VISCOSITY DRIFT CONTROL IN OVERBASED DETERGENTS

Abstract: Viscosity increase or drift occurs in overbased detergents over time and particularly at elevated temperatures. Viscosity drift is now controlled by the addition of additive amounts of a compound having an oleophilic group and further having secondary hydroxyl functionality. Additions of this control agent in amounts of 0.1 to 5.0 % and preferably 0.25 to 1.0 %, by weight effected minimal viscosity drift of no more than about 10 % in detergents stored for about 4 weeks at elevated temperatures of about 37 DEG C to 82 DEG C. The degree of viscosity drift control is proportional to the amount of control agent added to the overbased detergent. Preferred viscosity drift control agents are alkylated phenols such as dinonyl phenol, vegetable oils such as canola oil and jojoba oil, and carboxylic acids such as 12-hydroxy stearic acid. The viscosity drift control agent is particularly effective for highly overbased calcium sulfonates.

Description: VISCOSITY DRIFT CONTROL IN OVERBASED DETERGENTS BACKGROUND OF THE INVENTION Field of the Invention This invention relates to viscosity drift control in overbased detergents. Background and Discussion of the Prior Art Overbased detergents are extensively used in lubricating oils. Generally, the overbased detergent is shipped and stored prior to incorporation in the lubricating oil. The storage and shipping conditions often expose the detergent to temperatures substantially above ambient for long periods of time. It was found that some overbased detergents would, over time, and under elevated temperatures, increase in viscosity. This viscosity increase or drift caused the overbased detergent to be out of specification with the initially specified viscosity, and in certain cases the viscosity of the stored overbased detergent had sufficiently increased so as not to be suitable for blending and use in the lubricating oil. The lubricating oil art was directed away from overbased detergents having high viscosity because of handling and filterability problems, as discussed in U.S. 5,011,618 to Papke et al and U.S. 4,387,033 to Lenack et al. Overbased calcium sulfonate detergents were generally required to have a viscosity of no more than about 200 to 250 cSt at 100°C, but after several weeks of storage under elevated temperatures, the viscosity would drift to 400 cSt at 100°C or more. The increased or high viscosity overbased calcium sulfonate was then unsuitable for blending and use in lubricating oils. The overbased detergent art desired a viscosity drift control agent or system. While it was known in the lubricating oil art to add certain alkyl phenols and vegetable oils to finished blended lubricating oils to enhance certain performance characteristics, it was not known that limited amounts of such additives when added to an overbased detergent per se effectivelv controlled viscosity dnft in long term storage pπor to blending the detergent in a finished lubncating oil The term "viscosity dnft" as used hereinbefore and hereinafter means the change (increase) in viscosity over time The term "viscosity dnft control" as used hereinbefore and hereinafter means the reduction in the change (increase) in viscosity over time SUMMARY OF THF INVENTION A viscosirv dnft control svstem for overbased detergents is achieved by the addition ot additive amounts of a compound having an oleophilic group and having secondary hydroxyl functionality This viscosirv dnft control additive or agent when added in additive amounts to the overbased detergent results in a viscosity which over several weeks at elevated temperatures remams relatively unchanged or shghtlv elevated, whereas absent the agent, the viscosity would over time increase to a commercially unacceptable degree The agent of the present invention permits the overbased product to remain in specification The viscosity dnft control agent is effective in amounts of 0 1 to 5% by weight and preferably 0 25 to 1 0 0/ o bv weight m the overbased detergent These additive amounts of the viscosity dnft control agent reduce the viscosity dnft to less than a 10 0/ o increase in the initial viscosity over a penod of 4 weeks at elevated temperatures above about 35° C The viscosity control agent generally includes (1) vegetable oils, (2) carboxylic acids and (3) alkyl phenols -2 - DESCRIPTION OF THE PREFERRED EMBODIMENTS In one broad aspect, the viscosity drift control agents of the present invention include compounds