Aqueous polyurethane coating emulsion and method for its preparation

Abstract

The present application relates to the chemical industry field, especially to a kind of water-based polyurethane finishing agent emulsion and preparation method thereof.The preparation method provided by the present application, dihydric alcohol and isocyanate are mixed, heated and reacted;Then, hydrophilic chain extender is added, and the reaction continues;After that, cooling, catalyst and solvent are added, and the reaction continues;To obtain reactant 1;Then, neutralizing agent is added to the reactant 1 to carry out neutralization reaction;After that, water is added to disperse, and amine chain extender is added, stirred and reacted, and the solvent is removed, to obtain water-based polyurethane finishing agent emulsion.In which, dihydric alcohol is used with specific crystalline polycarbonate dihydric alcohol and hydroxyl-terminated polybutadiene, and the selection and condition control of other raw materials are combined, which can effectively improve the hydrolysis resistance, low-temperature bending resistance and dry-wet rubbing resistance of water-based polyurethane.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, and in particular to an aqueous polyurethane coating emulsion and its preparation method. Background Technology

[0002] Genuine leather undergoes a series of finishing processes before use to achieve its aesthetic appeal and durability. The gloss agent, as the final step in leather finishing, plays a crucial role in protecting the leather. This gloss layer prevents discoloration and coating damage caused by friction during long-term use. In daily use, the leather surface also comes into contact with water and other substances; if the gloss agent is not water-resistant, the leather coating will be damaged. Currently, water-based polyurethane gloss agents have poor hydrolysis resistance and low-temperature bending resistance. Summary of the Invention

[0003] In view of this, the present invention provides an aqueous polyurethane coating emulsion and a method for preparing the same. The aqueous polyurethane coating emulsion prepared by the present invention exhibits excellent abrasion resistance, wet rubbing resistance, hydrolysis resistance, and low-temperature flexural strength.

[0004] This invention provides a method for preparing a waterborne polyurethane coating agent, comprising the following steps: Diol and isocyanate are mixed and heated to react; then, a hydrophilic chain extender is added and the reaction continues; then, the mixture is cooled, a catalyst and a solvent are added, and the reaction continues to obtain reactant 1; then, a neutralizing agent is added to reactant 1 for neutralization reaction; then water is added for dispersion, then an amine chain extender is added, the mixture is stirred to react, and the solvent is removed to obtain a waterborne polyurethane coating emulsion. The diol is a crystalline polycarbonate diol and a hydroxyl-terminated polybutadiene.

[0005] Preferably, the mass ratio of the crystalline polycarbonate diol to the hydroxyl-terminated polybutadiene is 120:(30~50).

[0006] Preferably, the number average molecular weight of the crystalline polycarbonate diol is 2000; The number-average molecular weight of the hydroxyl-terminated polybutadiene is 2500.

[0007] Preferably, the isocyanate is 1,3-bis(1-isocyanate-1-methylethyl)benzene.

[0008] Preferably, the hydrophilic chain extender is dihydroxypropionic acid.

[0009] Preferably, the amine chain extender is hydrazine hydrate and diethylenetriamine; The mass ratio of hydrazine hydrate to diethylenetriamine is 1:(0.3~0.6).

[0010] Preferably, the catalyst is an organobismuth catalyst; The solvent is acetone; The neutralizing agent is triethylamine.

[0011] Preferably, the heating reaction is carried out at a temperature of 80-82°C for 2-5 hours. The continued reaction is carried out at a temperature of 80-82°C for 1-3 hours. The temperature for the subsequent reaction is 68~70℃, and the time is 1~3h.

[0012] Preferably, the amounts of each raw material, by weight, are as follows: Diols: 100-200 parts; Isocyanate: 80-150 parts; Hydrophilic chain extender: 15-25 parts; Catalyst: 0.2~0.4 parts; Solvent: 100-200 parts; Water: 500-1000 parts; Amine chain extender: 10-20 parts.

