CN112321799B - Epoxy resin for high-hardness and low-temperature curing type powder coating and preparation method thereof - Google Patents
Epoxy resin for high-hardness and low-temperature curing type powder coating and preparation method thereof Download PDFInfo
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- CN112321799B CN112321799B CN202011219253.XA CN202011219253A CN112321799B CN 112321799 B CN112321799 B CN 112321799B CN 202011219253 A CN202011219253 A CN 202011219253A CN 112321799 B CN112321799 B CN 112321799B
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- 239000003822 epoxy resin Substances 0.000 title claims abstract description 76
- 229920000647 polyepoxide Polymers 0.000 title claims abstract description 76
- 238000000576 coating method Methods 0.000 title claims abstract description 58
- 239000011248 coating agent Substances 0.000 title claims abstract description 54
- 239000000843 powder Substances 0.000 title claims abstract description 36
- 238000013035 low temperature curing Methods 0.000 title claims abstract description 14
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000003054 catalyst Substances 0.000 claims abstract description 15
- 239000002994 raw material Substances 0.000 claims abstract description 14
- PLDLPVSQYMQDBL-UHFFFAOYSA-N 2-[[3-(oxiran-2-ylmethoxy)-2,2-bis(oxiran-2-ylmethoxymethyl)propoxy]methyl]oxirane Chemical compound C1OC1COCC(COCC1OC1)(COCC1OC1)COCC1CO1 PLDLPVSQYMQDBL-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000009835 boiling Methods 0.000 claims abstract description 12
- DLYUQMMRRRQYAE-UHFFFAOYSA-N tetraphosphorus decaoxide Chemical compound O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 claims abstract description 12
- YIHRGKXNJGKSOT-UHFFFAOYSA-N 1,1,2,2,3,3-hexafluorobutan-1-ol Chemical compound CC(F)(F)C(F)(F)C(O)(F)F YIHRGKXNJGKSOT-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 9
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 9
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 claims abstract description 6
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims abstract description 6
- VANNPISTIUFMLH-UHFFFAOYSA-N glutaric anhydride Chemical compound O=C1CCCC(=O)O1 VANNPISTIUFMLH-UHFFFAOYSA-N 0.000 claims abstract description 6
- 238000006243 chemical reaction Methods 0.000 claims description 24
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 22
- 239000004593 Epoxy Substances 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 11
- JICUWGAMTRJHJV-UHFFFAOYSA-N 2-n,2-n,4-n,4-n,6-n,6-n-hexahydroxy-1,3,5-triazine-2,4,6-triamine Chemical compound ON(O)C1=NC(N(O)O)=NC(N(O)O)=N1 JICUWGAMTRJHJV-UHFFFAOYSA-N 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 8
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- 229920005989 resin Polymers 0.000 claims description 6
- 239000011347 resin Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 239000003002 pH adjusting agent Substances 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 238000000967 suction filtration Methods 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 3
- KXHPPCXNWTUNSB-UHFFFAOYSA-M benzyl(trimethyl)azanium;chloride Chemical group [Cl-].C[N+](C)(C)CC1=CC=CC=C1 KXHPPCXNWTUNSB-UHFFFAOYSA-M 0.000 claims description 2
- 239000008098 formaldehyde solution Substances 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000001723 curing Methods 0.000 abstract description 19
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 abstract description 11
- 239000003063 flame retardant Substances 0.000 abstract description 11
- 150000003839 salts Chemical class 0.000 abstract description 11
- 239000003795 chemical substances by application Substances 0.000 abstract description 8
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 abstract description 8
- 230000007935 neutral effect Effects 0.000 abstract description 8
- 238000004132 cross linking Methods 0.000 abstract description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 4
- 239000003595 mist Substances 0.000 abstract description 4
- 229910052736 halogen Inorganic materials 0.000 abstract description 2
- 150000002367 halogens Chemical class 0.000 abstract description 2
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 abstract description 2
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 2
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 abstract 2
- 229910000073 phosphorus hydride Inorganic materials 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 10
- 239000007921 spray Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 5