having both an oleophilic group and secondary hydroxyl functionality. It is to be understood that such secondary hydroxyl functionality pursuant to the present invention contemplates OH, OH-HO hydrogen bonding as in inter-fatty acid triglyceride hydrogen bonding (e.g., vegetable oils) and OH in the ester form of this functional group. The control agents or compounds are preferably of moderately high molecular weight (MW). The viscosity drift control agent has a molecular weight of about 150 to 1,000 or more, and as a practical matter, preferably between 280 and 1,000. It has been found that generally three classes of compounds fall within the aforesaid definition of viscosity drift control agents pursuant to the present invention. These classes of viscosity drift control agents include (1) vegetable oils, (2) carboxylic acids and (3) alkyl phenols, having an oleophilic group and further having secondary hydroxyl functionality. Suitable vegetable oils include canola oil, jojoba oil, sunflower oil, rapeseed oil, linseed oil, palm kernel oil and the like. Vegetable oils such as canola oil and jojoba oil are preferred. The alkyl phenols include mono, di, linear and branched alkyl phenols. The alkyl group of the alkyl phenol may have up to 40 carbon atoms, and preferably 6 to 20 carbon atoms. Useful alkyl phenols are heptyl phenols, octylphenols, dodecylphenols, nonylphenols and cyclohexyl phenols. It is to be understood that the terms "alkyl phenol" or "alkyl phenols" are used herein to represent one or more such alkyl phenols. Dinonyl phenol is a preferred alkyl phenol. Suitable carboxylic acids pursuant to the present invention include capric, lauric, myristic, palmitic, stearic, isostearic, arachidic, behenic, lignoceric, lauroleic, myristoleic, palmitoleic, oleic, gadoleic, erucic, ricinoleic, - 3 - Unoleic and linoleic acids A 12-hydroxy steaπc acid a preferred carboxylic acid It is to be noted that the aforesaid useful compounds contam an oleophihc group and also contain secondary hydroxyl functionality The control agent is effective in amounts of 0 1 to 5% by weight and preferably 0 25 to 1 0% The viscosity dnft control effect is proportional to the amount of agent added to the detergent The viscosity dnft effected by additive amounts of the control agents of the present mvention is less than about 10% over 4 weeks That is, the initial viscosity of the combination of the overbased detergent and control agent mcreases or dnfts less than about 10% over 4 weeks The controlled viscosity dnft is about 5 to 25 cSt at 100°C, wnere 0 1 to 5% by weight of the control agent is added to the overbased detergent and the detergent stored at about 46° C to 49° C for four weeks It has been generally found that detergents stored for about 4 weeks, particularly at elevated temperatures of above about 35° C, had viscosity dnfts of at least about 30% or more Where control agents of the present mvention are added to the detergent in additive amounts of 0 1 to 5% by weight, the viscosity dnft is generally reduced to about 10% to 15% over 4 weeks at such elevated temperatures In certain cases, the viscosity control agents of the present mvention reduced the viscosity dnft to less than about 10% over 4 weeks at elevated temperatures above about 35° C It has been found that one of the most preferred and most effective viscosity dnft control agents is an alkyl phenol, and particularly dinonyl phenol (DNP) It was found and as further demonstrated herein that about 0 5% by weight of DNP m a detergent reduced the viscosity dnft to less than about 10% where the detergent was stored at elevated temperatures of about 7° C -4 - to 82° C for about 4 weeks The lubricating oil art is particularly conservative in that it is reluctant to introduce new compounds into commercial lubricating oils. The alkyl phenols are particularly preferred because they bear structural similarity to phenates, which in one form are commercially useful overbased detergents. The use of an alkyl phenol, such as dinonyl phenol, is then perceived by the lubricating oil art as not introducing a structurally suspect compound in the lubricating oil blend which might result in adverse performance characteristics. Further, insofar as only 0.5% by weight of DNP is extremely effective, DNP is most preferred for its minimal use requirement and concomitant low cost, as well as for its structural acceptability The foregoing viscosity drift control agents are produced by procedures well know in the art