Abstract:
A method of metalworking including the step of applying to a metal object a synthetic aqueous lubricant composition. The composition comprises a water-soluble mixture of polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers, a water-soluble carboxylic acid, a water-soluble alkanolamine and water. The metalworking method preferably includes a step of either hot rolling or cold rolling. The method is especially suitable for use on aluminum and aluminum alloy material.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to metalworking operations such as the cold rolling and hot rolling of aluminum and aluminum alloys. More particularly, the invention relates to an aqueous synthetic lubricant composition for use in such metalworking operations. 
     In the rolling of metals such as aluminum and aluminum alloys, it is customary to flood the rolls and the workpiece with a coolant for the purpose of carrying away heat generated by the operation. It is also customary to employ the coolant in combination with various agents having load bearing and friction-modifying properties for reducing friction between the rolls and the workpiece. It has heretofore been the practice to use for such purpose aqueous compositions containing such lubricating agents as emulsified petroleum and non-petroleum additives. In order to perform satisfactorily on an industrial scale, an aqueous lubricant fluid must meet several important requirements. 
     Among the requirements for a satisfactory metalworking lubricant are corrosion-inhibiting properties and stability under conditions of operation. While various fluids may possess such characteristics, there are also other important requirements that should be met. Among these requirements is the avoidance of deposits on the rolls and workpiece following the rolling operation. Such deposits result from drying of the fluid, and they are difficult to remove. Other important requirements include avoidance of excessive foam formation. Metalworking lubricants in the form of aqueous solutions have generally not been able to satisfy all of the foregoing requirements prior to the present invention. 
     Metalworking methods using single phase aqueous lubricant compositions are known in the prior art. However, prior to the present invention, metalworking with single phase aqueous lubricant compositions was not in widespread commercial use because of the inability of such compositions to satisfy simultaneously each of the requirements listed above. 
     Beaubien et al. U.S. Pat. No. 2,825,693 claims a metalworking lubricant concentrate comprising about 5-20% each of a block polyoxypropylene-polyoxyethylene copolymer and a random polyoxypropylene-polyoxyethylene copolymer, about 1-12% each of sodium nitrite and ethanolamine, and about 0.01-5% of an unsaturated high molecular weight fatty acid. The block polyoxypropylene-polyoxyethylene copolymers disclosed by Beaubien et al. are not conjugated in the order polyoxypropylene-polyoxyethylene-polyoxypropylene, as claimed in the present invention. 
     Reamer U.S. Pat. No. 2,981,686 discloses an aqueous metalworking lubricant comprising a water-soluble hetero-copolymer of a mixture of oxyethylene and oxypropylene groups. The Reamer patent states that block copolymers of ethylene oxide and propylene oxide are undesirable in such lubricants because of the tendency of these copolymers to produce &#34;undesirable frictional problems, foaming, instability and the like&#34;. 
     Davis U.S. Pat. No. 3,374,171 claims a cutting fluid containing about 5-40% of a water-soluble alkanolamine, about 0.9-9% of a saturated organic acid having about 6-9 carbon atoms per molecule, and about 0.5-20% of a water-soluble polyoxyalkylene glycol. The Davis patent contains no specific teaching of the utility of polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers as ingredients of aqueous metalworking compositions. In addition, Davis cautions against the use of higher molecular weight saturated organic acids. He states that such higher organic acids can result in poor hard water stability, reduced corrosion-inhibiting properties and high foaming tendencies. These problems are said to lead to clogged filters, poor rust protection and reduced tool life in areas where hard water is encountered. 
     Felton U.S. Pat. No. 4,033,886 discloses a liquid suitable for the formation of a recyclable metalworking lubricant. The liquid is an aqueous solution containing a mixture of ethylene oxide-propylene oxide block copolymers, an alkanolamine cinnamate and a boron amine complex. The block copolymers have a central portion of polypropylene oxide with polyethylene oxide on each end (see column 2, lines 32-33). 
