Modified waterborne polyurethane emulsion as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a modified waterborne polyurethane emulsion as well as a preparation method and application thereof, and the preparation method comprises the following steps: step 1, fully mixing diisocyanate, glyceryl monooleate and long-chain diol, adding a catalyst, fully and uniformly mixing, and reacting in a protective atmosphere; 2, adding a micromolecular chain extender and a hydrophilic chain extender, and fully reacting; step 3, dropwise adding an end-capping reagent hydroxyethyl acrylate into the reaction system, and fully reacting; step 4, dropwise adding a neutralizing agent, continuously reacting, adding deionized water, and fully reacting to obtain the required modified waterborne polyurethane emulsion; the waterborne polyurethane obtained by the invention is used as a cotton fabric surface finishing agent, covers tiny concave-convex and flaws on the surface of cotton fiber, and forms a continuous film-shaped structure on the surface of the fiber, so that the whole surface is smoother, and the waterproof and antifouling properties of the fabric are favorably improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane preparation, and in particular to a modified waterborne polyurethane emulsion, a preparation method and application thereof. Background Art

[0002] In recent years, environmentally friendly and non-toxic water-based coatings have developed rapidly to reduce the emission of volatile organic compounds (VOCs). The main raw materials of polyurethane emulsions include polyisocyanates, polyols or polyamines, hydrophilic chain extenders, and additives. Nowadays, green and sustainable bio-based materials have become a hot research direction to replace petroleum resources. Waterborne polyurethane (WPU) modifications include acrylates, silicones, organic fluorines, and nanomaterials.

[0003] UV curing technology is widely used in waterborne polyurethane coatings due to its environmental protection and fast curing speed. UV-curable waterborne polyurethane acrylate (UV-WPUA) combines the advantages of WPU and acrylate, and has good flexibility, weather resistance, mechanical properties, etc. However, the existing WPU contains hydrophilic groups, which leads to poor water resistance of the film, and most of the hydrophobic and anti-fouling fabrics on the market use organic solvents or organic and water mixed solvents as finishing agents, which increases environmental pollution and limits the application field. Summary of the invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a modified waterborne polyurethane emulsion, a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is: a method for preparing a modified waterborne polyurethane emulsion, comprising the following steps: Step 1: fully mix diisocyanate, monoolein and long-chain diol, add catalyst, mix well and react under protective atmosphere; Step 2: Add small molecule chain extender and hydrophilic chain extender to fully react; Step 3: Add the end-capping agent hydroxyethyl acrylate dropwise into the reaction system to allow for sufficient reaction; Step 4: Add a neutralizing agent dropwise, continue the reaction, add deionized water, and after sufficient reaction, the desired modified waterborne polyurethane emulsion can be obtained; The molar ratio of diisocyanate, hydroxyethyl acrylate and long-chain diol is 1:0.33:0.26, and the addition amount of monooleyl glycerol is 0.5wt.% to 2.0wt.% of the total mass of the reactants.

[0006] Furthermore, the diisocyanate in step 1 is isophorone diisocyanate, and the long-chain diol is polytetramethylene glycol.

[0007] Furthermore, in step 1, the catalyst is dibutyltin diosilicate, and the reaction temperature is 80°C.

[0008] Furthermore, the small molecule chain extender in step 2 is 1,4-butanediol, and the hydrophilic chain extender is 2,2-dihydroxymethylpropionic acid; wherein the molar ratio of 1,4-butanediol, 2,2-dihydroxymethylpropionic acid and diisocyanate is 0.15-0.21:0.36:1.

[0009] Furthermore, during the reaction of the modified waterborne polyurethane emulsion, the isocyanate group content was monitored by acetone-di-n-butylamine titration method; after the isocyanate group content reached a preset value in step 3, the reaction temperature of the system was adjusted to 60°C.

[0010] Furthermore, in step 4, the neutralizing agent is triethylamine, and after sufficient reaction, the emulsion is allowed to stand for 12 h, and the solid content in the emulsion is 32 wt.%.

