CN114316214A - Amino-terminated dihydroxy modified epoxy resin and preparation method and application thereof - Google Patents
Amino-terminated dihydroxy modified epoxy resin and preparation method and application thereof Download PDFInfo
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- CN114316214A CN114316214A CN202210069913.3A CN202210069913A CN114316214A CN 114316214 A CN114316214 A CN 114316214A CN 202210069913 A CN202210069913 A CN 202210069913A CN 114316214 A CN114316214 A CN 114316214A
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Abstract
The invention discloses an amino-terminated dihydroxy modified epoxy resin and a preparation method and application thereof. The preparation raw materials of the terminal amino dihydroxy modified epoxy resin comprise raw material epoxy resin and dihydroxy monomers, wherein the raw material epoxy resin is modified by the dihydroxy monomers and then subjected to ring-opening reaction with polyetheramine and alcamines to prepare the terminal amino dihydroxy modified epoxy resin. The amino-terminated dihydroxy modified epoxy resin is applied to cationic electrophoretic resin emulsion and further applied to electrophoretic coating, and a paint film obtained by electrophoretic coating has the characteristic of good edge corrosion resistance, so that the protection capability on a workpiece can be improved, and the durability of the workpiece is improved.
Description
Technical Field
The invention belongs to the technical field of coatings, and particularly relates to an amino-terminated dihydroxy modified epoxy resin, and a preparation method and application thereof.
Background
The electrophoretic coating is originated from the 20 th century and the 30 th century, developed to the present, and has gradually developed a cathode electrophoretic coating with high corrosion resistance and decorative effect, and the cathode electrophoretic coating is widely applied to the automobile industry due to the characteristics of excellent corrosion resistance, high decorative property, high coating automation degree and the like, and is popularized and applied to the industrial fields of building materials, light industry, household appliances and the like, and the surface corrosion prevention and decoration of hardware and artware. Nowadays, electrophoretic paints are various, and among them, a cathode epoxy electrophoretic paint is a common one, which is usually prepared by compounding aminated epoxy resin with polyisocyanate curing agents, and dispersing the compound in an aqueous phase to form an emulsion. However, the traditional cathodic epoxy electrophoretic paint has poor edge corrosion resistance when in use.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides the amino-terminated dihydroxy modified epoxy resin, and the cathode electrophoretic coating prepared from the amino-terminated dihydroxy modified epoxy resin has the characteristic of good edge corrosion resistance.
The invention also provides a cationic electrophoresis resin emulsion.
The invention also provides a preparation method of the cationic electrophoresis resin emulsion.
The invention also provides a cathode electrophoretic coating.
The invention also provides a preparation method of the cathode electrophoretic coating.
The invention also provides application of the amino-terminated dihydroxy modified epoxy resin, the cationic electrophoretic resin emulsion and the cathode electrophoretic coating.
The invention provides an amino-terminated dihydroxy modified epoxy resin, which is prepared from raw materials including a raw material epoxy resin and a dihydroxy monomer, wherein the raw material epoxy resin is modified by the dihydroxy monomer and then subjected to ring-opening reaction with polyetheramine and an alcohol amine substance to obtain the amino-terminated dihydroxy modified epoxy resin.
The amino-terminated dihydroxy modified epoxy resin provided by the embodiment of the invention has at least the following beneficial effects: the invention utilizes a dihydroxy monomer to modify with raw material epoxy resin, and then uses polyether amine and alcamines to carry out ring-opening reaction with the raw material epoxy resin to obtain the amino-terminated dihydroxy modified epoxy resin. The obtained terminal amino dihydroxy modified epoxy resin is applied to cationic electrophoretic resin emulsion and further applied to electrophoretic coating, and a paint film obtained by electrophoretic coating has the characteristic of good edge corrosion resistance, so that the protection capability on a workpiece can be improved, and the durability of the workpiece is improved.
In some embodiments of the present invention, the molecular weight of the amine-terminated dihydroxy modified epoxy resin is 1500-.
In some embodiments of the invention, the dihydroxy monomer is a dihydroxy compound having a molecular weight between 200-1000.
In some preferred embodiments of the present invention, the dihydroxy monomer is a dihydroxy compound having a molecular weight of between 400-800.
The dihydroxy monomers of the present invention are limited primarily to molecular weight and number of hydroxyl groups. Compared with the molecular weight of the better dihydroxy monomer, the overlarge molecular weight can cause the molecular weight of the amino-terminated dihydroxy modified epoxy resin to be overlarge, so that the suspension stability of emulsified particles is poor when the amino-terminated dihydroxy modified epoxy resin is applied to cationic electrophoresis resin emulsion; if the molecular weight of the bishydroxy monomer is too small, the property of modifying the raw epoxy resin is not significant.
Meanwhile, the selected dihydroxy monomer has single molecular weight distribution, so that the quality of the amino-terminated dihydroxy modified epoxy resin and the cationic electrophoretic resin emulsion and electrophoretic paint applied to the epoxy resin are more stable, and the dihydroxy modification enables the main resin to form a straight-chain framework, which is beneficial to the formation of emulsified particle states when the epoxy resin is applied to the cationic electrophoretic resin emulsion, so that the uniformity of the cationic electrophoretic resin emulsion and electrophoretic paint is improved. The polyhydroxy group forms a network structure, and is not easy to form a state of emulsified particles.
In some embodiments of the invention, the dihydroxy monomer comprises at least one of bisphenol a, polyethylene glycol, polycaprolactone polyol, or bisphenol a polyether alcohol.
In some preferred embodiments of the invention, the dihydroxy monomer comprises at least one of bisphenol A, polyethylene glycol PEG-400, polycaprolactone polyol PCL-205, or benzoxegonine Hapten.
In some embodiments of the present invention, the raw epoxy resin has an epoxy equivalent weight of 188-.
In some embodiments of the present invention, the raw epoxy resin comprises at least one of a bisphenol a type epoxy resin, a bisphenol F type epoxy resin, a novolac epoxy resin, an aliphatic epoxy resin, or a glycidylamine epoxy resin.
Bisphenol a type epoxy resin: BPA; bisphenol F type epoxy resin: BPF.
The epoxy resin is the variety with highest corrosion resistance performance-price ratio in the current resin for the coating industry, and the bisphenol A type epoxy resin is more cheap and beautiful in all types of epoxy resin because of the special structure of the bisphenol A.
In some preferred embodiments of the present invention, the raw epoxy resin comprises a bisphenol a type epoxy resin having an epoxy equivalent weight of between 100 and 800.
Through the implementation mode, when the raw material epoxy resin with better epoxy equivalent is selected and the obtained amino-terminated dihydroxy modified epoxy resin is applied to cationic electrophoretic resin emulsion and electrophoretic paint, the stability of the cationic electrophoretic resin emulsion and electrophoretic paint can be improved, and the function of final electrophoretic coating can be improved. Compared with the raw material epoxy resin with better epoxy equivalent, the use of the raw material epoxy resin with too low epoxy equivalent can result in insufficient stability of cationic electrophoretic resin emulsion and electrophoretic paint, and finally the electrophoretic coating is too soft, resulting in poor function. If solid raw material epoxy resin with too high epoxy equivalent is used, the viscosity of the reaction process is too high, more solvents are needed to dilute and reduce the viscosity, and meanwhile, the problems of over-hardness and over-brittleness of the electrophoretic coating can be caused, the binding force with a workpiece is influenced, and further the salt spray resistance is reduced.
In some more preferred embodiments of the present invention, the raw epoxy resin comprises a bisphenol a type epoxy resin having an epoxy equivalent weight of between 188-540.
