A mixed organic engine coolant and a method of making the same

Abstract

The application belongs to the technical field of cooling liquid, and provides a mixed organic engine cooling liquid and a preparation method thereof.The cooling liquid comprises the following components in percentage by mass: 75-80% of ethylene glycol, 8-10% of polyethylene glycol-isooctanoic acid copolymer, 2-3% of chelating agent, 0.8-1.0% of corrosion inhibitor, 0.1-0.3% of defoaming agent and deionized water in remainder; the polyethylene glycol-isooctanoic acid copolymer is prepared from polyethylene glycol and isooctanoic acid, and the polyethylene glycol is PEG-2000 with a molecular weight of 2000.The application can ensure that the mixed organic engine cooling liquid has excellent metal corrosion prevention performance when meeting hard water.

Description

Technical Field

[0001] The invention belongs to the technical field of coolants, and in particular relates to a hybrid engine coolant and a preparation method thereof. Background Art

[0002] With the rapid development of the automotive industry, cars have become a fixture in countless households. Simultaneously, the performance requirements for automotive engine coolants are becoming increasingly stringent. Engine coolant, a coolant containing special additives, is used in liquid-cooled engine cooling systems operating under low-temperature conditions. Due to considerations regarding the use and safety of engine coolant, different countries and companies have established different standards to ensure the safety and reliability of engine coolant.

[0003] The development of engine coolants is significantly influenced by the structure and materials used in automotive engines. In recent years, the trend toward higher engine power has been towards higher power. To reduce drag, vehicles have generally adopted streamlined designs, resulting in smaller engine radiators and a continuously increasing heat load on the engine. To reduce vehicle weight and improve fuel economy, aluminum alloys are widely used not only in engine cooling systems, but also in other engine components. With all-aluminum engines now readily available on the market, corrosion protection for aluminum has become a key research focus both domestically and internationally. Phosphates, borates, and nitrites, among traditional inorganic salt additives, are significantly detrimental to corrosion protection of cast aluminum surfaces at high temperatures and can easily cause solder slag. Consequently, silicates are widely used as specific corrosion inhibitors for aluminum. However, silicates are prone to precipitation, clogging waterways and causing engine overheating. Even with the addition of silicate stabilizers, performance remains suboptimal. Consequently, the use of phosphates, borates, ammonium salts, silicates, and nitrites in modern automotive engine cooling systems is strictly restricted, meaning that inorganic coolants no longer meet demand.

[0004] Organic engine coolants developed relatively late compared to inorganic ones. However, compared to conventional inorganic salt corrosion inhibitors, the organic carboxylic acids in existing organic coolants are consumed more slowly, and their corrosion inhibition is primarily achieved through active adsorption. Therefore, organic coolants, with their advantages of low ion concentration, slow consumption, and long service life, will gradually and completely replace inorganic and inorganic-organic hybrid coolants.

[0005] However, the organic carboxylic acids in existing organic engine coolants easily combine with calcium and magnesium ions in water to form precipitates, resulting in the loss of the coolant's effective corrosion inhibition components, which in turn leads to poor maintenance of the metal corrosion protection performance of the organic engine coolant when encountering hard water. Summary of the Invention

[0006] In order to solve the problems existing in the background technology, the present invention provides a hybrid organic engine coolant and a preparation method thereof, which can ensure that the prepared hybrid organic engine coolant has excellent metal corrosion resistance when encountering hard water.

[0007] In order to achieve the above-mentioned objectives, in a first aspect, the present invention provides a hybrid organic engine coolant, which comprises the following components, calculated by mass percentage: 75-80% ethylene glycol, 8-10% polyethylene glycol-isooctanoic acid copolymer, 2-3% chelating agent, 0.8-1.0% corrosion inhibitor, 0.1-0.3% defoaming agent and deionized water as the balance; the polyethylene glycol-isooctanoic acid copolymer is prepared by copolymerization of polyethylene glycol and isooctanoic acid, and the polyethylene glycol is PEG-2000, and its molecular weight is 2000.

[0008] Furthermore, the preparation method of the polyethylene glycol-isooctanoic acid copolymer is as follows:

[0009] A1. Under nitrogen protection, add dehydrated polyethylene glycol and dry isooctanoic acid in a molar ratio of 1:(2.1-2.2) to a reactor, add a catalyst, raise the temperature to 100-105°C, and react for 5-6 hours. During this time, remove the generated water through a water separator to promote the right shift of the reaction equilibrium.

