CA1086155A - Methods for the application of hot melt metal working lubricants - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Metal working operations, especially drawing, are facilitated by applying to the metal a composition which provides lubricity thereto and which melts at about 30-100°C.
The composition preferably comprises an ester of a carboxylic acid, with a carboxylic acid or derivative thereof, a phospho-rus acid salt and an antioxidant being preferred optional ingredients. The composition may be applied in liquid form and solidifies on cooling to ambient and normal storage temperatures. Prior to application, the composition is preferably heated to a temperature higher than its melting temperature for ease of flow and uniform dispersion thereof onto the metal. In a preferred method of application, a reservoir is located beneath the composition applicator and composition is pumped therefrom to the applicator, preferably a roller coater, with excess composition being recirculated.
Steam may be used both to heat the composition to melting point and purge the pump and circulation piping at the start and finish of each run.

Description

15 6~S~

This invention re]ates to metal working operations.
More p~rticularly, it relates -to methods for lubricating metal during such operations and for applying lubricant to such metal.
Metal working operations, for example, rolling, forging, hot-pressing, blanking, bending, stamping, drawing, cutting, punching, spinning and the like generally employ a lubricant to facilitate the same. Lubricants greatly improve these operations in that they can reduce the power required for the operation, prevent sticking and decrease wear o dies, cutting bits and the like. In addition, they frequently provide rust inhibiting properties to the metal being treated.
; Since it is conventional to subject the metal to -~ various chemical treatments ~such as the application o con-version coating solutions) after working, a cleaning operation is necessary between the working step and the chemical treat-ment step. In addition to the above pxoperties, therefore, it is preferred that the working lubricant be easily removable from the metal surface by ordinary cleaning compositions.
Heretofore, the lubricants applied for the above purposes have ordinarily been liquids. The equipment used for the application of such liquids is often expensive to maintain and inconvenient to use. In addition, a dry-off oven is usually required to remove the water or solvent carrier from the liquid composition, which also greatly adds to the capital costs and operating and maintenance expenses of the method. Difficulties are also often encoun-tered in automatic feeding of metal blanks and otherwise ., ~
, :
' '. ' ' ' . ' 6~55 handling the metal because the liquid compositions which are normally applied to the metal make it wet and slippery and consequently difficult to handle.
A principal object of the present invention, there-- fore, is tG provide an improved metal working method.
A further ob~ect is to provide a method using lubricants which impart to the metal being worked a unique combination of properties including lubricity, corrosion resistance, extreme pressure properties and protection against wear of working parts, and which in addition are relatively easy to remove from the surface of the metal by cleaning after the working operation is completed.
Another object is to provide a method by which a solid metal working composition can be meIted and applied to the metal, thereby eliminating the need for dry-off ovens and their attendant drawbacks.
Still another object is to provide a method by which the composition, after application to the metal, solidifies to produce a non-blocking and relatively non-slippery film, thus allowing consistent and economical auto-matic feeding of blanks and material handling at reduced costs.
A still further object is to provide a method which permits the formation of a solid film of metal working composition on the surface of a metal workpiece by applying the melted composition to the metal surface while the latter j (e.g., as wirej~ tubing or the like) is moving through the application mean~ at relatively high speed.

-2-i5~i Other ob~ects will ;n part be obvious and will in part appear hereinafter.
According to this invention, the above objects are fulfilled by applying to the metal to be worked a composi~ion which provides lubricity thereto and which comprises an ester of a carboxylic acid, said composition melting at about 30 -100C. Preferably, the composition melts to form a readily flowable liquid which is capable of easy and efficient appli~
cation to the metal surface. One advantage of such a composi-tion (sometimes referred to hereinafter as the i'hot meltcomposition!') is that metals coated therewith are easier to handle under normal storage conditions than metals coated with previously known lubricants.
~` The principal necessary characterist~c of the hot melt composition is its capability of providing lubricity to ; the metal surface. For this purpose, lubricity may be defined in many ways which are well known to those skilled in the art, and in terms of a number of test methods which, in one way or another, simulate metal working operations. For the purpose of this invention, a composition is deemed to provide lubricity -` to a metal workpiece if its use results in a de~iation of 100 foot-pounds or less when tested by the following method:
A cold-rolled steel strip, 2" x 13 1/2", is drawn between two dies in an Instron Universal Tester, Model TT-C.
Prior to drawing, the edges of the strip are deburred and the strip is ~apor degreased and wiped with a clean cloth~ It i5 then coated uniformly with a drawing lubricant and mounted in ; the testing machine. The dies are tightened by means of a torque wrench set at 40 foot-pounds torque and the strip i5 pulled through the die fox two inches at the rate of five inches per minute. The force or "loadl~, in foot-pvunds, - required to pull the strip through ~he die~ and the deviation from a uniform load, are recorded on a chart.

