JP2019172774A - Coolant composition - Google Patents

Abstract

To provide a coolant composition that combines antifreeze and cooling performance without the need for ionization additives that lead to increased electrical conductivity.SOLUTION: The coolant composition of the present invention is characterized by containing water, ethylene glycol, and glycol dialkyl ether exhibiting a low critical solution temperature (LCST) type cloud point.SELECTED DRAWING: None

Description

  The present invention relates to a coolant composition.

  Cooling performance and non-freezing properties are required for a coolant for cooling an internal combustion engine of an automobile, a hybrid system, and the like.

  Patent Document 1 describes a coolant composition containing water and a surfactant having a cloud point. In Patent Document 1, this cooling liquid composition is mixed with water and a surfactant in a low temperature range (below the cloud point) to improve antifreeze, and a high temperature range (above the cloud point) where cooling performance is required. ) Describes that water and a surfactant are separated and only water functions as a cooling liquid, so that it exhibits high cooling performance.

  Patent Document 2 describes the use of a composition containing at least one polymer selected from polyetheramines exhibiting a lower critical solution temperature called LCST in the range of 20 to 80 ° C. as an antifreeze agent. ing. Patent Document 2 describes that the composition phase-separates at a temperature exceeding LCST, and the thermal conductivity is remarkably increased.

  Patent Document 3 describes an antifreeze containing at least one of propylene glycol, alkylene glycol monoalkyl ether, and a water-soluble compound having a viscosity of 1 mPa · s or less at 25 ° C. and water. Patent Document 3 describes that this antifreeze liquid retains good low-temperature viscosity despite its high safety and low environmental load. In Patent Document 3, alkylene glycol dialkyl ether is described as a compound that is water-soluble and has a viscosity at 25 ° C. of 1 mPa · s or less.

  In Patent Document 4, a multi-component cooling liquid containing water and an organic solvent is separated into an aqueous phase rich in water components and an organic phase rich in organic components in a low temperature state of 40 ° C. or lower, and 45 ° C. or higher. A coolant is described having a moisture content with an increased organic phase rich in organic components at high temperatures. Patent Document 4 further describes a method of circulating the coolant, in which the organic phase is circulated in a low temperature state, and the homogeneous phase in which the organic phase or the organic phase and the aqueous phase are dissolved is circulated in the high temperature state. ing. Patent Document 4 describes that this coolant has a large apparent specific heat in a high temperature range.

  Patent Document 5 describes a coolant containing methanol and / or glycol ethers, water, and glycols as a coolant for cooling the fuel cell. As specific examples of glycol ethers, alkylene glycol monoalkyl ethers are disclosed.

JP 2010-270256 A Special table 2014-514406 gazette JP 2004-189853 A JP2013-57036A JP2011-8942A

  Since water has a high heat transfer coefficient, a cooling liquid consisting only of water is excellent in terms of cooling performance. However, water freezes when it is below 0 ° C. Therefore, a glycol aqueous solution in which a glycol such as ethylene glycol or propylene glycol is added to water as an antifreezing agent is known as a base for a cooling liquid used even in a cryogenic environment.

Since glycol has a lower heat transfer coefficient than water, the cooling performance of the aqueous glycol solution is inferior to that of water.
Therefore, a coolant composition that satisfies both antifreeze and cooling performance is required.

  On the other hand, a coolant composition for cooling a fuel cell stack, a battery, an electric circuit board and the like is required to have insulating properties. For this purpose, it is desirable that the electric conductivity is low and the resistance is high. For example, a polyetheramine having a lower critical solution temperature called LCST in the range of 20 to 80 ° C. described in Patent Document 2 is ionized in water, and thus a coolant composition containing it has a high electrical conductivity. It is not suitable for applications where insulation is required.

  The present inventors have completed the following composition as a cooling liquid composition having both antifreezing properties and cooling performance without requiring an ionizing additive leading to an increase in electrical conductivity.

The coolant composition of the present invention comprises:
water,
It contains ethylene glycol and a glycol dialkyl ether exhibiting a low critical solution temperature (LCST) type cloud point.

  The glycol dialkyl ether is preferably one or more selected from diethylene glycol diethyl ether and triethylene glycol butyl methyl ether.

  According to the present invention, there is provided a coolant composition that has both antifreeze and cooling performance without requiring an ionizing additive that leads to an increase in electrical conductivity.

FIG. 1 is a schematic diagram showing an outline of a heat transfer coefficient measuring apparatus.

  The coolant composition of the present invention contains water and ethylene glycol as a base material, and further includes the glycol dialkyl ether exhibiting an LCST type cloud point, thereby producing the following effects. The lower critical solution temperature (LCST) refers to a temperature that changes from hydrophilic to hydrophobic as the temperature is raised. Glycol dialkyl ethers exhibiting an LCST type cloud point exhibit hydrophilicity at temperatures below the cloud point and dissolve in water, exhibit hydrophobicity at temperatures above the cloud point, and separate from water to form a dispersed phase in water.

