CN118165292A - Epoxy resin emulsion for high throwing power cathode electrophoresis paint and preparation method thereof - Google Patents
Epoxy resin emulsion for high throwing power cathode electrophoresis paint and preparation method thereof Download PDFInfo
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- CN118165292A CN118165292A CN202410221898.9A CN202410221898A CN118165292A CN 118165292 A CN118165292 A CN 118165292A CN 202410221898 A CN202410221898 A CN 202410221898A CN 118165292 A CN118165292 A CN 118165292A
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- epoxy resin
- throwing power
- resin emulsion
- power cathode
- emulsion
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- 239000003822 epoxy resin Substances 0.000 title claims abstract description 88
- 229920000647 polyepoxide Polymers 0.000 title claims abstract description 88
- 239000000839 emulsion Substances 0.000 title claims abstract description 55
- 239000003973 paint Substances 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 238000001962 electrophoresis Methods 0.000 title description 5
- 239000011248 coating agent Substances 0.000 claims abstract description 30
- 238000000576 coating method Methods 0.000 claims abstract description 30
- 229920005989 resin Polymers 0.000 claims abstract description 26
- 239000011347 resin Substances 0.000 claims abstract description 26
- 239000002904 solvent Substances 0.000 claims abstract description 25
- 229920000728 polyester Polymers 0.000 claims abstract description 14
- NSPSPMKCKIPQBH-UHFFFAOYSA-K bismuth;7,7-dimethyloctanoate Chemical compound [Bi+3].CC(C)(C)CCCCCC([O-])=O.CC(C)(C)CCCCCC([O-])=O.CC(C)(C)CCCCCC([O-])=O NSPSPMKCKIPQBH-UHFFFAOYSA-K 0.000 claims abstract description 9
- 238000006243 chemical reaction Methods 0.000 claims description 37
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 30
- 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 claims description 30
- 239000003054 catalyst Substances 0.000 claims description 27
- -1 amine compound Chemical class 0.000 claims description 19
- 239000003431 cross linking reagent Substances 0.000 claims description 18
- 239000004593 Epoxy Substances 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 15
- 150000002009 diols Chemical class 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 15
- 239000012948 isocyanate Substances 0.000 claims description 14
- 150000002513 isocyanates Chemical class 0.000 claims description 14
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 claims description 13
- 238000005576 amination reaction Methods 0.000 claims description 13
- 150000002576 ketones Chemical class 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 13
- 239000003795 chemical substances by application Substances 0.000 claims description 12
- 150000007524 organic acids Chemical class 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 claims description 10
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 10
- 239000004014 plasticizer Substances 0.000 claims description 10
- 239000011259 mixed solution Substances 0.000 claims description 9
- 229920000056 polyoxyethylene ether Polymers 0.000 claims description 9
- 229940051841 polyoxyethylene ether Drugs 0.000 claims description 9
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 claims description 9
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 8
- XXBDWLFCJWSEKW-UHFFFAOYSA-N dimethylbenzylamine Chemical compound CN(C)CC1=CC=CC=C1 XXBDWLFCJWSEKW-UHFFFAOYSA-N 0.000 claims description 8
- 229920001451 polypropylene glycol Polymers 0.000 claims description 8
- 230000020477 pH reduction Effects 0.000 claims description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- OPKOKAMJFNKNAS-UHFFFAOYSA-N N-methylethanolamine Chemical compound CNCCO OPKOKAMJFNKNAS-UHFFFAOYSA-N 0.000 claims description 6
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- IBLKWZIFZMJLFL-UHFFFAOYSA-N 1-phenoxypropan-2-ol Chemical compound CC(O)COC1=CC=CC=C1 IBLKWZIFZMJLFL-UHFFFAOYSA-N 0.000 claims description 5
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 5
- 238000004945 emulsification Methods 0.000 claims description 5
- OIAUFEASXQPCFE-UHFFFAOYSA-N formaldehyde;1,3-xylene Chemical compound O=C.CC1=CC=CC(C)=C1 OIAUFEASXQPCFE-UHFFFAOYSA-N 0.000 claims description 5
- 235000019253 formic acid Nutrition 0.000 claims description 5
- ARXJGSRGQADJSQ-UHFFFAOYSA-N 1-methoxypropan-2-ol Chemical compound COCC(C)O ARXJGSRGQADJSQ-UHFFFAOYSA-N 0.000 claims description 4
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 claims description 4
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 claims description 4
- UKLDJPRMSDWDSL-UHFFFAOYSA-L [dibutyl(dodecanoyloxy)stannyl] dodecanoate Chemical group CCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCC UKLDJPRMSDWDSL-UHFFFAOYSA-L 0.000 claims description 4
