Lignin-based waterborne polyurethane as well as preparation method and application thereof

Abstract

The invention discloses lignin-based waterborne polyurethane which is prepared from a system consisting of the following raw materials in parts by weight: 50 to 80 parts of bio-based poly (trimethylene ether glycol), 15 to 30 parts of 1, 5-pentamethylene diisocyanate, 1 to 20 parts of enzymatic hydrolysis lignin, 0.1 to 2 parts of a catalyst, 3 to 8 parts of a hydrophilic chain extender, 2.3 to 6.1 parts of a neutralizing agent and a second organic solvent for dissolving the enzymatic hydrolysis lignin, the mass ratio of the second organic solvent to the enzymatic hydrolysis lignin is (5-9): (0.5-4). The lignin-based waterborne polyurethane disclosed by the invention is simple in preparation method, high in bio-based content and good in emulsion stability, the lignin-based waterborne polyurethane has good tensile strength, flexibility and heat resistance after being cured into a film, the printing coating can be prepared without adding color paste, and a fabric treated by the printing coating is bright in color and soft in hand feeling.

Description

Technical Field

[0001] The invention belongs to the technical field of waterborne polyurethane materials, and in particular relates to lignin-based waterborne polyurethane and a preparation method and application thereof. Background Art

[0002] As the global awareness of environmental protection increases, countries are increasingly restricting the emission of volatile organic compounds (VOCs). Waterborne polyurethane coatings have gradually become an environmentally friendly material to replace traditional solvent-based polyurethane coatings due to their advantages such as solvent-free volatilization, low odor, non-flammability, good flexibility and bonding strength. However, the raw materials of traditional waterborne polyurethane coatings are mostly derived from petrochemical products. These raw materials are not only toxic and corrosive, but also non-renewable. With the depletion of petroleum resources, their application is limited.

[0003] Lignin is an aromatic compound abundant in nature. Since lignin contains multiple functional groups such as aliphatic hydroxyl and aromatic hydroxyl, it has the potential to be bio-based polyurethane. Enzymatic lignin is a new type of lignin obtained by microbial enzymatic hydrolysis. Compared with traditional alkali lignin and sulfate lignin, enzymatic lignin has multiple active groups and better reactivity. Its characteristics can be used to develop water-based polyurethane materials that are both environmentally friendly and high-performance. Summary of the invention

[0004] The first object of the present invention is to provide a lignin-based waterborne polyurethane to solve at least one of the above-mentioned technical problems.

[0005] The second object of the present invention is to provide a method for preparing lignin-based waterborne polyurethane to solve at least one of the above technical problems.

[0006] The third object of the present invention is to provide an application of lignin-based waterborne polyurethane to solve at least one of the above-mentioned technical problems.

[0007] According to a first aspect of the present invention, a lignin-based waterborne polyurethane is provided. The lignin-based waterborne polyurethane is prepared from a system consisting of the following raw materials in parts by weight: 50 to 80 parts of bio-based polyether diol, 15 to 30 parts of 1,5-pentanediisocyanate (PDI), 1 to 20 parts of enzymatic lignin (EL), 0.1 to 2 parts of a catalyst, 3 to 8 parts of a hydrophilic chain extender and 2.3 to 6.1 parts of a neutralizer, and a second organic solvent for dissolving the enzymatic lignin, wherein the mass ratio of the second organic solvent to the enzymatic lignin is (5 to 9):(0.5 to 4).

[0008] In some embodiments, the bio-based polyether glycol may be bio-based polytrimethylene ether glycol (PO3G).

[0009] The lignin-based waterborne polyurethane of the present invention uses bio-based materials such as bio-based polyether diol, 1,5-pentane diisocyanate and enzymatic lignin as raw materials, reduces the use of non-renewable petroleum-based materials, is green and environmentally friendly, and has good emulsion stability of the lignin-based waterborne polyurethane and has good thermal stability, tensile strength and flexibility after being cured into a film.

[0010] In some embodiments, the number average molecular weight of the bio-based polyether diol may be 500 to 2700.

[0011] In some embodiments, the number average molecular weight of the bio-based polyether diol may be 1,000.

[0012] In some embodiments, the number average molecular weight of the enzymatically hydrolyzed lignin may be 1,000 to 6,000.

