CN111320741B - Water-based blocked isocyanate curing agent, preparation method thereof, water-based paint and film product - Google Patents

Water-based blocked isocyanate curing agent, preparation method thereof, water-based paint and film product Download PDF

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CN111320741B
CN111320741B CN202010212193.2A CN202010212193A CN111320741B CN 111320741 B CN111320741 B CN 111320741B CN 202010212193 A CN202010212193 A CN 202010212193A CN 111320741 B CN111320741 B CN 111320741B
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blocked isocyanate
curing agent
isocyanate curing
agent
water
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CN111320741A (en
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喻佳
杨鹏飞
张�杰
黄鹂
胡启明
董军胜
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Hunan Xiangjiang Kansai Paint Changsha Co ltd
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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
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/80—Masked polyisocyanates
    • C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
    • C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
    • 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
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C08G18/12—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step using two or more compounds having active hydrogen in the first polymerisation step
    • 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
    • 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
    • C08G18/2815—Monohydroxy compounds
    • C08G18/283—Compounds containing ether groups, e.g. oxyalkylated monohydroxy compounds
    • 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
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/80—Masked polyisocyanates
    • C08G18/8003—Masked polyisocyanates masked with compounds having at least two groups containing active hydrogen
    • C08G18/8048—Masked polyisocyanates masked with compounds having at least two groups containing active hydrogen with compounds of C08G18/34
    • 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
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/80—Masked polyisocyanates
    • C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
    • C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
    • C08G18/8077—Oximes
    • 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
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/80—Masked polyisocyanates
    • C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
    • C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
    • C08G18/808—Monoamines
    • 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
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/06—Polyurethanes from polyesters

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Paints Or Removers (AREA)
  • Polyurethanes Or Polyureas (AREA)

Abstract

The invention relates to a water-based blocked isocyanate curing agent, a preparation method thereof, a water-based paint and a film coating product. The preparation raw materials of the water-based blocked isocyanate curing agent comprise: polyisocyanate monomer, sealant, hydrophilic grafting agent, chain extender, catalyst and diluting solvent; wherein the sealant is selected from at least one of an amino sealant, a hydroxyl sealant and an active methylene sealant; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500; the catalyst is an organometallic reagent. The obtained water-based blocked isocyanate curing agent is applied to coatings such as automobile middle-surface coatings, and can remarkably improve the flexibility of a coating film and reduce the cost on the premise of not influencing the crosslinking density and the performance of the coating film.

Description

Water-based blocked isocyanate curing agent, preparation method thereof, water-based paint and film product
Technical Field
The invention relates to the technical field of automobile coatings, in particular to a water-based blocked isocyanate curing agent, a preparation method thereof, a water-based coating and a coating product.
Background
The water-based blocked isocyanate curing agent is an auxiliary type curing resin which is not cured at normal temperature, is stable in storage and has emulsifying capacity, and is widely used in the technical field of middle coating of automobiles due to excellent stability. At present, in the technical field of automobile middle-surface coating, most of the water-based blocked isocyanate curing agents widely used in the market are curing agents derived from polyisocyanate trimers, and the problems of insufficient flexibility and high cost of coating films exist in coatings such as automobile middle-surface coating, so that the water-based blocked isocyanate curing agents are urgently needed to be provided for the coatings such as the automobile middle-surface coating, and the water-based blocked isocyanate curing agents can improve the flexibility of the coating films and reduce the cost on the premise of not influencing the crosslinking density and the performance of the coating films.
Disclosure of Invention
Therefore, the water-based blocked isocyanate curing agent, the preparation method thereof, the water-based paint and the coating product are needed to be provided, and the flexibility of the coating can be improved and the cost can be reduced on the premise of not influencing the crosslinking density and the performance of the coating.
In one aspect of the present invention, a water-based blocked isocyanate curing agent is provided, which is prepared from the following raw materials: polyisocyanate monomer, sealant, hydrophilic grafting agent, chain extender, catalyst and diluting solvent;
wherein the blocking agent is selected from at least one of an amino blocking agent, a hydroxyl blocking agent and an active methylene blocking agent; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500; the catalyst is an organometallic reagent.
