United States Patent [191
`Kardos et a1.
`
`[54] COOLANT COMPOSITION CONTAINING
`POTASSIUM FORMATE AND POTASSIUM
`ACETATE AND METHOD OF USE
`
`[75] Inventory Péti' X31105; 1TH)" .lfélmén; Jélsef
`Kern; Eszter N Kern, all of
`Buda est, Hun r
`p
`ga y
`,
`.
`
`_
`
`__
`
`_
`
`,
`
`[73] Asslgnee‘ Es?ikfnag’amrszagl Vegylmuveki
`SaJobabony, Hungary
`
`[21] Appl. No.: 563,782
`
`[22] Filed
`'
`
`A“ 3 1990
`g‘ ’
`
`.
`.
`I Related U's' Apphcanon Data
`commuano?-in-pm 0f Seri NO- 266,833,_N0v- 3, 1988,
`abandoned~
`
`[63]
`
`[51] Int. Cl.5 .............................................. .. C09K~5/00
`[52] US. Cl. ...................................... .. 252/79; 252/75;
`252/76; 252/77
`[58] Field of Search ...................... .. 252/ 76, 79, 75, 77
`
`IlllllllllllllllllllllIlllllllllllllllllllIllllIllllIllllllllllllllilllllll
`USOO5104562A
`[11]
`5,104,562
`Patent Number:
`[45] Date of Patent:
`Apr. 14, 1992
`
`[56]
`
`References Cited
`
`U'S' PATENT DOCUMENTS
`2,233,185 2/1941 Smith .................................. .. 252/76
`4,219,433 8/1980 M b t
`l.
`252 76
`4,332,209 7/l982 M22215: :t :1.
`252275
`4,587,028 5/1986 Darden ............................... .. 252/75
`_
`Primary Examiner-Paul Lieberman
`Assistant Examiner-Christine A. Skane
`
`Attorney, Agent, or Firm-Schweitzer Cornman &
`Gross
`
`ABSHMCT -
`[57]
`A frost resistant glycol-free coolant composition or
`process for cooling apparatus is used for cooling, with
`such composition, which comprises an aqueous solution
`of a water soluble alkali metal salt, or a mixture of two
`alkali metal salts. Particularly suitable alkali metal salts
`- are alkali metal acetate and alkali metal formate. De
`pending on the nature of the particular alkali metal salt
`or salts, and the extent of frostproofness that is required,
`the compositon can further contain urea and/or a gly
`col antifreeze, such as ethylene glycol. Optionally a
`corrosion inhibitor can also be used.
`_
`14 Claims, No Drawings
`
`PAGE 1 of 5
`
`PETITIONER'S EXHIBIT 1325
`
`

`
`COOLANT COMPOSITION CONTAINING
`POTASSIUM FORMATE AND POTASSIUM
`ACETATE AND METHOD OF USE
`
`5
`
`1
`
`This is a continuing application of US. Ser. No.
`266,883, ?led on Nov. 3, 1989, now abandoned.
`
`FIELD OF THE INVENTION
`The present invention relates to a cooling ?uid for
`internal combustion engines, more particularly to a
`glycol free cooling ?uid having increased frost resis
`tance. The cooling ?uid of the present invention is envi
`ronmentally safe, therefore its use is preferred not only
`for the cooling of internal combustion engines, but also
`for operating cooling towers of thermal power stations,
`industrial and household refrigerators and freezers,
`open and closed heat exchangers, solar collectors, dou
`blers and autoclaves used in the chemical industry, and
`generally providing equipment with protection against
`frost damage in case of freezing.
`'
`‘
`
`5,104,562
`2
`frost resistance, however, the low speci?c heat, high
`volatility, i.e. low boiling point as well as the risk of ?re
`and explosion all counsel against their use; all the more
`so, because certain members of this group of organic
`compounds, such as methanol are also poisonous, toxic
`and are therefore, unsafe to use in an industrial environ
`ment.
