A hyperbranched resin, its preparation method and application

Abstract

The present invention belongs to the field of coating materials, and relates to a hyperbranched resin, a preparation method thereof, and an application thereof in the preparation of an underwater-curable epoxy composition. The general structural formula of the hyperbranched resin is as follows: In the formula, m is a positive integer of 2 or more, and n is any positive integer. The present invention uses click chemistry and nucleophilic substitution to modify plant tannins, endows inherent toughness, and obtains a hyperbranched resin containing a dozen epoxy groups. It can not only eliminate potential compatibility problems of externally added toughening agents, but theoretically can form a super-dense network with up to 625 crosslinking nodes after curing, enabling the composition to have excellent resistance to media. This hyperbranched resin and its composition meet the requirements of various scenarios such as corrosion environments of all grades, low surface treatment, and thick underwater coatings, and can be used for corrosion protection of inland and marine facilities and equipment.

Description

Technical Field

[0001] The invention belongs to the field of coating materials and relates to a hyperbranched resin and a preparation method thereof, and application of the hyperbranched resin in the preparation of an underwater curable epoxy composition. Background Art

[0002] Epoxy compositions have excellent properties such as high bonding strength and low linear shrinkage. They have broad application prospects in many industries such as defect repair and structural reinforcement. They are often used as base coatings in light and heavy anti-corrosion projects on the market. However, traditional compositions (such as epoxy paints and adhesives) can usually only be used in dry environments. If there is moisture at the interface, it will directly affect the bonding effect. In order to achieve water-carrying operations (especially underwater operations), most material systems should be specially designed (including component refinement, resin or curing agent modification, etc.) to avoid negative interference from water molecules as much as possible. In addition, since phenolic epoxies are rich in adjacent benzene rings and are brittle, they often require system toughening; furthermore, the basic raw materials for resin synthesis currently rely mainly on petrochemicals, and bisphenol A / F / S has great physiological toxicity to the human body. Under the international trend of green and low-carbon, seeking recycling and renewable environmentally friendly methods is becoming a research hotspot.

[0003] Chinese patent application CN1752162A discloses a marine heavy-duty anticorrosive coating and its preparation method, which uses phenolic amine + ketimine as curing agent to achieve underwater construction with low surface treatment, but because the ordinary E-51 and E-44 systems are still used, the film flexibility (1-2mm), impact resistance (50kg.cm), adhesion (1-2 levels), chemical resistance (20% H 2 SO 4 , 20% NaOH, 3% NaCl for 21 days each without blistering or shedding) is not outstanding.

[0004] Similarly, Chinese patent application CN101492586A discloses a solvent-free epoxy heavy-duty anti-corrosion coating with low surface treatment and underwater coating, which is a distribution ratio of Group A and Group B. The distribution ratio of Group A is composed of 20-50 epoxy resin, 4-7 active diluent, 0.06-1 defoamer, 4-7 special fatty acid soap, 0.5-2 fumed silica, 5-10 mineral water absorbent, 20-50 filler, and 5-10 pigment. The distribution ratio of Group B is composed of 65-85 Mannich base curing agent and 15-35 organic nitrogen base. The use of low molecular weight epoxy resin, special fatty acid soap, organic nitrogen base, and mineral water absorbent can be used for coating in wet, rusty and underwater conditions, but its physical and chemical properties are also low (flexibility level 2, adhesion ≥4MPa, 10% H 2 SO 4 / 10%NaOH / 3%NaCl for 7 days each without cracking, blistering or falling off).

[0005] Chinese Patent CN107603423B discloses an underwater-curing long-acting anti-corrosion coating for marine steel structures and its preparation method, which consists of component A and component B with a weight ratio of 1.5:1 to 3:1. The composition and parts by weight of component A are as follows: 20-50 parts of phenolic-modified epoxy resin, 3-8 parts of reactive diluent, 25-55 parts of filler, 0.2-1 part of thixotropic agent, 0.3-1 part of wetting and dispersing agent, 0.3-0.8 part of defoaming agent, and 0.3-1 part of coupling agent; the composition and parts by weight of component B are as follows: 20-70 parts of curing agent I and 30-80 parts of curing agent II. The adhesion exceeds 14 MPa and the resistance to media is good. Unfortunately, the large number of rigid aromatic rings and high crosslinking density in phenolic epoxy may weaken the toughness of the coating while increasing the hardness and wear resistance.

[0006] To improve the brittleness of the epoxy curing network and make it both rigid and flexible, technicians often add liquid rubbers (polyethers, polysulfides, nitrile rubbers), core-shell macromolecules, hyperbranched polymers, nanoparticles, thermoplastic resins, liquid crystals, or promote the formation of IPNs, Semi-IPNs. For example, Chinese Patent Applications CN108192471A, CN102719174A, and CN108250910A all use polysulfide rubber for toughening, but it has a stinking smell, and the "sea-island" structure distributed in the network is also prone to induce serious interfacial phase separation.

[0007] In terms of green synthesis, Chinese Patent Application CN110256655A discloses a tannic acid-based multi-functional epoxy resin, which is prepared by allylating tannic acid and then epoxidizing some double bonds. There are at least two defects: 1. Peroxides are flammable and explosive, with high safety risks; 2. The sodium hydroxide and potassium hydroxide used are strongly alkaline, which easily causes tannic acid to directly crystallize into salts.

