United States Patent (19) 11) 4,104,291 Sabol Et Al
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United States Patent (19) 11) 4,104,291 Sabol et al. 45) Aug. 1, 1978 54 METAL DITHIOPHOSPHATES AND THEIR 3,562,306 2/1971 Blaha et al. ... ... 260/429.9 MANUEFACTURE 3,686,243 8/1972 Rigdon et al. .................... 260/429.9 (75) Inventors: Albert R. Sabol, Munster, Ind., OTHER PUBLICATIONS Nicholas C. Petrellis, Lisle, Ill. Perry, Chemical Engineer's Handbook, McGraw-Hill 73 Assignee: Standard Oil Company a corporation Book Co., N.Y., 4th Ed., pp. 21-23 to 21-25 (1963). of Indiana, Chicago, Ill. Primary Examiner-Helen M. S. Sneed 21 Appl. No.: 781,626 Attorney, Agent, or Firm-Frank J. Sroka; Arthur G. Gilkes; William T. McClain 22 Filed: Mar. 28, 1977 57 ABSTRACT 51 Int. Cl.’................................................ CO7F 3/06 52 U.S. Cl. ............................ 260/4299; 252/32.7 E; Disclosed are a process for the manufacture of metal 260/429 R; 260/439 R; 260/987 dithiophosphates especially the neutralization of dithio 58 Field of Search ................ 260/4299,987, 429R, phosphoric acids, and also the product made by such 260/439 R; 252/32.7 E process. The process for the continuous neutralization of dithiophosphoric acid with metal base comprises (56) References Cited contacting dithiophosphoric acid with metal base to U.S. PATENT DOCUMENTS form a neutralization mixture; passing said neutraliza 3,014,940 12/1961 Lynch et al. ................. 260/429.9 X tion mixture through a static mixer in order to achieve 3,086,939 4/1963 Tichelaar ..... ... 260/429.9 X mixing of the neutralization mixture and substantial 3,234,250 2/1966 Schneider et al. ................ 260/429.9 neutralization of said dithiophosphoric acid; cooling the 3,290,347 12/1966 Miller ................................ 260/429.9 substantially neutralized dithiophosphoric acid; and 3,293,181 12/1966 Stuart ............... ... 260/429.9 X 3,428,662 2/1969 Millendorf et al. ............... 260/429.9 recovering metal dithiophosphate. 3,442,804 5/1969 LeSuer et al. ....... ... 260/429.9 X 3,515,712 6/1970 Goldsmith .................... 260/429.9 X 13 Claims, 1 Drawing Figure 4,104,291 1. 2 ing dithiophosphoric acid with metal base to form a METAL DITHOPHOSPHATES AND THEIR neutralization mixture; passing said neutralization mix MANUFACTURE ture through a static mixer in order to achieve mixing of the neutralization mixture and substantial neutralization BACKGROUND of said dithiophosphoric acid; cooling the substantially This invention relates to the manufacture of metal neutralized dithiophosphoric acid; and recovering dithiophosphates and to the composition manufactured. metal dithiophosphate. More specifically this invention relates to a process for Static mixers are mixing devices that generally have the neutralization of dithiophosphoric acids. no mixing parts. They generally comprise pipes contain It is well known that various additives can be added 10 ing stationary baffle arrangements on the inside. Fluids to lubricating oils in order to improve various oil prop passing through these devices use the energy of the erties and to make a more satisfactory lubricant. An flowing fluid to produce mixing. Static mixers are avail tiwear agents are intended to decrease wear of machine able commercially, and Koch mixers are considered parts. Wear inhibitors for incorporation in motor oils quite suitable. and industrial oils are finding greater use as a result of 15 Preferably, after the neutralization mixture passes greater stress placed on moving parts in high perfor through the static mixer, the mixture is passed through mance engines. Numerous additives have been devel a vessel in order to increase the contact time between oped for use in such oil compositions to improve the the base and the dithiophosphoric acid in the mixture. lubricating characteristics thereof and thereby to lessen In this manner, essentially complete neutralization is the wear of the moving parts. 20 effected. It is also preferred to blow the neutralization Metal diaryl or dialkyl dithiophosphates, especially mixture with inert gas such as nitrogen in order to re zinc diaryl or dialkyl dithiophosphates (ZOP), have move water of neutralization after mixture has been long been used as antiwear additives and antioxidants in essentially completely neutralized. hydraulic oils, motor oils and automatic transmission In the neutralization reaction, about 0.5 to about 1.0 fluids. In the manufacture of such metal dithiophos 25 moles, preferably about 0.6 to about 0.8 moles, of metal phates, a dithiophosphoric acid is commonly neutral base per mole of dithiophosphoric acid is used. The ized with a base, such as zinc oxide or hydroxide. This neutralization is generally conducted at a temperature neutralization step does