  Under a low temperature condition below the cloud point of glycol dialkyl ether, the cooling liquid composition of the present invention dissolves water, ethylene glycol and glycol dialkyl ether to form a uniform liquid, and ethylene glycol and glycol dialkyl ether. Due to the action, the freezing temperature is lowered and antifreeze is imparted.

  On the other hand, under a high temperature condition higher than the cloud point of glycol dialkyl ether, the glycol dialkyl ether in the cooling liquid composition of the present invention separates from the substrate containing water and ethylene glycol to form a dispersed phase, A liquid continuous phase is formed. That is, under a high temperature condition, a dispersed phase containing glycol dialkyl ether is dispersed in a continuous phase composed of a base material containing water and ethylene glycol. By performing two-phase separation, the apparent ratio of water in the continuous phase increases, and the heat transfer coefficient of the continuous phase becomes higher than the heat transfer coefficient of the entire coolant composition. When heat is transferred through the two-phase separated coolant composition of the present invention, heat is transferred through the continuous phase having a good heat transfer rate, so the influence of the heat transfer rate of the dispersed phase is small, The heat transfer coefficient becomes dominant. For this reason, the cooling fluid composition of the present invention exhibits good cooling performance under high temperature conditions above the cloud point of glycol dialkyl ether.

  In addition, since the glycol dialkyl ether does not ionize in water and does not cause an increase in electrical conductivity, the cooling liquid composition of the present invention is useful for cooling in applications where insulation is required.

  The coolant composition of the present invention may contain at least water, ethylene glycol, and glycol dialkyl ether exhibiting an LCST type cloud point.

  The coolant composition of the present invention may further contain other components. Examples of other components include other glycol compounds such as propylene glycol, and monohydric or trihydric or higher alcohol compounds. The cooling composition of the present invention preferably does not contain components that ionize in water.

  The cloud point of glycol dialkyl ether showing LCST type cloud point used in the present invention is preferably 0 ° C. or higher and 80 ° C. or lower, more preferably 10 ° C. or higher and 70 ° C. or lower, more preferably 20 ° C. or higher and 50 ° C. or lower. It is as follows.

The glycol dialkyl ether showing the LCST type cloud point used in the present invention preferably has the following formula:
R ¹ — (O—R ³ ) _n —R ²
[Wherein, R ¹ and R ² are each independently preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group or n Most preferably a butyl group,
R ³ is preferably independently an alkylene group having 1 to 3 carbon atoms, more preferably an ethylene group, a 1,2-propylene group or a 1,3-propylene group, and an ethylene group or 1,2 -Most preferably a propylene group,
n is preferably an integer of 1 to 4, particularly preferably 2 or 3. ]
And particularly preferably one or more selected from diethylene glycol diethyl ether and triethylene glycol butyl methyl ether.

  In addition, since the cooling liquid composition which mix | blended polyoxyalkylene alkyl ether (nonionic surfactant which shows LCST type | mold cloud point) instead of said glycol dialkyl ether becomes large in foaming property, in a cooling fluid path | route Therefore, there is a problem that the air phase is easily mixed and the heat transfer rate is lowered (see Comparative Examples 3 to 5). The cooling liquid composition in which polyetheramines are blended in place of the glycol dialkyl ether has a problem that it has a high electrical conductivity and is not suitable for applications requiring insulation (see Comparative Examples 6 and 7). The cooling liquid composition in which polyethers are blended in place of the glycol dialkyl ether has a problem that the viscosity becomes high and the load on the liquid feeding pump increases, and heat transferability under high temperature conditions is inferior. (See Comparative Examples 8 and 9). The cooling liquid composition in which glycol monoalkyl ether is blended in place of the above-mentioned glycol dialkyl ether has a problem of poor heat transfer under high temperature conditions (see Comparative Examples 10 to 13).

  The mixing ratio of water, ethylene glycol, and glycol dialkyl ether showing LCST type cloud point in the cooling liquid composition of the present invention is not particularly limited, but the ratio of water: ethylene glycol to the total amount of the cooling liquid composition is Preferably, it is 80:20 to 55:45, more preferably 75:25 to 60:40, water is preferably 25 to 75% by weight, more preferably 30 to 65% by weight, and ethylene glycol is preferably 10 The glycol dialkyl ether exhibiting an LCST type cloud point is preferably 5 to 50% by weight, more preferably 20 to 50% by weight. More preferably, the total amount of water, ethylene glycol, and glycol dialkyl ether exhibiting an LCST type cloud point is preferably 80% by weight or more, more preferably 85% by weight or more, and more preferably 90% by weight based on the total amount of the coolant composition. % By weight or more, more preferably 95% by weight or more, more preferably 98% by weight or more.