[0010] A2. After the reaction is completed, the temperature is lowered to 70-80°C, acetic acid is added to neutralize the catalyst, and the mixture is stirred for 18-22 minutes to obtain a neutralized solution; toluene is added, the organic phase is separated, and the mixture is distilled under reduced pressure at 160-180°C under a vacuum degree of 0.01 MPa to obtain the polyethylene glycol-isooctanoic acid copolymer.

[0011] Furthermore, in A1, the preparation method of dehydrated polyethylene glycol is: dehydrating polyethylene glycol at 80°C and 0.0095 MPa vacuum for 2 hours to obtain the obtained product; the preparation method of dry isooctanoic acid is: drying isooctanoic acid over 4Å molecular sieves for 24 hours to obtain the obtained product.

[0012] Furthermore, in A1, the catalyst is p-toluenesulfonic acid, and its usage is 0.5-1% of the total mass of dehydrated polyethylene glycol and dry isooctanoic acid.

[0013] Furthermore, in A2, the molar amounts of the acetic acid and the catalyst are equal.

[0014] Furthermore, in A2, the volume ratio of toluene and neutralizing liquid is (0.9-1.1):1.

[0015] Furthermore, the chelating agent includes EDTA or sodium citrate.

[0016] Furthermore, the corrosion inhibitor includes benzotriazole or monobenzothiazole.

[0017] Furthermore, the defoaming agent is polydimethylsiloxane.

[0018] In a second aspect, the present invention provides a method for preparing the above-mentioned hybrid engine coolant, comprising the following steps:

[0019] S1. Ethylene glycol and deionized water were added to a reactor, stirred at 120-150 rpm for 30-50 min, and then polyethylene glycol-isooctanoic acid copolymer and corrosion inhibitor were added in sequence. The mixture was stirred at room temperature for 1 h to obtain a mixed solution 1.

[0020] S2. Add a chelating agent to the mixed solution obtained in S1, stir for 1 hour, then add a defoaming agent, and continue stirring for 15-30 minutes to obtain the mixed organic engine coolant.

[0021] This application has the following beneficial effects:

[0022] In the preparation of the hybrid organic engine coolant of the present invention, polyethylene glycol-isooctanoic acid copolymer and a chelating agent are added. The polyethylene glycol-isooctanoic acid copolymer is prepared by double-end esterification and grafting with polyethylene glycol with isooctanoic acid as the terminal group. The long-chain alkyl group of isooctanoic acid can be oriented on the metal surface to form a hydrophobic layer, which blocks water molecules and corrosive media (O2, H + ) penetration, and at the same time, the ether bond (-O-) of the polyethylene glycol main chain combines with water molecules to form a hydration layer, which prolongs the diffusion path of the corrosive medium and produces a direct hydrophobic barrier effect, achieving double protection and thus obtaining excellent metal corrosion resistance.

[0023] Calcium in hard water 2+ Mg 2+ It can occupy the active sites on the metal surface (such as Fe 2+ 、Al 3+ exposed areas), interferes with the directional arrangement of the alkyl chains of isooctanoic acid, affects its orderliness, weakens the density of the hydrophobic barrier, and causes the metal corrosion resistance to decrease when the coolant encounters hard water. However, the Ca in hard water 2+ Mg 2+ It does not consume polyethylene glycol-isooctanoic acid copolymer like directly consuming organic carboxylic acids. The impact of hard water ions on the copolymer is mainly manifested as physical interference / adsorption competition rather than chemical consumption. Therefore, the decline brought about here is very limited and significantly smaller than the direct consumption of organic carboxylic acids.

