WO1998004657A1

WO1998004657A1 - Lubricant for cold-rolling aluminium

Info

Publication number: WO1998004657A1
Application number: PCT/IB1996/000755
Authority: WO
Inventors: Takamitsu Endo; Fumio Minagawa; Tetsuro Hoshino
Original assignee: Exxon Research And Engineering Company
Priority date: 1996-07-29
Filing date: 1996-07-29
Publication date: 1998-02-05

Abstract

A method for cold-rolling aluminium which comprises providing on the surface of the aluminium a lubricant having a KV40 of from greater than 4 to 40 mm2/s comprising a base oil having a KV¿40? of from greater than 4 to 40 mm?2¿/s selected from (i) an iso-paraffin hydrocarbon mixture which is a hydrogenated higher olefin produced as a by-product in the polymerisation process for the manufacture of polybutene or higher olefins wherein the polymerisation is carried out using a mono-olefin containing three, four or five carbon atoms, or a mixture of two or more of the said mono-olefins ('heavy iso-paraffin'); (ii) a mixture of bio-paraffinic and naphthenic hydrocarbons which mixture is the heaviest fraction obtained in the alkylation process for the manufacture of alkylate wherein the alkylation is carried out using iso-butene and iso-butane as the feed hydrocarbons ('alkylation bottoms'); and (iii) a mixture of (i) and (iii). The lubricant has the advantage that it combines the properties of relatively high viscosity together with low-staining of the aluminium surface during heat treating.

Description

LUBRICANT FOR COLD-ROLLING ALUMINIUM

This invention relates to a lubricant for cold-rolling aluminium, especially aluminium sheet. More specifically, the invention relates to an oil for rolling aluminium sheet to be cold formed by deep drawing or the like for the production of articles such as beverage cans.

An important property of aluminium cold-rolling oils, in addition to providing satisfactory lubrication during the rolling process, is that of low-staining, that is that the surface of the aluminium is not stained, or not significantly stained, during the rolling process, in particular during heat treating of the aluminium which is usually required to enable effective and efficient cold-rolling. Generally narrow-cut kerosene- type oils having a kinematic viscosity at 40°C (KV40) of 2.0 to 4.0 mra^/s are used as roll oils as they exhibit adequate low staining properties. Japanese patent (Kokoku) 67-015387 describes an oil suitable for cold rolling aluminium foil which is an iso- paraffin having a kinematic viscosity at 38°C of 2.0 to 4.0 mm^/s, the oil being a low molecular weight by-product from the production of polybutene.

Although higher viscosity oils would be beneficial as cold-rolling lubricants, such oils have not been found suitable because of their tendency to stain the surface of the aluminium sheet. Higher viscosity oils, when used in the aluminium sheet rolling process, are beneficial because they provide many miniature dimples, known as oil pits, on the surface of the rolled aluminium sheet. These oil pits, which remain after the heat treating process, work as oil reservoirs to keep the cold forming oil (which is applied on the sheet surface at the cold forming process) on the sheet surface and, as a result, enable effective and efficient cold forming operations. However, because of their tendency to cause staining of the sheet surface, under current practices the higher viscosity oil is rinsed off prior to heat-treating of the aluminium sheet.

There is therefore a need for an aluminium cold-rolling oil which has a higher viscosity than those currently employed but which does not stain the aluminium surface. Accordingly the present invention provides a method for cold-rolling aluminium which comprises providing on the surface of the aluminium a lubricant having a KV40 of from greater than 4 to 40 m ^/s comprising a base oil having a KV40 of from greater than 4 to 40 mm^/s selected from (i) an iso-paraffin hydrocarbon mixture which is a hydrogenated higher olefin, having a carbon chain length of from 6 to 40 carbon atoms, produced as a by-product in the polymerisation process for the manufacture of polybutene or higher olefins wherein the polymerisation is carried out using a mono-olefin containing three, four or five carbon atoms, or a mixture of two or more of the said mono-olefins ("heavy iso-paraffin"), (11) a mixture of lso-paraffinic and naphthenic hydrocarbons which mixture is the heaviest fraction obtained in the alkylation process for the manufacture of alkylate wherein the alkylation is carried out using iso-butene and iso-butane as the feed hydrocarbons ("alkylation bottoms"), and (111) a mixture of (1) and (11).