- 238000011056 performance test Methods 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- DXZMANYCMVCPIM-UHFFFAOYSA-L zinc;diethylphosphinate Chemical compound [Zn+2].CCP([O-])(=O)CC.CCP([O-])(=O)CC DXZMANYCMVCPIM-UHFFFAOYSA-L 0.000 description 3
- BKCCAYLNRIRKDJ-UHFFFAOYSA-N 2-phenyl-4,5-dihydro-1h-imidazole Chemical compound N1CCN=C1C1=CC=CC=C1 BKCCAYLNRIRKDJ-UHFFFAOYSA-N 0.000 description 2
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000002966 varnish Substances 0.000 description 2
- LRWZZZWJMFNZIK-UHFFFAOYSA-N 2-chloro-3-methyloxirane Chemical compound CC1OC1Cl LRWZZZWJMFNZIK-UHFFFAOYSA-N 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000011094 fiberboard Substances 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- MGJURKDLIJVDEO-UHFFFAOYSA-N formaldehyde;hydrate Chemical compound O.O=C MGJURKDLIJVDEO-UHFFFAOYSA-N 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005453 pelletization Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000002952 polymeric resin Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
Classifications
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/50—Amines
- C08G59/504—Amines containing an atom other than nitrogen belonging to the amine group, carbon and hydrogen
-
- 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
- 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
-
- 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
- C09D5/18—Fireproof paints including high temperature resistant paints
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Paints Or Removers (AREA)
Abstract
Discloses a preparation method of epoxy resin for high-hardness and low-temperature curing powder coating, which comprises the following raw materials in parts by mole: 3-5 parts of melamine, 30-40 parts of formaldehyde, 3-6 parts of hexafluorobutanol, 15-25 parts of cyclohexane, 2-4 parts of phosphorus pentoxide, 6-11 parts of glutaric anhydride, 2-4 parts of pyromellitic dianhydride, 5-10 parts of pentaerythritol tetraglycidyl ether, a catalyst and a pH regulator. The obtained epoxy resin does not contain halogen elements, contains nitrogen, phosphine and other environment-friendly flame-retardant elements, has good flame-retardant performance, and has high crosslinking density of a coating film cured at low temperature with dicyandiamide curing agents, pencil hardness of more than 3H, water boiling resistance, neutral salt mist resistance and excellent flame-retardant performance.
Description
Technical Field
The invention belongs to the field of powder coating, and relates to a preparation method of epoxy resin for powder coating and the epoxy resin prepared by the method.
Background
The powder coating has the advantages of no pollution, energy and resource saving, good comprehensive performance of the coating film and the like, and is widely applied to surface coating in the fields of daily decoration, automobile industry and the like.
The pure epoxy resin powder coating has good adhesion and good solvent resistance of a coating film, and is applied to indoor coating. In order to further reduce energy consumption, low temperature curing of powder coatings has been a focus of research. At present, a curing system mainly comprises dicyandiamide and 2-phenylimidazoline, and although the curing temperature can be effectively reduced by using the 2-phenylimidazoline as a curing agent, a coating film is easy to damage due to low crosslinking density of the cured coating film, and the leveling property of the coating film is general after low-temperature curing.
With the improvement of the requirement for flame retardance in recent years, the traditional halogen flame retardance such as chlorine and bromine is gradually eliminated in indoor application due to high toxicity, and the halogen-free flame retardance becomes a new development direction of polymer resin materials.
In the powder coating epoxy resin variety, the most common is E-12 epoxy resin which 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, the curing activity is relatively low, the product and dicyandiamide curing agents generally need 180 ℃ to 200 ℃ to be fully cured, and the energy consumption is high. And the E-12 epoxy resin is generally hydrophobic, has low branching degree, does not contain flame retardant elements, has low crosslinking density of a cured coating, low hardness and easy damage, has relatively poor flame retardant property and neutral salt mist resistance, and cannot be used in the fields with higher requirements on hardness, halogen-free flame retardance and salt mist resistance.
