CN111978853A

CN111978853A - Waterborne polyurethane composite coating and preparation method thereof

Info

Publication number: CN111978853A
Application number: CN202010915803.5A
Authority: CN
Inventors: 刘国聪; 胡庭维
Original assignee: Hangzhou Lichai Cultural Goods Co ltd
Current assignee: Hangzhou Lichai Cultural Goods Co ltd
Priority date: 2020-09-03
Filing date: 2020-09-03
Publication date: 2020-11-24

Abstract

The invention discloses a waterborne polyurethane composite coating, which comprises the following raw materials in parts by weight: 20-30 parts of polytetrahydrofuran glycol, 1-3 parts of 1, 4-butanediol, 2-4 parts of 2, 2-dimethylolpropionic acid, 12-14 parts of isophorone diisocyanate, 4-6 parts of N, N-dimethylacetamide, 0.1-0.3 part of dibutyltin dilaurate, 16-20 parts of acetone, 300 parts of deionized water, 0.1-0.3 part of diethylenetriamine, 40-50 parts of modified epoxy resin, 0.1-0.3 part of defoaming agent, 0.1-0.3 part of wetting agent, 0.1-0.3 part of flatting agent and 0.1-0.3 part of thickening agent; the aerogel can form hydrogen bonds with the epoxy resin, the van der Waals acting force between molecules is enhanced, the modified epoxy resin is more favorable for improving the mechanical property of the coating, along with the increase of the molecular weight and the crosslinking density, the water diffusion inside is hindered, and the water resistance of the coating is improved.

Description

Waterborne polyurethane composite coating and preparation method thereof

Technical Field

The invention belongs to the technical field of water-based paint preparation, and particularly relates to a water-based polyurethane composite paint and a preparation method thereof.

Background

The polyurethane coating is a common coating at present, and has the characteristics of low film forming temperature, strong adhesive force, good wear resistance, high hardness, chemical resistance and good weather resistance. The waterborne polyurethane has the characteristics of high hardness, good toughness, excellent corrosion resistance and the like, but has low mechanical strength and poor water penetration resistance.

The invention patent CN103102718A discloses a waterborne polyurethane composite coating, which is characterized in that the coating is prepared from the following raw materials, by weight, 40-60 parts of a waterborne polyurethane emulsion, 12-25 parts of polyacrylic acid, 20-30 parts of polyisocyanate, 30-40 parts of a crosslinking agent, 10-15 parts of a filler and 80-100 parts of water. The waterborne polyurethane composite coating prepared by the invention combines the advantages of polyurethane coatings and polypropylene coatings, and has the characteristics of wear resistance, corrosion resistance, brightness, water resistance and good mechanical properties. In addition, the coating film of the polyurethane can be made into a high-hardness coating film and also can be made into an elastic coating film with good flexibility, so that the application range of the polyurethane coating is greatly enhanced.

Disclosure of Invention

In order to overcome the technical problems, the invention provides a waterborne polyurethane composite coating and a preparation method thereof.

The technical problems to be solved by the invention are as follows:

the molecular structure of the traditional waterborne polyurethane coating is mostly represented as a single chain segment structure, and is mostly represented as the defects of poor water resistance, low mechanical strength and the like, so that the application of the traditional waterborne polyurethane coating in the production and living fields is very limited.

The purpose of the invention can be realized by the following technical scheme:

the waterborne polyurethane composite coating comprises the following raw materials in parts by weight:

20-30 parts of polytetrahydrofuran glycol, 1-3 parts of 1, 4-butanediol, 2-4 parts of 2, 2-dimethylolpropionic acid, 12-14 parts of isophorone diisocyanate, 4-6 parts of N, N-dimethylacetamide, 0.1-0.3 part of dibutyltin dilaurate, 16-20 parts of acetone, 300 parts of deionized water, 0.1-0.3 part of diethylenetriamine, 40-50 parts of modified epoxy resin, 0.1-0.3 part of defoaming agent, 0.1-0.3 part of wetting agent, 0.1-0.3 part of flatting agent and 0.1-0.3 part of thickening agent;

the waterborne polyurethane composite coating is prepared by the following steps:

firstly, putting polytetrahydrofuran diol and 1, 4-butanediol into a three-neck flask, putting the three-neck flask into a vacuum drying oven with the temperature of 70-80 ℃, carrying out vacuum drying for 2-3h, taking out the flask after the drying is finished, cooling the three-neck flask to 20-30 ℃, adding 2, 2-dimethylolpropionic acid, isophorone diisocyanate, N-dimethylacetamide and dibutyltin dilaurate, setting the temperature to 80 ℃, reacting for 1-2h, cooling to 20-30 ℃, adding acetone, stirring for 50-70min, adding triethylamine, continuously stirring for 5-10min, adding 80 percent deionized water at the rotating speed of 1800 plus 2000r/min, stirring at high speed for 30min, then dropwise adding diethylenetriamine, continuously stirring at a high speed for 5-10min, and after stirring is finished, distilling under reduced pressure to remove acetone to prepare aqueous polyurethane emulsion;

and secondly, stirring the waterborne polyurethane emulsion and the epoxy resin at a high speed of 1500-80 r/min for 20-30min to obtain a pre-emulsion, adding the rest deionized water, the defoamer, the wetting agent, the flatting agent and the thickener into the pre-emulsion, and stirring for 50-70min at a temperature of 20-30 ℃ and a rotation speed of 500-600r/min to obtain the waterborne polyurethane composite coating.

Further, in the first step, the polytetrahydrofuran diol has an average molecular weight of 2000; in the second step, the defoaming agent is an organic silicon defoaming agent, the wetting agent is BYK-187, the leveling agent is BYK-350, and the thickening agent is an acrylic acid alkali swelling thickening agent.

Further, the modified epoxy resin is prepared by the following steps:

step S11, adding bisphenol A epoxy resin and propylene glycol monomethyl ether into a three-neck flask, stirring until the solution is transparent under the conditions that the temperature is set to be 60-70 ℃ and the rotating speed is 300-400r/min, keeping the temperature and the rotating speed unchanged, adding polyethylene glycol into the three-neck flask, continuously stirring at constant temperature until no crystallization occurs, and mixing boron trifluoride ethyl ether and propylene glycol monomethyl ether in a mass ratio of 5: adding the mixed solution of 1 into a three-necked bottle, dripping the mixed solution at a constant speed within 1h, and reacting at a constant temperature of 90 ℃ for 6h after finishing dripping to obtain a mixed solution A;

step S12, mixing aerogel and absolute ethyl alcohol according to a mass ratio of 1: 10, mixing, carrying out ultrasonic treatment for 30-40min under the condition that the frequency is 40-50kHz, adding a mixed solution of deionized water and aerogel and absolute ethyl alcohol into the mixed solution A, reacting for 20-30min at the temperature of 60-70 ℃, and then treating for 30-40min under the power of 60-70W by using an ultrasonic cell crusher to prepare the modified epoxy resin.

Further, in step S11, the polyethylene glycol is PEG-4000; the mass ratio of bisphenol A type epoxy resin, propylene glycol methyl ether, polyethylene glycol and boron trifluoride ethyl ether is 1: 2: 1: 0.1-0.3; in step S12, the mass ratio of the mixed solution a, deionized water, and aerogel is 1: 1: 0.1-0.3.

Further, the aerogel is prepared by the following steps:

step S21, adding halloysite into deionized water, stirring for 5-6h at the temperature of 20-30 ℃ and the rotation speed of 300-400r/min, separating for three times in a centrifuge at the rotation speed of 2000r/min after stirring is finished, performing suction filtration, washing filter residues for three times by using absolute ethyl alcohol, and drying the washed filter residues to constant weight at the temperature of 40-60 ℃ to obtain powder a;

step S22, mixing the powder a with an ethanol solution with the volume fraction of 50%, adding phenyl vinyl silicone oil and dibenzoyl peroxide, stirring for 5min, carrying out ultrasonic treatment for 1h under the condition of the frequency of 40-50kHz to prepare a mixed solution, putting the mixed solution into a vacuum bottle, pumping the vacuum bottle to vacuum by using a vacuum pump, and then heating for 40-60min under the condition of 70-80 ℃; keeping the temperature at 50-60 ℃ for 24h, continuing to heat at 80 ℃ for 1-3h after the heat preservation is finished, centrifuging at 8000r/min for 5min after the heating is finished, filtering to obtain filter residue, washing the filter residue with deionized water for three times, and drying at 40-60 ℃ to constant weight to obtain powder b;

