A method for preparing polyol for waterborne polyurethane

Abstract

The present application relates to the technical field of organic polymers, and more specifically, it relates to a method for preparing a polyol for waterborne polyurethane. A method for preparing a polyol for waterborne polyurethane comprises the following steps: mixing a hydrophobic dibasic acid and a diamine in a mass ratio of (10-25):1, heating to 130-160°C, and keeping the temperature for 1-5h; dripping an alcohol amine compound, dripping at 120-160°C for 2-8h, dripping, heating to 200-250°C, keeping the temperature for 1-5h, dehydrating, cooling to 90-110°C, and obtaining a target product; the mass ratio of the alcohol amine compound to the diamine is (2-10):1. The polyol of the present application is used for the preparation of waterborne polyurethane, which can make the waterborne polyurethane have both good hydrolysis resistance and mechanical properties.

Description

Technical Field

[0001] The present application relates to the technical field of organic polymers, and more specifically, to a method for preparing polyols for waterborne polyurethane. Background Art

[0002] Polyurethane (PU) refers to a class of compounds containing carbamate bonds (-NHCOO-). Since it was invented by German Professor Bayer in 1937, it has been widely used in various industrial fields such as automobiles, construction, textiles, clothing, energy, and military industry due to its excellent performance. Traditional solvent-based polyurethanes are widely used in coatings, adhesives, and other fields due to their short drying time, low film-forming temperature, and good bonding effect. However, solvent-based polyurethanes contain a large amount of toxic solvents such as toluene or xylene, which can cause harm to the environment. With the improvement of people's environmental awareness, water-based polyurethanes have gradually become a research hotspot because they contain no or a small amount of volatile organic solvents, and various water-based polyurethane products have sprung up.

[0003] Waterborne polyurethane is polymerized by isocyanate, polyester / polyether polyol, hydrophilic chain extender, etc. Among them, polyester / polyether polyol is the main component of waterborne polyurethane and has a great influence on the performance of waterborne polyurethane.

[0004] Polyester polyols are usually formed by the polycondensation of small molecule dibasic acids and small molecule diols. Polyester polyols contain a large number of ester groups. Waterborne polyurethane uses water as a dispersion medium. The ester groups are easily hydrolyzed, and the waterborne polyurethane molecules are easily destroyed, resulting in a decrease in the molecular weight and performance of waterborne polyurethane. Polyether polyols are copolymerized by propylene oxide, ethylene oxide, tetrahydrofuran, etc., and contain a large number of ether bonds. The ether bonds themselves are not easy to hydrolyze, but are hydrophilic and hygroscopic. The presence of a large number of ether bonds will cause the van der Waals force between waterborne polyurethane molecules to decrease, affecting its mechanical properties.

[0005] Therefore, there is an urgent need to develop a polyol for the preparation of waterborne polyurethane so that the waterborne polyurethane has both good hydrolysis resistance and mechanical properties. Summary of the invention

[0006] In order to solve the problem that waterborne polyurethane cannot have both good hydrolysis resistance and mechanical properties, the present application provides a method for preparing a polyol for waterborne polyurethane.

[0007] In a first aspect, the present application provides a method for preparing a polyol for waterborne polyurethane, using the following technical solution:

[0008] A method for preparing a polyol for waterborne polyurethane comprises the following steps:

[0009] The hydrophobic dibasic acid and the diamine are mixed in a mass ratio of (10-25):1, the temperature is raised to 130-160°C, and the reaction is kept warm for 1-5 hours; an alcohol amine compound is added dropwise at 120-160°C for 2-8 hours, after the addition is completed, the temperature is raised to 200-250°C, the reaction is kept warm for 1-5 hours, dehydrated, and cooled to 90-110°C to obtain the target product; the mass ratio of the alcohol amine compound to the diamine is (2-10):1.

