CN110437711B - Epoxy resin for low-temperature curing type B68 extinction powder and preparation method and application thereof - Google Patents
Epoxy resin for low-temperature curing type B68 extinction powder and preparation method and application thereof Download PDFInfo
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- 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
- C08G59/04—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof
- C08G59/06—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols
- C08G59/063—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols with epihalohydrins
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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
- C08G59/04—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof
- C08G59/06—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols
- C08G59/066—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols with chain extension or advancing agents
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- C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
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- 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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- 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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- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/42—Gloss-reducing agents
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
- C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
Abstract
The invention belongs to the technical field of powder coatings, and particularly relates to low-temperature curing type epoxy resin for B68 extinction powder, and a preparation method and application thereof. The epoxy resin for the low-temperature curing type B68 matting powder is prepared by polymerizing bisphenol A, epichlorohydrin, sodium hydroxide, 2-dimethylmalonic acid, terephthalic acid, toluene, E-44 epoxy resin with high epoxy activity and the like serving as raw materials, blocking by using high-activity monomer diethylene glycol diglycidyl ether as a blocking agent, and epoxy resin I and epoxy resin II are respectively prepared by adopting double formulas and then mixed to obtain the final epoxy resin product with relatively poor dispersion phase compatibility, soft chain segment and high activity, which is beneficial to obtaining a lower-gloss coating film, and because of different molecular chain segments, the activity difference is obvious, the softening point is relatively reduced, can realize full curing at 150 ℃/20min, not only greatly reduces energy consumption, but also can enable the gloss of a coating film to reach 5% or even lower.
Description
Technical Field
The invention belongs to the technical field of powder coatings, and particularly relates to low-temperature curing type epoxy resin for B68 extinction powder, and a preparation method and application thereof.
Background
The powder coating is 100% solid powder without organic solvent, which is different from oil-based coating and water-based coating, and the powder coating is a novel environment-friendly coating which does not use solvent or water as a dispersion medium but uses air as a dispersion medium, is uniformly coated on the surface of a workpiece and forms a coating film with special purpose after being heated. The powder coating has the advantages of no VOC, environmental protection, energy conservation, high construction efficiency, wide application range and the like, and gradually replaces organic solvent type coatings with the advantages of economy, environmental protection, high efficiency, excellent performance and the like, thereby becoming an important development direction in the coating industry and keeping a faster growth rate all the time. The polyester powder coating is widely applied to the coating field due to the characteristics of excellent durability, decoration, processing formability and the like.
Epoxy resin powder coating is a thermosetting powder coating with corrosion resistance and toughness, which is not only applied the earliest but also developed the fastest. The epoxy resin powder coating system is mainly composed of epoxy resin, pigment and filler, additives and curing agents. The epoxy resin powder coating is prepared by adopting an international general method for producing thermosetting powder coating, namely, the method comprises the steps of melt mixing extrusion, mixing, melt mixing extrusion, fine crushing and the like. Generally, in the preparation process of epoxy resin powder coating, solid resin with the epoxy equivalent of 700-1000 is mostly required to be selected as a film forming substance, and the curing agent mainly comprises dicyandiamide, dicyandiamide derivatives, acid anhydride, imidazole, cyclic ether, phenolic resin polyester resin, boron trifluoride amine complex and the like, and in industry, dicyandiamide, imidazole and cyclic ether are mostly adopted, while the most commonly used extinction curing agent in the field of low-gloss epoxy powder coating is B68 extinction curing agent. The B68 flatting curing agent is a complex of pyromellitic acid and 2-phenylimidazoline, and can be cured with E-12 epoxy resin to obtain a coating film with low gloss (< 10%), thereby obtaining a coating film surface with excellent decoration.
The common E-12 epoxy resin is obtained by directly reacting bisphenol A and epoxy chloropropane under the action of alkali, the molecular structure of the product is single, the activity of end group epoxy is influenced by the steric hindrance of bisphenol A, the activity is slightly low, the softening point is high, the full curing is difficult to realize at the temperature of below 180 ℃, the full curing can be realized generally at 185 ℃/20min even if the epoxy resin is cured with a B68 extinction curing agent, the energy consumption of a curing process is high, the impact performance of a coating film is poor, and the normal addition of the B68 extinction curing agent cannot be effectively extinguished to 5% or below due to the relatively uniform molecular chain of the epoxy resin.