not take place readily and com of about 100 to about 210 F, but preferably about 100 monly a large excess of the base is used in conjunction to about 170 F. with a neutralization promoter and high neutralization 30 Generally, this continuous neutralization process temperatures in order to achieve reasonably short reac results in rapid neutralization of dithiophosphoric acid tion time. Sometimes the use of promoters such as nitric and hence neutralization promoters are not generally acid can lead to undesirable side effects such as haze needed. However, in some cases it may be desirable to problems or instability. In many cases the neutralized use such promoters in order to increase throughput. product is difficult to filter and has a dark color, 35 Therefore it is contemplated that the various neutraliza It is an object of this invention to provide an im tion promoters such as nitric acid, C-C carboxylic proved process for the manufacture of metal dithiphos acids and their salts, dialkyl dithiophosphoric acids, and phates, especially neutralization of dithiophosphoric the like, can be present in the neutralization mixture acids. during the neutralization reaction. It is an object of this invention to provide an im 40 One of the more commercially significant applica proved process for the continuous neutralization of tions of this invention is in the manufacture of ZOP's. A dithiophosphoric acids requiring shorter neutralization process for the manufacture of zinc diaryl or dialkyl time, a minimum amount of excess metal base, and often dithiophosphates comprises reacting one mole of PS requiring no neutralization promoter. Further, this pro with about four moles of aryl or alkyl alcohol to form cess has a high throughput at minimum capital expendi 45 dithiophosphoric acid; contacting the dithiophosphoric ture. In many cases, highly effective dithiophosphates acid with a slurry of zinc oxide in oil to form a neutral are made which do not suffer possible detrimental af. ization mixture; passing said neutralization mixture fects of neutralization promoters, through a static mixer in order to achieve mixing of the SUMMARY OF THE INVENTION neutralization mixture and substantial neutralization of 50 said dithiophosphoric acid; cooling the substantially Disclosed are a process for the manufacture of metal neutralized dithiophosphoric acid and blowing with an dithiophosphates, especially the neutralization of dithio inert gas to remove water of neutralization; and recov phosphoric acids, and also the product made by such ering zinc dithiophosphates. process. Preferably the neutralization mixture is maintained at Metal dithiophosphates are generally made by the 55 a temperature below 210 F to minimize decomposition. reaction alcohol with PSs to form dithiophosphoric The aryl dithiophosphates are manufactured from acid orphosphoric acid ester. Most commonly the alco hydroxyl aryl compounds. These hydroxyl aryl com hols are alkyl, aryl or alkaryl. In some cases the PSs is pounds generally contain one, two or three aromatic reacted with a second compound in addition to alcohol. rings but most commonly contain a single aromatic However, dialkyl and diaryl dithiophosphoric acids are ring. Said hydroxyl aryl compounds may contain more preferred. In any event, the dithiophosphoric acid is than one hydroxy group but most commonly contain a then neutralized with metal base, especially zinc, bar single hydroxy group. The aromatic ring or rings may ium, cadmium, magnesium or nickel base. Zinc oxide is contain various other substitutions such as hydrocarbyl, the preferred base because of its low cost and because of chlorine, bromine, nitro and others. In some cases these the commercial significance of ZOP in the lubricating 65 substitutions do not enhance or detract from the effec oil field. tiveness of the additive. In no case should the substitu The process for the continuous neutralization of di tion interfere with the reaction with PSsor the neutral thiophosphoric acid with metal base comprises contact ization step. 4,104,291 3 4. Commonly, hydrocarby substitution of the hydroxy with diaryl dithiophosphoric acid for a time sufficient to aryl compound is desirable to order to improve the oil neutralize the acid and possibly also incorporate an solubility and effectiveness of neutralized metal dithio excess of zinc oxide so that the material is basic. The phosphates as lubricating oil additives. Therefore, hy neutralization reaction may usually be completed drocarbyl substituted hydroxy aryl compounds, such as within a period of from about 1 to about 30 minutes hydrocarbyl phenols, are preferred. depending on temperature, throughput, and mixing The most commonly used substituted phenols contain efficiencies. Commonly, good mixing is achieved and one or more hydrocarbyl groups having