[0011] A modified waterborne polyurethane emulsion, wherein the structure of the modified waterborne polyurethane in the modified waterborne polyurethane emulsion is as follows:

[0012] in: The structure is as follows: .

[0013] The invention discloses an application of a modified waterborne polyurethane emulsion, wherein the modified waterborne polyurethane emulsion is used for preparing a waterborne polyurethane adhesive film and is used as a cotton fabric finishing agent.

[0014] Furthermore, the preparation process of the waterborne polyurethane film is as follows: A photoinitiator is added to the modified waterborne polyurethane emulsion, and after uniform stirring and ultrasonication, the emulsion is placed in a mold, dried, and cured by ultraviolet light to obtain a waterborne polyurethane film.

[0015] Further, the cotton fabric finishing agent is used in the following process: Adding photoinitiator into modified waterborne polyurethane emulsion, stirring evenly and ultrasonicating; The cotton fabric was soaked in the ultrasonic modified waterborne polyurethane emulsion, and the excess modified waterborne polyurethane was squeezed out. After drying, UV light curing is sufficient.

[0016] The beneficial effects of the present invention are: (1) In the present invention, glyceryl monooleate and hydroxyethyl acrylate are added to the main chain of waterborne polyurethane, and the obtained waterborne polyurethane emulsion has excellent storage stability; (2) The waterborne polyurethane obtained by the present invention is cured by ultraviolet light, and the carbon-carbon double bonds are broken and cross-linked. After the hydrophobic long chain of monooleyl glycerol is subjected to high temperature, the hydrophobic alkyl long chain faces outward, and hydrogen bonds are formed between the waterborne polyurethane and the cotton fabric. The hydrophobic angle is greater than 120°, thereby improving its hydrophobicity. (3) The waterborne polyurethane obtained by the present invention is used as a surface finishing agent for cotton fabrics, which covers the tiny bumps and defects on the surface of cotton fibers. The continuous film-like structure formed on the fiber surface makes the overall surface smoother, which helps to improve the waterproof and antifouling properties of the fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process of the present invention.

[0018] Figure 2 The infrared spectra of the adhesive films obtained by UV curing in Example 2 and Comparative Example 2 of the present invention and the polyurethane obtained in Comparative Example 1 are shown.

[0019] Figure 3 The tensile strength and elongation at break curves of the films prepared from the waterborne polyurethanes obtained in Examples 1 to 4 of the present invention and Comparative Example 1 are shown.

[0020] Figure 4 is the SEM image of the cotton fabric used, a and b are images at different magnifications.

[0021] Figure 5 The SEM images of cotton fabric treated with the aqueous polyurethane emulsion obtained by the present invention are shown in Figure 1, and a and b are images at different magnifications.

[0022] Figure 6 The thermal stability curves of the films prepared from the waterborne polyurethanes obtained in Examples 1 to 4 of the present invention and Comparative Example 1 are shown.

[0023] Figure 7 The water contact angles of the films and the treated cotton fabrics prepared by the waterborne polyurethanes obtained in Examples 1 to 4 of the present invention and Comparative Example 1, a is the film, and b is the treated cotton fabric.

[0024] Figure 8 4 and 1. The figures are effect test diagrams of cotton fabrics treated with water-based polyurethane obtained in Examples 1 to 4 of the present invention and Comparative Example 1, a to c are schematic diagrams of mud anti-fouling of untreated cotton fabrics, d to f are schematic diagrams of mud anti-fouling of cotton fabrics treated with water-based polyurethane obtained in Example 1, g is a schematic diagram of the anti-fouling performance of untreated cotton fabrics to different liquids, h is a schematic diagram of the anti-fouling performance of cotton fabrics treated with water-based polyurethane obtained in Example 1 to different liquids, and i is the contact angle of the cotton fabric treated with water-based polyurethane obtained in Example 1 with different liquids.

[0025] Fig. 9Schematic diagram of particle size distribution of aqueous polyurethane emulsions obtained in Examples 1 to 4 of the present invention and Comparative Example 1.

[0026] Fig.10 The water contact angles of cotton fabrics treated with the waterborne polyurethane obtained in Example 2 of the present invention after different washing times are compared.

