A long-chain ester-based lubricating additive, its preparation method, and its application in titanium alloy cutting fluids.

Abstract

This invention discloses a long-chain ester-based lubricating additive, its preparation method, and its application in titanium alloy cutting fluid. The preparation method of the long-chain ester-based lubricating additive of this invention includes the following steps: (1) Adding sodium hydroxide to an organic solvent to completely dissolve it, adding aminocaproic acid to an alkaline solution, and then slowly adding cyanuric chloride under ice bath conditions. After the reaction, pouring the solution into dilute hydrochloric acid to precipitate the solid, filtering to separate the solid, washing, and drying to obtain an intermediate product; (2) Adding the intermediate product and a high carbon number fatty alcohol to an organic solvent. After the solid is completely dissolved, adding an esterification reaction catalyst to it, allowing it to react fully, removing the catalyst after the reaction, and then distilling to remove the solvent to obtain the long-chain ester-based lubricating additive. The long-chain ester-based lubricating additive of this invention, when added to titanium alloy cutting fluid as a lubricating additive, can significantly improve the lubrication performance of titanium alloy cutting fluid, effectively alleviate the burning problem of titanium alloy workpieces during processing, and ensure the processing quality of the workpieces; at the same time, because the long-chain ester-based lubricating additive also has good thermal stability, the cutting fluid has a long service life.

Description

Technical Field

[0001] This invention relates to a long-chain ester-based lubricating additive, and also to a method for preparing the above-mentioned long-chain ester-based lubricating additive and its application in titanium alloy cutting fluids. Background Technology

[0002] Titanium alloys, due to their low thermal conductivity, low plasticity, high high-temperature strength, high chemical reactivity, and high coefficient of friction, are widely used in aerospace and high-end manufacturing fields. However, they also bring challenges in machining: sharp increases in cutting temperature, severe work hardening, rapid tool wear, and a tendency for tool-workpiece adhesion and welding, affecting machining results and accuracy. Therefore, titanium alloy cutting fluids must meet core performance requirements such as extreme pressure lubrication, cooling and heat dissipation, and high-temperature stability.

[0003] Existing extreme pressure lubricants in titanium alloy cutting fluids mainly include sulfur-based (sulfide olefins), chlorine-based (chlorinated paraffins), and phosphate ester extreme pressure lubricants. However, existing additives have significant drawbacks: sulfur-based lubricants easily corrode workpieces, fail to meet environmental standards, and are prone to failure at high temperatures; chlorine-based lubricants are toxic and banned, and are highly corrosive; phosphate esters have poor resistance to hard water and easily cause cutting fluid spoilage. These common problems (unstable film formation at high temperatures, corrosion, poor environmental performance, etc.) limit the demand for high-precision cutting of titanium alloys. Esters, due to their good biodegradability and excellent lubricity, have become the preferred direction for green extreme pressure additives. However, traditional esters have structural defects: the adsorption sites of a single ester group are limited, they are prone to hydrolysis, and their stability is insufficient, making it difficult to simultaneously improve extreme pressure performance and thermal stability. Summary of the Invention

[0004] Objective of this invention: The objective of this invention is to provide a long-chain ester-based lubricant additive, which, by introducing multiple ester and amino active functional groups into its molecular structure, can form a stable adsorption film on a metal substrate (adsorbed onto the metal substrate through multiple polar adsorption sites), thereby effectively improving the extreme pressure lubrication performance of the cutting fluid and also exhibiting good thermal stability, thus enabling the cutting fluid to have a long service life; another objective of this invention is to provide a method for preparing the above-mentioned long-chain ester-based lubricant additive and its application in titanium alloy cutting fluids.

[0005] Technical solution: The long-chain ester-based lubricating additive of the present invention has the following general structural formula:

[0006]

[0007] Where R is C n H 2n+1 n can be any integer from 8 to 16.

[0008] The preparation method of the above-mentioned long-chain ester-based lubricating additive includes the following steps:

[0009] (1) Add sodium hydroxide to an organic solvent to dissolve it completely, add aminocaproic acid to an alkaline solution (activating the amino group to enhance nucleophilicity; neutralizing the generated HCl to promote the reaction to proceed in the forward direction), and slowly add cyanuric chloride under ice bath conditions. After the reaction, pour the solution into dilute hydrochloric acid to precipitate the solid, filter to separate the solid, wash and dry it to obtain the intermediate product.

