An oil-repellent polyurethane paint and a method for preparing the same

Abstract

The application relates to the technical field of paint, and particularly discloses an oil-resistant polyurethane paint and a preparation method thereof. The preparation method comprises the following steps: S1. mixing modified polyethylene wax powder with 15-25 wt% of a solvent and 10-20 wt% of polyurethane resin, heating to 65-80 DEG C and keeping stirring for 15-25 minutes, and cooling to below 40 DEG C to obtain a wax slurry; S2. mixing the remaining polyurethane resin with a reactive organosilicon oligomer at 25-35 DEG C, and stirring and reacting for 30-50 minutes; and S3. adding the wax slurry into the mixture in step S2, and then adding the remaining solvent and an additive, and stirring uniformly. Through the composite collocation of the reactive organosilicon oligomer and the surface-modified wax powder, a significant synergistic anti-pollution enhancement effect is generated; the reactive organosilicon forms a chemical bond in the polyurethane network, providing a persistent basic oil-repellent layer; and the modified wax powder builds a micro-nano rough structure on the surface of the coating, further improving the oil resistance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to an oil-resistant polyurethane paint and its preparation method. Background Technology

[0002] In high-end home furnishings, medical devices, and food processing equipment manufacturing, surfaces that are frequently touched and easily contaminated by oil require protective coatings to isolate them. These coatings are liquid materials (i.e., paint) before application and cure into a film (i.e., a coating layer) after application. The performance of the coating needs to resist grease adhesion, be easy to clean, and maintain these properties after long-term use.

[0003] To achieve these performance requirements, the coatings industry primarily employs solutions based on fluorinated compounds, such as Teflon. These materials significantly reduce the surface energy of the coating, providing excellent oil resistance and easy cleaning properties.

[0004] However, in practical applications, existing fluorinated coatings have revealed several issues regarding environmental protection and health. Studies have confirmed that many traditional fluorinated compounds are difficult to degrade in the natural environment and can accumulate in organisms, thus being classified as restricted "permanent chemicals." This directly leads to increasingly stringent regulatory restrictions on the production and application of such materials, posing significant compliance risks and potential brand image damage to downstream manufacturers. Therefore, the market needs to develop a new type of oil-resistant coating with low or even no fluorine content.

[0005] Existing fluorine-free alternative technologies mainly employ organosilicon or wax additives, but both have significant drawbacks. Organosilicon-modified coatings lack sufficient oil resistance, especially against heavy oil stains such as high-viscosity cooking oil and engine oil, where adhesion still occurs, failing to reach the level of fluorine-containing coatings. Furthermore, the introduction of organosilicon reduces the mechanical strength of the coating, leading to decreased wear resistance and adhesion, causing the anti-fouling layer to wear away and fail quickly under frequent scrubbing. While wax additives are inexpensive, their poor compatibility with resins makes them prone to leaching from the coating, resulting in only short-term oil resistance and a lack of long-term effectiveness.

[0006] It is evident that existing fluorine-free oil-resistant coating technologies struggle to balance environmental friendliness, oil resistance, and durability. Summary of the Invention

[0007] The purpose of this invention is to provide an oil-resistant polyurethane paint and its preparation method to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, according to one aspect of the present invention, an oil-resistant polyurethane paint is provided, comprising the following components by weight percentage:

[0009] 40-55 wt% polyurethane resin, 5-12 wt% reactive organosilicon oligomer, 2-7 wt% modified polyethylene wax powder, 25-35 wt% solvent and 0-3 wt% additives.

[0010] The additive is a leveling agent.

[0011] Preferably, the reactive organosilicon oligomer is a hydroxyl-terminated polydimethylsiloxane or an amino-terminated polydimethylsiloxane, with a number-average molecular weight of 1000-3000.

[0012] Preferably, the modified polyethylene wax micro powder is oxidized polyethylene wax or maleic anhydride-grafted polyethylene wax, with an acid value of 8-25 mg KOH / g and an average particle size of 2-15 μm.

[0013] Preferably, the polyurethane resin is an aliphatic isocyanate type polyurethane resin, and the aliphatic isocyanate isophorone diisocyanate or hydrogenated toluene diisocyanate.

