Degradable waterborne polyurethane emulsion and preparation method thereof
By introducing polylactic acid-polyester polyol copolymers and polyols with specific molecular weights, an organic polymer network is constructed, solving the problems of slow degradation and performance decline in traditional waterborne polyurethane emulsions. This results in high-performance and biodegradable waterborne polyurethane emulsions, expanding their application areas.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-15
- Publication Date
- 2026-04-10
AI Technical Summary
Traditional waterborne polyurethane emulsions degrade at extremely low rates in the natural environment, leading to microplastic accumulation and environmental pollution. Furthermore, biodegradable modifiers reduce the strength and film-forming properties of the emulsion, limiting its application in high-performance coatings and biomedicine.
By introducing polylactic acid-polyester polyol copolymers with specific molecular weights and combining them with polyols of different molecular weights, such as polypropylene adipate diol and polycarbonate diol, an organic polymer network is constructed to improve the biodegradability and film-forming properties of the emulsion.
This achievement enables waterborne polyurethane emulsions to exhibit high degradability, excellent mechanical properties, and good film-forming properties, expanding their applications in high-performance coatings and biomedicine, and aligning with the principles of green chemistry.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of polyurethane, and particularly relates to a degradable waterborne polyurethane emulsion and a preparation method thereof. BACKGROUND
[0002] The waterborne polyurethane emulsion has become one of the core materials in the fields of coatings, adhesives, leather processing, etc. due to its excellent film-forming performance, outstanding flexibility and strong adhesion. However, the rigidly connected main chain structure in the traditional waterborne polyurethane endows it with extremely strong chemical stability, hydrolysis resistance and anti-microbial erosion ability, resulting in extremely low degradation rate and extremely long complete mineralization process under natural conditions such as soil burial and marine environment. This stubborn non-biodegradability not only causes long-term retention and accumulation of microplastics and organic fragments in the ecological system, but also directly violates the core requirement of material sustainability of the green chemistry principle. At present, a large number of waste polyurethane products (such as foam packaging, disposable medical substrates, waste shoe sole synthetic leather, fishing equipment, etc.) are accumulated in large quantities in landfills, and continuously migrate to marine ecological systems through hydrological cycle, forming a cross-media pollution chain, which has become a global environmental governance challenge.
[0003] In order to solve the above problems, people have been trying to explore the preparation method of a new degradable waterborne polyurethane emulsion. Among them, the introduction of degradable polymers can effectively improve the environmental degradation activity of the waterborne polyurethane emulsion. However, the prepared degradable waterborne polyurethane emulsion often leads to the decrease of emulsion strength and film-forming performance, so it still faces significant limitations in industrial application. For example, the insufficient mechanical strength of the waterborne polyurethane emulsion limits the durability; defects are easily produced in the film-forming process, affecting the uniformity and surface integrity of the coating.
[0004] Therefore, the above-mentioned inherent defects seriously restrict the expanded application of the new degradable waterborne polyurethane emulsion in high-performance coating, degradable packaging and biomedical high-value-added scenarios. SUMMARY
[0005] In order to improve the mechanical strength and film-forming performance of the degradable waterborne polyurethane emulsion, the present application provides a degradable waterborne polyurethane emulsion and a preparation method thereof.
[0006] According to one aspect of the present application, a degradable waterborne polyurethane emulsion is provided. The raw materials for preparing the waterborne polyurethane emulsion include 10-20% diisocyanate and 75-85% polyol, calculated by mass percentage. The polyol includes polylactic acid-polyester polyol copolymer, polypropylene adipate diol and polycarbonate diol. The molecular weight of the polylactic acid-polyester polyol copolymer is 5000-15000; the molecular weight of the polypropylene adipate diol is 1500-2000; and the molecular weight of the polycarbonate diol is 1500-2000.
[0007] The present application introduces polylactic acid polyester polyol copolymer and cooperates with polyols of different molecular weight gradient to prepare water-based polyurethane, and the organic polymer network constructed not only gives the polyurethane emulsion good degradability, but also significantly improves the strength and film-forming property of the water-based polyurethane emulsion. This is likely because the entangled network formed by high molecular weight and low molecular weight polyols can not only improve the strength of the organic polymer network, but also improve the film-forming continuity. Thus, the water-based polyurethane emulsion provided by the present application overcomes the defects of the prior art that the degradable polymer causes the emulsion strength and film-forming property to decrease, provides a new technical route for the practical application of the degradable water-based polyurethane emulsion, and expands the application field thereof. Moreover, the raw materials and preparation method of the water-based polyurethane emulsion provided by the present application are environmentally friendly and meet the green chemistry concept.