By "iso-paraffin" is meant a hydrocarbon or hydrocarbon mixture of which at least 95 wt %, preferably at least 99 wt.%, more preferably at least 99.5 wt.%, consists of iso-paraffins. The heavy iso-paraffin typically has an initial boiling point of about 260°C and a final boiling point of 350°C. The alkylation bottoms preferably has an initial boiling point of about 260°C and a final boiling point of about 330°C

The above-defined heavy iso-paraffin and alkylation bottoms base oils have the advantage, when used in the process of cold-rolling aluminium, of providing low staining properties together with relatively high viscosity enabling the formation of oil pits on the surface of the aluminium as explained above.

Preferably the lubricant has a KV40 of from 5.0 to 40 rnm^/s, more preferably from 6 to 30 mm^s. Kinematic viscosity is measured according to standard test method ASTM D 445.

The lubricant base oil may consist solely of the heavy iso-paraffin and/or alkylation bottoms above, or may be mixed with other types of base oils and/or solvents, preferably other types of hydrocarbons, provided the overall viscosity of the resulting lubricant remains within KV40 of greater than 4 to 40 mm^/s. Preferably the proportion of heavy iso-paraffin and/or alkylation bottoms contained in the lubricant base oil is at least 50 wt.%, preferably at least 75 wt.%, more preferably at least 90 wt.%, and most preferably 100 wt.% Examples of suitable other hydrocarbons that may be mixed with the heavy iso-paraffin and or alkylation bottoms include narrow cut kerosene having a KV40 of 1.5 to 2.5 mrn^/s, n-paraffin having a KV40 of 1.5 to 2.5 ra ^/s, iso-paraffin having a KV40 of 1.5 to 4.0 mm^/s, and hydrogenated narrow cut kerosene having a KV40 of 1 5 to 4.0 ram^/s.

The lubricant may, if desired, contain conventional amounts of conventional additives suitable for use in aluminium cold-rolling oils These include, for example, load-bearing additives and antioxidants.

The method according to the invention is especially suitable for the cold- rolling of aluminium sheet, typically to a thickness of 0 2 to 0 5 mm

The invention shall now be illustrated by the following Examples.

Examples

The viscosity and staining tendency during aluminium sheet heat treating of a number of hydrocarbon base oils were determined and the results are given m Table 1. Kinematic viscosity was measured according to standard test ASTM D 445 at 40°C, and staining tendency according to the standard ALCOA stain test. In this test a 0.8 cm^ sample of the oil under test is spread uniformly over the surface of a special aluminium plate. These plates measure 143 mm in diameter by 1.6 mm in thickness and are available from the Aluminium Company of America ("ALCOA") under the designation "Interleaved QRR ARL #1 plates" The plate containing the oil sample is then heated in a muffle furnace for 30 minutes at 345°C. After cooling, the discolouration is compared with the stains produced by the similar treatment of a set of standard oils, each of which has been assigned an arbitrary number. The number of the standard oil which produces a colour most similar to the sample under test is reported as the Stain Number. The standard oil samples are also available from ALCOA. There are five samples in the set, numbered from 1 to 5.

A base oil meets the requirements of the present invention if it has a KV4Q of from greater than 4 to 40 mm^/s and a Stain Number of 1 or 2. TABLE 1

Viscosity Stain

Example Base Oil (mm-Vs) Number* 1

1 Narrow-cut kerosene 1.71 2 2 Narrow-cut kerosene 2.39 3 3 Narrow-cut kerosene 3.66 3+

4 Hydrogenated solvent (EXXSOL*⁷ D80) 1.61 1 5 Hydrogenated solvent (EXXSOL*⁷ DUO) 2.20 1 6 Hydrogenated solvent (EXXSOL*⁷ D130) 4.50 3

Lube base stock (from vacuum distillation) 6.80 3

8 Narrow-cut kerosene 2 + polybutene ^ 10.0 (*6) 9 Normal -paraffin 2 + polybutene 3 10.0 (*6) 10 ISO- paraffin^*^ + polybutene*^ 10.0 (*6) 11 Hydrogenated solvent 5 + polybutene 3 10.0 (*6)

12 Normal-paraffin 1.75 1 13 Normal-paraffin 2.44 1

14 ISO-paraffin (ISOPAR ^'*⁷ L) 1.64 1 15 ISO-paraffin (ISOPAR*⁷ M) 2.32 1 16 ISO-paraffin (by-product of polybutene) 6.89 1 17 ISO-paraffin (by-product of polybutene) 40.0 1 18 ISO-paraffin & naphthene mixture 7.41 1

(alkylation bottoms = ISOPAR*⁷ V)

