Waterborne polyurethane thickening agent and preparation method thereof

Abstract

The preparation method comprises the following steps: adding epoxy-terminated polyethylene oxide into a reaction container, and raising the temperature to 95 to 100 DEG C; averagely dividing the long-carbon-chain monocarboxyl compound into a plurality of parts by weight; adding a first part of long-carbon-chain monocarboxyl compound into the reaction container, reacting at 95-100 DEG C, adding one part of long-carbon-chain monocarboxyl compound every 1 hour until the last part of long-carbon-chain monocarboxyl compound is completely added, and continuously keeping the reaction temperature for 4 hours; and adding deionized water under the condition of 90-95 DEG C to obtain the waterborne polyurethane thickening agent. According to the invention, isocyanate monomers with high toxicity are not used, the molecular weight distribution of the product is narrow, the thickening efficiency is high, the molecular chain of the product contains hydroxyl active groups, and the product can participate in cross-linking curing of a coating. The series of thickeners prepared by the method can achieve a rheological effect of adjusting from a false plastic type to a Newton type in a water-based coating.

Description

Technical Field

[0001] The invention relates to the field of water-based thickeners, and in particular to a water-based polyurethane thickener and a preparation method thereof. Background Art

[0002] With the introduction of environmental protection laws and regulations in various countries and the increase of people's environmental awareness, water-based coatings are becoming more and more popular, and various coating companies and research institutions are investing more and more in the research of water-based coatings. However, water-based coatings, especially those with emulsion as film-forming material, often have very low viscosity and need to add thickeners to adjust their viscosity and rheological properties.

[0003] Among the existing thickener products, inorganic thickeners are generally thixotropic, resulting in poor leveling and limited application scope; cellulose thickeners are ultra-large molecular water-soluble resins, with low viscosity under high shear, which affects the fullness of the coating, strong thixotropy, which affects the leveling, and are prone to mold, and are now rarely used; acrylic acid ester alkali-swellable thickeners do not contain solvents, and mainly rely on carboxylates to provide hydrophilicity, which makes them easily affected by ions in the system and has a significant impact on the water resistance of the coating, limiting their application areas; polyurethane associative thickeners can adjust the rheological effect of the coating from pseudoplastic to Newtonian, and are not affected by the nature and concentration of ions in the system. They are currently a type of thickener with better comprehensive application effects. However, this type of thickener still has certain shortcomings:

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

[0005] (2) In industrial coatings with high requirements for water resistance, since the main chain of this type of thickener is water-soluble polyethylene glycol and cannot participate in the curing and cross-linking of the coating system, it has a certain negative impact on water resistance;

[0006] (3) Generally, waterborne polyurethane associative thickeners are obtained by gradual chain extension polymerization of diisocyanate and polyethylene glycol with a relatively small molecular weight to obtain an isocyanate-terminated polymer, which is then terminated with a hydrophobic monoalcohol. The molecular weight distribution of the synthesized product is relatively wide, resulting in a lower proportion of molecules with the best thickening performance molecular weight and a lower thickening efficiency. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a waterborne polyurethane thickener and a preparation method thereof.

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

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

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

[0011] Divide the long carbon chain monocarboxyl compound into multiple portions by weight; then add the first portion of the long carbon chain monocarboxyl compound into the reaction container, react at 95-100° C., add a portion of the long carbon chain monocarboxyl compound every 0.5-1 hour, and continue to maintain the reaction temperature for 4-6 hours after the last portion of the long carbon chain monocarboxyl compound is added;

[0012] At 90-95°C, deionized water is added to obtain a waterborne polyurethane thickener.

[0013] Furthermore, the epoxy-terminated polyethylene oxide has the structure shown below:

[0014]

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

[0016] Furthermore, the long carbon chain monocarboxyl compound is selected from one or more of caproic acid, caprylic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid.

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

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

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

[0020] In a second aspect, the present invention provides a water-based polyurethane thickener, which is achieved by adopting the following technical solution.

[0021] A water-based 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 product molecular weight distribution, and has high thickening efficiency. The product molecular chain contains hydroxyl active groups, which can participate in the cross-linking and curing of the coating and thus do not affect the water resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 2 4 is a graph showing the molecular weight analysis results of Example 4 of the present invention and Comparative Example 4;

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

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

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

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

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

[0031] Figure 8 It is a comparison diagram of the thickening curves of Example 6 of the present invention and Comparative Example 6 (pseudoplastic fluid). DETAILED DESCRIPTION

[0032] The present patent application is further described below in conjunction with embodiments.

