CN113501934A - Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof - Google Patents

Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof Download PDF

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CN113501934A
CN113501934A CN202110859213.XA CN202110859213A CN113501934A CN 113501934 A CN113501934 A CN 113501934A CN 202110859213 A CN202110859213 A CN 202110859213A CN 113501934 A CN113501934 A CN 113501934A
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epoxy resin
powder coating
xylene
mol
leveling
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CN113501934B (en
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胡军
方志和
胡红飞
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Huangshan Yuanrun New Material Technology Co ltd
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Huangshan Yuanrun New Material Technology Co ltd
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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
    • 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
    • C—CHEMISTRY; METALLURGY
    • 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
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • 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
    • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • 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
    • C09D5/033—Powdery paints characterised by the additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C08K2003/2237—Oxides; Hydroxides of metals of titanium
    • C08K2003/2241—Titanium dioxide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
    • C08K2003/3045—Sulfates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency

Abstract

An epoxy resin for self-leveling low-temperature curing powder coating and a preparation method thereof are disclosed, wherein tartaric acid, methacrylic acid, oleic acid, bisphenol A, E-51 liquid epoxy resin, hydrogen peroxide, xylene and the like are mainly used as raw materials to carry out reaction to obtain the epoxy resin with the epoxy equivalent of 660-710g/mol, a chain segment of the epoxy resin has a special esterification group, the epoxy resin has the function of rapidly promoting the leveling of a coating film, the esterification group still has an epoxy group, the curing activity is high, the powder coating containing 50:50 polyester resin can be cured at low temperature without adding an additional leveling agent, and the leveling grade and the gloss of the surface of the cured coating film are high.

Description

Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof
Technical Field
The invention belongs to the field of powder coatings, and particularly relates to an epoxy resin for a self-leveling low-temperature curing powder coating and a preparation method thereof.
Background
The powder coating is a solid powder synthetic resin coating composed of solid resin, pigment, filler, auxiliary agent and the like. Unlike conventional solvent-based coatings and water-based coatings, the dispersion medium is not a solvent and water, but air. It has the characteristics of no solvent pollution, 100 percent film forming and low energy consumption.
The common E-12 epoxy resin matched with the 50:50 polyester resin is obtained by directly reacting bisphenol A and epoxy chloropropane under the action of strong alkali, the molecular branching degree of the product is low, the epoxy equivalent is high, generally 800-900g/mol, the curing activity is low, the low-temperature curing is difficult to carry out, the curing can be carried out at a temperature of over 180 ℃, and the energy consumption is high.
In addition, a leveling agent is required to be added in a powder coating formula, and the dosage of the leveling agent is small, generally about 1% of the dosage in the powder coating formula, so that the leveling agent is difficult to be fully and uniformly mixed in the powder coating, the leveling property is poor, particularly in a low-temperature curing system, the insufficient leveling performance is more obvious, and a coating film with a high leveling grade is difficult to prepare.
In industry, in order to mix 1% of the leveling agent and the resin material uniformly, the mixture needs to stay in a mixer and a mill for a longer time, which causes higher energy consumption.
Therefore, a new epoxy resin for self-leveling low-temperature curing powder coating and a preparation method thereof are needed to solve the above technical problems.
Disclosure of Invention
The invention provides an epoxy resin for a self-leveling low-temperature curing powder coating, which comprises the following raw materials in parts by mole:
Figure BDA0003185219860000021
wherein the first catalyst is phosphotungstic acid or phosphomolybdic acid, and the second catalyst is triphenylphosphine.
The first catalyst plays a role in catalyzing esterification and epoxidation at the same time.
Wherein the hydrogen peroxide is added in the form of 30 wt% aqueous hydrogen peroxide, that is, 7 to 12 molar parts of hydrogen peroxide in total is added in the form of aqueous hydrogen peroxide.
Wherein the epoxy resin is colorless transparent particles, the epoxy equivalent is 660-710g/mol, the softening point is 78-84 ℃, and the iodine value is less than 1g/100 g.