[0008] Preferably, the mass ratio of the polylactic acid-polyester polyol copolymer in the polyol is 10-25%.
[0009] Preferably, the mass ratio of polypropylene adipate glycol:polycarbonate glycol is 0.5-5:1.
[0010] Preferably, the polylactic acid-polyester polyol copolymer comprises a polylactic acid-polyethylene adipate copolymer.
[0011] Preferably, the preparation method of the polylactic acid-polyethylene adipate copolymer comprises the following steps: preparing a levorotatory lactic acid-polyethylene adipate copolymer and a dextrorotatory lactic acid-polyethylene adipate copolymer, respectively; mixing lactide, polyethylene adipate and catalyst A under a protective gas atmosphere, wherein the lactide is levorotatory lactide or dextrorotatory lactide, and polymerizing at 130-150℃ for 5-7 hours; then, under the conditions of a temperature of 150-170℃ and a vacuum of 100 Pa absolute pressure, devolatilizing for 0.5-2 hours to obtain the levorotatory lactic acid-polyethylene adipate copolymer and the dextrorotatory lactic acid-polyethylene adipate copolymer, respectively; and preparing a polylactic acid-polyethylene adipate copolymer by mixing the levorotatory lactic acid-polyethylene adipate copolymer and the dextrorotatory lactic acid-polyethylene adipate copolymer to obtain the polylactic acid-polyethylene adipate copolymer by melt blending.
[0012] Preferably, the diisocyanate comprises at least one of isophorone diisocyanate and dicyclohexylmethane diisocyanate.
[0013] Preferably, the raw materials for preparing the water-based polyurethane emulsion further comprise 0.5-3% of a small molecule chain extender, calculated in terms of mass percentage.
[0014] Preferably, the small molecule chain extender comprises at least one of 1,4-butanediol and 1,6-hexanediol.
[0015] Preferably, the raw materials for preparing the aqueous polyurethane emulsion further comprise 1.5-5% of a hydrophilic chain extender, calculated in terms of mass percentage.
[0016] Preferably, the hydrophilic chain extender comprises at least one of dimethylol propanoic acid, dimethylol butanoic acid, and sodium N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonate.
[0017] Preferably, the raw materials for preparing the aqueous polyurethane emulsion further comprise 0.01-0.05% of a catalyst, calculated in terms of mass percentage.
[0018] Preferably, the catalyst comprises at least one of dibutyltin dilaurate and stannous octoate.
[0019] Preferably, the raw materials for preparing the aqueous polyurethane emulsion further comprise a neutralizing agent, and the neutralizing agent comprises at least one of triethylamine and N,N-dimethylethanolamine.
[0020] In a second aspect, the present application provides a method for preparing the aqueous polyurethane emulsion as described above, which comprises the following steps: S1. After the polylactic acid-polyester polyol copolymer is subjected to dehydration treatment under a protective gas atmosphere, diisocyanate, catalyst B, and a solvent are added and mixed, and the mixture is reacted at 80-100°C for 2-3 hours; S2. Subsequently, polypropylene glycol adipate diol and polycarbonate diol are added to the reaction system, and catalyst C is added, and the reaction is continued for 1-2 hours; S3. The reaction temperature is lowered to 50-70°C, and then small-molecule chain extender and hydrophilic chain extender are added, and the mixture is reacted for 2-3 hours to obtain a prepolymer; and S4. The prepolymer is subjected to neutralization reaction and emulsification reaction to obtain the aqueous polyurethane emulsion.
[0021] Preferably, in S4, after the neutralization reaction, the neutralization degree of the reaction system is 90-100%. DETAILED DESCRIPTION
[0022] In order to enable persons skilled in the art to better understand the technical solutions in the present application, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor should fall within the scope of protection of the present application.
[0023] Embodiment 1 1. Preparation of raw materials In this embodiment, the raw materials for preparing the aqueous polyurethane emulsion are prepared according to the formulation shown in Table 1.
[0024] The polylactic acid-polyethylene adipate copolymer is prepared by the following method.