[0008] Chinese Patent CN110790902B provides a tannic acid curing agent and its preparation method. The inventor introduces the long fatty chain of 10-undecenoyl chloride into tannic acid, and then links the terminal carboxyl group or alcohol-based thioether under ultraviolet light. The benzene ring structure contained in the curing agent can increase the rigidity of the epoxy coating film, and the undecenyl long fatty chain participates in the curing reaction, increasing the mobility of the network chain segments and greatly improving the toughness of the epoxy resin. However, the curing process is relatively cumbersome and requires three-stage progressive step-by-step heating. Summary of the Invention

[0009] The purpose of the present invention is to provide a hyperbranched resin and its preparation method, and its application in the preparation of an underwater-curing epoxy composition. The hyperbranched resin uses tannin as the matrix, and after modification, it has good toughness and can deeply participate in the crosslinking of the system; the prepared underwater-curing epoxy composition has low requirements for the surface treatment of the substrate, can be painted with rust, and can reach a film thickness of several hundred microns with a single coating.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] A hyperbranched resin, the general structural formula of which is

[0012]

[0013] In the formula, m is a positive integer of 2 or more, and n is any positive integer.

[0014] In one preferred embodiment, the sum of m and n does not exceed 16.

[0015] m and n are independently valued, but the sum of the two should not exceed 16. To improve the toughness of tannin, the number of carbon atoms in the graft chain should be as many as possible, but if the chain segment is too long, the reaction difficulty may increase due to steric hindrance.

[0016] The present invention also claims the preparation method of the hyperbranched resin, including the following steps (two-step method):

[0017] S1. α,ω-alkene / epoxyalkane and halo thiol are subjected to thiol-ene click chemistry to synthesize a long-chain halo epoxy pre-reactant;

[0018] S2. The long-chain halo epoxy pre-reactant undergoes nucleophilic substitution on the phenolic hydroxyl group in tannin to obtain the hyperbranched resin;

[0019] The α,ω-alkene / epoxyalkane is linear straight-chain, contains no less than 8 carbon atoms, has an alkenyl group at one end and an epoxy group at the other end in the molecule.

[0020] In one preferred embodiment, the molar ratio of the monomers n(tannin):n(α,ω-alkene / epoxyalkane):n(halo thiol) = 1:(32.5 - 50):(32.5 - 50), and n(α,ω-alkene / epoxyalkane):n(halo thiol) = (1 - 1.1):1. The amounts of α,ω-alkene / epoxyalkane and halo thiol are 32.5 - 50 times that of tannin. If the amount is too low, it is difficult to fully substitute tannin, and if it is too high, it is ineffective feeding.

[0021] In one preferred embodiment, the α,ω-alkene / epoxyalkane contains 8 - 12 carbon atoms.

[0022] In one preferred embodiment, the α,ω-alkene / epoxyalkane is at least one of 1,2-epoxy-7-octene and 1,2-epoxy-9-decene.

[0023] If the α,ω-alkene / epoxyalkane chain segment is too long or contains side branches, the steric hindrance with the benzene ring or (and) adjacent functional groups may be too large due to its own volume, making it difficult to fully substitute the phenolic hydroxyl group; if the chain segment is too short, it is not enough to effectively reduce the density of the rigid ring in tannin, affecting the toughening effect.

[0024] In one preferred embodiment, the halogenated mercaptan is selected from one or more of chloromercaptan, bromomercaptan, and iodomercaptan. Considering factors such as reagent price, reactivity, and conversion yield, bromomercaptan is preferred.

[0025] In one preferred embodiment, the bromomercaptan is one or more of 3-bromo-1-propanethiol, 2-bromoethanethiol, and 4-bromobenzyl mercaptan.

[0026] In one preferred embodiment, the thiol-ene click chemistry is achieved through Michael addition or photo(thermal) radical reaction. Since the electron-withdrawing ability of the double bond in the α,ω-terminal alkene / epoxyalkane is limited, Michael addition is difficult. Therefore, photo or thermal radical initiation is preferred, and photo radical initiation is further preferred. Photo radical initiation has mild reaction conditions (no heating required), good controllability (the reaction stops immediately when the light source is removed), high conversion rate, and basically no by-products are generated.

[0027] In one preferred embodiment, the photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphonate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether and its derivatives. One or a combination of two of ethyl 2,4,6-trimethylbenzoyl phenylphosphonate and 2-hydroxy-2-methyl-1-phenyl-1-propanone, which have good solubility, are preferred.

[0028] In one preferred embodiment, the addition amount of the photoinitiator is 0.5-3% of the total mass of the monomers.

[0029] In one preferred embodiment, the ultraviolet light irradiation intensity of the thiol-ene click chemistry is 10-100 mW / cm 2 , and the irradiation time is 0.5-2 h; preferably, the irradiation intensity is 20-50 mW / cm 2 , and the irradiation time is 0.5-1 h. Under this irradiation intensity and time, the reaction can occur sufficiently without destroying the product structure.

[0030] In one preferred embodiment, a solvent is further added in synthesis steps S1 and S2 to facilitate the dissolution of tannin and the smooth progress of the reaction; the solvents used in synthesis steps S1 and S2 can be the same or different.

