An acidic cleaning composition and its use

Abstract

The application discloses an acid cleaning composition and application thereof, and relates to the technical field of daily chemicals. The acid cleaning composition comprises the following components in percentage by mass: 20-50% of an acid cleaning agent; 2-7% of a bactericide; 0.1-2% of a thickening agent; 0.01-10% of other additives; and the balance of water; wherein the thickening agent is a pH / ion responsive microcapsule emulsion. The acid cleaning composition of the application adopts the pH / ion responsive microcapsule, which not only provides storage stability and suitable initial viscosity, but also intelligently responds and ruptures when used in dilution, releases additional active acid, synergistically enhances the cleaning effect, maintains the viscosity of the dilution liquid, and prolongs the action time of the effective components on the vertical surface.

Description

Technical Field

[0001] This invention relates to the field of daily chemical products, and more particularly to an acidic cleaning composition and its application, especially suitable for cleaning washing machine tubs. Background Technology

[0002] After prolonged use, a large amount of dirt accumulates in the space between the inner and outer drums of a washing machine (i.e., the washing machine tub). This dirt mainly includes limescale, soap scum, fabric fibers, human skin flakes, and microorganisms, forming dense and stubborn complex stains. These stains not only affect the washing effect but may also breed bacteria, causing secondary pollution to clothes and posing health risks.

[0003] For alkaline stains in washing machine tubs, acidic cleaners have better dissolving and removal effects compared to traditional oxidizing bleach. Several acidic cleaning solutions for washing machine tubs exist in the prior art. For example, Chinese patent application CN108774591A discloses an antibacterial and anti-mildew washing machine cleaner and conditioner, using a high proportion of nonionic surfactants and citric acid (≤20%) as cleaners to remove washing machine dirt, and selecting polyhexamethylene biguanide and didecyl dimethyl ammonium chloride as antibacterial agents, achieving a sterilization rate of >90% against common fungi and bacteria; however, it does not address the problem of foam overflow caused by high nonionic surfactant concentrations during use, nor does it address the thickening issue of the cleaner and conditioner. Chinese patent application CN107267296A discloses a liquid washing machine tub cleaner, which uses strong inorganic acids such as nitric acid and sulfuric acid as pickling agents, while introducing metal protectants and corrosion inhibitors to mitigate the corrosion problem of strong inorganic acids on the washing machine; however, nitric acid and sulfuric acid are highly corrosive inorganic acids, posing safety risks in raw material storage and product use. Chinese patent CN11760371A discloses an acidic cleaning agent composition with stable viscosity and shear thinning, which achieves a thickening effect with a low acid content. The application scenario is for the product concentrate to be applied directly to toilets and toilet bowls. It is not suitable for cleaning washing machine tubs because a large amount of tap water is used to dilute it in washing machine cleaning, and the cleaning effect is not ideal.

[0004] Therefore, there is an urgent need to develop an acidic cleaning composition that has excellent cleaning effect, high safety, and can maintain appropriate viscosity under diluted use conditions to prolong the action time. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the present invention provides an acidic cleaning composition with significant cleaning effect, good bactericidal performance and no significant decrease in viscosity after dilution, which is especially suitable for cleaning washing machine tubs.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0007] An acidic cleaning composition is provided, comprising the following components in weight percentages: Pickling agent 20%-50%; bactericide 2%-7%; thickener 0.1%-2%; other additives 0.01%-10%; balance is water; The pickling agent comprises α-hydroxycarboxylic acid and methanesulfonic acid; the bactericide comprises C8-C18 alkyl dimethyl benzyl ammonium chloride and double-chain quaternary ammonium salt; the thickener is a pH / ion-responsive microcapsule emulsion, which comprises microcapsules containing a core material encapsulated by a composite wall material formed of cationic modified nanocellulose and polyurea / polyurethane, wherein the core material contains citric acid and lactic acid, and some cationic modified nanocellulose is free outside the microcapsules.

[0008] In this invention, α-hydroxycarboxylic acid and methanesulfonic acid are compounded as pickling agents to powerfully dissolve alkaline stains such as scale and soap scum using a high content of organic acids. At the same time, α-hydroxycarboxylic acid can adsorb and form a film on the metal surface, which plays a certain role in corrosion inhibition and protection, reducing the risk of corrosion to the inner drum of the washing machine.

[0009] The bactericide of this invention adopts a compound system of single-chain C8-C18 alkyl dimethyl benzyl ammonium chloride and double-chain quaternary ammonium salt. This compound system can work synergistically, not only having a good killing effect on common bacteria, but also having excellent removal ability on fungi, and can achieve long-term antibacterial effect.

[0010] The thickener used in this invention is a pH / ion-responsive microcapsule emulsion with a specific structure. In this microcapsule emulsion, the composite wall material of the microcapsules is composed of cationic modified nanocellulose and polyurea / polyurethane, while the encapsulated core material contains citric acid and lactic acid. Some cationic modified nanocellulose is also free on the outside of the microcapsules. Under the low pH and high ionic strength storage environment of the composition, the microcapsule wall material is in a contracted state, the core material does not leak, the system remains stable, and it provides a moderate base viscosity. When the composition is diluted with water and applied to the surface to be cleaned, the dilution causes the pH value to increase and the ionic strength to decrease. The microcapsule wall material undergoes synergistic swelling and rupture, releasing the encapsulated citric acid and lactic acid, which work together with the external acid detergent to achieve a synergistic effect on cleaning. More importantly, this responsive structure and the free cationic modified nanocellulose allow the composition to maintain a relatively high viscosity after dilution, avoiding the problem of a sudden drop in viscosity after dilution with traditional thickeners. When cleaning the washing machine tub, a higher dilution viscosity helps the detergent adhere better to the vertical tub walls, prolonging the contact time between the pickling agent and the disinfectant and dirt and microorganisms, thus improving the overall cleaning and sterilization efficiency.