[0010] By adopting the above technical scheme, hydrophobic dibasic acid and diamine are polymerized, and then end-capped with alcoholamine compounds to obtain a polyol containing hydrolysis-resistant amide groups and hydrophobic segments. The presence of the hydrophobic segments can block some water molecules and reduce the possibility of hydrogen bonds between water molecules and polyol molecules. The polyol of the present application is used to prepare waterborne polyurethane, which can increase the possibility of hydrogen bond formation in waterborne polyurethane molecules and the cohesive energy of waterborne polyurethane molecules, thereby improving the mechanical properties of waterborne polyurethane. At the same time, a large number of hydrolysis-resistant amide groups are introduced into the waterborne polyurethane, which solves the problem that waterborne polyurethane cannot have both good hydrolysis resistance and mechanical properties.

[0011] Preferably, the mass ratio of the hydrophobic dibasic acid to the diamine is (10-15):1.

[0012] Preferably, the mass ratio of the alcoholamine compound to the diamine is (2-5):1.

[0013] Preferably, the hydrophobic dibasic acid is one or more of dodecanedioic acid, tridecanedicarboxylic acid, and dimer acid.

[0014] Preferably, the hydrophobic dibasic acid is a dimer acid.

[0015] By adopting the above technical scheme, the hydrophobic segment contained in the dimer acid is longer and has a better barrier effect on water molecules. The polyol prepared by using the dimer acid is used for the preparation of water-based polyurethane, which can further improve the hydrolysis resistance and mechanical properties of the water-based polyurethane.

[0016] Preferably, the diamine is one or more of hexamethylenediamine, cyclohexanediamine, benzimidazolediamine and benzoxazolediamine.

[0017] Preferably, the diamine is benzimidazole diamine and / or benzoxazole diamine.

[0018] By adopting the above technical scheme, both benzimidazole diamine and benzoxazole diamine have rigid structures, and benzimidazole diamine contains active hydrogen atoms, which can form intramolecular hydrogen bonds with other active groups to improve the cohesive energy of the molecule. The polyol prepared by using the two as raw materials has good mechanical properties. The polyol is then used in the preparation of water-based polyurethane, which can further improve the mechanical properties of the water-based polyurethane. Benzimidazole diamine and benzoxazole diamine synergistically enhance the hydrolysis resistance and mechanical properties of the finished water-based polyurethane.

[0019] Preferably, the diamine is prepared by compounding benzimidazole diamine and benzoxazole diamine in a mass ratio of 1:(3-7).

[0020] By adopting the above technical solution, when benzimidazole diamine and benzoxazole diamine are compounded according to the above ratio, the hydrolysis resistance and mechanical properties of the finished waterborne polyurethane can be further improved.

[0021] Preferably, the alcoholamine is one or more of ethanolamine, diethanolamine, 2-amino-2-methyl-propanol, and isopropanolamine.

[0022] In summary, this application has the following beneficial effects:

[0023] 1. The present application adopts the polymerization of hydrophobic dibasic acid and diamine, and then uses alcohol amine compounds to block the end to obtain a polyol containing hydrolysis-resistant amide groups and hydrophobic segments. The presence of the hydrophobic segments can block part of the water molecules and reduce the possibility of hydrogen bonds between water molecules and polyol molecules. The use of the polyol of the present application to prepare waterborne polyurethane can increase the possibility of hydrogen bond formation within the waterborne polyurethane molecules, increase the cohesive energy of the waterborne polyurethane molecules, thereby improving the mechanical properties of the waterborne polyurethane. At the same time, a large number of hydrolysis-resistant amide groups are introduced into the waterborne polyurethane, solving the problem that the waterborne polyurethane cannot have both good hydrolysis resistance and mechanical properties.

[0024] 2. The benzimidazole diamine and benzoxazole diamine used in the present application both have rigid structures, and the benzimidazole diamine contains active hydrogen atoms, which can form intramolecular hydrogen bonds with other active groups to improve the cohesive energy of the molecule. The polyol prepared using the two as raw materials has good mechanical properties. The polyol is then used in the preparation of waterborne polyurethane, which can further improve the mechanical properties of the waterborne polyurethane. The benzimidazole diamine and benzoxazole diamine synergistically enhance the hydrolysis resistance and mechanical properties of the finished waterborne polyurethane. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to embodiments.