[0024] The addition of chelating agents can preferentially complex Ca 2+ Mg 2+ , that is, directly consume the Ca in hard water 2+ Mg 2+, preventing it from occupying the metal active sites, ensuring the complete directional arrangement of the copolymer hydrophobic layer, and thus improving the ability of the prepared hybrid organic engine coolant to maintain the metal corrosion resistance when encountering hard water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 , a comparative trend chart of the metal corrosion resistance related test (mass loss) data of the coolants prepared in Examples 1 to 3 and Comparative Examples 1 to 3 in the test examples of the present invention;

[0026] Figure 2 , a comparative trend chart of the data on the ability to maintain the metal corrosion resistance (loss increase) of the coolants obtained in Examples 1 to 3 and Comparative Examples 1 to 3 in the test examples of the present invention when encountering hard water. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to the embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0029] Example 1: (1) The preparation method of polyethylene glycol-isooctanoic acid copolymer is as follows:

[0030] A1. Dehydrate polyethylene glycol at 80°C and 0.0095 MPa vacuum for 2 h to obtain dehydrated polyethylene glycol. Dry isooctanoic acid over 4Å molecular sieves for 24 h to obtain dry isooctanoic acid. The polyethylene glycol is PEG-2000, with a molecular weight of 2000.

[0031] Under nitrogen protection, dehydrated polyethylene glycol and dry isooctanoic acid were added to the reactor in a molar ratio of 1:2.15, and catalyst p-toluenesulfonic acid was added in an amount of 0.7% of the total mass of dehydrated polyethylene glycol and dry isooctanoic acid. The temperature was raised to 102°C and the reaction was carried out for 5.5 hours. During this period, the generated water was removed through a water separator to promote the right shift of the reaction equilibrium.

[0032] In this step, the molar ratio of dehydrated polyethylene glycol to dry isooctanoic acid is 1:2.15 to ensure complete double-end esterification and avoid single-end esterification byproducts. A nitrogen atmosphere is used to prevent potential side reactions such as oxidative degradation of the polyethylene glycol and decarboxylation of the isooctanoic acid at high temperatures. The temperature is controlled at 102°C to balance reaction rate and safety. Water removal during this process can shift the esterification equilibrium to the right.

[0033] A2. After the reaction is completed, cool to 75°C and add acetic acid to neutralize the catalyst in equal molar amounts. Stir for 20 minutes to obtain a neutralized solution. Add toluene in a volume ratio of 1:1 toluene to the neutralized solution. Separate the organic phase and distill under reduced pressure at 160-180°C under a vacuum of 0.01 MPa for 1.5 hours to obtain polyethylene glycol-isooctanoic acid copolymer.

[0034] (2) A mixed organic engine coolant consisting of the following components, calculated by mass percentage: 78% ethylene glycol, 9% polyethylene glycol-isooctanoic acid copolymer, 2.5% chelating agent, 0.9% corrosion inhibitor, 0.2% defoaming agent and the balance deionized water.

[0035] The preparation method of the hybrid engine coolant comprises the following steps:

[0036] S1. Ethylene glycol and deionized water were added into a reactor, and the mixture was stirred at 130 rpm for 40 min. Then, polyethylene glycol-isooctanoic acid copolymer and corrosion inhibitor were added in sequence, and the mixture was stirred at 80 rpm for 1 h at room temperature to obtain a mixed solution 1.

[0037] S2. Add a chelating agent to the mixed solution obtained in S1, stir at 130 rpm for 1 hour, add a defoaming agent, and stir at 60 rpm for 25 minutes to obtain a mixed organic engine coolant.

[0038] The chelating agent is EDTA, the corrosion inhibitor is benzotriazole, and the defoaming agent is polydimethylsiloxane.

[0039] Example 2: The difference between this example and Example 1 is that: a mixed organic engine coolant, calculated by mass percentage, consists of the following components: 75% ethylene glycol, 8% polyethylene glycol-isooctanoic acid copolymer, 2% chelating agent, 0.8% corrosion inhibitor, 0.1% defoaming agent and deionized water as the balance.

[0040] Example 3: The difference between this example and Example 1 is that: a mixed organic engine coolant, calculated by mass percentage, consists of the following components: 80% ethylene glycol, 10% polyethylene glycol-isooctanoic acid copolymer, 3% chelating agent, 1.0% corrosion inhibitor, 0.3% defoaming agent and deionized water as the balance.

[0041] Comparative Example 1: The difference between this comparative example and Example 1 is that in the components of the mixed organic engine coolant, the polyethylene glycol-isooctanoic acid copolymer is replaced by a mixture of polyethylene glycol and isooctanoic acid; and no chelating agent is added.