[0013] In some embodiments, the number average molecular weight of the enzymatically hydrolyzed lignin may be 1,300.

[0014] In some embodiments, the hydrophilic chain extender may be selected from at least one of 2,2-dimethylol propionic acid and 2,2-dimethylol butyric acid.

[0015] In some embodiments, the catalyst may be a bismuth catalyst. Specifically, the bismuth catalyst may be selected from at least one of organic bismuth, bismuth neodecanoate, and bismuth isooctanoate.

[0016] In some embodiments, the neutralizing agent may be selected from at least one of triethylamine, triethanolamine, sodium hydroxide, aqueous ammonia, and N-methyldiethanolamine.

[0017] According to a second aspect of the present invention, a method for preparing a lignin-based waterborne polyurethane is provided, the preparation method comprising the following steps:

[0018] S1, reacting the bio-based polyether diol and 1,5-pentane diisocyanate at 80-90° C. for 2-4 hours, then adding the first mixed solution, the hydrophilic chain extender and the catalyst, reacting at 70-80° C. for 4-6 hours, adding the first organic solvent, and obtaining a lignin-based waterborne polyurethane prepolymer;

[0019] S2, cooling the lignin-based waterborne polyurethane prepolymer to a temperature less than 50° C., adding a neutralizing agent to react for 10 to 20 minutes, adding water to emulsify the prepolymer, and removing the first organic solvent in vacuo at 40 to 50° C. to obtain the prepolymer;

[0020] The first mixed solution is obtained by dissolving enzymatically hydrolyzed lignin in a second organic solvent.

[0021] The preparation method of the lignin-based waterborne polyurethane of the invention introduces enzymatically hydrolyzed lignin into the waterborne polyurethane system, the waterborne polyurethane emulsion has a high bio-based content, the preparation method is simple and the cost is low.

[0022] In some embodiments, the first organic solvent may be selected from at least one of acetone and butanone.

[0023] In some embodiments, the second organic solvent can be selected from at least one of NN diethylformamide (DEF) and γ-valerolactone (GVL). Specifically, when EL is not added to the reaction system, the system is difficult to form a film, but it is difficult to dissolve when EL is introduced, so the second organic solvent is used to dissolve the enzymatic lignin. The selected second organic solvent is a green, environmentally friendly, and low-toxic organic solvent that can not only dissolve the enzymatic lignin, but also can be used in the production and manufacturing of the printing and dyeing industry where highly toxic organic solvents are prohibited.

[0024] In some embodiments, the mass ratio of enzymatically hydrolyzed lignin to the second organic solvent may be (0.5-4):(5-9).

[0025] In some embodiments, the mass ratio of enzymatically hydrolyzed lignin to the second organic solvent may be (0.5-2):(5-9).

[0026] In some embodiments, in step S2, the emulsification reaction may be stirred at a rotation speed of 800 to 900 r / min for 0.8 to 1.5 hours.

[0027] According to a third aspect of the present invention, there is provided application of lignin-based waterborne polyurethane in printing coating.

[0028] The lignin-based waterborne polyurethane of the present invention can be prepared into a printing paint. The whole process does not require the addition of traditional petroleum-based color paste. The printing paint is applied to the surface of the fabric by a mechanical or manual method. The fabric treated with the printing paint has bright colors, no obvious fading after overheating, high resilience, and soft touch.

[0029] In some embodiments, the printing coating includes the following components, by weight: 170 to 190 parts of lignin-based waterborne polyurethane, 0.5 to 1.5 parts of defoaming agent, 0.5 to 1.5 parts of pH regulator, 1.4 to 1.8 parts of nonionic emulsifier, 8 to 12 parts of humectant, 2 to 4 parts of thickener and 1.5 to 2.5 parts of cross-linking agent.

[0030] The beneficial effects of the present invention are:

[0031] (1) The lignin-based waterborne polyurethane of the present invention introduces enzymatic lignin into the reaction system of the waterborne polyurethane, which can not only modify the waterborne polyurethane to obtain a waterborne polyurethane with good emulsion stability, but also has good thermal stability, tensile strength and flexibility after being cured into a film, and improves flame retardancy. At the same time, the natural pigment in the lignin can be used as a natural dye for paint printing, which helps to alleviate the high energy consumption and high pollution problems caused by the large-scale use of industrial color pastes in the printing and dyeing industry.

