A sophorolipid polyethylene glycol monoester compound, a preparation method and application thereof

Abstract

The application provides a sophorolipid polyethylene glycol monoester compound and a preparation method and application thereof, the sophorolipid polyethylene glycol monoester compound has a structure shown in formula I, the sophorolipid polyethylene glycol monoester compound developed by the application has significantly improved water solubility, alkali resistance and hard water resistance while keeping the biological base characteristics, can be used as a biological base surfactant of an industrial cleaning agent, and improves the cleaning effect of the industrial cleaning agent.

Description

Technical Field

[0001] This invention belongs to the field of industrial cleaning agent technology, and relates to a sophorolipid polyethylene glycol monoester compound, its preparation method and application. Background Technology

[0002] Industrial cleaning agents are indispensable process aids in manufacturing, widely used in metal processing, machinery manufacturing, electronics, and optical components to remove processing oils, rust-preventive oils, lubricating greases, and other contaminants from the surfaces of materials such as metals, plastics, and glass. Based on their application methods, industrial cleaning agents can be divided into two main categories: solvent-based and water-based. Water-based cleaning agents, due to their high safety, low cost, and environmental friendliness, have become the mainstream products in the market. Water-based cleaning agents typically use surfactants as the core component, compounded with functional additives such as builders, corrosion inhibitors, and chelating agents. They achieve their cleaning purpose through the wetting, emulsifying, dispersing, and solubilizing effects of surfactants. With increasingly stringent environmental regulations, the development of biodegradable, low-toxicity, and low-harm bio-based surfactants has become an important development direction in the field of industrial cleaning agents.

[0003] Surfactants are key components determining the detergency of cleaning agents. Currently, commonly used surfactants in industrial cleaning agents mainly include alkylphenol polyoxyethylene ethers (NP / TX), alkylbenzene sulfonates (LAS), and alkyl glycosides (APG). While alkylphenol polyoxyethylene ether surfactants possess excellent emulsifying and detergency capabilities, their degradation products have endocrine effects, leading to usage restrictions in markets such as the EU. Anionic surfactants, such as dodecylbenzene sulfonates, are inexpensive, but they readily precipitate with calcium and magnesium ions under hard water conditions, affecting cleaning effectiveness and increasing formulation costs. Alkyl glycosides (APG) are inherently environmentally friendly, but their ability to clean heavy oil stains is weak. Therefore, developing novel surfactants that combine excellent detergency, good hard water resistance, and biodegradability is a pressing technical challenge for the industrial cleaning agent industry.

[0004] Sophorolipids are a class of biosurfactants produced by the fermentation of non-pathogenic yeasts (such as Starmerella bombicola), attracting considerable attention due to their structural diversity and excellent interfacial activity. Compared with chemically synthesized surfactants, sophorolipids possess significant advantages such as good biodegradability, low toxicity, and high environmental compatibility, making them typical green bio-based materials. In recent years, with advancements in biomanufacturing technology, the industrialization of bio-based surfactants such as sophorolipids has accelerated significantly. However, sophorolipids obtained from natural fermentation mainly exist in two forms: lactone and acid. Lactone-type sophorolipids are highly hydrophobic and have poor water solubility, making them difficult to apply directly to water-based cleaning systems. While acid-type sophorolipids possess some water solubility, their stability under high alkaline conditions is insufficient, and their complexation ability with calcium and magnesium ions is weak, requiring improvement in their resistance to hard water.

[0005] Therefore, how to develop industrial cleaning agents based on sophorolipids is a key research focus in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a sophorolipid polyethylene glycol monoester compound, its preparation method, and its applications. The sophorolipid polyethylene glycol monoester compound developed in this invention maintains its bio-based properties while significantly improving its water solubility, alkali resistance, and hard water resistance. It can be used as a bio-based surfactant in industrial cleaning agents to enhance their cleaning effectiveness.

