CN109384936B - Carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, cathode polyurethane electrophoretic paint and preparation methods thereof - Google Patents

Carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, cathode polyurethane electrophoretic paint and preparation methods thereof Download PDF

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CN109384936B
CN109384936B CN201811123586.5A CN201811123586A CN109384936B CN 109384936 B CN109384936 B CN 109384936B CN 201811123586 A CN201811123586 A CN 201811123586A CN 109384936 B CN109384936 B CN 109384936B
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polyurethane
resin
hydroxyl
electrophoretic
polyurethane electrophoretic
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CN109384936A (en
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李再峰
李再胜
张闯
李子健
李金�
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Qingdao University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G83/00—Macromolecular compounds not provided for in groups C08G2/00 - C08G81/00
    • C08G83/001—Macromolecular compounds containing organic and inorganic sequences, e.g. organic polymers grafted onto silica
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D187/00—Coating compositions based on unspecified macromolecular compounds, obtained otherwise than by polymerisation reactions only involving unsaturated carbon-to-carbon bonds
    • C09D187/005—Block or graft polymers not provided for in groups C09D101/00 - C09D185/04
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
    • C09D5/4476—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications comprising polymerisation in situ

Abstract

The invention provides a carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin, a cathode polyurethane electrophoretic paint and a preparation method thereof, belongs to the technical field of carbon nano tube grafting modification, can solve the technical problem that carbon nano tubes are easy to agglomerate in a water-based polymer matrix, and improves the stability and dispersion uniformity of the carbon nano tubes in water-based resin, thereby improving the mechanical property and functionality of the water-based polyurethane resin. The carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin is prepared by proportionally reacting oligomer polyol, trimethylolpropane, diisocyanate, hydroxyl carbon nanotubes, epoxy resin, a hydrophilic agent, a chain extender and a neutralization salt forming agent. The invention can be applied to the preparation of polyurethane paint film, the obtained paint film has excellent water resistance, acid resistance, conductivity and high hardness, the brightness and fullness of the polyurethane electrophoretic paint are more than 90, the hardness is more than 5H, the acid resistance reaches 46H, the water resistance is more than 4608H, the conductivity of the paint film can reach 8.29 multiplied by 10‑3S/cm。

Description

Carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, cathode polyurethane electrophoretic paint and preparation methods thereof
Technical Field
The invention belongs to the technical field of carbon nanotube grafting modification, and particularly relates to a carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, a cathode polyurethane electrophoretic paint and preparation methods thereof.
Background
With the continuous improvement of the performance index of the polyurethane electrophoretic paint in the market, the structural modification of the polyurethane resin by the methods of polyurethane internal crosslinking, polyurethane external crosslinking, two-dimensional sheet silicate particle compounding, epoxy resin grafting and the like is carried out successively. However, when the polyurethane electrophoretic paint with the conductive function is required, the conventional polyurethane electrophoretic paint cannot meet the application requirements.
At present, carbon nanotubes are reported to be particles with excellent electric and thermal conductivity, and the preparation of composite materials by hybridization of polymers and carbon nanotube nano-materials is one of the research hotspots in the field of material science. Carbon nano-meterThe conductivity of the tube can reach 1000-2000S-cm-1Compared with common inorganic filler, the carbon nano tube not only has the function of electric conduction, but also has better reinforcing and toughening effects on polymers, and is widely applied to a plurality of fields.
The polyurethane/carbon nanotube composite polyurethane material reported in the literature usually uses a physical blending method to realize hybrid composite of polyurethane and carbon nanotubes, or compounds carbon nanotubes and polyurethane through a coupling agent, and the existing composite technology does not solve the scientific and technical problems of non-uniform dispersion and easy agglomeration of carbon nanotubes in a polymer matrix, thereby affecting the dispersion uniformity of the carbon nanotubes in the composite material and reducing the modification effect of the carbon nanotubes on the mechanical properties and functionality of the polyurethane composite material. In addition, the modification of the carbon nano tube to the polymer is mainly focused on the aspect of composite modification of solid materials at present, the preparation of the water-based nano hybrid polyurethane coating is very little, and the main reason is that the density of the carbon nano tube is higher than that of the water-based polyurethane resin emulsion, and the carbon nano tube is easy to settle and unstable in the water-based polyurethane resin and cannot achieve the nano hybrid effect of the carbon nano tube.
