A high-density rigid polyurea coating and a method for preparing the same

Abstract

This application relates to a high-density rigid polyurea coating and its preparation method. The polyurea coating comprises component A and component B. The raw materials for component A include: 10-30 parts by weight of isocyanate-modified MDI, 5-20 parts by weight of polyether diol, 15-35 parts by weight of polymeric MDI, 30-45 parts by weight of barium sulfate, and 1-2 parts by weight of a first auxiliary agent. The raw materials for component B include: 30-50 parts by weight of polyether polyol, 10-20 parts by weight of an amino chain extender, 20-40 parts by weight of barium sulfate, 5-10 parts by weight of a dehydrating agent, 2-5 parts by weight of a color paste, 0.5-2 parts by weight of a second auxiliary agent, and 0.2-0.5 parts by weight of a catalyst. The addition of barium sulfate to both component A and component B of this polyurea coating successfully solves the problems of excessive filler and poor storage stability in component A (modified isocyanate component) of the polyurea coating, resulting in a polyurea coating with high density and excellent compactness, significantly improving the anti-corrosion performance of the coating.

Description

Technical Field

[0001] This application relates to the field of polyurea coating technology, and in particular to a high-density rigid polyurea coating and its preparation method. Background Technology

[0002] Polyurea is typically a two-component reactive molding process. Polyurea coatings have excellent corrosion resistance and anti-aging properties, especially in resistance to atmospheric corrosion, low acid and alkaline media, and inorganic salt solutions. They are also easy to apply on-site, have high adhesion, are not prone to cracking, and have strong impermeability. They are a new type of material in the field of corrosion protection, with the characteristics of long-lasting effect and wide applicability.

[0003] In the 1970s, 100% solid rigid polyurea anti-corrosion coating technology was successfully developed in North America. It has now become one of the most widely used anti-corrosion coating technologies in North America, representing the development direction of the coating industry in the 21st century. It has been successfully applied around the world for more than 30 years. Its spraying technology is advanced, the quality is stable, the coating cures quickly, the construction is convenient and fast, and the efficiency is extremely high. It can be widely used for anti-corrosion of various substrates such as steel, cast iron, and cement.

[0004] The prior art discloses a polyurea coating and its preparation method. The polyurea coating comprises component A and component B. Component A includes the following components by mass parts: 30-60 parts of polyisocyanate, 5-20 parts of acrylic-modified polyurethane emulsion, 5-20 parts of epoxy-modified acrylic resin, 10-15 parts of polycarbonate polyol, and 10-15 parts of polyether polyol. Component B includes the following components by mass parts: 20-35 parts of amino-terminated polyether, 20-30 parts of amino chain extender, 1-15 parts of modified nano-inorganic filler, 12-18 parts of organosilicon diamine, 10-15 parts of (meth)acrylate, 0.1-1 parts of leveling agent, and 0.1-1 parts of defoamer. This polyurea coating only adds a small amount of filler to component B, resulting in a low density and thin coating thickness. Therefore, the anti-corrosion performance of the coating needs further improvement, making it unsuitable for application in various heavy-duty industrial anti-corrosion fields. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a high-density rigid polyurea coating and its preparation method. Both components (component A and component B) of this polyurea coating contain barium sulfate filler, resulting in a polyurea coating with higher density and compactness, reaching a density of 1.5 kg / cm³. 3 This significantly improves the anti-corrosion performance of the coating, making it suitable for various industrial heavy-duty anti-corrosion applications.

[0006] Therefore, the first aspect of this application provides a high-density rigid polyurea coating, the polyurea coating comprising component A and component B;

[0007] Based on the weight parts of component A, the raw materials for preparing component A include: 10-30 parts by weight of isocyanate-modified MDI, 5-20 parts by weight of polyether diol, 15-35 parts by weight of polymeric MDI, 30-45 parts by weight of barium sulfate, and 1-2 parts by weight of the first auxiliary agent.

[0008] Based on the weight parts of component B, the raw materials for preparing component B include: 30-50 parts by weight of polyether polyol, 10-20 parts by weight of amino chain extender, 20-40 parts by weight of barium sulfate, 5-10 parts by weight of dehydrating agent, 2-5 parts by weight of color paste, 0.5-2 parts by weight of second auxiliary agent, and 0.2-0.5 parts by weight of catalyst.

