CA2409363A1 - Sandcasting pattern coating compositions - Google Patents

Abstract

Sand casting is an ald art. In this molding process sand is compacted around a pattern and the pattern is removed, leaving a mold cavity the shape of the pattern.
Molten metal can then be poured into the cavity to form the object. To increase the life of the mold, and to make removal of the pattern easier, the pattern must be coated with a protective material. Despite many available pattern coating compounds, mineral seal oil, and a mixture of mineral seal and clay, have been the commercial choices. Hereby the advantages of mineral seal oil-clay pattern coating compositions are retained without its detriments by utilizing a vegetable oil bare in a pattern coating composition to replace some or all of the mineral seal oil to provide biodegradable coating compositions with reduced VOC content.

Description

nticket No. oz42gs~zsl A. s CROSg.ItLF~RENCE TO RELATED ApPLICA~iiON
This $pplication claims priority from U_S. I'rav,isional Application No.
60IZ67,061, filed February 7, 2001.
BACKGrROUND OF ?8E INVENTION
This invention pertrtains to the casting of metals irt sand molds, and particularly tn mcthoda and materials for increasing the lures of the mold pattarns arhich ate employed ~.
The intruduction of a molten metal into a cavity, ar mold, where upon solidi~catiotr, the resulting casting becomes as object whose shape was determined by the mold, is an old art.
Es~~ally as old is read roaring. ~a this molding process a wood, metal or plastic pattern is fabricated in the shape of the part to be produced. Sand iS then cantpa~d around the patteta in suc:& a rovay that the top portion of the meld and the pattern ran be removed, leaving a mold cavity in the shape of tht pattern. Molten mttal is t'hert poured into the meld cavity.
It is well tcnowa that to increase the life of a mold and to matte the removal of the resting ZO easier, the surfaces of the meld Cavity most be raattd with a protective material. Ia the case of sand castings haw~wer it is the pattern which must be coated. Prior art coating compositions ha.~rever deal primarily with mold coatitlgs rather than pattern coatings.
Coatings for fatutdsy cores arid molds are basically mold release agents. They art need to obtain smoother casting s~ces with fewer defects. In its simplest form such a cogtin~g is sin~Iy a suspension of bentQnite, kaolin and other members of the montmorillonite group of ciay~; in water. As in the case ofmoldings, tlzc uae of sandca~it~ patterns is not without its oven problems. 3"he pattern surfaces etude and pit whoa. sucaesgive mold cavities are produced using them. 'When such erosion octuts, molding sands have a greater tendency tn adhere to the pattern when it is removed, affecting the mold cavity. Pattcra release cod in accvrdanec with the present invention provide ir~mYed release properties and increase the number of pocket rro. ozaz~s.zm moldslxpplication. Accordingly, in spite of available pattern costing compositions, mineral segl oul and mineral seal oil-clay coatings are still the commercial praferencc.
5U1NMAIt,Y of ?hIE 11~V>gN'I'IOI~
The present invention relates to a method ofptotecting foundry molds from eroding and pitting during sand seating by prc~retttihg adherence of casting satsd to surfaces of eastirig patter using a biodegradable and low YOC (volatile argaaic catnpound) pattern costing composition.
In acrordaxsce with one aspect of the iuventiar~, the method irrrolveg applying s vegetable oil-clay sition to the surfaces of a casting pattern in an amount sut~cient tn form a coating id which prevents that adherence and affords that prateCtion. the pattern coating composition in accordance with a particular embodiment of the invention is nzt tmnlsified vegetable oil, amd the clay ir~coxpcnated thzrein is an organophylic clay, included in the canting as such or as a clay water dispersible ausine mixhite. The emulsion, then, is a 413/60 to 6t1/4C7 by weight oil-wgter emulsicm, Ifl accordance with mother ~nbodizrlent of the prosent invention, a simple blend of vegetable oil with petroleum oils an$lor alcohol is ptovidctt as a pattern ding composition.
