Cooling liquid and preparation method thereof

Abstract

The invention discloses a cooling liquid and a preparation method thereof, and the cooling liquid comprises the following components in percentage by mass: 40.00-60.00% of ethylene glycol, 0.1-1.0% of organic alkali, 0.5-2.0% of composite corrosion inhibitor, 0.0001-0.001% of pigment, 0.0001-0.001% of defoaming agent and the balance of pure water. The composite corrosion inhibitor is a nonionic composition of aromatic acid Schiff base, organosilane and an azole substance in a mass ratio of 1: (0.5-0.8): (0.5-1.2). The aromatic acid Schiff base contains an aromatic ring pi bond, a substituent hydroxyl group thereof and a C = N double bond to form a pi-pi-p hyperconjugated system, the electron cloud density of the conjugated system is increased, the adsorbability of oxygen atoms and nitrogen atoms on the metal surface is improved, and metal protection is enhanced. An orderly and tightly arranged silane molecular layer of organosilane and a complex of aromatic acid Schiff base and an azole substance cooperate with each other to form an efficient composite film, and an anti-corrosion layer is formed on the surfaces of copper, aluminum and steel metal through the covalent bond action of Si-O bonds and the surface of a metal oxide layer and the adsorption action of lone pair electrons of oxygen / nitrogen elements on the metal. The efficient corrosion inhibition effect is achieved.

Description

Technical Field

[0001] The invention relates to a coolant for a new energy vehicle, and in particular to a coolant and a preparation method thereof. Background Art

[0002] With the continuous increase in automobile sales, the transportation industry has become one of the main sources of carbon emissions. In order to save energy and reduce emissions, new energy vehicles have developed rapidly. In order to achieve long-term endurance of electric commercial vehicles, mainstream car companies at home and abroad have laid out high-voltage platform architectures. This puts higher safety requirements on the cooling performance of the battery thermal management system. At present, most heavy-duty electric commercial vehicles use internal combustion engine cooling system coolant or traditional engine coolant. Organic antifreeze uses organic matter such as ethylene glycol to lower the freezing point of the coolant, which is suitable for lower temperature environments. At the same time, ethylene glycol is adsorbed on the metal surface to form a film, which plays an isolation and protection role. However, its conductivity is generally above 2000μs / cm. When high-conductivity coolant leaks onto uninsulated circuit boards and electrical connectors, it may cause short-circuit failure of high-voltage electronic devices, damage to equipment, and even cause failure of thermal management of the three-electric system, resulting in high-temperature out-of-control of the battery-battery fire or explosion. In addition, in order to meet the demand for endurance, most new energy vehicles choose lightweight materials. The coolant contacts various types of thin aluminum or non-metallic materials. The corrosion resistance of various materials varies. Traditional coolants generally contain organic, inorganic or metal salt corrosion inhibitors, which leads to high conductivity and increases safety hazards. Any fluid that has direct or indirect contact with the membrane electrode should not contain ions that cause potential harm to the membrane electrode; at the same time, the existing coolant has poor corrosion inhibition effect and compatibility with non-metallic materials such as nitrile rubber and fluororubber. Moreover, during the use of antifreeze coolant, ethylene glycol contacts oxygen to generate oxalic acid, the composition of the antifreeze changes, the pH value decreases, the conductivity of the coolant increases, and the corrosion rate of the device increases. The reduction of ethylene glycol content reduces the antifreeze and anti-boiling properties of the antifreeze. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to reduce the electrical conductivity of the coolant and improve the corrosion inhibition and compatibility of the coolant with various metals or non-metals, and to provide a coolant; another purpose of the present invention is to provide a method for preparing the coolant.

[0004] Technical solution: The coolant of the present invention, calculated by mass percentage, includes 40.00-60.00% of ethylene glycol, 0.1-1.0% of organic base, 0.5-2.0% of composite corrosion inhibitor, 0.0001-0.001% of pigment, 0.0001-0.001% of defoaming agent, and the balance is pure water; the composite corrosion inhibitor is a non-ionic corrosion inhibitor, which is a composition of aromatic acid Schiff base, organic silane, and nitrogen azole substances in a mass ratio of 1: (0.5-0.8): (0.5-1.2).

[0005] Furthermore, the aromatic acid Schiff base has the general formula:

[0006]

[0007] Wherein R1 is a C2-C6 straight chain alkyl or cycloalkyl, R2 and R3 are hydroxyl groups, and the hydroxyl group position can be any substituent position. Aromatic acid Schiff base contains aromatic ring π bond and its substituent hydroxyl group and C=N double bond to form a π-π-p hyperconjugated system. The electron cloud density of the conjugated system increases, which improves the adsorption of oxygen atoms and nitrogen atoms on the metal surface and enhances the protection of the metal.

