Flexible aqueous epoxy curing agent, its preparation method and application

Abstract

The present invention provides an anionic / nonionic aqueous epoxy curing agent, a preparation method thereof and an application. The raw materials of the aqueous epoxy curing agent include: 1 part of epoxy resin; 0.65 - 6 parts of polyamine compound; 0.1 - 1 part of anionic / nonionic emulsifier; 0.25 - 1.25 parts of monoepoxy active diluent. The anionic / nonionic aqueous epoxy curing agent of the present invention has controllable reaction activity, good hydrophilicity, good water dispersion performance, can be dispersed or dissolved in water, has good stability and construction performance, and the paint film prepared by matching with an epoxy resin emulsion has excellent impact resistance, flexibility, salt spray resistance and strong adhesion.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne epoxy coatings, and particularly relates to an anionic / nonionic waterborne epoxy curing agent, a preparation method thereof, and an application thereof. Background Art

[0002] Epoxy resin coatings have excellent adhesion, mechanical properties, and chemical resistance, and are widely used in fields such as coating anticorrosion, civil engineering, and adhesives. Since traditional solvent-based epoxy coatings contain organic volatiles such as formaldehyde and benzene, which seriously affect the ecological environment and human health, the research on waterborne epoxy coatings is an important trend in the development of coatings today. As a key component of the waterborne epoxy system, the curing agent plays a decisive role in the final performance of the paint film. At present, most of the waterborne epoxy curing agents on the market are dispersed in water by introducing nonionic hydrophilic groups or organic acids to neutralize and form salts. There are mainly two types of waterborne epoxy curing agents based on this method: one is an amide-modified curing agent, and the other is an epoxy-amine addition-modified curing agent. For example:

[0003] CN 1292008 A involves an amide-modified curing agent. After the curing agent modifies polyethylene glycol or poly(ethylene glycol-co-propylene glycol) to obtain a carboxyl-terminated polymer, an amide reaction is carried out with a polyamine to obtain a polyether-modified amide curing agent. The curing agent obtained by this preparation method is a water-dispersed type, and there is a certain problem with the compatibility between itself and the epoxy resin due to the large structural difference between the two; at the same time, the oxidation process of the carboxyl-terminated polyethylene glycol is cumbersome, the synthesis is relatively troublesome, and it is not suitable for industrialization.

[0004] CN 103261317 A proposes a curing agent modified based on an emulsifier. Since the emulsion and the curing agent have a relatively similar structure and good compatibility between the two, there will be an obvious thickening phenomenon and a suitable use window; however, the structure of this curing agent is relatively complex, requires multiple steps of reaction, and the preparation of some of its raw materials is relatively troublesome, and it has high requirements for industrial equipment.

[0005] In order to achieve the hydrophilicity of the curing agent, CN 1084864 A proposes to react oxidized polyethylene glycol with polyamine to prepare a polyamide curing agent. In addition to the technical difficulty of synthesis, an external catalyst is also required to achieve curing under room temperature conditions, and the situation of a fast-drying curing agent without the presence of a catalyst cannot be solved yet.

[0006] The preparation methods of room-temperature-curing waterborne epoxy curing agents are disclosed in US 4246148 and US 460840. Since these two patents mainly involve modified products of aliphatic polyamines, it means that the hydrophilicity of the products obtained after the ring-opening addition of aliphatic polyamines and bisphenol A-type epoxy resins decreases. To ensure good dispersibility of such curing agents in water, organic acids (such as acetic acid) are often added to the curing agents for neutralization and salt formation to improve hydrophilicity. However, the introduction of organic acids will cause flash rust on the metal coating film, resulting in a decline in the performance of the coating. Moreover, such curing agents are easily affected by pH changes. For example, instability is likely to occur when paired with alkaline pigments and fillers. Summary of the Invention

[0007] The first object of the present invention is to provide an anionic / non-ionic waterborne epoxy curing agent, which has a small emulsifier content, good stability, and good compatibility with epoxy resins.

[0008] The second object of the present invention is to provide a preparation method of the aforementioned anionic / non-ionic waterborne epoxy curing agent, and this preparation method is simple and easy to operate.

[0009] The third object of the present invention is to provide the application of the aforementioned anionic / non-ionic waterborne epoxy curing agent and the anionic / non-ionic waterborne epoxy curing agent prepared according to the aforementioned method in the preparation of epoxy resin coatings.