- 239000002981 blocking agent Substances 0.000 claims description 4
- 239000012975 dibutyltin dilaurate Substances 0.000 claims description 4
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 claims description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims description 4
- 229920001610 polycaprolactone Polymers 0.000 claims description 4
- 239000004632 polycaprolactone Substances 0.000 claims description 4
- BWDBEAQIHAEVLV-UHFFFAOYSA-N 6-methylheptan-1-ol Chemical compound CC(C)CCCCCO BWDBEAQIHAEVLV-UHFFFAOYSA-N 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 3
- 239000000539 dimer Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- LNOPIUAQISRISI-UHFFFAOYSA-N n'-hydroxy-2-propan-2-ylsulfonylethanimidamide Chemical compound CC(C)S(=O)(=O)CC(N)=NO LNOPIUAQISRISI-UHFFFAOYSA-N 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- OAYXUHPQHDHDDZ-UHFFFAOYSA-N 2-(2-butoxyethoxy)ethanol Chemical compound CCCCOCCOCCO OAYXUHPQHDHDDZ-UHFFFAOYSA-N 0.000 claims description 2
- UPGSWASWQBLSKZ-UHFFFAOYSA-N 2-hexoxyethanol Chemical compound CCCCCCOCCO UPGSWASWQBLSKZ-UHFFFAOYSA-N 0.000 claims description 2
- IMQLKJBTEOYOSI-GPIVLXJGSA-N Inositol-hexakisphosphate Chemical compound OP(O)(=O)O[C@H]1[C@H](OP(O)(O)=O)[C@@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@@H]1OP(O)(O)=O IMQLKJBTEOYOSI-GPIVLXJGSA-N 0.000 claims description 2
- UEEJHVSXFDXPFK-UHFFFAOYSA-N N-dimethylaminoethanol Chemical compound CN(C)CCO UEEJHVSXFDXPFK-UHFFFAOYSA-N 0.000 claims description 2
- IMQLKJBTEOYOSI-UHFFFAOYSA-N Phytic acid Natural products OP(O)(=O)OC1C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C1OP(O)(O)=O IMQLKJBTEOYOSI-UHFFFAOYSA-N 0.000 claims description 2
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 2
- 235000011054 acetic acid Nutrition 0.000 claims description 2
- 229960002887 deanol Drugs 0.000 claims description 2
- 239000012972 dimethylethanolamine Substances 0.000 claims description 2
- 239000004310 lactic acid Substances 0.000 claims description 2
- 235000014655 lactic acid Nutrition 0.000 claims description 2
- 239000000467 phytic acid Substances 0.000 claims description 2
- 229940068041 phytic acid Drugs 0.000 claims description 2
- 235000002949 phytic acid Nutrition 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 229940049676 bismuth hydroxide Drugs 0.000 abstract description 7
- TZSXPYWRDWEXHG-UHFFFAOYSA-K bismuth;trihydroxide Chemical compound [OH-].[OH-].[OH-].[Bi+3] TZSXPYWRDWEXHG-UHFFFAOYSA-K 0.000 abstract description 7
- 230000005856 abnormality Effects 0.000 abstract description 4
- 230000007062 hydrolysis Effects 0.000 abstract description 4
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 4
- 239000002245 particle Substances 0.000 abstract description 4
- 239000004721 Polyphenylene oxide Substances 0.000 abstract description 3
- 229920000570 polyether Polymers 0.000 abstract description 3
- 239000008367 deionised water Substances 0.000 description 7
- 229910021641 deionized water Inorganic materials 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 230000007935 neutral effect Effects 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- UIFVCPMLQXKEEU-UHFFFAOYSA-N 2,3-dimethylbenzaldehyde Chemical compound CC1=CC=CC(C=O)=C1C UIFVCPMLQXKEEU-UHFFFAOYSA-N 0.000 description 3
- 239000004971 Cross linker Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000001804 emulsifying effect Effects 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000006115 industrial coating Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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- Paints Or Removers (AREA)
Abstract
The invention discloses an epoxy resin emulsion for a high throwing power cathode electrophoretic coating and a preparation method thereof. The preparation method comprises the steps of preparing modified epoxy resin and preparing epoxy resin emulsion. According to the invention, the polyester and the polyether are adopted to simultaneously modify the epoxy resin, so that the flexibility and the molecular weight of the resin are improved; the solvent content in the emulsion system is reduced by increasing the molecular weight of the resin; the cost is low by introducing the drier bismuth neodecanoate into the resin system, and the risk of potential hydrolysis of bismuth hydroxide in the matched color paste is reduced; the resin emulsion formed by the invention has small particle size, stable emulsion, good curing performance, MEK wiping resistance of 40 times, no abnormality, obviously increased paint film flexibility, cupping and impact resistance, more than 50% throwing power of four boxes, obviously improved throwing power, excellent performances and suitability for coating of passenger car bodies and parts systems thereof.
