CN113501934B - 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 PDFInfo
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- CN113501934B CN113501934B CN202110859213.XA CN202110859213A CN113501934B CN 113501934 B CN113501934 B CN 113501934B CN 202110859213 A CN202110859213 A CN 202110859213A CN 113501934 B CN113501934 B CN 113501934B
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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
- C08G59/02—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
- 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
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- 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
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- 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
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- 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
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- 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
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- 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
The epoxy resin with epoxy equivalent of 660-710g/mol is prepared by using tartaric acid, methacrylic acid, oleic acid, bisphenol A, E-51 liquid epoxy resin, hydrogen peroxide, xylene and the like as raw materials to react, and has special esterification groups in chain segments, a function of rapidly promoting leveling of a coating film, epoxy groups still on the esterification groups, high curing activity, low-temperature curing of the powder coating containing 50:50 polyester resin without adding any additional leveling agent, and high leveling grade and gloss of the surface of the cured coating film.
Description
Technical Field
The invention belongs to the field of powder coatings, and particularly relates to an epoxy resin for 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 common solvent-based paint and water-based paint, its dispersion medium is not solvent and water, but air. It has the characteristics of no solvent pollution, 100% film formation and low energy consumption.
The common E-12 epoxy resin matched with 50:50 polyester resin is obtained by directly reacting bisphenol A and epichlorohydrin 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, the curing can be carried out at a temperature of 180 ℃ or higher, and the energy consumption is higher.
In addition, because the amount of the leveling agent is small, generally about 1% of the leveling agent is used in the powder coating formula, the leveling agent is difficult to be fully and uniformly mixed in the powder coating, so that poor leveling property is caused, and particularly in a low-temperature curing system, the phenomenon of insufficient leveling property is more obvious, and a coating film with high leveling grade is difficult to prepare.
In industry, in order to fully and uniformly mix 1% of the leveling agent with the resin material, the leveling agent needs to stay in a mixer and a mill for a long time, and high energy consumption is brought.
Therefore, a new epoxy resin for self-leveling low-temperature curing powder coating and a preparation method thereof are needed to solve the technical problems.
Disclosure of Invention
The invention provides an epoxy resin for self-leveling low-temperature curing powder coating, which comprises the following raw materials in parts by mole:
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 a 30wt% aqueous hydrogen peroxide solution, i.e. in the form of an aqueous hydrogen peroxide solution, in total 7-12 molar parts of hydrogen peroxide.
Wherein the appearance of 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/100g.
The invention also provides a preparation method of the epoxy resin for the self-leveling low-temperature curing type powder coating, which comprises the following steps:
(1) Adding the tartaric acid, the methacrylic acid, the oleic acid and the dimethylbenzene in the formula amount into a reaction kettle, starting stirring, adding the first catalyst in the formula amount after uniformly mixing, and heating to the boiling point of the dimethylbenzene to carry out esterification reaction with water;
(2) Sampling and detecting the hydroxyl value of a system reactant, cooling to 100-105 ℃ when the hydroxyl value is less than 5mgKOH/g, adding a formula amount of bisphenol A, E-51 liquid epoxy resin and a second catalyst, and carrying out chain extension reaction by heat preservation;
(3) Sampling and detecting the epoxy equivalent of the system polymer, and heating to 125-130 ℃ when the epoxy equivalent reaches 500-550g/mol, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) Sampling and detecting the epoxy equivalent of the system polymer, stopping the reaction when the epoxy equivalent reaches 700-750g/mol, cooling to 50-55 ℃, adding the formula amount of hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 50-55 ℃ by heat preservation;
(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 660-710g/mol, standing and layering, removing the aqueous phase of hydrogen peroxide, washing, then standing and removing the aqueous layer, thereby removing the catalyst and impurities (such as residual hydrogen peroxide and the like) to obtain an organic phase solution;
(6) Starting a vacuum system, heating to 115-120 ℃ under the condition of reduced pressure, and decompressing and removing dimethylbenzene and water from the organic phase solution;
(7) And after no obvious distillate is distilled out (namely, when the mass fraction of volatile components in a sampling test is less than 1 percent), removing vacuum, discharging, cooling, crushing and granulating to obtain the epoxy resin.
In the steps (2), (3), (4) and (5), the detection is carried out after the xylene solvent is removed in a vacuum oven.
