High-solid-content aqueous polyurethane and its internal-external emulsification preparation method and application

Abstract

The present invention discloses a high-solid-content aqueous polyurethane and an internal-external emulsification preparation method and application thereof, belonging to the technical field of polyurethanes. The present invention uses an internal-external emulsification method to prepare a high-solid-content aqueous polyurethane, which includes: mixing polyether polyol, isocyanate and chain extender, then adding a catalyst, after heating and reacting, cooling, then adding a neutralizing agent, after neutralization reaction, adding an external emulsifier to the system, and after external emulsification reaction, obtaining an aqueous polyurethane; the external emulsifier is an anionic external emulsifier, and the addition amount is 0.1% - 2.0% of the total mass of polyether polyol, isocyanate and chain extender. Under solvent-free conditions, the present invention simultaneously introduces sulfonic acid and carboxylic acid groups into the molecular structure of WPU, combines with an anionic external emulsifier, and significantly improves the solid content and stability of WPU by using the internal-external emulsification method, improves the comprehensive properties such as water absorption performance and mechanical properties, and makes it have good application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethanes, and particularly relates to a high-solid-content aqueous polyurethane and an internal-external emulsification preparation method and application thereof. Background Art

[0002] High-solid-content aqueous polyurethane (WPU) has obvious advantages compared with low-solid-content WPU due to its fast film-forming and drying speed, low energy consumption, high equipment utilization rate, and low transportation cost. However, there are many technical difficulties in its preparation process, among which the most prominent ones are reducing the system viscosity, maintaining the emulsion stability, and controlling the phase inversion point. The combined use of carboxylic acid / sulfonate endows the WPU emulsion with good stability. At the same time, by adjusting the raw material ratio, R value, and the dosage and compounding ratio of sulfonic acid / carboxylic acid hydrophilic chain extenders, the viscosity of the prepolymer is reduced, creating good conditions for the preparation of high-solid-content WPU. However, due to the limited content of hydrophilic groups in the prepolymer, the phase transition point cannot be advanced significantly, so the solid content of the prepared WPU is lower than 40%.

[0003] An external emulsifier is an amphiphilic molecule containing both hydrophilic and lipophilic groups. During emulsification, the external emulsifier can form micelles at the oil-water interface, with its hydrophilic end extending into the water and wrapping the latex particles inside, thus stably suspending them in water. At the same time, the use of an external emulsifier can reduce the surface tension of the dispersed phase and form a thin film or double electric layer on the surface of the droplets of the dispersed phase to prevent the droplets from aggregating and coagulating with each other, thereby improving the emulsion stability.

[0004] CN117003986A discloses an aqueous polyurethane dispersion, and its preparation raw materials include a combination of a prepolymer, a chain extender, and an external emulsifier. The preparation raw materials of the prepolymer include, by weight: 7-15 parts of isocyanate, 25-43 parts of polyol, and 0.2-2 parts of a reactive internal emulsifier. The isocyanate includes 1,5-pentamethylene diisocyanate; the mass percentage content of 1,5-pentamethylene diisocyanate in the isocyanate is ≥30%, and the external emulsifier includes any one or at least two combinations of an anionic surfactant, a cationic surfactant, a nonionic surfactant, polyvinyl alcohol, or water-soluble cellulose. This method studies the effects of the PDI content and NCO / OH ratio in the isocyanate component of the prepolymer on the viscosity, particle size, and solid content of the emulsion, but it does not involve the influence of the type of external emulsifier on the performance of WPU. Summary of the Invention

[0005] The present invention prepares a solvent-free carboxylic acid / sulfonic acid type WPU by introducing an external emulsifier and using an internal-external emulsification combination method, and optimizes the type and dosage of the external emulsifier, etc., to improve the solid content of the aqueous polyurethane and endow the WPU with smaller particle size, higher stability, more excellent water resistance, and mechanical properties.