[0025] Preparation of the L-lactic acid-polyethylene adipate copolymer: 200 parts of L-lactide, 800 parts of polyethylene adipate, and 0.1 part of stannous chloride are mixed under a nitrogen atmosphere, and polymerization is carried out at 140°C for 6 hours; then, devolatilization is carried out at a temperature of 70°C and under vacuum at 100 Pa absolute pressure for 1 hour to obtain the L-lactic acid-polyethylene adipate copolymer; Preparation of the D-lactic acid-polyethylene adipate copolymer: 200 parts of D-lactide, 800 parts of polyethylene adipate, and 0.1 part of stannous chloride are mixed under a nitrogen atmosphere, and polymerization is carried out at 140°C for 6 hours; then, devolatilization is carried out at a temperature of 70°C and under vacuum at 100 Pa absolute pressure for 1 hour to obtain the D-lactic acid-polyethylene adipate copolymer; Preparation of the polylactic acid-polyethylene adipate copolymer: the L-lactic acid-polyethylene adipate copolymer and the D-lactic acid-polyethylene adipate copolymer are mixed, and melt blending is carried out at 190°C for 6 hours to obtain the polylactic acid-polyethylene adipate copolymer.
[0026] Table 1. Formulation for preparing the aqueous polyurethane emulsion in this example
[0027] 2. Preparation of the aqueous polyurethane emulsion The aqueous polyurethane emulsion is prepared in this example according to the following method.
[0028] S1. After vacuum dehydration of the polylactic acid-polyester polyol copolymer under a nitrogen atmosphere, N-methyl pyrrolidone (NMP) is added, and the mixture is dissolved at 150°C and then cooled to 80°C; then, 36 parts of isophorone diisocyanate and 0.1 part of stannous octoate are added, and the mixture is reacted at 80°C for 2-3 hours; S2. Then, vacuum-dehydrated polypropylene adipate diol and polycarbonate diol, isophorone diisocyanate, and stannous octoate are added to the reaction system, and the mixture is further reacted at 80°C for 1-2 hours; S3. The reaction temperature is lowered to 50-70°C, then a small-molecule chain extender and a hydrophilic chain extender are added, and an appropriate amount of acetone is added to the reaction system to control the viscosity of the system; the mixture is reacted at 50-70°C for 2-3 hours to obtain a prepolymer; S4. 40 parts of triethylamine are added to the prepolymer, and then water is added to the mixture under high-speed shearing to emulsify the mixture; acetone is removed from the mixture under vacuum to obtain an aqueous polyurethane emulsion.
[0029] Example 2 1. Preparation of raw materials The raw materials for preparing the aqueous polyurethane emulsion were prepared according to the formulation shown in Table 2.
[0030] The polylactic acid-polyethylene adipate copolymer was prepared according to the method provided in Example 1.
[0031] Table 2. Formulation for preparing the aqueous polyurethane emulsion in this example
[0032] 2. Preparation of the aqueous polyurethane emulsion The aqueous polyurethane emulsion was prepared according to the following method.
[0033] S1. After vacuum dehydration of the polylactic acid-polyester polyol copolymer, N-methyl pyrrolidone (NMP) was added to dissolve at 150°C, and then cooled to 80°C. Then 10 parts of isophorone diisocyanate, 10 parts of dicyclohexyl methane diisocyanate, and 0.1 parts of stannous octoate were added, and reacted at 80°C for 2-3 hours; S2. Then, vacuum-dehydrated polypropylene adipate diol and polycarbonate diol, the remaining isophorone diisocyanate, dicyclohexyl methane diisocyanate, and stannous octoate were added to the reaction system, and the reaction was continued for 1-2 hours; S3. The reaction temperature was reduced to 50-70°C, then a small molecule chain extender and a hydrophilic chain extender were added, and an appropriate amount of acetone was added to the reaction system to control the viscosity of the system, and the reaction was continued for 2-3 hours to obtain a prepolymer; S4. 40 parts of triethylamine were added to the prepolymer, then emulsified with water under high-speed shearing, and the acetone was removed by vacuum to obtain an aqueous polyurethane emulsion.
[0034] Examples 3-8 Examples 3-8 were prepared according to the formulation and method provided in Example 1, except that the molecular weight of each polyol was used as a variable. The molecular weight of the polyol used in Example 1 is also listed in Table 3 for comparison. In addition to the above differences, the operation steps for preparing the aqueous polyurethane emulsion in Examples 3-8 were strictly consistent with those in Example 1.
