CN111944404A - Preparation method of special resin for water-based baking varnish with internal crosslinking function - Google Patents
Preparation method of special resin for water-based baking varnish with internal crosslinking function Download PDFInfo
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- CN111944404A CN111944404A CN202010803158.8A CN202010803158A CN111944404A CN 111944404 A CN111944404 A CN 111944404A CN 202010803158 A CN202010803158 A CN 202010803158A CN 111944404 A CN111944404 A CN 111944404A
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- 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
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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
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
- C08G18/6216—Polymers of alpha-beta ethylenically unsaturated carboxylic acids or of derivatives thereof
- C08G18/625—Polymers of alpha-beta ethylenically unsaturated carboxylic acids; hydrolyzed polymers of esters of these acids
- C08G18/6254—Polymers of alpha-beta ethylenically unsaturated carboxylic acids and of esters of these acids containing hydroxy groups
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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
- C08G18/8077—Oximes
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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
- C08G18/8093—Compounds containing active methylene groups
Abstract
The invention discloses a preparation method of a special resin for water-based baking varnish with an internal crosslinking function, which comprises the following steps: A. preparation of internal crosslinking monomer: mixing a sealing agent with a solvent without active hydrogen to obtain a mixture a, and dropwise adding the mixture a into diisocyanate to react under a stirring state to obtain an internal crosslinking monomer; B. synthesis of aqueous high-hydroxyl acrylic resin: b1, stirring and premixing reaction monomers and an initiator until the reaction monomers are completely dissolved to obtain a mixture B, wherein the reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid. According to the preparation method of the special resin for the water-based baking varnish with the internal crosslinking function, the prepared special resin for the water-based baking varnish has good water solubility and good internal crosslinking characteristics, and solves the problems of low crosslinking density, and poor physical properties such as hardness, salt spray resistance, scratch resistance, artificial sweat resistance and the like of the traditional water-based baking varnish film.
Description
Technical Field
The invention relates to the technical field of waterborne baking varnish resin, in particular to a preparation method of waterborne baking varnish special resin with an internal crosslinking function.
Background
With the increasing ecological consciousness of people, the development and application of environment-friendly materials are more and more emphasized, the environment-friendly water-based paint is widely concerned by people, and the special resin for the water-based paint taking the water-based acrylic resin as a matrix becomes one of research hotspots. With the continuous expansion of the application range of baking finish coatings, various decorative articles with high appearance requirements, such as household appliances, small hardware, office supplies and the like, are coated by adopting water-based baking finish, are particularly widely applied to the metal surface treatment of hardware products, and can replace the hardware material oil-based paint spraying, water washing paint spraying processes and surface electroplating coating processes of electroplating plants in the market, such as: the surface coating of window decoration products, door and window accessories, electroplating product sealing protection, bathroom products, locks, clothing products, decorative materials and the like is carried out by using aqueous baking finish coating, so that the coating appearance with various colors and metallic feelings can be obtained, the corrosion resistance and the binding force are improved, the environmental pressure generated by spray painting coating is avoided, the processing technology is simplified, and the application prospect is very wide. However, in the process of preparing paint for use, the addition of an external crosslinking agent to the existing waterborne baking paint resin can form a waterborne baking paint film with low crosslinking density, the hardness of the formed paint film is not high, and the physical properties such as salt spray resistance, scratch resistance and artificial sweat resistance are poor, so that the high requirements of high hardness and scratch resistance of the paint film can not be met.
Disclosure of Invention
Aiming at the problems brought forward by the background technology, the invention aims to provide a preparation method of a special resin for water-based baking paint with an internal crosslinking function, the prepared special resin for water-based baking paint has good water solubility and good internal crosslinking characteristics, and the problems of low crosslinking density, poor hardness, salt mist resistance, scratch resistance, artificial sweat resistance and other physical properties of the traditional water-based baking paint film are solved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing a sealing agent with a solvent without active hydrogen to obtain a mixture a, and dropwise adding the mixture a into diisocyanate to react under a stirring state to obtain an internal crosslinking monomer;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid;
b2, heating the organic cosolvent;
b3, dropwise adding the mixture B into the heated organic cosolvent for polymerization reaction to obtain the aqueous high-hydroxyl acrylic resin;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing the water-based high-hydroxyl acrylic resin with an internal crosslinking monomer for reaction to obtain hydroxyl acrylic resin with an internal crosslinking function;
D. resin neutralization and hydration: adding organic amine under stirring for neutralization reaction to obtain the special water-based baking varnish resin with the internal crosslinking function.
Preferably, in the step a, the diisocyanate is one or two of toluene diisocyanate and isophorone diisocyanate, and the blocking agent is at least one of methyl ethyl ketoxime, ethyl acetoacetate and acetylacetone.
Preferably, the ratio of the amount of isocyanate groups in the diisocyanate to the amount of reactive groups in the blocking agent is 1: (0.55-0.75).
Preferably, in the step a, the solvent without active hydrogen is at least one of ethyl acetate, butyl acetate, isopropyl acetate, tetrahydrofuran and dimethylformamide, and the amount of the solvent without active hydrogen is 40-60% of the total mass of the diisocyanate and the blocking agent.
