Waterborne polyurethane finish paint resistant to high-pressure water flushing as well as preparation method and application of waterborne polyurethane finish paint

Abstract

The invention discloses waterborne polyurethane finish paint resistant to high-pressure water flushing as well as a preparation method and application of the waterborne polyurethane finish paint. The finish paint is double-component finish paint and comprises a cross-linkable part and a curing part; wherein the cross-linkable part is prepared from the following raw materials in parts by weight: 40 to 70 parts of hydroxy acrylic acid secondary dispersion, 5 to 8 parts of waterborne polyurethane dispersion, 10 to 20 parts of pigment and filler and 3 to 10 parts of deionized water. According to the scheme, the problems of poor high-pressure water flushing resistance (especially 30MPa or above) and the like of the waterborne polyurethane finish paint are well solved.

Description

Technical Field

[0001] The present invention relates to the field of general industrial coatings. More specifically, it relates to a waterborne polyurethane topcoat resistant to high-pressure water flushing, its preparation method and application. Background Art

[0002] With the development of the economy and the improvement of people's living standards, environmental protection has received increasing attention. In the field of general industrial coatings, waterborne industrial paints use water instead of organic solvents as the dispersion medium, which can well reduce the emissions of toxic and harmful substances such as VOCs and heavy metals. Therefore, they are recognized worldwide as the most environmentally friendly coatings at present. Although waterborne industrial paints have been widely used internationally. In recent years, with the rapid development of China's economic level and science and technology, especially with the requirements of national environmental protection policies and the enhancement of people's environmental awareness, waterborne industrial paints will have a broader development space.

[0003] In recent years, the demand for waterborne industrial paints in the construction machinery field has been increasing, and the requirements for waterborne industrial paints in terms of manufacturing cost, performance, and constructability are expected to reach the level of traditional solvent-based coatings. For example, in actual situations, some construction machinery or heavy machinery and equipment need to have good resistance to high-pressure water flushing (such as above 15 MPa, above 20 MPa, above 25 MPa, or even above 30 MPa) due to their application environment or the reasons of their own structure. However, if high-temperature powder coatings are used to coat the surface of construction machinery or heavy machinery and equipment, it is difficult to adjust the color of the powder coatings, and the appearance of the paint film is difficult to meet the requirements; when conventional waterborne coatings are used to coat the surface of these construction machinery or heavy machinery and equipment, the coatings obtained are prone to problems such as damage and instantaneous peeling of the waterborne paint film when facing such high-pressure water flushing (especially above 30 MPa). Summary of the Invention

[0004] Based on the above facts, the purpose of the present invention is to provide a waterborne polyurethane topcoat resistant to high-pressure water flushing, its preparation method and application, so as to overcome the problems such as poor high-pressure water flushing resistance (especially above 30 MPa) of waterborne polyurethane topcoats for construction machinery or heavy machinery and equipment.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a waterborne polyurethane topcoat resistant to high-pressure water flushing. The topcoat is a two-component topcoat, comprising a crosslinkable part and a curing part; wherein:

[0007] In the crosslinkable part, the raw materials comprise the following components in parts by weight:

[0008] 40 - 70 parts of hydroxyl acrylic secondary dispersion, 5 - 8 parts of aqueous polyurethane dispersion, 10 - 20 parts of pigment filler, and 3 - 10 parts of deionized water.

[0009] Further, the hydroxyl content (based on solid content) of the hydroxyl acrylic secondary dispersion is 3.3 - 4.2%, the pH value is 7.5 - 8.5, the solid content is 43 - 46%, and the average particle size is 0.8 - 1.0 μm.

[0010] Further, the hydroxyl content (based on solid content) of the aqueous polyurethane dispersion is 1 - 5%, preferably 3.14%, the pH value is 7.5 - 8.5, the solid content is 39 - 41%, the average particle size is below 1.0 μm, preferably 0.8 - 1.0 μm.

[0011] Further, in the crosslinkable part, 1 - 6 parts of auxiliary agent are further included.

[0012] Further, the auxiliary agent contains 0.1 - 0.5 part of fumed aluminum oxide and / or 0.1 - 1 part of slip agent.

[0013] Further, 3 - 5 parts of cosolvent are further included in the raw materials of the crosslinkable part.

[0014] Further, the cosolvent is selected from one or more of propylene glycol monobutyl ether, ethylene glycol monobutyl ether, S - 100, and S - 150.

[0015] Further, in the curing part, the raw materials contain the following components in parts by weight:

[0016] 50 - 80 parts of aqueous HDI curing agent and 20 - 50 parts of solvent.

[0017] Further, the aqueous HDI curing agent is an organosilicon - modified HDI curing agent.

[0018] Further, 1 - 5 parts of silane coupling agent are further contained in the raw materials of the curing part.

[0019] Further, the silane coupling agent is selected from KH560.

