CN116041666B - Epoxy resin for high-leveling, low-temperature, fast-curing powder coating and preparation method thereof - Google Patents
Epoxy resin for high-leveling, low-temperature, fast-curing powder coating and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/02—Polycondensates containing more than one epoxy group per molecule
- C08G59/027—Polycondensates containing more than one epoxy group per molecule obtained by epoxidation of unsaturated precursor, e.g. polymer or monomer
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/02—Polycondensates containing more than one epoxy group per molecule
- C08G59/022—Polycondensates containing more than one epoxy group per molecule characterised by the preparation process or apparatus used
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/50—Amines
- C08G59/5046—Amines heterocyclic
- C08G59/5053—Amines heterocyclic containing only nitrogen as a heteroatom
- C08G59/5073—Amines heterocyclic containing only nitrogen as a heteroatom having two nitrogen atoms in the ring
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- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/03—Powdery paints
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Abstract
The invention relates to an epoxy resin for powder coating, which is prepared by using castor oil, dimethyl adipate, 4' -biphthalic acid, bisphenol A diglycidyl ether, methallyl alcohol, acetonitrile, hydrogen peroxide and the like as main raw materials and performing reaction, wherein the epoxy equivalent of the obtained epoxy resin is 560-610g/mol, the total chlorine is below 200ppm, the storage stability is better, the epoxy resin can be used for surface coating of precise instrument equipment, the epoxy resin adopts a special castor oil chain extension product as a main structure, the branching degree is good, the softening point of the product is extremely low, the low-temperature fluidity is excellent, the ultra-low-temperature rapid curing can be realized with 2-phenyl-4, 5-dihydroimidazole and the like, the leveling property is excellent, and other performances of a coating film can meet the conventional application requirements.
Description
Technical Field
The invention belongs to the technical field of chemical products, and particularly relates to epoxy resin for high-leveling low-temperature rapid-curing powder coating and a preparation method thereof.
Background
The powder coating has the advantages of environmental protection, energy saving, no VOC emission, convenient recycling and the like, has excellent protective performance and decorative performance, and has wider application in the common coating industry. Along with the extension of the powder coating to the special coating field, such as the coating of the surface of a precise instrument, such as the coating of a chromatographic instrument, the total chlorine content in the resin of the powder coating is required to be lower, generally less than 300ppm, so that the surface of the instrument cannot be corroded, and meanwhile, some precise instruments cannot withstand high temperature for a long time (such as less than 130 ℃ per 10 min) due to poor high temperature resistance, so that the new products are required to realize low-temperature rapid curing so as not to influence the performance of the precise instrument, and meanwhile, the resin also has excellent surface leveling performance so as to achieve the attractive effect. The epoxy resin in the current powder coating field is mainly E-12 epoxy resin, which is prepared by using epichlorohydrin and bisphenol A under the catalysis of sodium hydroxide, the total chlorine content of the obtained epoxy resin product is higher and is basically more than 4000ppm, and the application requirements of the special field are far less than those of the special field. Meanwhile, the E-12 epoxy resin has high softening point and insufficient branching degree, so that low-temperature rapid curing film formation is difficult to realize, and although some low-temperature cured epoxy resin products exist, the problem of molecular structure design is solved, so that the final product has obvious sticky hands, is extremely easy to agglomerate, causes poor storage stability and is difficult to industrialize, or the real combination of low-temperature rapid curing and high leveling performance cannot be realized.
Disclosure of Invention
In view of the above problems, the epoxy resin for powder coating of the present invention is obtained by reacting a main raw material including castor oil, dimethyl adipate, 4' -biphthalic acid, bisphenol a diglycidyl ether, methallyl alcohol, acetonitrile, and hydrogen peroxide. The epoxy resin has the epoxy equivalent of 560-610g/mol, total chlorine below 200ppm, no hand sticking phenomenon at normal temperature, and good storage stability, and can be used for surface coating of some precise instruments and equipment.
The epoxy resin for the powder coating comprises the following raw materials in parts by mole:
7-11 parts of castor oil;
8-13 parts of dimethyl adipate;
15-20 parts of 4,4' -biphenyl dicarboxylic acid;
11-17 parts of bisphenol A diglycidyl ether;
7-10 parts of methallyl alcohol;
50-70 parts of acetonitrile;
45-55 parts of hydrogen peroxide;
the raw materials also comprise a catalyst.
