CN113563565B - Thermo-sensitive solid amine curing agent and preparation method thereof - Google Patents
Thermo-sensitive solid amine curing agent and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a preparation method of a temperature-sensitive solid amine curing agent, which comprises the following steps: 1) mixing ketone-aldehyde resin and acid anhydride, reacting at a constant temperature of 90-120 ℃ for 3-6 h, and obtaining acid anhydride end-capped modified ketone-aldehyde resin after the reaction is finished; 2) and dissolving the acid anhydride end-capped modified ketone-aldehyde resin, adding an amine monomer solution for neutralization under the stirring condition, removing the solvent, and drying to obtain the thermo-sensitive solid amine curing agent. The temperature-sensitive solid amine curing agent can realize low-temperature curing, and the prepared powder coating has good storage stability, excellent performances of the cured coating, and good decorative and protective performances.
Description
Technical Field
The invention belongs to the technical field of powder coating curing agents, and particularly relates to a temperature-sensitive solid amine curing agent and a preparation method thereof.
Background
The traditional solvent-based paint contains a large amount of Volatile Organic Compounds (VOC), thereby not only polluting the environment and influencing the human health, but also destroying the ecological environment. The powder coating is used as a 4E (high production efficiency, excellent coating performance, economy and environmental protection) type coating variety, and more attention is paid.
Since the 20 th century and the 50 th century, the powder coating is rapidly developed due to the advantages of simple coating process and economy and environmental protection, is gradually replacing the traditional solvent-based coating, and is widely applied to the fields of metal protection, decoration, building and the like. The powder coating is divided into thermoplastic powder coating and thermosetting powder coating, and compared with the thermoplastic powder coating, the thermosetting powder coating has better film coating performance and wider application range. The thermosetting powder paint is mainly solid powder prepared by mixing resin, a curing agent, pigment, a filler, an auxiliary agent and the like, is coated on the surface of a coated object in an electrostatic spraying mode, and is melted and leveled by baking to be cured into a film.
TABLE 1 type of curing agent and characteristics of epoxy powder coating
The curing agent is an important component of the thermosetting powder coating, and can convert the structure of the powder coating into a three-dimensional net-shaped three-dimensional structure to form an insoluble high polymer, so that the powder coating has better mechanical properties, physical properties, corrosion resistance, chemical resistance and the like. Epoxy powder coatings are one of the most important types in the field of powder coatings, and the curing agents used in epoxy powder coatings can be divided into three main categories, namely: amines, acid anhydrides (carboxyl-terminated polyester resins), phenolic resins, etc., and the curing temperatures and storability of the conventional curing agents are shown in Table 1. The curing temperature of the traditional curing agent is high, and the requirements of low curing temperature and good storage stability are difficult to satisfy at the same time. Amine curing agents, which generally have higher reactivity, are the more commonly used type of epoxy resin curing agents. The amine curing agent has certain alkalinity, so that the amine curing agent can be salified with a carboxyl-containing compound to prepare the latent curing agent.
U.S. Pat. Nos. 4335228 and 4742148 and Chinese patent No. CN20100280192 propose the modification of monoimidazole and its derivatives with isocyanates to increase the pot life. U.S. patent 4358571 discloses the use of mono-imidazole which is first reacted with methyl acrylate and then neutralized with a low carbon chain fatty acid or dicarboxylic acid to shield the nitrogen atoms for extended shelf life at ambient temperature. Japanese patent application No. 9143250 discloses the preparation of monoimidazolium adipate compounds by reacting a long carbon chain substituted monoimidazole with adipic acid, which can be used as a curing accelerator for epoxy resins and dicyandiamide, or as a curing agent alone. Chinese patent CN102964568A salifies bisimidazole alkane and polycarboxylic acid to prepare the modified bisimidazole latent curing agent for epoxy resin, and the curing agent has certain latency at 25 ℃ and can rapidly promote the curing of epoxy resin at medium temperature. Ethylene acrylic acid copolymer, aminophenol and imidazole are salified by the Dow's sphere technology Co., Ltd to prepare a series of latent curing accelerators, the latent curing accelerators and epoxy resin are prepared into a single-component adhesive, the curing temperature of the epoxy resin can be greatly reduced, and the working life of the single-component adhesive can reach more than 6 months at 23 ℃.