[0013] The present invention also provides an aqueous polyurethane coating emulsion, which is prepared by the preparation method described in the above technical solution.

[0014] The preparation method provided by this invention involves mixing a diol and an isocyanate, heating and reacting them; then, adding a hydrophilic chain extender and continuing the reaction; subsequently, cooling, adding a catalyst and solvent, and continuing the reaction to obtain reactant 1; then, adding a neutralizing agent to reactant 1 for neutralization; then adding water for dispersion, adding an amine chain extender, stirring the reaction, removing the solvent, and obtaining a waterborne polyurethane coating emulsion. The diol used is a specific combination of crystalline polycarbonate diol and hydroxyl-terminated polybutadiene, and combined with the selection and control of other raw materials and conditions, which can effectively improve the hydrolysis resistance, low-temperature flexural strength, and dry / wet rubbing resistance of the waterborne polyurethane.

[0015] Experimental results show that the tabletop abrasion resistance of the product of this invention reaches level 4 or above, wet abrasion resistance reaches level 4 or above, jungle aging test reaches more than 10 weeks, and low temperature flexural resistance test reaches more than 110,000 cycles, demonstrating excellent abrasion resistance, wet abrasion resistance, hydrolysis resistance and low temperature flexural resistance. Detailed Implementation

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0017] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0018] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0019] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0020] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 100~110℃ means that the units for the left endpoint "100" and the right endpoint "110" are both in degrees Celsius.

[0021] This invention provides a method for preparing a waterborne polyurethane coating agent, comprising the following steps: Diol and isocyanate are mixed and heated to react; then, a hydrophilic chain extender is added and the reaction continues; then, the mixture is cooled, a catalyst and a solvent are added, and the reaction continues to obtain reactant 1; then, a neutralizing agent is added to reactant 1 for neutralization reaction; then water is added for dispersion, then an amine chain extender is added, the mixture is stirred to react, and the solvent is removed to obtain a waterborne polyurethane coating emulsion. The diol is a crystalline polycarbonate diol and a hydroxyl-terminated polybutadiene.

[0022] In this invention, the diol is a crystalline polycarbonate diol and hydroxyl-terminated polybutadiene. Preferably, the number-average molecular weight of the crystalline polycarbonate diol is 2000. Preferably, the number-average molecular weight of the hydroxyl-terminated polybutadiene is 2500. The preferred mass ratio of the crystalline polycarbonate diol to the hydroxyl-terminated polybutadiene is 120:(30~50), specifically 120:30, 120:40, or 120:50. This invention uses a combination of hydroxyl-terminated polybutadiene and crystalline polycarbonate diol as diol raw materials. The introduction of hydroxyl-terminated polybutadiene effectively improves the hydrolysis resistance, low-temperature flexural strength, and dry / wet rubbing resistance of waterborne polyurethane.

[0023] In this invention, the diol is preferably pre-dehydrated. The dehydration method is preferably vacuum dehydration. The temperature for vacuum dehydration is preferably 100-110°C, specifically 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, or 110°C. The degree of vacuum dehydration is preferably controlled to keep the water content below 0.05%.

[0024] In this invention, the isocyanate is preferably 1,3-bis(1-isocyanate-1-methylethyl)benzene.

[0025] In this invention, after dehydrating the diol, it is preferable to first cool the diol before mixing it with the isocyanate. The cooling is preferably to 70-60°C, specifically 60°C, 65°C, or 70°C. After cooling and mixing with the isocyanate, the mixture is heated for reaction. The preferred temperature for the heating reaction is 80-82°C, specifically 80°C, 81°C, or 82°C. The preferred reaction time is 2-5 hours, specifically 2 hours, 3 hours, 4 hours, or 5 hours.

