Teflon coating process for stirring knife of food processor

Abstract

The invention discloses a teflon coating process for a stirring knife of a food processor, and relates to the technical field of metal surface treatment, and the teflon coating process is technically characterized in that a stainless steel or titanium alloy stirring knife body is adopted as a base material; according to the pretreatment layer, a micron-scale and nano-scale composite rough structure is formed on the surface of the base material through rough spraying and fine spraying processes, glass sand (150-300 microns) is adopted for rough spraying to form a micron-scale (10-50 microns) concave-convex surface, and epoxy resin primer permeates into pits and is cured to form a barb structure; the technical effect is that the bonding strength of the coating and the base material is better and far exceeds the industrial standard, so that the coating can still be firmly attached to the surface of the stirring knife under the complex working conditions of high-speed rotation, high-frequency vibration and severe friction with food of a wall breaking machine, and the phenomenon that the coating falls off is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and particularly to a Teflon coating process for a stirring knife of a food processor. Background Art

[0002] Traditional stirring knives of food processors are mostly made of stainless steel. After long-term use, food residues are likely to remain, making cleaning difficult. Some coating technologies (such as single-layer Teflon spraying) have problems such as poor adhesion, easy peeling, and insufficient high-temperature resistance. During the high-speed stirring process, the coating wears, resulting in a short service life, affecting the wall-breaking efficiency and food safety. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a Teflon-coated stirring knife with high adhesion, wear resistance, non-stickiness, and high-temperature resistance, solving the problems of easy peeling, difficult cleaning, and short life of traditional coatings.

[0004] To achieve the above object, the present invention provides the following technical solution: A Teflon coating process for a stirring knife of a food processor, including:

[0005] The substrate is a stainless steel or titanium alloy stirring knife body;

[0006] A pretreatment layer, forming a micron-level and nano-level composite rough structure on the surface of the substrate through rough spraying and fine spraying processes. The rough spraying uses glass sand (150 - 300 μm) to form a micron-level (10 - 50 μm) uneven surface, and the epoxy resin primer penetrates into the pits and cures to form a barb structure;

[0007] The bottom layer is an epoxy resin primer layer with a thickness of 5 - 10 μm and an epoxy resin content of ≥95%;

[0008] The intermediate layer is a mixed layer of Teflon (PTFE) and nano-ceramic particles (SiO2 or Al2O3) with a thickness of 15 - 20 μm, a PTFE content of 80 - 85%, and a nano-ceramic particle content of 15 - 20%;

[0009] The surface layer is a modified Teflon layer containing graphene or carbon fiber with a thickness of 10 - 20 μm, a PTFE content of 70 - 75%, a graphene content of 5 - 10%, and a carbon fiber content of 15 - 20%;

[0010] Among them, the total thickness of the coating is 30 - 50 μm.

[0011] Preferably, the pretreatment layer includes:

[0012] Sandblasting treatment: The sand particle size is 100 - 150 μm, the pressure is 0.4 - 0.6 MPa, and the time is 5 - 10 minutes;

[0013] Chemical cleaning: The concentration of the alkaline cleaning agent is 5-10%, the temperature is 40-50°C, and the time is 10-15 minutes;

[0014] Plasma activation: The power is 300-500W, and the time is 3-5 minutes.

[0015] Preferably, the bottom layer coating temperature is 20-25°C, the humidity ≤ 60%; the intermediate layer coating temperature is 25-30°C, the humidity ≤ 50%; the surface layer coating temperature is 30-35°C, the humidity ≤ 40%.

[0016] Preferably, the abrasion resistance of the coating meets the Taber abrasion test, CS-10 wheel, 1 kg load, the wear amount after 5000 cycles < 5%, the water droplet contact angle > 110°, and the long-term temperature resistance range is -50°C - 300°C.

[0017] Preferably, the particle size of the nano-ceramic particles is 20-50 nm, the graphene is in a single-layer or few-layer structure (the number of layers ≤ 5), and the carbon fiber length is 1-10 μm.

