Bio-based environment-friendly windshield cleaning fluid

Abstract

The invention belongs to the technical field of automobile chemicals, and particularly relates to bio-based environment-friendly windshield cleaning fluid. Comprising 10%-35% of hyperbranched polyglycerol functionalized by a hydrophobic group, 5%-25% of a bio-based eutectic solvent, 0.5%-5% of a composite bio-based surfactant, 0.1%-1.0% of a bio-based chelating agent, 0.05%-0.5% of a proteolytic enzyme preparation, 0.1%-0.5% of a pH buffer agent, 0.05%-0.2% of a preservative and the balance of deionized water. By the adoption of the technical scheme, efficient cleaning and low-temperature anti-freezing performance on complex dirt can be achieved, meanwhile, damage to materials such as rubber and paint surfaces is avoided, a complete bio-based source and high biodegradability are achieved, and environmental friendliness and material safety are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of automotive chemical technology, specifically a bio-based environmentally friendly windshield washer fluid. Background Technology

[0002] Windshield washer fluid, commonly known as glass cleaner, is a key functional fluid for ensuring clear visibility and traffic safety. Its core technological requirement is the ability to quickly and effectively remove various complex contaminants such as dust, oil film, insect remains, bird droppings, and tree sap from the windshield surface under various climatic and driving conditions. Simultaneously, it must possess excellent antifreeze properties in low-temperature environments to prevent freezing and clogging of pipes and nozzles. To achieve these functional goals, existing technologies, after long-term development and market validation, have formed a technical solution with alcohol compounds as the main active ingredients. Specifically, these mainstream washer fluids typically use low molecular weight alcohols such as methanol, ethanol, or isopropanol as the core solvent and antifreeze agent, compounded with a certain amount of ethylene glycol to further enhance the antifreeze effect, and supplemented with anionic or nonionic surfactants to reduce the surface tension of the system and enhance its wetting and emulsifying ability for oily contaminants. The design principle of this technical solution lies in the fact that low-carbon alcohols not only have good water solubility, but their molecular structure also possesses a certain degree of oleophilicity, enabling them to effectively dissolve or disperse various polar and non-polar contaminants on the glass surface. Simultaneously, their extremely low eutectic point with water gives the cleaning fluid reliable low-temperature fluidity. It can be said that this alcohol-ethylene glycol-based formulation system, at the functional level, excellently solves the core technical problem of maintaining windshield cleanliness over a wide temperature range, forming the technological cornerstone of the current market.

[0003] However, with the continuous advancement of materials science in the automotive industry and the increasing global emphasis on environmental protection and sustainable development, some inherent properties of the aforementioned traditional technical solutions at the principle level have gradually revealed their inherent limitations and deep-seated contradictions when facing new challenges. The reason for this lies in the fact that the highly efficient cleaning and antifreeze performance of traditional cleaning fluids largely relies on highly volatile and permeable small-molecule organic solvents such as methanol and ethanol. While this chemical characteristic effectively removes dirt, it also brings potential corrosiveness to non-glass components of the vehicle. For example, rubber or elastomer components such as the sealing strips around the windshield and wiper blades, when exposed to high concentrations of alcohol solvents for extended periods, are prone to having their internal plasticizers and other small-molecule additives dissolved, leading to premature hardening, cracking, and decreased elasticity, thus significantly shortening their service life and affecting their functionality. Similarly, high concentrations of alcohol solvents also pose a certain risk of swelling and corrosion to vehicle paint surfaces, especially the clear coat layer; long-term repeated contact may lead to a decrease in paint gloss or microscopic damage. This trade-off between cleanliness and material compatibility was not prominent in the early days of vehicle manufacturing when materials were relatively simple and durability requirements were not high. However, with the trend of modern automobiles using a large number of precision polymer composite materials, special coatings and precision rubber products, it has evolved into a long-term reliability issue that cannot be ignored.

[0004] Furthermore, the environmental attributes and sustainability of this technological solution also face severe challenges. Methanol and ethanol, as the main components, are both volatile organic compounds (VOCs). Their large-scale volatilization during use places a burden on the atmospheric environment, contradicting increasingly stringent environmental regulations. At the same time, methanol itself has clear biotoxicity, and its production mainly relies on fossil resources, which is inconsistent with the strategic direction of a circular economy and carbon neutrality. Although the industry has tried to use bio-derived ethanol as an alternative, this has not fundamentally solved the problems of volatility and material compatibility. Essentially, traditional technological approaches have fallen into a dilemma: the chemical mechanisms upon which efficient cleaning and antifreeze rely are fundamentally at odds with the chemical properties required to achieve material mildness, environmental friendliness, and biodegradability. Simply reducing the alcohol concentration sacrifices core functionality, while finding alternative non-alcoholic small-molecule antifreeze agents often faces issues of cost, efficiency, or new toxicity.

[0005] Therefore, the present invention provides a bio-based, environmentally friendly windshield washer fluid. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: The present invention provides a bio-based environmentally friendly windshield washer fluid, comprising an aqueous composition containing, by total weight percentage: 10% to 35% of hydrophobically functionalized hyperbranched polyglycerol; 5% to 25% of a bio-based eutectic solvent; 0.5% to 5% of a complex bio-based surfactant; 0.1% to 1.0% of a bio-based chelating agent; 0.05% to 0.5% of a proteolytic enzyme preparation; 0.1% to 0.5% of a pH buffer; 0.05% to 0.2% of a preservative; and the balance being deionized water.

