Hyperbranched resin as well as preparation method and application thereof

Abstract

The invention belongs to the field of coating materials, and relates to hyperbranched resin and a preparation method thereof, and application of the hyperbranched resin in preparation of an underwater curable epoxy composition. In the general structural formula of the hyperbranched resin # imgabs0 #, m is a positive integer of 2 or more, and n is any positive integer. According to the invention, molecular modification is carried out on vegetable tannin by utilizing click chemistry and nucleophilic substitution, intrinsic toughness is endowed, and hyperbranched resin containing dozens of epoxy groups is obtained. According to the present invention, the potential compatibility problem of the external toughening agent can be eradicated, and the ultra-dense network having 625 cross-linking nodes can be formed theoretically after the curing so as to provide the excellent medium resistance of the composition; the hyperbranched resin and the composition thereof are suitable for various-grade corrosion environments, low surface treatment, underwater thick coating and other scene requirements, and can be used for corrosion protection of inland and ocean 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 a preparation method thereof, which uses phenolic amine + ketimine as a curing agent to achieve underwater construction with low surface treatment. However, since the ordinary E-51 and E-44 systems are still used, the paint film has poor flexibility (1 to 2 mm), impact resistance (50 kg.cm), adhesion (grade 1 to 2), and chemical resistance (20% H2SO4, 20% NaOH, 3% NaCl for 21 days each without blistering or falling off).

[0004] Similarly, Chinese patent application CN101492586A discloses a solvent-free epoxy heavy anticorrosive coating with low surface treatment and underwater coating, which is the 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. 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% H2SO4 / 10% NaOH / 3% NaCl for 7 days without cracking, bubbling, or falling off).

[0005] Chinese patent CN107603423B discloses an underwater curing marine steel structure long-term anticorrosive coating and its preparation method, which is composed of component A and component B with a weight ratio of 1.5:1 to 3:1. The composition and weight of component A are: 20-50 parts of phenolic modified epoxy resin, 3-8 parts of active diluent, 25-55 parts of filler, 0.2-1 part of thixotropic agent, 0.3-1 part of wetting dispersant, 0.3-0.8 part of defoamer and 0.3-1 part of coupling agent; the composition and weight of component B are: 20-70 parts of curing agent I and 30-80 parts of curing agent II. The adhesion exceeds 14MPa and the medium resistance is good. Unfortunately, the large number of rigid aromatic rings and high cross-linking density in phenolic epoxy are likely to weaken the toughness of the coating while increasing the hardness and wear resistance.

[0006] In order to improve the brittleness of epoxy cured network and make it both rigid and flexible, technicians often add liquid rubber (polyether, polysulfide, nitrile), core-shell macromolecules, hyperbranched polymers, nanoparticles, thermoplastic resins, liquid crystals, or promote the formation of IPN and Semi-IPN interpenetration. For example, Chinese patent applications CN108192471A, CN102719174A, and CN108250910A all use polysulfide rubber for toughening, but it has a foul odor, and the "sea-island" structure distributed in the network is also prone to induce severe interface phase separation.

[0007] In terms of green synthesis, Chinese patent application CN110256655A discloses a tannic acid-based multifunctional epoxy resin, which is obtained by allylating tannic acid and then promoting partial epoxidation of olefin bonds. It has at least two defects: 1. Peroxides are flammable and explosive, and have high safety risks; 2. The sodium hydroxide and potassium hydroxide used are highly alkaline, which can easily cause tannic acid to directly crystallize into salts.

[0008] Chinese patent CN110790902B provides a tannic acid curing agent and its preparation method. The inventor introduced the long fatty chain of 10-undecenoyl chloride into tannic acid, and then linked the terminal carboxyl or alcohol sulfide under ultraviolet light. The benzene ring structure contained in the curing agent can increase the rigidity of the epoxy coating, and the long undecenyl fatty chain participates in the curing reaction, which increases the activity of the network chain segment and greatly improves the toughness of the epoxy resin. However, the curing process is relatively cumbersome and requires three-stage progressive temperature rise. Summary of the invention

[0009] The present invention aims to provide a hyperbranched resin and a preparation method thereof, and use thereof in preparing an underwater curable epoxy composition. The hyperbranched resin is based on tannin, has good toughness after modification, and can deeply participate in system cross-linking; the prepared underwater curable epoxy composition has low requirements for substrate surface treatment, can be coated with rust, and can reach a film thickness of hundreds of microns in one coating.