The invention also provides a preparation method of the epoxy resin for the self-leveling low-temperature curing powder coating, which comprises the following steps:
(1) adding tartaric acid, methacrylic acid, oleic acid and xylene in a formula amount into a reaction kettle, starting stirring, uniformly mixing, adding a first catalyst in a formula amount, heating to the boiling point of the xylene, and carrying out esterification reaction with water;
(2) sampling and detecting the hydroxyl value of the reactant of the system, cooling to 100-105 ℃ when the hydroxyl value is less than 5mgKOH/g, then adding the bisphenol A, E-51 liquid epoxy resin and the second catalyst in the formula amount, and carrying out heat preservation and chain extension reaction;
(3) sampling and detecting the epoxy equivalent of the polymer of the system, and when the epoxy equivalent reaches 500-550g/mol, heating to 125-130 ℃, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) sampling and detecting the epoxy equivalent of the polymer of the system, stopping the reaction when the epoxy equivalent reaches 700-750g/mol, cooling to 50-55 ℃, adding a hydrogen peroxide aqueous solution with the formula amount, and carrying out thermal insulation at the temperature of 50-55 ℃ to carry out epoxidation reaction;
(5) sampling and detecting the iodine value of the polymer of the system, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 710g/mol in 660-710, standing and layering, removing the water phase of hydrogen peroxide, then washing, standing and removing the water layer so as to remove the catalyst and impurities (such as residual hydrogen peroxide and the like) and obtain an organic phase solution;
(6) starting a vacuum system, and heating to 115-120 ℃ under a reduced pressure condition to remove xylene and water from the organic phase solution under reduced pressure;
(7) and (3) after no obvious distillate is evaporated (namely when the mass fraction of volatile components in a sampling test is less than 1%), removing the vacuum, discharging, cooling, crushing and granulating to obtain the epoxy resin.
In the steps (2), (3), (4) and (5), sampling and detecting are carried out after removing the xylene solvent in a vacuum oven.
Wherein in the step (5), the washing is 1-2 times of washing by adding tap water with the mass 1-1.5 times of that of the xylene.
Wherein in the step (6), the vacuum degree is controlled to be between-0.097 and-0.099 MPa.
In the step (7), the discharging is discharging at a high temperature while the discharging is hot, and the cooling is cooling by using a steel strip with condensed water.
The invention also provides a self-leveling low-temperature curing powder coating which contains the epoxy resin.
Wherein the powder coating is a 50:50 mixed powder coating
The invention has the following beneficial technical effects:
the invention mainly uses tartaric acid, methacrylic acid, oleic acid, bisphenol A, E-51, hydrogen peroxide, xylene, phosphotungstic acid and the like as raw materials to carry out reaction to obtain the epoxy resin with the epoxy equivalent of 600-650g/mol and the iodine value of less than 1g/100 g.
The epoxy resin has a special esterification group in a chain segment, has a function of quickly promoting the leveling of a coating film, is still provided with an epoxy group, has high curing activity, can finally enable a 50:50 mixed powder coating to be fully cured at a low temperature (140 ℃/20min) without additionally adding a leveling agent, has very high leveling grade and gloss on the surface of the cured coating film, achieves the leveling grade above 7 grade and the gloss above 94.3 percent, does not need milling for too long time, saves energy, and has very important application value.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
The embodiment provides a preparation method of an epoxy resin for a self-leveling low-temperature curing powder coating, which comprises the following steps:
(1) adding 4.3 molar parts of tartaric acid, 8 molar parts of methacrylic acid, 2.5 molar parts of oleic acid and 26 molar parts of xylene into a reaction kettle, starting stirring, uniformly mixing, adding 0.035 molar part of phosphotungstic acid, heating to the boiling point of xylene, and carrying out esterification reaction with water;
