United States Patent to 11 4,011,057 Sayers 45) Mar. 8, 1977

54 HINDERED PHENOL ANTIOXIDANT 2,202,877 6, 1940 Stevens et al...... 4.4/78 COMPOSTION CONTAINING AN AMNO 2,459,597 - 1/1949 Stillson et al...... 44f78 X COMPOUND 2,521,425 9/1950 Thompson ...... 44f75 . . . 2,672,408 3/1954 Bonner ...... a------a a a a - - 44f72 (75 Inventor: George Alvin Sayers, Penns Grove, 2,793,943 5/1957 Moore ...... a- a - a a - - - a a - a - 44f72 N.J. 2,908,558 10/1959 Brimer...... ------44f75 73) Assignee: E. I. Du Pont de Nemours and 3,166,509 171965 Ecke ...... 44,178 Company, Wilmington, Del. Primary Examiner-Daniel E. Wyman 22 Filed: Apr. 16, 1974 Assistant Examiner-Mrs. Y. Harris-Smith

(21) Appl. No.:& was 461,391 Attorney, Agent, or Firm-James A. Costello 52 U.S. Cl...... 44/52; 4.4/72; 57 ABSTRACT 51l Int. Cl”...... 44/75; coL22 252/403 An improved antioxidant composition. . comprising hin 58) Field of Search ...... 44/52, 72, 75; 252/403; dered phenol antioxidant wherein the improvement 260/624 comprises, in combination with the hindered phenol, 8 from about 1% to 10%, by total weight, of at least one 56 References Cited amino compound having a pKb of from 0.3 to 8.0. UNITED STATES PATENTS 1,748,507 111930 Brooks ...... 44/52 12 Claims, No Drawings

401 1,057 1. 2 Ammonia has a pKa of 4.75 while substituted ammo HINDERED PHENOL ANTIOxIDANT nia compounds such as methylamine (pK 3.37), ethyl COMPOSTON CONTAINING AN AMNO amine (pK, 3.27), isopropylamine (pK 3.37), ethanol COMPOUND amine (pK 4.56) are slightly stronger bases than am monia. Guanidine, a very strong organic base has a pK, BACKGROUND OF THE INVENTION or 0.3. Generally, for an amino compound to have a 1. Field of the Invention pK of 8 or less the substituent on the amino nitrogen This invention concerns antioxidant compositions, will be attached to the nitrogen atom via an aliphatic or especially antioxidant compositions for gasoline. The cycloaliphatic carbon atom, even though such carbon compositions comprise primarily hindered phenols in O combination with a small amount of an amine. The atom can also have aromatic substituents. Thus, ben compositions are characterized by reduced crystalliza zylamine has a pKa of 4.70 while aniline (outside the tion temperature, lighter color, and enhanced antioxi invention) has a pKa of 9.30. The preferred amino dant efficiency, over compositions that are similar ex compound will have a pKa of from about 3 to about 5. cept that they do not have the amine present. 15 The preferred antioxidant compositions of this inven 2. Description of the Prior Art tion contain from about 3 to 6% of the amino com Phenolic antioxidants are preferred for modern gaso pound(s), based on total weight of the antioxidant. The lines which have relatively low olefin content, because amino compound(s) have been found, surprisingly, to of their low cost and increasing relative antioxidant exercise synergistic antioxidant qualities with the hin efficiency with decreasing olefin content of the gaso 20 dered phenols, even in the relatively small amounts of line. Principal commercially employed antioxidants are 10% or less that are contemplated herein. the alkylated phenols, N,N'-dialkylated para The hindered phenol portion of the antioxidant of phenylenediamines and N-alkylated para-amino this invention can be single phenols or mixtures of phenols. phenols. The term “hindered phenol' as employed Alkylated phenol antioxidants usually contain a ter 25 herein, depending on the context, includes mixtures of tiary alkyl group ortho to the hydroxyl group. Included hindered phenols. The preferred hindered phenol is are 2,6-ditert-butyl-4-methylphenol, 2,4-dimethyl-6- tertiary butylated phenol. Especially preferred is ter tert-butylphenol, 2,4-ditert-butylphenol, 2,6-ditert tiary butylated phenol containing at least about 60% of butylphenol, 2-tert.