JP2012241018A - Heat transfer medium comprising corrosion-resistant ionic liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer medium that, when used as a coolant, an anti-freeze, an antifreezing agent, a snow-melting agent or the like, suppresses corrosion of a substrate brought into contact therewith, is excellently heat-resistant, is liquid at ordinary temperature and fluid even at a low temperature, and reduces environmental loads.SOLUTION: The heat transfer medium comprises an ionic liquid represented by formula (I) (wherein R, R, Rand Rare each independently a 1-5C linear or branched alkyl group, or a functional group represented by the formula: -R-A (wherein Ris a 1-10C linear or branched alkylene group; and A is a functional group) and one to four of R, R, Rand Rare a functional group represented by the formula: -R-A; Xis an anion; A is a functional group affinitive to a substrate surface to be modified while the anion Xbears a functional group affinitive to the medium; and alternatively, A is a functional group affinitive to the medium while the anion Xbears a functional group affinitive to the substrate surface to be modified).

Description

  The present invention relates to a heat medium using an ionic liquid.

  In general, a substance composed of ionic bonds has a high melting temperature, but a substance composed of specific ions is melted at a temperature around room temperature, for example. Such an ionic liquid has the characteristics of being non-volatile and excellent in heat resistance, and further has high thermal conductivity, and in recent years, its application to various uses has become widespread.

  For example, glycols are widely used as cooling mediums such as coolants and antifreezes in cooling systems for internal combustion engines, fuel cells, etc., but ethylene glycol and propylene glycol are used for central nervous system paralysis and chronic liver disease. It is known that it is caused by the above, and is designated as a first-class designated chemical substance in the PRTR method.

  As an alternative to this, by using an ionic liquid as a base, it is possible to obtain a heat medium such as a cooling liquid or an antifreeze liquid that is superior in heat resistance to the case where a glycol such as ethylene glycol is used as a base. In recent years, automotive engines tend to have higher temperatures during operation to improve fuel economy and reduce harmful emissions. An ionic liquid is suitable as a base.

  For example, Patent Document 1 discloses 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium as a coolant for internal combustion engines, fuel cells, and the like. It has been proposed that an ionic liquid such as ethyl sulfate is used as a base and a rust inhibitor such as dipotassium phosphate, potassium sebacate, tolyltriazole, sodium nitrate is used in combination.

  In addition, the use of ionic liquid as a heat medium (working medium) of a heat pipe device is also being studied. The assumed operating temperature range of the heat pipe device is about -20 to 200 ° C. When water having a large latent heat of vaporization and excellent environmental performance and cost is used as the working medium of the heat pipe, it freezes when the operating temperature is below freezing point, and the operation as a heat pipe stops. Furthermore, the heat pipe may burst due to volume expansion during freezing. For this reason, it is known that water-soluble polymers and glycols are added to prevent freezing in order to prevent freezing. However, the additive itself has a vapor pressure, which may adversely affect the boiling condensation performance of the heat pipe. In addition, the operating temperature range of the heat pipe is limited to the decomposition temperature or less of the additive. In contrast, ionic liquids are non-volatile and have excellent heat resistance, and are therefore suitable as additives for heat pipe working media.

  For example, Patent Document 2 proposes using an aqueous solution of an ionic liquid as a working medium for a heat pipe. As the ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium iodide, and 1-ethyl-3-methylimidazolium trifluorosulfonate are used.

  Conventionally, there is a direct water spray snow melting technique in which a heat medium and snow and ice particles are in direct contact to exchange heat to prevent freezing of a road surface and the like and to melt snow. Examples of the heat medium include water, chlorides such as ethylene glycol, sodium chloride, potassium chloride, and calcium chloride, acetates such as sodium acetate and potassium acetate (Patent Document 4), and a combination of glycerin and a surfactant (Patent Document) 5) Or their aqueous solutions are known.

JP 2010-235889 A JP 2009-145038 A JP-A-60-243186 JP 2003-321668 A JP 2007-161807 A

  However, a heat medium such as a cooling liquid or an antifreeze liquid containing an ionic liquid as a base is corrosive to metals by the ionic liquid. For example, when the ionic liquid is ionized and the dissociated ions act on the metal surface, the corrosiveness of the metal used in the heat exchange device is increased and corrosion is likely to occur.

  In the technique described in Patent Document 1, a rust preventive agent is added because the ionic liquid used in the examples alone is corrosive to metals, but there is room for improvement in economy and the like.

