CA2227330A1

CA2227330A1 - Improved water soluble metal working fluids

Info

Publication number: CA2227330A1
Application number: CA002227330A
Authority: CA
Inventors: Dennis J. Kalota; David A. Martin; David C. Silverman
Original assignee: Individual
Current assignee: Solutia Inc
Priority date: 1995-07-20
Filing date: 1996-07-19
Publication date: 1997-02-06
Also published as: CN1196079A; AU6762596A; EP0854905A1; NO980239L; BR9610062A; JP2002503260A; KR19990029090A; WO1997004052A1; EP0854905A4; NO980239D0; PL324550A1

Abstract

There are disclosed improved water-soluble metal working fluids comprising polyaspartic acid, amides and salts thereof, a corrosion inhibitor(s) and a basic additive said additive having sufficient basicity and buffering power to maintain the pH of the composition above about 8.5 and preferably above about 9. Such compositions are useful as lubricants in processes to cut, bend, grind and shape both ferrous and non-ferrous metals and tend to maintain higher pH
values due to the incorporation of a basic additive. The polyaspartic acid and salts thereof are particularly advantageous in that the fluids can be easily disposed of after use without special treatment because polyaspartic acid and salts thereof are readily biodegradable.

Description

CA 02227330 1998-01-lg ~PROVED WATER SOLUBLE METAL WORKING FLIJIDS
This invention relates to novel water soluble metal w<"Lng fluids which are biodegradable and do not require ~ ;",;"~ More particularly, this invention relates to an improved formulation co.~
polyamino acid, salts and amides useful in cutting, ~ dh~g, S1~AP;~8 and other metal ~o-Ll-~ operations which require a metal working fluid. The ~icc1ose polyamino acid compounds have improved anticorrosive plu~ Lies and are cllv;l~,l....~nt~lly more acce~,lal~le than current oil cont~ining fluids.
BACKGROUND OF THE INVENTION
Because of the concern for environment~l factors, previously known oil-co. .~ g metal wc"ki"g fluids require re- l~iming or disposal by means other than by discha.ging them to con~"~on sewage l-~~ l sy~l~,..-S.
In some cases the cost of disposal has become a major cost in that the cost of disposal approaches the initial cost of the fluid.
Metal working fluids fulfill numerous functions in various metal working applications. Typically, such functions include removal of heat from the work piece and tool (cooling), reduction of friction among chips, tool and work piece (lubrication~, removal of metal debris produced by the work, reduction or inhibition of corrosion and prevention or reduction of build-up on edges as between the work piece and the tool. This combination of functions usually requires a formulation or co-~ ,ation of ingredients in the fluid to accomplish the best attributes required for a particular metal working operation.
Various fluids have been recently proposed to be substituted for 2~ oil-co.. ~i.. ;.. ~ metal-working fluids such as primary amides, ethyl~ne~ min~
tetraacetic acid, fatty acid esters, and alkanolamine salts. Such compounds can be replenished during use by dissolving tablets cont~ining such compounds during the useful life ofthe fluid. See U.S. Patent 4,144,188 to Sato.
Amines have also been found useful in cutting oils as ~ntih~cterial agents. Such amines include ~nilino~mines and arylalkylamine such a p-benzylaminophenol. See EPO 90-400732 to Noda et al.

As noted above, one of the problems occurring in il~lu:~L~ is the proper tiicro~l of metal wolkil~g fluids. The above lllenlioned amines are removed from the fluids by biodegr~ t;Qn ~C~IUiIhIg fs-r.iliti~s such as settling tanks, ll~ tanks and sludge ~ 1 tanks. Such a system is ~I;cslcsed S in J~PA.~,5e Patent 03181395. Other m~.thode of waste disposal and oil removal sysl~l~s are employed to comply with envifol.... -.l~l standards.
Worker s~nit~tion is always an issue with ~rcselllly employed oil-co.-l~ g water soluble metal- working fluids. Such fluids unavoidably come in contact with workers using the fluids in cutting, bentlin~ threading and other metal-working applications. Such oil-co.~l~i.. ;.. g fluids create a mist at the site of the work piece being operated on and such mist travels through the air in the vicinity of the m~chine and the operator thereof. Some attempts have been made to reduce the mist problem as is noted in British Patent 2,252,103. There is disclosed therein a polymeric thicL'P.nP,r coll~ ing copolyrner of acrylamide, sodium acrylate and N-n-octyl acrylamide. The copolymer is form~ ted with water soluble and water insoluble monomer.
Because of the misting and drift thereof in the workplace employing the commonly employed water-soluble metal-working fluids, there is usually associated with such work place a dictinctive odor which permeates the entire area. Usually such odor is unpleasant and is tolerated as a conditionwhich is unavoidable.
There is needed a highly biodegradable, odorless, non-misting water soluble metal working fluid, particularly useful in cutting operations.
Such a fluid would ~ pPnce with the need for disposal costs, and provide the 2~ work place with a more sanitary and acceptable atmosphere in which to work.
Various methods have been discovered to catalyze the polymerization of a dry mixture of aspartic acid to form polysuccinimide. The prt;r~ d catalyst to pelrol,ll in the dry environmenL is phosphoric acid. While phosrhoric acid has been known for many years to be an excellent catalyst for the thermal condPn~tion of aspartic acid, it has traditionally been employed in large qll~ntities so as to form a liquid or pasty mixture. However the use of relatively small ~mountC so as to ~-.A;-~l~;n a ~ y flowable powder is also known. For ~ le, it is ~licrlosed in U.S 5,142,062 to Knebel et al., that a weight ratio of aspartic/catalyst ratio in the range of from 1 :0.1 to 1 :2, can be employed. Also, Fox and Harada have published processes for thermal poly~o~ l ;on of a-amino acids in a public~tion entitled "Analytical Methods of Protein Ch~ r" wherein a l)locedu~c is des~-il,ed employing a mole ratio of aspartic/- catalyst of 1 :0.07. Also, Fox and Harada ~l;c- lose the use of polyl.ho~l.hc"ic acid as a very effective catalyst for the polycc n~e--~l ;
reaction of amino acids and inrlir~te that te~pe~L~Ires below that l ~ ~luir- d when o phosphoric acid is employed are possible.
In U.S. Patent 5,401,428 to Kalota et al., there is dicrlosed a utility of poly~&lLic acid, salts and amides in metal wo~kh~g. .AIth~us~h such saks are known from U.S. Patent 4,971,724 to Kalota et al. as being useful in ~qlleollc ~y~h..~ls as a corrosion inhibitor for ferrous metals, s~ l;s;l~ Iy, it has been found that the metal working fluids llicrlose~ in U.S. 5,401,428 are required to contain a corrosion inhibitor. Exposure of the liquids to air over time results in a fluid which reacts corrosively with metals thereby neC_ec;~ g the inclusion of a corrosion inhibitor. Even with a corrosion inhibitor present there is observed some degradation of the fluids due to aeration which occurs throughout normal use in metal working applications. There is needed a formulation of the metal working fluids of Kalota et al which will resist becoming corrosive upon continued exposure to air.
BRIEF DESCRIPTION OF THE INVENTION
There has now been discovered a new metal working fluid formulation col~ ;llg polyaspartic acids, salts and amides which are highly biodegradable, odorless and non-misting and a stabilizing amount of a basic additive, said additive having s ~ffici~-nt basicity and buffering power to ...~;..l~;.. the pH ofthe composition above about 8.5 and preferably above about 9. Such compositions have been found to be resistant to degradation due to aeration during metal working functions and to remain non-corrosive over extended periods of time.