[0008] The core innovation of this technical solution lies in its abandonment of the traditional approach of relying on small-molecule alcohols for cleaning and antifreeze. Instead, it constructs a multi-component synergistic system with a specific structured macromolecular polymer—functionalized hyperbranched polyglycerol (f-HPG) with hydrophobic groups—as the functional core, and compounded with a bio-based deep eutectic solvent (Bio-DES) to form a synergistic antifreeze system. Through the precise design and coupling of the structure and function of each component, this system produces a series of unexpected technical effects.

[0009] Furthermore, the hyperbranched polyglycerol functionalized with hydrophobic groups is a key component in the cleaning solution of this invention, responsible for both core cleaning and partial antifreeze functions. Chemically, it is a highly branched polyether polymer with a three-dimensional spherical topology, its backbone composed of glycerol monomers linked by ether bonds. As a specific embodiment of this invention, the hyperbranched polyglycerol has the following defined structural parameters: its weight-average molecular weight (Mw) is controlled within the range of 3,000 to 20,000 g / mol, a more preferred range being 5,000 to 10,000 g / mol; its degree of branching (DB), measured by 1H NMR spectroscopy using the method defined by Frey et al., is not less than 0.70, a more preferred range being 0.85 to 0.95; and its molecular weight distribution index (PDI) is less than 1.8. The functionalization of the hyperbranched polyglycerol refers to the formation of ester bonds through esterification reactions between a specific proportion of the terminal primary hydroxyl groups densely distributed on the outer edge of its molecule and a hydrophobic carboxylic acid derived from biomass. The hydrophobic carboxylic acid is levulinic acid, a platform compound derived from cellulose hydrolysis. The degree of functionalization, i.e., the degree of substitution (DS) of the levulinic ester group for the terminal hydroxyl group, is controlled within the range of 5% to 20%. The unique molecular structure of f-HPG endows it with a mechanism for multiple synergistic functions: Firstly, the polyether skeleton inside its molecule is lipophilic, while the large number of unreacted terminal hydroxyl groups on the molecular surface endow it with extremely strong hydrophilicity. This macromolecular amphiphilic structure makes it like a nano-sized micelle, which can effectively encapsulate and disperse non-polar contaminants such as oil films and resins. Secondly, the grafted acetylacetate group, with its carbonyl and terminal methyl structure, significantly enhances the affinity and solubilization ability for specific organic dirt, achieving targeted cleaning of complex dirt such as insect remains. Its cleaning efficiency is significantly higher than that of unfunctionalized hyperbranched polyglycerol. Thirdly, the densely distributed hydroxyl groups on its surface form numerous hydrogen bonds with water molecules, strongly binding them and inhibiting their crystallization orientation. This effectively disrupts the formation of ice crystal networks, giving the cleaning fluid inherent antifreeze properties. As a macromolecular polymer, its molecular size is much larger than the micropores of rubber or car paint coatings, preventing it from penetrating into the polymer matrix. This fundamentally eliminates swelling, plasticizer leaching, or chemical corrosion of these materials, achieving absolute material mildness.

[0010] Furthermore, the bio-based eutectic solvent is a key component in the synergistic effect with f-HPG to construct the low-temperature antifreeze system of the cleaning solution of this invention. The eutectic solvent is a eutectic mixture formed by mixing two or more solid compounds derived from biomass in a specific molar ratio, which, through intermolecular hydrogen bonding, forms a liquid mixture at room temperature. Its freezing point is much lower than the melting points of each individual component. Furthermore, the bio-based eutectic solvent is composed of choline chloride as a hydrogen bond acceptor and 1,3-propanediol as a hydrogen bond donor. Choline chloride can be prepared via bio-fermentation, and 1,3-propanediol can be prepared via corn syrup fermentation. The molar ratio of choline chloride to 1,3-propanediol is precisely controlled within the range of 1:2 to 1:4, with a preferred molar ratio of 1:3, at which the system has the lowest eutectic point. A significant synergistic antifreeze effect exists between this bio-based eutectic solvent and f-HPG: f-HPG physically interferes with crystallization through water binding, while the eutectic solvent provides antifreeze capability chemically through the classic principle of freezing point depression and its own extremely low freezing point. The combined antifreeze effect is far greater than the linear sum of the individual components, achieving antifreeze levels of, for example, -25°C or lower at relatively low addition amounts. This is a non-obvious synergistic effect. Meanwhile, this eutectic solvent has an extremely low vapor pressure, does not produce VOC emissions, and its ionic liquid properties endow it with excellent dissolving ability, making it suitable as a co-solvent to assist in the cleaning process.

