A water-based polyurethane thickener and its preparation method

Abstract

This invention discloses a waterborne polyurethane thickener and its preparation method, comprising the following steps: adding terminal epoxy group polyethylene oxide to a reaction vessel and heating to 95-100℃; dividing a long-chain monocarboxyl compound into multiple portions by weight; adding the first portion of the long-chain monocarboxyl compound to the reaction vessel and reacting at 95-100℃, adding one portion of the long-chain monocarboxyl compound every hour until the last portion is added, and maintaining the reaction temperature for 4 hours; adding deionized water at 90-95℃ to obtain the waterborne polyurethane thickener. This invention does not use highly toxic isocyanate monomers, has a narrow molecular weight distribution, high thickening efficiency, and the product's molecular chain contains hydroxyl active groups, which can participate in the cross-linking and curing of coatings. The series of thickeners prepared by this method can achieve rheological effects ranging from pseudoplastic to Newtonian in waterborne coatings.

Description

Technical Field

[0001] This invention relates to the field of water-based thickeners, and particularly to a water-based polyurethane thickener and its preparation method. Background Technology

[0002] With the introduction of environmental regulations in various countries and the increasing environmental awareness of the public, water-based coatings are becoming increasingly popular, and coating companies and research institutions are investing more and more in the research of water-based coatings. However, water-based coatings, especially those using emulsions as film-forming substances, often have very low viscosity and require the addition of thickeners to adjust their viscosity and rheological properties.

[0003] Among existing thickener products, inorganic thickeners generally have strong thixotropy, resulting in poor leveling properties and limiting their application range; cellulose thickeners are ultra-large molecular weight water-soluble resins, with low viscosity under high shear, affecting film fullness, strong thixotropy affecting leveling, and prone to mold growth, so they are now rarely used; acrylate alkali-swellable thickeners are solvent-free, relying mainly on carboxylates for hydrophilicity, making them susceptible to the influence of ions in the system and significantly affecting the water resistance of the coating, thus limiting their application areas; polyurethane associative thickeners can adjust the rheological effect of the coating from pseudoplastic to Newtonian and are unaffected by the nature and concentration of ions in the system, making them the best type of thickener in terms of overall application performance. However, this type of thickener still has some shortcomings:

[0004] (1) The synthesis process uses highly toxic and volatile isocyanate monomers, which can cause certain harm to the human body during the synthesis stage.

[0005] (2) In industrial coatings with high water resistance requirements, the main chain of such thickeners is water-soluble polyethylene glycol and cannot participate in the curing and crosslinking of the coating system, which has a certain negative impact on water resistance.

[0006] (3) Generally, waterborne polyurethane associative thickeners are obtained by stepwise chain extension polymerization of diisocyanate and polyethylene glycol with a relatively small molecular weight, resulting in isocyanate-terminated polymers, which are then capped with hydrophobic monohydric alcohols. The synthesized products have a wide molecular weight distribution, resulting in a low proportion of molecules with the best thickening performance and low thickening efficiency. Summary of the Invention

[0007] In order to solve the above-mentioned technical problems, the present invention provides an aqueous polyurethane thickener and its preparation method.

[0008] In a first aspect, the present invention provides a method for preparing an aqueous polyurethane thickener, which is achieved by the following technical solution.

[0009] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0010] Add epoxy-terminated polyethylene oxide to the reaction vessel and heat to 95-100℃;

[0011] Divide the long-chain monocarboxylic compound into multiple portions by weight; add the first portion of the long-chain monocarboxylic compound into the reaction vessel and react at 95-100℃. Add one portion of the long-chain monocarboxylic compound every 0.5-1 hour until the last portion of the long-chain monocarboxylic compound is added. Then continue to maintain the reaction temperature for 4-6 hours.

[0012] Adding deionized water at 90-95℃ yields a waterborne polyurethane thickener.

[0013] Furthermore, the terminal epoxy group polyoxyethylene has the following structure:

[0014]

[0015] Furthermore, the weight-average molecular weight of the terminal epoxy group polyethylene oxide is between 6,000 and 30,000.

[0016] Furthermore, the long-chain monocarboxylic acid compound is selected from one or more of hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid.

[0017] Furthermore, the ratio of the carboxyl equivalent of the long-chain monocarboxyl compound to the epoxy equivalent of the terminal epoxy polyethylene oxide is (0.9:1)-(1.1:1).

[0018] Furthermore, the weight ratio of the sum of the terminal epoxy group polyethylene oxide and the long carbon chain monocarboxyl compound to water is (0.2:0.8)-(0.4:0.6).

[0019] Furthermore, the long-chain monocarboxyl compound is divided into 3-10 parts by weight and added stepwise to the reaction vessel to participate in the reaction.