When diluted in water, such cc,~ osilions provide a highly desirable water-based metal-wcll~ g fiuid useful in such operations as cutting, threading, bending, ~rinrlin~ br5)?~hin~ tapping, pl~nin~ gear ch~pit~g ,, deep hole drilling/gundrilling, drilling, boring, hobbi-.g, milling, turning, sawing and ch~pin~ of various ferrous and non-ferrous metals After reading this specifi~tion those of skill in the art will recognize that such diverse metal working operations and m~teri~lc optimally will require din't;.G.
tiQne of the metal wul kh~g fluids and di~e~elll conc~ lion ratios of the various formulation components l~RIEF DESCRIPTION OF THE DRAWING
Figure 1 is a graphical repr~s~ont~ti~ n of data obtained in an ~I,c;.i...ent showing the effect on pH of carbon dioxide on an aqueous solution of sodium polyasp~ l~le co l ~; ~; g a small amount of sodium phosrh~te and bc~ol~iaLole.
DETAILED DESCRIPTION OF THE INVENTION
Typically, the metal-working fluids of this invention COIll~lisc an effective amount of pOl~as~ Lic acid or a salt or an amide thereof or any compound which provides an effective amount of the same in solution, preferably in concentrations in the range of from about 0 5% to about 70%, by weight in water This very broad range covers both the composition as used in metal working applications (working fluid) and as typically p~c~
colllnlel cially as a concentrate adapted for dilution prior to actual use as a wu.khlg fluid It has been found convenient to provide a working fluid by dilution of the commercial composition in a ratio of about 10 1 although other ratios may be employed Other concentrations and dilution ratios will be appa e .I to those skilled in the art Preferred compositions of this invention comprise from about 3% to about 25% polyaspartic acid, and p-ere-~bly from about 5% to about 20% salt or amide in water as the concentrate The working fluid would contain from about 0 15% to about 20% of the polymer upon dilution to form a working fluid although greater or lesser arnounts may be employed Any number of basic compounds can be used as additives to produce poly~s~,a.lic c~ oc;l;Qnc having improved stability in accol~anc~
with this invention. It is pler~,.led that the basic additive be at least somewhat soluble in water. Reç~lse ofthe small amount in solution actually l~uhed to S impart ~lal)ilily, the basic compounds need only be soluble to a relatively small extent to be effective. The basic additive should have s ~ ntly high basicity and ~d,.g power to effectively n.~;nl *;~ the pH of the polymer sQll~ti~n (Il.e~.llt;d as at 10% or below aqueous solution at normal room t~lllpcl~L~lre) above about 8.5 to about 11 and more plt ~el~bly from about 9 to about 10.5.
However, at effective levels, it should preferably not result in a pH of the polymer solution greater than about 11 because it might render the fluid more hazardous for use, particularly with respect to m~çhine operators.
FY,....PIe~ of suitable basic additives include alkali metal c~l,onales, alkali metal orthophosphate, alkali metal polyphosphates, alkali metal ~ tes~ alkali metal borates and the like, inrltlt1ing mixtures thereof.
Alkali metal carbonates are pl~r~.led in view of their low cost, applopl iale basicity, solubility characteristics and availability. The term "alkali metal" as employed herein means lithium, so-li--m pot~ccinm rubidium and cesium and mixtures thereof.
Preferably, the alkali metal employed in this invention is pot~cQ;~-m It has been found that potassium salts, as employed in this invention, result in metal working fluids having greater solubility in water and, more importantly, depress the freezing point of the composition below that of other commonly available and illc;A~en~ e alkali metals such as sodium.
Accordingly, it is pl ~rt;l, ed to employ the potassium ion in all of the steps employed to prepare compositions of this invention. That is, hydrolysis of the polysuc~inimide interm~ te, such hydrolysis being known in the art, is - pl ere.~bly performed with potassium hydroxide rather than the usual sodium hydroxide. The alkali metal basic additive is preferably potassium salt, particularly, potassium carbonate. However, some benefit is provided by employing at least a portion of the alkali metal as potassium and the rçm~indçr being another alkali metal such as soAi-~m For eY~mple, when the hydrolysis of the polys~ ;... de is pc;,ru-...ed by employing the commonly used sodium hydroxide, the basic additive may be a pOlA~s:-~.. salt such as pol~
carbonate.
The amount of basic additive employed to form a ~ d polya~al lic metal wo-Ll~ fluid can vary widely with good results and the .... effective level can be dete...~ ed for any sPl-octed additive by routine e,~ l;Qn in view ofthe present des~, iplion, k~epi~lg in mind the above noted prere.. ed pH ranges. In the use of sodium carbonate the p- ~;rt:--ed range is, by weight, from about 0.02% and up in a working fluid and up to about 7%
by weight of the sodium carbonate in a conce--l-~Le while a range of from 0.02% to about 4% and prt;rt;-~bly from about 1% to about 3% by weight of the sodium c~l,ona~e is especially p~cr~t;d in a conc~ .ale.
The basic additive of this invention is mixed with the polyaspartic solution by any typical and suitable rnixing or blending means. In the typical m~mlf~c.tllre of polyaspartic metal working fluids, polysucçinimide is usually first produced which is a solid material. This material is hydrolyzedby any typical known means, usually with an aqueous solution of a base, which renders the material in a liquid form. The basic additive is typically added to the liquid during the formulation step. Since only small amounts are employed the blending of the basic additive may be pe~r~l ",ed during the final stages ofplepa,~lion and p~ ging ofthe fluid. No special means of procedures are required so long as adequate mixing to obtain a uniformly con.ctituted formulation is achieved.
2~ With respect to the basic additive, sodium carbonate, any amount up to the solubility limit, may be employed. 13ecause solubility of the potassium salt is higher in such aqueous solutions, slightly higher a...ounls than sodium salts can be employed as for example 9% by weight in a co~-cc.. .l . ~ledsolution of the polyamide. However, the polyaspartic metal working fluid of this invention is typically p,t;l)a-ed as a concentrate co.. l~ i.. g in the range from about 2% to about 70% by weight or up to the solubility limit of CA 02227330 l998-Ol-l9 pol~,~pa"ic acid, salt or amide. When added to a conce.~ le ofthis lioll, the amount of sodium c~l,~ndle present may be in the range of from about 0.2% to about 7% by weight of the total mixture. In diluted form - for use in co,~ metal WUI~ing e~ a cQnc~ ale ofthis invention is typically diluted to about 0.7% with respect to the pol~ le polymer and ~om about 0.02% to about the solubility limit of sodium c~l,on~le pclllaps about 7% wLIch~,~cr is higher, or from about 0.03% to about 10% and preferably from about 0.08% to about 0.8% of pol~s~ ,n carbonate.
Various other additives may be employed in compositionc of this invention to ~nh~n~e or contribute p.~ .lies which enable broader filnctionc with respect to the use of the compositions in metal working applications. The types of additives include boundary lubricants, corrosion inhibitors, ox~ tion inhibitors, detergents and dispt;l~ l, visco~,ily index improves, emulsion modifiers, antiwear and antifriction agents and foam de~l.,;,sc"~,.
For example, additives may be employed to ~-h~ce boundary lubrication such as wear inhibitors, lubricity agents, extreme pressure agents, friction modifiers and the like. Typical examples of such additives are metal dialkyl dithiophosphates, metal diaryl dithiophosph~tçc, alkyl phosphates, alkali metal phosphates, tricresyl phosphate, 2-alkyl-4-,,,elcaplo-1,3,4-thi~ le~
metal dialkyldithiocarbonates, metal dialkyl phosphoro-lithio~tes wherein the metal is typically zinc, molybdenum, t-ln~ct~n or other metals, phosphorized fats and olefins, sulfurized or chlorinated fats and olefins and paraffins, fatty acids, c~bo~ylic acids and their salts, esters of fatty acids, organic molybdenum compounds, molybdenum ~liClllfidt?, graphite and borate dispersions. Such boundary lubrication additives are well known in the art.
Other additives useful herein include detergents and dispersant which provide filn~;tionc v Although the polyaspartic acid compounds of this invention function as corrosion inhibitors in a certain range of pH, corrosion inhibitors may be employed in compositions of this invention which will function in a pH