[0011] Furthermore, the composite bio-based surfactant reduces the surface tension of the cleaning solution, enhances its wetting properties on the glass surface, and improves its ability to penetrate and remove dirt. To achieve a broad-spectrum cleaning effect on various complex dirt types while maintaining the system's biodegradability, this invention employs a compound system of a nonionic surfactant and an anionic surfactant. Furthermore, the nonionic surfactant is an alkyl polysaccharide (APG) with 8 to 16 carbon atoms in its hydrophobic alkyl chain and an average degree of polymerization (DP) of 1.4 to 1.7 in its hydrophilic glucose units. The anionic surfactant is sodium cocoyl glutamate, an amino acid-based surfactant. The weight ratio of the alkyl polysaccharide to sodium cocoyl glutamate is controlled within the range of 2:1 to 5:1. The synergistic effect of this composite system is reflected in the following: the alkyl polysaccharide provides strong wetting, detergency, and emulsifying capabilities, while sodium cocoyl glutamate complements it with its extreme mildness, excellent calcium soap dispersing ability, and hard water resistance, and can protect the proteolytic enzymes in the formulation from inactivation, ensuring the stable functioning of each component.

[0012] Furthermore, the bio-based chelating agent functions to complex hardness ions such as calcium and magnesium in water, preventing them from reacting with dirt or surfactants to form insoluble precipitates (i.e., scale or soap scum), thereby maintaining the clarity and cleaning efficiency of the cleaning solution, especially in hard water areas. To implement the fully bio-based design principle, this invention uses tetrasodium glutamate diacetate (GLDA) as the chelating agent. GLDA, derived from L-glutamate, possesses excellent chelating ability and rapid biodegradability, making it a green alternative to the traditional chelating agent ethylenediaminetetraacetic acid (EDTA).

[0013] Furthermore, the proteolytic enzyme preparation is a special functional component introduced by the present invention for specific stubborn stains (such as insect carcasses, bird droppings, tree sap, and other protein-rich stains). Furthermore, the proteolytic enzyme preparation is a stabilized Bacillus subtilis protease. This Bacillus subtilis protease is recombinantly expressed and produced in a specific Bacillus licheniformis using genetic engineering methods, and is stabilized using borate-free microencapsulation technology to ensure its storage stability in aqueous liquid formulations. Its addition amount in the final cleaning solution formulation, in terms of activity units, is 5 to 20 Anson Units of protease activity per gram of cleaning solution. The mechanism of action of this Bacillus subtilis protease lies in its ability to specifically catalyze the hydrolysis of peptide bonds in large protein molecules, degrading them into water-soluble small peptides or amino acids. This transforms protein contaminants that were originally firmly adhered to the glass surface into substances that can be easily washed away by water, achieving highly efficient removal of biological contaminants that are difficult to treat with conventional cleaning agents.

[0014] Furthermore, the pH buffer is used to precisely maintain the pH value of the cleaning solution within a stable range that is favorable to all components. Furthermore, a buffer system composed of citric acid and sodium citrate is used to regulate and stabilize the pH of the final product within a weakly alkaline range of 7.5 to 8.5. This pH range represents an optimal balance for achieving several objectives: Firstly, this is the optimal pH environment for the proteolytic enzyme to exert its highest catalytic activity; Secondly, under these pH conditions, the ester bond structure of f-HPG exhibits optimal hydrolytic stability. Thirdly, this weakly alkaline environment is non-corrosive to both metallic and non-metallic materials, ensuring the safety of vehicle components.

[0015] The beneficial effects of this invention are as follows: By employing macromolecular f-HPG and a non-volatile eutectic solvent as the functional host, the penetration, swelling, and corrosion mechanisms of traditional small-molecule alcohol solvents on rubber, plastics, and automotive paint are completely avoided. In a 500-hour EPDM rubber immersion test, the rubber parts immersed in the samples of this invention showed a Shore A hardness change of less than 2% and a weight change of less than 1%, while the comparative samples treated with traditional methanol-based cleaning solutions showed a hardness increase of more than 15% and a weight loss of more than 5%, indicating that the product of this invention does not cause aging damage to rubber parts. It integrates the four functions of f-HPG macromolecular encapsulation and solubilization, low eutectic solvent-assisted dissolution, composite surfactant wetting and penetration, and proteolytic enzyme specific degradation, forming a three-dimensional and all-round cleaning network for mixed dirt such as oil film, dust, and biological residue. Its comprehensive cleaning efficiency is more than 30% higher than that of traditional alcohol-based products in standardized mixed dirt tests. The physical water-binding mechanism of f-HPG and the chemical freezing point lowering mechanism of the eutectic solvent mutually reinforce each other, so that when the f-HPG concentration is 20% and the eutectic solvent concentration is 15%, the freezing point of the system can reach below -35℃. However, when using 35% f-HPG or 35% eutectic solvent alone, the freezing point is above -20℃, showing a synergistic effect of 1+1 being much greater than 2. All core functional components in the formulation (f-HPG, eutectic solvent, surfactant, chelating agent, enzyme) are derived from renewable biomass resources, and their bio-based carbon content is greater than 95% as tested by ASTM D6866 standard. According to OECD 301F standard biodegradability testing, the composition of this invention exhibits a biodegradability rate exceeding 80% within 28 days, far higher than traditional products. Furthermore, since it contains no volatile organic compounds, its VOC content is almost zero, fully complying with the most stringent environmental regulations. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings; Figure 1 This is a component block diagram of a bio-based environmentally friendly windshield washer fluid of the present invention; Figure 2 This is a flowchart illustrating the preparation method of a bio-based environmentally friendly windshield washer fluid according to the present invention. Figure 3 This is a schematic diagram of the multi-dimensional collaborative cleaning mechanism of the present invention.