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

[0011] A hyperbranched resin having the general structural formula

[0012]

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

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

[0015] m and n have independent values, but their sum should not exceed 16. In order to improve the toughness of tannin, the number of carbon atoms in the grafted chain should be as large as possible, but if the chain segment is too long, the reaction may become more difficult due to steric hindrance.

[0016] The present invention also claims a method for preparing the hyperbranched resin, comprising the following steps (two-step method):

[0017] 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;

[0018] S2, nucleophilic substitution of the phenolic hydroxyl groups in the tannin by the long-chain halogenated epoxy pre-reactant to obtain the hyperbranched resin;

[0019] The α,ω-terminal olefin / epoxy alkane is a linear straight chain containing not less than 8 carbon atoms, with one end of the molecule being an olefin group and the other end being an epoxy group.

[0020] In one preferred embodiment, the monomer molar ratio n(tannin):n(α,ω-terminal olefin / alkylene oxide):n(halogenated mercaptan)=1:(32.5-50):(32.5-50), n(α,ω-terminal olefin / alkylene oxide):n(halogenated mercaptan)=(1-1.1):1. The amount of α,ω-terminal olefin / alkylene oxide and halogenated mercaptan is 32.5-50 times that of tannin. If it is too low, it is difficult to fully replace tannin, and if it is too high, it is ineffective.

[0021] In one preferred embodiment, the α,ω-terminal olefin / alkylene oxide contains 8 to 12 carbon atoms.

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

[0023] If the α,ω-terminal olefin / alkylene oxide chain segment is too long or contains side branches, it may be difficult to completely replace the phenolic hydroxyl group due to the steric hindrance caused by its own volume with the benzene ring or (and) adjacent functional groups; if the chain segment is too short, it will not be enough to effectively reduce the rigid ring density in the tannin, affecting the toughening effect.

[0024] In a preferred embodiment, the halogenated mercaptan is selected from one or more of chlorothiol, bromothiol, and iodothiol. Bromothiol is preferred in consideration of reagent price, reaction activity, conversion yield, etc.

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

[0026] In one preferred embodiment, the thiol-ene click chemistry is achieved by Michael addition or photo (thermal) free radical reaction. Since the electron-withdrawing ability of the α,ω-terminal olefin / epoxy alkane is limited, Michael addition is difficult, so light or thermal free radical initiation is preferred, and light free radical initiation is further preferred. The light free radical initiation reaction conditions are mild (no heating is required), the controllability is good (the reaction stops immediately when the light source is removed), the conversion rate is high, and basically no by-products are produced.

[0027] In one preferred embodiment, the photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxy-cyclohexyl-benzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzoin dimethyl ether and derivatives thereof, preferably one or a combination of ethyl 2,4,6-trimethylbenzoylphenylphosphonate and 2-hydroxy-2-methyl-1-phenyl-1-propanone with good solubility.

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

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

[0030] In one preferred embodiment, a solvent is further added in the synthesis steps S1 and S2 to facilitate the dissolution of the tannin and the smooth reaction; the solvents used in the 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, preferably N,N-dimethylformamide which is universally soluble.

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

[0033] In one preferred embodiment, an acid binder is added in the nucleophilic substitution reaction, and the molar ratio of the acid binder to the tannin is (32.5-50): 1. Due to the presence of the acid binder, the nucleophilic substitution can be carried out with only slight heating, thus avoiding the problem of excessive byproducts induced by excessive 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. In order to avoid sodium hydroxide, potassium hydroxide, potassium carbonate, and tetramethylammonium hydroxide being too alkaline, they are directly neutralized with the acidic tannin to form salts, and triethylamine, which is slightly weaker in alkalinity and moderate in price, is preferred.

[0035] Based on the same concept, the present invention also claims to protect the use of the hyperbranched resin in preparing an underwater curable epoxy composition.

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

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

[0038] When using, mix A and B in a mass ratio of (10-11):1 and stir thoroughly.

[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, preferably at least one of C12-14 alkyl glycidyl ether or cardanol glycidyl ether having excellent hydrophobicity and flexibility.