[0007] To achieve this objective, the present invention adopts the following technical solution: On one hand, the present invention provides a sophorolipid polyethylene glycol monoester compound, wherein the sophorolipid polyethylene glycol monoester compound has the structure shown in Formula I: ; Where n is an integer from 1 to 13 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13).

[0008] On the other hand, the present invention provides a method for preparing the sophorolipid polyethylene glycol monoester compound as described above, the preparation method comprising the following steps: The lactone-type sophorolipid reacts with polyethylene glycol under the catalysis of a catalyst to obtain the sophorolipid polyethylene glycol monoester compound shown in Formula I.

[0009] In this invention, polyethoxylated hydrophilic segments are introduced into the sophorolipid molecule through chemical modification. This significantly improves the sophorolipid's water solubility, alkali resistance, and hard water resistance while maintaining its bio-based properties. It can be used as a bio-based surfactant in industrial cleaning agents to enhance the cleaning effect of industrial cleaning agents.

[0010] Preferably, the weight-average molecular weight of the polyethylene glycol is 106 to 600, for example, 106, 150, 194, 200, 300, 400, 600, etc., preferably 150 to 400, and preferably any one or a combination of at least two of diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, polyethylene glycol 300 or polyethylene glycol 400.

[0011] Preferably, the molar ratio of the lactone-type sophorolipid to polyethylene glycol is 1:3 to 1:5, such as 1:3, 1:3.3, 1:3.6, 1:3.9, 1:4.2, 1:4.5, 1:4.8 or 1:5.

[0012] Preferably, the catalyst is selected from dodecylbenzenesulfonic acid.

[0013] Preferably, the amount of catalyst used is 10% to 12% of the total mass of lactone-type sophorolipid and polyethylene glycol (e.g., 10%, 10.5%, 11%, 11.5% or 12%, etc.).

[0014] Preferably, the reaction temperature is 70-90℃ (e.g., 70℃, 75℃, 80℃, 85℃ or 90℃, etc.), and the reaction time is 5-10h (e.g., 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h or 10h, etc.).

[0015] In this invention, the reaction temperature and time can be selected according to the specific choice of polyethylene glycol. For example, when the polyethylene glycol is diethylene glycol, the reaction temperature is 70-75°C and the reaction time is 5 hours; when the polyethylene glycol is triethylene glycol, the reaction temperature is 75-80°C and the reaction time is 6 hours; when the polyethylene glycol is tetraethylene glycol or polyethylene glycol 200, the reaction temperature is 80-85°C and the reaction time is 6-7 hours; when the polyethylene glycol is polyethylene glycol 400 or polyethylene glycol 600, the reaction temperature is 85-90°C and the reaction time is 8-10 hours.

[0016] In this invention, after the reaction is completed, the reaction solution is cooled, and then the pH is adjusted to 6.5-7.5 (e.g., 6.5, 7, or 7.5). During neutralization, the system temperature may rise, requiring control of the dropping rate and appropriate cooling. After neutralization, a pale yellow to amber viscous crude product is obtained. The crude product is purified to obtain the sophorolipid polyethylene glycol monoester compound.

[0017] In this invention, the reaction process can be described by the following reaction flow: .

[0018] The preparation method of the present invention is simple and the product yield is high (70%~85%).

[0019] On the other hand, the present invention provides the application of the sophorolipid polyethylene glycol monoester compound as described above in industrial cleaning agents.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The sophorolipid polyethylene glycol monoester compound of the present invention maintains its bio-based properties while significantly improving its water solubility, alkali resistance and hard water resistance. It can be used as a bio-based surfactant in industrial cleaning agents to improve the cleaning effect of industrial cleaning agents. Attached Figure Description