_3_ ' 1~ 55 The hot melt composition melts in the range of 30 -100C., as previously indicated. Thus, it is normally solid at ambient temperature and pressure. The preferred melting range is 35 - 70C., with 38 - 55C. being particularly desi-rable. When melted, the composition preferably forms a readily flowable liquid.
The principal ingredient of the hot melt composition is an ester of a carboxylic acid. (When used herein, the sin-gular forms "a" r "an", and "the" include the plural unless the context clearly dictates otherwise; thus, for example, "an e~ter" includes a mixture of two or more esters.) Typical esters are those of acids having the formula R(COOH)m and organic hydroxy compounds having the formula R'(OH)n, wherein each of m and n is an integer from 1 to 3 and each of R and ~' is a hydrocarbon~based radical. As used herein, the term "hydrocarbon-based radical" denotes a radical having predomi-nantly hydrocarbon character within the context of this inven-tion. Such radicals include the following:
(1) Hydrocarbon radicals, which may be aliphatic le.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl or cycloalkenyl), aromatic, aliphatic- and alicyclic-substituted aromatic, aromatic-substituted aliphatic and alicyclic, and the like.
- (2) Substituted hydrocarbon radical~, that is, ~ radicals containing non-hydrocarbon substituents which, in the - context of this invention, do not alter the predominantly hydrocarbon character of the radical. Suitable substituents of this type will be apparent to those skilled in the art.
- (3~ Hetero radicals; that is, radicals which, while predominantly hydrocarbon in character within the context of this invention, contain atoms other than carbon present in a chain or ring otherwise composed of carbon atoms. Suitable hetero atoms will be apparent to those skilled in the art and 5~ii include, for example, ni-trogen, oxygen and sulfur.
In ~eneral, no more -than about three su~stituents or hetero atoms, and preferably no more than one, will be present for each 10 carbon atoms in the hydrocarbon-based radical.
The acids and organic hydrox~v compounds are usually those in which R and R' are free from acetylenic and conjugated diene unsaturation and preferably contain no more than one olefinic double bond. Most often, there is no more than one such olefinic double bond per ester molecule.
The acid typically contains about 4 - 20 carbon atoms.
The preferred acids are the aliphatic polycarboxylic acids, especially those in which m is 2 or 3 and R is an alkyl or alky-lene radical, which may be branched or linear. Exemplary mono-carboxylic acids are propionic, butyric, stearic, oleic and benzoic, acids and exemplary polycarboxylic acids are maleic, fumaric, succinic, adipic, glutaric, pimelic, sebacic, azelaic, suberic, phthalic, isophthalic, citric and trimellitic acids.
The particularly preferred acids are the aliphatic dicarboxylic acids having about 5 - 10 carbon atoms.
The organic hydroxy compound typically contains at least about 10 and generally about 10 - 25 carbon atoms.
Usually, n is 1 and R' is an alkyl radical which may be bran-ched or linear. Exemplary organic hydroxy compounds are 1-butanol, 2-buten-1-ol, phenol, resorcinol, ethylene glycol, diethylene glycol, decanol, dodecanol, tetradecanol, stearyl alcohol, oleyl alcohol, eicosanol, and commercial mixtures of such alcohols. The preferred alcohols are saturated aliphatic alcohols containing at least about 10 carbon atoms, especially C14 20 alkanols ~that is, saturated monohydroxy alcohols) and more especially predominantly straight-chain alkanols.
From the above descriptions of suitable acids and organic hydroxy compounds, it will be apparent that a wide variety of carboxylic acid esters are contemplated for use according to this invention. These include both neutral esters B ~;

