Preparation method of nonionic flexible epoxy curing agent

Abstract

The present invention belongs to the technical field of epoxy curing agents, and specifically relates to a method for preparing a nonionic flexible epoxy curing agent. Add a polyether triol to water and stir evenly, then add a catalyst A to dissolve, heat up, condense and reflux, introduce oxygen, and react at a constant temperature to obtain a product A; after the product A is melted, add a monofunctional epoxy active diluent, stir evenly, add a catalyst B to react, and obtain a flexible intermediate; after the flexible intermediate is preheated, add it to an aliphatic polyamine to react at a constant temperature, and distill under reduced pressure to obtain a product B; an epoxy resin solution is added to the product B for a first constant temperature reaction, and then a dibasic acid is added for a second constant temperature reaction, and deionized water is added to obtain a nonionic flexible epoxy curing agent. The present invention introduces a hydrophilic group with a branched structure in the polyether triol to make the curing agent have the advantages of excellent impact resistance, high flexibility, and good water dispersibility, and can be stably dispersed in water without a cosolvent.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy curing agents, and particularly relates to a preparation method of a nonionic flexible epoxy curing agent. Background Art

[0002] Epoxy resin is a thermoplastic high molecular linear polymer with excellent adhesion, acid and alkali resistance and good stability. It is widely used in coatings, adhesives and other fields. However, uncured epoxy resin can soften and melt into a viscous liquid after being heated, and does not have good mechanical properties, chemical resistance and heat resistance. For this reason, a curing agent needs to be added for a curing reaction. The curing reaction is mainly based on the presence of active epoxy groups in the epoxy resin, which react with the curing agent to form a three-dimensional network structure to obtain a high molecular polymer with good performance. Therefore, the curing agent is the key to the practical application value of epoxy resin.

[0003] In recent years, as the harm of volatile organic compounds to the human body and the environment has attracted more and more attention, epoxy curing agents containing no or less organic volatiles have become the research focus of new epoxies. At present, common water-based epoxy curing agents are mainly divided into cationic, anionic and non-ionic curing agents according to their chemical properties. Anionic water-based epoxy resin curing agents are made by adding organic acids such as acetic acid to react with polyamines to form salts, which overcomes the shortcomings of fatty amines such as low hydrophilicity, high reactivity, high volatility and poor compatibility with epoxy resins. However, the organic acid added in the salt-forming step will reduce the stability of the curing agent, and will react with the metal substrate to reduce the corrosion resistance of the coating, and the cured paint film will be brittle and poor in acid resistance. However, the pH value of cationic water-based epoxy curing agents is generally low, and the film-forming property, permeability resistance and flexibility are poor, which limits its application and promotion in water-based epoxy resin coatings.

[0004] Chinese patent CN 104356357 A discloses a method for synthesizing a nonionic waterborne epoxy curing agent. Under the protection of dry nitrogen, a propylene glycol methyl ether solution of triethylenetetramine is put into a 500 ml four-necked reaction bottle equipped with a reflux condenser, a thermometer and a stirrer; polyether polyol diglycidyl ether is added dropwise, and the material dropping speed and material molar ratio are controlled to react to obtain an adduct of triethylenetetramine and polyether polyol diglycidyl ether; liquid epoxy resin is added dropwise according to a stoichiometric ratio to the propylene glycol methyl ether solution of the adduct of triethylenetetramine and polyether polyol diglycidyl ether after the residual triethylenetetramine is removed by vacuum distillation to synthesize the waterborne epoxy curing agent. The polyether polyol diglycidyl ether used in this patent has an unfixed hydroxyl content, and its reaction with triethanoltetramine is difficult to control. It is very easy to cause explosion and cross-linking during the reaction. The introduction of propylene glycol methyl ether solvent fails to effectively reduce the solvent content to make the curing agent zero VOC, and no amide group is introduced, which fails to better control the rheological properties and application period of the coating.