-butylphenol, 4,4'-methylene 2,4-ditert-butylphenol. The most preferred amino bis(2,6-ditert-butylphenol), 4,4'-thiobis(2,6-ditert.- 30 compound is 1,2-diaminopropane. butylphenol) and the like. Such phenols containing the The term hydrocarbyl as employed herein includes bulky tertiary alkyl group at one or both orthopositions aliphatic hydrocarbyl (such as alkyl and alkenyl), cy are often referred to as hindered phenols. cloaliphatic hydrocarbyl (such as cyclopentyl, cyclo Most hindered phenols are solids at ambient temper hexyl and cycloheptyl), and araliphatic hydrocarbyl atures or they are liquids which crystallize when ex 35 (such as benzyl, tolylyl, xylylyl and 2-phenylethyl). The posed to low temperatures such as are encountered total number of carbon atoms is preferably 1 to 20 during the winter months in colder climates. It is gener carbons. ally preferred that a gasoline additive be liquid for ease This invention also concerns a gasoline fuel composi of addition and lower costs. Using solvents to provide 40 tion containing the novel antioxidants of this invention. hindered phenol as concentrated solutions is not com pletely satisfactory since the phenols are still subject to The concentration of the antioxidants will usually be crystallization from solution at low temperatures. Fur from about 1 to 10 lbs. per 1,000 barrels. ther, the increased cost of preparing, handling and DETAELS OF THE INVENTION shipping solutions makes this unattractive. There is, 45 Hindered phenols are usually prepared by alkylation therefore, a need for a practical liquid hindered phenol of a phenol or an alkylphenol containing at least one antioxidant composition which is resistant to solidifica free ortho position with a 1,1-dialkylmonoolefin. More tion (crystallization) at relatively low temperatures. usually the 1,1-dialkylmonoolefin is isobutylene so that Also desirable would be for such composition to have the tertiary alkyl group introduced is the tertiary butyl good light color and good efficiency. 50 group. Methods of alkylating phenols with olefins are SUMMARY OF THE INVENTION well known in the art and the present invention is not This invention concerns an improved antioxidant dependent upon any particular method of preparation composition comprising hindered phenol antioxidant of the hindered phenols. wherein the improvement comprises, in combination 55 Most contemplated hindered phenol antioxidants are with the hindered phenol, from about 1% to 10%, by not single compounds but are mixtures of alkylated weight of the antioxidant composition, of at least one phenols. For example, when phenol is alkylated with amino compound having a pKa of from about 0.3 to isobutylene, the reaction mass generally contains two 8.0. or more of the following: 2-tert-butylphenol, 4-tert.- The amino compound can be ammonia or a hydro 60 butylphenol, 2,4-ditert-butylphenol, 2,6-ditert-butyl carbyl-substituted ammonia compound. The substi phenol and 2,4,6-tritert.-butylphenol. The composition tuted ammonia will contain up to about 49 carbon of the mixed hindered phenol depends, of course, upon atoms. The common characteristic of the contemplated the particular catalyst used, the ratio of isobutylene to amino compounds is that they are nitrogen bases of pK, the phenol used, and the reaction conditions such as 0.3 to 8.0. The smaller the pK the greater the base 65 time and temperature. strength of the amino compound, the term pK mean Most of the tertiary butylated phenols are solids at ing-log K where K is the basic dissociation constant ordinary temperatures as indicated by the melting of the amino compound in water at 25 C. points given below.