[0017] In the figure: 10, hyperbranched polyglycerol functionalized with hydrophobic groups; 20, bio-based eutectic solvent; 30, complex bio-based surfactant; 40, bio-based chelating agent; 50, proteolytic enzyme preparation; 60, pH buffer. Detailed Implementation

[0018] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0019] like Figures 1-3 As shown, an embodiment of the present invention provides a bio-based environmentally friendly windshield washer fluid. The composition of the washer fluid, by total weight percentage, comprises 10% to 35% of hydrophobically functionalized hyperbranched polyglycerol, 5% to 25% of a bio-based eutectic solvent, 0.5% to 5% of a complex bio-based surfactant, 0.1% to 1.0% of a bio-based chelating agent, 0.05% to 0.5% of a proteolytic enzyme preparation, 0.1% to 0.5% of a pH buffer, 0.05% to 0.2% of a preservative, and the balance being deionized water.

[0020] In some embodiments, hydrophobically functionalized hyperbranched polyglycerol (f-HPG) is a key component responsible for the core cleaning and partial antifreeze functions of this technical solution. Its molecular structure is that of a highly branched, three-dimensional spherical polyether polymer. Its preparation process begins with glycerol as a monomer, constructing a hyperbranched polyglycerol backbone through a condensation reaction. The structural parameters of this backbone are strictly controlled to ensure its final macroscopic physicochemical properties. As previously stated, its weight-average molecular weight (Mw) is precisely controlled within the range of 3,000 to 20,000 g / mol. In a more preferred embodiment, to achieve the best balance between solubility and film-forming properties, its weight-average molecular weight range is set to 5,000 to 10,000 g / mol. The degree of branching (DB) of the molecule is determined using the ¹H NMR integral method according to the analytical model established by Frey et al., and the value is required to be no less than 0.70 to ensure that the molecular structure is sufficiently compact and has a large number of terminal functional groups. Continuing from the above, in an optimized embodiment, its branching degree is as high as 0.85 to 0.95; Furthermore, its molecular weight distribution index (PDI), i.e., the ratio of weight-average molecular weight to number-average molecular weight, was controlled to be less than 1.8, indicating that the polymer system has high molecular weight uniformity. The functionalization step of this hyperbranched polyglycerol backbone refers to the selective chemical modification of the terminal primary hydroxyl groups densely distributed on its molecular periphery. The modifying agent used was levulinic acid, a bio-based carboxylic acid that can be further converted from furfural, a cellulose hydrolysis platform compound. Through esterification under the action of a catalyst, the carboxyl groups of levulinic acid condensed with the primary hydroxyl groups of polyglycerol to form ester bonds, thereby grafting hydrophobic levulinic acid ester groups onto the surface of the hydrophilic polyglycerol backbone. The degree of functionalization, i.e., the degree of substitution (DS) of the levulinic acid ester groups for the total number of available terminal hydroxyl groups, was precisely controlled within the range of 5% to 20%. This unique molecular structure design endows f-HPG with an intrinsic mechanism of multiple synergistic effects. Firstly, the polyether skeleton itself has a certain degree of lipophilicity, while the large number of unesterified terminal hydroxyl groups on the molecular surface endow it with extremely strong hydrophilicity and hydration ability, making the entire macromolecule exhibit amphiphilic properties similar to monomolecular micelles. It can effectively encapsulate non-polar contaminants such as oil films and resins in the hydrophobic cavities inside its molecules and stably disperse them in the aqueous phase. Secondly, the grafted acetylacetic acid ester group, with its carbonyl group and terminal methyl group, significantly enhances the polymer's affinity and solubilizing ability for specific organic stains, especially complex esters and ketones in insect remains and plant sap, achieving targeted cleaning of such stubborn stains. Thirdly, the high-density distribution of hydroxyl functional groups on its molecular surface can strongly bind surrounding water molecules by forming a large network of hydrogen bonds, effectively inhibiting the orderly arrangement and crystallization of water molecules at low temperatures. This physically disrupts the formation of ice crystal networks, providing fundamental antifreeze properties for the cleaning fluid. Crucially, as a large polymer with a molecular size at the nanoscale, it cannot penetrate into the microscopic network pores of rubber seals or vehicle paint coatings, thus fundamentally preventing damage to the polymer matrix such as swelling, plasticizer leaching, or chemical corrosion, ensuring excellent material mildness.