[0042] Specifically, a hybrid organic engine coolant is composed of the following components, calculated by mass percentage: 78% ethylene glycol, 9% mixture of polyethylene glycol and isooctanoic acid, 0.9% corrosion inhibitor, 0.2% defoamer and the balance deionized water (the pH of the coolant is adjusted to 9.0 using ammonia water as a pH adjuster).

[0043] The preparation method of the mixture of polyethylene glycol and isooctanoic acid is as follows: dehydrated polyethylene glycol and dry isooctanoic acid are mixed in a molar ratio of 1:2 to obtain the mixture.

[0044] Comparative Example 2: This comparative example differs from Example 1 in that no chelating agent is added to the components of the mixed organic engine coolant.

[0045] Specifically, a mixed organic engine coolant is composed of the following components, calculated by mass percentage: 78% ethylene glycol, 9% polyethylene glycol-isooctanoic acid copolymer, 0.9% corrosion inhibitor, 0.2% defoaming agent and the balance deionized water.

[0046] Comparative Example 3: The difference between this comparative example and Example 1 is that in the preparation of the polyethylene glycol-isooctanoic acid copolymer, the polyethylene glycol is PEG-800; and no chelating agent is added.

[0047] Test Example: Test Object: Example 1-Example 3 and Comparative Example 1-Comparative Example 3 were used to prepare a mixed organic engine coolant.

[0048] Test items and methods: ① Metal corrosion resistance: Tested with reference to ASTM D1384 (SH / T 0085) glassware corrosion test.

[0049] The specific method is as follows: assemble the cast aluminum test pieces in the order specified by the standard, then immerse the test pieces in beakers filled with the coolant of each test object (blank group, hard water group), and assemble the rubber stopper, thermometer, gas diffusion tube and reflux condenser as required. The diffusion head of the gas diffusion tube should be kept at a certain distance (about 13mm) from the test piece bundle to prevent the incoming air from directly contacting the test piece bundle. Place the assembled beaker on the heater, connect the water, electrical and gas lines, and continue the experiment at a temperature of 88±2℃ and an air flow of 100±10mL / min for 336 hours. After special treatment, weigh and calculate the weight loss (mass loss) value of the test piece before and after the experiment. The smaller the weight loss (mass loss) value of the blank group, the better the metal corrosion protection performance of the corresponding test object coolant.

[0050] According to BS 5117-1.5:1992, a prepared calcium chloride and magnesium sulfate solution (calcium chloride concentration: 0.24 mol / L, magnesium sulfate concentration: 0.06 mol / L) was diluted 50-fold with distilled water to obtain the test hard water. The blank group was prepared by mixing the test solution with deionized water in a 1:1 mass ratio. The hard water group was prepared by mixing the test solution with the test hard water in a 1:1 mass ratio.

[0051] ② Hard water resistance: Calculate the loss growth using the formula: Loss growth = mass loss of the hard water group - mass loss of the blank group. The smaller the value, the better the hard water resistance, which means the metal's ability to maintain anti-corrosion properties when encountering hard water is better.

[0052] Test results: See Table 1.

[0053] Table 1. Test result data of test examples

[0054]

[0055] Result analysis: analyze examples 1-3 in combination with table 1 data and Figure 1-Figure 2 It can be seen that the metal corrosion resistance of the mixed organic engine coolant prepared in the present application (examples 1-3) is excellent, and the metal corrosion resistance retention ability when encountering hard water is excellent.

[0056] Analyze examples 1 and comparative examples 1-3 in combination with table 1 data and Figure 1-Figure 2 Specifically, comparative example 1 and comparative example 2 are compared, it can be seen that the mixture of polyethylene glycol and isooctanoic acid in comparative example 1; while the polyethylene glycol-isooctanoic acid copolymer of the present application in comparative example 2. The results show that the metal corrosion resistance of the coolant prepared by comparative example 1 and comparative example 2 is not significantly different; however, the metal corrosion resistance retention ability of the coolant prepared by comparative example 2 when encountering hard water is significantly better than that of comparative example 1. It shows that the addition of polyethylene glycol-isooctanoic acid copolymer of the present application can significantly improve the metal corrosion resistance retention ability of the prepared coolant when encountering hard water.

[0057] This is mainly because the main metal corrosion resistant substance in the coolant prepared by comparative example 1 is isooctanoic acid in the mixture of polyethylene glycol and isooctanoic acid, which is directly consumed by Ca 2+ , Mg 2+ in hard water when encountering hard water, which seriously affects the metal corrosion resistance.