[0021] Figure 1 The image shows the infrared (ATR) spectrum of lactone-type sophorolipid (LSL). Figure 2 The image shows the infrared (ATR) spectrum of sophorolipid diethylene glycol monoester (SLP2). Figure 3 The infrared (ATR) spectrum of sophorolipid triethylene glycol monoester (SLP3) is shown. Figure 4 The image shows the infrared (ATR) spectrum of sophorolipid tetraethylene glycol monoester (SLP4). Figure 5 The image shows the infrared (ATR) spectrum of sophorolipid polyethylene glycol monoester (SLP200). Figure 6 The image shows the infrared (ATR) spectrum of sophorolipid polyethylene glycol monoester (SLP400). Figure 7 This is the infrared (ATR) spectrum of sophorolipid polyethylene glycol monoester (SLP600). Detailed Implementation

[0022] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0023] The lactone-type sophorolipid used in the embodiments of this invention was purchased from Maclean's.

[0024] Example 1 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP2), the structure of which is as follows: Its preparation method includes the following steps: Under a nitrogen atmosphere, 65.0 g (0.10 mol, molecular weight 650) of lactone-type sophorolipid and 42.4 g (0.40 mol, 4.0 equivalent) of diethylene glycol were added to a 500 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 50°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (12.0 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 70°C and stirred at this temperature for 5 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was reached when the lactone-type sophorolipid spot essentially disappeared. After the reaction was complete, the mixture was cooled to 50°C, and a 10% sodium hydroxide aqueous solution was slowly added dropwise to adjust the pH to 7.0. The temperature may rise during neutralization; the addition rate must be controlled accordingly. The neutralized reaction solution was transferred to a separatory funnel, and 150 mL of ethyl acetate and 150 mL of deionized water were added. After vigorous shaking, the mixture was allowed to stand and separate into layers. The lower aqueous phase was collected, and the upper organic phase was back-extracted once with 50 mL of deionized water. The aqueous phases were combined. The combined aqueous phases were transferred to a separatory funnel, and an equal volume of ethyl acetate (approximately 200 mL) was added. After vigorous shaking for 2–3 minutes, the mixture was allowed to stand and separate into layers. The organic phase was discarded, and the aqueous phase was extracted twice more with ethyl acetate (150 mL each time) until the color of the organic phase became significantly lighter. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45 °C to remove most of the water, yielding a pale yellow, transparent, viscous liquid. This liquid was dried in a vacuum drying oven at 40 °C to constant weight to obtain the sophorolipid-diethylene glycol monoester product, with a yield of approximately 72%.

[0025] For modified products like sophorolipid polyethylene glycol monoester, Fourier transform infrared spectroscopy (FTIR) is typically used to confirm the formation of the target product. The purpose is to confirm the opening of the lactone ring, the formation of ester bonds, and the introduction of ether bonds. The Fourier transform infrared spectrometer used was a Bruker ALPHA II, manufactured by Bruker (Germany), and the testing method was the ATR method.

[0026] The infrared characterization results show that, in comparison Figure 1 The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1 There is a distinct C=O stretching vibration characteristic peak of the lactone ring. The infrared characterization image of the target product, sophorolipid diethylene glycol monoester (SLP2), shows, as... Figure 2 Its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹.-1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the hydroxyl groups on the polyethylene glycol end groups and sophorolipids); at 1108 cm⁻¹ -1 A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0027] Example 2 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP3), the structure of which is as follows: Its preparation method includes the following steps: Under a nitrogen atmosphere, 65.0 g (0.10 mol, molecular weight 650) of lactone-type sophorolipid and 60.0 g (0.40 mol, 4.0 equivalent) of triethylene glycol were added to a 500 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 50°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (13.5 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 75°C and stirred at this temperature for 6 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was reached when the lactone-type sophorolipid spots essentially disappeared. After the reaction was complete, the mixture was cooled to 50°C, and a 10% sodium hydroxide aqueous solution was slowly added dropwise to adjust the pH to 7.0. The temperature may rise during neutralization; the addition rate must be controlled accordingly. The neutralized reaction solution was transferred to a separatory funnel, and 150 mL of ethyl acetate and 150 mL of deionized water were added. After vigorous shaking, the mixture was allowed to stand and separate into layers. The lower aqueous phase was collected, and the upper organic phase was back-extracted once with 50 mL of deionized water. The aqueous phases were combined. The combined aqueous phases were transferred to a separatory funnel, and an equal volume of ethyl acetate (approximately 200 mL) was added. After vigorous shaking for 2–3 minutes, the mixture was allowed to stand and separate into layers. The organic phase was discarded, and the aqueous phase was extracted twice more with ethyl acetate (150 mL each time) until the color of the organic phase became significantly lighter. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45 °C to remove most of the water, yielding a pale yellow, transparent, viscous liquid. This liquid was dried in a vacuum drying oven at 40 °C to constant weight to obtain the sophorolipid-triethylene glycol monoester product, with a yield of approximately 78%.