[0009] In existing two-component polyurea coatings, only a small amount of filler is added to component B, resulting in a low density. Increasing the filler content in component B leads to excessively high viscosity, which is detrimental to coating preparation and subsequent application. Therefore, the polyurea coating provided in this application incorporates filler (barium sulfate) in both components A and B, along with a specific preparation process, resulting in a high-density, highly compact coating that significantly improves its corrosion resistance. This makes it suitable for various heavy-duty industrial corrosion protection applications, such as electrolytic and electroplating tanks, chemical storage tanks, desulfurization flues, and chemical wastewater treatment plants.

[0010] In this application, the isocyanate-modified MDI is MDI50, which is a mixture containing MDI2,4 isomers and MDI4,4' isomers, and is a colorless or pale yellow transparent liquid at room temperature. The MDI50 used in this application is a commercially available product purchased from Wanhua Chemical Group Co., Ltd. The polyether diol, also known as dihydroxy polyether or propylene glycol polyether, has an average molecular weight of 1000–4000, and is a colorless or pale yellow transparent oily liquid, preferably with an average molecular weight of 1000.

[0011] In this application, the polymeric MDI, also known as crude MDI, is a mixture containing a certain proportion (35%–65%) of pure MDI and polyphenylene polyisocyanate. The polymeric MDI used in this application is a commercially available product purchased from Wanhua Chemical Group Co., Ltd. In this application, the polymeric MDI in component A, besides serving as the main raw material for polyurea coatings, also importantly acts as a dehydrating agent for barium sulfate filler, thereby chemically removing moisture from the barium sulfate filler during the preparation of component A.

[0012] In this application, the barium sulfate is precipitated barium sulfate, a powdered product with a particle size of 300-350 mesh. Barium sulfate is an inert filler of strong acid and strong base salts, exhibiting excellent acid, alkali, light, and weather resistance, and good fluidity. Using it as a filler can impart better corrosion resistance to coatings. Simultaneously, the product is white, and when used with colored pigments, it can enhance their color depth and brightness, and impart higher hardness and wear resistance to the coating. Furthermore, this application controls the barium sulfate content within 30-45 parts by weight, resulting in better overall performance of the final polyurea coating. If the barium sulfate content is too low, the density of the resulting polyurea coating will be low, failing to improve the density of the polyurea coating. If the barium sulfate content is too high, the residual moisture in the barium sulfate is difficult to remove completely, and it can also lead to excessively high viscosity of the resulting component A, or even clumping and other storage stability problems, which are detrimental to subsequent mixing and crosslinking with component B, thereby reducing the performance of the polyurea coating, and in severe cases, rendering the resulting polyurea coating unusable.

[0013] In this application, the polyether polyol in component B is selected from one or more of polyethylene glycol ether, polypropylene glycol ether, polyglycerol ether, polypentaerythritol ether, and polytetrahydrofuran ether. In some preferred embodiments, the polyether polyol is polyglycerol ether and / or polypentaerythritol ether, with an average molecular weight of 300-5000. The amino chain extender is diethyltoluenediamine (E-100) or dimethylthiotoluenediamine (E-300), preferably E-100.

[0014] In some embodiments, the first adjuvant is a wetting and dispersing agent.

[0015] Because barium sulfate filler is added to component A, it is prone to precipitation and agglomeration. Adding a wetting and dispersing agent can improve the dispersibility of the prepared component A, preventing the precipitation and agglomeration of barium sulfate particles during storage, thus improving the storage stability of component A. In this application, the wetting and dispersing agent is a conventional dispersant in the art, such as an organosilicon dispersant, whose commercial brands may include BYK-163, BYK-161, BYK-110, and BYK-P104s, etc.

[0016] In some embodiments, the dehydrating agent is a molecular sieve, wherein the molecular sieve is selected from at least one of 3A molecular sieve and 4A molecular sieve, preferably 3A molecular sieve.

[0017] The molecular sieve described in this application has good water absorption capacity. By adding the molecular sieve to component B, the moisture in the barium sulfate filler can be removed by physical means.