Description
Technical Field
The invention belongs to the field of electrophoretic coating, and in particular relates to an epoxy resin emulsion for a high throwing power cathode electrophoretic coating and a preparation method thereof.
Background
The electrophoretic paint is a paint which can make use of paint ions to rapidly swim to the surface of a coated object under the action of an electric field to form a layer of uniform and compact coating. As a novel paint with low pollution and excellent corrosion resistance, the paint is widely used in the field of industrial coating due to its excellent coating performance and high utilization rate. Due to the rapid development of the automobile industry, the epoxy cathode electrophoretic paint with excellent corrosion resistance is fully covered and applied in the automobile coating industry. However, due to various shapes of the cavity structure and parts of the automobile body, the interior of the cavity of the automobile body or the depth of the concave cavity in the part cannot be completely subjected to electrophoretic painting, so that the corrosion resistance of the cavity is lost. The capability of the inner cavity to paint is the throwing power of the electrophoretic paint. The higher the throwing power is, the stronger the inner cavity lacquering capability is, the smaller the difference between the inner film thickness and the outer film thickness is, and the better the corrosion resistance of the inner cavity and the gap is.
The prior epoxy cathode electrophoretic paint on the market has the highest throwing power of only about 40 percent. Such as me FT23-0025 emulsion. Therefore, for the coating requirements of complex car bodies and workpieces, electrophoresis products with higher throwing power are required to meet the demands of customers.
Disclosure of Invention
The invention aims to overcome the technical defects, and provides an epoxy resin emulsion for a high throwing power cathode electrophoretic coating and a preparation method thereof, which solve the technical problem that the electrophoretic coating in the prior art is difficult to meet the coating requirements of complex vehicle bodies and workpieces.
In a first aspect, the invention provides a method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating, which comprises the following steps:
Preparation of modified epoxy resin: uniformly mixing low-molecular epoxy resin, bisphenol A, polyester diol, bisphenol A polyoxyethylene ether and xylene formaldehyde resin, heating to 145-150 ℃, adding a first-step alkaline catalyst, performing a first chain extension reaction when the temperature naturally returns to 180-190 ℃ after the reaction is exothermic; after the first chain extension reaction is finished, cooling to 145-150 ℃, adding a second-step alkaline catalyst, and performing a second chain extension reaction; after the epoxy value reaches 0.92-0.93meq/g, adding an alcohol ether solvent, a totally-enclosed isocyanate crosslinking agent and an amine compound, uniformly mixing, and carrying out amination reaction to obtain modified epoxy resin;
preparation of epoxy resin emulsion: uniformly mixing the modified epoxy resin with polypropylene glycol 4000, a plasticizer, a drier and a leveling agent, then adding an organic acid for acidification reaction, and finally adding water into the acidified resin for emulsification to obtain the epoxy resin emulsion. Wherein the drier is bismuth neodecanoate.
In a second aspect, the present invention provides an epoxy resin emulsion for a high throwing power cathode electrophoretic coating, which is obtained by the preparation method of the epoxy resin emulsion for the high throwing power cathode electrophoretic coating provided in the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
According to the invention, the polyester and the polyether are adopted to simultaneously modify the epoxy resin, so that the flexibility and the molecular weight of the resin are improved; the solvent content in the emulsion system is reduced by increasing the molecular weight of the resin; the cost is low by introducing the drier bismuth neodecanoate into the resin system, and the risk of potential hydrolysis of bismuth hydroxide in the matched color paste is reduced; the resin emulsion formed by the invention has small particle size, stable emulsion, good curing performance, MEK wiping resistance of 40 times, no abnormality, obviously increased paint film flexibility, cupping and impact resistance, neutral salt fog resistance test of 1000 hours, throwing power of more than 50 percent (part of the resin emulsion can reach 60 percent) by using four boxes, obviously improved throwing power, excellent performances and suitability for coating of passenger car bodies and part systems thereof.
Detailed Description
The present invention will be described in further detail with reference to the following examples 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.