[0008] Furthermore, the nitrogen azole substance is one of benzotriazole and methylbenzotriazole, which contains a benzene ring and a nitrogen atom, has a π bond and a lone pair of electrons, is easily adsorbed on the surface of various metals or alloys, and complexes with the metal in the form of covalent bonds and coordination bonds to form a protective film to prevent metal corrosion.

[0009] Further, the organosilane is one of aminopropyl triethoxysilane, methyl trimethoxysilane, and vinyl trimethoxysilane. The organosilane forms an orderly and closely arranged silane molecular layer on the metal surface through the covalent bond of the SI-O bond and the adsorption of the lone pair of electrons of the N element on the metal. The organosilane is bonded to the complex of the aromatic acid Schiff base and the nitrogen azole complex to form an efficient composite film technology on the metal surface. The orderly and closely arranged silane molecular layer makes the composite film more uniform and tight, ensuring the coverage of the composite film on the metal surface; the aromatic acid Schiff base complex and the nitrogen azole complex complex complex the metal ions on the surface of the metal or alloy in different ways, so that more metal ions participate in the complexation, increase the bonding force between the composite film and the metal surface, and cover a wider area, with high coverage and large bonding force. Through the covalent bond of the SI-O bond on the surface of the metal oxide layer and the adsorption of the lone pair of electrons of the oxygen element / nitrogen element on the metal, it has a highly efficient corrosion inhibition effect on copper, aluminum and steel metals at the same time. In addition, the composite corrosion inhibitor is non-ionic and has no ionic groups introduced, which greatly reduces the electrical conductivity and further enhances the corrosion inhibition effect on copper, aluminum and steel metals.

[0010] Furthermore, the organic base is one of triethanolamine, triisopropanolamine, and cyclohexyldiethanolamine. A certain amount of organic base with good alkali reserve capacity is added to maintain the pH value in the alkaline range for a long time, thereby buffering the influence of the coolant oxidation acidification on metal corrosion.

[0011] Furthermore, the pigment is an azo dye Congo red, which gives the coolant a striking color to prevent misuse, and once leakage occurs during use, it can be discovered and handled in time.

[0012] Furthermore, the defoaming agent is a GPE type polyether copolymerized with ethylene oxide and propylene oxide, with a molecular weight of 3000, which can promptly and effectively treat the steam drum generated in the coolant to ensure the normal use of the coolant.

[0013] The method for manufacturing the coolant of the present invention comprises the following steps:

[0014] (S1) pure water and ethylene glycol are heated and stirred to mix;

[0015] (S2) adding an organic base and an organosilane, and continuing to heat, stir and mix;

[0016] (S3) adding aromatic acid Schiff base and nitrogen azole substances, and continuing to heat, stir and mix;

[0017] (S4) adding pigment and stirring and mixing at room temperature;

[0018] (S5) adding a defoaming agent and stirring and mixing at room temperature.

[0019] Furthermore, the heating and stirring temperature of steps (S1), (S2) and (S3) is 50-60°C. The appropriate heating temperature is beneficial to the stability and solubility of various additives, promotes the aromatic acid Schiff bases and nitrogen azole substances to form complexes with metal ions and combine with the orderly and tightly arranged silane molecular layer of the organic silane to form an efficient composite film.

[0020] Furthermore, the pigment and defoamer in steps (S4) and (S5) are pre-dissolved with ethylene glycol in an amount 10 times their own weight before being added. The pre-dissolution of ethylene glycol makes it easier to dissolve and mix into the mixed solution of other components, thereby increasing the stability of the coolant.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The aromatic acid Schiff base contains the aromatic ring π bond and its substituent hydroxyl group and the C=N double bond to form a π-π-p hyperconjugated system, and the electron cloud density of the conjugated system is increased, which improves the adsorption of oxygen atoms and nitrogen atoms on the metal surface and enhances the protection of the metal; 2. The orderly and closely arranged silane molecular layer of the organic silane cooperates with the complex of the aromatic acid Schiff base and the nitrogen azole substance to form a high-efficiency composite film, which is bonded to the metal oxide layer through the covalent bond of the Si-O bond. The lone pair electrons of oxygen and nitrogen are used to adsorb metals to form an anti-corrosion layer on the surface of copper, aluminum and steel metals, which plays a highly efficient corrosion inhibition role; 3. The non-ionic composite corrosion inhibitor does not introduce ionic groups, which reduces the conductivity of the coolant, and the conductivity is lower than 100uS / cm; 4. The coolant has good corrosion inhibition effect and good compatibility with non-metallic materials; 5. Polyester-grade ethylene glycol is used, and the additives do not contain boron, nitrite, nitrate and heavy metal elements, which meets the environmental protection requirements of ELV, RoHS and Reach. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described in detail below in conjunction with specific embodiments. Unless otherwise specified, all reagents used are commercially available reagents, ethylene glycol meets the quality specifications of GB / T 4649-2018 superior products, and pure water meets the quality specifications of GB / T 6682-2016 grade tertiary water.