Further, the catalyst is phosphotungstic acid, and the dosage is 0.8-1.5% of the total mass of castor oil.
Further, hydrogen peroxide adopts a hydrogen peroxide aqueous solution with the mass concentration of 25-50%.
The preparation method of the epoxy resin for the powder coating comprises the following steps:
A. Stirring and uniformly mixing the castor oil and the catalyst in the formula amount, heating to 90-100 ℃, starting a vacuum system, dropwise adding the dimethyl adipate in the formula amount for transesterification chain extension reaction, and continuing to perform heat preservation reaction after the dropwise adding is finished;
B. sampling, detecting by gas chromatography, obtaining a chain-extended intermediate when the content of free adipic acid dimethyl ester is lower than 2%, adding a formula amount of 4,4' -biphenyl dicarboxylic acid, continuing to perform chain extension and carboxyl end capping reaction with hydroxyl on the intermediate, and controlling the reaction temperature to be 115-120 ℃;
C. Sampling and detecting the hydroxyl value of the polymer, when the hydroxyl value of the polymer is lower than 5mgKOH/g, releasing vacuum, adding bisphenol A diglycidyl ether with the formula amount for chain extension reaction, and keeping the temperature at 115-120 ℃;
D. Sampling to detect the epoxy equivalent of the polymer, reducing the reaction temperature to 102-105 ℃ when the epoxy equivalent is more than 5000g/mol, and adding the methallyl alcohol with the formula amount to carry out esterification end-capping reaction;
E. Detecting the acid value of the polymer of the system, and starting a vacuum system when the acid value of the polymer is reduced to below 3 mgKOH/g;
F. When the content of methallyl alcohol in the system is lower than 0.5%, cooling to 57-63 ℃, adding acetonitrile with the formula amount to fully dissolve the polymer into one phase, dripping hydrogen peroxide aqueous solution, and continuing the thermal insulation epoxidation reaction after the dripping is completed;
G. sampling and detecting the iodine value of the polymer, heating to 110-115 ℃ when the iodine value is less than 1 (g/100 g), starting a vacuum system to sufficiently remove the solvent and unreacted hydrogen peroxide aqueous solution, stopping the reaction after no obvious distillate is distilled out, discharging at a high temperature, and performing post-treatment to obtain the epoxy resin.
Further, in the step A, the vacuum degree is controlled to be between-0.095 and-0.097 Mpa, and the dripping time is controlled to be between 1 and 1.5 hours.
Further, in the step B, the vacuum degree of the chain extension and carboxyl end capping reaction is still kept at-0.095 to-0.097 Mpa to sufficiently remove esterified water molecules to promote the reaction, and in the step E, the vacuum degree is controlled at-0.096 to-0.098 Mpa to remove excessive unreacted methallyl alcohol.
Further, in the step F, the dripping time is controlled to be 2-3h.
Further, in the step G, the vacuum degree of the vacuum system is controlled to be between-0.097 and-0.099 Mpa, no obvious distillate is distilled out, which means that the distillate is less than 1 drop in 30 seconds, and the post-treatment comprises cooling the epoxy resin by using a steel belt with condensed water, and then crushing and granulating.
The invention also relates to the application of the epoxy resin for powder coating or the epoxy resin for powder coating obtained by the preparation method in the low-temperature rapid curing powder coating, and preferably, the powder coating is sprayed by an electrostatic spray gun and then baked and cured to obtain the coating film.