Preferably, the reaction monomer comprises, by mass, 15-25 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 10-15 parts of hydroxyethyl methacrylate, 10-20 parts of hydroxypropyl methacrylate and 8-12 parts of acrylic acid.
Preferably, the amount of the initiator is 0.8-1.4% of the mass of the reaction monomer.
Preferably, in the step C, the ratio of the amount of hydroxyl groups in the aqueous high hydroxyl acrylic resin to the amount of the internal crosslinking monomer is 1: (0.25-0.55).
Preferably, in the step C, the reaction temperature of the mixing reaction of the water-based high hydroxyl acrylic resin and the internal crosslinking monomer is 60-80 ℃.
Preferably, in the step D, the amount of the organic amine is 80-100% of the amount of the substance of the reaction monomer acrylic acid.
Preferably, in the step D, the organic amine is at least one of triethylamine, N-dimethylethanolamine and 2-amino-2-methyl-1-propanol, the reaction temperature of the neutralization reaction is 60 to 80 ℃, and the neutralization time is 20 to 40 min.
Compared with the prior art, the invention has the following beneficial effects:
1. the internal crosslinking monomer, namely the semi-closed diisocyanate, is obtained by preparing the diisocyanate through the internal crosslinking monomer, then the water-based high-hydroxyl acrylic resin with hydroxyl as a crosslinking point is prepared, the internal crosslinking monomer is grafted on the water-based high-hydroxyl acrylic resin, and after water neutralization, the water-based baking varnish special resin with the internal crosslinking function is obtained, so that the resin has self-crosslinking capacity, the water-based baking varnish special resin with the internal crosslinking function has good water solubility and good internal crosslinking characteristics, and an external crosslinking agent (curing agent) is added in the paint preparation process, so that a paint film is cured in an internal crosslinking mode and an external crosslinking mode in the curing process, the crosslinking density of the paint film is effectively and greatly improved, and the limit that the highest crosslinking density of the water-based baking paint film formed by the traditional technology is not more than 70 percent is broken through, thereby greatly improving the physical properties of the paint film such as hardness, salt spray resistance, scratch resistance, artificial sweat resistance and the like;
2. the reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid, wherein the methyl methacrylate is a hard monomer, and the glass transition temperature Tg of the hard monomer is 106 ℃; the butyl acrylate is a soft monomer, the glass transition temperature Tg of the butyl acrylate is-56 ℃, the methyl methacrylate and the butyl acrylate provide proper glass transition temperature property for the waterborne baking varnish special resin with the internal crosslinking function, the hydroxyethyl methacrylate and the hydroxypropyl methacrylate provide hydroxyl which reacts with the internal crosslinking monomer as a crosslinking point for the water-based baking varnish special resin with the internal crosslinking function, the acrylic acid provides carboxyl groups for the hydroxyl acrylic resin with the internal crosslinking function, and after neutralization hydration reaction is carried out on the methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid, the special resin for the water-based baking varnish with the internal crosslinking function has good water solubility and good internal crosslinking characteristics;
3. the diisocyanate contains two isocyanate groups (-NCO), the reaction activity difference of the two isocyanate groups is large, the blocking agent reacts with the isocyanate groups (-NCO) with high reaction activity and small steric hindrance to obtain the semi-blocked diisocyanate, and the grafting effect of grafting the internal crosslinking monomer to the waterborne high-hydroxyl acrylic resin is guaranteed.
Detailed Description
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing a sealing agent with a solvent without active hydrogen to obtain a mixture a, and dropwise adding the mixture a into diisocyanate to react under a stirring state to obtain an internal crosslinking monomer;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid;
b2, heating the organic cosolvent;
b3, dropwise adding the mixture B into the heated organic cosolvent for polymerization reaction to obtain the aqueous high-hydroxyl acrylic resin;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing the water-based high-hydroxyl acrylic resin with an internal crosslinking monomer for reaction to obtain hydroxyl acrylic resin with an internal crosslinking function;
D. resin neutralization and hydration: adding organic amine under stirring for neutralization reaction to obtain the special water-based baking varnish resin with the internal crosslinking function.
The internal crosslinking monomer, namely the semi-closed diisocyanate, is obtained by preparing the diisocyanate through the internal crosslinking monomer, then the water-based high-hydroxyl acrylic resin with hydroxyl as a crosslinking point is prepared, the internal crosslinking monomer is grafted on the water-based high-hydroxyl acrylic resin, and after water neutralization, the water-based baking varnish special resin with the internal crosslinking function is obtained, so that the resin has self-crosslinking capacity, the water-based baking varnish special resin with the internal crosslinking function has good water solubility and good internal crosslinking characteristics, and an external crosslinking agent (curing agent) is added in the paint preparation process, so that a paint film is cured in an internal crosslinking mode and an external crosslinking mode in the curing process, the crosslinking density of the paint film is effectively and greatly improved, and the limit that the highest crosslinking density of the water-based baking paint film formed by the traditional technology is not more than 70 percent is broken through, and further greatly improves the physical properties of the paint film such as hardness, salt spray resistance, scratch resistance, artificial sweat resistance and the like.
The reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid, wherein the methyl methacrylate is a hard monomer, and the glass transition temperature Tg of the hard monomer is 106 ℃; the special water-based baking finish resin with the internal crosslinking function is characterized in that butyl acrylate is a soft monomer, the glass transition temperature Tg of the butyl acrylate is-56 ℃, methyl methacrylate and butyl acrylate provide proper glass transition temperature for the special water-based baking finish resin with the internal crosslinking function, hydroxyethyl methacrylate and hydroxypropyl methacrylate provide hydroxyl reacted with the internal crosslinking monomer as a crosslinking point, acrylic acid provides carboxyl groups for the hydroxyl acrylic resin with the internal crosslinking function, and after neutralization water-based reaction, the special water-based baking finish resin with the internal crosslinking function has good water solubility and good internal crosslinking characteristics.
Preferably, in the step a, the diisocyanate is one or two of toluene diisocyanate and isophorone diisocyanate, and the blocking agent is at least one of methyl ethyl ketoxime, ethyl acetoacetate and acetylacetone.
Preferably, the diisocyanate is isophorone diisocyanate.
The diisocyanate contains two isocyanate groups (-NCO), the reaction activity difference of the two isocyanate groups is large, the blocking agent reacts with the isocyanate groups (-NCO) with high reaction activity and small steric hindrance to obtain semi-blocked diisocyanate, and the grafting effect of grafting the internal crosslinking monomer to the waterborne high-hydroxyl acrylic resin is ensured;
the blocking agent is methyl ethyl ketoxime, ethyl acetoacetate and acetylacetone which have mild synthesis process and low deblocking temperature (about 125 ℃), if methanol or ethanol is used as the blocking agent, because the deblocking temperature of the methanol or the ethanol is more than 200 ℃, an external cross-linking agent (curing agent) is added in the paint preparation process, so that the paint film of the water-based baking paint is easy to yellow in the curing process.
In addition, the preparation of the crosslinking monomer in the step a can be carried out at room temperature.
Preferably, in the step a, the mixture a is dropwise added into diisocyanate for reaction for 20-40 min.
In the step A, the reaction time of dripping the mixture a into diisocyanate for reaction is 20-40 min, so that the preparation of the internal crosslinking monomer is ensured, and the reaction of the semi-closed diisocyanate is complete.
Preferably, the ratio of the amount of isocyanate groups in the diisocyanate to the amount of reactive groups in the blocking agent is 1: (0.55-0.75).
Preferably, the ratio of the amount of isocyanate groups in the diisocyanate to the amount of hydroxyl groups in the blocking agent is 1: 0.6.
if the amount of the blocking agent is too small, a small amount of the isocyanate groups (-NCO) having a small reactivity in the diisocyanate will react, resulting in that both the isocyanate groups (-NCO) of a part of the diisocyanate will not be blocked and gelling will easily occur in the preparation of the hydroxyl acrylic resin having an internal crosslinking function;
if the addition amount of the blocking agent is too large, the diisocyanate of which both ends are not blocked is too much, the semi-blocked diisocyanate capable of performing grafting reaction with the hydroxyl in the aqueous high-hydroxyl acrylic resin is too little, the grafting effect is poor, and the obtained aqueous baking varnish special resin with the internal crosslinking function has poor physical properties.
Preferably, in the step a, the solvent without active hydrogen is at least one of ethyl acetate, butyl acetate, isopropyl acetate, tetrahydrofuran and dimethylformamide, and the amount of the solvent without active hydrogen is 40-60% of the total mass of the diisocyanate and the blocking agent.
Preferably, the solvent containing no active hydrogen is used in an amount of 50% by mass based on the total mass of the diisocyanate and the blocking agent.
Preferably, the solubility of the solvent without active hydrogen in water is 8-12%.
The solvent without active hydrogen is used, so that the reaction of isocyanate (-NCO) in partial diisocyanate and active hydrogen in the solvent is avoided, and the reaction of the isocyanate (-NCO) in the diisocyanate and hydroxyl in the solvent can cause that the diisocyanate cannot be deblocked and loses the capability of re-reaction under mild conditions;
if the amount of the solvent containing no active hydrogen is too small, the dispersion uniformity of the mixture a dripped into the diisocyanate for reaction is poor, which easily causes too high local concentration, increases side reaction (isocyanate (-NCO) with small reaction activity in the diisocyanate reacts), reduces the obtained internal crosslinking monomer (semi-closed diisocyanate), increases double closed matters and non-closed matters, and makes the obtained special resin for water-based baking varnish with internal crosslinking function have poor physical properties.
Preferably, the reaction monomer comprises, by mass, 15-25 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 10-15 parts of hydroxyethyl methacrylate, 10-20 parts of hydroxypropyl methacrylate and 8-12 parts of acrylic acid.
Preferably, the reactive monomers comprise 20 parts by mass of methyl methacrylate, 20 parts by mass of butyl acrylate, 13 parts by mass of hydroxyethyl methacrylate, 15 parts by mass of hydroxypropyl methacrylate and 10 parts by mass of acrylic acid.
The reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid, wherein the methyl methacrylate is a hard monomer, and the glass transition temperature Tg of the hard monomer is 106 ℃; the butyl acrylate is a soft monomer, the glass transition temperature Tg of the butyl acrylate is-56 ℃, the methyl methacrylate and the butyl acrylate provide proper glass transition temperature property for the waterborne baking varnish special resin with the internal crosslinking function, the hydroxyethyl methacrylate and the hydroxypropyl methacrylate provide hydroxyl which reacts with the internal crosslinking monomer as a crosslinking point for the water-based baking varnish special resin with the internal crosslinking function, the acrylic acid provides carboxyl groups for the hydroxyl acrylic resin with the internal crosslinking function, and after neutralization hydration reaction is carried out on the methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid, the special resin for the water-based baking varnish with the internal crosslinking function has good water solubility and good internal crosslinking characteristics.
Preferably, the amount of the initiator is 0.8-1.4% of the mass of the reaction monomer.
Preferably, the amount of the initiator is 1.0% by mass of the reactive monomers.
If the amount of the initiator is too small, the polymerization of free radicals in the polymerization reaction cannot be continuously and stably carried out, if the amount of the initiator is too large, too many free radicals are generated in the polymerization reaction, so that the molecular weight of the obtained special resin for the water-based baking paint with the internal crosslinking function is small, the apparent viscosity is small, the viscosity of subsequent paint preparation is low, and a sagging phenomenon is easily generated during spraying, and meanwhile, because the molecular weight of the special resin for the water-based baking paint with the internal crosslinking function is small, the physical property is poor, and the physical property of a paint film formed after paint preparation is poor.
Preferably, in the step B1, the initiator is benzoyl peroxide or azobisisobutyronitrile.
The initiator adopts benzoyl peroxide or azodiisobutyronitrile, has moderate initiation activity and good use and storage safety, and ensures that the reaction process of the water-based high-hydroxyl acrylic resin is stably carried out.
Preferably, the organic cosolvent is a solvent without active hydrogen, and the organic cosolvent is at least one of ethyl acetate, butyl acetate, isopropyl acetate, tetrahydrofuran and dimethylformamide.
And using the solvent without active hydrogen to avoid the reaction of partial isocyanate group (-NCO) in the diisocyanate with active hydrogen in the solvent, and the reaction of the isocyanate group (-NCO) in the diisocyanate with hydroxyl in the solvent.
Preferably, in the step B2, the temperature of the heated organic cosolvent is 85 to 95 ℃.
The temperature of the organic cosolvent after heating is 85-95 ℃, a basic initiation temperature is provided for the initiator, a certain temperature rise space is provided for the heat release of the polymerization reaction, and the polar cosolvent is ensured not to evaporate when the reaction monomer and the initiator are dissolved.
Preferably, in the step B, the amount of the organic cosolvent is 25 to 40% by mass of the reaction monomer.
Preferably, in the step B, the amount of the organic cosolvent used is 30% by mass of the reaction monomers.
Preferably, in the step B3, the reaction temperature of the polymerization reaction is 90-120 ℃, and the reaction time is 2-4 hours.
Preferably, in the step B3, the reaction temperature of the polymerization reaction is 105 ℃.
If the reaction temperature of the polymerization reaction in the step B3 is too low, accumulation of the reaction monomer in the reaction system is easily caused, so that there is a risk of implosion during the polymerization reaction, and if the reaction temperature of the polymerization reaction in the step B3 is too high, the obtained waterborne baking varnish special-purpose resin with internal crosslinking function has a yellow color.
Preferably, in the step C, the ratio of the amount of hydroxyl groups in the aqueous high hydroxyl acrylic resin to the amount of the internal crosslinking monomer is 1: (0.25-0.55).
Preferably, the ratio of the amount of the hydroxyl groups in the aqueous high hydroxyl acrylic resin to the amount of the substance of the internal crosslinking monomer is 1: 0.4.
if the amount of the internal crosslinking monomer is too small, the grafting ratio of the water-based high-hydroxyl acrylic resin is too low, the grafting effect is not obvious, and if the amount of the internal crosslinking monomer is too large, the crosslinking performance of the obtained water-based baking varnish special resin with the internal crosslinking function is poor when an external crosslinking agent is added for crosslinking, and the physical performance of the obtained water-based baking varnish special resin with the internal crosslinking function is poor.
Preferably, in the step C, the reaction temperature of the mixing reaction of the water-based high hydroxyl acrylic resin and the internal crosslinking monomer is 60-80 ℃.
Preferably, in the step C, the reaction time for mixing and reacting the aqueous high hydroxyl acrylic resin and the internal crosslinking monomer is 2 hours.
If the reaction temperature of the mixing reaction of the aqueous high hydroxyl acrylic resin and the internal crosslinking monomer in the step C is too high, the blocked isocyanate (-NCO) in the internal crosslinking monomer is easily deblocked, and reacts with the hydroxyl (-OH) in the aqueous high hydroxyl acrylic resin in the reaction process, so that the synthesized hydroxyl acrylic resin gel with the internal crosslinking function is caused, and if the reaction temperature of the mixing reaction of the aqueous high hydroxyl acrylic resin and the internal crosslinking monomer in the step C is too low, the reaction of grafting the internal crosslinking monomer to the aqueous high hydroxyl acrylic resin is not enough to be completely carried out, so that the physical property of the obtained resin special for the aqueous baking varnish with the internal crosslinking function is poor.
Preferably, in the step D, the amount of the organic amine is 80-100% of the amount of the substance of the reaction monomer acrylic acid.
Preferably, in the step D, the organic amine is used in an amount of 90% of the amount of the substance of the reaction monomer acrylic acid.
The amount of the organic amine is 80-100% of the amount of the reaction monomer acrylic acid, the water-based degree of the resin reaches a high plateau period, and if the amount of the organic amine is too large, the water solubility of the obtained special resin for the water-based baking paint with the internal crosslinking function is not obviously improved, but the special resin for the water-based baking paint with the internal crosslinking function is easily yellowed, and the taste of the amine is aggravated.
Preferably, in the step D, the organic amine is at least one of triethylamine, N-dimethylethanolamine and 2-amino-2-methyl-1-propanol, the reaction temperature of the neutralization reaction is 60 to 80 ℃, and the neutralization time is 20 to 40 min.
Preferably, in the step D, the reaction temperature of the neutralization reaction is 70 ℃, and the neutralization time is 30 min.
The organic amine is at least one of triethylamine, N-dimethylethanolamine and 2-amino-2-methyl-1-propanol with moderate boiling point, if the boiling point of the organic amine is too low, the volatilization amount during neutralization is too large, the volatilization consumption is easy to be realized during storage, and if the boiling point of the organic amine is too high, the organic amine is not easy to overflow from a paint film, so that the performances of the paint film such as water resistance and salt fog resistance are influenced.
The neutralization time of the neutralization reaction is 20-40 min, and in this time period, the hydroxyl acrylic resin with the internal crosslinking function and the organic amine can be fully mixed, so that the mixing uniformity is good.
The technical solution of the present invention is further explained by the following embodiments.
And (3) performance testing:
1. and (3) hardness measurement: according to GB/T6739-2006 "color paints and varnishes: the hardness of the paint film is determined by a determination method of pencil method determination paint film hardness.
2. And (3) measuring the salt spray resistance: the salt spray resistance is measured according to the test method of GB/T2423.17 KA salt spray test method for testing the basic environmental test regulations of electrical and electronic products.
3. Solvent resistance (scratch resistance) determination: the same part of the paint film template was wiped repeatedly in butanone atmosphere under 1kg of force until the primer was exposed, and the total number of wipes was recorded.
4. And (3) measuring the artificial sweat resistance: according to ISO 12870: 1997 test methods of artificial sweat test Standard determine salt spray resistance.
Example 1
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 104g of a blocking agent (methyl ethyl ketoxime, M ═ 87) (namely the mass ratio of isocyanate in the diisocyanate to a substance of a reactive group in the blocking agent is 1: 0.6) with 139g of a solvent (butyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 50% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state, wherein the dropwise adding time is 30min to obtain an internal crosslinking monomer, and the solid content is 66.6%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 23.5g of organic cosolvent (isopropyl acetate) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 105 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 76.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 34g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.4) for reaction at 70 ℃ for 2h to obtain 134g of hydroxyl acrylic resin with an internal crosslinking function, wherein the solid content is 74%;
D. resin neutralization and hydration: and C, adding 10.5g of organic amine (dimethylethanolamine, M is 89) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under the stirring state for neutralization reaction at the reaction temperature of 70 ℃ for 30min to obtain the special water-based baking varnish resin with the internal crosslinking function.
Example 2
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 96g of a blocking agent (methyl ethyl ketoxime, M ═ 87) (namely the mass ratio of isocyanate in the diisocyanate to a reactive group in the blocking agent is 1: 0.55) with 191g of a solvent (isopropyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 60% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 222g of diisocyanate (isophorone isocyanate, M ═ 222) to react under a stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 62.2%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 20g of organic cosolvent (butyl acetate) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 120 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 79.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 90g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 51g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.55) for reaction at the temperature of 60 ℃ for 2h to obtain 141g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 73%;
D. resin neutralization and hydration: and C, adding 13.6g of organic amine (2-amino-2-methyl-1-propanol, wherein M is 89) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 20min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 3
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 195g of a blocking agent (ethyl acetoacetate, M ═ 130) (namely the ratio of the amount of isocyanate in the diisocyanate to the amount of a substance of a reactive group in the blocking agent is 1: 0.75) with 148g of a solvent (ethyl acetate) without active hydrogen (the amount of the solvent without active hydrogen is 40% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 71.4%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 31g of organic cosolvent (dimethylformamide) into a reaction bottle, and heating to 120 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 100 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 72%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 25g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.25) for reaction at 80 ℃ for 2h to obtain 125g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 71.7%;
D. resin neutralization and hydration: and C, adding 8g of organic amine (triethylamine, M is 101) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 40min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 4
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 210g of a blocking agent (ethyl acetoacetate, M ═ 130) (namely the ratio of the content of isocyanate in the diisocyanate to the content of a substance of a reactive group in the blocking agent is less than 1: 0.75) with 148g of a solvent (ethyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 40% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state, wherein the dropwise adding time is 30min to obtain an internal crosslinking monomer, and the solid content is 72%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 31g of organic cosolvent (dimethylformamide) into a reaction bottle, and heating to 120 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 100 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 71.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 25g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.25) for reaction at 80 ℃ for 2h to obtain 125g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 71.4%;
D. resin neutralization and hydration: and C, adding 8g of organic amine (triethylamine, M is 101) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 40min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 5