[0010] To achieve the first object of the invention, the following technical solutions are adopted:

[0011] A flexible waterborne epoxy curing agent, which is prepared from raw materials including the following parts by weight:

[0012]

[0013] Among them, the polyamine compound is any one or a combination of more than one of aliphatic polyamines, alicyclic polyamines, and aromatic polyamines; in a specific embodiment, the polyamine compound is selected from primary amines with at least 4 active hydrogens. For example, the aliphatic polyamine is an aliphatic diamine and / or an aliphatic triamine, the alicyclic polyamine is an alicyclic diamine and / or an alicyclic triamine, and the aromatic polyamine is an aromatic diamine and / or an aromatic triamine.

[0014] In a specific embodiment, the polyamine compound is any one or a combination of more than one of ethylenediamine, propylenediamine, butylenediamine, 2-methyl-1,5-pentanediamine, 1,6-hexanediamine, diethylenetriamine, m-xylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1-ethyl-1,3-propanediamine, p-aminodicyclohexylmethane, 2,2,4-trimethyl-1,6-hexanediamine, p-phenylenediamine, polyetheramine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, polyethyleneimine, and diethyltoluenediamine; preferably any one or a combination of more than one of m-xylenediamine, diethylenetriamine, polyetheramine, isophoronediamine, and triethylenetetramine.

[0015] Those skilled in the art understand that the epoxy resin described in the present invention refers to a compound containing at least 2 epoxy groups and can be an aliphatic epoxy resin and / or an aromatic epoxy resin. In one embodiment, the epoxy resin can be any one or a combination of more than one of polyol glycidyl ethers, polyphenol glycidyl ethers, and polycarboxylic acid glycidyl esters, preferably polyol glycidyl ethers and / or polyphenol glycidyl ethers; further preferably, the epoxy equivalent of the epoxy resin is 150 - 4000 g / mol, preferably 200 - 2000 g / mol, such as 300 g / mol, 500 g / mol, 700 g / mol, 1000 g / mol, 1500 g / mol, and 1800 g / mol. The molecular weight of the epoxy resin used in the present invention can be less than or equal to 1000 daltons. In a further embodiment, the epoxy resin is any one or a combination of more than one of bisphenol A type epoxy resin, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether. For example, the polyepoxide is epoxy resin E51 or epoxy resin E44.

[0016] In the present invention, the monoepoxy active diluent is any one or a combination of epoxy ethers of phenols, epoxy esters of unsaturated alcohols, epoxy esters of unsaturated carboxylic acids, aliphatic glycidyl ethers, and aromatic glycidyl ethers. In one embodiment, the monoepoxy active diluent is preferably any one or a combination of epoxy ethers of phenols, aliphatic glycidyl ethers with 1 to 18 carbon atoms, and aromatic glycidyl ethers with 10 to 18 carbon atoms. Those skilled in the art understand that the epoxy ethers of phenols are selected from epoxy ethers of phenol, epoxy ethers of cresol, epoxy ethers of phenols substituted with C1-C21 alkyl groups, epoxy ethers of phenols substituted with C7-C21 aralkyl groups, epoxy ethers of phenols substituted with C7-C21 alkaryl groups, cardanol glycidyl ether, and epoxy ethers of phenols substituted with alkoxy groups; the epoxy esters of unsaturated carboxylic acids are selected from monocarboxylic acid glycidyl esters (glycidyl octanoate, glycidyl decanoate, glycidyl laurate, glycidyl stearate, glycidyl arachidate), glycidyl neodecanoate, methyl epoxidized oleate, n-butyl epoxidized oleate, methyl epoxidized palmitoleate, and ethyl epoxidized linoleate. The aromatic glycidyl ethers with 10 to 18 carbon atoms are selected from phenyl glycidyl ether, o-tolyl glycidyl ether, and benzyl glycidyl ether. The aliphatic glycidyl ethers with 1 to 18 carbon atoms are selected from butyl glycidyl ether, aliphatic glycidyl ethers with 12 to 14 long alkyl chains, tert-butyl glycidyl ether, cyclohexyl glycidyl ether, allyl glycidyl ether, octyl glycidyl ether, isopropyl glycidyl ether, decyl glycidyl ether, and p-tert-butylphenyl glycidyl ether.

[0017] In a preferred embodiment, the monoepoxy active diluent is any one or a combination of cardanol glycidyl ether, butyl glycidyl ether, C12-C14 alkyl glycidyl ether, tolyl glycidyl ether, phenyl glycidyl ether, nonylphenyl glycidyl ether, and p-tert-butylphenyl glycidyl ether. In a further preferred embodiment, the monoepoxy active diluent is any one or a combination of butyl glycidyl ether, C12-C14 alkyl glycidyl ether, tolyl glycidyl ether, phenyl glycidyl ether, nonylphenyl glycidyl ether, and p-tert-butylphenyl glycidyl ether.

[0018] In the present invention, the anionic / nonionic emulsifier is shown in Formula I, and its molecular structure contains a nonionic segment and a sulfonate ion.