[0020] On the other hand, the present invention provides a preparation method of the aqueous polyurethane topcoat as described above, and the preparation method includes the step of preparing the crosslinkable part:

[0021] Mix the raw materials of the crosslinkable part including part of deionized water, part of hydroxyl acrylic secondary dispersion, and pigment filler;

[0022] Add another part of deionized water under stirring, mix well and grind to obtain a slurry with a fineness ≤ 10 μm;

[0023] Under stirring conditions, add the crosslinkable partial raw materials including the remaining hydroxyl acrylic secondary dispersion and aqueous polyurethane dispersion to the slurry, and adjust the viscosity with the materials including the remaining deionized water to obtain the crosslinkable part.

[0024] In another aspect, the present invention provides the application of the aqueous polyurethane topcoat as described above in the coating of high-pressure water flushing-resistant equipment.

[0025] Further, the high-pressure water flushing-resistant equipment is engineering machinery equipment or heavy machinery equipment.

[0026] Further, the engineering machinery equipment is an aerial work vehicle.

[0027] The beneficial effects of the present invention are as follows:

[0028] In the aqueous polyurethane topcoat with high-pressure water flushing resistance (preferably above 30 MPa) provided by the present invention, the combination of the hydroxyl acrylic secondary dispersion and the aqueous polyurethane dispersion, and the addition of preferably gaseous aluminum trioxide and / or slip additives endow the topcoat with excellent appearance, weather resistance, high-pressure water flushing resistance and other properties, effectively preventing phenomena such as film damage when the engineering machinery equipment or heavy machinery equipment is under high-pressure water flushing. Compared with high-temperature powder coatings, this aqueous polyurethane topcoat overcomes the problem of difficult color matching of powder coatings, and the film has a more excellent appearance DOI. At the same time, it also overcomes the problems of high baking energy consumption and low production efficiency of high-temperature powder coatings. Specific Embodiments

[0029] To illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the specific content described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0030] Due to the requirements of the application environment or the reasons of its own structure, engineering machinery equipment or heavy machinery equipment that needs to have good high-pressure water flushing resistance (such as above 15 MPa, above 20 MPa, above 25 MPa, or even above 30 MPa) is prone to surface damage and instantaneous peeling of the aqueous paint film when facing high-pressure water flushing (especially above 30 MPa). Specifically, for example: in the coating of aerial work vehicles, since some aerial work vehicles can be dozens of meters long, the water pressure of ordinary car washers is at most 10 MPa, which simply cannot reach this height, and thus a higher flushing water pressure is required, such as 30 MPa high-pressure water flushing. However, when holding at a distance of 5 - 15 cm (especially 10 cm) and an angle of 45 - 60° (especially 60°), when the ordinary aqueous paint film faces 30 MPa high-pressure water flushing, the surface paint film will be damaged or the coating will instantaneously peel off.

[0031] To at least solve the above-mentioned problems, a specific embodiment of the present invention provides a waterborne polyurethane topcoat resistant to high-pressure water flushing. The topcoat is a two-component topcoat, comprising a crosslinkable part and a curing part; wherein:

[0032] In the crosslinkable part, the raw materials contain the following components in parts by weight:

[0033] 40-70 parts of hydroxyl acrylic secondary dispersion, 5-8 parts of waterborne polyurethane dispersion (PUD), 10-20 parts of pigment and filler, and 3-10 parts of deionized water.

[0034] After applying this waterborne polyurethane topcoat on mechanical equipment, the formed coating film has a stable structure, a smooth and flat appearance, good gloss (especially 60° gloss), adhesion, hardness, weather resistance, chemical resistance, impact resistance, and high-pressure water resistance. In particular, it can withstand high-pressure water flushing of 30 MPa. When flushing with water for 20 seconds at a distance of 10 cm from the equipment at a 60° angle, the paint film is not damaged, which well solves the problems existing in the prior art and thus meets industrial needs.

[0035] In this embodiment, "resistant to high-pressure water flushing" means at least resistant to water flushing with a water pressure of more than 15 MPa, preferably more than 20 MPa, more preferably more than 25 MPa, and most preferably more than 30 MPa.

[0036] When performing high-pressure water flushing, especially at a short distance and small angle (distance 5-15 cm, 45-60°), the high water pressure hitting the paint film is like a water jet hitting the paint film, and ordinary paint films will be instantly damaged. Only when the crosslinking density of the topcoat reaches a certain level can it better resist such high-pressure water flushing. In some examples, the hydroxyl content (based on the solid content) of the hydroxyl acrylic secondary dispersion is 3.3-4.2%, the pH value is 7.5-8.5, the solid content is 43-46%, and the average particle size is 0.8-1.0 μm. At this time, the drying property and appearance gloss of the obtained topcoat meet the requirements, the hardness and toughness of the obtained composite coating are good, and the high-pressure water resistance can be improved to a certain extent. Exemplary hydroxyl contents of the hydroxyl acrylic secondary dispersion are 3.5-4.2%, 3.5-4%, 3.3-3.8%, 3.3-3.9%, 3.8-4.2%, 3.9-4.2%, 3.8%, 3.9%, etc. based on the solid content. Exemplary hydroxyl acrylic secondary dispersions include but are not limited to those selected from Wanhua's 2032, 2042, 3AH0519W of Guangdong Tongde, and so on.

