The present invention provides an antifreeze/coolant composition with polymeric polycarboxylates which prevents hard water precipitants and scale formation, is soluble in alcohol and alcohol/water mixtures, is compatible with other commonly used antifreeze/coolant components, does not corrode or damage automotive cooling systems and is effective at relatively low concentrations.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to antifreeze/coolant compositions and more 
specifically to antifreeze/coolant compositions with polycarboxylates. 
2. Description of the Prior Art 
Antifreeze/coolant technology in North America uses silicate as a corrosion 
inhibitor. Silicates are particularly useful in protecting aluminum 
automotive cooling system components. The silicate corrosion inhibitors 
generally also use a phosphate, usually in the form of an alkali metal 
salt, to help protect metal cooling system parts and also as a buffer to 
control the pH of the coolant. 
Often phosphate salts are used to help maintain a stable alkaline 
environment from which multiple corrosion inhibitors can most effectively 
function. Thus, the degradation of silicate and phosphate in an 
antifreeze/coolant can negatively impact the overall performance of the 
antifreeze/coolant. 
Traditionally antifreeze/coolant is sold at nearly one-hundred percent 
glycol content. This concentrated packaging allows for flexibility so that 
the user can dilute the antifreeze/coolant, as needed, with available 
water to obtain the required freeze/boil protection. However, corrosion 
protection is needed over the entire dilution range. 
Recently, there has been an increase in concern over the quality of water 
used to dilute the antifreeze/coolant. Water quality varies greatly with 
geographic location, population and degree of industrialization. 
One of the major problems is hard water control. The U.S. Geological Survey 
defines hard water in parts per million of ionic calcium. Magnesium is 
also commonly considered to be a hardness ion. Moderately hard water is 
from 25 to 50 ppm and hard water is defined as 50 to 75 ppm. Very hard 
water is considered to be above 75 ppm. At below 25 ppm, the soft water 
designation is used. 
When a typical North American antifreeze/coolant containing silicate and 
phosphate is mixed with very hard water, copious precipitates develop in a 
short period of time. Hard water salts can cause maintenance and 
operations difficulties at automotive manufacturing facilities. These 
precipitates may clog an automotive cooling system, resulting in reduced 
coolant flow, increased engine operating temperatures and shorter service 
life. These precipitates may circulate through the entire cooling system 
promoting erosion and wear, e.g. water pump damage through increased 
cavitation and seal abrasion. 
The presence of hard water and antifreeze/coolant in an automotive cooling 
system may also lead to scale formation. The scales can be formed from 
alkaline earth metal carbonate and phosphate deposition. These inorganic 
films tend to inhibit thermal transfer and thus reduce the efficiency of 
the cooling system. Inhibiting scale formation has long been a concern in 
aqueous cooling systems. For, example, U.S. Pat. No. 3,663,448 discloses 
scale inhibition for industrial cooling waters using amino phosphonate and 
polyacrylic acid compounds. U.S. Pat. No. 3,948,792 discloses an aqueous 
additive mixture to reduce and modify the amount of silicate scale formed 
in automotive cooling systems. 
In addition to the thermal, abrasive and physical problems presented by 
hard water precipitates, their chemical formation depletes the initial 
antifreeze/coolant. The hard water precipitates comprise silicate and 
phosphate salts. By reducing the available quantity of these corrosion 
inhibitors, the ability of the resultant liquid antifreeze/coolant to 
provide adequate corrosion protection, particularly for aluminum, is 
uncertain. The result is dependent upon the hardness of the water used and 
the initial silicate concentration of the antifreeze/coolant. 
In Europe, hard water is more prevalent than in North America. European 
antifreeze/coolant technology, while commonly using silicate corrosion 
inhibitors, differs from that of North America in that the technology 
concentrates on reduction of silicate precipitation. European patent 
245557 discloses the use of a variety of compounds including sodium 
polyacrylate to prevent alkaline earth metal silicate precipitation. 
However, in this patent phosphate is not used as a buffer in the coolant, 
thus simplifying the precipitation issue. 
