CN110452362B - Water-based blocked isocyanate curing agent, preparation method thereof and water-based paint - Google Patents
Water-based blocked isocyanate curing agent, preparation method thereof and water-based paint Download PDFInfo
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/2805—Compounds having only one group containing active hydrogen
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- C08G18/00—Polymeric products of isocyanates or isothiocyanates
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- C08G18/792—Nitrogen characterised by the polyisocyanates used, these having groups formed by oligomerisation of isocyanates or isothiocyanates containing isocyanurate groups formed by oligomerisation of aliphatic and/or cycloaliphatic isocyanates or isothiocyanates
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Abstract
The invention relates to a water-based blocked isocyanate curing agent, a preparation method thereof and a water-based paint. The water-based blocked isocyanate curing agent comprises the following raw materials: polyisocyanate trimer, polyethylene glycol monomethyl ether, polyether diol, a sealing agent, a cosolvent, alkali metal alkoxide and a neutralizer; the polyisocyanate is selected from at least one of aliphatic polyisocyanate trimer and aromatic polyisocyanate trimer, the polyethylene glycol monomethyl ether is selected from one of polyethylene glycol ether monohydric alcohol with the molecular weight of 300-2000, and the polyether dihydric alcohol has the molecular weight of 120-1000. The water-based blocked isocyanate curing agent can react with resins with active groups such as amino resin, polyester resin and the like in a coating formula, and a large number of flexible chain segment structures are introduced into a coating film, so that the energy release of the coating film when the coating film is subjected to stone impact can be delayed, the stone impact resistance of the coating film is further improved, and the coating film has stone impact resistance under the condition of low film thickness.
Description
Technical Field
The invention relates to the technical field of coatings, and particularly relates to a water-based blocked isocyanate curing agent, a preparation method thereof and a water-based coating.
Background
With the technological progress and the high speed of transportation, automobiles are more and more popular, the automobile speed is greatly improved, great convenience is brought to people, and meanwhile, higher requirements are provided for the surface coating of the automobiles. When an automobile is used as an important outdoor vehicle, the surface coating of the automobile body may be impacted by heavy objects such as sliding materials and road surface broken stones during actual driving, so that the coating is peeled off. Therefore, the stone impact resistance of the automobile coating needs to be improved, so that the damage of the automobile coating caused by the impact of heavy objects such as road macadam and the like is reduced, and the automobile is protected.
At present, the traditional automobile coating is mainly solvent-based, and the thickness of a coating film is generally designed to be about 40 mu m, so that the aim of resisting stone impact can be achieved. However, the discharge of VOCs (volatile organic compounds) in the solvent-based paint is harmful to human bodies and the environment, and with the enhancement of environmental awareness and the establishment of environmental regulations, the traditional solvent-based paint is gradually eliminated due to the fact that the content of VOCs exceeds the standard and the coating film is thick. In recent years, new coating systems have been designed mostly around how to reduce VOCs, however, no significant improvement in the thickness of the coating film has been seen. For example, although the waterborne polyurethane primer surfacer solves the problems that the automotive primer surfacer mainly uses a solvent type paint and uses water as a solvent, and the pollution to the environment is obviously reduced, the waterborne polyurethane primer surfacer needs to increase the thickness of a coating film to achieve the corresponding required stone impact resistance, and the thickness of the coating film needs to be more than 80 μm, so that the production cost is greatly increased.
In summary, in consideration of various factors such as environmental protection, energy consumption and cost, various automobile manufacturers want to reduce the thickness of the coating film as much as possible on the premise of meeting the performance of various aspects of the coating film, so as to reduce the energy consumption and the cost, achieve the purposes of energy conservation and emission reduction, and provide higher requirements for the automobile coating film. Therefore, it is highly desirable to develop an auxiliary crosslinking curing agent having excellent stone-impact resistance under low film thickness conditions, so as to improve the stone-impact resistance of the automotive coating film under low film thickness conditions.
Disclosure of Invention
Based on the above, there is a need for a water-based blocked isocyanate curing agent capable of improving the stone-impact resistance of an automobile coating film.