  Patent Document 3 proposes that a quaternary ammonium salt is used as an anti-freezing solution containing glycol and water, but not an ionic liquid as a corrosion inhibitor. However, since this quaternary ammonium salt has a high pH, it itself has corrosiveness to metals and has a limit in inhibiting corrosion.

  Also in the technique described in Patent Document 2, the ionic liquid used in the examples is corrosive to metals, and further improvement is required for lowering the freezing point.

  Of the conventional antifreezing agents and snow melting agents, ethylene glycol has a concern about toxicity as described above. Since chloride and acetate are crystallized, there are problems such as concentration restrictions, clogging of piping, dust, and the like, and acetate also has problems of odor. As for the combined use of glycerin and surfactant, glycerin is classified as a hazardous material class 4 (flammable liquid) class 3 petroleum by the Fire Service Act, and there are concerns about safety, and it is used in the examples of Patent Document 6 All of the surfactants are solid, and like the chlorides and acetates, there are problems such as concentration limitations, clogging of piping, and dust.

  In addition, chemical substances generally maintain their performance during the period of use, but there are not a few chemical substances that are released into the environment after use. Therefore, microbial enzymes are used in natural environments such as underground and in water. It is desirable to have the suitability of being decomposed into carbon dioxide, water, biomass, etc. by reaction or the like so as not to burden the environment, and in recent years, its importance has been increasing from the viewpoint of environmental protection.

  The present invention has been made in view of the circumstances as described above, and can suppress the corrosion of the substrate that comes into contact with the heat medium such as a cooling liquid, an antifreezing liquid, an antifreezing agent, a snow melting agent, It is an object to provide a heat medium that is non-volatile at high temperatures, has excellent heat resistance and non-flammability, is liquid at room temperature, can suppress clogging of dust, piping, etc., and can also reduce the environmental load. .

  In order to solve the above problems, the heat medium of the present invention is a heat medium that modifies the corrosion resistance of the substrate surface, and is represented by the following formula (I):

(Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a linear or branched alkyl group having 1 to 5 carbon atoms, or a functional group represented by -R ⁵ -A (R ⁵ is a carbon number) 1 to 10 linear or branched alkylene groups, A represents a functional group), and ^{1 to 4} of R ¹ , R ² , R ³ and R 4 are represented by -R ⁵ -A X ⁻ represents an anion, A represents a functional group having an affinity for the surface of the substrate to be modified, an anion X ⁻ has a functional group having an affinity for the medium, or A is a functional group having an affinity with a medium, and an anion X ⁻ has a functional group having an affinity for a substrate surface to be modified.

  In this heat medium, the ionic liquid represented by the formula (I) preferably forms a surface layer on the substrate.

  In this heat medium, A in the formula (I) is preferably a hydroxyl group or a carboxyl group.

In this heat medium, the anion X ⁻ of the formula (I) may have a hydroxyl group, a monocarboxylic acid ion or a dicarboxylic acid ion having 2 to 4 carbon atoms, a hydroxycyclohexanecarboxylic acid ion, or a carbon number of 1 to 3 alkyl sulfonate ions are preferred.

In this heating medium, the anion X ⁻ of the formula (I) is an acetate ion, a glycolate ion, a lactate ion, a tartrate ion, a 1,3,4,5-tetrahydroxycyclohexanecarboxylate ion, or a carbon number of 1 to 3. It is preferable that it is an alkyl sulfonate ion.

  The cooling liquid of the present invention is characterized by containing the above heat medium.

  The antifreeze liquid of the present invention is characterized by containing the above heat medium.

  The antifreezing agent of the present invention is characterized by containing the above heat medium.

  The snow melting agent of the present invention contains the above heat medium.

  According to the heat medium of the present invention, it is possible to suppress the corrosion of the substrate that comes into contact when used as a cooling liquid or an antifreeze liquid, and is non-volatile and excellent in heat resistance even at high temperatures, and is liquid at room temperature, When used as a medium, it has a low freezing point, exhibits fluidity even at low temperatures, and can reduce the burden on the environment.

  According to the heat medium of the present invention, when used as an antifreezing agent or a snow melting agent, it has low corrosiveness, so the influence on the corrosion of the metal in the use environment is small, and it is biodegradable and has an environmental impact. Can also be reduced. In addition, since the ionic liquid is liquid at room temperature, it remains liquid even when water volatilizes and does not become dust, there is no clogging of piping due to solidification, and it can be easily washed off due to its highly water-soluble structure. Is possible. And ionic liquid is nonflammable and highly safe.