[0035] Table 3. Variables involved in preparing the aqueous polyurethane emulsion in Examples 3-8
[0036] Example 9 This example is prepared by the formulation and method provided in Example 1, except that the mass fraction of the polylactic acid-polyethylene adipate copolymer used in the preparation of the waterborne polyurethane emulsion is 220 parts, and the content in the polyester polyol is 27.5%. The above adjustment is achieved by increasing or decreasing the mass content of polypropylene adipate diol and polycarbonate diol (keeping the mass ratio unchanged), and ensuring that the total mass fraction of each material in the formulation remains unchanged. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0037] Example 10 This example is prepared by the formulation and method provided in Example 1, except that the mass fraction of the polylactic acid-polyethylene adipate copolymer used in the preparation of the waterborne polyurethane emulsion is 220 parts, and the content in the polyester polyol is 27.5%. The above adjustment is achieved by increasing or decreasing the mass content of polypropylene adipate diol and polycarbonate diol (keeping the mass ratio unchanged), and ensuring that the total mass fraction of each material in the formulation remains unchanged. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0038] Example 11 This example is prepared by the formulation and method provided in Example 1, except that the mass fraction of the polylactic acid-polyethylene adipate copolymer used in the preparation of the waterborne polyurethane emulsion is 220 parts, and the content in the polyester polyol is 27.5%. The above adjustment is achieved by increasing or decreasing the mass content of polypropylene adipate diol and polycarbonate diol (keeping the mass ratio unchanged), and ensuring that the total mass fraction of each material in the formulation remains unchanged. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0039] Example 12 This example is prepared by the formulation and method provided in Example 1, except that the mass fraction of the polylactic acid-polyethylene adipate copolymer used in the preparation of the waterborne polyurethane emulsion is 220 parts, and the content in the polyester polyol is 27.5%. The above adjustment is achieved by increasing or decreasing the mass content of polypropylene adipate diol and polycarbonate diol (keeping the mass ratio unchanged), and ensuring that the total mass fraction of each material in the formulation remains unchanged. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0040] Example 13 This example is prepared by the formulation and method provided in Example 1, except that the mass fraction of the polylactic acid-polyethylene adipate copolymer used in the preparation of the waterborne polyurethane emulsion is 220 parts, and the content in the polyester polyol is 27.5%. The above adjustment is achieved by increasing or decreasing the mass content of polypropylene adipate diol and polycarbonate diol (keeping the mass ratio unchanged), and ensuring that the total mass fraction of each material in the formulation remains unchanged. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0041] Example 14 This example was prepared according to the formulation and method provided in Example 1, except that the poly(lactic acid-co-ethylene glycol adipate) copolymer was replaced by poly(lactic acid-co-1,3-butanediol adipate) copolymer in equal mass fraction. Except for the above difference, the steps of preparing the waterborne polyurethane emulsion in this example were strictly consistent with those in Example 1. Specifically, the poly(lactic acid-co-1,3-butanediol adipate) copolymer was prepared by the following method.
[0042] Preparation of poly(lactic acid-co-1,3-butanediol adipate) copolymer: 600 parts of L-lactide, 400 parts of poly(1,3-butanediol adipate), and 0.1 part of stannous chloride were mixed under a nitrogen atmosphere and polymerized at 140°C for 6 hours; then, under the conditions of a temperature of 70°C and a vacuum of 100 Pa absolute pressure, devolatilization was performed for 1 hour to obtain the poly(lactic acid-co-1,3-butanediol adipate) copolymer; Preparation of poly(lactic acid-co-1,3-butanediol adipate) copolymer: 600 parts of L-lactide, 400 parts of poly(1,3-butanediol adipate), and 0.1 part of stannous chloride were mixed under a nitrogen atmosphere and polymerized at 140°C for 6 hours; then, under the conditions of a temperature of 70°C and a vacuum of 100 Pa absolute pressure, devolatilization was performed for 1 hour to obtain the poly(lactic acid-co-1,3-butanediol adipate) copolymer; Preparation of poly(lactic acid-co-1,3-butanediol adipate) copolymer: 600 parts of L-lactide, 400 parts of poly(1,3-butanediol adipate), and 0.1 part of stannous chloride were mixed under a nitrogen atmosphere and polymerized at 140°C for 6 hours; then, under the conditions of a temperature of 70°C and a vacuum of 100 Pa absolute pressure, devolatilization was performed for 1 hour to obtain the poly(lactic acid-co-1,3-butanediol adipate) copolymer;
[0043] Comparative Example 1 1. Preparation of raw materials The raw materials for preparing the waterborne polyurethane emulsion were prepared according to the formulation shown in Table 4.