and are commercially available Canola oil is a particularly effective agent, and is readily commercially available and inexpensive, and for these reasons is another preferred viscosity drift control agent. The overbased detergents products are produced by procedures well known in the art and are commercially available Suitable detergents useful in the present inventions include the Group I and Group II metal sulfonates, phenates and carboxylates. Particularly useful for viscosity drift control are the overbased calcium sulfonate and phenates. Highly overbased sulfonates and phenates are particularly subject to increased viscosity, and the drift control agents of the present invention are particularly effective for these highly overbased products. Highly overbased sulfonates and phenates are those having a TBN in excess of about 200 and preferably more than 400. -5- Examples 1-3 A sample of an overbased calcium sulfonate, TBN 400, was produced by sulfonating a 310 to 700 SUS at 100°F petroleum oil and blending with 0 to 30% sulfonic acid made by sulfonating a synthetic, mainly dialkyl benzene alkylate having a molecular weight of 430 to 560. The sulfonic acid composition is overbased by carbonating in the presence of calcium hydroxide, solvent, alcohol and oil, according to procedures well known in the art. The product calcium sulfonate had an initial viscosity of 331 cSt at 100°C and was treated with dinonyl phenol (Example 1), canola oil (Example 2) and jojoba oil (Example 3) and held at about 46° C to about 49° C for several weeks during which time the viscosities were measured. Example 1 Dinonyl phenol Viscosities cSt (a), 100° C Amt. added Initial 1 wk 2 wks 3 wks 4 wks ( t.%) 0 331 cSt 377 cSt 402 cSt 424 cSt 446 cSt 0.25 275 cSt 280 cSt 289 cSt 294 cSt 300 cSt 0.50 257 cSt 262 cSt 268 cSt 276 cSt 280 cSt 1.00 238 cSt 245 cSt 250 cSt 256 cSt 259 cSt 2 226 cSt 231 cSt 236 cSt 241 cSt 246 cSt 3 210 cSt 210 cSt 212 cSt 214 cSt 216 cSt -6- Example 2 Canola Oil Viscosities cSt (a) 100° C Amt. added Initial 1 wk 2 wks 3 wks 4 wks (wt.%) 0.50 255 cSt 262 cSt 273 cSt 285 cSt 311 cSt 1.00 237 cSt 242 cSt 249 cSt 255 cSt 261 cSt 2 212 cSt 213 cSt 217 cSt 222 cSt 227 cSt 5 166 cSt 166 cSt 167 cSt 178 cSt 170 cSt Example 3 Jojoba Oil Viscosities cSt (a) 100 c C Amt. added Initial 1 wk 2 wks 3 wks 4 wks (wt.%) 5.00 142 cSt 147 cSt 150 cSt 154 cSt 155 cSt The results of Examples 1-3 demonstrate that dinonyl phenol and the vegetable oils, canola and jojoba oils, provide significant viscosity drift control under elevated temperatures of 46° C to 49° C over an extended period of 4 weeks. The viscosity drift using 0.2 to 5% of the control agent (i.e. dinonyl phenol, canola oil and jojoba oil), after four weeks under elevated temperatures of about 46° C to about 49° C, is no more than about 5 to 25 cSt at 100°C. Examples 1 and 2 further demonstrate that the viscosity drift control is proportional to the amount of agent added. -7- Example 4 An overbased calcium sulfonate having a 405 TBN was stored at 71 ° C to 82° C with diverse control agents added, and the viscosity was measured over several weeks. Additive Viscosity cSt (a) 100°C Amount (wt. %) initial 1 wk 2 wks 3 wks 4 wks none 268 289 320 360 405 0.5% dinonvlphenol 254 255 266 272 279 1.0% dinonv henol 235 245 246 253 257 2.0%) dinonvlphenol 233 231 236 243 246 2.0%) canola oil 170 180 180 187 193 2.0%) i-i-hydroxy 266 261 274 288 295 stearic acid 2.0%) jojoba oil 170 180 180 187 192 5.0%) jojoba oil 167 171 174 177 178 The results of Example 4 demonstrate that diverse viscosity drift control agents within the scope of the invention effeαively reduce viscosity drift to no more than about 10% for detergents stored for 4 weeks at elevated temperatures of 71 ° C to 82° C. Example 5 Controls An overbased calcium sulfonate having a 405 TBN was stored at 71° C to 82° C blended with additive amounts of diverse compounds not within the scope or definition of the invention, and the viscosity measured over several weeks. Additive Viscosity cSt (a). 100°C Amount (wt. %) initial 1 wk 2 wks 3 wks 4 wks none 268 289 320 360 405 2% water 230 265 310 355 402 2% Co-530 220 265 297 330 385 (ethoxvlated phenol! 1% Rhodamine T 226 242 280 320 362 Example 5 demonstrates that diverse compounds outside the scope of the definition of the present invention are not useful as viscosity drift control agents. Example 6 Dinonyl Phenol (DNP) The following Tables 6A and 6B (viscosity vs. temperature) report the viscosities of an overbased calcium sulfonate having a 400 TBN, with and without dinonyl phenol (DNP), respectively, where in both cases the detergent was stored for 4 weeks at the same specified temperatures. -9- Table 6A. 400 TBN Overbased Calcium Sulfonate Without DNP Viscosities cSt (a). 