US3013868A - Liquid hydrocarbon compositions - Google Patents

Description

United States Patent G 3,013,868 LIQUID HYDROCARBON COMPOSITIONS Thurston Skei, East Alton, and James E. Douglas, Godtrey, EL, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed May 27, 1959, Ser. No. 816,039 6 Claims. (Cl. 44-62) This invention relates to novel flammable liquid compositions and to novel additives therefor, and particularly to hydrocarbon liquids of increased electrical conductivity.

The danger of spark discharge over flammable liquids, because of the accumulation of static electrical charges therein, has been of increasing concern in recent years. Many explosions and fires in oil refineries, depots and tankers have been attributed to it. It is generally known that liquid hydrocarbons in particular have a very low electrical conductivity and that electrostatic charging of the liquid may therefore take place when the liquid moves relative to a surface or interface. Such a movement occurs whenever the liquid is pumped through a tube or pipe and is therefore unavoidable in the handling of hydrocarbon liquids. Electrostatic charging occurs to a particularly dangerous degree when hydrocarbons are pumped at high speeds, for example during the fueling of aircraft. However, some danger also exists when hydrocarbons are pumped at the lower velocities normally encountered in refineries.

It is already known that the danger of accumulation of static electrical charges can be avoided by incorporating in the liquid additives which increase the electrical conductivity of the liquid. This expedient allows electrostatic charges to dissipate to such a degree that the electrostatic potential between the liquid and surrounding material will not be such as to provoke a sparking discharge.

Unfortunately, however such conductivity additives are often most effective only for relatively short periods of time in storage, after which their effectiveness falls off to some extent and the conductivity of the liquid in which they have been incorporated accordingly decreases. This of course is quite undesirable because in distributing and marketing liquid hydrocarbons or other flammable liquids, variable periods of storage will necessarily be encountered.

It is accordingly a principal object of this invention to provide improved flammable liquids, especially in respect to the electrical conductivity thereof. It is another object of the invention to provide an improved electrical conductivity additive composition. A more particular object of the invention is to provide such an additive composition which can be added to flammable liquids to provide an increase in electrical conductivity of greater permanence in storage. Other objects will be apparent in the description of the invention.

An especially effective class of conductivity additives for flammable liquids, especially hydrocarbon liquids, consists of salts of metals having atomic numbers from 22 through 28 and relatively high molecular weight aromatic carboxylic or sulfonic acids. These metals all have variable valences and each can exist in the valence state +3. Such salts of chromium have been found to be especially effective in increasing the conductivity of hydrocarbons.

After extensive study and experimentation it has been found that danger from electrostatic phenomena can be virtually eliminated under normal handling conditions only if the conductivity of the flammable liquid in question is increased to at least about 2x10 ohmcmf as compared to the considerably lower conductivity of commercially pure hydrocarbon fluids, i.e. in the order of 1X up to about 1 l()- ohrncum- Thus in the usual case it is necessary to increase the conductivity of a. hydrocarbon liquid in the order offrom double to perhaps even one thousand-fold in order to avoid electrostatic hazards.

A number of theories have been proposed to explain the action of these conductivity additives. None of them seems to offer a complete explanation, but it has been uniformly thought that the mechanism involves the presence of ions. This of course is consonant with the basic mechanism of electrical conduction in all liquid materials whether generally classified as conductors, e.g. aqueous solutions of electrolytes, or as non-conductors, e.g. hydrocarbons, which are non-ionic. However, regardless of the theory, the addition of extremely minute quantities of such additives is at least initially effective, for example in the order of gram about 1 X 10- to about 1X10" from atom of such metals in the form of such salts per liter of the flammable liquid. At the very low concentrations, the conductivity imparted to the liquid by the conductivity additive is much more permanent than in the case of the higher concentrations. For example, when the concentration is l l0 gram atom of metal per liter of flammable liquid, or less, the conductivity benefit is retained for many days in storage. However, at higher concentrations, the conductivity benefit is gradually and sometimes very rapidly decreased, often to a level which is only a small fraction of the initial value.

It has now been discovered that such conductivity additives can be improved, especially in respect to the retention of high conductivity by solutions of flammable liquids containing them, by adding to such salts a nitrogencontaining copolymer comprising at least two monomers, viz., (A) an olefinic polymerizable compound containing an oil-solubilizing group which is preferably an aliphatic chain and at least 8 and preferably at least 12 carbon atoms long, and (B) an olefinic polymerizable compound which either contains nitrogen or is amenable to a chem ical reaction, after copolymerization, to incorporate nitrogen in'the copolymer, for example amidization. The composition of the invention is thus a conductivity additive composition (or a flammable liquid containing it) comprising substantial proportions each of (l) a salt of a metal having an atomic number from 22 through 28 and a relatively high molecular weight aromatic carboxylic or sulfonic acid, and (2) a copolymer as described above. In order to avoid misunderstanding, whenever the term conductivity additive is used hereinafter, it will be understood to mean a metal salt as defined herein; Whenever the term conductivity additive composition is used hereinafter, it will be understood to mean an additive composition in accordance with the invention, i.e.,

which also contains a nitrogen-containing copolymer as defined herein as well as the metal salt conductivity additive.