[0019]

[0020] Among them, R is a substituted or unsubstituted organic group, which can be an alkyl group, a cycloalkyl group or a phenyl group; R1 is a substituted or unsubstituted organic group, and the organic group can be an alkyl group or a cycloalkyl group; R2 is hydrogen, or a substituted or unsubstituted organic group, and the organic group can be an alkyl group or a cycloalkyl group; m is the degree of polymerization of the epoxy resin, 0 ≤ m ≤ 14, preferably 0 - 4; n is the repetition number of epoxyethane groups or epoxypropane groups, 6 ≤ n ≤ 220, preferably 10 - 170.

[0021] The second object of the present invention is to provide a preparation method of an anionic / nonionic emulsifier, which is prepared by reacting raw materials including the following components:

[0022] S1 At least one polyether polyol;

[0023] S2 At least one acid anhydride, wherein the molar ratio of the total amount of acid anhydride groups in S2 to the total amount of hydroxyl groups in the polyether polyol is (1 - 1.2):1, preferably (1 - 1.1):1;

[0024] S3 At least one epoxy resin, wherein the molar ratio of the total amount of epoxy groups in S3 to the total amount of carboxyl groups in the polyether - acid anhydride reactant is ≥2:1, preferably (2 - 3):1;

[0025] S4 At least one aminosulfonic acid or aminosulfonate, as shown in formula II, wherein R1 is a substituted or unsubstituted organic group, and the organic group can be an alkyl group or a cycloalkyl group. R2 is hydrogen or a substituted or unsubstituted organic group, and the organic group can be an alkyl group or a cycloalkyl group, wherein the alkyl group and the cycloalkyl group can be the same as or different from those in R1 respectively. Among them, the molar ratio of the active hydrogen in S4 to the total amount of epoxy groups in the reaction product of S1, S2, and S3 is ≤1:1. The aminosulfonate is prepared by alkali neutralization of aminosulfonic acid, and the active hydrogen in S4 refers to the hydrogen on the amino group. After the reaction of S1, S2, and S3, a reaction product containing epoxy groups will be obtained.

[0026]

[0027] In one embodiment, the general structural formula of the polyether polyol is as follows:

[0028]

[0029] Among them, R represents a hydrogen atom, a methyl group, an ethyl group, etc., an alkyl group with 1 - 12 carbon atoms, more preferably a hydrogen atom or an alkyl group with 1 - 4 carbon atoms; A represents a hydrogen atom or a methyl group; n represents the repetition number of epoxyethane groups or epoxypropane groups, 6 ≤ n ≤ 220, preferably 10 - 170. The number - average molecular weight of the polyether segment used in the present invention is 300 - 10000, preferably 500 - 8000.

[0030] The anhydride is an anhydride of a polycarboxylic acid having 2 to 4 carboxyl groups in the molecule, preferably an anhydride obtained by intramolecular dehydration of a polycarboxylic acid having 2 to 3 carboxyl groups, such as conventionally known anhydrides such as anhydrides from aromatic polycarboxylic acids or cycloaliphatic polycarboxylic acids, preferably anhydrides from aromatic polycarboxylic acids. Examples of the anhydride of an aromatic polycarboxylic acid include hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, benzophenone-3,3',4,4'-tetracarboxylic dianhydride, etc., and hexahydrophthalic anhydride and trimellitic anhydride are more preferred. In addition, examples of the anhydride of a cycloaliphatic polycarboxylic acid include hydrogenated trimellitic anhydride, hydrogenated pyromellitic dianhydride, etc.

[0031] In a specific embodiment, the preparation method of the anionic / nonionic emulsifier comprises the following steps:

[0032] (1) Mix components S1 and S2 evenly and react until the acid value in the system basically reaches or approaches the theoretical value to generate a polyether / anhydride reactant. The reaction temperature is 100 to 150 °C, and the reaction time is 2 to 5 h;

[0033] (2) Add component S3 and a catalyst to the reaction system in step (1) for a ring-opening reaction to obtain an emulsifier intermediate. The reaction temperature is 100 to 150 °C, and the reaction time is 2 to 5 h;

[0034] (3) Add the metered component S4 to the above emulsifier intermediate, stir and mix evenly for reaction to obtain an anionic / nonionic emulsifier. The reaction temperature is 60 to 100 °C, and the reaction time is 1 to 3 h.

[0035] The catalyst in the above step (2) is well known in the art, for example, it is one or more of triphenylphosphine, triphenylphosphine hydride, boron trifluoride diethyl etherate, quaternary ammonium salts, and its dosage is more than 0.05 wt% of the emulsifier intermediate, preferably 0.1 wt% to 0.5 wt%.

