CA1045622A

CA1045622A - Deep-drawing of metals coated with a thermoplastic rubber/oil dispersion

Info

Publication number: CA1045622A
Application number: CA194,358A
Authority: CA
Inventors: Klaas Van Henten; Dirk De Jager; Cornelis Couvee
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1973-03-09
Filing date: 1974-03-07
Publication date: 1979-01-02
Also published as: US3923673A; SE395472B; BE811992A; GB1466261A; AU6639774A; IT1013062B; JPS5025601A; FR2220577A1; FR2220577B1; NL7403136A; DE2411010A1

Abstract

A B S T R A C T

A lubricant suitable for non-destructive de-formation of metals comprising a suspension of a thermoplastic rubber in a non-volatile hydrocarbon oil. This lubricant is particularly suitable for deep-drawing of steel and also prevents corrosion of the steel during storage.

Description

1~45622 This invention relates to the non-destructive deformation, in particular deep-drawing, of metals, in particular ste~l.
Metals which are to be subjected to such deformation are usually treated with materials acting as lubricants, such as soft metals, greases, soaps, lubricating oils, solutions or dispersions of polymers in volatile hydrocarbons, in order to prevent mechanical damages at the drawing levels usually applied. Some of these lubricants can also serve as preservants, if already applied onto the stored metal sheets.
An important problem in the deep-drawing of metals is the stress distribution in the shaped articles, which in heavily stretched areas may even cause the material to break Further, for optimum results, it is desirable that the extension of the metal is uniform in all directions.
With the lubrica~ing materials normally used it appeared difficult to solve these problems, especially at high degrees of stretching.
It has no~ been found that these problems can very satisfactorily be solved and optimum results can be obtained by using as lubricant a suspension of thermoplastic rubber in a non-volatile hydrocarbon oil.
The present invention provides an improvement in a method for the non-destructive deformation of metals, the improvement comprising the use of a lubricant comprising from 1 to 75 weight per cent of a thermoplastic rubber which is a block copolymer having the formula A (- B-A)n or A-B ~ ~-A) wherein n is at least 1, A is a non-elastomeric polymer block, having a molecular weight between 2,000 and 100,000, of a monoalkenyl arene and B is an elastomeric block having a molecular weight between 25,000 and 1,000,000, of a conjugated diene which may have been partially or completely hydro-genated, suspended in a non-volatile hydrocarbon oil.
Suitable thermoplastic rubbers are block copolymers, having a linear or branched configuration. These may be represented by the two general formulae A ( B-A)n, representing the linear block copo-lymer, and A-~ ( ~~A)n, representing the branched or radial type of block C - 2 _ 1~45622 copolymer. In either formula the subscript n represents an integer usually between 1 and 5. The simplest block copolymer will, therefore, have the general configuration A-B-A, each A representing a non-elastomeric polymer block of a monoalkenyl arene and B representing an elastomeric block of a conjugated diene which blocks may have been partially or completely hydro-genated. Preferred copolymers are those based on polystyrene (A) and polybutadiene or polyisoprene (B) blocks. The block molecular weights are variable, but the blocks A usually have number average molecular weights between 2,000 and 100,000 and the blocks B between 25,000 and 1,000,000.
Other thermoplastic rubbers, such as thermoplastic polyurethane rubbers may be used as well.
Thermoplastic rubbers containing, e.g., fillers, oils, anti-oxidants, stabilizers, plasticizers and the like are also suitable for the purpose of this invention.

45~22 The present copolymers ln the ~orm of a ¢rumb, granulate or powder or as conoentrate in an aromatic solvent, such as toluene are mixed with the present oil. This oll, which pre~erably is a low-vlscosity lubrioatin~ oil, e.g., a splndle oil, should be o~
the parafrinic or naphthenic type i~ the thermoplastlc rubber contains polystyrene blocks. Pre~erably, the content Or aromatias is then below 40~w, such as below 20%w, in partlcular below 10%w. The disperslons ob-tained prererably contain 1-75%w, e.g., 5~50~w, in partioular 5-25~w Or the thermoplasti¢ rubber based on the total compositlon.
The viscosity or~ suoh dispersions should, prerer--ably, be low enough to make conventional appliaation ~ during sheet steel manura¢ture posslble, althou~h they oan be diluted with volatile oils, i~ neoessary.
The steel sheets may be ooated, e.g., by spray~ng, dipping or brushing w1th the present disperslons or w1th the diluted dlspersions to form an ultimate layer on said sheets having a thlokness o~ at least about 1 micron, preferably 5-400, e.g., 5-200 miorons.
During storage o~ the sheets oorroslon will be prevented~
whereas during deep-drawlng or~the sheets this ooating functions as deep-drawlng lubrioant. A speoial preserving oil is then no longer neoessary.
`