401 1,057 4 propyl)ethylamine, N,N-bis(3-hydroxypropyl)propyla nine, N-(2-hydroxypropyl)ethylamine, N,N-bis(2- Meltin 8. Point hydroxypropyl)methylamine, N,N-bis(triethoxylated)- Hindered Phenol O C. butylamine, N,N-bis(tetraethoxylated)oleylamine, 4-tert-butylphenol 98.4 2,4-ditert-butylphenol 56.5 N,N-bis(pentaethoxylated)oleylamine and the like. 2,6-ditert-butylphenol 39 iii. Cyclic amines of the formula, R-NY, where R is a 2,4,6-tritert-butylphenol 131 hydrogen or hydrocarbyl, y is a divalent connecting group such as -(CH2)-, where m = 4 to 6, -CHC H-NHCHCH-, -CHCH-O-CHCH-. Rep Commercial mixtures of tertiary butylphenols ordi O resentative examples are piperidine, N-methylpiperi narily have crystallization temperatures of from about dine, N-ethylpiperidine, piperazine, N-methylpipera 0 to about 30° C. By crystallization temperature is zine, N-ethylpiperazine, morpholine, N-methylmor meant the highest temperature at which a seeded sam pholine, N-ethyl morpholine and the like. ple of the phenol will develop crystals. The crystalliza iv. Amino compounds of the formula, tion temperature is therefore a measure of the ten 15 dency of the composition to solidify or form crystals. NR Since such antioxidant compositions are very often I exposed to temperatures lower than the crystallization RN-C-NR, temperature range of 0 to 30' C., particularly during the winter months in the coldersections of the northern 20 wherein R represents hydrogen or hydrocarbyl. This and southern hemispheres, partially or completely so class includes guanidine and alkylated guanidines such lidified compositions often result. as monomethylguanidine, dimethylguanidine, trimeth The hydrocarbyl-substituted ammonia compounds yiguanidine, tetramethylguanidine, pentamethylguani that are useful together with the antioxidants noted dine and the like alkylguanidines. above, can be primary, secondary, or tertiary amines 25 v. Polyamines of the formula, RN-(R'NR).R, and include one or more members from one or more of where R is hydrogen or hydrocarbyl, R' is alkylene of 2 the following groups. to 8 carbon atoms and x is 1 to 5. In the preferred i. Hydrocarbylamines of the formula, subclass, R is hydrogen or lower (C-C) alkyl. Repre sentative compounds are ethylenediamine, diethylene 30 triamine, triethylenetetramine, tetraethylenepenta R mine, pentaethylenehexamine, propylene(1,3)diamine, R-N-R, dipropylene(1,3)triamine, tripropylene(1,3)-tetramine, tetrapropylene(1,3)pentamine, pentapropylene(1,3- wherein each R represents hydrogen or a hydrocarbyl )hexamine, propylene(1,2)diamine, dipropylene(1,2)- group which has 1 to 24 carbon atoms, the R being 35 triamine, tripropylene(1,2)tetramine, tetra joined to the nitrogen atom through a saturated carbon. propylene (1,2)pentamine, pentapropylene(1,2)hex At least one of the R groups is a hydrocarbyl group. amine, 1,4-diaminobutane, 1,5-diaminopentane, 1,6- Representative compounds are primary, secondary diaminohexane, 1,8-diaminooctane. Included in the and tertiary amines such as methylamine, dimethylam polyalkylenepolyamines are substituted polyamines ine, trimethylamine, ethylamine, diethylamine, triethyl 40 such as N,N-dimethylpropylene(1,3)-diamine, N,N- amine, n-propylamine, di-n-propylamine, tri-n-propyla dimethylethylenediamine, N,N,N',N'-tetramethyle mine, isopropylamine, diisopropylamine, triisopropyla thylenediamine, and the like. mine, n-butylamine, di-n-butylamine, tri-n-butylamine, The exact amount of the amine that is used, within methylethylamine, dimethylethylamine, n-amylamine, the range of 1 to 10%, depends on the phenolic compo di-n-amylamine, n-hexylamine, di-n-hexylamine, 2 45 nent, the amine component and the effect desired. ethylhexylamine, n-decylamine, n-decenylamine, While the amount of reduction in the crystallization dodecylamine, stearylamine, oleylamine, N,N-di temperature of a hindered phenol depends upon the methyloleylamine, cyclohexylamine, dicyclohexyla particular phenol composition, and the particular mine, N-methylcyclohexylamine, N,N-dimethylcy amino compound employed, in every case a substantial clohexylamine, N,N-diethylcyclohexylamine, benzyl 50 reduction in crystallization temperature is obtained. amine, p-tolylylamine, n-xylylylamine and the like. Although the color of a hindered phenol composition Also included in (i) are mixed tertiary alkyl primary does not normally affect its antioxidant performance, amines having 12 to 14 carbon atoms (marketed as light-colored compositions are desirable. It has now "Primene" 81R) and mixed tertiary alkyl primary been found that incorporating amino compounds into amines having from 18 to 21 carbon atoms (Primene 55 an off-color or discolored hindered phenol composition JM-T). Also included are tertiary nonylamines consist usually results in a lighter colored product. ing mainly of C amine with small amounts of C8 and The present invention composition is added to distil Co amines; cocoamine, a mixture of C-8 n-alkyl pri late fuels to provide antioxidant protection thereto. mary amines with the C predominating; and tallowa The distillate fuels include