A water-based blocked isocyanate curing agent comprises the following raw materials: polyisocyanate trimer, polyethylene glycol monomethyl ether, polyether diol, a sealing agent, a cosolvent, alkali metal alkoxide and a neutralizer;
the polyisocyanate trimer is at least one selected from aliphatic polyisocyanate trimer and aromatic polyisocyanate trimer, the polyethylene glycol monomethyl ether is one selected from polyethylene glycol ether monohydric alcohol with the molecular weight of 300-2000, and the polyether dihydric alcohol has the molecular weight of 120-1000.
According to the waterborne blocked isocyanate curing agent, the polyethylene glycol monomethyl ether, the polyether diol and the polyisocyanate trimer are subjected to hydrophilic modification and chain extension reaction to form a long-chain structure and have hydrophilicity, the blocking agent blocks an-NCO group, so that an isocyanate group is inactive at normal temperature, blocking of the isocyanate group is realized, and further the waterborne blocked isocyanate curing agent is obtained.
In order to better understand the principle of the present invention that the waterborne blocked isocyanate curing agent improves the stone chip resistance of the coating film, the polyether diol participates in the chain extension reaction, so that a great amount of elastic structures with delayed energy release exist in the waterborne blocked isocyanate curing agent, and the structure of partial chain segments of the elastic structures is shown as the following formula (I):
in the formula (I), X is a main chain section of polyisocyanate trimer, Y is a functional group of polyethylene glycol monomethyl ether after removing hydrogen of terminal hydroxyl, Z is a functional group of polyether diol after removing hydrogen of terminal hydroxyl, and B is a functional group of a sealant after removing active hydrogen atoms.
It should be noted that the above formula (I) is only a structural schematic of the aqueous blocked isocyanate curing agent of the present invention, and does not represent an absolute configuration thereof.
The elastic structure can react with resins with active groups such as amino resin, polyester resin and the like in a coating formula, a large number of flexible chain segment structures are introduced when a coating is formed, the energy release of the coating when the coating is subjected to stone impact can be delayed, the stone impact resistance of the coating is further improved, and the coating has stone impact resistance under the condition of low film thickness.
In one embodiment, the raw materials comprise, by weight, 25% to 55% of polyisocyanate trimer, 2% to 15% of polyethylene glycol monomethyl ether, 0.1% to 10% of polyether glycol, 15% to 40% of a sealing agent, 2.8% to 30% of a cosolvent, 0.05% to 0.5% of alkali metal alkoxide, and 0.05% to 0.5% of a neutralizing agent.
In one embodiment, the polyether glycol is selected from at least one of diethylene glycol, polyethylene glycol, and polypropylene glycol; and/or
The blocking agent is selected from at least one of malonate blocking agent, amino blocking agent and oxime blocking agent; and/or
The cosolvent is at least one selected from saturated monohydric aliphatic alkanol with 1-8 carbon atoms; and/or
The alkali metal alkoxide is at least one selected from potassium tert-butoxide, sodium methoxide methanol solution and sodium ethoxide ethanol solution; and/or
The neutralizing agent is at least one selected from phosphoric acid and sulfuric acid.
In one embodiment, the polyether glycol is polyethylene glycol or polypropylene glycol; and/or
The blocking agent is malonate blocking agent; and/or
The polyisocyanate trimer is selected from at least one of isophorone diisocyanate (IPDI) trimer, Hexamethylene Diisocyanate (HDI) trimer and Toluene Diisocyanate (TDI) trimer.
In one embodiment, the molecular weight of the polyethylene glycol monomethyl ether is 300-1000, the molecular weight of the polyether glycol is 120-1000, the blocking agent is a malonate blocking agent, and an ester group of the malonate blocking agent is an alkoxy formyl group with 1-8 carbon atoms.
The invention also aims to provide a preparation method of the water-based blocked isocyanate curing agent, which comprises the following steps:
carrying out hydrophilic modification and chain extension on polyethylene glycol monomethyl ether, polyether diol and polyisocyanate to obtain a urethane prepolymer; the polyethylene glycol monomethyl ether is one selected from polyethylene glycol ether monohydric alcohol with the molecular weight of 300-2000, the polyether dihydric alcohol has the molecular weight of 120-1000, and the polyisocyanate trimer is at least one selected from aliphatic polyisocyanate trimer and aromatic polyisocyanate trimer;
pre-dispersing a sealing agent and alkali metal alkoxide to obtain a dispersion;
capping the urethane prepolymer with the dispersion at a temperature of 60 ℃ to 80 ℃ to obtain a mixture, and controlling the residual amount of-NCO groups in the mixture to be less than or equal to 0.4 wt%;
and mixing the mixture and a neutralizing agent to adjust the pH value, then removing the solvent, adding a cosolvent to adjust the solid content, and filtering to obtain the water-based blocked isocyanate curing agent.
In one embodiment, the temperature of the hydrophilic modification and chain extension is 40-90 ℃; the conditions for removing the solvent are as follows: the vacuum degree is-0.1 MPa to-0.099 MPa, and the temperature is 60 ℃ to 80 ℃.
In one embodiment, the pH value of the mixture and the neutralizing agent is adjusted to 7-10 after the mixture and the neutralizing agent are mixed, and the solid content is adjusted to 70-90 wt% by adding the cosolvent.
The invention also aims to provide a water-based paint which comprises the water-based blocked isocyanate curing agent or the water-based blocked isocyanate curing agent prepared by the preparation method.
In one embodiment, the water-based paint further comprises a main body resin selected from at least one of an amino resin and a polyester resin.
Compared with the prior art, the invention has the following beneficial effects:
(1) the water-based blocked isocyanate curing agent has good water dispersibility and good stability, has an elastic structure for delaying energy release, can react with resin in a coating formula, and introduces a large number of flexible chain segment structures into a formed coating, so that the energy release of the coating is facilitated when the coating is subjected to stone impact, and the stone impact resistance of the coating under the condition of low film thickness is improved.
(2) The aqueous blocked isocyanate curing agent has high solid content, no volatile NCO, no aromatic hydrocarbon and ether solvents and low VOCs emission.
(3) The preparation and synthesis process of the waterborne blocked isocyanate curing agent is simple and easy to realize.
(4) The water-based paint disclosed by the invention has good stone-impact resistance, so that when a coating film meets the corresponding stone-impact resistance requirement, the film thickness is reduced, the discharge of VOCs (volatile organic compounds) is reduced, and the energy consumption and the cost can be reduced.
Drawings
FIG. 1 is an infrared spectrum of a water-based blocked isocyanate curing agent of example 1 of the present invention;
FIG. 2 is an infrared spectrum of a water-based blocked isocyanate curing agent of example 2 of the present invention;
FIG. 3 is an infrared spectrum of a water-based blocked isocyanate curing agent of example 3 of the present invention;
FIG. 4 is an infrared spectrum of a water-based blocked isocyanate curing agent of example 4 of the present invention;
FIG. 5 is an infrared spectrum of a water-based blocked isocyanate curing agent of example 5 of the present invention.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
One embodiment of the present invention provides a water-based blocked isocyanate curing agent, which comprises the following raw materials: polyisocyanate trimer, polyethylene glycol monomethyl ether, polyether diol, a sealing agent, a cosolvent, alkali metal alkoxide and a neutralizer;
wherein the polyisocyanate trimer is at least one of aliphatic polyisocyanate trimer and aromatic polyisocyanate trimer, the polyethylene glycol monomethyl ether is one of polyethylene glycol ether monohydric alcohol with the molecular weight of 300-2000, and the polyether dihydric alcohol has the molecular weight of 120-1000.
The aliphatic polyisocyanate trimer is selected from one of aliphatic polyisocyanate trimers in which the hydrocarbon group is a straight chain structure and alicyclic polyisocyanate trimers in which the hydrocarbon group contains a carbon ring.
Thus, the hydrophilic modification and chain extension are carried out on the polyisocyanate by the polyethylene glycol monomethyl ether and the polyether diol to obtain the water-based blocked isocyanate curing agent with a long-chain elastic structure, and the water-based blocked isocyanate curing agent has good water dispersibility and good stability.
Researchers find in research that when the molecular weight of the polyethylene glycol monomethyl ether and the polyether glycol is small, a stable dispersion cannot be obtained after water dispersion; when the molecular weight is larger, the obtained water-based blocked isocyanate curing agent has stronger crystallinity and poorer water dispersibility. Therefore, the polyethylene glycol ether monohydric alcohol with the molecular weight of 300-2000 and the polyether dihydric alcohol with the molecular weight of 100-1000 are selected to carry out hydrophilic modification and chain extension on the polyisocyanate trimer, and the obtained water-based blocked isocyanate curing agent has good water dispersibility and good stability.
In one embodiment, the raw materials comprise, by weight, 25% to 55% of polyisocyanate trimer, 2% to 15% of polyethylene glycol monomethyl ether, 0.1% to 10% of polyether glycol, 15% to 40% of a sealing agent, 2.8% to 30% of a cosolvent, 0.05% to 0.5% of alkali metal alkoxide, and 0.05% to 0.5% of a neutralizing agent.
Further, the raw materials comprise, by weight, 30-55% of polyisocyanate trimer, 4-12% of polyethylene glycol monomethyl ether, 0.5-10% of polyether diol, 15-40% of sealant, 5-30% of cosolvent, 0.05-0.5% of alkali metal alkoxide and 0.05-0.5% of neutralizer.
In one embodiment, the polyisocyanate trimer is selected from at least one of isophorone diisocyanate trimer, hexamethylene diisocyanate trimer, and toluene diisocyanate trimer.
Preferably, the polyisocyanate trimer is selected from at least one of isophorone diisocyanate trimer and hexamethylene diisocyanate trimer.
In one embodiment, the molecular weight of the polyethylene glycol monomethyl ether is 300-1000.
In one embodiment, the molecular weight of the polyether glycol is 120-1000.
In one embodiment, the polyether glycol is selected from at least one of diethylene glycol, polyethylene glycol, and polypropylene glycol.
Preferably, the polyether glycol is at least one selected from polyethylene glycol having a molecular weight of 120-1000 and polypropylene glycol having a molecular weight of 120-1000.
In one embodiment, the blocking agent is selected from at least one of a malonate blocking agent, an amino blocking agent, and an oxime blocking agent.
In one embodiment, the blocking agent is a malonate blocking agent, and an ester group of the malonate blocking agent is an alkoxyformyl group having from C1 to C8, that is, an ester group of the malonate blocking agent is an alkoxyformyl group having from 1 to 8 carbon atoms.
For example, the blocking agent may be at least one selected from compounds having an alkoxycarbonyl group having 1 to 8 carbon atoms in the ester group, such as dimethyl malonate, diisopropyl malonate, and di-n-octyl malonate.
In one embodiment, the cosolvent is at least one selected from saturated monohydric aliphatic alkanols having 1-8 carbon atoms. Such as methanol, isopropanol, n-octanol, and the like.
In one embodiment, the alkali metal alkoxide is selected from at least one of potassium tert-butoxide, sodium methoxide in methanol, and sodium ethoxide in ethanol.
In one embodiment, the neutralizing agent is selected from at least one of phosphoric acid and sulfuric acid.
Another embodiment of the present invention is to provide a method for preparing the above aqueous blocked isocyanate curing agent, comprising the following steps S1 to S4.
S1, carrying out hydrophilic modification and chain extension on polyethylene glycol monomethyl ether, polyether diol and polyisocyanate to obtain the urethane prepolymer.
In an embodiment, before the step of performing hydrophilic modification and chain extension, the method further comprises a step of dehydrating the polyethylene glycol monomethyl ether and the polyether glycol, wherein the water content of the polyethylene glycol monomethyl ether and the polyether glycol is controlled to be less than 0.1 wt%.
Further, the dehydration conditions include: the vacuum degree is less than or equal to-0.099 MPa, the temperature is 80-105 ℃, and the time is 0.5-4 h.
Preferably, the vacuum degree is-0.1 MPa to-0.099 MPa.
In one embodiment, the temperature for hydrophilic modification and chain extension is from 40 ℃ to 90 ℃.
Specifically, polyethylene glycol monomethyl ether, polyethylene glycol and toluene are mixed, then the mixture is decompressed and dehydrated, and the toluene and water are used for azeotropic evaporation to take away the water in the polyethylene glycol monomethyl ether and the polyethylene glycol, so that the water content of the mixture of the polyethylene glycol monomethyl ether and the polyethylene glycol is between 0.01 and 0.1 weight percent; and then uniformly mixing the mixture with polyisocyanate and an organic solvent, heating to 40-90 ℃, and reacting for 1-3 h to obtain the carbamic acid prepolymer.
Furthermore, the dosage of the toluene is 5 to 15 percent of the weight of the polyethylene glycol monomethyl ether and the polyethylene glycol; the dosage of the organic solvent is 10-20% of the weight of the polyisocyanate, and the organic solvent can be selected from ethyl acetate, acetone, butanone and the like.
