A bio-based epoxy resin and a preparation method and application thereof

Abstract

The present application provides a kind of bio-based epoxy resin, and six circular ring is connected with epoxy group, so that the resin has more optimal weather resistance.The present application improves the stability of bio-based raw materials by catalytic hydrogenation reaction on bio-based raw materials, and increases the chemical chain of finished bio-based epoxy resin by etherification ring-opening-closing reaction, which is simple to operate and simple process.The bio-based epoxy resin of the present application can improve the weather resistance of the coating when applied in coating.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin preparation technology, specifically to a bio-based epoxy resin and its preparation method and application. Background Technology

[0002] Bisphenol A epoxy resins possess excellent comprehensive mechanical properties, high adhesive strength, low shrinkage, good thermal stability, and superior electrical insulation, making them widely used as resin matrices in coatings, adhesives, and composite materials in fields such as machinery, electronics, electrical appliances, and aerospace. However, due to the high crosslinking density of cured epoxy resins, resulting in high internal stress, they exhibit drawbacks such as poor toughness, fatigue resistance, heat resistance, and impact resistance, making it difficult to meet the performance requirements of many practical engineering technologies and thus limiting their application, particularly restricting their use in structural materials and other types of composite materials. Bisphenol A, one of the representative raw materials for bisphenol A epoxy resins, is classified as an endocrine disruptor and may have toxic side effects on humans, leading to its ban in many countries for use in food packaging and other fields. Furthermore, the vast majority of commercially available epoxy resins are derived from petrochemical resources, and with the global energy crisis and increasing environmental degradation, the development and exploration of new sustainable, renewable, non-toxic, and harmless raw materials to replace bisphenol A in the preparation of epoxy resins is becoming increasingly important.

[0003] The research and development of bio-based epoxy resins using environmentally friendly and renewable resources has become a research hotspot and an urgent issue for industrial development. Various plant resources, such as cellulose, vegetable oils, and plant phenols, have been used to prepare epoxy resins. Chinese patent application number CN202010672980.5 discloses a lignin oligomer epoxy resin and its preparation method. The resulting lignin oligomer epoxy resin possesses cured mechanical properties and excellent thermal stability comparable to bisphenol A epoxy resin, but its weather resistance is poor. Summary of the Invention

[0004] To address the lack of weather-resistant bio-based epoxy resins in existing technologies, this invention provides a bio-based epoxy resin with excellent weather resistance. In the bio-based epoxy resin obtained by this invention, six-ring epoxy groups are linked to epoxy groups, thus giving the resin superior weather resistance.

[0005] The specific technical solution of this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a bio-based epoxy resin, comprising the following steps:

[0007] (S1) Catalytic hydrogenation of bio-based raw materials yields hydrogenated bio-based raw materials;

[0008] (S2) Hydrogenated bio-based raw materials and epichlorohydrin undergo an etherification and ring-opening reaction under the action of a phase transfer catalyst;

[0009] (S3) undergoes a ring-closing reaction with a base to give an intermediate;

[0010] (S4) Repeat steps (S2) to (S3) to carry out the etherification ring-opening-ring-closing reaction, the chemical chain of the intermediate is extended, and a bio-based epoxy resin with epoxy groups at both ends is obtained.

[0011] In the above step (S1), the bio-based raw material is subjected to a catalytic hydrogenation reaction, which converts the carbon-carbon double bonds in its structure into carbon-carbon single bonds with higher stability, thereby improving the stability of the bio-based raw material and effectively reducing the photosensitive properties of the finished bio-based epoxy resin.

[0012] Preferably, the bio-based raw material is fucoxanthin.

[0013] Fucoxanthin, chemically named 3-(acetoxy)-6′,7′-disehydro-5,6-epoxy-5,5′,6,6′,7,8-hexahydro-3,5′-dihydro-8-oxo-β,β-carotene, has the molecular formula C2. 42 H 58 O6 has the following structure:

[0014] Fucoxanthin is environmentally friendly and renewable. It is widely found in various algae, marine phytoplankton, aquatic shellfish and other plants and animals, and its extraction methods and conditions are simple.

[0015] The reaction route of (S1) is as follows:

[0016] ;

[0017] The reaction route of (S2) is as follows:

[0018] ;

[0019] The reaction route of (S3) is as follows:

[0020] ;

[0021] The structure of the bio-based epoxy resin is as follows:

[0022] .

[0023] The bio-based epoxy resin has an epoxy equivalent of 370-390 g / eg, 6 ppm of organic chlorine, 0.2% hydrolyzable chlorine, a viscosity of 1500-2500 mPa·s (25℃), and 0.7% volatile organic compounds. Compared to bisphenol A epoxy resin, fucoxanthin does not contain benzene rings in its structure; its six-ring structure and epoxy groups provide the resin with superior weather resistance. Furthermore, the epoxy resin prepared using fucoxanthin as a bio-based raw material has longer C-C bonds, giving it superior flexibility. In addition, the structure of fucoxanthin is very special; the six-ring structure in the middle of the fucoxanthin molecular chain originally has an epoxy group attached to it. Therefore, in the prepared bio-based epoxy resin, when the epoxy group of the six-ring structure in the middle of the molecular chain and the epoxy groups at both ends react with the curing agent to form a film, it is easier to form a cross-linked interpenetrating network structure, which can give the coating superior corrosion resistance.