U.S. Pat. No. 4,487,712 discloses the use of polyacrylic acid as a silicate 
stabilizer to inhibit gelation. Gelation is a silicate depletion mechanism 
which occurs separately from hard water precipitation. 
In spite of these disclosures, there remains a need for a concentrated 
silicate-phosphate type antifreeze/coolant composition which prevents hard 
water precipitates and deposits upon dilution with hard water. 
SUMMARY OF THE INVENTION 
The present invention has met the above-described need by providing an 
antifreeze/coolant composition with polymeric polycarboxylates which 
prevents hard water precipitants and scale formation, is soluble in 
alcohol and alcohol/water mixtures, is compatible with other commonly used 
antifreeze/coolant components, does not corrode or damage automotive 
cooling systems and is effective at relatively low concentrations. 
It is an object to provide antifreeze/coolant compositions which are 
effective when diluted with hard water. 
It is another object of the present invention to use polymeric 
polycarboxylates in silicate-phosphate type antifreeze/coolant 
compositions to reduce or eliminate hard water precipitation. 
These and other objects of the present invention will be more fully 
understood from the following description of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides an antifreeze/coolant composition with 
polymeric polycarboxylates which prevents hard water precipitants and 
scale formation, is soluble in alcohol and alcohol/water mixtures, is 
compatible with other commonly used antifreeze/coolant components, does 
not corrode or damage automotive cooling systems and is effective at 
relatively low concentrations. 
The preferred class of polymeric polycarboxylates are based on polyacrylic 
acid (PAA) and/or polymaleic acid (PMA). These polymeric polycarboxylates 
are compatible with other components in the typical antifreeze/coolant 
composition, and present no additional toxicity or disposal concerns. 
The polycarboxylates used in the present invention have a molecular weight 
range of from 500 to about 250,000, with a preferred range of from 500 to 
12,000. More specifically, the most preferred additives have average 
molecular weights in the range of about 500 to 4000, and more specifically 
about 1300 to about 1800 and about 300 to about 4600. 
When reference is made to polycarboxylates within the context of the 
present invention it is understood to encompass those watersoluble homo- 
and copolymers having at least one monomeric unit containing C.sub.3-6 
monoethylenically unsaturated mono- or dicarboxylic acids or their salts. 
Suitable monocarboxylic acids of this type are for example, acrylic acid, 
methacrylic acid, ethacrylic acid, vinylacetic acid, allylacetic acid, and 
crotonic acid. The preferable monocarboxylic acids from this group are 
acrylic acid and methacrylic acid. A further component of the 
polycarboxylate comprises monoethylenically unsaturated C.sub.4-6 
dicarboxylic acids, for example, maleic acid, itaconic acid, citraconic 
acid, mesaconic acid, fumaric acid, or methylenemalonic acid. The 
preferred acid is maleic acid. 
Other organic substituents may be used as comonomers or as modifiers added 
along the polymer chain. Examples of such are shown as Formula I. 
##STR1## 
where R=H or a secondary alcohol such as isopropanol, X=COOH, COO.sup.- 
Na+, methylvinylether, isobutylene, vinyl acetate, acrylamide, or styrene, 
with the proviso that when R= a secondary alcohol, X=COOH or COO.sup.- Na+, 
and when X= any other above referenced group, R=H. The preferred 
polycarboxylates are a copolymer of acrylic acid and maleic acid, said 
copolymer having a molecular weight of 3000, and as sodium salt of 
polyacrylic acid modified with a secondary alcohol such a isopropanol, 
said polymer having a molecular weight of 4000. 
The polycarboxylates used in the present invention are obtained by methods 
well known to those skilled in the art. The general method of synthesis is 
via free acid radical polymerization. The polymerization may be carried out 
in an aqueous medium, in the presence of polymerization initiators, with or 
without regulants. The polymerization can take various forms; for example, 
the monomer(s) can be polymerized batchwise in the form of aqueous 
solutions. It is also possible to introduce into the polymerization 
reactor a portion of the monomer(s) and a portion of the initiator, to 
heat the mixture in an inert atmosphere to the polymerization temperature 
and then to add the remaining monomer(s) and initiator to the reactor at 
the rate of polymerization. Polymerization temperatures range from 
20.degree. C. to 200.degree. C. At temperatures above 100.degree. C., 
pressure vessels are employed. 