As mentioned above the conductivity additive of the aromatic carboxylic acids, especially alkyl hydroxyaryl- V carboxylic acids such as alkylated salicylic acids.

Salts of sulfonic acids'suitable as the conductivity additive in the compositions of the invention are preferably salts of the sulfonated dialkyl esters of aliphatic dicarboxylic acids, for example the sulfonated dioctyl ester of succinic acid. However, salts of petroleum sulfonic acids and of alkylated naphthalene sulfonic acids, e.g. dinonyl naphthalene sulfonic acid, are also useful.

The metal salt conductivity additive in the compositions of the invention is oil soluble and has a molecular weight of at least 200, preferably at least 500, preferably no more than 3000, especially up to about 2500.

Specific examples of particularly effective conductivity additives according to the invention are chromic diisopropylsalicylate, ferric diisopropylsalicylate, chromic dioctyl sulfosuccinate, vanadium petroleum sulfonate, titanium (III) salt of C -alkyl salicylic acid, cobaltic dioctyl sulfosuccinate, manganous salt of C -alkyl salicylic acid, and chromic salt of dinonylnaphthalene sulfonic acid.

EXAMPLE I The remarkable effectiveness of the particular class of conductivity additives of the compositions of the invention is illustrated by the following conductivity measurements.

Initial boiling point, 80 0.; end boiling point, 110 C.

Especially preferred conductivity additives for the purposes of the invention are the chromium salts of alkylsalicylic acids which contain at least one alkyl substituent having at least 8, preferably from to 22, carbon atoms. The preferred chromium salt is a trivalent chromiurn salt and may be either neutral or contain excess basicity. They are suitably prepared from the corresponding alkylsalicylic acids or the alkali metal salts thereof.

Several methods for preparing alkylsalicylic acids or alkali metal salts thereof are known. For example, they may be prepared in the following ways:

(1) Salicylic acid is reacted with an olefin or a mixture of olefins in the presence of a suitable condensing agent, such as sulfuric acid of 90 to 98% by weight concentration, boron trifiuoride or zinc chloride at a sufficiently high temperature to bring about the desired reaction.

(2) A nuclear acylated salicylic acid is subjected to the, well-known Clemmensen reduction. For example, octadecyl salicylic acid may be prepared by reduction of stearoyl salicylic acid with zinc and hydrochloric acid.

(3) Alkylation of phenol followed by conversion of the alkylphenols into alkali metal alkylphenates and carboxylation of these phenates according to the Kolbe method leads to alkali metal alkylsalicylates which may be converted, if desired, into the corresponding alkylsalicylic acids. For the technical preparation of alkylsalicylates or alkylsalicylic acids this method is preferred.

Referring to method (3) in more detail, phenol is first alkylated in any known way so as to obtain an alkyl phenol containing at least one alkyl substituent having 8 or more carbon atoms. For example, phenol may be alkylated with mixture of olefins containing 14 to 18 carbon atoms obtained by cracking of paraffin wax, so as to obtain a mixture of monoand di-C to C -alkylphenols. The alkylation is carried out in the presence of a catalyst, e.g. zinc chloride and hydrochloric acid. Then, the alkyl phenols are converted into alkali metal, e.g. sodium, alkylphenates. Any of the well-known meth ods for carrying out this conversion can be used. The

alkali metal alkyl phenated are carboxylated with CO according to the Kolbe method. The carboxylation may be carried out in the absence of a solvent, but is preferably carried out in the presence of an inert solvent, such as xylene. The carboxylation reaction does not go to completion and the reaction product (carboxylate) contains unconverted alkyl phenate. Furthermore, the carboxylate may contain other by-products, such as alkylphenols and alkali metal salts of dicarboxylic acids derived from the alkylphenates by the introduction of two carboxylate groups.

It is possible to remove the alkylphenates and alkylphenols from the carboxylate. For example, a xylene solution of the carboxylate may be freed from xylene by steam distillation, acidified and extracted with dilute ammonia solution. Another method consists in acidifying the carboxylate, and neutralizing it with an alkali metal hydroxide, whereby the alkylsalicylic acids are converted into the alkali metal salts and the alkylphenols remain unconverted; from a solution of a mixture of alkali metal salts of alkylsalicylic acids and alkylphenols in a wateralcohol mixture (e.g. 50% aqueous isopropanol) the alkyl phenols can be extracted by means of a liquid aliphatic hydrocarbon, such as pentane.

The preferred method for preparing the chromium al kyl-salicylates of the invention consists in reacting a solution of alkali metal alkylsalicylates, preferably in a hydrocarbon or an alcohol, with an alcoholic solution of an inorganic chromium salt. The following example illustrates this method.