[0031] In one preferred embodiment, the solvent is selected from one or more of methanol, ethanol, n-butanol, chloroform, 1,4-dioxane, N,N-dimethylformamide, and dimethyl sulfoxide. N,N-dimethylformamide, which is generally soluble, is preferred.

[0032] In one preferred embodiment, the temperature of the nucleophilic substitution reaction is 30 to 50 °C, and the reaction duration is 3 to 8 h.

[0033] In one preferred embodiment, an acid-binding agent is added in the nucleophilic substitution reaction; the molar ratio of the acid-binding agent to tannin is (32.5 to 50):1. Due to the presence of the acid-binding agent, the nucleophilic substitution can be carried out with only slight heating, avoiding the problem of too many by-products induced by too high temperature.

[0034] In one preferred embodiment, the acid-binding agent is selected from one or more of triethylamine, sodium hydroxide, potassium hydroxide, potassium carbonate, tetraethylammonium chloride, tetrabutylammonium bromide, and tetramethylammonium hydroxide. To avoid the too strong alkalinity of sodium hydroxide, potassium hydroxide, potassium carbonate, and tetramethylammonium hydroxide and directly neutralize and form salts with the slightly acidic tannin, triethylamine with slightly weaker alkalinity and moderate price is preferred.

[0035] Based on the same concept, the present invention also claims the application of the hyperbranched resin in the preparation of an underwater curable epoxy composition.

[0036] An underwater curable epoxy composition contains 50 to 65 parts by weight of the above hyperbranched resin.

[0037] In one preferred embodiment, the underwater curable epoxy composition includes two components, A and B; by weight, component A contains 50 to 65 parts of the above hyperbranched resin, 20 to 25 parts of an active diluent, 3 to 7 parts of a coupling agent, and 130 to 200 parts of an auxiliary agent and filler; component B contains 81 to 112 parts of a curing agent.

[0038] When in use, mix according to the mass ratio of A to B of (10 to 11):1 and stir well.

[0039] In one preferred embodiment, the active diluent is one or more of butyl glycidyl ether, benzyl glycidyl ether, C12-14 alkyl glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and cardanol glycidyl ether. At least one of C12-14 alkyl glycidyl ether or cardanol glycidyl ether with good hydrophobicity and flexibility is preferred.

[0040] Using an active diluent instead of an organic solvent can prepare a high solid content and solvent-free composition, avoiding the pollution of water quality caused by the precipitation of the solvent during underwater construction.

[0041] In one preferred embodiment, the coupling agent is selected from one or more of glycidyl ether (ester) -propyltrimethoxysilane, glycidyl ether (ester) -propyltriethoxysilane, glycidyl ether (ester) -propyltripropoxysilane, 2-(3,4 - epoxycyclohexyl) ethyltrimethoxysilane, 2-(3,4 - epoxycyclohexyl) ethyltriethoxysilane, 2-(3,4 - epoxycyclohexyl) ethyltripropoxysilane, titanate, aluminate, zirconate, preferably at least one of glycidyl ether -propyltrimethoxysilane and 2-(3,4 - epoxycyclohexyl) ethyltrimethoxysilane. Compared with the ester -bond compound, the ether bond is more flexible and more resistant to alkali hydrolysis.

[0042] Glycidyl ether -propyltrimethoxysilane and 2-(3,4 - epoxycyclohexyl) ethyltrimethoxysilane have low viscosity and good compatibility with the system. While promoting adhesion, methoxysilane can react with water faster and more easily than ethoxy (propoxy) silane (methanol is more easily removed than ethanol and propanol), and thus can remove the surface moisture of the composition more timely and efficiently, blocking the inward deep penetration of water vapor. It is known from practice that under the same addition amount, the water -removing rate of glycidyl ether -propyltrimethoxysilane is 0.4 - 1 times faster than that of glycidyl ether -propyltriethoxysilane, which can turn the wet surface into a hydrophobic state in the shortest possible time. Similarly, there is a similar rule between 2-(3,4 - epoxycyclohexyl) ethyltrimethoxysilane and 2-(3,4 - epoxycyclohexyl) ethyltriethoxysilane.

[0043] In one preferred embodiment, the auxiliaries and fillers include 0.5 - 1.5 parts of defoamer, 2 - 3 parts of wetting and dispersing agent, 0.5 - 1.5 parts of leveling agent, 3 - 5 parts of anti - settling agent, 4 - 8 parts of graphene oxide slurry, 15 - 30 parts of modified sepiolite, 40 - 60 parts of modified silica powder, 15 - 25 parts of hollow glass microspheres, and 50 - 65 parts of micaceous iron oxide.

[0044] In one preferred embodiment, the curing agent includes 40 - 60 parts of cashew shell oil phenolic amine, 40 - 50 parts of modified phenolic amine, and 1 - 2 parts of 2,4,6 - tris(dimethylaminomethyl)phenol.

[0045] In one preferred embodiment, the defoamer is a modified silicone or modified organofluorosilicon type, selected from one or more of BYK - 141, BYK - A530, BYK - A535, BYK - 066N.

[0046] In one preferred embodiment, the wetting and dispersing agent is a high - polymer alkyl ammonium salt type, selected from one or more of BYK - 9076, BYK - 110, BYK - W965.

