COOLING LUBRICANT FOR COLD ROLLING ALUMINUM

Abstract

Described is a cooling lubricant for cold rolling aluminum, which includes a mineral oil-based or synthetic base oil and a polyalkylene glycol or a compound with a polyalkylene oxide structure. Further, the cooling lubricant is not water-soluble or miscible with water, and the cooling lubricant is substantially free of fatty acids and fatty alcohols.

Claims

1. A use of a cooling lubricant for rolling aluminum, in particular for cold rolling aluminum, comprising: a mineral oil-based or synthetic base oil, a polyethylene glycol, polypropylene glycol, polybutylene glycol, an ethoxylated fatty alcohol or a mixture of at least two of the aforementioned compounds, wherein the cooling lubricant is not water-soluble or miscible with water, the cooling lubricant is substantially free of fatty acids and fatty alcohols, wherein substantially free means that a fatty acid as a lubricating additive is contained in a proportion of at most 0.2 wt. %, based on the mass of the cooling lubricant, and a fatty alcohol as a lubricating additive is contained in a proportion of at most 0.4 wt. %, based on the mass of the cooling lubricant, the cooling lubricant is free of straight-chain olefins.

2. The use of claim 1, wherein the proportion of the polyalkylene glycol or of the ethoxylated fatty alcohol in the cooling lubricant is 0.01 to 10 wt. %, based on the mass of the cooling lubricant.

3. The use of claim 1, wherein the ethoxylated fatty alcohol is a polyethylene glycol monododecyl ether, in particular a tetraethylene glycol monododecyl ether.

4. The use of claim 1, wherein the base oil of the cooling lubricant is present in a proportion of at least 85 wt. %, in particular of at least 90 wt. %, based on the mass of the cooling lubricant.

5. The use of claim 1, wherein the cooling lubricant contains a fatty acid ester in an amount of up to 10 wt. %, based on the mass of the cooling lubricant.

6. The use of claim 5, wherein the fatty acid ester is selected from methyl esters of saturated, straight-chain C.sub.10-14 fatty acids, in particular methyl dodecanoate.

7. A method for cold rolling an aluminum product that is free of visually discernible defect patterns caused by fatty acids, comprising using a cooling lubricant for cold rolling an aluminum strip, the cooling lubricant comprising: a mineral oil-based or synthetic base oil, a polyethylene glycol, polypropylene glycol, polybutylene glycol, an ethoxylated fatty alcohol or a mixture of at least two of the aforementioned compounds, wherein the cooling lubricant is not water-soluble or miscible with water, the cooling lubricant is substantially free of fatty acids and fatty alcohols, wherein substantially free means that a fatty acid as a lubricating additive is contained in a proportion of at most 0.2 wt. %, based on the mass of the cooling lubricant, and a fatty alcohol as a lubricating additive is contained in a proportion of at most 0.4 wt. %, based on the mass of the cooling lubricant, the cooling lubricant is free of straight-chain olefins.

Description

EXAMPLES

Example 1—Determination of the Coefficients of Friction of Various Lubricants

[0036] The lubricating properties of the cooling lubricant according to the invention were determined using an MTM2 mini-traction machine from PCS Instruments in standard configuration with a steel ball (diameter 19.05 mm) exerting a load and an aluminum test disk which is rotatable at different speeds. The load on the test disk by the ball (¾″ ball bearing steel AISI 52100 (100Cr6, 1.3505)) was set to 40 N (0.5 GPa contact pressure) and coefficients of friction (CF) at different rolling speeds of. The two mean values (MV) of the coefficients of friction measured at rolling speeds of 1 to 200 m/min are reproduced in Table 1 below. The disk was formed from an aluminum alloy AA1XXX. The slide/roll ratio (SRR) during the test was 50%. After the tribological test, the wettability of the aluminum test disks with respect to water was tested. For this purpose, drop tests with a drop volume of 5 μl were carried out with demineralized water on the disks next to the track. The standardized test procedure corresponds to the internal work instruction “Hydro CO 0620”. The kinematic viscosity was measured in accordance with DIN 51562 at 40° C.