[0040] By using active diluents instead of organic solvents, high-solid content, solvent-free compositions can be prepared to avoid water pollution caused by solvent precipitation during underwater construction.

[0041] In one preferred embodiment, the coupling agent is selected from one or more of glycidyl ether (ester) propyl trimethoxy silicon, glycidyl ether (ester) propyl triethoxy silicon, glycidyl ether (ester) propyl tripropoxy silicon, 2-(3,4-epoxycyclohexyl) ethyl trimethoxy silicon, 2-(3,4-epoxycyclohexyl) ethyl triethoxy silicon, 2-(3,4-epoxycyclohexyl) ethyl tripropoxy silicon, titanate, aluminate, zirconate, preferably at least one of glycidyl ether propyl trimethoxy silicon and 2-(3,4-epoxycyclohexyl) ethyl trimethoxy silicon. Compared with ester bond compounds, ether bonds are more flexible and more resistant to alkaline hydrolysis.

[0042] Glycidyl ether propyl trimethoxysilane and 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane have low viscosity and good compatibility with the system. While promoting adhesion, methoxysilane can react with water faster and more easily than ethyl (propyl) silicone (methanol is easier to remove than ethanol and propanol), thereby removing moisture from the surface of the composition more timely and efficiently, blocking water vapor from penetrating deep into the inner layer. Practice has shown that under the same dosage, the water removal rate of glycidyl ether propyl trimethoxysilane is 0.4 to 1 times faster than that of glycidyl ether propyl triethoxysilane, which can transform the wet surface into a hydrophobic state in the shortest possible time. Similarly, there is a similar rule between 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane and 2-(3,4-epoxycyclohexyl) ethyl triethoxysilane.

[0043] In one preferred embodiment, the additives and fillers include 0.5-1.5 parts of defoaming agent, 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 mica iron oxide.

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

[0045] In one preferred embodiment, the defoaming agent is modified organic silicon or modified organic fluorosilicone, selected from one or more of BYK-141, BYK-A530, BYK-A535, and BYK-066N.

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

[0047] Wetting and dispersing agents can improve the wetting and dispersibility of organic resins on inorganic powders, so that the hydrophilic surface of the powder is completely coated by epoxy or its diluent, thereby converting it 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] The anti-settling agent is added to prevent the high specific gravity filler in component A from segregating and stratifying 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, preferably modified polyethylene wax, and more preferably DeuRheo 202P produced by Hemmings. DeuRheo 202P does not require pre-activation and can be added at any stage of batching. It basically does not increase the viscosity of the system, and has a good wax texture, which can improve the hydrophobicity of the composition and make it difficult to be swollen, dissolved or dispersed by water.

[0050] In one preferred embodiment, the graphene oxide slurry is an oily paste with a graphene oxide concentration of 5 to 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 comply with the coatings industry's selection standards for raw materials.

[0052] There is no special limitation on the preparation process of components A and B, and conventional heavy-duty anti-corrosion coating production equipment is used according to normal procedures.

[0053] The composition can be applied by brush or roller above or below water, has low requirements on substrate treatment, and the thickness of the coating can reach 200 to 500 μm at one time.

[0054] The present invention will be further explained below:

[0055] Tannins are a common secondary metabolite with a wide range of stable sources. They are commonly found in the roots, stems, skins, leaves and fruits of plants. Compared with other natural extracts (such as soybean oil, castor oil, rapeseed oil, etc.), tannins 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-arm aromatic ester) and numerous reaction sites (25 highly active phenolic hydroxyl groups) provide the possibility for the synthesis of hyperbranched epoxies, 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. In addition, the excessive and dense benzene rings (10) also make it hard and brittle, making it unsuitable for direct application. After the modification of the present invention, a fatty long straight epoxy chain with a large number of carbon atoms is introduced one by one at the original phenolic hydroxyl position, which significantly reduces the intermolecular force and rigid ring density, improves the freedom of movement of the chain links, toughness and hydrophobicity, and enables it to be dissolved 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 cross-linking points (25×25) and good toughness, so that the composition has excellent density and impact resistance / medium resistance. Testing has confirmed that dense paint films can effectively resist the invasion of corrosive media. For example, ChemLINE784, a product of Advanced Polymer Coatings LLC (APC), has 784 cross-linking degrees (28×28) and is resistant to 5,000 solvents.