[0021] In some embodiments, the bio-based eutectic solvent (Bio-DES) is another key component that works synergistically with f-HPG to construct the efficient low-temperature antifreeze system of the cleaning fluid of the present invention. This eutectic solvent is essentially an analogue of an ionic liquid, consisting of two or more biomass-derived compounds that are solid at room temperature. After physical mixing in a specific molar ratio, the strong intermolecular hydrogen bonding interactions, such as the interaction between hydrogen bond acceptors and hydrogen bond donors, result in a mixture whose melting point (or freezing point) is much lower than that of any single component, thus exhibiting a stable liquid state at room temperature. In one specific embodiment, the bio-based eutectic solvent consists of choline chloride as a hydrogen bond acceptor and 1,3-propanediol as a hydrogen bond donor. Choline chloride can be industrially produced via microbial fermentation, while 1,3-propanediol can be prepared on a large scale via corn syrup fermentation; both are well-established bio-based chemicals. To obtain the lowest possible eutectic point, the molar ratio of choline chloride to 1,3-propanediol is precisely controlled within the range of 1:2 to 1:4, with a preferred molar ratio of 1:3. At this molar ratio, the freezing point of the system can be lowered to below -60°C. An unexpected synergistic antifreeze effect exists between this bio-based eutectic solvent and f-HPG. f-HPG binds water molecules through its high-density hydroxyl network, physically interfering with the kinetics of the crystallization process, while the eutectic solvent provides strong antifreeze capabilities from a chemothermodynamic perspective through the classical colligative principle—that the introduction of solute leads to a decrease in the solvent's freezing point—and its own extremely low freezing point. The combination of these two mechanisms produces a final antifreeze effect that is far greater than the value that could be predicted by linearly summing the antifreeze effects of each component acting alone, demonstrating a significant synergistic effect. Understandably, this effect enables the present invention to achieve antifreeze performance indicators such as -25°C, -40°C, or even lower, with relatively low total antifreeze addition. Furthermore, this eutectic solvent, due to its ionic properties, has an extremely low vapor pressure, produces almost no volatile organic compound (VOC) emissions, and as an excellent solvent itself, it can assist in dissolving certain polar contaminants on the glass surface, contributing to the cleaning process.

[0022] Furthermore, the composite bio-based surfactant plays a crucial role in this cleaning solution formulation by reducing the surface tension of the system, enhancing the wetting and spreading ability of the windshield substrate, and promoting the penetration, stripping, and emulsification dispersion of solid and liquid dirt. To achieve a broad-spectrum cleaning effect on the complex and diverse dirt in the road environment, while simultaneously ensuring the complete biodegradability of the entire formulation, this technical solution employs a compound system of a nonionic surfactant and an anionic surfactant. In one specific embodiment, the nonionic surfactant is an alkyl polyglucan glycoside (APG), preferably having 8 to 16 carbon atoms in its hydrophobic alkyl chain, a specific example being octyl / decyl glucoside (C8-10) or decyl / lauryl glucoside (C10-16); its hydrophilic end is a polysaccharide chain composed of glucose units, with an average degree of polymerization (DP) controlled between 1.4 and 1.7. The anionic surfactant is sodium cocoyl glutamate, an amino acid-based surfactant obtained by reacting natural coconut oil fatty acids with glutamic acid. To achieve the optimal performance balance, the weight ratio of alkyl polyglucan glycoside to sodium cocoyl glutamate is controlled within the range of 2:1 to 5:1. Understandably, the synergistic effect of this composite surfactant system is reflected in the following aspects: alkyl polysaccharide, as the main surfactant, provides strong wetting, detergency and emulsifying capabilities, especially effective against oily dirt; while sodium cocoyl glutamate serves as a functional complement with its extreme mildness, excellent foaming and foam stability, as well as its superior calcium soap dispersing ability and hard water resistance. More importantly, its amino acid structure can effectively protect the active structure of the proteolytic enzymes added to the formula, preventing them from becoming inactive due to surface activity during storage and use, thereby ensuring the long-term stability and synergistic effect of all functional components in the entire cleaning solution system.

[0023] In some embodiments, the present invention further includes a bio-based chelating agent, which functions to complex divalent metal ions such as calcium and magnesium in the cleaning solution dilution water and rainwater, i.e., so-called hardness ions. If these ions are not effectively controlled, they will react with fatty acids or anionic surfactants in the dirt to form insoluble precipitates, i.e., scale or soap scum. These precipitates will adhere to the glass surface to form spots and reduce the overall cleaning efficiency of the cleaning solution. In some embodiments, the present invention uses tetrasodium glutamate diacetate (GLDA) as a chelating agent. GLDA is a highly efficient and environmentally friendly chelating agent derived from the natural amino acid L-glutamic acid. It has excellent complexing ability for calcium and magnesium ions and can be rapidly and completely degraded by microorganisms in the environment. It is an ideal green alternative to traditional petroleum-based chelating agents such as ethylenediaminetetraacetic acid (EDTA) and its salts, ensuring that the cleaning solution maintains its clarity and high cleaning performance even when used in hard water areas.

[0024] In response to specific types of stubborn biological stains, such as insect carcasses, bird droppings, and dripping tree sap that have impacted the windshield during high-speed driving, this invention introduces a proteolytic enzyme preparation as a special functional component, based on real-world scenarios. These stains are mainly composed of proteins and polysaccharides, which are difficult to remove effectively with traditional cleaning agents. In one specific embodiment, the proteolytic enzyme preparation is a specially stabilized Bacillus subtilis protease. This Bacillus subtilis protease is obtained through recombinant expression, fermentation, and purification using modern genetic engineering techniques on a specific industrial strain such as Bacillus licheniformis. To ensure sufficient storage stability in liquid formulations rich in moisture and surfactants, the Bacillus subtilis protease preparation is encapsulated using advanced borate-free microencapsulation technology, forming a protective structure that allows for slow release in an aqueous environment or ruptures to release the active enzyme upon use. Its addition amount in the final cleaning solution formulation, measured in catalytic activity units, is precisely controlled to contain 5 to 20 Anson Units of protease activity per gram of cleaning solution. The mechanism of action of this Bacillus subtilis protease is highly specific; it efficiently catalyzes the hydrolysis of peptide bonds within large protein molecules, degrading water-insoluble and highly adhesive protein network structures into water-soluble small polypeptide or amino acid fragments. This process transforms the biological dirt that is originally firmly attached to the glass surface into a substance that can be easily washed away by water or windshield wipers, thus achieving targeted and efficient removal of biological dirt that is difficult to effectively remove with conventional chemical cleaning agents.