In some preferred embodiments of the present invention, the raw epoxy resin comprises a bisphenol a type epoxy resin having an epoxy equivalent weight of between 1000-2000.
In some embodiments of the invention, the molar ratio of the dihydroxy monomer to the starting epoxy resin is (2.0-2.2): 1.0.
in some embodiments of the present invention, the alcohol amine includes at least one of alcohol amine, diethanolamine, or methyl ethanolamine.
Wherein, the alcohol amine: n-methyldiethanolamine.
In some embodiments of the present invention, the main chain of the polyetheramine is a poly aliphatic ether structure, and the terminal reactive functional group is an amine group.
In some preferred embodiments of the present invention, the polyetheramine is a secondary difunctional amine terminated polyetheramine compound having a molecular weight between 200-1000.
Through the implementation mode, the polyether amine is an amination source, is a source for chain extension and pH buffering effect increase after the epoxy resin is subjected to double-hydroxyl modification, and has a leveling effect in the amino-terminated double-hydroxyl modified epoxy resin.
In some more preferred embodiments of the invention, the polyetheramine has a molecular weight of 200-400.
In a second aspect of the present invention, a cationic electrophoretic resin emulsion is provided, which comprises the following raw materials: the amino-terminated dihydroxy modified epoxy resin and the pyrolysis-sealed isocyanate curing agent.
In some embodiments of the present invention, the pyrolytic block isocyanate curing agent comprises at least one of a trimeric pyrolytic block isocyanate curing agent, a linear pyrolytic block isocyanate curing agent, or an MDI pyrolytic block isocyanate curing agent.
Through the above embodiment, the curing abilities of the trimerization type pyrolysis sealing isocyanate curing agent, the MDI type pyrolysis sealing isocyanate curing agent and the linear type pyrolysis sealing isocyanate curing agent are sequentially enhanced, that is, the same curing effect is achieved under the condition that other components are not changed, and the amounts of the trimerization type pyrolysis sealing isocyanate curing agent, the MDI type pyrolysis sealing isocyanate curing agent and the linear type pyrolysis sealing isocyanate curing agent are sequentially increased. In addition, the cationic electrophoretic resin emulsion is applied to a coating film obtained by the cathode electrophoretic coating, the thermal decomposition sealing type isocyanate curing agent has a leveling gain effect on the coating film, and the leveling gain effect of the linear thermal decomposition sealing type isocyanate curing agent, the MDI type thermal decomposition sealing type isocyanate curing agent and the trimerization type thermal decomposition sealing type isocyanate curing agent on the coating film is gradually weakened. Therefore, in the actual use process, two or three of the three curing agents can be adopted according to the needs, so that the leveling assisting effect is realized on the coating film while the low using amount of the curing agent is achieved.
In a third aspect of the present invention, a method for preparing the above cationic electrophoretic resin emulsion is provided, which comprises the following steps:
s1, modifying the raw material epoxy resin with a dihydroxy monomer, and performing ring-opening reaction with polyetheramine and an alcohol amine substance to obtain an amino-terminated dihydroxy modified epoxy resin;
s2, mixing the amino-terminated dihydroxy modified epoxy resin, the pyrolysis-sealed isocyanate curing agent and the film-forming auxiliary agent I to obtain electrophoretic resin raw pulp, and emulsifying the electrophoretic resin raw pulp in an acid environment to obtain the cationic electrophoretic resin emulsion.
The preparation method of the cationic electrophoretic resin emulsion has the characteristics of energy conservation, waste reduction and few VOC.
In some embodiments of the present invention, in step S1, the method includes the following steps:
s1-1, keeping the temperature of the mixture of the raw material epoxy resin and the dihydroxy monomer at 130-150 ℃ for 1-2 hours;
s1-2, adding polyetheramine and alcohol amine substances, and preserving heat for 1-2 hours at 90-110 ℃.
In some preferred embodiments of the present invention, in step S1, the following steps are included:
s1-1, taking 2-2.5 parts of raw material epoxy resin, stirring and heating to 150 ℃, adding 1 part of bisphenol A and 0.5 part of dihydroxy monomer, and keeping the temperature at 150 ℃ for 2 hours at 130-;
s1-2, adding 0.5 part of polyether amine, preserving heat for 1 hour at 90-110 ℃, adding 0.5-0.8 part of alcohol amine substance, preserving heat for 1 hour at 110-120 ℃.
FTIR is used to identify that the absorption peak of the epoxy functional group is completely disappeared, and the solvent-free terminal amino dihydroxy modified epoxy resin with 100 percent of solid content is prepared. Wherein, the polyether amine has the function of a chain extender, and the alcamines have the function of a ring-opening agent and can react with the epoxy functional groups.
In some preferred embodiments of the present invention, in step S1, the following steps are included:
s1-1, taking 2-4 parts of raw material epoxy resin and 0.5 part of diluting solvent, stirring and heating to 130 ℃, adding a dihydroxy monomer, stirring and heating, and vacuumizing; after the dihydroxy monomer is added, preserving the heat for 2 hours at the temperature of 130-150 ℃; s1-2, adding polyetheramine and alcohol amine substances to carry out ring-opening reaction, and keeping the temperature at 90-110 ℃ for 1-2 hours.
The amino-terminated dihydroxy modified epoxy resin with 100 percent of solvent-free solid content is prepared.
In step S1-1, the mixture of the epoxy resin and the dihydroxy monomer is evacuated to remove excess water vapor during the stirring and heating. After the dihydroxy monomer is added, the change of the absorption peak of the epoxy functional group is identified by an infrared spectrometer during the heat preservation at the temperature of 130-150 ℃.
In some more preferred embodiments of the present invention, in step S1-1, the dilution solvent includes at least one of ethyl acetate, isopropyl alcohol, or methyl isobutyl ketone.
In some embodiments of the present invention, in step S2, the amine-terminated dihydroxy-modified epoxy resin, the thermal decomposition-blocked isocyanate curing agent, and the film-forming aid i are mixed and emulsified in acidic water to obtain the cationic electrophoretic resin emulsion.
In some preferred embodiments of the present invention, in step S2, after the amine-terminated dihydroxy modified epoxy resin and the pyrolysis-blocked isocyanate curing agent are mixed, a film-forming aid i is added, wherein the film-forming aid i is an aqueous film-forming aid.
Through the embodiment, the aqueous film-forming assistant can help the paint film to level and increase the thickness of the paint film in the electrophoretic paint plating process.
In some more preferred embodiments of the present invention, the aqueous coalescent is an alcohol ether based compound.
In some more preferred embodiments of the invention, the aqueous coalescent includes at least one of propylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, ethylene glycol isooctyl ether, diethylene glycol butyl ether, propylene glycol phenyl ether, or dipropylene glycol butyl ether.
In some more preferred embodiments of the invention, the aqueous coalescent includes ethylene glycol butyl ether, propylene glycol butyl ether, and propylene glycol phenyl ether.
In some more preferred embodiments of the invention, the aqueous coalescent includes ethylene glycol butyl ether, propylene glycol butyl ether, and propylene glycol phenyl ether, wherein the ratio of parts by mass of the ethylene glycol butyl ether, the propylene glycol butyl ether, and the propylene glycol phenyl ether is (10-20): (10-20): (5-10).
In some more preferred embodiments of the invention, the aqueous coalescent includes ethylene glycol butyl ether, propylene glycol butyl ether, and propylene glycol phenyl ether, wherein the ratio of parts by mass of the ethylene glycol butyl ether, the propylene glycol butyl ether, and the propylene glycol phenyl ether is (15-17): (8-10): (3-5).