`Due to their various advantages, the aqueous ethyl
`ene glycol solutions marketed as heat transfer liquids
`under various trade names have been accepted in a wide
`range as frost resistant coolants. The advantage of these
`solutions is that glycol can be mixed with water without
`limitations, ?re and explosion risk is moderate, the spe
`ci?c heat is about twice as high as that of the aforemen
`tioned organic solvents, they are colorless, odorless and
`relatively frost resistant. Speci?c heat and solidi?cation
`point are functions of the glycol-water ratio. With the
`increase of water content the speci?c heat increases, but
`frost resistance decreases. The lowest solidi?cation
`point (-57“ C.) is associated with the eutectic composi
`tion. In this case the glycol content is 60% by volume.
`A further advantage is that in the practically important
`,compositions the glycol-water mixture does not freeze
`with a concomitant increase in volume. Consequently
`apparatus cooled with a glycol-water coolant will not
`be freezing.
`There are also disadvantages which limit the wider
`use of glycol based coolants. Ethylene glycol is very
`toxic and it can be easily confused with ethyl alcohol.
`The ingestion of ethylene glycol has led repeatedly to
`well publicized, occasionally fatal poisoning cases. Eth
`ylene glycol can also contaminate the environment, and
`grave consequences as a result if it gets into bodies of
`water, such as when the coolant is carelessly discarded,
`or when it leaks from defective equipment. The frost
`resistance of ethylene glycol can be only partially uti
`lized because for example an aqueous mixture of 1:1
`volume ratio has a freezing point of —38° C., but at
`—3l° C. it already shows a jelly-like nonthixotropic
`consistence, and is thus unsuitable for pumping. The so
`called ?uidity limit of —3l° C. cannot be further re
`duced even by modifying the glycol: water ratio, and
`this also means that below —30“ C. in complications,
`such as heat transfer processes were low viscosity is
`required the glycol-water mixture cannot be employed.
`' The frost resistance and ?uidity decrease, and the cor
`rosiveness of aqueous ethylene glycol increases in time,
`due to slow polymerization and acidic decomposition of
`the glycol. Therefore, the mixture has to be replaced
`from time to time, and this increases operating expenses.
`
`25
`
`BACKGROUND OF THE INVENTION
`The most generally used cooling ?uid is water in the
`temperature range above the freezing point. In addition
`to its ready availability, the advantage of water is that
`all liquids it has the highest speci?c heat. it has low
`viscosity and, as a result of its physical properties it has
`good heat conductivity. In addition to these important
`thermal characteristics, it has a relatively moderate
`corrosive effect, which can be further reduced by the
`addition of inhibitors.
`However, the disadvantage of water is that it is not
`frost-resistant. Upon freezing its volume increases by
`9%, leading to the frost damage of equipment.
`As used throughout the speci?cation and the claims,
`characterizing terms such as “frost free” or “resistant to
`freezing” means that a material so characterized does
`not freeze at least substantially below the freezing point
`of water. Also as used throughout the speci?cation and
`claims, terms such as “coolant” and “cooling ?uid" are
`used interchangeably with the same meaning.
`The frost resistance of water can be signi?cantly
`improved by the addition of electrolytes that stay dis
`solved even at low temperatures. This possibility is,
`however, very much limited by the fact that the use of
`acids and bases is not permissible in many places for
`industrial safety, environmental protection and due to
`their corrosive nature. From a cryoscopic aspect cal
`cium chloride has been proved to be most advanta
`geous, because by its addition a temperature of even
`about 50° C. can be attained, while the solution main
`tains its liquid state, and only a slight increase in viscos
`ity and a slight reduction in speci?c heat takes place. A
`much more serious problem, however, is the corrosion
`activating effect of the chloride ions, mainly in concen
`trated solutions. This effect which causes mostly a per
`foration corrosion, cannot be satisfactorily reduced
`even by the use of any known corrosion inhibitors.
`Solubility problems arise if other anions are used instead
`of chloride. When e.g. calcium sulfate is used, these
`problems can involve a low saturation concentration
`under all conditions, or when, for example, sodium
`sulfate or potassium nitrate is used, a dramatic decrease
`of saturation concentration will occur with decreasing
`temperature.