[0011] Furthermore, the preparation method of the pH / ion-responsive microcapsule emulsion includes the following steps: (1) An oil phase containing citric acid, lactic acid and polyisocyanate is mixed with an aqueous phase containing cationic modified nanocellulose and emulsified to form an oil-in-water Pickering emulsion; (2) A polyfunctional amine is added to the oil-in-water Pickering emulsion and a polymerization reaction occurs at the oil-water interface to form microcapsules with polyurea / polyurethane and cationic modified nanocellulose as composite wall materials and citric acid and lactic acid as core materials; (3) After the reaction is completed, cationic modified nanocellulose is added to obtain the pH / ion-responsive microcapsule emulsion.

[0012] Preferably, in step (1), the mass ratio of citric acid to lactic acid in the oil phase is (1.5-2.5):1, and the mass ratio of the total mass of citric acid and lactic acid to the mass of polyisocyanate is (2-5):1; the mass fraction of cationic modified nanocellulose in the aqueous phase is 0.5%-3.0%, and the mass ratio of the oil phase to the aqueous phase is 1:(3-5). The Pickering emulsion formed in step (1) refers to an emulsion formed by using solid particles (i.e., cationic modified nanocellulose) to replace traditional surfactants to stabilize the oil-water interface. This emulsion provides a stable template for subsequent interfacial polymerization to form composite wall material microcapsules.

[0013] Preferably, the cationic modified nanocellulose is selected from Matexcel's NAT-4003.

[0014] Preferably, in step (2), the molar ratio of the polyfunctional amine to the polyisocyanate in step (1) is (0.8-1.2):1, and the reaction temperature is 50-80℃.

[0015] Preferably, the polyisocyanate is isophorone diisocyanate; and the polyfunctional amine is diethylenetriamine.

[0016] Preferably, in step (3), cationic modified nanocellulose is added to achieve a mass concentration of 0.5%-1.5% in the system after the reaction, thereby obtaining the pH / ion-responsive microcapsule emulsion. The added cationic modified nanocellulose constitutes a component outside the microcapsules and works together with the cationic modified nanocellulose on the microcapsule wall material to provide unique rheological properties.

[0017] Preferably, the pH / ion-responsive microcapsules have a particle size of 1-100 μm, more preferably 10-30 μm. Controlling the particle size within this range helps to ensure stable dispersion of the microcapsules in the composition and ensures that they can effectively respond to environmental changes during application.

[0018] In some specific embodiments, the preparation method of the pH / ion-responsive microcapsule emulsion of the present invention is as follows: S1 oil phase preparation: Citric acid and lactic acid are mixed at a mass ratio of (1.5-2.5):1, heated to 45-55℃ to dissolve, and then polyisocyanate (preferably isophorone diisocyanate) is added and mixed evenly to obtain the oil phase; wherein, the mass ratio of the total mass of citric acid and lactic acid to the mass of polyisocyanate is (2-5):1. S2 Aqueous Phase Preparation: Disperse cationic modified nanocellulose in deionized water and adjust the pH to 3.0-4.0 to obtain an aqueous phase; the mass fraction of cationic modified nanocellulose in the aqueous phase is 0.5%-3.0%. S3 emulsification: The oil phase is slowly added to the water phase, with a mass ratio of oil phase to water phase of 1:(3-5). High-speed shear emulsification is carried out at a speed of 1000-2000 rpm for 10-30 minutes to form an oil-in-water Pickering emulsion. S4 Interfacial Polymerization: The oil-in-water Pickering emulsion from step S3 is transferred to a reaction vessel and heated to 50-80°C. Under stirring at 200-400 rpm, an aqueous solution of a polyfunctional amine (preferably diethylenetriamine) is slowly added dropwise, wherein the molar ratio of the polyfunctional amine to the polyisocyanate is (0.8-1.2):1. The reaction is maintained at this temperature for 1-3 hours to allow polymerization at the oil-water interface, forming microcapsules with polyurea / polyurethane and cationic modified nanocellulose as the composite wall material and citric acid and lactic acid as the core material. S5 Post-processing: After the reaction in step S4 is completed, cool to room temperature and wash the microcapsules 2-3 times with deionized water to remove unreacted monomers; adjust the pH of the system to 3.0-4.0 and add cationic modified nanocellulose to a final concentration of 0.5%-1.5% to obtain the pH / ion-responsive microcapsule emulsion, wherein the average particle size of the microcapsules is 10-30 micrometers.

[0019] Preferably, the α-hydroxycarboxylic acid is selected from at least two of glycolic acid, citric acid, and lactic acid; the methanesulfonic acid accounts for 2%-10% of the total mass of the acidic cleaning composition. More preferably, the α-hydroxycarboxylic acid comprises citric acid and lactic acid, and the total mass of the citric acid and lactic acid accounts for 18%-40% of the total mass of the acidic cleaning composition. By optimizing the ratio of different organic acids, it is possible to ensure cleaning power while also protecting the metal substrate.