[0056] It should be noted that in the "two-step method" modification, firstly, a long-chain halogenated epoxy is generated through mercapto-ene click reaction, and then the phenolic hydroxyl in the tannin is nucleophilically replaced. The order cannot be reversed. Although the halogenated mercaptan can react with the phenolic hydroxyl in the presence of an acid binder, the tannin strongly absorbs ultraviolet rays, and the subsequent light-induced mercapto-ene click reaction is likely to cause the tannin to blacken and deteriorate. This is also one of the potential risks of the prior art CN110790902B.

[0057] Interestingly, the phenolic hydroxyl groups in tannins can also react with Fe 2+ , Fe 3+ The ions quickly chelate to form a passivation layer, effectively controlling the γ-FeOOH→Fe3O4 crystal phase transformation and stabilizing the rust. This means that construction workers do not need to deeply remove rust from the metal substrate in advance, and can simply polish it (traditional heavy corrosion protection generally requires treatment to Sa2.5 level), and can even be painted directly with rust.

[0058] The study found that the characteristics of graphene oxide itself and the oxygen-containing sites (such as carboxyl and hydroxyl groups) at the edges or defective parts of the six-membered ring can improve the hardness, strength and adhesion of the system. At the same time, the ultra-thin nanosheet layer can shield and block the corrosive medium. The surface and internal micropores of the modified sepiolite are also conducive to capturing and storing Cl - 、SO4 2-ions, thereby better playing the role of corrosion inhibition and anti-corrosion. Hollow glass microspheres are light in density and good in fluidity, which can increase film thickness and increase the coating area per unit mass. Specific coupling agents can not only strengthen adhesion, but also promptly remove moisture from the slurry and substrate surface, making it relatively water-free for coating. As a commonly used underwater curing agent, phenalkamines mostly have low viscosity, low heat release, high activity, and a faster curing rate than ketimines, making them more suitable for low temperature environments.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] First, the molecular transformation of plant tannins was carried out by using click chemistry and nucleophilic substitution, which reduced the density and intermolecular force of the rigid benzene ring, extended the length of the chain segment of the five-arm aromatic ester configuration (the chain segment can deeply participate in the construction of the three-dimensional network), endowed with intrinsic toughness, enhanced the reaction activity, and obtained a hyperbranched resin containing more than a dozen epoxy groups. It can not only eliminate the potential compatibility problems of additional physical toughening agents, but also theoretically form an ultra-dense network with up to 625 cross-linked nodes after curing, effectively resisting the invasion of corrosive media. In addition, the "two-step method" has mild reaction conditions, is simple and easy to operate, consumes less energy (only slightly heated to 30-50°C), and the monomers used can be purchased on the market, which has expanded new ideas for the alternative synthesis of petrochemical bisphenol (bisphenol A, bisphenol F) epoxides.

[0061] Second, each raw material is strictly selected to ensure hydrophobicity. After being combined with cashew shell oil phenolic amine and modified phenolic amine that can be cured underwater at low temperature, the composition does not dissolve (swell), spread, or turn white in water. Even if it is disturbed by strong water flow, it can be aggregated into groups to meet the requirements of underwater construction. The substrate can be low-surface treated and coated with a thickness of 200 to 500 μm at a time. For large static marine facilities that cannot be returned to the factory or port for repair (maintenance) (such as power booster stations, oil and gas drilling platforms, offshore wind power / photovoltaic foundations, etc.), slight grinding can be used for coating. 1 to 2 coatings can meet the design requirements (the film thickness of conventional anti-corrosion coatings is only 100 to 200 μm at a time, and 3 to 5 recoatings are required), which greatly reduces the amount of offshore operations.

[0062] 3. With reasonable raw material matching, the composite material is solvent-free, has zero VOC emissions, does not pollute the water body, has a wide curing temperature range, does not require heating, and can form a film below 5°C; the coating is dense and tough, impact-resistant and bend-resistant, and has good adhesion. Tannin, graphene oxide, modified sepiolite, mica iron oxide, etc. promote each other and can alleviate or block H2O, O2, Cl - 、SO4 2- Etc. corrosion of metal substrates.