,~1 r~l~:
and acidic esters (~.g., monoe~ters of dicarboxyli.c acids) t but neutral esters are preferably used. Both mono- and bis-esters of polyhydroxy compounds are contemplated. Especially preferred are the neutral esters of adipic, azelaic or ~ebacic acid and C14_20 predominan-tly straight-chain alkanols or com-mercial mixtures of such alkanols.
The preferred hot melt compositions contain, in addi-tion to the esters described hereinabove, one or more rust inhibiting components and/or agents to improve extreme pressure properties.
~ mong the suitable rust inhibiting materials are -carboxylic acids ana derivative~ thereof. The term 'Iderivative"
as used herein with xeference to such carboxylic acids includes:
Anhydrides.
.~, .
Esters (acidic or neutral), especially those prepared from lower saturated aliphatic (the word "lower" meaning up to 7 carbo~
`~ atoms monohydroxy or polyhydroxy compounds (e.g,, methanol, ethanol, l-butanol, n-hexanol, ethylene glycol, pentaerythritol) or epoxides (e.g., ethylene oxide, propylene oxide). The epoxide-deri~ed esters as will , ~ . .
be readily understood, are hydroxy esters.
It will be appreciated that if the "derivative"
- is an ester, the hot melt composition comprises at least two esters.
Salts (neutral, acidic or basic) in which th cation is a Group I metal, a Group II metal, aluminum, tin, cobalt, lead, molybdenum, manga-nese, nickel or ammonium (the latter including substituted ammonium, i.e. amine) including salts of the free acias and of their hydroxy esters. The lithium salts are preferred for .' s~
the.ir antirus t properties.
Amides and amide-imide mixtures, especi-ally those derived from ~liphatic amines and more especially from lower aliphatic amines.
The preferred amines are the alkylene poly-amines, particularly ethylene polyamine~.
Derivatives of the type described above may be ob-tained from the acids by known reactions or sequenceæ of reactions.
The free acids, their lithium salts, and their an-hydrides are most useful. Preferred are the aliphatic mono-and polycarboxylic acids (and derivatives thereof as defined hereinabove) containing at least about 8 carbon atoms. Parti-cularly desirable are the dlbasic acids, especially the anhy-dride~ of succinic acids having a hydrocarbon-based substi-tuent (as defined hereinabove), such as those prepared by the reaction (more fully described hereinafter) of maleic acid or maleic anhydride with a hydrocarbon-basea compound containing at least about 6 carbon atoms, preferably about 6 - 75 and most often about 10 - 20 carbon atoms.
The hydrocarbon-based compounds preferred for the preparation of the substituted succinic acid are those derived from substantially saturated petroleum fractions and olefin polymers, particularly oligomers of monoolefins (especially terminal monoo1efins) having from 2 to about 10 carbon atoms.
Thus, the hydrocarbon~based compound may be derived from a ; polymer of ethylene~ propene, l-butene, 2-butene, isobutene,