It is a figure explaining the anti-corrosion action by the heat carrier of the present invention.

  The present invention is described in detail below.

  The heat medium of the present invention comprises an ionic liquid represented by the above formula (I).

In the formula (I), R ¹ , R ² , R ³ and R ⁴ are each independently a linear or branched alkyl group having 1 to 5 carbon atoms, or a functional group represented by —R ⁵ -A (R ⁵ is A straight chain or branched alkylene group having 1 to 10 carbon atoms, A represents a functional group), and ^{1 to 4} of R ¹ , R ² , R ³ , and R ⁴ are —R ⁵ —A It is a functional group shown by. X ^- represents an anion and has a functional group having an affinity for the substrate surface to be modified to a cation, a functional group having an affinity for the medium in the anion, or an affinity for the medium in the cation. The functional group has a functional group having an affinity for the substrate surface to be modified to an anion, and the functional group having an affinity for the substrate and medium constituting the A or anion X ⁻ may be the same or different. Good.

In the functional group represented by —R ⁵ —A, examples of the alkylene group having 1 to 10 carbon atoms of R ⁵ include a methylene group, an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, a methyltrimethylene group, and pentylene. Group, hexylene group, heptylene group, octylene group, nonylene group, decylene group and the like. Among them, those having 1 to 5 carbon atoms are preferable, those having 1 to 3 carbon atoms are more preferable, and a methylene group and an ethylene group are further preferable.

  A in formula (I) has a functional group having an affinity for the substrate or medium, specifically, for example, a hydroxyl group, an aldehyde group, a ketone group, a carboxyl group, a carbonyl group, a carbamic acid group, an ester group. , Amino group, hydrazine group, nitro group, amide group, urea group, thiocarboxyl group, dithiocarboxyl group, thiocarbamic acid group, dithiocarbamic acid group, thiol group, sulfo group, sulfonyl group, phosphoric acid group, phosphonic acid group, Examples of the functional group include a cyano group and an ether group. Among them, a hydroxyl group or a carboxyl group is preferable.

Among ^{R 1, R 2, R 3} , R 4, functional group represented by -R ⁵ -A is 1-4, introducing 1-4 a functional group represented by -R ⁵ -A Thus, the water solubility of the ionic liquid can be increased. In addition, biodegradability is improved by this functional group, and an ionic liquid excellent in environmental suitability can be obtained.

Examples of the linear or branched alkyl group having 1 to 5 carbon atoms of R ^{1 to} R ⁴ include, for example, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylbutyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group 2,2-dimethylpropyl group. Among them, those having 1 to 3 carbon atoms are preferable, and a methyl group and an ethyl group are more preferable.

When there are two or more functional groups represented by —R ⁵ —A, each A is independent of each other. For example, A may have both a hydroxyl group and a carboxyl group.

  The heat medium of the present invention has a functional group having an affinity for the surface of the substrate to be modified to a cation, a functional group having an affinity for the anion in the anion, or an affinity for the medium in the cation. By having a functional group and a functional group having an affinity for the base material surface to be modified to an anion, a surface layer of an ionic liquid is formed on the base material, and the corrosion inhibiting action can be improved.

  For example, as shown in FIG. 1, binding to the metal surface occurs on the cation side. Specifically, the metal oxide on the metal surface is bonded to the binding functional group (hydroxyl group). On the anion side, since the functional group is a hydrophilic functional group (hydroxycarboxylate ion), the affinity with water is increased. By these actions, it is considered that the ionic liquid forms a layer between the metal and water. Since corrosion occurs when water, oxygen, and metal come into contact with each other, formation of a surface layer of an ionic liquid can reduce such contact and suppress corrosion. This is an example, and for example, it may have a hydrophilic functional group on the cation side and a binding functional group with the substrate surface on the anion side.

  Examples of the bonding mode with the binding functional group to the substrate surface include hydrogen bonding, covalent bonding, coordination bonding, ionic bonding, van der Waals bonding, and the like. In some cases, for example, heat treatment or the like can be performed in order to promote these bonds.

From this point, in the formula (I), as the anion X ⁻ , an anion having a functional group having an affinity for a substrate or a medium, specifically, for example, a monocarboxylic acid ion having 2 to 4 carbon atoms And dicarboxylic acid ions (including hydroxycarboxylic acid ions), hydroxycyclohexanecarboxylic acid ions, alkylsulfonic acid ions, and the like. Of these, acetate ions, glycolate ions, lactate ions, tartrate ions, 1,3,4,5-tetrahydroxycyclohexanecarboxylate ions, and alkyl sulfonate ions having 1 to 3 carbon atoms are preferable.