[0033] The formula of Examples 1-6 is as follows (the data units in the table are all g)

[0034]

[0035] Example 1

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

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

[0038] (2) Add epoxy-terminated polyethylene oxide (Mw=10,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

[0039] (3) adding the first portion of caproic acid to the reaction vessel, reacting at 98° C., adding a portion of caproic acid every hour until the last portion of caproic acid is added, and maintaining the reaction temperature for 4 hours;

[0040] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0041] Example 2

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

[0043] (1) Divide lauric acid into 5 equal parts by weight;

[0044] (2) Add epoxy-terminated polyethylene oxide (Mw=10,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

[0045] (3) adding the first portion of dodecanoic acid to the reaction vessel, reacting at 98° C., adding a portion of dodecanoic acid every hour until the last portion of dodecanoic acid is added, and maintaining the reaction temperature for 4 hours;

[0046] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0047] Example 3

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

[0049] (1) Octadecanoic acid was divided into 5 parts by weight;

[0050] (2) Add epoxy-terminated polyethylene oxide (Mw=10,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

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

[0052] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0053] Example 4

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

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

[0056] (2) Add epoxy-terminated polyethylene oxide (Mw=20,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

[0057] (3) adding the first portion of caproic acid to the reaction vessel, reacting at 98° C., adding a portion of caproic acid every hour until the last portion of caproic acid is added, and maintaining the reaction temperature for 4 hours;

[0058] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0059] Example 5

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

[0061] (1) Divide lauric acid into 5 equal parts by weight;

[0062] (2) Add epoxy-terminated polyethylene oxide (Mw=20,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

[0063] (3) adding the first portion of dodecanoic acid to the reaction vessel, reacting at 98° C., adding a portion of dodecanoic acid every hour until the last portion of dodecanoic acid is added, and maintaining the reaction temperature for 4 hours;

[0064] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0065] Example 6

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

[0067] (1) Octadecanoic acid was divided into 5 parts by weight;

[0068] (2) Add epoxy-terminated polyethylene oxide (Mw=20,000) into a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, and heat to 98° C.

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

[0070] (4) Deionized water was added at 92°C to obtain an aqueous associative thickener.

[0071] The formulas of comparative examples 1-6 are as follows (the data units in the table are all g):

[0072]

[0073] Comparative Example 1

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

[0075] In a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, polyethylene glycol was added, the temperature was raised to 90°C, isophorone diisocyanate was added, and the reaction was kept warm for 3 hours, n-hexanol was added, and the reaction was kept warm for 4 hours, deionized water was added and stirred evenly to obtain a water-based polyurethane associative thickener.

[0076] Comparative Example 2

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

[0078] In a reaction vessel equipped with a stirrer, a thermometer and a reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, the reaction is kept warm for 3 hours, dodecanol is added, the reaction is kept warm for 4 hours, deionized water is added and stirred evenly to obtain a waterborne polyurethane associative thickener.

[0079] Comparative Example 3

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

[0081] In a reaction vessel equipped with a stirrer, a thermometer and a reflux device, polyethylene glycol was added, the temperature was raised to 90°C, isophorone diisocyanate was added, and the reaction was kept warm for 3 hours, octadecyl alcohol was added, and the reaction was kept warm for 4 hours, deionized water was added and stirred evenly to obtain a waterborne polyurethane associative thickener.

[0082] Comparative Example 4

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

[0084] In a reaction vessel equipped with a stirrer, a thermometer, and a reflux device, polyethylene glycol was added, the temperature was raised to 90°C, isophorone diisocyanate was added, and the reaction was kept warm for 3 hours, n-hexanol was added, and the reaction was kept warm for 4 hours, deionized water was added and stirred evenly to obtain a water-based polyurethane associative thickener.

[0085] Comparative Example 5

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

[0087] In a reaction vessel equipped with a stirrer, a thermometer and a reflux device, polyethylene glycol is added, the temperature is raised to 90°C, isophorone diisocyanate is added, the reaction is kept warm for 3 hours, dodecanol is added, the reaction is kept warm for 4 hours, deionized water is added and stirred evenly to obtain a waterborne polyurethane associative thickener.