The carboxyl containing monomers can be polymerized in the free carboxylic 
acid form, in the partial neutralized form, or completely neutralized. The 
neutralization is preferably effected with alkali metal or ammonium base. 
The polymerization initiators used are preferably water soluble free 
radical formers such as hydrogen peroxide, peroxodisulfates and mixtures 
of the two. The polymerization may also be started with water insoluble 
initiators such as dibenzoyl peroxide, dilaurylperoxide, or 
azodiisobutyronitrile. 
The polymerization may be carried out in the presence of regulants. 
Examples of such regulants include water soluble mercaptans, ammonium 
formate, and hydroxylammonium sulfate. 
Examples of the polycarboxylates which may be used in the present invention 
are those marketed by BASF under the trademark SOKALAN.RTM. 
polycarboxylates, which are available in aqueous polymer solutions. 
The polymeric polycarboxylate is effective at relatively low 
concentrations, generally about 100 to about 1000 ppm per total volume of 
antifreeze/coolant for very hard water. Generally the concentrated 
antifreeze/coolant is diluted about fifty percent in water. Precipitation 
prevention in soft water or hard water may be prevented at least about 10 
to 20 ppm. 
The preferred antifreeze/coolant composition is a silicate-phosphate type 
having about 94% antifreeze grade glycols and about 3% corrosion 
inhibitors, with the balance being water. While ethylene glycol is 
preferred in this present invention, propylene glycol or mixtures of 
ethylene glycol and propylene glycol may be used. The corrosion inhibitors 
generally are a mixture of azole compounds, nitrate salts, defoamers and 
other constituents in addition to the stabilized silicate and phosphate 
salts. The stabilized silicate technology is disclosed in U.S. Pat. Nos. 
4,370,255; 4,362,644 and 4,354,002, all hereby incorporated by reference. 
Antifreeze/coolant compositions are well-known in the art and many 
variations of the above-described composition will be useful in the 
invention. 
The following examples serve to further illustrate the present invention 
and should in no way be construed as limiting the scope thereof. 
EXAMPLES 
Materials 
The central standard from Volkswagenwerk AG, Audi NSU and Auto Union AG on 
Coolant Testing for Silicate Stability (P-VW 1426) was used as a screening 
tool. The test is based on storage of a coolant with a synthetic hard 
water. 
The composition of the synthetic hard water was made by dissolving 148 mg 
of sodium sulfate; 165 mg sodium chloride; 138 mg sodium bicarbonate; and 
275 mg calcium chloride in 1 liter of distilled water. This synthetic 
water is 100 ppm in ionic calcium, and thus is considered to be very hard 
water. 
The antifreeze/coolant used was approximately 94% antifreeze grade glycols 
and about 3% corrosion inhibitors. The corrosion inhibitors were 
stabilized silicate and phosphate salts, azole 6 compounds, nitrate salts 
and defoamers. 
Method 
The experimental method mixed 100 mls of antifreeze/coolant with an 
equivalent amount of synthetic hard water in a covered eight ounce glass 
bottle. The sample was then stored for ten days at 80.degree. C. Following 
storage, the samples were removed and evaluated for precipitates. Positive 
and negative controls were evaluated with each set of samples. 
The negative control was prepared as detailed above, and a large quantity 
of precipitates formed within hours of mixing, even at room temperature. 
Often the negative control solution was cloudy upon mixing. 
The positive control was made by mixing the antifreeze/ coolant with 
distilled water. No precipitation or clouding was noted. 
After separating the precipitates from the liquors of a negative control, 
following the 10 day test, chemical analyses were performed to determine 
the chemical composition of the hard water precipitates. Infrared analysis 
indicated the presence of silicates and phosphates in the solids. Ion 
chromatography indicated that the solids were 28% phosphate in 
composition. Expressed as calcium phosphate, this could account for 46% of 
the total solids in one sample. 