[0023] Example 1

[0024] The present embodiment provides a coolant with a freezing point of -25°C, and the coolant composition is as follows (mass percentage): 40.00% ethylene glycol, organic base: 0.8% cyclohexyldiethanolamine, composite corrosion inhibitor: 0.25% ethylenediamine Schiff base of p-hydroxybenzoic acid, 0.125% methyltrimethoxysilane, 0.125% methylbenzotriazole, 0.0001% azo dye Congo red, defoaming agent: 0.0001% of ethylene oxide and propylene oxide copolymer GPE type polyether, and the balance is 58.9898% pure water.

[0025] The method for preparing the above-mentioned coolant comprises the following steps:

[0026] (S1) Add pure water and ethylene glycol into the stirring kettle, start stirring, and heat and control the temperature to 50-60°C

[0027] (S2) adding cyclohexyldiethanolamine and methyltrimethoxysilane and stirring for 60 min;

[0028] (S3) adding ethylenediamine p-hydroxybenzoate Schiff base and methylbenzotriazole, and stirring for 60 minutes;

[0029] (S4) turning off the heating, pre-dissolving the azo dye Congo red with 10 times the mass of ethylene glycol, adding the pre-dissolved azo dye Congo red into the stirred tank, and stirring for 30 minutes;

[0030] (S5) The ethylene oxide and propylene oxide copolymer GPE type polyether is pre-dissolved in 10 times the mass of ethylene glycol and then added into a stirring tank and stirred for 30 minutes.

[0031] Example 2

[0032] The present embodiment provides a coolant with a freezing point of -35°C, and the coolant composition is as follows (mass percentage): 50.00% ethylene glycol, organic base: 1.0% triisopropanolamine, composite corrosion inhibitor: 0.25% Schiff base of m-hydroxybenzoic acid butanediamine, 0.20% vinyl trimethoxysilane, 0.3% benzotriazole, 0.0005% azo dye Congo red, defoaming agent: 0.0005% GPE type polyether copolymerized with ethylene oxide and propylene oxide, and the balance is 48.499% pure water.

[0033] The preparation method of the above cooling liquid is the same as that of Example 1.

[0034] Example 3

[0035] The present embodiment provides a coolant with a freezing point of -45°C, and the coolant composition is as follows (mass percentage): 60.00% ethylene glycol, organic base: 0.1% triethanolamine, composite corrosion inhibitor: 1.0% o-hydroxybenzoic acid cyclohexanediamine Schiff base, 0.5% aminopropyl triethoxysilane, 0.5% benzotriazole, 0.001% azo dye Congo red, defoaming agent: 0.001% ethylene oxide and propylene oxide copolymer GPE type polyether, and the balance is 39.848% pure water.

[0036] The preparation method of the above cooling liquid is the same as that of Example 1.

[0037] The coolants with different freezing points prepared in the above Examples 1-3 are environmentally friendly coolants that comply with ELV, RoHS, and Reach. The above coolants were subjected to conductivity tests (see Table 1), and the corrosion inhibition performance test results with red copper, brass, 20# steel, 3003 aluminum alloy, 4043 aluminum alloy, and 6063 aluminum alloy were tested (see Table 1).

[0038] Compared with Examples 1 to 3, the appearance, color, density, freezing point, boiling point, pH value, conductivity, and static corrosion performance all meet the performance requirements of "GB 29743.2 Motor Vehicle Coolant Part 2: Electric Vehicle Coolant". Examples 1 to 3 are all low-conductivity coolants that can meet the safe operation of the three-electric cooling system of electric vehicles, and have a good protective effect on the metal and non-metal materials in the three-electric cooling system. The composite corrosion inhibitor is selected from non-ionic type, and no ionic groups are introduced, and the conductivity is greatly reduced, which further strengthens the corrosion inhibition effect on copper, aluminum and steel metals. It has low conductivity safety performance, efficient metal (copper, aluminum, steel) corrosion protection performance, multiple non-metal (nylon resin, polyphenylene sulfide resin, EPDM rubber, silicone rubber) compatibility and excellent anti-scaling performance for the thermal management system of batteries, motors and electronic controls.