'Ihe pattern coating compositiotr in acactdance with this embodiment is also biodcgtadable attd has n low VOC contest.
Z0 Dl~?AILED DF.SCR'tP'T>rOlrt OF ?~ INVENTION
This ittvrntiors relates to an improvement of the pxocessts for coating sand casting patterns with a pattern coating cempasition w'hereiu the pattntn coating cnmpositiens are bivd.egcadable with a low Yf3C cantextt. 'the pattern canting composition in accordance rovith o»e embodiment is prepared by forming att aqueous emulsion of a vegetable ail using a water Z5 disps~sible amine and a clay reactive therewith s8 emulsifiers. It will be apprecigted that the amine arid the clay react to form an arganophylic clay, the quantity of organoph~rhc being sufficient to stabilize the emulsion, generally tvvo to five weight percent arganopbylia clay based an the weight ofthe oilwatct m>xture. ''fhe oil and water emulsion ofthis~
enzbvdiment presents a Docket Na_ 0?.~tZ9S-261 no volatility and no flasb point prnbletns. Furthermore, iri lieu of a slay and a dispersible amine, an. organophylic clay eau be used to stgbiliae the emulsion.
In acco!~s_rce wig ateother embodiment, :he pattern coating compveidan is prepared by bl~ding a vegetable ail with a viscosity t~educing additive. 'Examples of useful viscosity S reducing additives include petroleum ails and alcohols. the viscosity reducing additives cut be uswd alone or in combination to provide a composition having th$ desir~i viscosity, biodegtadability, release properfiies and VOC level.
Vegetable oils useful in the present invention ors not particulatly limited.
In genentl, any vegetable oil may be used. Exantplss of vegetable oils usefltl in the present invention include, but are not lita~ted to, tom oil, sesame ail, rapeseed oil, sunfloarer ail, palm oil, olive oil, coconut oil, peanut oil, soybean ail, canola. oil. Care oil is particularly useful.
Z'he viscosity of corn oil is t~rpically around 60-90 cps, typically ~0 cps, whereas mineral.
seal oil used in prior art methods harp a viscosity from about 7 to 2~ cps, Therefore, it mxy be desirable to reduce the viscosity of the vegetable oil base by blending the oil with a viscosity decneas3ng additive. The viscosity of the vegetable ail base cats be reduc$d by blending with a lower viscosity mata~ial, such as a petroleum ail, preferably x mineral seal oil, or an alaohal.
Alcohols are particularly use&I in raducistg the viscosity of the vegetable oil. AIcahols also irnprvve leveling of the cogtittg thereby providing a smoother, more uniform stuface. Typically, the roatiztg composition of the present irwention has a viscosity of bclweers about 1U and lOtl cps at 25 °C. In mute particular embvdinsents of the present invention, the viscosity of the cvs#ing coinpasition is betweet2 about 15.50 cpa. ~'he viscosity of the coating composition r~tn also extend beyond these ranges deperidirlg on the parrticulgr application lr~ethud.
l3sefvl sicohola isiclude straight or bxanched chain altmhols hsvittg fmm 1 to 4 carbon atoms. Illustrative alcohols include ~etha~nol, cthastol, isopropaaai, n-propauuol, isabutanoi, t-butanol, ere. Although asethanvl could be used as s visct>sity reducer, it is not recommended became of its associated Loxiaity. Bthanal, particularly corn alcohol, is a particularly us~u1 altobol for reducing the viscosity of a earn ail_ Iwrkct No. 024295-26I
The amount of alcohol uscd is the amount required to reduce the vegetable aii viscosity to the desired ie~el. The amount df alcohol, when present, calf range ftom U.5 to 10% based an the total weight of the compositiorr_ Corn oil and corn alcohol are typically used at a ratio of 95 to 5, but ca» range fi~am pate corn nil to abort 90d/Q corn oil aad about 10% Corn alcohol. Other vrgvtable ails and alcohots maybe used at similar levels.