In a first aspect, the invention provides a method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating, which comprises the following steps:
S1, preparing modified epoxy resin: uniformly mixing low-molecular epoxy resin, bisphenol A, polyester diol, bisphenol A polyoxyethylene ether and xylene formaldehyde resin, heating to 145-150 ℃, adding a first-step alkaline catalyst, performing a first chain extension reaction when the temperature naturally returns to 180-190 ℃ after the reaction is exothermic; after the first chain extension reaction is finished, cooling to 145-150 ℃, adding a second-step alkaline catalyst, and performing a second chain extension reaction; after the epoxy value reaches 0.92-0.93meq/g, adding an alcohol ether solvent, a totally-enclosed isocyanate crosslinking agent and an amine compound, uniformly mixing, and carrying out amination reaction to obtain modified epoxy resin; in the process, the temperature of the first chain extension reaction is controlled to be 180-190 ℃, so that the synthesis of polyester diol, bisphenol A polyoxyethylene ether and low-molecular epoxy resin is facilitated; if the epoxy value of the second chain extension product is higher, the throwing power of the high throwing power epoxy cathode electrophoresis coating product is lower; if the epoxy value central control index of the second chain extension product is low, the paint film is difficult to paint, the film thickness of the paint film is thin, and the neutral salt fog resistance of the product is affected.
S2, preparing epoxy resin emulsion: uniformly mixing the modified epoxy resin with polypropylene glycol 4000, a plasticizer, a drier and a leveling agent, then adding an organic acid for acidification reaction, and finally adding water into the acidified resin (water-emulsifiable cationized resin) for emulsification to obtain the epoxy resin emulsion. Wherein the drier is bismuth neodecanoate 3[C 10H19O2]－Bi3+.
According to the invention, the bismuth neodecanoate is added into the epoxy resin emulsion as the catalyst, so that the organic tin or bismuth hydroxide in a color paste grinding system can be replaced, the tin-free catalysis is more environment-friendly, the catalysis effect is better, and the potential risk of hydrolysis of bismuth hydroxide in a bath solution is avoided. Meanwhile, the invention can effectively avoid the defect of emulsion poor emulsion by adding the totally-enclosed isocyanate crosslinking agent before amination reaction.
According to the invention, the polyester and the polyether are adopted to simultaneously modify the epoxy resin, so that the flexibility and the molecular weight of the resin are improved; the solvent content in the emulsion system is reduced by increasing the molecular weight of the resin; the cost is low by introducing the drier bismuth neodecanoate into the resin system, and the risk of potential hydrolysis of bismuth hydroxide in the matched color paste is reduced; the resin emulsion formed by the invention has small particle size, stable emulsion, good curing performance, MEK wiping resistance of 40 times, no abnormality, obviously increased paint film flexibility, cupping and impact resistance, and neutral salt spray resistance test of 1000 hours, and the throwing power of more than 50 percent by using four boxes, obviously improved throwing power, excellent performances and suitability for coating of a passenger car body and a part system of the passenger car body.
Further, the epoxy equivalent of the low molecular epoxy resin is 180-190g/eq.
Still further, the low molecular epoxy resin is 128E epoxy resin.
Further, the polyester diol is one or more of dimer acid polyester diol and polycaprolactone diol.
Further, the alkaline catalyst is one or more of dimethylbenzylamine, diethanolamine, triethanolamine, dimethylethanolamine and triethylamine.
Further, the mass ratio of the low molecular epoxy resin to bisphenol A, polyester diol, bisphenol A polyoxyethylene ether and xylene formaldehyde resin is 1: (0.2-0.3): (0.05-0.15): (0.25-0.4): (0.15-0.2).
Further, the mass ratio of the low molecular epoxy resin to the total amount of the first-step alkaline catalyst and the second-step alkaline catalyst is 1: (0.005-0.01).
Further, the amount of the alkaline catalyst in the first step is 30% -40% of the total amount of the alkaline catalyst, and the amount of the alkaline catalyst in the second step is 60% -70% of the total amount of the alkaline catalyst.
Further, the time of the first chain extension reaction is 0.4 to 0.6 hours.
Further, the amine compound is one or more of methylethanolamine, diethanolamine, diethylenetriamine ketimine and triethylenetetramine ketimine.
Preferably, the amine compound is a mixture of methylethanolamine and diethylenetriamine ketimine, and the mass ratio of the amine compound to the diethylenetriamine ketimine is 1: (1.5-2).
Further, the mass ratio of the low molecular epoxy resin to the amine compound is 1: (0.15-0.3), further 1: (0.2-0.25).
Further, the temperature of the amination reaction is 110-120 ℃, and the time of the amination reaction is 2.5-3h.