3-pentene, l-octene or the like. Also useful are interpolymers -~ of olefins such as those illustratea above with other polymeriz-able ole~inic substances such as styrene, chloroprene, isoprene p~
methylstyrene, piperylene and the like. In general, these interpolymers should contain at least about 80%, preferably at least about 95%, on a weight basis of uni~ derived from the aliphatic monoolefins.
Other suitable hydrocarbon-based compounds are mix-tures of saturated aliphatic hydrocarbons such as highly refined high molecular weight white oils or synthetic alkanes.
In some instarlces, the hydrocarbon-based compound should contain an activating polar radical to facilitate its reaction with the low molecular weight acid-produclng compound.
; The preferred activating radicals are halogen atoms, especially chlorine, but other suitable radicals include sulfide, disul-fide, nitro, mercaptan, ketone and aldehyde groups.
As previously noted, the preferred method for pro-ducing the carboxylic acid or derivative thereof is by the reaction of maleic acid or anhydride with the hydrocarbon-based compound, especially with a material such as a propene oligo-mer. This reaction involves merely heating the two reactants at about 100 - 200C. in the presence or absence of a substan-. . .
` tially inert organic liquid diluent; an excess of a liquid ~ . , reactant may also serve as the reaction medium. Other suitablereactions lnclude oxidation with potassium permanganate, nitric acid or a similar oxidiziny agent of a hydrocarbon-substituted 1,4-butanediol or the like; ozonolysis of a hydrocarbon-substituted l,S-diene or the likei preparation of a bis-organometallic derivative of a hydrocarbon-substituted 1,2-dihalide or the like, followed by carbonation thereof with -`~ carbon dioxide; or preparation of a dinitrile followea by its hydrolysis. All of these reactions are well known in the art, as are the substituted succinic acids and derivatives thereof produced thereby.
The preferred extreme pressure agents are phosphorus acid salts of the formula R2(X2) - X3 w~l~reill M is a Group I m~t~ L Group II met~l, a]uminum, tin, cobalt, l~ad, molybdenum, manganese, nickel or ammonium, each of R and R is a hydrocarbon-based radical; ~ach of X , X , x3 and x4 is oxy~en or sulfur; and each of a and b is 0 or 1.
In the above formula, each of Rl and R2 i5 a hydrocarbon-based radical. Preferably, they are free from acetylenic and usually also from ethylenic unsaturation and have no more than about 30 carbon atoms, desirably no more than about 12 carbon atoms. They are usually hydrocarbon radicals such as methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, decyl, dodecyl, vinyl, decenyl, cyclohexyl, phenyl and the like, all isomers thereo~ being included. A particular preference i5 expressed for compounds in which Rl and R2 are lower alkyl radicals, the word "lower" being defined hereinabove.
It will be apparent that the phosphorus acids from which the ~alts are derived in~b dialkylphosphoric acids, dialkylphosphinic acids, and thio derivatives o~ such acids.
Especially preferred are the salts of phosphorodithioic acids;
'chat is, compounds in which a and b are each 1, Xl and x2 are each oxygen, and X3 and X4 are each sulfur. In these salts, M may be any of the metals previously enumerated or ammonium:
the later term includes subs~ltuted ammonium salts (i.e., amine salts). M is preferably zinc or lead, especially zinc.
The hot melt composition most often contains up to about 15~ by weight o the carboxylic acid or derivative there-" .
of and/or up to about 25% of the phosphorus acid salt, both of which are optional ingredients. In particular, this inven~ion includes compositions providing lubricity to metal and compri- -sing an ester of a carboxylic acid and at least one of a car-30 boxylic acid or derivative thereof and a phosphorus acid salt, each of said components being as defined hereinabove; said compositions melting at about 30 - 100C.
It is also within the scope of this invention to ,, ' , ~ _9~

.. , .. .. , _ . ... . . .. . .. . . . . . . .. . .. ... .. . .. .

~36~SS

incorporate other known aclditives i.n minor amounts (typically about 0.01 - 5.0% by weight) into the hot melt composikion.
Especially preferred other additives are antioxidants, typi-cally hindered phenols; such matexials are well known in the art. Other suitable additives include:
Surfactants, usually nonionic surfactants such as oxyalkylated phenols and the like.
Auxiliary extreme pressure agents such as chlorina-ted waxes, sulfurized hydrocarbons, sulfurized esters! etc.
Corrosion and wear inhibiting agents, and auxiliary rust lnhibiting agents.
Friction modifying agents, of which the ~ollowing are illustrative: Alkyl or alkenyl phosphates or phosphites in which the alkyl or alkenyl group contains about 10 - 40 carbon atoms, and metal salts thereo~, especi~ly zinc salts;
C10 20 fatty acid amides; C10 2~ alkyl amines, especially tallow amines, and ethoxylated derivatives thereof; salts of ,..
such amines with acids such.as boric ~acid or phosphoric acid which have been partially esteri.fied as noted above; C10_20 alkyl-substituted imidazolines and sim.ilar nitrogen hetero~
cycIes; sulfurized derivatives of sperm oil and other fatty oils; baslc barium or calcium salts of such oils or of amine~
formaldehyde condensates, especially those derived from tallow amines such as described above; and.gels derived rom basic alkaline.earth metal sulfonates.
~ ' - .
Melting point modifiers, typically relatively low melting point esters such as dioctyl-phthalate.
The hot melt composition may be prepared by intimate-ly blending the ingredients thereof, preferably in the liquid state, if more than one ingredient is involved. It may some-times be preferable to employ a substantially inert liquid diluent to insure intimate blending. By "substantially inert"
is meant a diluent which does not undergo any appreciable ~, --10--reac-ti.on with the inc3recli~nts of the composition under the cond.itions oE blending. Preferred as dilu~nts are liquids which are solvents for the ingredients being blended; suitable solvents will be apparent to those skilled in the art and preferably comprise non-polar liquids such as benzene, toluene, xylene, chlorobenzene and the like. After blending is com-plete, the diluent is preferably removed, typically by evaporation.
In the following table are listed typical hot melt compositions suitable for use in the method of this invention.