[0010] (2) Add intermediate products and high carbon number fatty alcohols to an organic solvent. After the solid is completely dissolved, add esterification reaction catalyst to it and react fully. After the reaction, remove the catalyst and then distill to remove the solvent to obtain long chain ester lubricating additive.

[0011] In step (1), the mass ratio of cyanuric chloride to aminocaproic acid is 1:2~3; the reaction temperature is 80~90℃; and the reaction time is 3~4h. The amount of sodium hydroxide added is 1.65~1.7mol / L.

[0012] In step (2), the structural formula of the high carbon number fatty alcohol is C n H 2n+1 OH, n is any integer from 8 to 16. The mass ratio of the intermediate product to the high carbon number fatty alcohol is 1:1 to 2; the reaction temperature is 80 to 100℃, and the reaction time is 8 to 10 h. The esterification reaction catalyst is p-toluenesulfonic acid.

[0013] The reaction equation for the method of this invention is as follows:

[0014]

[0015] The application of the above-mentioned long-chain ester-based lubricating additive in titanium alloy cutting fluid is as follows: the amount of the long-chain ester-based lubricating additive added to the titanium alloy cutting fluid is 2 to 5% of the mass of the titanium alloy cutting fluid.

[0016] The multi-amino structure in the long-chain ester-based lubricant additive of this invention allows it to form multi-site coordination bonds and hydrogen bonds for adsorption onto metal surfaces. This is stronger than the weak single-site adsorption of ester groups in polyesters, resulting in a more secure anchoring, less oil film detachment, and stable boundary lubrication. Secondly, the multifunctional groups in the molecular structure readily cross-link, superior to the linear or low cross-linking (weak interchain interactions) of ordinary polyesters, thus improving the load-bearing capacity of the resulting oil film and significantly enhancing its anti-wear and extreme pressure properties. Furthermore, the high rigidity of the nitrogen heterocycles in the molecular structure and the reduced exposure of ester groups through cross-linking structures lead to a significant increase in the thermal decomposition temperature.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The long-chain ester-based lubricating additive of the present invention, when added to titanium alloy cutting fluid as a lubricating additive, can significantly improve the lubrication performance of titanium alloy cutting fluid, effectively alleviate the burning problem of titanium alloy workpieces during processing, and ensure the processing quality of workpieces; at the same time, since the long-chain ester-based lubricating additive also has good thermal stability, the cutting fluid has a long service life. Attached Figure Description

[0018] Figure 1 The image shows the appearance of the long-chain ester-based lubricating additive (powder material) prepared in Example 2.

[0019] Figure 2 The infrared spectrum of the intermediate product obtained in Example 2;

[0020] Figure 3 The infrared spectrum of the long-chain ester-based lubricating additive prepared in Example 2 is shown. Detailed Implementation

[0021] Example 1

[0022] The preparation method of the long-chain ester-based lubricating additive of the present invention includes the following steps:

[0023] (1) Add sodium hydroxide (132g, 3.3mol) to 2L N,N-dimethylformamide to dissolve it completely, add aminocaproic acid (432g, 3.3mol) to the alkaline solution, and slowly add cyanuric chloride powder (193.6g, 1mol) under ice bath conditions (ice bath controls reaction selectivity and prevents hydrolysis of raw materials and self-condensation to produce other by-products). Then raise the temperature to 85℃ and keep the temperature for 3h. After the reaction is completed, pour it into dilute hydrochloric acid (mass concentration is 37%) to precipitate the solid, filter to separate the solid, wash the solid with ethanol and water, and dry to obtain the intermediate product;

[0024] (2) Add the intermediate product (555.7 g, 1.2 mol) and n-octanol (577.2 g, 3.6 mol) to 1 L of toluene, mix and stir until the solid is completely dissolved, then add p-toluenesulfonic acid (20.6 g, 0.12 mol), heat to 80 °C and stir for 8 h. After the reaction is complete, add saturated sodium bicarbonate solution (500 mL) to neutralize p-toluenesulfonic acid (saturated sodium bicarbonate neutralizes p-toluenesulfonic acid in toluene solution to form a precipitate), control pH=7~8 (when pH=7~8, it means that the neutralization reaction is complete), filter to remove the precipitate and finally distill to remove the solvent to obtain long-chain ester-based lubricating additive.