[0005] Chinese patent CN 106046325 A discloses a water-based epoxy curing agent and a water-based epoxy frame paint. The water-based epoxy curing agent is prepared from the following raw materials in parts by weight: 30-35 parts of triethylenetetramine, 1.2-1.7 parts of silane coupling agent, TMPEG 8-12, epoxy resin 0.1-0.4, aromatic glycidyl ether 8-13, nano-alumina 0.03-0.07; prepared according to the following steps: triethylenetetramine and silane coupling agent are added into a reaction container according to the above ratio, heated to 60°C under nitrogen protection while stirring, then TMPEG is added dropwise, and the temperature is kept for 3-4 hours after the addition is completed to obtain an intermediate; epoxy resin is added into the reaction container, slowly added dropwise at 60°C and reacted for 0.5-1 hour to obtain an intermediate-epoxy adduct; then aromatic glycidyl ether is added into the reaction container, reacted at 60°C for 2-3 hours, diluted with water to a solid content of 50%, and stirred for 0.5-1 hour; finally, nano-alumina is added and stirred evenly to obtain a water-based epoxy curing agent. This patent uses aminosilane coupling agents to participate in the reaction, and the coupling efficiency is relatively low, and the durability is poor in high temperature, high humidity and other environments; and the curing agent prepared by this method is not suitable for re-coating an intermediate coating or topcoat on the upper layer, which can easily cause the coating to fall off and the bonding effect between the coating layers is poor; the addition of nano-alumina can easily lead to agglomeration and cause the emulsion to break. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a nonionic flexible epoxy curing agent. The method takes into account the advantages of water resistance and long application period of amidated polyamine waterborne epoxy curing agent, introduces hydrophilic groups with branched structures of polyether triols, so that the curing agent has the advantages of excellent impact resistance, high flexibility and good water dispersibility, can be stably dispersed in water without a co-solvent, and takes into account the advantages of low-temperature curing of aliphatic curing agents, improves the water resistance of coatings and can be suitable for matching a variety of emulsions / resins, thereby facilitating the expansion of the application field of epoxy curing agents.

[0007] The preparation method of the nonionic flexible epoxy curing agent of the present invention comprises the following steps:

[0008] (1) Add polyether triol into water and stir evenly, then add catalyst A to dissolve, heat, condense and reflux, introduce oxygen, react at constant temperature, perform the first vacuum distillation, wash with solvent, filter to obtain clear liquid and perform the second vacuum distillation to obtain product A;

[0009] (2) After the product A is melted, a monofunctional epoxy active diluent is added, stirred evenly, and a catalyst B is added to react to obtain a flexible intermediate;

[0010] (3) The flexible intermediate is preheated and then added to aliphatic polyamine for constant temperature reaction, followed by vacuum distillation to obtain product B;

[0011] (4) dissolving the epoxy resin in a solvent to obtain an epoxy resin solution, adding the epoxy resin solution to the product B for a first isothermal reaction, then adding a dibasic acid for a second isothermal reaction, and adding deionized water to obtain a non-ionic flexible epoxy curing agent.

[0012] The molecular weight of the polyether triol described in step (1) is 170-1000.

[0013] The mass ratio of the polyether triol to water in step (1) is 150-350:60-150.

[0014] The stirring temperature in step (1) is 20-95°C.

[0015] The catalyst A described in step (1) is one or more of copper nitrate, ferric nitrate or potassium permanganate, and the mass of the catalyst A is 8-22% of the mass of the polyether triol.

[0016] The temperature in step (1) is raised to 100-150°C.

[0017] The oxygen described in step (1) is continuously introduced at a flow rate of 100-120 ml / min.

[0018] The isothermal reaction time in step (1) is 4-8 hours.

[0019] The temperature of the first reduced pressure distillation in step (1) is 70-100°C.

[0020] The solvent in step (1) is one or more of ethyl acetate, chloroform, dichloromethane or isopropanol.

[0021] The temperature of the second reduced pressure distillation in step (1) is 50-110°C.

[0022] The melting temperature in step (2) is 90-140°C.

[0023] The monofunctional epoxy reactive diluent described in step (2) is one or more of phenyl glycidyl ether, butyl glycidyl ether or o-toluene glycidyl ether, and the molar ratio of product A to the monofunctional epoxy reactive diluent is 1:0.8-1.3.

[0024] The catalyst B described in step (2) is one or more of tetraethylammonium bromide, tetrabutylammonium bromide, tin tetrachloride, boron trifluoride ether complex or boron trifluoride benzylamine complex, and the mass of the catalyst B is 0.1-2% of the mass of the product A.

[0025] The reaction temperature in step (2) is 90-140°C, and the reaction is carried out until the epoxy equivalent is ≥10000 g / eq.

[0026] The preheating temperature in step (3) is 40-80°C.