TABLE-US-00001 TABLE 1 CF MV Droplet Viscosity 0.2-200 size 5 μl of Lubricant sample mm.sup.2/s m/min water in mm Comments 1 Base oil 1.9 0.07; 3.1 Lubricating film 0.08 formation suboptimal; metal soap formation 2 Base oil + 0.9% fatty 1.9 0.06; 2.5 Good lubricating film; acid + 0.9% methyl 0.05 more abrasion in the laurate KSS but clean disk 3 Rolling oil with 1% 1.9 0.05; 3.1 Better lubricating film PAG* (viscosity 20 0.05 formation than pure mm.sup.2/s at 40° C.) rolling oil 4 Rolling oil with 2% 1.9 0.04; 3.5 Lubricating film PAG* (viscosity 20 0.04 formation good; mm.sup.2/s at 40° C.) minimal track on the ball 5 Rolling oil with 4% 2.0 0.03; 3.5 Hardly any abrasion PAG* (viscosity 20 0.03 mm.sup.2/s at 40° C.) 6 Rolling oil with 2% 1.9 0.06; 3.3 Good lubricating film PAG-containing 0.06 formation; some compound** (viscosity abrasion; acceptable 20 mm.sup.2/s at 40° C.) wetting 7 Rolling oil with 5% 2.0 0.05; 6.6 Good lubricating film PAG-containing 0.06 formation; some compound** (viscosity abrasion; good wetting 20 mm.sup.2/s at 40° C.) 8 Rolling oil with 10% 2.2 0.03; 10.7 Good lubricating film PAG-containing 0.03 formation; hardly any compound** (viscosity abrasion; very good 20 mm.sup.2/s at 40° C.) wetting 9 Rolling oil with 5% 2.1 0.06; 3.6 Lubricating film PAG*** (viscosity 33 0.08 formation good mm.sup.2/s at 40° C.) 10 Rolling oil with 5% 2.1 0.09; 4.5 Lubricating film PAG*** (viscosity 57 0.08 formation good; hardly mm.sup.2/s at 40° C.) any abrasion, hardly any track on the ball 11 Rolling oil with 5% 2.1 0.07; 3.5 Lubricating film PAG*** (viscosity 77 0.07 formation good; mm.sup.2/s at 40° C.) minimal track on the ball 12 Rolling oil with 5% 2.3 0.08; 3.3 Lubricating film PAG**** (viscosity 175 0.06 formation good; mm2/s at 40° C.) minimal track on the ball *PAG = an EO/PO copolymer with a kinematic viscosity of 20 mm.sup.2/s at 40° C. **a polyethylene glycol monododecyl ether having a kinematic viscosity of 20 mm.sup.2/s at 40° C. ***in each case: Polypropylene glycol) monobutyl ether with kinematic viscosities of 33, 57 and 77 mm.sup.2/s at 40° C. ****Mixture of polypropylene glycols with kinematic viscosities of 75 and 225 mm.sup.2/s at 40° C., viscosity of the mixture is 175 mm.sup.2/s at 40° C.

[0037] The formation of lubricating film with the base oil alone is suboptimal; metal soap is formed. Lubricant sample 2 provides a good lubricating film with more abrasion but with a clean disk. Lubricant sample 3 according to the invention provides better lubricating film formation. The same applies to sample 4, which moreover hardly shows any track on the ball. This also applies to sample 5 which provides hardly any abrasion. Samples 6 to 12 show good lubricating film formation. Samples 6 and 7 some abrasion, sample 8 shows hardly any abrasion. Sample 6 shows acceptable wetting with water, sample 7 good wetting and sample 8 very good wetting with water. Sample 10 delivers hardly any abrasion and hardly any track on the ball. Samples 11 and 12 provide minimal track on the ball.

Example 2 — Determination of the Wetting Angle After Rolling With Different Lubricants

[0038] An aluminum foil of an AA1XXX (type alloy was also used in the following test for determining the wetting angle on the surface of the foil. The contact angles (CA) were measured during wetting with water and with NMP. The wetting angle or contact angle was determined in the drop test at a drop volume of 5 μl with fully demineralized water or NMP using the drop shape analyzer DSA 10 from Krüss GmbH, Hamburg, Germany. The measurements are mean values of individual measurements at four different positions on the surface of the foil sample. The results of the measurements are shown in Table 2 below. Furthermore, the surface energy (SFE) was determined by determining the contact angle. Corresponding values are given in Table 2.

TABLE-US-00002 TABLE 2 Occupancy CA SFE CA vs. (total) vs. H.sub.2O mN/m NMP Rolling oil (base oil) 71° 30 32° Base oil with 0.1% fatty acid LA 87° 26 38° Base oil with 0.5% fatty acid LA 111°  20 67° Base oil with 1% fatty alcohol C12 78° 26 40° Base oil with 1% fatty alcohol C12/C14 92° 22 46° (70:30) Base oil with 2% fatty alcohol C12/C14 85° 22 43° (70:30) Base oil with 0.1% of a PAG-containing 74° 34 20° compound* (viscosity 20 mm.sup.2/s at 40° C.) Base oil with 0.5% of a PAG-containing 75° 29 24° compound* (viscosity 20 mm.sup.2/s at 40° C.) Base oil with 1% of a PAG-containing 69° 32 25° compound* (viscosity 20 mm.sup.2/s at 40° C.) Base oil with 0.5% PAG** (viscosity 77 53° 45 20° mm.sup.2/s at 40° C.) Base oil with 5% PAG** (viscosity 77 62° 37 17° mm.sup.2/s at 40° C.) *Polyethylene glycol monodecyl ether **Polypropylene glycol) monobutyl ether

[0039] The results reproduced in Table 2 show that the lubricants with a compound having a polyalkylene oxide structure result in aluminum products with considerably smaller contact angles, at least for NMP. This can be helpful for certain applications.

[0040] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0041] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0042] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.