The coolant composition of the present invention more preferably has the following physical properties:
(1) The cloud point is 0 to 80 ° C.
(2) having fluidity at −35 ° C.
(3) Heat transfer coefficient is larger than 50% aqueous solution of ethylene glycol,
(4) The 25 ° C. foaming property measured by the method defined in JIS K2234: 2006 is 4 mL or less, and
(5) One or more, more preferably 2 or more, more preferably 3 or more, more preferably 4 or more, and most preferably all of the electrical conductivity is 10 μS / cm or less. The measuring method of each physical property is as described in the examples.

  Hereinafter, embodiments of the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples.

  A cloud point, -35 degreeC fluidity | liquidity, 88 degreeC heat-transfer coefficient ratio, 25 degreeC electrical conductivity, 25 degreeC foaming property, and 25 degreeC viscosity were measured in the following procedures.

<Cloud point>
The test liquid was heated from room temperature, and the phase separation behavior of the test liquid was visually confirmed. The temperature at which phase separation began was read from the thermocouple and used as the cloud point.

<-35 ° C fluidity>
A glass container containing 30 g of the test solution was placed in a thermostatic bath maintained at −35 ° C., taken out after 4 hours, tilted to the side, and observed for fluidity. When the glass container containing the test solution was tilted, the liquid level of the test solution moved (sagging) was defined as “fluidity”, and when it did not move (sagging), “solidification” was defined.

<88 ° C heat transfer coefficient ratio>
It measured using the heat transfer rate measuring apparatus 20 shown in FIG.
The piping 21 in the apparatus 20 was filled with the test solution, and the test solution was circulated at a flow rate of 0.5 L / min using the pump 22. The flow rate was monitored by a flow meter 23. Water in the water tank A24 is heated by a heater (not shown) while being stirred by the stirrer 25, and has a role of keeping the test solution in the pipe 21 at a constant temperature. When the temperature of the test solution reached 88 ° C., pure water was poured into the water tank B26 and stirred with the stirrer 27. The time (min) until the temperature of pure water in the water tank B26 was changed from 25 ° C. to 35 ° C. was measured by the test solution passing through the pipe 21. From the following formula (1), the temperature rise rate (° C./min) of pure water in the water tank B26 by the test solution passing through the pipe 21 was obtained. In the same procedure, the rate of temperature increase (° C./min) when a 50 wt% ethylene glycol aqueous solution (EG 50 wt%) was used was determined. The ratio (88 ° C. heat transfer coefficient ratio) (%) of the temperature rise rate (° C./min) of the test solution to the temperature rise rate (° C./min) of EG 50 wt% was obtained by the following equation (2).

(1) Temperature rise rate (° C./min)=ΔT/t
(ΔT: pure temperature change (° C.), t: time required to heat pure from 25 ° C. to 35 ° C. (min))
(2) 88 ° C. heat transfer coefficient ratio (%) = (temperature rise rate of test solution / temperature rise rate of EG 50 wt%) × 100

<25 ° C electrical conductivity>
After the test solution was treated with an ion exchange resin, the temperature of the solution was adjusted to 25 ° C.
Electric conductivity at 25 ° C. was measured using a personal SC meter SC72 manufactured by Yokogawa Electric Corporation and a detector SC72 SN-11 (for pure water).

The following ion exchange resin was used.
The anion exchange resin is DIAION SA10A OH type manufactured by Mitsubishi Chemical Corporation. The cation exchange resin is DIAION SK1B H type manufactured by Mitsubishi Chemical Corporation. 1.4 g of exchange resin mixed at 8: 2) was added and stirred for 10 minutes.

<25 ° C foaming property>
It was measured according to Japanese Industrial Standards JIS K2234: 2006 antifreeze “foamability”.

<25 ° C viscosity>
Measurement was performed under the following conditions using a rheometer (MCR 102 manufactured by Anton Paar).
Measurement temperature: 25 ° C
Shear rate: 100s ^-1 constant Plate type: Parallel plate Plate diameter: 49.969mm
Gap: 0.5mm

<Composition and evaluation result of test solution>
Compositions (% by weight) of Examples 1 and 2 and Comparative Examples 1 to 13, cloud point, -35 ° C fluidity, 88 ° C heat transfer ratio, 25 ° C electrical conductivity, 25 ° C foaming property, 25 ° C viscosity The measured values are shown in the following table.

Claims (2)

water,
A coolant composition comprising ethylene glycol and a glycol dialkyl ether exhibiting a low critical solution temperature (LCST) type cloud point.   The coolant composition according to claim 1, wherein the glycol dialkyl ether is one or more selected from diethylene glycol diethyl ether and triethylene glycol butyl methyl ether.

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