[0018] Preferably, the wear amount of the coating after continuous use at a high speed of 30,000 revolutions per minute for 500 hours < 10 μm, and the food residue amount ≤ 2.8 mg / cm 2 。

[0019] Preferably, the mechanical bonding force between the epoxy resin primer and the substrate is improved by a barb structure, and the bonding strength ≥ 15 MPa.

[0020] Preferably, it includes the following steps:

[0021] (1) Substrate pretreatment: Perform sandblasting, chemical cleaning, and plasma activation in sequence;

[0022] (2) Coating in three times: Coat the bottom layer, intermediate layer, and surface layer in sequence by electrostatic spraying or dipping method;

[0023] (3) Step-by-step curing: In the first stage, pre-cure at 80°C for 0.5-1 hour, in the second stage, sinter at 200°C for 1-2 hours, and in the third stage, form a high-temperature film at 350°C for 0.5-1 hour.

[0024] Compared with the prior art, the present invention provides a Teflon coating process for the stirring blade of a food processor, which has the following beneficial effects: In terms of the bonding strength, the bonding strength between the coating and the substrate is better, far exceeding the industry standard. This characteristic enables the coating to firmly adhere to the surface of the stirring blade under the complex working conditions of high-speed rotation, high-frequency vibration, and intense friction with food in a wall breaker, effectively avoiding the occurrence of coating peeling. This not only extends the service life of the stirring blade, reduces the frequent replacement caused by coating damage, and lowers the user's usage cost, but also ensures the long-term stable operation of the wall breaker and improves the reliability of the product;

[0025] In terms of porosity control, the extremely low porosity effectively prevents external substances, such as food residues, moisture, acid-base substances, etc., from penetrating into the coating through the pores and then corroding or damaging the substrate. This greatly enhances the protective performance of the coating, protects the substrate of the stirring blade from various erosions, further extends the service life of the stirring blade, and also ensures that the wall breaker will not be affected by coating problems in terms of its performance and hygiene conditions during long-term use.

[0026] The acid resistance test results are particularly prominent, fully demonstrating that the coating has excellent chemical stability in an acidic environment. In daily use, a wall breaker is often used to process various foods containing acidic components, such as fruits and vegetables. The coating of the present invention can effectively resist the erosion of acidic substances, ensuring that the stirring blade will not corrode or its performance will not decline in an acidic environment. This not only guarantees the normal operation of the wall breaker, but more importantly, avoids the release of harmful substances that may be caused by coating corrosion, provides a safe and healthy food processing environment for users, and significantly improves the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the multi-layer structure of the blade in the present invention;

[0028] Figure 2 It is a sectional view of the blade pretreatment layer in the present invention;

[0029] Figure 3 It is a spraying effect diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Bonding strength test:

[0032] Test Standards: Refer to GB / T 9286-1998 "Cross-Cut Test for Paints and Varnishes Films" and ASTM D3359-17 "Standard Test Method for Measuring Adhesion by Tape Test". These two standards are widely used to evaluate the adhesion strength between the coating and the substrate.

[0033] Steps of the Test Method:

[0034] First, use a cross-cut tool to make a grid array of specific sizes on the coating surface. The side length of the grid is usually 1 mm (for harder coatings with better adhesion) or 2 mm (for relatively softer or less adhesive coatings). The cross-cut depth should penetrate the coating until the substrate surface.

[0035] Next, firmly attach a standard-compliant tape (such as 3M 600 tape) to the cross-cut area, ensuring full contact between the tape and the coating surface and excluding air bubbles.

[0036] Then, quickly and smoothly tear off the tape at an angle of approximately 90°.

[0037] Finally, by comparing with the standard rating chart, observe the peeling situation of the coating in the cross-cut area to determine the adhesion strength grade of the coating. According to the corresponding numerical range of the grade, convert to an approximate value of the adhesion strength (MPa). For example, grade 0 indicates no peeling of the coating and extremely high adhesion strength; grade 5 indicates large-area peeling of the coating and extremely low adhesion strength. In actual operation, an electronic tensile testing machine can also be used in combination with a special fixture to directly measure the force required to peel the coating from the substrate by stretching, and then accurately calculate the adhesion strength value (MPa).