Therefore, a new epoxy resin for low-temperature curing powder coating with high hardness, halogen-free flame retardation and excellent salt spray resistance is needed to solve the above technical problems.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of epoxy resin for low-temperature curing powder coating, which comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.08-0.15% of that of the pentaerythritol tetraglycidyl ether; and a pH adjusting agent.
Wherein the catalyst is benzyltrimethylammonium chloride.
Wherein the pH regulator comprises sodium carbonate and/or concentrated sulfuric acid.
Wherein the formaldehyde is a formaldehyde water solution with the formaldehyde mass content of 35%.
The preparation method of the epoxy resin for the powder coating comprises the following steps:
A. adding melamine and formaldehyde with a formula ratio into a reaction kettle, stirring, heating to 55-60 ℃, adding a pH regulator to regulate the pH value to 8-9, and reacting for 3-5 hours in a heat preservation manner;
B. stopping the reaction when a large amount of solid hexahydroxy melamine is separated out and the content of free melamine is lower than 2%, cooling to 5-10 ℃, and performing reduced pressure suction filtration to obtain a hexahydroxy melamine wet material;
C. b, adding the wet hexahydroxy melamine obtained in the step B, hexafluorobutanol and cyclohexane according to the formula ratio into a reaction kettle, stirring, adding a pH regulator to regulate the pH value to 3-3.5, heating to 85-90 ℃, and carrying out butylated reaction for 2-4 hours by using cyclohexane with water;
D. when the mass conversion rate of the hexafluorobutanol reaches more than 90 percent, heating to 100-120 ℃, removing the solvent, water and unreacted raw materials under reduced pressure, adding phosphorus pentoxide, glutaric anhydride and pyromellitic dianhydride in formula amount after no obvious water residue exists, gradually heating to 170-180 ℃ at the heating rate of 8-12 ℃/h, and then continuing to perform heat preservation reaction for 1-3h;
E. when the acid value of the resin reaches 60-70mgKOH/g, cooling to 120-130 ℃, and then adding pentaerythritol tetraglycidyl ether and a catalyst in a formula amount to perform epoxy end capping reaction for 1-3h;
F. stopping the reaction when the epoxy equivalent of the resin is 400-500g/mol and the acid value is less than 5mgKOH/g, washing with boiling water, removing the catalyst and impurities, and separating a water phase;
G. decompressing at 120-130 deg.c to eliminate water, discharging at high temperature, cooling epoxy resin, crushing and pelletizing.
Wherein, the pH regulator in the step A is sodium carbonate.
Wherein, the pH regulator in the step C is concentrated sulfuric acid.
And in the step F, washing with boiling water is carried out for a plurality of times, preferably 3 times, by respectively adding boiling water with the weight 1-1.5 times of the total weight of the materials.
The invention also provides the epoxy resin prepared by the preparation method of the epoxy resin for the powder coating.
Wherein the obtained epoxy resin has an epoxy equivalent of 400-500g/mol and a softening point of 80-86 ℃.
Wherein the obtained epoxy resin is colorless or pale yellow transparent particles in appearance.
The invention also provides a powder coating prepared by using the epoxy resin.
The beneficial technical effects of the invention are embodied in the following aspects:
the invention mainly uses melamine, formaldehyde, hexafluorobutanol, phosphorus pentoxide, glutaric anhydride, pyromellitic dianhydride, pentaerythritol tetraglycidyl ether and the like as raw materials to react to obtain the epoxy resin with the epoxy equivalent of 400-500g/mol, wherein:
1. the epoxy resin product which is prepared by using the polyhydroxy melamine as a matrix for chain extension has strong rigidity, high functionality and good flame retardant property;
2. hexafluorobutanol is used in the raw materials to introduce hydrophobic fluorine elements into epoxy resin molecules so as to improve the water resistance and salt spray resistance of the epoxy resin;
3. the raw materials are grafted and chain-extended by using high-activity phosphorus pentoxide, glutaric anhydride and pyromellitic dianhydride, so that the flexibility of chain segments is adjusted to ensure the shock resistance of the chain segments, and the rigidity and the flame retardant property of the chain segments are increased;
4. the epoxy resin blocked by pentaerythritol tetraglycidyl ether has high curing activity and low softening point;
5. the obtained epoxy resin and dicyandiamide curing agent are fully cured at low temperature (140 ℃/15 min), and the cured coating film has the advantages of high crosslinking density, high hardness (pencil hardness is more than 3H), water boiling resistance, flame retardance and excellent neutral salt spray resistance.