[0027] Fig.11 1 is a comparison of the XPS spectra of the cotton fabric treated with the waterborne polyurethane obtained in Example 2 of the present invention and the untreated cotton fabric, wherein a is the full XPS spectrum of the cotton fabric, b is the C1s fine spectrum of the untreated cotton fabric, and c is the C1s fine spectrum of the cotton fabric treated with the waterborne polyurethane obtained in Example 2. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] A method for preparing a modified waterborne polyurethane emulsion comprises the following steps: Step 1: fully mix diisocyanate, glyceryl monooleate GMO and long-chain diol, add catalyst, mix thoroughly and evenly, and react under protective atmosphere; diisocyanate is isophorone diisocyanate IPDI, long-chain diol is polytetramethylene ether diol PTMG-2000; catalyst is dibutyltin disilicate DBTDL, and reaction temperature is 80 °C.

[0030] Step 2: adding a small molecule chain extender and a hydrophilic chain extender to fully react; the small molecule chain extender is 1,4-butanediol BDO, and the hydrophilic chain extender is 2,2-dihydroxymethylpropionic acid DMPA; wherein the molar ratio of 1,4-butanediol, 2,2-dihydroxymethylpropionic acid and diisocyanate is 0.15-0.21:0.36:1.

[0031] Step 3: Add the end-capping agent hydroxyethyl acrylate HEA dropwise to the reaction system for sufficient reaction; during the reaction of the modified waterborne polyurethane emulsion, the isocyanate group content is monitored by acetone-di-n-butylamine titration method; after the isocyanate group content in step 3 reaches a preset value, the reaction temperature of the system is adjusted to 60°C.

[0032] Step 4: Add a neutralizing agent dropwise, continue the reaction, add deionized water, and after sufficient reaction, the desired modified waterborne polyurethane emulsion can be obtained; the neutralizing agent is triethylamine TEA, and after sufficient reaction, the emulsion is allowed to stand for 12 hours, and the solid content in the emulsion is 32 wt.%.

[0033] The molar ratio of diisocyanate, hydroxyethyl acrylate and long-chain diol is 1:0.33:0.26, and the addition amount of monooleyl glycerol is 0.5wt.% to 2.0wt.% of the total mass of the reactants.

[0034] In the embodiment of the present invention, the solid content of GMO accounts for 0.5 wt.% to 2.0 wt.% of the total mass of (IPDI+PTMG+BDO+HEA+DMPA+TEA+GMO).

[0035] Example 1 A method for preparing a modified waterborne polyurethane emulsion, the reaction process is as follows Figure 1 As shown, the following steps are included: Before the preparation, 4Å molecular sieves were first used to activate the required raw materials, including acetone (used as a solvent in the following examples), TEA, BDO, DBTDL, and HEA. The activated molecular sieves were placed in the above raw materials and dried for two weeks for use. PTMG and DMPA were dried and dehydrated in a vacuum drying oven at 120 °C for 2 h before use.

[0036] Step 1: Add 8 g of IPDI, 0.16 g of GMO and 18.56 g of dry PTMG-2000 into a four-necked flask, install a thermometer, a stirrer, and a condensation reflux device, place it in a water bath at 80 °C, add 0.02 mL of the catalyst dibutyltin disilicate DBTDL dropwise, keep a constant speed (700 r / min) to mix the solution evenly, and maintain the nitrogen atmosphere for 1 h.

[0037] Step 2: Add 0.58 g of a small molecule chain extender 1,4-butanediol BDO and 1.74 g of a hydrophilic chain extender 2,2-dihydroxymethylpropionic acid DMPA dried under vacuum to the reaction system obtained in step 1, and monitor the content of isocyanate groups by acetone-di-n-butylamine titration method.

[0038] Step 3: Add 1.39 g of the end-capping agent hydroxyethyl acrylate HEA dropwise to the reaction system, and continue the reaction until the isocyanate group content in the system reaches the theoretical value (determined according to actual conditions). The water bath temperature is lowered to 60 °C, and acetone is added to reduce the viscosity according to the conditions of the reaction system.