[0025] The structural formula of the long-chain ester-based lubricating additive prepared in Example 1 is as follows:

[0026]

[0027] Example 2

[0028] The preparation method of the long-chain ester-based lubricating additive of the present invention includes the following steps:

[0029] (1) Sodium hydroxide (132g, 3.3mol) was added to 2L of N,N-dimethylformamide to dissolve it completely. Aminocaproic acid (432g, 3.3mol) was added to the alkaline solution. Then, cyanuric chloride powder (193.6g, 1mol) was slowly added under ice bath conditions. The temperature was then raised to 85℃ and kept at that temperature for 3h. After the reaction was completed, the solid was poured into dilute hydrochloric acid (mass concentration of 37%) to precipitate. The solid was separated by filtration, washed with ethanol and water, and dried to obtain the intermediate product.

[0030] (2) Add intermediate product (555.7 g, 1.2 mol) and lauryl alcohol (669.6 g, 3.6 mol) to 1 L of toluene, mix and stir to completely dissolve the solid, then add p-toluenesulfonic acid (20.6 g, 0.12 mol), heat to 80 °C and stir for 8 h. After the reaction is complete, add saturated sodium bicarbonate solution (500 mL) to neutralize p-toluenesulfonic acid, control pH=7~8, filter to remove precipitate and finally distill to remove solvent to obtain long-chain ester-based lubricating additive.

[0031] The structural formula of the long-chain ester-based lubricant additive prepared in Example 2 is as follows:

[0032]

[0033] from Figure 2 1687cm -1 The characteristic peak of the carboxyl group to Figure 3 1747cm -1 The characteristic peaks of the ester group indicate that the long-chain ester-based lubricating additive of the present invention was successfully prepared by the reaction of the carboxyl group and the alcohol.

[0034] Example 3

[0035] The preparation method of the long-chain ester-based lubricating additive of the present invention includes the following steps:

[0036] (1) Sodium hydroxide (132g, 3.3mol) was added to 2L of N,N-dimethylformamide to dissolve it completely. Aminocaproic acid (432g, 3.3mol) was added to the alkaline solution. Then, cyanuric chloride powder (193.6g, 1mol) was slowly added under ice bath conditions. The temperature was then raised to 85℃ and kept at that temperature for 3h. After the reaction was completed, the solid was poured into dilute hydrochloric acid (mass concentration of 37%) to precipitate. The solid was separated by filtration, washed with ethanol and water, and dried to obtain the intermediate product.

[0037] (2) Add intermediate product (555.7g, 1.2mol) and palmitol (871.2g, 3.6mol) to 1L toluene, mix and stir to completely dissolve the solid, then add p-toluenesulfonic acid (20.6g, 0.12mol), heat to 80℃ and stir for 8h. After the reaction is complete, add saturated sodium bicarbonate solution (500mL) to neutralize p-toluenesulfonic acid, control pH=7~8, filter to remove precipitate and finally distill to remove solvent to obtain long-chain ester lubricating additive.

[0038] The structural formula of the long-chain ester-based lubricating additive obtained in Example 3 is as follows:

[0039]

[0040] Comparative Example 1

[0041] Commercially available synthetic ester additives are monoesters (isooctyl oleate).

[0042] Comparative Example 2

[0043] Commercially available synthetic ester additives are polyol esters (trimethylolpropane oleate).

[0044] Comparative Example 3

[0045] Commercially available synthetic ester additives are tetrameric ricinoleate.

[0046] The lubrication properties of the ester-based lubricating additives in Examples 1-3 and Comparative Examples 1-3 were tested:

[0047] The ester-based lubricating additives of Examples 1-3 and Comparative Examples 1-3 were added to 6 identical 100g water-based titanium alloy cutting fluids (the commercial model of the water-based titanium alloy cutting fluid is KR-C8026, and the amount of ester-based lubricating additive added to each group of water-based titanium alloy cutting fluids is 5g) (the lubricating additives of Examples 1-3 and Comparative Examples 1-3 were used to replace the original lubricant in the titanium alloy cutting fluid, that is, in the process of preparing the above-mentioned titanium alloy cutting fluids, the lubricants added were the lubricating additives of Examples 1-3 and Comparative Examples 1-3, respectively), and stirred until completely dissolved; then the titanium alloy cutting fluids were diluted with tap water to a working fluid with a mass concentration of 5% (5g of titanium alloy cutting fluid was added to 95g of water), and were respectively labeled as A1, A2, A3, B1, B2, and B3.

