A water-based polyurea coating material and its preparation method

Abstract

This invention relates to the application of nanotechnology in the field of coating materials, specifically an aqueous polyurea coating material and its preparation method. An aqueous polyurea coating material comprises two components, A and B. A is a prepolymer mainly composed of modified isocyanate, and B is a curing agent mainly composed of silicate aqueous solution. The key feature is the addition of a catalyst to component A in the aqueous polyurea coating. The catalyst is one or more of the following: a planar molecule with a macrocyclic conjugated π system, a complex formed by a planar molecule and a metal, or a polymer of planar molecules. The amount of catalyst added is 0.001-10 parts per 100 parts of component A. This invention uses different types of catalysts to improve the crosslinking degree of the system, increase the molecular weight of the in-situ polymer, and increase the density of the system, thereby improving the coating's corrosion resistance (such as salt spray resistance, resistance to immersion in acids, alkalis, and solvents) and mechanical properties (such as impact resistance, wear resistance, and hardness).

Description

Technical Field

[0001] This invention relates to the application of nanotechnology in the field of coating materials, specifically to an aqueous polyurea coating material and its preparation method. Background Technology

[0002] Nanotechnology is an emerging technology that has brought about a major revolution in the field of materials science. Since the properties of surface materials involved in corrosion protection are determined by their microstructure, the emergence and application of nanotechnology will undoubtedly bring tremendous opportunities for the development of corrosion control technology.

[0003] Studies have shown that modifying organic coating anticorrosive materials using nanotechnology can improve their overall performance, particularly increasing mechanical strength, hardness, adhesion, and enhancing light resistance, aging resistance, and weather resistance. For example, nanoparticles such as TiO, SiO2, ZnO, and FeO scatter ultraviolet light; adding these nanomaterials can effectively enhance the material's UV resistance, significantly improving aging resistance. Introducing a small amount of nanoparticles into the material can increase its sealing properties, achieving better waterproofing and anticorrosive effects. For inorganic coating materials, nanostructuring their structure can also significantly improve their plasticity and toughness. Several technologies for modifying anticorrosive materials using nanotechnology have already been patented. However, overall, this technology is still in its early stages and has enormous development potential.

[0004] Inorganic nanoparticles are typically introduced using melt mixing or other external mixing methods. However, voids usually exist between the inorganic particles and the polymer system, preventing complete wetting of the interface. This leads to particle aggregation and uneven dispersion. For anti-corrosion coatings, the system's protection of the substrate largely depends on physical barriers, and a lack of system density directly results in decreased anti-corrosion performance. Compared to the above methods, in-situ generated inorganic particles have a tighter interface with the polymer system, resulting in higher system density. Furthermore, in-situ generated inorganic particles are undoubtedly smaller and more uniformly distributed. Therefore, the method of in-situ generation of inorganic particles has gained attention in recent years.

[0005] Patents HU212033 and US5622999 disclose methods for controlling the reaction rate in water-in-oil emulsions of water glass / polyisocyanate using certain small-molecule phosphate esters. Specifically, small-molecule aliphatic phosphate esters and small-molecule aromatic phosphate esters are used as catalysts and plasticizers; the material is named 3P resin using the first letters of the three main materials, and the reaction time can be controlled between a few seconds and several hours. However, the resulting polysilicic acid / polysilicate particles have a size of 5-50 μm, which is relatively large and wide-ranging. Furthermore, another drawback of this product as a coating material is that the polymer molecular weight is insufficient, the crosslinking is too low, and the system density is inadequate.

[0006] Patent CN1993398A provides a mixed resin with improved mechanical and fracture properties on the aforementioned patented substrate, comprising vinyl esters and / or polyesters. This mixed resin reduces the silicate size to 1-5 μm, thereby improving the product's mechanical properties. However, as an anti-corrosion coating, the system's density is insufficient to withstand the intrusion of corrosive gases.

[0007] International patent WO13 / 016370 describes a process that involves adding certain polyols to react polysilicic acid with polyisocyanate to generate polysilicic acid / polyurethane nanocomposites. It utilizes hydrophilic polyols to create compatibility between the hydrophilic polysilicic acid and the hydrophobic organic components, and employs different emulsifiers to alter interfacial tension, thereby reducing the particle size in the W / O emulsion. However, these particle-reducing emulsifiers significantly affect the polyisocyanate / polyisourethane (trimerization) transition and the water / polyisocyanate (polyurea formation) reaction, making the reaction uncontrollable.