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 do not limit the invention.
The epoxy resins of examples 1-4 were prepared according to the following raw material formulations for examples 1-4, using the following method:
the preparation method of the epoxy resin comprises the following steps:
A. adding melamine and formaldehyde in a formula amount into a reaction kettle, stirring, heating to 55-60 ℃, adding a pH regulator to regulate the pH value to 8-9, and reacting for 3-5 hours in a heat preservation manner;
B. stopping the reaction when a large amount of solid hexahydroxy melamine is separated out and the content of free melamine is lower than 2%, cooling to 5-10 ℃, and performing reduced pressure suction filtration to obtain a hexahydroxy melamine wet material;
C. b, adding the wet hexahydroxy melamine material obtained in the step B, hexafluorobutanol and cyclohexane according to the formula ratio into a reaction kettle, stirring, adding a pH regulator to regulate the pH value to 3-3.5, heating to 85-90 ℃, and carrying out a butylated reaction for 2-4 hours;
D. when the mass conversion rate of the hexafluorobutanol reaches more than 90 percent, heating to 100-120 ℃, removing the solvent, water and unreacted raw materials under reduced pressure, adding phosphorus pentoxide, glutaric anhydride and pyromellitic dianhydride in a formula amount after no obvious water residue exists, gradually heating to 170-180 ℃ at the heating rate of 8-12 ℃/h, and then continuing to perform heat preservation reaction for 1-3h;
E. when the acid value of the resin reaches 60-70mgKOH/g, the temperature is reduced to 120-130 ℃, and then pentaerythritol tetraglycidyl ether and a catalyst with the formula amount are added for epoxy end capping reaction for 1-3h;
F. stopping the reaction when the epoxy equivalent of the resin is 400-500g/mol and the acid value is less than 5mgKOH/g, washing with boiling water, removing the catalyst and impurities, and separating a water phase;
G. and (3) after the water is removed under reduced pressure at 120-130 ℃, discharging the material while the material is hot at high temperature, then cooling the epoxy resin, and crushing and granulating the epoxy resin.
Example 1
The preparation method of the epoxy resin for the low-temperature curing powder coating comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.15 percent of that of the pentaerythritol tetraglycidyl ether.
The epoxy equivalent of the prepared epoxy resin is 492g/mol, and the softening point is 86 ℃.
Example 2
The preparation method of the epoxy resin for the low-temperature curing powder coating comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.08 percent of that of the pentaerythritol tetraglycidyl ether.
The epoxy equivalent of the prepared epoxy resin is 409g/mol, and the softening point is 80 ℃.
Example 3
The preparation method of the epoxy resin for the low-temperature curing powder coating comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.11 percent of that of the pentaerythritol tetraglycidyl ether.
The epoxy equivalent of the epoxy resin prepared was 425g/mol, softening point 81 ℃.
Example 4
The preparation method of the epoxy resin for the low-temperature curing powder coating comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.12 percent of that of the pentaerythritol tetraglycidyl ether.
The epoxy equivalent of the epoxy resin prepared was 476g/mol, and the softening point was 84 ℃.
The epoxy resins of examples 1 to 4 were mixed uniformly according to the following formulation of epoxy resin powder coating, melt-extruded by a twin-screw extruder (the screw temperature was controlled at 95 to 105 ℃), and then tabletted and crushed, and the flakes were pulverized and sieved to prepare a powder coating (160 to 180 mesh).