Wherein in the step (5), the washing is carried out 1-2 times by adding tap water with the mass which is 1-1.5 times of that of the dimethylbenzene.
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 hot high-temperature discharging, and the cooling is cooling by using a steel belt with condensed water.
The invention also provides a self-leveling low-temperature curing type 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, dimethylbenzene, phosphotungstic acid and the like as raw materials to react to obtain the epoxy resin with the epoxy equivalent of 600-650g/mol and the iodine value less than 1g/100g.
The chain segment of the epoxy resin has special esterified groups, has the function of rapidly promoting the leveling of a coating film, has epoxy groups on the esterified groups, has high curing activity, can fully cure the 50:50 mixed powder coating at low temperature (140 ℃/20 min) without adding any additional leveling agent, has very high leveling grade and luster on the surface of the cured coating film, has the leveling grade of more than 7 and the luster of more than 94.3 percent, does not need long-time grinding, saves energy and has very important application value.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The embodiment provides a preparation method of epoxy resin for self-leveling low-temperature curing type powder coating, which comprises the following steps:
(1) Adding 4.3 mol parts of tartaric acid, 8 mol parts of methacrylic acid, 2.5 mol parts of oleic acid and 26 mol parts of dimethylbenzene into a reaction kettle, starting stirring, adding 0.035 mol part of phosphotungstic acid after uniform mixing, and heating to the boiling point of dimethylbenzene to carry out esterification reaction with water;
(2) Sampling, removing xylene solvent in a vacuum oven, detecting the hydroxyl value of a reactant of a system, cooling to 101 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 12 mol parts of bisphenol A, 19 mol parts of E-51 liquid epoxy resin and 0.0025 mol parts of triphenylphosphine, and carrying out chain extension reaction by heat preservation;
(3) Sampling, removing the xylene solvent in a vacuum oven, detecting the epoxy equivalent of the system polymer, heating to 129 ℃ when the epoxy equivalent reaches 520g/mol, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) Sampling, removing xylene solvent in a vacuum oven, detecting the epoxy equivalent of the polymer in the system, stopping the reaction when the epoxy equivalent reaches 745g/mol, cooling to 50 ℃, adding 8 mol parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 50 ℃;
(5) Sampling, removing xylene solvent in a vacuum oven, detecting the iodine value of the system polymer, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 690g/mol, standing for layering, removing the water phase of hydrogen peroxide, adding tap water with the mass 1.4 times of the mass of the xylene for washing 2 times, standing, removing the water layer, and removing impurities such as 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 decompressing and removing dimethylbenzene and water from the organic phase solution, wherein the vacuum degree is controlled at-0.099 Mpa;
(7) And after no obvious distillate is distilled out (namely, when the mass fraction of volatile components in a sampling test is less than 1 percent), removing vacuum, discharging at high temperature while the distillate is hot, cooling by using a steel belt with condensed water, crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles with an epoxy equivalent of 690g/mol, a softening point of 79 ℃ and an iodine value of 0.8g/100g.
Example 2
The embodiment provides a preparation method of epoxy resin for self-leveling low-temperature curing type powder coating, which comprises the following steps:
(1) Adding 5.5 mol parts of tartaric acid, 7 mol parts of methacrylic acid, 4 mol parts of oleic acid and 21 mol parts of dimethylbenzene into a reaction kettle, starting stirring, adding 0.05 mol part of phosphomolybdic acid after uniformly mixing, and heating to the boiling point of dimethylbenzene to carry out esterification reaction with water;
(2) Sampling, removing xylene solvent in a vacuum oven, detecting the hydroxyl value of a reactant of a system, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 11 mol parts of bisphenol A, 19 mol parts of E-51 liquid epoxy resin and 0.003 mol part of triphenylphosphine, and carrying out chain extension reaction by heat preservation;
(3) Sampling, removing the xylene solvent in a vacuum oven, detecting the epoxy equivalent of the system polymer, heating to 125 ℃ when the epoxy equivalent reaches 537g/mol, and continuing to perform polymerization chain extension reaction at the temperature;
(4) Sampling, removing xylene solvent in a vacuum oven, detecting the epoxy equivalent of the polymer in the system, stopping the reaction when the epoxy equivalent reaches 721g/mol, cooling to 53 ℃, adding 12 mol parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 53 ℃;
(5) Sampling, removing xylene solvent in a vacuum oven, detecting the iodine value of the system polymer, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 665g/mol, standing for layering, removing the water phase of hydrogen peroxide, then adding tap water with the mass 1 time of the mass of the xylene for washing for 1 time, and then standing and removing the water layer, thereby removing impurities such as catalyst, residual hydrogen peroxide and the like, and obtaining an organic phase solution;
(6) Starting a vacuum system, heating to 117 ℃ under the condition of reduced pressure, and decompressing and removing solvents such as dimethylbenzene, water and the like from the organic phase solution, wherein the vacuum degree is controlled at-0.098 Mpa;
(7) And after no obvious distillate is distilled out (namely, when the mass fraction of volatile components in a sampling test is less than 1 percent), removing vacuum, discharging at high temperature while the distillate is hot, cooling by using a steel belt with condensed water, crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles with the epoxy equivalent of 665g/mol, the softening point of 83 ℃ and the iodine value of 0.9g/100g.