[0026] In this invention, after the above-mentioned heating reaction, it is preferable to first cool down before adding the hydrophilic chain extender. The cooling is preferably to 65-55°C, specifically 55°C, 60°C, or 65°C. After cooling and adding the hydrophilic chain extender, the reaction continues. The temperature for continuing the reaction is preferably 80-82°C, specifically 80°C, 81°C, or 82°C. The reaction time is preferably 1-3 hours, specifically 1 hour, 2 hours, or 3 hours. In this invention, the hydrophilic chain extender is preferably dihydroxypropionic acid.

[0027] In this invention, after the above-mentioned continued reaction, the temperature is lowered, and a catalyst and solvent are added. The cooling is preferably to 68-70°C, specifically 68°C, 69°C, or 70°C. The catalyst is preferably an organobismuth catalyst, more preferably bismuth caprylate. The solvent is preferably acetone. After adding the catalyst and solvent, the reaction continues. The temperature for this continued reaction is preferably 68-70°C, specifically 68°C, 69°C, or 70°C. The duration of this continued reaction is preferably 1-3 hours, specifically 1 hour, 2 hours, or 3 hours. During this continued reaction, the NCO content of the system is measured until the theoretical value is reached, at which point subsequent operations are performed. After the above reaction, reactant 1 is obtained.

[0028] In this invention, after the above reaction, a neutralizing agent is added to carry out a neutralization reaction. The neutralizing agent is preferably triethylamine. The temperature of the neutralization reaction is preferably 45~55℃, specifically 45℃, 50℃, or 55℃.

[0029] In this invention, after the above-described neutralization reaction, water is added for dispersion. The dispersion method is not particularly limited and can be any conventional dispersion method in the art, such as stirring to mix the materials evenly.

[0030] In this invention, after the above dispersion, an amine chain extender is added. The preferred amine chain extender is hydrazine hydrate and diethylenetriamine. The preferred mass ratio of hydrazine hydrate to diethylenetriamine is 1:(0.3~0.6), specifically 1:0.3, 1:0.4, 1:0.5, or 1:0.6. After adding the chain extender, the reaction is continued with stirring.

[0031] The preferred temperature for the stirring reaction is 40-50℃, specifically 40℃, 45℃, or 50℃. The preferred reaction time is 1-2 hours, specifically 1 hour or 2 hours. After the stirring reaction, the solvent (i.e., the solvent mentioned above, mainly acetone) is removed. The preferred method for solvent removal is vacuum removal. After solvent removal, a waterborne polyurethane coating emulsion is obtained, which is a waterborne polyurethane coating emulsion with high physical properties and high hydrolysis resistance.

[0032] In this invention, the amounts of each raw material, by weight, are as follows: Diols: 100-200 parts; Isocyanate: 80-150 parts; Hydrophilic chain extender: 15-25 parts; Catalyst: 0.2~0.4 parts; Solvent: 100-200 parts; Water: 500-1000 parts; Amine chain extender: 10-20 parts.

[0033] The diol can be in quantities of 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts, or 200 parts. The isocyanate can be in quantities of 80 parts, 90 parts, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, or 150 parts. The hydrophilic chain extender can be in quantities of 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts. The catalyst can be in quantities of 0.2 parts, 0.3 parts, or 0.4 parts. The specific amounts of the solvent can be 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts, or 200 parts. The specific amounts of the water can be 500 parts, 600 parts, 700 parts, 800 parts, 900 parts, or 1000 parts. The specific amounts of the amine chain extender can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, or 15 parts.

[0034] The present invention also provides an aqueous polyurethane coating emulsion, which is prepared by the preparation method described in the above technical solution.

[0035] The preparation method provided by this invention involves mixing a diol and an isocyanate, heating and reacting them; then, adding a hydrophilic chain extender and continuing the reaction; subsequently, cooling, adding a catalyst and solvent, and continuing the reaction to obtain reactant 1; then, adding a neutralizing agent to reactant 1 for neutralization; then adding water for dispersion, followed by adding an amine chain extender, stirring the reaction, and removing the solvent to obtain a waterborne polyurethane coating emulsion. The diol used is a specific combination of crystalline polycarbonate diol and hydroxyl-terminated polybutadiene, and combined with the selection and control of other raw materials, which effectively improves the hydrolysis resistance, low-temperature flexural strength, and dry / wet rubbing resistance of the waterborne polyurethane. The waterborne polyurethane coating emulsion prepared by this invention can be used as a paste resin for leather finishing to improve its physical properties, and also as a gloss layer for leather finishing, exhibiting versatility and a wide range of applications.