[0024] Preferably, the bio-based raw material is lutein.

[0025] Lutein, with the molecular formula C 40 H 56 O2, the structural formula is as follows:

[0026] ;

[0027] Lutein is widely available in nature and is a major component of pigments in plants such as corn, vegetables, fruits, and flowers. Extracting lutein is simple and convenient.

[0028] The reaction route of (S1) is as follows:

[0029] ;

[0030] The reaction route of (S2) is as follows:

[0031] ;

[0032] The reaction route of (S3) is as follows:

[0033] ;

[0034] The structure of the bio-based epoxy resin is as follows:

[0035] .

[0036] The bio-based epoxy resin has an epoxy equivalent of 580-620 g / eg, an organochlorine content of 8 ppm, a hydrolyzable chlorine content of 0.24%, a viscosity of 4500-6800 mPa·s (25℃), and volatile organic compounds of 0.4%. Compared to bisphenol A epoxy resin, lutein does not contain a benzene ring in its structure. After catalytic hydrogenation, the saturated six-ring ring is linked to the epoxy group, giving the resin better weather resistance. The epoxy resin prepared using lutein as a bio-based raw material has longer C-C bonds, giving the resin better flexibility.

[0037] Preferably, in step (S1), the catalyst is a Pd / γ-Al2O3 or Pd / γ-CaCO3 system, the support is alumina, the hydrogenation temperature is (-55 to -20) °C, and the space velocity is 1 to 3 h⁻¹. -1 The hydrogen-to-liquid ratio is (350~500):1, and the pressure is 1.5~2.0 MPa.

[0038] Preferably, in step (S2), the phase transfer catalyst is a quaternary ammonium salt phase transfer catalyst.

[0039] More preferably, in step (S2), the phase transfer catalyst is one or more of benzyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltrimethylammonium chloride.

[0040] Preferably, in step (S2), the molar ratio of the hydrogenated bio-based raw material to epichlorohydrin is 1:(4~5.5).

[0041] Preferably, in step (S2), the temperature of the etherification ring-opening reaction is 50–80 °C, and the time of the etherification ring-opening reaction is 2–5 h.

[0042] Preferably, in step (S3), the alkali is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0043] Preferably, in step (S3), the temperature of the closed-loop reaction is 50–80 °C, and the time of the closed-loop reaction is 1–3 h.

[0044] Secondly, the present invention provides a bio-based epoxy resin prepared by the above-described method for preparing bio-based epoxy resin.

[0045] Thirdly, the present invention provides an application of bio-based epoxy resin in weather-resistant coatings.

[0046] Preferably, the weather-resistant coating comprises coating component A and coating component B.

[0047] The coating component A, by weight, comprises the following ingredients:

[0048] 25-35 parts of bio-based epoxy resin

[0049] 35-50 parts of pigment

[0050] 25-30 parts of filler

[0051] 0.1 to 4 parts of auxiliary agent,

[0052] 7-10 parts diluent;

[0053] 2-5 parts reactive diluent;

[0054] The coating component B, by weight, comprises the following ingredients:

[0055] 14-22 parts of modified cycloaliphatic amine curing agent,

[0056] Solvent 0.1~2 parts,

[0057] 0.1 to 1 part of co-solvent;

[0058] The weather-resistant coating is prepared by mixing the components of coating A and coating B at a mass ratio of (4~6):1, and is ready for use after thorough mixing.

[0059] Preferably, the method for preparing the weather-resistant coating includes the following steps:

[0060] (SS1) Weigh each component according to the weight proportions specified in claim 7, and set aside for later use;

[0061] (SS2) Add the components of coating component A to the disperser, disperse and grind at a speed of 2000~4000 r / min for 1~4h, sieve to obtain coating component A with a particle size of less than 80 μm;

[0062] (SS3) Add the components of coating component B to the disperser and disperse at a speed of 2000~4000 r / min for 20~40 min to obtain coating component B;

[0063] (SS4) Mix paint component A and paint component B in a mass ratio of (4~6):1 to obtain the weather-resistant paint.

[0064] The bio-based epoxy resin of this invention is used in coatings and has weather-resistant properties. After the weather-resistant coating forms a coating layer, it relies on the barrier effect of the coating to prevent corrosive media such as water and chloride ions from penetrating the coating layer and reaching the substrate surface.