(2) sampling, removing a xylene solvent in a vacuum oven, detecting the hydroxyl value of a reactant of the system, cooling to 101 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 12 molar parts of bisphenol A, 19 molar parts of E-51 liquid epoxy resin and 0.0025 molar part of triphenylphosphine, and carrying out heat preservation and chain extension reaction;
(3) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, heating to 129 ℃ when the epoxy equivalent reaches 520g/mol, and continuing to perform polymerization chain extension reaction by keeping the temperature;
(4) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, stopping the reaction when the epoxy equivalent reaches 745g/mol, cooling to 50 ℃, adding 8 molar parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out thermal insulation at the temperature of 50 ℃ to carry out epoxidation reaction;
(5) sampling, removing a xylene solvent in a vacuum oven, detecting the iodine value of a system polymer, stopping reaction when the iodine value is less than 1 and the epoxy equivalent is 690g/mol, standing for layering, removing a water phase of hydrogen peroxide, adding tap water with the mass 1.4 times that of the xylene for washing for 2 times, standing, removing a water layer, and removing impurities such as a catalyst, residual hydrogen peroxide and the like to obtain an organic phase solution;
(6) starting a vacuum system, heating to 119 ℃ under a reduced pressure condition, and removing dimethylbenzene and water from the organic phase solution under reduced pressure, wherein the vacuum degree is controlled to be-0.099 Mpa;
(7) and (3) after no obvious distillate is evaporated (namely when the mass fraction of volatile components in a sampling test is less than 1%), removing the vacuum, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles, the epoxy equivalent is 690g/mol, the softening point is 79 ℃, and the iodine value is 0.8g/100 g.
Example 2
The embodiment provides a preparation method of an epoxy resin for a self-leveling low-temperature curing powder coating, which comprises the following steps:
(1) adding 5.5 molar parts of tartaric acid, 7 molar parts of methacrylic acid, 4 molar parts of oleic acid and 21 molar parts of xylene into a reaction kettle, starting stirring, uniformly mixing, adding 0.05 molar part of phosphomolybdic acid, heating to the boiling point of xylene, and carrying out esterification reaction with water;
(2) sampling, removing a xylene solvent in a vacuum oven, detecting the hydroxyl value of a system reactant, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 11 molar parts of bisphenol A, 19 molar parts of E-51 liquid epoxy resin and 0.003 molar part of triphenylphosphine, and carrying out heat preservation and chain extension reaction;
(3) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, heating to 125 ℃ when the epoxy equivalent reaches 537g/mol, and continuing to perform heat preservation for polymerization chain extension reaction;
(4) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, stopping the reaction when the epoxy equivalent reaches 721g/mol, cooling to 53 ℃, adding 12 molar parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out thermal insulation at 53 ℃ to carry out epoxidation reaction;
(5) sampling, removing a xylene solvent in a vacuum oven, detecting the iodine value of a system polymer, stopping reaction when the iodine value is less than 1 and the epoxy equivalent is 665g/mol, standing for layering, removing a water phase of hydrogen peroxide, adding tap water with the mass being 1 time of that of the xylene for washing for 1 time, standing, removing a water layer, removing impurities such as a catalyst and residual hydrogen peroxide, and obtaining an organic phase solution;
(6) starting a vacuum system, heating to 117 ℃ under a reduced pressure condition, and removing solvents such as dimethylbenzene, water and the like from the organic phase solution under a reduced pressure, wherein the vacuum degree is controlled to be-0.098 Mpa;
(7) and (3) after no obvious distillate is evaporated (namely when the mass fraction of volatile components in a sampling test is less than 1%), removing the vacuum, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles, the epoxy equivalent weight of the epoxy resin is 665g/mol, the softening point is 83 ℃, and the iodine value is 0.9g/100 g.