Therefore, the development of the epoxy resin for realizing the low-temperature curing type B68 extinction powder is of great significance.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide the epoxy resin for the low-temperature curing type B68 extinction powder, so as to solve the problems that the curing energy consumption is high and the product glossiness is influenced due to the high curing temperature of the E-12 epoxy resin in the prior art;
the second technical problem to be solved by the invention is to provide a preparation method of the epoxy resin for the low-temperature curing type B68 matting powder and an application of the epoxy resin for preparing an epoxy resin system powder coating.
In order to solve the technical problems, the epoxy resin for the low-temperature curing type B68 extinction powder comprises the following raw material components in molar content based on the total amount of the raw materials for preparation:
preferably, the preparation raw material also comprises a catalyst.
Specifically, the molar amount of the catalyst accounts for 0.1-0.2% of the total molar amount of the raw material components.
Specifically, the catalyst comprises benzyltrimethylammonium chloride and/or triphenylmethylphosphonium bromide.
The invention also discloses a method for preparing the epoxy resin for the low-temperature curing type B68 matting powder, which comprises the following steps:
(1) preparing sodium hydroxide solution with the formula amount of sodium hydroxide, adding the bisphenol A with the formula amount, and reacting at 30-40 ℃; then adding the epoxy chloropropane with the formula amount, reacting at 80-100 ℃, and stopping the reaction when the pH of the reaction system is less than 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding the diethylene glycol diglycidyl ether with the formula amount into the obtained bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction at 80-90 ℃, and stopping the reaction when the epoxy equivalent of the resin reaches 750-800eq/100g to obtain epoxy resin I for later use;
(3) uniformly mixing the toluene, the E-44 epoxy resin, the 2, 2-dimethylmalonic acid, the terephthalic acid and the catalyst according to the formula ratio, carrying out chain extension reaction at 90-105 ℃, and stopping the reaction when the epoxy equivalent of the resin reaches 800-850eq/100g to obtain epoxy resin II for later use;
(4) and (2) uniformly mixing the epoxy resin I and the epoxy resin II, reacting at the temperature of 80-90 ℃, removing the toluene solvent under vacuum reduced pressure when the epoxy equivalent reaches 830-860eq/100g, discharging at high temperature while the materials are hot, cooling, crushing and granulating to obtain the required low-temperature curing type epoxy resin for B68 extinction powder.
Specifically, in the step (1), the mass concentration of the sodium hydroxide solution is controlled to be 30-50 wt%.
Specifically, the step (2) further comprises the step of adding water to the epoxy resin I for washing and performing reduced pressure dehydration after the reaction is finished.
The invention also discloses application of the low-temperature curing type B68 extinction powder epoxy resin in preparation of powder coatings.
Specifically, the powder coating is a B68 curing system epoxy resin powder coating.
The invention also discloses a powder coating prepared from the low-temperature curing type B68 extinction powder epoxy resin.
The epoxy resin for the low-temperature curing type B68 matting powder is prepared by polymerizing bisphenol A, epichlorohydrin, sodium hydroxide, 2-dimethylmalonic acid, terephthalic acid, toluene, E-44 epoxy resin with high epoxy activity and the like serving as raw materials, blocking by using high-activity monomer diethylene glycol diglycidyl ether as a blocking agent, and epoxy resin I and epoxy resin II are respectively prepared by adopting double formulas and then mixed to obtain the final epoxy resin product with relatively poor dispersion phase compatibility, soft chain segment and high activity, which is beneficial to obtaining a lower-gloss coating film, and because of different molecular chain segments, the activity difference is obvious, the softening point is relatively reduced, can realize full curing at 150 ℃/20min, not only greatly reduces energy consumption, but also can enable the gloss of a coating film to reach 5% or even lower.
The low-temperature curing type B68 extinction epoxy resin for powder has high activity and relatively low softening point, can ensure good low-temperature leveling property, has low-temperature curing reactivity, extinction property, impact property, boiling water boiling resistance, luster, adhesive force and other properties which meet the application requirements of powder coating, has the film performance equivalent to that of the current common E-12 epoxy resin cured at normal temperature, has extinction effect superior to that of the common temperature cured film, can meet the application requirements of E-12 epoxy resin and B68 extinction curing agent cured at normal 185 ℃/20min in all aspects, can be used in low-temperature cured powder coating with the curing condition of 150 ℃/20min to obtain excellent comprehensive performance, and can meet the effect requirements of customers on products with 5 percent of glossiness and lower.