[0036] Preferably, the anionic / nonionic emulsifier has at least 1 epoxy group so as to participate in the reaction during curing. Those skilled in the art can understand that in the reaction of the anionic / nonionic emulsifier, the epoxy resin can be selected from any one or a combination of the foregoing epoxy resins.

[0037] The third object of the present invention is to provide a preparation method of an anionic / nonionic waterborne epoxy curing agent, comprising the following steps:

[0038] (1) Mix the epoxy resin and the anionic / nonionic epoxy active emulsifier to form a resin component;

[0039] (2) The resin component is added dropwise to the polyamine compound for ring-opening reaction. After the addition is completed, keep the temperature for 0.5 - 3 h, and then perform vacuum distillation to remove the excessive polyamine compound to obtain an intermediate.

[0040] (3) Optionally, in the presence of a solvent or water, the monocyclic epoxide is added dropwise to the intermediate for end-capping reaction. After the addition is completed, keep the temperature for 0.5 - 3 h to obtain an end-capped product.

[0041] (4) Deionized water is added to the end-capped product for mixing to obtain an anionic / nonionic aqueous epoxy curing agent.

[0042] Those skilled in the art understand that the solvent in step (3) is a commonly used organic solvent in the art, such as any one or a combination of propylene glycol methyl ether, ethylene glycol butyl ether, dipropylene glycol dimethyl ether, acetone, methyl ethyl ketone, and butanol.

[0043] Those skilled in the art understand that in step (2), in order to obtain the structure of the intermediate, it is necessary to ensure that the polyamine compound is in excess during the reaction. If the resin component is added too quickly, it will lead to too high a local resin component concentration, which will affect the structure of the obtained intermediate. Therefore, the resin component is added dropwise (preferably drop by drop) to the polyamine compound to avoid adverse effects caused by too fast addition.

[0044] Preferably, in step (2), the reaction temperature of the ring-opening reaction is 60 - 120 °C, preferably 80 - 100 °C, such as 85 °C, 90 °C, and 95 °C; the reaction time is 0.5 - 5 h, preferably 1 - 3 h, such as 1.5 h, 2 h, and 2.5 h.

[0045] Preferably, in step (3), the reaction temperature of the end-capping reaction is 60 - 120 °C, preferably 80 - 100 °C, such as 85 °C, 90 °C, and 95 °C; the dropping time of the monocyclic epoxide is 0.5 - 4 h, preferably 1 - 3 h, such as 1.5 h, 2 h, and 2.5 h.

[0046] According to the preparation method of the present invention, other non-ideal structures may be generated in the obtained flexible aqueous epoxy curing agent product (such as the structure obtained by the ring-opening reaction of one molecule of polyamine compound and multiple molecules of epoxy compound). However, the preparation process does not involve the separation of by-products, but uses them as a whole, and all evaluation effects are also based on the whole. The progress of the reaction is monitored by near-infrared method and nuclear magnetic method. The disappearance of epoxy groups proves the end of the reaction, and the performance indexes of the finally obtained aqueous epoxy curing agent system include: amine value, solid content, and pH value. In one embodiment, the amine value of the aqueous epoxy curing agent is 100-500 mgKOH / g, preferably 150-350 mgKOH / g, such as 200 mgKOH / g, 250 mgKOH / g, and 300 mgKOH / g; the solid content is 40-80 wt%; the pH value is 8-12, preferably 9-11, such as 9.5, 10, and 10.5.

[0047] Finally, the present invention provides the application of the aforementioned flexible aqueous epoxy curing agent and the flexible aqueous epoxy curing agent prepared according to the aforementioned method in the preparation of epoxy resin coatings.

[0048] The beneficial effects of the present invention are as follows:

[0049] (1) The anionic / non-ionic aqueous epoxy curing agent of the present invention has good hydrophilicity, good stability and construction performance. The epoxy resin structure is introduced into the main chain, thus ensuring good compatibility with epoxy resin.

[0050] (2) The anionic / non-ionic aqueous epoxy curing agent of the present invention can have very good stability with less emulsifier content, good water dispersion performance, can be dispersed or dissolved in water. When the epoxy resin coating prepared by using it in combination with epoxy resin emulsion is applied, the paint film has excellent salt spray resistance and water resistance.

[0051] (3) The preparation method of the anionic / non-ionic aqueous epoxy curing agent of the present invention has a simple process and is easy to operate. Specific Embodiments

[0052] The technical solutions and their effects of the present invention are further described below through specific examples. The following examples are only used to illustrate the content of the present invention and do not limit the protection scope of the present invention. Simple changes made to the present invention using the concept of the present invention are within the scope of protection required by the present invention.

[0053] The sources of raw materials used in the following examples and comparative examples are shown in Table 1.