[0065] In the bio-based epoxy resin structure prepared from fucoxanthin, an epoxy group is attached to a six-ring in the middle of the molecular chain. This epoxy group, along with the epoxy groups at both ends, can react with the curing agent to form a cross-linked, interpenetrating network structure, thus enabling the coating to exhibit superior corrosion resistance. Not only can it form a barrier coating on the surface of the substrate material, but the network structure can also work in conjunction with the passivation film formed on the substrate surface to prevent corrosion of the substrate material.

[0066] Preferably, the pigment is one or more of titanium dioxide, iron oxide red, and phosphorus titanium powder.

[0067] More preferably, the pigment is titanium phosphorus powder.

[0068] Phosphorus titanium powder can react with the substrate metal to quickly form a complete, dense, and stable passivation film. In the middle stage, it plays an anti-corrosion role by relying on the dual protection of the coating and the passivation film. In the later stage, the barrier effect of the coating gradually weakens, and the composite phosphorus titanium powder continues to react with the substrate metal to maintain the density and integrity of the passivation film and protect the substrate metal.

[0069] Preferably, the filler is one or more of wollastonite powder, mica powder, talc powder and barium sulfate.

[0070] Preferably, the additive is one or more of defoamers, wetting agents, and thixotropic agents.

[0071] Preferably, the diluent is one or more of toluene, benzyl alcohol, butyl acetate, and n-butanol.

[0072] Preferably, the modified alicyclic amine curing agent is a cashew nut phenol modified curing agent.

[0073] Preferably, the solvent is one or more of methyl isobutyl ketone, propylene glycol methyl ether, and propylene glycol methyl ether acetate.

[0074] Compared with the prior art, the beneficial effects of the present invention are:

[0075] (1) The present invention provides a method for preparing bio-based epoxy resin, which is simple to operate and has a simple process.

[0076] (2) This invention improves the stability of bio-based raw materials by catalytically hydrogenating them, converting the carbon-carbon double bonds in their structure into more stable carbon-carbon single bonds, and effectively reducing the photosensitive properties of the finished bio-based epoxy resin.

[0077] (3) Bio-based epoxy resin does not contain benzene rings. The six-ring rings are connected to the epoxy groups, giving the resin better weather resistance. It also has longer C-C bonds, resulting in excellent flexibility.

[0078] (4) The bio-based epoxy resin of the present invention can be used in coatings to improve the weather resistance of the coatings.

[0079] (5) When bio-based epoxy resin made from fucoxanthin reacts with curing agent to form film, it is easier to form cross-linked and interpenetrating network structure, thus exhibiting better corrosion resistance. Attached Figure Description

[0080] Figure 1 The electrochemical impedance spectroscopy (EIS) spectra of the coatings prepared in Example 5 and Comparative Example 2 are shown below; Figure 1 (a) is coating A from Example 5. Figure 1 (b) is coating F of Comparative Example 2.

[0081] Figure 2 The graph shows the results of accelerated UV aging tests on the coatings prepared in Example 8 and Comparative Example 1; wherein, Figure 2 (a) is coating D from Example 8. Figure 2 (b) is coating E of Comparative Example 1.

[0082] Figure 3 The image shows a comparison of gloss levels before and after accelerated UV aging tests of the coatings prepared in Example 8 and Comparative Example 1.

[0083] Figure 4 The graph shows the results of neutral salt spray tests on the coatings prepared in Example 5 and Comparative Example 2; wherein, Figure 3 (a) is coating A from Example 5. Figure 3 (b) is coating F of Comparative Example 2. Detailed Implementation

[0084] The present invention will be further described below with reference to embodiments.

[0085] General Implementation Examples

[0086] A method for preparing a bio-based epoxy resin includes the following steps:

[0087] (S1) Catalytic hydrogenation of bio-based raw materials yields hydrogenated bio-based raw materials;

[0088] (S2) Hydrogenated bio-based raw materials and epichlorohydrin undergo an etherification and ring-opening reaction under the action of a phase transfer catalyst;

[0089] (S3) undergoes a ring-closing reaction with a base to give an intermediate;

[0090] (S4) Repeat steps (S2) to (S3) to carry out the etherification ring-opening-ring-closing reaction, the chemical chain of the intermediate is extended, and a bio-based epoxy resin with epoxy groups at both ends is obtained.

[0091] Preferably, the bio-based raw material is fucoxanthin.

[0092] The reaction route of (S1) is as follows:

[0093] ;

[0094] The reaction route of (S2) is as follows:

[0095] ;

[0096] The reaction route of (S3) is as follows:

[0097] ;

[0098] The structure of the bio-based epoxy resin is as follows:

[0099] .

[0100] Preferably, the bio-based raw material is lutein.

[0101] The reaction route of (S1) is as follows:

[0102] ;

[0103] The reaction route of (S2) is as follows:

[0104] ;

[0105] The reaction route of (S3) is as follows:

[0106] ;

[0107] The structure of the bio-based epoxy resin is as follows:

[0108] .