[0047] Wetting and dispersing agents can improve the wetting and dispersibility of inorganic powders by organic resins, enabling the hydrophilic surface of the powders to be completely wrapped by epoxy or its diluents, thus transforming them into a hydrophobic state.

[0048] In one preferred embodiment, the leveling agent is selected from at least one of BYK-354, BYK-306, BYK-310, BYK-320, and BYK-333 to promote the flow and leveling of the slurry along the surface of the substrate.

[0049] An anti-settling agent is added to prevent the segregation and layering of heavy fillers in Component A during storage and transportation. In one preferred embodiment, the anti-settling agent is selected from at least one of modified polyethylene wax, polyamide wax, fumed silica, organic bentonite, hydrogenated castor oil, and cellulose ether. Modified polyethylene wax is preferred, and DeuRheo 202P produced by Elementis is further preferred. DeuRheo 202P does not require pre-activation and can be added at any stage of batching, basically does not increase the viscosity of the system, and has a good wax texture, which can enhance the hydrophobicity of the composition and make it not easily swollen, dissolved, or washed away by water.

[0050] In one preferred embodiment, the graphene oxide slurry is an oily paste with a graphene oxide concentration of 5-20% and has been stably dispersed.

[0051] There are no special requirements for modified sepiolite, modified silica powder, hollow glass microspheres, and mica iron oxide, but indicators such as fineness and purity should meet the selection standards of raw materials in the coating industry.

[0052] There are also no specific limitations on the preparation processes of Components A and B, and they are operated according to the normal process using conventional heavy-duty anti-corrosion coating production equipment.

[0053] The composition can be used for brushing or rolling operations above and below water, has low requirements for substrate treatment, and the thickness of a single coating film can reach 200-500 μm.

[0054] The following further explains the present invention:

[0055] Tannins, as a common class of secondary metabolites, are widely and stably sourced and are commonly present in the roots, stems, bark, leaves, and fruits of plants. Compared with other natural extracts (such as soybean oil, castor oil, rapeseed oil, etc.), they have low collection costs, and their quality is not affected by seasons and climate. They are ideal raw materials to replace petrochemical bisphenol A and bisphenol F. Their unique molecular configuration (which can be regarded as a five-armed aromatic ester) and numerous reaction sites (25 highly active phenolic hydroxyl groups) offer the possibility for synthesizing hyperbranched epoxy, curing agents, and toughening agents. However, due to the presence of large π bonds and phenolic hydroxyl groups in the tannin structure, the intermolecular forces are very strong, making it difficult to dissolve in weak (non)-polar solvents or epoxy / amine systems. Additionally, the excessive and dense benzene rings (10) also make it brittle, so it is not suitable for direct application. After being modified by the present invention, long straight aliphatic epoxy chains with multiple carbon atoms are introduced one by one at the original phenolic hydroxyl positions, significantly reducing the intermolecular forces and the density of rigid rings, enhancing the degree of freedom of chain segment movement, toughness, and hydrophobicity, and enabling it to dissolve in weak polar solvents or active diluents. In the subsequent curing stage, it can replace E-20 and E-44 resins to form a three-dimensional network with up to 625 crosslinking points (25×25) and good toughness, thereby endowing the composition with excellent density, impact resistance / medium resistance. Tests have confirmed that the dense paint film can effectively resist the intrusion of corrosive media. For example, the product ChemLINE784 of the American company APC (Advanced Polymer Coatings LLC) has 784 crosslinking degrees (28×28) and is resistant to 5000 solvents.

[0056] It should be noted that in the "two-step method" modification, first, long-chain halogenated epoxy is generated through thiol-ene click reaction, and then nucleophilic substitution occurs with the phenolic hydroxyl groups in tannins. The order cannot be reversed. Although halogenated thiols can react with phenolic hydroxyl groups first under the action of an acid-binding agent, due to the strong absorption of ultraviolet light by tannins, it is very likely to cause blackening and deterioration of tannins during the subsequent photo-initiated thiol-ene click reaction. This is probably one of the potential hidden dangers in the existing technology CN110790902B.

[0057] Interestingly, the phenolic hydroxyl groups in tannins can also rapidly chelate with Fe 2+ 、Fe 3+ ions to form a passivation layer, effectively controlling the γ-FeOOH→Fe 3 O 4 phase transformation and playing a role in stabilizing rust, enabling construction workers not to need to deeply remove rust from the metal substrate in advance. Simple grinding is sufficient (traditional heavy anti-corrosion generally requires treatment to Sa2.5 level), and even rusty painting can be directly carried out.