[0044] Table 4. Formulation for preparing the waterborne polyurethane emulsion in this example
[0045] 2. Preparation of the waterborne polyurethane emulsion The waterborne polyurethane emulsion was prepared according to the following method.
[0046] S1. Under a nitrogen atmosphere, vacuum-dried polypropylene glycol adipate diol, polycarbonate diol, isophorone diisocyanate, dicyclohexyl methane diisocyanate, and stannous octoate were reacted at 80°C for 1-2 hours; S2. The reaction temperature is reduced to 50-70℃, then a small molecule chain extender, a hydrophilic chain extender are added, and an appropriate amount of acetone is added to the reaction system to control the viscosity of the system, and the reaction is carried out for 2-3 hours to obtain a prepolymer; S3. 40 parts of triethylamine are added to the prepolymer, then emulsified under high-speed shearing, and the acetone is removed under vacuum to obtain a waterborne polyurethane emulsion.
[0047] Comparative Example 2 This comparative example is prepared according to the formula and method provided in Example 1, and the difference between this comparative example and Example 1 is that, in the preparation of the waterborne polyurethane emulsion, the polypropylene glycol adipate diol is not added in this comparative example, and an equal mass fraction of polycarbonate diol is used instead. Except for the above difference, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0048] Comparative Example 3 This comparative example is prepared according to the formula and method provided in Example 1, and the difference between this comparative example and Example 1 is that, in the preparation of the waterborne polyurethane emulsion, the polypropylene glycol adipate diol is not added in this comparative example, and an equal mass fraction of polycarbonate diol is used instead. Except for the above difference, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0049] Comparative Example 4 This comparative example is prepared according to the formula and method provided in Example 1, and the difference between this comparative example and Example 1 is that, in the preparation of the waterborne polyurethane emulsion, the molecular weight of the polypropylene glycol adipate diol used in this comparative example is 3000, and the molecular weight of the polycarbonate diol used is 2500. Except for the above difference, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0050] Comparative Example 5 This comparative example is prepared according to the formula and method provided in Example 1, and the difference between this comparative example and Example 1 is that, in the preparation of the waterborne polyurethane emulsion, the molecular weight of the polypropylene glycol adipate diol used in this comparative example is 1400, and the molecular weight of the polycarbonate diol used is 1400. Except for the above difference, the operation steps for preparing the waterborne polyurethane emulsion in this example are strictly consistent with those in Example 1.
[0051] Comparative Example 6 The waterborne polyurethane emulsion was prepared according to the formulation and method provided in Comparative Example 1, except that 1,6-hexanediol was used to replace polypropylene glycol adipate diol in an equal mass fraction, and 1,4-butanediol was used to replace polycarbonate diol in an equal mass fraction. Except for the above differences, the operation steps for preparing the waterborne polyurethane emulsion were strictly consistent with those in Example 1.
[0052] Test Example 1. Test Object To verify the technical effects of the present application, the waterborne polyurethane emulsions prepared in Examples 1-14 and Comparative Examples 1-6 were used as test samples. The test samples were placed in a teflon template and left to stand at room temperature for 7 days. After the moisture was slowly volatilized, the samples were placed in a vacuum drying oven at 75°C for 2 days to obtain a latex film with a thickness of 0.5 mm. In this test example, the obtained latex film was used as the test object.
[0053] 2. Test Method (1) Biodegradability: A rapid degradation experiment was conducted using a hydrothermal method to evaluate the biodegradability of the material. The specific steps included: first, weighing the initial mass of the prepared latex film, denoted as M1; then placing it in a 130°C, pH 12 environment for 10 hours of degradation; after the reaction was completed, the mixture was filtered, and the mass of the obtained solid residue was weighed, denoted as M2. The degradation rate was calculated by the following formula: degradation rate (%) = (M1-M2)*100% ÷ M1.
[0054] (2) Mechanical properties: Tensile strength and elongation at break were measured according to GB / T 1040-92 standard and using an AGS-J electronic universal testing machine.