[0032] (2) The preparation method of the lignin-based waterborne polyurethane of the present invention is simple and low in cost;

[0033] (3) The lignin-based waterborne polyurethane of the present invention can be used to prepare printing coatings. The fabric treated with the printing coatings has bright colors, soft hand feel, and high resilience. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The infrared spectra of the enzymatically hydrolyzed lignin of the present invention, the lignin-based waterborne polyurethane prepared in Examples 1 to 3, and the waterborne polyurethane prepared in Comparative Example 1;

[0035] Figure 2 The stress-strain curves of the cured films of the lignin-based waterborne polyurethanes prepared in Examples 1 to 3 of the present invention and the waterborne polyurethanes prepared in Comparative Example 1;

[0036] Figure 3 The particle size distribution diagram of the lignin-based waterborne polyurethanes prepared in Examples 1 to 3 of the present invention and the waterborne polyurethane prepared in Comparative Example 1;

[0037] Figure 4 XRD curves of the cured films of the lignin-based waterborne polyurethanes prepared in Examples 1 to 3 of the present invention and the waterborne polyurethanes prepared in Comparative Example 1;

[0038] Figure 5 TGA curves of the cured films of the lignin-based waterborne polyurethanes prepared in Examples 1 to 3 of the present invention and the waterborne polyurethanes prepared in Comparative Example 1;

[0039] Figure 6 DTG curves of the cured films of the lignin-based waterborne polyurethanes prepared in Examples 1 to 3 of the present invention and the waterborne polyurethanes prepared in Comparative Example 1;

[0040] Figure 7 (A) is a photo of the printing paint of Application Example 2 of the present invention applied on white cotton cloth; Figure 7 (B) is a photo of the printing paint of Application Example 3 of the present invention applied on white cotton cloth; Figure 7 (C) is a photo of the printing paint of Application Example 4 of the present invention applied on white cotton cloth;

[0041] Figure 8 (A) is a photo of the printing coating of Application Example 2 of the present invention applied on a swimsuit fabric; Figure 8 (B) is a photo of the printing coating of Application Example 3 of the present invention applied on a swimsuit fabric; Figure 8 (C) is a photo of the printed coating of Application Example 4 of the present invention applied on a swimsuit fabric. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials and reagents involved in the following examples can all be obtained from commercial channels.

[0043] The enzymatically hydrolyzed lignin used in the following examples was purchased from Xinyuan Biotechnology Co., Ltd., with a purity of more than 90%, a phenolic hydroxyl content of 8% to 16%, and a number average molecular weight of 1,300.

[0044] Example 1

[0045] This embodiment provides a method for preparing a lignin-based waterborne polyurethane, comprising the following steps:

[0046] 50 g PO3G (number average molecular weight of 1000) and 18 g PDI were added to a 1000 mL three-necked flask, reacted at 85 ° C for 3 h, and then the first mixed solution obtained by dissolving 1.7 g enzymatic lignin in 15 g GVL, 3 g DMPA and 0.2 g organic bismuth catalyst 8108 were added, reacted at 75 ° C for 5 h, and then 20 g acetone was added to adjust the viscosity of the system to obtain a prepolymer;

[0047] The prepolymer was cooled to below 50°C, 2.3g TEA was added for neutralization reaction for 15min, and then 100g deionized water was added for emulsification for 1h, and finally acetone was removed under vacuum at 45°C to obtain the obtained product. The bio-based content of the lignin-based waterborne polyurethane was calculated to be 88.69%.

[0048] Example 2

[0049] This embodiment provides a method for preparing lignin-based waterborne polyurethane, which is different from embodiment 1 in that the mass of enzymatically hydrolyzed lignin in this embodiment is 3.45 g. According to calculation, the bio-based content of the lignin-based waterborne polyurethane is 88.96%.

[0050] Example 3

[0051] This embodiment provides a method for preparing lignin-based waterborne polyurethane, which is different from Embodiment 1 in that the mass of enzymatically hydrolyzed lignin in this embodiment is 5.3 g. According to calculation, the bio-based content of the lignin-based waterborne polyurethane is 89.23%.