According to the invention, the amine monomer is sealed in a carboxyl-terminated ketoaldehyde resin system to obtain the temperature-sensitive solid amine curing agent, and the high-activity amine monomer is released through external temperature change, so that the epoxy resin powder coating is cured at a low temperature of 120 ℃, the cured coating has high crosslinking density, high hardness and excellent protection performance are ensured, and meanwhile, the active amine monomer is sealed in the room-temperature storage process, so that the powder coating has good storage stability.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a temperature-sensitive solid amine curing agent which is prepared by using ketone-aldehyde resin as a raw material and utilizing anhydride esterification and neutralization and salt formation of amine monomers, wherein the obtained temperature-sensitive solid amine curing agent can realize low-temperature curing, and the prepared powder coating has good storage stability, and the cured coating has excellent performances and good decorative and protective performances.
The invention also provides a preparation method of the temperature-sensitive solid amine curing agent.
Based on the purpose, the invention adopts the following technical scheme:
a preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) mixing ketone-aldehyde resin and acid anhydride, reacting at a constant temperature of 90-120 ℃ for 3-6 h (the stirring speed is 100-200 rpm), and obtaining acid anhydride end-capped modified ketone-aldehyde resin (the carboxyl amount is 0.70-2.20 mmol/g) after the reaction is finished;
2) dissolving the acid anhydride end-capped modified ketone-aldehyde resin (which can be dissolved by organic solvents such as ethanol, toluene and the like), dropwise adding an ethanol solution of an amine monomer under the condition of stirring at normal temperature, reacting for 20-40min after dropwise adding for neutralization and salt formation, removing the solvent, and drying to obtain the temperature-sensitive solid amine curing agent (the softening point is 60-120 ℃).
Specifically, in step 1), the acid anhydride may be one of phthalic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride, maleic anhydride, tetrahydrophthalic anhydride, and 4-methylhexahydrophthalic anhydride, but is not limited thereto; the molar ratio of the acid anhydride to the hydroxyl in the ketone-aldehyde resin is 1: 1-1.5.
Further, in the step 2), the molar ratio of carboxyl in the end-capped modified ketone-aldehyde resin to amino in the amine monomer is 1-1.5: 1.
Specifically, in step 2), the amine monomer refers to a compound having at least one primary, secondary or tertiary amine group.
Further preferably, suitable amine monomer compounds include ethylenediamine, hexamethylenediamine, m-phenylenediamine, m-xylylenediamine, 1, 3-diaminomethylcyclohexane, polyethylenepolyamine, diethylaminopropylamine, diaminodiphenylmethane, diaminodiphenylsulfone, isophoronediamine, N-aminoethylpiperazine, maleimide, triethylamine, trimethylamine, triethanolamine, etc., but are not limited thereto, and a mixture of different amine monomers may also be used.
Specifically, in the step 2), the amine monomer solution is obtained by dissolving an amine monomer in an organic solvent such as ethanol or methanol, and the concentration of the amine monomer solution is 0.1-1 mol/L.
Firstly, synthesizing the acid anhydride end-capped modified ketone-aldehyde resin.
The synthesis process will be described in detail with phthalic anhydride as an example. The principle of the phthalic anhydride end-capped modified ketone-aldehyde resin is as follows:
the molar ratio of acid anhydride to hydroxyl in ketone-aldehyde resin (cyclohexanone-formaldehyde resin, hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s, shown in figure 1) is 1: 1-1.5, phthalic anhydride and ketone-aldehyde resin are added into a reactor, the reaction is carried out at constant temperature of 90-120 ℃ for 3-6 h, the stirring speed is 100-200 rpm, the reaction product is cooled to room temperature after the reaction is finished, the product is crushed, unreacted substances are washed out by warm water, the product is dried in vacuum and crushed, the obtained product is PCFR, and the infrared spectrogram of the product is shown in figure 2.
And secondly, neutralizing the amine monomer to form salt.
The synthesis procedure will be described in detail by taking an example of the synthesis of a temperature-sensitive solid amine curing agent from PCFR and ethylenediamine. The basic principle of the reaction of ethylenediamine with PCFR is:
preparing 0.5 mol/L ethanol solution from ethylenediamine, slowly dripping (the dripping speed is about 10 ml/min) into the ethanol solution of PCFR, continuously reacting for 20min after the dripping is finished, removing the solvent, and drying to obtain the temperature-sensitive solid amine curing agent.