Further, the alcohol ether solvent is one or more of ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol phenyl ether and ethylene glycol hexyl ether.
Further, the mass ratio of the low molecular epoxy resin to the alcohol ether solvent is 1: (0.25-0.35).
Further, the mass ratio of the low molecular epoxy resin to the fully-enclosed isocyanate crosslinking agent is 1: (0.8-1.2).
Further, after the epoxy value reaches 0.92-0.93meq/g, adding alcohol ether solvent, totally-enclosed isocyanate crosslinking agent and amine compound, uniformly mixing, and performing amination reaction to obtain modified epoxy resin, wherein the process for obtaining the modified epoxy resin comprises the following steps of: after the epoxy value reaches 0.92-0.93meq/g, adding alcohol ether solvent, cooling to 100-110 ℃, adding fully-enclosed isocyanate curing agent, continuously stirring, cooling to 80-90 ℃, adding amide, and carrying out amination reaction for 2.5-3 h at 110-120 ℃.
Further, the totally-enclosed isocyanate crosslinking agent is obtained through the following steps:
Uniformly mixing Toluene Diisocyanate (TDI), a first ketone solvent and an organotin catalyst, then dropwise adding a mixed solution of a second ketone solvent and trimethylolpropane, keeping the temperature at 55-65 ℃, carrying out heat preservation reaction after the dropwise adding, and dropwise adding an alcohol ether sealing agent when the NCO value reaches 160-164mg/g, and controlling the temperature below 70 ℃ to obtain the totally-enclosed isocyanate crosslinking agent. If the NCO detected by the full-closed isocyanate crosslinking agent is higher, the high throwing power epoxy cathode electrophoretic coating can not reach an ideal result; if the NCO detected by the central control is low, the curing performance of the product is affected, and the neutral salt fog resistance of the product is further affected.
Wherein the organotin catalyst is dibutyl tin dilaurate.
Wherein the first ketone solvent and the second ketone solvent are respectively one or more of butanone and methyl isobutyl ketone.
Wherein the alcohol ether blocking agent is one or more of isooctyl alcohol, ethylene glycol butyl ether and diethylene glycol butyl ether.
Wherein, the mass ratio of toluene diisocyanate to the organotin catalyst to the trimethylolpropane to the alcohol ether blocking agent is 1: (0.0001-0.001): (0.2-0.3): (0.7-0.8).
Wherein the mass ratio of toluene diisocyanate to the total amount of the first ketone solvent and the second ketone solvent is 1: (0.25-0.35).
Wherein, in the mixed solution of the second ketone solvent and the trimethylolpropane, the mass ratio of butanone to the trimethylolpropane is 1: (1.2-1.6).
Wherein the solid content of the fully-enclosed isocyanate cross-linking agent is 85-90%.
Further, the addition amount of the polypropylene glycol 4000 is 0.3% -0.5% of the modified epoxy resin.
Further, the plasticizer is Loxanol PL5060,5060 plasticizer.
Further, the addition amount of the plasticizer is 1% -3% of the modified epoxy resin.
Further, the addition amount of the drier is 0.05-0.2% of the modified epoxy resin.
Further, the addition amount of the leveling agent is 0.2% -0.5% of the modified epoxy resin.
Further, the organic acid is one or more of formic acid, sulfamic acid, acetic acid, lactic acid and phytic acid.
Preferably, the organic acid is formic acid.
Further, the addition amount of the organic acid is 1-2% of the modified epoxy resin.
Further, the organic acid is added in the form of an aqueous solution.
Further, in the organic acid solution, the concentration of the organic acid is 10% -30%.
Further, the organic acid is added in a dropwise manner, the dropwise adding temperature is 80-85 ℃, and the dropwise adding time is 20-40min.
Further, the temperature of the acidification reaction is 80-82 ℃, and the time of the acidification reaction is 1-1.5h.
Further, in the emulsification process, the addition amount of water is 1.2-1.8 times of that of the modified epoxy resin.
In a second aspect, the present invention provides an epoxy resin emulsion for a high throwing power cathode electrophoretic coating, which is obtained by the preparation method of the epoxy resin emulsion for the high throwing power cathode electrophoretic coating provided in the first aspect.