[0027] The addition time described in step (3) is 1-2h.

[0028] The aliphatic polyamine described in step (3) is one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,5-pentanediamine or 2-methyl-1,5-pentanediamine.

[0029] The reaction temperature in step (3) is 130-190°C and the reaction time is 3-6h.

[0030] The epoxy resin described in step (4) is one or more of bisphenol A epoxy resin E-21, E-20, E-42, E-44 or E51.

[0031] The solvent described in step (4) is one or more of xylene, toluene, ethylene glycol propyl ether or ethylene glycol butyl ether.

[0032] The epoxy resin solution in step (4) contains 60-90 wt.% of epoxy resin.

[0033] The mass ratio of the epoxy resin to the flexible intermediate in step (4) is 60-160:120-230.

[0034] The addition time described in step (4) is 1-2h.

[0035] The first isothermal reaction in step (4) is carried out at a temperature of 60-120° C., and the first isothermal reaction is carried out until the epoxy equivalent is ≥10000 g / eq.

[0036] The dibasic acid described in step (4) is one or more of glutaric acid, adipic acid, terephthalic acid, azelaic acid or 1,4-cyclohexanedicarboxylic acid, and the molar ratio of the epoxy resin to the dibasic acid is 8-15:1.

[0037] The second isothermal reaction temperature in step (4) is 130-190° C., and the second isothermal reaction time is 2-5 h.

[0038] The solid content of the non-ionic flexible epoxy curing agent described in step (4) is 40-55%.

[0039] The preparation method of the nonionic flexible epoxy curing agent of the present invention comprises the following specific steps:

[0040] (1) Add polyether triol into water at 20-95°C and stir evenly, then add catalyst A to dissolve, heat to 100-150°C after the materials are evenly distributed, condense and reflux, introduce oxygen, react at constant temperature for 4-8h, perform the first vacuum distillation at 70-100°C to remove water, wash with solvent, filter the clear liquid and perform the second vacuum distillation to obtain product A (oxidize the triol to tricarboxylic acid);

[0041] (2) melt the product A at 90-140°C, then add a monofunctional epoxy active diluent, stir evenly, add catalyst B, control the reaction temperature at 90-140°C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0042] (3) FIMED is heated to 40-80°C and added dropwise to the aliphatic polyamine at a reaction temperature of 130-190°C. The addition time is controlled within 1-2 hours, and then the reaction is carried out at a constant temperature for 3-6 hours. The excess aliphatic polyamine is then removed by vacuum distillation to obtain product B.

[0043] (4) Dissolve the epoxy resin in a solvent to obtain an epoxy resin solution, add the epoxy resin solution dropwise to product B, and control the dropping time within 1-2 hours. Then, carry out a first isothermal reaction at 60-120°C until the epoxy equivalent is ≥10000 g / eq, then add a dibasic acid, and carry out a second isothermal reaction at 130-190°C for 2-5 hours. Add deionized water to make the solid content 40-55%, and obtain a non-ionic flexible epoxy curing agent.

[0044] The reduced pressure distillation in step (3) removes excess aliphatic polyamine accounting for 60-85% of the total amount of aliphatic polyamine input.

[0045] The nonionic flexible epoxy curing agent prepared by the invention has a total amine value of 160-350 mgKOH / g and an active hydrogen equivalent of 220-450 g / mol.

[0046] The present invention synthesizes an intermediate with a polyether triol skeleton, and improves the hydrophilicity of the product by oxidizing alcohol to acid, so that it has a certain hydrophilic ability. Compared with the intermediate prepared by synthesizing with polyether diol as the skeleton, the intermediate has a branched structure. Due to the presence of the branch, its structure is transformed from a linear structure to a planar structure, and has stronger flexibility, so that it has stronger flexibility and impact resistance when applied to coatings. At the same time, the increase of the branch improves the compactness of the molecular structure, the coating is more compact and has enhanced penetration resistance, and takes into account the water solubility of the curing agent, so that it is better combined with the epoxy emulsion, and the hydrophilic group is not easy to migrate to the coating surface during the curing process, thereby improving the water resistance of the coating and the coating is not easy to whiten. The present invention does not introduce impurity ions such as chloride ions, which is beneficial to the salt spray resistance of the coating and can be better applied to the field of metal corrosion protection.