[0028] The infrared characterization results show that, in comparison Figure 1 The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1 There is a distinct C=O stretching vibration characteristic peak of the lactone ring. The infrared characterization image of the target product, sophorolipid triethylene glycol monoester (SLP3), shows... Figure 3The results show that its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹. -1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the triethylene glycol terminal group and the hydroxyl group on the sophorolipid); at 1102 cm⁻¹ -1 A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0029] Example 3 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP4), the structure of which is as follows: Its preparation method includes the following steps: Under a nitrogen atmosphere, lactone-type sophorolipid (65.0 g, 0.10 mol, molecular weight 650) and tetraethylene glycol (77.6 g, 0.40 mol, 4.0 equivalent) were added to a 500 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 50°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (15.0 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 80°C and stirred at this temperature for 7 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was reached when the lactone-type sophorolipid spot essentially disappeared. After the reaction was complete, the mixture was cooled to 50°C, and a 10% sodium hydroxide aqueous solution was slowly added dropwise to adjust the pH to 7.0. The temperature may rise during neutralization, so the addition rate needs to be controlled. The neutralized reaction solution was transferred to a separatory funnel, and 150 mL of ethyl acetate and 150 mL of deionized water were added. After vigorous shaking and standing, the layers were separated. The lower aqueous phase was collected, and the upper organic phase was back-extracted once with 50 mL of deionized water. The aqueous phases were combined. The combined aqueous phases were transferred to a separatory funnel, and an equal volume of ethyl acetate (approximately 200 mL) was added. After vigorous shaking for 2–3 minutes, the layers were allowed to separate. The organic phase was discarded, and the aqueous phase was extracted twice more with ethyl acetate (150 mL each time) until the color of the organic phase became significantly lighter. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45 °C to remove most of the water, yielding a pale yellow, transparent, viscous liquid. This liquid was dried in a vacuum drying oven at 40 °C to constant weight to obtain the sophorolipid-tetraethylene glycol monoester product, with a yield of approximately 75%.

[0030] The infrared characterization results show that, in comparison Figure 1The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1 There is a distinct C=O stretching vibration characteristic peak of the lactone ring. The infrared characterization image of the target product, sophorolipid tetraethylene glycol monoester (SLP4), shows... Figure 4 The results show that its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹. -1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the hydroxyl groups on the polyethylene glycol end groups and sophorolipids); at 1100 cm⁻¹ -1 A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0031] Example 4 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP200), the structure of which is as follows: The degree of polymerization n (approximately) is 3.9 to 4.4.