EXAMPLE II (A) PREPARATION OF CARBOXYLATE Phenol is alkylated in the presence of zinc chloride and hydrochloric acid with a mixture of olefins containing 14 to 18 carbon atoms obtained by cracking of paraffin wax. The alkylphenol is dissolved in xylene and converted into the corresponding sodium alkylphenates by heating with a 45% by weight aqueous solution of sodium hydroxide. The water is removed by azeotropic distillation. The phenate, dissolved in xylene, is carboxylated with CO under super-atmospheric pressure. Exclusive of the xylene, the carboxylate still contains 38% by weight of unconverted sodium alkylphenates.

(B) PREPARATION OF "PURE" CHROMIUM Cri-lS-ALKYL SALICYLATES The carboxylate described under A is stirred for 2 hours at a temperature of to C. with a excess of 10% aqueous sulfuric acid. The mixture is allowed to stratify for 3 hours and then the lower aqueous layer containing sodium sulfate and excess sulfuric acid is removed.

The upper layer is neutralized at room temperature with a 15% solution of sodium hydroxide in 50% aqueous isopropanol. The quantity of sodium hydroxide added is equivalent to the acid value of the xylene solution and the end point of the neutralization is controlled by means of phenolphthalein. Under these circumstances the alkylsalicylic acids are converted into the corresponding sodium salts but the alkylphenols are not converted into sodium alkylphenates.

The solution obtained in this way is extracted with pentane whereby the alkylphenols and the xylene are removed.

The remaining solution is evaporated to dryness and the residue is dissolved in ethanol. The solution is heated to 75 C. and at this temperature a 10% excess of a 15% solution of chromium nitrate in ethanol is gradually added. The alcohol is distilled off at a maximum bottom temperature of 100 C., 30% by volume of benzene is added and any remaining alcohol as well as any water which may be present in the mixture (eg, Water of crystallization of the chromium nitrate) is removed by azcotropic distillation. The anhydrous mixture is cooled to room temperature and the precipitated sodium nitrate is removed by filtration.

" off.

Finally, the solvent (benzene) is distilled E to leave chromium C all ylsalicylates (hereinafter called product B).

(C) PREPARATION OF CHROMIUM C14-1s-ALKYLSALI- CYLATES CONTAINING ALKYL PHENOL The carboxylate described under A is stirred for 2 hours at a temperature of 80 to 90 C. with a 100% excess of aqueous sulfuric acid. The mixture is allowed to stratify for 3 hours. Then the lower aqueous layer containing sodium sulfate and excess sulfuric acid is removed.

The upper layer is neutralized at room temperature with a solution of potassium hydroxide in ethanol. The quantity of potassium hydroxide added is equivalent to the acid value of the xylene solution and the end point of the The carboxylate described under A is mixed with a 30% aqueous solution of sodium hydroxide, the mixture is heated and after adding a further quantity of xylene the Water is removed by azeotropic distillation. The quantity of sodium hydroxide used is equivalent to the quantity of sodium alkylsalicylates present in the carboxylate. It is assumed that under these circumstances the OH groups of the sodium alkylsalicylates are converted into ONa groups.

The solution is then treated with a solution of chromium nitrate in methanol as described under D.

The product (hereinafter called product E-l) has a chromium content of 4.78% by weight.

If the carboxylate is treated with a double amount of 15 sodium hydroxide, the end product (hereinafter called neutralization is controlled by means of phenolphthalem. product v has a chromium content of 554% by Under these circumstances the alkylsalicyclic acids are Weight This product apparently contains an @Xcess converted into the corresponding potassium salts but the of chromium hydroxide but it is not Char how this alkylphenols are not converted into alkylphenates. a chromiumvhydroxide is bound in the product The 891mm Obtamed 1n thls Way 15 heated to Although the methods described above are the preand at thls temperafure a exvcess of a 30mm) of ferred ones for the preparation of the conductivity salts chrolPlum filtrate ethanol 15 gladuauy q T of the invention, it is clear that any other suitable method culatlon of the ReCQiSSaTY amount of q r mtrate 15 can be used for their preparation without unduly affecting based P f Value of the ac1dlfied carboxylatetheir property of increasing the electrical conductivity The alcohol 1s distilled off at a maximum bottom temperaf organic liquids in Which they may be incorporated ture of 100 C., by volume of benzene is added and any remaining alcohol as well as any water which may be EXAMPLE III present in the mixture (e.g. water of crystallization of the chromium nitrate and water formed during the neutraliza- The remarkable conductivity benefits of the salts of tion of the alkylsalicylic acids with the potassium hydrox- 30 Example II are shown in Table II, wherein measured ide) is removed by azeotropic distillation. The anhyspecific conductivities are given for the products B, C, D, drous mixture is cooled to room temperature and the pre- 13-1 and 13-2 at various concentrations in gasoline having cipitated potassium nitrate is removed by filtration. Fian initial boiling Point Of alld an d iling nally, the solvent (xylene-l-benzene) is distilled off. point of 110 C.

Table II Concentration, Conductivity of Solution, ohmernr Gram Atom Metal per Liter Product B Product 0 Product D Product E-l Product E-Q 1 10 011 1o .024Xl0' .024 10 1 10- 11 10- .24x10- .25 10 1 1o- 1.1 10 2.6X10-13 2.s5 1tr 1 10 s.4 10 24x10- 25 10- 1 10 130 1o- 290 1o- '490x10- 1 10 3,000 10 The product (hereinafter called product C) has a EXAMPLE IV chromium content of 2.20% by weight.