[0037] The content of the exemplary hydroxyl acrylic secondary dispersion includes, but is not limited to, 50 - 70 parts, 50 - 65 parts, 50 - 60 parts, 50 - 58 parts, 50 - 57 parts, 57 - 70 parts, 57 - 65 parts, 57 - 60 parts, 57 - 70 parts, 57 - 58 parts, 58 - 70 parts, 58 - 65 parts, 65 - 70 parts, 50 parts, 57 parts, 58 parts, 65 parts, 70 parts, etc.

[0038] In this embodiment, for the aqueous polyurethane dispersion, the hydroxyl content (based on the solid content) of the aqueous polyurethane dispersion is 1 - 5%, preferably 3.14%, the pH value is 7.5 - 8.5, the solid content is 39 - 41%, and the average particle size is below 1.0 μm, preferably 0.8 - 1.0 μm. Its dosage includes, but is not limited to, 6 - 8 parts, 8 parts, etc.

[0039] The hydroxyl acrylic secondary dispersion is semi - transparent. Generally, the resin particles are relatively small, and its film - forming property is better than that of the primary dispersion. Its paint film leveling, gloss, and fullness are all superior to those of the primary dispersion. The aqueous polyurethane dispersion refers to a material formed by dispersing polyurethane resin in water, which has excellent heat resistance, chemical resistance, water resistance, and weather resistance. At the same time, it also has the same toughness and durability as solvent - based polyurethane. In this embodiment, by using the hydroxyl acrylic secondary dispersion with good hardness performance as the main resin and compounding it with PUD in proportion, the excellent properties of both are combined, the defects of each other are overcome, and the cost is reduced simultaneously, so as to prepare an aqueous industrial coating with good high - pressure water - flushing resistance, excellent hardness, and good flexibility performance and good use value. In this embodiment, the small addition of PUD ensures sufficient toughness of the coating, and well overcomes the problem that when the total film thickness of the matching of the aqueous epoxy primer and the aqueous polyurethane topcoat reaches more than 90 microns, it is easy to have insufficient toughness and brittle cracking directly when flushing with water.

[0040] In some examples, in the cross - linkable part, additives are further included. The addition amount of the additives can be 1 - 6 parts.

[0041] If the paint film is too hard, it can resist external scratches and damages; if the paint film is too soft and there is not enough toughness to support it, when the water pressure hits, it cannot immediately recover its deformation, and the paint film will be directly damaged or leave many pits. In some preferred examples, the additives include 0.1 - 0.5 parts of fumed aluminum trioxide and / or 0.1 - 1 part of slip additive. Among them, the addition of fumed aluminum trioxide can well improve the hardness and high - pressure water - flushing resistance of the paint film. Exemplary contents of fumed aluminum trioxide are 0.2 - 0.5 parts, 0.5 parts, etc. The use of the slip additive can better reduce the impact of high - pressure water flushing and improve the high - pressure water - flushing resistance. Exemplary slip additives are 0.5 - 5 parts, 0.5 - 1 part, 0.5 parts, etc.

[0042] The slip aid is preferably of the silicone type, which helps with leveling and provides good slip properties, such as BYK-333, Shenzhu SN-4970, etc.

[0043] According to actual needs, the additive may optionally contain one or several of a dispersant, an antifoaming agent, a substrate wetting agent, a rheology aid, a flash rust inhibitor, a pH regulator, etc.

[0044] Exemplary dispersants include but are not limited to the BYK-DISPERSANT-2015 dispersant, etc. The addition amount of the dispersant can be 1-2 parts.

[0045] Exemplary antifoaming agents include but are not limited to the SURFYNOL 104PG-50 acetylenic diol surfactant, the BYKETOL-WA antifoaming agent, etc. The addition amount of the antifoaming agent can be 1-3 parts, 1-2 parts, etc.

[0046] Exemplary substrate wetting agents include but are not limited to the TEGO Twin 4100 leveling agent, etc. The addition amount of the substrate wetting agent can be 0.2-0.8 parts.

[0047] Exemplary rheology aids include but are not limited to the rheology aid ACRYSOL RM-12W, etc. The addition amount of the rheology aid can be 0.2-1.0 parts.

[0048] Exemplary flash rust inhibitors include but are not limited to ASCOTRAN-H10, etc. The addition amount of the flash rust inhibitor can be 0.1-0.5 parts, etc.

[0049] Exemplary pH regulators include but are not limited to DMEA, etc. Its addition amount can be 0.5-2 parts, 0.8-1.5 parts, etc.

[0050] In this embodiment, the pigment in the pigment and filler is an organic or inorganic pigment that can be used in industrial coatings, and different pigments are selected according to different colors; the filler includes but is not limited to precipitated barium sulfate that does not cause matting.