[0054] Table 1 Sources of raw materials used in Examples 1-12 and Comparative Examples 1-3 of the present invention

[0055]

[0056]

[0057] The testing methods are as follows:

[0058] The pendulum hardness refers to GB / T 1730 "Determination of film hardness - Pendulum damping test";

[0059] The adhesion refers to GB / T 9286 "Cross - cut test for paints and varnishes films";

[0060] The water resistance refers to GB / T 1733 "Determination of water resistance of films";

[0061] The salt - spray resistance refers to GB / T 1765 "Method for preparation of films for determining resistance to damp heat, salt spray and weathering (artificial accelerated)".

[0062] 30 - day thermal storage stability test of water - borne epoxy curing agent: Place the sample to be tested in an oven at a constant temperature of 50 °C and test whether stratification occurs within 30 days.

[0063] Amine value test of water - borne epoxy curing agent: Test by titration method. First, dissolve the sample to be tested in methanol, then add di - n - butylamine - chlorobenzene solution to it, and conduct potentiometric titration with a standard hydrochloric acid solution until a mutation occurs. Conduct a blank titration in the same way. The final result is calculated based on the mass of KOH equivalent to the sample, with the unit of mgKOH / g.

[0064] Infrared spectrum test: During the reaction process of preparing the water - borne epoxy curing agent, take samples from the reaction system as the samples to be tested; then use a Fourier transform infrared spectrometer to measure the samples to be tested until the peak at 913 cm -1 Wave number (epoxy group) disappears, and it is considered that the reaction is complete.

[0065] Nuclear magnetic resonance test: During the reaction process of preparing the water - borne epoxy curing agent, take samples from the reaction system as the samples to be tested; then dissolve the samples to be tested with deuterated reagents, and then use nuclear magnetic resonance to conduct hydrogen spectrum analysis on the dissolved samples to be tested. The hydrogen of the epoxy group has an absorption peak at approximately 4.3 chemical shift. Until the signal peak here completely disappears, it is considered that the reaction is complete.

[0066] In the following examples and comparative examples, through comprehensive consideration of these two testing methods of infrared spectrum and nuclear magnetic resonance, the reaction end - point of the water - borne epoxy curing agent during the preparation process is judged. That is, when the signal peaks of the epoxy group disappear as shown by both testing methods, it can be judged that the water - borne epoxy curing agent reaches the reaction end - point during the preparation process.

[0067] Examples 1 - 3 (i.e., S1 - 3)

[0068] Preparation of anionic / nonionic emulsifier

[0069] Example 1 (i.e., S1)

[0070] Inject 1000 g of dehydrated and molten polyethylene glycol 2000 into the kettle, then add 140 g of hexahydrophthalic anhydride into the reaction kettle, heat up to 100 °C, and react (esterification reaction) for about 5 h. After sampling and testing that the acid value of the system reaches the theoretical value, a polyether-acid anhydride reactant is obtained; then inject 575 g of epoxy resin E44 into it, stir evenly, add 1.7 g of triphenylphosphine (catalyst), and react at a constant temperature of 100 °C for 5 h. After testing that the acid value reaches the theoretical value, cool down to 100 °C. Add 235 g of 3-(cyclohexylamino)-propanesulfonic acid (neutralized with NaOH, 40% aqueous solution containing water) to the above system, and react at a constant temperature of 100 °C for 1 h and then discharge to obtain anionic / nonionic emulsifier A1. Let the molar ratio of the total amount of acid anhydride groups in the acid anhydride of the polycarboxylic acid to the total amount of hydroxyl groups in the polyether polyol be n1, then n1 = 1.1:1; let the molar ratio of the total amount of epoxy groups in the epoxy resin to the total amount of carboxyl groups in the polyether-acid anhydride reactant be n2, then n2 = 2.5:1; let the molar ratio of the active hydrogen in the aminosulfonic acid / aminosulfonate to the epoxy groups in the reaction product of the polyether / acid anhydride / epoxy resin be n3, then n3 = 1:2.

[0071] Among them, the theoretical value of the acid value: refers to the milligrams of KOH required to neutralize 1 g of the target product sample, with the unit of mgKOH / g;

[0072] The measured value of the acid value: It is tested by titration method. First, dissolve the sample to be tested (actual product sample) in an acetone-aqueous solution, and perform potentiometric titration with a standard NaOH solution until a mutation occurs, and perform a blank titration in the same way. The final result is calculated based on the mass equivalent to KOH, with the unit of mgKOH / g.

[0073] Examples 2 - 3 (i.e., S2 - 3)

[0074] Prepare anionic / nonionic emulsifiers A2 and A3 according to the method of Example 1, and the reaction conditions are shown in Table 3.