[0038] Porosity Test:

[0039] Test Standards: Adopt the relevant methods for porosity determination in GB / T 11376-1997 "Phosphate Conversion Coatings on Metals", and ASTM B276-16 "Standard Test Method for Measuring Porosity in Metallic Coatings by Nitric Acid Vapor Test". These standards provide a reliable basis for accurately measuring the porosity of the coating.

[0040] Steps of the Test Method:

[0041] Nitric Acid Vapor Method: Place the specimen with the coating in a sealed container filled with nitric acid vapor. The concentration of nitric acid vapor in the container needs to be strictly controlled within the standard-specified range. Maintain at a certain temperature (such as 50 ± 5 °C) for a specific time (such as 30 minutes). Since nitric acid vapor will react chemically with the substrate exposed in the coating pores, the reaction products will form specific corrosion marks on the coating surface. By observing and counting the number of corrosion points per unit area and combining with the total coating area, the porosity of the coating can be calculated.

[0042] Metallographic microscope method: First, prepare metallographic samples of the coated specimens. Cut, grind, and polish the specimens until the surface of the coating is flat and smooth. Then, observe the cross-section of the coating under a metallographic microscope, use image analysis software to measure the total area of pores in the coating cross-section, and compare it with the total area of the coating to obtain the porosity. To improve the measurement accuracy, measurements need to be taken at multiple different positions and the average value is taken as the final result.

[0043] Acid resistance test, resistivity change rate test:

[0044] Test standards: According to GB / T1765 - 1979(1989) "Method of Preparation of Films for Determination of Resistance to Damp Heat, Salt Spray, and Weathering (Artificial Acceleration)" and relevant test standards for the acid resistance of electronic materials. These standards ensure the accurate test of the resistivity change of the coating in a simulated acidic environment.

[0045] Test method steps: First, use a four-probe resistivity tester to measure the initial resistivity value of the coating and record the data. Then, immerse the coated specimen in an acidic solution with a specific concentration (such as sulfuric acid solution with a pH value of 2), and keep the solution temperature at 25 ± 2°C. Take out the specimen at regular time intervals (such as every 24 hours), rinse it thoroughly with deionized water and dry it, and then measure the resistivity value of the coating again. Calculate the resistivity change rate, and the formula is: Resistivity change rate = (Final resistivity value - Initial resistivity value) / Initial resistivity value × 100%. By comparing the resistivity change rates at different time points, evaluate the resistivity stability of the coating in an acidic environment.

[0046] Mass loss rate test:

[0047] Test standards: Refer to GB / T9274 - 1988 "Determination of Resistance of Paints and Varnishes to Liquid Media". This standard provides a standardized method for evaluating the mass stability of the coating in liquid media (such as acidic solutions).

[0048] Test method steps: Accurately weigh the initial mass (m1) of the coated specimen, completely immerse the specimen in an acidic solution (such as hydrochloric acid solution with a concentration of 5%), and the volume of the solution should ensure that the specimen is fully immersed and not affected by the evaporation of the solution. Immerse it at a certain temperature (such as 40 ± 2°C) for a specified time (such as 72 hours). Take out the specimen, rinse off the residual acidic substances on the surface with deionized water, and then dry it in a low-temperature oven to a constant weight, and accurately weigh the mass of the specimen again (m2). Calculate the mass loss rate, and the formula is: Mass loss rate = (m1 - m2) / m1 × 100%. Judge the corrosion resistance of the coating in an acidic environment according to the size of the mass loss rate.

[0049] Wear Measurement Test, Test National Standard: Currently, there is no specific national standard for the wear measurement of the Teflon coating on the stirring blade of a food processor. However, relevant material wear test standards such as GB / T 12444-2016 "Test Methods for Wear of Metallic Materials - Characterization of Wear Test Results" can be referred to. This standard stipulates the methods for characterizing the wear test results of metallic materials and provides general guiding principles for the wear measurement of various materials.

[0050] Test Steps:

[0051] Specimen Preparation: Cut representative specimens from the stirring blades of food processors in actual use. If direct cutting is not possible, simulate specimens with the same coating process as the stirring blade need to be fabricated, with dimensions generally about 50 mm in length × 20 mm in width × 5 mm in thickness. Ensure that the coating on the specimen surface is complete and defect-free, and wipe it clean with cleaning agents such as alcohol, and set it aside after drying.