[0051] In this embodiment, the raw materials of the crosslinkable part further contain a cosolvent. The cosolvent balances the water and oil phases in the two-component waterborne polyurethane system and plays a crucial role in aspects such as the storage stability and appearance gloss of the system. The addition amount of the cosolvent can be 3-5 parts. Preferably, the cosolvent includes but is not limited to one or several selected from propylene glycol butyl ether, ethylene glycol butyl ether, S-100, and S-150.

[0052] In the curing part, it mainly consists of a curing agent. In some technical solutions, in the curing part, the raw materials contain the following components in parts by weight:

[0053] 50-80 parts of a waterborne HDI curing agent and 20-50 parts of a solvent.

[0054] Preferably, the aqueous HDI curing agent is a silicone-modified HDI curing agent. Compared with conventional isocyanate curing agents, the silicone-modified HDI curing agent has better resin compatibility, can greatly reduce surface defects caused by poor compatibility on the film surface, and at the same time provides excellent water resistance. In addition, curing with this aqueous HDI curing agent makes the crosslinking density of the film larger, and the obtained coating has better hardness and toughness. Specific methods for modifying HDI curing agent with silicone include but are not limited to incorporating silicone into hexamethylene diisocyanate during the synthesis stage, which is a conventional method in this field and will not be elaborated here.

[0055] Exemplary aqueous HDI curing agents include but are not limited to, for example, Wanhua 269A, Wannate HT-100.

[0056] In the raw materials of the curing part, a silane coupling agent and / or a dehydrating agent can also be added according to actual needs.

[0057] The addition of the silane coupling agent can better ensure the adhesion between the topcoat and the primer. Preferably, the silane coupling agent includes but is not limited to being selected from KH560, Shin-Etsu KBM-403, etc. The addition amount of the silane coupling agent includes but is not limited to 0 - 5 parts, 0 part, 1 - 5 parts, etc.

[0058] The function of the dehydrating agent (i.e., water repellent) includes eliminating moisture in the curing agent system. The addition amount of the dehydrating agent Additive OF includes but is not limited to 0 - 2 parts, 1 - 2 parts, etc.

[0059] The function of the above solvent includes diluting the curing agent, which helps to mix evenly better during the paint mixing stage, and can be, for example, DBE, etc. Preferably, the solvent addition amount is 20 - 40 parts, etc.

[0060] In some examples, in the crosslinkable part, the total mass fraction of the raw materials is 100 parts.

[0061] In some examples, in the curing part, the total mass fraction of the raw materials is 100 parts.

[0062] In the aqueous polyurethane topcoat of this embodiment, the mass ratio of the crosslinkable part to the curing part is preferably (3 - 10):1, more preferably 3:1. By selecting an appropriate NCO:OH ratio, the crosslinking density is maximized.

[0063] According to another specific embodiment of the present invention, there is provided a method for preparing the aqueous polyurethane topcoat as described above, including the step of preparing the crosslinkable part:

[0064] Mix the raw materials of the crosslinkable part including part of deionized water, part of hydroxy acrylic secondary dispersion, and pigments and fillers evenly;

[0065] Add another portion of deionized water under stirring, mix well and grind until a slurry with a fineness ≤ 10 μm is obtained;

[0066] Under stirring, add the crosslinkable partial raw materials including the remaining hydroxyl acrylic secondary dispersion and aqueous polyurethane dispersion to the slurry, and adjust the viscosity with the materials including the remaining deionized water to obtain the crosslinkable portion.

[0067] In some specific examples, the preparation of the crosslinkable portion specifically includes the following steps:

[0068] Mix a portion of deionized water, a portion of hydroxyl acrylic secondary dispersion, a dispersant, a portion of co-solvent, an antifoaming agent, fumed aluminum oxide, a slip aid, a pigment filler, and a portion of pH regulator, and stir (preferably at a stirring rate of 600 - 800 rpm) for 10 - 20 minutes;

[0069] Add a portion of deionized water while stirring, continue stirring (preferably stir for 20 minutes at a stirring rate of 600 - 800 rpm), mix well to obtain a pre-mixed first slurry;

[0070] Grind the pre-mixed first slurry with a sand mill (preferably with a controlled temperature below 40°C) and screen it to obtain a second slurry with a fineness ≤ 10 μm;

[0071] Under stirring, add the remaining hydroxyl acrylic secondary dispersion, PUD, a leveling agent, an anti-flash rust agent, and the remaining portion of co-solvent, mix well, then adjust the viscosity with the remaining deionized water and a rheology aid, and adjust the pH with the remaining pH regulator, mix well to obtain the crosslinkable portion.

[0072] In some other examples, the preparation of the curing portion includes the following steps:

[0073] Mix the components in the curing portion raw materials to obtain the curing portion.

[0074] In some more specific examples, the preparation of the curing portion includes the following steps:

[0075] Add the aqueous HDI curing agent, coupling agent, solvent, and dehydrating agent in the curing portion raw materials to the container in sequence, mix well to obtain the curing portion.