`Hydrocarbons, alcohols, and ketones- of a low carbon
`atom number are very advantageous with respect to
`
`35
`
`DISCLOSURE OF THE INVENTION
`The invention is aimed at maintaining the advantages
`of glycol based aqueous coolants, and eliminating their
`disadvantages, and ensuring an optional arbitrary mix
`ing ratio of the new coolant with conventional glycol
`based coolant media. Consequently with conventional
`ethylene glycol coolant was imposed as a requirement,
`because we had to consider the possibility of mixing the
`occurrence of mistaken or mixing due to stock manage
`ment requirements.
`We'have found that in an aqueous medium alkali
`metal salts of certain anions, suitably acetates and for
`mates in combination with each other optionally with
`additional water soluble organic compounds, such as
`formamide and/or urea containing an intensively hy
`drophilic substituent with or without an added glycol,
`result in such an extreme reduction in freezing point,
`
`65
`
`PAGE 2 of 5
`
`PETITIONER'S EXHIBIT 1325
`
`

`
`20
`
`25
`
`30
`
`5,104,562
`4
`3
`to be compensated by organic compounds containing
`which is not even approached when the individual com
`the optional hydrophilic substituents and/or by ethyl
`ponents, are separately dissolved in water.
`In fact, the resultant freezing point decrease, calcu
`ene glycol.
`lated on the basis of additivity in freezing point reduc
`In this case the advantage of not using glycol at all is
`tions as determined separately for each component, lags
`lost, and only the advance of reduced glycol content
`far behind the freezing point reduction actually
`can be realized. This means that in the case of the fol
`lowing Example I, 80% less glycol is necessary for
`achieved by the mixture of the above mentioned com
`ponents. This very signi?cant extra effect is convinc
`achieving an identical drop in freezing point calculated
`ingly proven for example, with potassium acetate and
`for the same volume of the liquid, than for the conven
`tional, purely glycol-based compositions.
`potassium formate. In a concentrated aqueous solution
`of potassium acetate the achievable freezing point that
`According to none embodiment of the invention this
`is -38° C. (—36.4° F.) and in the case of potassium
`80% glycol portion can now be replaced with environ
`formate the solution freezes at ~35” C. (—3l° F.). This
`mentally friendly materials. If, however, the acetate
`means that compared to the freezing point of water, the
`salt-formate salt mixture is a salt each of the potassium
`decrease of the freezing point is the same. On the other
`cation, the glycol can be fully eliminated. If desired, it
`hand if these two potassium compounds are “dissolved”
`can be replaced with compounds which are harmless to
`in water in combination with each other, employing the
`the environment and would not be hazardous to health.
`compositions to be described later, a composition is
`Frost resistance and ?uidity are also increased in com
`obtained that is liquid at 70“ C., or even at lower tem
`parison to the glycol-based cooling ?uid of identical
`peratures. Nevertheless, such an extreme frost resis
`water content, as shown by the following Example 2.
`tance is very rarely required in practice. Therefore, and
`Those potassium acetate, potassium formate combi
`also for more economical operation it is advisable to
`nations are particularly advantageous for decreasing the .
`dilute the liquid with water to the extent that the result
`‘ freezing point, wherein the mass ratio of the two anions
`ing solution should, remain frost resistant under the
`is adjusted that the quantity (mass) of acetate in the ?uid
`given climatic conditions with full safety. This ap
`should be suitably approximately six times of that of the
`proach is also justi?ed by the fact that in all cases the
`formate. By increasing the relative concentration of the
`speci?c heat and ?uidity of the liquid increase on dilu
`more expensive and due to corrosive characteristics
`tion.
`also more disadvantageous formate ions, the freezing
`In connection with the liquids of the present inven
`point depression already achieved cannot be practically
`tion, including the aforementioned acetate and formate
`improved, but if a more moderate frost resistance is also
`mixtures, the use of expressions such as “dissolving”
`sufficient in a geographic area of speci?ed climate, then
`and "solution” may not necessarily be theoretically
`the concentration of the formate additive can be arbi
`accurate, because the structures of the liquids are more
`trarily reduced, sometimes even entirely omitted.
`similar to molten matter than to aqueous solutions.