[0020] Preferably, the C8-C18 alkyl dimethyl benzyl ammonium chloride is a C12-C14 alkyl dimethyl benzyl ammonium chloride; the double-chain quaternary ammonium salt is selected from at least one of symmetrical didecyl dimethyl ammonium chloride and asymmetrical decyl octyl dimethyl ammonium chloride. More preferably, the C8-C18 alkyl dimethyl benzyl ammonium chloride is an alkyl dimethyl benzyl ammonium chloride containing a mixture of C12 and C14. This type of quaternary ammonium salt complex system exhibits good compatibility and excellent broad-spectrum bactericidal properties under acidic conditions.

[0021] Preferably, the other additives include at least one of chelating agents and colorants. More preferably, the chelating agent is selected from at least one of citrate, ethylenediaminetetraacetic acid, ethylenediaminetetramethylene phosphate, and hydroxyethylidene diphosphate. The chelating agent can further chelate calcium and magnesium ions in the water, enhancing the cleaning effect.

[0022] Furthermore, the acidic cleaning composition also contains a fragrance, the fragrance comprising 0.1%-2% of the total mass of the acidic cleaning composition, the fragrance comprising liquid fragrance and / or microcapsule fragrance.

[0023] The present invention further provides a method for preparing the above-mentioned acidic cleaning composition, comprising the following steps: (1) Heat water to 55±2℃, add the pickling agent while stirring, and stir until evenly dispersed; (2) Add the bactericide and chelating agent in sequence and stir until homogeneous; (3) Add the thickener (pH / ion-responsive microcapsule emulsion), fragrance and colorant, and stir until homogeneous to obtain the acidic cleaning composition.

[0024] The acidic cleaning composition described above can be used to clean washing machine tubs.

[0025] Furthermore, the method of using the acidic cleaning composition of the present invention is well known to those skilled in the art. According to the instructions for use, an appropriate amount of acidic cleaning agent is added to the detergent dispenser or directly into the inner drum of the washing machine. The drum self-cleaning mode is turned on, and after completing one drum self-cleaning cycle, the washing machine can be given a cleaning and sterilization effect.

[0026] This invention employs a high content of α-hydroxycarboxylic acid and methanesulfonic acid as a compound pickling agent, which can powerfully dissolve alkaline stains in the washing machine tub and protect the inner drum of the washing machine by utilizing the metal corrosion inhibition properties of α-hydroxycarboxylic acid, thus combining high-efficiency cleaning with low corrosiveness. A compound system of C8-C18 alkyl dimethyl benzyl ammonium chloride and double-chain quaternary ammonium salt is used as a bactericide, exhibiting excellent bactericidal and inhibitory effects on both bacteria and fungi, and achieving long-lasting antibacterial effects. A pH / ion-responsive microcapsule emulsion with a specific structure is used as a thickener, solving the problems of thickening difficulties in high-acid, high-ion systems and viscosity retention after dilution. The pH / ion-responsive microcapsules of this invention not only provide storage stability and suitable initial viscosity, but also intelligently respond and rupture upon dilution, releasing additional active acid to synergistically enhance the cleaning effect while maintaining the viscosity of the diluted liquid, extending the contact time of the active components on vertical surfaces. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a diagram of the testing apparatus for measuring the cleanliness of the material according to the present invention; Figure 2 This is a diagram showing the effect of cleaning the dirty sheets in a washing machine tub using the acidic cleaning composition of Example 3 of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0031] To better understand the technical content of the present invention, the technical solution of the present invention will be further introduced and explained below with reference to specific embodiments.

[0032] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the compositions of the present invention. Unless otherwise specified, all masses of the listed ingredients give an amount of active substance and therefore do not include solvents or byproducts that may be present in commercially available materials. The term "percentage by mass" may be expressed by the symbol "%".

[0033] Unless otherwise specified, all molecular weights in this document are weight-average molecular weights expressed in Daltons.

[0034] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0035] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and components may be added without affecting the final result. The term “comprising” also includes the terms “consisting of” and “substantially consisting of.” The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. The term “not containing” means not intentionally added, specifically meaning less than 0.01% by mass.

[0036] Acidic cleaning composition Acidic cleaning compositions refer to liquid acidic cleaning agents. Following the instructions, add an appropriate amount of acidic cleaning agent to the detergent dispenser or directly into the washing machine drum. Activate the drum self-cleaning mode. After one drum self-cleaning cycle, it provides cleaning and disinfection to the washing machine drum without damaging it. Acidic cleaning agents generally contain acidic detergents (in this invention, hydroxycarboxylic acids and methanesulfonic acid) or oxygen bleaching agents, disinfectants, and may also contain fragrances and other additives.

[0037] Pickling agent In this invention, the pickling agent comprises 20-50% by mass in the acidic cleaning composition. The pickling agent of this invention is composed of α-hydroxycarboxylic acid and methanesulfonic acid. The α-hydroxycarboxylic acid may be glycolic acid, citric acid, or lactic acid, preferably citric acid and lactic acid.

[0038] disinfectant In this invention, the disinfectant comprises 2-7% by mass in the acidic cleaning composition. The disinfectant of this invention is composed of C12-C18 alkyl dimethyl benzyl ammonium chloride and a double-chain quaternary ammonium salt.

[0039] Furthermore, C12-C18 alkyl dimethyl benzyl ammonium chloride is C12-C14 alkyl dimethyl benzyl ammonium chloride, and commercially available products such as Tor's MICROCARE QT and Lonza's LONZAGARD BKC are available.

[0040] Furthermore, the double-chain quaternary ammonium salt is either a symmetrically double-chain diecryldimethylammonium chloride or an asymmetrically double-chain decyloctyldimethylammonium chloride, and can be selected from commercial products such as Lonza's STARCARE 2240 and Bardac® 2050.

