A method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion

Abstract

The present invention belongs to the technical field of waterborne polyurethane, and specifically relates to a method for synthesizing an internally cross-linked cationic waterborne polyurethane emulsion. The method comprises the following steps: 1) reacting glycidol and diethanolamine until the infrared spectrum analysis shows that the glycidol and diethanolamine are at 908 cm ‑1 and 845cm ‑1 The epoxy groups disappear, the reaction is stopped, and the product EDEOA, a tertiary amino crosslinking agent, is obtained as a light yellow viscous liquid; 2) polyol and diisocyanate are added to a reactor and heated and kept warm under stirring for reaction; 3) solvent, tertiary amino crosslinking agent, tertiary amino small molecule alcohol amine chain extender, solvent and catalyst are then added to react to obtain a polyurethane intermediate; 4) a neutralizing agent is then added to the reaction system for neutralization reaction, and the temperature is lowered after the reaction is completed; 5) water is added to quickly disperse the mixture uniformly, and the solvent is removed in vacuo to obtain a waterborne polyurethane emulsion. The present invention mainly solves the technical problems existing in the synthesis of cationic waterborne polyurethanes, such as poor emulsion stability, low film mechanical properties, and poor water and solvent resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of waterborne polyurethane, and particularly relates to a method for synthesizing an internally cross-linked cationic waterborne polyurethane emulsion. Background Art

[0002] With the increasing awareness of environmental protection and the restriction of volatile organic compound (VOC) emissions, waterborne polyurethane (WPU) is becoming increasingly popular among consumers from the perspectives of technology, applicability and environment due to its advantages such as non-toxicity, non-flammability, environmental friendliness, chemical resistance, scratch resistance, moisture resistance and breathability, as well as good adhesion to a variety of substrates. It is widely used in adhesives and coatings for various substrates (such as leather, textiles, metal, plastic, glass and wood, etc.). Although anionic waterborne polyurethane (AWPU) currently dominates the market, cationic waterborne polyurethane (CWPU) also has many advantages over AWPU in special applications (such as adhesives, antibacterial coatings and drug delivery). For example, CWPU has good wettability, adhesion and film-forming properties for various polymers such as hydrophobic polyester and acrylic fibers, and is widely used in chemical fiber coating finishing. Cationic hydrophilic chain extender is an essential component for the stable dispersion of CWPU in water. However, due to its insufficient emulsification ability, the water absorption rate of the obtained CWPU film is much higher than that of AWPU, resulting in poor water resistance of CWPU. In particular, linear CWPU is difficult to meet long-term use requirements.

[0003] Currently, there are numerous reports on the modification of AWPU, including cross-linking, epoxy resins, silicones, acrylate resins, and inorganic nanomaterials. These methods are also commonly used in the modification of CWPU. Cross-linking is an effective method for maintaining high water resistance, heat resistance, mechanical properties, and adhesive properties. Cross-linking can be categorized as internal or external. External cross-linking is generally achieved by adding an external cross-linking agent, such as a two-component adhesive or coating, which is added during the actual application process. Common cross-linking agents include amino resins or polyaziridines. Amino resins release toxic formaldehyde during use, while aziridines have a strong ammonia odor. External cross-linking agents also have drawbacks such as inconvenient on-site metering and a short pot life (i.e., they must be used within a specified time, otherwise they will gel and be wasted). This limits their application. Internal cross-linking agents are typically introduced into the WPU structure during synthesis by introducing triols such as trimethylolpropane (TMP), glycerol (GLY), castor oil, soybean oil polyols, or triamines such as diethylenetriamine. This method can be used as a single-component or two-component coating and adhesive at the same time, and has the advantages of easy operation, water resistance, heat resistance and good mechanical properties. Its disadvantage is that only a small amount of cross-linking agent can be introduced, otherwise the viscosity of the prepolymer will increase, resulting in difficulty in dispersion and even gelation. For example, CN106149381A discloses a cationic silicone-modified PUA fabric coating adhesive with a self-cross-linking structure and a preparation method thereof, which is to prepare a silicone-modified hydrazine-terminated WPU emulsion and a hydrazide-containing polyacrylate emulsion respectively, and then mix the two emulsions in a certain proportion to obtain a self-cross-linking silicone-modified PUA fabric coating adhesive. The use of harmful cross-linking agents is avoided, and the coating finishing of nylon fabrics also has the advantages of environmental protection, high water pressure resistance, good mechanical properties, low cost, and dyeability. CN106084141A discloses a method for preparing acrylate-modified WPU using soybean oil polyol. Two soybean oil polyols are mixed in different proportions, and then polyaddition-polymerized with isocyanate to obtain WPU, which is then graft-copolymerized with acrylate monomers. The resulting acrylate-modified WPU has the characteristics of high branching and crosslinking, high heat resistance of the coating, low brittleness, high transparency, strong scratch resistance, bright and full, strong impact resistance and high adhesion. CN104974313B discloses a method for preparing WPU based on glycidyl methacrylate, which is to react diisocyanate with macromolecular polyol, small molecule diol and hydrophilic chain extender, and then add end-capping agent to obtain double-bond terminated polyurethane prepolymer, and then add glycidyl methacrylate for copolymerization to obtain a block cationic waterborne polyurethane with controllable epoxy groups. The epoxy groups in its structure can be cured, crosslinked, modified, etc. with amines, polyacids or polyisocyanate compounds to obtain CWPU with smaller particle size, narrower particle size distribution and higher emulsion storage stability.Rao Zhou et al. (Coatings Industry, 2012, 42(11):27-30) used castor oil to synthesize internally cross-linked cationic WPU, which improved the heat resistance of its film.