     It is a principal object of the present invention to provide a metalworking method employing a lubricant composition having acceptable load bearing and friction-modifying properties, corrosion-inhibition ability and chemical stability under ordinary operating conditions, and avoidance of deposits on tools and workpieces following operations in which the lubricant composition is used. 
     It is a related object of the invention to provide a lubricant composition accomplishing the foregoing objectives while at the same time avoiding excessive production of foam. 
     Additional objects and advantages of the present invention will become apparent to persons skilled in the art from the following specification. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a metalworking method employing an aqueous synthetic lubricant having good lubricating properties in metal fabricating operations. The lubricant is especially suitable for use in the hot rolling and cold rolling of aluminum and aluminum alloys into sheet form. 
     The lubricant composition comprises a water-soluble mixture of polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers, a water-soluble carboxylic acid, a water-soluble alkanolamine and water. A preferred composition also contains an antifoam agent. 
     The polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers comprise about 1.0-20wt% of the composition. The average molecular weight of polyoxypropylene chains in the mixture is at least 900, and the polyoxyethylene chains constitute about 10-80 wt% of the mixture. 
     The carboxylic acid comprises about 0.5-10 wt% of the composition and may be a saturated or unsaturated C 11  to C 36  mono- or dicarboxylic acid. The acid is preferably a saturated or monounsaturated C 12  to C 20  monocarboxylic acid. Two particularly preferred carboxylic acids are oleic acid and lauric acid. 
     The water-soluble alkanolamine comprises about 0.5-10 wt% of the composition. Some particularly preferred alkanolamines are triethanolamine, diethanolamine and ethyldiisopropanolamine. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The metalworking method of the invention is suitable for use with both ferrous and non-ferrous metals. The method can include such operations as rolling, drawing and ironing, machining and others. The lubricant composition employed in the method exhibits satisfactory load bearing and friction modifying properties when used for either hot rolling or cold rolling of aluminum alloys. 
     The term &#34;hot rolling&#34; refers to rolling that takes place at a metal entry temperature of approximately 450°-1000° F. for aluminum alloys. Hot rolling is typically used to reduce slabs of aluminum alloy material that are several inches thick into sheets having a thickness of about 1/8 inch. 
     The term &#34;cold rolling&#34; refers to rolling in which metal entry temperature may range from approximately ambient temperature to about 450° F. for aluminum alloys. Metal entry temperature is ordinarily about ambient temperture. Cold rolling is typically used to reduce sheets of aluminum alloy material about 1/8 inch thick into lesser thicknesses. 
     One ingredient of the lubricant composition is a water-soluble mixture of polyoxyethylene-polyoxypropylene block copolyers containing a single polyoxyethylene chain and two polyoxypropylene chains attached to the polyoxyethylene chain. These block copolymers have the general formula ##STR1## The average molecular weight of polyoxypropylene chains in the mixture is at least 900, and the polyoxyethylene chains in the mixture consititute about 10-80 wt% of the mixture. The average molecular weight of polyoxypropylene chains in the mixture is preferably about 1000 to 3100. In a preferred mixture, the average molecular weight of polyoxypropylene chains in the mixture is about 1700, and polyoxyethylene chains constitute about 20wt% of the mixture. 
     Such materials are sold under the trade name &#34;Pluronic R&#34; by BASF Wyandotte Corporation of Wyandotte, Mich. The mixture of block copolymers constitutes about 1.0-20 wt% of the lubricant composition, generally about 2.5-10 wt%. One example contains about 5 wt% of a mixture of block polyoxypropylene-polyoxyethylene-polyoxypropylene copolymers wherein the average molecular weight of polyoxypropylene chains in the mixture is about 1700, and the polyoxyethylene chains constitute about 20 wt% of the mixture. This mixture is sold under the trade designation &#34;17R2&#34;. The mixture of block copolymers functions as an additive solubilizer, viscosity builder and antiwear agent in the lubricant composition. 