(D) PREPARATION OF CHROMIUM A'LKYLSALICYL- ATES CONTAINING CHROMIUM ALKYLPHENATES To the carboxylate described under A" a solution of chromium nitrate in methanol is added and the mixture is heated to complete the reaction. The quantity of chromium nitrate used is equivalent to the sodium content of the carboxylate. The alcohol is distilled off at a maximum bottom temperature of 100 C., benzene is added and any remaining alcohol as well as any water which may be present in the mixture, is removed by azeotropic distillation. The anhydrous mixture is cooled to room temperature and the precipitated sodium nitrate is removed by filtration. Finally, the solvents are distilled The product (hereinafter called product D) has a chromium content of 3.08% by weight.

(E) PREPARATION OF IBASIC CHROMIUM ALKYL- SALICYLATES CONTAINING CHROMIUM ALKYL- "0 PHENA'IES The term basic chromium alkylsalicylates is used to indicate alkylsalicylates which contain more chromium than is equivalent to the CCOH-groups of the alkylsalicylic acids.

A special advantage of the chromium salts as conductivity additives in the present invention is due to'the fact that they are not leached from hydrocarbon solutions by water. This is shown in this example.

Various solutions of product B in a gasoline having an initial boiling point of 35 9 C. and an end boiling point of C. were prepared and the conductivityof these solutions measured both before and after shaking with 7 equal volumes of water and settling in contact with the water for 4 days. The results were as follows:

As discussed above, however, the conductivity falls off 7 somewhat in the case of the higher concentration, 1X10 gram atom chromium per liter.

EXAMPLE V In many cases it is desirable to use the conductivity additives in conjunction with other compounds which synergistically augment the direct conductivity benefits of these salts, on the principles described in theBritish Patent No. 749,898 to N. V. dc 'BataafschePetroleum Maatschappij, published June 6, 1956. The following table, Table IV, gives the specific conductivities in ohm-- cm.- measured on the gasoline of Example 111 containing the products C, D and 13-1 in a concentration of 1X10- gram atom of chromium per liter alone and together with calcium dioctyl sulfosuccinate, also at a concentration of 1X10 gram atom of calcium per liter:

Concentrations of suchsynergists are suitably from about 1X10 to about 1 1()- mol per liter, preferably about 1, 10- to about 1 10- mol per liter, .of the flammable liquid.

The other essential ingredient of the compositions of the invention, the oil-soluble nitrogen-containing copolymer can be selected from a very wide class of such compounds. Preferred such copolymers are the copolymers :of a vinylpyridine and at least one ester of an acrylic ;acid and a long chain aliphatic alcohol containing at Eleast carbon atoms, as described in Barnum et al., US. 2,839,512, June 17, 1958. For the sake of brevity, ;the disclosure of this patent is incorporated herein by reference for a complete description of the preferred copolymers.

Other oil-soluble nitrogen-containing copolymers particularly suitable in the compositions of the invention are the oil-soluble, basic amino nitrogen-containing addition-type polymers of a plurality of polymerizable ethylenically unsaturated compounds, at least one of which is amine-free and contains from 8 to about 18 carbon atom in an aliphatic hydrocarbon chain which is a side chain in the polymer, and one of which contains a basic amino nitrogen atom in a side chain, as described in Catlin et al,, US. 2,737,452, March '6, 1956. For the sake of brevity, the disclosure of this patent, too, is incorporated herein by reference for a complete description of such suitable copolymers. Preferred such basic amino nitrogen-containing copolymers are those in which the amino compound is a dialkylaminoalkyl acrylate such as diethylaminoethyl methacrylate,for example the threecomponent copolymer of lauryl methacrylate styrene and diethylaminoethyl methacrylate (45 :45: 10 ratio).

Other oil-soluble nitrogen-containing copolymers particularly suitable in the compositions of the invention are the copolymers of an N-vinyl-Z-pyrrolidone and at least one C (average)-alkyl ester of an acrylic acid, as described in the Belgian patent to Rohm and Haas Company, Belg. 550,442, or in the Canadian patent to Sachs, Can. 560,549, July 22, 1958. Again for the sake of brevity, the disclosures of these patents, too, are incorporated herein by reference for a complete description of such suitable copolymers. Especially preferred such copolymers are those of N-vinyl-2-pyrrolidone itself and a mixture of alkyl methacrylates the alkyl (esterifying) groups of which are obtained from a commercial mixture of C to C primary alcohols, in which copolymer the 'acids and the long chain aliphatic alcohols.

ratio of the N-vinyl pyrrolidone structure to the methacrylate ester structure is about 1 to 5 or 6.

Still other oil-soluble nitrogen-containing copolymers particularly suitable in the compositions of the invention are the copolymers of an alpha olefin having at least 10 carbon atoms and an ester of an acrylic acid and a C alianol, at least 10% of the ester groups of which copolymers have been amidized with an amine containing a substituent polar group, especially NR or Where R is a hydrocarbyl group, as described in Bondi et al., US. 2,800,452, July 23, 1957. Again for the sake of brevity, the disclosure of this patent, too, is incorporated herein by reference for a complete description of such suitable copolymers.