Compared with the prior art, the invention has the following beneficial effects:
the temperature-sensitive solid amine curing agent provided by the invention is a modified polyamine latent curing agent, takes ketone-aldehyde resin as a framework, has higher thermal deformation temperature, and improves the heat resistance, corrosion resistance and mechanical properties of a resin cured product. When the curing agent is mixed in an epoxy resin system, the amine monomer with high activity is released under the heating condition, the epoxy resin is initiated to be crosslinked to cure the film, carboxyl groups at two ends of the end-capped and modified ketone-aldehyde resin can also partially participate in curing, meanwhile, the end-capped and modified ketone-aldehyde resin remained in the curing system can improve the mechanical property of the curing system, and the hardness of the cured coating reaches 5H-6H. The curing agent has better storage stability under the condition of room temperature, has small dependence on equipment and process, and can be better applied to large-scale automatic production.
Drawings
FIG. 1 is a photograph showing the appearance of a cyclohexanone-formaldehyde resin as a raw material in each example of the present invention;
FIG. 2 is an infrared spectrum of a modified ketoaldehyde resin (PCFR) end-capped using phthalic anhydride as an example according to the present invention; a: a ketone-aldehyde resin; b: PCFR (polycarbonate-derived flame retardant). As can be seen from FIG. 2, the peaks of the stretching vibration absorption peaks of the hydroxyl group (-OH) appearing near 3380 cm-1 and the carbon-oxygen bond (C-O) corresponding to the hydroxyl group appearing around 1026 cm-1 are strongly attenuated, the stretching vibration absorption peak of the carbon-oxygen bond (C = O) corresponding to the ester group appears at 1196 cm-1, and the stretching vibration absorption peak of the carbon-oxygen bond (C = O) corresponding to the carboxyl group appears at 1600 cm-1;
FIG. 3 is an infrared spectrum of a temperature-sensitive solid amine curing agent synthesized by using ethylenediamine as an example in example 1 of the present invention; a: before neutralization of ethylenediamine; b: neutralizing with ethylenediamine. As can be seen from FIG. 3, after neutralization with ethylenediamine, a stretching vibration absorption peak corresponding to carboxylate appears at 1543 cm-1;
FIG. 4 is a photograph of the powder coating of example 5 after it has been spray cured on tin plate.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited thereto.
In the following examples, the ketone-aldehyde resin is a cyclohexanone-formaldehyde resin as an example, and the method of the present invention will be explained in detail. The ketone-aldehyde resin can be purchased from common commercial products directly or prepared by adopting the prior art, for example, refer to patents CN2019110460983 (a high weather resistance ketone-aldehyde glycidyl ether epoxy resin and a preparation method thereof), CN2018103743381 (a preparation method for synthesizing the ketone-aldehyde resin by solid base catalysis), and the master paper "synthesis and functional modification of water-based ketone-aldehyde resin".
Example 1
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.30 g (0.0493 mol) of phthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl group amount (namely acid value) is 2.10 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. Taking 1.15g (0.0191 mol) of ethylenediamine, preparing into 0.5 mol/L ethanol solution, slowly dripping (the dripping speed is about 10 ml/min) into the acid anhydride end-capped modified ketone-aldehyde resin, continuously reacting for 20min after finishing dripping, then performing rotary evaporation at 45 ℃ to remove the solvent, and drying at 45 ℃ in vacuum for 12 h to obtain the powdered temperature-sensitive solid amine curing agent.
Example 2
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.86 g (0.0507 mol) of tetrahydrophthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 100 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl group content is 2.07 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. 1.13 g (0.0188 mol) of ethylenediamine is taken and prepared into 0.5 mol/L ethanol solution, slowly dropwise added (the dropwise adding speed is about 10 ml/min) into the end-capped modified ketone-aldehyde resin, the reaction is continued for 30min after the dropwise adding is finished, then the solvent is removed by rotary evaporation at 45 ℃, and the powdered temperature-sensitive solid amine curing agent can be obtained by drying at 45 ℃ for 12 h.