[0109] Preferably, in step (S1), the catalyst is a Pd / γ-Al2O3 or Pd / γ-CaCO3 system, the support is alumina, the hydrogenation temperature is (-55 to -20) °C, and the space velocity is 1 to 3 h⁻¹. -1 The hydrogen-to-liquid ratio is (350~500):1, and the pressure is 1.5~2.0 MPa.

[0110] Preferably, in step (S2), the phase transfer catalyst is a quaternary ammonium salt phase transfer catalyst.

[0111] More preferably, in step (S2), the phase transfer catalyst is one or more of benzyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltrimethylammonium chloride.

[0112] Preferably, in step (S2), the molar ratio of the hydrogenated bio-based raw material to epichlorohydrin is 1:(4~5.5).

[0113] Preferably, in step (S2), the temperature of the etherification ring-opening reaction is 50–80 °C, and the time of the etherification ring-opening reaction is 2–5 h.

[0114] Preferably, in step (S3), the alkali is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0115] Preferably, in step (S3), the temperature of the closed-loop reaction is 50–80 °C, and the time of the closed-loop reaction is 1–3 h.

[0116] A bio-based epoxy resin prepared by the above-described method for preparing bio-based epoxy resin.

[0117] Application of a bio-based epoxy resin in weather-resistant coatings.

[0118] Preferably, the weather-resistant coating comprises coating component A and coating component B.

[0119] The coating component A, by weight, comprises the following ingredients:

[0120] 25-35 parts of bio-based epoxy resin

[0121] 35-50 parts of pigment

[0122] 25-30 parts of filler

[0123] 0.1 to 4 parts of auxiliary agent,

[0124] 7-10 parts diluent;

[0125] 2-5 parts reactive diluent;

[0126] The coating component B, by weight, comprises the following ingredients:

[0127] 14-22 parts of modified cycloaliphatic amine curing agent,

[0128] Solvent 0.1~2 parts,

[0129] 0.1 to 1 part of co-solvent;

[0130] The weather-resistant coating is prepared by mixing the components of coating A and coating B at a mass ratio of (4~6):1, and is ready for use after thorough mixing.

[0131] Preferably, the method for preparing the weather-resistant coating includes the following steps:

[0132] (SS1) Weigh each component according to the weight proportions specified in claim 7, and set aside for later use;

[0133] (SS2) Add the components of coating component A to the disperser, disperse and grind at a speed of 2000~4000 r / min for 1~4h, sieve to obtain coating component A with a particle size of less than 80 μm;

[0134] (SS3) Add the components of coating component B to the disperser and disperse at a speed of 2000~4000 r / min for 20~40 min to obtain coating component B;

[0135] (SS4) Mix paint component A and paint component B in a mass ratio of (4~6):1 to obtain the weather-resistant paint.

[0136] Preferably, the pigment is one or more of titanium dioxide, iron oxide red, and phosphorus titanium powder.

[0137] Preferably, the filler is one or more of wollastonite powder, mica powder, talc powder and barium sulfate.

[0138] Preferably, the additive is one or more of defoamers, wetting agents, and thixotropic agents.

[0139] Preferably, the diluent is one or more of toluene, benzyl alcohol, butyl acetate, and n-butanol.

[0140] Preferably, the modified alicyclic amine curing agent is a cashew nut phenol modified curing agent.

[0141] Preferably, the solvent is one or more of methyl isobutyl ketone, propylene glycol methyl ether, and propylene glycol methyl ether acetate.

[0142] Example 1

[0143] A method for preparing epoxy resin using fucoxanthin as a raw material includes the following steps:

[0144] (1) Catalytic hydrogenation of fucoxanthin: 300 g of fucoxanthin was weighed to prepare a solution, and 1500 g of n-hexane was used as the solvent. The experiment was carried out in fractions on a 250 mL hydrogenation apparatus using an adiabatic circulation process. The catalyst was a Pd / γ-Al2O3 system with noble metals as the active components, and the support was perforated alumina. The inlet temperature was -55 ℃ and the space velocity was 1 h. -1 The hydrogen-to-liquid ratio is 350:1, and the reaction pressure is 1.5 MPa. The chemical reaction formula is as follows:

[0145]

[0146] After the hydrogenation reaction was completed, the solution was concentrated at 75 °C and then freeze-dried at -20 °C to obtain the more stable compound hydrogenated fucoxanthin.

[0147] (2) Etherification reaction of hydrogenated fucoxanone with epichlorohydrin: 215.64 g of hydrogenated fucoxanone and 186 g of epichlorohydrin were added to a 500 mL four-necked flask equipped with an electric stirrer, a reflux condenser and a thermometer. The temperature was raised to 65 °C. After complete dissolution, 1.8 g of benzyltriethylammonium chloride catalyst was added and the reaction was carried out for 3.5 h.

[0148] (3) Closed-ring synthesis of fucoxanthin epoxy resin: Keep the temperature at 65 ℃, start by adding 72 g of 25% NaOH solution dropwise for 1.5 h, maintain the temperature and continue the reaction for 2.5 h to carry out the closed-ring reaction.