[0018] In some embodiments, the second additive is a wetting and dispersing agent, and the catalyst is an organic bismuth catalyst.

[0019] In this application, the wetting and dispersing agent in the second additive also improves the dispersibility of the prepared component B, avoids the precipitation and agglomeration of barium sulfate particles, and provides better dispersion stability. The organic bismuth catalyst is an environmentally friendly catalyst that promotes gelation. It can catalyze the reaction between hydroxyl groups and isocyanates, avoid the occurrence of NCO side reactions, reduce CO2 generation, and make the resulting coating more dense and have stronger corrosion resistance.

[0020] In some embodiments, the polyurea coating is applied by mixing component A and component B in a volume ratio of (0.8–1.2):(0.8–1.2) before spraying.

[0021] In some specific embodiments, the polyurea coating is applied by mixing component A and component B at a volume ratio of 1:1 before spraying.

[0022] In this application, components A and B need to be preheated to 35-40°C before mixing. This is because both components A and B contain barium sulfate filler, resulting in relatively high viscosity. Preheating effectively reduces the viscosity of components A and B, making them easier to mix evenly.

[0023] A second aspect of this application provides a method for preparing a polyurea coating as described in the first aspect of this application, the method comprising the preparation of component A and component B; wherein the preparation of component A comprises the following steps:

[0024] S1, barium sulfate, polymeric MDI and the first additive are mixed and then pressed into a grout, and then placed in a sealed container and sealed with nitrogen to obtain barium sulfate grout;

[0025] S2, the polyether diol is vacuum-extracted into the reactor, then isocyanate-modified MDI is added for addition polymerization. After the reaction is completed, the barium sulfate slurry is added, and after heat preservation, component A is obtained.

[0026] The polyurea coating described in this application contains barium sulfate filler in component A. However, the moisture in the barium sulfate filler cannot be completely removed. This causes the isocyanate to react with residual moisture in the coating system during subsequent coating preparation, generating CO2 gas. Simultaneously, the polyurea coating cures too quickly, preventing the generated CO2 gas from escaping in time. This CO2 gas then forms pores within the coating, resulting in pinholes or bubbles on the surface. This reduces the coating's density and impermeability, thus lowering its anti-corrosion performance. Therefore, the method described in this application involves thoroughly and uniformly mixing barium sulfate, polymeric MDI, and the first additive before nitrogen purging and sealing for a certain period. This allows the residual moisture in the barium sulfate to fully react with a small portion of the polymeric MDI, and the moisture in the barium sulfate filler to fully react with NCO before component A preparation. Component A prepared using this method not only significantly increases the density of the final polyurea coating and exhibits good stability, but also provides excellent coating density and impermeability, thereby significantly improving the coating's anti-corrosion performance.

[0027] In some implementations, the sealing time in step S1 is 25 to 35 days.

[0028] In this application, step S1 is a dehydration step. Since the dehydration process is very slow, a relatively long storage time is required to effectively remove moisture from the barium sulfate packing. In some specific embodiments, the storage time can be, for example, 28 days (4 weeks).

[0029] In some embodiments, in step S2, the temperature of the addition polymerization reaction is 75–85°C, and the time is 2–3 hours; the holding time is 20–40 minutes.

[0030] Under the aforementioned conditions of addition polymerization, this application provides a more favorable environment for the reaction between polyether diol and isocyanate-modified MDI. Furthermore, after adding the barium sulfate slurry to the reactor, maintaining the temperature at 75–85°C for 20–40 minutes, preferably 30 minutes, serves two purposes: first, if there is still residual moisture in the barium sulfate slurry, the heat treatment allows the isocyanate to further consume this residual moisture, providing a safety margin; second, because the barium sulfate slurry is relatively thick and has high viscosity, stirring at a higher temperature for 20–40 minutes ensures thorough and uniform mixing of the barium sulfate slurry with the addition polymerization product, resulting in better uniformity of the prepared component A.

[0031] In some embodiments, the preparation of component B includes the following steps:

[0032] T1, barium sulfate, polyether polyol from the first part, dehydrating agent and second auxiliary agent are thoroughly mixed and then grouted, and then placed in a sealed container and sealed with nitrogen to obtain component B grout.