Example 3
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 8.52 g (0.0597 mol) of 4-methylhexahydrophthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 200 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl amount is 2.06 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. 1.15g (0.0191 mol) of ethylenediamine is taken to prepare 0.5 mol/L ethanol solution, slowly dropwise added (the dropwise adding speed is about 10 ml/min) into the end-capped modified ketone-aldehyde resin, the reaction is continued for 40min after the dropwise addition is finished, then the solvent is removed by rotary evaporation at 45 ℃, and the powdered temperature-sensitive solid amine curing agent can be obtained by drying at 45 ℃ for 12 h.
Example 4
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 1.48 mmol/g, softening point is 80 ℃) and 4.98 g of phthalic anhydride (0.0336 mol) into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the ketone-aldehyde resin with the acid anhydride end-capping modification, wherein the carboxyl group content is 1.24 mmol/g;
2) 20 g of the above-mentioned acid anhydride-terminated modified ketone-aldehyde resin was dissolved in toluene. 0.68 g (0.0113 mol) of ethylenediamine is taken to prepare 0.5 mol/L ethanol solution, slowly dropwise added (the dropwise adding speed is about 10 ml/min) into the end-capped modified ketone-aldehyde resin, the reaction is continued for 20min after the dropwise adding is finished, then the solvent is removed by rotary evaporation at 45 ℃, and the powdered temperature-sensitive solid amine curing agent can be obtained by drying at 45 ℃ for 12 h.
Example 5
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value of 0.86 mmol/g, softening point of 120 ℃) and 3.02 g (0.0195 mol) of phthalic anhydride are added into a three-neck flask, the mixture is reacted for 3 hours at constant temperature (stirring speed of 150 rpm) under the conditions of reaction temperature of 120 ℃ and mechanical stirring, after the reaction is finished, the mixture is cooled to room temperature and crushed, the unreacted substances are removed by washing at 55 ℃ and the generated solid is dried and ground into powder, and the acid anhydride end-capped modified ketone-aldehyde resin is obtained, wherein the carboxyl group content is 0.70 mmol/g.
2) 20 g of the above-mentioned acid anhydride-terminated modified ketone-aldehyde resin was dissolved in toluene. 0.38 g (0.0064 mol) of ethylenediamine is taken to prepare 0.5 mol/L ethanol solution, slowly dropwise added (the dropwise adding speed is about 10 ml/min) into the end-capped modified ketone-aldehyde resin, the reaction is continued for 20min after the dropwise addition is finished, then the solvent is removed by rotary evaporation at 45 ℃, and the powdered temperature-sensitive solid amine curing agent can be obtained by drying at 45 ℃ for 12 h.
Example 6
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.30 g (0.0493 mol) of phthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl group content is 2.10 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. Taking 3.25 g (0.0191 mol) of isophorone diamine and preparing 0.5 mol/L ethanol solution, slowly dripping (the dripping speed is about 10 ml/min) into the acid anhydride end-capped modified ketone-aldehyde resin, continuing to react for 20min after finishing dripping, then removing the solvent by rotary evaporation at 45 ℃, and drying for 12 h at 45 ℃ in vacuum to obtain the powdered temperature-sensitive solid amine curing agent.
Example 7
A preparation method of a temperature-sensitive solid amine curing agent comprises the following steps:
1) adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.30 g (0.0493 mol) of phthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl group content is 2.10 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. Taking 2.07 g (0.0191 mol) of m-phenylenediamine, preparing 0.5 mol/L ethanol solution, slowly dripping (the dripping speed is about 10 ml/min) into the acid anhydride end-capped modified ketone-aldehyde resin, continuously reacting for 20min after finishing dripping, then performing rotary evaporation at 45 ℃ to remove the solvent, and drying at 45 ℃ in vacuum for 12 h to obtain the powdered temperature-sensitive solid amine curing agent.
Example 8
1) Adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.30 g (0.0493 mol) of phthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after reaction, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl amount is 2.10 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. Taking 2.60 g (0.0191 mol) of m-xylylenediamine, preparing 0.5 mol/L ethanol solution, slowly dropwise adding (the dropwise adding speed is about 10 ml/min) into the acid anhydride end-capped modified ketone-aldehyde resin, continuing to react for 20min after the dropwise adding is finished, then performing rotary evaporation at 45 ℃ to remove the solvent, and drying at 45 ℃ for 12 h in vacuum to obtain the powdered temperature-sensitive solid amine curing agent.