[0026] Unless otherwise specified, the specifications of the raw materials used in the following examples and comparative examples are shown in Table 1.

[0027] Table 1. Raw material specifications

[0028] raw material Specification Antioxidants Model: 3019 Dimer acid Molecular weight: 564.923 Polyester polyols Brand: hk-3152 Polyether polyols Model: WANOL F3135

[0029] Example

[0030] Example 1

[0031] A polyol for waterborne polyurethane, the formula of which is as follows:

[0032] 10kg dodecanedioic acid, 1kg hexamethylenediamine, 2kg ethanolamine, 30g antioxidant

[0033] A polyol for waterborne polyurethane is prepared according to the following steps:

[0034] Add dodecanedioic acid, crushed hexamethylenediamine solid and antioxidant into the reaction kettle, gradually heat up to 130°C with stirring, and keep warm for reaction for 5 hours; add ethanolamine dropwise at 120°C for 8 hours, and after the addition is completed, heat up to 200°C, and continue to keep warm for reaction for 5 hours. During the insulation process, start the condenser to circulate water, and the generated water vapor condenses and flows into the receiving tank; start the vacuum pump to remove the produced water, and stop the vacuum dehydration when the vacuum degree in the kettle exceeds 0.095MPa; after the dehydration is completed, the material is cooled to 90°C, discharged and packaged to obtain the target product.

[0035] Example 2

[0036] A polyol for waterborne polyurethane, the formula of which is as follows:

[0037] 10kg dodecanedioic acid, 1kg hexamethylenediamine, 2kg ethanolamine, 30g antioxidant

[0038] A polyol for waterborne polyurethane is prepared according to the following steps:

[0039] Add dodecanedioic acid, crushed hexamethylenediamine solid and antioxidant into the reaction kettle, gradually heat up to 160°C while stirring, and keep warm for reaction for 1 hour; add ethanolamine dropwise at 160°C for 2 hours, and after the addition is completed, heat up to 250°C, and continue to keep warm for reaction for 1 hour. During the insulation process, start the condenser to circulate water, and the generated water vapor condenses and flows into the receiving tank; start the vacuum pump to remove the produced water, and stop the vacuum dehydration when the vacuum degree in the kettle exceeds 0.095MPa; after the dehydration is completed, the material is cooled to 110°C, discharged and packaged to obtain the target product.

[0040] Example 3

[0041] A polyol for waterborne polyurethane, the formula of which is as follows:

[0042] 10kg dodecanedioic acid, 1kg hexamethylenediamine, 2kg ethanolamine, 30g antioxidant

[0043] A polyol for waterborne polyurethane is prepared according to the following steps:

[0044] Add dodecanedioic acid, crushed hexamethylenediamine solid and antioxidant into the reaction kettle, gradually heat up to 140°C with stirring, and keep warm for reaction for 2 hours; add ethanolamine dropwise at 150°C for 4 hours, and after the addition is completed, heat up to 220°C, and continue to keep warm for reaction for 3 hours. During the insulation process, start the condenser to circulate water, and the generated water vapor condenses and flows into the receiving tank; start the vacuum pump to remove the produced water, and stop the vacuum dehydration when the vacuum degree in the kettle exceeds 0.095MPa; after the dehydration is completed, the material is cooled to 100°C, discharged and packaged to obtain the target product.

[0045] Example 4

[0046] A polyol for waterborne polyurethane, which is different from Example 1 in that the components of the raw materials are different. The specific components are as follows: 8.93 kg of dodecanedioic acid, 0.37 kg of hexamethylenediamine, 3.7 kg of ethanolamine, and 30 g of antioxidant

[0047] Example 5

[0048] A polyol for waterborne polyurethane, which is different from Example 1 in that the components of the raw materials are different. The specific components are as follows: 10.78 kg of dodecanedioic acid, 0.72 kg of hexamethylenediamine, 1.5 kg of ethanolamine, and 30 g of antioxidant.