Detailed Description
Example 1
The epoxy resin for the low-temperature curing type B68 extinction powder is prepared from the following raw material components in percentage by mole:
the preparation method of the epoxy resin for the low-temperature curing type B68 matting powder comprises the following steps:
(1) adding water into sodium hydroxide with the formula amount to prepare a sodium hydroxide solution with the solid content of 30%, pumping the sodium hydroxide solution into a reaction kettle I, heating to 30 ℃, adding bisphenol A with the formula amount, and carrying out heat preservation reaction for 1-2 hours; then adding epoxy chloropropane with the formula amount, carrying out heat preservation reaction at 80 ℃ for 2-4h, and stopping the reaction when the pH value of the solution is tested to be below 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding diethylene glycol diglycidyl ether with the formula amount into the bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction for 1-2h at 80 ℃, then sampling and testing the epoxy equivalent of the epoxy resin, stopping the reaction when the epoxy equivalent is 750-800eq/100g, separating out a water phase and an epoxy resin phase, washing the epoxy resin for 5-8 times, wherein the mass of water for each time is one third of the mass of the resin, and finally carrying out reduced pressure dehydration on the epoxy resin to obtain epoxy resin I for later use;
(3) taking another reaction kettle II, adding toluene, E-44 epoxy resin, 2-dimethylmalonic acid, terephthalic acid and a catalyst in a formula amount, heating to 90 ℃ to perform chain extension reaction for 2-4h, and stopping the reaction when the epoxy equivalent of the resin is 800-850eq/100g to obtain epoxy resin II;
(4) adding the epoxy resin I reserved in the reaction kettle I into a reaction kettle II, mixing and reacting the epoxy resin I with the epoxy resin II at 80 ℃ for 1-2h, starting vacuum to remove a toluene solvent by decompression when the epoxy equivalent is 830-860eq/100g, discharging at high temperature while the epoxy resin is hot, 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 in this example was tested as colorless transparent particles with an epoxy equivalent of 845eq/100g and a softening point of 84 ℃.
Example 2
The epoxy resin for the low-temperature curing type B68 extinction powder is prepared from the following raw material components in percentage by mole:
the preparation method of the epoxy resin for the low-temperature curing type B68 matting powder comprises the following steps:
(1) adding water into sodium hydroxide with the formula amount to prepare a sodium hydroxide solution with the solid content of 40%, pumping the sodium hydroxide solution into a reaction kettle I, heating to 35 ℃, adding bisphenol A with the formula amount, and carrying out heat preservation reaction for 1-2 hours; then adding epoxy chloropropane with the formula amount, carrying out heat preservation reaction at 90 ℃ for 2-4h, and stopping the reaction when the pH value of the solution is tested to be below 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding diethylene glycol diglycidyl ether with the formula amount into the bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction for 1-2h at 85 ℃, then sampling and testing the epoxy equivalent of the epoxy resin, stopping the reaction when the epoxy equivalent is 750-800eq/100g, separating out a water phase and an epoxy resin phase, washing the epoxy resin for 5-8 times, wherein the mass of water for each time is one third of the mass of the resin, and finally carrying out reduced pressure dehydration on the epoxy resin to obtain epoxy resin I for later use;
(3) taking another reaction kettle II, adding toluene, E-44 epoxy resin, 2-dimethylmalonic acid, terephthalic acid and a catalyst in a formula amount, heating to 100 ℃ to perform chain extension reaction for 2-4h, and stopping the reaction when the epoxy equivalent of the resin is 800-850eq/100g to obtain epoxy resin II;
(4) adding the epoxy resin I reserved in the reaction kettle I into a reaction kettle II, mixing and reacting the epoxy resin I with the epoxy resin II at 85 ℃ for 1-2h, starting vacuum to remove a toluene solvent under reduced pressure when the epoxy equivalent is 830-860eq/100g, discharging at high temperature while the epoxy resin is hot, 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 in this example was tested as colorless transparent particles with an epoxy equivalent of 858eq/100g and a softening point of 86 ℃.