[0006] The present invention first provides a method for preparing an inner-outer emulsified high-solid-content aqueous polyurethane, which comprises the following steps:

[0007] Mix a polyether polyol, an isocyanate and a chain extender, then add a catalyst, after heating and reacting, cool down, then add a neutralizer, after neutralization reaction, add an external emulsifier to the system, and after external emulsification reaction, obtain an aqueous polyurethane;

[0008] Wherein, the molar ratio of the isocyanate to the total molar amount of the polyether polyol and the chain extender is 1 to 3;

[0009] The chain extender is a combination of chain extender A and chain extender B;

[0010] The chain extender A is at least one of DMPA (2,2-dimethylolpropionic acid) or DMBA (2,2-dimethylolbutyric acid);

[0011] The chain extender B is at least one of BES-Na (N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt) or AAS-Na (2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt);

[0012] The addition amount of the chain extender B accounts for 1 to 20% of the total mass of chain extender A and chain extender B;

[0013] The addition amount of the chain extender accounts for 1% to 5% of the total mass of the polyether polyol, the isocyanate and the chain extender;

[0014] The external emulsifier is an anionic external emulsifier;

[0015] The addition amount of the external emulsifier is 0.1% to 2.0% of the total mass of the polyether polyol, the isocyanate and the chain extender.

[0016] Preferably, in the above preparation method, the chain extender is a combination of DMPA and BES-Na, and the addition amount of BES-Na accounts for 5 to 10% of the total mass of DMPA and BES-Na.

[0017] Preferably, in the above preparation method, the addition amount of the chain extender accounts for 3% to 4% of the total mass of the polyether polyol, the isocyanate and the chain extender.

[0018] Preferably, in the above preparation method, the external emulsifier is SDS (sodium dodecyl sulfate) or LAS (sodium dodecylbenzenesulfonate).

[0019] Preferably, in the above preparation method, the addition amount of the external emulsifier is 1% to 1.5% of the total mass of the polyether polyol, the isocyanate and the chain extender.

[0020] More preferably, in the above preparation method, the addition amount of the external emulsifier is 1.5% of the total mass of the polyether polyol, isocyanate and chain extender.

[0021] Preferably, in the above preparation method, the external emulsifier is added dropwise into the system in the form of an external emulsifier aqueous solution, and the mass concentration of the external emulsifier aqueous solution is 10-20 g / L.

[0022] Among them, in the above preparation method, the polyether polyol is at least one of polyester polyol, polycaprolactone polyol, polycarbonate polyol, polyethylene oxide polyol, polypropylene oxide polyol, ethylene oxide-propylene oxide copolymer polyol, polytetrahydrofuran polyol, poly-1,3-propanediol ether polyol, vegetable oil polyol, polyester amide polyol, polysulfide polyol, polyacetal polyol, polyolefin polyol or polysiloxane polyol.

[0023] Preferably, in the above preparation method, the polyether polyol is polyether N210.

[0024] Among them, in the above preparation method, the number average molecular weight of the polyether polyol is 300-5000.

[0025] Preferably, in the above preparation method, the number average molecular weight of the polyether polyol is 500-1500.

[0026] Among them, in the above preparation method, the isocyanate is at least one of IPDI (isophorone diisocyanate), MDI (diphenylmethane diisocyanate), HDI (hexamethylene diisocyanate), TDI (toluene diisocyanate) or HMDI (dicyclohexylmethane diisocyanate).

[0027] Preferably, in the above preparation method, the isocyanate is IPDI (isophorone diisocyanate).

[0028] Preferably, in the above preparation method, the molar ratio of the isocyanate to the total molar amount of the polyether polyol and the chain extender is 1.3-1.7.

[0029] More preferably, in the above preparation method, the molar ratio of the isocyanate to the total molar amount of the polyether polyol and the chain extender is 1.5.

[0030] Among them, in the above preparation method, the catalyst can be a common catalyst used in the synthesis of aqueous polyurethane in the art, such as dibutyltin dilaurate or organic bismuth catalyst Valikat Bi2010, etc.; the addition amount of the catalyst is generally a catalytic amount added dropwise to the system. Specifically, the addition amount of the catalyst is generally 1-10% of the molar amount of the polyether polyol.

[0031] Among them, in the above preparation method, the neutralizing agent is at least one of alkali metal hydroxides, alkali metal carbonates, 2-amino-2-methyl-1-propanol, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, ammonia water or triethylamine.

[0032] Preferably, in the above preparation method, the neutralizing agent is NaOH, KOH, ammonia water or triethylamine.