[0052] Example 4

[0053] This embodiment provides a method for preparing lignin-based waterborne polyurethane, which is different from Embodiment 1 in that the mass of enzymatically hydrolyzed lignin in this embodiment is 7.2 g. According to calculation, the bio-based content of the lignin-based waterborne polyurethane is 89.49%.

[0054] Example 5

[0055] This embodiment provides a method for preparing lignin-based waterborne polyurethane, which is different from Embodiment 1 in that the mass of enzymatically hydrolyzed lignin in this embodiment is 9.2 g. According to calculation, the bio-based content of the lignin-based waterborne polyurethane is 89.75%.

[0056] Example 6

[0057] This embodiment provides a method for preparing lignin-based waterborne polyurethane, which is different from embodiment 1 in that the mass of enzymatically hydrolyzed lignin in this embodiment is 11.4 g. According to calculation, the bio-based content of the lignin-based waterborne polyurethane is 90.02%.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing waterborne polyurethane, comprising the following steps:

[0060] 50 g PO3G (number average molecular weight of 1000) and 18 g PDI were added to a 1000 mL three-necked flask, and the mixture was reacted at 85° C. for 3 h. Then, 3 g DMPA and 0.2 g organic bismuth catalyst 8108 were added to the reaction system, and the mixture was reacted at 75° C. for 5 h. Then, 20 g acetone was added to the reaction system to adjust the viscosity of the system, and a prepolymer was obtained.

[0061] The prepolymer was cooled to below 50°C, 2.3g TEA was added for neutralization for 15min, and then 100g deionized water was added for emulsification for 1h, and the acetone was removed in vacuo to obtain the waterborne polyurethane. The biobased content of the waterborne polyurethane was calculated to be 88.42%.

[0062] Application Example 1

[0063] This application example provides a printing coating, which includes the following components, in parts by weight: 180 parts of lignin-based waterborne polyurethane, 0.5-1.5 parts of defoaming agent, 1 part of pH regulator, 1.6 parts of nonionic emulsifier, 10 parts of humectant, 2-4 parts of thickener and 2 parts of cross-linking agent.

[0064] Application Example 2

[0065] This application example provides a printing coating, which includes the following components, in parts by weight: 180 parts of the lignin-based waterborne polyurethane prepared in Example 1, 1 part of the silicone defoamer HY310, 1 part of the pH regulator diethanolamine, 1.6 parts of the nonionic emulsifier AEO-9, 10 parts of the moisturizer propylene glycol, 3 parts of the thickener TT 935 and 2 parts of the cross-linking agent aziridine.

[0066] Application Example 3

[0067] This application example provides a printing coating, which includes the following components, in parts by weight: 180 parts of the lignin-based waterborne polyurethane prepared in Example 2, 1 part of the silicone defoamer HY310, 1 part of the pH regulator diethanolamine, 1.6 parts of the nonionic emulsifier AEO-9, 10 parts of the moisturizer propylene glycol, 3 parts of the thickener TT 935 and 2 parts of the cross-linking agent aziridine.

[0068] Application Example 4

[0069] This application example provides a printing coating, which includes the following components, in parts by weight: 180 parts of the lignin-based waterborne polyurethane prepared in Example 3, 1 part of the silicone defoamer HY310, 1 part of the pH regulator diethanolamine, 1.6 parts of the nonionic emulsifier AEO-9, 10 parts of the moisturizer propylene glycol, 3 parts of the thickener TT 935 and 2 parts of the cross-linking agent aziridine.

[0070] Test Example 1

[0071] In this test example, Fourier transform infrared spectroscopy was used to characterize the structures of the lignin-based waterborne polyurethanes of Examples 1 to 3, the waterborne polyurethane of Comparative Example 1, and the enzymatic lignin (EL) used in the examples of the present invention. The transmission medium was a 25 mm × 4 mm potassium bromide window, and the scanning range was 4000 to 500 cm -1 .