[0055] (3) Water resistance: The film-forming sample was immersed in warm water at 40°C for 1 hour, and then observed for whitening or peeling. If the film did not whiten and remained intact, the water resistance was qualified.
[0056] (4) Film-forming performance: The film was visually inspected under a magnifying glass for transparency / half-transparency, absence of cracks, and surface smoothness. If there were no cracks and the surface was smooth, the film-forming performance was good.
[0057] 3. Test Results and Analysis The test results of the present test example are shown in Table 5. From the data of Examples 1-8 and Comparative Examples 1-6, it can be seen that in the aqueous polyurethane emulsion provided by the present application, the molecular weight of the polylactic acid-polyethylene adipate copolymer, the molecular weight of the polypropylene adipate diol, and the molecular weight of the polycarbonate diol collectively affect the degradation performance, mechanical properties, and film-forming properties of the emulsion. Specifically, from the data of Example 1 and Examples 3-4, it can be seen that the introduction of the polylactic acid-polyethylene adipate copolymer and the reasonable control of its molecular weight have a significant positive effect on the degradation rate, and a degradation rate of more than 80% can be achieved when the molecular weight is in the range of 5000 to 15000, while in Comparative Example 1, which does not add the copolymer, the degradation rate is significantly reduced to 45.7%, indicating that the copolymer as a degradable segment effectively promotes the biodegradability of the material.
[0058] In terms of mechanical properties, the molecular weight of the polylactic acid-polyethylene adipate copolymer shows a certain positive correlation with the tensile strength and elongation at break, for example, in Example 3, when the molecular weight is 15000, the tensile strength reaches 28.9 MPa, and the elongation at break is 739%, showing excellent mechanical properties. In addition, the polypropylene adipate diol and the polycarbonate diol also significantly affect the strength and toughness of the material. In Comparative Examples 2 and 3, which do not add polycarbonate diol or polypropylene adipate diol, respectively, the tensile strength and elongation at break are significantly lower than those of other examples, indicating that there is a synergistic strengthening effect between the polylactic acid-polyethylene adipate copolymer, the polycarbonate diol, and the polypropylene adipate diol.
[0059] In particular, combining the data measured in Examples 5-8 and Comparative Examples 4-5, it can be found that when the molecular weight of the polypropylene adipate diol is in the range of 1500-2000 and the molecular weight of the polycarbonate diol is in the range of 1500-2000, an effective entanglement network can be formed with the polylactic acid-polyethylene adipate copolymer, enhancing the interaction between polymer chains and thus improving the overall mechanical properties of the latex film; when the molecular weight of the polypropylene adipate diol and the molecular weight of the polycarbonate diol are too large or too small, the degradation rate and mechanical properties of the prepared latex film decrease. In Comparative Example 6, which does not add polypropylene adipate diol and polycarbonate diol, the performance of the latex film is further deteriorated, with a tensile strength of only 10.1 MPa and an elongation at break of only 381%. Therefore, the above data fully demonstrate that in the aqueous polyurethane emulsion provided by the present application, the polylactic acid-polyethylene adipate copolymer, the polycarbonate diol, and the polypropylene adipate diol are indispensable, and excessively high or low molecular weights of the above three polyols will weaken the synergistic effect between them, affecting the integrity and continuity of the network structure.
[0060] And based on the data of Example 1, Examples 9-10, the mass ratio of polylactic acid-polyester polyol copolymer can affect the degradation rate and mechanical properties of the latex film, and with the increase of the mass ratio of polylactic acid-polyester polyol copolymer, the degradation rate and mechanical properties of the latex film show a trend of first increasing and then decreasing. Combined with the data, it can be shown that the polylactic acid-polyester polyol copolymer has a preferred range of 10% to 25% in the polyol, which can achieve more excellent degradation performance and mechanical properties, which may be due to the copolymer content affecting the density and hydrolysis activity of the degradable segment.
[0061] In Examples 1, Examples 11-13, it is disclosed that the ratio of polypropylene adipate glycol and polycarbonate diol can affect the mechanical properties of the latex film. Combined with the data, when the ratio of polypropylene adipate glycol and polycarbonate diol is in the range of 0.5-5:1, it is helpful to form an effective polymer entanglement network, improve the segment flexibility and intermolecular forces, and thus improve the strength and toughness of the latex film.
[0062] In addition, based on the data of Example 1 and Example 14, using polylactic acid-polyethylene adipate copolymer to prepare waterborne polyurethane emulsion has better comprehensive performance.