1~4562Z
During deep-drawln~ the present dispersions effect a uni~orm stress distribution, thus preventing breakage, and provide uniform elongation o~ the metal in all directions.
The present dispersions can readily be removed using normal cleaning agents.
This invention will now be eluoidated by the ~ollowing Example.
EXAMPLE
Dispersions of a thermoplastia rubber according to the invention, nsmely a polystyrene/polybutadiene/
polystyrene block ¢opolymer, molecular weights 14,ooo/64, 000jl4,000, (polymer A) in a conventional para~finic/naphthenic extender oil of spindle oll ]5 viscosity, were made and compared with:
Oil Bj a conventional deep-drawing pure lubricating oil containing no polymer;
Oil C, a commer¢ially available deep-drawing lubricant being a~suspension o~ a polyacrylate, in a lubricating oil, with untreated sheets, and with polymer A per se.
The present dispersions were dlssolved in toluene and the solution was applied in su~icient amounts to the steel test sheets to give a coatlng thickness o~

_5_ ~45622 10 microns The reference oils were also app]ied in su~ficient amounts to give a coating thickness Or 10 microns.
The thickness Or the steel sheek was 0.75 mm.
The following tests were carried out.
Swift cupping test (deep-draw ~orce) A circular metal sheet, coated on both sides, is clamped between a holder and a drawing ring. A metal oup is formed by punching. During punchlng the material is allowed to flow ~rom between the clamps through the ring with the result that the thlclcness of the cup is about equal to that of the original sheet. In this test the punching ~orce is a measure ~or the e~rectiveness of the lubricant used; the lower the force, the better.
Erichsen test (stretch-draw depth) A circular metal sheet, coated on one side, is ; clamped between a holder and a drawing ring, but with a high force, which keeps the sheet in position during de~ormation. All sur~ace increases during deformation have there~ore to be provided by the metal sheet itselr, resulting in reduced thickness and ultimately in break-age. The greater the drawing depth at break, the better the per~ormance according to this test.

1q)45622 _esults Poly~er A pbw lOO -75 - 5o 25- ~ ~ Oil Oil Untreated Extender oil pbw O ~5 5o 75 100 B C ,l ~ _. .~. _ _ .__ _ . . . . ._ Deep draw force tons l~.l ~9 3.6 ~.5 4.8 4.7 4.2 4.g Stretch draw depth mm 11.8 11,8 11.9 10.4 10.5 10.9 10.4 ~ _ ~
From this T~ble it ~ollows that especially as to deep draw force ~he presen~ di.spersions, ln particular those containing less t~lan about 50,~ of polymer A, are superlor to t.he comm~rcially available lubricants and polymer A per se.
i

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a method for the non-destructive deformation of metals, the improvement comprising the use of a lubricant comprising from 1 to 75 weight per cent of a thermoplastic rubber which is a block copolymer having the wherein n is at least 1, A is a non-elastomeric polymer block, having a molecular weight between 2,000 and 100,000, of a monoalkenyl arene and B is an elastomeric block having a molecular weight between 25,000 and 1,000,000, of a conjugated diene which may have been partially or completely hydrogenated, suspended in a non-volatile hydrocarbon oil.

2. A method according to claim 1, wherein n = 1.

3. A method according to claim 1, wherein A is a polystyrene block and B is a polybutadiene or polyisoprene block.

4. A method according to any one of claims 1, 2 or 3, wherein the hydrocarbon oil is a paraffinic or naphthenic oil.

5. A method according to any one of claims 1 - 3, wherein the proportion of thermoplastic rubber is 5-50%w, based on the total composition.

6. A method according to any one of claims 1 - 3, wherein the proportion of thermoplastic rubber is 5-25%w, based on the total composition.

7. A method according to claim 1 for the deep drawing of steel.

8. A method according to claim 7, wherein said lubricant is applied during steel sheet manufacture to prevent corrosion of the steel sheets during storage before deep-drawing.

9. A method according to claim 7, wherein the layer of the lubricant on the metal surface has a thickness of at least about 1 micron.

10. A method according to claim 8 wherein the layer of the lubricant on the metal surface has a thickness of at least about 1 micron.

11. A method according to claim 9 or 10, wherein said thickness is 5-400 microns.

12. A method according to claim 9 or 10, wherein said thickness is 5-200 microns.