Energy Dispersive Spectroscopy (EDS) showed the presence of potassium, 
sodium, and calcium in addition to confirming the presence of phosphorous 
and silicon in the solid precipitates. A solid sample of hard water 
precipitate was 63% potassium phosphate and this was determined to be the 
primary constituent. 
To eliminate the hard water precipitate formation, a number of materials 
were evaluated for their solubility in an ethylene glycol based 
antifreeze/coolant. If soluble, the effect of the additive versus 
concentration in the screening coolant was established using the hard 
water storage stability test. The materials evaluated in this manner are 
identified in Table 1 which summarizes the results obtained. 
To pass the hard water storage stability test, no precipitates should be 
present in the bottom of the glass bottle when the sample is removed from 
the oven and evaluated. The clarity of the liquors is noted but not a 
criteria for evaluation. No suspended material or gel should be noted in a 
passing sample. Figures stated for concentration of additive used are at 
dilution with hard water and normalized for activity or concentration of 
additive. All solid materials are assumed pure. 
TABLE 1A 
______________________________________ 
SOKALAN .RTM. Polycarboxylates 
Additive 
Chemical Ave. M.W. Solubility Result 
Name Comps'n (g/mole) (yes/no) 
______________________________________ 
CP 2 PMA/Methylvinyl- 
70,000 No 
ether 
CP 5 PMA/PAA 70,000 No 
CP 45 PMA/PAA 70,000 No 
CP 7 PMA/PAA 50,000 No 
CP 8 PMA/PAA 150,000 No 
CP 9 PMA/Olefin 12,000 Yes 
PM 10 PMA 1,000 Yes 
CP 10 Modified PAA 4,000 Yes 
CP 10 S Modified PAA 4,000 Yes 
CP 12 S PMA/PAA 3,000 Yes 
CP 13 S Modified PAA 20,000 Yes 
PA 15 PAA 1,200 Yes 
PA 20 PAA 2,500 Yes 
PA 25 PN 
PAA 4,000 Yes 
PA 30 PAA 8,000 Yes 
PA 40 PAA 15,000 No 
PA 50 PAA 30,000 Yes 
PA 70 PAA 70,000 Yes 
PA 75 PAA 76,000 Yes 
PA 80 S PAA 100,000 Yes 
PA 110 S 
PAA 250,000 Yes 
______________________________________ 
TABLE 1B 
______________________________________ 
Commercially Available Polycarboxylates 
Solubility 
Additive Chemical Ave. M.W. Result 
Name Comps'n (g/mole) (yes/no) 
______________________________________ 
Colloid 211.sup.1 
PAA 3,400 Yes 
Belclene 200.sup.2 
PMA 270 Yes 
Belclene 201 
PMA 450 Yes 
Belclene 283 
PMA 1,600 Yes 
Belclene 400 
Polyanionic 4,000 Yes 
Belclene 500 
Phophino- 1,300 Yes 
carboxylic Acid 
Good-rite K732.sup.3 
PAA 5,400 Yes 
Good-rite K752 
PAA 2,000 Yes 
Carbopol 672.sup.4 
PAA+ N/A++ No 
Carbopol 674 
PAA+ N/A++ No 
Carbopol 1610 
PAA+ N/A++ No 
______________________________________ 
.sup.1 Colloid is a trade product of Colloid, Inc. 
.sup.2 Belclene is a trade product of Ciba Geigy. 
.sup.3 Carbopol is a trade product of BF Goodrich. 
TABLE 1C 
______________________________________ 
Other Materials 
Solubility 
Additive Chemical Ave. M.W. Result 
Name Comps'n (g/mole) (yes/no) 
______________________________________ 
Sokalan .RTM. DCS 
Dicarboxylic N/A Yes 
Acid Salts 
Chelator Sodium Gluconate 
218 Yes 
PVP Polyvinyl- N/A Yes 
pyrrolidone 
______________________________________ 
average experimentally determined by gel permeation 
chromatography (GPC). The parameters are as follows: 
GPC Parameters: 
Column Set 250 + 120 Ultrahydrogel at 50 
degrees C. 