[0048] The lubrication performance of water-based titanium alloy cutting fluid was tested using a Microtap G8II tapping torque tester. The rotational speed was 1200 r / min. A titanium alloy-specific tap was used, and the test plate was TC4 titanium alloy. The presence of lubricant affects the torque value; better lubricity results in a lower average torque value, and vice versa. Generally, the average of five tests conducted for a given lubricant additive is recorded as the final average torque value. The test results can be expressed as a simple torque value (unit: N·m).

[0049] Table 1 shows the lubrication results for tapping torque.

[0050] Maximum value 138 98 85 100 120 112 90 average value 120 81 65 84 92 90 72

[0051] As shown in Table 1, short-chain fatty acids have weaker rust-preventive properties than medium- and long-chain fatty acids. However, excessively long carbon chains result in poor fluidity, strong adsorption but decreased spreadability, leading to a decline in lubrication performance. The long-chain ester-based lubricant of this invention exhibits superior lubrication performance compared to polymeric esters, polyol esters, and monoesters. This is because the lubrication performance of ester compounds is determined by their molecular structure: the lone pairs of oxygen atoms in the ester chain of the long-chain ester-based lubricant of this invention readily form bonds with the metal surface. Under the premise of a fixed relative molecular mass, the more functional groups the ester group has, the greater the polarity of the ester molecule, and the higher its affinity for the metal. In addition, the polyamino structure in the molecular structure can form multi-site coordination bonds and hydrogen bonds to adsorb onto the metal surface, which is stronger than the weak single-site adsorption of ester groups in polyesters. The anchoring is stronger, the oil film is less likely to fall off, and thus the boundary lubrication is more stable. Finally, the nitrogen heterocycle in the molecular structure is more rigid, the cross-linking structure reduces the exposure of ester groups, and the thermal decomposition temperature is higher. In contrast, the only ester groups in ordinary polyesters are easily thermally decomposed at the high temperatures generated during processing, leading to easy oil film failure.

[0052] After the titanium alloy cutting fluid A2 prepared above was used continuously for 7 days under titanium alloy cutting conditions, the fluid was taken back for tapping torque lubrication test, and the results are shown in Table 2.

[0053] Table 2

[0054] Maximum value 87 average value 66

[0055] As shown in Table 2, the tapping torque value of the bath solution is basically the same as that before processing (when the working fluid is first prepared), indicating that the lubricating additive of the present invention has good thermal stability, thereby enabling the titanium alloy cutting fluid to have a long service life.

Claims

1. A long-chain ester-based lubricating additive, characterized in that, Its general structural formula is as follows: ； Where R is C n H 2n+1 n can be any integer from 8 to 16.

2. The method for preparing the long-chain ester-based lubricating additive according to claim 1, characterized in that, Includes the following steps: (1) Add sodium hydroxide to the organic solvent to dissolve it completely, add aminocaproic acid to the alkaline solution, and slowly add cyanuric chloride under ice bath conditions. After the reaction, pour it into dilute hydrochloric acid to precipitate the solid, filter to separate the solid, wash and dry it to obtain the intermediate product. (2) Add intermediate products and high carbon number fatty alcohols to an organic solvent. After the solid is completely dissolved, add esterification reaction catalyst to it and react fully. After the reaction, remove the catalyst and then distill to remove the solvent to obtain long chain ester lubricating additive.

3. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (1), the mass ratio of cyanuric chloride and aminocaproic acid is 1:2~3.

4. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (1), the reaction temperature is 80~90℃ and the reaction time is 3~4h.

5. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (2), the structural formula of the high carbon number fatty alcohol is C n H 2n+1 OH, n takes any integer from 8 to 16.

6. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (2), the mass ratio of the intermediate product to the high carbon number fatty alcohol is 1:1~2.

7. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (2), the reaction temperature is 80~100℃ and the reaction time is 8~10h.

8. The method for preparing the long-chain ester-based lubricating additive according to claim 2, characterized in that: In step (2), the esterification reaction catalyst is p-toluenesulfonic acid.

9. The application of the long-chain ester-based lubricating additive according to claim 1 in titanium alloy cutting fluid, characterized in that: In the titanium alloy cutting fluid, the amount of the long-chain ester-based lubricating additive added is 2-5% of the mass of the titanium alloy cutting fluid.

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