Powder lubricant based on fatty acids and fatty acid glycerides and use thereof

Abstract

A dry lubricant composition in powder form is provided based on a mixture of alkali metal salts of fatty acids and fatty acid glycerides which is useful in the production of aluminium cans in a deep drawing process, wherein the formed aluminium cans are immediately further processed to yield thin inorganic and/or organic protective coatings. The invention also encompasses the use of the lubricating powder for cold forming of aluminium as well as a process for the deep drawing of aluminium cans.

Claims

1. A lubricating powder comprising: a) more than 60 wt.-% of at least one alkali metal salt of a fatty acid, b) at least one fatty acid mono-, di- or triglyceride, wherein the lubricating powder has a weight ratio of compounds according to component a) to compounds according to component b) that is not greater than 30, wherein component b) is selected from mono-, di-, tri-glycerides and combinations thereof which are based on C10-C22 fatty acids, while the glycerides have an iodine value of 50 to 130.

2. A lubricating powder comprising: a) more than 60 wt.-% of at least one alkali metal salt of a fatty acid, b) at least one fatty acid mono-, di- or triglyceride, wherein the lubricating powder has a weight ratio of compounds according to component a) to compounds according to component b) that is not greater than 30, wherein component b) comprises triglycerides based on alkoxylated fatty acids having a degree of alkoxylation of at least 20, but not more than 50.

3. The lubricating powder according to claim 1, wherein the at least one alkali metal salt of a fatty acid is selected from alkali metal salts of C10-C22 fatty acids having not more than one unsaturated carbon-carbon bond.

4. The lubricating powder according to claim 2, wherein the at least one alkali metal salt of a fatty acid is selected from stearates.

5. The lubricating powder according to claim 2, wherein compounds according to component a) are present in an amount of at least 70 wt.-%, but less than 95 wt.-% based on the total composition of the lubricating powder.

6. The lubricating powder according to claim 1, wherein compounds according to component a) are present in an amount of at least 75 wt.-%, but less than 90 wt.-% based on the total composition of the lubricating powder.

7. The lubricating powder according to claim 1, wherein component b) is selected from said diglycerides, triglycerides and combinations thereof; and wherein component b) further comprises triglycerides based on alkoxylated fatty acids having a degree of alkoxylation of at least 20, but not more than 50.

8. The lubricating powder according to claim 1, wherein component b) is selected from mono-, di-, tri-glycerides and combinations thereof which are based on C14-C20 fatty acids, while the glycerides have an iodine value of 70 to 95.

9. The lubricating powder according to claim 2, wherein component b) further comprises triglycerides based on non-alkoxylated fatty acids with an iodine value of 80 to 100 g I.sub.2/100 g.

10. The lubricating powder according to claim 9, wherein overall proportion of alkoxylated triglycerides amounts to at least 20 wt.-% based on the total amount of compounds according to component b).

11. The lubricating powder according to claim 2, wherein compounds according to component b) are present in an amount of at least 2 wt.-%, but not more than 20 wt.-%, based on the total composition of the lubricating powder.

12. The lubricating powder according to claim 2, further comprising component c) at least one alkali metal lignosulfonate present in an amount of at least 0.1 wt.-%, but less than 5 wt.-% based on the total composition of the lubricating powder.

13. A lubricating powder comprising: a) more than 60 wt.-% of at least one alkali metal salt of a fatty acid, b) at least one fatty acid mono-, di- or triglyceride, and c) at least one alkali metal lignosulfonate present in an amount of at least 0.1 wt. %, but less than 5 wt. % based on the total composition of the lubricating powder wherein the lubricating powder has a weight ratio of compounds according to component a) to compounds according to component b) that is not greater than 30, wherein component a) comprises alkali metal salts of saturated C10-C22 fatty acids; component a) being present in an amount of at least 70 wt.-%, but less than 90 wt.-% based on the total composition of the lubricating powder; and component b) comprises: 1) triglycerides based on alkoxylated fatty acids having a degree of alkoxylation of at least 20, but not more than 50; and 2) triglycerides based on non-alkoxylated fatty acids based on C14-C20 fatty acids; component b) being present in an amount of at least 4 wt.-%, but not more than 20 wt.-% based on the total composition of the powder.

14. The lubricating powder according to claim 13, further comprising component d) at least one extreme pressure additive present in an amount of 1 to 8 wt.-% based on the total composition of the lubricating powder.