CA 02227330 1998-01-l9 range in which the poly~s~lic acid, salt or amide may not fimetinn as a corrosion ;.~h;~ r. Typical but not limiting ~ , l of corrosion ;.~
known in the art and useful herein include zinc c,l~c,l-lale, dithiophos~ es such as zinc dithiopho~l.h ~le, metal s~lfon~tes wl-e ,,n the metal is an alkaliS metal, ~lk~n~ .,.;n.~$ such as eth~nsl~mine and s~,l,s~ led ~lkAn9l~ ps W~ the backbone of the alkyl group is sllbstit~lted to provide various pl ~Jpel Lies, alkyl amines such as h~"~yl~l-,nc and triethanol amine, borate ~...po~.(ls such as sodium borate and mixtures of borates with amines, c&~ ylic acids inrlll-iing polyd~ ic acid at high pH (10 and above)and alkyl amino carboxylic acids particularly useful in hard water, sodium molybdate, boric acid ester such as monobenzyl borate and boric acid with various ethanol amines (also acting as a biostat), benzoic acid, nitro derivatives of benzoic acid, A~ ol~i.lm ben70~te, hydroxybenzoic acid, sodium be~o~le~
triethanolamine salts of carboxylic acids with a carb~ ~y---ell~yl thin group such as 1-1-(carboxymethylthio)--n~leç~noic acid triethanol amine salt, be.~ot-;a~ole, tolyltriazole and other C~-C~ alkylbenzol. iazoles.
A more thorough review of corrosion inhibitors are provided by Aruna R~h~dl~r in a publication entitled "Chromate Substitutes For Corrosion Inhibitors in Cooling Water Systems" appealing in Corrosion Reviews, 11(1-2), pp. 105-122, 1993 which is incorporated herein by reference.
In particular, an alkali metal phosphate, p, e~, ~bly potassium or sodium orthophosphate, is p-~re"ed and is adv~nt~geQl1cly in~ ded in compositions of this invention to complement the corrosion inhibitor. Thus compositions of this invention comprise, in a pl e~llt;d embodiment a corrosion inhibitor and a comr~rn~nt~ry co~rosion inhibitor comprising an alkali metal orthophosph~te. The compl~ . y alkali metal orthophosphate is employed in amounts depending on the metal working operation in the range of from about 0.1% to about 10% by weight in the working fluid. Other concentrations will be app~t;,-l to those of o,dh~a y skill in the art as the arnount of polyarnino polymer is ~dj~sted in concentrate as well as working fluid embodimf~nte.