[0072] Figure 1 The infrared spectra of EL, the lignin-based waterborne polyurethanes prepared in Examples 1 to 3, and the waterborne polyurethanes prepared in Comparative Example 1 are shown in FIG. Figure 1 It can be seen that the products of Examples 1 to 3 and Comparative Example 1 have a -1 No characteristic absorption peak of isocyanate group (-N=C=O) was observed, indicating that the isocyanate group of PDI reacted completely with the hydroxyl group of PO3G. -1 Nearby (1713cm -1 The absorption peak at 2930 cm-1 is attributed to the stretching vibration of C=O in the carbonyl group, which is the result of hydrogen bonding and dipole-dipole interaction. -1 and 1369cm -1 The bands near 2864 cm-1 correspond to the antisymmetric stretching and bending vibrations of -CH3. -1 The absorption peaks near are respectively attributed to the symmetrical stretching vibration of the methylene (-CH2-) group. Compared with the infrared spectrum of the product of Comparative Example 1, the infrared spectra of the lignin-based waterborne polyurethanes of Examples 1 to 3 have an absorption peak at 3337 cm -1 The absorption band at 1713 cm -1 、1037cm -1The characteristic peak at 3340 cm-1 becomes stronger, indicating that EL is successfully introduced into the waterborne polyurethane system. The above data show that the lignin-based waterborne polyurethane is successfully synthesized. Comparing the infrared spectrum curves of the products of Examples 1 to 3, it is found that with the increase of EL content, the absorption peak at 3340 cm-1 increases. -1 Nearby (3337cm -1 ) gradually broadens, and the combined peak intensity increases with the increase of EL content.

[0073] Test Example 2

[0074] In this test example, tensile properties of the cured films of the lignin-based waterborne polyurethane (EL-WPU) prepared in Examples 1 to 3 and the waterborne polyurethane prepared in Comparative Example 1 were tested.

[0075] Preparation of cured film: The lignin-based waterborne polyurethanes prepared in Examples 1 to 3 and the waterborne polyurethane prepared in Comparative Example 1 were weighed respectively and placed in a culture dish, dried at room temperature for 8 h, and then dried in an electric constant temperature blast drying oven at 60° C. for 12 h.

[0076] The tensile properties of the cured film were tested using an electronic universal testing machine according to GB / T 1040.2-2006. The crosshead speed was set to 20 mm / min, and the sample size was 40.0 mm × 10.0 mm × 0.5 mm (length × width × thickness). The tensile properties test results are shown in Table 1 and Figure 2 shown.

[0077] Table 1 Tensile strength test of lignin-based waterborne polyurethane cured film

[0078] sample Tensile strength(MPa) Elongation at break (%) Comparative Example 1 0.56 405.69 Example 1 2 816.87 Example 2 3.62 1412.89 Example 3 3.26 2230.22

[0079] As can be seen from Table 1, when enzymatic lignin (EL) is added to waterborne polyurethane, the tensile strength and elongation at break are significantly increased. The reason may be that the structure of EL contains a large number of rigid benzene ring structures. When EL reacts with other raw materials, the EL-WPU molecular chain is tightly cross-linked internally, and EL enters the polymer molecular chain as a hard segment to form a complex network structure, thereby increasing the mechanical properties of the cured film. At the same time, EL can be used as a filler to fill the gaps between polymer molecular chains, thereby increasing the physical connection density of the polymer. In addition, EL rich in hydroxyl groups and waterborne polyurethane dispersions can produce hydrogen bonds, enhance their compatibility, and establish stable interfacial interactions. Therefore, the addition of EL can improve the mechanical properties of waterborne polyurethane cured films. Comparing the tensile strength test results of the cured films of Examples 1 to 3, it is found that as the content of EL in EL-WPU increases, the tensile strength of the cured film first increases and then decreases, and the elongation at break increases. The reason why the tensile strength of the lignin-based waterborne polyurethane cured film of Example 3 is lower than that of the lignin-based waterborne polyurethane cured film of Example 2 is that excessive EL exists in the emulsion system in the form of a filler, which increases the gaps between molecular chains. The reason why the elongation at break increases with the increase of EL addition is that, on the one hand, the low molecular weight components in EL can act as plasticizers, reduce the interaction force between polymer molecular chains in the matrix material, make the chain segments easier to slide, and thus improve the flexibility and elongation at break of the material; on the other hand, the addition of EL will affect the entanglement and movement trend of the EL-WPU molecular chain, making it more conducive to the plastic deformation of waterborne polyurethane, thereby improving the elongation at break.