[0004] In summary, the water resistance and heat resistance of cationic waterborne polyurethane (CWPU) films have been improved to a certain extent by using different crosslinking modification methods. However, the synthesis of a tetrafunctional crosslinker containing tertiary amino groups by reacting glycidol and diethanolamine for the synthesis of cationic waterborne polyurethane has not been reported. Summary of the Invention

[0005] To address the problems of internal crosslinkers without tertiary amine groups, such as increased prepolymer viscosity, difficulty dispersing, larger emulsion particle size, and poor storage stability, this invention synthesized a tetrafunctional crosslinker containing tertiary amino groups for use in the preparation of CWPU. This crosslinker serves the dual functions of increasing the degree of crosslinking and acting as a cationic center. It exhibits excellent dispersion stability and water and solvent resistance, and is expected to find applications in fabric finishing (for color fixation, shrinkage prevention, and pilling prevention) and as a primer for difficult-to-adhere metals.

[0006] The present invention utilizes the reaction of the epoxy groups in the glycidol (GLY) structure with the amino groups in diethanolamine (DEOA) to produce a tetrafunctional crosslinker containing tertiary amino groups for use as an internal crosslinker in the synthesis of CWPU. While diethanolamine and triethanolamine (TEOA) can also be used as crosslinkers, the different reactivity of the amino and hydroxyl groups in their structures can easily lead to gel formation during prepolymer synthesis. The crosslinker synthesized in the present invention contains three primary hydroxyl groups, one secondary hydroxyl group, and one tertiary amino group. By rationally combining this crosslinker with the hydrophilic chain extender N-methyldiethanolamine, a prepolymer with moderate viscosity can be obtained. After neutralization and dispersion, a transparent or translucent emulsion with small particle size and excellent dispersion stability is obtained, thus achieving the invention's objectives.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for synthesizing an internally cross-linked cationic waterborne polyurethane emulsion comprises the following steps:

[0009] Step 1: react glycidol (GLY) and diethanolamine (DEOA) until the infrared spectrum shows a peak at 908 cm -1 and 845cm -1 The epoxy groups disappear, the reaction stops, and a light yellow viscous liquid product EDEOA (N, N-dihydroxyethyl-2-hydroxypropanolamine) is obtained, which is a tertiary amino crosslinking agent;

[0010] Step 2: adding the dehydrated polyol and diisocyanate into a reactor, heating and maintaining the reaction under stirring to obtain an isocyanate-terminated prepolymer;

[0011] Step 3, then adding a solvent, the tertiary amino crosslinking agent obtained in step 1, the tertiary amino small molecule alcohol amine chain extender and the catalyst to react, and after the reaction is completed, a polyurethane intermediate containing an ionized group is obtained; analyzing the NCO% content by di-n-butylamine back titration method and cooling after reaching the theoretical value;

[0012] Step 4, adding a neutralizing agent to the reaction system to carry out a neutralization reaction, and cooling the system after the reaction is completed;

[0013] Step 5, slowly adding deionized water to the reaction system under rapid stirring and uniformly dispersing the mixture, heating the mixture, and removing the solvent in vacuo to obtain a transparent or translucent cationic waterborne polyurethane emulsion;

[0014] The reaction formula of the EDEOA is:

[0015]

[0016] Furthermore, in step 1, the molar ratio of glycidol to diethanolamine is 1:1.05-1.10; in step 2, the molar ratio of polyol to diisocyanate is 3-3.6:1; and in step 3, the molar ratio of tertiary amino crosslinking agent to tertiary amino chain extender is 0.05-0.1:0.75.