[0032] Its preparation method includes the following steps: Under a nitrogen atmosphere, 65.0 g (0.10 mol, molecular weight 650) of lactone-type sophorolipid and 80.0 g (0.40 mol, molecular weight 200) of polyethylene glycol 200 were added to a 500 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 60°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (16.0 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 85°C and stirred for 8 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was reached when the lactone-type sophorolipid spots essentially disappeared. Due to the long molecular chain of polyethylene glycol 200 and the high viscosity of the reaction system, the stirring speed needed to be appropriately increased to ensure uniform mixing. After the reaction, the mixture was cooled to 50°C, and the pH was adjusted to 7.0 by slowly adding 10% sodium hydroxide aqueous solution. The temperature may rise during neutralization, so the adding rate needs to be controlled. The neutralized reaction solution was transferred to a separatory funnel, and 150 mL of ethyl acetate and 150 mL of deionized water were added. After thorough shaking, the mixture was allowed to stand and separate into layers. The lower aqueous phase was collected, and the upper organic phase was back-extracted once with 50 mL of deionized water. The aqueous phases were combined. The combined aqueous phases were transferred to a separatory funnel, and an equal volume of ethyl acetate (approximately 200 mL) was added. After vigorous shaking for 2-3 minutes, the mixture was allowed to stand and separate into layers. The organic phase was discarded, and the aqueous phase was repeatedly extracted twice with ethyl acetate (150 mL each time) until the organic phase became significantly lighter in color. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45°C to remove most of the water, yielding a pale yellow, transparent, viscous liquid. This liquid was dried in a vacuum drying oven at 40°C to constant weight to obtain the sophorolipid-polyethylene glycol 200 monoester product, with a yield of approximately 70%.

[0033] The infrared characterization results show that, in comparison Figure 1 The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1 There is a distinct C=O stretching vibration characteristic peak of the lactone ring. The infrared characterization image of the target product, sophorolipid polyethylene glycol monoester (SLP200), shows... Figure 5 The results show that its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹. -1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the hydroxyl groups on the polyethylene glycol end groups and sophorolipids); at 1089 cm⁻¹ -1A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0034] Example 5 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP400), the structure of which is as follows: The degree of polymerization n (approximately) is 8.2 to 9.1.

[0035] Its preparation method includes the following steps: Under a nitrogen atmosphere, 65.0 g (0.10 mol, molecular weight 650) of lactone-type sophorolipid and 160.0 g (0.40 mol, molecular weight 400) of polyethylene glycol 400 were added to a 500 mL three-necked flask equipped with a powerful mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 60°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (25.0 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 90°C and stirred at this temperature for 9 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was reached when the lactone-type sophorolipid spots essentially disappeared. Due to the high viscosity of this reaction system, vigorous mechanical stirring was necessary to ensure uniform mass transfer. After the reaction, the mixture was cooled to 50°C, and the pH was adjusted to 7.0 by slowly adding 10% sodium hydroxide aqueous solution. The temperature of the system may rise during neutralization, so the adding rate needs to be controlled. The neutralized reaction solution was transferred to a separatory funnel, and 200 mL of ethyl acetate and 200 mL of deionized water were added. After thorough shaking, the mixture was allowed to stand and separate into layers. The lower aqueous phase was collected, and the upper organic phase was back-extracted once with 50 mL of deionized water. The aqueous phases were combined. The combined aqueous phases were transferred to a separatory funnel, and an equal volume of ethyl acetate (approximately 250 mL) was added. After vigorous shaking for 2-3 minutes, the mixture was allowed to stand and separate into layers. The organic phase was discarded, and the aqueous phase was repeatedly extracted twice with ethyl acetate (150 mL each time) until the color of the organic phase became significantly lighter. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45°C to remove most of the water, yielding a pale yellow, transparent, viscous liquid. This liquid was dried in a vacuum drying oven at 40°C to constant weight to obtain the sophorolipid-polyethylene glycol 400 monoester product, with a yield of approximately 65%.

[0036] The infrared characterization results show that, in comparison Figure 1 The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1There are obvious characteristic peaks of C=O stretching vibration of the lactone ring. The infrared characterization image of the target product, sophorolipid polyethylene glycol monoester (SLP400), shows, as... Figure 6 Its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹. -1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the hydroxyl groups on the polyethylene glycol end groups and sophorolipids); at 1092 cm⁻¹ -1 A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0037] Example 6 This embodiment provides a sophorolipid polyethylene glycol monoester compound (SLP600), the structure of which is as follows: The degree of polymerization n (approximately) is 12.5 to 13.9.