And spraying the powder coating on the medium-density fiberboard substrate subjected to surface treatment by using an electrostatic spray gun, and curing at the temperature of 140 ℃/15min to obtain a coating with the thickness of 70-80 mu m.
The epoxy resin powder coating comprises the following components in parts by weight:
wherein the dicyandiamide curing agent is purchased from Liu' an Jietongda new material Co., ltd, model SA2830.
Comparative example 1
The epoxy resin of the present invention was replaced with a commercially available ordinary E-12 epoxy resin as comparative example 1, having an epoxy equivalent of 824g/mol and a softening point of 98 ℃ and available from Huangshan Tianma New Material science and technology Co., ltd. According to the formula of the epoxy resin powder coating (because the epoxy equivalent of the E-12 epoxy resin is higher than that of the product of the invention, when the E-12 epoxy resin is adopted, 575 parts of epoxy resin, 25 parts of dicyandiamide curing agent and other components and the using amount are unchanged in the formula) and the curing condition (140 ℃/15 min), the plate is made, and the film coating thickness is 70-80 mu m.
Comparative example 2
The epoxy resin of the present invention was replaced with a commercially available ordinary E-12 epoxy resin as comparative example 2 having an epoxy equivalent of 824g/mol and a softening point of 98 ℃ and available from Huangshan Tianma New Material science and technology Co., ltd. According to the formula of the epoxy resin powder coating (since the epoxy equivalent of the E-12 epoxy resin is higher than that of the product of the invention, when the E-12 epoxy resin is adopted, 575 parts of epoxy resin, 25 parts of dicyandiamide curing agent and the other components and the using amount are unchanged in the formula), the curing condition is adjusted to 180 ℃/15min, and the plate is manufactured, wherein the coating thickness is 70-80 mu m.
The epoxy resin powder coating coatings prepared in examples 1 to 4 and comparative examples 1 to 2 described above were subjected to performance tests. The test criteria are as follows:
the coating index detection is carried out according to GB/T21776-2008 'Standard guidelines for powder coating and coating detection';
the hardness test is carried out according to GB/T6739-2006 paint film hardness measured by a color paint and varnish pencil method, the pencil hardness parameter is 5B-4B-3B-2B-B-HB-F-H-2H-3H-4H-5H, and the hardness grade gradually increases from left to right;
the neutral salt spray resistance performance test is carried out according to the standard GB/T1771-2007 determination of neutral salt spray resistance performance of colored paint and varnish;
the flame retardant property is detected according to GB/T2406.2-2009 (index of oxygen for plastics) method for determining combustion behavior by adopting a type I sample and a method B-diffusion ignition method of 8.2.3.
The results of the performance tests are shown in table 1.
TABLE 1 results of performance test of epoxy resin powder coatings of examples and comparative examples
As can be seen from the comparison of examples 1-4 and comparative examples 1-2 in Table 1, the pure epoxy resin powder coating prepared by matching the epoxy resin obtained by the invention and the dicyandiamide curing agent through the mutual matching and synergistic effect of the components has the advantages of higher coating film gloss and excellent impact resistance after low-temperature curing at 140 ℃/15min, particularly high hardness caused by high crosslinking density, which reaches 3H or more, superior neutral salt spray resistance and boiling resistance, excellent flame resistance by combining self halogen-free flame-retardant elements such as nitrogen, phosphorus and the like, and the limited oxygen index reaches more than 34 percent, and belongs to a flame-retardant substance.
The comparative example 1 uses the common E-12 epoxy resin to replace the epoxy resin of the invention, and because the epoxy activity of the E-12 epoxy resin is low, the curing and leveling process can not be smoothly completed at 140 ℃/15min, so that the coating is rough, and has poor mechanical property and corrosion resistance, which are expressed in that the gloss, the impact resistance, the neutral salt spray resistance and the boiling water resistance are poor, and almost no flame retardant property exists, and the coating belongs to flammable substances.