[0047] In the present invention, the dibasic acid is introduced to react with the amine to reduce the primary amine content, thereby extending the drying time of the curing agent and improving the rheological properties, thereby increasing the applicable period of the coating, improving the coating coating properties and glossiness, and making the curing agent more conducive to industrial use. The amide group obtained by the reaction of the introduced dibasic acid with the amine can also effectively inhibit the foaming and shrinkage cavities of the coating, making the coating surface smoother and flatter, and improving the appearance quality of the coating.

[0048] The nonionic flexible epoxy curing agent prepared by the present invention has a good hydrophilic and lipophilic balance and can be dried at room temperature (low temperature). The coating prepared with the matching emulsion has good impact resistance, flexibility, water resistance and excellent corrosion resistance, does not contain organic solvents, and can be matched with a variety of emulsions / resins for application in multiple fields such as flooring and metal corrosion protection.

[0049] The beneficial effects of the present invention are as follows:

[0050] (1) The present invention adjusts the hydrophilic and lipophilic properties of the curing agent by introducing hydrophilic segments such as polyether triols and aliphatic polyamines into the molecule; oxidizes the polyol to a polyacid, which reacts with an amine to form an amide group, thereby improving the hydrophilicity of the curing agent and making the curing agent have good water solubility. The coating prepared by mixing the curing agent with an epoxy emulsion has high density, excellent adhesion (≤ Grade 1), water resistance of 168h (up to 30d with some matching coatings) and neutral salt spray resistance of up to 500h or more.

[0051] (2) The curing agent of the present invention introduces ether flexible segments such as polyether triol into the molecule, and the coating prepared with the matching epoxy emulsion has super flexibility 1mm and impact resistance, and its impact resistance can reach 100kg·cm.

[0052] (3) The curing agent of the present invention does not introduce organic volatiles, does not contain VOC, and has good environmental protection.

[0053] (4) The curing agent of the present invention has mild preparation conditions and can be cured at room temperature. The curing agent has a longer shelf life and reduced side reactions with primary amines, water and CO2 by capping with a single functional group.

[0054] (5) The curing agent is a water-soluble curing agent that can be directly compatible with a variety of epoxy resins or emulsions. It has strong emulsification ability and adaptability, can be cured at room temperature, and can be used in a variety of fields depending on different emulsions / resins. DETAILED DESCRIPTION

[0055] The present invention is further described below with reference to the embodiments.

[0056] The nonionic flexible epoxy curing agent prepared in the present invention and its coating performance are characterized by the following methods and standards:

[0057] Solid content test of curing agent: Test in accordance with GBT1725-2007 "Determination of non-volatile matter content of paints, varnishes and plastics";

[0058] The viscosity of the curing agent was tested using a Brookfield rotational viscometer DV2T;

[0059] Coating performance test: Drying time, impact resistance, flexibility, and adhesion tests use tinplate, with a coating thickness of 23±3μm; other tests use Q215 steel plates, with a coating thickness of 40±5μm;

[0060] The paint film performance test is carried out according to the following method:

[0061] Drying time: Tested in accordance with GBT1728-2020 "Determination of drying time of paint film and putty film";

[0062] Impact resistance: Tested in accordance with GB / T1732-2020 "Determination of impact resistance of paint films";

[0063] Flexibility: Tested in accordance with GBT1731-2020 "Determination of flexibility of paint and putty films";

[0064] Adhesion: Tested in accordance with GBT9286-2021 "Scratch test for paints and varnishes";

[0065] Hardness: Tested in accordance with GBT6739-2006 "Paint and varnish pencil method for determination of paint film hardness";

[0066] Water resistance: Tested in accordance with the provisions of GB / T1733-1993 Class A;

[0067] Acid resistance: Tested in accordance with the provisions of GB / T9274-1988 Class A;

[0068] Alkali resistance: Tested in accordance with the provisions of GB / T9274-1988 Class A;

[0069] Neutral salt spray resistance: Tested in accordance with GBT1771-2007 "Determination of neutral salt spray resistance of paints and varnishes".