[0041] Thickener In this invention, the thickener has a mass percentage content of 0.1-2% in the acidic cleaning composition. A pH / ion-responsive adaptive microcapsule emulsion is used, with a composite wall material composed of cationic modified nanocellulose and polyurea / polyurethane microcapsules. The microspheres encapsulate citric acid and an acid solution, while some cationic modified nanocellulose remains free outside the microcapsules. The microcapsule particle size is 1-100 μm, preferably 10-30 μm.

[0042] spices The fragrance in this invention comprises at least one of unencapsulated liquid fragrance and microencapsulated fragrance, and is present in the acidic cleaning composition at a mass percentage of 0.1-2%, preferably 0.2-1%. Suitable fragrances for this invention can be selected from commercially available products, such as those purchased from Firmenich, Givaudan, Symrise, International Fragrance Company, or other suitable sources.

[0043] Chelating agents The acidic cleaning composition of the present invention may selectively include a chelating agent, which may be at least one selected from citrate, ethylenediaminetetraacetic acid, ethylenediaminetetramethylene phosphate, and hydroxyethylidene diphosphate.

[0044] Furthermore, it can be sodium citrate, EDTA-2Na, or HEDP-2Na.

[0045] Colorant The acidic cleaning composition of the present invention may selectively include a colorant, preferably a water-soluble polymer pigment, and particularly a pigment suitable for use in acidic systems.

[0046] Performance testing and its standards 1. Viscosity testing methods Using an LVDV-Ⅱ+ Pro digital viscometer, place the composition in a beaker or cylindrical container with a diameter of not less than 70 mm, accurately control the temperature at 25±0.1℃, use a model 3 rotor, adjust the height of the viscometer and the composition until the liquid level mark on the rotor is level with the liquid surface, turn on the instrument switch, set the speed to 12, and let the rotor rotate in the liquid. After several rotations (generally 20-30 seconds), wait for the pointer to stabilize before taking the reading. The unit is mPa·s.

[0047] 2. Viscosity evaluation criteria The smaller the viscosity difference of the composition before and after diluting it 5 times with tap water, the more desirable the viscosity. The viscosity estimation criteria are shown in Table 1. Table 1 Evaluation Criteria for the Impact on Viscosity Here, "﹣" indicates that the viscosity difference before and after dilution is ideal, while the more "+" signs there are, the greater the viscosity difference, which is not the desired effect.

[0048] 3. Methods for determining the cyst rupture rate The stability of pH / ion-responsive microcapsules in the composition was observed using scanning electron microscopy (SEM) or optical microscopy (OM). To avoid microcapsule overlap, the microcapsules were diluted 10 times with pure water and gently stirred before sampling and observation.

[0049] Microcapsules with collapsed, cracked, or porous surfaces, or with leakage of contents, are classified as ruptured microcapsules. Microcapsules with intact spherical shapes, smooth surfaces, no dents or cracks, or incompletely ruptured surfaces are classified as intact microcapsules. Samples are taken from the upper, middle, and lower layers of the composition sample, and at least 200 microcapsules need to be counted.

[0050] The calculation formula is as follows: Encapsulation rupture rate = Σ number of ruptured microcapsules / Σ total number of microcapsules × 100%.

[0051] 4. Evaluation criteria for cyst rupture rate Composition storage stage: When the composition is placed at a temperature of 37±2℃ for 4 weeks, the capsule rupture rate is ≤10%. When the composition is placed at a temperature of 45±2℃ for 4 weeks, the rupture rate is ≤15%.

[0052] The composition is diluted with water as follows: When diluted 100 times with water, the encapsulation rate is ≥70% when the pH value is above 5.5 and the ionic strength is low. 5. Stability Testing Methods High temperature stability: After the composition is bottled and sealed, it is placed at 45±2℃ for 4 weeks and then restored to room temperature of 25±5℃ to observe the appearance and measure the viscosity. At the same time, the integrity of the microcapsule structure is observed under a microscope and the microcapsule rupture rate is recorded.

[0053] Room temperature stability: After the composition is bottled and sealed, it is kept at 25±5℃ for 4 weeks for comparison with high temperature stability samples.

[0054] 6. Stability Evaluation Criteria "—" indicates that the appearance of the sample did not change significantly after high-temperature stability, with no obvious layering, precipitation or floating, and the microcapsule rupture rate was ≤15% after viscosity change; "+" indicates that after the sample has reached high temperature stability, the appearance shows layering or flocculent matter in the aqueous solution, and there are many cases of microcapsules rupture. The number of "+" indicates the severity of layering and / or rupture. More "+" indicates more obvious abnormalities and more unstable samples.

[0055] 7. Cleanliness Measurement Method Purchase an old washing machine that has been used for a long time and has never been cleaned from a second-hand store. Disassemble it and cut the inner drum (i.e., the washing machine tub) into small strips as sludge sheets. Secure one half of the sludge sheet to the agitator with a rubber band or clip. Soak the other half of the sludge sheet in a 1% acidic cleaning solution at a water temperature of 70°C, a spin speed of 200 rpm, and a time of 60 minutes.

[0056] The test setup diagram is visible. Figure 1 .

[0057] 8. Cleanliness Evaluation Methods Thirty volunteers (male to female ratio of 1:1, aged 25-55) were selected to conduct a sensory evaluation of the dirty flakes in the cleaned washing machine drum. The uncleaned flakes served as a reference and were scored as 0 points. The cleaned flakes (the parts soaked in the aqueous solution of the composition) were scored according to their cleanliness, with higher scores for cleaner parts, ranging from 0 to 5 points.