[0058] Research has found that the self-characteristics of graphene oxide and the oxygen-containing sites (such as carboxyl groups and hydroxyl groups) at the edges or defect sites of the six-membered rings can enhance the hardness, strength, and adhesion of the system. At the same time, the ultrathin nanosheets can shield and block corrosive media. The surface and internal micropores of modified sepiolite are also conducive to capturing and storing Cl- and SO 4 2- ions, thus better achieving the purpose of corrosion inhibition and anti-corrosion. Hollow glass microspheres have low density and good fluidity, which can increase the film thickness and improve the coating area per unit mass. And specific coupling agents can not only strengthen the adhesion, but also timely remove the moisture on the surface of the slurry and the substrate, making it in a relatively water-free state for better painting. As a commonly used underwater curing agent at present, phenolic amines mostly have low viscosity, low exotherm, high activity, and a faster curing rate compared to ketimine, and are more suitable for low-temperature environments.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] First, molecular modification of plant tannins is carried out by click chemistry and nucleophilic substitution, reducing the density of rigid benzene rings and intermolecular forces, extending the chain length of the penta-armed aromatic ester configuration (this chain segment can deeply participate in the construction of the three-dimensional network), endowing inherent toughness, strengthening the reaction activity, and obtaining a hyperbranched resin containing a dozen epoxy groups. It can not only eliminate potential compatibility problems of physically adding additional toughening agents, and theoretically can form a super-dense network with up to 625 crosslinking nodes after curing, effectively resisting the intrusion of corrosive media. In addition, the "two-step method" has mild reaction conditions, is simple and easy to operate, consumes less energy (only requires mild heating to 30 - 50 °C), and the monomers used can be purchased in the market, expanding new ideas for the alternative synthesis of petrochemical-based bisphenol (bisphenol A, bisphenol F) epoxy.

[0061] Second, each raw material is strictly selected to ensure hydrophobicity. After being combined with cardanol phenolic amine and modified phenolic amine that can cure at low temperature underwater, the composition does not dissolve (swell), diffuse, or turn white in water, and can aggregate into a mass even under strong water flow disturbance, meeting the requirements of underwater construction. The substrate can be treated with low surface treatment, and a single thick coating can reach 200 - 500 μm. For large static offshore facilities (such as power booster stations, oil and gas drilling platforms, offshore wind power / solar photovoltaic foundations, etc.) that cannot be returned to the factory or port for repair (maintenance), only slight grinding is required for painting, and 1 - 2 coatings can meet the design requirements (the conventional anti-corrosion coating has a single-film thickness of only 100 - 200 μm and requires 3 - 5 recoatings), greatly reducing the amount of offshore operations.

[0062] Third, with a reasonable combination of raw materials, the composition is solvent-free, has zero VOC emissions, does not pollute the water body where it is located, has a wide curing temperature range, does not require heating, and can form a film even below 5 °C; the coating is both dense and tough, resistant to impact and bending, and has good adhesion. Tannins, graphene oxide, modified sepiolite, mica iron oxide, etc. promote each other, and can relieve or block the erosion of H 2 O, O 2 , Cl - and SO 4 2- on the metal substrate.

[0063] In view of the above characteristics, this hyperbranched resin and its compositions can meet the requirements of various scenarios such as corrosion environments of all grades, low surface treatment, and thick underwater coatings, and can be used but not limited to the corrosion protection of inland and marine facilities and equipment. Brief Description of the Drawings

[0064] Figure 1 is the ideal configuration of the hyperbranched resin;

[0065] Figure 2 is the characteristic peak of the hyperbranched resin in infrared (FT-IR);

[0066] Figure 3 is the corrosion resistance mechanism of the crosslinked network of the hyperbranched resin;

[0067] Figure 4 is the rusty coating after low surface treatment of the substrate by the composition of Example 2;

[0068] Figure 5 are the pull-off adhesion, impact toughness, and salt spray resistance effects of the composition of Example 1;

[0069] Figure 6 is the comparison of the underwater curing ability between the composition of Example 1 and the conventional epoxy micaceous iron oxide paint. Detailed Description of the Specific Embodiments

[0070] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. On the premise of no conflict, the embodiments and the features of the embodiments in the present invention can be combined with each other.

[0071] The sample preparation and performance testing are based on "General Preparation Method for Paint Films (GB / T 1727-2021)", "Standard Test Panels for Paints and Varnishes (GB / T 9271-2008)", "Method for Determining Impact Resistance of Paint Films (GB / T 1732-2020)", "Method for Determining Flexibility of Paint Films and Putty Films (GB / T 1731-2020)", "Determination of Resistance to Neutral Salt Spray of Paints and Varnishes (GB / T 1771-2007)", "Pull-off Adhesion Test for Paints and Varnishes (GB / T 5210-2006)", "Determination of Film Hardness of Paints and Varnishes by Pencil Method (GB / T 6739-2006)", etc. The raw materials and reagents are purchased through normal commercial channels. The judgment criteria for the resistance to water, acids, alkalis, salts, and salt spray are whether the paint film blisters, cracks, peels off, or rusts after a certain period of testing.

[0072] Example 1

[0073] Synthesize hyperbranched resin 1:

[0074] S1. Weigh 0.11 mol of 1,2-epoxy-9-decene. After dissolving it in 100 mL of N,N-dimethylformamide, add 0.1 mol of 3-bromo-1-propanethiol and 2,4,6-trimethylbenzoyl diphenylphosphine oxide accounting for 1.5% of the total mass of the monomers. Continuously stir and irradiate with ultraviolet light at a wavelength of 365 nm (intensity 40 mW / cm 2 ) for 50 min under N protection. Then remove the light source. After extraction and purification, it is ready for use. 2

[0075] S2. In a reaction kettle equipped with a thermometer, a powerful stirrer, a constant pressure dropping funnel, and an N 2 protection device and containing 0.002 mol of tannin / N,N-dimethylformamide solution, slowly drop 0.1 mol of triethylamine and the pre-reactant prepared in step S1 respectively. After reacting at 45 ± 2 °C for 7 h, filter out triethylamine bromate, and then wash it 3 - 5 times with saturated NaHCO 3 aqueous solution until it is neutral. Further purify and dry to obtain a yellowish-brown highly viscous liquid.