[0070] Example 1

[0071] (1) Add 350 g of polyether triol (molecular weight 700) to a 1000 ml four-necked flask, heat in an oil bath at 60°C, add 150 g of water and stir evenly, then add 49 g of ferric nitrate nonahydrate and 26 g of potassium permanganate to dissolve, heat to 130°C after the materials are uniform, condense and reflux, introduce oxygen, and react at a constant temperature for 6 h, perform the first reduced pressure distillation at 90°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second reduced pressure distillation at 90°C to obtain product A;

[0072] (2) Add 375 g of product A into a 500 ml four-necked flask and melt it at 120°C. Then add 82 g of o-toluene glycidyl ether, stir evenly, add 0.46 g of catalyst tetrabutylammonium bromide, control the reaction temperature at 120°C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0073] (3) Take 228.5g of FIMED, heat it to 60°C and add it dropwise to a 1000ml four-necked flask containing 435g of triethylenetetramine. The reaction temperature is adjusted to 180°C. The addition time is 1.5h, and then the reaction is kept at a constant temperature for 4.5h. Then, 347.3g of excess triethylenetetramine is removed by vacuum distillation to obtain product B.

[0074] (4) 145.5 g of epoxy resin E21 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E21 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product B for 1.5 h, followed by a first isothermal reaction at 80 °C until the epoxy equivalent was ≥10000 g / eq, and then 2.3 g of adipic acid was added, followed by a second isothermal reaction at 180 °C for 4 h, and then deionized water was added to obtain a non-ionic flexible epoxy curing agent.

[0075] Example 2

[0076] (1) Add 225 g of polyether triol (molecular weight 450) to a 500 ml four-necked flask, heat in an oil bath at 70°C, add 100 g of water and stir evenly, then add 12.6 g of copper nitrate trihydrate and 18 g of potassium permanganate to dissolve, heat to 130°C after the materials are uniform, condense and reflux, introduce oxygen, and react at a constant temperature for 8 h, perform the first vacuum distillation at 90°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation at 90°C to obtain product A;

[0077] (2) Add 249 g of product A into a 500 ml four-necked flask and melt it at 120°C. Then add 65 g of o-toluene glycidyl ether, stir evenly, add 0.49 g of tetraethylammonium bromide as a catalyst, control the reaction temperature at 120°C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0078] (3) 157 g of FIMED was heated to 60°C and added dropwise to a 1000 ml four-necked flask containing 410 g of triethylenetetramine. The reaction temperature was adjusted to 180°C. The addition time was 1.5 h, and then the reaction was kept at a constant temperature for 4.5 h. Subsequently, 329.6 g of excess triethylenetetramine was removed by vacuum distillation to obtain product B.

[0079] (4) 156.3 g of epoxy resin E20 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E20 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product B for 1.5 h, followed by a first isothermal reaction at 80 °C until the epoxy equivalent was ≥10000 g / eq, and then 4.5 g of adipic acid was added, followed by a second isothermal reaction at 180 °C for 4 h, and then deionized water was added to obtain a non-ionic flexible epoxy curing agent.

[0080] Example 3

[0081] (1) Add 150 g of polyether triol (molecular weight 300) to a 500 ml four-necked flask, heat in an oil bath at 55°C, add 60 g of water and stir evenly, then add 16 g of ferric nitrate nonahydrate and 14 g of potassium permanganate to dissolve, heat to 130°C after the materials are evenly distributed, condense and reflux, introduce oxygen, and react at a constant temperature for 8 h. Perform the first vacuum distillation at 90°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation at 100°C to obtain product A;

[0082] (2) Add 175.5 g of product A into a 500 ml four-necked flask and melt it at 90 °C. Then add 65 g of butyl glycidyl ether, stir evenly, add 0.49 g of tetraethylammonium bromide as a catalyst, control the reaction temperature at 100 °C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0083] (3) 120.3 g of FIMED was heated to 60°C and added dropwise to a 1000 ml four-necked flask containing 410 g of triethylenetetramine. The reaction temperature was adjusted to 170°C. The addition time was 1.5 h, and then the reaction was kept at a constant temperature for 4.5 h. Subsequently, 329.6 g of excess triethylenetetramine was removed by vacuum distillation to obtain product B.

[0084] (4) 156.3 g of epoxy resin E20 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E20 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product B for 1.5 h, followed by a first isothermal reaction at 90 °C until the epoxy equivalent was ≥10000 g / eq, and then 4.6 g of adipic acid was added, followed by a second isothermal reaction at 180 °C for 4 h, and then deionized water was added to obtain a non-ionic flexible epoxy curing agent.

