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CN-122011877-A - Electrodepositable cationic emulsion and preparation method thereof

CN122011877ACN 122011877 ACN122011877 ACN 122011877ACN-122011877-A

Abstract

The invention discloses electrodepositable cationic emulsion which comprises, by mass, 16% -19% of epoxy resin, 4% -6% of polyether resin, 0.02-0.08% of a catalyst, 10-12% of a cross-linking agent, 2-6% of an acrylic copolymer, 2.8-3.6% of an amination reagent, 2-4% of an auxiliary agent, 0.2-2% of a first solvent, 0.1-0.4% of a neutralizing agent and the balance of pure water. The invention adopts the emulsion and pigment slurry to form the working solution of the electrophoretic paint, and the working solution of the electrophoretic paint can obviously reduce the generation of flow marks in the coating construction process, thereby eliminating coating defects caused by the flow marks and additional polishing afterwards, and greatly improving the production quality and reducing the production time and the cost in the recoating process.

Inventors

  • WANG JINGQIANG
  • ZUO HAN
  • XU YIDING
  • ZHANG ZIJIAN

Assignees

  • 上海金力泰化工股份有限公司

Dates

Publication Date
20260512
Application Date
20260116

Claims (10)

  1. 1. The electrodepositable cationic emulsion is characterized by comprising, by mass, 16% -19% of epoxy resin, 4% -6% of polyether resin, 10% -12% of a cross-linking agent, 2% -6.5% of an acrylic copolymer, 2.8% -3.6% of an amination reagent, 2% -4% of an auxiliary agent, 0.2% -2% of a first solvent, 0.1% -0.4% of a neutralizing agent and the balance of pure water.
  2. 2. The electrodepositable cationic emulsion of claim 1 wherein said acrylic copolymer is obtained by free radical polymerization and comprises, by mass, 28-32% of a second solvent, 3-15% of styrene, 9-12% of hydroxypropyl methacrylate, 23-35% of isooctyl methacrylate, 19-23% of glycidyl methacrylate, and 1-2% of an initiator.
  3. 3. The electrodepositable cationic emulsion of claim 2 wherein said second solvent is selected from the group consisting of propylene glycol methyl ether, methyl isobutyl ketone, and ethylene glycol butyl ether; The initiator is selected from any one or a combination of a plurality of benzoyl peroxide, di-tert-butyl peroxide or di-tert-amyl peroxide.
  4. 4. Electrodepositable cationic emulsion according to claim 1 or 2, characterized in that the glass transition temperature of the acrylic copolymer is 15-30 ℃.
  5. 5. Electrodepositable cationic emulsion according to claim 1 or 2, characterized in that the mass percentage of acrylic copolymer is 2-4.03% or 4.03-6.45%.
  6. 6. The electrodepositable cationic emulsion of claim 1, wherein said polyether resin is a bisphenol a polyoxyethylene ether polymer; The epoxy resin is obtained by chain extension of small molecular epoxy resin and bisphenol A under the action of a catalyst at the temperature of 140-160 ℃, the mass fraction of the small molecular epoxy resin in the electrodepositable cationic emulsion is 16-19%, the mass fraction of the bisphenol A in the electrodepositable cationic emulsion is 4-6%, and the mass fraction of the catalyst in the electrodepositable cationic emulsion is 0.02-0.08%; The catalyst is selected from one or more of N, N-dimethylbenzylamine, tetrabutylammonium bromide, tetraethylammonium bromide or triphenylphosphine.
  7. 7. The electrodepositable cationic emulsion of claim 1, wherein said crosslinker is a fully blocked addition reaction product of a polyisocyanate; The auxiliary agent is one or more of polyether polyol leveling auxiliary agent, polyacetal film forming auxiliary agent, microgel shrinkage-resistant auxiliary agent or rosin acid drier; the amination reagent is selected from any one or more of diethanolamine, methyl monoethanolamine, dimethylaminopropylamine, diethylenetriamine or ketimine of polyethylene polyamine; the first solvent is selected from any one or a combination of a plurality of ethylene glycol butyl ether, diethylene glycol butyl ether, ethylene glycol monohexyl ether and ethylene glycol isooctyl ether; the neutralizer is any one or more of lactic acid, sulfamic acid, formic acid, methanesulfonic acid or salicylic acid.
  8. 8. A method of preparing an electrodepositable cationic emulsion according to any one of claims 6 to 7, comprising: Adding epoxy resin and polyether resin into a reaction bottle, heating to 130-150 ℃ under the protection of nitrogen and stirring, then adding a catalyst, reacting for 2-4 hours at 140-160 ℃, detecting that the epoxy equivalent reaches 1140-1160, adding an acrylic copolymer and a cross-linking agent, cooling to 100-120 ℃, adding an amination reagent, and reacting for 2-3 hours at 100-130 ℃; B, mixing the neutralizer and 1/5 of pure water into acid water base material for standby; And C, adding a solvent to cool the materials in the reaction bottle after the reaction in the step A is finished, adding an acid water base material to stir uniformly after the temperature is cooled to below 100 ℃, and then adding the rest 4/5 pure water into the reaction bottle under stirring to form electrodepositable cationic emulsion.
  9. 9. The preparation method of the electrodepositable cationic emulsion according to claim 8, wherein the preparation method of the cross-linking agent is characterized in that polyisocyanate monomers and methyl isobutyl ketone are put into a reaction bottle, the temperature is raised to 55-65 ℃ under the protection of nitrogen under the stirring state, a dibutyltin dilaurate catalyst is added, the temperature is stabilized to 60+/-2 ℃, a dropping funnel is used for slowly dropping ethylene glycol butyl ether to dissolve the blocking agent into a transparent mixed solution, the dropping is finished for 2-3 hours, after the dropping is finished, trimethylolpropane is added after the heat preservation is carried out for 3 hours, the temperature is raised to 90-100 ℃, the heat preservation is carried out until NCO groups disappear, and the cross-linking agent is obtained for standby.
  10. 10. The preparation method of the electrodepositable cationic emulsion according to claim 8, wherein the preparation method of the acrylic copolymer is characterized in that monomer styrene, hydroxypropyl methacrylate, isooctyl methacrylate, glycidyl methacrylate and 99.3% of initiator are uniformly mixed in advance to obtain a mixture, then 1/2 amount of second solvent is added into a reaction bottle, the mixture is added dropwise by using a dropping funnel under the protection of nitrogen gas, 3-4h of dropwise addition is finished, the temperature is kept for 2.5-3.5h after dropwise addition is finished, then the mixture of the rest second solvent and the initiator is added at one time, the temperature is kept at 120-130 ℃ for 1.5-2.5h, and the solid content is 65-75% of acrylic copolymer is obtained after cooling.

Description

Electrodepositable cationic emulsion and preparation method thereof Technical Field The invention belongs to the technical field of cathode electrophoretic coating, and particularly relates to electrodepositable cationic emulsion and a preparation method thereof. Background The cathode electrophoretic coating has the characteristics of good corrosion resistance, high electrophoretic permeability, small environmental pollution and the like, and is favored, and at present, the domestic automobile body electrophoretic coating almost completely adopts the cathode electrophoretic coating. However, on the electrophoretic coating line, due to the complex structure of the vehicle body and parts, the electrophoretic bath liquid remained in the lap joint gap and the cavity concave body cannot be removed by normal draining and blowing processes. Residual bath liquid is continuously gathered during baking, and overflows from a crack or an inner cavity to the surface of a workpiece to form paint film flow mark defects. The subsequent working section needs to carry out additional working procedures such as grinding, polishing, even recoating and the like, so that an electrophoretic paint film is damaged, the corrosion resistance of the paint film is reduced, the production labor cost is increased, and the potential quality risk is also caused. It is therefore desirable to provide an emulsion for an electrocoat that reduces flow mark defects during a coating application process. Disclosure of Invention In view of the above, the invention provides an emulsion for electrodepositable electrophoretic paint and a preparation method thereof, and the emulsion and pigment slurry are combined to form a working solution of the electrophoretic paint, which can obviously reduce the generation of flow marks in the coating construction process, thereby eliminating coating defects caused by the flow marks and extra polishing afterwards, and greatly improving the production quality and reducing the production time and cost in the recoating process. In order to achieve the above purpose, the technical scheme of the invention is as follows: The invention provides electrodepositable cationic emulsion, which comprises, by mass, 16% -19% of epoxy resin, 4% -6% of polyether resin, 10% -12% of a cross-linking agent, 2% -6.5% of an acrylic copolymer, 2.8% -3.6% of an amination reagent, 2% -4% of an auxiliary agent, 0.2% -2% of a first solvent, 0.1% -0.4% of a neutralizing agent and the balance of pure water. Preferably, the acrylic copolymer is obtained by free radical polymerization, and comprises, by mass, 28-32% of a second solvent, 3-15% of styrene, 9-12% of hydroxypropyl methacrylate, 23-35% of isooctyl methacrylate, 19-23% of glycidyl methacrylate and 1-2% of an initiator. Preferably, the second solvent is any one or a combination of a plurality of propylene glycol methyl ether, methyl isobutyl ketone or ethylene glycol butyl ether; The initiator is selected from any one or a combination of a plurality of benzoyl peroxide, di-tert-butyl peroxide or di-tert-amyl peroxide. Preferably, the glass transition temperature of the acrylic acid copolymer is 15-30 ℃, the glass transition temperature of the acrylic acid copolymer needs to be strictly controlled, the appearance of a subsequent electrophoretic paint film is poor if the glass transition temperature of the acrylic acid copolymer is too high, the flow mark reduction effect of the electrophoretic paint working solution in the coating construction process is not obvious if the glass transition temperature of the acrylic acid copolymer is too low, the flow mark of the electrophoretic paint working solution in the coating construction process in the required range is obviously reduced, and the appearance of a paint film in the later period is attractive. Preferably, the mass percentage of the acrylic acid copolymer is 2-4.03% or 4.03-6.45%, the mass percentage of the acrylic acid copolymer needs to be strictly controlled, the addition amount of the acrylic acid copolymer is less than 2%, the problem of flow marks in the coating construction process cannot be solved, and the problem of the flow marks cannot be obviously reduced when the addition amount exceeds 6.5%. Preferably, the polyether resin is bisphenol a polyoxyethylene ether polymer. Preferably, the epoxy resin is obtained by chain extension of small molecular epoxy resin and bisphenol A under the action of a catalyst at 140-160 ℃, the mass fraction of the small molecular epoxy resin in the electrodepositable cationic emulsion is 16-19%, the mass fraction of the bisphenol A in the electrodepositable cationic emulsion is 4-6%, and the mass fraction of the catalyst in the electrodepositable cationic emulsion is 0.02-0.08%. Preferably, the catalyst is selected from any one or more of N, N-dimethylbenzylamine, tetrabutylammonium bromide, tetraethylammonium bromide and triphenylphosphine. Preferably, the crosslinker is a fully blocked addit