[0025] Finally, to ensure that the various functional components in the cleaning solution, especially the proteolytic enzymes and the ester bond structure in f-HPG, can function stably in their optimal environment, this invention also includes a pH buffer. Its function is to precisely regulate and stabilize the pH value of the finished cleaning solution within a predetermined range that is beneficial to all components. In one specific embodiment, the present invention employs a buffer system composed of citric acid and sodium citrate. By precisely adjusting the ratio of the two, the pH value of the final product is stabilized within a weakly alkaline range of 7.5 to 8.5. This pH range is the optimal equilibrium point determined after extensive experimental optimization. Firstly, this is the optimal pH environment for the selected subtilisin protease to exert its highest catalytic activity; Secondly, under these weakly alkaline conditions, the acetylacetate bond on the f-HPG molecule has the best hydrolytic stability, which can effectively prevent degradation during long-term storage and loss of its targeted cleaning function. Third, this pH range exhibits excellent chemical inertness to common materials in vehicles, such as metals, plastics, rubber, and paint, posing no risk of corrosion and ensuring absolute safety for all vehicle components.

[0026] To further illustrate the technical solution and practical effects of the present invention, several specific embodiments and comparative examples are listed below, and their key performance is tested and compared.

[0027] Example 1: A bio-based, environmentally friendly windshield washer fluid designed with an antifreeze temperature of -25°C This embodiment provides a standard cleaning solution with the following composition and weight percentages: hyperbranched polyglycerol functionalized with levulinic acid (weight-average molecular weight Mw of 8,000 g / mol, degree of branching DB of 0.90, and degree of substitution of levulinic acid ester group DS of 10%) 22.0%; bio-based eutectic solvent (premixed from choline chloride and 1,3-propanediol in a molar ratio of 1:3) 15.0%; composite bio-based surfactant (composed of alkyl polysaccharide C8-10, DP=1.5, and sodium cocoyl glutamate in a weight ratio of 3:1) 2.0%; tetrasodium glutamate diacetate (added in its 40% aqueous solution) 0.5%; stabilized Bacillus subtilis protease preparation (activity specification of 10 AU / g) 0.2%; buffer composed of citric acid and sodium citrate 0.3%; composite preservative composed of potassium sorbate and sodium benzoate in a weight ratio of 1:1 0.1%; the remaining components are deionized water, added to 100%.

[0028] The preparation method of this cleaning solution includes the following engineering steps: First, in a stainless steel reactor equipped with a stirring device and a temperature control jacket, add deionized water equal to 80% of the total weight of the formula and start medium-speed stirring. Then, at room temperature, add citric acid / sodium citrate buffer, tetrasodium glutamate diacetate aqueous solution, and composite preservative to the reactor in sequence, and continue stirring until all solid materials are completely dissolved to form a clear solution; Next, the temperature of the material inside the reactor is raised to 40°C by a temperature control jacket. At this temperature, hyperbranched polyglycerol powder functionalized with levulinic acid is slowly added into the vortex. This temperature is maintained and the mixture is stirred continuously for 1 hour to ensure that the macromolecular polymer is fully hydrated, swollen and finally dissolved to form a uniform and transparent viscous solution. Subsequently, the temperature inside the reactor was lowered to room temperature (approximately 25°C), and the bio-based eutectic solvent liquid prepared in another container was added. Stirring was continued for 30 minutes to ensure thorough mixing of the two phases. Next, while stirring at a low speed, add the complex bio-based surfactant component, being careful to control the stirring speed to avoid generating excessive foam, and stir until the system is uniformly mixed. Then, while maintaining low-speed stirring, add the stabilized Bacillus subtilis protease preparation, and gently stir for 15 minutes to ensure it is uniformly dispersed in the liquid; Finally, use a calibrated pH meter to check the pH value of the solution. If there is a deviation, fine-tune it with a small amount of dilute citric acid solution or sodium citrate solution until the pH value stabilizes within the range of 8.0 ± 0.2. After confirming that the pH is qualified, add the remaining deionized water to the total amount designed in the formula, and continue stirring for 10 minutes to ensure that the final product is completely homogeneous. The result is a clear, phase-free finished cleaning solution.

[0029] Example 2: A heavy-duty cleaning fluid designed for an antifreeze temperature of -40℃ This embodiment provides a cleaning solution suitable for extremely cold regions, the composition and weight percentage of which are as follows: hyperbranched polyglycerol functionalized with levulinic acid (Mw=6,000 g / mol, DB=0.88, DS=15%) 30.0%; bio-based eutectic solvent (choline chloride and 1,3-propanediol, molar ratio 1:3.5) 25.0%; complex bio-based surfactant (alkyl polyglycoside C10-16, DP=1.6, and sodium cocoyl glutamate, weight ratio 4:1) 3.0%; tetrasodium glutamate diacetate (40% aqueous solution) 0.8%; stabilized Bacillus subtilis protease preparation (activity 15 AU / g) 0.4%; citric acid / sodium citrate buffer 0.4%; potassium sorbate / sodium benzoate preservative (weight ratio 1:1) 0.15%; deionized water, balance to 100%. The preparation method is the same as the engineering steps described in Example 1.