In some embodiments of the present invention, in step S2, the ratio of the parts by weight of the amino-terminated dihydroxy-modified epoxy resin, the thermal decomposition-blocked isocyanate curing agent and the film-forming assistant i is 100: (50-70): (10-15).
In some embodiments of the present invention, in step S2, the emulsifying step of the electrophoretic resin syrup includes: and adding the electrophoretic resin raw pulp into the mixed solution of water and acid, stirring, adding water again, and stirring to obtain the cationic electrophoretic resin emulsion.
In some preferred embodiments of the present invention, in step S2, the emulsifying step of the electrophoretic resin syrup includes: adding water and acid into an emulsification tank, stirring at 350rpm of 300-.
In some more preferred embodiments of the present invention, in step S2, the emulsifying step of the virgin electrophoresis resin slurry includes: adding 200 parts by weight of 180-wall-modified-resin water and acid into an emulsification tank, keeping the temperature at 20-30 ℃, stirring at 350rpm of 300-wall-modified-resin, heating the temperature to 65-75 ℃, adding 310 parts by weight of 290-wall-modified-resin raw pulp into the emulsification tank at the speed of 0.1-0.2L/min, stirring for 30 minutes, adjusting the stirring speed to 600rpm of 500-wall-modified-resin, adding 350 parts by weight of 320-wall-modified-resin water, and continuously stirring for 1 hour to obtain the cationic electrophoretic resin emulsion.
In some preferred embodiments of the present invention, the cationic electrophoretic resin emulsion has a mass fraction of solids of 33 to 36%.
In some more preferred embodiments of the present invention, the cationic electrophoretic resin emulsion has a mass fraction of solids of 34 to 36%.
In some more preferred embodiments of the present invention, the cationic electrophoretic resin emulsion has a pH of 5.7 to 6.3.
In some more preferred embodiments of the present invention, the cationic electrophoretic resin emulsion has an electrical conductivity of 2300-2800. mu.S/cm.
In some preferred embodiments of the present invention, the ratio of the electrophoretic resin syrup to the water to the acid in parts by mass is 100: (130-150): (3-5).
In some preferred embodiments of the present invention, the acid may be at least one of an inorganic acid or an organic acid.
In some more preferred embodiments of the invention, the acid is an organic acid.
In some more preferred embodiments of the present invention, the organic acid comprises at least one of acetic acid, lactic acid, or sulfamic acid.
In some more preferred embodiments of the invention, the organic acid is lactic acid.
In some embodiments of the present invention, the preparation method further comprises preparing a pyrolytic blocked isocyanate curing agent, comprising the steps of:
s2-a1, adding a sealing agent I into a diisocyanate compound under a protective environment, and then adding a catalyst I to obtain a mixture I;
and S2-a2, adding a chain extender I into the mixture I, and then adding a film-forming assistant II to obtain the pyrolysis-sealed isocyanate curing agent.
In some preferred embodiments of the present invention, in step S2-a1, the diisocyanate compound is dropped with the blocking agent i at 30 ℃ under nitrogen atmosphere, the dropping time of the blocking agent i is 2-4 hours, then the catalyst i is added, and the reaction is carried out for 1-2 hours to obtain the mixture i;
in some more preferred embodiments of the present invention, in step S2-a1, a diisocyanate compound having an NCO content of 0.9 to 1.1 molar equivalent parts is taken, stirred and added dropwise with a blocking agent I having a hydroxyl content of 0.5 to 0.51 molar equivalent parts at a temperature of 20 ℃ or less under a nitrogen atmosphere, at a temperature of 30 ℃ or less and within 2 to 4 hours, and the blocking agent I is added dropwise; then adding 0.04-0.05 weight part of catalyst I, and reacting for 1-2 hours.
In some more preferred embodiments of the present invention, in step S2-a1, a diisocyanate compound having an NCO content of 0.9 to 1.1 molar equivalent parts is charged into a reactor, nitrogen is introduced, stirring is carried out, and at a temperature of 20 ℃ or lower, a blocking agent I having a hydroxyl content of 0.5 to 0.51 molar equivalent parts is added dropwise, at a temperature of 30 ℃ or lower and within 2 to 4 hours, and the blocking agent I is added dropwise; then, 0.04 to 0.05 part by weight of catalyst I was added and the reaction was continued for 1 to 2 hours until the NCO equivalent value reached the expected value I.
In some more preferred embodiments of the present invention, the catalyst i is at least one of an organotin catalyst or an organobismuth catalyst.
In some preferred embodiments of the present invention, in step S2-a2, the temperature is raised to 60 ℃, chain extender I with the total hydroxyl content of 0.5-0.55 molar equivalent parts is added to the mixture I, and the temperature is controlled to be not higher than 90 ℃; after the chain extender I is added, heating to 95-105 ℃, and preserving heat for 1-2 hours; and adding a film forming assistant II for reducing viscosity and cooling to obtain the pyrolysis-sealed isocyanate curing agent.
In some more preferred embodiments of the present invention, in step S2-a2, the temperature is raised to 60 ℃, chain extender i with total hydroxyl content of 0.5-0.55 molar equivalent parts is added to the mixture i in batches, the diisocyanate compound chain extender i is a compound consisting of two to four isocyanates, and the temperature is controlled to be not higher than 90 ℃; after the chain extender I is added, heating to 95-105 ℃, preserving heat for 1-2 hours, heating to 110-120 ℃, preserving heat for 1 hour, and identifying the disappearance of isocyanate group peak by using an infrared spectrometer; and adding a film forming assistant II for reducing viscosity and cooling to obtain the pyrolysis-sealed isocyanate curing agent.
In some preferred embodiments of the present invention, the pyrolysis-blocked isocyanate curing agent has a solid content of 50 to 90%.
In some preferred embodiments of the present invention, the isocyanate compound is at least one of a difunctional group of isocyanate monomer, a di-isomer of isocyanate, or a tri-isomer of isocyanate.
In some more preferred embodiments of the present invention, the isocyanate compound is a difunctional isocyanate monomer.
In some preferred embodiments of the present invention, the isocyanate compound comprises an aliphatic diisocyanate compound or an aromatic diisocyanate compound.
In some more preferred embodiments of the present invention, the aliphatic diisocyanate compound includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, or 1, 1-methylene-bis (4-isocyanatocyclohexane).
Hexamethylene diisocyanate: HDI; isophorone diisocyanate: IPDI; 1.1-Methylene-bis (4-isocyanatocyclohexane: H)12MDI。
In some more preferred embodiments of the present invention, the aromatic diisocyanate compound includes at least one of xylene diisocyanate, diphenylmethane diisocyanate, or xylylene diisocyanate.
Xylene diisocyanate: TDI; diphenylmethane diisocyanate: MDI; xylylene diisocyanate: XDI.
In some more preferred embodiments of the present invention, the isocyanate compound comprises at least one of isophorone diisocyanate, xylene diisocyanate, or diphenylmethane diisocyanate.
In some more preferred embodiments of the present invention, the isocyanate compound comprises isophorone diisocyanate.
In some preferred embodiments of the present invention, the blocking agent i comprises at least one of alcohols, alcohol ethers or amines having active hydrogen.
In some more preferred embodiments of the invention, the blocking agent i comprises at least one of methanol, butyl glycol ether, hexyl glycol ether, butyl glycol butyl ether or butanone oxime, diethanolamine or polyetheramine.
In some preferred embodiments of the present invention, the chain extender i includes at least one of a diol compound or a triol compound.
In some more preferred embodiments of the present invention, the chain extender i comprises at least one of polyethylene glycol, polypropylene glycol, or trimethylolpropane.
In some preferred embodiments of the invention, the coalescent II is an alcohol ether based compound.