[0033] Among them, in the above preparation method, the molar ratio of the neutralizing agent to the chain extender is 0.9 to 1.1.

[0034] Preferably, in the above preparation method, the molar ratio of the neutralizing agent to the chain extender is 0.99 to 1.01.

[0035] Among them, in the above preparation method, the temperature of the temperature-raising reaction is 60 to 100 °C.

[0036] Among them, in the above preparation method, the time of the temperature-raising reaction is 2 to 6 h.

[0037] Among them, in the above preparation method, the temperature reduction is to reduce the temperature to below 30 °C.

[0038] Among them, in the above preparation method, the time of the neutralization reaction is 10 to 60 min.

[0039] Among them, in the above preparation method, the stirring speed of the external emulsification reaction is 200 to 800 rpm.

[0040] Among them, in the above preparation method, the time of the external emulsification reaction is 0.5 to 2 h.

[0041] The present invention also provides a high-solid-content aqueous polyurethane, which is prepared by the above preparation method. The solid content of the aqueous polyurethane is not less than 48%. The aqueous polyurethane has excellent stability, its storage stability > 6 months, and it can be diluted with water in any proportion without precipitation.

[0042] The high-solid-content aqueous polyurethane provided by the present invention has excellent properties. Therefore, the present invention also provides the application of the above aqueous polyurethane in inks, coatings, adhesives or textiles.

[0043] Advantages of the present invention:

[0044] The present invention adopts the method of combining internal-external emulsification, uses carboxylic acid and sulfonate compounds as chain extenders, explores the emulsification effects of non-ionic and anionic external emulsifiers, and the influence of the dosage of external emulsifier on the properties of WPU, and prepares a WPU emulsion with a solid content of about 50%. Under the condition of solvent-free, by introducing sulfonic acid and carboxylic acid into the molecular structure of WPU simultaneously and combining with an anionic external emulsifier, the present invention significantly improves the solid content and stability of WPU, and enhances the comprehensive properties such as water absorption performance and mechanical properties of WPU. The obtained WPU with high solid content can be diluted with water arbitrarily and has good application value. Description of the Drawings

[0045] Figure 1 It is the reaction formula for preparing WPU in the examples.

[0046] Figure 2 It is the particle size distribution diagram of WPU emulsions with different LAS contents.

[0047] Figure 3 It is the infrared analysis spectrum of WPU films with LAS contents of 0 and 1.5%.

[0048] Figure 4 It is the test result diagram of the water absorption performance of WPU films with different LAS contents.

[0049] Figure 5 It is the test result diagram of the mechanical properties of WPU films with different LAS contents. Detailed Embodiments

[0050] The present invention will be further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the described examples.

[0051] The raw materials used in the examples of the present invention are shown in Table 1. All purchased reagents are used directly without secondary purification.

[0052] Table 1 Raw Materials Required for Material Preparation

[0053]

[0054] The analysis and test methods in the examples of the present invention are as follows:

[0055] 1. Fourier transform infrared spectroscopy (FT-IR) test: It is carried out at room temperature, and the scanning range is from 4000 cm -1 to 400 cm -1 .

[0056] 2. Appearance of emulsion: Visually observe the physical forms such as the color, state, and uniformity of the sample. Observe the color of the WPU emulsion and whether there are phenomena such as yellowing, gelation, and delamination.

[0057] 3. Mechanical stability: Add equal masses of the prepared WPU emulsion into the same centrifuge tubes, place them in a centrifuge, and centrifuge at 3000 r / min for 15 min. If the emulsion does not show stratification or precipitation, it proves that the emulsion can be stably stored for more than 6 months.

[0058] 4. Storage stability: Let it stand at room temperature and observe whether there is stratification. The standing stratification time is used as an index for stability determination.

[0059] 5. Determination of solid content: The solid content is tested according to GB1725 - 2007. Weigh 1 - 2 g of the WPU emulsion sample and put it into a dry weighing bottle, then place it in a constant temperature oven at (105 + 2)°C and dry until constant weight (the difference between two weighings is not more than 0.001 g, take the minimum value). The calculation of the solid content of the emulsion is shown in Equation (1), and Equation (1) is: X=(W 1 -W 0 ) / W×100%.