[0039] Step 4: 1.44 g of neutralizing agent triethylamine TEA was added dropwise to neutralize the carboxylic acid in the reaction, and the reaction lasted for 1 h; the speed was increased (higher than the above constant speed), deionized water was added (added according to the solid content), and the reaction was continued for 1 h. A modified waterborne polyurethane emulsion GWPU with a solid content of 32% (0.5% GWPU in the subsequent figures) was obtained, the solution was taken out and placed for 12 h, and the acetone was removed by vacuum distillation for standby use.

[0040] Example 2 The other steps of this example are the same as those of Example 1, except that the amount of GMO added in step 1 is 0.32 g (1% GWPU in subsequent figures).

[0041] Example 3 The other steps of this example are the same as those of Example 1, except that the amount of GMO added in step 1 is 0.48 g (1.5% GWPU in subsequent figures).

[0042] Example 4 The other steps of this embodiment are the same as those of embodiment 1, except that the amount of GMO added in step 1 is 0.65 (2% GWPU in subsequent figures) g.

[0043] Example 5 The other steps of this example are the same as those of Example 2, except that the amount of BDO added in step 2 is 0.48 g.

[0044] Example 6 The other steps of this example are the same as those of Example 2, except that the amount of BDO added in step 2 is 0.68 g.

[0045] Comparative Example 1 The other steps of this embodiment are the same as those of embodiment 1, except that GMO is not added in step 1, and the obtained emulsion is referred to as WPU.

[0046] For testing, the emulsions prepared in the above examples and comparative examples were prepared into films using the following methods: Take a certain amount of GWPU emulsion, add 3% photoinitiator 2959, stir evenly, ultrasonicate at 25 ℃ for 20 min, take 10 g of the mixture and pour it into a polytetrafluoroethylene mold, leave it at room temperature to dry the surface, then put it in a vacuum oven at 80 ℃ for 12 h, UV-cured for 30 s, and put it in a forced air drying oven for use.

[0047] For testing, the emulsions prepared in the above examples and comparative examples were used to treat cotton fabrics using the following methods: Add 3% photoinitiator 2959 to a certain amount of GWPU emulsion and stir evenly. Ultrasonicate at 25°C for 20 min, soak a 25 mm × 25 mm square cotton fabric in the ultrasonicated GWPU for 10 min, press out the excess GWPU, dry it in a vacuum drying oven at 80°C for 3 h, then perform UV curing to obtain a sample, and put it in a forced air drying oven for later use.

[0048] The aqueous polyurethane emulsions obtained in the above examples and comparative examples are transparent and blue in appearance. The emulsion containing GMO was centrifuged at 3000 rpm for 15 min, and the emulsion did not show stratification or precipitation, and remained stable, with a storage stability of at least 6 months.

[0049] The FTIR spectrum of the film UV-1%GWPU obtained by UV curing the polyurethane emulsions in Example 2, Comparative Example 1 and Example 2 of the present invention is as follows: Figure 2 As shown in the figure, it can be seen that 3329cm -1 The NH bond stretching vibration absorption peak is at 1541cm -1 The bending vibration absorption peak of NH bond is at 2937cm -1 and 2853cm -1 The stretching vibration peaks of CH3- and CH2-, 1705 cm -1 These peaks are carbonyl (C=O) stretching vibration absorption peaks. The appearance of these peaks indicates the formation of carbamate groups. -1 and 1238cm -1 These are the stretching vibration peaks of esterified COC and CO. -1 In this range, the peaks of 1%GWPU and UV-1%GWPU are enhanced. The peaks of 1%GWPU and UV-1%GWPU are at 1705cm -1 The carbonyl peak at 1628 cm-1 of WPU and 1% GWPU is also enhanced compared with WPU, which indicates that GMO has been successfully introduced into waterborne polyurethane as a chain extender. -1 The absorption peak at the center is caused by the stretching vibration of C=C, while the infrared curve of UV-1%GWPU film does not have it. After UV curing, the unsaturated double bonds in the WPU film undergo cross-linking polymerization reaction under the action of photoinitiator.