[0076] In the above preparation method, the hydroxyl acrylic secondary dispersion is preferably added in two steps. Among them, adding a small amount of hydroxyl acrylic secondary dispersion in the pre-mixing stage is beneficial for grinding to the specified fineness.

[0077] In this embodiment, it preferably further includes the preparation of the curing portion, and the specific preparation method includes: mixing the components in the curing portion raw materials.

[0078] According to another specific embodiment of the present invention, there is provided an application of the waterborne polyurethane topcoat as described above in the coating of high-pressure water flushing resistant equipment.

[0079] Exemplarily, the high-pressure water flushing resistant equipment is construction machinery equipment or heavy machinery equipment.

[0080] Exemplarily, the construction machinery equipment is an aerial work platform.

[0081] In some examples, the waterborne polyurethane topcoat is used in combination with a waterborne epoxy primer. Among them, the waterborne epoxy primer can be a waterborne epoxy primer commonly used in the art.

[0082] In some specific examples, in the application of coating the aerial work platform with the waterborne polyurethane topcoat, it is preferably used in combination with a waterborne epoxy primer. When the aerial work platform coated with this waterborne polyurethane topcoat is flushed with high-pressure water at 30 MPa, when the water flushing distance is 10 cm and the angle is 60°, the paint film is not damaged.

[0083] The technical solution of the present invention will be described below in conjunction with some specific embodiments:

[0084] Examples 1-4

[0085] The high-pressure water flushing resistant polyurethane topcoat of this example comprises a crosslinkable part A and a curing part B. Among them, the raw material composition of the crosslinkable part A is shown in Table 1, and the raw material composition of the curing part B is shown in Table 2.

[0086] Table 1 Component A

[0087]

[0088] Table 2 Component B

[0089]

[0090]

[0091] Table 3 Resins corresponding to raw material No. 1 and No. 12 in Component A

[0092]

[0093] The preparation steps of the above waterborne polyurethane topcoat are as follows:

[0094] (1) According to the formula of Component A in Table 1, in a large vat, under the condition of medium-speed stirring, put materials 1-10 in sequence, stir for 10-20 minutes under the stirring condition of 600-800 rpm, add material 11 along the container wall while stirring, and continue to stir for 20 minutes to obtain a preliminarily mixed first slurry;

[0095] (2) Start grinding and dispersing the first slurry on a sand mill. The slurry passes through a sieve to obtain a second slurry with a fineness ≤ 10 μm.

[0096] (3) While stirring, add materials 12 - 15 to the second slurry, continue stirring for 20 minutes until uniform, adjust the viscosity with materials 16 and 17, and adjust the pH value with material 18. Continue stirring for 20 minutes until uniform to obtain Component A.

[0097] (4) According to the formulation of Component B in Table 2, in a large vat, add materials 1 - 4 in sequence under the condition of medium - speed stirring, and continue stirring for 20 minutes under the stirring condition of 600 - 800 rpm to obtain Component B.

[0098] (5) Mix Component A and Component B in the mass ratio as shown in Table 3. Among them, in Table 3, the NCO:OH ratio in the formulation of each example is 1.3 to obtain the water - borne polyurethane topcoats of Examples 1 - 4.

[0099] Test Example

[0100] Obtain the main technical indicators of the above - mentioned topcoat paint according to the conventional detection methods in the art. The specific detection methods and results are shown in Table 4 below. In Table 4, Topcoat 1 - Topcoat 4 are the topcoats of Examples 1 - 4 respectively.

[0101] Table 4 Performance Detection and Results

[0102]

[0103] It can be determined from the above results in Table 4 that the NCO / OH ratio of Component A and Component B in Examples 1 - 4 is the same, but the selection of the hydroxyl - acrylic secondary dispersion resin in Component A is different. Specifically, the hydroxyl ratios of the hydroxyl - acrylic secondary dispersion are 2.0%, 3.3%, 3.9%, and 4.2% respectively. The drying property and appearance gloss of the prepared water - borne polyurethane topcoats meet the requirements, and there is no obvious difference in the hardness and flexibility of the composite coatings. However, in the test of high - pressure water flushing resistance, the medium - high hydroxyl hydroxyl - acrylic secondary dispersion resin is significantly better than the low - hydroxyl hydroxyl - acrylic secondary dispersion resin, but neither can pass the 30 MPa high - pressure water flushing test.

[0104] Examples 5 - 8

[0105] The polyurethane topcoat with high - pressure water flushing resistance in this example contains a cross - linkable part A and Component B. Among them, the raw material composition of the cross - linkable part A is shown in Table 5 (where the topcoats of Examples 5 - 8 are Topcoat 5 - Topcoat 8 in Table 5 respectively), and the raw material composition of the curing part B is shown in Table 6.