Still other oil-soluble nitrogen-containing copolymers particularly suitable in the compositions of the invention are the copolymers containing (A) at least one oil-solubilizing compound having an ethylenic linkage and a group of 4 to 30 aliphatic carbon atoms and which is copolymerizable through said linkage and (B) at least one amide of an alpha, beta-unsaturated carboxylic acid of from 3 to 6 carbon atoms, with from 1 to .15 units of the ethylenic component (A) being present in the copolymer for each unit of the amide component (B), as described in the British patent to California Research Corporation, Br. 759,517, published October 17, 1956. Again for the sake of brevity, the disclosure of this patent, too, is incorporated herein by reference for a complete description of such suitable copolymers.

For the purposes of the present invention the oil-soluble nitrogen-containing copolymers should have molecular weights in the range 5000 to 2,500,000 as determined by the light scattering technique described in Chem. Rev., vol. 40, page 319 (1948), preferably from 50,000 to 1,000,000, or most especially from 100,000 to 650,000. Also, the nitrogen content of the copolymer is important; it should be at least 0.1% by weight of the copolymer and preferably not more than 8%, but more especially at least 1% and not more than 5% by Weight the copolymer having an inherent viscosity of from about 0.1 to 3.0 as determined at 0.1% weight volume concentration in benzene at 25 C.

A particularly preferred class of copolymers for the purposes of the present invention are copolymers of the type described in the above Barnum et al. patent but which also contain, as one ofthe monomers, an ester of an acrylic acid and a lower alkanol, viz., special copolymers of 1) a vinylpyridine, (2) a mixture of at least two dissimilar esters of an acrylic acid and long chain alcohols containing at least a pair of esters derived from alcohols which diflFer by at least 4 carbon atoms and which are present in a mol ratio to one another of from 1:10 to 10:1, and (3) at least one ester of an acrylic acid and a lower alkanol containing no more than 6 carbon atoms, such as methyl .methacrylate or butyl methacrylate, in which copolymer the mol ratio of the vinylpyridine to the esters is from 1:15 to 2:1 and the lower alkyl ester is from lO-to 75 mol percent of the total esters.

The vinylpyridines used in making these special copolymers may be exemplified by 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, 4- methyl-Z-vinylpyridine, S-ethyl-Lvinylpyridine and butyl-S-vinylpyridine, and the like. Particularly preferred groups comprise 2-, 3- and 4-vinylpyridines and the lower alkyl-substituted derivatives thereof.

The long chain acrylate esters used in the preparation of these special copolymers include the esters of acrylic Examples of the acrylic acids include acrylic acid and the alphasubstituted acrylic acids such as methacrylic acid, ethacrylic acid, alpha-phenyl acrylic acid, alpha-cyclohexyl acrylic acid and chloroacrylic acid. The long-chain'aliphatic alcohols used in the esterification of these acids may be exemplified by decyl, lauryl, cetyl, stearyl, eicosanyl, nonadecanyl, and the like alcohols and mixtures thereof. Particularly preferred esters to be used are the acrylic acid and methacrylic acid esters of aliphatic monohydric alcohols, and especially alkyl alcohols, containing from 14 to 20 carbon atoms.

Specific examples of these long chain acrylic acid esters include, among others, decyl acrylate, lauryl acrylate, stearyl acrylate, decyl methacrylate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, eicosanyl acrylate, docosanyl acrylate and the like, and mixtures thereof.

As noted, a mixture of two or more of these long chain acrylate esters is used in making the new copolymers. Illustrative examples of these mixtures include, among others dodecyl methacrylate/octadecyl methacrylate, tetradecyl acrylate/octadecyl methacrylate, decyl methacrylate/octadecyl methacrylate, tetradecyl methacrylate/ hexadecyl methacrylate, tetradecyl acrylate/octadecyl methacrylate, dodecyl methacrylate/eicosanyl acrylate, and the like. In these mixtures there is a wide difference in the number of carbon atoms of the alcohol portion, i.e., at least 4 carbon atoms, and the mol ratio of such differing esters should be 1:10 to :1, preferably 1:4 to 4:1. Particularly superior results are obtained when one of the acrylate esters is a C to C acrylate ester and the other is a c to C acrylate ester.

In considering the above mixtures, it should be noted that an ester of acrylic acid or methacrylic acid and technical lauryl alcohol, which is a mixture of straight chain alcohols, should not be considered such a mixture as described above since copolymers of lauryl (technical) methacrylate and a vinylpyridine will not havethe required ratio of dissimilar alkyl chains or the average alkyl chain length which is required of such preferred special copolymers.

The third type of component used in making these special copolymers is an ester of an acrylic acid and a lower aliphatic alcohol of not more than 6 carbon atoms. Examples of these lower acrylates include, among others, the acrylic acid and methacrylic acid esters of methanol, ethanol, butanol, hexanol, isobutyl alcohol and propanol.