[0033] T2, the remaining polyether polyol and amino chain extender are added to the reactor, the temperature is raised to 50-60°C, then the color paste and catalyst are added, mixed, and then the B component slurry is added. After mixing again, the B component is obtained.

[0034] In this application, before preparing component B, the moisture in the barium sulfate filler is removed. Specifically, barium sulfate, a portion of the polyether polyol, the dehydrating agent, and the second additive are thoroughly and uniformly mixed and then sealed with nitrogen. This allows the dehydrating agent to effectively adsorb the residual moisture in the barium sulfate, thereby removing the free moisture from the barium sulfate.

[0035] In some embodiments, in step T1, the polyether polyol in the first portion accounts for 30-40 wt% of the total amount of polyether polyol. In this application, when dehydrating the filler in component B, a portion of liquid polyether polyol is added as a dehydration carrier, allowing the barium sulfate, dehydrating agent, and second additive to mix thoroughly to form a slurry, which further facilitates the adsorption and removal of residual moisture from the filler by the dehydrating agent.

[0036] In some embodiments, the storage time is 25 to 35 days. Similarly, since the adsorption and dehydration process is also a very slow process, a longer storage time is required to effectively adsorb and remove moisture from the barium sulfate packing. In some specific embodiments, the storage time can be, for example, 28 days.

[0037] The beneficial technical effects of this application are as follows: Barium sulfate filler is added to both component A and component B of the polyurea coating provided in this application, which makes the polyurea coating have a higher density; at the same time, with the specific preparation process, the density and impermeability of the coating are more excellent, thereby significantly improving the anti-corrosion performance of the coating. It can be well applied to various industrial heavy anti-corrosion fields, such as electrolytic and electroplating tanks, chemical storage tanks, desulfurization flues and chemical wastewater ponds, etc., with good application prospects. Detailed Implementation

[0038] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0039] The isocyanate-modified MDI and polymeric MDI used in the following examples were purchased from Wanhua Chemical Group Co., Ltd.; the average molecular weight of the polyether diol was 1000; the barium sulfate was powdered precipitated barium sulfate with an average particle size of 325 mesh; the polyether polyols were polypropylene triol ether and polypentaerythritol ether with average molecular weights of 700 and 300, respectively; the amino chain extender was diethyltoluene diamine (E-100); the commercial brand name of the wetting and dispersing agent was BYK-110; and the dehydrating agent was 3A molecular sieve.

[0040] Example 1: Preparation of polyurea coating

[0041] 1. Preparation of component A:

[0042] The raw materials for preparing component A are as follows: 20 parts by weight of isocyanate-modified MDI, 15 parts by weight of polyether diol, 25 parts by weight of polymeric MDI, 38 parts by weight of precipitated barium sulfate and 2 parts by weight of BYK-110.

[0043] The preparation process for component A is as follows:

[0044] (1) Mix precipitated barium sulfate, polymeric MDI and BYK-110 evenly in proportion, press with a three-roll press, measure and record the viscosity, and put into a sealed container and seal with nitrogen. After 4 weeks of storage, the viscosity is qualified, and barium sulfate slurry is obtained and kept for later use.

[0045] (2) The polyether diol was vacuum-extracted into the reactor containing component A, heated to 50°C, and isocyanate-modified MDI was added to carry out an addition polymerization reaction at 80°C for 2 hours. Then, barium sulfate slurry was added and kept at 0.5 hours. The temperature was then lowered to below 50°C to obtain component A. The component was then discharged, stored, and protected with nitrogen.

[0046] 2. Preparation of component B:

[0047] The raw materials for preparing component B are as follows: 39 parts by weight of polypropylene triol ether, 3 parts by weight of polypentaerythritol ether, 15 parts by weight of E-100, 32 parts by weight of barium sulfate, 6 parts by weight of dehydrating agent, 3 parts by weight of color paste, 1.5 parts by weight of BYK-110 and 0.5 parts by weight of organic bismuth catalyst.