  The ionic liquid of formula (I) can be obtained with a low melting point and high water solubility by selecting the functional group, characteristic group and anion of the quaternary ammonium cation. It is liquid.

  The ionic liquid of formula (I) has a pour point of preferably −10 ° C. or lower, more preferably −20 ° C. or lower, and still more preferably −50 ° C. or lower. The pour point is a value measured according to JIS K 2269-1980.

  The ionic liquid of formula (I) has a solubility in water at room temperature (25 ° C.) of preferably 150 g / 100 g water or more, more preferably 550 g / 100 g water or more, and further preferably 900 g / 100 g water or more.

  For example, the ionic liquid of formula (I) can have a 28-day BOD degradation degree of 60% or more by a biodegradability test based on the OECD (Economic Cooperation and Development Organization) test guideline 301C method. Among the OECD test guideline 301, the OECD test guideline 301C method is an easily decomposable substance that has a decomposition degree of 60% or more determined from the 28-day biochemical oxygen demand (BOD). Since it is quickly decomposed in an aerobic water environment, it does not remain in the environment and the influence on the environment can be reduced.

  In other words, chemical substances are stable during use, but are often discharged into the environment after use. For example, when used under conditions open to the environment, it is desirable that the biodegradability is high and the environmental load is small. In recent years, environmental problems represented by industrial waste have become serious, and it has become an important responsibility of companies to reduce waste. In this respect, chemical substances with high biodegradability are decomposed by microorganisms without being incinerated after disposal, leading to waste reduction. In the background as described above, the ionic liquid of the formula (I) having high biodegradability contributes to reducing the environmental load.

  Specifically, the ionic liquid of the formula (I) includes organic halogen compounds such as alkylene halohydrins, monohaloalkyl carboxylic acids, alkyl halides, etc. corresponding to the structure of the formula (I), alkyl amines, alkanol amines, amino acids, etc. It can be synthesized by reaction with an amine compound.

For example, in an ionic liquid in which A has a hydroxyl group as a functional group represented by -R ⁵ -A, the organic halogen compound corresponding to the structure of formula (I) and an amine compound are reacted in a solvent such as acetonitrile. After the reaction, the precipitated solid is filtered and washed, and then the next step is anion exchange. When anion exchange is performed, the reaction product obtained is reacted with an acid corresponding to X ⁻ in formula (I) in water. Alternatively, it can be obtained by synthesizing a quaternary ammonium hydroxide salt using an ion exchange resin or the like and then reacting an acid corresponding to X ⁻ in water. As the ion exchange resin to be used, for example, a strongly basic ion exchange resin commercially available for water treatment or catalyst can be used. Then, the target compound can be obtained by distilling off water under reduced pressure and washing.

The ion liquid having a A carboxyl group as a functional group represented by -R ⁵ -A is the organic halogen compound and an amine compound are reacted in a solvent such as acetonitrile at an amine compound over conditions. After the reaction, by treating with an acid having the target anion, the alkylcarboxylic acid amine salt in the quaternary ammonium salt can be converted into a carboxyl group and simultaneously anion exchange can be performed. Depending on the target anion, the obtained quaternary ammonium salt can be obtained by reacting an acid corresponding to X ⁻ in water after synthesizing a quaternary ammonium hydroxide salt using an ion exchange resin or the like. Can do. As the ion exchange resin to be used, for example, a strongly basic ion exchange resin commercially available for water treatment or catalyst can be used. Then, the target compound can be obtained by distilling off water under reduced pressure and washing.

  The heat medium of the present invention is water, methanol, isopropyl alcohol and other alcohol solvents, acetone, methyl ethyl ketone and other ketone solvents, ethyl acetate and other ester solvents, tetrahydrofuran, diisopropyl ether and other ethers as necessary depending on the use conditions. Solvents, amide solvents such as N, N-dimethylformamide, aromatic solvents such as toluene, ethylene glycol, polyethylene glycol, vegetable oils, animal oils, mineral oils, synthetic oils and other additive components Even if it is a configuration containing such various solvents, the heat medium of the present invention acts on the surface of the metal substrate to suppress the problem that the corrosion of the metal is promoted, Heat exchange can be satisfactorily performed.