[0088] Comparative Example 6

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

[0090] In a reaction vessel equipped with a stirrer, a thermometer and a reflux device, polyethylene glycol was added, the temperature was raised to 90°C, isophorone diisocyanate was added, and the reaction was kept warm for 3 hours, octadecyl alcohol was added, and the reaction was kept warm for 4 hours, deionized water was added and stirred evenly to obtain a waterborne polyurethane associative thickener.

[0091] Performance Testing

[0092] 1. Molecular weight analysis

[0093] like Figure 1-2 As shown, Figure 1 It is the molecular weight analysis diagram of Example 1 and Comparative Example 1, Figure 2 It is a molecular weight analysis diagram of Example 4 and Comparative Example 4. From the molecular weight analysis results of the above examples and comparative examples, it can be seen that when Mw is close, the molecular weight distribution of the examples is close to about 1.1, and the molecular weight distribution of the comparative example is wider, resulting in the presence of more molecules with low thickening efficiency, which reduces the thickening efficiency (it should be noted that the synthesis methods of Examples 2 and 3 are the same as those of Example 1, and the molecular weights are close, and the analysis results are no longer shown here; the synthesis methods of Comparative Examples 2 and 3 are the same as those of Comparative Example 1, and the molecular weights are close, and the analysis results are no longer shown here; the synthesis methods of Examples 5 and 6 are the same as those of Example 4, and the molecular weights are close, and the analysis results are no longer shown here; the synthesis methods of Comparative Examples 5 and 6 are the same as those of Comparative Example 4, and the molecular weights are close, and the analysis results are no longer shown here; the synthesis methods of Comparative Examples 5 and 6 are the same as those of Comparative Example 4, and the molecular weights are close, and the analysis results are no longer 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 used in the same formula white paint. Through adjustment, three fluids with rheological properties were obtained, wherein Example 1 and Comparative Example 1 and Example 4 and Comparative Example 4 were Newtonian fluids, Example 2 and Comparative Example 2 and Example 5 and Comparative Example 5 were balanced fluids, and Example 3 and Comparative Example 3 and Example 6 and Comparative Example 6 were pseudoplastic fluids.

[0096] from Figure 3-8 From the thickening curves of the embodiment and the comparative example, the thickening curve of the embodiment is higher than that of the comparative example, which indicates that the implementation effect of the present invention is better than that of the commonly used associative thickeners on the market, and at the same time, it has no effect on the water resistance of the two-component coating.

[0097] The water resistance test of the coating is shown in the table below.

[0098]

[0099] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an aqueous polyurethane thickener, characterized in that: The following steps are involved: Add epoxy-terminated polyethylene oxide into the reaction vessel and heat to 95-100°C; Divide the long carbon chain monocarboxyl compound into multiple portions by weight; then add the first portion of the long carbon chain monocarboxyl compound into the reaction container, react at 95-100° C., add a portion of the long carbon chain monocarboxyl compound every 0.5-1 hour, and continue to maintain the reaction temperature for 4-6 hours after the last portion of the long carbon chain monocarboxyl compound is added; At 90-95°C, deionized water is added to obtain a waterborne polyurethane thickener.

2. The method for preparing an aqueous polyurethane thickener according to claim 1, characterized in that: The epoxy-terminated polyethylene oxide has the structure shown below:

3. The method for preparing an aqueous polyurethane thickener according to claim 1 or 2, characterized in that: The weight average molecular weight of the epoxy-terminated polyethylene oxide is 6,000-30,000.

4. The method for preparing an aqueous polyurethane thickener according to claim 1, characterized in that: The long carbon chain monocarboxyl compound is selected from one or more of caproic acid, caprylic acid, capric acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid and octadecanoic acid.

5. The method for preparing an aqueous polyurethane thickener according to claim 1, characterized in that: The ratio of the carboxyl equivalent of the long carbon chain monocarboxyl compound to the epoxy equivalent of the epoxy-terminated polyethylene oxide is (0.9:1)-(1.1:1).

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

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

8. An aqueous polyurethane thickener prepared by the preparation method according to any one of claims 1 to 7.

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