[0052] Equipment Selection: Select a wear testing machine that can simulate a high-speed rotation of 30,000 revolutions per minute, such as a pin-on-disc wear testing machine. Its rotational speed range should cover the test requirements, and it should have a stable rotational speed control and loading system.

[0053] Install the Specimen: Firmly install the prepared specimen in the corresponding position of the wear testing machine, ensuring that the installation is secure and the specimen will not displace or shake during rotation.

[0054] Set Parameters: Set the rotational speed of the wear testing machine to 30,000 revolutions per minute, apply a certain simulated working load (equivalently converted according to the resistance suffered by the actual stirring blade during operation, generally 1 - 5 N), and set the continuous operation time to 500 hours. At the same time, set the lubrication conditions of the testing machine (such as using a food-grade lubricating oil similar to the working environment of the actual wall breaker, with the drip rate controlled at 5 - 10 drops per minute).

[0055] Start the Test: Start the wear testing machine and start timing. During the entire test process, closely observe the operating status of the testing machine to ensure the stability of parameters such as rotational speed and load. Check whether there are any abnormal situations with the specimen, such as loosening or detachment, at regular intervals (such as every 1 hour).

[0056] Measure the Wear Amount: After the test is completed, wait for the specimen to cool to room temperature. Use measuring equipment such as a surface profilometer with a precision of 0.01 μm or a laser confocal microscope to uniformly select multiple measurement points (generally not less than 10) on the specimen surface, measure the change in coating thickness at each point before and after the test, and take the average value as the wear amount of the specimen. Calculate the average value of the wear amounts of multiple specimens, which is the wear amount of this batch of coatings after continuous use at a high speed of 30,000 revolutions per minute for 500 hours.

[0057] Food residue test, test national standard: refer to GB4806.9-2023 "National Food Safety Standard Food Contact Metal Materials and Products" and related food contact material migration test standards. Although GB4806.9-2023 standard does not directly target food residues, it puts forward general requirements for the safety and hygiene of food contact metal materials and products, and provides relevant guidance for food residue testing.

[0058] Test steps:

[0059] Simulated food preparation: Choose simulated food that is similar to the food that the blender processes daily, such as mixed fruit puree (including common fruits such as apples, oranges, bananas, etc., mixed in a certain proportion and beaten into a puree). The amount of simulated food must ensure that it can fully cover the contact area of ​​the blender when it is working.

[0060] Test equipment preparation: Use a mixing device of the same model as the actual blender or one that simulates the working conditions of the actual blender, install the mixing blade on the device, and ensure that it is installed correctly and that the mixing blade can operate normally.

[0061] Apply simulated food: Apply the prepared simulated food evenly on the coating surface of the mixing knife. The coating thickness should be controlled at about 1-2mm to ensure that the coating surface is completely covered.

[0062] Mixing operation: Start the mixing equipment and run it at a speed of 30,000 rpm for 500 hours. During the operation, add an appropriate amount of simulated food at regular intervals (such as 1 hour) to keep the mixing blade in contact with the food at all times, simulating the continuous processing situation in actual work.

[0063] Cleaning and collecting residual food: After the mixing operation is completed, stop the device and wait for the mixing blade to stop rotating. Use deionized water to slowly rinse the surface of the mixing blade. The water flow rate should not be too high to avoid washing away residual food that is difficult to clean. Collect the rinse water in a clean container.

[0064] Separation and measurement of residual food: The collected flushing water is filtered through a filter device (such as a microporous filter membrane with a pore size of 0.45 μm) to retain the residual food particles on the filter membrane. Then, the filter membrane together with the retained residual food is placed in an oven and dried at 60-80°C to constant weight. Use an electronic balance with an accuracy of 0.1 mg to weigh the total mass (m1) of the dried filter membrane and the residual food, and then subtract the initial mass of the filter membrane (m2) to obtain the mass of the residual food (m=m1-m2).

[0065] Calculate the amount of food residue: Measure the effective contact area of ​​the mixing blade coating (which can be obtained by measuring the size of the mixing blade and calculating the surface area of ​​the part in contact with the food) in cm 2. Divide the mass (mg) of the residual food by the effective contact area (cm 2 ) of the coating to obtain the food residue amount (mg / cm 2 ). Conduct the same test on multiple stirrer blade specimens and calculate the average value as the test result of the food residue amount of this batch of coatings.

[0066] Wear amount test. Name of the wear testing machine: Pin-on-Disc Wear Tester, Model: UMT-3. This model has a wide speed range and can be accurately adjusted to 30,000 revolutions per minute. It has a stable loading system and can meet the requirements of simulating actual working loads.

[0067] Measuring equipment. Name of the instrument: Surface Profiler, Model: DektakXT. The measurement accuracy can reach 0.01μm. It can accurately measure the microscopic profile changes on the coating surface and then accurately obtain the coating thickness changes.

[0068] Name of the instrument: Laser Confocal Microscope; Model LSM900. By performing three-dimensional imaging on the surface of the specimen, it can clearly observe the coating changes at the microscopic scale and assist in accurately measuring the coating thickness changes. Its high-precision measurement ability meets the test requirements.

[0069] Food residue amount test. Name of the stirring equipment: High-speed stirrer for laboratory use (if simulating an actual blender);

[0070] Model: IKARW20digital. It can set the speed to 30,000 revolutions per minute through a program, simulate the working state of a blender, and has good adaptability for installing stirrer blades.

[0071] Name of the filtration device: Microporous Membrane Filter, Model: Swinnex-25. It is adapted to a microporous membrane with a pore size of 0.45μm and can effectively intercept residual food particles.

[0072] Name of the oven: Electrothermal Blast Drying Oven, Model: DHG-9070A. The temperature control range is from room temperature +5°C to 300°C, and it can stably maintain a drying temperature of 60 - 80°C to ensure that the residual food and the filter membrane can be dried to a constant weight.

[0073] Name of the electronic balance: Analytical Balance, Model: BSA224S-CW. The accuracy can reach 0.1mg. It can accurately weigh the mass of the filter membrane and the residual food to ensure the accuracy of calculating the food residue amount.

[0074] Example 1: A Teflon coating process for the stirrer blade of a food processor, specifically including substrate pretreatment:

[0075] Perform sandblasting on the stainless steel substrate. Select sand grains with a size of 100μm and sandblast for 5 minutes at a pressure of 0.4MPa;

[0076] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 5%, and clean it at a temperature of 40°C for 10 minutes;

[0077] Perform plasma activation with a power setting of 300W and a time of 3 minutes;

[0078] Bottom layer coating: Coat the bottom layer of epoxy resin primer by electrostatic spraying method, control the primer thickness to be 5μm, the coating temperature to be 20°C, and the humidity to be 60%;

[0079] Intermediate layer coating: Coat the intermediate layer by dipping method, the intermediate layer thickness is 15μm, the PTFE content is 80%, the nano-ceramic particle content is 20%, the coating temperature is 25°C, and the humidity is 50%;

[0080] Top layer coating: Coat the top layer by electrostatic spraying method, the top layer thickness is 10μm, the PTFE content is 70%, the graphene content is 10%, the carbon fiber content is 20%, the coating temperature is 30°C, and the humidity is 40%;

[0081] Stepwise curing:

[0082] In the first stage, pre-cure at 80°C for 0.5 hours;

[0083] In the second stage, raise the temperature to 200°C and sinter for 1 hour;

[0084] In the third stage, form a film at a high temperature of 350°C for 0.5 hours.

[0085] Example 2, Substrate pretreatment:

[0086] Perform sandblasting on the stainless steel substrate, select sand grain size of 120μm, and sandblast for 7 minutes under a pressure of 0.5MPa;

[0087] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 7%, and clean it at a temperature of 45°C for 12 minutes;

[0088] Perform plasma activation with a power setting of 400W and a time of 4 minutes;

[0089] Bottom layer coating: Coat the bottom layer of epoxy resin primer by electrostatic spraying method, control the primer thickness to be 7μm, the coating temperature to be 22°C, and the humidity to be 58%;

[0090] Intermediate layer coating: Coat the intermediate layer by dipping method, the intermediate layer thickness is 17μm, the PTFE content is 82%, the nano-ceramic particle content is 18%, the coating temperature is 27°C, and the humidity is 48%;

[0091] Top layer coating: Coat the top layer by electrostatic spraying method, the top layer thickness is 13μm, the PTFE content is 72%, the graphene content is 8%, the carbon fiber content is 20%, the coating temperature is 32°C, and the humidity is 38%;

[0092] Stepwise curing:

[0093] In the first stage, pre-cure at 80 °C for 0.7 hours;

[0094] In the second stage, heat up to 200 °C and sinter for 1.5 hours;

[0095] In the third stage, form a film at 350 °C for 0.7 hours.

[0096] Example 3, Substrate pretreatment:

[0097] Sandblast the stainless steel substrate, select sand grain size of 150 μm, and sandblast for 10 minutes under a pressure of 0.6 MPa;

[0098] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 10%, and clean at 50 °C for 15 minutes;

[0099] Perform plasma activation, set the power to 500 W, and the time to 5 minutes;

[0100] Bottom layer coating: Coat the bottom layer epoxy resin primer by electrostatic spraying method, control the primer thickness to 10 μm, coating temperature to 25 °C, and humidity to 55%;

[0101] Intermediate layer coating: Coat the intermediate layer by impregnation method, the intermediate layer thickness is 20 μm, PTFE content is 85%, nano-ceramic particle content is 15%, coating temperature is 30 °C, and humidity is 45%;

[0102] Top layer coating: Coat the top layer by electrostatic spraying method, the top layer thickness is 20 μm, PTFE content is 75%, graphene content is 5%, and carbon fiber content is 20%, coating temperature is 35 °C, and humidity is 35%;

[0103] Stepwise curing:

[0104] In the first stage, pre-cure at 80 °C for 1 hour;

[0105] In the second stage, heat up to 200 °C and sinter for 2 hours;

[0106] In the third stage, form a film at 350 °C for 1 hour.

[0107] Example 4: Substrate pretreatment:

[0108] Sandblast the titanium alloy substrate, select sand grain size of 100 μm, and sandblast for 5 minutes under a pressure of 0.4 MPa;

[0109] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 5%, and clean at 40 °C for 10 minutes;

[0110] Perform plasma activation with a power setting of 300 W for 3 minutes;

[0111] Bottom layer coating: Coat the bottom layer epoxy resin primer using the electrostatic spraying method, controlling the primer thickness to be 5 μm, the coating temperature to be 20 °C, and the humidity to be 60%;

[0112] Intermediate layer coating: Coat the intermediate layer by the dipping method, with the intermediate layer thickness being 15 μm, the PTFE content being 80%, the nano-ceramic particle content being 20%, the coating temperature being 25 °C, and the humidity being 50%;

[0113] Top layer coating: Coat the top layer using the electrostatic spraying method, with the top layer thickness being 10 μm, the PTFE content being 70%, the graphene content being 10%, and the carbon fiber content being 20%, the coating temperature being 30 °C, and the humidity being 40%;

[0114] Stepwise curing:

[0115] In the first stage, pre-cure at 80 °C for 0.5 hours;

[0116] In the second stage, raise the temperature to 200 °C and sinter for 1 hour;

[0117] In the third stage, form a film at 350 °C for 0.5 hours.

[0118] Example 5: Substrate pretreatment:

[0119] Perform sandblasting on the titanium alloy substrate, select sand grains with a size of 120 μm, and sandblast for 7 minutes under a pressure of 0.5 MPa;

[0120] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 7% and clean it at 45 °C for 12 minutes;

[0121] Perform plasma activation with a power setting of 400 W for 4 minutes;

[0122] Bottom layer coating: Coat the bottom layer epoxy resin primer using the electrostatic spraying method, controlling the primer thickness to be 7 μm, the coating temperature to be 22 °C, and the humidity to be 58%;

[0123] Intermediate layer coating: Coat the intermediate layer by the dipping method, with the intermediate layer thickness being 17 μm, the PTFE content being 82%, the nano-ceramic particle content being 18%, the coating temperature being 27 °C, and the humidity being 48%;

[0124] Top layer coating: Coat the top layer using the electrostatic spraying method, with the top layer thickness being 13 μm, the PTFE content being 72%, the graphene content being 8%, and the carbon fiber content being 20%, the coating temperature being 32 °C, and the humidity being 38%;

[0125] Stepwise curing:

[0126] In the first stage, pre-cure at 80 °C for 0.7 hours;

[0127] In the second stage, heat up to 200 °C and sinter for 1.5 hours;

[0128] In the third stage, form a film at 350 °C under high temperature for 0.7 hours.

[0129] Example 6: Substrate pretreatment:

[0130] Perform sandblasting on the titanium alloy substrate, select sand grains with a size of 150 μm, and sandblast for 10 minutes under a pressure of 0.6 MPa;

[0131] Put the sandblasted substrate into an alkaline cleaning agent with a concentration of 10%, and clean it at 50 °C for 15 minutes;

[0132] Perform plasma activation, set the power to 500 W, and the time to 5 minutes;

[0133] Bottom layer coating: Coat the bottom layer of epoxy resin primer by electrostatic spraying method, control the primer thickness to 10 μm, the coating temperature to 25 °C, and the humidity to 55%;

[0134] Intermediate layer coating: Coat the intermediate layer by dipping method, the intermediate layer thickness is 20 μm, the PTFE content is 85%, the nano-ceramic particle content is 15%, the coating temperature is 30 °C, and the humidity is 45%;

[0135] Surface layer coating: Coat the surface layer by electrostatic spraying method, the surface layer thickness is 20 μm, the PTFE content is 75%, the graphene content is 5%, the carbon fiber content is 20%, the coating temperature is 35 °C, and the humidity is 35%;

[0136] Stepwise curing:

[0137] In the first stage, pre-cure at 80 °C for 1 hour;

[0138] In the second stage, heat up to 200 °C and sinter for 2 hours;

[0139] In the third stage, form a film at 350 °C under high temperature for 1 hour.

[0140] Perform performance tests on the food processor stirring knives with Teflon coatings obtained in Examples 1, 2, 3, 4, 5, and 6, specifically including bond strength, porosity, and acid resistance. The specific test results are shown in Tables 1 and 2.

[0141] Table 1 shows the test results of bond strength and porosity in the examples

[0142] Test sample Bonding strength (MPa) Porosity (%) Example 1 35.5 0.54 Example 2 45.2 5.2 Example 3 52.8 2.1 Example 4 48.6 1.8 Example 5 55.9 2.5 Example 6 62.30 3.1

[0143] Table 2 shows the test results of acid resistance in the examples

[0144] Test sample Resistance change rate (%) Mass damage rate (%) Example 1 8.00 3 Example 2 7.00 2.5 Example 3 6.00 2.1 Example 4 8.00 1.8 Example 5 10.00 2.2 Example 6 9.00 4.1

[0145] The Teflon coating of the stirring blade of the food processor of the present invention has been tested and shown significant advantages in many aspects. The bonding strength is ≥35 MPa. Thanks to the unique pretreatment layer process, a composite rough structure and barbs are formed, ensuring the stable adhesion of the coating under complex working conditions and extending the life of the stirring blade. The porosity is ≤5.2%, effectively blocking external erosion and enhancing the protection ability. In the acid resistance test, the resistance change rate is ≤10%, and the mass loss rate <5%. The materials of each layer cooperate to endow the coating with chemical stability, ensuring stable operation when processing acidic foods and bringing a better user experience to users.

[0146] Perform performance tests on the stirring blades of the food processors with Teflon coatings obtained in Examples 1, 2, 3, 4, 5, and 6, specifically including wear amount and food residue amount tests. The specific test results are shown in Table 3.

[0147] Table 3 shows the test results of wear amount and food residue amount in the examples

[0148] Test sample Wear amount (μm) <![CDATA[Food residue amount (mg / cm 2 )]]> Example 1 8.50 2.5 Example 2 7.80 2.3 Example 3 9.20 2.6 Example 4 8.00 2.4 Example 5 8.80 2.7 Example 6 9.00 2.2

[0149] From the above data, it can be seen that after the coatings in each example are continuously used for 500 hours at a high speed of 30,000 revolutions per minute, the wear amount is less than 10 μm, and the food residue amount is less than or equal to 2.8 mg / cm 2 , fully verifying that the coating of the present invention has good wear resistance and low food residue characteristics in high-speed and long-term use scenarios, and can effectively ensure the efficient and stable operation of the stirring blade of the food processor.

[0150] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements, or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all covered by the protection scope of the present invention.

Claims

1. A Teflon coating for the stirring blade of a food processor, characterized in that, Comprising: A substrate which is a stainless steel or titanium alloy stirring knife body; A pretreatment layer, which forms a micron-level and nano-level composite rough structure on the surface of the substrate through rough spraying and fine spraying processes. For rough spraying, glass sand with a size of 150 - 300 μm is used to form a micron-level uneven surface with a height difference of 10 - 50 μm, and after the epoxy resin primer penetrates into the pits and cures, a barb structure is formed; The bottom layer is an epoxy resin primer layer with a thickness of 5 - 10 μm and an epoxy resin content of ≥ 95%; The intermediate layer is a mixed layer of PTFE and nano-ceramic particles with a thickness of 15 - 20 μm, a PTFE content of 80 - 85%, and a nano-ceramic particle content of 15 - 20%; The surface layer is a modified PTFE layer containing graphene or carbon fiber with a thickness of 10 - 20 μm, a PTFE content of 70 - 75%, a graphene content of 5 - 10%, and a carbon fiber content of 15 - 20%; Wherein, the total thickness of the coating is 30 - 50 μm.

2. The Teflon coating of the stirring blade of a food processor according to claim 1, wherein: The pretreatment layer includes: Sandblasting treatment: The sand particle size is 100 - 150 μm, the pressure is 0.4 - 0.6 MPa, and the time is 5 - 10 minutes; Chemical cleaning: The concentration of the alkaline cleaning agent is 5 - 10%, the temperature is 40 - 50 °C, and the time is 10 - 15 minutes; Plasma activation: The power is 300 - 500 W, and the time is 3 - 5 minutes.

3. The Teflon coating of the stirring blade of a food processor according to claim 1, characterized in that: The coating temperature of the bottom layer is 20 - 25 °C and the humidity ≤ 60%; the coating temperature of the intermediate layer is 25 - 30 °C and the humidity ≤ 50%; the coating temperature of the surface layer is 30 - 35 °C and the humidity ≤ 40%.

4. The Teflon coating of the stirring blade of a food processor according to claim 1, wherein: The particle size of the nano-ceramic particles is 20 - 50 nm, the graphene is in a single-layer or few-layer structure with the number of layers ≤ 5, and the carbon fiber length is 1 - 10 μm.

5. The Teflon coating of the stirring blade of a food processor according to claim 1, characterized in that: The wear amount of the said coating is < 10 μm after continuous use for 500 hours at a high speed of 30,000 revolutions per minute, and the food residue amount ≤ 2.8 mg / cm 2 .

6. The Teflon coating of the stirring blade of a food processor according to claim 1, characterized in that: The mechanical bonding force between the epoxy resin primer and the substrate is enhanced by the barb structure, and the bonding strength ≥ 35 MPa.

7. A preparation process for a Teflon coating of a stirring knife of a food processor according to any one of claims 1-6, characterized in that, Including the following steps: (1) Substrate pretreatment: Successively carry out sandblasting treatment, chemical cleaning, and plasma activation; (2) Coating in three times: Successively coat the bottom layer, intermediate layer, and surface layer by electrostatic spraying or dipping method; (3) Step-by-step curing: In the first stage, pre-cure at 80 °C for 0.5 - 1 hour, in the second stage, sinter at 200 °C for 1 - 2 hours, and in the third stage, form a high-temperature film at 350 °C for 0.5 - 1 hour.

Images