Example 3
The epoxy resin for the low-temperature curing type B68 extinction powder is prepared from the following raw material components in percentage by mole:
the preparation method of the epoxy resin for the low-temperature curing type B68 matting powder comprises the following steps:
(1) adding water into sodium hydroxide with the formula amount to prepare a sodium hydroxide solution with the solid content of 50%, pumping the sodium hydroxide solution into a reaction kettle I, heating to 40 ℃, adding bisphenol A with the formula amount, and carrying out heat preservation reaction for 1-2 hours; then adding epoxy chloropropane with the formula amount, carrying out heat preservation reaction at 100 ℃ for 2-4h, and stopping the reaction when the pH value of the solution is tested to be below 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding diethylene glycol diglycidyl ether with the formula amount into the bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction for 1-2h at 90 ℃, then sampling and testing the epoxy equivalent of the epoxy resin, stopping the reaction when the epoxy equivalent is 750-800eq/100g, separating out a water phase and an epoxy resin phase, washing the epoxy resin for 5-8 times, wherein the mass of water for each time is one third of the mass of the resin, and finally carrying out reduced pressure dehydration on the epoxy resin to obtain epoxy resin I for later use;
(3) taking another reaction kettle II, adding toluene, E-44 epoxy resin, 2-dimethylmalonic acid, terephthalic acid and a catalyst in a formula amount, heating to 105 ℃ to perform chain extension reaction for 2-4h, and stopping the reaction when the epoxy equivalent of the resin is 800-850eq/100g to obtain epoxy resin II;
(4) adding the epoxy resin I reserved in the reaction kettle I into a reaction kettle II, mixing and reacting the epoxy resin I with the epoxy resin II at 90 ℃ for 1-2h, starting vacuum to remove a toluene solvent by decompression when the epoxy equivalent is 830-860eq/100g, discharging at high temperature while the epoxy resin is hot, 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 in this example was tested as colorless transparent particles with an epoxy equivalent of 834eq/100g and a softening point of 88 ℃.
Example 4
The epoxy resin for the low-temperature curing type B68 extinction powder is prepared from the following raw material components in percentage by mole:
the preparation method of the epoxy resin for the low-temperature curing type B68 matting powder comprises the following steps:
(1) adding water into sodium hydroxide with the formula amount to prepare a sodium hydroxide solution with the solid content of 40%, pumping the sodium hydroxide solution into a reaction kettle I, heating to 35 ℃, adding bisphenol A with the formula amount, and carrying out heat preservation reaction for 1-2 hours; then adding epoxy chloropropane with the formula amount, carrying out heat preservation reaction at 90 ℃ for 2-4h, and stopping the reaction when the pH value of the solution is tested to be below 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding diethylene glycol diglycidyl ether with the formula amount into the bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction for 1-2h at 85 ℃, then sampling and testing the epoxy equivalent of the epoxy resin, stopping the reaction when the epoxy equivalent is 750-800eq/100g, separating out a water phase and an epoxy resin phase, washing the epoxy resin for 5-8 times, wherein the mass of water for each time is one third of the mass of the resin, and finally carrying out reduced pressure dehydration on the epoxy resin to obtain epoxy resin I for later use;
(3) taking another reaction kettle II, adding toluene, E-44 epoxy resin, 2-dimethylmalonic acid, terephthalic acid and a catalyst in a formula amount, heating to 95 ℃ to perform chain extension reaction for 2-4h, and stopping the reaction when the epoxy equivalent of the resin is 800-850eq/100g to obtain epoxy resin II;
(4) adding the epoxy resin I reserved in the reaction kettle I into a reaction kettle II, mixing and reacting the epoxy resin I with the epoxy resin II at 85 ℃ for 1-2h, starting vacuum to remove a toluene solvent under reduced pressure when the epoxy equivalent is 830-860eq/100g, discharging at high temperature while the epoxy resin is hot, 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 in this example was tested as colorless transparent particles with an epoxy equivalent of 852eq/100g and a softening point of 85 ℃.
Comparative example 1
The epoxy resin of this comparative example had the same raw material composition as example 2 except that diethylene glycol diglycidyl ether was not contained.
According to tests, the epoxy equivalent of the epoxy resin prepared by the comparative example is 1130eq/100g, and the softening point is 95 ℃.
Comparative example 2
The composition of the epoxy resin of this comparative example was the same as that of example 2 except that 2, 2-dimethylmalonic acid was not contained.