For example, a method for preparing an epoxy resin for powder coating comprises the following steps:
A. Adding castor oil and a catalyst with the formula amount into a reaction kettle, starting stirring and uniformly mixing, heating to 90-100 ℃, starting a vacuum system, controlling the vacuum degree to be-0.095-0.097 Mpa, then dripping dimethyl adipate with the formula amount for carrying out transesterification chain extension reaction, controlling the dripping time to be 1-1.5h, and continuing to carry out heat preservation reaction after dripping is finished;
B. Sampling and detecting by gas chromatography, when the content of free adipic acid dimethyl ester is lower than 2%, indicating that the adipic acid dimethyl ester has undergone transesterification reaction with hydroxyl groups on castor oil molecules to obtain a chain-extended intermediate, adding a formula amount of 4,4' -biphenyl dicarboxylic acid to continue to undergo chain extension and carboxyl end capping reaction with the hydroxyl groups on the intermediate, controlling the reaction temperature to 115-120 ℃, and maintaining the vacuum degree to-0.095-0.097 Mpa to sufficiently remove esterified water molecules to promote the reaction;
C. Sampling and detecting the hydroxyl value of the polymer, when the hydroxyl value of the polymer is lower than 5mgKOH/g, releasing vacuum, adding bisphenol A diglycidyl ether with the formula amount for chain extension reaction, and keeping the temperature at 115-120 ℃;
D. Sampling and detecting the epoxy equivalent of the polymer, when the epoxy equivalent is more than 5000g/mol, indicating that bisphenol A diglycidyl ether has reacted completely, reducing the reaction temperature to 102-105 ℃ at the moment, and adding the methallyl alcohol with the formula amount to perform esterification end-capping reaction;
E. Detecting the acid value of the polymer of the system, and when the acid value of the polymer is reduced to below 3mgKOH/g, indicating that the carboxyl in the polymer chain segment is completely esterified, starting a vacuum system, and controlling the vacuum degree to be between-0.096 and-0.098 Mpa to remove excessive unreacted methallyl alcohol;
F. When the content of methallyl alcohol in the system is lower than 0.5%, cooling to 57-63 ℃, adding acetonitrile with the formula amount to fully dissolve the polymer into one phase, dropwise adding hydrogen peroxide water solution, controlling the dropwise adding time to be 2-3h, and continuing the thermal insulation epoxidation reaction after the dropwise adding is completed;
G. Sampling to detect the iodine value of the polymer, when the iodine value is less than 1 (g/100 g), indicating that unsaturated double bonds in the polymer are completely epoxidized, heating to 110-115 ℃ at the moment, starting a vacuum system to sufficiently remove solvent and unreacted hydrogen peroxide water solution, controlling the vacuum degree to be-0.097-0.099 Mpa, stopping the reaction after no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), discharging at high temperature, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The obtained product is light yellow transparent particles, has epoxy equivalent weight of 560-610g/mol, softening point of 75-80 ℃ and total chlorine content of <200ppm.
The epoxy resin system powder paint formula adopted by the invention can comprise 2-phenyl-4, 5-dihydroimidazole, titanium dioxide, barium sulfate and other auxiliary fillers commonly used in the field besides the epoxy resin prepared by the method. The preparation method of the coating comprises the steps of uniformly mixing all materials, extruding by a double-screw extruder, tabletting, crushing, and then crushing and sieving the tablet to prepare the powder coating. The powder coating is sprayed on the tinplate base material after surface treatment by adopting an electrostatic spray gun, the film thickness is 70-80 mu m, and then the coating film is obtained after baking and solidification.
The invention has the beneficial effects that:
the epoxy resin is obtained by using castor oil, dimethyl adipate, 4' -biphthalic acid, bisphenol A diglycidyl ether, methallyl alcohol, acetonitrile, hydrogen peroxide and the like as main raw materials for reaction. The epoxy resin has the epoxy equivalent of 560-610g/mol, total chlorine below 200ppm, no hand sticking phenomenon at normal temperature, and good storage stability, and can be used for surface coating of some precise instruments and equipment. Meanwhile, the epoxy resin adopts a special castor oil chain extension product as a main structure, the branching degree is good, the softening point of the product is extremely low, the low-temperature fluidity is excellent (at 125 ℃) and the epoxy resin has high-activity epoxy groups, can realize low-temperature rapid curing with 2-phenyl-4, 5-dihydroimidazole and the like, has excellent leveling property, and can meet the conventional application requirements on other performances of a coating film. The method is prepared by taking castor oil as a main raw material, not only develops a novel epoxy resin product for the powder coating industry, but also provides a novel approach for the high added value industrialization of biomass castor oil series products.
Detailed Description
For the purposes of promoting an understanding of the invention, reference will now be made in detail to various exemplary embodiments of the invention, which should not be considered as limiting the invention in any way, but rather as describing in more detail certain aspects, features and embodiments of the invention.
The raw materials are all commercial common industrial grade raw materials.
Example 1
The epoxy resin for the powder coating comprises the following raw materials in parts by mole:
7 parts of castor oil;
8 parts of dimethyl adipate;
16 parts of 4,4' -biphenyl dicarboxylic acid;
12 parts of bisphenol A diglycidyl ether;
7 parts of methallyl alcohol;
52 parts of acetonitrile;
46 parts of hydrogen peroxide;
the catalyst is phosphotungstic acid, and the dosage is 1% of the total mass of castor oil.