[0017] Furthermore, the reaction temperature in step 1 is room temperature to 60°C, and the reaction time is 3 to 6 hours; the reaction temperature in step 2 for the heating and insulation reaction is 70 to 90°C, and the reaction time is 2 to 3 hours; the reaction temperature in step 3 is 50 to 70°C, and the reaction time is 2 to 3 hours; and the cooling in step 3 is to reduce the temperature to 40 to 60°C.

[0018] Furthermore, the neutralization reaction temperature in step 4 is 40-60°C and the time is 20-40 minutes; and the cooling in step 4 is to reduce the temperature to 30-40°C.

[0019] Furthermore, the heating temperature in step 5 is 40-60° C., the temperature for removing the solvent in step 5 is 40-60° C., and the removal time is 60-90 min.

[0020] The temperature range selected in each step is based on considerations of reaction efficiency, operational processability and energy consumption.

[0021] Furthermore, the polyol in step 2 is polyester diol; and the diisocyanate in step 2 is aliphatic diisocyanate or aromatic diisocyanate.

[0022] Polyester diol is one of the main raw materials for synthesizing polyurethanes. However, the performance requirements vary depending on the application, and the type of polyol selected also varies. In the synthesis of cationic polyurethanes, in order to improve the water and solvent resistance of the film, the selected polyol has strong crystallinity. This not only gives the film better mechanical properties, but also improves the film's water and solvent resistance.

[0023] Furthermore, the solvent in step 3 is one of acetone, butanone, dimethylformamide or N-methylpyrrolidone; the tertiary amino small molecule alcohol amine chain extender in step 3 is one of N-hydroxyethylpiperazine, N-methyldiethanolamine, and N-ethyldiethanolamine; the catalyst in step 3 is one of dibutyltin dilaurate, stannous octoate or triethylenediamine; and the neutralizer in step 4 is one of glacial acetic acid, glycolic acid or acetic anhydride.

[0024] Furthermore, the hydroxyl value of the product in step 1 is 1260-1280; the molecular weight range of the polyol in step 2 is 1000-2000; the amount of the catalyst added in step 3 is 5-50 ppm of the total reactants; and the amount of deionized water added in step 5 is measured based on a solid content of 25%-35%.

[0025] Furthermore, the polyester diol is one of polyadipate, poly-ε-caprolactone diol or polycarbonate diol; the aliphatic diisocyanate is 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H 12 The aromatic diisocyanate is one of toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI).

[0026] Furthermore, the polyadipate is one of polyethylene adipate (PEA), polybutylene adipate (PBA), polyethylene adipate-propylene glycol ester (PEPA), polyethylene adipate-butylene glycol ester (PEBA), polyethylene adipate (PHA) or polyethylene adipate-neopentyl glycol ester; the polyε-caprolactone diol is one of PCL-210N or PCL-220N; the polycarbonate diol is one of polyethylene glycol carbonate (such as PCDL-6001, PCDL-6002) or polyethylene glycol pentanediol carbonate (such as PCDL-5651, PCDL-5652) or a mixture of any proportions.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The raw materials of this method are easy to obtain and the cost is low;

[0029] 2. The synthesized N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) is characterized by containing four hydroxyl functional groups and one tertiary amino group. The synthesized tertiary amine crosslinker is a viscous liquid, which is easy to handle. Its multiple functional groups allow the introduction of more crosslinking points with less crosslinker to enhance mechanical properties and improve water and solvent resistance. The tertiary amino groups of the crosslinker and the chain extender are simultaneously neutralized to form quaternary ammonium salt ions, making the emulsion stability of CWPU significantly better than that of CWPU modified with epoxy and silane coupling agents.