[0038] Its preparation method includes the following steps: Under a nitrogen atmosphere, 65.0 g (0.10 mol, molecular weight 650) of lactone-type sophorolipid and 240.0 g (0.40 mol, molecular weight 600) of polyethylene glycol 600 were added to a 500 mL three-necked flask equipped with a powerful mechanical stirrer, thermometer, and reflux condenser. The mixture was stirred and heated to 60°C to ensure thorough mixing of the reactants. Dodecylbenzenesulfonic acid (32.0 g, approximately 11% of the total reactants) was slowly added dropwise to the system, with the temperature controlled to remain above 70°C during the addition. After the addition was complete, the reaction mixture was heated to 90°C and stirred at this temperature for 10 hours. The reaction progress was monitored by thin-layer chromatography (developing solvent: chloroform:methanol:water = 65:25:4, iodine vapor for color development). The reaction endpoint was defined as the near disappearance of the lactone-type sophorolipid spots. Due to the long molecular chain of polyethylene glycol 600, the reaction system has a high viscosity, requiring vigorous mechanical stirring to ensure uniform mass transfer. The stirring speed can be appropriately increased. After the reaction, cool the mixture to 50°C and slowly add a 10% sodium hydroxide aqueous solution to adjust the pH to 7.0. The system temperature may rise during neutralization, so the adding rate needs to be controlled. Transfer the neutralized reaction solution to a separatory funnel, add 250 mL of ethyl acetate and 200 mL of deionized water, shake thoroughly, and allow to separate into layers. Collect the lower aqueous phase, and back-extract the upper organic phase once with 50 mL of deionized water. Combine the aqueous phases. Transfer the combined aqueous phases to a separatory funnel, add an equal volume of ethyl acetate (approximately 250 mL), shake vigorously for 2-3 minutes, and allow to separate into layers. Discard the organic phase. Repeat the extraction of the aqueous phase twice with ethyl acetate (150 mL each time) until the organic phase becomes significantly lighter in color. The purified aqueous phase was concentrated by rotary evaporation under reduced pressure at 45°C to remove most of the water, resulting in a pale yellow, transparent, viscous liquid. This liquid was then dried in a vacuum drying oven at 40°C to constant weight, yielding sophorolipid-polyethylene glycol 600 monoester product with a yield of approximately 60%.

[0039] The infrared characterization results show that, in comparison Figure 1 The reactant raw material, lactone-type sophorolipid (LSL), showed that lactone-type sophorolipid was at 1745 cm⁻¹. -1 There is a distinct C=O stretching vibration characteristic peak of the lactone ring. The infrared characterization image of the target product, sophorolipid polyethylene glycol monoester (SLP600), shows... Figure 7 The results show that its lactone ring characteristic peak (1745 cm⁻¹) -1 The disappearance or significant weakening of the lactone ring indicates that the lactone ring has opened; and at 1735 cm -1 A C=O stretching vibration peak of the ester group appears at 3400 cm⁻¹; simultaneously, a peak appears at 3400 cm⁻¹. -1 A broad and strong hydroxyl (-OH) stretching vibration peak appears nearby (originating from the hydroxyl groups on the polyethylene glycol end groups and sophorolipids); at 1102 cm⁻¹ -1A strong absorption peak appears nearby, which is the stretching vibration of the ether bond in the polyoxyethylene chain (COC), and the intensity increases with the increase of the polyethylene glycol chain length.

[0040] Test Example 1 The cleaning tank solutions to be tested were prepared by distilling water with 0.5%, 1%, and 2% of the solutions from Examples 1, 2, 3, 4, 5, and 6, and NP-10 (PetroChina), LAS (BASF), APG (Zhejiang Zanyu Technology), and 2% soda ash (China Salt Chemical). The prepared cleaning solution was kept at a constant temperature of 60±2℃. A comparative test was conducted on 45# steel sheets coated with artificial oil (preparation method: GB / T 35759-2017 "Metal Cleaning Agents"). The steel sheets were first soaked for 3 minutes, then rinsed for 3 minutes, and then rinsed and dried. The cleaning efficiency of different surfactants under the same conditions was tested based on the change in the weight of the oil on the steel sheets before and after the test.