     The polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers are formed by the sequential addition of ethylene oxide and then propylene oxide to an ethylene glycol base. These conjugated or block copolymers are described in greater detail in Jackson et al. U.S. Pat. No. 3,036,118 issued May 22, 1962. The disclosure of said Jackson et al. patent is incorporated by reference to the extent not inconsistent with the present invention. 
     A second ingredient of the composition is a water-soluble carboxylic acid having the general formula 
     
         C.sub.m H.sub.2m-n-r+2 (COOH).sub.r 
    
     where m is an integer from 11 to 36, n=0, 2, 4 or 6 and r=1 or 2. The carboxylic acid is preferably a saturated or monounsaturated C 12  to C 20  monocarboxylic acid. Two preferred monocarboxylic acids are oleic acid and lauric acid. 
     An alternative formulation of the lubricant composition includes a dimeric unsaturated fatty acid, such as dilinoleic acid. Dimeric fatty acids are also commercially available as &#34;dimer acids&#34;, usually containing a total of about 32 to 36 carbon atoms. These acids result from the dimerization of polyunsaturated fatty acids containing from 16 to 18 carbon atoms. 
     The water-soluble carboxylic acid comprises about 0.5-10 wt% of the composition, preferably about 0.5-5 wt%. Compositions containing about 1-2 wt% of the acid are quite suitable. Two preferred lubricant compositions include 1 wt% oleic acid and 2 wt% oleic acid, respectively. The carboxylic acid functions as a load bearing and friction modifying additive in the composition. 
     A third ingredient of the composition is a water-soluble alkanolamine. Some suitable alkanolamines are monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethyl-ethanolamine, aminoethyl-ethanolamine, methyl-diethanolamine, N-acetyl ethanolamine, phenylethanolamine, phenyldiethanolamine, mono-, di- and triisopropanolamine, and mixtures of any of the foregoing alkanolamines. The preferred alkanolamines are triethanolamine, diethanolamine and ethyldiisopropanolamine. 
     The water-soluble alkanolamine comprises about 0.5-10 wt% of the lubricant composition, preferably about 0.5-3 wt%. Two preferred compositions include 0.8 wt% triethanolamine and 1.6 wt% triethanolamine, respectively. The alkanolamine has the function of partially or completely converting the carboxylic acid into amine soap. The alkanolamine should preferably be present in sufficient concentration that at least one amine group is present for each carboxyl group in the carboxylic acid. 
     In the preferred form, the lubricant composition of the invention also contains a defoaming agent. One preferred composition contains about 50-100 ppm (about 0.005-0.01 wt%) of a non-silicone defoaming agent. This agent comprises organic and silica derivatives dispersed in a solvent and is sold commerically by Mazer Chemicals Inc. of Gurnee, Ill. as its MAZU DF 2502 defoamer. A less preferred lubricant composition comprises about 25 ppm (about 0.0025 wt%) of a silicone defoaming agent. The defoaming agent is chosen so as to produce suitable reductions in foam while at the same time avoiding deposits on metal surfaces that affect coating or paint adhesion. 
     The lubricant composition may also include about 0.5-10 wt% of a water-soluble polyoxyethylene or polyoxypropylene alcohol or a water-soluble carboxylic acid ester of such alcohol. Two suitable esters are a monostearate of a polyethylene glycol having a molecular weight of about 400, and a dioleate of a polyethylene glycol having a molecular weight of about 1000. These esters are typically added to form about 1 wt% of the lubricant composition. The esters add to lubricity of the composition. 
     Additional additives known to persons skilled in the art may be desirable under certain conditions. Such additives may include biocides, oxidation inhibitors and corrosion inhibitors. 