Example 3
The embodiment provides a preparation method of epoxy resin for self-leveling low-temperature curing type powder coating, which comprises the following steps:
(1) Adding 6 mole parts of tartaric acid, 8.5 mole parts of methacrylic acid, 3.8 mole parts of oleic acid and 24 mole parts of dimethylbenzene into a reaction kettle, starting stirring, adding 0.04 mole part of phosphotungstic acid after uniformly mixing, and then heating to the boiling point of dimethylbenzene to carry out esterification reaction with water;
(2) Sampling, removing xylene solvent in a vacuum oven, detecting the hydroxyl value of a reactant of a system, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 14 mole parts of bisphenol A, 21 mole parts of E-51 liquid epoxy resin and 0.0035 mole parts of triphenylphosphine, and carrying out chain extension reaction by heat preservation;
(3) Sampling, removing the xylene solvent in a vacuum oven, detecting the epoxy equivalent of the system polymer, heating to 127 ℃ when the epoxy equivalent reaches 518g/mol, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) Sampling, removing xylene solvent in a vacuum oven, detecting the epoxy equivalent of the polymer in the system, stopping the reaction when the epoxy equivalent reaches 732g/mol, cooling to 55 ℃, adding 11 mol parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 55 ℃;
(5) Sampling, removing xylene solvent in a vacuum oven, detecting the iodine value of the system polymer, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 700g/mol, standing for layering, removing the water phase of hydrogen peroxide, adding tap water with the mass 1.5 times of the mass of the xylene for washing 2 times, standing, removing the water layer, and removing impurities such as catalyst, residual hydrogen peroxide and the like to obtain an organic phase solution;
(6) Starting a vacuum system, heating to 116 ℃ under the condition of reduced pressure, and decompressing and removing solvents such as dimethylbenzene, water and the like from the organic phase solution, wherein the vacuum degree is controlled at-0.098 Mpa;
(7) And after no obvious distillate is distilled out (namely, when the mass fraction of volatile components in a sampling test is less than 1 percent), removing vacuum, discharging at high temperature while the distillate is hot, cooling by using a steel belt with condensed water, crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles with an epoxy equivalent of 700g/mol, a softening point of 83 ℃ and an iodine value of 0.8g/100g.