[0058] 9. Sterilization rate test method In this invention, the sterilization rate refers to the ability of the acidic cleaning composition to kill or inhibit different bacteria and fungi, as specified in QB / T2738-2012 "Evaluation Method for Antibacterial and Bacteriostatic Effects of Daily Chemical Products". The effective concentration is 1%, and the effective time is 15 minutes. The target bacterial species include: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Candida albicans ATCC 10231, and Trichophyton rubrum ATCC 28188, etc.

[0059] 10. Sterilization rate evaluation criteria The sterilization rate of the sample is calculated using the following formula: Sterilization rate (%) = (number of viable bacteria in control sample - number of viable bacteria in test sample) / number of viable bacteria in control sample × 100%; When the sterilization rate is <50%, it has no sterilization effect on the bacteria; when the sterilization rate is ≥50%, it has sterilization effect. The higher the sterilization rate, the better the removal effect on the bacteria.

[0060] 11. Long-lasting antibacterial test method After treating the washing machine drum slices with an acidic cleaning composition, they were aseptically dried in an oven at 36°C. Simultaneously, the washing machine drum slices were treated with sterile hard water as a control sample. Test bacterial suspensions were inoculated onto both the sample and the control sample, and eluted immediately and after a period of incubation, respectively. The number of viable bacteria in the eluent was measured, the inhibition rate was calculated, and the antibacterial effect of the sample was evaluated.

[0061] 12. Evaluation criteria for long-lasting antibacterial effect Formula for calculating antibacterial rate: ; Ct The number of viable bacteria measured after the control sample is inoculated and cultured for a period of time; T t The number of viable bacteria is the number of bacteria measured after the sample has been inoculated and cultured for a period of time.

[0062] When the inhibition rate is <90%, it means that it does not have a long-lasting antibacterial effect of t hours or days on the target bacteria; when the inhibition rate is ≥90%, it means that it has a long-lasting antibacterial effect of t hours or days on the target bacteria. The higher the inhibition rate, the better the long-lasting antibacterial effect on the target bacteria.

[0063] 13. Methods for determining the corrosivity of stainless steel 304 stainless steel is the mainstream choice for washing machine inner drums, but it exhibits a certain degree of corrosivity under strong acidic conditions. The corrosivity of 304 stainless steel sheets was determined according to GB / T 38498-2020, "Evaluation Method for Corrosion Resistance of Metals in Disinfectants". The test conditions were: a 1:100 solution of acidic cleaning agent was prepared in a beaker, and three metal test pieces were placed in the solution and continuously immersed for 72 hours.

[0064] 14. Corrosion Assessment and Classification Standards Table 2 Corrosion Assessment Classification Standards In the following examples or comparative examples, the following abbreviations will be used and have the indicated functions.

[0065] Citric acid: Citric acid monohydrate, an acid pickling agent, neutralizes alkaline scale and has a cleaning effect.

[0066] Lactic acid: A pickling agent that neutralizes alkaline scale and has a cleaning effect.

[0067] Methylsulfonic acid: A pickling agent that neutralizes alkaline scale and has a cleaning effect.

[0068] Glycolic acid: an acid detergent that neutralizes alkaline scale and has a cleaning effect.

[0069] 1227: C12-C14 dimethylbenzylammonium chloride, a disinfectant that has a sterilizing effect.

[0070] 2240: Didecyl dimethyl ammonium chloride, a disinfectant that has a sterilizing effect.

[0071] HPMC: White powder, hydroxypropyl methylcellulose, thickener, gives the composition a viscous texture.

[0072] Ethomeen O / 12: Bis(2-hydroxyethoxy)oleylamine, acidic thickener.

[0073] Sodium xylenesulfonate: a water-reducing agent, used in combination with amine oxide O / 12 to achieve a thickening effect.

[0074] Cationic modified nanocellulose: Matexcel's NAT-4003.

[0075] The preparation method of pH / ion-responsive microcapsule emulsion A (hereinafter referred to as microcapsule emulsion A) is as follows: S1 oil phase preparation: Citric acid and lactic acid are mixed at a mass ratio of 2:1, heated to 50°C to dissolve, and then isophorone diisocyanate is added and mixed evenly to obtain the oil phase; wherein, the mass ratio of the total mass of citric acid and lactic acid to the mass of isophorone diisocyanate is 3.5:1. S2 Aqueous Phase Preparation: Cationic modified nanocellulose was dispersed in deionized water, and the pH was adjusted to 3.5 to obtain an aqueous phase; the mass fraction of cationic modified nanocellulose in the aqueous phase was 2.5%. S3 emulsification: The oil phase is slowly added to the water phase at a mass ratio of 1:4. High-speed shear emulsification is carried out at 1500 rpm for 20 minutes to form an oil-in-water Pickering emulsion. S4 Interfacial Polymerization: The oil-in-water Pickering emulsion from step S3 was transferred to a reaction vessel, heated to 65°C, and an aqueous solution of diethylenetriamine was slowly added dropwise while stirring at 300 rpm. The molar ratio of diethylenetriamine to isophorone diisocyanate was 1:1. The reaction was maintained at this temperature for 2 hours to allow polymerization at the oil-water interface, forming microcapsules with polyurea / polyurethane and cationic modified nanocellulose as the composite wall material and citric acid and lactic acid as the core material. S5 Post-processing: After the reaction in step S4 is completed, cool to room temperature, wash the microcapsules three times with deionized water to remove unreacted monomers; adjust the pH of the system to 3.5, and add cationic modified nanocellulose to a final concentration of 1.0% to obtain the pH / ion-responsive microcapsule emulsion A.