[0076] Epoxy composition preparation process:

[0077] (1) Add 60 parts of the above hyperbranched resin 1, 23 parts of C12-14 alkyl glycidyl ether, 5 parts of glycidyl ether propyl trimethoxysilane, 1 part of BYK-A530, 2.5 parts of BYK-9076, 1 part of BYK-306, 4 parts of DeuRheo 202P, and 6 parts of graphene oxide slurry into the kettle at one time. Disperse at 800 - 1000 rpm for 15 - 30 min, and then batch add 25 parts of modified sepiolite, 50 parts of modified silica powder, 20 parts of hollow glass microspheres, and 55 parts of mica iron oxide. Disperse at a high speed of 1500 - 2000 rpm for 1 - 1.5 h (during which the temperature rise of the mixed material is controlled not to exceed 40 °C by water cooling) to obtain a paste-like component A.

[0078] (2) Stir 54 parts of cashew shell oil phenolic amine, 45 parts of modified phenolic amine, and 1 part of 2,4,6-tris(dimethylaminomethyl)phenol at 1000 - 1200 rpm for 10 - 15 min until uniform to obtain component B.

[0079] (3) During actual use, mix component A and component B at a mass ratio of 10:1 and stir at 400 - 600 rpm for 3 - 5 min until fully mixed. If the temperature is too low (≤10 °C), the mixed slurry can be left to stand and cure for 5 - 10 min before construction.

[0080] Example 2

[0081] Synthesis of hyperbranched resin 2:

[0082] ​S1. Weigh 0.105 mol of 1,2-epoxy-9-decene. After dissolving it in 100 mL of N,N-dimethylformamide, add 0.1 mol of 3-bromo-1-propanethiol and 2-hydroxy-2-methyl-1-phenyl-1-propanone accounting for 2% of the total mass of the monomers. Continuously stir and irradiate with ultraviolet light at a wavelength of 365 nm (intensity 30 mW / cm 2 ) for 1 h under N protection. Then remove the light source. After extraction and purification, it is ready for use. 2

[0083] S2. In a reaction kettle equipped with a thermometer, a powerful stirrer, a constant-pressure dropping funnel, and an N 2 protection device and containing 0.003 mol of tannin / N,N-dimethylformamide solution, slowly drop 0.1 mol of triethylamine and the pre-reacted product prepared in step S1 respectively. After reacting at 40 ± 2 °C for 8 h, filter out triethylamine bromate, and then wash it with saturated NaHCO 3 aqueous solution 3 - 5 times until neutral. Further purify and dry to obtain a yellowish-brown highly viscous liquid.

[0084] Epoxy composition preparation process:

[0085] (1) Add 65 parts of hyperbranched resin 2, 22 parts of cardanol glycidyl ether, 6 parts of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 1 part of BYK-066N, 3 parts of BYK-110, 1.5 parts of BYK-354, 5 parts of DeuRheo 202P, and 8 parts of graphene oxide slurry into the kettle at one time. Disperse at 800 - 1000 rpm for 15 - 30 min, then batch add 28 parts of modified sepiolite, 45 parts of modified silica powder, 25 parts of hollow glass microspheres, and 60 parts of mica iron oxide. Disperse at a high speed of 1500 - 2000 rpm for 1 - 1.5 h (during which water cooling is used to control the temperature of the mixed material not to exceed 40 °C) to obtain a paste-like component A.

[0086] (2) Stir 54 parts of cardanol shell oil phenolic amine, 45 parts of modified phenolic amine, and 1 part of 2,4,6-tris(dimethylaminomethyl)phenol at 1000 - 1200 rpm for 10 - 15 min until uniform to obtain component B.

[0087] (3) During actual use, mix components A and B at a mass ratio of 11:1 and stir at 400 - 600 rpm for 3 - 5 min until fully mixed. If the temperature is too low (≤10 °C), the mixed slurry can be left to stand and cure for 5 - 10 min before construction.

[0088] Comparative example 1

[0089] Replace hyperbranched resin 1 with traditional E-20 and E-44 epoxy (mass ratio 1:1) in equal amounts. The remaining materials, dosages, preparation, and usage methods of the composition are the same as those in Example 1. ​

[0090] Comparative Example 2

[0091] Except for not adding graphene oxide slurry (dosage 0 part), the other materials, dosages, preparation and usage methods of the composition are the same as those in Example 1.

[0092] Comparative Example 3

[0093] Except for not adding modified sepiolite (dosage 0 part), the other materials, dosages, preparation and usage methods of the composition are the same as those in Example 2.

[0094] The performances of the epoxy compositions in Examples 1-2 and Comparative Examples 1-3 are shown in Table 1 below.