Example 4
The embodiment provides a preparation method of epoxy resin for self-leveling low-temperature curing type powder coating, which comprises the following steps:
(1) Adding 5.5 mol parts of tartaric acid, 7 mol parts of methacrylic acid, 4 mol parts of oleic acid and 29 mol parts of dimethylbenzene into a reaction kettle, starting stirring, adding 0.055 mol part of phosphomolybdic acid after uniformly mixing, and heating to the boiling point of dimethylbenzene to carry out esterification reaction with water;
(2) Sampling, removing xylene solvent in a vacuum oven, detecting the hydroxyl value of a reactant of a system, cooling to 102 ℃ when the hydroxyl value is less than 5mgKOH/g, adding 13 mol parts of bisphenol A, 21 mol parts of E-51 liquid epoxy resin and 0.002 mol part of triphenylphosphine, and carrying out chain extension reaction by heat preservation;
(3) Sampling, removing the xylene solvent in a vacuum oven, detecting the epoxy equivalent of the system polymer, heating to 130 ℃ when the epoxy equivalent reaches 525g/mol, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) Sampling, removing xylene solvent in a vacuum oven, detecting the epoxy equivalent of the polymer in the system, stopping the reaction when the epoxy equivalent reaches 745g/mol, cooling to 52 ℃, adding 10 mol parts of hydrogen peroxide in the form of 30% hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 52 ℃;
(5) Sampling, removing xylene solvent in a vacuum oven, detecting the iodine value of the system polymer, stopping the reaction when the iodine value is less than 1 and the epoxy equivalent is 708g/mol, standing for layering, removing the water phase of hydrogen peroxide, adding tap water with the mass 1 time of the mass of the xylene for washing 2 times, standing, removing the water layer, and removing impurities such as catalyst, residual hydrogen peroxide and the like to obtain an organic phase solution;
(6) Starting a vacuum system, heating to 120 ℃ under the condition of reduced pressure, and decompressing and removing solvents such as dimethylbenzene, water and the like from the organic phase solution, wherein the vacuum degree is controlled at-0.099 Mpa;
(7) And after no obvious distillate is distilled out (namely, when the mass fraction of volatile components in a sampling test is less than 1 percent), removing vacuum, discharging at high temperature while the distillate is hot, cooling by using a steel belt with condensed water, crushing and granulating to obtain the epoxy resin.
The epoxy resin is colorless transparent particles with the epoxy equivalent of 660-708g/mol, the softening point of 81 ℃ and the iodine value of 0.7g/100g.
Comparative example 1
As comparative example 1, a commercially available ordinary E-12 epoxy resin was used instead of the epoxy resin of the present invention, which had an epoxy equivalent of 798g/mol and a softening point of 92℃and was purchased from Huangshan brocade Peak practical Co.
Powder coatings and coatings were prepared using the epoxy resins of examples 1-4 and comparative example 1, respectively, and performance tests were performed.
Preparation of powder coating: the materials were uniformly mixed according to the powder coating formulation shown in the following Table 1, extruded at a low temperature (screw temperature was controlled at 95 to 100 ℃) by a twin screw extruder, pressed into pieces, crushed, and then crushed and sieved to prepare powder coatings (160 to 180 mesh) for use in the preparation of the coatings of examples A1 to A4 and comparative examples B1 to B3.
Wherein, in preparing the powder coating used for the coating of comparative example B3, the mixing time and grinding time of each material were increased by 30 minutes compared with each of examples 1 to 4.
The 50:50 polyester resin model is SJ3702, and is purchased from Anhui Shenjian new material Co., ltd; the polishing formulation number GLP588 was purchased from Ningbo south sea chemical Co.
And (3) preparing a coating: the powder coatings were sprayed on the surface-treated tin plate substrates using an electrostatic spray gun with a film thickness of 80 to 90 μm, and after curing under the conditions shown in Table 1, the coatings numbered as examples A1 to A4 and comparative examples B1 to B3, respectively, were obtained.
TABLE 1 parameters for the preparation of the 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 respective materials were increased by 30min compared with those of the respective examples 1 to 4
Performance test:
and (3) coating index detection: according to GB/T21776-2008 'powder coating and coating detection standard guide';
leveling grade: according to JB-T3998-1999 coating leveling scratch determination method, wherein the higher the leveling grade is, the better the leveling of the surface of the coating film is;
adhesion test: according to GB/T9286-1998, cross-hatch test of color paint and varnish film, wherein smaller numbers indicate better adhesion.
Table 2 shows the results of the performance test of the coatings of examples A1 to A4 and comparative examples B1 to B3 described above.
TABLE 2 results of Performance test of the coatings of examples A1-A4 and comparative examples B1-B4
As can be seen from the comparison of examples 1-4 and comparative examples 1-3 in Table 1, the epoxy resin and 50:50 polyester resin obtained by the mutual cooperation and synergistic effect of the components form a powder coating system, the mixing and grinding time is not required to be additionally increased, and the prepared powder coating has higher coating film gloss, high self-leveling grade, excellent impact resistance, excellent adhesive force and excellent boiling performance after being cured at a low temperature of 140 ℃/20 min.
In comparative example 1, the epoxy resin of the invention is replaced by the common E-12 epoxy resin, no additional leveling agent is added, and the epoxy activity of the E-12 epoxy resin is low, so that the curing and leveling process cannot be successfully completed at 140 ℃/20min, and the coating film is rough and has poor mechanical properties.