[0039] In Examples 1 to 3, the aromatic acid Schiff base contains the aromatic ring π bond and its substituent hydroxyl group and C=N double bond to form a π-π-p hyperconjugated system. The electron cloud density of the conjugated system increases, which improves the adsorption of oxygen atoms and nitrogen atoms on the metal surface and enhances the protection of the metal. The organosilane forms an orderly and tightly arranged silane molecular layer on the metal surface through the covalent bond between the SI-O bond and the surface of the metal oxide layer and the adsorption of the lone pair of electrons of the N element on the metal. The technology of forming an efficient composite film on the metal surface by the complex of organic silane bonded aromatic acid Schiff base and nitrogen azole complex. The ordered and tightly arranged silane molecular layer makes the composite film more uniform and tight, ensuring the coverage of the composite film on the metal surface; the complex of aromatic acid Schiff base and nitrogen azole complex complexes the metal ions on the surface of metal or alloy in different ways, so that more metal ions participate in the complexation, increase the binding force between the composite film and the metal surface, cover a wider area, have a high coverage rate and a large binding force, and play an efficient corrosion inhibition role on copper, aluminum and steel metals at the same time through the covalent bond of SI-O bond on the surface of metal oxide layer and the adsorption of lone pair electrons of oxygen / nitrogen element on metal. In addition, the composite corrosion inhibitor is non-ionic, no ionic groups are introduced, the conductivity is greatly reduced, and the corrosion inhibition effect on copper, aluminum and steel metals is further enhanced.

[0040] Table 1 Coolant conductivity and corrosion inhibition performance test results

[0041]

[0042] Compared with Examples 1 to 3, the conductivity of Examples 1 and 3 is relatively low. At this time, the ratio of aromatic acid Schiff base, nitrogen azole and organosilane in the composite corrosion inhibitor is 2:1:1. The complex of aromatic acid Schiff base and nitrogen azole complex are complexed with more metal ions on the surface of metal or alloy in different ways, and then form a composite film with the regular and orderly silane molecules of organosilane with a suitable ratio, so that the bonding force between the composite film and the metal surface is stronger and the coverage area is wider. The high coverage and strong bonding force together ensure the corrosion inhibition effect of the composite corrosion inhibitor on copper, aluminum and steel metals. The freezing point temperature of the coolant is adjusted by adjusting the amount of ethylene glycol, and the amount of the composite corrosion inhibitor is increased according to the increase in the amount of ethylene glycol, so that it meets the use environment while reducing the conductivity, ensuring the corrosion inhibition effect on various types of thin aluminum or non-metallic materials.

[0043] The compatibility of the coolants with different freezing points prepared in the above Examples 1-3 with EPDM rubber was tested, taking EPDM rubber as an example (see Table 2).

[0044] Table 2 Coolant compatibility test results

[0045]

[0046] Comparing Examples 1 to 3 with commercial coolants, the volume changes and hardness changes are small, and the compatibility with non-metallic materials is good.

Claims

1. A cooling liquid, characterized in that: Calculated by mass percentage, it includes 40.00-60.00% of ethylene glycol, 0.1-1.0% of organic base, 0.5-2.0% of composite corrosion inhibitor, 0.0001-0.001% of pigment, 0.0001-0.001% of defoaming agent, and the balance is pure water; the composite corrosion inhibitor is a non-ionic corrosion inhibitor, which is a composition of aromatic acid Schiff base, organic silane, and nitrogen azole substances in a mass ratio of 1: (0.5-0.8): (0.5-1.2).

2. The electric vehicle coolant according to claim 1, characterized in that: The general formula of the aromatic acid Schiff base is: Wherein R1 is a C2-C6 straight-chain alkyl or cycloalkyl group, R2 and R3 are hydroxyl groups, and the position of the hydroxyl group can be any substituent position.

3. The coolant according to claim 1, characterized in that: The organosilane is one of aminopropyltriethoxysilane, methyltrimethoxysilane and vinyltrimethoxysilane.

4. The coolant according to claim 1, characterized in that: The azole substance is one of benzotriazole and methylbenzotriazole.

5. The coolant according to claim 1, characterized in that: The organic base is one of triethanolamine, triisopropanolamine and cyclohexyldiethanolamine.

6. The coolant according to claim 1, characterized in that: The pigment is azo dye Congo red.

7. The coolant according to claim 1, characterized in that: The defoamer is a GPE type polyether copolymerized by ethylene oxide and propylene oxide, and has a molecular weight of 3000.

8. A method for producing the coolant according to any one of claims 1 to 7, characterized in that: The steps include: (S1) pure water and ethylene glycol are heated and stirred to mix; (S2) adding an organic base and an organosilane, and continuing to heat, stir and mix; (S3) adding aromatic acid Schiff base and nitrogen azole substances, and continuing to heat, stir and mix; (S4) adding pigment and stirring and mixing at room temperature; (S5) adding a defoaming agent and stirring and mixing at room temperature.

9. The method for manufacturing a coolant according to claim 8, characterized in that: The heating and stirring temperature of the steps (S1), (S2) and (S3) is 50-60°C.

10. The method for manufacturing a coolant according to claim 8, characterized in that: The pigment and defoamer in steps (S4) and (S5) are pre-dissolved in ethylene glycol with 10 times the mass of the pigment and defoamer before being added.

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