fuel oils, aviation gasoline mine, a mixture of stearyl, palmityl and oleylamines. and motor gasoline. The invention composition is par ii. Hydroxyalkyl- and hydroxy(alkyleneoxy) alkyla ticularly useful in gasolines, both aviation and motor. mines of the formula, RN (R'O)H, where R is hydro The distillate fuels can contain other additives normally gen, hydrocarbyl, or (R'O).H, wherein R' is alkylene used, including antiknock compounds, such as tetra of 2 to 3 carbon atoms and x is from 1 to 5. Exemplify ethylead, tetramethyllead, mixed alkyllead, lead scav ing compounds are ethanolamine, diethanolamine, 65 enging agents, anticing agents, anticorrosion agents, triethanolamine, propanolamine, dipropanolamine, dyes, carburetor detergents and the like, as long as the tripropanolamine, N-(2-hydroxyethyl)methylamine, primary antioxidant function of the novel compositions N,N-bis(2-hydroxyethyl)methylamine, N-(3-hydroxy is not compromised. 4.0 1 1,057 5 6 The following Examples illustrate the invention. The ASTM D1500, which involves matching of the color of commercial hindered phenols designated Preparations the sample versus glass color standards. The results are l-8, were all mixed tertiary butylated phenols wherein expressed in terms of ASTM color which ranges from the major component was 60 to 65% by weight of 2,4- 0.5 to 8.0 in 0.5 increments, the higher the value the di-tert-butylphenol. Other components were 2 to 7% darker the color. When the color of the sample is inter of 2-tert.-butylphenol, 2 to 7% of 4-tert-butylphenol, mediate between two standard glasses, the value corre and 15% to 20 of 2,4,6-tri-tert-butylphenol, balance sponding to the darker glass standard is given the prefix primarily poly-isobutylene. All of the Preparations L. were made commercially by the same general proce The results are summarized in Table wherein tem dure. They were, however, selected from different lots. 10 peratures are given to the nearest whole degree Centi The constituency of each of the Preparations fell within grade. TABLE CRYSTALLIZATION TEMPERATURES AND ASTM COLORS Crystallization Hindered Phenol Amine (5 wt.%) Temperature ASTM Color o C. A. C. Preparation One 24 m 2.5 monoethanolamine below -18 42- L 2.0 isopropylamine -3 27 L 2.5 1,2-diaminopropane below -18 42+ L 2.0 Preparation 2 One 3. w 4.() monoethanolamine below -18 21- L 3.5 isopropylamine below -18: 21- 4.0 1,2-diaminopropane below -18 2 Preparation 3 One 24 w L 2.5 monoethanolaminc 24 2.() isopropylamine l 13 L 2.0 1,2-diaminopropane below -18 42- L 1.5 Preparation 4 Oe 24 1.5 monoethanolamine 9 15 15 isopropylamine 13 1 L 1.5 1,2-diaminopropane 5 9 15 Preparation 5 O 21 w 4.5 tetraethylenepentamine below -13 34- 3.5 triethylenetetramine below -13 34- 3.0 dicthylenetriamine below -13 34- 30 Preparation 6 One 14 5% ammonia below -18 32 the range set out above and, although possible, it is not The results of Table 1 clearly show that the amino likely that any two of the Preparations had identical compounds markedly reduce the crystallization tem constituency by weight. perature, there being some variability in the size of the crystallization temperature reduction depending upon EXAMPLE 1 40 the particular hindered phenol treated. The results also The effectiveness of the amines in reducing the crys show that the amino compounds improve the color of tallization temperatures of commercial hindered phe the hindered phenols, particularly those phenols which nol antioxidants was demonstrated by determining the have high ASTM colors. highest temperature at which crystal formation occurs in seeded samples. 45 EXAMPLE 2 The crystallization temperature was determined by This Example shows the effect of the amine concen placing 40 ml of the liquid phenol in a Dewar tube of tration on the crystallization temperature. The proce three-fourths inch diameter. The phenol sample was dure described in the previous Example was used to seeded with about 5 mg of solid 2,4-di-tert-butyl determine the crystallization temperature. The hin phenol and a thermometer and a stirrer (a length of 50 dered phenol used was commercial sample, Prepara wire with coils at the end) were placed in the sample. tion 7. The tube was then placed in a larger Dewar flask con The results, summarized below to the nearest whole taining acetone. Solid carbon dioxide (dry ice) was C., show that further lowering of the crystallization added to acetone in the larger Dewar flask and the temperature is obtained with the increasing concentra sample was cooled slowly. Cooling and stirring were 55 tion of amine. In this particular batch of commercial continued until the formation of solid was observed. hindered phenol, 4 to 5 weight percent of the amine is The temperature at which the solid formation took sufficient to lower the crystallization temperature to place was recorded as the crystallization temperature. about -18°C. If a lower crystallization temperature is Colors of the hindered phenols with and without desired, it is clear that concentrations of amine greater amine additives were measured by the method of than 5% will provide it.