The term "corrosion inhill;tor as employed herein include those which when c n,ployed with other components of co"~poc;l ;onc of this invention exhibit corrosion h~h;l,ilion.
Typical ~~ ale Cc..-po~;l;onc ofthis invention in parts by S weight ~ rted for dilution to l)re~ a ~olking fluid, is shown below in Table I. The cc""posilions in Table I are shown in parts by weight.
A typical conce"Ll ~le composition of this invention is an ~ql)eO~lS sollltion COl~ from about 3% to about 30% by weight, of the salt or amide of poly~ lic acid to~th~r with about 1% to about 10% by weight corrosion inhibitor and from about 200 ppm to about 5% by weight of the sol-lfion of a basic additive.

o ~ o -- ~ O ~ ~ o~ o C~
'U~
o o _ o ~-- ~ o o ~ 1-- o ~ _ ~ oo t-- ~ ~ ~ ~. o o ~ ~, o cn ~ o o ~ ~ o o ~ ~ o X

~ o ~' ~ ~ o ~ ~ '~ o o _ _ o ~ X

~ ~ ~ ~ ~ ~ ~ ~ o ~q C ,~ ~ o C ~ ~ _ ~ ~o E ' E V~ ", E C ~

The co~ ,o~;L;ol~ of this invention may also contain minor . of catalyst e.,.~'o~_d in the thermal colldene~ti- n reaction of L-&S~ ;C acid wl,~, el~ the polymer was made. Typically such catalyst is an acid . such as phosl~h~.l;c acid which is converted to the corre$ron-lin~ salt and salts S of the pyroph<-sph~tç by-product during hydrolysis of the sucrinim-ide polymer.
Typical oxi~tion i~ o~ may also be ;nco~Jo~led into the os;l;ons ofthis invention and include for ~ ,~le zinc and other metal d;Ll"ophos~ AI~c, hindered ph~nolc~ metal phenol s-llfirlec, metal-free phenol s~llfi~lee, aromatic amines as well as .r,i~lulGs thereo~
Rec~ ce many operations in which co""~osiLions ofthis invention are employed create partic~ tee that must be carried away from metal s~ cç, there are employed in co..,posilions ofthis invention delel~ ,..ls and d;,l.e,~ll. Typical d;s~ (s) include polyamine s~crinimi~lec~ line oxides, h~d~ y benzyl polyamines, polyl.yd.~,~y sucçinic esters and polyamine amide imil~7olines and mixtures thereo~ Typical detergents include metal sulfonates, overbased metal sulfonates, metal phenate s~lfid~s, overbased metal phenate s--lfidee, metal salicylates and metal thiophosphonates and mixtures thereof.
Tht;rero,e, compositions of this invention may also include surf~ct~nte, extreme pressure agents, buffers, thickeners, antimicrobial agents and other adjuvants commonly employed in such compositions and mixtures thereo~
Concentrate compositions of this invention most conveniently employed coll"n~l cially and adapted for dilution prior to use will preferably contain potassium salts of the various co",ponents in varying ranges of concG.,I.~Iion but typically co"""ising by weight from about 0.5% potassium poly~s~ L~le, or up to its solubility limit, from about 0.1% to about 10%
potassium orthophosphate dibasic as a con,pl~ nt~ry corrosion inhibitor, from about 0.02% to about its solubility limit pe,l,aps about 9.5%, of potassium carbonate, and from about 200 ppm to about 3% by weight of a corrosion inhibitor. As noted above the plG~IIGd corrosion inhibitor is tolyltriazole which co~ .-ises by weight about 40 to about 0% 4-methyl-lH-benLol.;azole and about 60% to about 100% S-methyl-lH-b.-~ol~ le Those of skill in the art will re~ogrli7e that the solubility limits of co...~,on~,..l~ will be '-~ClfYi by the ~ iUl~ of other colllponellls. Other useful corrosion inh;bitors include all,~ ,.~olli~oles, such as Cl-C4 alkylhç-~ul~;~oles and butylbf-)~ol-i~le.
The pOl~/a ~ lic acid of this invention is preferably provided by the thermal con~çn~tiQn of aspartic acid. Polyas~ ~ic acid can also be p- ~pa~ed by the polyl..e.i~alion of other mol~Glllt:l ~ such as mono -or -----olliulll m~le~tp~ mono -or ~ mmnnil-m fumarate, and m~lç~mic acid.
Many di~.~nL processes are known for such purpose. For PY~mp!P, there has rcce-~lly been discovered a continno~ process employing a tray dryer wherein the aspartic acid is introduced into the top level of trays which cyclically travel in the hc,.i~;ûl~ plane to deliver the ~eacling ...alf ~ ial to the next s~
lower level of trays. The resi(lPnce time in the dryer is controlled by the number of tray levels, the tray rotation rate, circulation of heated gas, such as air, through the dryer, and tempe.~ re. The le,l,l)e,al~lre in such a device is usually in the range offrom about 180~C to about 350~C with a residence time in the range of from about 0.~ to about 6 hours. A typical tray dryer is co....ne,.,;ally available from the Wyssmont Company, Inco.~lo. aLed, Fort Lee, New Jersey.
Another tray dryer which may be employed in such process is a tray dryer commPrcially produced by Krauss Maffei of Florence, Kentucky. In the Krauss Maffei tray dryer, heated trays are stationary and the reaCI~tlll iS
moved across each plate by axially l oL~ g plows or shovels. The reactant alternatively falls from one tray level to the next at the internal or external edge of the tray. The reactant is directly heated by the trays.
While there are several isomers of aspartic acid which may be employed to prepare polyaspartic acid, such as D-, L- or DL-aspartic acid, it ispl er~. . c;d herein to employ L-aspartic acid.
If a catalyst is employed the reaction, re~i~1çnce time in the dryer may be less, in the range of from about 30 minl~tçs to about 2 hours, depending upon other factors noted above. It has lGce~ y been discovered that carbon dioxide in the cir~l1stinp ga~c catalyzes the thermal con~enC~tion when present in h...O.~ of at least about 5%, by volume. ~mol-nts of carbon dioxide in the circulated gas is usually about 10%, by volume.
Various other reactors can be employed to produce the poly~7phl ~ic acid of this hl~ ion. Typical reactors indude the List reactor coll-mel-;ially available from Aerni, A.G. Augst, Switzerland and the LittlefordReactor such as the model FM 130 Laboratory Mixer and larger pro~ ~iQn models available from the Littleford Bros. Inc., Florence, KY.