In comparative example 2, the curing conditions in comparative example 1 are adjusted from 140 ℃/15min of low-temperature curing to 180 ℃/15min of high-temperature curing, so that the full curing of the coating can be realized, and the appearance, the gloss and the impact resistance of the coating can meet the requirements, but because the common E-12 epoxy resin has a complete linear structure, low functionality and no special hydrophobic components, the cross-linking density of the final coating is low, the hardness is general, the pencil hardness can only reach H, and the long-time neutral salt mist resistance and the boiling water resistance are far inferior to those of the epoxy resin product of the invention, the cured coating still belongs to a combustible substance, and the limiting oxygen index is far lower than that of the product of the invention.
Claims (9)
1. A preparation method of epoxy resin for high-hardness and low-temperature curing powder coating comprises the following raw materials in parts by mole:
the molar amount of the catalyst is 0.08-0.15% of that of the pentaerythritol tetraglycidyl ether; and a pH adjusting agent;
the preparation method of the epoxy resin for the powder coating comprises the following steps:
A. adding melamine and formaldehyde with a formula ratio into a reaction kettle, stirring, heating to 55-60 ℃, adding a pH regulator to regulate the pH value to 8-9, and reacting for 3-5 hours in a heat preservation manner;
B. stopping the reaction when a large amount of solid hexahydroxy melamine is separated out and the content of free melamine is lower than 2%, cooling to 5-10 ℃, and performing reduced pressure suction filtration to obtain a hexahydroxy melamine wet material;
C. b, adding the wet hexahydroxy melamine material obtained in the step B, hexafluorobutanol and cyclohexane according to the formula ratio into a reaction kettle, stirring, adding a pH regulator to regulate the pH value to 3-3.5, heating to 85-90 ℃, and carrying out a butylated reaction for 2-4 hours by using cyclohexane with water;
D. when the mass conversion rate of the hexafluorobutanol reaches more than 90 percent, heating to 100-120 ℃, removing the solvent, water and unreacted raw materials under reduced pressure, adding phosphorus pentoxide, glutaric anhydride and pyromellitic dianhydride in the formula amount after no obvious water remains, gradually heating to 170-180 ℃ at the heating rate of 8-12 ℃/h, and continuing to perform heat preservation reaction for 1-3h;
E. when the acid value of the resin reaches 60-70mgKOH/g, cooling to 120-130 ℃, and then adding pentaerythritol tetraglycidyl ether and a catalyst in a formula amount to perform epoxy end capping reaction for 1-3h;
F. stopping reaction when the epoxy equivalent of the resin is 400-500g/mol and the acid value is less than 5mgKOH/g, washing with boiling water, removing the catalyst and impurities, and separating a water phase;
G. and (3) after the water is removed under reduced pressure at 120-130 ℃, discharging the material while the material is hot at high temperature, then cooling the epoxy resin, and crushing and granulating the epoxy resin.
2. The method of preparing an epoxy resin for powder coating according to claim 1, wherein the catalyst is benzyltrimethylammonium chloride.
3. The method of preparing an epoxy resin for powder coating according to claim 1, wherein the pH adjuster comprises sodium carbonate and/or concentrated sulfuric acid.
4. The process for producing an epoxy resin for powder coating according to claim 1, wherein the formaldehyde is an aqueous formaldehyde solution having a formaldehyde content of 35% by mass.
5. The method of preparing an epoxy resin for powder coating according to claim 1, wherein in the step F, the washing with boiling water is performed several times as much as the washing with boiling water added in an amount of 1 to 1.5 times the total mass of the materials, respectively.
6. The epoxy resin obtained by the method for producing an epoxy resin for powder coating according to any one of claims 1 to 5.
7. The epoxy resin according to claim 6, wherein the epoxy resin has an epoxy equivalent weight of 400 to 500 g/mol.
8. The epoxy resin according to claim 6 or 7, wherein the epoxy resin has a softening point of 80-86 ℃.
9. Powder coatings prepared with an epoxy resin according to any of claims 6 to 8.
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