`On the other hand, it should be taken into consider
`Therefore, such materials which cannot be truly char
`ation that in the cooling systems of internal combustion
`acterized as an aqueous “solution” are also referred to
`engines, the liquid can bring about simultaneous corro
`herein as an aqueous “preparation”.
`sion of various structural materials in metallic contact
`Since the added compounds appear completely to
`with each other. This is the possibility of coupled metal
`destroy the original liquid structure of water, the physi
`corrosion, also called contact corrosion, which can
`cal-chemical laws which otherwise determine the freez
`multiply the severity of corrosion. Therefore, the pro
`ing point of an aqueous solution. For example, the law
`tection of the cooling system could be further insured
`of molecular freezing point depression, is no longer
`by the addition of corrosion inhibitors. Although devel
`even approximately valid. Principally, those non-water
`opment of a new inhibitor composition was not the
`components become overwhelming, the molar freezing
`subject of this invention, some corrosion inhibitors
`point depressions of which exceed that of water. On the
`known for other uses are listed below, which, as we
`other hand, the competitive hydrolysis of alkalimetal
`found, provide appropriate protection._
`salts, such as of formate and acetateions prevents the
`It is an object of this invention to provide a frost
`development of a long-range order characteristic for a
`resistant aqueous coolant composition containing alkali
`solid crystalline phase. This can occur to such an extent
`metal, suitably potassium acetate and potassium formate
`that it leads to extremely low freezing points signi?
`50
`as main components, signi?cantly shifting the acetate
`cantly deviating from those expected on the basis of
`formate ratio to the advantage of acetate, or optionally,
`additivity and interpolation calculations. This is demon
`in the case of a moderate frost resistance requirement,
`strated by numerical data.
`entirely omitting the formate additive, while in the case
`Our other recognition was that the speci?c charge of
`where a higher frost resistance demanded the formate
`alkali metal cations plays a signi?cant role in depressing
`55
`concentration can reach 25% of the acetate concentra
`freezing point. For example, if sodium cation is used
`tion. In the case of extremely high frost resistance re
`instead of potassium in the acetate-formate salt combi
`nation, the low freezing point provided by potassium
`quirement, the water content in the mixture can be
`reduced to 30% by mass in the mixture, while in the
`. cationcannot even be approached. Without intending
`'case of a more moderate frost resistance requirement,
`to be bound, we believe that the reason for this is that
`the water content can be increased such as by the dilu-a
`the sodium cation vhas a higher speci?c charge, i.e.
`tion of concentrate.
`lower mass,v establishes a greater ?eld strength in its
`It can be mentioned as guidance that in the case of a
`own environment, thus the water dipoles are oriented
`1:6 formate-acetate anion concentration ratio which is
`more effectively, resulting in a more’ limited heat mo
`generally considered to be optimum, by increasing the
`tion. All this leads to a smaller decrease of freezing
`water content to 65%, the freezing point is —25° C. and
`point, even‘at identical molar concentrations. There
`fore, if the composition is intended to be established
`with the above mentioned 30% by mass water- content
`the freezing point is below —80° C.
`with sodium cations, their freezing point raising effect is
`
`60
`
`40
`
`45
`
`65
`
`PAGE 3 of 5
`
`PETITIONER'S EXHIBIT 1325
`
`

`
`5,104,562
`6
`C., viscosity at 22° C.; 2.3 cSt., density at 20° C.: 1.19
`g/cm3, speci?c heat in the 20° to 25° C. range: 3.27
`J/"C.cm3 or 2.75 J/°C.g. The liquid freezes without
`expansion.
`
`EXAMPLE 3
`Frost Resistant Liquid Mixtures Having Differing
`Glycol Content
`Conventional glycol-based and the glycol-free frost
`resistant liquids are mixed and are used in such combi
`nation. It was experimentally determined that the two
`liquids can be mixed in any desired ratio, and the prop
`erties of the liquids produced in this way were also
`determined as a function of mixing proportion.
`It was determined as a function of mixing proportion.
`It was determined that the characteristics change
`monotonously although not linearly with the composi
`tion. These conditions are re?ected by the freezing
`point data of the various mixtures of glycol-based cool
`ing liquid with the trade name “Prevent” (in which the
`glycol content is nearly 50% by volume) and the liquid
`speci?ed in Example 2, according to the following ta
`ble.
`Fluid according to
`
`25
`
`Example 2
`' % by volume
`
`Prevent
`% by volume
`
`Freezing point
`°C.
`
`100
`75
`50
`25
`0
`
`O
`25
`50
`75
`100
`
`5
`It is difficult to determine and specify a classically
`understood freezing point in solution according to the
`present invention, because the liquid is rather viscous in
`this concentration range, and it changes gradually to a
`state resembling a glass-type consistency. Therefore, no
`well de?ned freezing point can be determined experi
`mentally at that concentration. Thus as used herein,
`“freezing point” refers rather to the temperature at
`which with decreasing temperature ice crystals will
`?rst start to appear, and “solidi?cation point” refers to
`the point where the liquid phase disappears.
`A further object of this invention is to provide a
`composition which is suitable for use at more moderate
`frost resistance requirements, wherein sodium cations
`are used instead of potassium cations, In this case the
`use of other freezing point depressing components is
`such as of urea, also becomes necessary. In this embodi
`ment of the invention ethylene glycol may also be used.
`By the use of this liquid the disadvantages of using
`glycol are only partly eliminated. A frost resistance of
`about —30° C. can be achieved with the liquid if the
`concentrations of the acetate and formate anions are
`nearly the same and the mass concentration of urea and
`optionally of glycol approach of reach that of the for
`mate and acetate ions.
`A particularly advantageous coolant composition in
`accordance with the present invention comprises from
`about 3 to about 9 parts by weight water, from about 1
`to about 2 parts by weight potassium formate, from
`about 1 to about 9 parts by weight potassium acetate,
`from O to about 1.5 parts by weight urea, and from 0 to
`about 1.5 parts by weight of a glycol.
`Both coolant varieties can optionally be mixed in any
`ratio with a glycol based coolant, with the result that
`the well known disadvantages of glycol are proportion
`ate to the increasing glycol content of the mixture.
`Fluid compositions according to the invention can be
`produced in several varieties on the basis of the princi
`ples and data described above. Nevertheless, the follow
`ing illustrative examples set forth some speci?c compo
`sitions and properties of the coolant liquids of the pres
`ent invention.
`
`It can be seen that even if interpolation is not possible,
`the characteristics assume intermediate values which
`change monotonously with the ratio of the two compo
`nents. The viscosity values change in a similar manner.
`The viscosity of the liquid of Example 2 is lower at all
`temperatures than that of the glycol-based frost resis
`tant liquid and it can be pumped even at a temperature
`below — 30° C., i.e. it is fluid throughout above its freez
`ing point. It is also important that at any composition
`the liquid mixture freezes without expansion.
`Any variety of the liquid compositions according to
`the invention, such as of the Examples, can ‘also be
`produced from the formate and acetate salts as starting
`materials prepared separately by mixing the appropriate
`acid and base, or can be obtained from commercial
`sources. The process according to the examples is con
`sidered to be more advantageous because generally the
`acids and bases are available as the more easily accessi
`ble basic materials.
`Consequently, the advantages of coolants of the pres
`ent invention, as demonstrated quantitatively in the
`examples, is that the disadvantages resulting from the
`use of glycol in the conventional glycol water coolant
`can be partly eliminated in certain embodiments of the
`coolant compositions of the invention and fully in oth
`ers, without impairing the advantages of the conven
`tional coolants. In fact in employing the glycol-free
`embodiments of the invention, frost resistance and ?uid
`ity improve signi?cantly when compared with the con
`ventional coolants, and thereby the temperature range
`usefulness of the coolant is signi?cantly broadened.
`A further advantage was achieved by the glycol-free
`embodiments of the coolants of the present invention,
`
`EXAMPLE 1
`Frost Resistant Coolant with Reduced Glycol Content
`42.6 parts by weight of water, 14.9 parts by weight of
`sodium hydroxide, 10.6 parts by weight of urea, 11.0
`parts by weight of glycol, 10.9 parts by weight of 98%
`formic acid and 10.9 parts by weight of 99.5% acetic
`acid have been mixed, and to this mixture 5 g of Na
`50
`benzoate and l g of benzotriazole inhibitor has been
`added per liter of coolant. The characteristics of the
`resulting coolant are pH: 7.2, density at 20“ C.: 1.210
`g/cm3, boiling point: 111° C., viscosity at 20° C.: 5.9
`cSt, at 99° C.: 1.2 cSt, speci?c heat at 25° C.: 3.9 J/°C.