[0149] (4) Repeat steps (2) and (3) above 5 times each to continue the etherification ring-opening-ring-closing reaction, achieve chemical chain growth, and obtain the finished epoxy resin.

[0150] (5) Separation of products: Filter to remove solids such as NaCl and phase transfer catalyst generated in the reaction, add 180 g of toluene for extraction, and obtain a clear and transparent oily liquid. Transfer the oily liquid to a separatory funnel, and wash the oil layer and water layer repeatedly with distilled water at 40 °C until neutral. Take the oil layer and transfer it to a rotary evaporator to distill and remove water, toluene and unreacted epichlorohydrin, thus obtaining liquid epoxy resin A.

[0151] Example 2

[0152] A method for preparing epoxy resin using fucoxanthin as a raw material includes the following steps:

[0153] (1) Catalytic hydrogenation of fucoxanthin: 300 g of fucoxanthin was weighed to prepare a solution, and 1500 g of n-hexane was used as the solvent. The experiment was carried out in fractions on a 250 mL hydrogenation apparatus using an adiabatic circulation process. The catalyst was a Pd / γ-Al2O3 system with noble metals as the active components, and the support was perforated alumina. The inlet temperature was -20 ℃ and the space velocity was 3 h⁻¹. -1 The hydrogen-to-liquid ratio is 500:1, and the reaction pressure is 2 MPa. The chemical reaction formula is as follows:

[0154]

[0155] After the hydrogenation reaction was completed, the solution was concentrated at 75 °C and then freeze-dried at -20 °C to obtain the more stable compound hydrogenated fucoxanthin.

[0156] (2) Etherification reaction of hydrogenated fucoxanone with epichlorohydrin: 269.56 g of hydrogenated fucoxanone and 186 g of epichlorohydrin were added to a 500 mL four-necked flask equipped with an electric stirrer, a reflux condenser and a thermometer. The temperature was raised to 50 °C. After complete dissolution, 1 g of benzyltriethylammonium chloride and 1 g of benzyltrimethylammonium chloride were added. The reaction was allowed to proceed for 5 h.

[0157] (3) Closed-ring synthesis of fucoxanthin epoxy resin: Keep the temperature at 50 ℃, start by adding 101 g of 25% KOH solution dropwise for 2 h, maintain the temperature and continue the reaction for 3 h to carry out the closed-ring reaction.

[0158] (4) Repeat steps (2) and (3) twice each to continue the etherification ring-opening and ring-closing reaction, thereby achieving chemical chain growth and obtaining the finished epoxy resin.

[0159] (5) Separation of products: Filter to remove solids such as KCl and phase transfer catalyst generated in the reaction, add 180 g of toluene for extraction, and obtain a clear and transparent oily liquid. Transfer the oily liquid to a separatory funnel, and wash the oil layer and water layer repeatedly with distilled water at 40 °C until neutral. Take the oil layer and transfer it to a rotary evaporator to distill and remove water, toluene and unreacted epichlorohydrin, thus obtaining liquid epoxy resin B.

[0160] Example 3

[0161] A method for preparing epoxy resin using fucoxanthin as a raw material includes the following steps:

[0162] (1) Catalytic hydrogenation of fucoxanthin: 300 g of fucoxanthin was weighed to prepare a solution, and 1500 g of n-hexane was used as the solvent. The experiment was carried out in fractions on a 250 mL hydrogenation apparatus using an adiabatic circulation process. The catalyst was a Pd / γ-Al2O3 system with noble metals as the active components, and the support was perforated alumina. The inlet temperature was -35 ℃ and the space velocity was 2 h⁻¹. -1 The hydrogen-to-liquid ratio is 400:1, and the reaction pressure is 1.5 MPa. The chemical reaction formula is as follows:

[0163]

[0164] After the hydrogenation reaction was completed, the solution was concentrated at 75 °C and then freeze-dried at -20 °C to obtain the more stable compound hydrogenated fucoxanthin.

[0165] (2) Etherification reaction of hydrogenated fucoxanone with epichlorohydrin: 296.51 g of hydrogenated fucoxanone and 186 g of epichlorohydrin were added to a 500 mL four-necked flask equipped with an electric stirrer, a reflux condenser and a thermometer. The temperature was raised to 80 °C. After complete dissolution, 1.8 g of benzyltrimethylammonium bromide catalyst was added and the reaction was allowed to proceed for 2 h.

[0166] (3) Closed-ring synthesis of fucoxanthin epoxy resin: Keep the temperature at 80 ℃, start by adding 133 g of Ca(OH)2 solution with a mass fraction of 25% for 3 h, and continue the reaction for 1 h while maintaining the temperature to carry out the closed-ring reaction.

[0167] (4) Repeat steps (2) and (3) once each to continue the etherification ring-opening and ring-closing reaction, thereby achieving chemical chain growth and obtaining the finished epoxy resin.