[0030] 3. It has a high solid content (≥25wt%), a film tensile strength of 4.0-12.0MPa, an elongation at break >300%, a water absorption rate ≤20wt%, a swelling rate in ethyl acetate ≤50wt%, and a swelling rate in acetone ≤40wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 IR spectra of glycidol (GLY), diethanolamine (DEOA) and N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) in the present invention. DETAILED DESCRIPTION

[0032] The polyols (polyester / and polyether diols) used in the following examples were dehydrated at 120° C. and a vacuum degree of -0.09 to -0.095 MPa for 2 h before use, and then sealed and stored for later use.

[0033] The solvents used in the following examples were treated with molecular sieves for 3 hours of water absorption before use. The reactor was equipped with a stirrer, a thermometer and a condenser.

[0034] The performance tests in the following embodiments are:

[0035] (1) Particle size test: The particle size of the emulsion was measured by a winner2005B laser particle size analyzer produced by Jinan Micro-Nano Particle Instrument Co., Ltd.

[0036] (2) Viscosity determination: The viscosity of the emulsion was measured using a rotational viscometer NDJ-1.

[0037] (3) Mechanical properties test

[0038] Slowly pour 40-50g of the prepared emulsion into a 100×100×1.5mm glass mold, bake under an infrared lamp for 12-24 hours, and then dry in a vacuum oven at 30-60°C for 2-4 hours to obtain a WPU film with a thickness of 0.5-1.0mm. After standing at room temperature for one to two weeks, measure its mechanical properties according to the national standard GB / T528-1992.

[0039] (4) Liquid resistance test

[0040] Water and solvent resistance tests were conducted in accordance with the national standard GB / T1690-2010. The sample size was 25 × 25 × (0.5-1) mm, the test temperature was room temperature, and the immersion time was 24 hours.

[0041] Example 1

[0042] Step 1: glycidol and diethanolamine were added into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser in a molar ratio of 1:1.05, and reacted at room temperature to 60°C for 3 to 6 hours. The infrared spectrum was analyzed at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1265;

[0043] Step 2: adding 0.04 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 85° C. with stirring and keeping the temperature for 2 hours to obtain an isocyanate-terminated prepolymer;

[0044] Step 3: 30 g of acetone, 0.0042 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.0512 mol of N-methyldiethanolamine (MDEA) chain extender, and 30 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 60° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained; the NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value;

[0045] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 30 minutes. After the reaction is completed, cool to 40°C.

[0046] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0047] The CWPU emulsion has a solid content of 25.9wt%, a viscosity of 40mPa·s, and a storage stability of more than 6 months. The film has a tensile strength of 7.94MPa and an elongation at break of 577%. The film has a water absorption of 18.07wt%, and exhibits swelling ratios of 21.15wt% in acetone and 49.78wt% in ethyl acetate.

[0048] Example 2

[0049] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277;

[0050] Step 2: adding 0.04 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 80° C. with stirring and keeping the temperature for reaction for 2 hours to obtain an isocyanate-terminated prepolymer;

[0051] Step 3: 30 g of butanone, 0.0036 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.053 mol of N-methyldiethanolamine (MDEA) chain extender, and 40 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 55° C. for 2 h. After the reaction, the NCO% content was analyzed by back titration with di-n-butylamine until it reached the theoretical value and the temperature was lowered to 50° C.;

[0052] Step 4: Add 0.057 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 50°C;

[0053] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed, the temperature is raised to 60° C., and the solvent is removed under vacuum at 60° C. for 60 minutes to obtain a blue transparent CWPU emulsion.

[0054] The emulsion has a solids content of 26.7 wt%. Its viscosity is 222.5 mPaS. The film exhibits a tensile strength of 4.08 MPa and an elongation at break of 644%. The film has a water absorption of 20.0 wt%. Its swelling ratios in acetone and ethyl acetate are 39.12 wt%, and 48.14 wt%.

[0055] Example 3

[0056] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277.

[0057] Step 2: adding 0.015 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.015 mol of dehydrated polycarbonate diol (PCDL-5652, molecular weight 2000) and 0.09 mol of 1,6-hexamethylene diisocyanate (HDI) to a reactor, heating to 85° C. with stirring and keeping the temperature for 2 hours to prepare an isocyanate-terminated prepolymer;

[0058] Step 3: 30 g of butanone, 0.0034 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.037 mol of N-methyldiethanolamine (MDEA) chain extender, and 40 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 55° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained; the NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value;

[0059] Step 4: Add 0.04 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 35°C;

[0060] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0061] The emulsion has a solids content of 29.8 wt %. Its viscosity is 270 mPaS. The film exhibits a tensile strength of 5.2 MPa and an elongation at break of 348%. The film has a water absorption rate of 11.48%, and a swelling rate of 31.15 wt % in acetone and 45.32 wt % in ethyl acetate.