[0030] Example 3: An economical all-season cleaning solution This embodiment provides a cleaning solution suitable for mild climatic conditions, the composition and weight percentage of which are as follows: hyperbranched polyglycerol functionalized with levulinic acid (Mw=10,000 g / mol, DB=0.92, DS=8%) 12.0%; bio-based eutectic solvent (choline chloride and 1,3-propanediol, molar ratio 1:2.5) 8.0%; composite bio-based surfactant (alkyl polyglycoside C8-10, DP=1.5, and sodium cocoyl glutamate, weight ratio 3:1) 1.5%; tetrasodium glutamate diacetate (40% aqueous solution) 0.3%; stabilized Bacillus subtilis protease preparation (activity 8 AU / g) 0.15%; citric acid / sodium citrate buffer 0.2%; potassium sorbate / sodium benzoate preservative (weight ratio 1:1) 0.1%; deionized water, balance to 100%. The preparation method is the same as the engineering steps described in Example 1.

[0031] Comparative Example 1: A conventional methanol-based cleaning solution To compare performance, a cleaning solution representing the prior art was prepared, with the following composition and weight percentages: methanol 35.0%; ethylene glycol 5.0%; sodium dodecylbenzenesulfonate 0.5%; disodium ethylenediaminetetraacetate (EDTA-2Na) 0.1%; appropriate amounts of dye and fragrance; deionized water, balance to 100%.

[0032] Comparative Example 2: A cleaning solution using unfunctionalized hyperbranched polyglycerol To verify the role of levulinate group functionalization in f-HPG, this comparative example was prepared. Its formulation was exactly the same as that of Example 1, except that the levulinate-functionalized hyperbranched polyglycerol was replaced with an equal amount of un-levulinate-functionalized hyperbranched polyglycerol (Mw=8,000 g / mol) with the same structural parameters.

[0033] Comparative Example 3: A cleaning solution without bio-based eutectic solvent To verify the synergistic antifreeze effect between f-HPG and bio-based eutectic solvents, this comparative example was prepared. Except for the antifreeze component, its formulation was identical to that of Example 1. This formulation did not contain bio-based eutectic solvents. To achieve the same theoretical total antifreeze content as Example 1 (total antifreeze content 22.0% + 15.0% = 37.0%), the content of levulinic acid-functionalized hyperbranched polyglycerol (parameters same as Example 1) was increased to 37.0%.

[0034] A series of standardized performance tests were conducted on the samples prepared in Examples 1, 2, and 3, as well as Comparative Examples 1, 2, and 3, to quantitatively evaluate their technical effects. The test items and results are summarized in the table below:

[0035] The following conclusions can be drawn from the experimental data in the table above: First, regarding antifreeze performance, Example 1 achieved a lower freezing point (-27.2℃ vs -26.5℃) with a total antifreeze content (37%) comparable to Comparative Example 1 (40%), demonstrating the effectiveness of the synergistic system of this invention. More importantly, the comparison between Example 1 and Comparative Example 3 clearly reveals the synergistic effect: with a total antifreeze content of 37% in both examples, the freezing point of Example 1 (f-HPG and DES compound) is significantly lower than that of Comparative Example 3 (f-HPG only) at -18.8℃. This indicates that the combination of the two antifreeze components produces a non-linear additive effect far greater than 1+1, representing an unexpected technological advancement. Meanwhile, the freezing point of Comparative Example 2 (-19.5℃) is also significantly higher than that of Example 1, indicating that the introduction of the acetylacetate group also contributes to enhancing the interaction with water molecules, thus positively contributing to the antifreeze performance.

[0036] Secondly, regarding cleaning efficiency, all embodiments of the present invention (ΔL* > 82) exhibited cleaning capabilities far exceeding those of conventional methanol-based products (Comparative Example 1, ΔL* = 65.7). The comparison between Example 1 and Comparative Example 2 is particularly important. With all other components identical, the cleaning efficiency index for complex stains containing protein mimics jumped from 71.3 to 85.6 simply because acetylacetate groups were grafted onto the hyperbranched polyglycerol backbone. This strongly demonstrates the decisive, albeit non-obvious, role of the hydrophobic functionalization in enhancing the targeted cleaning ability for specific stubborn stains.

[0037] Finally, regarding material compatibility, the test results revealed a fundamental difference. All embodiments of the present invention (1, 2, 3) showed negligible effects on the weight and hardness of EPDM rubber samples after a rigorous 70°C, 500-hour accelerated aging test (weight change rate <1%, hardness change ≤2), demonstrating excellent safety for critical automotive rubber components. In stark contrast, conventional methanol-based cleaning solutions (Comparative Example 1) resulted in significant mass loss (-5.8%) and hardening (16 units increase in hardness) in the rubber samples, typical of solvent extraction of plasticizers and chemical aging phenomena. This comparison irrefutably proves that the present invention, by employing macromolecular polymers and non-volatile solvents as the functional components, fundamentally solves the problem of corrosive damage to vehicle materials caused by traditional products.