S2, pre-dispersing the sealing agent and the alkali metal alkoxide to obtain a dispersion.
Specifically, the blocking agent and alkali metal alkoxide are predispersed at room temperature.
Therefore, the sealant and the alkali metal alkoxide are pre-dispersed, so that the sealant and the alkali metal alkoxide are uniformly dispersed, the operation is convenient, and the catalysis efficiency can be effectively improved.
It is understood that the steps S1 and S2 are not sequential, and may be performed simultaneously, or alternatively, one of the steps S1 or S2 may be performed first.
S3, end-capping the urethane prepolymer obtained in the step S1 and the dispersion obtained in the step S2 at a temperature of 60 to 80 ℃ to obtain a mixture, and controlling the residual amount of-NCO groups in the mixture to be less than or equal to 0.4 wt%.
In one embodiment, the capping time is 3 to 8 hours.
S4, mixing the mixture obtained in the step S3 and a neutralizing agent to adjust the pH value, then removing the solvent, adding a cosolvent to adjust the solid content, and filtering to obtain the water-based blocked isocyanate curing agent.
Specifically, a neutralizing agent is added into the mixture obtained in step S3, the pH value of the mixture is adjusted, then the solvent is removed under reduced pressure, and then a cosolvent is added to adjust the solid content of the mixed system, thereby obtaining the water-based blocked isocyanate curing agent.
In one embodiment, the conditions for removing the solvent are: the vacuum degree is-0.1 MPa to-0.099 MPa, and the temperature is 60 ℃ to 80 ℃.
In one embodiment, the pH value of the water-based blocked isocyanate curing agent is 7-10, and the solid content of the water-based blocked isocyanate curing agent is 70-90 wt%.
The invention also aims to provide a water-based paint which comprises the water-based blocked isocyanate curing agent or the water-based blocked isocyanate curing agent prepared by the preparation method.
In one embodiment, the water-based paint further comprises a main body resin, and the main body resin is at least one selected from amino resin and polyester resin.
The waterborne coating containing the waterborne blocked isocyanate curing agent has an elastic structure and can react with main resin in the waterborne coating, so that a large number of flexible chain segment structures are introduced into a coating, the coating releases energy when being subjected to stone impact, and the stone impact resistance of the coating under the condition of low film thickness is improved.
The following are specific examples
The residual amount of NCO is measured according to GB12009.4-89, method for measuring content of polymethylene polyphenyl isocyanate radical;
the stone impact resistance grade is measured according to a stone impact resistance test method of DIN EN ISO 20567-1;
the impact grade is measured according to the GB1732-79 impact test method;
the cup bulge grade is measured according to the cup bulge test method of GB/T9753-2007;
in the case where no particular mention is made, commercially available products are used as the starting materials.
The compounding ratios of the examples are shown in Table 1 below.
TABLE 1
Note: "-" indicates no addition, the same applies below.
The preparation method of each example is as follows:
example 1
(1) Placing polyethylene glycol monomethyl ether (MPEG1000) and polyethylene glycol (PEG1000) in a four-neck round-bottom flask, adding toluene (the amount of toluene is 10% of the weight of polyethylene glycol monomethyl ether), inserting a thermometer, starting an oil pump, removing water under reduced pressure (vacuum degree of-0.099 MPa, temperature of 80 deg.C, time of 4h), controlling the water content of the mixture to 0.07%, and cooling to 40 deg.C.
(2) And (2) installing a reflux condenser, a thermocouple, a thermometer and a nitrogen pipe on the four-mouth round-bottom flask, adding ethyl acetate (the amount of the ethyl acetate is 10-20% of the total volume of the reaction system) and HDI trimer polyisocyanate in a stirring state, blowing nitrogen gas simultaneously, dispersing for 15min, then heating to 90 ℃, stopping blowing the nitrogen gas, and reacting for 2h to obtain the urethane prepolymer.
(3) Alkali metal salts of alcohols (sodium methoxide) and malonate blocking agent (diisopropyl malonate) are pre-dispersed at room temperature to obtain malonate and alkali metal alkoxide dispersion.
(4) And (3) after the complete reaction of the urethane prepolymer, cooling to 30 ℃, carrying out end capping on the dispersion in the step (3) at the temperature of 60 ℃ for 8 hours until the NCO is less than or equal to 0.4%, and stopping the reaction after the end capping is finished.
(5) Adding phosphoric acid, neutralizing for 20min, and removing the solvent under reduced pressure to obtain a solid content of 100%; adding isopropanol, adjusting the solid content to 75.16%, adjusting the pH value to 8.0, adding 400-mesh diatomite, filtering and discharging to obtain the water-based blocked isocyanate curing agent for improving the stone-impact resistance of the coating.
Example 2
(1) Placing polyethylene glycol monomethyl ether (MPEG300) and polyethylene glycol (PEG500) in a four-neck round-bottom flask, adding toluene (10 wt% of polyethylene glycol monomethyl ether), inserting a thermometer, starting an oil pump, removing water under reduced pressure (vacuum degree of-0.099 MPa, temperature of 99 deg.C, and time of 2 hr), controlling the water content of the mixture to 0.1%, and cooling to 40 deg.C.
(2) A reflux condenser, a thermocouple, a thermometer and a nitrogen tube were attached to the four-necked round-bottomed flask, and ethyl acetate and IPDI trimer polyisocyanate were added while stirring, and nitrogen gas was blown into the flask to disperse the polyisocyanate for 15min, and then the temperature was raised to 90 ℃ to stop blowing nitrogen gas, and the reaction was carried out for 2 hours to obtain a urethane prepolymer.
(3) Alkali metal salt of alcohol (potassium tert-butoxide) and malonate blocking agent (dimethyl malonate) are pre-dispersed at room temperature to obtain malonate and alkali metal alkoxide dispersion.
(4) And (3) after the complete reaction of the urethane prepolymer, cooling to 30 ℃, carrying out end capping on the dispersion in the step (3) at 70 ℃ for 5 hours until the NCO is less than or equal to 0.4%, and stopping the reaction after the end capping is finished.
(5) Adding sulfuric acid, neutralizing for 20min, and removing the solvent under reduced pressure to obtain a solid content of 100%; adding methanol, adjusting the solid content to 80%, adjusting the pH value to 7.5, adding 400-mesh diatomite, filtering and discharging to obtain the water-based blocked isocyanate curing agent for improving the stone-impact resistance of the coating.
Example 3
(1) Placing polyethylene glycol monomethyl ether (MPEG600) and polypropylene glycol (PPG500) in a four-neck round-bottom flask, adding toluene (10 wt% of polyethylene glycol monomethyl ether), inserting a thermometer, starting an oil pump, removing water under reduced pressure (vacuum degree of-0.099 MPa, temperature of 105 deg.C, time of 0.5 hr), controlling the water content of the mixture to 0.07%, and cooling to 40 deg.C.
(2) A reflux condenser, a thermocouple, a thermometer and a nitrogen tube were attached to the four-necked round-bottomed flask, and while stirring, ethyl acetate and HDI trimer polyisocyanate were added and while blowing nitrogen gas, dispersed for 15min, and then heated to 90 ℃ to stop blowing nitrogen gas and reacted for 2 hours to obtain a urethane prepolymer.
(3) Alkali metal salts of alcohols (sodium methoxide methanol solution) and malonate blocking agent (di-n-octyl malonate) are pre-dispersed at room temperature to obtain malonate and alkali metal alkoxide dispersion.
(4) And (3) after the complete reaction of the urethane prepolymer, cooling to 30 ℃, carrying out end capping on the dispersion in the step (3) at 80 ℃ for 3 hours until the NCO is less than or equal to 0.4%, and stopping the reaction after the end capping is finished.
(5) Adding phosphoric acid, neutralizing for 20min, and removing the solvent under reduced pressure to obtain a solid content of 100%; adding n-octanol, adjusting the solid content to 90%, adjusting the pH value to 9.0, adding 400-mesh diatomite, filtering and discharging to obtain the water-based blocked isocyanate curing agent for improving the stone-impact resistance of the coating.
Example 4
(1) Placing polyethylene glycol monomethyl ether (MPEG600) and polyethylene glycol (PEG1000) in a four-neck round-bottom flask, adding toluene (10 wt% of polyethylene glycol monomethyl ether), inserting a thermometer, starting an oil pump, removing water under reduced pressure (vacuum degree of-0.099 MPa, temperature of 99 deg.C, and time of 4 hr), controlling the water content of the mixture at 0.07%, and cooling to 40 deg.C.
(2) A reflux condenser, a thermocouple, a thermometer and a nitrogen tube were attached to the four-necked round-bottomed flask, and ethyl acetate and IPDI trimer polyisocyanate were added while stirring, and nitrogen gas was blown into the flask to disperse the polyisocyanate for 15min, and then the temperature was raised to 90 ℃ to stop blowing nitrogen gas, and the reaction was carried out for 2 hours to obtain a urethane prepolymer.
(3) Pre-dispersing alkali metal salt of alcohol (sodium ethoxide ethanol solution) and malonate sealing agent (diisopropyl malonate) at room temperature to obtain malonate and alkali metal salt dispersion.
(4) And (3) after the complete reaction of the urethane prepolymer, cooling to 30 ℃, carrying out end capping on the dispersion in the step (3) at 70 ℃ for 5 hours until the NCO is less than or equal to 0.4%, and stopping the reaction after the end capping is finished.
(5) Adding phosphoric acid, neutralizing for 20min, and removing the solvent under reduced pressure to obtain a solid content of 100%; adding isopropanol, adjusting the solid content to 70%, adjusting the pH value to 8.0, adding 400-mesh diatomite, filtering and discharging to obtain the water-based blocked isocyanate curing agent for improving the stone-impact resistance of the coating.
Example 5
(1) Placing polyethylene glycol monomethyl ether (MPEG600) and diethylene glycol in a four-neck round-bottom flask, adding toluene (10 wt% of polyethylene glycol monomethyl ether), inserting a thermometer, starting an oil pump, removing water under reduced pressure (vacuum degree of-0.099 MPa, temperature of 80 deg.C, and time of 4h), controlling the water content of the mixture to 0.07%, and cooling to 40 deg.C.
(2) A reflux condenser, a thermocouple, a thermometer and a nitrogen tube were attached to the four-necked round-bottomed flask, and while stirring, ethyl acetate and HDI trimer polyisocyanate were added and while blowing nitrogen gas, dispersed for 15min, and then heated to 90 ℃ to stop blowing nitrogen gas and reacted for 2 hours to obtain a urethane prepolymer.
(3) Alkali metal salts of alcohol (sodium methoxide) and malonate blocking agent (diisopropyl malonate) are pre-dispersed at room temperature to obtain malonate and alkali metal salt dispersion.
(4) And (3) after the complete reaction of the urethane prepolymer, cooling to 30 ℃, carrying out end capping on the dispersion in the step (3) at 70 ℃ for 5 hours until the NCO is less than or equal to 0.4%, and stopping the reaction after the end capping is finished.
(5) Adding phosphoric acid, neutralizing for 20min, and removing the solvent under reduced pressure to obtain a solid content of 100%; adding isopropanol, adjusting the solid content to 75%, adjusting the pH value to 8.0, adding 400-mesh diatomite, filtering and discharging to obtain the water-based blocked isocyanate curing agent for improving the stone-impact resistance of the coating.
Performance testing
1. And scanning the waterborne blocked isocyanate curing agents of examples 1-5 by using an infrared spectrometer, wherein the obtained infrared spectra are shown in figures 1-5.
2. According to the coating formula shown in Table 2, the waterborne blocked isocyanate curing agents for improving the stone-impact resistance of the coating prepared in the examples 1 to 5 are prepared into corresponding waterborne coatings 1 to 5 and a comparative coating 1, Corsia
BL 2867 aqueous blocked polyisocyanate curing agent was formulated into comparative coatings for the relevant evaluation of coating performance parameters.
Comparative coating 1, prepared according to the curing agent in comparative coating 1 of Table 2
TABLE 2
The water-based coatings 1-5 and the comparative coatings 1-2 are prepared into middle coatings with different thicknesses, a 508 Eschka multiple impact tester is used for carrying out a stone impact resistance experiment test according to DIN EN ISO 20567-1 standard, an impact experiment test is carried out according to GB1732-79 standard, a cup bulge experiment test is carried out according to GB/T9753-2007 standard, and the experiment results are shown in Table 3.
TABLE 3
As shown in Table 3, the test of the paint performance parameters is related to the scientific research
Compared with BL 2867 waterborne blocked polyisocyanate curing agent, the waterborne blocked isocyanate curing agent for improving the stone-impact resistance of the coating prepared in examples 1-5 has the stone-impact resistance grade and the cupped convex grade which are obviously superior to those of the waterborne blocked isocyanate curing agent for improving the stone-impact resistance of the coating under the condition of low film thickness
BL 2867, also have more obvious advantage under the condition of high membrane thickness, can show the stone-impact resistance performance, impact rating, the convex grade of cup that promote the coating; meanwhile, various indexes of the appearance, acid resistance, alkali resistance, weather resistance and the like of the coating are detected, and the performance requirements can be met.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
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 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. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The water-based paint is characterized in that raw materials of the water-based paint comprise main resin and a water-based blocked isocyanate curing agent, and the water-based blocked isocyanate curing agent comprises the following components in percentage by weight: 30 to 55 percent of polyisocyanate trimer, 4 to 12 percent of polyethylene glycol monomethyl ether, 0.5 to 10 percent of polyether glycol, 15 to 40 percent of sealant, 5 to 30 percent of cosolvent, 0.05 to 0.5 percent of alkali metal alkoxide and 0.05 to 0.5 percent of neutralizer;
the polyisocyanate trimer is hexamethylene diisocyanate trimer, the polyethylene glycol monomethyl ether is selected from one of polyethylene glycol ether monohydric alcohol with the molecular weight of 300-1000, and the polyether dihydric alcohol has the molecular weight of 120-1000;
the main body resin is selected from at least one of amino resin and polyester resin.
2. The water-based paint according to claim 1, wherein the raw materials of the water-based blocked isocyanate curing agent comprise the following components in percentage by weight: 31.46% polyisocyanate trimer, 11.22% polyethylene glycol monomethyl ether, 3.75% polyether diol, 28.11% blocking agent, 24.84% co-solvent, 0.37% alkali metal alkoxide and 0.25% neutralizing agent.
3. The aqueous coating material according to claim 1 or 2, wherein the polyether glycol is at least one selected from the group consisting of polyethylene glycol and polypropylene glycol; and/or
The blocking agent is selected from at least one of malonate blocking agent, amino blocking agent and oxime blocking agent; and/or
The cosolvent is at least one selected from saturated monohydric aliphatic alkanol with 1-8 carbon atoms; and/or
The alkali metal alkoxide is at least one selected from potassium tert-butoxide, sodium methoxide methanol solution and sodium ethoxide ethanol solution; and/or
The neutralizing agent is at least one selected from phosphoric acid and sulfuric acid.
4. The aqueous coating material according to claim 1,
the blocking agent is malonate blocking agent.
5. The water-based paint according to claim 1, wherein the blocking agent is a malonate blocking agent, and an ester group of the malonate blocking agent is an alkoxyformyl group having 1-8 carbon atoms.
6. The aqueous coating of claim 1 wherein the blocking agent is selected from at least one of dimethyl malonate, diisopropyl malonate, and di-n-octyl malonate.
7. The aqueous coating of claim 1, wherein the polyether glycol is PEG 1000.
8. The aqueous coating material of claim 1, wherein the step of preparing the aqueous blocked isocyanate curing agent comprises the steps of:
carrying out hydrophilic modification and chain extension on the polyethylene glycol monomethyl ether, the polyether diol and the polyisocyanate trimer to obtain a urethane prepolymer;
pre-dispersing the blocking agent and the alkali metal alkoxide to obtain a dispersion;
capping the urethane prepolymer with the dispersion at a temperature of 60 ℃ to 80 ℃ to obtain a mixture, and controlling the residual amount of-NCO groups in the mixture to be less than or equal to 0.4 wt%;
and mixing the mixture with the neutralizer, removing the solvent, adding the cosolvent, and filtering to obtain the waterborne blocked isocyanate curing agent.
9. The water-based paint according to claim 8, wherein the temperature of the hydrophilic modification and chain extension is 40-90 ℃; the conditions for removing the solvent are as follows: the vacuum degree is-0.1 MPa to-0.099 MPa, and the temperature is 60 ℃ to 80 ℃.
10. The water-based paint as claimed in claim 8, wherein the pH value of the mixture and the neutralizing agent is adjusted to 7-10 after mixing, and the solid content is adjusted to 70-90 wt% by adding the cosolvent.
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