  Examples of the base material on which the heat medium of the present invention modifies corrosion resistance include equipment parts and devices formed of metal materials. Examples of metal materials include aluminum, copper, iron, zinc, Examples thereof include alloys of these metals such as magnesium, manganese, molybdenum, chromium, nickel, tin, lead. Examples of the medium include water, alcohol solvents such as methanol and isopropyl alcohol, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, ether solvents such as tetrahydrofuran and diisopropyl ether, N, N-dimethyl. Examples include amide solvents such as formamide, aromatic solvents such as toluene, ethylene glycol, polyethylene glycol, vegetable oils, animal oils, mineral oils, synthetic oils, and other additive components.

  The heat medium of the present invention can suppress corrosion, is non-volatile at high temperatures, has better heat resistance than when a glycol such as ethylene glycol is used as a base, is liquid at room temperature, and has a freezing point. Is low and exhibits fluidity even at low temperatures, and can also reduce the environmental burden. For example, it is a base for coolants and antifreezes for devices and equipment used at high temperatures such as internal combustion engines, fuel cells, heat pipes, motors, etc. As anti-freezing agent and snow melting agent by spraying and coating on roads, runways, glass, etc., or spraying and coating on circulating temporary toilets and residential facilities (entrances, doors, toilets, drain traps, etc.) It can be used suitably.

  The coolant or antifreeze using the heat medium of the present invention can be used, for example, by circulating inside a liquid-cooled internal combustion engine such as an automobile engine or a part of a heating heater in a house, and is frozen by lowering the freezing point. It is possible to prevent rupture of capillaries in the radiator.

  By using the heat medium of the present invention as the working medium of the heat pipe device, the working medium does not change or decompose even at high temperatures, and the working medium does not freeze even below freezing, and the heat pipe has a wide operating temperature range from below freezing to high temperatures. An apparatus can be provided. Further, since the ionic liquid has an extremely low vapor pressure, it does not adversely affect the boiling condensation performance of the heat pipe device.

  The heat medium of the present invention forms a surface layer of ionic liquid on the surface of the substrate, thereby suppressing permeation of oxygen and water and reducing corrosivity. Therefore, application to uses other than the above-mentioned cooling liquid, antifreeze liquid, antifreezing agent, and snow melting agent is also possible based on the effect. For example, the heat medium of the present invention can be used as a lubricating oil. This lubricating oil contains a corrosion-resistant ionic liquid as a base oil and can be used on the surface of a member exposed to friction and sliding. In the lubricating oil, if necessary, for example, other base oil components such as mineral oil and synthetic oil and other additives can be appropriately blended.

  This lubricating oil has excellent corrosion control, does not require a corrosion inhibitor, is economically excellent, biodegradable and has a low environmental load, has low vapor pressure even at low viscosity, and has a risk of ignition. In addition, it has excellent heat resistance, has friction characteristics comparable to conventional hydrocarbon lubricants, and can be used for a long time even under extremely severe conditions such as high temperature and vacuum. It has characteristics.

  Therefore, for example, internal combustion engines, torque transmission devices, plain bearings, rolling bearings, ball screws, rolling guide devices such as rolling guide surfaces, clutch built-in rotation transmission devices, power steering devices, oil-impregnated bearings, fluid bearings, compression devices, reciprocating compression Machine, turbocharger, chain, gear, oil pressure, vacuum pump, sputtering deposition equipment, vapor deposition, sublimation vacuum deposition equipment, ion implantation equipment for injection into silicon wafers, liquid crystal, organic EL, plasma, etc. Display element manufacturing equipment used for thin display manufacturing, watch parts, hard disks, refrigerators, cutting, rolling, drawing, rolling, forging, heat treatment, heat medium, washing, etc., shock absorbers, brakes, sealing devices, aircraft And aerospace equipment such as artificial satellites.

  Further, by forming the surface layer of the ionic liquid, effects such as improvement of water wettability and antistatic properties are also expected, and even wider application development is possible due to the effects.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
<Synthesis Example 1>
A compound represented by the following formula was synthesized.

  2-Bromoethanol (167.26 g, 1.34 mol) and dimethylethylamine (293.70 g, 4.02 mol) were reacted in acetonitrile (850 ml) at room temperature for 24 hours. After the reaction, the precipitated solid was filtered off and washed to obtain a quaternary ammonium bromide salt (246.14 g, 1.24 mol).