[0080] Test Example 3

[0081] In this test example, the particle size of the lignin-based waterborne polyurethane prepared in Examples 1 to 3 and the waterborne polyurethane prepared in Comparative Example 1 was tested.

[0082] The aqueous polyurethane emulsion was diluted 100 times with distilled water, and the particle size distribution and Zeta potential of the dispersion were analyzed using a laser particle size analyzer.

[0083] Figure 3 The particle size test results of waterborne polyurethane emulsion are shown in Figure 1. Figure 3 It can be seen that when enzymatic lignin (EL) is added to the waterborne polyurethane emulsion, the particle size of lignin-based waterborne polyurethane increases significantly. As the amount of EL added increases, the particle size of lignin-based waterborne polyurethane gradually increases, because the EL structure contains a rigid benzene ring structure. When the amount of EL added is too much, it will cause agglomeration and adhesion between particles, resulting in an increase in the particle size of the emulsion and an increase in the width of the particle size distribution.

[0084] Table 2 Zeta potential of waterborne polyurethane emulsion

[0085] sample Zeta potential (mV) Comparative Example 1 30.2 Example 1 34.8 Example 2 35.6 Example 3 40.3

[0086] Table 2 shows the Zeta potential test results of different waterborne polyurethane emulsions. As can be seen from Table 2, the Zeta potential of the lignin-based waterborne polyurethanes of Examples 1 to 3 is greater than 30, indicating that the prepared lignin-based waterborne polyurethanes have good storage stability. In addition, the Zeta potential of the lignin-based waterborne polyurethanes of Examples 1 to 3 is greater than the Zeta potential of the waterborne polyurethane of Comparative Example 1, and the Zeta potential increases with the increase in the amount of EL added, indicating that the introduction of EL effectively improves the emulsion stability of the waterborne polyurethane.

[0087] Test Example 4

[0088] In this test example, XRD test was performed on the cured films of the lignin-based waterborne polyurethane (EL-WPU) prepared in Examples 1 to 3 and the waterborne polyurethane emulsion prepared in Comparative Example 1.

[0089] The crystallinity of the cured film was analyzed using a Bruker D2 advanced instrument (Bruker, Ettlingen), with the tube voltage maintained at 30 kV and the tube current maintained at 10 mA. The scanning angle was 5° to 60° with a step size of 0.02°.

[0090] Figure 4 is the XRD curve of the cured film of waterborne polyurethane emulsion. Figure 4 It can be seen that in the range of 2θ of 5° to 60°, the XRD curves of each waterborne polyurethane cured film have similar trends, and a diffuse diffraction peak appears near 2θ=20°. The peak intensity of the diffraction peak of the cured film of the waterborne polyurethane emulsion of Comparative Example 1 is the highest. As the amount of EL added increases, the peak intensity of the waterborne polyurethane cured film gradually decreases, indicating that the addition of EL will reduce the crystallinity of the waterborne polyurethane cured film, which may be because EL and the waterborne polyurethane dispersion form hydrogen bonds, and the hard segment increases the crystallization barrier effect of the soft segment, indicating that the cured film of the lignin-based waterborne polyurethane of the present invention may have good flexibility.

[0091] Test Example 5

[0092] In this test example, the thermal stability of the cured films of the lignin-based waterborne polyurethane (EL-WPU) prepared in Examples 1 to 3 and the waterborne polyurethane emulsion prepared in Comparative Example 1 was tested.

[0093] The thermal stability performance test was carried out using a thermal analyzer, in which the nitrogen flow rate was set to 20 mL / min, the heating rate was 10°C / min, and the test temperature range was 25°C to 800°C.

[0094] The thermal decomposition curves of all waterborne polyurethane cured films are similar and can be divided into three stages. In the first stage, the mass loss of the film is between 40-250°C, which may be caused by the evaporation of a small amount of residual water and residual catalysts and solvents. In the second stage, 250-380°C belongs to the thermal decomposition of the hard segment of the polyurethane, including the breaking of chemical bonds such as urethane. In the third stage, the mass loss of the film after 380-500°C belongs to the further thermal degradation of the soft segment such as polyols and EL. Table 3 shows the thermal decomposition data of waterborne polyurethane emulsion-cured films.

