Abstract:
The invention relates to an aqueous mixture of esters and acids from the reaction of at least one polyhydric alcohol and at least one monoacid and at least one diacid coupled with a surfactant and an effective amount of base to solubilize the mixture.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to water-soluble or water-dispersible physical blends of a mixture of polymeric esters, polymeric partially esterified acids, salts derived thereof, and polyethylene glycol fatty esters. These blends can be used effectively in processing metal parts made of a variety of metals such as steel and aluminum.  
         BACKGROUND OF THE INVENTION  
         [0002]    The machining industry employs lubricants which are often described generically as metal working fluids to reduce friction and wear generated during metal processes. If a metal working fluid is used by diluting it further with tap water, the fluid is called a coolant or a soluble oil. Coolants by definition contain no petroleum-derived oils, but rather water-soluble or water-dispersible components and are formulated using water as a base carrier for all other components. By contrast, soluble oils consist of both oil-soluble and water-soluble components with a petroleum oil being used as the base carrier for all other components.  
           [0003]    Coolants are generally preferred due to the fact that they contain no petroleum oil which is not readily biodegradable, and therefore, undesirable in subsequent waste water treatment processing. Coolants may contain water-soluble additives which can be ethoxylated surfactants, polyol esters of carboxylic acids, salts of fatty acids, or salts of chlorinated fatty acids. The salts can be sodium, potassium, or amine salts. The amine salts can be made by neutralizing fatty acids with alkanolamines such as monoethanolamine and triethanolamine.  
           [0004]    Presently, soluble oils used in processing steel and aluminum often contain chlorinated additives which are synthesized by substituting hydrogen atom in the hydrocarbon chains of paraffin waxes with chlorine atoms. Soluble oils containing chlorine function extremely well in processing steel and aluminum. Chlorine-containing soluble oils are the metal working fluids of choice for most severe applications involving both steel and aluminum. The drawback for this type of metal working fluid again is waste water treatment involving the separation of water-insoluble petroleum oil and the disposal of chorine-containing additives.  
           [0005]    At the present, commercial water-soluble additives tend to create a foaming problem when a coolant is circulated during use. If the fatty acid is a chlorine-containing additive such as chlorinated stearic acid commonly used for processing steel and aluminum, its amine salt can cause severe foaming and corrosion. Additionally, there is a concurrent concerted effort in the machining industry to avoid all chlorine and amine-containing additives due to the costly procedures required to separate and treat chlorine-containing waste which can generate hydrochloric acid if incinerated. Amines are also undesirable due to the possibility of formation of carcinogenic nitrosamine in used coolant. In addition to the amine salts, sodium and potassium salts of fatty acids can be utilized as an alternative way to solubilize fatty acids which otherwise are insoluble in water. However, the solutions or dilutions of these salts tend to foam severely, and their foams in many cases are very stable, breaking at a very slow rate.  
           [0006]    Moreover, another deficiency in the prior art is that the best coolant thus far in the market cannot match the performance of chlorine-containing soluble oil in processing aluminum parts. Again, soluble oils are less desirable than coolants due to more difficulty in treating petroleum oil and other insoluble additives. Therefore, it is highly desirable to develop a coolant totally free of petroleum oil which can perform equally well to soluble oil counterpart in aluminum applications.  
           [0007]    The water-dispersible lubricating additive combination described in this invention satisfies all the foregoing mentioned deficiencies of the prior art. It can consist of either amine, sodium, or potassium salts of polymeric esters or partially esterified polymeric carboxylic acids. And its sodium or potassium salts are very low-foaming in nature due to the high molecular weights of the polymeric esters and acids. The coolant can be made amine-free by employing sodium or potassium hydroxide in forming the corresponding salts. It can be used to formulate chlorine-free coolant as it contains no chlorine. It can be used to formulate a very effective coolant in processing aluminum with a comparable performance to a chlorine-containing soluble oil which so far is the best in the market for such an application. The coolant of the present invention is highly desirable due to the non-toxic nature of all its components.  
         SUMMARY OF THE INVENTION  
         [0008]    In accordance with the present invention, there is provided a water-dispersible lubricating additive combination which removes essentially all of the foregoing mentioned deficiencies of the prior art. The invention covers physical blends of a mixture of polymeric esters, polymeric partially esterified acids, salts derived therefrom, and a polyethylene glycol fatty ester.  
           [0009]    It is an object of this invention to formulate a low foaming coolant which contains either amine, sodium, or potassium salts of polymeric esters or partially esterified polymeric carboxylic acids.  
           [0010]    It is another object of this invention to formulate a low foaming coolant which is amine-free by employing sodium or potassium hydroxide in forming the corresponding salts.  
           [0011]    It is yet another object of this invention to formulate a chlorine-free coolant.  
           [0012]    It is still yet another object of this invention to formulate a coolant which is non-toxic.  
           [0013]    It is,a further object of this invention to formulate a coolant which is low-foaming in nature due to the high molecular weights of the polymeric esters and acids.  
           [0014]    These and other objects of this invention will be evident when viewed in light of the detailed description and the pending claims.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0015]    Two major components are believed to be responsible for the performance of the novel lubricating additive blend: (1) the polymeric esters and partially esterified acids; and (2) a polyol ester of a fatty acid.  
           [0016]    The first major performance component which is described herein as “complex” or “polymeric” esters and partially esterified acids mean a mixture of esters and acids from the reaction of two or more of monohydric aliphatic alcohols, monobasic aliphatic acids, aliphatic glycols or polyglycols, polyhydric aliphatic alcohols, dibasic aliphatic acids, or polybasic aliphatic acids, where at least one polyhydric alcohol and at least one polybasic acid are used. The preferred monobasic acid is isostearic acid or oleic acid. The preferred polybasic acids are sebacic acid, adipic acid, azelaic acid and dimethylpropionic acid. The preferred polyhydric alcohols are pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylolpropane. The polyols can have internal ether linkages. These alcohols and carboxylic acids used in preparing polymeric esters have either straight or branched chains, and hydrocarbon chain lengths ranging from 4 to 25 carbon atoms.  
           [0017]    This kind of polymeric esters and acids have a final form of a clear viscous fluid with an acid number of 4 to 65 mg KOH per gram of sample. As the polymeric component inherently contains some partially esterified acids, it can be converted into the corresponding salts by neutralizing the acids with a strong base such as sodium hydroxide or alkanolamines in order to achieve a water-soluble or water-dispersible form, applicable to a coolant formulation.  
           [0018]    Thus far, there is no commercial product equivalent to the salts of polymeric esters and acids. The present commercial unneutralized mixture of polymeric esters and acids are Syn-Esters GY-series offered by Gateway Additive Division of Lubrizol Corporation. The polymeric esters and acids described herein were also described in U.S. Pat. Nos. 3,016,353, 4,130,494, 5,798,322 which describe the synthetic methods, compositions of the polymeric esters or end uses and lubricating formulation containing such a polymeric esters and acids. However, none of these patents cover the use of such an additive composition in a water-dispersible or water-reducible lubricant application or coolant.  
           [0019]    The second major component is an ester of a polyethylene glycol and a fatty acid. This component, besides providing additional lubricity, provides a coupling or solubilizing effect to the salts of polymeric acids and esters helping the latter to disperse more easily in water. This polyol ester can be substituted successfully with the following similar chemical class of surfactants or couplers such as polyoxyethylene alkyl esters, nonionic surfactants, ethoxylated alcohol, polyethyleneglycols, poly(ethyleneoxy)ethanol, alcohol ethoxylates, ethoxylated carboxylic acid esters, ethoxylated phosphate esters, polyethylene glycol fatty ester, ethoxylated fatty acids, amine ethoxylate, or hydroxy alkanolamine ethoxylated, alkyl amide ethoxylate.  
           [0020]    All these above-mentioned chemicals might have been described more than once using different terminology. For ethoxylated alcohols, their derived carboxylic esters and phosphate esters are also covered in this invention. All these coupling surfactants or esters share the common characteristic of either containing ethylene oxide or ether linkages,—(CH2CH2O)—.  
           [0021]    A physical blend of the following composition can be made simply by mixing all components together without any heating or special treatment: 
       