[0106] Table 5 Component A

[0107]

[0108] Table 6 Component B

[0109] Raw material number Raw material Dosage (wt%) 1 Wannate HT-100 60 2 KH560 5 3 DBE solvent 33.5 4 Water repellent Additive OF 1.5 Total 100

[0110] The preparation steps of the above-mentioned waterborne polyurethane topcoat are as follows:

[0111] (1) According to the formulation of Component A in Table 5, in a large vat, under the condition of medium-speed stirring, materials 1-10 are sequentially added. Under the stirring condition of 600-800 rpm, it is stirred for 10-20 minutes. While stirring, material 11 is added along the container wall, and stirring is continued for 20 minutes to obtain a pre-mixed first slurry;

[0112] (2) Start grinding and dispersing the first slurry on a sand mill. The slurry passes through a sieve to obtain a second slurry with a fineness ≤ 10 μm;

[0113] (3) While stirring, add materials 12-15 to the second slurry, continue stirring for 20 minutes until uniform. Adjust the viscosity with materials 16 and 17, and adjust the pH value with material 18. Continue stirring for 20 minutes until uniform to obtain Component A.

[0114] (4) According to the formulation of Component B in Table 6, in a large vat, under the condition of medium-speed stirring, materials 1-4 are sequentially added. Under the stirring condition of 600-800 rpm, continue stirring for 20 minutes to obtain Component B;

[0115] (5) Mix Component A and Component B in Table 5 and Table 6 in a certain mass ratio. Specifically, the mass ratio of Component A to Component B in topcoat 5 is 5:1, in topcoat 6 is 4:1, in topcoat 7 is 3.5:1, and in topcoat 8 is 3:1 to obtain the waterborne polyurethane topcoats in Examples 5-8.

[0116] Test Example

[0117] The above-mentioned topcoat paint is obtained with various main technical indicators according to the conventional detection means in the art. The specific detection methods and detection results are shown in Table 7 below.

[0118] Table 7 Performance Detection and Results

[0119]

[0120] From the above results in Table 7, it can be determined that in Examples 5-8 (NCO:OH = 1.3), the raw materials of Component A and Component B are the same, and the secondary hydroxyl acrylate dispersion is 3AH0519W (hydroxyl value is 3.9%). The difference is that the contents of the secondary hydroxyl acrylate dispersion are 50 parts, 58 parts, 65 parts, and 70 parts respectively. The drying property and appearance gloss of the prepared waterborne polyurethane topcoat meet the requirements. As the resin content in the formed composite coating increases, the hardness tends to decrease, and the toughness increases but not significantly. The high-pressure water flushing resistance performance gets better as the resin content of the secondary hydroxyl acrylate dispersion increases, but none of them passed the 30 MPa high-pressure water flushing test.

[0121] Examples 9-12

[0122] The polyurethane topcoat with high-pressure water flushing resistance in this example comprises a crosslinkable part A and a component B. Among them, the raw material composition of the crosslinkable part A is shown in Table 8 (wherein, the topcoats of Examples 9-12 are respectively topcoat 9-topcoat 12 in Table 8); the raw material composition of the curing part B is shown in Table 9.

[0123] Table 8 Component A

[0124]

[0125] Table 9 Component B

[0126] Raw material number Raw material Dosage of each component (wt%) 1 Wannate HT-100 60 2 KH560 5 3 DBE solvent 33.5 4 Water repellent Additive OF 1.5 Total 100

[0127] The preparation steps of the above waterborne polyurethane topcoat are as follows:

[0128] (1) According to the formula of Component A in Table 8, in a large vat, under the condition of medium-speed stirring, add materials 1-10 in sequence, stir for 10-20 minutes under the stirring condition of 600-800 rpm, and while stirring, add the remaining deionized water of material 11 along the container wall, and continue to stir for 20 minutes to obtain a pre-mixed first slurry;

[0129] (2) Start grinding and dispersing the first slurry on a sand mill, and pass the slurry through a sieve to obtain a second slurry with a fineness ≤ 10 μm;

[0130] (3) While stirring, add materials 12-16 to the second slurry, continue to stir for 20 minutes until uniform, adjust the viscosity with materials 17 and 18, and adjust the PH value with material 19, and continue to stir for 20 minutes until uniform to obtain Component A;

[0131] (4) According to the formula of Component B in Table 9, in a large vat, under the condition of medium-speed stirring, add materials 1-4 in sequence, and continue to stir for 20 minutes under the stirring condition of 600-800 rpm to obtain Component B;

[0132] (5) Mix component A and component B in Table 8 and Table 9 in a certain mass ratio. Specifically, the mass ratio of component A to component B in topcoat 9 is 3.5:1, in topcoat 10 is 4:1, in topcoat 11 is 4:1, and in topcoat 12 is 4:1, to obtain the waterborne polyurethane topcoats in Examples 9 - 12.

[0133] Test example

[0134] Obtain the main technical indicators of the above topcoat paints by conventional detection means in the art. The specific detection methods and results are shown in Table 10 below.