[0020] Secondly, the present invention provides an aqueous polyurethane thickener, which is achieved by the following technical solution.

[0021] An aqueous polyurethane thickener prepared by the above preparation method.

[0022] This application has the following beneficial effects.

[0023] The waterborne polyurethane thickener of the present invention does not use highly toxic isocyanate monomers, has a narrow molecular weight distribution, high thickening efficiency, and contains hydroxyl active groups in the product molecular chain, which can participate in the cross-linking and curing of the coating without affecting the water resistance of the coating. Attached Figure Description

[0024] Figure 1 This is a graph showing the molecular weight analysis results of Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 2 These are the molecular weight analysis results of Example 4 and Comparative Example 4 of the present invention;

[0026] Figure 3 This is a comparison chart of the thickening curves (Newtonian fluid) of Embodiment 1 and Comparative Example 1 of the present invention;

[0027] Figure 4 This is a comparison chart of the thickening curves (equilibrium fluid) of Embodiment 2 and Comparative Example 2 of the present invention;

[0028] Figure 5 This is a comparison chart of the thickening curves (pseudoplastic fluid) of Example 3 and Comparative Example 3 of the present invention;

[0029] Figure 6 This is a comparison chart of the thickening curves (Newtonian fluid) of Embodiment 4 and Comparative Example 4 of the present invention;

[0030] Figure 7 This is a comparison chart of the thickening curves (equilibrium fluid) of Embodiment 5 and Comparative Example 5 of the present invention;

[0031] Figure 8 This is a comparison chart of the thickening curves (pseudoplastic fluid) of Example 6 and Comparative Example 6 of the present invention. Detailed Implementation

[0032] The present patent application will be further described below with reference to the embodiments.

[0033] The formulations for Examples 1-6 are shown in the table below (all data in the table are in grams).

[0034]

[0035] Example 1

[0036] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0037] (1) Divide hexanoic acid into 5 equal parts by weight;

[0038] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 10000) and heat to 98°C;

[0039] (3) Add the first portion of hexanoic acid to the reaction vessel and react at 98°C. Add one portion of hexanoic acid every hour until the last portion of hexanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0040] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0041] Example 2

[0042] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0043] (1) Divide the dodecanoic acid into 5 equal portions by weight;

[0044] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 10000) and heat to 98°C;

[0045] (3) Add the first portion of dodecanoic acid to the reaction vessel and react at 98°C. Add one portion of dodecanoic acid every hour until the last portion of dodecanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0046] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0047] Example 3

[0048] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0049] (1) Divide the stearic acid into 5 equal parts by weight;

[0050] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 10000) and heat to 98°C;

[0051] (3) Add the first portion of octadecanoic acid to the reaction vessel and react at 98°C. Add one portion of octadecanoic acid every hour until the last portion of octadecanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0052] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0053] Example 4

[0054] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0055] (1) Divide hexanoic acid into 5 equal parts by weight;

[0056] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 20000) and heat to 98°C;

[0057] (3) Add the first portion of hexanoic acid to the reaction vessel and react at 98°C. Add one portion of hexanoic acid every hour until the last portion of hexanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0058] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0059] Example 5

[0060] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0061] (1) Divide the dodecanoic acid into 5 equal portions by weight;

[0062] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 20000) and heat to 98°C;

[0063] (3) Add the first portion of dodecanoic acid to the reaction vessel and react at 98°C. Add one portion of dodecanoic acid every hour until the last portion of dodecanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0064] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0065] Example 6

[0066] A method for preparing an aqueous polyurethane thickener includes the following steps:

[0067] (1) Divide the stearic acid into 5 equal parts by weight;

[0068] (2) In a reaction vessel equipped with a stirrer, thermometer and reflux device, add epoxy-terminated polyethylene oxide (Mw = 20000) and heat to 98°C;

[0069] (3) Add the first portion of octadecanoic acid to the reaction vessel and react at 98°C. Add one portion of octadecanoic acid every hour until the last portion of octadecanoic acid is added. Then continue to maintain the reaction temperature for 4 hours.

[0070] (4) Add deionized water at 92℃ to obtain a water-based associative thickener.

[0071] The formulations for Comparative Examples 1-6 are shown in the table below (all data in the table are in grams).

[0072]

[0073] Comparative Example 1

[0074] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0075] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, the reaction is maintained at this temperature for 3 hours, n-hexanol is added, the reaction is maintained at this temperature for 4 hours, deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0076] Comparative Example 2

[0077] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0078] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, and the reaction is maintained at this temperature for 3 hours. Dodecanol is added, and the reaction is maintained at this temperature for 4 hours. Deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0079] Comparative Example 3

[0080] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0081] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, and the reaction is maintained at this temperature for 3 hours. Then, octadecyl alcohol is added, and the reaction is maintained at this temperature for 4 hours. Finally, deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0082] Comparative Example 4

[0083] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0084] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, the reaction is maintained at this temperature for 3 hours, n-hexanol is added, the reaction is maintained at this temperature for 4 hours, deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0085] Comparative Example 5

[0086] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0087] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, and the reaction is maintained at this temperature for 3 hours. Dodecanol is added, and the reaction is maintained at this temperature for 4 hours. Deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0088] Comparative Example 6

[0089] A method for preparing an aqueous polyurethane associative thickener includes the following steps:

[0090] In a reaction vessel equipped with a stirrer, thermometer, and reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, and the reaction is maintained at this temperature for 3 hours. Then, octadecyl alcohol is added, and the reaction is maintained at this temperature for 4 hours. Finally, deionized water is added and stirred until homogeneous to obtain an aqueous polyurethane associative thickener.

[0091] Performance testing

[0092] 1. Molecular weight analysis

[0093] like Figure 1-2 As shown, Figure 1 The graphs show the molecular weight analysis results for Example 1 and Comparative Example 1. Figure 2 The following are molecular weight analysis charts for Example 4 and Comparative Example 4. From the molecular weight analysis results of the above examples and comparative examples, it can be seen that, with similar Mw values, the molecular weight distribution of the examples is close to 1.1, while the molecular weight distribution of the comparative examples is wider, resulting in the presence of more molecules with lower thickening efficiency, thus reducing the thickening efficiency. (It should be noted that Example 2 and Example 3 were synthesized using the same method as Example 1, and their molecular weights are similar; therefore, the analysis results are not shown here. Comparative Examples 2 and 3 were synthesized using the same method as Comparative Example 1, and their molecular weights are similar; therefore, the analysis results are not shown here. Example 5 and Example 6 were synthesized using the same method as Example 4, and their molecular weights are similar; therefore, the analysis results are not shown here. Comparative Examples 5 and 6 were synthesized using the same method as Comparative Example 4, and their molecular weights are similar; therefore, the analysis results are not shown here.)

[0094] 2. Thickening effect and water resistance

[0095] The aqueous thickeners obtained in Examples 1-6 and the thickeners obtained in Comparative Examples 1-6 were applied in the same formulation of white paint. By adjustment, three types of fluids with different rheological properties were obtained: Examples 1 and Comparative Example 1, as well as Examples 4 and Comparative Example 4, were Newtonian fluids; Examples 2 and Comparative Example 2, as well as Examples 5 and Comparative Example 5, were equilibrium fluids; and Examples 3 and Comparative Example 3, as well as Examples 6 and Comparative Example 6, were pseudoplastic fluids.

[0096] from Figure 3-8 Based on the thickening curves of the embodiments and the comparative examples, the thickening curve of the embodiments is higher than that of the comparative examples, indicating that the implementation effect of the present invention is better than that of commonly used associative thickeners on the market, while having no effect on the water resistance of the two-component coating.

[0097] The water resistance test results for the coating are shown in the table below.

[0098]

[0099] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous polyurethane thickener, characterized in that: Includes the following steps: Add epoxy-terminated polyethylene oxide to the reaction vessel and heat to 95-100℃; Divide the long-chain monocarboxylic compound into multiple portions by weight; add the first portion of the long-chain monocarboxylic compound into the reaction vessel and react at 95-100℃. Add one portion of the long-chain monocarboxylic compound every 0.5-1 hour until the last portion of the long-chain monocarboxylic compound is added. Then continue to maintain the reaction temperature for 4-6 hours. Adding deionized water at 90-95℃ yields a waterborne polyurethane thickener. The terminal epoxy group polyethylene oxide has the following structure: ； The weight-average molecular weight of the terminal epoxy group polyethylene oxide is between 6,000 and 30,000. The long-chain monocarboxylic acid compound is selected from one or more of hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid; The ratio of the carboxyl equivalent of the long-chain monocarboxyl compound to the epoxy equivalent of the terminal epoxy polyethylene oxide is (0.9:1) to (1.1:1).

2. The method for preparing an aqueous polyurethane thickener according to claim 1, characterized in that: The weight ratio of the sum of the terminal epoxy group polyoxyethylene and the long carbon chain monocarboxyl compound to water is (0.2:0.8)-(0.4:0.6).

3. The method for preparing an aqueous polyurethane thickener according to claim 1, characterized in that: The long-chain monocarboxyl compound is divided into 3-10 parts by weight and added to the reaction vessel step by step to participate in the reaction.

4. An aqueous polyurethane thickener prepared by any one of the preparation methods described in claims 1-3.

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