[0076] The preparation method of pH / ion-responsive microcapsule emulsion B (hereinafter referred to as microcapsule emulsion B) is as follows: S1 oil phase preparation: Citric acid and lactic acid are mixed at a mass ratio of 1.5:1, heated to 45°C to dissolve, and then isophorone diisocyanate is added and mixed evenly to obtain the oil phase; wherein, the mass ratio of the total mass of citric acid and lactic acid to the mass of isophorone diisocyanate is 2:1. S2 Aqueous Phase Preparation: Cationic modified nanocellulose was dispersed in deionized water, and the pH was adjusted to 3.0 to obtain an aqueous phase; the mass fraction of cationic modified nanocellulose in the aqueous phase was 0.5%; S3 emulsification: The oil phase is slowly added to the water phase at a mass ratio of 1:3. High-speed shear emulsification is carried out at 1000 rpm for 30 minutes to form an oil-in-water Pickering emulsion. S4 Interfacial Polymerization: The oil-in-water Pickering emulsion from step S3 was transferred to a reaction vessel, heated to 50°C, and an aqueous solution of diethylenetriamine was slowly added dropwise while stirring at 400 rpm. The molar ratio of diethylenetriamine to isophorone diisocyanate was 0.8:1. The reaction was maintained at this temperature for 1 hour to allow polymerization at the oil-water interface, forming microcapsules with polyurea / polyurethane and cationic modified nanocellulose as the composite wall material and citric acid and lactic acid as the core material. S5 Post-processing: After the reaction in step S4 is completed, cool to room temperature, wash the microcapsules twice with deionized water to remove unreacted monomers; adjust the pH of the system to 3.0, and add cationic modified nanocellulose to a final concentration of 0.5% to obtain the pH / ion-responsive microcapsule emulsion B.

[0077] The preparation method of pH / ion-responsive microcapsule emulsion C (hereinafter referred to as microcapsule emulsion C) is as follows: S1 oil phase preparation: Citric acid and lactic acid are mixed at a mass ratio of 2.5:1, heated to 55°C to dissolve, and then isophorone diisocyanate is added and mixed evenly to obtain the oil phase; wherein, the mass ratio of the total mass of citric acid and lactic acid to the mass of isophorone diisocyanate is 5:1. S2 Aqueous Phase Preparation: Cationic modified nanocellulose was dispersed in deionized water, and the pH was adjusted to 4.0 to obtain an aqueous phase; the mass fraction of cationic modified nanocellulose in the aqueous phase was 3.0%. S3 emulsification: The oil phase is slowly added to the water phase at a mass ratio of 1:5. High-speed shear emulsification is carried out at a speed of 2000 rpm for 10 minutes to form an oil-in-water Pickering emulsion. S4 Interfacial Polymerization: The oil-in-water Pickering emulsion from step S3 was transferred to a reaction vessel, heated to 80°C, and an aqueous solution of diethylenetriamine was slowly added dropwise while stirring at 200 rpm. The molar ratio of diethylenetriamine to isophorone diisocyanate was 1.2:1. The reaction was maintained at this temperature for 3 hours to allow polymerization at the oil-water interface, forming microcapsules with polyurea / polyurethane and cationic modified nanocellulose as the composite wall material and citric acid and lactic acid as the core material. S5 Post-processing: After the reaction in step S4 is completed, cool to room temperature, wash the microcapsules three times with deionized water to remove unreacted monomers; adjust the pH of the system to 4.0, and add cationic modified nanocellulose to a final concentration of 1.5% to obtain the pH / ion-responsive microcapsule emulsion C.

[0078] The preparation method of microcapsule emulsion D is as follows: The preparation method of microcapsule emulsion D differs from that of pH / ion-responsive microcapsule emulsion A in that, in the S2 aqueous phase preparation step, carboxylated nanocellulose (such as TL007 and TL001 from Nanjing Tianlu Nanotechnology Co., Ltd.) is used instead of cationic modified nanocellulose, while the other steps are the same.

[0079] The preparation method of microcapsule emulsion E is as follows: The preparation method of microcapsule emulsion E differs from that of pH / ion-responsive microcapsule emulsion A in that the S5 post-processing step does not include the operation of "adding cationic modified nanocellulose to a final concentration of 1.0%", while the other steps are the same.

[0080] The acidic cleaning compositions of Examples 1-3 and Comparative Examples 1-6 were prepared according to the raw material composition in Table 3. The only difference between the acidic cleaning compositions is the raw materials and their content; all other conditions (such as preparation methods) are the same.

[0081] Table 3. Formulation composition (mass percentage, %) of Examples 1-3 and Comparative Examples 1-6 The cleaning power and stainless steel corrosion resistance of the acidic cleaning compositions of Examples 1-3 and Comparative Examples 1-6 were tested, and the test results are shown in Table 4 below: Table 4 Test results of Examples 1-3 and Comparative Examples 1-6 As shown in Table 4, Comparative Examples 1, 2, and 3 all had a certain cleaning effect on the stained washing machine tub, but the effect was not ideal. Comparative Example 4 had a better cleaning effect on the stained washing machine tub, but long-term use might cause corrosion to the washing machine tub. The total organic acid content of Comparative Example 1 and Example 1 was similar. Example 1, with the addition of methanesulfonic acid, showed a significant improvement in cleaning effect. The total acid content of Comparative Example 6 exceeded 50%, and although its cleaning power was ideal, the absence of lactic acid might cause slight corrosion to the washing machine tub. The cleaning effect of Example 3 was as follows... Figure 2 As shown.