[0135] Table 10 Performance detection and results

[0136]

[0137] It can be determined from the above results in Table 10 that in Examples 9 - 12 (NCO:OH = 1.3), the same hydroxyl acrylate secondary dispersion resin 3AH0519W (hydroxyl value of 3.9%) is used, and different contents of waterborne polyurethane dispersions are matched. The contents of the waterborne polyurethane dispersions are 0 parts, 8 parts, 15 parts, and 25 parts respectively. The drying property and appearance gloss of the prepared waterborne polyurethane topcoats meet the requirements. As the content of the waterborne polyurethane dispersion increases in the composite coating formed by painting, the hardness decreases significantly, and the toughness increases significantly. However, the high-pressure water flushing resistance performance is the best when the content of the waterborne polyurethane dispersion is 8 wt%. If the content of the waterborne polyurethane dispersion is too low, the toughness of the obtained composite coating is insufficient; if the content of the waterborne polyurethane dispersion is too high, the hardness of the obtained composite coating decreases, but neither can pass the 30 MPa high-pressure water flushing test.

[0138] Examples 13 - 16

[0139] The polyurethane topcoat with high-pressure water flushing resistance in this example contains a crosslinkable part A and component B. Among them, the raw material composition of the crosslinkable part A is shown in Table 11 (where the topcoats in Examples 13 - 16 are topcoats 13 - topcoat 16 in Table 11 respectively); the raw material composition of the curing part B is shown in Table 12.

[0140] Table 11 Component A

[0141]

[0142] Table 12 Component B

[0143] Raw material number Raw material Dosage of each component (wt%) 1 Wannate HT-100 60 2 KH560 5 3 DBE solvent 33.5 4 Water repellent Additive OF 1.5 Total 100

[0144] The preparation steps of the above waterborne polyurethane topcoat are as follows:

[0145] (1) According to the formulation of Component A in Table 11, in a large vat, under the condition of medium-speed stirring, sequentially add Materials 1 - 12, stir for 10 - 20 minutes under the stirring condition of 600 - 800 rpm, and add Material 13 along the container wall while stirring, then continue to stir for 20 minutes to obtain a pre-mixed first slurry;

[0146] (2) Start grinding and dispersing the first slurry on a sand mill, and pass the slurry through a sieve to obtain a second slurry with a fineness ≤ 10 μm;

[0147] (3) While stirring, add Materials 14 - 18 to the second slurry, continue to stir for 20 minutes until homogeneous, adjust the viscosity with Materials 19 and 20, and adjust the pH value with Material 21, then continue to stir for 20 minutes until homogeneous to obtain Component A.

[0148] (4) According to the formulation of Component B in Table 12, in a large vat, under the condition of medium-speed stirring, sequentially add Materials 1 - 4, and continue to stir for 20 minutes under the stirring condition of 600 - 800 rpm to obtain Component B;

[0149] (5) Mix Component A and Component B in Table 11 and Table 12 in a certain mass ratio. The mass ratio of Component A to Component B in Topcoat 13 is 4:1, in Topcoat 14 is 4:1, in Topcoat 15 is 4:1, and in Topcoat 16 is 4:1, to obtain Waterborne Polyurethane Topcoats Examples 13 - 16.

[0150] Test Example

[0151] Obtain the main technical indicators of the above topcoat paints according to the conventional detection methods in the art. The specific detection methods and results are shown in Table 13 below.

[0152] Table 13 Performance Detection and Results

[0153]

[0154] From the above results in Table 13, it can be determined that in the formulations of Examples 13 - 16, the hydroxyl acrylic secondary dispersion in Component A is 3AH0519W (hydroxyl value is 3.9%), combined with 8 wt% of waterborne polyurethane dispersion, adding special additives gas-phase aluminum trioxide and slip additives, the drying property, appearance gloss, toughness, and hardness of the prepared waterborne polyurethane topcoat meet the requirements. With the addition of gas-phase aluminum trioxide and slip additives in Component A of the topcoat, the hardness of the formed composite coating increases, and the flexibility is not affected. For example, in Topcoat 16, when both gas-phase aluminum trioxide and slip additives are added to the formulation of Component A, the obtained composite layer can withstand high-pressure water flushing at 30 MPa.

[0155] Examples 17 - 18

[0156] The high-pressure water-resistant polyurethane topcoat of this embodiment comprises a crosslinkable part A and a component B. Among them, the raw material composition of the crosslinkable part A is shown in Table 14 (wherein, the topcoats of Examples 17-18 are respectively the topcoat 17 - topcoat 18 in Table 14); the raw material composition of the curing part B is shown in Table 15.

[0157] Table 14 Component A

[0158]

[0159]

[0160] Table 15 Component B

[0161] Raw material number Raw material Dosage of each component (wt%) 1 Curing agent 60 2 KH560 5 3 DBE solvent 33.5 4 Water repellent Additive OF 1.5 Total 100

[0162] The preparation steps of the above-mentioned waterborne polyurethane topcoat are as follows:

[0163] (1) According to the formula of Component A in Table 14, in a large vat, under the condition of medium-speed stirring, put materials 1 - 12 in sequence, stir for 10 - 20 minutes under the stirring condition of 600 - 800 rpm, and while stirring, add the remaining deionized water of material 13 along the container wall, and continue to stir for 20 minutes to obtain a pre-mixed first slurry;

[0164] (2) Start grinding and dispersing the first slurry on a sand mill, and pass the slurry through a sieve to obtain a second slurry with a fineness ≤ 10 μm;

[0165] (3) While stirring, add materials 14 - 18 to the second slurry, continue to stir for 20 minutes until uniform, adjust the viscosity with materials 19 and 20, and adjust the PH value with material 21, and continue to stir for 20 minutes until uniform to obtain Component A.