Example 9
1) Adding 25.00g of cyclohexanone-formaldehyde resin (hydroxyl value is 2.23 mmol/g, viscosity is 1500 mPa.s) and 7.30 g (0.0493 mol) of phthalic anhydride into a three-neck flask, reacting at 90 ℃ under the condition of mechanical stirring for 3h (stirring speed is 150 rpm), cooling to room temperature after the reaction is finished, crushing, washing with water at 55 ℃ to remove unreacted substances, drying and grinding the generated solid into powder to obtain the acid anhydride end-capped modified ketone-aldehyde resin, wherein the carboxyl group content is 2.10 mmol/g;
2) 20 g of the acid anhydride end-capped modified ketone-aldehyde resin is dissolved in ethanol. 3.79 g (0.0191 mol) of diaminodiphenylmethane is taken and prepared into 0.5 mol/L ethanol solution, slowly dropwise added (the dropwise adding speed is about 10 ml/min) into the acid anhydride end-capped modified ketone-aldehyde resin, the reaction is continued for 20min after the dropwise adding is finished, then the solvent is removed by rotary evaporation at 45 ℃, and the powdery temperature-sensitive solid amine curing agent can be obtained by drying at 45 ℃ for 12 h in vacuum.
The performance parameters (active hydrogen equivalent of curing agent, heat release temperature, etc.) of the temperature-sensitive solid amine curing agent prepared in the above examples 1 to 9 are shown in table 2 below.
TABLE 2 Performance parameters of the temperature-sensitive solid amine curing agent prepared in the example
The smaller the active hydrogen equivalent of the curing agent, the smaller the mass of curing agent required for the same mass of epoxy resin, enabling further cost savings. The heat release temperature ensures that the curing agent can release active amine at a proper temperature (60-120 ℃) to perform curing reaction with the epoxy resin; but shows latency at lower temperature and has good storage stability. As can be seen from the data in Table 2, the temperature-sensitive amino curing agents prepared in examples 1 to 9 all achieved 120 ℃ low temperature curing of epoxy resin powder coatings.
Application test 1
15g of the temperature-sensitive solid amine curing agent prepared in example 5, 100 g of E12 epoxy resin and 60 g of precipitated barium sulfate are taken, mixed uniformly and subjected to electrostatic spraying on a tinplate and a carbon steel plate, and the mixture is placed in a constant-temperature oven at 100 ℃ for 6 hours, so that the thickness of the prepared coating is 60 micrometers, the appearance is shown in figure 4, and the comprehensive performance is shown in table 3.
Table 3 coating performance tests are based on the following national standards:
acid resistance: GB/T9274-1988 determination of liquid-resistant medium of colored paint and varnish (soaking method);
alkali resistance: GB/T9274-1988 determination of liquid-resistant medium of colored paint and varnish (soaking method);
boiling water resistance: GB/T1733 + 1993 paint film water resistance test method (boiling water resistance test);
salt spray resistance: GB/T1771-2007 color paint and varnish neutral salt spray resistance performance measurement;
impact strength: GB/T1732-1993 method for determining the impact resistance of a paint film;
pencil hardness: GB/T6739-;
adhesion force: GB/T9286-1998 paint and varnish paint film marking test;
bending property: GB/T6742-2007 color paint and varnish bending test (cylindrical axis).
The spraying process comprises the following steps: NPES-604 epoxy resin is used as matrix resin, the product obtained in example 5 is used as an epoxy resin curing agent, the epoxy resin and the curing agent are mixed according to a certain proportion, and then the mixture is ball-milled in a planetary ball mill for 10 hours and sieved by a 100-mesh screen to obtain the uniformly mixed powder coating. Carrying out oil and rust removal treatment on the surface of a test plate by using a tinplate according to the national standard GB/T9271-plus 2008 'color paint and varnish standard test plate', vertically placing the treated test plate in a spraying box, turning on a power switch of a spraying machine, setting the working voltage of the spraying machine to be 60 KV, putting powder into a powder supply cup, adjusting the output air pressure of an air compressor to be 0.4 MPa, and uniformly spraying powder coating on the surface of the test plate. And then, putting the test piece into an oven at 120 ℃ for curing for 4h to obtain a product as shown in FIG. 4. From figure 4 we can see that the surface of the coating cured using example 5 has good gloss and leveling.