[0095] Table 1. Comprehensive performances of the epoxy compositions in the examples and comparative examples

[0096]

[0097]

[0098] After detection, 1 in the 1H NMR spectrum, the hydrogen peak originally attributed to the tannin phenolic hydroxyl group at the chemical shift δ = 9.3 - 10 ppm is greatly weakened, and the epoxy peak at 2.8 - 3.0 ppm, the ether bond peak at 3.8 - 3.9 ppm, and the methylene proton signal adjacent to the S atom at 2.2 - 2.6 ppm are enhanced. In the FT-IR spectrum ( Figure 2 ), the hydroxyl absorption peak at 3300 - 3500 cm -1 is significantly weakened. At the same time, new methylene absorption peaks appear near 2841 cm -1 and 2936 cm -1 . Epoxy peaks appear at 910 cm -1 , 1083 cm -1 , and 1250 cm -1 . The dual characterizations show that the thiol-ene click and nucleophilic substitution are successful. There are nearly 19 epoxy groups in one molecule of the hyperbranched resin 1, which means that the grafting rate of phenolic hydroxyl groups exceeds 75% (19 / 25); due to the difference in monomer dosage, the number of epoxy groups in resin 2 is slightly less (about 12), and the three-dimensional network crosslinking density is lower than that of the former, resulting in slightly lower water / acid / alkali / salt water / salt spray resistance of the film layer, but still far exceeding Comparative Example 1 and Chinese Patent Applications CN1752162A and CN101492586A, and the decrease in underwater adhesion is slight compared to the dry state (verified by synchronous experiments). Among them, the residual and incompletely etherified phenolic hydroxyl groups (6 - 13) can also promote crosslinking, and the film-forming temperature of Examples 1-2 and related Comparative Examples 2-3 is as low as 3 °C. In fact, the bifunctional E-44 and E-20 epoxies can only form 4 crosslinking points (2×2), with a large grid spacing and poor compactness, resulting in unreliable underwater bonding and being easily invaded and penetrated by corrosive media ( Figure 3a), and the highly cross-linked (19×19) hyperbranched resin makes the mesh pores smaller, which can well shield the penetration of H 2 O, O 2 , Cl - , SO 4 2- etc. ([[]] Figure 3 b), after 5400h of neutral salt spray resistance in Example 1, the unilateral corrosion expansion at the scratched part is less than 1mm ([[]] Figure 5 c). At the same time, due to the incorporation of C13 fatty long chains ([[]] Figure 1 ), the original brittleness of tannin is improved. The hyperbranched resin has excellent toughness. The impact strength ([[]] Figure 5 b) and bendability of Examples 1 and 2 are better than those of Comparative Example 1 (Table 1).

[0099] In addition, relying on the chelating and rust-stabilizing effect of the residual hydroxyl groups in tannin, Examples 1 and 2 and Comparative Examples 2 and 3 only need low surface treatment (Sa2.0 Vs. Sa2.5) of the substrate before construction, and can even be directly painted over rust ([[]] Figure 4 ). The 500μm high film thickness also reduces the construction amount, bringing great convenience to offshore operations (the single coating of Comparative Example 1 is only 100 - 150μm, and it is easy to sag when too thick).

[0100] The application of graphene oxide improves the bonding strength ([[]] Figure 5 a) and hardness of the system, and can also shield and block corrosive media with ultra-thin two-dimensional sheets. The relevant indicators of Comparative Example 2 are inferior to those of Example 1.

[0101] The micropores and electrostatic action of modified sepiolite adsorb and store SO 4 2- , Cl - ions. After canceling the addition, the acid resistance, NaCl brine resistance and Cl - penetration resistance of Comparative Example 3 are inferior to those of Example 2.

[0102] Figure 6 This is a comparison of the underwater curing ability between the composition of Example 1 and conventional epoxy micaceous iron oxide paint. Example 1 contains a variety of highly hydrophobic components such as C12 - 14 alkyl glycidyl ether, glycidyl ether propyl trimethoxysilane, graphene oxide, DeuRheo202P, cashew shell oil phenolic amine, and modified phenolic amine suitable for underwater construction. It still shows its original color in water, does not dissolve and has no precipitation, and the water quality is clear and transparent ([[]] Figure 6 a), can be cured at room temperature for 12h, and firmly adheres to the glass dish. Even if the bottom of the dish is broken, it is difficult to peel off the adhesive layer ([[]] Figure 6b). Conventional epoxy micaceous iron paint uses ordinary E-44 and E-20 resins, which are mixed with talcum powder, titanium dioxide, micaceous iron oxide, polyamide, etc., and are generally diluted with solvents such as xylene and n-butanol. It is generally only used in dry occasions; the curing agent turns white and floats on the water surface when it encounters water, and hydrophilic materials dissolve out. Figure 6 c), After 12 hours, the adhesive layer is still slightly sticky, has low adhesion to the bottom of the dish, and is easy to remove. Figure 6 d).

[0103] However, it should be pointed out that the above performances are the overall manifestation of the synergistic gain of each component in the composition, and are closely related to factors such as the coating density and flow thixotropy. For example, even if sepiolite is not added, the acid / saline / Cl - penetration / salt spray resistance of Comparative Example 3 is still better than that of Comparative Example 1; Comparative Example 1 also contains hollow glass microspheres, but the single-layer film thickness is much lower than that of other cases.