Example 1
(1) Preparation of crosslinker 1 #: 434.7 parts of toluene diisocyanate, 51.2 parts of butanone and 0.2 part of dibutyltin dilaurate are added into a reaction bottle, a mixed solution of 76.2 parts of butanone and 108 parts of trimethylolpropane is dripped at the temperature of 40 ℃, the reaction temperature is kept at 55-65 ℃, when the NCO value reaches 161.5+/-2 mg/g after the dripping is detected after the heat preservation is carried out for 1 hour, 329.7 parts of ethylene glycol butyl ether sealing agent is dripped, and the reaction temperature is controlled below 70 ℃ to obtain the fully-sealed cross-linking agent with the solid content of 87.2+/-2%.
(2) Preparation of modified epoxy resin: 239.24 parts of epoxy resin (128E epoxy resin), 61.14 parts of bisphenol A, 68.18 parts of bisphenol A polyoxyethylene ether, 17.40 parts of polycaprolactone diol and 45.3 parts of dimethylbenzaldehyde resin are put into a reaction bottle, the temperature is raised to 146 ℃, 0.52 part of dimethylbenzylamine is added for the first time, the reaction is an exothermic reaction, when the temperature naturally rises to 180-190 ℃, the temperature is kept for half an hour, 0.94 part of dimethylbenzylamine is added for the second time, the temperature is lowered to 145-150 ℃, the temperature is kept until the detected epoxy value reaches 0.92-0.93meq/g, 40 parts of ethylene glycol butyl ether and 27 parts of propylene glycol phenyl ether are added, the temperature is lowered to 100-110 ℃, 241.88 parts of cross-linking agent 1#is added, the mixture is uniformly mixed, 17.5 parts of methylethanolamine and 31.5 parts of diethylenetriamine imine are added at 90 ℃, and the temperature is raised to 110-120 ℃ for heat-preserving amination for 3 hours.
(3) Preparation of epoxy resin emulsion: cooling the resin after heat preservation, then adding 3.24 parts of polypropylene glycol 4000, 17.24 parts of Loxanol PL and 5060 plasticizer, 1.1 parts of drier (bismuth neodecanoate) and 3.24 parts of flatting agent, uniformly mixing, beginning to dropwise add a mixed solution of 12.06 parts of formic acid and 53.86 parts of deionized water at 85 ℃, after 0.6 hour dropwise adding, then preserving heat at 80-82 ℃ and stirring for 1.5 hours, and finally discharging the acidified resin into 1120 parts of deionized water at 20-25 ℃ and emulsifying to obtain the target emulsion 1.
Example 2
(1) Preparation of crosslinker 1 #: as in example 1.
(2) Preparation of modified epoxy resin: 221.48 parts of epoxy resin (128E epoxy resin), 56.6 parts of bisphenol A, 80.52 parts of bisphenol A polyoxyethylene ether, 15.20 parts of polycaprolactone diol, 14.5 parts of dimer acid polyester diol and 41.94 parts of dimethylbenzaldehyde resin are put into a reaction bottle, the temperature is raised to 146 ℃, 0.48 part of dimethylbenzylamine is added for the first time, the reaction is an exothermic reaction, when the temperature naturally rises to 180-190 ℃, the temperature is kept for half an hour, the temperature is lowered to 145-150 ℃, 0.86 part of dimethylbenzylamine is added for the second time, the temperature is kept on until the detected epoxy value reaches 0.92-0.93meq/g, 36.68 parts of ethylene glycol butyl ether and 25.19 parts of propylene glycol phenyl ether are added, the temperature is lowered to 100-110 ℃, 224.58 parts of cross-linking agent 1 is added, the mixture is uniformly mixed, 16.22 parts of methylethanolamine and 29.12 parts of diethylenetriamine imine are added at 90 ℃, the temperature is raised to 110-120 ℃, and the temperature is kept for amination for 3 hours.
(3) Preparation of epoxy resin emulsion: cooling the resin after heat preservation, then adding 3.00 parts of polypropylene glycol 4000, 16.00 parts of Loxanol PL and 5060 plasticizer, 1.1 parts of drier (bismuth neodecanoate) and 3.00 parts of flatting agent, uniformly mixing, beginning to dropwise add a mixed solution of 11.2 parts of formic acid and 50.00 parts of deionized water at 85 ℃, after 0.6h dropwise adding, then preserving heat at 80-82 ℃ and stirring for 1.5h, and finally discharging the acidified resin into 1183.12 parts of deionized water at 20-25 ℃ and emulsifying to obtain the target emulsion 2.