[0075] Table 2 Reaction conditions of anionic / nonionic emulsifiers in S1 - 3

[0076]

[0077] Examples 4 - 8 and Comparative Examples 1 - 5

[0078] Preparation of nonionic waterborne epoxy curing agent

[0079] Example 4 (i.e., S4)

[0080] (1) Add 80 g of epoxy resin E51 and 40 g of anionic / non-ionic epoxy active emulsifier A1 to a beaker, and stir and mix to form a homogeneous and stable resin component; (2) Add 280 g of isophorone diamine to a reaction flask, and preheat the temperature to 80 °C; gradually drip the above resin component into the reaction flask through a peristaltic pump for ring-opening reaction. The dripping time is 2 h, and after the dripping is completed, keep warm for 1 h; then, use a vacuum pump to carry out vacuum distillation on the materials in the reaction flask to remove the excess isophorone diamine in the reaction system; (3) Then add 40 g of glycol methyl ether to the system, and then gradually drip 100 g of phenyl glycidyl ether into the reaction flask through a peristaltic pump for reaction. The dripping time is 1 h, and after the dripping is completed, keep warm for 1 h; (4) After the reaction is completed, add 360 g of deionized water thereto, stir and mix evenly, and then discharge to obtain a non-ionic aqueous epoxy curing agent C1. The obtained non-ionic aqueous epoxy curing agent C1 has a solid content of 45 wt%, an amine value of 150 mg KOH / g, and a pH of 10.

[0081] Examples 5-8 (i.e., S5-8) and Comparative Examples 1-5 (i.e., D1-5)

[0082] Prepare anionic / non-ionic aqueous epoxy curing agents C2-5 and C1'-5' according to the method of Example 4. The substances and dosages used in Examples 4-8 are shown in Table 3, the substances and dosages used in Comparative Examples 1-5 are shown in Table 4, the reaction conditions of each step in Examples 4-8 and Comparative Examples 1-5 are shown in Table 5, and the relevant parameters of the obtained anionic / non-ionic aqueous epoxy curing agents are shown in Table 6.

[0083] Table 3 Substances and dosages used in S4-8

[0084]

[0085]

[0086] Table 4 Substances and dosages used in D1-5

[0087]

[0088] Table 5 Reaction conditions of each step in S4-8 and D1-5 and the obtained products

[0089]

[0090] Table 6 Relevant parameters of the obtained aqueous epoxy curing agents in S4-8 and D1-5

[0091]

[0092] Performance test:

[0093] The anionic / nonionic aqueous epoxy curing agents C1-5 and C1'-5' prepared in Examples 4-8 and Comparative Examples 1-5 were mixed with the aqueous epoxy emulsion to prepare paint films. Among them, the formulations of Component A and Component B used for preparing the paint films are shown in Tables 7 and 8 below.

[0094] Table 7 Formulation of Component A

[0095]

[0096] Table 8 Formulations of Component B corresponding to S4-8 and D1-3

[0097]

[0098] The Component A obtained according to Table 1 and the Component B obtained according to Table 2 were mixed at a mass ratio of 10:1. After stirring for 15 min, a small amount of deionized water was added to adjust to the construction viscosity (the viscosity of the 4# cup was 20 - 50 s, that is, the sample flowed down from the 4# cup within 20 - 50 s) to obtain a mixed paint solution; then the mixed paint solution was made into plates according to the industry operation standard (flash drying and leveling for 10 min and baking at 80 °C for 30 min) to obtain paint films Q1-5 and Q1'-5' respectively. After the paint films Q1-5 and Q1'-5' were left to cure under standard conditions of 23 ± 2 °C and humidity of 50 ± 5% for 7 d, various tests were carried out according to the corresponding test methods.

[0099] After the prepared paint films were tested according to the corresponding test methods, the obtained performance test results are shown in Table 9.

[0100] Table 9 Properties of the aqueous epoxy curing agents obtained in S4-8 and D1-5 and the paint films Q1-5 and Q1'-5' prepared therefrom

[0101]

[0102] All tests were carried out in accordance with national standards, specifically as described in the previous test method section; the resistance data were the test results after 20 days of tracking.

[0103] Among them, the grade of the adhesion test result is from 0 to 5 levels, with 0 level having the best adhesion and 5 level being the worst;

[0104] The grade of the water resistance test result is from 0 to 5 levels, with 5 level being the best and 0 level being the worst;

[0105] The grade of the salt spray resistance test result is from 0 to 5 levels, with 5 level being the best and 0 level being the worst.