    
    
     EXAMPLE #1  
       [0022]    The synthesis of the polymeric acids and esters may be effected as follows. Into a 1000-ml four-necked round bottom flask, equipped with a nitrogen sparger, a Celsius thermometer, a reflux condenser, and a mechanical mixer, 615.55 grams or 2.1244 moles oleic acid; 186.25 grams or 0.9223 mole sebacic acid; 136.00 grams or 1.0000 mole pentaerythritol; and 1 gram methane sulfonic acid catalyst were charged. Subsequently, gradual heating was applied along with gentle nitrogen sparging. The batch was refluxed at 120-135° C. for about one hour to dissolve most of pentaerythritol. After one hour, the reflux condenser was removed to allow the cooking temperature gradually rose to the final temperature of 150° C. The batch was maintained at 150° C. with a gentle nitrogen sweep until an acid number of 13-65 mg KOH/g, preferably 14-40 mg KOH/g or a predetermined value was obtained.  
       EXAMPLE #2  
       [0023]    A water-dispersible lubricating blend or coolant was made by blending the polymeric acids esters cited in Example #1 with a polyethylene glycol oleate (PEG 400) (M.W. 400), and with the other ingredients, and having the following composition on a weight percentage basis.  
                                                   Components   Weight %                           Polymeric esters and acids (Ex. #1)    45.85%           Polyethylene glycol (PEG 400) oleate    27.51%           20% caustic solution    6.99%           Propylene glycol    6.30%           Tap water    5.90%           TOTAL   100.00%                      
 