15. The lubricating powder according to claim 14, further comprising component e) at least one organic solvent present in an amount of at least 1 wt.-%, but less than 10 wt.-%, based on the total composition of the lubricating powder.

16. A method of using a lubricating powder according to claim 13, comprising applying the lubricating powder to aluminum material prior to cold forming of aluminum parts.

17. A process for producing aluminum cans comprising steps of: a) placing a multitude of aluminum flats and a lubricating powder according to claim 2 in one container; b) vibrating or tumbling the container to thereby coat the aluminum flats with a lubricating film of the lubricating powder; c) deep-drawing the aluminum flats into cans through punching; and optionally d) cleaning and degreasing of the aluminum cans.

Description

EXAMPLES

(1) Different powder lubricants of this invention (Table 1) have been applied to aluminium discs prior to the forming cylindrical thin walled aluminium cans through impact extrusion.

(2) A thin layer of this lubricant was applied to the surface of aluminium discs with a diameter of 74 mm and a thickness of 6 mm by tumbling a specific amount of lubricant powder so that a theoretical loading of 7.8 grams per square meter of the aluminium discs was given. The tumbling was performed for 20 minutes at 15-22 rpm.

(3) The lubricated discs were then subjected to impact extrusion to form the body of a can with a defined length L of the cylindrical axis and wall thickness W of the can (L=259 mm; W=0.74 mm). For this specific type of cold forming a horizontal impact extrusion press was used. The punch and the die were made of tungsten carbide. Each lubricant powder of Table 1 gave rise to a successful punching so that the desired shape without material failure was attained and no significant undulations with regard to the wall thickness were observed.

(4) Table 2 shows that reasonable good adherence of the powder to the aluminium discs is achieved for all powder lubricants. Nevertheless, it is evident that lubricants based on fatty acid salts of zinc reveal the poorest loading yield after tumbling as well as the poorest cleanability of the aluminium cans after punching (see V1). The use of a sodium stearate in combination with a fatty acid glyceride gives always rise to good loading yields above 80% (see E1-E4). The cleanability is still also governed by the presence and type of solvents used while the lubricant that contains diethylene glycol monobutyl ether having a E.sub.T(30) value of above 180 kJ/mol is easy to clean with a mild alkaline cleaner (see E2 vs E3). The same solvent is also beneficial to attain a very homogenous appearance of the powdered discs (see E2 vs E1).

(5) TABLE-US-00001 TABLE 1 Lubricant Powder Compositions V1 E1 E2 E3 E4 wt.-% wt.-% wt.-% wt.-% wt.-% Component a) zinc stearate 68 — — — — sodium stearate 17 85 86.8 86.8 86.8 Component b) glycerol trioleate — 5 3 3 — ethoxylated castor oil (40 EO) — 5 3.9 3.9 5.3 Component c) sodium lignosulfonate 10 2.5 0.3 0.3 — Component d) butylated triphenyl phosphate ester 2.5 — — — 5.3 zinc dialkyl dithiophosphate 2.5 — 2 2 2.6 Component e) diethylene glycol monobutyl ether — — 4 — — mixture of dimethyl — — — 4 — glutarate/dimethylsuccinate

(6) TABLE-US-00002 TABLE 2 Test Results V1 E1 E2 E3 E4 Efficiency Yield/% .sup.1 57 100 95 88 85 Cleanability .sup.2 ⊙ + + X N/A Adherence .sup.3 + + + + + Dust formation .sup.4 X + + + N/A Appearance Staining .sup.5 S SM S S S .sup.1 determined based on weight difference of 20 Al discs before and after tumbling .sup.2 dip alkaline cleaning (8 wt.-% Bonderite CAK 509; Fa. Henkel AG) for 2 min at 70° C: ⊙ poor, significant amount of residual powder X difficult, some amount of residual powder + easy, no residual powder .sup.3 assessed visually after powdered disc was dropped with his shell on a black metal plate from a height of 10 cm ⊙ poor, most of powder fell off X sufficient, some powder fell off + good, almost no powder fell off .sup.4 assessed after tumbling ⊙ significant X visible + not visible .sup.5 visual assessment of diameter of stains after tumbling L large (>10 mm) M medium (5-10 mm) SM small to medium (2-5 mm) S small (<2 mm)