[0048] The preparation process of component B is as follows:

[0049] (1) Precipitated barium sulfate, 30 wt% of polypropylene glycerol ether and polypentaerythritol ether, 3A molecular sieve and BYK-110 were mixed evenly in proportion, slurried by three roller pressing, the viscosity was measured and recorded, and the mixture was sealed in a nitrogen-filled container. After 4 weeks of storage, the viscosity was found to be qualified, and the B component slurry was obtained and kept for later use.

[0050] (2) Add the remaining polypropylene triol ether and polypentaerythritol ether, amino chain extender E-100 to the B component reactor in proportion, heat to 55°C, then add color paste and organic bismuth catalyst, mix for 0.5 hours, then add B component slurry, mix again for 0.5 hours to prepare B component, discharge, store and nitrogen protection.

[0051] Example 2: Preparation of polyurea coating

[0052] The preparation process is basically the same as in Example 1, except that the raw materials for component A are as follows: 20 parts by weight of isocyanate-modified MDI, 15 parts by weight of polyether diol, 25 parts by weight of polymeric MDI, 30 parts by weight of precipitated barium sulfate and 2 parts by weight of BYK-110.

[0053] The raw materials for component B are as follows: 39 parts by weight of polypropylene triol ether, 3 parts by weight of polypentaerythritol ether, 15 parts by weight of E-100, 25 parts by weight of barium sulfate, 5 parts by weight of dehydrating agent, 3 parts by weight of color paste, 1.5 parts by weight of BYK-110 and 0.5 parts by weight of organic bismuth catalyst.

[0054] Example 3: Preparation of polyurea coating

[0055] The preparation process is basically the same as in Example 1, except that the raw materials for component A are as follows: 20 parts by weight of isocyanate-modified MDI, 15 parts by weight of polyether diol, 25 parts by weight of polymeric MDI, 48 parts by weight of precipitated barium sulfate and 2 parts by weight of BYK-110.

[0056] The raw materials for component B are as follows: 39 parts by weight of polypropylene triol ether, 3 parts by weight of polypentaerythritol ether, 15 parts by weight of E-100, 40 parts by weight of barium sulfate, 8 parts by weight of dehydrating agent, 3 parts by weight of color paste, 1.5 parts by weight of BYK-110 and 0.5 parts by weight of organic bismuth catalyst.

[0057] Comparative Example 1: Preparation of Polyurea Coating

[0058] The preparation process is basically the same as in Example 1, except that the preparation process of component A is as follows:

[0059] The preparation process for component A is as follows:

[0060] Polyether diol was vacuum-evacuated into the reactor containing component A, and the temperature was raised to 50°C. Isocyanate-modified MDI was added to initiate an addition polymerization reaction at 80°C for 2 hours. Then, precipitated barium sulfate, polymeric MDI, and BYK-110 were added, and the mixture was kept at this temperature for 0.5 hours. The temperature was then lowered to below 50°C to obtain component A. The component was then discharged, stored, and protected with nitrogen.

[0061] The preparation process of component B is as follows:

[0062] Polypropylene triol ether, polypentaerythritol ether, and amino chain extender E-100 were added to the reaction vessel of component B in proportion. The temperature was raised to 55°C, and then color paste and organic bismuth catalyst were added. After mixing for 0.5 hours, precipitated barium sulfate, 3A molecular sieve and BYK-110 were added, and the mixture was mixed again for 0.5 hours to prepare component B. The material was discharged, stored and protected with nitrogen.

[0063] Comparative Example 2: Preparation of Polyurea Coating

[0064] 1. Preparation of component A:

[0065] The raw materials for preparing component A are as follows: 20 parts by weight of isocyanate-modified MDI, 15 parts by weight of polyether diol and 25 parts by weight of polymeric MDI.

[0066] The preparation process for component A is as follows:

[0067] (1) The polyether diol was vacuum-extracted into the reactor containing component A, heated to 50°C, and isocyanate-modified MDI was added to carry out an addition polymerization reaction at 80°C for 2 hours. Then, polymerized MDI was added and kept at 0.5 hours. The temperature was lowered to below 50°C to obtain component A. The component was then discharged, stored, and protected with nitrogen.