[0082] The acidic cleaning compositions of Examples 4-6 and Comparative Examples 7-8 were prepared according to the raw material composition in Table 5. The only difference between the acidic cleaning compositions is the raw materials and their content, while other conditions (such as preparation methods) are the same.

[0083] Table 5. Formulation composition of Examples 4-6, Comparative Examples 7 and 8 Viscosity tests and stability monitoring were conducted on the acidic cleaning compositions of Examples 4-6 and Comparative Examples 7 and 8, including viscosity at room temperature, viscosity after 4 weeks of heat storage at 45±2℃, and viscosity after dilution with tap water by 5 times. Viscosity was evaluated according to viscosity evaluation standards, and the test results are shown in Table 6 below: Table 6 Test results of Examples 4-6, Comparative Examples 7 and 8 As can be seen from the test results in Table 6, Comparative Example 7 had a relatively ideal initial viscosity, but it became almost non-viscous after 4 weeks of heat storage, indicating extremely poor viscosity stability. Comparative Example 8, even with the addition of a relatively large amount of thickening component, still could not achieve a good initial viscosity, and its viscosity almost disappeared after 4 weeks of heat storage. In Examples 4, 5, and 6, the viscosity was significantly improved with increasing amounts of pH / ion-responsive microcapsule emulsion. Furthermore, the viscosity was well maintained after 4 weeks of heat storage, and even after dilution with tap water five times, an ideal viscosity was still achieved, enhancing the adhesion of the composition to the washing machine tub and prolonging the effective action time.

[0084] The acidic cleaning compositions of Examples 7 and Comparative Examples 9-11 were prepared according to the raw material composition in Table 7. The only difference between the acidic cleaning compositions is the raw materials and their content, while other conditions (such as preparation methods) are the same.

[0085] Table 7. Formulation composition of Comparative Examples 9-11 and Example 6 As shown in Table 7, Example 7 was prepared by adding 1% of the microcapsule emulsion of the present invention and having a methanesulfonic acid content of 10%, Comparative Example 9 was prepared without adding the pH / ion-responsive microcapsule emulsion of the present invention, and Comparative Examples 10 and 11 were prepared with microcapsule emulsions not prepared by the method of the present invention.

[0086] Viscosity tests and capsule rupture rate determinations were performed on the acidic cleaning compositions (pH approximately 0.7) of Examples 7, 10, and 11, including capsule rupture rates after 4 weeks of storage at 37±2°C and 4 weeks of storage at 45±2°C.

[0087] The acidic cleaning compositions (pH approximately 0.7) of Examples 7, 10, and 11 were diluted with phosphate buffer solutions with pH values ​​of 3.0, 5.5, and 8.0, respectively, to obtain 1% (w / w) diluents (the pH of the diluent solution is the same as the pH of the phosphate buffer solution), and the encapsulation rate of the diluent solutions was measured.

[0088] The acidic cleaning compositions (pH approximately 0.7) of Examples 7 and Comparative Examples 9-11 were diluted with phosphate buffer solutions with pH values ​​of 3.0, 5.5, and 8.0, respectively, to obtain 1% (w / w) diluents (the pH of the diluents is the same as the pH of the phosphate buffer solution). The cleaning power of the diluents was then tested and evaluated.

[0089] The test results are shown in Table 8 below.

[0090] Table 8. Detection results of Example 7 and Comparative Examples 9-11 As shown in Table 8, the composition containing the pH / ion-responsive microcapsule emulsion of the present invention (Example 7) exhibits a low encapsulation rate during storage, indicating a stable state. Upon dilution, the pH value increases and the ionic strength decreases. The microcapsules respond to the pH and ion concentration, swelling and releasing organic acids from the core material, thus increasing the encapsulation rate and providing a synergistic cleaning effect. When the pH value is 5.5, equivalent to a high-fold dilution in tap water, the cleaning efficiency can be improved by approximately 18% compared to Comparative Example 9 (without the pH / ion-responsive microcapsule emulsion of the present invention). When the microcapsules come into contact with alkaline dirt in the washing tub, the local pH value may rise to above 8.0, resulting in an improvement in cleaning efficiency of approximately 23% compared to Comparative Example 9 (without the pH / ion-responsive microcapsule emulsion of the present invention).

[0091] The acidic cleaning compositions of Examples 8-10 and Comparative Examples 12-14 were prepared according to the raw material composition in Table 9. The only difference between the acidic cleaning compositions is the raw materials and their content; all other conditions (e.g., preparation methods) are the same.

[0092] Table 9. Formulation composition (mass percentage, %) of Examples 8-10 and Comparative Examples 12-14 The acidic cleaning compositions of Examples 8-10 and Comparative Examples 12-14 were subjected to antibacterial and antimicrobial tests, and the results are shown in Table 10 below.