[0036] Experimental results show that the tabletop abrasion resistance of the product of this invention reaches level 4 or above, wet abrasion resistance reaches level 4 or above, jungle aging test reaches more than 10 weeks, and low temperature flexural resistance test reaches more than 110,000 cycles, demonstrating excellent abrasion resistance, wet abrasion resistance, hydrolysis resistance and low temperature flexural resistance.

[0037] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0038] Example 1 1. Raw materials: Crystalline polycarbonate diol (molecular weight 2000): 120g; Hydroxyl-terminated polybutadiene (molecular weight 2500): 30g; 1,3-Bis(1-isocyanate-1-methylethyl)benzene: 100g; Dihydroxypropionic acid: 20g; Organobismuth catalyst bismuth caprylate: 0.2g; Acetone: 150g; Neutralizing agent triethylamine: 15g; Water: 950g; Amine chain extender: 16g (hydrazine hydrate to diethylenetriamine mass ratio of 1:0.4).

[0039] 2. Preparation: Crystalline polycarbonate diol and hydroxyl-terminated polybutadiene were added to the reaction mixture and vacuum dehydrated at 100-110℃, with the moisture content controlled below 0.05%. Then, the temperature was lowered to 60℃, and 1,3-bis(1-isocyanate-1-methylethyl)benzene was added, reacting at 80-82℃ for 2 hours. The temperature was then lowered to 60℃, and dihydroxypropionic acid was added, followed by a further reaction at 80-82℃ for 3 hours. Next, the temperature was lowered to 65℃, and an organic bismuth catalyst and acetone were added, reacting for another 3 hours, after which the NCO content was tested and found to be within acceptable limits. Finally, the temperature was lowered to 50℃, and triethylamine was added for neutralization, followed by water dispersion for 3 minutes. Then, an amine chain extender was added, and the mixture was stirred for 2 hours. Finally, acetone was removed under vacuum to obtain a solvent-free waterborne polyurethane coating emulsion.

[0040] Example 2 The method was implemented according to Example 1, except that the amount of hydroxyl-terminated polybutadiene was increased to 40g.

[0041] Example 3 The method was implemented according to Example 1, except that the amount of hydroxyl-terminated polybutadiene was increased to 50g.

[0042] Example 4 The method was implemented according to Example 2, except that the amount of 1,3-bis(1-isocyanate-1-methylethyl)benzene was increased to 110g.

[0043] Example 5 The method was implemented according to Example 2, except that the amount of 1,3-bis(1-isocyanate-1-methylethyl)benzene was increased to 120g.

[0044] Example 6 The method was implemented according to Example 2, except that the amount of 1,3-bis(1-isocyanate-1-methylethyl)benzene was increased to 130g.

[0045] Comparative Example 1 The implementation follows Example 1, except that the diol is replaced with liquid polycarbonate diol (molecular weight 2000), the isocyanate is replaced with dicyclohexylmethane-4,4'-diisocyanate, and the amine chain extender is replaced with ethylenediamine.

[0046] Comparative Example 2 Implemented according to Example 1, except that: the hydroxyl-terminated polybutadiene is replaced with crystalline polycarbonate diol (i.e., all diols are single crystalline polycarbonate diols).

[0047] Comparative Example 3 The implementation follows Example 1, except that the crystalline polycarbonate diol is replaced with hydroxyl-terminated polybutadiene (i.e., all diols are made of a single type of hydroxyl-terminated polybutadiene).

[0048] Product Testing : Performance tests were conducted on each embodiment and comparative product, and the results are shown in Table 1.