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 96g of a blocking agent (methyl ethyl ketoxime, M ═ 87) (namely the mass ratio of isocyanate in the diisocyanate to a reactive group in the blocking agent is 1: 0.55) with 191g of a solvent (isopropyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 60% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 222g of diisocyanate (isophorone isocyanate, M ═ 222) to react under a stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 62.2%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 20g of organic cosolvent (butyl acetate) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 120 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 78.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 90g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 51g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.55) for reaction at the temperature of 60 ℃ for 2h to obtain 141g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 72%;
D. resin neutralization and hydration: and C, adding 13.6g of organic amine (2-amino-2-methyl-1-propanol, wherein M is 89) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 20min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 6
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 96g of a blocking agent (methyl ethyl ketoxime, M ═ 87) (namely the mass ratio of isocyanate in the diisocyanate to a reactive group in the blocking agent is 1: 0.55) with 191g of a solvent (isopropyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 60% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 222g of diisocyanate (isophorone isocyanate, M ═ 222) to react under a stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 62.4%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 20g of organic cosolvent (butyl acetate) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 120 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 79%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 90g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 60g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is less than 1: 0.55) for reaction at the temperature of 60 ℃ for 2h to obtain 141g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 77%;
D. resin neutralization and hydration: and C, adding 13.6g of organic amine (2-amino-2-methyl-1-propanol, wherein M is 89) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 20min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 7
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 80g of a blocking agent (methyl ethyl ketoxime, M ═ 87) (namely the ratio of the content of isocyanate in diisocyanate to the content of a substance of a reactive group in the blocking agent is more than 1: 0.55) with 191g of a solvent (isopropyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is 60% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 222g of diisocyanate (isophorone isocyanate, M ═ 222) to react under a stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 61.3%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 20g of organic cosolvent (butyl acetate) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 120 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 78.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 90g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 51g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.55) for reaction at the temperature of 60 ℃ for 2h to obtain 141g of the hydroxyl acrylic resin with the internal crosslinking function and the solid content of 72.2%;
D. resin neutralization and hydration: and C, adding 13.6g of organic amine (2-amino-2-methyl-1-propanol, wherein M is 89) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 20min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 8
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 195g of a blocking agent (ethyl acetoacetate, M ═ 130) (namely the ratio of the amount of isocyanate in the diisocyanate to the amount of a substance of a reactive group in the blocking agent is 1: 0.75) with 130g of a solvent (ethyl acetate) without active hydrogen (the using amount of the solvent without active hydrogen is less than 40% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state, wherein the dropwise adding time is 30min to obtain an internal crosslinking monomer, and the solid content is 74%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 31g of organic cosolvent (dimethylformamide) into a reaction bottle, and heating to 120 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 100 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 71.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 25g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.25) for reaction at 80 ℃ for 2h to obtain 125g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 72%;
D. resin neutralization and hydration: and C, adding 8g of organic amine (triethylamine, M is 101) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 40min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 9
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 195g of a blocking agent (ethyl acetoacetate, M ═ 130) (namely the ratio of the amount of isocyanate in the diisocyanate to the amount of a substance of a reactive group in the blocking agent is 1: 0.75) with 148g of a solvent (ethyl acetate) without active hydrogen (the amount of the solvent without active hydrogen is 40% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 71.4%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 31g of organic cosolvent (dimethylformamide) into a reaction bottle, and heating to 120 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 100 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 71.5%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 25g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is 1: 0.25) for reaction at 80 ℃ for 2h to obtain 125g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 71.5%;
D. resin neutralization and hydration: and C, adding 8g of organic amine (triethylamine, M is 101) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 40min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Example 10
A preparation method of special water-based baking varnish resin with an internal crosslinking function comprises the following steps:
A. preparation of internal crosslinking monomer: mixing 195g of a blocking agent (ethyl acetoacetate, M ═ 130) (namely the ratio of the amount of isocyanate in the diisocyanate to the amount of a substance of a reactive group in the blocking agent is 1: 0.75) with 148g of a solvent (ethyl acetate) without active hydrogen (the amount of the solvent without active hydrogen is 40% of the total mass of the diisocyanate and the blocking agent) to obtain a mixture a, dropwise adding the mixture a into 174g of diisocyanate (toluene diisocyanate, M ═ 174) to react under the stirring state for 30min to obtain an internal crosslinking monomer with the solid content of 71.4%;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
b2, adding 31g of organic cosolvent (dimethylformamide) into a reaction bottle, and heating to 120 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, preserving the heat at 100 ℃ for 3 hours, and carrying out polymerization reaction to obtain the water-based high-hydroxyl acrylic resin with the solid content of 71.6%;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing 100g of the aqueous high-hydroxyl acrylic resin prepared in the step B with 20g of the internal crosslinking monomer prepared in the step A (the mass ratio of hydroxyl in the aqueous high-hydroxyl acrylic resin to the internal crosslinking monomer is more than 1: 0.25) for reaction at the temperature of 80 ℃ for 2h to obtain 125g of the hydroxyl acrylic resin with the internal crosslinking function, wherein the solid content is 71.5%;
D. resin neutralization and hydration: and C, adding 8g of organic amine (triethylamine, M is 101) into the hydroxy acrylic resin with the internal crosslinking function obtained in the step C under a stirring state for neutralization reaction at the reaction temperature of 80 ℃ for 40min to obtain the special resin for the water-based baking varnish with the internal crosslinking function.
Comparative example 1
A preparation method of baking varnish resin comprises the following steps:
a1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture b, wherein the reaction monomers are used in the following amounts by mass (1 part by mass is 1 g):
| serial number | Reactive monomer | Quality of |
| 1 | Methacrylic acid methyl ester | 20g |
| 2 | Acrylic acid butyl ester | 20g |
| 3 | Hydroxyethyl methacrylate (M130) | 10g |
| 4 | Acrylic acid isooctyl ester | 10g |
| 5 | Acrylic acid (M ═ 72) | 8g |
| Small counter | 68g | |
| 6 | Initiator (azobisisobutyronitrile) | 0.6g |
| 7 | Organic cosolvent (ethylene glycol monobutyl ether) | 42g |
B2, adding 42g of organic cosolvent (ethylene glycol monobutyl ether) into a reaction bottle, and heating to 90 ℃ under the stirring state;
b3, dropwise adding the mixture B into the heated organic cosolvent for 3 hours, and carrying out heat preservation at 100 ℃ for 3 hours to carry out polymerization reaction to obtain the baking varnish resin.
Using the baking varnish resins prepared in examples 1 to 11 and comparative example 1, aqueous baking varnish preparation was carried out according to the following formulation using a conventional aqueous baking varnish preparation process:
the water-based baking varnish comprises the following raw materials in parts by weight: 48 parts of baking varnish resin, 12 parts of cyante 325 amino resin, 4 parts of cyante epoxy phosphate, 0.5 part of BYK024 defoaming agent, 0.2 part of Tego245 wetting agent, 0.2 part of Tego450 leveling agent, 8 parts of BCS white water, 6.5 parts of ethanol and 22.5 parts of pure water, which are prepared in examples 1 to 11 and comparative example 1.
And (3) carrying out performance test on the prepared paint film to obtain the following performance test results:
TABLE 1 Performance test of examples and comparative examples
From the test results, the water-based baking varnish paint films of the examples 1 to 3 have excellent performance, and have the performance characteristics of high hardness, high salt mist resistance, high scratch resistance and high artificial sweat resistance, the examples 1 to three are characterized in that diisocyanate is prepared by the internal crosslinking monomer to obtain the internal crosslinking monomer, namely semi-blocked diisocyanate, then the water-based high-hydroxyl acrylic resin with hydroxyl as a crosslinking point is prepared, the internal crosslinking monomer is grafted on the water-based high-hydroxyl acrylic resin, and after neutralization and hydration, the water-based baking varnish special resin with the internal crosslinking function is obtained, the resin is endowed with the self-crosslinking capacity, the water-based baking varnish special resin with the internal crosslinking function has good water solubility and also has good internal crosslinking characteristics, and in the paint preparation process, an external crosslinking agent (curing agent) is added to enable the paint film to be cured, the paint film is cured in an internal and external crosslinking mode, so that the crosslinking density of the paint film is effectively and greatly improved, and the physical properties of the paint film, such as hardness, salt mist resistance, scratch resistance, artificial sweat resistance and the like, are further greatly improved;
example 4 since the ratio of the amount of isocyanate groups in the diisocyanate to the amount of species of reactive groups in the blocking agent during the preparation of the internal crosslinking monomer is less than 1: 0.75, namely, the addition amount of the blocking agent is too much, so that the diisocyanate of which both ends are not blocked is too much, the semi-blocked diisocyanate capable of performing grafting reaction with the hydroxyl in the waterborne high hydroxyl acrylic resin is too little, the grafting effect is poor, and the physical properties of the obtained waterborne baking varnish special resin with the internal crosslinking function are poorer than those of the waterborne baking varnish in examples 1 to 3;
example 5 in the preparation process of the waterborne high hydroxyl acrylic resin, the initiator is used in an amount which is more than 1.4% of the mass of the reaction monomer, the initiator is used in an excessive amount, and the free radicals generated in the polymerization reaction are too much, so that the obtained waterborne baking varnish special resin with the internal crosslinking function has a small molecular weight and a small apparent viscosity, the subsequent paint preparation viscosity is low, and the sagging phenomenon is generated during painting, and meanwhile, the waterborne baking varnish special resin with the internal crosslinking function has a small molecular weight, poor physical properties and lower hardness than the baking varnish paint films of examples 1 to 3.
Example 6 since the ratio of the hydroxyl groups in the aqueous high hydroxyl acrylic resin to the amount of species of the internal crosslinking monomer is less than 1: 0.55, the amount of the internal crosslinking monomer is too large, the crosslinking performance of the obtained special resin for the water-based baking paint with the internal crosslinking function is poor when an external crosslinking agent is added for crosslinking, and the physical performance of the prepared paint film is poor;
example 7 since the ratio of isocyanate groups in the diisocyanate to the amount of species of reactive groups in the blocking agent during the preparation of the internal crosslinking monomer is greater than 1: 0.55, namely, the addition amount of the blocking agent is too small, so that two isocyanate groups (-NCO) of part of the diisocyanate are not blocked, gelation easily occurs in the preparation of the hydroxyl acrylic resin with the internal crosslinking function, and the hardness, the salt fog resistance, the solvent resistance and the artificial sweat resistance of the prepared paint film are poorer than those of the paint films prepared in the examples 1 to 3;
example 8 since the amount of the active hydrogen-free solvent used was less than 40% of the total mass of the diisocyanate and the blocking agent, the resulting internal crosslinking monomer (semi-blocked diisocyanate) was reduced, the amount of double blocks and unblocked material was increased, and the physical properties of the resulting paint film were poor;
example 9 in the process of synthesizing the aqueous high hydroxyl acrylic resin, since the amount of the initiator is less than 0.8% by mass of the reaction monomer, the amount of the initiator is too small to ensure that the polymerization of the free radicals in the polymerization reaction is continuously and stably performed, and the physical properties of the prepared paint film are poor;
example 10 since the ratio of the amount of hydroxyl groups in the aqueous high hydroxyl acrylic resin to the amount of species of the internal crosslinking monomer is greater than 1: 0.25, namely the addition amount of the internal crosslinking monomer is too small, so that the grafting rate of the water-based high-hydroxyl acrylic resin is too low, the grafting effect is not obvious, the internal crosslinking effect of a paint film is poor, and the hardness, the salt spray resistance, the solvent resistance and the artificial sweat resistance of the prepared paint film are poorer than those of the paint films prepared in the embodiments 1 to 3;
comparative example 1 a conventional aqueous baking varnish resin was used for baking varnish preparation, and due to the low crosslinking density of the resin, the hardness of the formed paint film was low and the physical properties of salt spray resistance, scratch resistance, artificial sweat resistance, etc. were poor, failing to meet the high requirements for high hardness and scratch resistance of the paint film.
The technical principle of the present invention is described above in connection with specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.
Claims (10)
1. A preparation method of special resin for water-based baking varnish with an internal crosslinking function is characterized by comprising the following steps:
A. preparation of internal crosslinking monomer: mixing a sealing agent with a solvent without active hydrogen to obtain a mixture a, and dropwise adding the mixture a into diisocyanate to react under a stirring state to obtain an internal crosslinking monomer;
B. synthesis of aqueous high-hydroxyl acrylic resin:
b1, stirring and premixing reaction monomers and an initiator until the reaction monomers and the initiator are completely dissolved to obtain a mixture B, wherein the reaction monomers comprise methyl methacrylate, butyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and acrylic acid;
b2, heating the organic cosolvent;
b3, dropwise adding the mixture B into the heated organic cosolvent for polymerization reaction to obtain the aqueous high-hydroxyl acrylic resin;
C. preparation of hydroxy acrylic resin with internal crosslinking function: mixing the water-based high-hydroxyl acrylic resin with an internal crosslinking monomer for reaction to obtain hydroxyl acrylic resin with an internal crosslinking function;
D. resin neutralization and hydration: adding organic amine under stirring for neutralization reaction to obtain the special water-based baking varnish resin with the internal crosslinking function.
2. The method for preparing the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step A, the diisocyanate is one or two of toluene diisocyanate and isophorone diisocyanate, and the blocking agent is at least one of methyl ethyl ketoxime, ethyl acetoacetate and acetylacetone.
3. The method for preparing the special resin for the water-based baking paint with the internal crosslinking function according to claim 1, wherein the ratio of the amount of the isocyanate group in the diisocyanate to the amount of the substance of the reactive group in the blocking agent is 1: (0.55-0.75).
4. The method for preparing the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step A, the solvent without active hydrogen is at least one of ethyl acetate, butyl acetate, isopropyl acetate, tetrahydrofuran and dimethylformamide, and the amount of the solvent without active hydrogen is 40-60% of the total mass of the diisocyanate and the sealant.
5. The preparation method of the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein the reaction monomers comprise, by mass, 15-25 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 10-15 parts of hydroxyethyl methacrylate, 10-20 parts of hydroxypropyl methacrylate and 8-12 parts of acrylic acid.
6. The preparation method of the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein the amount of the initiator is 0.8-1.4% of the mass of the reaction monomer.
7. The method for preparing the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step C, the ratio of the hydroxyl groups in the water-based high hydroxyl acrylic resin to the amount of the internal crosslinking monomer is 1: (0.25-0.55).
8. The method for preparing the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step C, the reaction temperature of the mixing reaction of the water-based high hydroxyl acrylic resin and the internal crosslinking monomer is 60-80 ℃.
9. The method for preparing the special resin for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step D, the amount of the organic amine is 80-100% of the amount of the substance of the reaction monomer acrylic acid.
10. The preparation method of the resin special for the water-based baking varnish with the internal crosslinking function according to claim 1, wherein in the step D, the organic amine is at least one of triethylamine, N-dimethylethanolamine and 2-amino-2-methyl-1-propanol, the reaction temperature of the neutralization reaction is 60-80 ℃, and the neutralization time is 20-40 min.
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| 马景松等: "水分散型半封端TDI接枝丙烯酸树脂的制备及性能", 《聚氨酯工业》 * |
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| CN113248658A (en) * | 2021-06-17 | 2021-08-13 | 韶关盛怡文具有限公司 | High-viscoelasticity resin special for space pen ink, preparation method and ink using resin |
| CN113248658B (en) * | 2021-06-17 | 2022-04-19 | 韶关盛怡文具有限公司 | High-viscoelasticity resin special for space pen ink, preparation method and ink using resin |
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