The T ittl~ford mixer provides sufficient agitation to produce a fluid bed condition and may be equipped with a chopper to break up any lumps or clumps of particles that develop and to provide additional shear forces to the fluid bed. The ~t~fion provided by the mixer is s~lfficient to "~ the particles in a sul~s~ ;Ally free-flowing state throughout the time period of thereaction. Typically, the Littleford mixer is operated at a temperature of at least about 180~C and is capable of ~ g the heated bed at a temperature in the range of about 180~C to about 250~C or higher for a time sl-ffi-i~nt to polymerize the aspartic acid. The mixer is desirably equipped to provide a purge gas stream through the reactor. In accordance with this invention the gas stream is provided with sl-fficient amounts of carbon dioxide so as to catalyze the con.1enc~tion reaction, thus greatly reducing the amount of time toreach complete polymerization of the aspartic acid.
The usual thermal concl~n~tion reaction of aspartic acid produces the polys~lccinimide intermerli~te The interrnediate is easily hydrolyzed by alkaline solution to polyaspartic acid salt. Examples of an alkaline solutions are alkali metal hydroxides, triethanolamine (TEA) and the like, ammonium hydroxide, and the like.
Any water-soluble salts of polyaspartic acid in~ ing those which can be produced by the thermal con~enc~tion of L-aspartic acid may be employed in the metal-working composition of this invention. Typical water soluble salts include alkali metal salts, a,l"l,o~ m, organic ammonium and mixtures thereo~ The term "alkali metal" e~-cc,...l-~cs~s lithium, so~ m pot~CQ;~lm cesium and n ' ' and l~u~lur~s thereof. The organic ~-.. ~-~
salts useful herein include those p~ep~d from the low mol~clll~r weight organic amines, i.e. having a mt lec~ r weight below about 270. Organic --amines usefu! herein include the alkyl amines, alkylene amines, alkanol a--mines.
Typical organic amines include propylamine, isoplvpylamine, ~lhyl&~ e~
isobutylamine, n-amylamine, hexylamine, heptylamine, o-;lyl~l...le, nonylamine, decylamine, undccl.y~ -ne, dode~,yl~ h~Y~decylamine, hept~dc~,yl~lfule, ocatde-;ylall-lne, and basic amino acids such as Iysine.
No matter which reactor is employed, the poly~s~,~ lic acid or salt thereof produced by the thermal c~m~l~n~tic)n of L-aspartic acid, is usefulin this invention. It has been discovered that this polymer provides sllfficipntlubrication to permit metal wo.king operations on ferrous and non-ferrous metals.
Any molecular weight of polyaspartic acid may be usefully employed herein.
Poly~s~ Lic acid derived from other sources are also useful in the compositions and method of this invention. For example, polyaspartic acid can be derived from the polycont~nc~tion processes employing maleic acid or derivatives thereof such as are known from U.S. Patents 3,846,380 to Fujimoto et al., U.S. 4,839,461 to Boehmke, U.S. 4,696,981 to Harada et al, all of which are incorporated herein by reference. While not p-ef~:-- t;d, copolymers of amino acids can also be employed in the process of this invention such as copolymers prcpa~ed accor.ling to U.S. Patent 4,590,260 to Harada et al.
2~ The water based metal-working fluids of this invention are particularly adv~nt~geous in that there is e~nti~lly no odor ~soci~ted with water solutions of polyaspartic acid or salts or amines thereof. Further, it hasbeen observed that the fluid dramatically reduces any mist around the tool wo~ g area as is comrnon with water-based oil co..l~ining fluids. Because of the virtual lack of mist formation the work area is .~ i l-ed virtually free of dçflected fluid leaving the m~hinçry and worker subst~nti~lly free of CA 02227330 lsss-ol-ls c~ --;--Al;Ol~ by the metal w~"hin~, fluid in"~ this invention. The water-based metsl-wol~;ng fluids ofthis invention are most advAnt~o-l~ in that the active ill~ ~iiClll, pol~ lic acid or salts have been found to have a rapid rate of biodegrA~lAti~n The biodegradability of the metal wolLng fluids of this invention allows their disposal through normal means such as by d;scl.~ ~ into a sewage Ll ~ system. The cost ad~lla~,~,s of such a fluid ofthis invention are obvious in view ofthe environm~ntAl concellls ros llting inalternative means of disposal.
Tests with non-ferrous metals such âS brass and copper in~ Ate that not only is the work place relatively free of co~ ;on but that the workpiece lenl&,l,s relatively free of ~iccolQring deposits. In fact, it has been observed that the aqueous solutions of the salts of polyaspartic acid are corrosion inhibitors as in-lic~ted by U.S. Patent 4,971,724 to Kalota et al.
The~role, metals, particularly ferrous metals, are free of harmful deposits and are, in fact protected from corrosion by the metal-working fluids of this invention. However the corrosion inhibiting effect of ~queo~ls solutions of pOlyas~ lic acid extend to those solutions having a pH in the range of from sbout 8.5 and above. If the formulation employed with the polyaspartic acid or derivative of this invention results in an aqueous solution having a pH of about10 or below it is lt;co.. e~-~ed that additional anti-corrosion inhibitors be illcOllJolated into the formulation of the metal-working fluid of this invention.
However, it has been shown in Figure 1 that during extended use of the fluids in actual practice, the pH of the polyaspa;tic compositions of this invention tend to decrease due to contact with acidifying agents such as the carbon dioxide from the atmosphere. Therefore, it is co"l",on practice to include additional corrosion inhibitor(s) in compositions of this invention. The amount of corrosion inhibitor can vary widely depending upon the particular inhibitor and the envh-ol"l~e"l in which the fluid is employed. For example, if zinc ~ chromate is the corrosion inhibitor effective amounts range upwards from as little as 50 ppm in the working fluid.

The metal-wo-khlg fluids of this invention are useful in the various metal-wc,.Lng app~ ;on~ such as were noted above with any ~-u..-be of types of metals. In particular they are useful in w~ .ing ferrous metals and alloys such as iron, steel (carbon steel and low alloy carbon steel), cast iron,~' ' '- steels, nickel-based alloys, and cobalt-co.~ . alloys and the like.
Non f~.~ous metals and alloys which can be worked with fluids ofthis invention are copper, brass, I;~ min~m, bronze, and m~ c ~---- and the like. Such metals are safely worked with lubricity supplied by the water based fluids of this invention.
A particularly important function of a metal wu-ki-~g fluid of this invention in cutting operations is the function of cooling so as to .~
Iower tempe.~ re of the tool as well as the work le...pe.~ re. Such control aids in ~--;--;- ~ ~;,;- .g tool wear and di~lu- liGn of the workpiece. Another function of the metal w~ ing fluid of this invention is lubrication which reduces friction as b~l~een the tool and chips produced during the cutting operation as well as reduction of the friction between the tool and the workpiece. In cutting operations of various types there are typically produced chips of small pieces of metal which are advantageously carried away from the workpiece as soon as possible so that they do not jam the cutting tool.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following example, a laboratory model of a tray dryer was employed having two trays which passed the reactant material from one to the other thereby sim~ ting the conditions of a cc,m-nt;- ~,ially available tray dryer r~f~ d to above. The reactant material was passed from one tray to the other so as to equal the desired number of tray levels of the CO--~IC. ~,ial model. The tray dryer, ~im~ ting the Wyssmont Turbo Dryer, available from the Wy~,...onl Company, Fort Lee, NJ was operated with the ~d~ition of 1 kg of ~aspartic acid per tray level at a depth of 2.5 cm on the trays. A total of 28 tray levels was employed. Circulated air te-~ re through the dryer of 305~C was .,.~ ed throughout the experiment. Air velocity was CA 02227330 lsss-ol-ls ed at 114.3 meters per minute and tray roLalion was set at 3 ...;~ s per revolution. An amount of carbon dioxide was fed into the air supply to provide a total amount of 10 percent, by volume, carbon dioxide in the air c~ .vl;.~g the ~~le,ial on the trays. ~:r~ were taken from the trays at S various ~ ~ion times and analyzed for the amount of conversion to polymer, pEI,color(APHA),and ~la ~ r weight. Thedataob~ edappearsinTable II below.

T.ARr F II
Sample TimeMol. wL Color pH % Conv.
No. (n~in) Po1ymer 9402 112 9.17 53.66 2 64 9333 471 9.82 99.00 1 5 3 70 9263 565 9.26 99.06 4 90 8792 1069 10.01 99.16 An C~IJe~ t;llL was condllcted to show the effect of carbon dioxide on the pH of the polyaspartic metal working fluids of this invention. A
1% aqueous solution of sodium polyas~,a~a~e cont~ining residual ~1500 ppm as P04) sodium phosphate was subjected to aeration with a gaseous mixture of 2.5% carbon dioxide by volume in nitrogen as well as pure nitrogen. The data iS present in Figure 1 wherein Curve A is the data obtained with pure nitrogen and Curve B is the data obtained with the blend of carbon dioxide and nitrogen.
The rapid decline in pH as shown by Curve B indicates the infl~lçnce of carbon dioxide on pH of the solution. As shown in Fig. 1, the solution aerated with gas Co~ i..g carbon dioxide quickly (within a few hours) inr~ic~teCl a pH of about 7 while the pH of the solution aerated with only nitrogen ~ n~ P,d eccP.nti~lly unr-h~np~e~

An accel~,.a~ed te~st was p.,.r~ll-lcd to show the effect of a basic additive on the ~ y ofthe pH of a metal wolki~l~, fluid and thus the tc.ldency of the fluid to beco. ..c corrosive to metals. S~mp~ ~ s of polys~crinim:1e ~)lG~,~ed by various means were hydrolyzed and rull~
for use as metal wolLI~ fluids. One set of s pl~F was p~ d from catalyst free aspartic acid (Sample A) and another set was pl ~al t;d from pOl~ ~ Lc produced in the prcs_.lcc of phosphoric acid at 7.5% by weight of the aspartic acid (Sample B). S~mrles were plepaled having the following form~ tion and ~ te~l to equal pH by addition of acid or base as required:

Sodium Polyasp~l~Le 1% by weight Be~ullia~ole 950 ppm Disodium Ph~ sph~te 1500 ppm (as PO~) pH 9.60 Water 693 g A third sample, tap water, (Sample C) adjusted to a pH of 9.6 with sodium hydroxide was used as a control. Ambient air, typically co..~ 0.033%
carbon dioxide, was entrained through the liquid samples at a cons~ rate of greater than 200cc/min at ambient room tempe,~ re and pressure. The pH of each solution was measured once per day for six days. Amounts of sodium c~l,o~ e from 250 ppm to 1000 ppm were added to each sample at the beginning of the test. The results of the test is shown below in Table III.

TART ~ m S~nple A A A B B B C
N~CO~ 250 500 1000 250 5001000 3.5 h~. 9.32 9.43 9.43 9.379.319.34 7.94 1 Dny 8.89 9.17 9.24 9.00 9.089.078.05 2Days 8.84 9.01 9.11 8.88 8.879.047.92 3 Days 8.84 8.97 9.08 8.87 8.879.047.92 4 Days 8.80 8.94 9.04 8.80 8.849.037.84 5 Days 8.80 8.92 9.04 8.81 8.859.008.03 6 Days 8.83 8.95 9.05 8.80 8.869.038.02 From the above data it is noted that sodium carbonate was effective at all levels in ~ g higher pH levels than found in the tap water. Also, at 1000 ppm level the pH reached an equilibrium at 9 or above after 2 days. It is known that at a pH of 9 or above corrosion levels are reduced to an incigrlific~nt level. The addition of the basic additive ~ .es the pH at an acceptable level in the accelerated test which indicates that the working fluid would not degrade by normal use for a relatively long period of time Polyaspartic acid, sodium salt, was prepaled by means of a Wyssmont Turbo Dryer in the presence of 7.5% phosphoric acid catalyst. The acid polymer was hydrolysed with sodium hydroxide and diluted to a 1% by weight aqueous solution. Two batches of the polyaspartic polymer were form~ ted with benzotriazole, which has a pKa of 8.3. Any effect on pH in this test is not ~ffected by the benzotriazole since the pKa is below the pH of the test solutions. In one batch, co,~ g 200 ppm bel3~0ll iaz~1e, no sodium carbonate was added and in the other batch co,~l~h-il-g 950 ppm benzotriazole, sodium carbonate was added at a concentration of 1000 ppm. Each batch of cutting fluid was employed as the cutting fluid in a Okuma LB 10 cutting ...~ l.;.-c.. The pH of each batch of cutting fluid was measured initially, after 1 day and after 5 days. Each batch was used to cut 300 pieces of 1018 steel down ~om 2.54 cm to 0.934 cm using a ~;1~ i DMN G432MA insert.
The parting tool was a ~A~rl~es;er M50. The results of periodic pH tests from the periodic pH measurement of the pol~/asp~ lic polymer cutting fluid are shown below in Table IV.
TABLE IV

No Carbonate 1000 ppm Carbonate Start 9.8 10.3 1 day 8.91 9.91 5 days 8.16 9.78 The results inrii~te that a level of 1000 ppm sodium callJGl~ale st~bili7ed the pH ofthe polyaspartic polymer cutting fluid while the pH ofthe cutting fluid without a basic additive c~erlined below the desired pH level of 9to 9.5.

Typically, a pl ef~, I t;d composition of this invention can be ~ ,pared by polymerizing L-aspartic acid as described in Example 4 and then hydrolyzing the resulting polysuccinimide by charging a suitable vessel with thefollowing amounts in parts by weight shown in Table V below:
TABLE V
Charge Amount Polysuccinimide 106 Water 1 072 50% KOH 133 To the potassium polyaspartate produced by the above described hydrolysis procedure there is then added 21 parts of dipotassium CA 02227330 lsss-ol-ls WO 97/040s2 PCT/US96/11993 l~h~sl.k~P, 17.7 parts of pot~si~lrn carbonate and 13.5 parts oftolylL. ~le The tolylL~;azole is co...~ ecl of a mixture co.~ g 40% 4-methyl-lH-be.~ol~i~zole and 60% 5-methyl-1H-be~ ole. In the use oftolyllli~le, it is de~ to ...~;..l~i.- the level above about 900 ppm in the w~ fluid S for best results.

To dp-~on~ ale the de~es~;on ofthe Lee~ing point in compositions ofthis il.~e..lioll achieved by incol~,ol~Lion ofthe p~l~c~ .. ion instead of the sodium ion, the three compositions described in Table I above were tested by subjecting them to cooling while noting the visual observation of the composition with respect to homog~nPity and freezing point. The results appear in Table VI below. The composition, in percent by weight were as follows:
TABLE VI
15 CompositionFreezing Point - ~C Precipitate ~,) ~C
Sodium Salt -1~C +10 Potassium Salt -6~C no ppt.
Mixed Salt -3~C trace (~ -0~

From the above data it is evident that the potassium salt is highly adv~nt~geous in that it has a ~ignific~ntly reduced freezing temperature.As significant at the reduced freezing tell-pe-~L-Ire is the fact that no p.t;cipilate was observed, even at the freezing te-l-pe~LLIre inr~ic~ting that no separation of the solution into di~l~;llL phases occurred. Therefore, the effect of freezing the potassium salt mixture is not as deleterious as either the sodium salt or mixed salt compositions which would require further mixing to redistribute the separated phases of the composition due to the occurrence of freezing tenl~ lures.
Although the invention has been described in terms of specific embodiments which are set forth in considerable detail, it should be understood that this d~sc. i~Lion iS by way of illU~L.aLiOll only of effective CO-I.pQc~ c and of c~ ivc A'~O"'~I" of ~".polle.-l~ and that the invention is not l-~cc~.ily limited thereto, since alternative embo~lim~ntc and Opclal;llg lec~ ues will bec~ al)p~ to those skilled in the art (in view of the ~iicclQsllre.) S Ac~li,-~ly, mo~lificqtiQns are contemplqted which can be made wilLoul de~.~ Iin~, from the spirit and scope of the described invention.

Claims

WHAT IS CLAIMED IS:
1. In a method of metal working wherein a lubricant is provided for said metal, the improvement which comprises providing an aqueous solution of a polyaspartic polymer selected from the group consisting of the acid, salt or amide thereof, a corrosion inhibitor and a stabilizing amount of abasic additive, said basic additive having sufficient basicity and buffering power to maintain the pH of the composition above about 8.5.
2. The method of Claim 1, wherein said pH is maintained above about 9.
3. The method of Claim 1 wherein the polyaspartic polymer is potassium polyaspartate, the basic additive is an alkali metal salt or amine salt or ammonium salt and the corrosion inhibitor is tolyltriazole or benzotriazole or an alkylbenzotriazole.
4. The method of Claim 3, wherein said alkali metal salt is a potassium salt and the corrosion inhibitor is tolyltriazole.
5. The method of Claim 3 wherein the tolyltriazole or benzotriazole is present in amount of at least about 100 ppm and preferably about 900 ppm.
6. The method of Claim 5 wherein the tolyltriazole or benzotriazole is present as a mixture comprising about zero to about 40%
4-methyl-1H-benzotriazole and about 60% to about 100% 5-methyl-1H-benzotriazole 7. The method of Claim 1 wherein the solution contains from about 0.05% to about 70%, and preferably from about 0.5% to about 2% by weight, of said polymer, wherein the corrosion inhibitor is tolyltriazole or benzotriazole or an alkylbenzotriazole and wherein the basic additive is potassium carbonate.
8. The method of Claim 7 wherein the solution contains from about 0.05% to about 70% by weight of said polymer and wherein the basic additive is present in the range of from 0.02% to about 8% by weight of said solution.