Crystallization Temperature Wt. Amine in Hindered Phenol O 2 3 4. 5 Amine C. o C. A C. A. C. C. A. C. o C. A. C. o C. A. C. l,2-diaminopropane 23 8 5 2 -2 25 -17 40 401 1,057 7 8 -continued Crystallization Temperature Wt. 9%. Amine in Hindered Phenol () 2 3 4. 5 Amine o C. o C. A. C. C. A. C. o C. A. C. o C. A. C. o C. A. C. ethanolamine 23 7 6 2 --2 2 -6 29 -8 4.

EXAMPLE 3 oxygenbreak is atmosphere determined. at This 100 is C.the and time the in time hours to atthe which lead Antioxidant efficiencies of hindered phenols contain a pressure drop of 2 psi within 15 minutes occurs fol ing amino compounds were determined by the ASTM lowed by a drop of at least 2 psi in the next 15 minutes. D525 method. The test consists of heating a sample of The time to lead break is indicative of the oxidative gasoline (50 ml) in a bomb pressurized with oxygen to 15 breakdown of the lead antiknock composition. A time 100 psi (7.0 kg per sq. cm.) at 100° C. and measuring to lead break of sixteen hours is considered satisfactory the time necessary for the break point. The break point performance. The efficiency of the commercial antioxi is a point in the pressure-time curve that is preceded by dant was arbitrarily set at 100. Said antioxidant was the a pressure drop of exactly 2 psi (0.15 kg per sq. cm.) same as that employed in Example 3 (and Table 2). within 15 minutes and succeeded by a drop of not less 20 The fuel was commercial aviation 100/130 grade gaso than 2 psi in 15 minutes. The induction time is the time line containing 3 ml/gallon of tetraethyllead. Primene elapsed between the placing of the bomb in the bath 81R (Rohm and Haas) designates a product containing and the break point at 100°C. The longer the induction mixed t-alkyl primary amines of 12 to 14 carbon atoms. period, the more efficient the antioxidant. The results summarized in Table 3 show that the The antioxidant efficiencies given below are based on 25 hindered phenol compositions of the present invention antioxidant efficiencies arbitrarily fixed at 100 for the are highly effective in stabilizing leaded aviation gaso gasolines containing the commercial hindered phenol line. It can be seen that the efficiency of each invention antioxidant alone with no amine present. The gasolines composition is more than double that of the hindered used in the test were three different regular grade gaso phenol itself. lines, each containing 3 mls. per gallon of tetraethyl- 0 TABLE 3 lead anitknock composition. The results summarized in Table 2 show that the antioxdant- efficie ncy caused by Antioxidant lbs./1000Barrels LeadHours Break to AntioxidantEfficiency the hindered phenol composition containing the amino compound is greater than that caused by the hindered None o 6 phenol (Preparation 8) alone. The results are surpris- Preparation 8 8.4 2 100 ing, since the amino compounds themselves provide very little antioxidant activity. 21 250 TABLE 2 Comparison of Antioxidant Efficiency Antioxidant Efficiency in Antioxidant lbs./000 bbls. Gasoline A Gasoline B Gasoline C Preparation 8 O 100 6 100 6 100 Monoethanolamine ().5 39 O 12 Isopropylamine 0.5 36 24 12 1,2-Diaminopropane 0.5 54 37 26 Preparation 8 and 9.5 22 Monocthanolamine 0.5 Preparation 8 and 5.7 126 07 Monoethanolamine 0.3 Preparation 8 and 9.5 24 Isopropylamine 0.5 Preparation 8 and 5.7 34 105 Isopropylamine 0.3 Preparation 8 and 9.5 144 1,2-Diaminopropane 0.5 Preparation 8 and 5.7 32 106 1,2-Diaminopropane 0.3