[0050] The tensile strength and elongation at break of the cornea obtained by UV-curing the modified aqueous polyurethane emulsions obtained in Examples 1 to 4 of the present invention and Comparative Example 1 are as follows: Figure 3 As shown in the figure, it can be seen that with the increase of GMO addition, the tensile strength and elongation at break both tend to increase first and then decrease. The carbon-carbon double bond of the end-capping agent HEA can increase the cross-linking density of the system. The increase in cross-linking degree is conducive to promoting the bonding and movement between the molecular chains after UV curing, so that the molecular chains are bound and no relative slip occurs. The tensile strength of WPU is 5 MPa and the elongation at break is 1122%. When the GMO content is 0.5%, the maximum tensile strength is 11 MPa and the maximum elongation at break is 1553%. The GMO content gradually replaces the BDO content in the system, resulting in an increase in the cross-linking density in the system; the hydroxyl and ester groups in the structure of the long fat hydrophobic chain extender increase the hydrogen bond strength in the system; GMO acts as an internal plasticizer and lubricant to improve the toughness of the GWPU film. When too much GMO is introduced, the molecular chain is too long and the molecular weight is too high, resulting in too many hard segments and too high cross-linking, which affects the degree of reaction, and the tensile strength and elongation at break of UV-GWPU are reduced.

[0051] Figure 4 The SEM images of the cotton fabric used in the present invention are shown in the left and right figures at different magnifications. As can be seen from the figure, the cotton fibers are randomly interwoven to form the skeleton of the fabric. There are gaps between the fibers, and the fiber surface is rough with tiny bumps and flaws.

[0052] The SEM image of the cotton fabric treated with the polyurethane emulsion obtained in Example 2 is as follows: Figure 5 As shown in the figure, the left and right figures are schematic diagrams of different magnifications. It can be seen from the figure that the treated fibers are arranged more closely and there is GWPU filling between the fibers. Compared with the untreated cotton fabric, the surface of the treated cotton fiber is smoother. The GWPU covers the tiny bumps and flaws on the surface of the cotton fiber, and forms a continuous membrane structure on the fiber surface, making the overall surface smoother. This smooth surface helps to improve the waterproof and anti-fouling properties of the fabric.

[0053] Figure 6 The TG curves of the films obtained by UV-curing the aqueous polyurethane emulsions obtained in Examples 1 to 4 of the present invention and Comparative Example 1, namely, UV-GWPU, are shown in Figure 5. -5 %)、10wt%(T -10 %)、50wt%(T -50 %) and the temperature at which the maximum weight loss rate occurs (T max ) as shown in Table 1.

[0054] from Figure 6 It can be seen that the thermal decomposition of UV-GWPU is mainly divided into two stages. The first stage is around 300 ℃, and the carbamate group (-NH-COO-) in the hard segment of WPU is thermally broken and decomposed; the second stage is around 400 ℃, and the soft segment in the molecular chain is thermally decomposed. The initial degradation temperature is 250 ℃, indicating that the UV-cured WPU causes a polymerization reaction to obtain a cross-linked structure. The thermal decomposition below 250 ℃ may be caused by the evaporation of residual organic solvents and water in the film from the system, causing weight loss.

[0055] The thermal decomposition temperature of the soft segment of GMO-modified WPU is significantly increased. The long-chain alkyl and the inherently high thermal decomposition temperature of GMO are added to WPU as chain extenders. The long-chain alkyl is evenly arranged during the film formation process, and the film is more dense, which makes the thermal decomposition temperature higher. Compared with WPU without GMO, the thermal decomposition temperature is higher. With the increase of GMO addition, the cured film T -5% first increases and then decreases. When the addition amount of GMO is 0.5%, the thermogravimetric residue rate is higher, the heat resistance is better, and the thermal decomposition temperature is the highest. If the amount of GMO introduced is too large, the unsaturated double bonds will destroy the original molecular structure under certain conditions; change the interaction force between the polyurethane molecular chains, causing the arrangement and stacking of the molecular chains to become loose, thereby reducing thermal stability; it will also change the cross-linking density, making the molecular chains too rigid and easy to break when heated.