According to the waterborne blocked isocyanate curing agent, a part of-NCO groups of a polyisocyanate monomer are blocked by the blocking agent, hydrophilic modification is carried out by the hydrophilic grafting agent, chain extension is carried out by the chain extender, compared with an isocyanurate six-membered ring structure in the traditional waterborne blocked isocyanate curing agent, the rigidity of the curing agent is reduced, and meanwhile, the waterborne blocked isocyanate curing agent has a large number of point-line chain structures, so that the waterborne blocked isocyanate curing agent has more excellent free space turnover capacity and multiple crosslinking points, and the waterborne blocked isocyanate curing agent is applied to coatings such as automotive middle-surface coatings, can remarkably improve the flexibility of a coating film and reduce the cost on the premise of not influencing the crosslinking density and performance of the coating film.
In some embodiments, in the preparation raw materials, by weight percentage, the polyisocyanate monomer is 25% to 40%, the blocking agent is 6% to 35%, the hydrophilic grafting agent is 5% to 40%, the chain extender is 4% to 8%, the catalyst is 0.05% to 0.15%, and the diluting solvent is 10% to 30%.
In some of these embodiments, the polyisocyanate monomer is selected from at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and 4, 4-dicyclohexylmethane diisocyanate.
In some of these embodiments, the blocking agent is selected from at least one of 3, 5-dimethylpyrazole, 1,2, 4-triazole, diisopropylamine, methyl ethyl ketone oxime, diisopropyl malonate, and diethyl malonate.
In some of the embodiments, the hydrophilic grafting agent is selected from polyethylene glycol monomethyl ether compounds with the number average molecular weight of 300-2000.
In some of these embodiments, the chain extender is selected from polyols having a hydroxyl number greater than or equal to 3.
In some of these embodiments, the catalyst is selected from one of an organotin reagent and an organic alkali metal salt.
In some of these embodiments, the diluent solvent is a polyether solvent.
In another aspect of the present invention, a method for preparing a water-based blocked isocyanate curing agent is provided, which comprises the following steps:
carrying out end-capping reaction on a polyisocyanate monomer and a blocking agent under the action of a diluting solvent to obtain a first urethane prepolymer;
carrying out grafting reaction on the first urethane prepolymer and a hydrophilic grafting agent under the action of a catalyst to obtain a second urethane prepolymer;
carrying out chain extension reaction on the second carbamate prepolymer and a chain extender, and adding a diluting solvent to adjust the solid content of the system to obtain a water-based blocked isocyanate curing agent;
wherein the blocking agent is selected from at least one of an amino blocking agent, a hydroxyl blocking agent and an active methylene blocking agent; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500; the catalyst is an organometallic reagent.
In some embodiments, the reaction temperature of the end capping reaction is 60-60 ℃, and the end capping reaction is controlled to be finished when the mass content of-NCO groups in the reaction system is 11.8-16.4%;
the reaction temperature of the grafting reaction is 60-60 ℃, and the grafting reaction is finished when the mass content of-NCO groups in the reaction system is controlled to be 6.2-11.3%;
the reaction temperature of the chain extension reaction is 60-60 ℃, and the chain extension reaction is finished when the mass content of-NCO groups in the reaction system is less than or equal to 0.1%.
In another aspect of the present invention, a water-based paint is provided, which includes a main resin and a water-based blocked isocyanate curing agent, wherein the water-based blocked isocyanate curing agent is any one of the above water-based blocked isocyanate curing agents or the water-based blocked isocyanate curing agent prepared by any one of the above preparation methods.
In some of these embodiments, the host resin is selected from at least one of an amino resin and a polyester resin.
In another aspect of the present invention, there is provided a coated article comprising a coating film formed from any one of the aqueous coating materials described above.
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.
The technical personnel find that the curing agent which is widely used in the market and is derived from polyisocyanate trimer has a structure with isocyanurate six-membered rigid ring, so that the curing agent has stronger rigidity, and the curing agent is used for surface coating in automobiles to cause insufficient flexibility of a coating film. In addition, the polyisocyanate tripolymer on the market is high in price, and the waterborne blocked isocyanate curing agent derived by taking the tripolymer as a matrix curing agent is more expensive. In addition, how to ensure that the crosslinking density and the performance of the coating film are not influenced while improving the flexibility of the coating film is also one of the technical difficulties.
Based on the above, one embodiment of the present invention provides a water-based blocked isocyanate curing agent, which is prepared from the following raw materials: polyisocyanate monomer, blocking agent, hydrophilic grafting agent, chain extender, catalyst and diluting solvent.
Wherein the sealant is selected from at least one of an amino sealant, a hydroxyl sealant and an active methylene sealant; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500; the catalyst is an organometallic reagent.
According to the waterborne blocked isocyanate curing agent, a part of-NCO groups of a polyisocyanate monomer are blocked by the blocking agent, hydrophilic modification is carried out by the hydrophilic grafting agent, chain extension is carried out by the chain extender, compared with an isocyanurate six-membered ring structure in the traditional waterborne blocked isocyanate curing agent, the rigidity of the curing agent is reduced, and meanwhile, the waterborne blocked isocyanate curing agent has a large number of point-line chain structures, so that the waterborne blocked isocyanate curing agent has more excellent free space turnover capacity and multiple crosslinking points, and the waterborne blocked isocyanate curing agent is applied to coatings such as automotive middle-surface coatings, can remarkably improve the flexibility of a coating film and reduce the cost on the premise of not influencing the crosslinking density and performance of the coating film.
In some embodiments, in the preparation raw materials, by weight percentage, the polyisocyanate monomer is 25% to 40%, the blocking agent is 6% to 35%, the hydrophilic grafting agent is 5% to 40%, the chain extender is 4% to 8%, the catalyst is 0.05% to 0.15%, and the diluting solvent is 10% to 30%. By controlling the proportion of the components, the solid content of the water-based blocked isocyanate curing agent is higher, the viscosity is lower, the VOC content is lower, and the volatile NCO content is low.
Further, in the preparation raw materials, by weight, 29-39% of polyisocyanate monomer, 10-33% of blocking agent, 7-40% of hydrophilic grafting agent, 4-8% of chain extender, 0.05-0.15% of catalyst and 10-30% of diluting solvent.
Furthermore, in the preparation raw materials, by weight percentage, the polyisocyanate monomer accounts for 29-39%, the blocking agent accounts for 10-33%, the hydrophilic grafting agent accounts for 10-25%, the chain extender accounts for 5-8%, the catalyst accounts for 0.05-0.15%, and the diluting solvent accounts for 20-30%.
In some of these embodiments, the polyisocyanate monomer is selected from Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), Toluene Diisocyanate (TDI), and 4, 4-dicyclohexylmethane diisocyanate (H)12MDI).
In some of these embodiments, the blocking agent is selected from at least one of 3, 5-dimethylpyrazole, 1,2, 4-triazole, diisopropylamine, methyl ethyl ketone oxime, diisopropyl malonate, and diethyl malonate.
In some of the embodiments, the hydrophilic grafting agent is selected from polyethylene glycol monomethyl ether compounds with the number average molecular weight of 300-2000. Further, the hydrophilic grafting agent is selected from polyethylene glycol monomethyl ether compounds with the number average molecular weight of 500-1000. Specifically, the hydrophilic grafting agent is selected from at least one of MPEG300, MPEG500 and MPEG1000, preferably the hydrophilic grafting agent is selected from at least one of MPEG500 and MPEG 1000.
In some of the embodiments, the chain extender is selected from polyhydroxy compounds with hydroxyl number being equal to or more than 3, and further, the chain extender is selected from at least one of trimethylolethane, trimethylolpropane and pentaerythritol. Preferably, the chain extender is selected from at least one of trimethylolethane and trimethylolpropane.
In some of these embodiments, the catalyst is selected from one of an organotin reagent and an organic alkali metal salt. Further, the catalyst is at least one selected from dibutyltin dilaurate and sodium methoxide methanol solution.
In some of these embodiments, the diluent solvent is a polyether solvent; further, the diluting solvent is at least one selected from the group consisting of polydiethylene glycol dimethyl ether and polydipropylene glycol dimethyl ether.
An embodiment of the present invention further provides a method for preparing any one of the above aqueous blocked isocyanate curing agents, including the following steps S10 to S30:
step S10: and carrying out end-capping reaction on a polyisocyanate monomer and a blocking agent under the action of a diluting solvent to obtain a first urethane prepolymer.