[0168] (5) Separation of products: Filter to remove solids such as CaCl2 and phase transfer catalyst generated in the reaction, add 180 g of toluene for extraction, and obtain a clear and transparent oily liquid. Transfer the oily liquid to a separatory funnel, and wash the oil layer and water layer repeatedly with distilled water at 40 °C until neutral. Take the oil layer and transfer it to a rotary evaporator to distill and remove water, toluene and unreacted epichlorohydrin, thus obtaining liquid epoxy resin C.

[0169] Example 4

[0170] A method for preparing epoxy resin using lutein as a raw material includes the following steps:

[0171] (1) Catalytic hydrogenation of lutein: 300 g of lutein was weighed to prepare a solution, and 1500 g of anhydrous ethanol was used as the solvent. The experiment was carried out in several stages on a 250 mL hydrogenation apparatus using an adiabatic circulation process. The catalyst was a Pd / γ-CaCO3 system with noble metals as the active components. The inlet temperature was -20 ℃ and the space velocity was 2 h⁻¹. -1 The hydrogen-to-liquid ratio is 450:1, and the reaction pressure is 1.5 MPa. The chemical reaction formula is as follows:

[0172]

[0173] After the hydrogenation reaction was completed, the solution was concentrated at 80 °C and then freeze-dried at -20 °C to obtain the more stable compound hydrogenated lutein.

[0174] (2) Etherification reaction of hydrogenated lutein with epichlorohydrin: 295 g of hydrogenated lutein and 185 g of epichlorohydrin were added to a 500 mL four-necked flask equipped with an electric stirrer, a reflux condenser and a thermometer. The temperature was raised to 65 °C. After complete dissolution, 1.8 g of benzyltrimethylammonium bromide catalyst was added and the reaction was carried out for 3.5 h.

[0175] (3) Closed-ring synthesis of lutein epoxy resin: Keep the temperature at 65 ℃, start by adding 72 g of 25% NaOH solution dropwise for 1.5 h, maintain the temperature and continue the reaction for 2.5 h to carry out the closed-ring reaction.

[0176] (4) Repeat steps (2) and (3) once each to continue the etherification ring-opening and ring-closing reaction, thereby achieving chemical chain growth and obtaining the finished epoxy resin.

[0177] (5) Separation of products: Filter to remove solids such as NaCl and phase transfer catalyst generated in the reaction, add 180 g of toluene for extraction, and obtain a clear and transparent oily liquid. Transfer the oily liquid to a separatory funnel, and wash the oil layer and water layer repeatedly with distilled water at 40 °C until neutral. Take the oil layer and transfer it to a rotary evaporator to distill and remove water, toluene and unreacted epichlorohydrin, thus obtaining liquid epoxy resin D.

[0178] Example 5

[0179] A method for preparing a coating includes the following steps:

[0180] Prepare the raw materials in the weight proportions shown in Table 1. Add liquid epoxy resin A, pigments and fillers, additives, diluents, and reactive diluents sequentially into the hopper of a high-speed disperser in the order of "from liquid to powder, from low density to high density," and disperse and grind at 3000 r / min for 2 h until the fineness reaches below 80 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 3000 r / min for 30 min to obtain coating component B. Mix coating component A and coating component B at a mass ratio of 5:1 to obtain coating A. The electrochemical impedance spectroscopy of coating A is shown below. Figure 1 As shown in (a).

[0181] Depend on Figure 1 (a) It can be seen that the maximum impedance value of the sample in Example 5 reaches 2500 kΩ·m. -2 The sample exhibits very high overall impedance and excellent barrier properties against corrosive media such as water and chloride ions. Furthermore, after immersion for a period of time, the impedance spectrum of the sample in Example 5 shows two arcs, indicating that the sample of this invention not only forms a coating on the surface of the substrate material to provide a barrier effect, but also forms a passivation film on the surface of the substrate material, thereby preventing corrosion of the substrate material.

[0182] Table 1 Ingredients List

[0183] Example

[0184] A method for preparing a coating includes the following steps:

[0185] Prepare the raw materials in the proportions shown in Table 1 by weight. Add the liquid epoxy resin B, pigments and fillers, additives, diluents, and reactive diluents sequentially into the hopper of a high-speed disperser in the order of "from liquid to powder, from low density to high density," and disperse and grind at 2000 r / min for 4 h until the fineness reaches below 80 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 2000 r / min for 40 min to obtain coating component B. Mix coating component A and coating component B uniformly at a mass ratio of 6:1 to obtain coating B.

[0186] Example 7

[0187] A method for preparing a coating includes the following steps:

[0188] Prepare the raw materials in the proportions shown in Table 1 by weight. Add the liquid epoxy resin C, pigments and fillers, additives, diluents, and reactive diluents sequentially into the hopper of a high-speed disperser in the order of "from liquid to powder, from low density to high density," and disperse and grind at 4000 r / min for 1 h until the fineness reaches below 80 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 4000 r / min for 20 min to obtain coating component B. Mix coating component A and coating component B uniformly at a mass ratio of 4:1 to obtain coating C.