[0056] The introduction of GMO makes GWPU T -5 , T -10 and T -50 The thermal stability of GWPU film can be significantly enhanced by replacing the hydrophilic chain extender with a long aliphatic hydrophobic chain. Because GMO has a high thermal decomposition temperature, and the 18-carbon aliphatic long chain easily causes entanglement between molecules, thus improving the thermal stability of the film. The increase in the cross-linking degree of the system and the improvement in the strength of hydrogen bonds may also affect the thermal stability of GWPU film.

[0057] Table 1. Initial degradation temperature of the film obtained from the aqueous polyurethane emulsions of Examples 1 to 4 and Comparative Example 1

[0058] The aqueous polyurethane emulsions obtained in Examples 1 to 4 and Comparative Example 1 were prepared into films according to the above steps, and the water contact angles thereof were as follows: Figure 7 As shown in a, the water contact angle of cotton fabric after being treated according to the above steps is as follows Figure 7 As shown in b. Figure 7 As can be seen in Figure a, the water contact angles of WPU, 0.5%GWPU, 1%GWPU, 1.5%GWPU and 2%GWPU are 65.2°, 69.2°, 73.1°, 76.7° and 80.0° respectively. With the increase of GMO content, the water contact angle increases. GMO is introduced into UV-WPUA as a chain extender. GMO contains long-chain hydrophobic alkane groups, which can increase the content of long-chain alkanes in the molecule, thereby improving the water contact angle of the GWPU film. Figure 7 As can be seen in Figure b, the water contact angles of the treated cotton fabrics are 105.2°, 111.5°, 114.2°, 118.6°, and 126.4°, respectively. Compared with the VU-GWPU film, the water contact angle of the UV-CGWPU surface has been greatly improved, which may be due to the formation of hydrogen bonds between the carbamate bonds in the GWPU and the hydroxyl groups on the surface of the cotton fabric during the drying process. With the increase of the content of GMO, the content of the hydrophilic chain extender BDO decreases, and the content of the long-chain alkane GMO increases, so that more -CH2CH3 is arranged neatly on the surface of the fabric to form a hydrophobic layer.

[0059] The statistical results of the water contact angles of the film and the treated cotton fabric are shown in Table 2.

[0060] Table 2. Water contact angles of films and treated cotton fabrics with different GMO contents

[0061] Figure 8 This is a test diagram of the effect of treating cotton fabric with water-based polyurethane obtained in Examples 1 to 4 of the present invention and Comparative Example 1. Figure 8 Figures a to c are schematic diagrams of soil antifouling of untreated cotton fabrics. Soil is used instead of solid pollutants. It can be seen from the figure that the surface of the fabric is contaminated after the cotton fabric is removed from the water. Figure 8 Figures d to f are schematic diagrams of the soil antifouling of cotton fabric treated with waterborne polyurethane obtained in Example 1. It can be seen from the figure that when the soil is placed on the modified fabric, put into water and then removed, the soil on the surface of the fabric completely disappears. The cotton fabric is only partially wetted in water, and the soil on the surface has just dissolved in water. The concentration of muddy water is high, and some wetting points on the surface of the cotton fabric diffuse, so that the cotton fabric continues to absorb water and just absorbs high-concentration muddy water. When the hydrophobic fabric is underwater, there are a lot of gaps between the modified fabric and the water, and the water cannot wet the surface of the fabric, showing that water takes away pollutants and the fabric surface is self-cleaning.

[0062] Figure 8 Figure g is a schematic diagram of the antifouling performance of untreated cotton fabric to different liquids, which shows the effect of different pollutants on the surface of the fabric before modification for 5 minutes. It can be seen from the figure that all the pollutant droplets dropped on the surface of the cotton fabric have penetrated into the fabric surface.

[0063] Figure 8 Figure h is a schematic diagram of the antifouling performance of the cotton fabric treated with waterborne polyurethane obtained in Example 1 to different liquids, which is the effect of different pollutants on the surface of the modified fabric for 5 minutes. It can be seen from the figure that the polluted droplets are all present in spherical shape on the surface of the modified fabric, and there is no residue on the surface of the fabric after the droplets are absorbed.