In some more preferred embodiments of the invention, the coalescent II is at least one of propylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, ethylene glycol isooctyl ether, diethylene glycol butyl ether, propylene glycol phenyl ether, or dipropylene glycol butyl ether.
In some preferred embodiments of the present invention, the molar ratio of the isocyanate compound, the blocking agent i and the chain extender i is 2: (1-1.2): (1-1.2).
In some more preferred embodiments of the present invention, the molar ratio of the isocyanate compound, the blocking agent i and the chain extender i is 2: (1-1.1): (1-1.1).
In some more preferred embodiments of the present invention, the molar ratio of the isocyanate compound, the blocking agent i and the chain extender i is 2: (1-1.05): (1-1.05).
In some embodiments of the present invention, the preparation method further comprises preparing a pyrolytic blocked isocyanate curing agent, comprising the steps of:
s2-b1, adding a sealing agent II into a diisocyanate compound under a protective environment to obtain a mixture II;
s2-b2, and adding a film-forming assistant III into the mixture II to obtain the pyrolysis-blocking isocyanate curing agent.
In some preferred embodiments of the present invention, in step S2-b1, the diisocyanate compound is added dropwise with the blocking agent under nitrogen atmosphere, and the addition of the blocking agent is completed within 2 to 4 hours to obtain a mixture ii;
in some more preferred embodiments of the present invention, in step S2-b1, a diisocyanate compound having an NCO content of 1.0 molar equivalent part is charged into a reactor, nitrogen gas is introduced, stirring is carried out, dropwise addition of a blocking agent II having a hydroxyl content of 1.0 to 1.1 molar equivalent parts is started, and dropwise addition is completed within 2 to 4 hours while the temperature is maintained at 50 ℃ or lower.
In some preferred embodiments of the present invention, in step S2-b2, the temperature is raised to 80-100 ℃, the temperature is maintained for 1-2 hours, and the disappearance of the isocyanate group peak is identified by an infrared spectrometer; and adding a film forming assistant III for reducing viscosity and cooling to obtain the pyrolysis-sealed isocyanate curing agent.
In some preferred embodiments of the present invention, the pyrolysis-blocked isocyanate curing agent has a solid content of 50 to 90%.
In some preferred embodiments of the present invention, the isocyanate compound comprises a trimer of an aliphatic diisocyanate compound or a trimer of an aromatic diisocyanate compound.
In some more preferred embodiments of the present invention, the trimer of the aliphatic diisocyanate compound includes a trimer of hexamethylene diisocyanate.
In some more preferred embodiments of the present invention, the trimer of aliphatic diisocyanate compounds includes at least one of N-3300, N-3390, HDT-100 or HT-100.
Wherein, N-3300 (Kesichuang); n-3390 (Kesichun); HDT-100 (Rodiya); HT-100 (Wanhua).
In some preferred embodiments of the present invention, the trimer of the aromatic diisocyanate compound is a trimer of isophorone diisocyanate.
In some more preferred embodiments of the present invention, the aromatic diisocyanate compound trimer includes Z-4470 (Colesine).
Wherein, Z-4470 (scientific).
In some preferred embodiments of the present invention, the blocking agent ii comprises at least one of alcohols, alcohol ethers or amines having active hydrogen.
In some more preferred embodiments of the invention, the blocking agent ii comprises at least one of methanol, butyl glycol ether, hexyl glycol ether, butyl glycol butyl ether or butanone oxime, diethanolamine or polyetheramine.
In some preferred embodiments of the invention, the coalescent III is an alcohol ether based compound.
In some more preferred embodiments of the invention, the coalescent III is at least one of propylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, ethylene glycol isooctyl ether, diethylene glycol butyl ether, propylene glycol phenyl ether, or dipropylene glycol butyl ether.
In some embodiments of the present invention, the preparation method further comprises preparing a pyrolytic blocked isocyanate curing agent, comprising the steps of:
s2-c1, stirring diisocyanate compound with NCO content of 0.9-1.1 molar equivalent parts in nitrogen environment, maintaining the temperature below 20 ℃, starting to dropwise add sealant III with hydroxyl content of 0.5-0.51 molar equivalent parts, completing dropwise addition within 2-4 hours, and keeping the temperature below 30 ℃ in the period; then adding 0.04-0.05 weight part of catalyst II, and reacting for 1-2 hours;
heating to 60 ℃ in S2-c2, adding a chain extender II with the total hydroxyl content of 0.5-0.55 molar equivalent parts into the mixture I in batches, and chain-extending the diisocyanate compound into a compound consisting of two to four isocyanates, wherein the temperature is controlled to be not higher than 90 ℃; after the chain extender II is added, the temperature is raised to 95-105 ℃, the temperature is kept for 1-2 hours, then the temperature is raised to 110-120 ℃, and the temperature is kept for 1 hour; and adding 400 parts by weight of 200-400 parts of solvent, and cooling to obtain the pyrolysis sealing type isocyanate curing agent.
In some embodiments of the invention, the solvent is an organic solvent free of active hydrogen.
In some preferred embodiments of the present invention, the solvent comprises at least one of ethyl acetate, butyl acetate, methyl isobutyl ketone, xylene, or propylene glycol methyl ether acetate.
In some preferred embodiments of the invention, the solvent is propylene glycol methyl ether acetate.
In some embodiments of the invention, the blocking agent III is the same composition as the blocking agent II, the catalyst II is the same composition as the catalyst I, and the chain extender II is the same composition as the chain extender I.
In a fourth aspect of the present invention, a cathodic electrophoretic coating is provided, which comprises the above cationic electrophoretic resin emulsion.
In some embodiments of the present invention, the cathode electrophoretic paint further comprises an electrophoretic paste and water.
In some embodiments of the present invention, the ratio of the cationic electrophoretic resin emulsion to the electrophoretic color paste to the water in parts by mass is (3-7): 1: (5-7).
In some preferred embodiments of the present invention, the ratio of the cationic electrophoretic resin emulsion to the electrophoretic color paste to the water in parts by mass is (4-6): 1: (5-6).
In some more preferred embodiments of the present invention, the ratio of the cationic electrophoretic resin emulsion to the electrophoretic color paste to the water in parts by mass is 4: 1: 5.
the electrophoretic color paste can be electrophoretic black paste, and can be obtained from the market, such as Nippon, Youli and Daqiong.
In some more preferred embodiments of the present invention, the water has an electrical conductivity of 50. mu.S/cm or less.
In some more preferred embodiments of the invention, the water has an electrical conductivity of 20. mu.S/cm or less.
In some more preferred embodiments of the present invention, the water has an electrical conductivity of 10. mu.S/cm or less.
In some embodiments of the invention, the cathodic electrocoat has a solids content of 18-20%.
In some embodiments of the invention, the cathodic electrocoat has a pH of 5.7-6.1.
In some preferred embodiments of the present invention, the cathodic electrocoating has a pH of 5.9-6.1.
In some preferred embodiments of the present invention, the cathodic electrocoating has a pH of 5.7-5.9.
In some embodiments of the invention, the cathode electrophoretic coating has an electrical conductivity of 1000-.
In some preferred embodiments of the present invention, the cathode electrophoretic coating has an electrical conductivity of 1200-1500. mu.S/cm.
In a fifth aspect of the present invention, a method for preparing the cathode electrophoretic coating is provided, which includes the following steps: and stirring and curing the cationic electrophoretic resin emulsion, the electrophoretic color paste and water to obtain the cathode electrophoretic coating.
In some embodiments of the invention, the maturation time is 24 hours.
In a sixth aspect of the present invention, a method for using the cathode electrophoretic coating is provided, which includes the following steps: and (3) performing electrophoretic paint plating by using the cathode electrophoretic paint as an electrophoretic paint.