       EXAMPLE #3  
       [0024]    A foaming test was performed using the blend of Example #2.  
         [0025]    100 mls of a 2% aqueous dilution of Example #2 was placed in 100 ml graduated cylinder which was also equipped with a glass stopper. The whole cylinder was shaken violently for about ten times. The initial foam height was measured in term of milliliters of foam generated. The rate of foam breaking was also observed.  
                                       Sample   Initial Foam Height   Foam Breaking                   2% Example #2 in water      3 ml   very fast       2% sodium salt of chlorinated stearic acid (32% Cl)   &gt;50 ml   very slow                  
 
       EXAMPLE #4  
       [0026]    [0026]                                             A FALEX EP Test (ASTM D 2670-67) was performed with the following results.            Sample   Falex EP Max. Load   Torque               2% Example #2 in water   4,000 lbs   51 lb-in.       2% sodium salt of chlorinated stearic acid (32% Cl)   4,000 lbs   64 lb-in.                    
         [0027]    A maximum load of 4,000 pounds out of a possible 4,500 pounds is indicative of very good performance for a coolant. The blend of Example #1 which is formulated in Example #2 of this invention performed equally well to a sodium salt of a chlorinated stearic acid, which is a commercial additive standard for a high performance coolant.  
       EXAMPLE #5  
       [0028]    A tapping torque test was performed with aluminum parts, using a MegaTap II -G8 unit manufactured by MicroTap USA Inc.  
                                                 Sample   Average Torque                                2% Example #2 in water   94   N-cm       2% commercial soluble oil (15% Cl)   94   N-cm       2% sodium salt of chlorinated stearic acid (32% Cl)   100   N-cm       100% tap water (no additive)   &gt;120   N-cm                  
 
         [0029]    A good lubricant should generate the least friction or the least torque during such an operation as tapping. This test illustrates that the blend of Example #1 as formulated in Example #2 of this invention is essentially equivalent to the chlorinated soluble oil which is the best candidate in processing aluminum. It also illustrates that Example #2 is far better than a typical commercial coolant represented here by the solution of sodium salt of chlorinated stearic acid.  
       EXAMPLE #6  
       [0030]    A tapping torque test was performed with steel parts, using a MegaTap II-G8 unit manufactured by MicroTap USA Inc.  
                                                   Sample   Average Torque                           2% Example #2 in water   181 N-cm           2% commercial soluble oil (15% Cl)   183 N-cm                      
 
         [0031]    A difference of two percent or higher in the average tapping torque is statistically significant based on field correlation. In this example, the two lubricating solutions are considered equal in performance on steel.  
       EXAMPLE #7  
       [0032]    A corrosion test was performed using polished metal strips of steel, copper, or aluminum which were submersed in a 2% testing solution of Example #2 inside a closed glass jar. The whole set-up was then placed in 70° C. oven for 24 hours. And any staining observed on the metallic surface was noted.  
                                   Sample   Staining                   2% Example #2 in water   no stain on copper strip           no rust on steel strip           slight stain on aluminum strip (same as pure           water)                  
 
         [0033]    Example #2 of this invention is non-corrosive to a variety of metallic surfaces.  
       EXAMPLE #8-#14  
       [0034]    A series of polymeric acids and esters were prepared in accordance with the following molar quantities evidenced in the table. Into a 1000-ml four-necked round bottom flask, equipped with a nitrogen sparger, a Celsius thermometer, a reflux condenser, and a mechanical mixer, a diacid, a monoacid and pentaerythritol were charged with a catalytic amount of methane sulfonic acid catalyst. Subsequently, a gradual heating was applied along with gentle nitrogen sparging. The batch was refluxed at 120-135° C. for about one hour to dissolve most of pentaerythritol. After one hour of refluxing, the reflux condenser was removed to allow the cooking temperature gradually rose to the final temperature of 150° C. The batch was maintained at 150° C. with a gentle nitrogen sweep until an acid number of 13-65, preferably 14-40 mg KOH/g was obtained.  
                                                                                             Moles   Ex. #8   Ex. #9   Ex. #10   Ex. #11   Ex. #12   Ex. #13   Ex. #14                                sebacic acid   1.00   0.91   0.92   0.92   0.92   0.93           azelaic acid                           0.92       isostearic acid                       2.19       oleic acid   2.01   2.15   2.12   2.12   2.12   —   2.12       pentaerythritol   1.00   1.00   1.00   1.00   1.00   1.00   1.00       SSU/100° F. of   gelled   115,494   15,793   3,700   651   18,294   30,250       polymeric acids/esters       mg KOH/g of       13.1   26.0   47.2   65.2   21.6   23.9       polymeric acids/esters       Clarity of Coolant   N/A   hazy   clear   clear   clear   clear   clear       (Example #2)       Tapping torque   N/A       94   96   105   93.5   94       (N-cm) (1)         Tapping efficiency (2)     N/A       100   98   87.5   100.5   100.0       Falex EP Load (lbs) (3)     N/A       4,000   4,000   3,250   4,000   4,000                                          
 