[0060] In Equation (1): X—the solid content of the sample, %; W 1 —the total mass of the dried sample and the weighing bottle, g; W 0 —the mass of the weighing bottle, g; W—the mass of the sample, g.

[0061] 6. Water absorption test: Take the dried WPU film, weigh it to get m 0 , put it into deionized water. After placing it at room temperature for 24 h, take it out, fully blot the residual water on the surface with filter paper, weigh it to get m 1 . Conduct 3 parallel experiments. According to Equation (2), the water absorption of WPU can be calculated. Equation (2) is: Water absorption=(m 1 -m 0 ) / m 0 ×100%.

[0062] In Equation (2): m 0 —the mass of the dried WPU film, g; m 1 —the mass of the WPU film after water absorption, g.

[0063] 7. Particle size test: The particle size of the emulsion is measured by a Zeta potential and nanoparticle size analyzer.

[0064] 8. Differential scanning calorimetry (DSC): It is carried out in an N 2 atmosphere. The sample mass is 6 - 10 mg, the temperature range is - 50 - 150°C, and the heating and cooling rates are 10°C / min.

[0065] 9. Thermogravimetric analysis test (TGA): In N 2It is carried out under an atmosphere, with a heating rate of 20 °C / min, a temperature range of 30 - 700 °C, and the sample weight range is 3 - 10 mg.

[0066] 10. Mechanical property test: According to the standard of GB / T 1040.1 - 2018, the mechanical properties are tested with a microcomputer-controlled electronic universal testing machine, the tensile rate is 50 mm / min, and the average value is taken after repeating 5 times.

[0067] 11. Pencil hardness: The pencil hardness of the WPU coating is tested according to the method of GB / T6739 - 1996, and the test range is: 6H - 6B. Place the coating sample horizontally and fix it. Fix the pencil on the trolley, which is at a 45° angle to the coating surface. Push the trolley to make the pencil leave a scratch on the coating surface, and observe the damage degree of the coating surface after cleaning with a soft brush.

[0068] 12. Adhesion: The adhesion grade of the coating is tested according to the method of GB / T9286 - 1998. Use a cross cutter to draw grids on the coating at an interval of 1 mm. Subsequently, use 3M tape to closely adhere to the coating film surface, and then tear off the tape at a stable speed. By observing the number of peeled grids on the paint film, the adhesion grade of the paint film can be evaluated. The adhesion grade is divided into six grades, namely 0, 1, 2, 3, 4, 5, where grade 0 represents the best adhesion. The judgment criteria are shown in Table 2.

[0069] Table 2 Classification of Adhesion Test Results

[0070]

[0071] 13. Contact angle test (CA): The hydrophobicity of the WPU film surface is tested using a contact angle tester. The average value is taken after five tests.

[0072] Experimental method of the embodiment of the present invention:

[0073] 1. Preparation of WPU emulsion by internal-external emulsification combination method:

[0074] The synthesis process is as Figure 1 shown. Polyether N210 is dehydrated by heating under reduced pressure and then reserved. According to Table 3, the metered polyether N210, IPDI, DMPA, and BES-Na are added to a three-necked flask, and dibutyltin dilaurate is added dropwise at one time. The reaction is carried out at 80 °C for 4 h. After the reaction is completed, the temperature is lowered to below 30 °C, and the metered TEA is added, and the reaction is carried out for 30 min. After neutralization, the external emulsifier (fatty alcohol polyoxyethylene ether, polyethylene glycol dioleate, SDS or LAS, mass concentration 15 g / L) dissolved in water is slowly and uniformly added dropwise within 5 min, and sheared under high-speed stirring for 1 h to obtain the WPU emulsion.

[0075] Table 3 Formulations of WPU with Different R Values

[0076]

[0077] In Table 3, the calculation method of the raw material dosage is as follows:

[0078] (1). First, specify the R value, determine the dosages of polyether N210, DMPA, and BES-Na, and calculate the dosage of IPDI using the R value to ensure that W 扩链剂 % = 2% - 5%; R = -NCO / -OH, that is, the molar ratio of IPDI to the total molar amount of polyether N210, DMPA, and BES-Na, and W 扩链剂 % = (m DMPA + m BES-Na ) / m 预聚物 , m 预聚物 = m 聚醚N210 + m IPDI + m DMPA + m BES-Na , where m represents mass with the unit g.