EXAMPLE 4 60

Stabilization- of aviation gasoline with the phenol Preparation 8 8.0 compositions of the present invention was demon- and monocthanol- 0.4 strated according to the ASTM D873 method. The test amine consists of heating the gasoline in a bomb filled with 22 267 oxygen for a certain length of time and the amounts of 65 P ion 8 8.0 - -- soluble gum, insoluble gum and precipitate formed are E.aat 0.4 weighed. With leaded aviation gasoline a modification 32 used in the industry consists of heating a sample in an

H 401 1,057 9 10 TABLE 3-continued alkylene of 2 to 3 carbon atoms and x is from 1 to 5, lbs./1000 Hours to Antioxidant iii. cyclic amines of the formula, R-NY, where R is Antioxidant Barrels Lead Break Efficiency hydrogen or hydrocarbyl, Y is the divalent con 24 300 5 necting group -(CH2)-, where m = 4 to 6, Preparationrrd 8 0.48.0 -CHCH-NHCHCH- Or -CH2C and 1,2-diamino H-O-CH2CH2-, propane iv. amino compounds of the formula, 22 267 Preparation 8 8.0 ) 10 NR and 2-ethyl- 0.4 II hexylamine RN-C-NR, 22 267 wherein R represents hydrogen or hydrocarbyl, Preparation 8 15 and "Primene' v. polyamines of the formula, RN-(R'NR).R, where 81R } 89) R is hydrogen or hydrocarbyl, R' is alkylene of 2 to 8 carbon atoms and x is 1 to 5, and - vi. ammonia. 2. A composition according to claim 1 wherein the The embodiments of the invention in which an exclu 20 hindered phenol antioxidant is tertiary butylated phe sive property or privilege is claimed are defined as nol. follows: 3. A composition according to claim 2 wherein the 1. In an antioxidant composition comprising hin tertiary butylated phenol comprises at least 60% of dered phenol antioxidant, the improvement compris 2,4-ditert.-butylphenol. 25 4. A composition according to claim 1 wherein the ing, in combination with the hindered phenol, from 1% amino compound is 1,2-diaminopropane. to 10%, based on the combined weight, of at least one 5. A composition according to claim 1 wherein the amino compound having a pKa of from 0.3 to 8.0, the amino compound comprises from 3 to 6% of the com amino compound being selected from the group con bined weight of the antioxidant. sisting of 30 6. A composition according to claim 2 wherein the i. hydrocarbylamines of the formula, amino compound is 1,2-diaminopropane. 7. A composition according to claim 2 wherein the R amino compound is monoethanolamine. 8. A composition according to claim 2 wherein the R-N-R, 35 amino compound is isopropylamine. 9. A composition according to claim 3 wherein the wherein each R represents hydrogen or a hydrocarbyl amino compound is 1,2-diaminopropane. group which has 1 to 24 carbon atoms, the R being 10. A composition according to claim 3 wherein the joined to the nitrogen atom through a saturated carbon, amino compound is monoethanolamine. 40 11. A composition according to claim 3 wherein the at least one of the R groups being a hydrocarbyl group, amino compound is isopropylamine. ii. hydroxyalkyl- and hydroxy(alkyleneoxy) alkyla 12. A composition according to claim 1 wherein the mines of the formula, RN(R'O)H, where R is pKa of the amino compound is between 3 to 5. hydrogen, hydrocarbyl, or (R'O), H, wherein R' is ck :k :k : xk 45

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