~ . ' . ' .~ ' .
,, ~,.

. , ' ''' ~" '."' ' ' ' ' ' ' ' ` , , .
.. .

:` ' ' ' ,. ~ : - . ,.~' ' ,.

', . ' , .

:

ss I In I o u~
W I r~

u~ l o l u~
,~ ~ r~
.
l ~ o ~ o o ~q c~ l l o ~: ~
~:, o l o ~ :

: : :
:
~l ~: 0 . h ~ O ~ ~ O I V
,; . a) ~ ~ ~ rl ~ O~
O Id rl O a~
. ~ ~ rl S-l~rl ~rl . ~ ~ q~ ~ nl h ~: O~rl u In ~ o ca ~ ~ Q, u~
. . O ~ u h :~ U ~ h . .
~I tQ a) ~1 u~ ~ ~1 ~1 0 O ~) r-l . -1~ ~ r~. ~d Q. O ~
o a) u~ ~ O a~ 0 ~:4 ~ ~ ~1 . O h a) ~ 1 R ~ O
~r r~ O ~o (d ~ ' U X
~r~ o ~ ~ u 4 - ~ ~d ~r~ o ~ u ~, I,q ~ .
: - S~ . C) ~ ~ ~~rJ ~ CO
~ ,~ r~r~ U
H ~rl O ~ V~1 0 ~O U ~ O ~
~ ~-1 0N ~-1 0 0Cl E3 .. rd ~ U S~0 ~ C~ h ~
. . . S~ O~ ~ r~ h S'l X 0 0 Sl X 0 0 0 , ~ U ~r~
I ~ 1~ S~ V G U
,1 ~ O ~ ~ r~ 0 æ ~ N

'' . ~' ,' . . ' .

5~i ~ ny mc~-t~l to bf~ ~o:rkecl may be -treated according to the method of this inven~ion; examples are ferrous metals, aluminum, copper, magnesium, titanium, zinc and manganese as well as alloys thereof and al~oys containing other elements such as silicon.
The method of this invention includes any method by which a metal workpiece may be coated with the hot melt com-position prior to or concurrently with the working operation.
For example, a cutting blade or drawing die may be coated with the composition which is then transferred to the workpiece by contact. More usually, however, the workpiece is coated with the hot melt composition before the working operation. Thus, ~?
this invention also contemplates a metal workpiece having on its surface a film of the hot melt composition, whether in solid or liquid form. The hot melt composition will ordinarily forM a continuous film over the entire surface of the work-piece. However/ it is also within the scope of this invention to form a film on less than the entire surface of the work-piece~
The physical state of the hot melt composition during application to the metal surface is not critical. Thus, it may be applied as a solid (as by rubbing) or as a liquid (as by brushing, spraying, dipping flooding, roller aoating, reverse roller coating or the like). For ease and convenience of application, it is preferably applied in the liquid state, and-when this is done the metal may be subsequently cooled where-upon the hot melt composition ~olidifies, or it may be passed directly to the metal working operation while the composition ~ is in the liquid state. Oné of the advantages of this inven- -~
tion, however, is that the hot melt composition solidifies to form a solid, ~on-blocklng, non-slippery film on the metal workpiece, thus permitting convenient and safe material hand-ling at reduced cost.