`cm3 or 3.2 J/°C.g. The solidi?cation point of the cool
`ant is at —35° C., with starting turbidity at —-28° C. The
`fluid freezes without expansion.
`EXAMPLE 2
`Glycol Free Environmentally Friendly Frost Resistant
`Coolant
`407 g of potassium hydroxide, 56.2 ml of 98% formic
`acid, 353.4 ml of 99.5% acetic acid and 807 ml of water
`have been mixed to form a premix, and the inhibitor
`additive described in Example 1 was added to the pre
`mix. The resulting liquid had the following characteris
`tics: pH 9.3, freezing point --45“ C., boiling point 110°
`
`65
`
`55
`
`PAGE 4 of 5
`
`PETITIONER'S EXHIBIT 1325
`
`

`
`7
`because the components that are employed cannot poly
`merize or be subjected to acidic decomposition. The
`coolants of the present invention can be need much
`larger than conventional coolants, increasing industrial
`safety, and decreasing costs.
`Comparative freezing point experiments were con
`ducted in which a saltwater molar ratio of 1:4.72 was
`employed throughout. The acetate and formate of po
`tassium were employed, as indicated. I
`
`Molar ratio within salt
`Acetate to Formats
`Freezing point ‘C.
`
`allznone
`nonezall
`6:1
`9:1
`1:2
`5:1
`
`-38
`—35
`-70
`—57
`—48
`—63
`
`20
`
`5,104,562
`8
`4. The coolant composition of claim 1, further com
`prising from about 0.1 to about 1.0 percent by mass of a
`corrosion inhibitor.
`'
`5. The coolant composition of claim 4, wherein said
`corrosion inhibitor is one or more of benzoic acid, so
`dium benzoate, potassium benzoate, and benzotriazole.
`6. Thecoolant composition of claim 1, comprising
`from about 4 to about 6 times as much of the potassium
`acetate than the potassium formate.
`7. The 'coolant composition of claim 6, which com
`prises at least about 30 percent by mass of water.
`8. A process for cooling apparatus in need of cooling
`with a liquid coolant, which comprises disposing within
`a space in the apparatus adapted to contain a liquid
`coolant, a coolant which is an aqueous solution of about
`1 to about 2 parts by weight of potassium formate, and
`potassium acetate.
`9. The process of claim 8, wherein the coolant further
`comprises a water soluble organic compound.
`10. The process of claim 9, wherein said water soluble
`organic compound is one or more of a formamide and
`urea that contains an intensivelyhydrophilic substitu
`
`‘ We claim:
`‘
`1. A coolant composition, comprising from about 3 to
`about 9 parts by weight water, from about 1 to about 2
`parts by weight of potassium formate, from about 1 to
`about 9 parts by weight of potassium acetate, from 0 to
`about 1.5 parts by weight urea, and from 0 to about 1.5
`parts by weight of a glycol.
`2. The coolant composition of claim 1, comprising at
`least about 0.5 parts by weight urea.
`3. The coolant composition of claim 1, comprising
`from about 4 to about 7 parts by weight potassium ace
`tate and from about 1 to about 1.5 parts by weight potas
`sium for'mate.
`
`. £111.
`
`11. The process of claim 10, the coolant further com
`prising a glycol coolant ingredient.
`12. The process of claim 11, wherein said glycol cool
`ant ingredient is ethylene glycol.
`13. The process of claim 8,‘ the and said coolant fur
`ther comprising a corrosion inhibitor.
`14. The process of claim 8, wherein the water content
`of the coolant is adjusted according to the frost resis~
`tance desired.
`
`* i i
`
`it
`
`i
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`PAGE 5 of 5
`
`PETITIONER'S EXHIBIT 1325