[0085] Example 4

[0086] (1) Add 150 g of polyether triol (molecular weight 300) to a 500 ml four-necked flask, heat in an oil bath at 60°C, add 60 g of water and stir evenly, then add 16 g of copper nitrate trihydrate and 14 g of potassium permanganate to dissolve, heat to 150°C after the materials are evenly distributed, condense and reflux, introduce oxygen, and react at a constant temperature for 4 h. Perform the first vacuum distillation at 100°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation at 80°C to obtain product A;

[0087] (2) Add 175.5 g of product A into a 500 ml four-necked flask and melt it at 100 °C. Then add 82 g of o-toluene glycidyl ether, stir evenly, add 0.49 g of catalyst tetrabutylammonium bromide, control the reaction temperature at 120 °C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0088] (3) 128.8 g of FIMED was heated to 70°C and added dropwise to a 500 ml four-necked flask containing 325.8 g of 2-methyl-1,5-pentanediamine. The reaction temperature was adjusted to 170°C. The addition time was 2 h, and then the reaction was kept at a constant temperature for 3.5 h. Subsequently, 253.8 g of excess 2-methyl-1,5-pentanediamine was removed by vacuum distillation to obtain product B.

[0089] (4) 71 g of epoxy resin E44 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E44 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product B for 2 h, followed by a first isothermal reaction at 100 °C until the epoxy equivalent was ≥10000 g / eq, and then 2.3 g of adipic acid was added, followed by a second isothermal reaction at 190 °C for 4 h, and then deionized water was added to obtain a non-ionic flexible epoxy curing agent.

[0090] Example 5

[0091] (1) Add 150 g of polyether triol (molecular weight 300) to a 500 ml four-necked flask, heat in an oil bath at 60°C, add 60 g of water and stir evenly, then add 16 g of ferric nitrate nonahydrate and 14 g of potassium permanganate to dissolve, heat to 100°C after the materials are uniform, condense and reflux, introduce oxygen, react at a constant temperature for 8 h, perform the first vacuum distillation at 70°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation at 100°C to obtain product A;

[0092] (2) Add 175.5 g of product A into a 500 ml four-necked flask and melt it at 120°C. Then add 82 g of o-toluene glycidyl ether, stir evenly, add 0.49 g of catalyst tetrabutylammonium bromide, control the reaction temperature at 140°C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0093] (3) 128.8 g of FIMED was heated to 80°C and added dropwise to a 500 ml four-necked flask containing 286 g of 1,5-pentanediamine. The reaction temperature was adjusted to 170°C. The addition time was 1 hour, and then the reaction was kept at a constant temperature for 4 hours. Subsequently, 231.2 g of excess 1,5-pentanediamine was removed by vacuum distillation to obtain product B.

[0094] (4) 61.4 g of epoxy resin E51 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E51 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product B for 1.5 h, followed by a first isothermal reaction at 80 °C until the epoxy equivalent was ≥10000 g / eq, and then 30.1 g of adipic acid was added, followed by a second isothermal reaction at 160 °C for 5 h, and then deionized water was added to obtain a non-ionic flexible epoxy curing agent.

[0095] Comparative Example 1

[0096] (1) Add 157.5 g of polyether diol (molecular weight 315) to a 500 ml four-necked flask, heat in an oil bath at 60°C, add 60 g of water and stir evenly, then add 12 g of ferric nitrate nonahydrate and 10 g of potassium permanganate to dissolve, heat to 130°C after the materials are uniform, condense and reflux, introduce oxygen, and react at a constant temperature for 8 h. Perform the first vacuum distillation at 90°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation to obtain product a (oxidize the diol to dicarboxylic acid);

[0097] (2) Add 175.5 g of product a into a 500 ml four-necked flask and melt at 120° C. Then add 41 g of o-toluene glycidyl ether, stir evenly, add 0.49 g of catalyst tetrabutylammonium bromide, control the reaction temperature at 120° C., and react until the epoxy equivalent is ≥10000 g / eq to obtain an intermediate;

[0098] (3) Take 200g of the intermediate, heat it to 60°C and add it dropwise to a 500ml four-necked flask containing 300g of 1,5-pentanediamine. The reaction temperature is adjusted to 170°C. The addition time is 1.5h, and then the reaction is kept at a constant temperature for 4.5h. Then, the excess 1,5-pentanediamine (221g) is removed by vacuum distillation to obtain product b.