9. The method of claim 1 wherein the metal working is a cutting operation selected from the group consisting of threading, grinding, shaping, turning, milling or drilling and the like.
10. The method of Claim 1 wherein the metal working is bending.
11. The method of Claim 1 wherein the metal is a ferrous metal or alloy selected from the group consisting of iron, steel (carbon steel and lowalloy steel), cast iron stainless steels, nickel based alloys, cobalt containingalloys, and the like.
12. The method of Claim 1 wherein the metal is a non-ferrous metal or alloy selected from the group consisting of copper, bronze, brass, titanium, alumminum, magnesium and the like.
13. A metal working composition comprising an aqueous solution of a polyaspartic polymer selected from the group consisting of the acid, salt or amide thereof wherein the concentration of said polymer is in the range of from about 0.05% to about 70%, a corrosion inhibitor(s) and a stabilizing amount of a basic additive, said basic additive having sufficient basicity and buffering power to maintain the pH of the composition above about 8.5.
14. The composition of Claim 13, whereby said pH is maintained above about 9.
15. The composition of Claim 13 wherein said corrosion inhibitor(s) is present in the range of from about 50 ppm to about 15 percent byweight and wherein said basic additive maintains a pH in the range of from about 8.5 to about 11.
16. The composition of Claim 15 wherein the basic additive is potassium carbonate and the corrosion inhibitor is tolyltriazole.
17. The composition of Claim 16 wherein the tolyltriazole is present as a mixture comprising from about zero to about 40% 4-methyl-1H-benzotriazole and from about 100% to about 60%
5-methyl-1H-benzotriazole.
18. The composition of Claim 16 wherein the tolyltriazole is present as a mixture comprising about 100% 5-methyl-1H-benzotriazole.
19. The composition of Claim 13 wherein the concentration of the polyaspartic polymer is at least about 0.05% by weight of the solution, the corrosion inhibitor is tolyltriazole and is present in an amount in the range offrom about 0.01% to about 2% by weight together with a complementary corrosion inhibitor comprising a water soluble alkali metal or ammonium phosphate in the range of from about 0.1% to about 10% by weight.
20. The composition of Claim 19 wherein the alkali metal phosphate is selected from the group consisting of sodium or potassium orthophosphate.
21. The composition of Claim 20 wherein the polymer is an alkali metal salt.
22. The composition of Claim 21 wherein the salt is a potassium salt.
23. The composition of Claim 22 wherein the polymer is an amide.

24. A metal working composition concentrate adapted for dilution to prepare a working fluid comprising an aqueous solution of potassium polyaspartate, a basic additive, said basic additive having sufficientbasicity and buffering power to maintain the pH of the composition above about 8.5, a corrosion inhibitor and from about 1% to about 10%, by weight, of a complementary corrosion inhibitor comprising potassium orthophosphate.
25. The composition of Claim 24, wherein the pH is maintained above about 9 and the basic additive is potassium carbonate.
26. A metal working composition of Claim 24 wherein the potassium polyaspartate is present in the range of from about 0.5% up to about its solubility limit and the corrosion inhibitor is tolyltriazole wherein said tolyltriazole comprises from about zero to about 40% 4-methyl-1H-benzotriazole and from about 100% to about 60% 5-methyl-1H-benzotriazole, by weight.
27. A metal working composition of Claim 26 wherein the tolyltriazole is present in the range of from about 0.1 % to about 2% by weight. 28. A metal working composition of Claim 24 wherein the corrosion inhibitor is a salt of benzoic acid.
29. A metal working composition of Claim 24 wherein the corrosion inhibitor is selected from the group consisting of sodium benzoate and ammonium benzoate.
30. A metal working composition concentrate adapted for dilution comprising by weight from about 0.5% to its solubility limit of potassium polyaspartate, from about 0.2% to about 9% potassium carbonate, about 0.3% to about 2% of a corrosion inhibitor and a complementary corrosion inhibitor comprising from about 1% to about 10% potassium orthophosphate.
31. A composition of Claim 30 wherein the corrosion inhibitor is tolyltriazole.

32. A composition of Claim 31 wherein said tolyltriazole comprises from about zero to about 40% 4-methyl-1H-bezotriazole and from about 100% to about 60% 5-methyl-1H-benzotriazole, by weight.
33. The method of Claim 32 wherein the solution contains from about 0.5% to about 70%, by weight, of said polymer, wherein the corrosion inhibitor is alkylbenzotriazole or tolyltriazole or benzotriazole and wherein the basic additive is sodium carbonate.
34. The method of Claim 33 wherein the solution contains from about 0.5% or up to its solubility limit by weight, of said polymer and wherein the sodium carbonate is present up to about 7% by weight of said solution 35. The method of Claim 33 wherein the metal working is a cutting selected from the group consisting of threading, grinding, shaping turning, drilling and milling.
36. The method of Claim 33 wherein the metal working is bending.
37. The method of Claim 33 wherein the metal is a ferrous metal or alloy selected from the group consisting of iron, steel (carbon steel and low alloy steel), cast iron, stainless steels, nickel based alloys, cobalt containing alloys.
38. The method of Claim 33 wherein the metal is a non-ferrous metal or alloy selected from the group consisting of copper, bronze, brass, titanium aluminum and magnesium.
39. The composition of Claim 33 wherein the basic additive is a mixture of sodium and potassium carbonates and the corrosion inhibitor is benzotriazole or tolyltriazole or an alkylbenzotriazole.
40. The composition of Claim 39 wherein the concentration of the corrosion inhibitor is in the range of from about 50 ppm to about 15% by weight.

41. The composition of Claim 1 further containing a minor amount of sodium orthophosphate retained from the polymerization process to obtain said polyaspartic polymer.
42. The composition of Claim 1 wherein the polymer is an alkali metal salt.
43. The composition of Claim 1 wherein the polymer is an ammonium salt or amine salt.
44. The composition of Claim 1 wherein the polymer is an de.
45. A metal working composition comprising an aqueous solution of sodium polyaspartate, a basic additive, said additive having sufficient basicity and buffering power to maintain the pH of the composition above about 8.5, a minor amount of sodium orthophosphate and a corrosion inhibitor and potassium othrophosphate.
46. A metal working composition of Claim 45 wherein the sodium polyaspartate is present in the range of from about 0.5% to about its solubility limit and the corrosion inhibitor is benzotriazole or alkylbenzotriazole or tolytriazole.
47. A metal working composition of Claim 45 wherein the corrosion inhibitor additives are present in the range of from about 50 ppm to 15% by weight.
48. The method of Claim 1 wherein the solution contains from about 0.5% to about 70%, by weight, of said polymer, wherein the corrosion inhibitor is benzotriazole and wherein the basic additive is sodium carbonate.
49. The method of Colaim 2 wherein the solution contains from about 5% to about 15% by weight, of said polymer and wherein the sodium carbonate is present up to abut 7% by weight of said solution 50. The method of claim 2 wherein the metal working is a cutting selected from the group consisting of threading, grinding and shaping.