In some embodiments of the present invention, the cathodic electrophoretic paint is an electrophoretic paint, and a cathode and an anode are respectively immersed in the electrophoretic paint under stirring conditions, and the cathode and the anode are respectively connected to a negative electrode and a positive electrode of a dc power supply, and are subjected to electrophoretic painting to form an electrophoretic paint film on the surface of the cathode.
In some embodiments of the invention, the paint film has a thickness of 18 to 20 micrometers.
In some embodiments of the invention, the pencil hardness of the paint film is from 2H to 4H.
In some embodiments of the present invention, the paint film has a gloss of 60 to 80 under the condition of 60 degrees gloss.
In some preferred embodiments of the invention, the material to be coated which is subjected to phosphating pretreatment is used as a cathode in an electrophoretic coating under continuous stirring and is connected with a negative electrode of a direct current power supply; immersing the anode in the electrophoretic coating, and connecting the anode with the positive electrode of a direct current power supply; and carrying out electrophoretic paint plating and thermosetting to obtain the paint film.
In some embodiments of the invention, the cathodic electrocoat is controlled to a temperature of between 28-32 ℃ with continuous agitation; immersing the cold-rolled steel plate subjected to the phosphating pretreatment in an electrophoretic coating to be used as a cathode, and connecting the cathode with a negative electrode of a direct-current power supply; taking a stainless steel sheet immersed in the electrophoretic paint as an anode, and connecting the stainless steel sheet with the anode of a direct-current power supply; performing electrophoretic paint plating under the conditions of constant voltage of 120-180V and operation time of 60-120 seconds; and taking out the painted cold-rolled steel plate, cleaning with water, drying, and then putting into an oven for thermocuring, wherein the thermocuring condition is that the temperature is 160-200 ℃, and the baking time is 20-40 minutes, so as to obtain the electrophoretic coating paint film.
The thickness of a paint film prepared by the method is 18-20 micrometers, the pencil hardness is 2H-4H, the gloss (60 degrees) is 60-80, the salt spray of a blade can reach 168 hours, and the rust points are less than 5.
The seventh aspect of the present invention provides the application of the above cationic electrophoretic resin emulsion or the above cathodic electrophoretic coating in the technical field of electrophoretic coating.
In some embodiments of the present invention, the above cationic electrophoretic resin emulsion or the above cathodic electrophoretic paint is used in an automotive coating, an electric appliance coating or a building material coating.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
Wherein, the reagents and raw materials used in the invention are commercially available.
Example 1
The embodiment discloses an amino-terminated dihydroxy modified epoxy resin, which is prepared from the raw materials shown in table 1, wherein the dihydroxy monomer comprises bisphenol a and benzodecgonine haptene, and the benzodecgonine haptene is bisphenol a polyether alcohol. The main chain of the polyether amine is a polymer with a polyester fatty ether structure and an active functional group at the tail end of the polymer is amino, and the molecular weight of the polyether amine is 200-400.
TABLE 1
The preparation process comprises the following steps: NPEL-128 was added to a 1L split glass reaction vessel equipped with a stirrer, reflux condenser and temperature control, stirred and warmed to 130 ℃. After the temperature is reached, adding Benzoylecgonine Hapten, bisphenol A and bis-diethylene glycol butyl ether formal, then adding benzyl dimethylamine as a catalyst, and keeping the temperature for 2 hours at the temperature of 130-. Then adding polyether amine, preserving heat for 1 hour at 90-110 ℃, then adding methyl ethanolamine, preserving heat for 1 hour at 110-120 ℃, and then adding dodecanol ester for dilution. Finally, the amino-terminated dihydroxy modified epoxy resin is obtained.
The diethylene glycol monobutyl ether formal in the embodiment is a compound without active hydroxyl, can not affect the reaction of other hydroxyl in the reaction, is used as a diluent, has a boiling point of over 300 ℃, is not listed as an organic solvent of VOC, and reduces the use of VOC components in the experimental process.
Benzoylecogenine Hapten in the examples is used as a compound for epoxy modification, increases the flexibility of the main resin thereof, can make the coating film have ductility (flex test <1mm), and makes the appearance more glossy and flat because of leveling property.
Wherein, the alcohol amine substance or polyether amine is a cationic active hydride, the representative meaning of which is primary amine and secondary amine, and the two have more than one active hydrogen for reaction. When the alcohol amine substance is used for assisting in curing, one more hydroxyl group helps to react with isocyanate, and the reaction rate is higher because the hydroxyl group is the first-order hydroxyl group. The polyether amine has a large molecular weight, so that the soft characteristic of the polyether amine can also help the leveling of a coating film.
The xylylenediamine in this embodiment can double the molecular weight of the original main resin by bridging, so that the original physical properties are enhanced by increasing the molecular chain segment, and the additional amine can improve the emulsion stability of the main resin, thereby achieving the increase of the salt spray performance.
The amino-terminated dihydroxy modified epoxy resin prepared in this example is an epoxy main resin segment of an aqueous electrophoretic resin, and the molecular weight is between 1500-3000 according to GPC detection, which determines the basic performance and appearance of the final coating film.
Example 2
The embodiment discloses a cationic electrophoresis resin emulsion (cationic electrophoresis resin emulsion I for short) and application thereof, wherein the raw materials of the cationic electrophoresis resin emulsion I comprise the amino-terminated dihydroxy modified epoxy resin prepared in the embodiment 1, and the components of the amino-terminated dihydroxy modified epoxy resin are shown in the following table 2:
TABLE 2
| Composition (I) | Parts by weight |
| Amino-terminated dihydroxy modified epoxy resin | 159.50 |
| Pyrolysis-sealed isocyanate curing agent I | 128.59 |
| Lactic acid | 11.96 |
| Pure water | 564.87 |
| BYK-3480 | 5.05 |
Wherein BYK-3480 is BYK leveling anti-pitting agent.
The preparation process comprises the following steps: adding amido dihydroxy modified epoxy resin and pyrolysis-sealed isocyanate curing agent I into a 1L separation type glass reaction vessel equipped with a stirrer, a reflux condenser and a temperature controller, wherein the temperature of is 65-75 ℃, BYK-3480 is added, is added for stirring for 20 minutes, lactic acid and pure water are added, and the high-speed stirring is carried out for 1 hour at the temperature of 70 ℃.
The prepared cationic electrophoresis resin emulsion I is a slightly yellowish white emulsion, the solid content is 34-37%, the pH value is 5.7-6.3, and the conductivity is 2000-2800 mu S/cm.
This example discloses a cathode electrophoretic coating, which comprises the cationic electrophoretic resin emulsion i prepared in this example, and the components of which are shown in table 3:
TABLE 3
| Composition (I) | Parts by weight |
| Cationic electrophoresis resin emulsion I | 400 |
| Electrophoretic black paste | 100 |
| Pure water | 500 |
The preparation process comprises the following steps: and sequentially adding the cationic electrophoretic resin emulsion I, the electrophoretic black paste and pure water into a proper container, stirring and curing for 24 hours to obtain the cathode electrophoretic coating.
The prepared cathode electrophoretic coating has the solid content of 18-20%, the pH value of 5.5-5.8 and the conductivity of 1000-.
Example 3
The embodiment discloses cationic electrophoresis resin emulsion (cationic electrophoresis resin emulsion II for short) and application thereof, wherein the raw material of the cationic electrophoresis resin emulsion II comprises the amino-terminated dihydroxy modified epoxy resin prepared in the embodiment 1, and the difference of the cationic electrophoresis resin emulsion II from the embodiment 2 is that a pyrolysis-sealed isocyanate curing agent II is adopted as a curing agent.