[0063] In view of the above characteristics, this hyperbranched resin and its composition are suitable for various scenarios such as various levels of corrosion environments, low surface treatment, underwater thick coating, etc., and can be used for but not limited to corrosion protection of inland and marine facilities and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0066] Figure 3 The corrosion resistance mechanism of the cross-linked network of hyperbranched resin;

[0067] Figure 4 Rust coating after low surface treatment of substrate with the composition of Example 2;

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

[0069] Figure 6 The underwater curing ability of the composition of Example 1 is compared with that of conventional epoxy iron oxide paint. DETAILED DESCRIPTION

[0070] The present invention is described in detail below with reference to the accompanying drawings and in combination with embodiments. The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

[0071] Sample preparation and performance testing are based on "General Preparation Method for Paint Film (GB / T 1727-2021)", "Standard Test Plate for Paint and Varnish (GB / T 9271-2008)", "Determination of Impact Resistance of Paint Film (GB / T 1732-2020)", "Determination of Flexibility of Paint and Putty Film (GB / T 1731-2020)", "Determination of Neutral Salt Spray Resistance of Paint and Varnish (GB / T 1771-2007)", "Adhesion Test of Paint and Varnish by Pull-off Method (GB / T 5210-2006)", "Determination of Film Hardness by Pencil Method for Paint and Varnish (GB / T 6739-2006)", etc. Raw materials and reagents are purchased through normal commercial channels. The criteria for judging the ability to resist water, acid, alkali, salt and salt spray are whether the coating film is bubbling, cracking, falling off or rusting after a period of testing.

[0072] Example 1

[0073] Synthesis of hyperbranched resin 1:

[0074] S1. Weigh 0.11 mol of 1,2-epoxy-9-decene, dissolve it in 100 mL of N,N-dimethylformamide, add 0.1 mol of 3-bromo-1-propanethiol and 1.5% of the total weight of the monomers, and continue stirring while irradiating with 365 nm ultraviolet light (intensity 40 mW / cm 2) After 50 minutes, remove the light source and set aside for extraction and purification.

[0075] S2. In a reaction kettle equipped with a thermometer, a powerful stirrer, a constant pressure dropping funnel, a N2 protection device and containing 0.002 mol tannin / N,N-dimethylformamide solution, slowly drop 0.1 mol triethylamine and the pre-reactant prepared in step S1 respectively. After reacting at 45±2°C for 7 hours, filter out triethylamine bromate, and then wash with saturated NaHCO3 aqueous solution 3 to 5 times until neutral. Further purify and dry to obtain a yellow-brown highly viscous liquid.

[0076] Epoxy composition preparation process:

[0077] (1) 60 parts of the above-mentioned 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 are added into a material kettle at one time, and dispersed at 800-1000 rpm for 15-30 min. Then, 25 parts of modified sepiolite, 50 parts of modified silica powder, 20 parts of hollow glass microspheres, and 55 parts of mica iron oxide are added in batches, and dispersed at a high speed of 1500-2000 rpm for 1-1.5 h (during which the heating temperature of the mixed material is controlled to be no higher than 40° C. by water cooling), to obtain a paste-like component A.

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

[0079] (3) In actual use, components A and B are mixed at a mass ratio of 10:1 at 400-600 rpm for 3-5 minutes to be fully mixed. If the temperature is too low (≤10°C), the mixed slurry can be left to mature for 5-10 minutes before construction.

[0080] Example 2

[0081] Synthesis of hyperbranched resin 2:

[0082] S1. Weigh 0.105 mol of 1,2-epoxy-9-decene, dissolve it in 100 mL of N,N-dimethylformamide, add 0.1 mol of 3-bromo-1-propanethiol and 2% of the total weight of 2-hydroxy-2-methyl-1-phenyl-1-propanone, continue stirring and irradiate with 365 nm ultraviolet light (intensity 30 mW / cm 2 ) After 1 hour, remove the light source and set aside for use after extraction and purification.

[0083] S2. In a reaction kettle equipped with a thermometer, a powerful stirrer, a constant pressure dropping funnel, a N2 protection device and containing 0.003 mol tannin / N,N-dimethylformamide solution, slowly drop 0.1 mol triethylamine and the pre-reactant prepared in step S1 respectively. After reacting at 40±2°C for 8 h, filter out triethylamine bromate, then wash with saturated NaHCO3 aqueous solution 3 to 5 times until neutral, further purify and dry to obtain a yellow-brown highly viscous liquid.