The hydrogen peroxide adopts a hydrogen peroxide water solution with the mass concentration of 48 percent.
The preparation method of the epoxy resin for the powder coating comprises the following steps:
A. Adding the castor oil and the catalyst with the formula amount into a reaction kettle, starting stirring and uniformly mixing, heating to 100 ℃, starting a vacuum system, controlling the vacuum degree to be-0.097 Mpa, then dripping the dimethyl adipate with the formula amount for carrying out transesterification chain extension reaction, controlling the dripping time to be 1.5h, and continuing to carry out heat preservation reaction after dripping is finished;
B. Sampling and detecting by gas chromatography, when the content of free dimethyl adipate is lower than 2%, indicating that dimethyl adipate has undergone transesterification reaction with hydroxyl groups on castor oil molecules to obtain a chain-extended intermediate, adding a formula amount of 4,4' -biphenyl dicarboxylic acid to continue the chain-extended and carboxyl end-capping reaction with the hydroxyl groups on the intermediate, controlling the reaction temperature at 120 ℃, and maintaining the vacuum degree at-0.097 Mpa to sufficiently remove esterified water molecules to promote the reaction;
C. Sampling and detecting the hydroxyl value of the polymer, when the hydroxyl value of the polymer is lower than 5mgKOH/g, releasing vacuum, adding bisphenol A diglycidyl ether with the formula amount for chain extension reaction, and keeping the temperature at 120 ℃;
D. sampling and detecting the epoxy equivalent of the polymer, when the epoxy equivalent is more than 5000g/mol, indicating that bisphenol A diglycidyl ether has reacted completely, reducing the reaction temperature to 105 ℃, and adding the methallyl alcohol with the formula amount to perform esterification end-capping reaction;
E. Detecting the acid value of the polymer of the system, and when the acid value of the polymer is reduced to below 3mgKOH/g, indicating that the carboxyl in the polymer chain segment is completely esterified, starting a vacuum system, and controlling the vacuum degree to be-0.098 Mpa to remove excessive unreacted methallyl alcohol;
F. when the content of methallyl alcohol in the system is lower than 0.5%, cooling to 63 ℃, adding acetonitrile with the formula amount to fully dissolve the polymer into one phase, dropwise adding hydrogen peroxide water solution, controlling the dropwise adding time to be 3h, and continuing to perform thermal insulation epoxidation reaction after the dropwise adding is completed;
G. Sampling to detect the iodine value of the polymer, when the iodine value is less than 1 (g/100 g), indicating that unsaturated double bonds in the polymer are completely epoxidized, heating to 115 ℃ at the moment, starting a vacuum system to sufficiently remove solvent and unreacted hydrogen peroxide water solution, controlling the vacuum degree to be-0.099 Mpa, stopping the reaction after no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), discharging at high temperature, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The epoxy resin prepared had an epoxy equivalent of 589g/mol, a softening point of 78℃and a total chlorine of 188ppm.
Example 2
The epoxy resin for the powder coating comprises the following raw materials in parts by mole:
the catalyst is phosphotungstic acid, and the dosage is 1.5 percent of the total mass of castor oil.
The hydrogen peroxide adopts a hydrogen peroxide water solution with the mass concentration of 30 percent.
The preparation method is the same as in example 1.
The product obtained was pale yellow transparent granules with an epoxide equivalent of 575g/mol, a softening point of 77℃and a total chlorine content of 182ppm.
Example 3
The epoxy resin for the powder coating comprises the following raw materials in parts by mole:
the catalyst is phosphotungstic acid, and the dosage is 1.5 percent of the total mass of castor oil.
The hydrogen peroxide adopts a hydrogen peroxide water solution with the mass concentration of 40 percent.
The preparation method is the same as in example 1.
The product obtained was pale yellow transparent granules with an epoxide equivalent of 597g/mol, a softening point of 79℃and a total chlorine content of 173ppm.
Example 4
The epoxy resin for the powder coating comprises the following raw materials in parts by mole:
The catalyst is phosphotungstic acid, and the dosage is 0.8 percent of the total mass of castor oil.
The hydrogen peroxide adopts a hydrogen peroxide water solution with the mass concentration of 40 percent.
The preparation method is the same as in example 1.
The product obtained was pale yellow transparent granules with an epoxide equivalent of 566g/mol, a softening point of 75℃and a total chlorine content of 168ppm.