[0189] Example 8

[0190] A method for preparing a coating includes the following steps:

[0191] Prepare the raw materials in the proportions shown in Table 1 by weight. Add the liquid epoxy resin D, pigments and fillers, additives, diluents, and reactive diluents sequentially into the hopper of a high-speed disperser in the order of "from liquid to powder, from low density to high density," and disperse and grind at 3000 r / min for 2 h until the fineness reaches below 50 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 3000 r / min for 30 min to obtain coating component B. Mix coating component A and coating component B at a mass ratio of 5:1 to obtain coating D.

[0192] Comparative Example 1

[0193] A method for preparing a coating includes the following steps:

[0194] Prepare the raw materials in the proportions shown in Table 1 by weight. Add the bisphenol A epoxy resin, pigments and fillers, additives, diluents, and reactive diluents sequentially to the hopper of a high-speed disperser in the order of "liquid to powder, low density to high density," and disperse and grind at 3000 r / min for 2 h until the fineness reaches below 50 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 3000 r / min for 30 min to obtain coating component B. Mix coating component A and coating component B at a mass ratio of 5:1 to obtain coating E.

[0195] Comparative Example 2

[0196] A method for preparing a coating includes the following steps:

[0197] Prepare the raw materials in the proportions shown in Table 1 by weight. Add the bisphenol A epoxy resin, pigments and fillers, additives, diluents, and reactive diluents sequentially to the hopper of a high-speed disperser in the order of "liquid to powder, low density to high density," and disperse and grind at 3000 r / min for 2 h until the fineness reaches below 50 μm. Sieve to obtain coating component A. Add the solvent and co-solvent to the modified cycloaliphatic amine curing agent and disperse at 3000 r / min for 30 min to obtain coating component B. Mix coating component A and coating component B at a mass ratio of 5:1 to obtain coating F. The electrochemical impedance spectroscopy of coating F is shown below. Figure 1 As shown in (b).

[0198] Comparing with Example 5, it can be seen that both samples from Comparative Example 2 and Example 5 exhibit very high overall impedance, with the maximum impedance value reaching 2500 kΩ·m. -2 This indicates that the coating has excellent barrier properties against corrosive media such as water and chloride ions. However, the impedance spectrum of Comparative Example 2 consistently shows a single large arc, indicating that the barrier effect of the coating is the only factor preventing corrosion of the substrate material. Furthermore, as the immersion time increases, the radius of the arc decreases, meaning that the barrier effect of the coating weakens.

[0199] Based on theoretical and experimental research, our team discovered that the bio-based epoxy resin structure prepared using fucoxanthin as a raw material has an epoxy group attached to the six-ring in the middle of the molecular chain. This epoxy group, along with the epoxy groups at both ends, can react with the curing agent to form a cross-linked, interpenetrating network structure, thus enabling the coating to exhibit superior corrosion resistance. Not only can it form a barrier coating on the surface of the substrate material, but the network structure can also work in conjunction with the passivation film formed on the substrate material surface to prevent corrosion.

[0200] Test Example 1

[0201] Accelerated UV aging tests were conducted on the products obtained in Examples 5-8 and Comparative Examples 1-2:

[0202] The coated samples were placed in an LZW-050A UV aging test chamber manufactured by Shanghai Yiheng Technology Co., Ltd., for accelerated UV aging testing. The test environment temperature was set at 60 ℃ and the radiation intensity at 0.77 W / m². 2 The test lasted for 15 days. Based on the CIELAB color system, the paint color on the sample surface after the aging test was measured, and the color difference value was calculated. The results are shown in Table 2. Figure 2 This is a comparison chart of the accelerated UV aging test results for Example 8 and Comparative Example 1. Figure 3 The image shows a comparison of gloss levels before and after accelerated UV aging tests for Example 8 and Comparative Example 1.

[0203] Table 2 Color difference results of accelerated UV aging test

[0204]

[0205] As shown in Table 2, the coatings prepared in Comparative Examples 1-2 exhibited significant color difference values, especially Comparative Example 1, which had a color difference value as high as 222.84. After the test, the surface color of the sample test area changed from red to pinkish-white, completely losing its gloss and showing severe chalking. In contrast, the coatings prepared in Examples 5-8 showed no significant difference in gloss, color, or surface condition between the test areas and untested areas, with color difference values ​​all less than 10, especially Example 8, where the color difference value was only 2.06. The weather resistance of the bio-based epoxy resin coating prepared by this invention is significantly superior to that of conventional products prepared with bisphenol A epoxy resin in the prior art.

[0206] Based on experimental and theoretical research, the team of this invention discovered that the bio-based epoxy resin structure of this invention does not contain benzene rings, and its six-ring structure is connected to epoxy groups, thus exhibiting superior weather resistance. When applied to coatings, the bio-based epoxy resin improves the weather resistance of the coatings.