This third component is used only in certain specific amounts. It has been found that the ester of the acrylic acids and the aliphatic alcohol containing not more than 6 carbon atoms should be employed in no more than 75 mol percent of the total acrylate ester mixture, i.e. the total of the mixture of long chain esters and the lower aliphatic monohydric alcohol containing not more than 6 carbon atoms. Preferably the lower acrylate ester is employed in amounts varying from 15% to 60% by weight of the total acrylate ester mixture.

EXAMPLE VI A mixture of 2.52 mol of stearyl methacrylate, 5.04 mol of lauryl methacrylate, 0.83 mol of methyl methacrylate and 1 mol of Z-methyl-S-vinyl pyridine and 0.2% wt. of alpha, alpha aodiisobutyronitrile dissolved in a minor amount of acetate for solubility was placed in a reaction vessel and reacted for about 2448 hours at 65 C. with stirring in a nitrogen atmosphere. The polymer was then dispersed in equal volumes of benzene and thereafter precipitated with 5-10 volumes of a mixture of acetone and methanol. This was repeated and a stearyl methacrylate/lauryl methacrylate/methyl methacrylate/2- methyl-5-vinyl-pyridine polymer having a nitrogen content of 0.60% by weight and a molecular weight in excess of 750,000 was recovered.

Following essentially the procedure of Example VI, other polymers are prepared from monomer mixtures in the molar proportions as shown in Table V.

, will be seen below.

SMA=stearyl methacrylatc; LMA=laury1 mcthacrylate; MMA: methyl mcthaerylate; BMA=butyl methacrylate; MVP=2-methyl-5- viuylpyridinc EVP fi-ethyhZ-viuylpyridine.

Other examples of useful polymers for the purpose of the invention include: dodecyl acrylate/stearyl acrylate/ ethyl methacrylate/vinylpyridine; hexadecyl methacrylate/stearyl methacryla te/propyl methacrylate/ 2-methyl- 5-vinylpyridine, lauryl methacrylate/stearyl methacrylate/ eth-yl methacrylate/S-ethyl-2-vinylpyridine and decyl methacrylate/octadecyl methacrylate/butyl methacrylate/ vinyl pyridine in which the mol ratios of the total ester mixture to the vinylpyridine are ratios of from 1:2 to 15:1, respectively, and in which the amounts of methyl, ethyl, propyl or butyl acrylate or methacrylate in the ester mixtures are amounts of from 10 to and preferably from 15 to 60 mol percent of the total ester mixture.

EXAMPLE XXI 29.3% stearyl methacrylate, 49.7% lauryl methacrylate, 16% methyl methacrylate and 5.0% methyl Vinylpyridine were charged to a 300-gallon stainless steel autoclave. A 50/ 50 mixture of benzene and neutral petroleum oil was then added to the autoclave so as to furnish 1 part of the mixture per 3 parts of the total monomer. 0.25% of ditert-butyl peroxide was then added and the mixture heated at 120 C. for about seven hours. At the completion of the reaction, the benzene was stripped off to final conditions of 120 C. and 10 mm. Hg with nitrogen sparging. The benzene-free product was then diluted with neutral oil to a polymer content of about 30% by weight and filtered at 120 C.

The conductivity additive composition of the invention must contain very substantial amounts of the copolymer in proportion to the metal salt. It is generally necessary that the weight ratio of copolymer to metal in the metal salt conductivity additive be at least 20:1, more especially at least 50:1, and preferably even at least 200:1. On the other hand it will rarely be necessary that a weight ratio greater than 5000:1 of copolymer to metal in the metal salt be used, and, in order to minimize water sensi tivity of hydrocarbon liquids, especially fuels, into which the composition is incorporated, it is desirable that this ratio be no greater than 2000:1. It .is particularly preferred that this ratio be no greater than 1500:1.

These proportions of the copolymer appear to be very sumption of the conductivity additive composition, and therefore that of the copolymer, is very small indeed, a

Suitable hydrocarbon base liquids into which the conductivity additive composition'of the invention can be advantageously incorporated are those normally boiling Within the range of from about -40 F. to about 700 F., i.e., those which are generally referred toas hydrocarbon distillates. The invention is particularly applicable to petroleum distillates in the gasoline and kerosene boiling ranges, such as gasoline (both automotive and aviation), aviation turbine fuel of the JP-l, JP4 and JP-S mineral spirits, rubber solvent, lacquer diluent, insecticide base, kersosene, and special boiling range solvents of all kinds such as direct cuts of xylenes and non-aromatics boiling in or near the xylene range, or similar toluene or benzene cuts, and also extracts and rafiinates (e.g. from S or furfural extraction) obtained from such cuts. The invention is of greatest benefit and importance in the case of aviation turbine fuels, especially of the kerosene type, because of the extreme danger of static electrical charges in such fuels.