[0106] It can be seen from the performance test results in Table 9 that:

[0107] The aqueous epoxy curing agent prepared in Examples 4-8 has good thermal storage stability and no delamination phenomenon, indicating that the introduction of anionic / nonionic hydrophilic groups improves the hydrophilicity of the aqueous epoxy curing agent and enables it to disperse well in water; at the same time, the properties of the paint film prepared from it, such as adhesion, water resistance, salt spray resistance, activation period, and pendulum hardness, are excellent.

[0108] In Comparative Example 1, when preparing the curing agent, no anionic / nonionic emulsifier was added, and the prepared curing agent had poor hydrophilicity and delamination occurred.

[0109] In Comparative Example 2, when preparing the curing agent, a small amount of anionic / nonionic emulsifier was added, and the amount of nonionic groups introduced into the system was small. The prepared curing agent also had poor hydrophilicity and delamination occurred.

[0110] In Comparative Example 3, due to the addition of an excessive amount of anionic / nonionic emulsifier, the curing agent was too hydrophilic, and the water resistance and salt spray resistance of the paint film prepared from it were poor.

[0111] In Comparative Example 4, the conventional ionic emulsifier sodium dodecylbenzenesulfonate was used as the emulsifier, and the addition amount was the same as that of the anionic / nonionic emulsifier in Example S4. The prepared aqueous curing agent had poor stability, and the water resistance and salt spray resistance of the paint film prepared from it were also poor.

[0112] In Comparative Example 5, the conventional nonionic emulsifier polysorbate-20 was used as the emulsifier, and the addition amount was the same as that of the anionic / nonionic emulsifier in Example S4. The prepared aqueous curing agent had poor stability, and the water resistance and salt spray resistance of the paint film prepared from it were also poor.

[0113] From the comparison between Examples 7-12 and Comparative Examples 1-5, it can be seen that the nonionic aqueous epoxy curing agent prepared by the present invention not only has good stability, but also when it is used to prepare an epoxy resin coating, the properties of the finally prepared paint film, such as adhesion, water resistance, salt spray resistance, activation period, and pendulum hardness, are all good; while when the curing agent prepared without adding or adding a small amount of nonionic epoxy active emulsifier, it not only has poor stability and is prone to delamination, but also when it is used to prepare an epoxy resin coating, the properties of the finally prepared paint film, such as adhesion, water resistance, salt spray resistance, activation period, and pendulum hardness, are all poor; while when the curing agent prepared by adding an excessive amount of nonionic epoxy active emulsifier, although it does not delaminate, when it is used to prepare an epoxy resin coating, the properties of the finally prepared paint film, such as adhesion, water resistance, salt spray resistance, activation period, and pendulum hardness, are all poor. And when using the same amount of conventional anionic emulsifier or conventional nonionic emulsifier alone, the prepared curing agent has poor hydrophilicity and poor stability, and delamination occurs during storage, and the adhesion, salt spray resistance, water resistance, etc. of the paint film prepared from it are also poor.

Claims

1. A flexible waterborne epoxy curing agent, which is prepared from raw materials comprising the following parts by weight: The anionic / nonionic emulsifier is shown in Formula I, wherein, R is a substituted or unsubstituted organic group, selected from alkyl, cycloalkyl or phenyl; R1 is a substituted or unsubstituted organic group, selected from alkyl or cycloalkyl; R2 is hydrogen, or a substituted or unsubstituted organic group, and the organic group is selected from alkyl or cycloalkyl; m is the degree of polymerization of the epoxy resin, 0 ≤ m ≤ 14; n is the repetition number of oxyethylene group or oxypropylene group, 6 ≤ n ≤ 220.

2. The flexible waterborne epoxy curing agent according to claim 1, characterized in that, the epoxy resin is one or more of aliphatic epoxy resin and / or aromatic epoxy resin.

3. The flexible waterborne epoxy curing agent according to claim 1, characterized in that, the epoxy resin is any one or a combination of polyol glycidyl ether, polyphenol glycidyl ether and polycarboxylic acid glycidyl ester.

4. The flexible waterborne epoxy curing agent according to claim 1, characterized in that, the polyamine compound is any one or a combination of ethylenediamine, propylenediamine, butylenediamine, 2-methyl-1,5-pentanediamine, 1,6-hexanediamine, diethylenetriamine, m-xylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1-ethyl-1,3-propanediamine, p-aminodicyclohexylmethane, 2,2,4-trimethyl-1,6-hexanediamine, p-phenylenediamine, polyetheramine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, polyethyleneimine and diethyltoluenediamine.

5. The flexible waterborne epoxy curing agent according to any one of claims 1-4, characterized in that, in Formula I, m is the degree of polymerization of the epoxy resin, m is 0-4; n is the repetition number of oxyethylene group or oxypropylene group, n is 10-170.