[0079] (2). The dosage of dibutyltin dilaurate is about 0.3 g each time. Dibutyltin dilaurate is a catalyst, and it is only necessary to ensure that the dosage is basically the same each time.

[0080] (3). TEA is a neutralizing agent, and its molar amount is consistent with the total molar amount of DMPA and BES-Na.

[0081] (4). The addition amount of the external emulsifier W 外乳化剂 % = 0, 0.5%, 1.0%, 1.5% or 2.0%, and W 外乳化剂 % = m 外乳化剂 / m 预聚物 .

[0082] 2. Preparation of WPU film:

[0083] At room temperature, pour the emulsion evenly into a 1 cm × 8 cm polytetrafluoroethylene plate, dry at room temperature for 48 h, and then place it in a vacuum oven at 80 °C for drying to obtain the WPU film, which is stored for later use.

[0084] Example 1: Influence of the type of external emulsifier on the properties of WPU emulsion and film

[0085] Using DMPA and BES-Na as chain extenders, maintaining R = 1.5, neutralization degree 100%, BES-Na accounting for 6% of the total amount of chain extenders, and the total content of chain extenders (W 扩链剂 % = m 扩链剂 / m 预聚体The content is about 3.55%. Fatty alcohol polyoxyethylene ether (AEO-9), polyethylene glycol dioleate (Emerest2648), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (LAS) were respectively selected as external emulsifiers. Keeping the dosage of the external emulsifier at 1.5% of the total mass of the prepolymer, the influence of the type of external emulsifier on the properties of WPU is shown in Table 4.

[0086] Table 4 Influence of the type of external emulsifier on the properties of WPU

[0087]

[0088] As can be seen from Table 4, the use of external emulsifiers significantly increased the solid content of WPU. The solid content of WPU prepared by the internal-external emulsification method was maintained at about 50%. This is because during emulsification, the lipophilic end-chain structure in the external emulsifier can be better miscible with the polymer, and its hydrophilic end can interact with water molecules, improving the hydrophilicity of the prepolymer, facilitating the advance of the phase transition point, and thus increasing the solid content of WPU. The appearance of WPU with anionic external emulsifiers (LAS, SDS) is better than that of WPU with non-ionic external emulsifiers (AEO-9, Emerest2648). This is because anionic external emulsifiers can ionize in water, forming a stable double electric layer on the surface of latex particles. Due to the electrostatic repulsion, the latex particles can be more stably suspended in water, which is more conducive to the formation of emulsions with smaller particle sizes. Macroscopically, the emulsion appears milky white with a slight blue light. The stability of WPU synthesized with Emerest2648 as the external emulsifier is poor because the HLB (hydrophilic-lipophilic balance) value of Emerest2648 is small [HLB (LAS) = 10.6, HLB (SDS) = 40, HLB (AEO-9) = 12.5, HLB (Emerest2648) = 7.5], and its emulsifying performance is poor, resulting in poor stability of the WPU emulsion.

[0089] Example 2: Influence of the content of external emulsifier on the properties of WPU emulsion and film

[0090] 1. Considering the emulsion properties comprehensively, on the basis of Example 1, LAS was selected as the external emulsifier, and the other conditions remained unchanged. Only the dosage of the external emulsifier (w LAS % = m LAS / m 预聚体 ) was changed. Then, the influence of the content of the external emulsifier on the properties of the WPU emulsion and film is shown in Table 5.