Through tests, the epoxy equivalent of the epoxy resin prepared by the comparative example is 720eq/100g, and the softening point is 92 ℃.
Comparative example 3
The composition of the epoxy resin of this comparative example was the same as that of example 2 except that no terephthalic acid was contained.
Through tests, the epoxy equivalent of the epoxy resin prepared by the comparative example is 760eq/100g, and the softening point is 80 ℃.
Examples of the experiments
The epoxy resins prepared in examples 1-4 of the invention and comparative examples 1-3 are respectively taken to prepare B68 extinction powder coating according to the following components, and the specific formula is as follows:
the raw materials in the formula are common materials sold in the market, wherein the B68 extinction curing agent is purchased from Huangshan Huahui science and technology Limited company under the trademark HC68, and the flatting agent and the brightener are purchased from Ningbo south sea chemical Limited company under the trademarks GLP388 and BLC701 respectively.
As comparative example 4, epoxy resin I (epoxy equivalent: 780eq/100g, softening point: 83 ℃ C.) which is an intermediate prepared in example 2 was used in place of the low-temperature curing type epoxy resin described in the present invention.
As comparative example 5, epoxy resin II (epoxy equivalent: 820eq/100g, softening point: 88 ℃ C.) as an intermediate prepared in example 2 was used in place of the low-temperature curing type epoxy resin described in the present invention.
The conventional commercially available E-12 epoxy resin (epoxy equivalent: 870eq/100g, softening point 93 ℃ C.) was used in place of the low-temperature curable epoxy resin of the present invention as comparative example 6.
The conventional E-12 epoxy resin (epoxy equivalent: 870eq/100g, softening point 93 ℃ C.) available on the market was used in place of the low-temperature curable epoxy resin of the present invention, and curing was carried out at 185 ℃/20min to give comparative example 7.
Preparation of powder coating: mixing the materials uniformly according to the formula of B68 matting powder coating, extruding, tabletting and crushing by a double-screw extruder, and then crushing and sieving the tablets to prepare powder coating (180 meshes); and spraying the powder coating on the galvanized iron substrate subjected to surface treatment by using an electrostatic spray gun, and curing at the temperature of 150 ℃/20min to obtain the coating.
The detection of the coating index is carried out according to GB/T21776 2008 'Standard guide for powder coating and coating thereof' and the adhesion level test is carried out according to GB/T9286 1998 'test for marking out paint films of colored paint and varnish'.
Epoxy resins prepared by the above examples and comparative examples coating formulations according to the invention were prepared and tested for coating properties as shown in table 1 below.
TABLE 1 powder coating Performance test data
From the data in table 1 above, it can be seen that the epoxy resin prepared in examples 1-4 of the present invention, through the synergistic effect between the components, is used in the B68 extinction cured powder coating, and the low temperature curing reactivity, extinction property, such as impact resistance, boiling water resistance, gloss, adhesion, etc., all meet the application requirements of the powder coating, so that the epoxy resin obtained has excellent comprehensive properties when used in the low temperature cured powder coating with the curing condition of 150 ℃/20 min.
In contrast, the epoxy resins prepared in comparative examples 1 to 3 have defects in film appearance, solid gloss, curing and impact properties due to the absence of individual related components. For example, the lack of diethylene glycol diglycidyl ether can cause the epoxy activity of the end group I of the obtained epoxy resin to be low, the epoxy resin can not be completely cured at 150 ℃/20min, the impact property is deteriorated, and the adhesive force and the boiling water resistance of a coating film can not meet the requirements (see comparative example 1); the lack of 2, 2-dimethylmalonic acid and terephthalic acid in comparative examples 2 and 3 results in poor impact resistance of the resulting epoxy resin II, which affects adhesion and boil resistance of the final epoxy resin.
As the data in comparative examples 4-5, the epoxy resin I or the epoxy resin II is used alone, and because the activity of the epoxy functional group is relatively single and relatively high, the curing crosslinking with the B68 extinction curing agent can be realized, but the extinction effect is general and the gloss is slightly high; the mixed epoxy resin system formed by mixing the epoxy resin I and the epoxy resin II has epoxy functional patterns with different activities, so that the speed is different from that of B68 curing, and the extinction effect is obvious.
