Waterborne hyperbranched polyurethane dispersing agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a water-based hyperbranched polyurethane dispersing agent as well as a preparation method and application thereof. The structural formula of the polyurethane dispersant is as follows: # imgabs0 # m1, m2, m3, p1, p2 and p3 are all greater than or equal to 0 and are not 0 at the same time; hO-R1-OH is of a polyethylene glycol structure; hO-R2-OH is a monomer structure of dihydric alcohol with carboxyl groups; the OCN-R3-NCO is a monomer structure of the diisocyanate; and the # imgabs 1 # is at least one of a hexamethylene diisocyanate tripolymer structure and a hexamethylene diisocyanate biuret structure. The polyurethane dispersant provided by the invention has good dispersibility and anti-freezing property, and can be used as a dispersant and an anti-freezing agent of a water-based acrylic coating.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to an aqueous hyperbranched polyurethane dispersant and a preparation method and application thereof. Background Art

[0002] Water-based acrylic anti-corrosion coatings have been widely used in the field of light corrosion protection. The freeze-thaw stability of water-based acrylic anti-corrosion coatings is a very important property, especially during winter construction. At present, the method to solve the freeze-thaw stability of water-based acrylic coatings is to add antifreeze. Antifreeze is mainly divided into two categories, one is polyols (easily soluble in water), such as propylene glycol, glycerol, etc.; the other is surfactant type.

[0003] The principle of polyol antifreeze to improve freeze-thaw stability is to lower the freezing point of water-based paint. There are two principles for polyol antifreeze to lower the freezing point. One is to change the physical properties of the solution, that is, the addition of polyol antifreeze can lower the freezing point of the overall solution; the other is chemical force. Polyol antifreeze can form strong hydrogen bonds with water, which can reduce the ability of water molecules to form ice crystals. At the same time, this hydrogen bond can also destroy the hydrogen bond network between water molecules, affect the crystallization of water molecules, and lower the freezing point. The principle of surfactant antifreeze to improve freeze-thaw stability is unknown. Surfactants generally have the functions of dispersing, wetting and even thickening. Therefore, they can also be used as wetting dispersants or thickeners in water-based paints, or wetting dispersants can also serve as antifreeze agents, and thickeners (alkali swelling thickeners of acrylic emulsion type) can also serve as antifreeze agents. That is, polyol antifreeze is generally added to the paint formula in the form of a single-functional additive, and surfactant antifreeze is generally added as an additive that takes into account two functions.

[0004] In addition to being added to the coating formula as an additive, surfactant-type antifreeze agents can also be added to the system during the synthesis stage of water-based acrylic emulsions to improve the antifreeze-thaw performance of the acrylic emulsion itself. At this time, surfactant-type antifreeze agents have an emulsifying effect. Therefore, surfactant-type antifreeze agents are used as emulsifiers for the synthesis of acrylic emulsions to obtain modified acrylic emulsions with antifreeze properties. There are two methods for adding surfactant-type antifreeze agents to the synthesis process of acrylic emulsions. One is that surfactant-type antifreeze agents are used as non-reactive emulsifiers. This type of technical route often requires functional monomers to participate in polymerization to ensure good antifreeze-thaw performance; the other is that surfactant-type antifreeze agents are used as reactive emulsifiers or reactive raw materials to participate in acrylic polymerization reactions. In addition, there is a class of auxiliary resins, such as water-based polyurethane resins, which are used to improve the antifreeze performance of the system, but there is no relevant research on water-based polyurethane as an antifreeze agent, because the resin is a macromolecule and the molecular weight of the additive is much smaller than that of the resin as a film-forming substance.

[0005] Therefore, it is of great significance to provide a polyurethane dispersant that can be applied to water-based acrylic paint and has dispersing and antifreezing properties. Summary of the invention

[0006] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art and at least provide a beneficial choice. Specifically, the present invention provides a polyurethane dispersant, which can be used as a dispersant and an antifreeze agent. When applied to a water-based acrylic paint, it has the effects of dispersing and antifreezing.

[0007] The inventive concept of the present invention: the water-based hyperbranched polyurethane of the present invention is a self-emulsifying resin system, which can be understood as a surfactant. Theoretically, the molecular weight is small and it cannot be used as a film-forming resin, but can be used as an auxiliary agent. The molecular structure of polyurethane contains a large number of ether bonds and carboxyl groups, which belong to hydrophilic segments, and diol monomers are hydrophilic segment providers; the hydrophobic segments are urethane bonds, and polyisocyanate monomers are hydrophobic segment providers, so they can be used as dispersants. In addition, the water-based hyperbranched polyurethane of the present invention has a large number of hydrophilic segments. In the water-based acrylic paint system, in addition to dispersing powder, it can also help emulsify resins and improve the hydrophilicity of latex particles in acrylic paints, and its volume will further swell. The principle of volume swelling is that the hydrophobic part inside the latex particles is not reduced, but the hydrophilicity of the surfactant on the surface of the latex particles is improved, then the solvable segments on the surface of the latex particles increase, and the solvated hydrophilic segments form a solvation layer on the surface of the latex particles, and the solvation layer will thicken, and the volume of the latex particles will further swell and increase. During freezing and thawing, the frozen water volume increases and squeezes the latex particles. Because of the existence of the solvation layer, the thickened solvation layer will reduce the squeezing of the latex particles by the increased volume of water after freezing, and the freeze-thaw stability will be improved. At the same time, water-based hyperbranched polyurethane has a large number of hydroxyl groups and ether bonds, and it also has the characteristics of polyol antifreeze agents, that is, its large number of hydrophilic groups can form strong hydrogen bonds with water, and hydrogen bonds can reduce the ability of water molecules to form ice crystals. At the same time, this hydrogen bond can also destroy the hydrogen bond network between water molecules, affecting the crystallization of water molecules, lowering the freezing point, and playing an antifreeze role.

[0008] Therefore, the water-based hyperbranched polyurethane prepared by the present invention can be used as a dispersant and an antifreeze agent. When used as an antifreeze agent, it has the antifreeze characteristics of polyol surfactants and the characteristics of surfactant antifreeze agents. However, it cannot be used as a film-forming substance, and the auxiliary resin is added to the water-based acrylic acid system and can only be added as an auxiliary agent.

[0009] Therefore, the first aspect of the present invention provides an aqueous hyperbranched polyurethane dispersant.

[0010] Specifically, the structural formula of the aqueous hyperbranched polyurethane dispersant is:

[0011]

[0012] Wherein, the values ​​of m1, m2, m3, p1, p2, and p3 are all greater than or equal to 0, and are not 0 at the same time;

[0013] HO-R1-OH is a polyethylene glycol structure, and the structure in the general structural formula is -O-R1-O-;

[0014] HO-R2-OH is a monomer structure of a diol having a carboxyl group; the structure in the general structural formula is -O-R2-O-;

[0015] OCN-R3-NCO is a monomer structure of diisocyanate; the structure in the general structural formula is

[0016] It is at least one of a hexamethylene diisocyanate trimer structure and a hexamethylene diisocyanate biuret structure, and the structure in the general structural formula is:

[0017]

[0018] Specifically, HO-R1-OH is a polyethylene glycol structure, that is

[0019] Specifically, the structural formula of the hexamethylene diisocyanate trimer structure is:

[0020]

[0021] Specifically, the structural formula of the hexamethylene diisocyanate biuret structure is:

[0022]

[0023] Preferably, the monomer structure of the diol having a carboxyl group includes a dihydroxycarboxylic acid.

[0024] Preferably, the dihydroxycarboxylic acid comprises at least one of dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, dihydroxysuccinic acid, dihydroxymethylvaleric acid and dihydroxysuccinic acid.

[0025] Preferably, the monomer structure of the diisocyanate includes at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0026] The second aspect of the present invention provides a method for preparing the aqueous hyperbranched polyurethane dispersant described in the first aspect of the present invention.

[0027] Specifically, the preparation method of the aqueous hyperbranched polyurethane dispersant comprises the following steps:

[0028] (1) mixing polyethylene glycol and carboxyl-containing diol, adding an organic solvent, heating, and then adding diisocyanate to react to obtain a polyurethane segment small molecule with a hydroxyl terminal group;

[0029] (2) mixing the polyurethane segment small molecule with a hydroxyl terminal obtained in step (1) with the B3 monomer, and reacting them to obtain the polyurethane dispersant;

[0030] The B3 monomer includes at least one of HDI trimer and HDI biuret.

[0031] Preferably, in step (1), the polyethylene glycol, the carboxyl-containing diol and the organic solvent are all subjected to a dehydration treatment; the dehydration treatment of the polyethylene glycol and the carboxyl-containing diol is carried out in a drying manner; the dehydration treatment of the organic solvent is completed by mixing the organic solvent and the adsorption material and allowing the mixture to stand.

[0032] Preferably, in step (1), the organic solvent comprises acetone.

[0033] Preferably, the polyethylene glycol is dried by vacuum dehydration, the temperature of the vacuum dehydration is 100-130°C, and the time of the vacuum dehydration is 1.5-2.5h; further preferably, the temperature of the vacuum dehydration is 110-120°C, and the time of the vacuum dehydration is 1.8-2.2h.

[0034] Preferably, the drying temperature of the carboxyl-containing diol is 70-90°C, and the drying time of the carboxyl-containing diol is 20-28h; further preferably, the drying temperature of the carboxyl-containing diol is 75-85°C, and the drying time of the carboxyl-containing diol is 22-26h; further preferably, the drying temperature of the carboxyl-containing diol is 80°C, and the drying time of the carboxyl-containing diol is 24h.

[0035] Specifically, the carboxyl-containing diol is dried in a vacuum drying oven.

[0036] Preferably, the standing time is 65-80 hours; further preferably, the standing time is 68-75 hours; further preferably, the standing time is 72 hours.

[0037] Preferably, the standing time is the time for the adsorption material to be immersed in the organic solvent to achieve the purpose of water removal.

[0038] Preferably, the adsorption material comprises a molecular sieve.

[0039] Preferably, in step (1), the molecular weight of the polyethylene glycol is 200-800, that is, the molecular weight of HO-R1-OH is 200-800.

[0040] Preferably, the polyethylene glycol includes at least one of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800.

[0041] Preferably, in step (1), the carboxyl-containing diol includes a dihydroxycarboxylic acid; further preferably, the dihydroxycarboxylic acid includes at least one of dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, dihydroxysuccinic acid, dihydroxymethylvaleric acid, and dihydroxysuccinic acid.

[0042] Preferably, in step (1), the molar ratio of the polyethylene glycol to the carboxyl-containing diol is (0.45-2.2):1; further preferably, in step (1), the molar ratio of the polyethylene glycol to the carboxyl-containing diol is (0.5-2):1.

[0043] Preferably, in step (1), the temperature after heating is 70-90°C; further preferably, in step (1), the temperature after heating is 75-85°C; further preferably, in step (1), the temperature after heating is 80°C.

[0044] Preferably, in step (1), the reaction temperature is 70-90°C, and the reaction time is 2.5-3.5h; further preferably, the reaction temperature is 75-85°C, and the reaction time is 2.7-3.3h; further preferably, the reaction temperature is 80°C, and the reaction time is 3h.

[0045] Preferably, in step (1), the reaction is carried out under a nitrogen atmosphere.

[0046] Preferably, in step (1), the reaction further includes a process of adding a catalyst.

[0047] Preferably, the catalyst comprises dibutyltin dilaurate (DBTDL).

[0048] Preferably, in step (1), the ratio of the sum of the amounts of the polyethylene glycol and the carboxyl-containing diol to the amount of the catalyst is 0.3 mol: (0.16-0.50) g; further preferably, the ratio of the sum of the amounts of the polyethylene glycol and the carboxyl-containing diol to the amount of the catalyst is 0.3 mol: (0.18-0.45) g; further preferably, the ratio of the sum of the amounts of the polyethylene glycol and the carboxyl-containing diol to the amount of the catalyst is 0.3 mol: (0.2-0.4) g.

[0049] Preferably, in step (1), the molar ratio of the diisocyanate to the sum of the hydroxyl groups in the polyethylene glycol and the carboxyl-containing diol is (0.4-0.8):1; further preferably, the molar ratio of the diisocyanate to the sum of the hydroxyl groups in the polyethylene glycol and the carboxyl-containing diol is (0.45-0.73):1; further preferably, the molar ratio of the diisocyanate to the sum of the hydroxyl groups in the polyethylene glycol and the carboxyl-containing diol is 1:2-2:3.

[0050] Preferably, in step (1), the diisocyanate includes at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0051] Preferably, in step (2), the ratio of the amount of the polyurethane segment small molecules with hydroxyl end groups to the amount of the B3 monomer is (2.5-3.5):1; further preferably, the ratio of the amount of the polyurethane segment small molecules with hydroxyl end groups to the amount of the B3 monomer is (2.7-3.3):1; further preferably, the ratio of the amount of the polyurethane segment small molecules with hydroxyl end groups to the amount of the B3 monomer is 3:1.

[0052] Preferably, in step (2), the reaction temperature is 70-90°C, and the reaction time is 3-5h; further preferably, the reaction temperature is 75-85°C, and the reaction time is 3.5-4.5h; further preferably, the reaction temperature is 80°C, and the reaction time is 4h.

[0053] Preferably, in step (2), a solvent is added during the reaction to adjust the viscosity.

[0054] Preferably, the solvent comprises acetone.

[0055] Preferably, in step (2), the reaction further comprises adding a neutralizing agent and water, and performing a process of reduced pressure distillation.

[0056] Preferably, the neutralizing agent comprises triethylamine.

[0057] Preferably, the reduced pressure distillation method comprises rotary evaporation.

[0058] Specifically, the purpose of the reduced pressure distillation is to remove acetone.

[0059] A third aspect of the present invention provides an acrylic coating.

[0060] Specifically, the acrylic coating comprises acrylic resin, the aqueous hyperbranched polyurethane dispersant described in the first aspect of the present invention and water.

[0061] Preferably, the acrylic paint further comprises at least one of a defoamer, a pigment, a filler, a film-forming aid, and a thickener; further preferably, the acrylic paint further comprises a defoamer, a pigment, a filler, a film-forming aid, and a thickener.

[0062] Preferably, the acrylic coating comprises, by weight, 0.9-2.2 parts of an aqueous hyperbranched polyurethane dispersant, 40-55 parts of an acrylic resin, 0.45-1.1 parts of a defoamer, 4.5-11 parts of a pigment, 18-33 parts of a filler, 2.2-3.3 parts of a film-forming aid, 0.27-0.65 parts of a thickener, and 11-20 parts of water.

[0063] Further preferably, the acrylic coating comprises, by weight, 1-2 parts of an aqueous hyperbranched polyurethane dispersant, 45-50 parts of an acrylic resin, 0.5-1 parts of a defoamer, 5-10 parts of a pigment, 20-30 parts of a filler, 2.5-3 parts of a film-forming aid, 0.3-0.6 parts of a thickener, and 12-18 parts of water.

[0064] Preferably, the acrylic paint is a water-based acrylic paint; further preferably, the acrylic paint is a water-based acrylic primer.

[0065] Preferably, the defoaming agent comprises a polyether-modified silicone defoaming agent.

[0066] Preferably, the acrylic resin comprises a resin having a minimum film forming temperature (MFFT) of 20-25° C. and a solid content of 45-48%.

[0067] Preferably, the acrylic resin is a water-based acrylic resin.

[0068] Preferably, the pigment includes at least one of titanium dioxide, red iron oxide, black iron oxide and yellow iron oxide.

[0069] Preferably, the filler includes at least one of feldspar powder, silica powder, talc powder and heavy calcium powder.

[0070] Preferably, the film-forming aid includes at least one of alcohol ester dodecanedione, propylene glycol phenyl ether (ppH), and dipropylene glycol butyl ether (DPnB).

[0071] Preferably, the thickener comprises at least one of a low shear polyurethane thickener and an alkali swelling thickener.

[0072] Preferably, the method for preparing the acrylic paint comprises the following steps:

[0073] The raw material components are mixed uniformly to prepare the acrylic paint.

[0074] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0075] (1) The molecular structure of the water-based hyperbranched polyurethane dispersant of the present invention contains a large number of ether bonds and carboxylate groups, which are hydrophilic segments, and the diol monomer is the provider of the hydrophilic segment; the hydrophobic segment is the urethane bond, and the polyisocyanate monomer is the provider of the hydrophobic segment, so it can be used as a dispersant for water-based acrylic coatings.

[0076] (2) The water-based hyperbranched polyurethane of the present invention has a large number of hydrophilic segments. In the water-based acrylic paint system, in addition to dispersing the powder, it can also help emulsify the resin, improve the hydrophilicity of the latex particles, and further swell its volume. At the same time, the water-based hyperbranched polyurethane has a large number of hydroxyl groups and ether bonds, and it also has the characteristics of polyol antifreeze agents, that is, its large number of hydrophilic groups can form strong hydrogen bonds with water, and hydrogen bonds can reduce the ability of water molecules to form ice crystals. At the same time, this hydrogen bond can also destroy the hydrogen bond network between water molecules themselves, affect the crystallization of water molecules, reduce the freezing point, and play an antifreeze role. It can be used as an antifreeze agent for water-based acrylic paint.

[0077] (3) When the water-based hyperbranched polyurethane of the present invention is used as an antifreeze agent, it has the antifreeze characteristics of polyol surfactants and also has the characteristics of surfactant antifreeze agents. However, it cannot be used as a film-forming substance. When an auxiliary resin is added to a water-based acrylic acid system, it can only be added as an auxiliary agent.

[0078] (4) The preparation method of the present invention is simple, the process operation is easy to implement, and it is convenient for large-scale promotion and application. DETAILED DESCRIPTION

[0079] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0080] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0081] Example 1

[0082] The structural formula of an aqueous hyperbranched polyurethane dispersant is:

[0083]

[0084] Among them, the values ​​of m1, m2, m3, p1, p2, and p3 are all greater than or equal to 0, and they are not 0 at the same time;

[0085] HO-R1-OH is a polyethylene glycol structure; HO-R2-OH is a 2,2'-dihydroxymethylbutyric acid structure; OCN-R3-NCO is a toluene diisocyanate structure;

[0086] It is a HDI trimer structure.

[0087] A method for preparing an aqueous hyperbranched polyurethane dispersant comprises the following steps:

[0088] (1) Polyethylene glycol 200 (PEG200) was dehydrated in a round-bottom flask at 115°C under vacuum for 2 h; 2,2'-dihydroxymethylbutyric acid (DMBA) was dried in a vacuum oven at 80°C for 24 h; acetone was used The molecular sieve was soaked for three days to remove water; PEG200, DMBA and acetone after dehydration were obtained; the remaining raw materials were not treated and used directly;

[0089] (2) 0.1 mol of PEG200 and 0.2 mol of DMBA after dehydration treatment were added to a 250 mL four-necked flask equipped with a condensation reflux device, a mechanical stirrer and nitrogen, and then 60 mL of acetone solution was added, the temperature was raised to 80°C, 0.15 mol of toluene diisocyanate (TDI) and 0.2 g of dibutyltin dilaurate as a catalyst were added, and the reaction was carried out under this condition for 3 hours to obtain a polyurethane segment small molecule with a hydroxyl end group, wherein TDI and PEG 200. The molar ratio of the sum of hydroxyl groups in DMBA (NCO / OH) is 1:2; then add 0.05 mol of B3 monomer HDI trimer, in which the molar ratio of the small molecule polyurethane segment with hydroxyl end group to HDI trimer is 3:1, and continue the reaction for 4 hours. During the reaction, 50 mL of acetone solution can be added to dilute the viscosity, and then 30 g of triethylamine and 100 g of deionized water are added; finally, the acetone in the solution is removed by rotary evaporation to obtain an aqueous hyperbranched polyurethane dispersant.

[0090] Example 2

[0091] The structural formula of an aqueous hyperbranched polyurethane dispersant is:

[0092]

[0093] Among them, the values ​​of m1, m2, m3, p1, p2, and p3 are all greater than or equal to 0, and they are not 0 at the same time;

[0094] HO-R1-OH is a polyethylene glycol structure; HO-R2-OH is a 2,2'-dihydroxymethylbutyric acid structure; OCN-R3-NCO is an IPDI structure;

[0095] It is a HDI biuret structure.

[0096] A method for preparing an aqueous hyperbranched polyurethane dispersant comprises the following steps:

[0097] (1) PEG200 was vacuum dehydrated in a round-bottom flask at 120°C for 2 h; DMBA was dried in a vacuum oven at 80°C for 24 h; acetone was used The molecular sieve was soaked for three days to remove water; PEG200, DMBA and acetone after dehydration were obtained; the remaining raw materials were not treated and used directly;

[0098] (2) 0.15 mol of PEG200 and 0.15 mol of DMBA after dehydration treatment were added to a 250 mL four-necked flask equipped with a condensation reflux device, a mechanical stirrer and nitrogen, and then 60 mL of acetone solution was added, the temperature was raised to 80 ° C, 0.175 mol of diisocyanate monomer (the molar ratio of IPDI to HDI was 1:1) and 0.3 g of catalyst dibutyltin dilaurate were added, and the reaction was carried out under this condition for 3 hours to obtain a polyurethane segment small molecule with a hydroxyl terminal group, wherein diisocyanate The molar ratio of the acid ester monomer to the sum of the hydroxyl groups in PEG200 and DMBA (NCO / OH) is 3.5:6; then 0.042 mol of B3 monomer HDI biuret is added, in which the molar ratio of the polyurethane segment small molecule with a hydroxyl terminal group to the HDI trimer is 3:1, and the reaction is continued for 4 hours. During the reaction, 50 mL of acetone solution can be added at any time to dilute the viscosity, and then 30 g of triethylamine and 100 g of deionized water are added; finally, the acetone in the solution is removed by rotary evaporation to obtain an aqueous hyperbranched polyurethane dispersant.

[0099] Example 3

[0100] The structural formula of an aqueous hyperbranched polyurethane dispersant is:

[0101]

[0102] Among them, the values ​​of m1, m2, m3, p1, p2, and p3 are all greater than or equal to 0, and they are not 0 at the same time;

[0103] HO-R1-OH is a polyethylene glycol structure; HO-R2-OH is a 2,2'-dihydroxymethylbutyric acid structure; OCN-R3-NCO is an MDI structure;

[0104] It is a HDI trimer structure.

[0105] A method for preparing an aqueous hyperbranched polyurethane dispersant comprises the following steps:

[0106] (1) PEG200 was dehydrated in a round-bottom flask at 110°C under vacuum for 2 h; DMBA was dried in a vacuum oven at 80°C for 24 h; acetone was used The molecular sieve was soaked for three days to remove water; PEG200, DMBA and acetone after dehydration were obtained; the remaining raw materials were not treated and used directly;

[0107] (2) 0.2 mol of PEG200 and 0.1 mol of DMBA after dehydration treatment were added to a 250 mL four-necked flask equipped with a condensation reflux device, a mechanical stirrer and nitrogen, and then 60 mL of acetone solution was added, the temperature was raised to 80°C, 0.175 mol of diisocyanate monomer (the molar ratio of MDI, HDI and LDI was 1:1:1) and 0.4 g of catalyst dibutyltin dilaurate were added, and the reaction was carried out under this condition for 3 hours to obtain a polyurethane segment small molecule with a hydroxyl terminal group, wherein the diisocyanate The molar ratio of isocyanate monomer to the sum of hydroxyl groups in PEG200 and DMBA (NCO / OH) is 2:3; then 0.042 mol of B3 monomer HDI biuret is added, in which the molar ratio of the polyurethane segment small molecule with a hydroxyl terminal group to the HDI trimer is 3:1, and the reaction is continued for 4 hours. During the reaction, 50 mL of acetone solution can be added at any time to dilute the viscosity, and then 30 g of triethylamine and 100 g of deionized water are added; finally, the acetone in the solution is removed by rotary evaporation to obtain an aqueous hyperbranched polyurethane dispersant.

[0108] Application Example 1

[0109] A water-based acrylic primer comprises, by weight, 12 parts of water, 2 parts of the water-based hyperbranched polyurethane dispersant of Example 1, 45 parts of a water-based acrylic resin (2081A of Henghe Yongsheng); 0.5 parts of a defoamer (SN-6791 of Shenzhu Technology); 7.7 parts of a pigment titanium dioxide; 30 parts of a filler heavy calcium powder; 2.5 parts of a film-forming aid ppH; and 0.3 parts of a thickener (a low-shear polyurethane thickener U-905 of Wanhua Chemical).

[0110] A method for preparing a water-based acrylic primer comprises the following steps:

[0111] Water, the water-based hyperbranched polyurethane dispersant of Example 1, water-based acrylic resin, defoamer, pigment, filler, film-forming aid, and thickener were added to the dispersion tank in sequence, stirred evenly at high speed, and filtered through 200 meshes to obtain a water-based acrylic primer.

[0112] Application Example 2

[0113] A water-based acrylic primer comprises, by weight, 16 parts of water, 1.5 parts of a water-based hyperbranched polyurethane dispersant of Example 2, 50 parts of a water-based acrylic resin (Badford's 3712); 0.8 parts of a defoamer (Digo's 901W); 5 parts of a pigment, red iron oxide; 23.5 parts of a filler (the ratio of feldspar powder to talc powder is 1:1); 2.8 parts of a film-forming aid, alcohol ester twelve; and 0.4 parts of a thickener (Puwei's low-shear alkali swelling thickener H-120).

[0114] A method for preparing a water-based acrylic primer comprises the following steps:

[0115] Water, the water-based hyperbranched polyurethane dispersant of Example 2, water-based acrylic resin, defoamer, pigment, filler, film-forming aid, and thickener were added to the dispersion tank in sequence, stirred evenly at high speed, and filtered through 200 mesh to obtain a water-based acrylic primer.

[0116] Application Example 3

[0117] A water-based acrylic primer comprises, by weight, 18 parts of water, 1 part of the water-based hyperbranched polyurethane dispersant of Example 3, 46.4 parts of water-based acrylic resin (725 of Hengshui Xinguang), 1 part of defoamer (BYK-024 of BYK Chemical), 10 parts of pigment (the ratio of black iron oxide to yellow iron oxide is 1:1), 20 parts of filler (the ratio of silicon micropowder to heavy calcium powder is 1:1), 3 parts of film-forming aid DPnB, and 0.6 part of thickener (polyurethane thickener XS-83 of Gotai Low Shear).

[0118] A method for preparing a water-based acrylic primer comprises the following steps:

[0119] Water, the water-based hyperbranched polyurethane dispersant of Example 3, water-based acrylic resin, defoamer, pigment, filler, film-forming aid, and thickener were added to the dispersion tank in sequence, stirred evenly at high speed, and filtered through 200 mesh to obtain a water-based acrylic primer.

[0120] Comparative application example 1

[0121] Comparative Application Example 1 does not add dispersant. Specifically, by weight, the water-based acrylic primer includes 15 parts of water, 50 parts of water-based acrylic resin (Badford's 3712); 1 part of defoamer (Di Gao's 901W); 10 parts of pigment red iron oxide; 21 parts of filler heavy calcium powder; 2.5 parts of film-forming aid alcohol ester twelve; and 0.5 parts of thickener (Cotai low-shear polyurethane thickener XS-83).

[0122] The preparation method of water-based acrylic primer comprises the following steps:

[0123] Add water, water-based acrylic resin, defoamer, pigment, filler, film-forming aid and thickener into the dispersion tank in sequence, stir evenly at high speed, and filter through 200 meshes to obtain the water-based acrylic primer.

[0124] Comparative Application Example 2

[0125] The only difference between Comparative Application Example 2 and Application Example 2 is that Comparative Application Example 2 uses an equal amount of dispersant Dow 731A (polycarboxylate ammonium salt dispersant) to replace the aqueous hyperbranched polyurethane dispersant in Application Example 2, and the rest is the same as Application Example 2.

[0126] Comparative Application Example 3

[0127] The only difference between Comparative Application Example 3 and Application Example 3 is that Comparative Application Example 3 uses an equal amount of antifreeze agent propylene glycol to replace the aqueous hyperbranched polyurethane dispersant in Application Example 3, and the rest is the same as Application Example 3.

[0128] Performance Testing

[0129] The water-based acrylic primers of Example 1-3 and Comparative Example 1-3 were tested. The test items and test methods are as follows:

[0130] Freeze-thaw stability: The water-based acrylic primers of Application Examples 1-3 and Comparative Application Examples 1-3 were placed in a refrigerator at -5°C for 16 hours, and then placed at room temperature for 8 hours. This was one cycle, and a total of 10 cycles were tested. If there was no abnormality, it passed; if there was hard precipitation, demulsification or mud, it failed.

[0131] Storage stability: The water-based acrylic primers of Application Examples 1-3 and Comparative Application Examples 1-3 were placed in an oven at 50°C for 30 days. If there was no abnormality or soft precipitation, it passed; if there was hard precipitation, it failed.

[0132] Among them, soft sedimentation means that there is sedimentation at the bottom of the primer, but it is very slight and can continue to be mechanically dispersed evenly.

[0133] Hard sedimentation means that the primer appears to settle, and the settled part is very hard and cannot be further dispersed evenly by mechanical means.

[0134] The demulsification or mudification phenomenon means that the entire paint appears to be in a mud-like or blocky state after testing. The viscosity is very high and it can no longer be dispersed evenly by mechanical stirring.

[0135] The performance test results of the water-based acrylic primers of Application Examples 1-3 and Comparative Application Examples 1-3 are shown in Table 1.

[0136] Table 1: Performance test results of water-based acrylic primers in application examples 1-3 and comparative application examples 1-3

[0137]

[0138] It can be seen from Table 1 that the waterborne acrylic primer prepared by the present invention has good freeze-thaw stability and storage stability, which also shows that the polyurethane dispersant of the present invention has good dispersing and antifreeze effects.

[0139] Comparative Application Example 1 does not add a polyurethane dispersant, so that the freeze-thaw stability and storage stability of the water-based acrylic primer of Comparative Application Example 1 are significantly worse than those of Application Example 1.

[0140] Comparative Application Example 2 uses other types of dispersants, so that the freeze-thaw stability and storage stability of the water-based acrylic primer of Comparative Application Example 2 are significantly worse than those of Application Example 2.

[0141] Comparative Application Example 3 uses other types of antifreeze agents, so that the freeze-thaw stability and storage stability of the water-based acrylic primer of Comparative Application Example 3 are significantly worse than those of Application Example 3.

[0142] It can be seen from comparative application examples 1 and 2 that good dispersion and antifreeze effects cannot be achieved without adding dispersants or adding other types of dispersants. It can be seen from comparative application example 3 that good dispersion and antifreeze effects cannot be achieved by adding other types of antifreeze agents.

[0143] In summary, the molecular structure of the polyurethane of the present invention contains a large number of ether bonds and carboxylic acids, which belong to hydrophilic segments, and diol monomers are all hydrophilic segment providers; the hydrophobic segment is a carbamate bond, and the polyisocyanate monomer is a hydrophobic segment provider, so it can be used as a dispersant for water-based acrylic paint. At the same time, the water-based hyperbranched polyurethane has a large number of hydroxyl groups and ether bonds, has the characteristics of polyol antifreeze agents, and can be used as an antifreeze agent for water-based acrylic paint. The polyurethane dispersant of the present invention has good dispersing and antifreeze effects, so that the water-based acrylic paint has good freeze-thaw stability and storage stability.

[0144] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A polyurethane dispersant, characterized in that: The general structural formula of the polyurethane dispersant is: Wherein, the values ​​of m1, m2, m3, p1, p2, and p3 are all greater than or equal to 0, and are not 0 at the same time; HO-R1-OH is a polyethylene glycol structure, and the structure in the general structural formula is -O-R1-O-; HO-R2-OH is a monomer structure of a diol having a carboxyl group; the structure in the general structural formula is -O-R2-O-; OCN-R3-NCO is a monomer structure of diisocyanate; the structure in the general structural formula is It is at least one of a hexamethylene diisocyanate trimer structure and a hexamethylene diisocyanate biuret structure, and the structure in the general structural formula is:

2. The polyurethane dispersant according to claim 1, characterized in that The monomer structure of the diol having a carboxyl group includes a dihydroxycarboxylic acid.

3. The polyurethane dispersant according to claim 2, characterized in that The dihydroxycarboxylic acid includes at least one of dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, dihydroxysuccinic acid, dihydroxymethylvaleric acid, and dihydroxysuccinic acid; and / or the monomer structure of the diisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

4. The method for preparing the polyurethane dispersant according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing polyethylene glycol and carboxyl-containing diol, adding an organic solvent, heating, and then adding diisocyanate to react to obtain a polyurethane segment small molecule with a hydroxyl terminal group; (2) mixing the polyurethane segment small molecule with a hydroxyl terminal obtained in step (1) with the B3 monomer, and reacting them to obtain the polyurethane dispersant; The B3 monomer includes at least one of hexamethylene diisocyanate trimer and hexamethylene diisocyanate biuret.

5. The preparation method according to claim 4, characterized in that: In step (1), the polyethylene glycol, the carboxyl-containing diol and the organic solvent are all subjected to a dehydration treatment; the dehydration treatment of the polyethylene glycol and the carboxyl-containing diol is carried out in a drying manner; the dehydration treatment of the organic solvent is completed by mixing the organic solvent and the adsorption material and allowing the mixture to stand; and / or the organic solvent comprises acetone.

6. The preparation method according to claim 5, characterized in that: The polyethylene glycol is dried by vacuum dehydration, the vacuum dehydration temperature is 100-130°C, and the vacuum dehydration time is 1.5-2.5h; and / or, the carboxyl-containing diol is dried at a temperature of 70-90°C, and the carboxyl-containing diol is dried for 20-28h; and / or, the standing time is 65-80h.

7. The preparation method according to claim 4, characterized in that: In step (1), the molecular weight of the polyethylene glycol is 200-800; and / or the molar ratio of the polyethylene glycol to the carboxyl-containing diol is (0.45-2.2):1; and / or the temperature after the heating is 70-90°C; and / or the reaction temperature is 70-90°C, and the reaction time is 2.5-3.5h; and / or the reaction also includes a process of adding a catalyst before the reaction; and / or the molar ratio of the diisocyanate to the sum of the hydroxyl groups in the polyethylene glycol and the carboxyl-containing diol is (0.4-0.8):

1.

8. The preparation method according to claim 4, characterized in that: In step (2), the ratio of the amount of the polyurethane segment small molecule with a hydroxyl terminal group to the amount of the B3 monomer is (2.5-3.5):1; and / or, the reaction temperature is 70-90°C, and the reaction time is 3-5h; and / or, a solvent is added during the reaction to adjust the viscosity; and / or, after the reaction, a neutralizing agent and water are added, and a reduced pressure distillation process is performed.

9. An acrylic paint, characterized in that: The invention comprises acrylic resin, the polyurethane dispersant according to any one of claims 1 to 3 and water.

10. The acrylic paint according to claim 9, characterized in that The acrylic paint further comprises at least one of a defoamer, a pigment, a filler, a film-forming aid, and a thickener.

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