Comparative example 1
(1) Preparation of crosslinker # 2: adding 207.8 parts of toluene diisocyanate, 19.2 parts of methyl isobutyl ketone and 0.1 part of dibutyltin dilaurate into a reaction bottle, beginning to dropwise add a mixed solution of 20.1 parts of methyl isobutyl ketone and 28.4 parts of trimethylolpropane at 40 ℃, keeping the reaction temperature at 55-65 ℃, when the NCO value reaches 267+/-2 mg/g after the completion of dropwise addition, dropwise adding a mixed solution of 60.5 parts of isooctanol and 152.7 parts of ethylene glycol butyl ether after the completion of dropwise addition, keeping the temperature for 1h, and adding 11.3 parts of ethylene glycol butyl ether for dilution to obtain a cross-linking agent No. 2 with the solid content of 89.0+/-2%.
(2) Preparation of modified epoxy resin: 218 parts of epoxy resin (128E epoxy resin), 56.5 parts of bisphenol A, 80 parts of bisphenol A polyoxyethylene ether and 33.5 parts of dimethylbenzaldehyde resin are put into a reaction bottle, the temperature is raised to 146 ℃, 0.56 part of dimethylbenzylamine is added for the first time, the reaction is exothermic, when the temperature naturally rises to 180-190 ℃, the temperature is kept for half an hour, 1.02 part of dimethylbenzylamine is added for the second time, the temperature is kept until the detected epoxy value reaches 0.98-1.00meq/g, 57.36 parts of ethylene glycol butyl ether and 9.64 parts of propylene glycol phenyl ether are added, the temperature is lowered to 100-110 ℃, 245.4 parts of cross-linking agent 2# is added, the mixture is uniformly mixed, 19.08 parts of methylethanolamine and 34.26 parts of diethylenetriamine ketone imine are added at 90 ℃, and the temperature is raised to 110-120 ℃ for heat-preserving amination for 3 hours.
(3) Preparation of epoxy resin emulsion: cooling the resin after heat preservation, then adding 3.18 parts of polypropylene glycol 4000, 17.5 parts of Loxanol PL and 5060 plasticizer and 3.16 parts of flatting agent, uniformly mixing, then beginning to dropwise add a mixed solution of 11.86 parts of sulfamic acid and 48.72 parts of deionized water at 85 ℃, after the completion of dropwise adding for 0.6h, then preserving heat at 80-82 ℃ and stirring for 1.5h, and finally discharging the acidified resin into 1126.4 parts of deionized water at 20-25 ℃ to emulsify to obtain the comparative emulsion 1.
Test group
The emulsions obtained in examples 1-2 and comparative examples above were each formulated as an emulsion: color paste: deionized water = 4:1:5, carrying out electrophoresis tank matching in proportion. Wherein, the color paste used in the matching of the examples 1-2 is grinding color paste without drier (bismuth hydroxide is removed based on the FT24-7334 mortar of I.S., grinding mortar of laboratory), and the comparative example 1 is grinding color paste with bismuth hydroxide drier (FT 24-7334 mortar of I.S.). The throwing power test is four boxes detection method, the curing time is 48h, and the construction condition is 240V/180s. The emulsion parameters and paint film properties of each example and comparative example are shown in Table 1.
TABLE 1
As can be seen from Table 1, in the examples of the present invention, the molecular weight is smaller because the NCO value of the totally enclosed polyurethane is 161.5.+ -.2 mg/g; meanwhile, the epoxy value of the modified epoxy resin is 0.92-0.93meq/g, the molecular weight is larger, the emulsion particle size of the obtained product is small, the emulsion is stable, the product is matched with the color paste of the epoxy cathode electrophoretic paint of the company, the curing performance is good, the MEK wiping resistance is 40 times without abnormality, the paint film flexibility, the cupping and the impact resistance are obviously increased, the neutral salt spray resistance test can reach 1000 hours, and the throwing power is over 50 percent by using four boxes.
The above-described embodiments of the present invention do not limit the scope of the present invention. Any of various other corresponding changes and modifications made according to the technical idea of the present invention should be included in the scope of the claims of the present invention.
Claims (10)
1. The preparation method of the epoxy resin emulsion for the high throwing power cathode electrophoretic coating is characterized by comprising the following steps of:
Preparation of modified epoxy resin: uniformly mixing low-molecular epoxy resin, bisphenol A, polyester diol, bisphenol A polyoxyethylene ether and xylene formaldehyde resin, heating to 145-150 ℃, adding a first-step alkaline catalyst, performing a first chain extension reaction when the temperature naturally returns to 180-190 ℃ after the reaction is exothermic; after the first chain extension reaction is finished, cooling to 145-150 ℃, adding a second-step alkaline catalyst, and performing a second chain extension reaction; after the epoxy value reaches 0.92-0.93meq/g, adding an alcohol ether solvent, a totally-enclosed isocyanate crosslinking agent and an amine compound, uniformly mixing, and carrying out amination reaction to obtain modified epoxy resin;
Preparation of epoxy resin emulsion: uniformly mixing the modified epoxy resin with polypropylene glycol 4000, a plasticizer, a drier and a leveling agent, then adding an organic acid for acidification reaction, and finally adding water into the acidified resin for emulsification to obtain an epoxy resin emulsion; wherein the drier is bismuth neodecanoate.