and S23, adding the powder b and sodium dodecyl sulfate into deionized water, carrying out ultrasonic treatment for 20-30min under the condition of frequency of 40-50kHz, adding cyclohexane and stirring for 30-40min after the ultrasonic treatment is finished to obtain a mixed solution, then adding the mixed solution into a three-necked bottle, raising the temperature of the system to 70-80 ℃, adding benzoyl peroxide, keeping the temperature unchanged after the heating is finished, keeping the temperature for 24h, carrying out suction filtration after the heat preservation is finished, washing filter residues for three times by using the deionized water, and drying the filter residues to constant weight at 50-70 ℃ to obtain the aerogel.

Further, in step S21, the dosage ratio of the halloysite to the deionized water is 5-10g:50 mL; in step S22, the mass ratio of the powder a, the 50% volume fraction ethanol solution, the sodium dodecyl sulfate, the phenyl vinyl silicone oil, and the dibenzoyl peroxide is 0.1 to 0.3: 100: 1-1.2: 0.05: 0.02; in step S23, the amount ratio of the powder b, sodium dodecyl sulfate, deionized water, cyclohexane and benzoyl peroxide is 0.5 g: 1 g: 20-40 mL: 5-15 mL: 0.05-0.1 g.

Further, the preparation method of the waterborne polyurethane composite coating comprises the following steps:

firstly, putting polytetrahydrofuran diol and 1, 4-butanediol into a three-neck flask, putting the three-neck flask into a vacuum drying oven with the temperature of 70-80 ℃, carrying out vacuum drying for 2-3h, taking out the flask after the drying is finished, cooling the flask to 20-30 ℃, adding 2, 2-dimethylolpropionic acid, isophorone diisocyanate, N-dimethylacetamide and dibutyltin dilaurate, setting the temperature to 80 ℃, reacting for 1-2h, cooling to 20-30 ℃, adding acetone, stirring for 50-70min, then adding triethylamine, continuously stirring for 5-10min, adding 80 percent deionized water at the rotating speed of 1800 plus 2000r/min, stirring at high speed for 30min, then dropwise adding diethylenetriamine, continuously stirring at a high speed for 5-10min, and after stirring is finished, distilling under reduced pressure to remove acetone to prepare aqueous polyurethane emulsion;

The invention has the beneficial effects that:

halloysite and a silane coupling agent are chemically modified and grafted on the surface of the halloysite through physical or chemical bond, so that the dispersibility and compatibility of the aerogel in a polymer are improved, the prepared aerogel is added into a prepared coating as a filler, the internal structure of the aerogel is a net structure, a large number of holes exist, a micro-nano structure is formed on the surface of the coating by adding the aerogel, and the hydrophobicity is increased. The mechanical strength of the coating is obviously improved after the aerogel is used as an inorganic filler, and different carriers can be loaded while the aerogel is used as the filler, so that the coating has better anti-icing performance and other functions; the aerogel contains a large number of hydroxyl structures, can be combined with polar groups on the epoxy resin to form a compact network space structure, can form hydrogen bonds with the epoxy resin, enhances the van der Waals acting force between molecules, and is more favorable for improving the mechanical property of the coating by the modified epoxy resin.

The epoxy resin has excellent properties such as high strength, low shrinkage and good stability. The existence of hydroxyl, ether bond and epoxy group enables the epoxy resin to easily react with functional groups of other substances to generate stable chemical bonds, especially the ring opening of the epoxy group, and a stable three-way cross-linking structure can be formed. Therefore, the performance of the modified epoxy resin is superior to that of phenolic resin in acid resistance, corrosion resistance and the like, the modified epoxy resin and polyurethane are simple to modify, and the epoxy resin is easy to open a ring or has hydroxyl and can directly react with the prepolymer of the polyurethane. The modified epoxy resin contains an-OH group which can react with-NCO in the polyurethane prepolymer, an epoxy group, a benzene ring and an ether bond. In the reaction process, an epoxy resin chain segment is connected into a polyurethane prepolymer, crosslinking points in an emulsion system are increased along with the increase of the addition amount of the modified epoxy resin, the emulsion system is easy to form a compact crosslinking network due to the ring opening of an epoxy group, the rigid structure proportion in the polyurethane structure is increased, the emulsion particle size is gradually increased, the space network is enhanced, the inter-molecular distance is increased, the intermolecular force of the coating is increased along with the increase of the molecular weight and the crosslinking density, the diffusion of water into the interior is blocked, and the water resistance of the coating is improved.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

20 parts of polytetrahydrofuran diol, 1 part of 1, 4-butanediol, 2 parts of 2, 2-dimethylolpropionic acid, 12 parts of isophorone diisocyanate, 4 parts of N, N-dimethylacetamide, 0.1 part of dibutyltin dilaurate, 16 parts of acetone, 200 parts of deionized water, 0.1 part of diethylenetriamine, 40 parts of modified epoxy resin, 0.1 part of defoaming agent, 0.1 part of wetting agent, 0.1 part of flatting agent and 0.1 part of thickening agent;

firstly, putting polytetrahydrofuran diol and 1, 4-butanediol into a three-neck flask, putting the three-neck flask into a vacuum drying oven at 70 ℃, carrying out vacuum drying for 2h, taking out the flask after drying is finished, cooling the three-neck flask to 20 ℃, adding 2, 2-dimethylolpropionic acid, isophorone diisocyanate, N-dimethylacetamide and dibutyltin dilaurate, setting the temperature to 80 ℃, reacting for 1h, cooling to 20 ℃, adding acetone, stirring for 50min, adding triethylamine, continuously stirring for 5min, adding 80% deionized water at the rotating speed of 1800r/min, stirring at a high speed for 30min, adding diethylenetriamine, continuously stirring at a high speed for 5min, and after stirring is finished, carrying out reduced pressure distillation to remove the acetone to obtain an aqueous polyurethane emulsion;

and secondly, stirring the waterborne polyurethane emulsion and the epoxy resin at a high speed for 20min at a rotating speed of 1500r/min to obtain a pre-emulsion, adding the rest deionized water, the defoaming agent, the wetting agent, the flatting agent and the thickening agent into the pre-emulsion, and stirring for 50min at a temperature of 20 ℃ and a rotating speed of 500r/min to obtain the waterborne polyurethane composite coating.

Wherein, in the first step, the polytetrahydrofuran diol has an average molecular weight of 2000; in the second step, the defoaming agent is an organic silicon defoaming agent, the wetting agent is BYK-187, the leveling agent is BYK-350, and the thickening agent is an acrylic acid alkali swelling thickening agent.

Wherein the modified epoxy resin is prepared by the following steps:

step S11, adding bisphenol A epoxy resin and propylene glycol monomethyl ether into a three-neck flask, stirring until the solution is transparent under the conditions that the temperature is set to be 60 ℃ and the rotating speed is 300r/min, keeping the temperature and the rotating speed unchanged, adding polyethylene glycol into the three-neck flask, continuously stirring at constant temperature until no crystallization occurs, and mixing boron trifluoride ethyl ether and propylene glycol monomethyl ether in a mass ratio of 5: adding the mixed solution of 1 into a three-necked bottle, dripping the mixed solution at a constant speed within 1h, and reacting at a constant temperature of 90 ℃ for 6h after finishing dripping to obtain a mixed solution A;

step S12, mixing aerogel and absolute ethyl alcohol according to a mass ratio of 1: 10, mixing, carrying out ultrasonic treatment for 30min under the condition that the frequency is 40kHz, adding a mixed solution of deionized water and aerogel and absolute ethyl alcohol into the mixed solution A, reacting for 20min at the temperature of 60 ℃, and then treating for 30min under the power of 60W by using an ultrasonic cell crusher to prepare the modified epoxy resin.

Wherein, in the step S11, the polyethylene glycol is PEG-4000; the mass ratio of bisphenol A type epoxy resin, propylene glycol methyl ether, polyethylene glycol and boron trifluoride ethyl ether is 1: 2: 1: 0.1; in step S12, the mass ratio of the mixed solution a, deionized water, and aerogel is 1: 1: 0.1.

wherein the aerogel is prepared by the following steps:

step S21, adding halloysite into deionized water, stirring for 5 hours at the temperature of 20 ℃ and the rotating speed of 300r/min, separating for three times in a centrifugal machine at the rotating speed of 2000r/min after stirring is finished, performing suction filtration, washing filter residues for three times by using absolute ethyl alcohol, and drying the washed filter residues to constant weight at the temperature of 40 ℃ to obtain powder a;

step S22, mixing the powder a with an ethanol solution with the volume fraction of 50%, adding phenyl vinyl silicone oil and dibenzoyl peroxide, stirring for 5min, carrying out ultrasonic treatment for 1h under the condition of 40kHz frequency to prepare a mixed solution, putting the mixed solution into a vacuum bottle, pumping the vacuum bottle to vacuum by using a vacuum pump, and then heating for 40min under the condition of 70 ℃; keeping the temperature at 50 ℃ for 24h, continuing to heat at 80 ℃ for 1h after the heat preservation is finished, centrifuging at 8000r/min for 5min after the heating is finished, filtering to obtain filter residue, washing the filter residue with deionized water for three times, and drying at 40 ℃ to constant weight to obtain powder b;

and S23, adding the powder b and sodium dodecyl sulfate into deionized water, carrying out ultrasonic treatment for 20min under the condition of the frequency of 40kHz, adding cyclohexane and stirring for 30min after the ultrasonic treatment is finished to obtain a mixed solution, then adding the mixed solution into a three-necked bottle, raising the temperature of the system to 70 ℃, adding benzoyl peroxide, keeping the temperature unchanged after the heating is finished, keeping the temperature for 24h, carrying out suction filtration after the heat preservation is finished, washing filter residues for three times by using the deionized water, and drying the filter residues to constant weight under the condition of 50 ℃ to obtain the aerogel.

In step S21, the using amount ratio of halloysite to deionized water is 5g:50 mL; in step S22, the mass ratio of the powder a, the 50% volume fraction ethanol solution, the sodium dodecyl sulfate, the phenyl vinyl silicone oil, and the dibenzoyl peroxide is 0.1: 100: 1: 0.05: 0.02; in step S23, the amount ratio of the powder b, sodium dodecyl sulfate, deionized water, cyclohexane and benzoyl peroxide is 0.5 g: 1 g: 20mL of: 5mL of: 0.05 g.

Example 2

25 parts of polytetrahydrofuran diol, 2 parts of 1, 4-butanediol, 3 parts of 2, 2-dimethylolpropionic acid, 13 parts of isophorone diisocyanate, 5 parts of N, N-dimethylacetamide, 0.2 part of dibutyltin dilaurate, 18 parts of acetone, 250 parts of deionized water, 0.2 part of diethylenetriamine, 45 parts of modified epoxy resin, 0.2 part of defoaming agent, 0.2 part of wetting agent, 0.2 part of flatting agent and 0.2 part of thickening agent;

firstly, putting polytetrahydrofuran diol and 1, 4-butanediol into a three-neck flask, putting the three-neck flask into a vacuum drying oven at 75 ℃, carrying out vacuum drying for 2.5h, taking out the flask after drying, cooling the three-neck flask to 25 ℃, adding 2, 2-dimethylolpropionic acid, isophorone diisocyanate, N-dimethylacetamide and dibutyltin dilaurate, setting the temperature to 80 ℃, reacting for 1.5h, cooling to 25 ℃, adding acetone, stirring for 60min, adding triethylamine, continuously stirring for 8min, adding 80% deionized water at the rotating speed of 1900r/min, stirring at a high speed for 30min, adding diethylenetriamine, continuously stirring at a high speed for 8min, and after stirring, carrying out reduced pressure distillation to remove the acetone to obtain an aqueous polyurethane emulsion;

and secondly, stirring the waterborne polyurethane emulsion and the epoxy resin at a high speed for 25min at a rotating speed of 1600r/min to obtain a pre-emulsion, adding the rest deionized water, a defoaming agent, a wetting agent, a flatting agent and a thickening agent into the pre-emulsion, and stirring for 60min at a temperature of 25 ℃ and a rotating speed of 550r/min to obtain the waterborne polyurethane composite coating.