         [0035]    Therefore, what has been shown is that by reacting: (1) at least one polyhydric alcohol; (2) at least one polybasic acid; and (3) at least one monobasic acid, then combining the mentioned polymeric acid esters with a polyester of a fatty acid, a water-soluble coolant can be formulated with properties superior or equal to those oil-based formulations present used. In a preferred embodiment, the polyesters or polymeric acid esters composition will have a viscosity of about 100,000 to about 600 SSU at 100° F. and an acid number of about 13-65 mg KOH/g.  
         [0036]    Therefore, what has been shown is that the molar ratio of the charge for polymeric acid ester synthesis should fall within the following range: diacid/monoacid/polyhydric alcohol of 0.6-1.4/1.6-2.4/1.0, more preferably, 0.8-1.2/1.8-2.2/1.0, most preferably, 0.9/2.1/1.0.  
                                       Component   General Formula   Preferred Mole Ratio                   mono acids   R 1 —CO 2 H   0.91           wherein R 1  is selected from the group consisting of           C 5-20  alkyl, C 5-20  alkenyl, C 6-26  aryl, C 6-30  alkaryl and           C 6-30  aralkyl, including branched and straight chain           moieties       diacids   HO 2 C—R 2 —CO 2 H   2.12           wherein R 2  is selected from the group consisting of           C 2-36  alkyl, C 3-36  alkenyl, C 6-42  aryl, C 6-42  alkaryl and           C 6-42  aralkyl, including branched and straight chain           moieties               polyhydric alcohols                                 1.00                   and                                                                 wherein           each R 3  is selected independently from the group           consisting of H, (R 4 ) n OH, C 1-12  alkyl, C 2-14  alkenyl,           C 6-36  aryl, C 6-36  alkaryl and C 6-36  aralkyl, including           branched and straight chain moieties;           R 4  is selected from the group consisting of C 1-8             alkyl, C 2-8  alkenyl, including branched and straight           chain moieties;           R 5  and R 6  are independently selected from the           group consisting of R 4 ;           x is an integral value from 2-4 inclusive;           y is an integral value from 0 to 1 inclusive;           z is an integral value from 0 to 1 inclusive; and           n is an integral value from 0 to 1 inclusive.               alkylene glycol fatty acid ester                                                 wherein           R 7  is selected from the group consisting of C 2-36             alkyl, C 3-36  alkenyl, C 6-42  aryl, C 6-42  alkaryl and C 6-42             aralkyl, including branched and straight chain           moieties;           R 8  is selected from the group consisting of C 1-6  alkyl           and C 2-8  alkylene;           a is an integral value from 1 to 40.                  
 
         [0037]    It is of course recognized that both branched and unbranched moieties are included in the Markush formulations presented above. It is additionally defined that when the term “alkaryl” is used, that a moiety that combines both alkyl and aryl groups is meant, and that the aryl properties predominate, and that when the term “aralkyl” is used, that a moiety that combines both aryl and alkyl groups is meant, and that the alkyl properties predominate.  
         [0038]    In a preferred embodiment, the physical properties of the polymeric acid esters should be:  
                                                   Property   Value                           Acidity or mg KOH/g sample   15-40           Optimal acidity   24           Viscosity, SSU/100° F.    4,000-30,000           Optimal Viscosity   15,000                      
 
         [0039]    While not being held to any one theory of operation or methodology, it is believed that at least some mono acids are necessary to practice the invention to tie up some base and minimize crosslinking as well as control the molecular weight of the polymeric acid esters, which could crosslink and gel if the molecular weight is too high. The amount of base added can vary within experimental ranges determined by the amount required to make the composition water-soluble. The polyesters formed are believed to be highly branched and “star-like” moieties. Before neutralization, they are water insoluble, but after addition of a sufficient quantity of base, they become water-soluble.  
         [0040]    This invention has been described in detail with reference to specific embodiments thereof, including the respective best modes for carrying out each embodiment. It shall be understood that these illustrations are by way of example and not by way of limitation.