2. The method for preparing the epoxy resin emulsion for the high throwing power cathode electrophoretic coating according to claim 1, wherein the mass ratio of the low molecular epoxy resin to bisphenol a, polyester diol, bisphenol a polyoxyethylene ether and xylene formaldehyde resin is 1: (0.2-0.3): (0.05-0.15): (0.25-0.4): (0.15-0.2); the mass ratio of the low molecular epoxy resin to the total amount of the first-step alkaline catalyst and the second-step alkaline catalyst is 1: (0.005-0.01); the mass ratio of the low molecular epoxy resin to the alcohol ether solvent is 1: (0.25-0.35); the mass ratio of the low molecular epoxy resin to the fully-enclosed isocyanate crosslinking agent is 1: (0.8-1.2); the mass ratio of the low molecular epoxy resin to the amine compound is 1: (0.15-0.3).
3. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the amount of the basic catalyst in the first step is 30 to 40% of the total amount of the basic catalyst, and the amount of the basic catalyst in the second step is 60 to 70% of the total amount of the basic catalyst.
4. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the polyester diol is one or more of dimer acid polyester diol and polycaprolactone diol; the alkaline catalyst is one or more of dimethylbenzylamine, diethanolamine, triethanolamine, dimethylethanolamine and triethylamine; the alcohol ether solvent is one or more of ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol phenyl ether and ethylene glycol hexyl ether; the amine compound is one or more of methylethanolamine, diethanolamine, diethylenetriamine ketimine and triethylenetetramine ketimine.
5. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the time of the first chain extension reaction is 0.4 to 0.6 hours; the temperature of the amination reaction is 110-120 ℃, and the time of the amination reaction is 2.5-3h.
6. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the totally enclosed isocyanate crosslinking agent is obtained by the steps of:
Uniformly mixing toluene diisocyanate, a first ketone solvent and an organotin catalyst, then dropwise adding a mixed solution of a second ketone solvent and trimethylolpropane, keeping the temperature at 55-65 ℃, carrying out heat preservation reaction after the dropwise adding is finished, and dropwise adding an alcohol ether sealing agent when the NCO value reaches 160-164mg/g, and controlling the temperature below 70 ℃ to obtain the totally-enclosed isocyanate crosslinking agent.
7. The method for producing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 6, wherein the organotin catalyst is dibutyltin dilaurate; the first ketone solvent and the second ketone solvent are one or more of butanone and methyl isobutyl ketone respectively; the alcohol ether blocking agent is one or more of isooctyl alcohol, ethylene glycol butyl ether and diethylene glycol butyl ether; the mass ratio of toluene diisocyanate to the organotin catalyst to the trimethylolpropane to the alcohol ether blocking agent is 1: (0.0001-0.001): (0.2-0.3): (0.7-0.8); the mass ratio of the toluene diisocyanate to the total amount of the first ketone solvent and the second ketone solvent is 1: (0.25-0.35).
8. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the addition amount of the polypropylene glycol 4000 is 0.3% -0.5% of modified epoxy resin; the addition amount of the plasticizer is 1% -3% of the modified epoxy resin; the addition amount of the drier is 0.05% -0.2% of the modified epoxy resin; the addition amount of the leveling agent is 0.2% -0.5% of the modified epoxy resin; the organic acid is one or more of formic acid, sulfamic acid, acetic acid, lactic acid and phytic acid; the addition amount of the organic acid is 1-2% of the modified epoxy resin.
9. The method for preparing an epoxy resin emulsion for a high throwing power cathode electrophoretic coating according to claim 1, wherein the temperature of the acidification reaction is 80-82 ℃, and the time of the acidification reaction is 1-1.5 hours; in the emulsification process, the addition amount of water is 1.2-1.8 times of that of the modified epoxy resin.
10. An epoxy resin emulsion for high throwing power cathode electrophoretic paint, which is characterized in that the epoxy resin emulsion for high throwing power cathode electrophoretic paint is obtained by the preparation method of the epoxy resin emulsion for high throwing power cathode electrophoretic paint according to any one of claims 1 to 9.
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