The obtained quaternary ammonium bromide salt (246.14 g, 1.24 mol) and methanesulfonic acid (257.57 g, 2.68 mol) were reacted in water (600 ml) at room temperature for 24 hours, and then water was distilled off under reduced pressure. A yellow liquid was obtained. The obtained liquid was washed to obtain 158.40 g of the above compound as a colorless transparent liquid.
FT-IR (KBr): 3360cm ^-1 : OH stretching vibration 2923cm ^-1 : CH stretching vibration
_{^{1 H-NMR (D 2 O}} 400MHz): δ 1.24 (t, 3H, CH 3 CH 2 N +), δ 2.72 (s, 3H, CH 3 SO 3 -), δ 3.03 (s, 6H, CH 3 N ⁺ ), δ 3.38 (q, 4H, CH ₂ N ⁺ ), δ 3.95 (t, 2H, N ⁺ CH ₂ CH ₂ OH).
Elemental analysis: Actual measurement C: 39.12% H: 9.09% N: 6.68% S: 15.34%
Theoretical value C: 39.42% H: 8.98% N: 6.57% S: 15.03%
<Synthesis Example 2>
A compound represented by the following formula was synthesized.

  The quaternary ammonium bromide salt (100.00 g, 0.50 mol) obtained in Synthesis Example 1 was dissolved in ion-exchanged water and charged with an ion-exchange resin (Diaion SA10A manufactured by Mitsubishi Chemical Corporation) substituted for OH type. By passing through a column, a quaternary ammonium hydroxide salt (66.05 g, 0.49 mol) was obtained.

The obtained quaternary ammonium hydroxide salt (50.00 g, 0.37 mol) and glycolic acid (56.25 g, 0.74 mol) were reacted with water (100 ml) at room temperature for 24 hours. A liquid was obtained. The obtained liquid was washed to obtain 57.17 g of the above compound as a yellow transparent liquid.
FT-IR (KBr): 3320cm ^-1 : OH stretching vibration 2985cm ^-1 : CH stretching vibration
1580cm ^-1 : COO ^- stretching vibration
¹ H-NMR (D ₂ O 400MHz): δ 1.23 (t, 3H, CH ₃ CH ₂ N ⁺ ), δ 2.98 (s, 6H, CH ₃ N ⁺ ), δ 3.34 (q, 4H, CH ₂ N ⁺ ), δ 3.95 (m, 2H , N + CH 2 CH 2 OH), δ 3.96 (s, 2H, CH 2 COO -).
¹³ C-NMR (D ₂ O 100 MHz): δ 177.85 (CH ₂ C OO ⁻ ).
Elemental analysis: actual measurement C: 49.50% H: 10.25% N: 6.98%
Theoretical value C: 49.72% H: 9.91% N: 7.25%
<Synthesis Example 3>
A compound represented by the following formula was synthesized.

After reacting the quaternary ammonium hydroxide salt obtained in Synthesis Example 2 (50.00 g, 0.37 mol) and acetic acid (44.44 g, 0.74 mol) with water (100 ml) at room temperature for 24 hours, water was distilled off under reduced pressure. As a result, a yellow liquid was obtained. The obtained liquid was washed to obtain 52.43 g of the above compound as a yellow transparent liquid.
FT-IR (KBr): 3330cm ^-1 : OH stretching vibration 2980cm ^-1 : CH stretching vibration
1580cm ^-1 : COO ^- stretching vibration
_{^{1 H-NMR (D 2 O}} 400MHz): δ 1.26 (t, 3H, CH 3 CH 2 N +), δ 1.84 (s, 3H, CH 3 COO -), δ 3.02 (s, 6H, CH 3 N + ), δ 3.38 (q, 4H, CH ₂ N ⁺ ), δ 3.94 (t, 2H, N ⁺ CH ₂ CH ₂ OH).
¹³ C-NMR (D ₂ O 100 MHz): δ 183.09 (CH ₃ C OO ⁻ ).
Elemental analysis: actual measurement C: 54.00% H: 10.98% N: 7.60%
Theoretical value C: 54.21% H: 10.80% N: 7.90%
<Synthesis Example 4>
A compound represented by the following formula was synthesized.

  3-Bromopropionic acid (150.00 g, 0.98 mol) and dimethylethylamine (358.39 g, 4.90 mol) were reacted in acetonitrile (750 ml) at room temperature for 24 hours. After the reaction, the precipitated solid was filtered off and washed to obtain a quaternary ammonium bromide salt (204.76 g, 0.68 mol).