6. The flexible waterborne epoxy curing agent according to any one of claims 1-4, characterized in that, the monoepoxy active diluent is any one or a combination of epoxy ethers of phenols, epoxy esters of unsaturated alcohols, epoxy esters of unsaturated carboxylic acids, aliphatic glycidyl ethers and aromatic glycidyl ethers.

7. The flexible waterborne epoxy curing agent according to claim 6, characterized in that, the monoepoxy active diluent is any one or a combination of cardanol glycidyl ether, butyl glycidyl ether, C12-C14 alkyl glycidyl ether, tolyl glycidyl ether, phenyl glycidyl ether, nonylphenyl glycidyl ether and p-tert-butylphenyl glycidyl ether.

8. The flexible waterborne epoxy curing agent according to any one of claims 1-4, characterized in that, the anionic / nonionic emulsifier is prepared by reacting raw materials comprising the following components: S1 at least one polyether polyol; S2 at least one acid anhydride, wherein the molar ratio of the total amount of acid anhydride groups in S2 to the total amount of hydroxyl groups in the polyether polyol is (1-1.2):1; S3 at least one epoxy resin, wherein the molar ratio of the total amount of epoxy groups in S3 to the total amount of carboxyl groups in the polyether-anhydride reactant is ≥2:1; S4 At least one sulfamic acid or sulfamate, as shown in Formula II, wherein R 1 is a substituted or unsubstituted organic group, and R 2 is hydrogen or a substituted or unsubstituted organic group, and the organic group is an alkyl group or a cycloalkyl group; wherein the molar ratio of the active hydrogen in S4 to the total amount of epoxy groups in the reaction product of S1, S2, and S3 is ≤1:

1.

9. The flexible aqueous epoxy curing agent according to claim 8, characterized in that the molar ratio of the total amount of acid anhydride groups in S2 to the total amount of hydroxyl groups in the polyether polyol is (1 - 1.1):1; S3 At least one epoxy resin, wherein the molar ratio of the total amount of epoxy groups in S3 to the total amount of carboxyl groups in the polyether - acid anhydride reactant is (2 - 3):

1.

10. The flexible aqueous epoxy curing agent according to claim 8, characterized in that the acid anhydride is an acid anhydride of a polycarboxylic acid having 2 - 4 carboxyl groups in the molecule.

11. The flexible aqueous epoxy curing agent according to claim 10, characterized in that the acid anhydride is an acid anhydride obtained by intramolecular dehydration of a polycarboxylic acid having 2 - 3 carboxyl groups in the molecule.

12. The flexible aqueous epoxy curing agent according to claim 11, characterized in that the acid anhydride is an acid anhydride derived from an aromatic polycarboxylic acid or a cycloaliphatic polycarboxylic acid.

13. The flexible aqueous epoxy curing agent according to claim 12, characterized in that the acid anhydride of the aromatic polycarboxylic acid is selected from hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, benzophenone - 3,3’,4,4’ - tetracarboxylic dianhydride; as the acid anhydride of the cycloaliphatic polycarboxylic acid, it is selected from hydrogenated trimellitic anhydride, hydrogenated pyromellitic dianhydride.

14. The flexible aqueous epoxy curing agent according to claim 8, characterized in that the preparation method of the anionic / nonionic emulsifier comprises the following steps: (1) Mix components S1 and S2 evenly and react until the acid value in the system reaches the theoretical value to generate a polyether / acid anhydride reactant, the reaction temperature is 100 - 150 °C, and the reaction time is 2 - 5 h; (2) Add component S3 and a catalyst to the reaction system in step (1) for ring - opening reaction to obtain an emulsifier intermediate, the reaction temperature is 100 - 150 °C, and the reaction time is 2 - 5 h; (3) Add the metered component S4 to the above emulsifier intermediate, stir and mix evenly for reaction to obtain an anionic / nonionic emulsifier, the reaction temperature is 60 - 100 °C, and the reaction time is 1 - 3 h.

15. The flexible aqueous epoxy curing agent according to any one of claims 1 - 4, characterized in that it comprises the following steps: (1) Mix the epoxy resin and the anionic / nonionic epoxy emulsifier to form a resin component; (2) Drop the resin component into the polyamine compound for ring - opening reaction, keep warm for 0.5 - 3 h after dropping, and then carry out vacuum distillation to remove the excessive polyamine compound to obtain an intermediate; (3) Optionally, in the presence of a solvent, drop the mono - epoxy active diluent into the intermediate for end - capping reaction, keep warm for 0.5 - 3 h after dropping to obtain an end - capped product; (4) Add deionized water to the end - capped product for mixing to obtain an anionic / nonionic aqueous epoxy curing agent.

16. Use of the flexible aqueous epoxy curing agent according to any one of claims 1-15 in the preparation of an epoxy resin coating.

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