[0068] 2. Preparation of component B:

[0069] The raw materials for preparing component B are as follows: 39 parts by weight of polyglycerol ether, 3 parts by weight of polypentaerythritol ether, 15 parts by weight of E-100, 3 parts by weight of color paste and 0.5 parts by weight of organic bismuth catalyst. Polyglycerol ether, polypentaerythritol ether, and amino chain extender E-100 are added to the reaction vessel of component B in proportion, heated to 55°C, and then the color paste and organic bismuth catalyst are added. After mixing for 0.5 hours, the mixture is discharged, stored, and protected with nitrogen.

[0070] Test Example 1

[0071] The A and B component samples prepared in Examples 1-3 and Comparative Examples 1-2 were sealed and stored for a period of time (more than 2 weeks is recommended) before being sprayed onto the plates, and then the physical properties and corrosion resistance were tested.

[0072] Preheat components A and B of the polyurea coating to 40℃ and stir thoroughly. Using professional polyurea spraying equipment, set the material temperature to 60℃ and the pressure to 2000psi, and spray the coating onto a sample under high temperature and high pressure. The sample dimensions are 50cm x 50cm (length x width) with an average thickness of 1.5mm. After demolding, cure at room temperature for 7 days, and then perform physical performance testing (the physical performance testing methods are based on the national standard GB / T23446-2009 for sprayed polyurea).

[0073] The performance indicators of the prepared polyurea coating are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] As shown in Table 1, among all the examples and comparative examples, the polyurea coating prepared in Example 1 has the best overall performance. This indicates that the preferred content of barium sulfate in component A is 38 parts by weight, and the preferred content of barium sulfate in component B is 32 parts by weight. Furthermore, dehydration treatment of components A and B before preparation is essential. The polyurea coating prepared in Example 2 has similar physical properties to that of Example 1, except for a lower density. However, due to the lower amount of barium sulfate added, the overall material cost is higher. In Example 3, component A was found to be very viscous before spraying. Preheating to 40°C did not allow for normal spraying; further heating to 55°C was required for the spraying machine to function properly. The physical properties of the sample were also worse than those of Example 1, with a higher water absorption rate, indicating poorer density in Example 3. The reason for this is that the barium sulfate filler content was too high; even with a dehydration process, the moisture was not completely removed, leaving some residue. On the one hand, the cross-linking effect will make component A very viscous, and it must be preheated to a high temperature to mix evenly with component B; on the other hand, both components A and B have a small amount of residual moisture, which will cause some bubbles to be generated in the coating and reduce the density of the coating.

[0078] In Comparative Example 1, since barium sulfate was not dehydrated before the preparation of components A and B, but was added directly during the preparation, after components A and B were stored for a period of time, it was found that component A was very viscous and had a large amount of lumps before spraying. Even with heating to a very high temperature, the spraying machine could not work properly and the spraying process had to be abandoned.

[0079] Comparative Example 2 is a polyurea coating without added barium sulfate. The overall physical properties of the material preparation are not much different from those of Example 1, except that the density is too low and the material cost is high.

[0080] The test results of Examples 1-3 and Comparative Examples 1-2 in Table 1 show that in order to improve the physical properties of sprayed polyurea, a reasonable amount of additive is important, but the dehydration treatment of barium sulfate filler is an indispensable step.

[0081] Test Example 2: Corrosion Resistance Test of Polyurea Coating

[0082] The testing process is as follows:

[0083] Select a two-opening iron container and apply a 3mm thick coating. Allow it to cure for 7 days at room temperature.

[0084] In the two coated iron containers mentioned above, 20% sulfuric acid and 40% caustic soda solutions were added respectively. The containers were opened, covered with a transparent film, and placed outdoors to be exposed to sunlight. After 6 months, the condition of the coating and the corrosion of the iron containers were observed (the polyurea coating was damaged, and the iron containers were observed for rust spots and peeling). The anti-corrosion performance of the polyurea coatings prepared in Examples 1-3 and Comparative Examples 1-2 were tested according to the above test methods, and the test results are shown in Table 2.

[0085] Table 2

[0086]

[0087] Comparative Example 2 shows a polyurea coating prepared without barium sulfate. This coating exhibits certain anti-corrosion properties, but its anti-corrosion performance is inferior to that of Example 1. This is because barium sulfate, as a strong acid and strong base salt, is resistant to the corrosion of strong acids and bases. After dehydration, barium sulfate acts as a skeleton in the polyurea coating, while also reinforcing its anti-corrosion properties. Most importantly, it fills the pores in the anti-corrosion coating, extending the erosion path of the corrosive medium and playing a crucial role in improving its anti-corrosion performance.