Example 3
The embodiment provides a preparation method of an epoxy resin for a self-leveling low-temperature curing powder coating, which comprises the following steps:
(1) adding 6 molar parts of tartaric acid, 8.5 molar parts of methacrylic acid, 3.8 molar parts of oleic acid and 24 molar parts of xylene into a reaction kettle, starting stirring, uniformly mixing, adding 0.04 molar part of phosphotungstic acid, heating to the boiling point of xylene, and carrying out esterification reaction with water;
(2) sampling, removing a xylene solvent in a vacuum oven, detecting the hydroxyl value of a system reactant, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 14 molar parts of bisphenol A, 21 molar parts of E-51 liquid epoxy resin and 0.0035 molar parts of triphenylphosphine, and carrying out heat preservation and chain extension reaction;
(3) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, raising the temperature to 127 ℃ when the epoxy equivalent reaches 518g/mol, and continuing to perform polymerization chain extension reaction by keeping the temperature;
(4) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, stopping the reaction when the epoxy equivalent reaches 732g/mol, cooling to 55 ℃, adding 11 molar parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out thermal insulation at 55 ℃ to carry out epoxidation reaction;
(5) sampling, removing a xylene solvent in a vacuum oven, detecting the iodine value of a system polymer, stopping reaction when the iodine value is less than 1 and the epoxy equivalent is 700g/mol, standing for layering, removing a water phase of hydrogen peroxide, adding tap water with the mass 1.5 times that of the xylene for washing for 2 times, standing, removing a water layer, and removing impurities such as a catalyst, residual hydrogen peroxide and the like to obtain an organic phase solution;
(6) starting a vacuum system, heating to 116 ℃ under a reduced pressure condition, and removing solvents such as dimethylbenzene, water and the like from the organic phase solution under a reduced pressure, wherein the vacuum degree is controlled to be-0.098 Mpa;
(7) and (3) after no obvious distillate is evaporated (namely when the mass fraction of volatile components in a sampling test is less than 1%), removing the vacuum, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles, the epoxy equivalent is 700g/mol, the softening point is 83 ℃, and the iodine value is 0.8g/100 g.
Example 4
The embodiment provides a preparation method of an epoxy resin for a self-leveling low-temperature curing powder coating, which comprises the following steps:
(1) adding 5.5 molar parts of tartaric acid, 7 molar parts of methacrylic acid, 4 molar parts of oleic acid and 29 molar parts of xylene into a reaction kettle, starting stirring, uniformly mixing, adding 0.055 molar part of phosphomolybdic acid, heating to the boiling point of xylene, and carrying out esterification reaction with water;
(2) sampling, removing a xylene solvent in a vacuum oven, detecting the hydroxyl value of a system reactant, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 13 molar parts of bisphenol A, 21 molar parts of E-51 liquid epoxy resin and 0.002 molar part of triphenylphosphine, and carrying out heat preservation and chain extension reaction;
(3) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, heating to 130 ℃ when the epoxy equivalent reaches 525g/mol, and continuing to perform polymerization chain extension reaction by keeping the temperature;
(4) sampling, removing a xylene solvent in a vacuum oven, detecting the epoxy equivalent of a system polymer, stopping the reaction when the epoxy equivalent reaches 745g/mol, cooling to 52 ℃, adding 10 molar parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out thermal insulation at the temperature of 52 ℃ to carry out epoxidation reaction;
(5) sampling, removing a xylene solvent in a vacuum oven, detecting the iodine value of a system polymer, stopping reaction when the iodine value is less than 1 and the epoxy equivalent is 708g/mol, standing for layering, removing a water phase of hydrogen peroxide, adding tap water with the mass 1 time that of the xylene for washing for 2 times, standing, removing a water layer, and removing impurities such as a catalyst, residual hydrogen peroxide and the like to obtain an organic phase solution;
(6) starting a vacuum system, heating to 120 ℃ under a reduced pressure condition, and removing solvents such as dimethylbenzene, water and the like from the organic phase solution under a reduced pressure, wherein the vacuum degree is controlled to be-0.099 Mpa;
(7) and (3) after no obvious distillate is evaporated (namely when the mass fraction of volatile components in a sampling test is less than 1%), removing the vacuum, discharging at high temperature, cooling by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles, the epoxy equivalent is 660-708g/mol, the softening point is 81 ℃, and the iodine value is 0.7g/100 g.
Comparative example 1
A commercially available ordinary E-12 epoxy resin was used as comparative example 1 in place of the epoxy resin of the present invention, which had an epoxy equivalent of 798g/mol and a softening point of 92 ℃ and was obtained from Huangshan Jinfeng industries, Ltd.