[0014] Preferably, the solvent is a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene, wherein n-butyl acetate accounts for 40-60% of the total mass of the solvent, propylene glycol methyl ether acetate accounts for 20-40%, and xylene accounts for 10-30%.

[0015] According to another aspect of the present invention, a method for preparing an oil-resistant polyurethane paint is provided, comprising the following steps:

[0016] S1. Mix modified polyethylene wax micro powder with 15-25wt% solvent and 10-20wt% polyurethane resin, heat to 65-80°C and stir for 15-25 minutes, then cool to below 40°C to obtain wax slurry;

[0017] S2. Mix the remaining polyurethane resin with the reactive organosilicon oligomer at 25-35°C and stir for 30-50 minutes.

[0018] S3. Add the wax slurry to the mixture from step S2, then add the remaining solvent and additives, and stir until homogeneous;

[0019] S4. Disperse the mixture using a high-speed disperser at 2200-2800 rpm for 25-35 minutes until the fineness is ≤25μm.

[0020] Preferably, the heating and stirring rate in step S1 is 1200-1800 rpm.

[0021] Preferably, the mixing and stirring rate of the reactive organosilicon oligomer and polyurethane resin in step S2 is 400-550 rpm.

[0022] Preferably, the rotation speed of the dispersion process in step S4 is 2200-2800 rpm.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) By combining reactive organosilicon oligomers with surface-modified wax micropowders, a significant synergistic antifouling enhancement effect is generated. The reactive organosilicon forms chemical bonds in the polyurethane network, providing a durable basic oleophobic layer, while the modified wax micropowders construct micro-nano rough structures on the coating surface, further enhancing oil resistance. The synergistic effect of the two increases the contact angle of the coating with common oil stains such as edible oil and engine oil, and also reduces the external force required for cleaning, achieving antifouling performance close to that of fluorine-containing coatings under fluorine-free conditions.

[0025] (2) The innovative step-by-step preparation process solves the problem of uneven dispersion and easy phase separation of organosilicon and wax powder in the resin system by first preparing wax slurry and then carrying out silane pre-reaction. This process ensures that the functional components exist in the system in the optimal form, so that the components of the final coating surface are evenly distributed, avoiding the problem of uneven anti-fouling performance that is easy to be generated by traditional blending process.

[0026] (3) By chemically anchoring reactive organosilicon oligomers, organosilicon components are firmly bonded to the polyurethane network structure, which fundamentally overcomes the problem of decreased coating mechanical properties caused by physical blending of organosilicon. The resulting coating maintains excellent oil resistance while significantly improving wear resistance compared to traditional organosilicon modified coatings, achieving a good balance between stain resistance and mechanical strength. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The composition of the oil-resistant polyurethane paint of the present invention comprises, by weight percentage, the following components:

[0029] 40-55% polyurethane resin serves as the film-forming substance of the system, forming the basic framework of the coating.

[0030] 5-12% reactive organosilicon oligomers and 2-7% modified polyethylene wax micropowder, as key functional components, impart durable oil resistance to the coating through a synergistic effect.

[0031] 25-35% solvent is used to adjust the viscosity of the system to meet construction requirements;

[0032] Additives of 0-3% are used to improve the production, storage, or application performance of paints.

[0033] The additive is a leveling agent.

[0034] The leveling agent can be a polyether-modified polysiloxane leveling agent or an acrylate leveling agent, such as BYK-333 or TEGO Glide 410.

[0035] The specific types and amounts of additives used in the following examples are merely illustrative examples of achieving the corresponding functions.

[0036] Example 1: An oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0037] 40wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 5wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 2wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 10 mg KOH / g and an average particle size of 8 μm), 32wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene), and 1wt% additive (the additive is leveling agent BYK-333).

[0038] A method for preparing an oil-resistant polyurethane paint includes the following steps:

[0039] S1. Mix 2wt% modified polyethylene wax powder, 15wt% solvent and 15wt% polyurethane resin, heat to 70°C and stir for 20 minutes, cool to below 40°C to obtain a uniform wax slurry.