[0093] Table 10. Results of antibacterial and antimicrobial tests for Examples 8-10 and Comparative Examples 12-14 As shown in Table 10, the acidic cleaning composition 12 of the comparative example contains a large amount of organic acid, which has a good sterilization rate against Staphylococcus aureus, but has no effect on fungi such as Candida albicans and Trichophyton rubrum. Based on Comparative Example 12, Comparative Example 13 introduced benzalkonium chloride 1227, but the removal effect on fungi was still limited. Example 8, based on Comparative Example 12, adopted a composition scheme of single and double-chain quaternary ammonium salts, which significantly improved the effect on Candida albicans and Trichophyton rubrum, and achieved a 7-day long-term antibacterial effect against Escherichia coli. With the increase of the amount of sterilizing agents 1227 and 2240, ideal results were also achieved for fungi such as Trichophyton rubrum that are difficult to remove. Example 8, based on Comparative Example 14, introduced an adaptive microcapsule emulsion, and unexpectedly found that it had a synergistic effect on the sterilization rate of Candida albicans and Trichophyton rubrum, as well as the 7-day long-term antibacterial effect against Escherichia coli.

[0094] The acidic cleaning compositions of Examples 11-19 were prepared according to the raw material composition in Table 11. The only difference between the acidic cleaning compositions is the raw material and content of the components, while other conditions (e.g., preparation method) are the same.

[0095] Table 11. Formulation composition (mass percentage, %) for Examples 11-19 The acidic cleaning compositions of Examples 11-19 were subjected to viscosity tests at room temperature and viscosity tests after dilution with tap water by 5 times. The stability, viscosity, and capsule rupture rate were tested after heat storage at 45±2℃ for 4 weeks. The cleaning power and sterilization tests were also evaluated. The results are shown in Table 12 below.

[0096] Table 12 Test results of Examples 11-19 In summary, the acidic cleaning composition provided by this invention, by using three organic acids in optimal proportions as pickling agents, can efficiently remove alkaline dirt from the washing machine tub. Simultaneously, it introduces C8-C18 alkyl dimethyl benzyl ammonium chloride and double-chain quaternary ammonium salt as antibacterial agents, exhibiting excellent antibacterial effects against bacteria and fungi, and achieving long-lasting antibacterial activity against Escherichia coli for 7 days. Furthermore, a cationic pH / ion-responsive microcapsule emulsion is selected as a thickener, giving the composition a viscous texture that maintains good viscosity after appropriate dilution with water, thereby improving the cleaning efficiency and antibacterial effect of the composition.

[0097] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An acidic cleaning composition, characterized in that, It contains the following components by mass percentage: Pickling agent 20%-50%; bactericide 2%-7%; Thickener 0.1%-2%; Other additives: 0.01%-10%; The remainder is water; The pickling agent contains α-hydroxycarboxylic acid and methanesulfonic acid; The bactericide comprises C8-C18 alkyl dimethyl benzyl ammonium chloride and a double-chain quaternary ammonium salt; The thickener is a pH / ion-responsive microcapsule emulsion, which contains microcapsules containing a core material encapsulated by a composite wall material formed of cationic modified nanocellulose and polyurea / polyurethane. The core material contains citric acid and lactic acid, and some cationic modified nanocellulose is free outside the microcapsules.

2. The acidic cleaning composition according to claim 1, characterized in that, The preparation method of the pH / ion-responsive microcapsule emulsion includes the following steps: (1) An oil phase containing citric acid, lactic acid and polyisocyanate is mixed with an aqueous phase containing cationic modified nanocellulose and emulsified to form an oil-in-water Pickering emulsion; (2) A polyfunctional amine is added to the oil-in-water Pickering emulsion and a polymerization reaction occurs at the oil-water interface to form microcapsules with polyurea / polyurethane and cationic modified nanocellulose as composite wall materials and citric acid and lactic acid as core materials; (3) After the reaction is completed, cationic modified nanocellulose is added to obtain the pH / ion-responsive microcapsule emulsion.

3. The acidic cleaning composition according to claim 2, characterized in that, In step (1), the mass ratio of citric acid to lactic acid in the oil phase is (1.5-2.5):1, and the mass ratio of the total mass of citric acid and lactic acid to the mass of polyisocyanate is (2-5):1; the mass fraction of cationic modified nanocellulose in the aqueous phase is 0.5%-3.0%, and the mass ratio of the oil phase to the aqueous phase is 1:(3-5).

4. The acidic cleaning composition according to claim 3, characterized in that, In step (2), the molar ratio of the polyfunctional amine to the polyisocyanate in step (1) is (0.8-1.2):1, and the reaction temperature is 50-80℃.

5. The acidic cleaning composition according to claim 4, characterized in that, The polyisocyanate is isophorone diisocyanate; the polyfunctional amine is diethylenetriamine.

6. The acidic cleaning composition according to claim 5, characterized in that, In step (3), cationic modified nanocellulose is added to make its mass concentration in the system reach 0.5%-1.5% after the reaction is completed.

7. The acidic cleaning composition according to claim 1, characterized in that, The pH / ion-responsive microcapsules have a particle size of 1-100 μm.

8. The acidic cleaning composition according to claim 1, characterized in that, The α-hydroxycarboxylic acid is selected from at least two of glycolic acid, citric acid, and lactic acid; the methanesulfonic acid accounts for 2%-10% of the total mass of the acidic cleaning composition.

9. The acidic cleaning composition according to claim 1, characterized in that, The C8-C18 alkyl dimethyl benzyl ammonium chloride is a C12-C14 alkyl dimethyl benzyl ammonium chloride; the double-chain quaternary ammonium salt is selected from at least one of symmetrical dialcyl dimethyl ammonium chloride and asymmetrical decyl octyl dimethyl ammonium chloride.

10. The use of the acidic cleaning composition according to any one of claims 1-9 in cleaning a washing machine tub.

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