[0084] Epoxy composition preparation process:

[0085] (1) 65 parts of the above-mentioned hyperbranched resin 2, 22 parts of cardanol glycidyl ether, 6 parts of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 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 were added into a material kettle at one time, and dispersed at 800-1000 rpm for 15-30 min. Then, 28 parts of modified sepiolite, 45 parts of modified silica powder, 25 parts of hollow glass microspheres, and 60 parts of mica iron oxide were added in batches, and dispersed at a high speed of 1500-2000 rpm for 1-1.5 h (during which the mixed material was cooled by water to control the heating temperature of the mixed material to be no higher than 40° C.), to obtain a paste-like component A.

[0086] (2) 54 parts of cashew nut oil phenol amine, 45 parts of modified phenol amine, and 1 part of 2,4,6-tris(dimethylaminomethyl)phenol were stirred at 1000-1200 rpm for 10-15 minutes until they were uniform, to obtain component B.

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

[0088] Comparative Example 1

[0089] The hyperbranched resin 1 was replaced by equal amounts of conventional E-20 and E-44 epoxy (mass ratio 1:1). The remaining materials, dosage, formulation and use method of the composition were the same as those in Example 1.

[0090] Comparative Example 2

[0091] Except that no graphene oxide slurry was added (0 part added), the remaining materials, dosage, preparation and use method of the composition were the same as those in Example 1.

[0092] Comparative Example 3

[0093] Except that no modified sepiolite was added (0 part), the other materials, dosage, preparation and use method of the composition were the same as those in Example 2.

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

[0095] Table 1. Comprehensive properties of epoxy compositions of Examples and Comparative Examples

[0096]

[0097]

[0098] After testing, 1 In the H NMR spectrum, the hydrogen peak at the shift of δ = 9.3-10 ppm, which was originally attributed to the phenolic hydroxyl group of the tannin, was greatly weakened, and the epoxy peak at 2.8-3.0 ppm, the ether bond at 3.8-3.9 ppm, and the methylene proton signal adjacent to the S atom at 2.2-2.6 ppm were enhanced. FT-IR spectrum ( Figure 2 ) 3300~3500cm -1 The hydroxyl absorption peak at 2841cm -1 、2936cm -1 A new methylene absorption peak is added nearby, 910cm -1 、1083cm -1 、1250cm -1 Epoxy peaks appear at , and dual characterization shows that thiol-ene click and nucleophilic substitution are successful. Hyperbranched resin 1 has nearly 19 epoxy groups in the molecule, which means that the phenolic hydroxyl grafting rate 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 cross-linking density is not as good as the former, resulting in slightly lower water / acid / alkali / salt water / salt spray resistance of the film layer, but it is still far superior to comparative example 1 and Chinese patent applications CN1752162A and CN101492586A, and the underwater adhesion decreases slightly relative to the dry state (confirmed by synchronous experiments). Among them, the residual, incompletely etherified phenolic hydroxyl groups (6 to 13) can also promote cross-linking, and the film-forming temperature of Examples 1 to 2 and related comparative examples 2 to 3 is as low as 3°C. In fact, the bifunctionality of E-44 and E-20 epoxy can only form 4 cross-linking points (2×2), with large grid spacing, poor density, unreliable underwater bonding, and easy to be invaded and penetrated by corrosive media ( Figure 3 a), while the high cross-linking (19×19) of the hyperbranched resin makes the mesh smaller, which can effectively shield H2O, O2, Cl - 、SO4 2- The penetration of Figure 3 b), after 5400h of neutral salt spray, the unilateral corrosion expansion of the scratch is less than 1mm ( Figure 5 c). At the same time, thanks to the addition of C13 fatty long chains ( Figure 1 ), the original brittleness of tannin is improved, and the hyperbranched resin has excellent toughness. The impact strength of Examples 1 and 2 ( Figure 5b) The bendability is better than that of Comparative Example 1 (Table 1).

