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(11) | EP 0 115 926 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Aqueous metal-working lubricant containing polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers |
| (57) An aqueous metalworking lubricant composition comprising a water-soluble mixture
of polyoxypropylene-polyoxyethylene-polyoxypropylene block copolymers, a water-soluble
carboxylic acid, a water-soluble alkanolamine and water. A preferred lubricant composition
also comprises an antifoam agent. The lubricant composition is suitable for both cold
rolling and hot rolling of metals such as aluminum and aluminum alloys. A method of
metalworking includes applying said lubricant composition during operations such as
hot or cold rolling. |
[0001] The present invention relates to lubricant compositions and more particularly to water-soluble lubricant compositions suitable for use in metalworking operations such as the cold rolling and hot rolling of aluminum and aluminum alloys, and the invention relates to such metalworking operations.
[0002] 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 pro- perties 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.
[0003] Among the requirements for a satisfactory metalworking lubricant are corrosion-inhibiting properties and stability under conditions of operation. While various fluids may posses 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.
[0004] Aqueous metalworking lubricant compositions are known in the prior art. However, prior to the present invention, aqueous metalworking lubricants were not placed into widespread commercial use because of their inability to satisfy simultaneously each of the requirements listed above.
[0005] Beaubien et al. U.S. Patent 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 conjugated in the order EO-PO-EO ("EO" denotes polyoxyethylene and "PO" denotes polyoxypropylene), rather than being the PO-EO-PO block copolymers of the present invention.
[0006] Reamer U.S. Patent 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 "undesirable frictional problems, foaming, instability and the like".
[0007] Davis U.S. Patent No. 3,374,171 claims a cutting fluid containing about 5-40% of a water-soluble alkanolamine, about 0.1-9% 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 PO-EO-PO 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.
[0008] Felton U.S. Patent 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).
[0009] It is a principal object of the present invention to provide an aqueous metalworking 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 metalworking operations in which the composition is used.
[0010] 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.
[0011] According to the present invention there is provided a lubricant composition which includes a block polyoxypropylene-polyoxyethylene copolymer, characterized by comprising
(a) about 1.0-20 wt% of a water-soluble mixture of polyoxyethylene-polyoxypropylene block copolymers containing a single polyoxyethylene chain and two polyoxypropylene chains attached to the polyoxyethylene chain, the average molecular weight of the polyoxypropylene chains in the mixture being at least 900 and the polyoxyethylene chains in the mixture constituting about 10-80 wt%, preferably about 20 wt%, of the mixture;
(b) about 0.5-10 wt%, preferably 0.5-5 or 1-2 wt%, of a water-soluble carboxylic acid
of the general formula
where m is an integer from 11 to 36, n = 0, 2, 4 or 6 and r = 1 or 2;
(c) about 0.5-10 wt% of a water-soluble alkanolamine; and
(d) remainder, water.
[0012] Further in accordance with the present invention there is provided a method of metalworking such as cold or hot rolling of aluminum or aluminum alloys, characterized by applying to a metal object a synthetic lubricant composition in accordance with the lubricant composition of this invention, and, optionally, hot rolling or cold rolling the metal object.
[0013] In accordance with the present invention, there is provided an aqueous synthetic metalworking 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 and foil form.
[0014] The lubricant comprises a water-soluble mixture of PO-EO-PO block copolymers, a water-soluble carboxylic acid, a water-soluble alkanolamine and water. A preferred lubricant composition also contains an antifoam agent.
[0015] The PO-EO-PO block copolymers comprise about l.0-20 wt% 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.
[0016] The carboxylic acid comprises about 0.5-10 wt% of the composition and may be a saturated or unsaturated c11 to C36 mono- or dicarboxylic acid. The acid is preferably a saturated or monounsaturated C12 to C20 monocarboxylic acid. Two preferred carboxylic acids are oleic acid and lauric acid.
[0017] The water-soluble alkanolamine comprises about 0.5-10 wt% of the composition. Some particularly preferred alkanolamines are triethanolamine, diethanolamine and ethyldiisopropanolamine.
[0018] The aqueous synthetic metalworking lubricant composition of the invention is suitable for use with both ferrous and non-ferrous metals. The lubricant composition can be used in such operations as rolling, drawing and ironing, machining and others. The lubricant composition exhibits satisfactory load bearing and friction modifying properties when used for either hot rolling or cold rolling of aluminum alloys.
[0019] The term "hot rolling" refers to rolling that takes place at a metal entry temperature of approximately 232-538°C. (450-1000°F.) for aluminum alloys. Hot rolling is typically-used to reduce slabs of aluminum alloy material that are about 8 cm (several inches) thick into sheets having a thickness of about 3 mm (1/8 inch).
[0020] The term "cold rolling" refers to rolling in which metal entry temperature may range from approximately ambient temperature to about 232°c. (450°F.) for aluminum alloys. Metal entry temperature is ordinarily about ambient temperature. Cold rolling is typically used to reduce sheets of aluminum alloy material about 3 mm (1/8 inch) thick into lesser thicknesses.