[0008] Therefore, the purpose of this invention is to improve the crosslinking degree of the system by using different types of catalysts, increase the molecular weight of the in-situ polymer, and increase the density of the system, thereby improving the coating's corrosion resistance (such as salt spray resistance, resistance to immersion in acid, alkali, solvent and other media) and mechanical properties (such as impact resistance, wear resistance, hardness, etc.). Summary of the Invention

[0009] To address the above problems, this invention provides an aqueous polyurea coating material and its preparation method.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A waterborne polyurea coating material consists of two components, A and B. A is a prepolymer based on modified isocyanate, and B is a curing agent based on silicate aqueous solution. A catalyst is added to component A in the waterborne polyurea coating; the catalyst's function is to catalyze the reaction between component A and component B.

[0012] The catalyst is one or more of the following: a planar molecule with a macrocyclic conjugated π system, a complex formed by a planar molecule and a metal, or a polymer of a planar molecule. The amount of catalyst added is 0.001-10 parts of component A (component A is calculated as 100 parts).

[0013] The purpose of adding the catalyst is to reduce the activation energy required for the reaction between component A and component B, and to increase the degree of reaction between the modified isocyanate in component A and the water and silicates in component B. For two-component reactive coatings classified as A and B, where the reaction occurs after mixing, adding a suitable catalyst to the system can increase the degree of cross-linking within a limited "reaction window," reduce the proportion of remaining unreacted prepolymers or monomers in the system, and improve the film's durability.

[0014] These functional compounds with conjugated systems possess excellent coordination capabilities, allowing them to coordinate with most metal ions in the periodic table (such as lanthanides, argentides, and some main group metals). These metal coordination compounds exhibit strong catalytic activity.

[0015] The planar molecule with a macrocyclic conjugated π system is a tetrapyrrole compound or its derivative; including but not limited to porphyrin compounds and their derivatives, porphyrin compounds and their derivatives, porphyrin phthalocyanine compounds and their derivatives, porphyrin dimers and polymers, phthalocyanine dimers and polymers, etc., preferably porphyrin (H2P) and metalloporphyrin [MP] (n-2)+ ] as well as one or more mixtures of porphyrin dimers or polymers.

[0016] The metal in the complex is Li. + Na + K + Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Fe 3+ Al 3+ etc.; including monovalent metal ions (Li + Na + K + Coordination generates binuclear monolayer complexes, while coordination of divalent metals mostly generates monolayer complexes (Fe). 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ etc.), trivalent metals (Fe 3+ Al 3+ The “semi-sandwich” structure formed by tetrapyrrole compounds and chain molecules formed by tetravalent metal ions, etc.

[0017] Metalloporphyrins include conventional metalloporphyrins and SAT metalloporphyrins. The macrocycle size of porphyrins is suitable for a wide range of metal ions, such as Co, with radii in the range of 55-80 pm. 2+ Ni 2+ Cu 2+ Zn 2+ Suitable for embedding as conventional metalloporphyrins, but when the radius of the metal ion is too large, exceeding 80 pm, such as Fe... 2+ Cd 2+ Hg 2+ Pd 2+ If it cannot be completely embedded in the porphyrin macrocycle, it will be located on the outside of the macrocycle, forming SAT metalloporphyrin.

[0018] The polymer of the planar molecules is a dimer or polymer of a tetrapyrrole compound.

[0019] The tetrapyrrole compound is one or more of porphyrin compounds, porphyrin compounds, and porphyrin phthalocyanine compounds.

[0020] The polymer of the planar molecules is one or more of the following: monomeric metal porphyrins, porphyrin dimers, porphyrin trimers, porphyrin polymers, or metal porphyrin compounds interacting with small molecules that have coordination ability to form hybrid compounds.

[0021] The porphyrin dimers and polymers mentioned include, but are not limited to, monomeric metalloporphyrins, porphyrin dimers, porphyrin trimers, porphyrin polymers, or compounds that are formed by the interaction of metalloporphyrin compounds (including monomeric metalloporphyrins, porphyrin dimers, porphyrin trimers, etc.) with additional small molecules with coordination ability to form mixed one-dimensional chains, two-dimensional planes, or compounds with three-dimensional spatial configurations, such as meso-tetraphenylhydroxyporphyrin, meso-tetraphenylcarboxyporphyrin, meso-tetraphenylhydroxyporphyrin, cyclic porphyrins, trimer porphyrins, bisporphyrins, etc.