As already indicated the concentration of the metal-containing salt necessary to adequately protect a hydrocarbon liquid from electrostatic phenomena is extremely minute. In general it is only necessary to provide in the hydr0- carbon liquid a concentration of the metal salt equivalent to at least l lO gram atom of the metal per liter of the hydrocarbon liquid, although in some cases no more than 1X 10* gram atom will be needed. On the other hand, because it is not desirable to incorporate in a hydrocarbon liquid too much of an ash-containing additive, it is preferred to use no more than l 10- or preferably no more than 1 10 gram atom of the metal in the form of the metal salt per liter of hydrocarbon liquid. Especially suitable concentrations are from about 1X10 to about 1 l0- gram atom of the metal per liter of hydrocarbon liquid. When the lowest of these concentrations are used, for example 1 l() to l 10- gram atom of metal. the conductivity benefits while relatively smaller are nevertheless relatively well retained by the hydrocarbon liquid. This is shown above in Example IV where there was no loss of conductivity in the case of 1X 10 mols and even 1X l0 mols chromium per liter of gasoline after 4 days. However the loss became very significant at 1X 10* mols chromium per liter of gasoline, and as will be shown in Example XXII below, becomes very large in the case of higher concentrations and in a heavier hydrocarbon liquid.

EXAMPLE- XXII The deleterious effect of aging on a somewhat heavier hydrocarbon liquid, a range fuel, containing a conductivity additive was observed as follows. The range fuel had the following characteristics:

Gravity, API 43.3 Saybolt color 28 Flash point, TCC, "F 143 ASTM distillation, F.:

I.B.P 348 10% 376 50% 90% 95% evap 508 E? 524 To each of a pair of duplicate samples of this range fuel was added 0.385 part per million by weight of chromium C -alkylsalicylate (Cr content 5.9% by weight), i.e., 3.5 X10 gram atoms chromium per liter of the fuel or 1.8x 10 grams chromium per liter of fuel, and 0.44 part per million by weight of calcium dioctyl sulfosuccinate, i.e., 4 10 gram atom of calcium per liter of fuel (fuel composition A). To each of another pair of duplicate samples of this range fuel were added the same concentration of the same chromium C -alkylsalicylate and the same calcium dioctyl sulfosuccinates and additionally 10 ppm. by weight of the copolymer of Example XXI, i.e., 0.008 gm. of the copolymer per liter (fuel composition B). Fuel composition B thus contained the copolymer and metal of the metal salt conductivity additive in a weight raito of copolymer to metal (i.e., chromium) of about 450:1.

Each of these doped samples was shaken with water, to simulate the important influence of the usual presence of an aqueous phase during commerciai handling of hydro- 12 carbon liquids. The conductivities 0f the fuel samples were measured both initially and after aging for 16 hours; the results were as follows:

Conductivity, ohm cmr Initial Aged Fuel Composition A 19 (10- 4X10- Duplicate 5x10 Fuel Composition,l3. 21X10- 12 l0 Duplicate IOXID- It is thus seen that the fuel composition in accordance with the invention (fuel composition B) retained 2 to 3 times the conductivity retained by the composition not containing the copolymer.

EXAMPLE XXIII EXAMPLES XXIV In another series of experiments, the same concentration of the conductivity additive, chromium C -alkylsalicylates, as used in Example XXII was added to a white spirit (boiling to C.) with and without the same concentration of the copolymer of Example XXI as used in Example XXII. In this case part of each sample was shaken with water and part was not. The conductivities were measured several times over a storage period, as follows:

Conduetivities, ohmcm.-

Without the Willi the Storage Time, Days copolymer Copolymer Shaken Shaken Dry with Dry with water water The above data shows that in this case the copolymer not onzy prevented conductivity loss on storage, but if an thing promoted a conductivity gain.

In addition to the synergists such as calcium dioctyl sulfosuccinate as described above, still other optional ingredients may advantageously be used in the compositions of the invention. A particularly preferred class of such optional additional ingredients is the class of metal deactivators containing the structural group:

a. I I I I it.

wherein R is an alkylene radical containing from 1 through 4 carbon atoms, preferably ethylene or 1,2-propylene. These metal deactivators thus include, and are preferably, the compounds described in Downing et al., US. 2,181,121, November 28, 1939, and in White et al., US. 2,285,878, June 9, 1942. It is preferred that the metal deactivators, except for the oxygen and nitrogen atoms in the above structural group, be entirely hydrocarbon and that the molecular weight thereof be not more than 300. The especially preferred metal deactivator in the compositions of the invention is the compound N,N-disalicyiidene-1,2-propanediamine; however, another preferred compound is bis(l-acetonyl-ethylidene)-ethanediamine, which through keto-enol tautomerism contains the above group.

The concentration of such metal deactivators in the compositions of the invention should *be at least one gram mol thereof per gram atom of metal in the metal salt conductivity additive. It is preferred that at least 5, and more especially at least gram mols of the meta] deactivator be present per gram atom of metal of the metal salt conductivity additive. Much higher concentrations of the metal deactivator can effectively be present without adversely affecting the conductivity benefits of the metal salt, even up to about 1000 or more gram mols of the metal deactivator per gram atom of metal in the conductivity additive. In general, however, economics and other considerations will dictate the use of no more than about 100, or preferably no more than about 80 gram mols of metal deactivator per gram atom of metal in the metal salt.