[0088] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A high-density rigid polyurea coating, characterized in that, The polyurea coating comprises component A and component B, and both components A and B contain barium sulfate filler in their raw materials. Based on the weight parts of component A, the raw materials for preparing component A include: 10-30 parts by weight of isocyanate-modified MDI, 5-20 parts by weight of polyether diol, 15-35 parts by weight of polymeric MDI, 30-45 parts by weight of barium sulfate, and 1-2 parts by weight of the first auxiliary agent. The preparation of component A includes the following steps: S1, barium sulfate, polymeric MDI and the first additive are mixed and then pressed into a grout, which is then placed in a sealed container and sealed with nitrogen to obtain barium sulfate grout; S2, the polyether diol is vacuum-extracted into the reactor, then isocyanate-modified MDI is added for addition polymerization reaction, and after the reaction is completed, the barium sulfate slurry is added and kept at the temperature to obtain component A; In step S1, the sealing time is 25-35 days; in step S2, the temperature of the addition polymerization reaction is 75-85℃, and the time is 2-3 hours; the heat preservation time is 20-40 minutes. Based on the weight parts of component B, the raw materials for preparing component B include: 30-50 parts by weight of polyether polyol, 10-20 parts by weight of amino chain extender, 20-40 parts by weight of barium sulfate, 5-10 parts by weight of dehydrating agent, 2-5 parts by weight of color paste, 0.5-2 parts by weight of second auxiliary agent, and 0.2-0.5 parts by weight of catalyst; the catalyst is an organobismuth catalyst. The preparation of component B includes the following steps: T1, barium sulfate, polyether polyol from the first part, dehydrating agent and second auxiliary agent are mixed and then grouted, and then placed in a sealed container and sealed with nitrogen to obtain component B grout; T2, the remaining polyether polyol and amino chain extender are added to the reactor, the temperature is raised to 50~60℃, then the color paste and catalyst are added, mixed, and then the B component slurry is added. After mixing again, the B component is obtained. In step T1, the first part of the polyether polyol accounts for 30-40 wt% of the total amount of polyether polyol used; the sealing time is 25-35 days.

2. The polyurea coating according to claim 1, characterized in that, The first additive is a wetting and dispersing agent.

3. The polyurea coating according to claim 1 or 2, characterized in that, The dehydrating agent is a molecular sieve, and the molecular sieve is selected from at least one of 3A molecular sieve and 4A molecular sieve.

4. The polyurea coating according to claim 1 or 2, characterized in that, When using the polyurea coating, the components A and B are mixed at a volume ratio of (0.8~1.2): (0.8~1.2) and then sprayed.

5. A method for preparing a polyurea coating as described in any one of claims 1-4, characterized in that, The method includes the preparation of component A and component B; wherein the preparation of component A includes the following steps: S1, barium sulfate, polymeric MDI and the first additive are mixed and then pressed into a grout, which is then placed in a sealed container and sealed with nitrogen to obtain barium sulfate grout; S2, the polyether diol is vacuum-extracted into the reactor, then isocyanate-modified MDI is added for addition polymerization reaction, and after the reaction is completed, the barium sulfate slurry is added and kept at the temperature to obtain component A; In step S1, the sealing time is 25-35 days; in step S2, the temperature of the addition polymerization reaction is 75-85℃, and the time is 2-3 hours; the heat preservation time is 20-40 minutes. The preparation of component B includes the following steps: T1, barium sulfate, polyether polyol from the first part, dehydrating agent and second auxiliary agent are mixed and then grouted, and then placed in a sealed container and sealed with nitrogen to obtain component B grout; T2, the remaining polyether polyol and amino chain extender are added to the reactor, the temperature is raised to 50~60℃, then the color paste and catalyst are added, mixed, and then the B component slurry is added. After mixing again, the B component is obtained. In step T1, the first part of the polyether polyol accounts for 30-40 wt% of the total amount of polyether polyol used; the sealing time is 25-35 days.

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