[0091] Table 5 Influence of the content of external emulsifier on the properties of WPU

[0092]

[0093] As can be seen from Table 5, as the amount of external emulsifier increases, the appearance of the emulsion gradually changes from milky white to milky white with a slight blue tint, the stability gradually increases, and the solid content increases. This is because the content of hydrophilic groups in the WPU prepolymer is relatively small. Without adding an external emulsifier, when the solid content is controlled above 50%, the prepolymer cannot be successfully emulsified, and phenomena such as flocculation may occur, resulting in poor emulsion stability. After adding the external emulsifier, the hydrophilicity of the prepolymer increases, and the emulsification performance improves. As the amount of external emulsifier increases, the prepolymer is more easily dispersed into latex particles with smaller particle sizes, and the macroscopic manifestation is that the emulsion has a slight blue tint and enhanced stability. It is worth mentioning that when the addition amount of the external emulsifier reaches more than 1.5%, the solid content of the emulsion tends to be stable. This is because when the amount of the external emulsifier increases to a certain value, the critical micelle concentration is reached. After reaching this concentration, the surface tension of the emulsion tends to be stable, with little change, and the emulsification effect improvement is not obvious. Therefore, selecting the external emulsifier dosage near the critical micelle concentration can maximize the emulsification effect.

[0094] 2. Detect the particle size of the WPU emulsion synthesized in this example. The influence of different external emulsifier contents on the particle size of the WPU emulsion is shown in Table 6 and Figure 2 as follows.

[0095] Table 6 Average particle size of WPU emulsions with different external emulsifier contents

[0096]

[0097] As can be seen from Table 6 and Figure 2 it can be known that the particle size of the WPU emulsion synthesized in this example shows a single-peak distribution, and its distribution range gradually narrows with the increase of the external emulsifier content. As the external emulsifier content increases, the average particle size of the emulsion decreases from 320.58 nm to 148.19 nm. This is because the particle size of the emulsion is affected by various factors such as the hydrophilicity of the prepolymer, molecular weight, and shear speed. When other factors are controlled unchanged, the influence of the hydrophilicity of the prepolymer on the particle size dominates. With the increase of the external emulsifier content, the hydrophilicity of the WPU prepolymer increases, the number of charged ionic groups on the surface of the latex particles increases, and it is more easily dispersed into smaller latex particles. The emulsion particle size decreases, and at the same time, the size of the latex particles is more uniform, and the emulsion particle size distribution narrows.

[0098] 3. Conduct infrared analysis on the WPU films obtained when the w LAS % is 0 and 1.5%. The results are as Figure 3 follows.

[0099] As Figure 3It can be seen that the characteristic peak positions of the WPU prepared by the internal-external emulsification method are basically the same as those of the WPU prepared by the internal emulsification method, indicating the successful synthesis of the WPU. Compared with the infrared spectrum of the WPU without external emulsifier, the infrared spectrum of the WPU with external emulsifier shows slight shifts and enhancements at wavelengths of 3326 cm -1 、1709 cm -1 、1094 cm -1 、1019 cm -1 . This is caused by the overlap of the characteristic peaks of LAS. The infrared spectrum of the WPU containing external emulsifier does not show new characteristic absorption peaks, indicating that no new chemical bonds are formed between LAS and WPU, and there is only physical adsorption and embedding of the external emulsifier on the latex particles.

[0100] 4. Detect the water absorption performance of the WPU film synthesized in this example. The influence of different external emulsifier contents on the water absorption performance of the WPU film is as Figure 4 shown.

[0101] It can be seen from Figure 4 that as the content of the external emulsifier increases, the water absorption rate of each sample shows a trend of first decreasing and then increasing, while the water contact angle shows a trend of first increasing and then decreasing. This is because the external emulsifier is a surfactant. During the process of emulsion drying into a film, the external emulsifier tends to aggregate on the surface of the film, preventing water molecules from entering the interior of the film. However, the improvement of the water resistance of the film by the external emulsifier is limited. The external emulsifier LAS used in this example is sulfonate, and sulfonic acid is a medium-strong acid in organic substances with good ionization performance and good water solubility in aqueous solution. The increase in its dosage will increase the hydrophilicity of the film, resulting in an increase in the water absorption rate of the WPU film with the increase of its content and a decrease in the water contact angle.

[0102] 5. Detect the mechanical properties of the WPU film synthesized in this example. The influence of different external emulsifier contents on the mechanical properties of the WPU film is as Figure 5 shown.