[0049] Example 6

[0050] A polyol for waterborne polyurethane, which is different from Example 1 in that the components of the raw materials are different. The specific components are as follows: 8.2 kg of dodecanedioic acid, 0.8 kg of hexamethylenediamine, 4 kg of ethanolamine, and 30 g of antioxidant.

[0051] Example 7

[0052] A polyol for waterborne polyurethane, which is different from Example 1 in that the hydrophobic dibasic acid is selected differently. In this example, dodecanedioic acid is replaced with tridecanedicarboxylic acid in equal moles.

[0053] Example 8

[0054] A polyol for waterborne polyurethane, which is different from Example 1 in that the hydrophobic dibasic acid is selected differently. In this example, dodecanedioic acid is replaced with dimer acid in equal moles.

[0055] Example 9

[0056] A polyol for waterborne polyurethane, which is different from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 1H-benzo[D]imidazole-5,6-diamine in equal moles.

[0057] Example 10

[0058] A polyol for waterborne polyurethane, which is different from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 2,6-diaminobenzoxazole in equal moles.

[0059] Embodiment 11

[0060] A polyol for waterborne polyurethane, which differs from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 0.5kg 1H-benzo[D]imidazole-5,6-diamine+0.5kg 2,6-diaminobenzoxazole.

[0061] Example 12

[0062] A polyol for waterborne polyurethane, which differs from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 0.1 kg 1H-benzo[D]imidazole-5,6-diamine+0.9 kg 2,6-diaminobenzoxazole.

[0063] Embodiment 13

[0064] A polyol for waterborne polyurethane, which differs from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 0.25kg 1H-benzo[D]imidazole-5,6-diamine+0.75kg 2,6-diaminobenzoxazole.

[0065] Embodiment 14

[0066] A polyol for waterborne polyurethane, which differs from Example 1 in that the diamine is selected differently. In this example, hexamethylenediamine is replaced with 0.125kg 1H-benzo[D]imidazole-5,6-diamine+0.875kg 2,6-diaminobenzoxazole.

[0067] Embodiment 15

[0068] A polyol for waterborne polyurethane, which is different from Example 1 in that the choice of ethanolamine compound is different. In this example, ethanolamine is replaced by isopropanolamine in equal moles.

[0069] Comparative Example

[0070] Comparative Example 1

[0071] A polyol for waterborne polyurethane, the dibasic acid is selected differently, and the present application replaces dodecanedioic acid with adipic acid in equal moles.

[0072] Application Examples and Comparative Examples

[0073] The polyols prepared in Examples 1-15 and Comparative Example 1 were used to synthesize waterborne polyurethane according to the following steps:

[0074] Polyol is reacted with 2,2-dimethylol propionic acid and diphenylmethane diisocyanate to obtain a prepolymer, and a chain extender is added to the prepolymer to react to obtain a waterborne polyurethane. The sources of the polyols in each application example are shown in Table 2 below:

[0075] Table 2. Sources of polyols

[0076]

[0077] Application Comparative Example 2

[0078] A waterborne polyurethane, which differs from Application Example 1 in that the source of the polyol is different. In this application comparative example, the polyol prepared in Example 1 is replaced by polyester polyol in an equimolar manner.

[0079] Application Comparative Example 3

[0080] A waterborne polyurethane, which differs from Application Example 1 in that the source of the polyol is different. In this application comparative example, the polyol prepared in Example 1 is replaced by polyether polyol in an equimolar manner.

[0081] Detection Methods

[0082] At 25°C, pour the water-based polyurethane into a 12cm×8cm mold made of polytetrafluoroethylene, spread it evenly with a glass rod, and place it in a relatively flat place for about a week to allow most of the water to evaporate at room temperature. Then put the mold into an oven and dry it at 80°C for one hour. After drying, take out the cured film and put it in a drying dish for later use. According to GB13022-91, the film is cut into 6mm×100mm dumbbell shapes with a cutting machine and a cutter, and the tensile strength of the water-based polyurethane is measured at 25°C. The experimental instrument is the AG-Xplus universal electronic material testing machine of Shimadzu Corporation of Japan. The tensile rate is fixed at 100mm / min. The specific test results are shown in Table 3 below;