[0041] The test results are shown in Table 1 below: Table 1 Results analysis: Under standard cleaning conditions, the cleaning rates of modified sophorolipids in Examples 3, 4 and 5 at different concentrations were all higher than those of the other three commonly used surfactants. In particular, the sample prepared in Example 4 showed significantly better results. Test Example 2 Prepare 50 ml of 1.0% aqueous solutions of each of Examples 1, 2, 3, 4, 5, 6, NP-10, LAS, and APG in stoppered test tubes using hard water with hardnesses of 250 mg / L, 500 mg / L, and 1000 mg / L. After sealing the tubes, slowly invert them once per second for 10 times to ensure thorough mixing (each test tube corresponds to one sample + one type of hard water). Avoid foaming during the process. Then, let the test tubes stand at (20±2)℃ for 2 hours and observe the state of the solution in the test tubes visually. Record the appearance of the solution in the test tubes at this time and grade the stability (grading criteria: clear and transparent 5 points; milky 4 points; turbid: 3 points; small amount of precipitate or coagulation: 2 points; large amount of precipitate or coagulation: 1 point).

[0042] The test results are shown in Table 2 below: Table 2 Results analysis: The modified sophorolipids in Examples 4, 5 and 6 showed good stability in hard water of different hardness and concentrations, demonstrating excellent hard water resistance.

[0043] In summary, the modified sophorolipids in Examples 4 and 5 have the advantage of being easily biodegradable compared to the environmentally unfriendly NP-10. Compared to LAS, they have stronger resistance to hard water. Compared to APG, they have better cleaning power. Therefore, modified sophorolipids are more suitable as the core component of efficient, green, and widely adaptable industrial cleaning agents, and can be widely used in various industrial cleaning scenarios such as metal degreasing and equipment cleaning.

[0044] The applicant declares that this invention illustrates the sophorolipid polyethylene glycol monoester compound, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A sophorolipid polyethylene glycol monoester compound, characterized in that, The sophorolipid polyethylene glycol monoester compound has the structure shown in Formula I: ； Where n is an integer between 2 and 13.

2. The method for preparing the sophorolipid polyethylene glycol monoester compound according to claim 1, characterized in that, The preparation method includes the following steps: The lactone-type sophorolipid reacts with polyethylene glycol under the catalysis of a catalyst to obtain the sophorolipid polyethylene glycol monoester compound shown in Formula I.

3. The preparation method according to claim 2, characterized in that, The weight-average molecular weight of the polyethylene glycol is 106-600, preferably 150-400.

4. The preparation method according to claim 3, characterized in that, The polyethylene glycol is any one or a combination of at least two of diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, polyethylene glycol 400, or polyethylene glycol 600.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the lactone-type sophorolipid to polyethylene glycol is 1:3 to 1:

5.

6. The preparation method according to any one of claims 2-5, characterized in that, The catalyst is selected from long-chain alkyl sulfonic acids.

7. The preparation method according to claim 6, characterized in that, The long-chain alkyl sulfonic acid is any one or a combination of at least two of C8-C16 alkylbenzene sulfonic acid, C8-C16 alkyl sulfonic acid, or C8-C16 alkylnaphthalene sulfonic acid, preferably dodecylbenzene sulfonic acid.

8. The preparation method according to any one of claims 2-7, characterized in that, The amount of catalyst used is 10% to 12% of the total mass of lactone-type sophorolipid and polyethylene glycol.

9. The preparation method according to any one of claims 2-8, characterized in that, The reaction temperature is 70-90℃, and the reaction time is 5-10h.

10. The application of the sophorolipid polyethylene glycol monoester compound according to claim 1 in industrial cleaning agents.

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