[0063] In summary, by introducing polylactic acid-polyethylene adipate copolymer with a specific molecular weight range, and cooperatively matching moderate molecular weight polypropylene adipate glycol and polycarbonate diol, a waterborne polyurethane emulsion with high degradability, excellent mechanical properties and good film-forming property is successfully constructed, effectively overcoming the problem of strength and film-forming property of degradable materials. It embodies obvious technical advantages and green environmental protection characteristics.
[0064] Table 5. Test results
[0065] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.
Claims
1. A biodegradable aqueous polyurethane emulsion, characterized in that, The raw materials for preparing the waterborne polyurethane emulsion, calculated by mass percentage, include 10-20% diisocyanate and 75-85% polyol; the polyol includes polylactic acid-polyester polyol copolymer, polypropylene adipate diol, and polycarbonate diol. The molecular weight of the polylactic acid-polyester polyol copolymer is 5000~15000; The molecular weight of the poly(propylene adipate) diol is 1500-2000. The polycarbonate diol has a molecular weight of 1500-2000.
2. The aqueous polyurethane emulsion as described in claim 1, characterized in that, The polylactic acid-polyester polyol copolymer accounts for 10-25% of the mass of the polyol.
3. The aqueous polyurethane emulsion as described in claim 1 or 2, characterized in that, The mass ratio of the poly(propylene adipate) diol to the polycarbonate diol is 0.5 to 5:
1.
4. The aqueous polyurethane emulsion as described in claim 1, characterized in that, The polylactic acid-polyester polyol copolymer includes polylactic acid-polyethylene adipate copolymer.
5. The aqueous polyurethane emulsion as described in claim 4, characterized in that, The preparation method of the polylactic acid-polyethylene adipate copolymer includes the following steps: L-lactic acid-polyethylene adipate copolymer and D-lactic acid-polyethylene adipate copolymer were prepared separately: Under a nitrogen atmosphere, lactide, polyethylene adipate, and catalyst A were mixed, wherein the lactide was either L-lactic acid or D-lactic acid, and polymerized at 130-150°C for 5-7 hours; subsequently, the mixture was devolatilized at 150-170°C and under a vacuum of 100 Pa absolute pressure for 0.5-2 hours to obtain the L-lactic acid-polyethylene adipate copolymer and the D-lactic acid-polyethylene adipate copolymer, respectively. Preparation of polylactic acid-polyethylene adipate copolymer: The L-lactic acid-polyethylene adipate copolymer and the D-lactic acid-polyethylene adipate copolymer are mixed and melt-blended to obtain the polylactic acid-polyethylene adipate copolymer.
6. The aqueous polyurethane emulsion as described in claim 1, characterized in that, The diisocyanate includes at least one of isophorone diisocyanate and dicyclohexylmethane diisocyanate.
7. The aqueous polyurethane emulsion as described in claim 1, characterized in that, The raw materials for preparing the aqueous polyurethane emulsion also include a small molecule chain extender, which includes at least one of 1,4-butanediol and 1,6-hexanediol.
8. The aqueous polyurethane emulsion as described in claim 1, characterized in that, The raw materials for preparing the aqueous polyurethane emulsion also include a hydrophilic chain extender, which includes at least one of dimethylolpropionic acid, dimethylolbutyric acid, and sodium N,N-di(2-hydroxyethyl)-2-aminoethanesulfonate.
9. A method for preparing the aqueous polyurethane emulsion as described in any one of claims 1 to 8, characterized in that, The method includes the following steps: S1. Under a protective gas atmosphere, the polylactic acid-polyester polyol copolymer is dehydrated, then the diisocyanate, catalyst B, and solvent are added and mixed, and the mixture is reacted at 80~100°C for 2~3 hours. S2. Then add the poly(propylene adipate) glycol, the polycarbonate glycol, and catalyst C to the reaction system, and continue the reaction at a constant temperature for 1-2 hours; S3. Reduce the reaction temperature to 50~70℃, then add small molecule chain extender and hydrophilic chain extender and react for 2~3 hours to obtain the prepolymer; S4. The prepolymer is subjected to a neutralization reaction and an emulsification reaction to obtain the aqueous polyurethane emulsion.
10. The method as described in claim 9, characterized in that, In S4, after the neutralization reaction, the degree of neutralization of the reaction system is 90-100%.