19 84.0 wt% Example 16 + 16.0 wt% Example 1 5.0 1 20 93.0 wt% Example 16 + 7.0 wt% Example 1 6.0 1 21 85.0 wt% Example 16 + 15.0 wt% Example 4 5.0 1 22 77.0 wt% Example 16 + 23.0 wt% Example 5 5.0 1 23 83.0 wt% Example 16 + 17.0 wt% Example 12 5.0 1 24 73.5 wt% Example 16 + 26.5 wt% Example 13 5.0 1 25 85.0 wt% Example 16 + 15.0 wt% Example 14 5.0 1 26 75.5 wt% Example 16 + 24.5 wt% Example 15 5.0 1 27 74.0 wt% Example 17 + 26.0 wt% Example 4 10.0 1 28 88.5 wt% Example 17 + 11.5 wt% Example 4 20.0 1 29 95.5 wt% Example 17 + 4.5 wt% Example 4 30.0 1 30 20.0 wt% Example 17 + 80.0 wt% Example 18 10.0 1 31 62.5 wt% Example 17 + 37.5 wt% Example 18 20.0 1 32 85.0 wt% Example 17 + 15.0 wt% Example 18 30.0 1 33 62.0 wt% Example 16 + 38.0 wt% Example 18 7.1 1 NOTES: The lower figure indicates the better staining quality.

Rating "1" and "2" are acceptable low staining property.

*2 1.76 mm^/s, @ 40 deg. C viscosity *3 Average molecular weight = 2,650 *4 ISOPAR^*7 M (2.32 mm^/s, @ 40 deg. C) *5 EXXSOL*⁷ DUO (2.2 mm /s, @ 40 deg. C) *6 cannot be rated in Alcoa stain test scale, but clearly observed mesh shape stain with brown colour on the surface of test piece.

EXXSOL and ISOPAR are trade marks of Exxon

Corporation and the products can be obtained from the operating affiliates thereof.

From the results it can be seen that the only base oils meeting the requirements of the present invention are the iso-paraffin by-product of the production of polybutene (Examples 16 and 17), the alkylation bottoms (Example 18), and mixtures containing one or more of these base oils (Examples 19 to 33). Therefore it is only these base oils that are able to provide the combined benefits as a lubricant for cold-rolling aluminium of high viscosity and low staining.

Claims

CLAIMS:

1. A method for cold-rollmg aluminium which comprises providing on the surface of the aluminium a lubricant having a kinematic viscosity at 40°C of from greater than 4 to 40 mm^/s (ASTM D 455) and comprising a base oil having a kinematic viscosity at 40°C of from greater than 4 to 40 mrn^/s (ASTM D 455) selected from (I) an iso-paraffin hydrocarbon mixture which is a hydrogenated higher olefin produced as a by-product in the polymerisation process for the manufacture of polybutene or higher olefins wherein the polymerisation is carried out using a mono- olefin containing three, four or five carbon atoms, or a mixture of two or more of the said mono-olefins, (n) a mixture of lso-paraffinic and naphthenic hydrocarbons which mixture is the heaviest fraction obtained in the alkylation process for the manufacture of alkylate wherein the alkylation is carried out using isobutene and isobutane as the feed hydrocarbons, and (in) a mixture of (I) and (n).

2. A method according to claim 1 for cold-rolhng aluminium sheet.

3. A method according to claim 1 for cold-rolling aluminium sheet for cold forming.

4. A method according to any preceding claim wherein the base oil comprises a mixture of (I), (n) or (m) as defined m claim 1 and a hydrocarbon selected from narrow cut kerosene having a kinematic viscosity at 40°C of 1.5 to 2.5 rnrn^/s, n-paraffin having a kinematic viscosity at 40°C of 1 5 to 2 5 mm^/s, iso-paraffin having a kinematic viscosity at 40°C of 1.5 to 4.0 mm^/s, and a hydrogenated hydrocarbon solvent having a kinematic viscosity at 40°C of 1 5 to 4.0 mm^/s.

5. A method according to any preceding claim wherein the base oil comprises at least 50 wt.% of (I), (u) or (in) as defined in claim 1.

6. Use of a base oil having a kinematic viscosity at 40°C of from greater than 4 to 40 mm^/s (ASTM D 455) in a lubricant for the cold rolling of aluminium, the lubricant having a kinematic viscosity at 40°C of from greater than 4 to 40 mm^/s (ASTM D 455) and the base oil being selected from (0, 00 and (in) as defined in claim 1.