.
--13-- :

S
To thi~ end, the pres~nt inven-tion also includes a method (hereinafter sometlmes referred to as "th~ application method of this inven~ion") o~ apply;ng to a metal workpiece a metal working composition, such as the hot melt composition described her~inabove, which is a solid at ambient temperature and pressure, said method comprising the steps of heating the composition to cause it to melt and maintaining the temperature thereof for ease of flow and uniform dispersion thereof onto the me~al, applying the melted composition to the metal work-piece to form a film of such composition thereon, and allowingthe film of said composition to cool and solidi~y.
The surface temperature of the metal at the time the hot melt composition is applied may vary, for example, from ambient temperature to just below the decomposition temperature thereof. Factors which will influence or determine the temper-ature of the metal at the time the composition is applied in-clude processes which the metal is sub~ected to prior or subse-quent to application of the composition, the melting point of the composition, and the temperature thereof at the time of application. Using the hot melt compositions described herein-~' . , abovej-metal surface temperatures of about 20 - 125C. at the time of application have been found particularly useful. The temperature of the hot melt compositlon should be higher than i'cs melting temperature (preferably at least 10C. higher and usually about 20 - 40C. higher) at the time of application for ease of flow and uniform dispersion of the composition onto the metal and coverage thereby.
The melted hot melt composition may be applied to the metal in a minimum of space utllizing existing equipment such ~- 30 as coilers used in steel mills prior to coiling, and because it quickly solidifies at ambient temperatures and becomes dry, non-blocking and relatively non-slippery, standard handling equipment such as lifting and feeding rollers. Stackers, and ~' . ' '.

, .

5~
so oll may ~I].SO ~)c us~d. rch~ appli~ation method o this inven-tion also eliminates the nee~ ~or a dry-oEf oven since there is no water or solvent to remove rom the hot melt composition.
In the annexed drawings:
Figure 1 i5 a schematic diagram showing a metal pro-cessing lin~ or system including an illustrative apparatus for applying the hot melt composition to a metal workpiece in accordance with application method of this invention;
Fi~ure 2 is an enlar~ed schematic transverse section through the reservoir and applicator of the apparatus used to coat the metal workpiece with such composit~on, taken on the plane of the line 2-2 of Figure l; and Figure 3 is a partial transverse section on the plane of the line 3-3 of Figure 2.
In Figure 1 there is schematicall~ shown a metal sheet or strip material processing line L including in the line a : preferred apparatus 1 for appl~ing the hot melt composition to the metal workpiece S, which may be in the form of strips or sheets of material cut into desired lengths as shown or may . 20 consist o~ a continuous coil of strip material which may either be recoiled after passing through-the apparatus or cut into sheets and stacked using conventional uncoilers, recoilers and/or destacker and stacker equipment and the like. Regard-less of the length of the metal workpiece S, it may be trans-. ported through the material processing line L on conventional -- ~. conveyor and ~eed rolls~3. :
.
~ In the illustrative coating apparatus shown in Fig~
.
~ ures 1 and 2, a reservoir 5 for the hot melt composition M is : .
located near (preferably beneath) the applicator which applies ~ ~-the composition to the metal. The composition is desirably heated as by passing through heating means such as a steam coil 6 (although electrical or other heating methods are also suitable) which ls usually located in-reservoir 5 and which is . -15-, . , . . ' . ,: , . .

adapted to provide cJood temp~rature control over a suitable range such as 30 - 850c., to cause the composition to melt and to remain liquid until aft~r i-t has been applied to the metal ~, but at the same time to insure aga.inst its being heated above its decomposition temperature.
The liquid composition is pumped by p~np 15 through' circulation piping 11 to the applicator. Pump lS should, of course, have suff.icient capacity to supply liquid composition to the applicator at the desired pressure, e.g., lO psi, and simultaneously to recirculate a portion of said composition ' back to the reservoir as described hereinafte~.
As previously noted, the applicator ma~ be a spray head, brushing or flooding means, roll~r coater or the like.
Roller coaters are preferred; the one shown in Figures 2 and .
3 comprises two rubber coa$ing rolls 8 (which may be heated), one for coating each side o workpiece S. As shown in ~igure 3, doctor rolls 9, in contact with coating rolls 8, can,be - horizontally adjusted so as to regulate the thickness of com-posltion M on the coating rolls, which themselves may be ver-tically adjusted so as to regulate the amount of said composi-tion transferred to the workpiece 5. Drip trays lO underneath , ,the applicator feed excess hot'melt composition back to reser-voir 50 ~ ' The 10w of hot melt composition M to the applicator : . . .
may be controlled by means o valves 1~... To aid in such con-: trol, a portion of the flow of such composition through circu-.~ , . . .
lation piping ll is desirably caused to bypass the applicator and recirculate to the reservoir 5 through a suitable bypass , conduit 12 and valve 13.
The use of steam, e~pecially low pressure steam, as the source of heat for melting and maintaining the temperature , 'of the composition has the advanta~e that the steam may be ; introduced into the circulation piping ll through a conduit . . .. . . ..... .....

8~ ~S
16 and valve 17 botll at t~ e start o~ a ~un to preheat the same and also at th~ finish oE a run to prevent compo.si-tion solidi-ficatioll and buildup tllerei~ lternatively, circulating piping 11 may be providea with a jacket to permit circulation of steam around it at both the start and finish of a run. The discharge line 18 for th~ steam ~rom steam coil 6 to condensate trap 19 also desirably passes around or through the housing of pump 15 to prevent solidification and accumulation of hot melt composition therewithin.
In addition to, or in place of, the use oE an appli-cator (such as that shown in Figure 2) adapted to meter the hot melt composition onto the metal surface, other methods for re~ulating the thickness of the film of such composition on the surface may be employed. These include control of the temperature of the composition and/or the metal, selection of compositions having different melting points (t~q~higher the melting point~ the more rapidly solidification will occur and the thicker will be the film thereof, other ~actors being the same), and regulating the rate of cooling of the metal after~
~0 the composition has been applied there-to. Film thickness may ~-~
al90 be regulated by the use of suitable removal means such as - ~`
heated squeegee rolls, an air blast of regulated temperature, or the llke.
Since the hot melt composition does not contain any water or other solvent, no dry-off oven is required to dry the metal after exiting from the coating apparatus 1. However, a . .
suitable distance should preferably be provided rom such exit of the métal from the coating apparatus before the metal is .. . .
stacked or recoiled to allow the coating of hot melt composi-30 tion to cool to its solidification temperature to form a solid, `~
usually continuous film on the metal; for example, a distance of 40 feet if the metal is moving at a rate of 600 feet per minute. This distance wi~l vary, not only with variations in .
~ ~ -17-`' :

t~le rate of travel of the metal, but alxo with variations in the type of thickness of th~ metal as well as its temperature.
In Figure 1, for instance, thcre is shown a cleaning bath 25 for cleaning mill oil from the metal wi th good temperature control over a range such as 35 - 75C.; also a water rinse bath 26 which may have good temperature control over a similar temperature range. Adjacent the downstream end of the cleaner bath 25 there is desirably provided a pair or squeegee rolls 27 to avoid rinse contamination. Likewise, similar squeegee rolls 28 are desirably provided adjacent the downstream end of the rinse bath 26, which may be supplemented by an air blast.

. .
The method of this invention, when e~ployed substan-tially as described herein, results in the production oE metal .
workpieces which are adequately lubricated for subsequent wor-king operations, especia~y drawing; protected against rust;
` ~ and easily cleanable by commercial cleaning methods~
~, ' ' . ' ' ' .
.
':
, ~', . - .

, ': , ' ', ' :
- ,. :
' ' , . :

-,

Claims (4)

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

1. A method of applying to a metal workpiece a metal working composition which is a solid at ambient tempera-ture and pressure and which comprises at least one ester of an aliphatic polycarboxylic acid containing about 4-20 carbon atoms and at least one alkanol containing at least about 10 carbon atoms, comprising the steps of heating the composition to cause it to melt and maintaining the temperature thereof fox ease of flow and uniform dispersion thereof onto the metal, applying the melted composition to the metal workpiece to form a film of such composition thereon, and allowing the film of said composition to cool and solidify.

2. A method according to Claim 1, wherein the melted composition is pumped through circulation piping to an applica-tor, and the metal is conveyed past such applicator which applies said composition to the metal.

3. A method according to Claim 2, wherein the compo-sition is stored and heated in a reservoir, and a portion of the melted composition which is pumped from the reservoir is caused to bypass the applicator and recirculate to the reser-voir to control the flow of such composition to the applicator.

4. A method according to Claim 2, wherein steam is used to heat the composition, and steam is also introduced into the circulation piping at the start of a run to preheat the same and at the finish of a run to prevent buildup of such composi-tion therein.