[0021] One ingredient of the lubricant composition is a water-soluble mixture of EO-PO block copolymers containing a single EO chain and two PO chains attached to the EO chain. These block copolymers have the general formula
The average molecular weight of PO chains in the mixture is at least 900, and the EO chains in the mixture constitute about 10-80 wt% of the mixture. The average molecular weight of PO chains in the mixture is preferably about 1000 to 3100. In one preferred mixture, the average molecular weight of PO chains in the mixture is about 1700, and EO chains constitute about 20 wt% of the mixture.
[0022] Such materials are sold under the trade name "Pluronic R" by BASF Wyandotte Corporation of Wyandotte, Michigan. The mixture of block copolymers constitutes about 1.0-20 wt% of the lubricant composition, generally about 2.5-10 wt%. One typical example contains about 5 wt% of a mixture of block PO-EO-PO copolymers wherein the average molecular weight of PO chains in the mixture is about 1700, and the EO chains constitute about 20 wt% of the mixture. This mixture is sold under the trade designation "17R2". The mixture of block copolymers functions as an additive solubilizer, viscosity builder and antiwear agent in the lubricant composition.
[0023] The PO-EO-PO 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. Patent No. 3,036,118 issued May 22, 1962.
[0024] A second ingredient of the composition is a water-soluble carboxylic acid having the general formula
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 C12 to C20 monocarboxylic acid. Two particularly preferred monocarboxylic acids are oleic acid and lauric acid.
[0025] 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 "dimer acids", 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. For example, the term "C16-C18 dimer acids" refers to a commercially available dimerization product of mixed c16-c18 polyunsaturated fatty acids.
[0026] 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 suitable 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.
[0027] A third ingredient of the composition is a water-soluble alkanolamine. Some suitable alkanolamines are monoethanolamine, diethanolamine, triethanolamine, dimethyl-ethanolamine, 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.
[0028] The water-soluble alkanolamine comprises about 0.5-l0 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.
[0029] In the preferred form, the lubricant composition of the invention also contains a defoaming agent. One preferred composition contains about 50-100 ppm (about .005-.01 wt%) of a non-silicone defoaming agent. This agent comprises organic and silica derivatives dispersed in a solvent and is sold commercially by Mazer Chemicals Inc. of Gurnee, Illinois as its MAZU DF 2502 defoamer. A less preferred lubricant composition comprises about 25 ppm (about .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.
[0030] 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.
[0031] 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
[0032] Some examples of preferred lubricant compositions made in accordance with the invention are as follows:
1. A lubricant composition which includes a block polyoxypropylene-polyoxyethylene
copolymer, characterized by comprising
(a) about 1.0-20 wt% of a water-soluble mixture of polyoxyethylene-polyoxypropylene block copolymers containing a single polyoxyethylene chain and two polyoxypropylene chains attached to the polyoxyethylene chain, the average molecular weight of the polyoxypropylene chains in the mixture being at least 900 and the polyoxyethylene chains in the mixture constituting about 10-80 wt%, preferably about 20 wt%, of the mixture;
(b) about 0.5-10 wt%, preferably 0.5-5 or 1-2 wt%, of a water-soluble carboxylic acid
of the general formula
where m is an integer from 11 to 36, n = 0, 2, 4 or 6 and r = 1 or 2;
(c) about 0.5-10 wt% of a water-soluble alkanolamine; and
(d) remainder, water.
2. The lubricant composition of claim 1, characterized in that the average molecular
weight of polyoxypropylene chains in the mixture is about 1000 to 3100.
3. The lubricant composition of claim 1 or 2, characterized in that the mixture of
polyoxyethylene-polyoxypropylene block copolymers comprises about 2.5-10 wt%, preferably
5 wt%, of the composition.
4. The lubricant composition of any of the preceding claims, characterized in that
said carboxylic acid comprises a saturated or monounsaturated C12 to C20 monocarboxylic acid, preferably oleic acid or lauric acid.
5. The lubricant composition of any of the preceding claims, characterized in that
said alkanolamine consists of triethanolamine, diethanolamine or ethyldiisopropanolamine,
or mixtures thereof, and preferably is triethanolamine.
6. The lubricant composition of any of the preceding claims, characterized by further
comprising
(e) an antifoam agent, preferably comprising about 50-100 ppm of the composition.
7. The lubricant composition of any of the preceding claims, characterized by further
comprising
(f) about 0.5-10 wt% of a water-soluble polyoxyethylene or polyoxypropylene alcohol or a water-soluble carboxylic acid ester of a polyoxyethylene or polyoxypropylene alcohol, wherein said alcohol or ester preferably comprises about 1 wt% of the composition.
8. A method of metalworking such as cold or hot rolling of aluminum or aluminum alloys,
characterized by applying to a metal object a synthetic lubricant composition in accordance
with any one of the preceding claims, and, optionally, hot rolling or cold rolling
the metal object.
9. The metalworking method of claim 8, characterized by further including the step
of hot rolling the metal object at a temperature of about 232-538°C. (450-1000°F.).
10. The metalworking method of claim 8, characterized by further including the step
of cold rolling the metal object at approximately ambient temperature to 232°C. (450°F.).