Comparative example 1 commercially available ordinary E-12 epoxy resin, epoxy equivalent 838g/mol, softening point 89 ℃ and total chlorine 4850ppm, purchased from Anhui Hengyuanzhuan New Material Co., ltd.
Comparative example 2 the remainder was the same as comparative example 1, with curing conditions of 180℃per 10min.
Application example the epoxy resin system powder paint formulation is generally as follows in parts by weight:
The powder coating formulation used in comparative example 1 was the same as above, and the amount of 2-phenyl-4, 5-dihydroimidazole alone as a curing agent was adjusted to 42 parts due to the difference in epoxy equivalent.
The preparation of the paint coating comprises the steps of uniformly mixing all materials according to the requirements of the powder paint formula, extruding by a double-screw extruder, tabletting, crushing, and crushing and sieving the tablet materials to prepare the powder paint. The powder coating is sprayed on the tinplate base material after surface treatment by adopting an electrostatic spray gun, the film thickness is 70-80 mu m, and then the coating film is obtained after baking and curing at 125 ℃ for 8 min.
The method for measuring the total chlorine is according to GB/T12007.3-1989 'method for measuring the total chlorine content of epoxy resin', the detection of coating indexes is according to GB/T21776-2008 'standard guide for detecting powder coating and coating thereof', the leveling property is according to PCI leveling grade, the larger the number is, the better the leveling is, and the adhesive force grade is according to GB/T9286-1998 'cross-cut test of color paint and varnish film'.
TABLE 1 comparison of storage stability of examples 1-4 and comparative example 1
Note that since the epoxy resins used in comparative example 1 and comparative example 2 are the same type of resin, the storage stability was compared with comparative example 1 alone.
As can be seen from Table 1, the storage stability of the product of the invention at different temperatures is not greatly different from that of the common bisphenol A type E-12 epoxy resin product sold at present, and the product can basically meet the conventional storage and application requirements of downstream customers.
TABLE 2 film Properties of the coatings obtained in examples 1 to 4 and comparative examples 1 to 2
As can be seen from Table 2, the epoxy resin of the invention realizes the characteristics of relatively low softening point and high activity epoxy group of the product by chain extension reaction of related flexible and rigid structural chain segments under the structure of taking castor oil as a main chain segment, the total chlorine of the product is lower than 200ppm, and the storage stability of the product can meet the requirements of conventional products in the market. The method is also superior in the aspect of coating application effect, has better appearance, impact and gloss of a coating film after rapid curing at a low temperature of 125 ℃ per 8min, simultaneously gives consideration to excellent leveling and adhesive force performance, has a leveling grade of more than 6 grades and an adhesive force of 0 grade, can meet the application requirements of special fields such as chromatographic instruments and the like, is prepared by taking castor oil as a main raw material, and provides a novel epoxy resin product for the powder coating industry and a novel approach for the high added value industrialization of biomass castor oil series products.
While comparative examples 1-2 were prepared using conventional E-12 epoxy resins, which were too high in total chlorine to meet the requirements, and because of their linear chain segment structure and low-density epoxy groups, they were too high in softening point and too low in epoxy activity to achieve effective curing at 125℃per 8min, whereas comparative example 2 was elevated to conventional curing conditions (180℃per 10 min), sufficient curing could be achieved, and gloss, impact properties, adhesion, etc. after curing were not much different from the products of the present invention, but slightly inferior to the products of the present invention in leveling properties, etc.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (7)
1. An epoxy resin for powder coating is characterized in that the epoxy resin is obtained by reacting raw materials including castor oil, dimethyl adipate, 4' -biphthalic acid, bisphenol A diglycidyl ether, methallyl alcohol, acetonitrile and hydrogen peroxide;
Wherein the raw materials comprise the following components in parts by mole:
The raw materials also comprise catalyst phosphotungstic acid, and the dosage is 0.8-1.5% of the total mass of castor oil;
the preparation method of the epoxy resin for the powder coating comprises the following steps:
A. Stirring and uniformly mixing the castor oil and the catalyst in the formula amount, heating to 90-100 ℃, starting a vacuum system, dropwise adding the dimethyl adipate in the formula amount for transesterification chain extension reaction, and continuing to perform heat preservation reaction after the dropwise adding is finished;