[0083] The waterborne polyurethane cured film was placed in a constant temperature and humidity chamber for hydrolysis reaction. After one week, it was taken out and the tensile strength of the cured film after hydrolysis was tested according to the above method. The retention rate of the tensile strength was calculated (tensile strength retention rate = tensile strength after hydrolysis / tensile strength before hydrolysis) to characterize the hydrolysis resistance of the waterborne polyurethane. The higher the retention rate of the tensile strength, the better the hydrolysis resistance. The experimental equipment used was a SPX-150C constant temperature and humidity test chamber. The test conditions were: temperature 65°C, humidity 95%. The specific test results are shown in Table 3 below.

[0084] Table 3. Performance test of waterborne polyurethane

[0085]

[0086] As can be seen from Table 3, the polyol prepared in the embodiment of the present application is used for the preparation of waterborne polyurethane, and the prepared waterborne polyurethane has a tensile strength of ≥32.6 MPa, good mechanical properties, a tensile strength retention rate of ≥85.9%, a high tensile strength retention rate, and good hydrolysis resistance, which solves the problem that waterborne polyurethane cannot have both good hydrolysis resistance and mechanical properties.

[0087] Combining Application Example 1 and Application Comparative Examples 2-3 and Table 3, it can be seen that the tensile strength retention rate of the waterborne polyurethane prepared in Application Example 1 is much greater than that in Application Comparative Example 2, and the tensile strength is much greater than that in Application Comparative Example 3. This may be because: the polyol selected in Application Comparative Example 2 is polyester polyol, which contains a large number of ester bonds, which are easily hydrolyzed; and the polyol selected in Application Comparative Example 3 is polyether polyol, which contains a large number of ether bonds. The ether bonds themselves are not easily hydrolyzed, but are hydrophilic and hygroscopic. The presence of a large number of ether bonds will cause the van der Waals force between waterborne polyurethane molecules to decrease, affecting its mechanical properties.

[0088] The polyol selected in Application Example 1 comes from Example 1. In Example 1, hydrophobic dibasic acid and diamine are polymerized, and then end-capped with an alcoholamine compound to obtain a polyol containing a hydrolysis-resistant amide group and a hydrophobic segment. The presence of the hydrophobic segment can block some water molecules and reduce the possibility of water molecules and polyol molecules forming hydrogen bonds. The use of the polyol of the present application to prepare water-based polyurethane can increase the possibility of hydrogen bond formation within the water-based polyurethane molecules, increase the cohesive energy of the water-based polyurethane molecules, thereby improving the mechanical properties of the water-based polyurethane. At the same time, a large number of hydrolysis-resistant amide groups are introduced into the water-based polyurethane, solving the problem that the water-based polyurethane cannot have both good hydrolysis resistance and mechanical properties.

[0089] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing a polyol for waterborne polyurethane, characterized in that: The steps include: The hydrophobic dibasic acid and the diamine are mixed in a mass ratio of (10-15):1, the temperature is raised to 130-160°C, and the reaction is kept at this temperature for 1-5 hours; the alcohol amine compound is added dropwise at 120-160°C for 2-8 hours, after the addition is completed, the temperature is raised to 200-250°C, the reaction is kept at this temperature for 1-5 hours, dehydrated, and the temperature is lowered to 90-110°C to obtain the target product; The mass ratio of the alcoholamine compound to the diamine is (2-5):1; The diamine is prepared by compounding 1H-benzo[D]imidazole-5,6-diamine and 2,6-diaminobenzoxazole in a mass ratio of 1:(3-7); The hydrophobic dibasic acid is one or more of dodecanedioic acid, tridecanedicarboxylic acid, and dimer acid.

2. The method for preparing a polyol for waterborne polyurethane according to claim 1, characterized in that: The hydrophobic dibasic acid is a dimer acid.

3. The method for preparing a polyol for waterborne polyurethane according to claim 1, characterized in that: The alcoholamine is one or more of ethanolamine, diethanolamine, 2-amino-2-methyl-propanol, and isopropanolamine.

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