[0099] (4) 72 g of epoxy resin E51 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E51 accounted for 80 wt.%), and the epoxy resin solution was added dropwise to product b for 1.5 h, followed by a first isothermal reaction at 80 °C until the epoxy equivalent was ≥10000 g / eq, and then 26 g of adipic acid was added, followed by a second isothermal reaction at 180 °C for 4 h, and then deionized water was added to obtain a curing agent.

[0100] Comparative Example 2

[0101] (1) Add 150 g of polyether triol (molecular weight 300) to a 500 ml four-necked flask, heat in an oil bath at 60°C, add 60 g of water and stir evenly, then add 16 g of ferric nitrate nonahydrate and 14 g of potassium permanganate to dissolve, heat to 100°C after the materials are uniform, condense and reflux, introduce oxygen, react at a constant temperature for 8 h, perform the first vacuum distillation at 70°C to remove water, then wash with isopropanol and dichloromethane, filter the clear liquid and perform the second vacuum distillation at 100°C to obtain product A;

[0102] (2) Add 175.5 g of product A into a 500 ml four-necked flask and melt it at 120°C. Then add 82 g of o-toluene glycidyl ether, stir evenly, add 0.49 g of catalyst tetrabutylammonium bromide, control the reaction temperature at 140°C, and react until the epoxy equivalent is ≥10000 g / eq to obtain a flexible intermediate (FIMED);

[0103] (3) 128.8 g of FIMED was heated to 80°C and added dropwise to a 500 ml four-necked flask containing 286 g of 1,5-pentanediamine. The reaction temperature was adjusted to 170°C. The addition time was 1 hour, and then the reaction was kept at a constant temperature for 4 hours. Subsequently, 231.2 g of excess 1,5-pentanediamine was removed by vacuum distillation to obtain product B.

[0104] (4) 61.4 g of epoxy resin E51 was dissolved in xylene to obtain an epoxy resin solution (epoxy resin E51 accounted for 80 wt.%). The epoxy resin solution was added dropwise to product B for 1.5 h. The mixture was then reacted at 80° C. until the epoxy equivalent was ≥10,000 g / eq. Deionized water was then added to obtain a curing agent.

[0105] After testing, the performance parameters of the curing agents prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1.

[0106]

[0107] Application Example 1

[0108] The nonionic flexible epoxy curing agent prepared in Example 1 was mixed with liquid epoxy resin E-51 (epoxy equivalent 196 g / eq) at a molar ratio of epoxy group to amino hydrogen of 1:0.8, and then diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to a test plate using an applicator and a brush coating method.

[0109] Application Example 2

[0110] The nonionic flexible epoxy curing agent prepared in Example 2 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) at a molar ratio of epoxy group to amino hydrogen of 1:0.8, and diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to a test plate using an applicator and a brush coating method.

[0111] Application Example 3

[0112] The nonionic flexible epoxy curing agent prepared in Example 3 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) at a molar ratio of epoxy group to amino hydrogen of 1:0.8, and then diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to a test plate using an applicator and a brush coating method.

[0113] Application Example 4

[0114] The nonionic flexible epoxy curing agent prepared in Example 4 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) at a molar ratio of epoxy group to amino hydrogen of 1:0.8, and diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to a test plate using an applicator and a brush coating method.

[0115] Application Example 5

[0116] The nonionic flexible epoxy curing agent prepared in Example 5 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) at a molar ratio of epoxy group to amino hydrogen of 1:0.8, and diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to a test plate using an applicator and a brush coating method.

[0117] Application Example 6

[0118] The curing agent prepared in the above comparative example 1 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) according to the molar ratio of epoxy group to amino hydrogen of 1:0.8, and diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to the test plate using an applicator and a brush coating method.

[0119] Application Example 7

[0120] The curing agent prepared in the above comparative example 2 was mixed with the epoxy emulsion Ancarez AR555 (epoxy equivalent 1300 g / eq) according to the molar ratio of epoxy group to amino hydrogen of 1:0.8, and diluted with water to a system solid content of 40% to obtain a two-component water-based epoxy resin varnish, which was applied to the test plate using an applicator and a brush coating method.

[0121] Application example 1 is applied to the flooring field, and application examples 2-7 are applied to metal corrosion protection. The test results of the coating performance prepared by application examples 1-7 (maintained at 23±2℃ for 7 days after curing) are shown in Table 2.