[0064] Figure 8 i is the contact angle of the cotton fabric treated with waterborne polyurethane obtained in Example 1 with different liquids (part of the liquid in h). It can be seen from the figure that the contact angles of tea, ink, coffee, milk, and milk tea are all greater than 110°. The modified cotton fabric is hydrophobic due to the chemical structure of GWPU, which makes it still have good anti-fouling and cleaning performance.

[0065] Fig. 9The particle size distribution curve of the aqueous polyurethane emulsion obtained in Examples 1 to 4 of the present invention and Comparative Example 1 is shown in the figure. It can be seen from the figure that the average particle sizes of WPU, 0.5% GWPU, 1% GWPU, 1.5% GWPU and 2% GWPU are 27 nm, 31 nm, 33.5 nm, 36.8 nm and 44.2 nm, respectively. It can be seen from the figure that as the content of GMO increases, the number of long fatty hydrophobic chains increases significantly, the average particle size of the polymer emulsion gradually increases, the particle size distribution becomes wider, all emulsion particle size distributions show a single peak, and the emulsion stability is relatively excellent. GMO is added as a chain extender to increase the proportion of GMO, so that the number of hydrophobic long fatty side chains in the aqueous polyurethane molecular chain increases, and hydrophobic micelles are formed in the emulsion, and the hydrophilicity is weakened.

[0066] Fig.10 The comparison of water contact angles of cotton fabrics treated with waterborne polyurethane obtained in Example 2 of the present invention after different washing times. The water resistance results of cotton fabrics treated with Example 2 are as follows: Fig.10 As shown in the figure, it can be seen that after 0, 5, 10, 15, and 20 washes, the water contact angles of the cotton fabric are 114.2°, 110.6°, 106.2°, 104.2°, and 98.1°, respectively. It can be seen that after multiple washes, the hydrophobicity of the prepared fabric decreases to varying degrees, but overall, the decrease is small, and even after 20 washes, the water contact angle remains above 90°, indicating that the fabric has good wash resistance.

[0067] Fig.11 1 is a comparison of the XPS spectra of the cotton fabric treated with the waterborne polyurethane obtained in Example 2 of the present invention and the untreated cotton fabric, wherein a is the full XPS spectrum of the cotton fabric, b is the C1s fine spectrum of the untreated cotton fabric, and c is the C1s fine spectrum of the cotton fabric treated with the waterborne polyurethane obtained in Example 2. Fig.11 In a, it can be seen that the main components of cotton fabric are carbon (C) and oxygen (O), and their corresponding peak positions are located at C1s (284.6 eV) and O1s (532.7 eV). The cotton fabric treated with 1% GWPU has an N element N1s peak at 398.8 eV, which is the N element on the isocyanate. The results show that GWPU has been successfully attached to the fabric surface.

[0068] from Fig.11As can be seen in b and c, in cotton fabric and cotton fabric treated with 1% GWPU, CC and CH groups correspond to the peak at 284.8 eV. By splitting the peak of C1s on untreated cotton fabric, it was found that the valence bonds connected to carbon atoms include CC and CH at 284.8 eV, CO at 266.3 eV, and O=CO at 289.2 eV. Splitting the peak of C1s on cotton fabric treated with 1% GWPU also showed the presence of CC and CH, CO, and O=CO. These results indicate that the introduction of GWPU did not significantly change the basic chemical environment of carbon atoms on the surface of cotton fabric, but did introduce new chemical elements (N) and possible chemical bonds (such as urethane bonds in polyurethane), thereby achieving the modification of cotton fabric.