Powder coatings and coatings were prepared separately using the epoxy resins of examples 1-4 and comparative example 1 above and tested for properties.
Preparation of powder coating: the materials were mixed according to the powder coating formulation shown in Table 1 below, extruded at low temperature (screw temperature controlled at 95-100 ℃) using a twin screw extruder, tabletted, crushed, and then the flakes were crushed and sieved to prepare powder coatings (160 mesh 180 mesh) for coatings of examples A1-A4 and comparative examples B1-B3.
In the preparation of the powder coating for the coating of comparative example B3, the mixing time and the milling time of the individual materials were increased by 30min compared with the individual examples 1 to 4.
Wherein the 50:50 polyester resin has the model of SJ3702 and is purchased from Anhui Shenjian New materials GmbH; brightener type GLP588, available from Ningbo south sea chemical Co.
Preparing a coating: the powder coating was sprayed onto the surface-treated tinplate substrate using an electrostatic spray gun to a film thickness of 80-90 μm and cured under the conditions shown in Table 1 to give coatings numbered as examples A1-A4 and comparative examples B1-B3, respectively.
TABLE 1 preparation parameters for the coatings of examples A1-A4 and comparative examples B1-B3
Figure BDA0003185219860000101
*: in the preparation of the powder coating for the coating of comparative example B3, the mixing time and the milling time of the individual materials were increased by 30min compared with the individual examples 1 to 4
And (3) performance testing:
and (3) detection of coating indexes: according to GB/T21776 & 2008 & ltStandard guidelines for testing powder coatings and coatings thereof & gt;
leveling grade: according to JB-T3998-1999 coating leveling scratch test method, wherein the higher the leveling grade is, the better the leveling of the coating surface is;
and (3) testing the adhesive force: this is done according to GB/T9286-1998 test for marking out paint and varnish films, where a smaller number indicates better adhesion.
Table 2 shows the results of the performance tests of the coatings of examples A1-A4 and comparative examples B1-B3 described above.
TABLE 2 results of the Performance test of the coatings of examples A1-A4 and comparative examples B1-B4
Figure BDA0003185219860000111
As can be seen from the comparison between examples 1-4 and comparative examples 1-3 in Table 1, the epoxy resin obtained by the invention and 50:50 polyester resin form a powder coating system through the mutual matching and synergistic effect of the components, no additional mixing and grinding time is needed, and the prepared powder coating has high coating film gloss after being cured at the low temperature of 140 ℃/20min, high coating film self-leveling grade, excellent impact resistance and excellent adhesion and boiling water performance.
Comparative example 1 since the epoxy resin of the present invention was replaced with the general E-12 epoxy resin and no additional leveling agent was added, the curing and leveling process could not be smoothly completed at 140 ℃/20min due to the low epoxy termination activity of the E-12 epoxy resin, resulting in a rough coating film and poor mechanical properties.
In comparative example 2, the curing conditions in comparative example 1 were adjusted from 140 ℃/20min for low temperature curing to 180 ℃/20min for high temperature curing, and sufficient curing of the coating film could be achieved, but since no additional leveling agent was added, the final coating film had poor leveling grade, low surface gloss, and relatively poor adhesion and boiling water resistance.
In the comparative example 3, a leveling agent is additionally used on the basis of the comparative example 2, the material mixing time and the powder grinding time are increased by 30min compared with those of the examples 1-4, the full curing of the coating can be realized, the final coating has relatively good leveling (but still weaker than those of the examples 1-4), the surface gloss is moderate, the adhesive force and the boiling water resistance can basically meet the requirements, and the energy consumption for preparing the powder coating and the energy consumption for curing the coating are obviously higher than those of the product of the invention.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (9)

1. An epoxy resin for self-leveling low-temperature curing powder coating comprises the following raw materials in parts by mole:
Figure FDA0003185219850000011
wherein the first catalyst is phosphotungstic acid or phosphomolybdic acid, and the second catalyst is triphenylphosphine.
2. The epoxy resin for powder coating according to claims 1 to 3, wherein the hydrogen peroxide is added in the form of a 30 wt% aqueous solution of hydrogen peroxide.