[0049] The emulsion and isocyanate crosslinking agent were mixed evenly at a ratio of 100:3, and then sprayed onto the surface of the semi-finished leather. After spraying, the mixture was dried at 90-100℃ for 5-10 minutes. After drying, the mixture was allowed to stand for 24 hours before the following tests were conducted: (1) Benchtop abrasion test: The abrasion resistance test method is carried out according to QB / T 2726-2005. The test conditions are CS-10 abrasion wheel, 1kg, 2000 cycles. After abrasion, the wear condition of the leather surface is observed and graded as follows: Grade 1 - severe damage, Grade 2 - large area damage, Grade 3 - obvious wear, slight tear, Grade 4 - obvious wear, no tear, Grade 5 - slight abrasion, no damage.

[0050] (2) Wet rubbing resistance test: Tested and rated according to GB-T 3920-2008.

[0051] (3) Jungle aging test (hydrolysis resistance): Test and grade according to method A in QB_T 4671-2014.

[0052] (4) Low temperature bending resistance test: The test shall be conducted in accordance with QBT 2714-2005.

[0053] Table 1: Test results of each embodiment and comparative example As can be seen from the test results in the table above, the products of Examples 1-6 of this invention achieve a tabletop abrasion resistance of level 4 or higher, wet abrasion resistance of level 4 or higher, jungle aging test of over 10 weeks, and low-temperature flexural strength test of over 110,000 cycles. Therefore, the products of this invention exhibit excellent abrasion resistance, wet abrasion resistance, hydrolysis resistance, and low-temperature flexural strength. Compared with the examples, the performance of Comparative Examples 1-3 deteriorates, proving that the specific raw material combination used in this invention can effectively improve the overall performance of the product.

[0054] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a waterborne polyurethane coating agent, characterized in that, Includes the following steps: Diol and isocyanate are mixed and heated to react; then, a hydrophilic chain extender is added and the reaction continues; then, the mixture is cooled, a catalyst and a solvent are added, and the reaction continues to obtain reactant 1; then, a neutralizing agent is added to reactant 1 for neutralization reaction; then water is added for dispersion, then an amine chain extender is added, the mixture is stirred to react, and the solvent is removed to obtain a waterborne polyurethane coating emulsion. The diol is a crystalline polycarbonate diol and a hydroxyl-terminated polybutadiene; the mass ratio of the crystalline polycarbonate diol to the hydroxyl-terminated polybutadiene is 120:(30~50). The isocyanate is 1,3-bis(1-isocyanate-1-methylethyl)benzene; The amine chain extender is hydrazine hydrate and diethylenetriamine; the mass ratio of hydrazine hydrate to diethylenetriamine is 1:(0.3~0.6).

2. The preparation method according to claim 1, characterized in that, The number-average molecular weight of the crystalline polycarbonate diol is 2000; The number-average molecular weight of the hydroxyl-terminated polybutadiene is 2500.

3. The preparation method according to claim 1, characterized in that, The hydrophilic chain extender is dihydroxypropionic acid.

4. The preparation method according to claim 1, characterized in that, The catalyst is an organic bismuth catalyst; The solvent is acetone; The neutralizing agent is triethylamine.

5. The preparation method according to claim 1, characterized in that, The heating reaction is carried out at a temperature of 80~82℃ for 2~5 hours. The continued reaction is carried out at a temperature of 80-82°C for 1-3 hours. The temperature for the subsequent reaction is 68~70℃, and the time is 1~3h.

6. The preparation method according to claim 1, characterized in that, The amounts of each raw material, by weight, are as follows: Diols: 100-200 parts; Isocyanate: 80-150 parts; Hydrophilic chain extender: 15-25 parts; Catalyst: 0.2~0.4 parts; Solvent: 100-200 parts; Water: 500-1000 parts; Amine chain extender: 10-20 parts.

7. A water-based polyurethane coating emulsion, characterized in that, It is prepared by any one of claims 1 to 6.

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