The pattern rooting compc~ition of the present invention may use pctroleurn oiI es s viscosity reducct blended with vegetable oil. A blend ofpe~oleum oil and vegetable ail is advantageous in that the vegetable oil naturally contains fatty acids_ Thetefare, it is not neccgsary to separately add fatty acids daring preparation of the pattern coating composition to obtain desiral release properties. Blends prepared i» accozdance with this diment of the invention typically cantsih fcvm about 10% to 90'/o petroleum ail based on the fatal weight of !he cc»nposition.
Although fatty acids as~e not rcq>ured to be added in the pattern coafing compositions, they can be added to ettbance ieleaso pmperties_ the fatty reins useful in accordance with the present invention are Iong chain fatty gcids such as Coo - C~ saturated, mean-unsxtnrrated err di-unsattuat~ carboxylic acids which ~ liquids at room tempetat~c, preferred long chain fatty acids are mono-unsaturated Cn-CZO rstboxylic acids which are liquids at room temperature.
Examples of useful fatty acids include, but are not limited to, paltnitic acid, stearic acid, myristic acid, lauric acid, oleic acid, Iinolcic 8cid, at~d Iinoleuic acid, A
particularllr useful fatty acid is Q oleic acid. The fatty acid portion of the fottntllation cari range from 0 to 10°/n bled oa weight_ Typical amounts of fatty acid v~il1 range from 1 to 3% by weight.
Organophylic clays for years have provided viscosities and suspending properties reqflfdrillitlg mans. Tho pattern coating composition ttf certain etnbadimerits ofthis i»~ezition borrows from this drilling mud alt. Consequently, orgxrtopbylit clays themselves are ZS v~ell known. They ate prepared by treating a clay with arJ amine or an amine salt. USUally the clay gtnine t~iore is elected by mixing a clay dispersion with about 5t7 to 200 milvequi~al~ts of am~e per 100 grams of clay. Amines which sari be inoatporated in the etriulsion, err which cgn ire reacted with the days to farm csrganvphylir~emulsifying agents are 'high molecular weight I)oCkrt No. 024295-261 straight chaia and cyclic aliphatic amines. Desirable atnittes are those having $ix to twenty four carbon atoms in the alkyl chains, for example, hexyl amine, heptyl smirte, decyl amine, uadecyl amine, tridecyl araiae, pentadecyl gmine, heptadecyl amine, cetyl amine, and cyclic tertiary amines such as tall oil or cottonseed oil imidaznlines as well ~ their salts.
The clays nvnnally utilized in true preparation of organophylic plays gnd hsmce those preferred herein arc those vontainitlg aluminum and magucsium atoms along with the silica which is characteristic of such clays. "ibis includes such clays as bentonite, attapulgitc, sepiolite and palygors~te, but excludes muscovite or mica and kaol#nitic clays. Agsfsz, it will be appreciated that the orgxnophylic clays c~ be prepared in situ. Tht>x, in addition to incorporating, for example, octadecyhaxt;maniutn betttonite in a vegetable oiI-water mixture, bentonitc and octadecyi amine acetate eau be included to the mixture to form.
the desired emulsion.
The pattern coating campvsition of the presort invemtiou is applied in au ~nouttt sut~ticnt to provide the desired release properties from the casting pattern.
Typically, this will correspond to a coating thickness of from about 2 to about Ia mils. In accordance with particular erribodiments of the present inventinrr, the coating is applied at a Coating thickne8s affmm about 6 tc~ 8 mils. Of course, additional material can be applied to increase release properties.
'fhc pattern coating composition of the present invention is advar~tggeous is that it is biodegradable. Vegetable oils and alcohals are highly degradable, pufiicularly ~.mde~r aerobic conditions. Accordingly, the hiodegrudable pattern coating cotrlpogitir.~s of the present invcntiaa are more envitnnmentally friendly thgtt the prier art petroleum hydnscarbon based compoaitivns_ f~avittg ,given the teachings of tb~s irrvcntion, it will new be illustrated by mesas of specific exatugles.

Docket Nd. oza2gs-zs t An emulsion is prepared using corn oil and water to form the fallcsyving composition.
MATLiuAL ~Ax,~S BY wEIG~
wr rrr..~.rr_ ~: O?a X11 ~8tet Amiae* 200 Bentanite 2b0 '~1-h~dtoxYethY1-2-#a11 vi1 imidazoline 'f he abv~e materials, when mEixed in go ordinary mixer, produce a stable eurrolsion, which is not affected by cold or hot temperattttes. When $oget~, the matrariat returns to s stable emulsio~tt after minor mixing. Wheat used on the pattern face so a glen sand molding facility the product gives excellent results.
Even though n desirgble, stable emulsion is forsaed 'hy the pror~dure of Example 1. at times it ro~rill be desirable to incotpornte ceetai~n additives in the Composition.. This is illustrated by the example which follows.

Following the pmcadure of Example 1 a parting composition v~aa rnede using the same t 5 materials plus additional indents to frtrther improve the stability mtd application properties of the product. 'fhe iagredieats were as follows:
MA~B~LL PARTS BY WEIG$T

Corn ail 4600 ~iTater 4730 $eat~ite 23a Amine" 230 Isaptopanvi 230 Oleic acid 1p0 'Amine = Octgdcxyl amine acetate G

t r L~cscket N'v. X24295-261 When used in an. r~rdingry mixer, the forc~irtg ingredients produce a stable emulsion which is nttt affected >ay cold yr hot tempexatt~res. When frozen, the material s tra s. stile e~nul~it~tt aver minor rr~ixinlg When applied to tht pattern face in a glen sand molding facility.
'i'~e composition anll wet the surface ofthe pattern with an improved e~ciency.
EXAMPLE ~
Follow~ng Example 1 a psttE~n eoatiflg «imposition was prepared using additiongl ingredients.
NIATE~ PAxtTS BY WEIGHT

Com oil 4550 Water 4550 Diisopxopanol 23d Hexaarine 3d0 Attapulgite 230 Oleic acid 10o Isopropariol Z~0 This cotnposiliQn has the advantage ttrat it will requite less mixing action in att ordinary mi~s:er to form a stable etnulsion_ LXAi~PLE 4 Following Pxample 1 a sand castixtg pattern coating area prepated using the folla~ving ingredients:
_ MATER,~L PARTB BY WEIGI~~' Corn oi l 2000 water zooo ~aopropanol 100 Oleic acid 50 Ortganc~phylic 100 clsy*

*Octadecylamntonitrtn berttotaite Docket Na. 024295-261 The foregoing matetials when mixed in an ordinary mixer produce a stable emulsion wlhich is not afi'ected by cold or hot temperatures. When frozen. the material returns to a stable emulsion aR,er minor mixing. When used on the pattern face in s facility the product gives excellent results, yielding cagtin$s whirls are extretncly smooth.
EXAMPLL 5 (C011~'ARAT'IV~) A presently manufactured product in the industry has she fnl'ldwir~g composition:
M,pI,TF~tt~A,~, PARTS $Y 1~VEIGgfi Mineral s~1 oil g70 oleic acid 3Q
~s product was tested by a commercial testing laboratory and was found to have a Flash Point of 129° to 13 S°C. The parting composition of Fxamplc 3 whsou similarly tested did not have a flash point on heating try 100°C, and at that paint the water vapor zxtingaished the frame.
hrs a pattern coating coaipositiort, the formula of ~~camplc 3 was superior to thgt ofExample 5 because ofthe inclusion of the clay-amine compbtmd.
E~CAI~'LE ~
A sand casting pattern coating wgs prepared using the fvllav~ring ingredients:
n~TE.~L PAfLTS BY wi~iGgr Corn oiI 4750 Ethanol 250 f~ocket No. 024295-2G1 This oontpasition has the advaiztage over example 5 that it will require 3tss asxtezial for the application gs a pattern coating and a higher flash point of greater than 300°F. Since the ta~!,eta? szs~.:ng industry is based ;tpon molten metal used in the facility, higher flesh points are pt~efetred. In addition, this compbsition has the advasttage that it does not require the gddition of oleic ecid_ EXA'tVfPLE 7 A sand casting pattern coating was prepared using the follvvving ingraiis~nts:
MA'~LRiAL PAltrB BY wEiG~"i' Corn oil 3500 Mineral seal oil ISUa is 'This composition has the advantage over example 5 that it will requirE Iess material for the application as s pattern coating. Tn additioa, this composition hss the advantage that it does not require the addition of oleic geld A sad casting pattern costing was prepared using the following ing~dients:
MA~I'F~IAL PA_R3'S BX WEIG$T
Corn oiI 25D0 Mineral seal oil 25t>a This composition has the advantage aver example 7 that it has a lowea~
viscosity and would remit in easier application.
g Ethanol 250 boclcet No. 024295-261 A sand casting pattern coating was prep~d usit~ the fotlawing ingredients:
MATLRIAL PAR't'9 $Y WItIG~
Ccrn ail 2375 Mineral seal coil 2375 Ethanot 250 This composition has the ad~~rtt~ge ovor example $ ih tb~t it has yet a louver visGasity at~d would result its easier application, but would have a lcywer flash point.

A sand castiag pattern coating vwas prepared using the foiln~srissg >~rodients:
MAC pAR?S BY IGI~
corn oil 1 svo Mineral seat oil 35~
This eo~mposatinn has the advgnta~e over examples 7, 8 aad 9 that it has the lows viscosity that would be prtferrod when simple spraying applications ate employed. For example, this c;v'mposition would be useful for hand w~pin$, altetnettve spray methods, or other methods 1 S pres~,rntly used in the foundry industry.

Dockat No. 024295-261 EXAMpY,E 1.1 A particularly usefl~l sand casting pattern coating was prapared in accvrdarCe with the fo4lt~wing:
S
MATERI~rL pAIfIS gY W~iGI~1' Corn oil 4g petroleum oil 4g Alcohol 2 Fatty Acid The foregoit>$ examples are illvx'trataiuns of the variety of aiding said partings which can be mgde by this invention. When ctiatirigs of fivm I00 mil to three-sixteenth ineh thiotGnesscs arc applied adherence to the removed pattern is so minimal that the resulting cavity is l0 devoid of pits and deterioration. Traditionally, solvent systems have b~
wed ~ p~~g materials for pattern feces. 'I'ha~e compvsitiotts generally consisted of art dil solvent along with organic additives such as oleic acid, waxes, pera~sts, sued the like. ?he blue of vegetable oil with g viscosity reducer and the emulsification of the vegetable oil with atttiae-clay mixtures yr orgaxtvphyiiC clays provides an itnptuvcd composition without tht disadvantages efprior art 15 s5rstems.
Sand casting pattxrn coatings prcpartd in accordance ~arith the preset itwetttion also provide improved emis$ion chgtacteristics as compared to petroleum based pettaern coatings_ As indicated in Table 1, sand casting pstte~t compositions prepared in accordance with the present irrve~rrtrvn emit sigttificaatly Less benzene per grain of release agent when tested in accordance 20 with the emission test nttthad for release agents established by the AFS
(Amerirait Foundrymetfs Society). Release agents having emission characteristics of less than 4 tog bena~aae per gram of release agent are as improvement aver the prior art petroleum based sample, Docket No. DZ4295-261 TABLE I
EMISSI01~1 CHARA.CTEIiISTICS OF PATTERN COATINGS
EXAMPLE MA'rER~ ~ ~ BE1~FZENE

PER g OF

RE~.EASE AGE1~IT

Petmleum $ased Liquidd.25 C antivc Partir~

s vegetable Oil Base 2.61 Liquid P

9 Blended Petroleum. 3.35 and Vegetable Oil $a$ed Liquid P

~E~~ Liq~d Pattin 0.37 The sand casting pattecri Coatings of the prescttt invention alga provide reduced VOC's as measured by EPA method 24, Futthernwre, the egad pattern coatings in accordance with the prese~at invention ate biodegradable ~arhereas the petroleum based coatings of the prior art are not.
beta relgting Lo VOC and biodegradability are pmvided in Table 2 along with other chatacteristics of the pattern coatings of the present invention {Examples 1, 6 and 9) compared to prior art petroleum based coatings (Example 5)_ TABLL Z
CZ~ARACT$TtrSTICS OF PATTERN COATINGS
EXAMPLE S ~ OIN G 9 1 Physical PropertyPehole'uan. Vegetable)dP~talata~s Water Based Based Liduid porting Oil HaledaadVe~6kO~ Liquid Parting Liquid $asedl~d Pattin Flash Point in 275 Greater Greg t'hgn Water Vapor F 2~0 Closed Cu than 200 Bxt. Flame V'iscosi s 10 47 15 167 9 ecific Gaavi 0.$ 0.9 1.86 p_9 VOC (1'bs/g~al) 4.2 0.29 2.9 3.6 Method 2d.

Biode bill No Yes Yes Nvt beEermined Biodegradability~ 91 15-23 _ Not bete~mined ~ 2f ',~~ life in ~
days lz bucket Na_ n24295-261 As the examples show, ~ariaus modifiaatians are possible within the spirit cf this invetitiow. L~t addition :3 ia~dients illustrated, such additizes as surfactants, eithet- anionic, cationic or nongaianic and other emulsifying sg~ts rare b~ esnplayrd. it bas alregdy bcsn empltasiaed that e'sther the orophylic clay or the amine and the clay can be incorporgted in the composition dwing the miring stage. These attd other rarnificstiotu grill actor to those Skilled in the art. Such wdriations gre deemed to be within the scope cf this invention.
!3

Claims (25)

1. In the process of protecting foundry molds from eroding and pitting during sandcasting by preventing adherence of molding sand to mold pattern surfaces, wherein a pattern coating composition is applied to the mold pattern surfaces in an amount sufficient to form a coating thereon which prevents adherence of sand to the mold pattern, the improvement comprising coating the mold pattern surfaces with a pattern coating composition comprising vegetable oil, water, a water dispersible amine, and a clay reactive with the amine to form an organophylic clay.

2. The process of claim 1 wherein said pattern coating composition further comprises an alcohol.

3. The process of claim 1 wherein the vegetable oil is corn oil, the amine is an oil soluble, water dispersible monobasic cyclic tertiary amine and the clay reactive therewith is attapulgite.

4. The process of claim 3 wherein said pattern coating composition further comprises ethanol.

5. The process of claim 1 wherein the dispersible amine and the clay are prereacted to form the organophylic clay.

6. The process of claim 4 wherein the organophylic clay is octadecyl ammonium bentonite.

7. In the method of protecting foundry molds from eroding and pitting during sandcasting by preventing adherence of molding sand to mold pattern surfaces, wherein a pattern coating composition is applied to the mold pattern surfaces in an amount sufficient to form a coating thereon which prevents adherence of sand to the mold pattern, the improvement comprising coating the mold pattern surfaces with a pattern coating composition comprising vegetable oil and a viscosity reducer selected from the group consisting of mineral seal oil, alcohol and mixtures thereof.

8. The method of claim 7 wherein said pattern coating composition comprises from about 90% to 10% vegetable oil and 10 to 90% mineral seal oil.

9. The method of claim 8 wherein said pattern coating composition comprises approximately equal parts vegetable oil and mineral seal oil.

10. The method of claim 8, further comprising alcohol.

11. The method of claim 10 wherein said alcohol is present from about 0.5 to 10% by weight of the composition.

12. The method of claim 7 wherein said viscosity reducer comprises alcohol.

13. The method of claim 12 wherein said pattern coating composition comprises from about 90% to 99.5% vegetable oil and about 0.5% to 10% alcohol.

14. The method of claim 7 wherein said vegetable oil is selected from the group consisting of corn oil, sesame oil, rapeseed oil, sunflower oil, palm oil, coconut oil, peanut oil, soybean oil, canola oil and mixture thereof.

15. The method of claim 14 wherein said vegetable oil comprises corn oil.

16. The method of claim 12 wherein said alcohol is selected from the group consisting of ethanol, propanol, butanol and combinations thereof.

17. The method of claim 16 wherein said alcohol comprises ethanol.

18. The method of claim 17 wherein said vegetable oil comprises corn oil.

19. The method of claim 7 wherein said pattern coating composition further comprises a long chain fatty acid selected from the group consisting of palmitic acid, stearic acid, myristic acid, lauric acid, oleic acid, linoleic acid, linolenic acid and mixtures thereof.

20. The method of claim 19 wherein said long chant fatty acid comprises oleic acid.

21. The method of claim 20 wherein said viscosity reducer comprises a mixture of mineral seal oil and alcohol.

22. The method of claim 21 wherein said vegetable oil and said mineral seal oil are present in said composition in approximately equal parts.

23. A method for facilitating release of molding sand from mold pattern surfaces comprising applying to the mold pattern surfaces an effective amount of a biodegradable pattern coating composition, wherein the biodegradable pattern costing composition comprises vegetable oil;
a viscosity reducer selected from the group consisting of petroleum oil and alcohol, and optionally a fatty acid.

24. The method of claim 23 wherein said pattern coating composition has a volatile organic compound (VOC) content of less than 3.8 lbs/gal as measured by EPA
method 24.

25. The method of claim 23 wherein said pattern coating composition emits less than 4.0 mg benzene per gram of the composition when tested in accordance with the AFS emission test method for release coatings.

25. The method of claim 23 wherein said pattern coating composition comprises approximately equal parts vegetable oil and petroleum oil.

27. The method of claim 26 wherein said pattern coating composition further comprises oleic acid and alcohol.

28. The method of claim 27 wherein said vegetable oil comprises corn oil and said petroleum oil comprises mineral seal oil.