100° C Temperature 37.8° C 48.9° C 65.6° C 82.2° C initial 193 cSt 193 cSt 193 cSt 193 cSt 1 wk 194 cSt 203 cSt 207 cSt 209 cSt 2 wks 196 cSt 201 cSt 216 cSt 216 cSt 3 wks 203 cSt 220 cSt 232 cSt 236 cSt 4 wks 207 cSt 228 cSt 251 cSt 265 cSt Table 6B. Same 400 TBN Overbased Calcium Sulfonate with 0.5% DNP Viscosities cSt (a). 100° C Temperature 37.8° C 48.9° C 65.6° C 82.2° C initial 181 cSt 181 cSt 181 cSt 181 cSt l wk 183 cSt 186 cSt 184 cSt 188 cSt 2 wks 178 cSt 182 cSt 186 cSt 189 cSt 3 wks 181 cSt 186 cSt 191 cSt 195 cSt 4 wks 187 cSt 189 cSt 193 cSt 201 cSt The results of Tables 6A and 6B clearly demonstrate that with the use of a 0.5% DNP drift control agent, the viscosity readings of a 400 TBN calcium sulfonate detergent were relatively stable over four weeks, even at the elevated temperatures at which the tests were conducted. More specifically, where the overbased calcium sulfonate detergent was stored at temperatures of from about 37° C to 82° C for 4 weeks, with 0.5% DNP and without DNP, it was further demonstrated that the DNP controlled viscosity drift to less than about 10%. ■ 10- While the invention is demonstrated for certain alkyl phenols, vegetable oils and ca r boxylic acids, it is to be understood that all such compounds having an oleophilic group and also having secondary hydroxyl functionality are within the contemplation of the invention. -11-

Claims: WHAT IS CLAIMED IS 1. In combination, an overbased detergent and a viscosity drift control agent for the detergent, said agent comprising an oleophilic group and further comprising secondary hydroxyl functionality, whereby with the agent present in an additive amount, over time, the detergent viscosity drift is reduced. 2 The combination of claim 1. wherein the detergent comprises at least one selected from a sulfonate, phenate and carboxylate 3 The combination of claim 1 , wherein the detergent comprises an overbased calcium sulfonate 4 The combination of claim 1, wherein the detergent comprises an overbased calcium phenate 5 The combination of ciaim 1 , wherein the agent comprises an alkyl phenol 6 The combination of claim 5, wherein the alkyl phenol comprises dinonyl phenol. 7 The combination of claim 1, wherein the agent comprises a vegetable oil. - 12 8 The combination of claim 7, wherein the vegetable oil comprises canola oil 9 The combination of claim 7, wherein the vegetable oil comprises jojoba oil. 10 The combination of claim 1, wherein the agent comprises a carboxylic acid. 11 The combination of claim 10, wherein the carboxylic acid comprises an hydroxy stearic acid. 12 The combination of claim 1, wherein the viscosity drift is no more than about 5 to 25 cSt at 100°C with the combination at about 46° C to about 49° C for about 4 weeks. 13 The combination of claim 1, wherein the agent is present in an amount of about 0.1% to 5.0%) by weight. 14 The combination of claim 1, wherein the agent is present in an amount of 0.25 to 1.0% by weight 15 The combination of claim 1, wherein the viscosity drift is less than about 10% over 4 weeks. 13 16. In combination, an overbased detergent and a viscosity control agent for the detergent, said agent comprising an alkyl phenol having an oleophilic group and secondary hydroxyl functionality, whereby with the agent present in an additive amount, over time, the detergent viscosity drift is reduced. 17. The combination of claim 16, wherein the alkyl phenol comprises dinonyl phenol. 18. The combination of claim 16, wherein the agent is present in amounts of 0.1 to 5% by weight. 19. The combination of claim 18, wherein the viscosity drift is no more than about 10% with the detergent stored for 4 weeks. 20. The combination of claim 19, wherein the detergent is stored at temperatures from about 37° C to 82° C. 21. The combination of claim 20, wherein the detergent comprises dinonyl phenol. 22. The combination of claim 21, wherein the dinonyl phenol is present in no more than about 0.5% per weight. - 14 -

Inventors: ELIADES THEO I, MATHEWS LEONARD, MUIR RONALD J, ELIADES, THEO, I., MATHEWS, LEONARD, MUIR, RONALD, J.
Applicants: WITCO CORP, WITCO CORPORATION
Application year: 1999
Main classification: C10M159
IPC codes: C10M159, C10M163, C10N30