[0022] Both porphyrins and metalloporphyrins have 22 π electrons, a property that allows for strong π-π interactions, making them prone to forming two types of aggregate structures during self-assembly: H-type and J-type. The J-type structure consists of monomer molecules arranged side-by-side in one dimension, while the H-type aggregate structure consists of porphyrin monomers arranged face-to-face.

[0023] The phthalocyanine dimers and polymers include, but are not limited to, μ-carbon / nitrogen / oxygen-linked phthalocyanines, planar binuclear phthalocyanines, planar binuclear naphtholines, and sandwich-type rare earth compounds based on planar binuclear phthalocyanines.

[0024] The catalyst is one or more of porphyrin, porphyrin derivative, metalloporphyrin, metalloporphyrin derivative, porphyrin dimer, and porphyrin polymer.

[0025] The waterborne polyurea coating material is a two-component system consisting of two components, A and B, which are mixed in a mass ratio of 1.3:1 to 2.5:1. Component A (per 100 parts) comprises 20-80 parts modified isocyanate, 0.001-10 parts catalyst, 5-70 parts plasticizer, 0.01-10 parts additives, and 0-30 parts pigment or filler.

[0026] Component B (per 100 parts): 40-60 parts silicate, 40-60 parts deionized water, and 0.01-2 parts surfactant.

[0027] The modified isocyanate is one or more of polyisocyanate, blocked isocyanate, isocyanate monomer, difunctional isocyanate prepolymer, and polyfunctional isocyanate prepolymer.

[0028] Additives include one or more of the following: defoamers, wetting agents, leveling agents, thickeners, and antifungal agents. The selection of these additives must follow the following principle: the additives do not contain hydroxyl, amino, or carboxyl groups, otherwise they will not be able to coexist with modified isocyanates.

[0029] Pigments / fillers are one or more of pigments, bentonite, silica, and talc.

[0030] The plasticizer is an organophosphate compound, including but not limited to one or more of the following: triethyl phosphate, trihexyl phosphate, trimethyl phosphate, triphenyl phosphate, toluene-xylene phosphate, tri(xyl) phosphate, triisobutyl phosphate, tri(2-chloropropyl) phosphate, diphenyl isooctyl phosphate, tri(2-chloroethyl) phosphate, diphenyl isodecanyl phosphate, triisopropylphenyl phosphate, tributoxyethyl phosphate, triisopropylphenyl phosphate, triisopropylphenyl phosphate, tri(1,3-dichloroisopropyl) phosphate, and tert-butylbenzene diphenyl phosphate.

[0031] The surfactant is a nonionic surfactant;

[0032] Water glass is an aqueous solution of sodium silicate and / or potassium silicate, with a modulus of 2.0-6.0.

[0033] A method for preparing a waterborne polyurea coating material,

[0034] ① To obtain component A, add the modified isocyanate to the dispersion vessel according to the above proportion, then add the catalyst and plasticizer in sequence, stir for 10-20 minutes to obtain a slurry; then add pigments / fillers (pigments or fillers) to the slurry and disperse at 1000-2000r for 1-2 hours until the slurry is stable; then add the additives to the stable slurry, stir for 10-20 minutes, and filter to obtain component A;

[0035] ② Dissolve the silicate in deionized water according to the above proportion until it is clear and transparent, filter, add surfactant, disperse at 1000-2000r for 2-5 minutes to obtain component B;

[0036] ③ Mix the above-obtained components A and B at a ratio of 1.3:1 to 2.5:1 (by mass) (mix immediately before use) to obtain the coating material.

[0037] In step ②, silicate is added to deionized water in the above proportion, and the high modulus silicate is dissolved at 50-70℃ and 3-4MPa until it is clear and transparent.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] ① This solves the problem of low mechanical strength of coating materials caused by low polymerization and low crosslinking of active monomers in the system, and simultaneously increases the compressive strength, flexural strength, wear resistance, flexibility and impact resistance of the material.

[0040] ② The increased density of the original system enhances the corrosion resistance of the coating system, as well as its resistance to salt spray and acid, alkali, and solvent immersion corrosion. Detailed Implementation

[0041] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] The coating material of this invention uses different types of catalysts to improve the crosslinking degree of the system, increase the molecular weight of the in-situ polymer, and increase the density of the system, thereby improving the coating's corrosion resistance (such as salt spray resistance, resistance to immersion in acid, alkali, solvent and other media) and mechanical properties (such as impact resistance, wear resistance, hardness, etc.).