In addition to the ingredients specified above, the conductivity additive composition of the invention can advantageously contain sufficient mineral oil, such as kerosene, xylene, gasoline, naphtha, etc., to give the additive composition sufiicient fluidity for easy handling.

EXAMPLE XXV A particularly preferred conductivity additive composition in accordance with the invention is one containing product E-2, i.e. chromium C -alkylsalicylate prepared as described in Example II above, and additionally, 450 parts by weight (for each part by weight chromium in the chromium material present) of the copolymer of Example XXt, and 50 gram mols of N,N'disalicylidene-l, Z-propanediamine per gram atom of chromium in the chromium material present.

EXAMPLE XXVI A particularly preferred hydrocarbon fuel composition in accordance with the invention is a jet fuel of the kerosene type containing a sufficient quantity of the additive composition of Example XXV that the concentration of chromium metal in the jet fuel is 0.03 part per million by weight.

We claim as our invention:

1. A conductivity composition consisting essentially of (1) a chromium alkyl salicylate having a molecular weight of 5002500 and (2) a copolymer of a vinyl pyridine and at least one ester of an acrylic acid and a long chain aliphatic alcohol containing at least 10 carbon atoms, the mol ratio of the vinyl pyridine to ester being from 1:15 to 2:1, said copolymer having an average molecular Weight between 5 10 to 25 10 the weight and 5000:1.

2. The composition in accordance with claim 1, wherein the oil soluble nitrogen-containing copolymer is a copolymer of (1) a monovinyl-substituted pyridine of the group consisting of pyridines substituted on one of the ring carbon atoms with, as the sole substituted substituent, a vinyl group, and derivatives of the aforedescribed vinylpyridines having a lower alkyl group substituted on a ring carbon atom and (2) a mixture of a C to C alkyl ester of an acrylic acid of the group consisting of acrylic acid and methacrylic acid and a C to C alkyl ester of an acrylic acid of the group consisting of acrylic acid and methacrylic acid.

3. A liquid hydrocarbon fuel composition consisting essentially of hydrocarbons boiling in the range of from -40 F. to 700 F. and a composition according to claim 1, in an amount suificient to provide said fuel composition with 1X10 to 1 10 gram atoms of chromium in the form of the salicylate per liter of hydrocarbon.

4. The liquid hydrocarbon fuel composition according to claim 3 containing in addition 1 10 to 1 10- mols per liter of a calcium dialkyl sulfosuccinate.

5. The liquid hydrocarbon fuel composition according to claim 3 wherein the copolymer is one formed by copolymerization of 29.3% stearyl methacrylate, 49.7% lauryl methacrylate, 16% methyl methacrylate and 5.0% 2-methyl-5-vinyl pyridine.

6. A conductivity additive composition consisting essentially of (1) a chromium alkylsalicylate having a molecular weight of from about 500 to about 2500 and (2) a copolymer of a vinylpyridine, a mixture of at least two dissimilar esters of an acrylic acid and long chain alcohols which mixture contains at least one pair of esters derived from alcohols differing by at least 4 carbon atoms and being present in a mol ratio to one another of from 1:10 to 10: 1, and at least one ester of an acrylic acid and a lower aikanol containing no more than 6 carbon atoms, in which copolymer the mol ratio of the vinylpyridine to the total esters is from 1:15 to 2:1 and the ester of the lower alkanol is from 10 to mol percent of the total esters, the weight ratio of copolymer to chromium being between 20:1 and 5000:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,737,452 Catlin et a1. Mar. 6, 1956 2,800,452 Bondi et al. July 23, 1957 2,839,512 Barnum et a1. June 17, 1958 FOREIGN PATENTS 749,898 Great Britain June 6, 1956

Claims (2)

1. A CONDUCTIVITY COMPOSITION CONSISTING ESSENTIALLY OF (1) A CHROMIUM ALKYL SALICYLATE HAVING A MOLECULAR WEIGHT OF 500-2500 AND (2) A COPOLYMER OF A VINYL PYRIDINE AND AT LEAST ONE ESTER OF AN ACRYLIC ACID AND A LONG CHAIN ALIPHATIC ALCOHOL CONTAINING AT LEAST 10 CARBON ATOMS, THE MOL RATIO OF THE VINYL PYRIDINE TO ESTER BEING FROM 1:15 TO 2:1, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT BETWEEN 5X10**3 TO 25X10**5, THE WEIGHT RATIO OF COPOLYMER TO CHROMIUM BEING BETWEEN 20:1 AND 5000:1.

3. A LIQUID HYDROCARBON FUEL COMPOSITION CONSISTING ESSENTIALLY OF HYDROCARBONS BOILING IN THE RANGE OF FROM -40*F. TO 700*F. AND A COMPOSITION ACCORDING TO CLAIM 1, IN AN AMOUNT SUFFICIENT TO PROVIDE SAID FUEL COMPOSITION WITH 1X10**-3 TO 1X10**-9 GRAM ATOMS OF CHROMIUM IN THE FORM OF THE SALICYLATE PER LITER OF HYDROCARBON.