[0099] In addition, relying on the chelating and stabilizing effect of the residual hydroxyl groups in the tannin, the substrates of Examples 1 and 2 and Comparative Examples 2 and 3 only need to be subjected to low surface treatment (Sa2.0 vs. Sa2.5) before construction, and can even be directly coated with rust ( Figure 4 ), the high film thickness of 500μm also reduces the construction workload, bringing great convenience to marine operations (Comparative Example 1 only coats 100-150μm at a time, and it is easy to sag if it is too thick).

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

[0101] The micropores and electrostatic effect of modified sepiolite adsorb and store SO4 2- , Cl - ions, after removing the doping, comparative example 3 is acid-resistant, NaCl-resistant, and Cl-resistant - The penetration is not as good as Example 2.

[0102] Figure 6 The underwater curing ability of the composition of Example 1 is compared with that of conventional epoxy iron oxide paint. Example 1 contains a variety of highly hydrophobic components suitable for underwater construction, such as C12-14 alkyl glycidyl ether, glycidyl ether propyl trimethoxysilane, graphene oxide, DeuRheo202P, cashew shell oil phenol amine, modified phenol amine, etc., which still shows the original color in water, does not dissolve, does not precipitate, and the water quality is clear and transparent ( Figure 6 a), it can be cured at room temperature for 12 hours, and it is firmly bonded to the glass dish. Even if the bottom of the dish is broken, it is difficult to peel off the adhesive layer ( Figure 6 b). Conventional epoxy micaceous iron paint uses common E-44 and E-20 resins with talcum powder, titanium dioxide, micaceous iron oxide, polyamide, etc., and is mostly diluted with solvents such as xylene and n-butanol. It is generally only used in dry occasions; the curing agent turns white when it comes into contact with water and floats on the water surface, and the hydrophilic material dissolves ( 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 properties are the overall performance of the synergistic benefits of each component in the composition, and are closely related to factors such as coating density and flow thixotropy. - The penetration / salt spray ability is still better than that of Comparative Example 1; Comparative Example 1 also contains hollow glass microspheres, but the thickness of the film formed at one time is much lower than that of other cases.

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

[0105] 1. If the hyperbranched resin 1 is not synthesized in advance, the monomers, acid binders, solvents and photoinitiators used in the preparation steps S1 and S2 are simply mixed according to the original addition ratio, and the same mass is added to the epoxy composition instead of the hyperbranched resin 1. The remaining materials, dosage, preparation and use methods of the composition are the same as those in Example 1. Experiments have found that due to the strong polarity of tannin, it must be dissolved in N,N-dimethylformamide before it can be incorporated into the composition system, but the presence of solvents is not conducive to the latter's underwater construction (polluting water bodies). Under daily sunlight and room temperature, thiol-ene click and nucleophilic substitution basically do not occur, and most of the phenolic hydroxyl groups in the tannin cannot be successfully etherified, so that the coating is still sticky after several days, the paint film has a low degree of crosslinking, is brittle, and has an impact strength of only 25cm.kg -1 , the bending capacity is greater than 5mm, and the pull-off adhesion is less than 2MPa, which is no longer suitable for corrosion protection.

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

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

[0108] In summary, through the green transformation of plant tannins, hyperbranched multi-active toughening resins were obtained, which provided a feasible reference for the alternative synthesis of petrochemical epoxy. After being matched with graphene oxide, specific coupling agents, cashew nut shell oil phenolic amine and other components, it can be low-surface treated, thickly coated with rust, and cured underwater, and can meet the protection needs of various levels of corrosion environments such as inland and marine.

[0109] The contents of the above embodiments should be understood as these embodiments are only used to more clearly explain the present invention, rather than to limit the scope of the present invention. After referring to the present invention, the modifications of various equivalent forms of the present embodiment inspired by the same technical personnel fall into 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 an arbitrary positive integer.

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, 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 a linear straight chain containing not less than 8 carbon atoms, with one end of the molecule being an olefin group and the other end being an epoxy group.

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

1.

4. The preparation method according to claim 2, characterized in that: The α,ω-terminal olefin / epoxy alkane contains 8 to 12 carbon atoms.

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

6. 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.

7. The preparation method according to claim 6, 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; preferably irradiation intensity 20~50mW / cm 2 , irradiation time 0.5~1h.

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

9. 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.

10. The underwater curable epoxy composition according to claim 9, 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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