[0104] The present invention also tried the following possible solutions:

[0105] 1. If hyperbranched resin 1 is not synthesized in advance, only the monomers, acid-binding agents, solvents, and photoinitiators used in preparation steps S1 and S2 are simply mixed according to the original addition ratio, and an equal mass is used to replace hyperbranched resin 1 and added to the epoxy composition. The remaining materials, dosages, preparation, and usage methods of the composition are the same as those in Example 1. Experiments found that: due to the strong polarity of tannin, it needs to be dissolved in N,N-dimethylformamide before it can be incorporated into the composition system, but the presence of the solvent is not conducive to the underwater construction of the latter (polluting the water body). Under daily sunlight and room temperature, thiol-ene click and nucleophilic substitution hardly occur, and most of the phenolic hydroxyl groups in tannin cannot be successfully etherified, resulting in the coating still being sticky after several days, with low crosslinking degree and brittle film quality, and the impact strength is only 25 cm.kg -1 、The flexibility is greater than 5 mm, and the pull-off adhesion is less than 2 MPa, and it is no longer suitable for corrosion protection.

[0106] 2. If 3-bromo-1-propanethiol is not added in step S1, the thiol-ene click cannot proceed. In the subsequent step S2, due to the low temperature (30-50 °C), it is difficult for the phenolic hydroxyl groups in tannin to promote the ring-opening of 1,2-epoxy-9-decene; in addition, 1,2-epoxy-9-decene only has an epoxy group at one end and cannot crosslink with the B-component curing agent to form a network, and the short molecular chains formed are not enough to support the necessary mechanical strength and density required for the anti-corrosion paint film.

[0107] 3. If 1,2-epoxy-9-decene is not added in step S1, the thiol-ene click cannot proceed either. Although 3-bromo-1-propanethiol can still undergo nucleophilic substitution with tannin, the modified tannin only increases the carbon chain length by 3, and the density of the rigid benzene ring is not substantially reduced, and the toughness is limited. More seriously, the composition lacks a macromolecular film-forming resin (this modified tannin does not contain epoxy groups), so it cannot form a film.

[0108] In summary, through the green modification of plant tannins, a hyperbranched multi-functional toughening resin is obtained, providing a feasible reference for the alternative synthesis of petrochemical-based epoxy resins. After being combined with components such as graphene oxide, specific coupling agents, and cashew shell oil phenolic amines, it can be used for low surface treatment, thick coating with rust, and underwater curing, and can meet the protection requirements in various corrosion environments such as inland and marine areas.

[0109] The content clarified in the above embodiments should be understood that these embodiments are only used to more clearly interpret the present invention, rather than limiting the scope of the present invention. After referring to the present invention, various equivalent forms of modification made by those skilled in the art inspired by this fall within the protection scope defined by the appended claims of the present invention.

Claims

1. A hyperbranched resin, characterized in that its general structural formula is as follows: In the formula, m is a positive integer of 2 or more, and n is any positive integer; the sum of m and n does not exceed 16; The preparation method of the hyperbranched resin comprises the following steps: S1, α,ω-terminal olefin / epoxy alkylene and halogenated thiol are subjected to thiol-ene click chemistry to synthesize long-chain halogenated epoxy pre-reactant; S2, nucleophilic substitution of the phenolic hydroxyl groups in the tannin by the long-chain halogenated epoxy pre-reactant to obtain the hyperbranched resin; The α,ω-terminal olefin / epoxy alkane is at least one of 1,2-epoxy-7-octene and 1,2-epoxy-9-decene.

2. The method for preparing a hyperbranched resin according to claim 1, wherein The following steps are involved: S1, α,ω-terminal olefin / epoxy alkylene and halogenated thiol are subjected to thiol-ene click chemistry to synthesize long-chain halogenated epoxy pre-reactant; S2, the long-chain halogenated epoxy pre-reactant nucleophilically replaces the phenolic hydroxyl groups in the tannin to obtain the hyperbranched resin.

3. The preparation method according to claim 2, characterized in that: The molar amounts of α,ω-terminal olefin / alkylene oxide and halogenated mercaptan are both 32.5 to 50 times of that of tannin, and the molar ratio n(α,ω-terminal olefin / alkylene oxide):n(halogenated mercaptan)=(1 to 1.1):

1.

4. The preparation method according to claim 2, characterized in that: The halogenated mercaptan is selected from one or more of chlorothiol, bromothiol and iodothiol.

5. The preparation method according to claim 2, characterized in that: The thiol-ene click chemistry is achieved by Michael addition, photoradical reaction or thermal radical reaction.

6. The preparation method according to claim 5, characterized in that: The photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxy-cyclohexyl-benzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether and their derivatives; the ultraviolet irradiation intensity of the mercapto-ene click chemistry is 10 to 100 mW / cm 2 , irradiation time 0.5~2h.

7. The preparation method according to any one of claims 2 to 6, characterized in that: In the nucleophilic substitution, the reaction temperature is 30-50° C. and the reaction time is 3-8 hours.

8. An underwater curable epoxy composition, characterized in that: The invention comprises two components, A and B. By weight, the component A comprises 50 to 65 parts of the hyperbranched resin as claimed in claim 1, 20 to 25 parts of an active diluent, 3 to 7 parts of a coupling agent, and 130 to 200 parts of an auxiliary agent and a filler, and the component B comprises 81 to 112 parts of a curing agent. When used, the components A and B are mixed in a mass ratio of (10 to 11):

1.

9. The underwater curable epoxy composition according to claim 8, characterized in that: The curing agent comprises 40-60 parts of cashew nut shell oil phenol aldehyde amine, 40-50 parts of modified phenol aldehyde amine and 1-2 parts of 2,4,6-tris(dimethylaminomethyl)phenol.

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