[0043] Example 1

[0044] An inorganic nanoparticle-modified polyurethane / polyurea coating material is prepared according to the following ratio:

[0045]

[0046] Note: The defoamer is Tego 900.

[0047] The leveling agent is Tego410.

[0048] The wetting agent is BYK 2151.

[0049] The surfactant is XP-50.

[0050] Meanwhile, the defoamer, leveling agent, and wetting agent in the above formula can be replaced accordingly based on the existing additives used in preparing coating materials.

[0051] The preparation method of inorganic nanoparticle-modified polyurethane / polyurea coating materials is as follows:

[0052] ① Add 50 parts of modified polymerized MDI to the dispersion vessel, then add 6 parts of tributyl phosphate and 29 parts of triphenyl phosphate in sequence, and stir for 10 minutes;

[0053] ② Add 3 parts carbon black and 10 parts bentonite to the above slurry, and disperse at 1000-2000r for 1-2 hours until the slurry is stable;

[0054] ③ Add 0.3 parts wetting agent, 0.4 parts leveling agent, and 0.3 parts defoamer to the above stabilized slurry in sequence, stir for 10 minutes, and filter to obtain component A.

[0055] ④ Dissolve 40 parts of potassium silicate in 60 parts of deionized water until clear and transparent, filter, and obtain component B.

[0056] ⑤ Mix the obtained component A and component B at a ratio of 1.7:1 to 2.0:1 (mass ratio) (mix immediately before use).

[0057] Example 2-25

[0058] The phthalocyanine in the formulation of Example 1 was replaced as shown in Table 1, while other components and ratios remained unchanged. Inorganic nanoparticle-modified polyurethane / polyurea coating materials with different compositions and ratios were obtained according to the preparation method described in Example 1.

[0059] Comparative Examples 1 and 2

[0060] Comparative Example 1 is a system in Example 1 with no additional catalyst added, and all other components and ratios remaining unchanged;

[0061] Comparative Example 2 was prepared by adding dibutyltin dilaurate, a commonly used polyurethane / polyurea reaction catalyst, while keeping other components and ratios unchanged.

[0062] Table 1. Types of catalysts in the examples

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Note: All porphyrin catalysts used in the experiment were provided by Yuanjiang Hualong Catalysis Technology Co., Ltd.

[0071] Dibutyltin dilaurate was provided by Hangzhou Ruike Chemical Co., Ltd.

[0072] The coating materials obtained in the above embodiments and comparative examples were subjected to performance tests (see Tables 2 and 3): the test was conducted in accordance with ISO-12944 "Paint protection systems for corrosion protection of steel structures".

[0073] Table 2 Mechanical performance test data for each embodiment

[0074]

[0075]

[0076] Table 3 Corrosion resistance test data for each embodiment

[0077]

[0078]

[0079]

[0080] As can be seen from Tables 2 and 3, the products of Examples 1-27 all exhibit superior performance compared to Comparative Examples 1 and 2. Specifically, regarding mechanical properties, the compressive strength of the products of Examples 1-27 is between 15-30 MPa, while the compressive strengths of Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) are only 8 MPa and 12 MPa, respectively. The flexural strength of the products of Examples 1-27 is in the range of 32-50 MPa, while the flexural strengths of Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) are only 20 MPa and 18 MPa, respectively. The tensile strength of the products of Examples 1-25 is between 8-16 MPa, while the tensile strengths of Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) are only 5 MPa. The abrasion loss of the products of Examples 1-25 is between 20-40 mg, while the tensile strengths of Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) are 55 mg and 48 mg, respectively. The products of Examples 1-27 all exhibited a flexibility of <3mm, while the products of Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) both had a flexibility of 5mm, indicating that the products were brittle and easily broken. Table 3 shows that the salt spray resistance data for Examples 1-25 were all >1000h, with corrosion spread of less than 1mm and post-corrosion adhesion >3MPa. In contrast, Comparative Example 1 (without catalyst) and Comparative Example 2 (with conventional catalyst) only exhibited salt spray resistance of 200h and 350h respectively, with corrosion spread of 4mm and no post-corrosion adhesion.

