Note: Descriptions are shown in the official language in which they were submitted.
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~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.
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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
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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.
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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
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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
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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
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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
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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.
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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.
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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 ~
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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
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12
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
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13
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
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14
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
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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.
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16
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
EXAMPLE 1
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
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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
EXAMPLE 2
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~
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EXAMPLE 3
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.
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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
EXAMPLE 4
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
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...~ 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.
EXAMPLE 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
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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.
EXAMPLE 6
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
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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.