[0038] In summary, the bio-based environmentally friendly windshield washer fluid provided by this invention has achieved breakthroughs in multiple dimensions, including high-efficiency cleaning, reliable antifreeze, absolute material safety, and complete environmental friendliness, through its unique component design and synergistic mechanism. Its technical effects have significant, non-obvious, advantages over existing technologies.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A bio-based, environmentally friendly windshield washer fluid, characterized in that, The cleaning solution is an aqueous composition comprising the following components by total weight percentage: 10% to 35% of hydrophobic functionalized hyperbranched polyglycerol (10); 5% to 25% of bio-based eutectic solvent (20); 0.5% to 5% of a complex bio-based surfactant (30); 0.1% to 1.0% of bio-based chelating agents (40); 0.05% to 0.5% of proteolytic enzyme preparations (50); 0.1% to 0.5% pH buffer (60); 0.05% to 0.2% preservative; The remaining portion is deionized water.

2. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The hydrophobic functionalized hyperbranched polyglycerol (10) has a chemical structure obtained by esterifying the terminal primary hydroxyl groups of the hyperbranched polyglycerol with levulinic acid. The weight-average molecular weight (Mw) of the hyperbranched polyglycerol backbone is controlled in the range of 3,000 to 20,000 g / mol. Its degree of branching (DB) is determined by nuclear magnetic resonance hydrogen spectroscopy using the method defined by Frey et al., and its value is not less than 0.

70. Its molecular weight distribution index (PDI) is less than 1.

8. The degree of substitution (DS) of the terminal hydroxyl groups of the levulinic acid is controlled within the range of 5% to 20%, thereby endowing the hyperbranched polyglycerol macromolecule with amphiphilic structural properties, enabling it to encapsulate and disperse non-polar contaminants, while inhibiting water molecule crystallization by forming hydrogen bonds with water molecules through the densely distributed hydroxyl groups on its surface.

3. The bio-based environmentally friendly windshield washer fluid according to claim 2, characterized in that, The hydrophobic-functionalized hyperbranched polyglycerol (10) has a weight-average molecular weight (Mw) of 5,000 to 10,000 g / mol and a degree of branching (DB) of 0.85 to 0.

95.

4. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The bio-based eutectic solvent (20) is composed of choline chloride as a hydrogen bond acceptor and 1,3-propanediol as a hydrogen bond donor. The molar ratio of choline chloride to 1,3-propanediol is precisely controlled within the range of 1:2 to 1:4 to achieve an extremely low freezing point and to synergistically provide antifreeze properties with the hydrophobically functionalized hyperbranched polyglycerol (10). The choline chloride can be prepared by bio-fermentation and the 1,3-propanediol can be prepared by fermentation of corn syrup.

5. The bio-based environmentally friendly windshield washer fluid according to claim 4, characterized in that, The molar ratio of choline chloride to 1,3-propanediol is 1:

3.

6. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The composite bio-based surfactant (30) comprises a compound system of a nonionic surfactant and an anionic surfactant; The nonionic surfactant is an alkyl polysaccharide (APG) with 8 to 16 carbon atoms in its hydrophobic alkyl chain and an average degree of polymerization (DP) of 1.4 to 1.7 in its hydrophilic glucose units. The anionic surfactant is sodium cocoyl glutamate; the weight ratio of the alkyl polysaccharide to sodium cocoyl glutamate is controlled within the range of 2:1 to 5:

1. The composite system works synergistically to reduce the surface tension of the cleaning solution, enhance the wetting performance of the glass surface and the ability to penetrate and remove dirt, while protecting the proteolytic enzyme (50) in the formula from inactivation.

7. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The proteolytic enzyme preparation (50) is a stabilized Bacillus subtilis protease, which is recombinantly expressed and produced in a specific Bacillus species through genetic engineering and is stabilized by encapsulation using borate-free microencapsulation technology to ensure its storage stability in aqueous liquid formulations. The amount of the proteolytic enzyme preparation (50) added to the final cleaning solution formulation, in terms of activity units, is 5 to 20 Anson Units of protease activity per gram of cleaning solution. The subtilis protease can specifically catalyze the hydrolysis of peptide bonds in large protein molecules, degrading them into small molecule polypeptides or amino acids that are easily soluble in water.

8. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The pH buffer (60) is a buffer system composed of citric acid and sodium citrate. Its function is to regulate and stabilize the pH of the cleaning solution in a weakly alkaline range of 7.5 to 8.5, so as to maintain the highest catalytic activity of the proteolytic enzyme (50) and ensure the hydrolytic stability of the ester bond structure in the hydrophobic group-functionalized hyperbranched polyglycerol (10).

9. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The bio-based chelating agent (40) is tetrasodium glutamate diacetate (GLDA), which is prepared from L-glutamic acid and is used to complex hardness ions such as calcium and magnesium in water to prevent them from forming insoluble precipitates.

10. The bio-based environmentally friendly windshield washer fluid according to claim 1, characterized in that, The content of the hydrophobic functionalized hyperbranched polyglycerol (10) is 20% to 25%, and the content of the bio-based eutectic solvent (20) is 12% to 18%, to synergistically achieve the excellent cleaning and antifreeze properties and material compatibility of the cleaning fluid.

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