[0081] Comparing the data in Table 2 with Examples 1-27, Examples 19-25 are the best examples, exhibiting superior mechanical properties and corrosion resistance. Table 2 shows that the products generated using porphyrin derivative dimers (Examples 19-25) generally have higher mechanical properties than the monomers, with compressive strengths ranging from 24-30 MPa, especially Example 19. The products generated using porphyrin derivatives (Examples 1-18) have compressive strengths of 12-20 MPa. The flexural strengths of the products generated in Examples 1-18 are 35-45 MPa, while those in Examples 19-25 are between 42-48 MPa, with Example 19 having a flexural strength of 48 MPa. Tensile strengths are relatively similar, ranging from 8-16 MPa for Examples 1-25, while Example 19 has a tensile strength of 16 MPa. In terms of abrasion resistance, Examples 1-27 have an abrasion resistance between 20-40 mg, classifying them as ultra-abrasion-resistant materials, while Example 19 has an abrasion resistance of 21 mg. Examples 12, 13, 17-19, and 23-25 ​​exhibit good flexibility (1 mm). Examples 26-27 use the same catalyst as Example 19, but with different dosages. The flexibility, flexural strength, and abrasion resistance of Examples 26 and 27 are slightly inferior to those of Example 19. The compressive strength of Example 27 is roughly the same as that of Example 19.

[0082] Table 3 shows that the salt spray resistance of products in Examples 1-27 all exceeded 1000 hours, while commercially available water-based products generally only withstand around 500 hours. Comparing Examples 1-27, Example 19 withstood 3000 hours of salt spray with an intact coating, showing no blistering, rusting, or peeling. Furthermore, after 3000 hours, the corrosion spread was only a few millimeters, and the adhesion after corrosion was 7.5 MPa, indicating good corrosion resistance. In addition, the salt spray resistance of products in Examples 1-18 was generally between 1000-2000 hours, while the salt spray resistance of products in Examples 19-27 all exceeded 2500 hours. This indicates that the porphyrin dimer has a strong catalytic ability in this system, increasing the system density and thus enhancing the coating's protective ability against the metal substrate.

Claims

1. A water-based polyurea coating material, comprising two components, A and B, wherein, A is a prepolymer mainly composed of modified isocyanate, and B is a curing agent mainly composed of silicate aqueous solution. The coating is characterized by the addition of a catalyst to component A; the two components A and B are mixed in a mass ratio of 1.3:1-2.5:1; component A, based on 100 parts, contains 20-80 parts modified isocyanate, 0.001-10 parts catalyst, 5-70 parts plasticizer, 0.01-10 parts additives, and 0-30 parts pigment or filler; component B, based on 100 parts, contains 40-60 parts silicate, 40-60 parts deionized water, and 0.01-2 parts surfactant. The catalyst is one or more of the following: a complex formed by a planar molecule with a macrocyclic conjugated π system and a metal, or a polymer of planar molecules. The amount of catalyst added accounts for 0.001-10 parts of component A, and component A is calculated as 100 parts. The planar molecule with a macrocyclic conjugated π system is a tetrapyrrole compound or its derivative; the metal in the formed complex is Li. + Na + K + Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Fe 3+ Or Al 3+ The polymer of the planar molecules is one or more of the hybrid compounds formed by the interaction of metallophyllin compounds and small molecules with coordination ability.

2. The waterborne polyurea coating material according to claim 1, characterized in that: The modified isocyanate is one or more of polyisocyanate, blocked isocyanate, isocyanate monomer, and multifunctional isocyanate prepolymer; Additives include one or more of the following: defoamers, wetting agents, leveling agents, thickeners, and mildew inhibitors; The pigments / fillers are one or more of pigments, bentonite, and talc; The plasticizer is an organophosphate compound; The surfactant is a nonionic surfactant; Water glass is an aqueous solution of sodium silicate and / or potassium silicate, with a modulus of 2.0-6.

0.

3. A method for preparing the waterborne polyurea coating material according to claim 1, characterized in that: Step ① Obtaining Component A: Add the modified isocyanate to the dispersion vessel according to the ratio, then add the catalyst and plasticizer in sequence, stir for 10-20 minutes to obtain a slurry; then add pigments / fillers to the slurry and disperse at 1000-2000r for 1-2 hours until the slurry is stable; then add the additives to the stable slurry, stir for 10-20 minutes, and filter to obtain Component A; Step ② Add silicate to deionized water in proportion and dissolve until clear and transparent. Filter, add surfactant, and disperse at 1000-2000r for 2-5 minutes to obtain component B; Step ③: Mix component A and component B at a mass ratio of 1.3:1 to 2.5:1 to obtain the coating material.

4. The method for preparing the waterborne polyurea coating material according to claim 3, characterized in that: In step ②, silicate is added to deionized water in proportion, and the high-modulus silicate is dissolved at 50-70℃ and 3-4MPa until it becomes clear and transparent.

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