The prepared cationic electrophoresis resin emulsion II is a slightly yellowish white emulsion, the solid content is 34-37%, the pH value is 5.7-6.3, and the conductivity is 2000-2800 mu S/cm.
This example discloses a cathodic electrophoretic paint, which is different from example 2 in that the raw material comprises the cationic electrophoretic resin emulsion II prepared in this example.
The prepared cathode electrophoretic coating has the solid content of 18-20%, the pH value of 5.5-5.8 and the conductivity of 1000-.
Comparative example 1
The comparative example discloses an amino-terminated bisphenol A epoxy resin (abbreviated as main epoxy resin I), which is prepared from raw materials without comprising dihydroxy monomers and polyether amine, and the raw material components are shown in Table 4:
TABLE 4
| Composition (I) | Parts by weight |
| NPES-904 | 164.70 |
| Ethylene glycol monobutyl ether | 5.31 |
| Methylethanolamine | 19.56 |
| Ethylene glycol monobutyl ether | 30.51 |
The preparation process comprises the following steps: NPES-904 is added into a 1L separating glass reaction vessel equipped with a stirrer, a reflux condenser tube and a temperature controller, ethylene glycol monobutyl ether (5.31 parts) is added for dissolution, and the mixture is stirred and heated to 90 ℃. After the temperature is reached, methylethanolamine is added, the temperature is naturally raised to 120 ℃, and the temperature is kept for 1 hour. Then, ethylene glycol monobutyl ether (30.51 parts) was added to dilute. To obtain the amino-terminated bisphenol A type epoxy resin.
The molecular weight of the prepared main epoxy resin I and the epoxy main resin section of the waterborne electrophoretic resin is between 1500-3000 according to GPC detection, and the basic performance and the appearance of the final coating film are determined.
Comparative example 2
The comparative example discloses an amine-terminated modified epoxy resin (short for main epoxy resin II), which does not contain polyether amine and comprises the following raw materials in the following components in percentage by weight as shown in Table 5:
TABLE 5
| Composition (I) | Parts by weight |
| NPES-901 | 132.91 |
| Benzoylecgonine Hapten | 26.58 |
| Benzyl dimethylamine | 0.5 |
| Ethylene glycol monobutyl ether | 5.21 |
| Methylethanolamine | 15.15 |
| Ethylene glycol monobutyl ether | 41.31 |
The preparation process comprises the following steps: NPES-901 is added into a 1L separated glass reaction vessel which is provided with a stirrer, a reflux condenser tube and a temperature controller, then part of ethylene glycol monobutyl ether (5.21 parts) is added for dissolution, and the mixture is stirred and heated to 150 ℃. After the temperature reached, Benzoylecgonine Hapten (bisphenol A polyether alcohol) was added, and then xylylenediamine was added as a catalyst, followed by heat preservation at 130-. Then, methylethanolamine is added, the temperature is kept at 110-120 ℃ for 1 hour, and the rest ethylene glycol monobutyl ether (41.31 parts) is added for dilution. To obtain the terminal amino modified epoxy resin. Wherein, benzoylergonine Hapten has a soft chain structure, and can modify resin and optimize the leveling effect of a coating film.
The molecular weight of the prepared main epoxy resin II and the epoxy main resin section of the waterborne electrophoretic resin is between 1500-3000 according to GPC detection, and the basic performance and the appearance of the final coating film are determined.
Comparative example 3
The comparative example discloses an electrophoretic emulsion (abbreviated as electrophoretic emulsion I) and application thereof, which is different from the cationic electrophoretic resin emulsion I in example 2 in that: the main body resin adopted in the comparative example is the main body epoxy resin I prepared in the comparative example 1, and the curing agent adopted is a pyrolysis-blocked isocyanate curing agent III.
The prepared electrophoretic emulsion is slightly yellowish white emulsion, the solid content is 34-37%, the pH value is 5.7-6.3, and the conductivity is 2000-2800 mu S/cm.
The comparative example discloses a cathode electrophoretic paint, which is different from the cathode electrophoretic paint in example 2 in that the electrophoretic paint emulsion used in the comparative example is electrophoretic emulsion I.
Comparative example 4
The comparative example discloses an electrophoretic emulsion (abbreviated as electrophoretic emulsion II) and application thereof, which is different from the cationic electrophoretic resin emulsion I in the example 2 in that: the main body resin adopted in the comparative example is the main body epoxy resin II prepared in the comparative example 2, and the curing agent adopted is the pyrolysis-blocking isocyanate curing agent I.
The prepared electrophoretic emulsion is slightly yellowish white emulsion, the solid content is 34-37%, the pH value is 5.7-6.3, and the conductivity is 2000-2800 mu S/cm.
The comparative example discloses a cathode electrophoretic paint, which is different from the cathode electrophoretic paint in example 2 in that the electrophoretic paint emulsion used in the comparative example is an electrophoretic emulsion II.
Comparative example 5
The comparative example discloses an electrophoretic emulsion (abbreviated as electrophoretic emulsion III) and application thereof, which is different from the cationic electrophoretic resin emulsion I in the example 2 in that: the main body resin adopted in the comparative example is the main body epoxy resin II prepared in the comparative example 2, and the curing agent adopted is a pyrolysis-blocked isocyanate curing agent II.
The prepared electrophoretic emulsion is slightly yellowish white emulsion, the solid content is 34-37%, the pH value is 5.7-6.3, and the conductivity is 2000-2800 mu S/cm.
The present comparative example discloses a cathode electrophoretic paint, which is different from the cathode electrophoretic paint of example 2 in that the electrophoretic paint emulsion used in the present comparative example is electrophoretic emulsion iii.
The components and preparation processes of the pyrolysis seal type isocyanate curing agent I, the pyrolysis seal type isocyanate curing agent II, the pyrolysis seal type isocyanate curing agent III and the electrophoresis black paste used in the above examples and comparative examples comprise:
(1) the thermal decomposition sealing type isocyanate curing agent I is a trimerization thermal decomposition sealing type isocyanate curing agent, and the raw material components are shown in the following table 6:
TABLE 6
| Composition (I) | Parts by weight |
| TDI | 39.49 |
| Ethylene glycol monohexyl ether | 33.57 |
| XC-6212 | 0.08 |
| TMP | 10.27 |
| Ethylene glycol butyl ether | 16.59 |
Wherein XC-6212 is American King's bismuth catalyst;
the preparation process comprises the following steps: adding TDI into a separated glass reaction vessel equipped with a stirrer, a reflux condenser tube and a temperature controller, introducing nitrogen, starting stirring, maintaining the temperature of an ice bath below 20 ℃, starting to dropwise add ethylene glycol monohexyl ether, completing dropwise adding within 2 hours, and keeping the temperature below 30 ℃ in the period. Then, XC-6212 was added thereto, and the reaction was continued for 1 hour. Then adding TMP in batches, heating to 90-100 ℃, preserving heat for 2 hours, heating to 110-120 ℃, and preserving heat for 1 hour. The disappearance of the isocyanate group (NCO) peak was confirmed by an infrared spectrometer. Adding ethylene glycol monobutyl ether, cooling, discharging for standby, thereby preparing the pyrolysis sealing type isocyanate curing agent with the solid content of 80-85%.
(2) The pyrolysis-blocked isocyanate curing agent II is a linear pyrolysis-blocked isocyanate curing agent and comprises the following raw material components in the following table 7:
TABLE 7
| Composition (I) | Parts by weight |
| TDI | 34.27 |
| Ethylene glycol monohexyl ether | 29.13 |
| XC-6212 | 0.07 |
| Polyethylene glycol | 19.94 |
| Ethylene glycol butyl ether | 16.68 |
Wherein XC-6212 is American King's bismuth catalyst;
the preparation process comprises the following steps: adding TDI into a separated glass reaction container equipped with a stirrer, a reflux condenser tube and a temperature controller, introducing nitrogen, starting stirring, maintaining the temperature of an ice bath below 20 ℃, starting to dropwise add ethylene glycol monohexyl ether, completing dropwise adding within 2 hours, and keeping the temperature below 30 ℃ in the period. Then, XC-6212 was added thereto, and the reaction was continued for 1 hour. Then adding TMP in batches, heating to 90-100 ℃, preserving heat for 2 hours, heating to 110-120 ℃, and preserving heat for 1 hour. The disappearance of the isocyanate group (NCO) peak was confirmed by an infrared spectrometer. Adding ethylene glycol monobutyl ether, cooling, discharging for standby, thereby preparing the pyrolysis sealing type isocyanate curing agent with the solid content of 80-85%.
(3) The pyrolysis-blocked isocyanate curing agent III is an MDI-type pyrolysis-blocked isocyanate curing agent, and the raw material components are shown in Table 8:
TABLE 8
| Composition (I) | Parts by weight |
| MDI | 50.07 |
| Methanol | 3.21 |
| XC-6212 | 0.07 |
| Ethylene glycol monohexyl ether | 30.04 |
| Ethylene glycol monobutyl ether | 16.60 |
Wherein XC-6212 is American King's bismuth catalyst;
the preparation process comprises the following steps: adding MDI into a separated glass reaction vessel provided with a stirrer, a reflux condenser tube and a temperature controller, introducing nitrogen, starting stirring, maintaining the temperature of an ice bath below 20 ℃, starting dropwise adding methanol, completing dropwise adding within 2 hours, and keeping the temperature below 30 ℃ in the period. Then, XC-6212 was added thereto, and the reaction was continued for 1 hour. Then adding ethylene glycol monohexyl ether, heating to 90-100 deg.C, and holding the temp. for 2 hr. The disappearance of the isocyanate group (NCO) peak was confirmed by an infrared spectrometer. And adding ethylene glycol monobutyl ether, cooling, and discharging for later use to prepare the curing agent pyrolysis-sealed isocyanate curing agent with the solid content of 80-85%. The ethylene glycol monohexyl ether is a sealant, and can protect the active isocyanate functional group on MDI and be removed when the MDI is baked and heated.
(4) The electrophoretic black paste comprises the following raw materials in percentage by weight as shown in Table 9:
TABLE 9
| Composition (I) | Parts by weight |
| DiSPERBYK-190 | 78.00 |
| Ethylene glycol butyl ether | 15.00 |
| Carbon black | 40.00 |
| Kaolin clay | 220.00 |
| DBTO | 11.6 |
| Surfynol 104E | 1.40 |
| Benzoylecgonine Hapten | 122.00 |
| Pure water | 512.00 |
Wherein, the DiSPERBYK-190 is BYK wetting dispersant; surfynol 104E is BYK humectant.
The preparation process comprises the following steps: adding DiSPERBYK-190 and ethylene glycol monobutyl ether into a proper grinding cylinder, pre-dispersing uniformly, sequentially adding carbon black, kaolin, DBTO, Surfynol 104E, benzophenone Hapten and pure water, mixing uniformly, adding 1-2mm zirconium beads, grinding at high speed until the granularity is greater than the fineness of a scraper blade by 6.5, and filtering to obtain black paste. The prepared color paste has a solid content of 45-50% and a viscosity of less than 600cps at 25 ℃.
Test examples
The performance test of the cathodic electrophoretic coating and Nippon coating prepared in examples 2-3 and comparative examples 3-5 is carried out in the test example, which specifically comprises the following steps:
after the cathode electrophoretic coating working solution is obtained, a coating film (paint film) with normal appearance can be obtained on a cold-rolled sheet of the zinc phosphide coating film through electrophoresis after an electrophoresis operation step and subsequent curing conditions. The blade treated with the zinc phosphide coating film was subjected to further electrophoresis, and the required performance evaluations (including component differences) were as shown in table 10 below.
Wherein the electrophoresis operation step comprises: controlling the temperature of the cathode electrophoretic coating to be between 28 and 32 ℃ under the condition of continuous stirring; taking a cold-rolled sheet of the zinc phosphide coating (or a blade for processing the zinc phosphide coating) as a cathode immersed in the electrophoretic paint, and connecting the cold-rolled sheet with the cathode of a direct-current power supply; taking a stainless steel sheet immersed in the electrophoretic paint as an anode, and connecting the stainless steel sheet with the anode of a direct-current power supply; performing electrophoretic paint plating under the conditions of constant voltage of 120-180V and operation time of 60-120 seconds; and taking out the painted cold-rolled steel plate, washing with water, drying, and then putting into an oven for thermocuring, wherein the thermocuring condition is that the temperature is 170 ℃ and the baking time is 20 minutes, so as to obtain the electrophoretic coating paint film.
Curing conditions are as follows: MIBK was wiped back and forth 50 times without discoloration or change in appearance;
adhesion force: a lattice method, 1mm × 1mm × 100, 90 ° angle;
salt spray resistance: neutral salt fog, 500 hours, and the scratching and forking peristalsis is less than or equal to 1.5 mm;
blade salt spray: GM-9502P 168 hour salt spray, number of knife edge rust spots.
TABLE 10 cathodic electrophoretic coating Performance test results Table
As can be seen from table 10, in examples 2 to 3, after the amine-terminated dihydroxy modified epoxy resin prepared in example 1 was used as a main resin, the performance of the edge salt fog was significantly improved, and when the trimerization type thermal decomposition-blocking isocyanate curing agent (thermal decomposition-blocking isocyanate curing agent i) was used, a network structure with better salt fog resistance was generated during curing, so that the number of rust spots on the final edge was reduced to less than 5.
In summary, in the present invention, firstly, a dihydroxy monomer is modified with a raw material epoxy resin, and then a polyether amine and an alcohol amine substance are subjected to a ring-opening reaction with the dihydroxy monomer modified epoxy resin to obtain an amino-terminated dihydroxy modified epoxy resin. And mixing the amino-terminated dihydroxy modified epoxy resin and the thermally-blocked isocyanate curing agent, and further dispersing the mixture in acidic water to form the cationic electrophoresis resin emulsion. And mixing the cationic electrophoretic resin emulsion, the electrophoretic black paste and water in proportion to obtain the cathode electrophoretic coating. And (3) electrophoretic coating is carried out on the phosphatized cold-rolled steel plate by using the cathodic electrophoretic coating, a film with the thickness of 18-20 microns is formed after thermosetting, the salt fog of a blade can reach 168 hours, and the rust points are less than 5.
The electrophoretic paint is a thermosetting film forming system, the main resin is a compound with hydroxyl at the side end, and the curing agent is an isocyanate curing system. Because the emulsion of the electrophoretic paint is water-based and has two components of main resin and curing agent, and the isocyanate group reacts with the hydroxyl group of water, the isocyanate group (NCO) in the curing agent must be blocked and protected in advance to form a so-called blocked isocyanate curing agent, so that the long-term stability of the working solution of the electrophoretic paint in an electrophoretic paint tank can be ensured, and the protection is removed for curing reaction when the working solution is baked.