    
    
     EXAMPLES 
     Some examples of suitable lubricant compositions for practicing the metalworking method of the invention are as follows: 
     
         __________________________________________________________________________ExampleIngredient          Content (wt %)__________________________________________________________________________1    A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1700 and the polyoxyethylene chainsconstitute about 20 wt % of themixture (Pluronic 17R2)Oleic acid          2Triethanolamine     1.6Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder2    A mixture of polyoxpropylene-                    5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1700 and the polyoxyethylene chainsconstitute about 20 wt % of themixture (Pluronic 17R2)Oleic acid          1Triethanolamine     0.8Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder3    A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxpropylene chains is about1700 and the polyoxyethylene chainsconstitute about 20 wt % of themixture (Pluronic 17R2)Dimer acid          2Triethanolamine     2.4Polyethylene glycol (400)                    1monostearateNon-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder4    A mixture of polyoxypropylene-                    5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about2500 and the polyoxyethylene chainsconstitute about 40 wt % of themixture (Pluronic 25R4)Lauric acid         1Ethyldiisopropanolamine                    2Polyethylene glycol (1000) Dioleate                    1Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder5    A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about3100 and the polyoxyethylene chainsconstitute about 10 wt % of themixture (Pluronic 31R1)Oleic acid          2Triethanolamine     0.5Diethanolamine      1Defoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder6    A mixture of polyoxypropylene-                    5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about2500 and the polyoxyethylene chainsconstitute about 50 wt % of themixture (Pluronic 25R5)Oleic acid          0.5Dimer acid          0.5Triethanolamine     1Defoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder7    A mixture of polyoxypropylene-                    7polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about3100 and the polyoxyethylene chainsconstitute about 40 wt % of themixture (Pluronic 31R4)Oleic acid          2Aminoethyl-ethanolamine                    1Polyethylene glycol (600)                    1monolaurateDefoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder8    A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1700 and the polyoxyethylene chainsconstitute about 40 wt % of themixture (Pluronic 17R4)Isostearic acid     3Diethanolamine      1Polyoxyethylene (12) lauryl ether                    1Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder9    A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1000 and the polyoxyethylene chainsconstitute about 50 wt % of themixture (Pluronic 10R5)Isostearic acid     2Diethanolamine      1Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder10   A mixture of polyoxypropylene-                    7polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1700 and the polyoxyethylene chainsconstitute about 80 wt % of themixture (Pluronic 17R8)Oleic acid          2Triethanolamine     1.6Defoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder11   A mixture of polyoxypropylene-                    5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about2500 and the polyoxyethylene chainsconstitute about 10 wt % of themixture (Pluronic 25R1)Linoleic acid       1Monoethanolamine    0.5Defoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder12   A mixture of polyoxypropylene-                    7.5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about3100 and the polyoxyethylene chainsconstitute about 20 wt % of themixture (Pluronic 31R2)Oleic acid          4Diethanolamine      1.5Non-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder13   A mixture of polyoxypropylene-                    5polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxpropylene chains is about1000 and the polyoxyethylene chainsconstitute about 50 wt % of themixture (Pluronic 10R5)Lauric acid         1.5Monoethanolamine    1Polyethylene glycol (4000)                    1distearateNon-silicone defoamer                    50-100 ppm(MAZU DF 2502)Water               Remainder14   A mixture of polyoxypropylene-                    10polyoxyethylene-polyoxypropyleneblock copolymers in which theaverage molecular weight of thepolyoxypropylene chains is about1700 and the polyoxyethylene chainsconstitute about 20 wt % of themixture (Pluronic 17R2)Isostearic acid     1Lauric acid         1Diethanolamine      1.5Polyethylene glycol (400)                    1monolaurateDefoamer (MAZU DF 2502)                    50-100 ppmWater               Remainder__________________________________________________________________________ 
    
     The method of the present invention works suprisingly well for either hot rolling and cold rolling of aluminum alloys. 
     The foregoing description of my invention has been made with reference to some preferred embodiments. Persons skilled in the art will understand that numerous changes and modifications can be made in the invention without departing from the spirit and scope of the following claims.