[0103] It can be seen from Figure 5 that as the dosage of the external emulsifier increases, the tensile strength of the film decreases slightly, and the elongation at break first rises slightly and then decreases. This is because LAS is added to the WPU as an additive, which can improve the emulsion performance. However, as its addition amount gradually increases, it may interfere with the interaction between polyurethane segments, reduce the entanglement of molecular segments and the hydrogen bond interaction between molecules, resulting in a decrease in the mechanical properties of the WPU film. At the same time, if the addition amount of LAS is too large, problems such as uneven dispersion may occur, resulting in the formation of a small number of defects in the film and a decrease in mechanical properties.

[0104] In summary, by introducing an external emulsifier and using the internal-external emulsification combination method to prepare solvent-free carboxylic acid / sulfonic acid type WPU, the solid content of the WPU emulsion can be significantly increased (from 38% to 50%); the emulsification effect of anionic external emulsifiers is significantly better than that of non-ionic external emulsifiers. Among them, the solid content of WPU prepared with LAS as the external emulsifier is slightly higher than that of WPU prepared with SDS as the external emulsifier; the use of external emulsifiers gives the WPU emulsion smaller particle size and higher stability, but an increase in its dosage is not conducive to the improvement of the water resistance and mechanical properties of the film. When LAS is used as the external emulsifier and the dosage is 1.5%, the solid content of the WPU emulsion reaches 51.41%, the average particle size of the WPU emulsion is 189.15 nm, the tensile strength of the WPU film is 1.6 Mpa, the elongation at break is 610.7%, the hardness reaches 5H, and the adhesion grade is 0, with the best comprehensive performance.

Claims

1. An internal-external emulsification method for preparing high solid content waterborne polyurethane, characterized in that: The following steps are involved: The polyether polyol, isocyanate and chain extender are mixed, and then a catalyst is added, and after the temperature is raised for reaction, the temperature is lowered, and then a neutralizer is added. After the neutralization reaction, an external emulsifier is added to the system, and after the external emulsification reaction, a waterborne polyurethane is obtained; Wherein, the ratio of the molar amount of the isocyanate to the total molar amount of the polyether polyol and the chain extender is 1.5 to 1.7; The chain extender is a combination of DMPA and BES-Na, and the amount of BES-Na added accounts for 5-10% of the total mass of DMPA and BES-Na; The amount of the chain extender added is 1% to 5% of the total mass of the polyether polyol, isocyanate and chain extender; The external emulsifier is LAS; The amount of the external emulsifier added is 1% to 1.5% of the total mass of the polyether polyol, isocyanate and chain extender; The polyether polyol is polyether N210; The isocyanate is IPDI; The catalyst is dibutyltin dilaurate.

2. The method for preparing high solid content waterborne polyurethane by internal-external emulsification according to claim 1, characterized in that: The added amount of the chain extender accounts for 3% to 4% of the total mass of the polyether polyol, isocyanate and the chain extender.

3. The method for preparing high solid content waterborne polyurethane by internal-external emulsification according to claim 1, characterized in that: The external emulsifier is added dropwise into the system in the form of an aqueous solution of the external emulsifier, and the mass concentration of the aqueous solution of the external emulsifier is 10-20 g / L.

4. The method for preparing high solid content waterborne polyurethane by internal-external emulsification according to claim 1, characterized in that: At least one of the following is met: The neutralizing agent is at least one of 2-amino-2-methyl-1-propanol, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, ammonia water or triethylamine; The molar ratio of the neutralizing agent to the molar ratio of the chain extender is 0.9 to 1.

1.

5. The method for preparing high solid content waterborne polyurethane by internal-external emulsification according to claim 1, characterized in that: At least one of the following is met: The temperature of the temperature-raising reaction is 60-100°C; The temperature reaction time is 2 to 6 hours; The cooling is to cool to below 30°C; The neutralization reaction time is 10 to 60 minutes; The stirring speed of the external emulsification reaction is 200-800 rpm; The time of the external emulsification reaction is 0.5 to 2 hours.

6. The waterborne polyurethane prepared by the internal-external emulsification preparation method of high solid content waterborne polyurethane according to any one of claims 1 to 5 is characterized in that: The solid content of the obtained waterborne polyurethane is not less than 48%.

7. Use of the aqueous polyurethane prepared by the internal-external emulsification preparation method of the high-solid content aqueous polyurethane according to any one of claims 1 to 5 or the aqueous polyurethane according to claim 6 in inks, coatings, adhesives or textiles.

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