3. The epoxy resin for powder coating according to claim 1, wherein the epoxy resin has an epoxy equivalent of 660-710g/mol, a softening point of 78-84 ℃ and an iodine value of < 1g/100 g.
4. The method for preparing an epoxy resin for powder coating according to claim 1, comprising:
(1) adding tartaric acid, methacrylic acid, oleic acid and xylene in a formula amount into a reaction kettle, starting stirring, uniformly mixing, adding a first catalyst in a formula amount, heating to the boiling point of the xylene, and carrying out esterification reaction with water;
(2) sampling and detecting the hydroxyl value of the reactant of the system, cooling to 100-105 ℃ when the hydroxyl value is less than 5mgKOH/g, then adding the bisphenol A, E-51 liquid epoxy resin and the second catalyst in the formula amount, and carrying out heat preservation and chain extension reaction;
(3) sampling and detecting the epoxy equivalent of the polymer of the system, and when the epoxy equivalent reaches 500-550g/mol, heating to 125-130 ℃, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) sampling and detecting the epoxy equivalent of the polymer of the system, stopping the reaction when the epoxy equivalent reaches 700-750g/mol, cooling to 50-55 ℃, adding a hydrogen peroxide aqueous solution with the formula amount, and carrying out thermal insulation at the temperature of 50-55 ℃ to carry out epoxidation reaction;
(5) sampling and detecting the iodine value of the system polymer, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 710g/mol in 660-710g/mol, standing and layering, removing the water phase of hydrogen peroxide, then washing, standing and removing the water layer so as to remove the catalyst and residual impurities and obtain an organic phase solution;
(6) starting a vacuum system, and heating to 115-120 ℃ under a reduced pressure condition to remove xylene and water from the organic phase solution under reduced pressure;
(7) and after no obvious distillate is evaporated, removing vacuum, discharging, cooling, crushing and granulating to obtain the epoxy resin.
5. The process for producing an epoxy resin for powder coating according to claim 4, wherein in the steps (2), (3), (4) and (5), the sampling test is conducted after removing the xylene solvent in a vacuum oven.
6. The method of preparing an epoxy resin for powder coating according to claim 4, wherein the washing in the step (5) is 1 to 2 times of washing with tap water added in an amount of 1 to 1.5 times by mass of xylene.
7. The method of preparing an epoxy resin for powder coating according to claim 4, wherein in the step (6), the degree of vacuum is controlled to be-0.097 to-0.099 MPa.
8. A self-leveling low-temperature-curable powder coating comprising the epoxy resin according to any one of claims 1 to 3.
9. The powder coating of claim 8, wherein the powder coating is a 50:50 hybrid powder coating.
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CN115572368A (en) * 2022-09-05 2023-01-06 黄山市源润新材料科技有限公司 Epoxy resin for wear-resistant and high-leveling powder coating and preparation method thereof

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WO1995025145A1 (en) * 1994-03-15 1995-09-21 Nippon Carbide Kogyo Kabushiki Kaisha Powder paint, method of manufacturing the same, and method of painting using the paint
CN111378097A (en) * 2020-04-22 2020-07-07 黄山市源润新材料科技有限公司 Epoxy resin for gasoline and salt fog resistant self-extinction 50/50 powder and preparation method thereof
CN111848883A (en) * 2020-07-07 2020-10-30 黄山市科美新材料有限公司 Preparation method of waterborne acrylic modified epoxy resin and coating thereof

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WO1995025145A1 (en) * 1994-03-15 1995-09-21 Nippon Carbide Kogyo Kabushiki Kaisha Powder paint, method of manufacturing the same, and method of painting using the paint
CN111378097A (en) * 2020-04-22 2020-07-07 黄山市源润新材料科技有限公司 Epoxy resin for gasoline and salt fog resistant self-extinction 50/50 powder and preparation method thereof
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Publication number Priority date Publication date Assignee Title
CN115572368A (en) * 2022-09-05 2023-01-06 黄山市源润新材料科技有限公司 Epoxy resin for wear-resistant and high-leveling 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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