[0062] Example 4

[0063] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277;

[0064] Step 2: adding 0.025 mol of dehydrated polycarbonate diol (PCDL-6002, molecular weight 2000) and 0.09 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 85° C. with stirring and keeping the temperature for 2 hours to obtain an isocyanate-terminated prepolymer;

[0065] Step 3: 30 g of butanone, 0.0032 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.031 mol of N-methyldiethanolamine (MDEA) as a chain extender, and 60 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 55° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained; the NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value;

[0066] Step 4: Add 0.034 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 35°C;

[0067] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 55° C., and the solvent is removed under vacuum at 55° C. for 60 minutes to obtain a blue transparent CWPU emulsion.

[0068] The emulsion has a solid content of 27.6 wt %. Its viscosity is 30 mPaS. The film exhibits a tensile strength of 8.52 MPa and an elongation at break of 605%. The film has a water absorption rate of 9.94%. Its swelling ratios in acetone and ethyl acetate are 25.88 wt %, and 40.36 wt %.

[0069] Example 5

[0070] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277.

[0071] Step 2: 0.04 mol of dehydrated poly-ε-caprolactone diol (PCL-210N, molecular weight 1000) and 0.12 mol of toluene diisocyanate (TDI) were added to a reactor, heated to 80° C. with stirring and kept warm for 2 hours to obtain an isocyanate-terminated prepolymer;

[0072] Step 3: 60 g of butanone, 0.0042 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.0512 mol of N-methyldiethanolamine (MDEA) chain extender, and 20 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 55° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained; the NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value;

[0073] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; then cool to 35°C;

[0074] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed, and the temperature is raised to 45° C.; and the solvent is removed under vacuum at 45° C. for 85 minutes to obtain a blue transparent CWPU emulsion.

[0075] The emulsion has a solids content of 29.9 wt% and a viscosity of 80 mPaS. The film exhibits a tensile strength of 11.27 MPa and an elongation at break of 532.3% at room temperature. The film has a water absorption rate of 3.06%, and a swelling rate of 37.78 wt% in acetone and 49.76 wt% in ethyl acetate.

[0076] Example 6

[0077] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277;

[0078] Step 2: adding 0.04 mol of dehydrated poly(1,4-butylene adipate) (PBA, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 85° C. with stirring and keeping the temperature for 2 hours to obtain an isocyanate-terminated prepolymer;

[0079] Step 3: 50 g of acetone, 0.0042 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.0512 mol of N-methyldiethanolamine (MDEA) as a chain extender, and 20 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 60° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained. The NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value.

[0080] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 30 minutes. After the reaction is completed, cool to 40°C.

[0081] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0082] The emulsion has a solid content of 28.05 wt %. Its viscosity is 12.5 mPaS. The film exhibits a tensile strength of 6.46 MPa and an elongation at break of 858.75%. The film has a water absorption rate of 9.83%. Its swelling ratio in acetone is 19.14 wt %, and in ethyl acetate it is 34.09 wt %.

[0083] Example 7

[0084] Step 1: add glycidol and diethanolamine in a molar ratio of 1:1.1 into a 500 mL three-necked flask equipped with a thermometer, a mechanical stirrer and a reflux condenser, and react at room temperature to 60°C for 3 to 6 hours. The infrared spectrum analysis shows that the concentration of glycidol at 908 cm -1 and 845cm -1 The epoxy groups disappear and the reaction stops (see Figure 1 ) to obtain the target product N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA) as a light yellow viscous liquid with an analytical hydroxyl value of 1277;

[0085] Step 2: 0.04 mol of dehydrated polycarbonate diol (PCDL-5651, molecular weight 1000) and 0.14 mol of toluene diisocyanate (TDI) were added to a reactor, heated to 80° C. with stirring and kept warm for 2 hours to obtain an isocyanate-terminated prepolymer;

[0086] Step 3: 30 g of acetone, 0.0085 mol of N,N-dihydroxyethyl-2-hydroxypropanolamine (EDEOA), 0.062 mol of N-methyldiethanolamine (MDEA) as a chain extender, and 5 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 60° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained. The NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 40° C. after reaching the theoretical value.