The obtained quaternary ammonium bromide salt (204.76 g, 0.68 mol) and methanesulfonic acid (235.47 g, 2.45 mol) were reacted in water (500 ml) at room temperature for 24 hours, and then water was distilled off under reduced pressure. A yellow liquid was obtained. The obtained liquid was washed to obtain 85.60 g of the above compound as a colorless transparent liquid.
FT-IR (KBr): 2961cm ^-1 : CH stretching vibration 1728cm ^-1 : C = O stretching vibration
_{^{1 H-NMR (D 2 O}} 400MHz): δ 1.35 (t, 3H, CH 3 CH 2 N +), δ 2.70 (s, 3H, CH 3 SO 3 -), δ 2.97 (t, 2H, N + CH ₂ CH ₂ COOH), δ 3.10 (s, 6H, CH ₃ N ⁺ ), δ 3.46 (q, 2H, CH ₃ CH ₂ N ⁺ ), δ 3.66 (q, 2H, N ⁺ CH ₂ CH ₂ COOH).
¹³ C-NMR (D ₂ O 100 MHz): δ 171.66 (CH ₂ C OOH).
Elemental analysis: actual measurement C: 39.51% H: 8.12% N: 5.76% S: 12.98%
Theoretical value C: 39.82% H: 7.94% N: 5.80% S: 13.29%
The compounds of Examples other than those shown in the following table were synthesized according to the above synthesis examples. Moreover, the compound of the comparative example used what was synthesize | combined by the well-known method according to said synthesis example.
[Corrosion test]
The test was conducted on a 1/10 scale (1 L → 100 ml) with reference to JIS K 2234. The sample was mixed and adjusted to 22.5 ml of sample and 52.5 ml of water for a total of 75 ml. A 1/10 scale metal piece specified in JIS K 2234 was put into a sample and kept at a liquid temperature of 88 ° C. for 336 hours. After washing, the mass, area, and pH of the solution were measured, and the weight change rate and pH change of the metal pieces were calculated to evaluate the corrosivity. The weight change rate was calculated according to the following formula. When the corrosivity test of ethylene glycol and propylene glycol was conducted by this test method and the weight change rate was calculated, Al was less than 5% and Cu was less than 1%. From these results, Al was less than 5%, and Cu was less than 1% as low corrosivity. The standard value of JIS K 2234 was used for the pH change. Other conditions and test operations conformed to JIS K 2234.

[Biodegradability test]
The biodegradability test was conducted in accordance with the OECD test guideline 301C method. In this test, general activated sludge was used as a microbial source, and 300 mL of the prepared standard test broth was added to a concentration of microbial source 30 mg / l and test substance 100 mg / l, respectively. A period of 28 days was performed using aniline as a standard substance. The decomposition rate was determined by measuring the biochemical oxygen demand (BOD) using an Actac BOD sensor and calculating the degree of decomposition from the calculated theoretical oxygen demand value. Specifically, the case where the BOD degradation degree for 28 days was 60% or more was evaluated as easily degradable.
[Pour point]
The test was conducted in accordance with JIS K 2269-1980. A sample prepared as a 75% aqueous solution was charged to a specified test tube in a volume of 45 mL, placed in a water bath heated to 45 ° C., and then cooled by a specified method. Place the test tube with the equipment set as specified in the cooling bath, and remove the test tube from the cooling bath every time the sample temperature drops from 0 ° C to -70 ° C by 2.5 ° C, and gently incline the sample in the test tube. I confirmed what to do. The temperature at which the sample stopped moving at all for 5 seconds was read, and 2.5 ° C. was added to this temperature to obtain the pour point. The assumed operating temperature range lower limit of −20 ° C. of the heat pipe device was used as an index value.
[Fused ice test]
After putting 20 g of water in a petri dish with a diameter of 90 mm and leaving it in a low temperature constant temperature room at −10 ° C. for 24 hours to obtain ice, 1 g of the sample was sprayed with the temperature kept at −10 ° C. Six hours after spraying, the amount of melted liquid was measured, and the ice melting rate was calculated according to the following formula.

<Examples 1-5, Comparative Examples 1-6>
The compounds shown in Tables 1 to 3 were measured for corrosivity test, biodegradability test, and pour point. Al was used for the metal piece of the corrosion test.

  The results are shown in Tables 1 to 3.