[0095] Table 3 Thermal decomposition data of waterborne polyurethane cured film

[0096] sample <![CDATA[T 10％ (℃)]]> <![CDATA[T 50％ (℃)]]> <h2 style=";text-align:left;direction:ltr"><![CDATA[T <h2 style=";text-align:left;direction:ltr"> max <h2 style=";text-align:left;direction:ltr"> (1st / 2nd)(℃)]]><h2 style=";text-align:left;direction:ltr"> Comparative Example 1 317.5 383.5 258.33 / 396.66 Example 1 325 400.66 216.4 / 416.83 Example 2 324.66 398.83 265 / 408.5 Example 3 326.66 400.33 261.5 / 411.83

[0097] It can be seen from Table 3 that the maximum thermal decomposition temperature (T max ) first increases and then decreases with the increase of EL addition, indicating that adding an appropriate amount of EL to the polymer can effectively improve thermal stability and slow down the pyrolysis process. The maximum thermal decomposition temperature of Example 2 and Example 3 is lower than that of Example 1. This may be because the benzene ring structure contained in EL is cross-linked with the molecular chain, thereby forming a complex cross-linked structure in the polymer, which acts as a thermal barrier to the molecular chain, thereby delaying the pyrolysis process of EL-WPU.

[0098] Figure 5 is the TGA curve of the cured film of different waterborne polyurethane emulsions. Figure 6 is the DTG curve of the cured film of different waterborne polyurethane emulsions. Figure 5 It can be seen that the residual carbon rate increases with the increase of EL addition. Figure 6 It can be seen that the thermal decomposition temperatures of the EL-WPU cured films of Examples 1 to 3 are all higher than that of the aqueous polyurethane emulsion cured film of Comparative Example 1, indicating that the addition of EL can effectively improve the heat resistance of the polymer.

[0099] Test Example 6

[0100] In this test example, the printing coating obtained by mixing the components in Application Examples 2 to 4 was screen-printed (3 knives × 3 times) on 25cm×25cm white cotton cloth and swimsuit cloth, and the printed white cotton cloth and swimsuit cloth were placed in an overheater at 135°C for 2 minutes.

[0101] The overheated white cotton cloth and swimsuit cloth were tested for elasticity by hand feel. The fabric was stretched from the high elastic direction, and the cracks on the fabric surface were observed. The elasticity was divided into 5 levels according to the cracks. Level 1: The initial pull was relatively strong, and then suddenly the force was reduced. The cracks were wide and long and very obvious, and the original fabric color could be seen; Level 2: The initial pull was relatively strong, and then the force was reduced suddenly. The cracks were obvious but thinner than Level 1, and there were obvious cracks; Level 3: The initial pull was relatively strong, and then the force gradually decreased, the cracks became shorter and fewer, and there were obvious gaps; Level 4: The initial pull was relatively strong, and the force was not significantly reduced, the cracks were not obvious, and there were some gaps; Level 5: The initial pull was strong, and the force remained unchanged, there were no cracks, and there were several point-shaped gaps.

[0102] Figure 7 This is a real picture of printing paint applied on white cotton cloth. Figure 8 The following is a photo of the printed paint applied to the swimsuit fabric to observe the color change of the fabric. It is found that the fabric treated with the printed paint has bright colors and no obvious fading after overheating, indicating that the printed paint has good thermal stability and can be printed on the fabric. In addition, the beating test of the printed paint found that the addition of EL improves the dispersion and leveling properties of the printed color paste. Figure 7 and Figure 8 It can also be seen that the printing paste has good fluidity and can evenly cover the fabric surface.

[0103] The fabric treated with the printing coating was found to be soft to the touch, and the elasticity test showed that the elasticity test results of the fabric treated with the printing coatings of Application Examples 2 to 4 were level 5, while the elasticity test results of the fabric treated with the printing coating of the formulation in Table 4 according to the same method were level 2, indicating that the fabric treated with the printing coating containing enzymatic lignin has high resilience.