[0058] While the main metal corrosion resistant substance in the coolant prepared by comparative example 2 is the polyethylene glycol-isooctanoic acid copolymer of the present application, which is prepared by esterification grafting with isooctanoic acid as the end group and polyethylene glycol. The long-chain alkyl of isooctanoic acid can be oriented on the metal surface to form a hydrophobic layer, hindering the penetration of water molecules and corrosion medium (O2, H + ), and the ether bond (-O-) of the polyethylene glycol main chain combines with water molecules to form a hydration layer, prolonging the diffusion path of the corrosion medium, producing a direct hydrophobic barrier effect, and thus obtaining excellent metal corrosion resistance. Ca 2+ , Mg 2+ in hard water will not directly consume polyethylene glycol-isooctanoic acid copolymer like directly consuming organic carboxylic acid, so the decline of the metal corrosion resistance of the coolant when encountering hard water is very limited, which is significantly smaller than the influence of the consumption of organic carboxylic acid.

[0059] Specifically, a comparison between Comparative Examples 2 and 3 shows that the polyethylene glycol used in the preparation of the polyethylene glycol-isooctanoic acid copolymer in Comparative Example 2 is PEG-2000, with a molecular weight of 2000; while the polyethylene glycol used in the preparation of the polyethylene glycol-isooctanoic acid copolymer in Comparative Example 3 is PEG-800, with a molecular weight of 800. As a result, the coolant prepared in Comparative Example 2 exhibits superior metal corrosion protection compared to that of Comparative Example 3; furthermore, the coolant prepared in Comparative Example 2 also significantly outperforms Comparative Example 3 in its ability to retain metal corrosion protection in the presence of hard water. This indicates that, in the preparation of the polyethylene glycol-isooctanoic acid copolymer of the present invention, the use of long-chain PEG (molecular weight 2000) is more beneficial than the use of short-chain PEG (molecular weight 800) to improve the metal corrosion protection of the resulting coolant and its ability to retain metal corrosion protection in the presence of hard water.

[0060] This is mainly because long-chain PEG (molecular weight 2000) enhances the thickness of the hydration layer and buffers ionic interference; in comparison, short-chain PEG (molecular weight 800) has a weaker barrier.

[0061] By comparison with Example 1, it can be seen that in the preparation of the hybrid organic engine coolant of the present invention, the addition of the component polyethylene glycol-isooctanoic acid copolymer and the addition of a chelating agent have little effect on the metal corrosion resistance of the hybrid organic engine coolant finally obtained. However, it can further improve the ability of the hybrid organic engine coolant finally obtained to maintain the metal corrosion resistance when encountering hard water.

[0062] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0063] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A hybrid engine coolant, characterized in that: The invention comprises the following components by mass percentage: 75-80% ethylene glycol, 8-10% polyethylene glycol-isooctanoic acid copolymer, 2-3% chelating agent, 0.8-1.0% corrosion inhibitor, 0.1-0.3% defoaming agent and the balance deionized water; the polyethylene glycol is PEG-2000 with a molecular weight of 2000; the polyethylene glycol-isooctanoic acid copolymer is prepared by using isooctanoic acid as the end group and being esterified and grafted with polyethylene glycol at both ends.

2. The hybrid engine coolant according to claim 1, characterized in that: The chelating agents include EDTA or sodium citrate.

3. The hybrid engine coolant according to claim 1, characterized in that: The corrosion inhibitor includes benzotriazole.

4. The hybrid engine coolant according to claim 1, characterized in that: The defoaming agent is polydimethylsiloxane.

5. A method for preparing a hybrid engine coolant according to any one of claims 1 to 4, characterized in that: The steps include: S1. Ethylene glycol and deionized water were added to a reactor, stirred at 120-150 rpm for 30-50 min, and then polyethylene glycol-isooctanoic acid copolymer and corrosion inhibitor were added in sequence. The mixture was stirred at room temperature for 1 h to obtain a mixed solution 1. S2. Add a chelating agent to the mixed solution obtained in S1, stir for 1 hour, then add a defoaming agent, and continue stirring for 15-30 minutes to obtain the mixed organic engine coolant.

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