[0087] Step 4: Add 0.0705 mol of glacial acetic acid to the reaction system and neutralize at 40°C for 20 minutes. After the reaction is completed, cool to 30°C.

[0088] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed, the temperature is raised to 40° C., and the solvent is removed under vacuum at 40° C. for 90 minutes to obtain a blue transparent CWPU emulsion.

[0089] The emulsion has a solids content of 25.7 wt %. Its viscosity is 1080 mPaS. The film exhibits a tensile strength of 9.26 MPa and an elongation at break of 465.6% at room temperature. The film has a water absorption rate of 10.10%. Its swelling ratios in acetone and ethyl acetate are 37.65 wt %, and 39.16 wt %.

[0090] Comparative Example 1

[0091] Step 1: Substitute commercial diethanolamine (DEOA) for the synthetic product of Example 1;

[0092] Step 2: adding 0.04 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 80° C. with stirring and keeping the temperature for reaction for 2 hours to obtain an isocyanate-terminated prepolymer;

[0093] Step 3: 30 g of acetone, 0.0042 mol of diethanolamine (DEOA), 0.0512 mol of N-methyldiethanolamine (MDEA) as a chain extender, and 30 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 55° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained. The NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value.

[0094] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 40°C;

[0095] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0096] The emulsion has a solids content of 29.02 wt%. Its viscosity is 35 mPaS. The film exhibits a tensile strength of 1.81 MPa and an elongation at break of 236.9% at room temperature. Its water absorption is 31.18%. Its swelling ratio in acetone is -25.5 wt%, and in ethyl acetate it is 50.53 wt%.

[0097] Comparative Example 2

[0098] Step 1: Substitute commercial triethanolamine (TEOA) for the synthetic product of Example 1;

[0099] Step 2: adding 0.04 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) into a reactor, heating to 85° C. with stirring and keeping the temperature for 2 hours to obtain an isocyanate-terminated prepolymer;

[0100] Step 3: 30 g of acetone, 0.0042 mol of triethanolamine (EDEOA), 0.0512 mol of N-methyldiethanolamine (MDEA) as a chain extender, and 30 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 60° C. for 2 h. After the reaction, a polyurethane intermediate containing an ionized group was obtained. The NCO% content was analyzed by back titration with di-n-butylamine, and the temperature was lowered to 50° C. after reaching the theoretical value.

[0101] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 40°C;

[0102] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0103] The emulsion has a solids content of 30 wt% and a viscosity of 490 mPaS. The film exhibits a tensile strength of 2.8 MPa and an elongation at break of 93.3% at room temperature. The film has a water absorption rate of 31.36% and a swelling rate of -32.81 wt% in acetone and -34.73 wt% in ethyl acetate.

[0104] Comparative Example 3

[0105] Step 1: Instead of using a tertiary amine crosslinking agent, a diol chain extender containing a tertiary amino group is used;

[0106] Step 2: 0.04 mol of dehydrated polycarbonate diol (PCDL-6001, molecular weight 1000) and 0.12 mol of 1,6-hexamethylene diisocyanate (HDI) were added to a reactor, heated to 80° C. with stirring and kept for reaction for 2 hours;

[0107] Step 3: 30 g of acetone, 0.055 mol of N-methyldiethanolamine (MDEA) chain extender, and 30 ppm of dibutyltin dilaurate catalyst (T-12) were added, and the mixture was reacted at 60° C. for 2 h. After the reaction was completed, the NCO% content was analyzed by back titration with di-n-butylamine and the temperature was lowered to 50° C. after reaching the theoretical value.

[0108] Step 4: Add 0.055 mol of glacial acetic acid to the reaction system and neutralize at 50°C for 20 minutes; after the reaction is completed, cool to 40°C;

[0109] Step 5: Deionized water with a solid content of 30% is slowly added to the reaction system under rapid stirring and evenly dispersed. The temperature is raised to 50° C., and the solvent is removed under vacuum at 50° C. for 70 minutes to obtain a blue transparent CWPU emulsion.

[0110] The emulsion has a solids content of 36.92 wt% and a viscosity of 830 mPaS. The film exhibits a tensile strength of 3.82 MPa and an elongation at break of 665.4% at room temperature. The film has a water absorption rate of 40%, dissolves in acetone, and has a swelling rate of 73.71 wt% in ethyl acetate.