Disclosure of Invention
The invention provides a carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin, a cathode polyurethane electrophoretic paint and a preparation method thereof, the obtained polyurethane electrophoretic resin solves the technical problem that the carbon nano tube is easy to agglomerate in a water-based polymer matrix, and improves the stability and the dispersion uniformity of the carbon nano tube in the water-based resin, thereby improving the mechanical property and the functionality of the water-based polyurethane resin.
In order to achieve the aim, the invention provides a carbon nanotube-grafted hydroxyl-terminated polyurethane electrophoretic resin which is prepared from the following raw materials in percentage by weight:
Figure BDA0001811887930000021
preferably, the oligomer polyol is a polycarbonate diol, a polycaprolactone diol, or a mixture thereof, and the oligomer polyol has a relative molecular weight of 500-.
Preferably, the diisocyanate is isophorone diisocyanate, toluene diisocyanate, or a mixture thereof.
Preferably, the hydrophilic agent is at least one of N-methyldiethanolamine and triethanolamine; the epoxy resin is E-44 epoxy resin; the chain extender is neopentyl glycol; the neutralization salt forming agent is lactic acid, oxalic acid or tartaric acid.
The invention also provides a preparation method of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, which comprises the following steps:
drying hydroxyl carbon nanotubes in vacuum at the temperature of 100-120 ℃, mixing the hydroxyl carbon nanotubes with toluene diisocyanate, carrying out ultrasonic reaction at the temperature of 60-80 ℃, then centrifuging at a high speed to obtain activated carbon nanotubes modified by oil-soluble isocyanate groups, dissolving the activated carbon nanotubes in isophorone diisocyanate, and uniformly mixing to obtain a mixture of the isocyanate-modified carbon nanotubes and isophorone diisocyanate;
dehydrating oligomer polyalcohol and trimethylolpropane, and then adding a mixture of an isocyanic acid radical modified carbon nano tube and isophorone diisocyanate to carry out polymerization reaction;
adding a hydrophilic agent into the polymerization reaction system in the presence of a solvent for reaction at the temperature of 30-50 ℃ for 2-4 h;
continuously adding a chain extender and epoxy resin into the reaction system in the presence of a solvent for reaction at the temperature of 70-90 ℃ for 2-4 h;
and continuously adding a neutralization salt forming agent into the reaction system for reaction at the temperature of 10-40 ℃ for 0.5-2h to obtain the carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin.
Preferably, the dehydration treatment temperature is 100-120 ℃, and the dehydration treatment time is 1.0-1.5 h; the polymerization temperature is 50-70 ℃, and the polymerization time is 2-3 h.
Preferably, the solvent is at least one of 1, 4-dioxane, N-methylpyrrolidone, ethylene glycol butyl ether, and N, N-dimethylformamide.
Preferably, an organotin or organolead-based catalyst is added to the polymerization reaction system when a hydrophilic agent is added to the polymerization reaction system.
The invention also provides a cathode polyurethane electrophoretic paint which is prepared from the following raw materials in percentage by mass:
the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin according to the technical scheme comprises the following components: 24.5 to 26.4 percent
Cationic water-dispersible blocked isocyanate: 6.6 to 7.0 percent
Propylene glycol phenyl ether: 0.73 to 0.74 percent
Deionized water: 65.9 to 68.1 percent.
Preferably, the cationic water-dispersible blocked isocyanate and the propylene glycol phenyl ether are added into the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin according to the technical scheme, mixed and stirred, emulsified and sheared by deionized water to obtain the polyurethane electrodeposition coating, and the polyurethane electrodeposition coating is subjected to film forming by an electrophoresis coating process, baking and secondary crosslinking baking to form a film.
Compared with the prior art, the invention has the advantages and positive effects that:
1. according to the invention, when the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin is prepared, multi-step stepwise polymerization reaction is adopted, and the reaction does not involve the generation of small molecules such as wastewater and waste gas, so that the method is safe, environment-friendly and environment-friendly;
2. reacting a plurality of hydroxyl functional groups on the carbon nano tube with diisocyanate to prepare an isocyanate modified activated carbon nano tube, and dissolving the activated carbon nano tube and isophorone to form a nano hybrid mixed isocyanate mixture;
3. in-situ polymerization is adopted to graft the carbon nano tube to the molecular main chain of polyurethane, so that the macromolecular chain coating of the carbon nano tube is finished after the polyurethane macromolecule peels off the carbon nano tube, the sedimentation phenomenon caused by self-assembly aggregation of the carbon nano tube is reduced, the stability of the polyurethane/carbon nano tube composite electrodeposition resin is improved, the common technical problem of sedimentation of the carbon nano tube in water-based resin is solved, the nano effect of the carbon nano tube can be fully exerted, and the comprehensive performance of the polyurethane electrodeposition coating is improved;
4. the hydroxyl-terminated polyurethane nano hybrid electrodeposition resin grafted by the cationic water dispersible blocked isocyanate and the carbon nano tube can be mixed and exist stably in any proportion, the phenomenon of precipitation is avoided after emulsification in water, the blocked isocyanate can deblock an isocyanato (-NCO) functional group at high temperature under high-temperature baking of an obtained electrophoresis paint film, and the blocked isocyanate and the hydroxyl in the resin are subjected to chemical crosslinking reaction, so that the chemical corrosion resistance of the polyurethane paint film is improved;
5. the paint film formed by curing the polyurethane electrophoretic paint has excellent water resistance, acid resistance, conductivity and high hardness, the brightness and fullness of the polyurethane electrophoretic paint are more than 90, the hardness is more than 5H, the acid resistance reaches 46H, the water resistance is more than 4608H, and the conductivity of the paint film can reach 8.29 multiplied by 10-3S/cm。
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin which is prepared from the following raw materials in percentage by mass:
Figure BDA0001811887930000041
Figure BDA0001811887930000051
the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin provided by the embodiment of the invention utilizes toluene diisocyanate to perform reaction modification on the hydroxyl carbon nanotube, so as to prepare the carbon nanotube modified by isocyanate group reaction. The surface of the prepared carbon nano tube has reactive isocyanate active functional groups, so the carbon nano tube can be chemically connected with a molecular main chain of polyurethane through chemical reaction by using an in-situ polymerization method to form the novel polyurethane/carbon nano tube composite electrodeposition resin of the carbon nano tube grafted macromolecular main chain, the technical problem that the carbon nano tube is easy to settle in water-based resin is better solved, the stability of the carbon nano tube hybrid electrodeposition coating can be effectively improved, the comprehensive properties of a subsequently prepared water-based polyurethane coating film, such as hardness, wear resistance, chemical resistance, water resistance, acid resistance and mechanical properties, and the polyurethane electrodeposition coating film is endowed with good conductivity and antistatic property.
In an alternative embodiment, the oligomer polyol is a polycarbonate diol, a polycaprolactone diol, or a mixture thereof, and the oligomer polyol has a relative molecular weight of 500-2000, preferably a relative molecular weight of 1000. In an alternative embodiment, the diisocyanate is isophorone diisocyanate, toluene diisocyanate, or a mixture thereof. In an alternative embodiment, the hydrophilic agent is at least one of N-methyldiethanolamine and triethanolamine; the epoxy resin is E-44 epoxy resin; the chain extender is neopentyl glycol; the neutralization salt forming agent is lactic acid, oxalic acid or tartaric acid.
The above examples specifically define the oligomer polyol, diisocyanate, hydrophilic agent, chain extender, epoxy resin and neutralizing salt former for use in the reaction to ensure that the desired properties are achieved. It will be understood that, in principle, a person skilled in the art could reasonably substitute the substances listed in the above examples on the basis of common knowledge, but after many verifications, it was found that the combination of the substitution could not be compared with the product obtained in the present application and the properties of the electrophoretic paint prepared.
The invention also provides a preparation method of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, which comprises the following steps:
s1: drying hydroxyl carbon nanotubes in vacuum at the temperature of 100-120 ℃, mixing the hydroxyl carbon nanotubes with toluene diisocyanate, carrying out ultrasonic reaction at the temperature of 60-80 ℃, then centrifuging at a high speed to obtain activated carbon nanotubes modified by oil-soluble isocyanate groups, dissolving the activated carbon nanotubes in isophorone diisocyanate, and uniformly mixing to obtain a mixture of the isocyanate-modified carbon nanotubes and isophorone diisocyanate;
in the step, the hydroxyl carbon nano tube is dried firstly, the purpose is to remove the absorbed water with hydrogen bonding effect, and the drying time can be 2-3h for full drying, and can be adjusted according to the actual condition. And then, toluene diisocyanate is used for carrying out reaction modification on the hydroxyl carbon nano tube to prepare the carbon nano tube modified by the isocyanate group reaction. The surface of the prepared carbon nano tube has reactive isocyanate active functional groups, so the carbon nano tube can be chemically connected with a molecular main chain of polyurethane through chemical reaction by using an in-situ polymerization method to form the novel polyurethane/carbon nano tube composite electrodeposition resin of the carbon nano tube grafted macromolecular main chain, the technical problem that the carbon nano tube is easy to settle in water-based polyurethane resin is well solved, and the stability of the carbon nano tube hybrid electrodeposition coating is improved.
S2: dehydrating oligomer polyalcohol and trimethylolpropane, and then adding a mixture of an isocyanic acid radical modified carbon nano tube and isophorone diisocyanate to carry out polymerization reaction;
in the step, the hydroxyl-terminated polymer is easy to absorb water molecules in the air due to hydrogen bonding, the water molecules must be removed in vacuum at high temperature in the first step process, otherwise, a small amount of water molecules cause the reaction of the polyol mixture and the diisocyanate mixture to fail due to the cross-linking reaction, and the next step of gradual polymerization chain extension reaction cannot be carried out. In order to ensure sufficient dehydration between the oligomer polyol and the trimethylolpropane, in a preferred embodiment, the dehydration treatment temperature is 100-120 ℃, and the dehydration treatment time is 1.0-1.5 h; the polymerization temperature is 50-70 ℃, and the polymerization time is 2-3 h. The person skilled in the art can adjust the dehydration, polymerization temperature and time by adjusting them as desired, within the ranges given above or by adjusting them as desired, so long as both dehydration and polymerization are sufficiently carried out.
S3: adding a hydrophilic agent into the polymerization reaction system in the presence of a solvent for reaction at the temperature of 30-50 ℃ for 2-4 h;
in the step, the hydrophilic chain extender is added, so that the gradual polymerization chain extension reaction can be carried out on the hydrophilic chain extender and the prepolymer prepared in the step S2, and hydrophilic functional group tertiary nitrogen atoms are introduced into the polyurethane macromolecular main chain, so that the synthesized carbon nanotube hybrid polymer can be ensured to be self-emulsified and dispersed in water. It is to be understood that the limitation of the reaction temperature and time of the above reaction system may be variably adjusted by those skilled in the art within the above range or according to the above range according to actual circumstances, as long as the reaction is sufficiently performed. In addition, in an alternative embodiment, an organic tin or organic lead catalyst can be added into the reaction system, so that the reaction can be successfully carried out at a low temperature, and a designed composition can be prepared.
S4: under the condition of solvent, continuously adding a chain extender and epoxy resin into the reaction system for reaction, wherein the reaction temperature is 70-90 ℃, and the reaction time is 2-4 h;
in the step, the hydrophilic chain extender is subjected to gradual polymerization chain extension reaction at low temperature to complete the chain extension effect of macromolecules, and the hydrophilic functional groups are introduced into the macromolecule chains to make the polymer possibly dispersed in water. The epoxy resin also plays a role in chain extension or grafting, and the existence of the epoxy molecular structure improves the acid and alkali resistance and the water resistance of the polyurethane resin. It should be noted that, in this step, both the chain extender and the epoxy resin are specifically defined, where the chain extender is neopentyl glycol, and the epoxy resin is E-44 epoxy resin, so that the neopentyl glycol chain extender can be ensured to play a role in improving the flexibility of the polyurethane paint film.
S5: and continuously adding a neutralization salt forming agent into the reaction system for reaction at the temperature of 10-40 ℃ for 0.5-2h to obtain the carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin.
In the step, the acid salt agent is added to neutralize hydrogen protons and tertiary nitrogen atom acid and base to form salt, so that the polyurethane resin has stronger hydrophilic capacity, and the polyurethane resin can be fully emulsified and dispersed in water by using less hydrophilic agent. It is to be understood that the limitation of the reaction temperature and time of the above reaction system may be variably adjusted by those skilled in the art within the above range or according to the above range according to actual circumstances, as long as the reaction is sufficiently performed. In addition, in the above step, the solvent is at least one of 1, 4-dioxane, N-methylpyrrolidone, ethylene glycol butyl ether and N, N-dimethylformamide, and these solvents are all easily soluble in water, can be preferably used in the system, and 1, 4-dioxane is preferable in view of potential effects on human health. The embodiment of the invention also provides the electrophoretic paint which is prepared from the following raw materials in percentage by weight: carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin: 24.5% -26.4%, cationic water dispersible blocked isocyanate: 6.6% -7.0%, propylene glycol phenyl ether: 0.73% -0.74%, deionized water: 65.9 to 68.1 percent.
In an optional embodiment, the cationic water-dispersible blocked isocyanate and the propylene glycol phenyl ether are added into the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin according to the technical scheme, mixed and stirred, emulsified and sheared by deionized water to obtain the polyurethane electrodeposition coating, and the polyurethane electrodeposition coating is subjected to an electrophoresis coating process to form a film, is baked, and is subjected to secondary crosslinking baking to form the film.
The cathode polyurethane electrophoretic paint and the preparation method thereof provided by the embodiment adopt the water dispersible blocked isocyanate and the hydroxyl-terminated polyurethane nano hybrid electrodeposition resin grafted by the carbon nano tube, can be stably mixed in any proportion, have no precipitation phenomenon after emulsification in water, and can deblock the blocked isocyanate to form an isocyanate-NCO functional group at high temperature of the obtained electrophoretic paint, and generate a chemical crosslinking reaction with hydroxyl in the resin, so that the chemical corrosion resistance of a polyurethane paint film is effectively improved. The obtained paint film has excellent propertiesWater resistance, acid resistance, electric conductivity and high hardness, the brightness and fullness of the polyurethane electrophoretic paint are more than 90, the hardness is more than 5H, the acid resistance reaches 46H, the water resistance is more than 4608H, and the electric conductivity of the paint film can reach 8.29 multiplied by 10-3S/cm。
It will be understood that, according to the core idea of the present invention, this is achieved not only by preparing cathodic polyurethane electrophoretic paint films based on cationic electrodeposition paints, but also by preparing anodic polyurethane electrophoretic paint films based on anionic electrodeposition paints. Specifically, when the anionic electrodeposition coating is prepared, the cationic water-dispersible blocked isocyanate used in the preparation of the cathode polyurethane electrophoretic paint film is replaced by the anionic water-dispersible blocked isocyanate when the anode polyurethane electrophoretic paint film is further prepared, and the anode polyurethane electrophoretic paint film can be prepared on the premise that other conditions are not changed. The preparation process of the anode polyurethane electrophoretic paint film prepared based on the method is easy to control, the reaction is stable, and the method is mainly used for electrophoretic coating of aluminum profiles.
In order to more clearly and specifically describe the carbon nanotube-grafted hydroxyl-terminated polyurethane electrophoretic resin, the cathode polyurethane electrophoretic paint and the preparation method thereof according to the embodiments of the present invention, the following description will be given with reference to specific examples.
Example 1
Taking 11.1g of polycarbonate diol and 1.0g of trimethylolpropane, and dehydrating for 1h at 90 ℃; adding 44.7g of a mixture containing 0.3g of isocyanate modified carbon nano tube and isophorone diisocyanate into the reaction in the previous step, and reacting for 2 hours at 80 ℃; then adding 13.5g N-methyldiethanolamine in the presence of 1, 4-dioxane serving as a solvent, and reacting for 2 hours at 40 ℃; then adding 4.8g of epoxy resin and 9.8g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction for 2 hours at 80 ℃; and finally, cooling to 30 ℃, adding 6.8g of glacial acetic acid, 6g of n-butyl alcohol and 12g of butyl glycol ether for neutralization reaction for 1h to obtain the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin.
And adding 11.1g of cationic water dispersible blocked isocyanate and 1.4g of propylene glycol phenyl ether into 48g of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing in water, forming a film through electrodeposition, baking in an oven at 80 ℃ for 30min, heating to 140 ℃, keeping for 1h, and performing secondary crosslinking to obtain the electrophoretic paint.
Example 2
Taking 13.9g of polycarbonate diol and 1.2g of trimethylolpropane, and dehydrating for 1h at 90 ℃; adding 55.9g of a mixture containing 0.75g of isocyanate modified carbon nano tube and isophorone diisocyanate into the reaction in the previous step, and reacting for 2 hours at 80 ℃; then adding 16.9g N-methyldiethanolamine in the presence of 1, 4-dioxane serving as a solvent, and reacting for 2 hours at 40 ℃; then adding 6.1g of epoxy resin and 12.3g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction for 2 hours at 80 ℃; and finally, cooling to 30 ℃, adding 8.5g of glacial acetic acid, 7.5g of n-butyl alcohol and 15g of ethylene glycol butyl ether for neutralization reaction for 1h to obtain the carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin.
And then taking 60g of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, adding 14.13g of cationic water dispersible blocked isocyanate and 1.8g of propylene glycol phenyl ether into the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing the mixture in water, forming a film through electrodeposition, baking the film in an oven at the temperature of 80 ℃ for 30min, heating the film to 140 ℃, keeping the temperature for 1h, and carrying out secondary crosslinking to obtain the electrophoretic paint.
Example 3
Taking 16.70g of polycarbonate diol and 1.5g of trimethylolpropane, and dehydrating for 1h at 90 ℃; taking a mixture containing 1.4g of isocyanate modified carbon nano tube and isophorone diisocyanate, adding 67.1g of isophorone diisocyanate into the mixture, and reacting the mixture in the reaction of the previous step at 80 ℃ for 2 h; then adding 20.2g of N-methyldiethanolamine in the presence of a solvent 1, 4-dioxane, and reacting for 2 hours at 40 ℃; then adding 7.3g of epoxy resin and 14.8g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction for 2 hours at 80 ℃; and finally, cooling to 30 ℃, adding 10.2g of glacial acetic acid, 9g of n-butyl alcohol and 18g of ethylene glycol butyl ether for neutralization reaction for 1h to obtain the carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin.
And then taking 72g of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, adding 16.6g of cationic water dispersible blocked isocyanate and 2.2g of propylene glycol phenyl ether into the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing the mixture in water, forming a film through electrodeposition, baking the film in an oven at the temperature of 80 ℃ for 30min, heating the film to 140 ℃ and keeping the temperature for 1h, and carrying out secondary crosslinking to obtain the electrophoretic paint.
Example 4
17.6g of polycarbonate diol and 1.6g of trimethylolpropane are taken and dehydrated for 1h at the temperature of 90 ℃; adding 70.8g of a mixture containing 1.9g of the carbon nano tube modified by the isocyanate group and the isophorone diisocyanate into the reaction in the previous step, and reacting for 2 hours at 80 ℃; then in the presence of a solvent 1, 4-dioxane, adding 21.4g of N-methyldiethanolamine, and reacting for 2 hours at 40 ℃; adding 7.714g of epoxy resin and 15.6g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction at 80 ℃ for 2 hours; and finally, cooling to 30 ℃, adding 10.8g of glacial acetic acid, 9.5g of n-butyl alcohol and 19g of butyl glycol ether, and neutralizing for 1h to obtain the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin.
And taking 76g of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, adding 17.6g of cationic water dispersible blocked isocyanate and 2.3g of propylene glycol phenyl ether into the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing the mixture in water, forming a film through electrodeposition, baking the film in an oven at the temperature of 80 ℃ for 30min, heating to 140 ℃ and keeping for 1h, and carrying out secondary crosslinking to obtain the electrophoretic paint.
Example 5
Taking 18.6g of polycarbonate diol and 1.7g of trimethylolpropane, and dehydrating for 1h at 90 ℃; adding 74.5g of a mixture containing 2.5g of the carbon nano tube modified by the isocyanate group and the isophorone diisocyanate into the reaction in the previous step, and reacting for 2 hours at 80 ℃; then adding 22.5g of N-methyldiethanolamine in the presence of a solvent 1, 4-dioxane, and reacting for 2 hours at 40 ℃; then adding 8.1g of epoxy resin and 16.4g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction for 2 hours at 80 ℃; and finally, cooling to 30 ℃, adding 11.3g of glacial acetic acid, 10g of n-butyl alcohol and 20g of ethylene glycol butyl ether, and carrying out neutralization reaction for 1h to obtain the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin.
And adding 18.5g of cationic water dispersible blocked isocyanate and 2.4g of propylene glycol phenyl ether into 80g of the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing in water, forming a film through electrodeposition, baking in an oven at 80 ℃ for 30min, heating to 140 ℃, keeping for 1h, and performing secondary crosslinking to obtain the electrophoretic paint.
Comparative example 1
9.3g of polycarbonate diol and 0.83g of trimethylolpropane are taken and dehydrated for 1h at the temperature of 90 ℃; 37.2g of isophorone diisocyanate were added. Reacting for 2 hours at 80 ℃; then adding 11.2g N-methyldiethanolamine in the presence of a solvent 1, 4-dioxane, and reacting for 2 hours at 40 ℃; then adding 4.1g of epoxy resin and 8.2g of neopentyl glycol in the presence of a solvent 1, 4-dioxane, and carrying out chain extension reaction for 2 hours at 80 ℃; and finally, cooling to 30 ℃, adding 5.6g of lactic acid, 5g of n-butyl alcohol and 10g of ethylene glycol monomethyl ether for neutralization reaction for 1h to obtain the hydroxyl-terminated polyurethane electrophoretic resin.
And then taking 40g of the hydroxyl-terminated polyurethane electrophoretic resin, adding 9.42g of cationic water dispersible blocked isocyanate and 1.2g of propylene glycol phenyl ether into the hydroxyl-terminated polyurethane electrophoretic resin, emulsifying and shearing the mixture in water, forming a film through electrodeposition, baking the film in an oven at the temperature of 80 ℃ for 30min, heating the film to the temperature of 140 ℃, keeping the temperature for 1h, and carrying out secondary crosslinking to obtain the electrophoretic paint.
Performance testing
The electrodeposition paints obtained in the above examples 1 to 5 and comparative example 1 were subjected to the following performance tests, and the results are shown in Table 1.
Gloss: the gloss of the paint films was tested according to GB/T9754-2007 using a WGG Portable mirror gloss Meter.
Pencil hardness: the hardness of the paint film was tested with a pencil hardness meter according to GB/T6739-2006.
Water resistance: the water resistance of the paint film was tested with reference to the test method 4761-2014 waterborne polyurethane coating.
Acid resistance: according to GB/T9274-1988, the paint film is soaked in a hydrochloric acid solution with the mass fraction of 5% until the surface of the paint film shows a whitening sign, and the time taken for the paint film to whiten is recorded.
Conductivity: the conductivity of the paint films was measured using a Ransburg, U.S. 76652-03 conductivity meter.
TABLE 1 comparison of the Properties of the electrodeposition paints obtained in examples 1 to 5 and comparative example 1
Figure BDA0001811887930000121
As can be seen from the data in Table 1, in the formula of the carbon nanotube hybrid polyurethane electrodeposition resin, compared with the blank formula in comparative example 1, the pencil hardness of the polyurethane paint film is increased from 4H to 5H, the key index of measuring the acid resistance of the cationic electrodeposition paint is also increased from 8H to 46H of the blank, and the coating performance of the paint film is greatly improved. Most importantly, the carbon nano tube is grafted on the molecular main chain of polyurethane, the polyurethane paint film is endowed with conductive functionality, the internal quality of the cathode polyurethane electrophoretic paint film is greatly improved by the nano effect of the carbon nano tube, and the market innovation of the polyurethane electrodeposition paint is improved.

Claims (7)

1. The cathode polyurethane electrophoretic paint is characterized by being prepared from the following raw materials in percentage by mass:
carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin: 24.5 to 26.4 percent
Cationic water-dispersible blocked isocyanate: 6.6 to 7.0 percent
Propylene glycol phenyl ether: 0.73 to 0.74 percent
Deionized water: 65.9% -68.1%;
the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin is prepared from the following raw materials in percentage by mass:
oligomer polyol 6.06% -17.24%
0 to 1.73 percent of trimethylolpropane
46.0 to 51.4 percent of diisocyanate
0.5 to 1.25 percent of hydroxyl carbon nano-tube
5.05 to 5.64 percent of epoxy resin
14.0 to 15.6 percent of hydrophilic agent
Chain extender 10.2% -11.4%
7.03% -7.85% of a neutralization salt forming agent;
the carbon nanotube grafted hydroxyl-terminated polyurethane electrophoretic resin is prepared by the following method:
drying hydroxyl carbon nanotubes in vacuum at the temperature of 100-120 ℃, mixing the hydroxyl carbon nanotubes with toluene diisocyanate, carrying out ultrasonic reaction at the temperature of 60-80 ℃, then centrifuging at a high speed to obtain activated carbon nanotubes modified by oil-soluble isocyanate groups, dissolving the activated carbon nanotubes in isophorone diisocyanate, and uniformly mixing to obtain a mixture of the isocyanate-modified carbon nanotubes and isophorone diisocyanate;
dehydrating oligomer polyalcohol and trimethylolpropane, and then adding a mixture of an isocyanic acid radical modified carbon nano tube and isophorone diisocyanate to carry out polymerization reaction;
adding a hydrophilic agent into the polymerization reaction system in the presence of a solvent for reaction at the temperature of 30-50 ℃ for 2-4 h;
continuously adding a chain extender and epoxy resin into the reaction system in the presence of a solvent for reaction at the temperature of 70-90 ℃ for 2-4 h;
and continuously adding a neutralization salt forming agent into the reaction system for reaction at the temperature of 10-40 ℃ for 0.5-2h to obtain the carbon nano tube grafted hydroxyl-terminated polyurethane electrophoretic resin.
2. The cathodic polyurethane electrophoretic paint as defined in claim 1, wherein the oligomer polyol is polycarbonate diol, polycaprolactone diol or a mixture thereof, and the relative molecular weight of the oligomer polyol is 500-.
3. The cathodic polyurethane electrophoretic paint according to claim 1, wherein the hydrophilic agent is at least one of N-methyldiethanolamine and triethanolamine; the epoxy resin is E-44 epoxy resin; the chain extender is neopentyl glycol; the neutralization salt forming agent is lactic acid, oxalic acid or tartaric acid.
4. The cathodic polyurethane electrophoretic paint as defined in claim 1, wherein the dehydration treatment temperature is 100-120 ℃, and the dehydration treatment time is 1.0-1.5 h; the polymerization temperature is 50-70 ℃, and the polymerization time is 2-3 h.
5. The cathodic polyurethane electrophoretic paint according to claim 1, wherein the solvent is at least one of 1, 4-dioxane, N-methylpyrrolidone, ethylene glycol butyl ether, and N, N-dimethylformamide.
6. The cathodic polyurethane electrophoretic paint according to claim 1, wherein an organotin or organolead-based catalyst is added to the polymerization reaction system when a hydrophilic agent is added to the polymerization reaction system.
7. The preparation method of the cathode polyurethane electrophoretic paint according to any one of claims 1 to 6, wherein the cationic water dispersible blocked isocyanate and the propylene glycol phenyl ether are added into the carbon nanotube branched hydroxyl-terminated polyurethane electrophoretic resin, mixed and stirred, and emulsified and sheared by deionized water to obtain the polyurethane electrodeposition paint, and the polyurethane electrodeposition paint is formed into a film by an electrophoretic coating process and baked for secondary crosslinking to obtain the electrophoretic paint.
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