Application test 2
15g of the temperature-sensitive solid amine curing agent prepared in example 3, 100 g of E12 epoxy resin, 20 g of titanium dioxide and 40 g of precipitated barium sulfate are taken to be fully and uniformly mixed, the mixture is electrostatically sprayed on a tinplate and a carbon steel plate, the mixture is placed in a constant-temperature oven at 100 ℃ for 6 hours, the thickness of the prepared coating is 60 mu m, and the comprehensive properties of the coating are shown in Table 3.
TABLE 3 coating Performance parameters
The titanium dioxide and the barium sulfate as the powder coating pigment filler have similar properties, and the cost of the coating can be effectively saved by replacing part of the titanium dioxide with the barium sulfate under the condition of ensuring that the filler amount is not changed. As can be seen from Table 3, example 3 with the addition of barium sulfate can achieve the effect of the pure titanium dioxide of example 1 in coating performance.
The temperature-sensitive solid amine curing agent is prepared by taking ketone-aldehyde resin as a raw material and utilizing anhydride esterification and neutralization and salt formation of amine monomers, the obtained temperature-sensitive solid amine curing agent can realize low-temperature curing, and the prepared powder coating has good storage stability, and the cured coating has excellent performances and good decorative and protective performances.
Claims (7)
1. The preparation method of the temperature-sensitive solid amine curing agent is characterized by comprising the following steps:
1) mixing ketone-aldehyde resin and acid anhydride, reacting at a constant temperature of 90-120 ℃ for 3-6 h, and obtaining acid anhydride end-capped modified ketone-aldehyde resin after the reaction is finished;
2) dissolving the acid anhydride end-capped modified ketone-aldehyde resin, adding an amine monomer solution under the stirring condition for neutralization reaction for 20-40min, removing the solvent, and drying to obtain the thermo-sensitive solid amine curing agent.
2. The method for preparing a temperature-sensitive solid amine curing agent according to claim 1, wherein in step 1), the acid anhydride is one of phthalic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride, maleic anhydride, tetrahydrophthalic anhydride, and 4-methylhexahydrophthalic anhydride; the molar ratio of the acid anhydride to the hydroxyl in the ketone-aldehyde resin is 1: 1-1.5.
3. The preparation method of the temperature-sensitive solid amine curing agent according to claim 1, wherein in the step 2), the molar ratio of carboxyl in the end-capping modified ketone-aldehyde resin to amino in the amine monomer is 1-1.5: 1.
4. The method for preparing a temperature-sensitive solid amine curing agent according to claim 1, wherein in step 2), the amine monomer is a compound having at least one primary, secondary or tertiary amine group.
5. The method for preparing a temperature-sensitive solid amine curing agent according to claim 4, wherein the amine monomer comprises one or more compounds selected from the group consisting of ethylenediamine, hexamethylenediamine, m-phenylenediamine, m-xylylenediamine, 1, 3-diaminomethylcyclohexane, polyethylenepolyamine, diethylaminopropylamine, diaminodiphenylmethane, diaminodiphenylsulfone, isophoronediamine, N-aminoethylpiperazine, maleimide, triethylamine, trimethylamine, and triethanolamine in any ratio.
6. The preparation method of the temperature-sensitive solid amine curing agent according to claim 5, wherein in the step 2), the amine monomer solution is obtained by dissolving an amine monomer in an ethanol or methanol organic solvent, and the concentration of the amine monomer solution is 0.1-1 mol/L.
7. The temperature-sensitive solid amine curing agent prepared by the preparation method of any one of claims 1 to 6.
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| CN1597723A (en) * | 2003-08-22 | 2005-03-23 | 德古萨公司 | Ketone-aldehyde resins, process for preparing them, and their use |
| CN111440280A (en) * | 2020-05-06 | 2020-07-24 | 郑州大学 | Ketone-aldehyde resin-based reactive anionic emulsifier and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1597723A (en) * | 2003-08-22 | 2005-03-23 | 德古萨公司 | Ketone-aldehyde resins, process for preparing them, and their use |
| CN111440280A (en) * | 2020-05-06 | 2020-07-24 | 郑州大学 | Ketone-aldehyde resin-based reactive anionic emulsifier and preparation method thereof |
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| Title |
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| 固体碱催化水性酮醛树脂的合成;胥鹏等;《广西师范大学学报(自然科学版)》;20200531;第38卷(第3期);70-79 * |
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