  From Tables 1 to 3, the compounds (ionic liquids) of Examples 1 to 5 are stable in pH in the corrosivity test and have low corrosivity, and are easily decomposable in the biodegradability test. It was below 50 ° C.

On the other hand, Comparative Examples 1 to 3 using a compound that does not have a functional group having an affinity for a substrate or a medium as a cation or an anion have pH fluctuation and corrosivity in a corrosive test. In comparison, the difference was recognized remarkably, and pH variations and corrosivity were also observed in Comparative Examples 4 to 6 using a compound having an imidazole cation (ionic liquid). In all cases, the pour point was higher than that of Examples 1 to 5 and the index value was −20 ° C. or higher, and the degree of BOD degradation in the biodegradability test was less than 60%.
<Examples 6 to 13 and Comparative Examples 7 to 13>
The compounds shown in Tables 4 to 6 were subjected to a corrosivity test, a biodegradability test, and a pour point measurement. Cu was used for the metal piece of the corrosion test.

  The results are shown in Tables 4-6.

  From Tables 4 to 6, the compounds (ionic liquids) of Examples 6 to 13 (including those overlapping with the above) have stable pH and low corrosivity in the corrosive test, and are easily decomposed in the biodegradability test. The pour points were all -50 ° C or lower.

  On the other hand, Comparative Examples 7 to 9 using a compound having no functional group having an affinity for a substrate or a medium as a cation or an anion have pH fluctuation and corrosivity in the corrosive test. In comparison, the difference was remarkably recognized, and furthermore, Comparative Examples 10 to 13 using a compound having an imidazole cation (ionic liquid) also showed pH fluctuation and corrosivity. In all cases, the pour point was higher than that of Examples 6 to 13 and the index value was -20 ° C or higher, and the degree of BOD degradation in the biodegradability test was less than 60%.

As shown in the above results, the compounds of Examples have binding functional groups on the cations and functional groups having affinity with the medium on the anions as shown in FIG. It is considered that the ionic liquid layer was formed on the surface of the metal piece and became significantly less corrosive than the compound of the comparative example because it has a functional group having affinity with the medium for the group and cation. It is done. Thus, the compounds of the examples are particularly suitable as a heat medium for inhibiting corrosion. Further, since all of the pour points are −50 ° C. or less, it is suitable as a cooling liquid or antifreeze liquid.
<Examples 14 to 18>
The compound shown in Table 7 was subjected to an ice melting test. The results are shown in Table 7.

  From Table 7, the ionic liquids of Examples 14 to 18 all show a melting rate of 10% or more, and the pour points are all easily decomposable at -50 ° C. or less. Etc. are suitable.

Claims (9)

A heat medium that modifies the corrosion resistance of the surface of a substrate, which is represented by the following formula (I):
(Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a linear or branched alkyl group having 1 to 5 carbon atoms, or a functional group represented by -R ⁵ -A (R ⁵ is a carbon number) 1 to 10 linear or branched alkylene groups, A represents a functional group), and ^{1 to 4} of R ¹ , R ² , R ³ and R 4 are represented by -R ⁵ -A X ⁻ represents an anion, A represents a functional group having an affinity for the surface of the substrate to be modified, an anion X ⁻ has a functional group having an affinity for the medium, or A is a functional group having an affinity for the medium, and anion X ⁻ has a functional group having an affinity for the surface of the substrate to be modified. .   The heat medium according to claim 1, wherein the ionic liquid represented by the formula (I) forms a surface layer on the substrate.   The heat medium according to claim 1 or 2, wherein A in the formula (I) is a hydroxyl group or a carboxyl group. The anion X ⁻ of the formula (I) is a monocarboxylic acid ion or dicarboxylic acid ion having 2 to 4 carbon atoms which may have a hydroxyl group, a hydroxycyclohexanecarboxylic acid ion, or an alkylsulfonic acid ion having 1 to 3 carbon atoms. The heat medium according to claim 1, wherein the heat medium is a heat medium. The anion X ^{− in the} formula (I) is an acetate ion, glycolate ion, lactate ion, tartrate ion, 1,3,4,5-tetrahydroxycyclohexanecarboxylate ion, or alkyl sulfonate ion having 1 to 3 carbon atoms. The heat medium according to claim 4, wherein the heat medium is present.   A cooling liquid comprising the heat medium according to claim 1.   An antifreeze containing the heat medium according to any one of claims 1 to 5.   An antifreezing agent comprising the heat medium according to claim 1.   A snow melting agent comprising the heat medium according to claim 1.