[0069] The present invention introduces monoolein and hydroxyethyl acrylate into the main chain of waterborne polyurethane, and the prepared waterborne polyurethane emulsion has excellent storage stability, and the prepared waterborne polyurethane cotton fabric. After ultraviolet light curing, the carbon-carbon double bond is disconnected and cross-linked, and the hydrophobic long chain of monoolein is subjected to high temperature, and the hydrophobic alkyl long chain is outward, and hydrogen bonds are formed between the waterborne polyurethane and the cotton fabric, and the hydrophobic angle is greater than 120°, thereby improving the hydrophobicity. Since monoolein is used as a chain extender, hydroxyethyl acrylate is connected to the waterborne polyurethane as a capping agent; the waterborne polyurethane is used as a surface finishing agent for cotton fabric, covering the tiny bumps and defects on the surface of the cotton fiber, and the continuous film-like structure formed on the fiber surface makes the overall surface smoother. This smooth surface helps to improve the waterproof and anti-fouling properties of the fabric. The material has broad prospects in the fields of medical treatment, outdoor clothing, etc.

Claims

1. A method for preparing a modified aqueous polyurethane emulsion, characterized in that: The following steps are involved: Step 1: fully mix diisocyanate, monoolein and long-chain diol, add catalyst, mix well and react under protective atmosphere; Step 2: Add small molecule chain extender and hydrophilic chain extender to fully react; Step 3: Add the end-capping agent hydroxyethyl acrylate dropwise into the reaction system to allow for sufficient reaction; Step 4: Add a neutralizing agent dropwise, continue the reaction, add deionized water, and after sufficient reaction, the desired modified waterborne polyurethane emulsion can be obtained; The molar ratio of diisocyanate, hydroxyethyl acrylate and long-chain diol is 1:0.33:0.26, and the addition amount of monooleyl glycerol is 0.5wt.% to 2.0wt.% of the total mass of the reactants.

2. The method for preparing a modified aqueous polyurethane emulsion according to claim 1, characterized in that: The diisocyanate in step 1 is isophorone diisocyanate, and the long-chain diol is polytetramethylene glycol.

3. The method for preparing a modified aqueous polyurethane emulsion according to claim 1, characterized in that: In step 1, the catalyst is dibutyltin disilicate, and the reaction temperature is 80°C.

4. The method for preparing a modified aqueous polyurethane emulsion according to claim 1, characterized in that: The small molecule chain extender in step 2 is 1,4-butanediol, and the hydrophilic chain extender is 2,2-dimethylolpropionic acid; wherein the molar ratio of 1,4-butanediol, 2,2-dimethylolpropionic acid and diisocyanate is 0.15-0.21:0.36:

1.

5. The method for preparing a modified aqueous polyurethane emulsion according to claim 1, characterized in that: During the reaction of the modified waterborne polyurethane emulsion, the isocyanate group content was monitored by acetone-di-n-butylamine titration method; after the isocyanate group content reached a preset value in step 3, the reaction temperature of the system was adjusted to 60°C.

6. The method for preparing a modified aqueous polyurethane emulsion according to claim 1, characterized in that: In step 4, the neutralizing agent is triethylamine. After sufficient reaction, the emulsion is allowed to stand for 12 h, and the solid content in the emulsion is 32 wt.%.

7. The modified aqueous polyurethane emulsion obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The structure of the modified waterborne polyurethane in the modified waterborne polyurethane emulsion is as follows: in: The structure is as follows: .

8. The use of a modified waterborne polyurethane emulsion as claimed in claim 7, characterized in that: The modified aqueous polyurethane emulsion is used for preparing aqueous polyurethane adhesive film and is used as a cotton fabric finishing agent.

9. The use of a modified aqueous polyurethane emulsion according to claim 8, characterized in that: The preparation process of the waterborne polyurethane film is as follows: A photoinitiator is added to the modified waterborne polyurethane emulsion, and after uniform stirring and ultrasonic treatment, the emulsion is placed in a mold, dried, and cured by ultraviolet light to obtain a waterborne polyurethane film.

10. The use of a modified aqueous polyurethane emulsion according to claim 8, characterized in that: The cotton fabric finishing agent is used as follows: Adding photoinitiator into modified waterborne polyurethane emulsion, stirring evenly and ultrasonicating; The cotton fabric was soaked in the ultrasonic modified waterborne polyurethane emulsion, and the excess modified waterborne polyurethane was squeezed out. After drying, UV light curing is sufficient.

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