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
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.
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.
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.
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.
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.
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
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.
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.
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.
It is yet another object of this invention to formulate a chlorine-free coolant.
It is still yet another object of this invention to formulate a coolant which is non-toxic.
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.
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
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.
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.
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.
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.
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.
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)—.
A physical blend of the following composition can be made simply by mixing all components together without any heating or special treatment: