Preparation method of polyurea polyurethane thickening and thixotropic agent for waterborne coatings

Abstract

The invention discloses a preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, which relates to the technical fields of polymer materials and thickening and thixotropic agents for coatings. The method includes preparing an NCO-terminated prepolymer, carrying out a chain extension reaction on the NCO-terminated prepolymer to obtain a mixture; adding a monofunctional long-chain amine compound to the obtained mixture and reacting to obtain a water-soluble viscous and highly transparent paste; detecting the residual amino group content in the obtained highly transparent paste, and adding a low-reactivity diisocyanate to the reaction kettle according to the amino group content to obtain the polyurea polyurethane thickening and thixotropic agent for waterborne coatings. The polyurea polyurethane thickening and thixotropic agent of the invention has a large molecular weight and many branched-chain molecules, showing better thickening property, and the critical micelle concentration of the thickening agent is low and the dosage is small. It has excellent applicability to the viscosity of waterborne coatings at different temperatures and shear rates.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials and thickening and thixotropic agents for coatings, and specifically relates to a preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings. Background Art

[0002] The waterborne coating from preparation to film formation includes four processes: manufacturing, storage, construction, and leveling and film formation. The functions of the thickening and thixotropic agent are different in each process. The existing thickening and thixotropic agents are generally formed by pre-polymerization reaction of isocyanate and anhydrous polyethylene glycol substances to form branched isocyanate-capped macromolecules, and then capped with monofunctional alcohols or amines. However, the existing thickening and thixotropic agents have the following disadvantages in the preparation process:

[0003] First, the branched isocyanate-capped macromolecules obtained by pre-polymerization of isocyanate and polyethylene glycol substances have a large molecular weight and a low density of association sites, resulting in poor thickening effect.

[0004] Second, the introduction of urethane bonds and urea bonds can greatly improve the thickening and thixotropic effects of the thickener. However, the density of urea bonds introduced in the current thickener during synthesis is low, and even if a large amount of urea bonds are introduced, their distribution in the thickener is extremely uneven.

[0005] Third, due to the high viscosity of substances in the preparation process, a large amount of organic solvents need to be used. During later use, the organic solvents need to be removed by vacuum pumping. The process is not environmentally friendly and wastes resources and energy. In addition, the temperature is relatively high during the synthesis process, and there are many side reactions, which affect the final performance of the thickener. Summary of the Invention

[0006] To solve the above problems, the purpose of the present invention is to provide a preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0007] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0008] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, comprising the following steps:

[0009] ① Prepare the NCO-capped prepolymer: By weight, add 35-50 parts of difunctional isocyanate and 35-50 parts of polyethylene glycol to the reactor, stir and heat up to 60-85 °C, keep for 30-90 minutes, add 0.001-0.005 parts of polymerization catalyst thereto, and stir and react for 0.5-2 hours to obtain an NCO-capped prepolymer containing ureido groups and polyurethane groups;

[0010] The polyethylene glycol is one or two of polyethylene glycols with a molecular weight of 200-4000, and the water content is 0.8-1‰;

[0011] ②Chain extension reaction of NCO-terminated prepolymer: Control the temperature of the reaction kettle at 60-85 °C. Add 16-25 parts of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ① successively, stir and mix evenly, cool down by introducing circulating water, and add 280-450 parts of deionized water in 3-5 times within 30-60 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20-30 minutes to obtain a mixture; at this time, the viscosity of the mixture at 25 °C is generally in the range of 45000-47000 mpas;

[0012] ③Add 0.5-5 parts of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 20-45 °C for 1-2 hours to obtain a water-soluble viscous and highly transparent paste;

[0013] The monofunctional long-chain amine compound is an alkyl primary amine with C4-C18 or / and an alkyl secondary amine with C4-C22;

[0014] ④Detect the residual amine group content in the highly transparent paste obtained in step ③, and add 0-0.5 parts of low-reactivity diisocyanate to the reaction kettle according to the amine group content to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0015] Preferably, the polyethylene glycol is a mixture of two of polyethylene glycols with a molecular weight of 400-1000.

[0016] Preferably, the bifunctional isocyanate is one, two or three of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 4,4-diisocyanate dicyclohexylmethane.

[0017] Preferably, the trifunctional isocyanate is one, two or three of hexamethylene diisocyanate biuret, diphenylmethane diisocyanate trimer, toluene diisocyanate trimer, isophorone diisocyanate trimer, hexamethylene diisocyanate trimer, 4,4-diisocyanate dicyclohexylmethane trimer.

[0018] Preferably, the low-reactivity diisocyanate is one or two of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and 4,4-diisocyanate dicyclohexylmethane.

[0019] Preferably, the monofunctional long-chain amine compound is one or two of octadecyl primary amine, di-n-butylamine or hexadecyl secondary amine.

[0020] Preferably, after the addition of deionized water in step ②, 20 - 30 parts of small molecule polyethylene glycol are further added, the temperature of the reaction kettle does not exceed 30 °C, and the reaction continues for 20 - 30 minutes to obtain a mixture; at this time, the viscosity value of the mixture is generally 46000 - 48000 mpas.

[0021] The molecular weight of the small molecule polyethylene glycol is 200, 400 or 600.

[0022] The present invention has the following advantages compared with the prior art:

[0023] The polyurea polyurethane thickening and thixotropic agent of the present invention uses polyethylene glycol with a specific water content and diisocyanate for prepolymerization reaction. The prepolymer not only contains urethane bonds formed by polyethylene glycol and diisocyanate, but also contains urea bonds produced by the reaction of diisocyanate and water. And because the formation rates of urethane bonds and urea bonds are not much different, the urea bonds and urethane bonds are arranged alternately; then the prepolymer is end-capped with a large amount of deionized water to crosslink and extend the chain to produce a large number of urea bonds, and a large number of urea bonds can greatly improve the thickening and thixotropic properties of the product.

[0024] In the molecular chain of the polyurea polyurethane thickening and thixotropic agent of the present invention, more urethane bonds and urea bonds are introduced and are evenly distributed. By using the hydrogen bond action inside the molecule, two or more associative thickening molecules can be associated. And when the energy provided exceeds the hydrogen bond energy, the hydrogen bond can be opened and restored to the single molecule state. This structure not only retains the associativity but also increases the weak crosslinking of hydrogen bonds. Due to the associative structure between molecules, the formation of a hydrophilic network is promoted, thus showing thixotropic behavior.

[0025] The polyurea polyurethane thickening and thixotropic agent of the present invention has a large molecular weight and many branched molecules, showing better thickening properties, and the critical micelle concentration of the thickening agent is low, with less dosage. It has excellent applicability to the viscosity of waterborne coatings at different temperatures and shear rates. This is because at low shear rates, although intramolecular association occurs, the high density of polar hydrophilic bonds can also play an active thickening and thixotropic role. As the shear rate increases, the thermal motion of the molecules in the system accelerates, its molecular chain unfolds, releasing more hydrogen bond binding groups, and the molecular chain shows more thickening effects.

[0026] During the preparation process of the present invention, the prepolymer molecules are in a molten state at a temperature of about 70°C, and the reaction temperature throughout the process is controlled below 80°C, with very few side reactions occurring. In the product, except for the substances participating in the reaction, all is water. The entire reaction is completed in the solvent phase and the water phase. The small molecule reactants in the solvent phase not only provide the phase environment for the chemical reaction as a solvent but also participate in the reaction as reactants. The entire reaction does not produce any volatile organic compounds, and the organic substances participating in the reaction are also completely consumed to become non-volatile macromolecular hydrophilic substances. The entire reaction can be considered as a chemical reaction occurring completely in the water phase, and the whole process is green and environmentally friendly with low energy consumption. Detailed implementation mode

[0027] The object of the present invention is to provide a preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings. The polyurea polyurethane thickening and thixotropic agent of the present invention mainly includes two components, and the structural general formulas are shown in Formula I and Formula II.

[0028]

[0029] Among them, A = DI—U 1 —Gn—U 1 —DI, B = U 2 -DI, M = B n4 A m3 B n1 A m1 B n2 A m2 B n3 , Gn is a polyethylene glycol residue, U 1 is a urethane bond, U 2 is a urea bond, DI is an isocyanate residue, R is a residue of a capped monoamine, and O is a trimer residue;

[0030] The m 1 , m 2 , m 3 , n 1 , n 2 , n 3 , a, b, c, d have values of integers between 0 and 10.

[0031] The manufacturers or models of the raw materials of the trifunctional isocyanate of the present invention are as follows: hexamethylene diisocyanate biuret (Desmodur N-75), toluene diisocyanate trimer (Desmodur 1351), isophorone diisocyanate trimer (Evonik T1890 / 100, Desmodur Z 4470), hexamethylene diisocyanate trimer (BASF HI100, Covestro N3300, Wanhua HT-100).

[0032] The present invention will be further described below in conjunction with specific embodiments.

[0033] Example 1

[0034] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings comprises the following steps:

[0035] ① Preparation of NCO-terminated prepolymer: Add 3.5 kg of difunctional isocyanate and 3.5 kg of polyethylene glycol into a reactor, stir and heat up to 60 °C, keep for 30 minutes, add 0.0001 kg of polymerization catalyst thereto, and stir and react for 2 hours to obtain an NCO-terminated prepolymer containing ureido and polyurethane groups;

[0036] The polyethylene glycol is polyethylene glycol with a molecular weight of 200 and a water content of 0.8‰;

[0037] The difunctional isocyanate is diphenylmethane diisocyanate;

[0038] ② Chain extension reaction of NCO-terminated prepolymer: Control the temperature of the reaction kettle at 60 °C, successively add 1.6 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ①, stir and mix evenly, cool down by introducing circulating water, add 28 kg of deionized water in 3 portions within 30 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20 minutes to obtain a mixture; at this time, the measured viscosity value is 45050 mpas;

[0039] The trifunctional isocyanate is biuret of hexamethylene diisocyanate;

[0040] ③ Add 0.5 kg of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 20 °C for 2 hours to obtain a water-soluble viscous and highly transparent paste;

[0041] The monofunctional long-chain amine compound is di-n-butylamine;

[0042] ④ Detect that the residual amine group content in the highly transparent paste obtained in step ③ is 0, and there is no need to add low-reactivity diisocyanate to the reaction kettle to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0043] Example 2

[0044] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings comprises the following steps:

[0045] ① Preparation of NCO-terminated prepolymer: Add 5 kg of difunctional isocyanate and 5 kg of polyethylene glycol into a reactor, stir and heat up to 85 °C, keep for 90 minutes, add 0.0001 kg of polymerization catalyst thereto, and stir and react for 0.5 hour to obtain an NCO-terminated prepolymer containing ureido and polyurethane groups;

[0046] The polyethylene glycol is polyethylene glycol with a molecular weight of 4000 and a water content of 1‰;

[0047] The difunctional isocyanate is toluene diisocyanate;

[0048] ② NCO-capped prepolymer chain extension reaction: Control the temperature of the reaction kettle at 85°C. Add 2.5 kg of trifunctional isocyanate to the NCO-capped prepolymer obtained in step ① successively, stir and mix evenly, cool down by introducing circulating water, add 45 kg of deionized water in 5 portions within 60 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30°C, and continue to react for 30 minutes to obtain a mixture; at this time, the viscosity value of the mixture is detected to be 46980 mpas;

[0049] The trifunctional isocyanate is diphenylmethane diisocyanate trimer;

[0050] ③ Add 0.5 kg of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 45°C for 1 hour to obtain a water-soluble viscous and highly transparent paste;

[0051] The monofunctional long-chain amine compound is octadecyl primary amine;

[0052] ④ Detect the residual amine group content in the highly transparent paste obtained in step ③ (the percentage content is 0.0059%), convert it to the molar number of amine groups as 0.12 mol, add 0.12 * 1.5 = 0.18 mol of diisocyanate, and add 222 * 0.18 = 40 g of isophorone diisocyanate to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings. 3 The percentage content is 0.0059%, and the molar number of amine groups is converted to 0.12 mol. Add 0.12 * 1.5 = 0.18 mol of diisocyanate, and add 222 * 0.18 = 40 g of isophorone diisocyanate to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0053] Example 3

[0054] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, comprising the following steps:

[0055] ① Preparation of NCO-capped prepolymer: Add 4 kg of difunctional isocyanate and 4.5 kg of polyethylene glycol to a reactor, stir and heat up to 70°C, keep for 45 minutes, add 0.0003 kg of polymerization catalyst thereto, and stir and react for 1 hour to obtain an NCO-capped prepolymer containing urea groups and polyurethane groups;

[0056] The polyethylene glycol is a mixture of polyethylene glycol with a molecular weight of 400 and 600 in a mass ratio of 2:3, and the water content is 0.9‰; the difunctional isocyanate is isophorone diisocyanate;

[0057] ②Chain extension reaction of NCO-terminated prepolymer: Control the temperature of the reaction kettle at 70 °C. Add 1.8 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ① successively, stir and mix evenly, cool down by passing through circulating water, and add 40 kg of deionized water in 4 portions within 40 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 25 minutes to obtain a mixture; at this time, the viscosity value of the mixture is detected to be 46050 mpas;

[0058] The trifunctional isocyanate is hexamethylene diisocyanate trimer;

[0059] ③Add 0.3 kg of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 30 °C for 1.5 hours to obtain a water-soluble viscous and highly transparent paste;

[0060] The monofunctional long-chain amine compound is cetyl secondary amine;

[0061] ④Detect that the residual amino group content in the highly transparent paste obtained in step ③ is 0.0072%, and add 50 g of hexamethylene diisocyanate to the reaction kettle according to the amino group content to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0062] Example 4

[0063] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, comprising the following steps:

[0064] ①Preparation of NCO-terminated prepolymer: Add 3.8 kg of difunctional isocyanate and 4 kg of polyethylene glycol to a reactor, stir and heat up to 75 °C, keep for 60 minutes, add 0.0004 kg of polymerization catalyst thereto, and stir and react for 1.5 hours to obtain an NCO-terminated prepolymer containing urea groups and polyurethane groups;

[0065] The polyethylene glycol is obtained by mixing polyethylene glycol with molecular weights of 200 and 1000 in a mass ratio of 1:1, and the water content is 1‰; the difunctional isocyanate is obtained by mixing 4,4-diisocyanate dicyclohexylmethane and hexamethylene diisocyanate in a mass ratio of 1:1;

[0066] ②Chain extension reaction of NCO-terminated prepolymer: Control the temperature of the reaction kettle at 80 °C. Add 2 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ① successively, stir and mix evenly, cool down by passing through circulating water, and add 30 kg of deionized water in 4 portions within 50 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 25 minutes to obtain a mixture; at this time, the viscosity value of the mixture is 45500 mpas;

[0067] The trifunctional isocyanate is obtained by mixing isophorone diisocyanate trimer and 4,4-diisocyanate dicyclohexylmethane trimer in a mass ratio of 2:3;

[0068] ③ Add 0.2 kg of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 30 °C for 1.5 hours to obtain a water-soluble viscous and highly transparent paste;

[0069] The monofunctional long-chain amine compound is obtained by mixing butyl primary amine and docosyl secondary amine in a mass ratio of 1:1;

[0070] ④ Detect that the residual amino group content in the highly transparent paste obtained in step ③ is 0.0067%, and add 46 g of 4,4-diisocyanate dicyclohexylmethane to the reaction kettle according to the amino group content to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0071] Example 5

[0072] A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, comprising the following steps:

[0073] ① Prepare an NCO-terminated prepolymer: Add 4.5 kg of bifunctional isocyanate and 3.8 kg of polyethylene glycol to a reactor, stir and heat up to 65 °C, hold for 45 minutes, add 0.0002 kg of polymerization catalyst thereto, and stir and react for 1 hour to obtain an NCO-terminated prepolymer containing urea groups and polyurethane groups;

[0074] The polyethylene glycol is obtained by mixing polyethylene glycol with a molecular weight of 400 and 3000 in a mass ratio of 9:1, and the water content is 1‰; the bifunctional isocyanate is obtained by mixing toluene diisocyanate and hexamethylene diisocyanate in a mass ratio of 2:3;

[0075] ② NCO-terminated prepolymer chain extension reaction: Control the temperature of the reaction kettle at 75 °C, add 2 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ① successively, stir and mix evenly, cool down by passing through circulating water, and add 30 kg of deionized water in 3 portions within 45 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20 - 30 minutes to obtain a mixture; at this time, the viscosity value of the mixture is detected to be 46800 mpas;

[0076] The trifunctional isocyanate is obtained by mixing diphenylmethane diisocyanate trimer and hexamethylene diisocyanate trimer in a mass ratio of 1:1;

[0077] ③ Add 0.3 kg of monofunctional long-chain amine compound to the mixture obtained in step ②, and react at 30 °C for 1.5 hours to obtain a water-soluble viscous and highly transparent paste;

[0078] The monofunctional long-chain amine compound is obtained by mixing octadecyl primary amine and hexadecyl secondary amine in a mass ratio of 1:2;

[0079] ④ Detect that the residual amino group content in the highly transparent paste obtained in step ③ is 0, and obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0080] Example 6

[0081] The steps are the same as those in Example 3, except that in step ②, it is an NCO-terminated prepolymer chain extension reaction: control the temperature of the reaction kettle at 70 °C, and successively add 1.8 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ①, stir and mix evenly, cool down by passing through circulating water, add 40 kg of deionized water in 4 portions within 40 minutes, and after the addition of deionized water is completed, continue to add 2 kg of polyethylene glycol with a molecular weight of 400 to the reaction kettle, and react for 25 minutes to obtain a mixture; at this time, the viscosity value of the mixture is detected to be 47150 mpas.

[0082] Example 7

[0083] The steps are the same as those in Example 4, except that in step ②, it is an NCO-terminated prepolymer chain extension reaction: control the temperature of the reaction kettle at 80 °C, and successively add 2 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ①, stir and mix evenly, cool down by passing through circulating water, add 30 kg of deionized water in 4 portions within 50 minutes, and after the addition of deionized water is completed, continue to add 3 kg of polyethylene glycol with a molecular weight of 200 to the reaction kettle, and the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20 - 30 minutes to obtain a mixture; at this time, the viscosity value of the mixture is 46850 mpas.

[0084] Example 8

[0085] The steps are the same as those in Example 5, except that in step ②, it is an NCO-terminated prepolymer chain extension reaction: control the temperature of the reaction kettle at 75 °C, and successively add 2 kg of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ①, stir and mix evenly, cool down by passing through circulating water, add 30 kg of deionized water in 3 portions within 45 minutes, and after the addition of deionized water is completed, continue to add 2.5 kg of polyethylene glycol with a molecular weight of 600 to the reaction kettle, and the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20 - 30 minutes to obtain a mixture; at this time, the viscosity value of the mixture is detected to be 47850 mpas.

[0086] In the examples of the present invention, the method for detecting the residual amino group content in the highly transparent paste obtained in step ③ is titration with a HCl standard solution (methyl red - bromocresol green indicator) or an electrochemical method.

[0087] Comparative Example 1

[0088] The reaction was carried out using polyethylene glycol without water treatment. The reaction process, raw materials added were the same as in Example 5 to prepare an NCO-terminated prepolymer: 450 g of difunctional isocyanate and 380 g of polyethylene glycol were added to a reactor, stirred and heated to 65 °C, maintained for 45 minutes, 0.02 g of polymerization catalyst was added thereto, and stirred for reaction. As the stirring proceeded, the viscosity of the reactants became increasingly large. If the stirring was not timely, local explosive polymerization would occur, and at this time, an NCO-terminated prepolymer containing ureido and polyurethane groups could not be formed.

[0089] The polyethylene glycol was obtained by mixing polyethylene glycol with a molecular weight of 400 and 3000 in a mass ratio of 9:1, and the water content was 1%; the difunctional isocyanate was obtained by mixing toluene diisocyanate and hexamethylene diisocyanate in a mass ratio of 2:3.

[0090] Comparative Example 2

[0091] The reaction was carried out using polyethylene glycol that had been treated to a water content of less than 1‰. The remaining steps were exactly the same as in Example 5 to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings.

[0092] The polyurea polyurethane thickening and thixotropic agents obtained in Examples 1 to 8 were applied to waterborne acrylic polyurethane coatings. Based on parts by mass, the paint was formulated according to the formula in Table 1.

[0093] Table 1 Formulation of waterborne acrylic polyurethane coating

[0094]

[0095]

[0096] The above materials were added to a mixing kettle and dispersed at a rotation speed of 1500 r / min for 90 min, then a thickener was added and dispersed at a high speed of 1500 r / min for 10 min. After standing for 30 min, the rotational viscosity of the system at 25 °C was measured using an NDJ-5 digital display rotational viscometer. Finally, the rotational viscosities of the formulated paint systems at 25 °C with different thickener addition amounts are shown in Table 2. For Comparative Example 3, the thickeners BYK-420 and RHEOBYK-H 7500VF were mixed in a weight ratio of 1:1.

[0097] Table 2 Relationship between the viscosity of waterborne acrylic polyurethane coating and the addition amount of thickener

[0098]

[0099] As can be seen from the results in Table 2, the polyurea polyurethane thickening and thixotropic agent for waterborne coatings prepared by the present invention can achieve good thickening effects at relatively low thickener addition amounts. And at the same addition amount, compared with the existing thickeners, the thickening performance obtained by the present invention is excellent. The coating surface of the prepared sample pieces is smooth and flat without defects, and all other performance indicators fully meet the product usage requirements.

[0100] In Comparative Example 2, since the water in polyethylene glycol was removed relatively thoroughly, the prepolymer only contained urethane bonds formed by polyethylene glycol and diisocyanate, and the amount of urea bonds produced by the reaction of diisocyanate and water was extremely small, and a prepolymer with an alternating arrangement of urea bonds and urethane bonds could not be formed. Therefore, the thickening performance of the final product was poor. And compared with Examples 6 - 8 and Examples 3 - 5, after using small - molecule polyethylene glycol for chain extension, the viscosity of the final product can be greatly increased, and the thickening effect is better.

[0101] The polyurea polyurethane thickening and thixotropic agents for waterborne coatings obtained in Examples 1 - 8 were applied to latex paints. By mass, the paint was formulated according to the recipe in Table 3.

[0102] Table 3 Recipe of latex paint

[0103] Material Name Parts by Weight of Material Dispersant TCP-8045 0.50 Defoamer 681F 0.12 Wetting Agent NP-10 0.35 Titanium Dioxide 11.20 Light Calcium Carbonate 19.25 Talc Powder 7.50 Film-Forming Aid 1.60 Propylene Glycol 1.8 AP-95 Multifunctional Additive 0.11 Emulsion for Architectural Coatings 30.00 Deionized Water 27.00

[0104] The components in Table 3 were added to a mixing reactor according to the weight ratio, dispersed at a rotation speed of 1500 r / min for 90 min, then the thickener was added, and high - speed dispersed at a rotation speed of 1500 r / min for 10 min. After standing for 30 min, the rotational viscosity of the system at 25 °C was measured using an NDJ - 5 digital display rotational viscometer. Finally, the rotational viscosities of the paint formulation system at 25 °C with different thickener addition amounts are shown in Table 4. In Comparative Example 4, the thickeners ATTAGEL50 and BASF DSX3116 were mixed in a weight ratio of 1:2.

[0105] Table 4 Relationship between the viscosity of latex paint and the thickener addition amount

[0106]

[0107]

[0108] As can be seen from the results in Table 4, the polyurea polyurethane thickener prepared by the present invention can achieve good thickening efficiency at a relatively low addition amount of the thickener. And at the same addition amount, compared with Comparative Example 4, the thickening performance of this example is excellent. In Comparative Example 2, since the water in polyethylene glycol was removed relatively thoroughly, the prepolymer only contained urethane bonds formed by polyethylene glycol and diisocyanate, and the amount of urea bonds produced by the reaction of diisocyanate and water was extremely small, and a prepolymer with an alternating arrangement of urea bonds and urethane bonds could not be formed. Therefore, the thickening performance of the final product was worse than that of Example 5.

[0109] Compared with Examples 3-5, in Examples 6-8, after chain extension with small molecule polyethylene glycol, the viscosity of the final product can be greatly increased, and the thickening effect is better. The coating surface of the sample sheet prepared in the example is smooth and flat without defects, and other performance indicators also fully meet the requirements of product use.

[0110] It can be seen from the data of the above test examples that the polyurea polyurethane thickener prepared by the method of the present invention has the characteristics of strong thickening ability, low dosage and good leveling property. And it is applicable to various water-soluble coatings, having broad application prospects.

Claims

1. A preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings, characterized in that: It includes the following steps: ① Preparation of NCO-terminated prepolymer: By weight, add 35-50 parts of difunctional isocyanate and 35-50 parts of polyethylene glycol to a reactor, stir and heat up to 60-85 °C, keep for 30-90 minutes, add 0.001-0.005 parts of polymerization catalyst thereto, and stir and react for 0.5-2 hours to obtain an NCO-terminated prepolymer containing ureido and polyurethane groups; The polyethylene glycol is one or two of polyethylene glycols with a molecular weight of 200-4000, and the water content is 0.8-1‰; ② Chain extension reaction of NCO-terminated prepolymer: Control the temperature of the reaction kettle at 60-85 °C, successively add 16-25 parts of trifunctional isocyanate to the NCO-terminated prepolymer obtained in step ①, stir and mix evenly, cool down by passing through circulating water, and add 280-450 parts of deionized water in 3-5 times within 30-60 minutes. After the addition of deionized water is completed, the temperature of the reaction kettle does not exceed 30 °C, and continue to react for 20-30 minutes to obtain a mixture; ③ Add 0.5-5 parts of monofunctional long-chain amine compounds to the mixture obtained in step ②, and react at 20-45 °C for 1-2 hours to obtain a water-soluble viscous and highly transparent paste; The monofunctional long-chain amine compound is an alkyl primary amine of C4-C18 or / and an alkyl secondary amine of C4-C22; ④ Detect the residual amine group content in the highly transparent paste obtained in step ③, and add 0-0.5 parts of low-reactivity diisocyanate to the reaction kettle according to the amine group content to obtain a polyurea polyurethane thickening and thixotropic agent for waterborne coatings; The low-reactivity diisocyanate is one or two of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and 4,4-diisocyanatodicyclohexylmethane.

2. The preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings according to claim 1, characterized in that: The polyethylene glycol is a mixture of two of polyethylene glycols with a molecular weight of 400-1000.

3. The preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings according to claim 1, characterized in that: The difunctional isocyanate is one, two or three of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and 4,4-diisocyanatodicyclohexylmethane.

4. The preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings according to claim 1, characterized in that: The trifunctional isocyanate is one, two or three of biuret of hexamethylene diisocyanate, trimer of diphenylmethane diisocyanate, trimer of toluene diisocyanate, trimer of isophorone diisocyanate, trimer of hexamethylene diisocyanate, and trimer of 4,4-diisocyanatodicyclohexylmethane.

5. The preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings according to claim 1, characterized in that: The monofunctional long-chain amine compound is one or two of octadecyl primary amine, di-n-butylamine or hexadecyl secondary amine.

6. The preparation method of a polyurea polyurethane thickening and thixotropic agent for waterborne coatings according to claim 1, characterized in that: In step ②, after the addition of deionized water is completed, 20-30 parts of polyethylene glycol are continuously added, the temperature of the reaction kettle does not exceed 30 °C, and the reaction continues for 20-30 minutes to obtain a mixture; The molecular weight of the polyethylene glycol is 200, 400 or 600.

Images