[0166] (4) According to the formula of Component B in Table 15, in a large vat, under the condition of medium-speed stirring, put materials 1 - 4 in sequence, and continue to stir for 20 minutes under the stirring condition of 600 - 800 rpm to obtain Component B;

[0167] (5) Match Component A and Component B in Tables 13 and 14. Among them, the B-component curing agent HDI of the topcoat 17 is the unmodified Wanhua HT - 100, and the mass ratio of Component A to Component B is 4:1; the B-component curing agent of the topcoat 18 is Wanhua 269A (organosilicon-modified hexamethylene diisocyanate curing agent, with better water resistance and weather resistance), and the mass ratio of Component A to Component B is 3.5:1 to obtain the waterborne polyurethane topcoats of Examples 17 - 18.

[0168] Test Example

[0169] The above topcoat paint is tested by conventional testing methods in the art to obtain the main technical indicators. The specific testing methods and results are shown in Table 16 below.

[0170] Table 16 Performance Testing and Results

[0171]

[0172] As can be seen from Table 16, in the technical solutions of Examples 17-18 (NCO:OH = 1.3), the obtained composite coatings meet the requirements in terms of appearance, gloss, drying property, salt spray, and weather resistance tests, and can all pass the 30 MPa high-pressure water flushing test. However, compared with the unmodified Wanhua HT-100 waterborne HDI curing agent used in Example 17, the waterborne HDI curing agent 269A in Example 18 gives a better high-pressure water flushing resistance effect for the obtained composite coating.

[0173] Obviously, the above examples of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A waterborne polyurethane topcoat resistant to high-pressure water flushing, characterized in that, The topcoat is a two-component topcoat, comprising a crosslinkable part and a curing part; wherein: In the crosslinkable part, the raw materials comprise the following components in parts by weight: 40-70 parts of hydroxyl acrylic secondary dispersion, 5-8 parts of aqueous polyurethane dispersion, 10-20 parts of pigment and filler, and 3-10 parts of deionized water.

2. The waterborne polyurethane topcoat according to claim 1, characterized in that, The hydroxyl content of the hydroxyl acrylic secondary dispersion is 3.3-4.2% based on the solid content, the pH value is 7.5-8.5, the solid content is 43-46%, and the average particle size is 0.8-1.0 μm; and / or The hydroxyl content of the aqueous polyurethane dispersion is 1-5% based on the solid content, the pH value is 7.5-8.5, the solid content is 39-41%, and the average particle size is below 1.0 μm, preferably 0.8-1.0 μm.

3. The waterborne polyurethane topcoat according to claim 1, characterized in that, In the crosslinkable part, 1-6 parts of additives are further comprised; The additives comprise 0.1-0.5 part of fumed aluminum trioxide and / or 0.1-1 part of slip additive.

4. The waterborne polyurethane topcoat according to claim 1, characterized in that, 3-5 parts of cosolvent are further comprised in the raw materials of the crosslinkable part; Preferably, the cosolvent is selected from one or more of propylene glycol butyl ether, ethylene glycol butyl ether, S-100 and S-150.

5. The waterborne polyurethane topcoat according to claim 1, characterized in that, In the curing part, the raw materials comprise the following components in parts by weight: 50-80 parts of aqueous HDI curing agent and 20-50 parts of solvent.

6. The waterborne polyurethane topcoat according to claim 5, wherein The aqueous HDI curing agent is an organosilicon-modified HDI curing agent.

7. The waterborne polyurethane topcoat according to claim 5, characterized in that, 1-5 parts of silane coupling agent are further contained in the raw materials of the curing part; Preferably, the silane coupling agent is selected from KH560.

8. The preparation method of the aqueous polyurethane topcoat according to any one of claims 1-7, characterized in that, It includes the step of preparing the crosslinkable part: Mix the raw materials of the crosslinkable part comprising part of deionized water, part of hydroxyl acrylic secondary dispersion, and pigment and filler; Add another part of deionized water under stirring, and grind after mixing until a slurry with a fineness ≤ 10 μm is obtained; Under stirring, add the raw materials of the crosslinkable part comprising the remaining hydroxyl acrylic secondary dispersion and aqueous polyurethane dispersion, and adjust the viscosity with the material comprising the remaining deionized water to obtain the crosslinkable part.

9. Application of the aqueous polyurethane topcoat according to any one of claims 1-7 in the coating of high-pressure water flushing equipment.

10. The application according to claim 9, wherein The high-pressure water flushing equipment is engineering mechanical equipment or heavy mechanical equipment; Preferably, the engineering mechanical equipment is an aerial work platform.

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