In comparative example 2, the curing condition in comparative example 1 was 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, low surface gloss, and relatively poor adhesion and boiling water resistance.
In the comparative example 3, the leveling agent is additionally used on the basis of the comparative example 2, the material mixing time and the grinding time are increased by 30 minutes compared with those of the examples 1-4, the full curing of the coating can be realized, the leveling of the final coating is relatively better (but still weaker than that of the examples 1-4), the surface gloss is moderate, the adhesion and boiling water boiling resistance basically meet the requirements, but 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 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. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (9)
1. The preparation method of the epoxy resin for the self-leveling low-temperature cured powder coating comprises the following steps of:
wherein the first catalyst is phosphotungstic acid or phosphomolybdic acid, and the second catalyst is triphenylphosphine;
the preparation method of the epoxy resin for the powder coating comprises the following steps:
(1) Adding the tartaric acid, the methacrylic acid, the oleic acid and the dimethylbenzene in the formula amount into a reaction kettle, starting stirring, adding the first catalyst in the formula amount after uniformly mixing, and heating to the boiling point of the dimethylbenzene to carry out esterification reaction with water;
(2) Sampling and detecting the hydroxyl value of a system reactant, cooling to 100-105 ℃ when the hydroxyl value is less than 5mgKOH/g, adding a formula amount of bisphenol A, E-51 liquid epoxy resin and a second catalyst, and carrying out chain extension reaction by heat preservation;
(3) Sampling and detecting the epoxy equivalent of the system polymer, and heating to 125-130 ℃ when the epoxy equivalent reaches 500-550g/mol, and continuing to perform polymerization chain extension reaction by heat preservation;
(4) Sampling and detecting the epoxy equivalent of the system polymer, stopping the reaction when the epoxy equivalent reaches 700-750g/mol, cooling to 50-55 ℃, adding the formula amount of hydrogen peroxide aqueous solution, and carrying out epoxidation reaction at the temperature of 50-55 ℃ by heat preservation;
(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 660-710g/mol, standing and layering, removing the aqueous phase of hydrogen peroxide, washing, and then standing and removing the aqueous layer to remove the catalyst and residual impurities, thereby obtaining an organic phase solution;
(6) Starting a vacuum system, heating to 115-120 ℃ under the condition of reduced pressure, and decompressing and removing dimethylbenzene and water from the organic phase solution;
(7) And after no obvious distillate is distilled out, releasing vacuum, discharging, cooling, crushing and granulating to obtain the epoxy resin.
2. The method for producing an epoxy resin for powder coating according to claim 1, wherein the hydrogen peroxide is added in the form of a 30wt% aqueous hydrogen peroxide solution.
3. The process for producing an epoxy resin for powder coating according to claim 1 or 2, wherein the epoxy equivalent of the resulting epoxy resin for powder coating is 660-710g/mol, the softening point is 78-84 ℃ and the iodine value is < 1g/100g.
4. The method for producing an epoxy resin for powder coating according to claim 1 or 2, wherein in the steps (2), (3), (4) and (5), the sampling test is performed after removing the xylene solvent in a vacuum oven.
5. The method for producing an epoxy resin for powder coating according to claim 1 or 2, wherein in the step (5), the washing is performed 1 to 2 times by adding tap water having a mass 1 to 1.5 times the mass of xylene.
6. The method for producing an epoxy resin for powder coating according to claim 1 or 2, wherein in the step (6), the vacuum degree is controlled to-0.097 to-0.099 Mpa.
7. An epoxy resin for self-leveling low-temperature cured powder coating, which is prepared by the preparation method of the epoxy resin for self-leveling low-temperature cured powder coating according to any one of claims 1 to 6.
8. A self-leveling low-temperature-curable powder coating material comprising the epoxy resin according to claim 7.
9. The powder coating of claim 8, wherein the powder coating is a 50:50 hybrid powder coating.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110859213.XA CN113501934B (en) | 2021-07-28 | 2021-07-28 | Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof |
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| CN202110859213.XA CN113501934B (en) | 2021-07-28 | 2021-07-28 | Epoxy resin for self-leveling low-temperature curing powder coating and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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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 |
| 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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| Publication number | Priority date | Publication date | Assignee | Title |
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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 |
| 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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