[0104] Table 4 Printing coating formula

[0105] raw material Weight Comparative Example 1 Aqueous Polyurethane Prepared 180 copies HY310 1 serving Diethanolamine 1 serving AEO-9 1.6 servings Propylene glycol 10 servings TT935 3 servings Aziridine 2 servings

[0106] In summary, compared with the prior art, the beneficial effects of this technical solution are:

[0107] (1) By introducing enzymatic lignin into the waterborne polyurethane system, a lignin-based waterborne polyurethane with a high bio-based content is prepared, and the preparation method is simple, green and environmentally friendly, and low in cost;

[0108] (2) Without EL, the system is difficult to form a film. After adding EL, enzymatic lignin can be used as a film-forming aid for waterborne polyurethane, solving the technical problem of difficult film formation when PO3G and PDI are used to prepare waterborne polyurethane. In addition, the addition of EL improves the dispersion and leveling of the pigment. The natural pigment can be used as a pigment for printing coatings. No color paste is needed to prepare printing coatings, thereby alleviating the environmental pollution and sewage discharge problems caused by the large-scale use of dyes in the printing and dyeing industry;

[0109] (3) The lignin-based waterborne polyurethane of the present invention has good tensile strength, flexibility and heat resistance after being cured into a film. The printing coating prepared with the lignin-based waterborne polyurethane as the raw material is coated on the fabric, and the color is bright. The fabric does not fade significantly after overheating, has high resilience and a soft feel.

[0110] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. Lignin-based waterborne polyurethane, characterized in that The system is prepared from the following raw materials, which are calculated in parts by weight: 50 to 80 parts of bio-based polytrimethylene ether glycol, 15 to 30 parts of 1,5-pentanediisocyanate, 1 to 20 parts of enzymatic lignin, 0.1 to 2 parts of a catalyst, 3 to 8 parts of a hydrophilic chain extender and 2.3 to 6.1 parts of a neutralizer, and a second organic solvent for dissolving the enzymatic lignin, wherein the mass ratio of the second organic solvent to the enzymatic lignin is (5 to 9):(0.5 to 4).

2. The lignin-based waterborne polyurethane according to claim 1, characterized in that: The number average molecular weight of the bio-based polytrimethylene ether glycol is 500-2700, and the number average molecular weight of the enzymatically hydrolyzed lignin is 1000-6000.

3. The lignin-based waterborne polyurethane according to claim 1, characterized in that: The catalyst is selected from at least one of organic bismuth, bismuth neodecanoate and bismuth isooctanoate; the hydrophilic chain extender is selected from at least one of 2,2-dihydroxymethylpropionic acid and 2,2-dihydroxymethylbutyric acid.

4. The lignin-based waterborne polyurethane according to claim 1, characterized in that The neutralizing agent is selected from at least one of triethylamine, triethanolamine, sodium hydroxide, ammonia water, and N-methyldiethanolamine.

5. The lignin-based waterborne polyurethane according to claim 1, characterized in that: The second organic solvent is selected from at least one of NN diethylformamide and γ-valerolactone.

6. The method for preparing the lignin-based waterborne polyurethane according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1, reacting a bio-based polyether diol and 1,5-pentane diisocyanate at 80-90° C., then adding a first mixed solution, a hydrophilic chain extender and a catalyst, reacting at 70-80° C., adding a first organic solvent, and obtaining a lignin-based waterborne polyurethane prepolymer; S2, cooling the lignin-based waterborne polyurethane prepolymer to a temperature less than 50° C., adding a neutralizing agent for reaction, adding water for emulsification reaction, and removing the first organic solvent in vacuo at 40-50° C. to obtain; Wherein, the first mixed solution is prepared by dissolving the enzymatically hydrolyzed lignin in a second organic solvent.

7. The preparation method according to claim 6, characterized in that: The first organic solvent is selected from at least one of acetone and butanone.

8. The preparation method according to claim 6, characterized in that: In step S2, the emulsification reaction step is to stir at a rotation speed of 800 to 900 r / min.

9. Use of the lignin-based waterborne polyurethane according to any one of claims 1 to 5 in printing coatings.

10. The use according to claim 9, characterized in that: The printing coating comprises the following components in parts by weight: 170 to 190 parts of lignin-based waterborne polyurethane, 0.5 to 1.5 parts of defoaming agent, 0.5 to 1.5 parts of pH regulator, 1.4 to 1.8 parts of nonionic emulsifier, 8 to 12 parts of humectant, 2 to 4 parts of thickener and 1.5 to 2.5 parts of crosslinking agent.

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