[0040] S2. Mix the remaining 25wt% polyurethane resin with 5wt% reactive organosilicon oligomer at 30°C and stir for 40 minutes.

[0041] S3. Add the wax slurry prepared in step S1 to the mixture obtained in step S2, then add 17wt% of the remaining solvent and 1wt% of the additives, and stir until homogeneous.

[0042] S4. The mixture obtained in step S3 is dispersed in a high-speed disperser at 2500 rpm for 30 minutes until the fineness is ≤25μm, thus obtaining the oil-resistant polyurethane paint.

[0043] Example 2: An oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0044] 47 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 8.5 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 4.5 wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 12 mg KOH / g and an average particle size of 5 μm), and 30 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate, and xylene).

[0045] A method for preparing an oil-resistant polyurethane paint includes the following steps:

[0046] S1. Mix 4.5wt% modified polyethylene wax powder, 15wt% solvent and 15wt% polyurethane resin, heat to 70°C and stir for 20 minutes, cool to below 40°C to obtain a uniform wax slurry.

[0047] S2. Mix the remaining 32wt% polyurethane resin with 8.5wt% reactive organosilicon oligomer at 30°C and stir for 40 minutes.

[0048] S3. Add the wax slurry prepared in step S1 to the mixture obtained in step S2, then add the remaining solvent (15 wt%) and additives, and stir until homogeneous.

[0049] S4. The mixture obtained in step S3 is dispersed in a high-speed disperser at 2500 rpm for 30 minutes until the fineness is ≤25μm, thus obtaining the oil-resistant polyurethane paint.

[0050] Example 3: An oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0051] 55 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 12 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 7 wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 12 mg KOH / g and an average particle size of 5 μm), 25 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene), and 1 wt% additive (the additive is leveling agent BYK-333).

[0052] A method for preparing an oil-resistant polyurethane paint includes the following steps:

[0053] S1. Mix 7wt% modified polyethylene wax powder, 15wt% solvent and 15wt% polyurethane resin, heat to 70°C and stir for 20 minutes, cool to below 40°C to obtain a uniform wax slurry.

[0054] S2. Mix the remaining 40wt% polyurethane resin with 12wt% reactive organosilicon oligomer at 30°C and stir for 40 minutes.

[0055] S3. Add the wax slurry prepared in step S1 to the mixture obtained in step S2, then add 10wt% of the remaining solvent and 1wt% of the additives, and stir until homogeneous.

[0056] S4. The mixture obtained in step S3 is dispersed in a high-speed disperser at 2500 rpm for 30 minutes until the fineness is ≤25μm, thus obtaining the oil-resistant polyurethane paint.

[0057] Example 4: An oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0058] 50 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 10 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 5 wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 12 mg KOH / g and an average particle size of 5 μm), 32 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene), and 3 wt% additive (the additive is leveling agent BYK-333).

[0059] A method for preparing an oil-resistant polyurethane paint includes the following steps:

[0060] S1. Mix 5wt% modified polyethylene wax powder, 15wt% solvent and 15wt% polyurethane resin, heat to 70°C and stir for 20 minutes, then cool to below 40°C to obtain a uniform wax slurry.

[0061] S2. Mix the remaining 35wt% polyurethane resin with 10wt% reactive organosilicon oligomer at 30°C and stir for 40 minutes.

[0062] S3. Add the wax slurry prepared in step S1 to the mixture obtained in step S2, then add 17wt% of the remaining solvent and 3wt% of the additives, and stir until homogeneous.

[0063] S4. The mixture obtained in step S3 is dispersed in a high-speed disperser at 2500 rpm for 30 minutes until the fineness is ≤25μm, thus obtaining the oil-resistant polyurethane paint.

[0064] Example 5: An oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0065] 50 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 10 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 5 wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 12 mg KOH / g and an average particle size of 5 μm), 35 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene), and 1 wt% additive (the additive is leveling agent BYK-333).

[0066] A method for preparing an oil-resistant polyurethane paint includes the following steps:

[0067] S1. Mix 5wt% modified polyethylene wax powder, 15wt% solvent and 15wt% polyurethane resin, heat to 70°C and stir for 20 minutes, then cool to below 40°C to obtain a uniform wax slurry.

[0068] S2. Mix the remaining 35wt% polyurethane resin with 10wt% reactive organosilicon oligomer at 30°C and stir for 40 minutes.

[0069] S3. Add the wax slurry prepared in step S1 to the mixture obtained in step S2, then add 20wt% of the remaining solvent and 1wt% of the additives, and stir until homogeneous.

[0070] S4. The mixture obtained in step S3 is dispersed in a high-speed disperser at 2500 rpm for 30 minutes until the fineness is ≤25μm, thus obtaining the oil-resistant polyurethane paint.

[0071] Comparative Example 1, an oil-resistant polyurethane paint, comprises the following components by weight percentage:

[0072] 47 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 8.5 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 0 wt% modified polyethylene wax micro powder, and 30 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene).

[0073] A method for preparing an oil-resistant polyurethane paint is the same as in Example 2.

[0074] Comparative Example 2, an oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0075] 47 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 0 wt% reactive organosilicon oligomer, 4.5 wt% modified polyethylene wax micro powder (selected as oxidized polyethylene wax, acid value 12 mg KOH / g, average particle size 5 μm), and 30 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene).

[0076] A method for preparing an oil-resistant polyurethane paint is the same as in Example 2.

[0077] Comparative Example 3, an oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0078] 47 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 8.5 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 4.5 wt% unmodified polyethylene wax micropowder (selected as ordinary polyethylene wax, with an acid value of 0 mg KOH / g and an average particle size of 8 μm), and 30 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate, and xylene).

[0079] A method for preparing an oil-resistant polyurethane paint is the same as in Example 2.

[0080] Comparative Example 4, an oil-resistant polyurethane paint, comprising the following components by weight percentage:

[0081] 47 wt% polyurethane resin (selected as aliphatic isocyanate type polyurethane resin, using isophorone diisocyanate as raw material), 8.5 wt% reactive organosilicon oligomer (selected as hydroxyl-terminated polydimethylsiloxane, with a number average molecular weight of about 1500), 4.5 wt% modified polyethylene wax micropowder (selected as oxidized polyethylene wax, with an acid value of 12 mg KOH / g and an average particle size of 10 μm), and 30 wt% solvent (selected as a mixture of n-butyl acetate, propylene glycol methyl ether acetate, and xylene).

[0082] A method for preparing an oil-resistant polyurethane paint is the same as in Example 2.

[0083] The polyurethane paint film samples obtained from the examples and comparative examples were subjected to the following performance tests.

[0084] I. Oil Stain Resistance Test

[0085] 1) Contact angle test

[0086] Test objective: To quantitatively evaluate the wettability of a coating surface to liquids, directly characterizing its hydrophobic and oleophobic properties. A larger contact angle indicates poorer wettability of the liquid on the material surface and better anti-adhesion performance of the coating.

[0087] Quantitative indicator: Static contact angle (unit: °), reporting the contact angle values ​​of three liquids: water, glycerol, and hexadecane.

[0088] Test standard: GB / T30693-2014 "Test method for surface wetting tension of plastic products".

[0089] Test method: Prepare a smooth, flat paint film sample (at least 100mm × 100mm). At room temperature, using a contact angle meter and the seated drop method, gently drop a specified volume (usually 2-5μL) of test liquid onto the coating surface. Analyze the droplet profile using the instrument software and calculate the static contact angle value. Measure each sample at least 5 times at different locations and take the average value.

[0090] 2) Ease of cleaning test

[0091] Test objective: To simulate the ease of cleaning a contaminated coating in actual use, and to comprehensively evaluate the coating's stain resistance and stain release properties.

[0092] Quantitative indicator: Number of wipes required to completely remove stains (unit: wipes).

[0093] Test standard: Refer to the test approach for ease of cleaning in GB / T38139-2019 "Test Method for Antibacterial Properties of Nanomaterials in Nanotechnology".

[0094] Test Method: Prepare a paint film sample. Using a pipette, add 0.1 mL of a standard stain (such as cooking oil, engine oil, soy sauce, etc.) to the sample surface, cover with a thin film, and apply a 1 kg weight. Let it stand for 24 hours. Remove the weight and film. Using a scrub resistance tester (or manually), hold a standard damp cotton cloth (containing a specific cleaning agent) and apply a specific load (e.g., 500 g) at a fixed frequency, wiping back and forth. Observe after every 50 wipings until the stain is completely removed. Record the total number of wipings.

[0095] II. Durability Testing

[0096] 1) Abrasion resistance test

[0097] Test objective: To evaluate the ability of a coating surface to resist mechanical friction and to verify whether anti-fouling components (such as silicone) are chemically anchored to prevent a decrease in abrasion resistance.

[0098] Quantitative indicator: abrasion loss (unit: mg). The less weight loss, the better the abrasion resistance.

[0099] Test standard: GB / T1768-2006 Determination of abrasion resistance of paints and varnishes by rotating rubber grinding wheel method.

[0100] Test method: Prepare a paint film of specified thickness on a flat substrate (such as tinplate). Using an abrasion testing machine, select a specific abrasion wheel, apply a load of 500g or 1000g, and rotate a certain number of times. Weigh the test plate before and after the test using a precision balance, and calculate the mass loss.

[0101] 2) Scrub resistance test

[0102] Test objective: To simulate frequent cleaning scenarios and comprehensively evaluate the coating's durability against scrubbing and media erosion, as well as its stain resistance.

[0103] Quantitative indicator: number of scrubs (unit: times). The higher the number of scrubs, the better the durability.

[0104] Test standard: GB / T9266-2009 "Determination of scrub resistance of architectural coatings".

[0105] Test Method: Prepare a paint film sample. Fix the sample in the test tank of the scrub resistance tester, pour in a soap solution of the specified concentration (e.g., 0.5%), and immerse the brush bristles in the soap solution to half their height. Start the machine and have the brush repeatedly scrub the surface of the sample at a fixed frequency until the substrate is exposed in a 100mm × 100mm area in the center of the sample. Record the number of scrubs.

[0106] 3) Long-term effectiveness test

[0107] Test objective: To predict and evaluate the long-term durability of the coating's anti-fouling performance by simulating harsh environments and accelerating coating aging.

[0108] Quantitative indicators: contact angle retention rate after aging (%), or ease of cleaning after aging (change in the number of wipes).

[0109] Test standard: GB / T1865-2009 Paints and varnishes - Artificial weathering and artificial radiation exposure (filtered xenon arc radiation)

[0110] Test method: Prepare a paint film sample. Place the sample in a xenon lamp aging test chamber and conduct an accelerated aging test for a certain period of time according to the standard set cyclic conditions (such as light exposure and spraying). After aging, remove the sample, condition it under standard conditions for 24 hours, and then retest its contact angle and ease of cleaning according to the aforementioned method, and compare the results with the data before aging.

[0111] III. Mechanical and Physical Performance Testing

[0112] 1) Adhesion test

[0113] Test objective: To evaluate the strength of the bond between the coating and the substrate or between the coatings themselves, and to verify that the basic adhesion properties of the formulation are not sacrificed due to the addition of functional components.

[0114] Quantitative indicator: Adhesion level (0-5, 0 being the best).

[0115] Test standard: GB / T9286-2021 "Cross-cut test for paints and varnishes".

[0116] Test Method: Prepare a paint film sample. Using a cross-cutting tool (blade spacing 1mm or 2mm), cut 6 or 11 parallel cuts into the coating, down to the substrate. Repeat the above operation by rotating 90° to form a grid pattern. Gently brush away debris with a soft brush, then apply and quickly peel off the coating using a hand-pressing or tape method. Rate the degree of coating peeling in the grid areas according to the standard chart.

[0117] 2) Hardness test

[0118] Test objective: To evaluate the coating surface's ability to resist indentation, scratching, or abrasion by foreign objects, and to verify the overall mechanical strength of the coating.

[0119] Quantitative indicators: pencil hardness grade (such as H, 2H, 3H, etc.), or pendulum damping time (unit: seconds, s).

[0120] Test standards: GB / T6739-2006 "Determination of Hardness of Paints and Varnishes by Pencil Method"; GB / T1730-2007 "Damping Test of Paints and Varnishes".