As in the data of comparative examples 6 to 7, with the commercially available general E-12 epoxy resin, the low temperature reactivity of the epoxy functional group was not high due to the segment and steric hindrance of bisphenol A, complete curing could not be achieved at 150 ℃/20min, the coating film performance was poor (see comparative example 6), and it was possible to achieve a good cured coating film at the normal curing conditions of 185 ℃/20min (see comparative example 7).
In conclusion, the epoxy resin for the low-temperature curing type B68 extinction powder prepared by the scheme can be fully cured at 150 ℃/20min together with a B68 extinction curing agent, the film coating performance is equivalent to that of a film coating cured by the conventional common E-12 epoxy resin at normal temperature, and meanwhile, due to the particularity of the formula and the process, the extinction effect is superior to that of the film coating cured by the common E-12 epoxy resin at normal temperature.
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 (8)
1. The epoxy resin for the low-temperature curing type B68 matting powder is characterized by comprising the following raw material components in molar content based on the total preparation raw materials:
8-25mol% of bisphenol A;
6-20mol% of epoxy chloropropane;
7-17mol% of sodium hydroxide;
3-16mol% of diethylene glycol diglycidyl ether;
8-36mol% of E-44 epoxy resin;
7-25mol% of 2, 2-dimethyl malonic acid;
5-18mol% of terephthalic acid;
5-15mol% of toluene;
the preparation raw material also comprises a catalyst; the molar usage of the catalyst accounts for 0.1-0.2% of the total molar weight of the raw material components.
2. The epoxy resin for low-temperature curing type B68 matting powder according to claim 1, wherein the catalyst comprises benzyltrimethylammonium chloride and/or triphenylmethylphosphonium bromide.
3. A method for preparing the epoxy resin for the low-temperature curing type B68 extinction powder, which is characterized by comprising the following steps:
(1) preparing sodium hydroxide solution with the formula amount of sodium hydroxide, adding the bisphenol A with the formula amount, and reacting at 30-40 ℃; then adding the epoxy chloropropane with the formula amount, reacting at 80-100 ℃, and stopping the reaction when the pH of the reaction system is less than 9.5 to obtain bisphenol A end-capped epoxy resin;
(2) adding the diethylene glycol diglycidyl ether with the formula amount into the obtained bisphenol A end-capped epoxy resin mixed material, carrying out end-capping reaction at 80-90 ℃, and stopping the reaction when the epoxy equivalent of the resin reaches 750-800eq/100g to obtain epoxy resin I for later use;
(3) uniformly mixing the toluene, the E-44 epoxy resin, the 2, 2-dimethylmalonic acid, the terephthalic acid and the catalyst according to the formula ratio, carrying out chain extension reaction at 90-105 ℃, and stopping the reaction when the epoxy equivalent of the resin reaches 800-850eq/100g to obtain epoxy resin II for later use;
(4) and (2) uniformly mixing the epoxy resin I and the epoxy resin II, reacting at the temperature of 80-90 ℃, removing the toluene solvent under vacuum reduced pressure when the epoxy equivalent reaches 830-860eq/100g, discharging at high temperature while the materials are hot, cooling, crushing and granulating to obtain the required low-temperature curing type epoxy resin for B68 extinction powder.
4. The method for preparing the epoxy resin for the low-temperature curing type B68 matting powder according to claim 3, wherein in the step (1), the mass concentration of the sodium hydroxide solution is controlled to be 30-50 wt%.
5. The method for preparing the epoxy resin for the low-temperature curing type B68 matting powder according to claim 3 or 4, wherein the step (2) further comprises the step of adding water to the epoxy resin I after the reaction is finished, washing the epoxy resin I and dehydrating the epoxy resin I under reduced pressure.
6. Use of the epoxy resin for low temperature curing type B68 matting powder according to claim 1 or 2 for preparing powder coating.
7. Use according to claim 6, characterized in that the powder coating is a B68 cure system epoxy powder coating.
8. A powder coating prepared from the epoxy resin for the low-temperature curing type B68 matting powder according to claim 1 or 2.
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| CN104693150A (en) * | 2015-02-17 | 2015-06-10 | 南通职业大学 | Flexible epoxy resin and preparation method thereof |
| CN109749054A (en) * | 2018-12-13 | 2019-05-14 | 珠海宏昌电子材料有限公司 | A kind of extinction powder coating epoxy resin and its preparation method and application |
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