Wherein the modified epoxy resin is prepared by the following steps:

step S11, adding bisphenol A epoxy resin and propylene glycol monomethyl ether into a three-neck flask, stirring until the solution is transparent under the conditions that the temperature is set to 65 ℃ and the rotating speed is 350r/min, keeping the temperature and the rotating speed unchanged, adding polyethylene glycol into the three-neck flask, continuously stirring at constant temperature until no crystallization occurs, and mixing boron trifluoride ethyl ether and propylene glycol monomethyl ether in a mass ratio of 5: adding the mixed solution of 1 into a three-necked bottle, dripping the mixed solution at a constant speed within 1h, and reacting at a constant temperature of 90 ℃ for 6h after finishing dripping to obtain a mixed solution A;

step S12, mixing aerogel and absolute ethyl alcohol according to a mass ratio of 1: 10, mixing, carrying out ultrasonic treatment for 35min under the condition that the frequency is 40kHz, adding a mixed solution of deionized water and aerogel and absolute ethyl alcohol into the mixed solution A, reacting for 25min at 65 ℃, and then treating for 35min under the power of 65W by using an ultrasonic cell crusher to prepare the modified epoxy resin.

Wherein, in the step S11, the polyethylene glycol is PEG-4000; the mass ratio of bisphenol A type epoxy resin, propylene glycol methyl ether, polyethylene glycol and boron trifluoride ethyl ether is 1: 2: 1: 0.2; in step S12, the mass ratio of the mixed solution a, deionized water, and aerogel is 1: 1: 0.2.

wherein the aerogel is prepared by the following steps:

step S21, adding halloysite into deionized water, stirring for 5.5h at 25 ℃ and 350r/min, separating for three times at 2000r/min in a centrifugal machine after stirring, performing suction filtration, washing filter residues for three times with absolute ethyl alcohol, and drying the washed filter residues to constant weight at 50 ℃ to obtain powder a;

step S22, mixing the powder a with an ethanol solution with the volume fraction of 50%, adding phenyl vinyl silicone oil and dibenzoyl peroxide, stirring for 5min, carrying out ultrasonic treatment for 1h under the condition of 40kHz frequency to prepare a mixed solution, putting the mixed solution into a vacuum bottle, pumping the vacuum bottle to vacuum by using a vacuum pump, and then heating for 50min under the condition of 75 ℃; keeping the temperature at 55 ℃ for 24h, continuing to heat for 2h at 80 ℃ after the heat preservation is finished, centrifuging at 8000r/min for 5min after the heating is finished, filtering to obtain filter residue, washing the filter residue with deionized water for three times, and drying at 50 ℃ to constant weight to obtain powder b;

and S23, adding the powder b and sodium dodecyl sulfate into deionized water, carrying out ultrasonic treatment for 25min under the condition of frequency of 40kHz, adding cyclohexane and stirring for 35min after the ultrasonic treatment is finished to obtain a mixed solution, then adding the mixed solution into a three-necked bottle, raising the temperature of the system to 75 ℃, adding benzoyl peroxide, keeping the temperature unchanged after the heating is finished, keeping the temperature for 24h, carrying out suction filtration after the heat preservation is finished, washing filter residues for three times by using the deionized water, and drying at 60 ℃ to constant weight to obtain the aerogel.

In step S21, the using amount ratio of halloysite to deionized water is 8g to 50 mL; in step S22, the mass ratio of the powder a, the 50% volume fraction ethanol solution, the sodium dodecyl sulfate, the phenyl vinyl silicone oil, and the dibenzoyl peroxide is 0.2: 100: 1.1: 0.05: 0.02; in step S23, the amount ratio of the powder b, sodium dodecyl sulfate, deionized water, cyclohexane and benzoyl peroxide is 0.5 g: 1 g: 30mL of: 10mL of: 0.08 g.

Example 3

30 parts of polytetrahydrofuran diol, 3 parts of 1, 4-butanediol, 4 parts of 2, 2-dimethylolpropionic acid, 14 parts of isophorone diisocyanate, 6 parts of N, N-dimethylacetamide, 0.3 part of dibutyltin dilaurate, 20 parts of acetone, 300 parts of deionized water, 0.3 part of diethylenetriamine, 50 parts of modified epoxy resin, 0.3 part of defoaming agent, 0.3 part of wetting agent, 0.3 part of flatting agent and 0.3 part of thickening agent;

firstly, putting polytetrahydrofuran diol and 1, 4-butanediol into a three-neck flask, putting the three-neck flask into a vacuum drying oven at 80 ℃, carrying out vacuum drying for 3h, taking out the flask after drying, cooling the three-neck flask to 30 ℃, adding 2, 2-dimethylolpropionic acid, isophorone diisocyanate, N-dimethylacetamide and dibutyltin dilaurate, setting the temperature to 80 ℃, reacting for 2h, cooling to 30 ℃, adding acetone, stirring for 70min, then adding triethylamine, continuously stirring for 10min, adding 80% deionized water at the rotating speed of 2000r/min, stirring at a high speed for 30min, then adding diethylenetriamine, continuously stirring at a high speed for 10min, and after stirring, carrying out reduced pressure distillation to remove the acetone to obtain an aqueous polyurethane emulsion;

and secondly, stirring the waterborne polyurethane emulsion and the epoxy resin at a high speed for 30min at a rotating speed of 1700r/min to obtain a pre-emulsion, adding the rest deionized water, the defoaming agent, the wetting agent, the flatting agent and the thickening agent into the pre-emulsion, and stirring for 70min at a temperature of 30 ℃ and a rotating speed of 600r/min to obtain the waterborne polyurethane composite coating.

Wherein the modified epoxy resin is prepared by the following steps:

step S11, adding bisphenol A epoxy resin and propylene glycol monomethyl ether into a three-neck flask, stirring until the solution is transparent under the conditions that the temperature is set to be 70 ℃ and the rotating speed is 400r/min, keeping the temperature and the rotating speed unchanged, adding polyethylene glycol into the three-neck flask, continuously stirring at constant temperature until no crystallization occurs, and mixing boron trifluoride ethyl ether and propylene glycol monomethyl ether in a mass ratio of 5: adding the mixed solution of 1 into a three-necked bottle, dripping the mixed solution at a constant speed within 1h, and reacting at a constant temperature of 90 ℃ for 6h after finishing dripping to obtain a mixed solution A;

step S12, mixing aerogel and absolute ethyl alcohol according to a mass ratio of 1: 10, mixing, carrying out ultrasonic treatment for 40min under the condition that the frequency is 50kHz, adding a mixed solution of deionized water and aerogel and absolute ethyl alcohol into the mixed solution A, reacting for 30min at 70 ℃, and then treating for 40min under the power of 70W by using an ultrasonic cell crusher to prepare the modified epoxy resin.

Wherein, in the step S11, the polyethylene glycol is PEG-4000; the mass ratio of bisphenol A type epoxy resin, propylene glycol methyl ether, polyethylene glycol and boron trifluoride ethyl ether is 1: 2: 1: 0.3; in step S12, the mass ratio of the mixed solution a, deionized water, and aerogel is 1: 1: 0.3.

wherein the aerogel is prepared by the following steps:

step S21, adding halloysite into deionized water, stirring for 6 hours at the temperature of 30 ℃ and the rotating speed of 400r/min, separating for three times in a centrifugal machine at the rotating speed of 2000r/min after stirring is finished, performing suction filtration, washing filter residues for three times by using absolute ethyl alcohol, and drying the washed filter residues to constant weight at the temperature of 60 ℃ to obtain powder a;

step S22, mixing the powder a with an ethanol solution with the volume fraction of 50%, adding phenyl vinyl silicone oil and dibenzoyl peroxide, stirring for 5min, carrying out ultrasonic treatment for 1h under the condition of the frequency of 50kHz to prepare a mixed solution, putting the mixed solution into a vacuum bottle, pumping the vacuum bottle to vacuum by using a vacuum pump, and then heating for 60min under the condition of 80 ℃; keeping the temperature at 60 ℃ for 24h, continuing heating for 3h at 80 ℃ after the temperature is kept, centrifuging at 8000r/min for 5min after the heating is finished, filtering to obtain filter residue, washing the filter residue with deionized water for three times, and drying at 60 ℃ to constant weight to obtain powder b;

and S23, adding the powder b and sodium dodecyl sulfate into deionized water, carrying out ultrasonic treatment for 30min under the condition of the frequency of 50kHz, adding cyclohexane and stirring for 40min after the ultrasonic treatment is finished to obtain a mixed solution, then adding the mixed solution into a three-necked bottle, raising the temperature of the system to 80 ℃, adding benzoyl peroxide, keeping the temperature unchanged after the heating is finished, keeping the temperature for 24h, carrying out suction filtration after the heat preservation is finished, washing filter residues for three times by using the deionized water, and drying the filter residues to constant weight at 70 ℃ to obtain the aerogel.

In step S21, the using amount ratio of halloysite to deionized water is 10g to 50 mL; in step S22, the mass ratio of the powder a, the 50% volume fraction ethanol solution, the sodium dodecyl sulfate, the phenyl vinyl silicone oil, and the dibenzoyl peroxide is 0.3: 100: 1.2: 0.05: 0.02; in step S23, the amount ratio of the powder b, sodium dodecyl sulfate, deionized water, cyclohexane and benzoyl peroxide is 0.5 g: 1 g: 40mL of: 15mL of: 0.1 g.

Comparative example 1

The modified epoxy resin in example 1 was replaced with bisphenol A type epoxy resin, and the remaining preparation process was unchanged.

Comparative example 2

The comparative example is a common waterborne polyurethane composite coating in the market.

Table 1 shows the results of the comprehensive performance tests of the coatings prepared in examples 1 to 3 and comparative examples 1 to 2:

TABLE 1

Detecting items

Example 1

Example 2

Example 3

Comparative example 1

Comparative example2

Standard of merit

Time to surface dry (min)

≤10

≤15

GB/T1728-1979

Actual drying time (min)

≤20

≤30

GB/T1728-1979

Adhesion force

Level 1

GB/T9286-1998

Tensile strength/MPa

16.54

17.21

17.25

14.56

14.31

GB/T16421-1996

Elongation at break/%

30.79

31.52

31.26

26.54

26.31

GB/T16421-1996

Water-resistant time/h

170

171

175

118

120

GB/T1733-1993

Water absorption/%)

9.21

8.36

9.11

18.36

18.51

GB/T10834-2008

The coating thickness of each of examples 1 to 3 and comparative examples 1 to 2 was less than 300 μm, and it can be seen from table 1 above that the coating prepared in examples 1 to 3 was superior to the coating prepared in comparative examples 1 to 2 in both tensile strength and water-resistant time, because the aerogel can form hydrogen bonds with the epoxy resin, the van der waals force between molecules is increased, the modified epoxy resin is more favorable for improving the mechanical properties of the coating, and as the molecular weight and the crosslinking density are increased, water diffusion into the interior is hindered, and the water resistance of the coating is improved.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is illustrative and explanatory only and is not intended to be exhaustive or to limit the invention to the precise embodiments described, and various modifications, additions, and substitutions may be made by those skilled in the art without departing from the scope of the invention or exceeding the scope of the claims.

Claims

1. The waterborne polyurethane composite coating is characterized by comprising the following raw materials in parts by weight:

2. The aqueous polyurethane composite coating according to claim 1, wherein in the first step, the polytetrahydrofuran diol has an average molecular weight of 2000; in the second step, the defoaming agent is an organic silicon defoaming agent, the wetting agent is BYK-187, the leveling agent is BYK-350, and the thickening agent is an acrylic acid alkali swelling thickening agent.

3. The waterborne polyurethane composite coating of claim 1, wherein the modified epoxy resin is prepared by the following steps:

4. The waterborne polyurethane composite coating of claim 3, wherein in step S11, the polyethylene glycol is PEG-4000; the mass ratio of bisphenol A type epoxy resin, propylene glycol methyl ether, polyethylene glycol and boron trifluoride ethyl ether is 1: 2: 1: 0.1-0.3; in step S12, the mass ratio of the mixed solution a, deionized water, and aerogel is 1: 1: 0.1-0.3.

5. The waterborne polyurethane composite coating of claim 3, wherein the aerogel is prepared by the following steps:

6. The waterborne polyurethane composite coating of claim 5, wherein in step S21, the amount ratio of halloysite to deionized water is 5-10g:50 mL; in step S22, the mass ratio of the powder a, the 50% volume fraction ethanol solution, the sodium dodecyl sulfate, the phenyl vinyl silicone oil, and the dibenzoyl peroxide is 0.1 to 0.3: 100: 1-1.2: 0.05: 0.02; in step S23, the amount ratio of the powder b, sodium dodecyl sulfate, deionized water, cyclohexane and benzoyl peroxide is 0.5 g: 1 g: 20-40 mL: 5-15 mL: 0.05-0.1 g.

7. The preparation method of the waterborne polyurethane composite coating according to claim 1, wherein the preparation method comprises the following steps: