2,999,064 Patented Sept. 5, 1961. United States Patent Office 2 heavy duty applications, in which the pressure per unit 2,999,064 of area is relatively high, an aqueous cutting fluid embody. STABLE AOUEOUS. CUTTING FLUID ing the invention preferably, contains, in addition to the Clyde A. Suhan, Perrysburg, Ohio, assignor to Master reaction product of boric acid and the aliphatic amine, a Chemical Corporation, Toledo, Ohio, a corporation of reaction product of such an amine and an unsaturated Ohio . ; . fatty acid having from 18 to 22 carbon atoms in which No Drawing. Filed Feb. 11, 1959, Ser. No. 792,472 any substituent consists of a single hydroxy group. The 9 Claims. (C. 252-34.7) number of radicals of such fatty acid in the composition This is a continuation-in-part of application Ser. No. preferably is from 4 to 24 the number of boric acid 616,611, filed October 18, 1956, application Ser. No. 512, 10 radicals, but may be a smaller proportion, for example. 893, filed June 2, 1955, and application Ser. No. 253,553, 4 or % the number of boric acid radicals. filed October 27, 1951 (now abandoned). It has been discovered that an aqueous cutting fluid This invention relates to an aqueous cutting fluid that embodying the invention has superior stability. More is superior to prior aqueous cutting fluids in stability and over, a cutting fluid embodying the invention is an ex in other properties. 5 cellent corrosion inhibitor for cast iron and steel. It also Aqueous cutting fluids are of great potential value be inhibits the growth of bacteria and fungi, and is not irritat cause of their superior cooling action. However, an aque ing to the skin or otherwise harmful to the operator. ous cutting fluid, in order to be satisfactory, must meet It has been found that the incorporation of a nonionic certain strict requirements. wetting agent in an aqueous cutting fluid embodying the One of the requirements that an aqueous cutting fluid 20 invention is highly advantageous in preventing separation must meet is that it must contain ingredients which, in of the ingredients of a concentrated solution, and in pre relatively small concentrations, impart powerful lubricat serving the clarity of a dilute solution particularly when ing properties to the aqueous composition. Such ingredi hard water is used, ents, like the other ingredients in an aqueous cutting fluid, Another ingredient that may be used very advanta must be effective in relatively small concentrations. The 25 geously in a cutting fluid embodying the invention is a gel use of any such ingredients of an aqueous cutting fluid in forming solvent of the class consisting of higher alcohols a substantial concentration is not feasible because it would and ethers. One important advantage of such an ingredi entail prohibitive expense and would seriously impair the ent is that it makes it possible to incorporate a silicone cooling action of the fluid. antifoam agent, Another requirement that an aqueous cutting fluid must 30 BORIC ACD meet is that it must not contain any ingredient that pre cipitates upon mixing with hard water or during use of The boric acid used in preparing an aqueous cutting the cutting fluid. fluid of the invention may be obtained by using ordinary A further requirement of an aqueous cutting fluid is boric acid (i.e., orthoboric acid, HBOs) or any other that is must not contain any ingredient that may be irritat 35 boron compound that forms boric acid in aqueous solu ing to the skin. tion, for example, metaboric acid or boric oxide. It is A still further requirement is that an aqueous cutting believed that the boric acid forms an addition product fluid must have corrosion inhibiting properties so that it or salt with the amine in a cutting fluid of the invention. does not cause rusting or corrosion of any of the com The boric acid in a cutting fluid of the invention acts mon metals. 40 as a rust inhibitor. Furthermore, an addition product Still another requirement is that an aqueous cutting fluid of boric acid and an amine is a syrupy liquid and does must be bactericidal and fungicidal in character so that not precipitate out of the cutting fluid. In addition, boric the growth of bacteria or fungi is prevented. acid, unlike phosphoric acid and other acids whose salts An aqueous cutting fluid is not commercially acceptable have been employed in cutting fluids, has bactericidal if it has an offensive odor. This is one reason why the 45 properties. - fluid should not be capable of supporting the growth of AMNE bacteria or fungi, since such growth is usually accom The aliphatic amines which can be used in the practice panied by the development of an offensive odor as well of the invention, each of which has from 1 to 3 aliphatic as by formation of a precipitate. radicals, each containing from 1 to 4 carbon atoms, and An aqueous cutting fluid also should be substantially 50 has at least one hydroxy group attached to a carbon transparent so that it does not interfere with the visibility atom, include primary, secondary and tertiary alkylol of the work, and should not foam excessively. amines such as mono-, di- or triethanolamine. These The aqueous cutting fluids heretofore known have not amines are water soluable and are free from offensive met the foregoing requirements satisfactorily. odor. The preferred amine for use in the practice of the The principal object of the invention is to provide a 55 invention is triethanolamine, which ordinarily comprises novel aqueous cutting fluid which is not irritating to the minor amounts of mono- or diethanolamine, and has no skin, has an exceptionally high lubricating action, inhibits odor; its mildly alkaline properties aid in making the corrosion of common metals, remains free from precipita present cutting fluids extremely low in toxicity and ab tion and from offensive odor and is substantially trans solutely safe against dermatitis; and, in combination with parent. More specific objects and advantages are apparent 60 boric acid, it is an excellent rust inhibitor for cast iron from the following description, which discloses and illus and steel. trates the invention and is not intended to limit its scope. A stable aqueous cutting fluid embodying the invention OTHER INGREDIENTS THAT MAY BE USED comprises a reaction product of boric acid and an aliphatic An unsaturated fatty acid, having from 18 to 22 car amine having from 1 to 3 aliphatic radicals each of which 65 bon atoms, in which any substituent consists of a single contains from 1 to 4 carbon atoms, and having at least hydroxy group, when used in preparing a cutting fluid one hydroxy group attached to a carbon atom. An aque embodying the invention, is believed to react with the ous cutting fluid embodying the invention gives excellent amine to form a salt that acts as a very effective wetting results in applications in which the pressure per unit of agent. The function of a wetting agent in an aqueous area is relatively low, such as surface grinding operations 70 cutting fluid is to reduce the surface tension and increase in which a large surface is being ground or in which a the lubricity. (Water cannot be used alone as a cutting number of pieces are being ground simultaneously. For fluid, of course, because of its rusting properties, etc.) 2,999,064 3. 4. The unsaturated fatty acids used in the practice of the in phosphate, trioctyl triyolyglycol tetrapolyphosphate, glyc vention (in the form of amine salts) are effective lubri eryl monoricinoleate, 2-amino-2-methyl-1-propanol, tetra cants which inhibit the corrosion of cast iron and steel. octyl pyrophosphate, mono-olleyl dipolyglycol o-phos Furthermore, the amine salts of unsaturated fatty acids phate, diethylene glycol monooleate, diglycol dinaph used in the practice of the invention are not irritating to thenate, ethyl phosphate, polyoxyalkylene sorbitan mono the skin. oleate, n-nonyl alcohol, n-butyl phthalate and substantially The fatty acids which may be used in the practice of completely fluorinated hydrocarbons having from 5 to 10 the invention include the unsaturated acids derived from carbon atoms. Of these substances, the silicon com vegetable oils, such as oleic, linoleic, elaidic, linolenic, pounds, particularly silicones, are by far the most effective. erucic and eleostearic acids. (A saturated fatty acid The preferred antifoam agents include silicones having such as stearic acid is undesirable in the practice of the the general formula invention because its amine salts are solid pastes. Amine salts of saturated fatty acids such as coconut oil fatty acids (primarily lauric acid), on the other hand, not "(s). only are too thin liquids but also are irritating to the skin.) s wherein R is a saturated straight, branched or closed Ricinoleic acid may be used in the practice of the inven chain hydrocarbon group having up to 24 carbon atoms, in tion, although the use of ricinoleic acid produces a cut is the average number of such radicals per silicon atom ting fluid that has less body and lower viscosity than a and X is an integer greater than 1; and saturated alkyl cutting fluid produced by the use of oleic acid. Tri silicates having the general formula ethanolamine is preferred in the practice of the invention 20 not only for the reasons hereinbefore stated, but also be (RZ)Si=0 or (RZ) Si cause its salts with the unsubstituted higher unsaturated in which R is the same as in the above formula and Z fatty acids that may be used in the practice of the inven is oxygen, sulfur, selenium or tellurium.