[0111] Any matters not described in detail in this specification are prior art known to those skilled in the art. Although the above description of the present invention is based on specific embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion, characterized in that: The following steps are involved: Step 1: react glycidol and diethanolamine until the infrared spectrum shows a peak at 908 cm -1 and 845cm -1 The epoxy groups disappear, the reaction stops, and the product EDEOA, a tertiary amino crosslinking agent, is obtained as a light yellow viscous liquid; Step 2: adding the dehydrated polyol and diisocyanate into a reactor, heating and maintaining the reaction under stirring to obtain an isocyanate-terminated prepolymer; Step 3, then adding a solvent, the tertiary amino crosslinking agent obtained in step 1, the tertiary amino small molecule alcohol amine chain extender and the catalyst to react, and after the reaction is completed, a polyurethane intermediate containing an ionized group is obtained; after the NCO% content reaches the theoretical value by back titration analysis using di-n-butylamine, the temperature is lowered; Step 4, adding a neutralizing agent to the reaction system to carry out a neutralization reaction, and cooling the system after the reaction is completed; Step 5: slowly adding deionized water to the reaction system under rapid stirring and uniformly dispersing the mixture, heating the mixture, and removing the solvent in vacuo to obtain a transparent or translucent emulsion, which is a cationic waterborne polyurethane emulsion; The reaction formula of the EDEOA is: 。 2. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, wherein: The molar ratio of glycidol to diethanolamine in step 1 is 1:1.05-1.10; the molar ratio of polyol to diisocyanate in step 2 is 3-3.6:1; and the molar ratio of tertiary amino crosslinking agent to tertiary amino small molecule alcoholamine chain extender in step 3 is 0.05-0.10:0.

75.

3. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The reaction temperature in step 1 is room temperature to 60°C, and the reaction time is 3 to 6 hours; the reaction temperature in step 2 for the heating and insulation reaction is 70 to 90°C, and the reaction time is 2 to 3 hours; the reaction temperature in step 3 is 50 to 70°C, and the reaction time is 2 to 3 hours; and the cooling in step 3 is to reduce the temperature to 40 to 60°C.

4. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The neutralization reaction temperature in step 4 is 40-60° C. and the reaction time is 20-40 min. The cooling in step 4 is to reduce the temperature to 30-40° C.

5. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The heating temperature in step 5 is 40-60° C., the temperature for removing the solvent in step 5 is 40-60° C., and the removal time is 60-90 minutes.

6. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The polyol in step 2 is polyester diol; and the diisocyanate in step 2 is aliphatic diisocyanate or aromatic diisocyanate.

7. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The solvent in step 3 is one of acetone, butanone, dimethylformamide or N-methylpyrrolidone; the tertiary amino small molecule alcohol amine chain extender in step 3 is one of N-hydroxyethylpiperazine, N-methyldiethanolamine, and N-ethyldiethanolamine; the catalyst in step 3 is one of dibutyltin dilaurate, stannous octoate or triethylenediamine; and the neutralizer in step 4 is one of glacial acetic acid, glycolic acid or acetic anhydride.

8. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 1, characterized in that: The hydroxyl value of the product in step 1 is 1260-1280 mgKOH / g; the molecular weight range of the polyol in step 2 is 1000-2000; the amount of the catalyst added in step 3 is 5-50 ppm of the total reactants; and the amount of deionized water added in step 5 is measured based on a solid content of 25%-35%.

9. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 6, characterized in that: The polyester diol is one of polyadipate, poly-ε-caprolactone diol or polycarbonate diol; the aliphatic diisocyanate is one of 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and xylylenediisocyanate; the aromatic diisocyanate is one of toluene diisocyanate and 4,4'-diphenylmethane diisocyanate.

10. The method for synthesizing an internally cross-linked cationic aqueous polyurethane emulsion according to claim 9, characterized in that: The polyadipate is one of polyethylene adipate, polybutylene adipate, polyethylene adipate-propylene glycol, polyethylene adipate-butylene glycol, polyethylene adipate-hexanediol or polyethylene adipate-neopentyl glycol; the polyε-caprolactone diol is one of PCL-210N or PCL-220N; the polycarbonate diol is one of polyhexanediol carbonate or polyhexanediol pentanediol carbonate or a mixture of any proportions of the poly(hexanediol) carbonate.

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