Mobile Phase 0.1M sodium phosphate buffer at pH 6.7 
Flow Rate 0.6 mL/minute 
Sample Injection 
100 micro-liters of 1 mg/ml 
Detector differential refractometer 
Standards Polyacrylic Acid Standards 
It was necessary to extrapolate from the calibration to 
obtain molecular weight averages for some of the lower 
weight Belclene additives. The results should be 
considered as estimates. 
+ chemical composition from MSDS supplied by 
manufacturer. 
++ not available, the average molecular weights are in the 
hundreds of thousands to millions based on viscosity 
data. 
______________________________________ 
Table 1 shows that not all polycarboxylates are soluble in ethylene glycol 
and that solubility is not a clear function of molecular weight. The 
solubility also seems to be dependent upon the chemical composition. 
However, Table 1 shows that generally larger molecular weight PMA/PAA 
copolymers are less soluble than larger molecular weight PAAs. 
The extremely large molecular weight moieties, the Carbopols, were not 
completely soluble in ethylene glycol. Since these materials could break 
up during automotive cooling system use and resultant smaller components 
dissolve and function, it was decided to test these materials further. 
Table 2 summarizes the results of the synthetic hard water storage testing 
for the additives. 
TABLE 2A 
______________________________________ 
SOKALAN .RTM. Polycarboxylates 
Min. Pass Level or 
Additive Max. Level Tested 
Test Benefit 
Name (ppm) Results (yes/no) 
______________________________________ 
CP 9 200 Fail No 
PM 10 200 Fail Yes 
CP 10 50 Pass Yes 
CP 10 S 50 Pass Yes 
CP 12 S 50 Pass Yes 
CP 13 S 250 Pass Yes 
PA 15 500 Fail Yes 
PA 20 500 Fail Yes 
PA 30 500 Fail Yes 
PA 50 500 Fail Yes 
PA 70 500 Fail No 
PA 75 500 Fail No 
PA 80 S 250 Pass Yes 
PA 110 S 250 Pass Yes 
______________________________________ 
TABLE 2B 
______________________________________ 
Commercially Available Polycarboxylates 
Min. Pass Level or 
Additive Max. Level Tested 
Test Benefit 
Name (ppm) Results (yes/no) 
______________________________________ 
Colloid 211 
500 Fail Yes 
Belclene 200 
500 Fail Yes 
Belclene 201 
500 Fail No 
Belclene 283 
500 Pass Yes 
Belclene 400 
500 Pass Yes 
Belclene 500 
500 Pass Yes 
Good-rite K732 
200 Pass Yes 
Good-rite K752 
100 Pass Yes 
Carbopol 672 
300 Fail&gt; No 
Carbopol 674 
300 Fail&gt; Yes 
Carbopol 1610 
300 Fail&gt; Yes 
______________________________________ 
TABLE 2C 
______________________________________ 
Other Materials 
Min. Pass Level or 
Additive Max. Level Tested 
Test Benefit 
Name (ppm) Results (yes/no) 
______________________________________ 
Sokalan .RTM. DCS 
2,000 Fail No 
Sodium Gluconate 
20,000 Fail No 
PVP 250 Fail No 
______________________________________ 
&gt;material evaluated despite incomplete solubility. 
Table 2 shows that a variety of polycarboxylates are effective at allowing 
a silicate-phosphate based coolant to pass the synthetic hard water 
storage test. Although some additives strictly fail the test, they 
produced some clear, positive effects by reducing the amount or kind of 
precipitates or both. Some additives provided no ability to pass the test 
nor any beneficial factors to the screening coolant. In these two latter 
fail cases, it is possible that increasing the level of additive may 
provide improvement. 
The most effective additives, based on minimum concentration required to 
pass the test, were Sokalan.RTM. CP 10, CP 10 S and CP 12 S. The next best 
performers included Sokalan.RTM. PA 20 and Good-rite K-752. 