Meanwhile, in the conventional process for preparing the electrophoretic coating, in order to avoid the serious consequences of nonuniform reaction and even gelation caused by overhigh viscosity of the system, an organic solvent must be properly added at each stage to reduce viscosity. Meanwhile, in the latter half of the reaction, since the molecular weight of the resin gradually increases from 2000 to 2500 or more due to the addition reaction of amination, more bubbles entrapped in the reaction under continuous stirring are difficult to remove from the highly viscous resin, and more diluting solvents are required to reduce the side effect of foaming in the reaction, and a pressure bubble suppressing step is often used to achieve the effect of a low solvent addition amount. The invention uses the ether solvent with high boiling point as the diluent, can avoid releasing in the atmosphere during baking, does not need to carry out the step of vacuum solvent pumping which wastes time and energy after the electrophoretic coating is finished, and is the commodity of the corrosion-resistant electrophoretic coating with low heating decrement after the completion.
The traditional film-forming auxiliary agent usually adopts an alcohol ether solvent, which has high water content and easily influences the accuracy of the proceeding direction of the reaction due to the hydroxyl functional group, thereby causing the occurrence of side reaction. Therefore, methyl isobutyl ketone is generally used for dilution of the chain extension reaction, but too much solvent causes poor appearance of the coating film, and a step of removing the solvent is instead required in the emulsification stage, and the boiling point is 116 ℃, so that additional temperature rise and pressure reduction are required for assistance. This step increases the cost of the solvent and also increases the overall time of the reaction. The invention uses the ether solvent with high boiling point, which can avoid the situation, the ether has no active functional group, so the ether can be added at the front end of the reaction to replace methyl isobutyl ketone, and does not cause other reaction routes (side reactions), and the addition amount can be greatly reduced due to the pressurization foam inhibition process, thereby achieving the effects of reducing the cost and reducing VOC.
The invention discloses a novel electrophoretic coating and a preparation process thereof, which can improve the protective capability of workpieces, improve the durability of the workpieces, reduce heating decrement, are different from the traditional electrophoretic coating processing process, and have the characteristics of energy conservation, waste reduction and VOC reduction. The product obtained by using the dihydroxy monomer and the epoxy monomer serves as a backbone, the branched chain structure is used for increasing the steric hindrance of the main chain segment of the resin to enhance the stability of the emulsion, the branched chain structure is softer and has the effect of modifying the appearance of a coating, and finally three amines are used for matching and opening an epoxy ring, wherein polyether amine can provide an emulsified amine functional group, long-chain polyether also has the effect of modifying the appearance of the coating, and the blocked polyisocyanate is matched as a curing agent. Dispersing the obtained product in acidic water to obtain the cathodic electrophoretic coating emulsion.
The invention utilizes a dihydroxy monomer to modify with raw material epoxy resin, and then uses polyether amine and alcamines to carry out ring-opening reaction with the raw material epoxy resin to obtain the amino-terminated dihydroxy modified epoxy resin. The obtained amino-terminated dihydroxy modified epoxy resin is applied to cationic electrophoretic resin emulsion and further applied to electrophoretic coating, in the electrophoretic coating process, the proportion of dihydroxy monomers (such as bisphenol A) is increased, so that the hardness of a coating film is improved, the fluidity of the coating film (in a preparation process) is reduced when the coating film is wet, the coating film generated by main resin is reduced during baking, and the polyetheramine has the opportunity to generate a coating effect when the polyetheramine flows to the edge, so that the edge of a workpiece is coated, the workpiece has the characteristic of good edge corrosion resistance, the protection capability of the workpiece is improved, and the durability of the workpiece is improved.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (10)
1. The amino-terminated dihydroxy modified epoxy resin is characterized in that raw materials for preparing the amino-terminated dihydroxy modified epoxy resin comprise raw material epoxy resin and dihydroxy monomers, wherein the raw material epoxy resin is modified by the dihydroxy monomers and then subjected to ring-opening reaction with polyetheramine and alcamines to prepare the amino-terminated dihydroxy modified epoxy resin.
2. The amino-terminated dihydroxy modified epoxy resin as claimed in claim 1, wherein the molecular weight of said amino-terminated dihydroxy modified epoxy resin is 1500-3000; preferably, the dihydroxy monomer is a dihydroxy compound with a molecular weight of between 200-1000; preferably, the dihydroxy monomer comprises at least one of bisphenol a, polyethylene glycol, polycaprolactone polyol, or bisphenol a polyether alcohol.
3. The amino-terminated dihydroxy modified epoxy resin as claimed in claim 1, wherein the epoxy equivalent of said raw epoxy resin is 188-2000; preferably, the raw epoxy resin includes at least one of a bisphenol a type epoxy resin, a bisphenol F type epoxy resin, a novolac epoxy resin, an aliphatic epoxy resin, or a glycidyl amine epoxy resin; preferably, the molar ratio of the dihydroxy monomer to the starting epoxy resin is (2.0-2.2): 1.0.
4. the amino-terminated dihydroxy modified epoxy resin according to claim 1, wherein said alcohol amine comprises at least one of alcohol amine, diethanolamine or methyl ethanolamine; preferably, the main chain of the polyether amine is a polyester fatty ether structure, and the terminal active functional group is a polymer of amino; preferably, the molecular weight of the polyetheramine is 200-400.
5. The cationic electrophoresis resin emulsion is characterized by comprising the following raw materials: the amine-terminated bishydroxy-modified epoxy resin according to any one of claims 1 to 4, and a thermally blocked isocyanate curing agent.
6. The cationic electrophoretic resin emulsion according to claim 5, wherein the thermal decomposition-blocked isocyanate curing agent comprises at least one of a trimeric thermal decomposition-blocked isocyanate curing agent, a linear thermal decomposition-blocked isocyanate curing agent, or a MDI thermal decomposition-blocked isocyanate curing agent.
7. A method for preparing the cationic electrophoretic resin emulsion according to claim 5, comprising the steps of:
s1, modifying the raw material epoxy resin with a dihydroxy monomer, and performing ring-opening reaction with polyetheramine and an alcohol amine substance to obtain an amino-terminated dihydroxy modified epoxy resin;
s2, mixing the amino-terminated dihydroxy modified epoxy resin, the pyrolysis-sealed isocyanate curing agent and the film-forming auxiliary agent I to obtain electrophoretic resin raw pulp, and emulsifying the electrophoretic resin raw pulp in an acid environment to obtain the cationic electrophoretic resin emulsion.
8. A cathodic electrodeposition coating comprising the cationic electrodeposition resin emulsion according to any one of claims 5 to 6 or the cationic electrodeposition resin emulsion obtained by the method according to claim 7.
9. The method for preparing the cathodic electrocoating of claim 8, comprising the steps of: and stirring and curing the cationic electrophoretic resin emulsion, the electrophoretic color paste and water to obtain the cathode electrophoretic coating.
10. The use of the amine-terminated bishydroxy modified epoxy resin as defined in any one of claims 1 to 4, the cationic electrophoretic resin emulsion as defined in any one of claims 5 to 6, the cationic electrophoretic resin emulsion prepared by the method as defined in claim 7, the cathodic electrophoretic paint as defined in claim 8, or the cathodic electrophoretic paint prepared by the method as defined in claim 9 in the technical field of electrophoretic painting.
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| CN103497617A (en) * | 2013-09-09 | 2014-01-08 | 湖南工程学院 | Preparation method for self-emulsified cationic epoxy emulsion |
| CN110117458A (en) * | 2019-06-11 | 2019-08-13 | 浙江铭孚金属涂装科技有限公司 | A kind of preparation method and its application method of environment-friendly type cation electrophoretic coating lotion |
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| CN114907758A (en) * | 2022-05-17 | 2022-08-16 | 浙江伟星实业发展股份有限公司 | Napagi dermatoglyph paint and preparation method and application thereof |
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