[0207] Test Example 2

[0208] The products obtained in Example 5 and Comparative Example 2 were subjected to a neutral salt spray test:

[0209] Scratches were made on a coated sample, which was then placed in a salt spray chamber and sprayed with neutral salt spray for 1440 hours. The sample was then removed from the salt spray chamber. The results are as follows: Figure 4 As shown.

[0210] Depend on Figure 4 It can be seen that the coating prepared in Example 5 of the present invention is still in good service condition and has excellent application performance, without defects such as pitting, blistering, or powdering; while the coating prepared in Comparative Example 2 showed a large amount of blistering and rust, especially at the scratched and damaged areas, where a large amount of rust liquid flowed out.

[0211] Based on theoretical and experimental research, our team discovered that the bio-based epoxy resin structure prepared using fucoxanthin as a raw material has an epoxy group attached to the six-ring in the middle of the molecular chain. This epoxy group, along with the epoxy groups at both ends, can react with the curing agent to form a cross-linked, interpenetrating network structure, thus enabling the coating to exhibit superior corrosion resistance. Not only can it form a barrier coating on the surface of the substrate material, but the network structure can also work in conjunction with the passivation film formed on the substrate material surface to prevent corrosion.

[0212] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0213] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based epoxy resin, characterized in that, Includes the following steps: (S1) Catalytic hydrogenation of bio-based raw materials yields hydrogenated bio-based raw materials; (S2) Hydrogenated bio-based raw materials and epichlorohydrin undergo an etherification and ring-opening reaction under the action of a phase transfer catalyst; (S3) undergoes a ring-closing reaction with a base to give an intermediate; (S4) Repeat steps (S2) to (S3) to carry out the etherification ring-opening-ring-closing reaction, the chemical chain of the intermediate is extended, and a bio-based epoxy resin with epoxy groups at both ends is obtained. The bio-based raw material is fucoxanthin, with the following structure: ； The bio-based raw material is lutein, with the following structural formula: 。 2. The method for preparing a bio-based epoxy resin as described in claim 1, characterized in that, The bio-based raw material is fucoxanthin, and the reaction route of (S1) is as follows: ； The reaction route of (S2) is as follows: ； The reaction route of (S3) is as follows: ； The structural formula of the bio-based epoxy resin is as follows: 。 3. The method for preparing a bio-based epoxy resin as described in claim 1, characterized in that, The bio-based raw material is lutein, and the reaction route of (S1) is as follows: ； The reaction route of (S2) is as follows: ； The reaction route of (S3) is as follows: ； The structural formula of the bio-based epoxy resin is as follows: 。 4. A method for preparing a bio-based epoxy resin as described in claim 1, 2, or 3, characterized in that, In step (S1), the catalyst is a Pd / γ-Al2O3 or Pd / γ-CaCO3 system, the support is alumina, the hydrogenation temperature is (-55 to -20) °C, and the space velocity is 1 to 3 h⁻¹. -1 The hydrogen-to-liquid ratio is (350~500):1, and the pressure is 1.5~2.0 MPa.

5. The method for preparing a bio-based epoxy resin as described in claim 1, 2, or 3, characterized in that, In step (S2), the phase transfer catalyst is a quaternary ammonium salt phase transfer catalyst.

6. The method for preparing a bio-based epoxy resin as described in claim 5, characterized in that, In step (S2), the phase transfer catalyst is one or more of benzyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltrimethylammonium chloride.

7. A bio-based epoxy resin prepared by the method of any one of claims 1-6.

8. The application of the bio-based epoxy resin as described in claim 7 in weather-resistant coatings.

9. The application as described in claim 8, characterized in that, The weather-resistant coating comprises coating component A and coating component B. The coating component A, by weight, comprises the following ingredients: 25-35 parts of bio-based epoxy resin 35-50 parts of pigment 25-30 parts of filler 0.1 to 4 parts of auxiliary agent, 7-10 parts diluent; 2-5 parts reactive diluent; The coating component B, by weight, comprises the following ingredients: 14-22 parts of modified cycloaliphatic amine curing agent, Solvent 0.1~2 parts, 0.1 to 1 part of co-solvent; The weather-resistant coating is prepared by mixing the components of coating A and coating B at a mass ratio of (4~6):1, and is ready for use after thorough mixing.

10. The application as described in claim 9, characterized in that, The preparation method of the weather-resistant coating includes the following steps: (SS1) Weigh each component according to the weight proportions specified in claim 9, and set aside for later use; (SS2) Add the components of coating component A to the disperser, disperse and grind at a speed of 2000~4000 r / min for 1~4 h, sieve to obtain coating component A with a particle size of less than 80 μm; (SS3) Add the components of coating component B to the disperser and disperse at a speed of 2000~4000 r / min for 20~40 min to obtain coating component B; (SS4) Mix paint component A and paint component B in a mass ratio of (4~6):1 to obtain the weather-resistant paint.

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