B. sampling, detecting by gas chromatography, obtaining a chain-extended intermediate when the content of free adipic acid dimethyl ester is lower than 2%, adding a formula amount of 4,4' -biphenyl dicarboxylic acid, continuing to perform chain extension and carboxyl end capping reaction with hydroxyl on the intermediate, and controlling the reaction temperature to be 115-120 ℃;
C. B, sampling and detecting the hydroxyl value of the product in the step B, when the hydroxyl value of the product is lower than 5mgKOH/g, releasing vacuum, adding the bisphenol A diglycidyl ether with the formula amount for chain extension reaction, and keeping the temperature at 115-120 ℃;
D. c, sampling and detecting the epoxy equivalent of the product in the step C, and when the epoxy equivalent is more than 5000g/mol, reducing the reaction temperature to 102-105 ℃, and adding the methallyl alcohol with the formula amount to carry out esterification end-capping reaction;
E. Detecting the acid value of the product of the system in the step D, and starting a vacuum system when the acid value of the product is reduced to be lower than 3 mgKOH/g;
F. When the content of methallyl alcohol in the system is lower than 0.5%, cooling to 57-63 ℃, adding acetonitrile with the formula amount to fully dissolve the product into one phase, dripping hydrogen peroxide aqueous solution, and continuing the thermal insulation epoxidation reaction after the dripping is completed;
G. And F, sampling and detecting the iodine value of the product in the step F, heating to 110-115 ℃ when the iodine value is less than 1 (g/100 g), starting a vacuum system to sufficiently remove the solvent and unreacted hydrogen peroxide aqueous solution, stopping the reaction after no obvious distillate is distilled out, discharging at a high temperature, and performing post-treatment to obtain the epoxy resin.
2. An epoxy resin for powder coating as claimed in claim 1, further characterized in that hydrogen peroxide is an aqueous hydrogen peroxide solution having a mass concentration of 25 to 50%.
3. The epoxy resin for powder coating according to claim 1, further characterized in that in the step A of the preparation method, the vacuum degree is controlled to be-0.095 to-0.097 MPa, and the dropping time is controlled to be 1-1.5h.
4. The epoxy resin for powder coating according to claim 1, further characterized in that in the step B of the preparation method, the vacuum degree of chain extension and carboxyl end capping reaction is maintained at-0.095 to-0.097 MPa to sufficiently remove esterified water molecules to promote the reaction, and in the step E, the vacuum degree is controlled at-0.096 to-0.098 MPa to remove excessive unreacted methallyl alcohol.
5. The epoxy resin for powder coating according to claim 1, further characterized in that in the step F of the preparation method, the dropping time is controlled to be 2-3 hours.
6. An epoxy resin for powder coating according to claim 1, further characterized in that in said step G of the production method, the vacuum degree of the vacuum system is controlled to be-0.097 to-0.099 Mpa, no significant distillate is distilled out means that less than 1 drop of distillate is distilled out within 30 seconds, and the post-treatment comprises cooling the epoxy resin with a steel belt with condensed water, followed by crushing and granulating.
7. Use of the epoxy resin for powder coating according to any one of claims 1-6 in low temperature fast curing powder coating, wherein the powder coating is baked and cured after being sprayed by an electrostatic spray gun to obtain a coating film.
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| CN109679118A (en) * | 2018-12-02 | 2019-04-26 | 廊坊立邦涂料有限公司 | A kind of phosphate modified cationic microgel, Preparation method and use |
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| CN113501934B (en) * | 2021-07-28 | 2023-06-30 | 黄山市源润新材料科技有限公司 | Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof |
| CN115572368B (en) * | 2022-09-05 | 2024-03-22 | 黄山市源润新材料科技有限公司 | Wear-resistant high-leveling epoxy resin for powder coating and preparation method thereof |
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| CN103068941A (en) * | 2010-06-23 | 2013-04-24 | 陶氏环球技术有限责任公司 | Powder coatings compositions |
| CN109679118A (en) * | 2018-12-02 | 2019-04-26 | 廊坊立邦涂料有限公司 | A kind of phosphate modified cationic microgel, Preparation method and use |
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Denomination of invention: High flow leveling low temperature rapid curing powder coating epoxy resin and preparation method Granted publication date: 20241129 Pledgee: Huangshan Branch of Postal Savings Bank of China Ltd. Pledgor: Anhui Hengtai New Material Technology Co.,Ltd. Registration number: Y2025980050314 |
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