was then refluxed. The alcohol which collected in the water trap was removed from time to time.

When all the alcohol had been removed, the reaction mixture was cooled and the dropping tunnel was charged with 7.5 mm. (=0.05 mole) of phosphorus oxychloride, and 7.5 cc. toluene. The latter was then added to the reaction mixture drop by drop with rapid stirring. When all the chloride had been added, the mixture was refluxed tori hour.

After cooling. the reaction mixture was poured into water, acidified with hydrochloric acid and extracted with ether. The extract was washed. and dried. and the solvents were finally removed under reduced pressure at C.

The tri-ester was obtained as a. viscous dark red oil.

This invention is not intended to be limited by any of the specific examples which have been given merely for the sake of illustration, but only by the appended claims in which it is intended to cover all novelty inherent in the invention as well as all modifications coming within the scope and spirit or the invention.

What is claimed is: 1. Liquid phosphorus acid esters of petroleum Y a Number 9 ing above 150 C. at 6 mm. 'pressure, said esters being soluble in hydrocarbon oils at room temperature in all proportions.

2. Liquid phosphorus esters of petroleum phenols having at least 11 carbon atoms and boiling above 150 C. at 6 mm. absolute pressure, said esters being soluble in hydrocarbonoils at room temperature in all proportions and said esters boiling about 300 C., at 2 mm. absolute pressure.

LOUIS A. MIKESKA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,033,918 Britton Mar. 17, 1936 OTHER REFERENCES Story et al., Ind, and Eng. Chem", vol. 20, DD. 359-364 (1928).

15 Williams et al., Jour. Am. Chem. Soc.," V01a57,

Gruse, Petroleum and Its Products," 1st ed., 1938, pp. 40-41.