The sodium gluconate, PVP and dicarboxylic acid salts were not effective 
additives for hard water precipitates. The lower molecular weight 
distributed Belclene PMA's were only able to modify the precipitates 
formed. The Carbopols tested resulted in some benefit in two cases. This 
is surprising because they were not entirely soluble. It is speculated 
that complete solubility may not be necessary, but that if the portion of 
the additive which is very active can be solubilized, that additive will 
have some benefit. However, the most preferred additives are entirely 
soluble. 
The most effective additives tested were Sokalan.RTM. CP 10, Sokalan.RTM. 
CP 10 S and Sokalan.RTM. CP 12 S (trademark of BASF Corp., Parsippany, 
N.J.). S denotes the free acid form of the polycarboxylate and the absence 
of the S indicates a neutralized sodium salt. All free acid materials would 
be neutralized in the alkaline, buffered antifreeze/coolant mixture. 
Neutralization may affect the solubility of larger molecular weight 
additives. 
Sokalan.RTM. CP 10 S was chosen for further evaluation to explore 17 its 
effect on the corrosion inhibitor package in the base screening coolant. 
Although the Sokalan.RTM. CP 10 S containing coolant passed the storage 
test at the equivalent of 50 ppm, the concentration was increased to 375 
ppm in order to exaggerate any concentration dependent effects and 
evaluated by the ASTM D1384-87 standard test method. ASTM D1384-87 is a 
corrosion test method for engine coolants in glassware. The changes in 
weight for the control antifreeze/coolant and the antifreeze/coolant with 
the additive (375 ppm Sokalan.RTM. CP 10 S)are shown in Table 3. The 
specification required to pass ASTM D1384-87 is also given as a reference. 
All weight changes are in mg/coupon. 
TABLE 3 
______________________________________ 
Base Coolant + 
Metal Coupon 
Spec. to Pass 
Base Coolant 
Additive 
______________________________________ 
Copper -10 -0.6 -1.1 
2006 Solder 
-30 +0.3 -0.6 
Brass -10 -2.4 -9.0 
Mild Steel 
-10 +0.6 -0.1 
Cast Iron -10 -0.8 -6.1 
Aluminum -30 +6.1 +2.6 
______________________________________ 
Table 3 shows that the addition of 375 ppm Sokalan.RTM. CP 10 S to the 
screening coolant did not significantly alter the weight change results, 
nor the outcome of the test. Thus, the polycarboxylate additive is 
compatible with the corrosion inhibitors present in the 
antifreeze/coolant. The addition of the additive causes no further 
corrosion to standard cooling system metals. 
Sokalan.RTM. CP 12 S polycarboxylate was added to commercial 
antifreeze/coolants to evaluate its effect by the hard water stability 
test. Table 4 shows the results of this test. The Table shows the amount 
of additive required in solution for each coolant/hard water mixture to 
pass the storage stability test. In all cases, the commercial products 
mixed with the synthetic hard water with no additive failed the test. 
TABLE 4 
______________________________________ 
Commercial Product 
Level of Sokalan .RTM. CP 12 S 
Antifreeze/Coolant 
Required to Pass (in ppm) 
______________________________________ 
ZEREX .RTM..sup.a 
50 
PRESTONE II .RTM..sup.b 
100 
PEAK .RTM..sup.c 
50 
TEXACO .RTM..sup.d 
250 
______________________________________ 
.sup.a ZEREX .RTM. is a registered trademark of BASF Corp. 
.sup.b PRESTONE II .RTM. is a registered trademark of First Brands Corp. 
.sup.c PEAK .RTM. is a registered trademark of Old World Trading. 
.sup.d TEXACO .RTM. is a registered trademark of Texaco Oil Company. 
Table 5 shows that the addition of a polycarboxylate to commercial 
silicate-phosphate type antifreeze/coolants provides improved formulations 
which do not exhibit precipitates upon mixing with very hard water. The 
levels of the additive required for the various commercial 
antifreeze/coolants were generally similar, but not identical. 
Whereas particular embodiments of the invention have been described above 
for purposes of illustration, it will be appreciated by those skilled in 
the art that numerous variations of the details may be made without 
departing from the invention as described in the appended claims.