Wherein the blocking agent is selected from at least one of an amino blocking agent, a hydroxyl blocking agent and an active methylene blocking agent. Further, the polyisocyanate monomer is selected from Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), Toluene Diisocyanate (TDI) and 4, 4-dicyclohexylmethane diisocyanate (H)12MDI).
The structure of the polyisocyanate monomer is represented by OCN-X-NCO, the structure of the blocking agent is represented by HB, and the reaction process of step S10 is as follows:
Figure BDA0002423208450000051
thus, in step S10, a part of-NCO groups are blocked by a blocking agent, so as to avoid the problem that a large amount of-NCO groups react with carbamate to generate allophanate under the alkaline condition of the grafting reaction in step S20, so that the resin is gelatinized, and the grafting reaction is difficult to carry out.
Further, the reaction temperature of the end capping reaction is 60-60 ℃, and the end capping reaction is finished when the mass content of-NCO groups in the reaction system is controlled to be 11.8-16.4%.
Step S20: and carrying out grafting reaction on the first urethane prepolymer and a hydrophilic grafting agent under the action of a catalyst to obtain a second urethane prepolymer.
Wherein the hydrophilic grafting agent is polyethylene glycol monomethyl ether compound, and the catalyst is an organometallic reagent, so the reaction condition of step S20 is an alkaline condition.
When the structure of the hydrophilic grafting agent is represented by HA, the reaction process of step S20 is as follows:
Figure BDA0002423208450000061
further, the reaction temperature of the grafting reaction is 60-60 ℃, and the grafting reaction is finished when the mass content of-NCO groups in the reaction system is controlled to be 6.2-11.3%.
Step S30: and (3) carrying out chain extension reaction on the second carbamate prepolymer and a chain extender, and adding a diluting solvent to adjust the solid content of the system to obtain the water-based blocked isocyanate curing agent.
Wherein the chain extender is a polyol having a molecular weight of less than 500. The reaction process of step S30 is as follows:
Figure BDA0002423208450000062
in some embodiments, in the preparation raw materials, by weight percentage, the polyisocyanate monomer is 25% to 40%, the blocking agent is 6% to 35%, the hydrophilic grafting agent is 5% to 40%, the chain extender is 4% to 8%, the catalyst is 0.05% to 0.15%, and the diluting solvent is 10% to 30%. The adding amount of the diluting solvent in the step S10 is 5-10% of the total amount of the preparation raw materials; the amount of the diluting solvent added in step S30 is the remaining diluting solvent.
Further, the diluting solvent is a polyether solvent; further, the diluting solvent is at least one selected from the group consisting of polydiethylene glycol dimethyl ether and polydipropylene glycol dimethyl ether.
Further, the reaction temperature of the chain extension reaction is 60-60 ℃, and the chain extension reaction is finished when the mass content of-NCO groups in the reaction system is controlled to be less than or equal to 0.1%.
The preparation method of the water-based blocked isocyanate curing agent has the advantages of low price and easy obtainment of raw materials and simple synthesis process. And, blocking part of-NCO groups of the polyisocyanate monomer by a blocking agent, carrying out hydrophilic modification on the polyisocyanate monomer by a hydrophilic grafting agent, and then carrying out chain extension on the polyisocyanate monomer by a chain extender, so that the reaction is smoothly carried out.
The invention also provides a water-based paint which comprises main resin and the water-based blocked isocyanate curing agent, wherein the water-based blocked isocyanate curing agent is any one of the water-based blocked isocyanate curing agents.
Any one of the waterborne blocked isocyanate curing agents contained in the waterborne coating can react with a main resin in the waterborne coating, so that a large amount of point-line flexible chain segment structures are introduced into a coating film formed by the coating, the coating film has very excellent flexibility, and the multi-crosslinking sites of the waterborne blocked isocyanate curing agent can ensure that the crosslinking density of the coating film is not reduced.
Further, the main resin is at least one selected from the group consisting of an amino resin and a polyester resin.
Further, the host resin is selected from amino resins and polyester resins; further, the water-based paint also comprises a dispersing agent, carbon black, titanium dioxide, talcum powder, a defoaming and leveling agent, an anti-shrinkage auxiliary agent, a pH regulator, a fumed silica anti-settling agent, dipropylene glycol methyl ether, isooctyl alcohol and water.
It will be appreciated that the aqueous coating may be prepared by mixing the components thereof with one another.
An embodiment of the present invention also provides a coated article including a coating film formed from any of the above aqueous coating materials.
Furthermore, the water-based paint can be used for middle coating and top coating of automobiles, and the coated products are automobiles.
It is understood that the formation of the coating film by the aqueous coating material can be achieved by coating and curing.
The following are specific examples.
In the case where no particular mention is made, commercially available products are used as the starting materials.
The residual NCO content of the reaction system is measured by referring to a method for measuring the content of polymethylene polyphenyl isocyanate radical in GB 12006.4-86.
Determination of the solid content: determined by DIN EN ISO 3251 at 130 ℃; 60 minutes, initial mass 1.0 g.
The following is a table of compounding ratios for each example, as shown in table 1.
TABLE 1
Figure BDA0002423208450000081
Figure BDA0002423208450000091
Wherein the mass content of the sodium methoxide methanol solution is 30 wt%.
Specifically, the preparation method of the aqueous blocked isocyanate curing agent of examples 1 to 2 is as follows:
1) diluting a diisocyanate monomer by using a diluting solvent (5 wt%), heating to 80 ℃, slowly adding a sealing agent, and carrying out heat preservation until NCO reaches a numerical value shown in Table 2 to obtain a urethane prepolymer I;
2) slowly adding a hydrophilic grafting agent and 2 drops of catalyst into the urethane prepolymer I, and carrying out heat preservation until NCO reaches a value shown in Table 2 to obtain a urethane prepolymer II;
3) adding a chain extender into the urethane prepolymer II in 3 batches, keeping the temperature until the NCO is less than or equal to 0.1 wt%, adding the balance of a diluting solvent to adjust the solid content, filtering by a 10-micron filter element, and taking the filtrate to obtain the water-based blocked isocyanate curing agent.
Specifically, the preparation method of the aqueous blocked isocyanate curing agent of examples 3 to 6 was as follows:
1) diluting a diisocyanate monomer by using a diluting solvent (10 wt%), heating to 80 ℃, slowly adding a sealing agent, and carrying out heat preservation until NCO reaches a numerical value shown in Table 2 to obtain a urethane prepolymer I;
2) slowly adding a hydrophilic grafting agent and 2 drops of catalyst into the urethane prepolymer I, and carrying out heat preservation until NCO reaches a value shown in Table 2 to obtain a urethane prepolymer II;
3) adding a chain extender into the urethane prepolymer II in 3 batches, keeping the temperature until the NCO is less than or equal to 0.1 wt%, adding the balance of a diluting solvent to adjust the solid content, filtering by a 10-micron filter element, and taking the filtrate to obtain the water-based blocked isocyanate curing agent.
Specific data of NCO contents (wt%) at the end of step 1) and step 2) in the preparation methods of examples 1 to 6 are shown in Table 2:
TABLE 2
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Step 1) 13.2％ 12.6％ 16.4％ 15.6％ 11.8％ 12.5％
Step 2) 6.2％ 7.7％ 11.3％ 8.6％ 8.6％ 6.6％
The following are examples of the production of aqueous coating materials using the above aqueous blocked isocyanate curing agents and examples of the performance test of coating films formed from the aqueous coating materials.
The aqueous blocked isocyanate curing agents obtained in examples 1 to 6 were formulated into corresponding aqueous coating materials 1 to 6 according to the formulation of the aqueous coating materials shown in Table 3.
Scientific wound
Figure BDA0002423208450000102
XL 7270 waterborne blocked polyisocyanate curing agent comparative coating 1 was formulated and comparative coating 2 was formulated with the self-made curing agent for relevant evaluation of coating performance parameters.
Note: the self-made curing agent was prepared in example 7 of patent document CN106563182A previously filed by the applicant.
Wherein, kesichuang
Figure BDA0002423208450000103
XL 7270 aqueous blocked polyisocyanate curing agent is an ionic aqueous dispersion curing agent, and a self-prepared curing agent is a nonionic curing agent.
The specific preparation methods of the water-based paint 1-6 and the comparative paint 1-2 are as follows: the components of the coating are mixed evenly.
TABLE 3
Figure BDA0002423208450000101
Figure BDA0002423208450000111
Figure BDA0002423208450000121
The water-based paint 1-6 and the comparative paint 1-2 are coated on the electrophoretic panel to form a coating film, and the performance tests of the coating film on the cross-linking density, the impact grade and the cup crown grade under the low film thickness and the high film thickness are respectively carried out, and the experimental results are shown in table 4. Wherein the flexibility of the film exhibits impact and cupping rating properties.
Wherein the impact grade is measured by an impact test method according to GB 1732-76;
the cup bulge grade is measured according to a cup bulge test method of GB/T6753-2007;
measurement of crosslinking density of coating film: measured by the Geiger fraction; the Geiger fraction test method comprises the following steps: the completely cured coating film, which is referred to as mass m, is scraped off from the glass plate with a clean iron sheet0Placing the weighed coating film in methanol/acetone (volume ratio of 1:1), refluxing at 60 ℃ for 6h, then placing the coating film in a constant-temperature drying oven at 30 ℃ for drying for 24h, and weighing the coating film mass m1。
Figure BDA0002423208450000122
The larger the Geiger fraction is, the higher the crosslinking density of the coating film is; the values for crosslink density in table 4 correspond to the bit cap fraction in%.
TABLE 4
Figure BDA0002423208450000123
Figure BDA0002423208450000131
From the paint performance parameter test, the following results can be obtained:
with scientific wound
Figure BDA0002423208450000132
Compared with the XL 7270 blocked isocyanate curing agent and the self-product curing agent, the waterborne blocked polyisocyanate curing agent prepared in the examples 1-6 can improve the impact and cup bulge grades of a coating film obviously on the premise of not reducing the crosslinking density of the coating film and not influencing other properties of the coating film.
Meanwhile, the appearance (GB/T1743-76 (86)) of the coating, the adhesion (HKSTM-2624), the water resistance (NES M0007[2014]57), the humidity and heat resistance (GB/T1740-.
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 (13)

1. The water-based blocked isocyanate curing agent is characterized by comprising the following preparation raw materials in percentage by weight: 25-40% of polyisocyanate monomer, 6-35% of sealant, 5-40% of hydrophilic grafting agent, 4-8% of chain extender, 0.05-0.15% of catalyst and 10-30% of diluting solvent;
wherein the blocking agent is selected from at least one of an amino blocking agent, a hydroxyl blocking agent and an active methylene blocking agent; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500 and the hydroxyl number of more than or equal to 3; the catalyst is an organometallic reagent;
the preparation method of the water-based blocked isocyanate curing agent comprises the following steps:
carrying out end-capping reaction on the polyisocyanate monomer and the blocking agent under the action of the diluting solvent, wherein the end-capping reaction is finished when the mass content of-NCO groups in a reaction system is 11.8-16.4%, so as to obtain a first urethane prepolymer;
carrying out grafting reaction on the first urethane prepolymer and the hydrophilic grafting agent under the action of the catalyst, wherein the grafting reaction is finished when the mass content of-NCO groups in a reaction system is 6.2-11.3%, so as to obtain a second urethane prepolymer;
and carrying out chain extension reaction on the second carbamate prepolymer and the chain extender, and adding a diluting solvent to adjust the solid content of the system to obtain the water-based blocked isocyanate curing agent.
2. The water-based blocked isocyanate curing agent according to claim 1, wherein the polyisocyanate monomer is 29 to 39 wt%, the blocking agent is 10 to 33 wt%, the hydrophilic grafting agent is 7 to 40 wt%, the chain extender is 4 to 8 wt%, the catalyst is 0.05 to 0.15 wt%, and the diluent solvent is 10 to 30 wt% of the preparation raw materials.
3. The aqueous blocked isocyanate curing agent according to claim 1 or 2, wherein the polyisocyanate monomer is at least one selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate and 4, 4-dicyclohexylmethane diisocyanate.
4. The aqueous blocked isocyanate curing agent of claim 1 or 2, wherein the blocking agent is at least one selected from the group consisting of 3, 5-dimethylpyrazole, 1,2, 4-triazole, diisopropylamine, methyl ethyl ketone oxime, diisopropyl malonate, and diethyl malonate.
5. The aqueous blocked isocyanate curing agent according to claim 1 or 2, wherein the hydrophilic grafting agent is selected from polyethylene glycol monomethyl ether compounds having a number average molecular weight of 300 to 2000.
6. The aqueous blocked isocyanate curing agent of claim 1 or 2, wherein the chain extender is at least one selected from the group consisting of trimethylolethane, trimethylolpropane and pentaerythritol.
7. The aqueous blocked isocyanate curing agent of claim 1 or 2, wherein the catalyst is selected from one of an organotin reagent and an organic alkali metal salt.
8. The aqueous blocked isocyanate curing agent of claim 1 or 2, wherein the diluent solvent is a polyether solvent.
9. The preparation method of the water-based blocked isocyanate curing agent is characterized by comprising the following preparation raw materials in percentage by weight: 25-40% of polyisocyanate monomer, 6-35% of sealant, 5-40% of hydrophilic grafting agent, 4-8% of chain extender, 0.05-0.15% of catalyst and 10-30% of diluting solvent; the preparation method comprises the following steps:
carrying out end capping reaction on a polyisocyanate monomer and a sealing agent under the action of a diluting solvent to obtain a first urethane prepolymer, wherein the end capping reaction is finished when the mass content of-NCO groups in a reaction system is 11.8-16.4%;
carrying out grafting reaction on the first urethane prepolymer and a hydrophilic grafting agent under the action of a catalyst to obtain a second urethane prepolymer, wherein the grafting reaction is finished when the mass content of-NCO groups in a reaction system is 6.2-11.3%;
carrying out chain extension reaction on the second carbamate prepolymer and a chain extender, and adding a diluting solvent to adjust the solid content of the system to obtain a water-based blocked isocyanate curing agent;
wherein the blocking agent is selected from at least one of an amino blocking agent, a hydroxyl blocking agent and an active methylene blocking agent; the hydrophilic grafting agent is a polyethylene glycol monomethyl ether compound; the chain extender is a polyhydroxy compound with the molecular weight of less than 500 and the hydroxyl number of more than or equal to 3; the catalyst is an organometallic reagent.
10. The method for preparing the aqueous blocked isocyanate curing agent according to claim 9, wherein the reaction temperature of the blocking reaction is 60 to 90 ℃;
the reaction temperature of the grafting reaction is 60-90 ℃;
the reaction temperature of the chain extension reaction is 60-90 ℃, and the chain extension reaction is finished when the mass content of-NCO groups in a reaction system is less than or equal to 0.1%.
11. A water-based paint, which is characterized by comprising a main resin and a water-based blocked isocyanate curing agent, wherein the water-based blocked isocyanate curing agent is the water-based blocked isocyanate curing agent as defined in any one of claims 1 to 8 or the water-based blocked isocyanate curing agent prepared by the preparation method as defined in claim 9 or 10.
12. The aqueous coating material according to claim 11, wherein the host resin is at least one selected from the group consisting of an amino resin and a polyester resin.
13. A coated article comprising a coating film formed from the aqueous coating composition according to any one of claims 11 to 12.
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CA2202605A1 (en) * 1996-04-17 1997-10-17 Beate Baumbach Aqueous or water-dilutable blocked polyisocyanates and their use for preparing polyurethane clearcoats having substantially reduced thermal yellowing
CN103554430A (en) * 2013-10-10 2014-02-05 陕西科技大学 Preparation method for enclosed type polyisocyanates cross-linking agent aqueous emulsion
CN109593182A (en) * 2018-11-08 2019-04-09 湖南湘江关西涂料有限公司 Non-ion aqueous blocked polyisocyanates curing agent and preparation method thereof, water paint
CN110042661A (en) * 2019-03-22 2019-07-23 东莞东阳光科研发有限公司 Finishing agent composition, finishing agent and its preparation method and application

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CA2202605A1 (en) * 1996-04-17 1997-10-17 Beate Baumbach Aqueous or water-dilutable blocked polyisocyanates and their use for preparing polyurethane clearcoats having substantially reduced thermal yellowing
CN103554430A (en) * 2013-10-10 2014-02-05 陕西科技大学 Preparation method for enclosed type polyisocyanates cross-linking agent aqueous emulsion
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