[0122]

[0123] It can be seen from Table 2 that the product prepared by the nonionic flexible epoxy curing agent of the present invention has excellent flexibility and impact resistance. Compared with the product produced by the curing agent prepared by polyether diol in Application Example 6, Application Examples 1-5 have obvious advantages in flexibility, impact resistance, alkali resistance and neutral salt spray resistance. Compared with the product produced by the curing agent prepared without adding adipic acid in Application Example 7, the introduction of adipic acid in Application Examples 1-5 has a more obvious advantage in the application period of the coating. According to Application Examples 1-5, the present invention can select different resins / emulsions for application in the field of epoxy flooring / metal corrosion protection.

Claims

1. A method for preparing a nonionic flexible epoxy curing agent, characterized in that The steps include: (1) Add polyether triol into water and stir evenly, then add catalyst A to dissolve, heat, condense and reflux, introduce oxygen, react at constant temperature, perform the first vacuum distillation, wash with solvent, filter to obtain clear liquid and perform the second vacuum distillation to obtain product A; (2) After the product A is melted, a monofunctional epoxy active diluent is added, stirred evenly, and a catalyst B is added to react to obtain a flexible intermediate; (3) The flexible intermediate is preheated and then added to aliphatic polyamine for constant temperature reaction, followed by vacuum distillation to obtain product B; (4) dissolving an epoxy resin in a solvent to obtain an epoxy resin solution, adding the epoxy resin solution to product B for a first isothermal reaction, then adding a dibasic acid for a second isothermal reaction, and adding deionized water to obtain a nonionic flexible epoxy curing agent; The molecular weight of the polyether triol described in step (1) is 170-1000, and the mass ratio of the polyether triol to water is 150-350:60-150; The stirring temperature in step (1) is 20-95°C, the catalyst A is one or more of copper nitrate, ferric nitrate or potassium permanganate, the mass of the catalyst A is 8-22% of the mass of the polyether triol, the temperature is raised to 100-150°C, and the constant temperature reaction time is 4-8h; The melting temperature in step (2) is 90-140°C; The monofunctional epoxy reactive diluent in step (2) is one or more of phenyl glycidyl ether, butyl glycidyl ether or o-toluene glycidyl ether, and the molar ratio of product A to the monofunctional epoxy reactive diluent is 1:0.8-1.3; The catalyst B in step (2) is one or more of tetraethylammonium bromide, tetrabutylammonium bromide, tin tetrachloride, boron trifluoride ether complex or boron trifluoride benzylamine complex, the mass of the catalyst B is 0.1-2% of the mass of the product A, the reaction temperature is 90-140°C, and the reaction is carried out until the epoxy equivalent is ≥10000g / eq; The preheating temperature in step (3) is 40-80°C, the addition time is 1-2h, the aliphatic polyamine is one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,5-pentanediamine or 2-methyl-1,5-pentanediamine, the reaction temperature is 130-190°C, and the reaction time is 3-6h; The epoxy resin in step (4) is one or more of bisphenol A epoxy resin E-21, E-20, E-42, E-44 or E51, the epoxy resin accounts for 60-90wt.% of the epoxy resin solution, and the mass ratio of the epoxy resin to the flexible intermediate is 60-160:120-230; The addition time in step (4) is 1-2 hours, the first isothermal reaction temperature is 60-120°C, the first isothermal reaction is carried out until the epoxy equivalent is ≥10000 g / eq, the dibasic acid is one or more of glutaric acid, adipic acid, terephthalic acid, azelaic acid or 1,4-cyclohexanedicarboxylic acid, the molar ratio of epoxy resin to dibasic acid is 8-15:1, the second isothermal reaction temperature is 130-190°C, and the second isothermal reaction time is 2-5 hours; The solid content of the non-ionic flexible epoxy curing agent described in step (4) is 40-55%.

2. The method for preparing the nonionic flexible epoxy curing agent according to claim 1, characterized in that The temperature of the first vacuum distillation in step (1) is 70-100°C, the solvent is one or more of ethyl acetate, chloroform, dichloromethane or isopropanol, and the temperature of the second vacuum distillation is 50-110°C.

3. The method for preparing the nonionic flexible epoxy curing agent according to claim 1, characterized in that The solvent described in step (4) is one or more of xylene, toluene, ethylene glycol propyl ether or ethylene glycol butyl ether.

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