[0121] Test method:

[0122] Pencil Hardness Method: Prepare a paint film sample. Hold a set of drawing pencils of known hardness (from 6B to 9H) at a 45° angle to the sample and move them forward at approximately 1 cm / s, applying uniform force (enough to prevent the pencil from breaking). Find the hardest pencil that leaves at least two scratches without damaging the paint film; this hardness is the paint film pencil hardness.

[0123] Pendulum Damping Method: A coating film is prepared on a glass plate. Using a pendulum damping hardness tester, the pendulum needle is placed on the coating film surface, and the pendulum is swung to make it swing. The time required for the swing amplitude to decrease from 6° to 3° is recorded and compared with the swing time on the glass plate to calculate the damping time or hardness percentage.

[0124] Table 1: Oil Stain Resistance Test

[0125]

[0126] Comparative Example 1 uses a conventional organosilicon modification scheme without introducing a synergistic system of reactive organosilicon and modified wax powder. Its hexadecane contact angle is 85°, which is at the common level in the industry (80-90°). It requires 50 wipes to clean, which reflects the bottleneck problem of poor anti-adhesion of current technology against heavy oil stains (such as engine oil and cooking oil). The cleaning difficulty is significantly higher than the industry's acceptable threshold (>40 wipes is "difficult to clean").

[0127] In Examples 1-5, after simultaneously introducing reactive organosilicon (5-12 wt%) and modified wax micropowder (2-7 wt%), the hexadecane contact angle increased from 85° to 102-108°, an improvement of 19-27%; the easy-to-clean property decreased from 50 cycles to 30-35 cycles, a reduction of 30-40%. Example 2 (108° / 30 cycles) showed the best performance, with improvements of 27% and 40% compared to the baseline, indicating that the synergistic effect of "reactive organosilicon + modified wax micropowder" significantly overcomes the limitations of existing technologies. When reactive organosilicon ≥ 8.5 wt% and wax micropowder ≥ 4.5 wt% (Examples 2 and 3), the hexadecane contact angle simultaneously > 105°, and the easy-to-clean property < 32 cycles, an improvement of another order of magnitude compared to the baseline, proving that the micro-nano structure network formed after the three components are combined is superior to the sum of the individual effects of each component. While pursuing high oleophobicity, the embodiments maintain a water contact angle of 104-108° and a glycerol contact angle of 97-101°, which is at the same hydrophobic level as Comparative Example 1. This avoids the performance imbalance of "high oleophobicity" accompanied by "low hydrophobicity" and shows good overall balance.

[0128] Comparative Example 2 (lacking reactive organosilicon) showed a sharp drop in hexadecane contact angle to 75°, while its easy-to-clean properties increased to 60 cycles, representing a 14-20% deterioration compared to the complete formulation. Comparative Example 3 (unmodified wax micropowder) had a contact angle of 90° and an easy-to-clean properties of 45 cycles, a 5-10% decrease compared to the complete formulation. Comparative Example 4 (wax micropowder with excessively large particle size) had a contact angle of 95° and an easy-to-clean properties of 40 cycles, a 5-15% decrease compared to the complete formulation. The data directly demonstrate that the absence of any key component prevents the construction of an effective micro / nano structure, and the interruption of the synergistic effect leads to a decline in oleophobic properties.

[0129] Examples 1 to 5 all achieved a hexadecane contact angle ≥102° and easy-to-clean properties ≤35 times under process conditions of 70°C, 20 minutes, and 2500rpm, demonstrating that the present invention has a practical tolerance of ≥5°C for process parameter fluctuations, thus proving that it can solve the problem of heavy oil stain adhesion.

[0130] Table 2: Durability Tests

[0131]

[0132] Comparative Example 1 uses a conventional organosilicon modification scheme without introducing a synergistic system of reactive organosilicon and modified wax powder. Its wear resistance loss is 15.0 mg, which is at the common level in the industry (12-18 mg). The adhesion remains at level 1 (the best standard level), but the wear resistance is significantly exceeded (>12 mg is considered easy to wear). This confirms that "heavy oil stains cause rapid coating failure" and objectively reflects the core defect of the current technology in terms of durability, namely, oil stain penetration accelerates coating wear, and poor cleanability and insufficient wear resistance form a dual failure mechanism.

[0133] In Examples 1 to 5, after simultaneously introducing reactive organosilicon (5-12 wt%) and modified wax micropowder (2-7 wt%), the abrasion resistance mass loss decreased from 15.0 mg to 8.0-9.5 mg, a reduction of 46.7-36.7%, significantly better than Comparative Example 1; adhesion remained at Grade 2 (meeting the standard, allowing slight peeling), and weather resistance ΔE 2.5-2.9 fluctuated within ±5% compared to Comparative Example 1 (2.8), indicating that the improvement in oleophobicity did not sacrifice basic durability. Example 2 (8.0 mg / Grade 2) performed best, with a reduction of 46.7% compared to Comparative Example 1. When reactive organosilicon ≥ 8.5 wt% and wax micropowder ≥ 4.5 wt% (Examples 2 and 3), the abrasion resistance was simultaneously < 8.5 mg, a further reduction of one order of magnitude compared to the baseline, proving that the micro-nano structure network formed after the three components were combined was superior to the sum of the individual effects of each component.

[0134] Comparative Example 2 (lacking reactive organosilicon) showed a sharp increase in wear resistance to 25.0 mg, a 66.7% deterioration compared to Comparative Example 1; Comparative Example 3 (unmodified wax powder) showed a wear resistance of 18.0 mg, a 20.0% deterioration compared to Comparative Example 1; and Comparative Example 4 (wax powder with excessively large particle size) showed a wear resistance of 16.0 mg, a 6.7% deterioration compared to Comparative Example 1. The data directly indicate that the absence of any key component leads to the destruction of the micro / nano structure, interruption of the synergistic effect, and a positive correlation between the degree of wear resistance reduction and the intensity of component absence.

[0135] Examples 1 to 5 all achieved abrasion resistance ≤9.5mg and adhesion ≤2 grade under process conditions of 70°C, 20 minutes, and 2500rpm, demonstrating that the present invention has a practical tolerance of ≥5°C for process parameter fluctuations, providing operability for industrial-scale applications and thus solving the problem of coating failure caused by oil adhesion.

[0136] Table 3: Mechanical and Physical Performance Tests

[0137]

[0138] Comparative Example 1 uses a conventional organosilicon modification scheme without introducing a synergistic system of reactive organosilicon and modified wax powder. Its tensile strength is 25.0 MPa, hardness is 85 Shore A, elastic modulus is 2500 MPa, and bulk density is 1200 kg / m³, which is at the common level in the industry (tensile strength 20-30 MPa). This objectively reflects the basic mechanical strength performance of the current technology. That is, the coating is susceptible to oil stains, which leads to a decline in mechanical properties. Oil stain penetration causes internal stress accumulation, which makes the tensile strength only reach the lower limit of ordinary polyurethane coatings. The bulk density of 1200 kg / m³ indicates that the coating density is moderate, but it lacks an anti-oil stain strengthening mechanism, resulting in insufficient mechanical stability.

[0139] In Examples 1 to 5, after simultaneously introducing reactive organosilicon (5-12 wt%) and modified wax micropowder (2-7 wt%), the tensile strength increased from 25.0 MPa to 28.5-35.0 MPa, an increase of 14-40%, which was significantly better than Comparative Example 1. The hardness (85-87 Shore A), elastic modulus (2500-2600 MPa), and bulk density (1205-1215 kg / m³) fluctuated within ±5% compared with Comparative Example 1, indicating that the improvement in oleophobicity did not sacrifice the basic mechanical properties. Example 2 (35.0 MPa / 85 Shore A) showed the best performance, with a 40% improvement over Comparative Example 1. When the reactive organosilicon content was ≥8.5 wt% and the wax micropowder content was ≥4.5 wt% (Examples 2 and 3), the tensile strength was simultaneously >33.5 MPa, a further 14% improvement over the baseline. This demonstrates that the micro-nano structure network formed after the three components were combined is superior to the sum of the individual effects of each component, effectively suppressing the internal stress caused by oil penetration and achieving synergistic optimization of mechanical strength and oleophobicity.

[0140] Comparative Example 2 (lacking reactive organosilicon) showed a sharp drop in tensile strength to 18.0 MPa, a 28.0% deterioration compared to Comparative Example 1; Comparative Example 3 (unmodified wax powder) showed a tensile strength of 22.0 MPa, a 12.0% deterioration; and Comparative Example 4 (wax powder with excessively large particle size) showed a tensile strength of 23.5 MPa, a 6.0% deterioration. The data directly demonstrate that the absence of any key component leads to the destruction of the micro / nano structure and the interruption of the synergistic effect. The magnitude of the tensile strength decline is positively correlated with the intensity of component absence, confirming the synergistic necessity of "reactive organosilicon + modified wax powder".

[0141] Examples 1 to 5 all achieved tensile strength ≥28.5MPa and hardness ≤87 Shore A under process conditions of 70°C, 20 minutes, and 2500rpm, demonstrating that the present invention has a tolerance of ≥5°C for process parameter fluctuations, providing operability for industrial-scale applications and thus solving the problem of mechanical performance degradation caused by oil contamination.

[0142] The above content is merely an example and illustration of the concept of the present invention. Any modifications or additions to the specific embodiments described, or substitutions made by those skilled in the art, shall fall within the scope of protection claimed by the present invention.

Claims

1. An oil-repellent polyurethane paint, characterized in that, comprise the following components by mass percentage: 40-55wt% of polyurethane resin, 5-12wt% of reactive silicone oligomer, 2-7wt% of modified polyethylene wax micro powder, 25-35wt% of solvent and 0-3wt% of auxiliary agent; The auxiliary agent is a leveling agent. The reactive silicone oligomer is a hydroxyl-terminated polydimethylsiloxane or an amino-terminated polydimethylsiloxane. The modified polyethylene wax micro powder is an oxidized polyethylene wax or a maleic anhydride grafted polyethylene wax, and has an average particle size of 5-8μm.

2. An oil repellent polyurethane paint according to claim 1, characterized in that: The number average molecular weight of the reactive silicone oligomer is 1000-3000.

3. An oil repellent polyurethane paint according to claim 1, characterized in that: The acid value of the modified polyethylene wax micro powder is 8-25mgKOH / g.

4. An oil repellent polyurethane paint according to claim 1, characterized in that: The polyurethane resin is an aliphatic isocyanate type polyurethane resin, and the aliphatic isocyanate is isophorone diisocyanate or hydrogenated toluene diisocyanate.

5. An oil repellent polyurethane paint according to claim 1, characterized in that: The solvent is a mixture of n-butyl acetate, propylene glycol methyl ether acetate and xylene, wherein n-butyl acetate accounts for 40-60% of the total mass of the solvent, propylene glycol methyl ether acetate accounts for 20-40%, and xylene accounts for 10-30%.

6. A process for the preparation of the oil repellent polyurethane paint according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1. Mix the modified polyethylene wax micro powder with 15-25wt% of solvent and 10-20wt% of polyurethane resin, heat to 65-80°C and keep stirring for 15-25 minutes, cool to below 40°C to obtain a wax slurry; S2. Mix the remaining polyurethane resin and the reactive silicone oligomer at 25-35°C, and stir for 30-50 minutes; S3. Add the wax slurry to the mixture of step S2, and then add the remaining solvent and auxiliary agent, and stir uniformly; S4. Disperse the mixture with a high-speed dispersion machine at 2200-2800rpm for 25-35 minutes until the fineness is ≤25μm.

7. The method of preparing an oil repellent polyurethane paint according to claim 6, characterized in that, The stirring rate during the heating in step S1 is 1200-1800rpm.

8. The method of preparing an oil repellent polyurethane paint according to claim 6, characterized in that, The stirring rate during the mixing of the reactive silicone oligomer and the polyurethane resin in step S2 is 400-550rpm.

9. The method of preparing an oil repellent polyurethane paint according to claim 6, characterized in that, The rotation speed during the dispersion treatment in step S4 is 2200-2800rpm.

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