A method for preparing a bio-based polyol

Abstract

The application provides a preparation method of a bio-based polyol, wherein the method comprises: mixing a solid solute with an acidic solvent to obtain an acidic black liquor; adding a polyol solvent to the acidic black liquor, and then performing evaporation and filtration to obtain an intermediate; and adding a neutralizing agent to the intermediate to obtain a bio-based polyol. The bio-based polyol prepared by the method provided in the application has a viscosity of at least 4.7, which is much better than the prior art. The polyol prepared by the method provided in the application successfully overcomes the problem of high viscosity or solid state caused by the rigid structure of traditional lignin-based polyols while maintaining a high bio-based content.

Description

Technical Field

[0001] This application relates to the field of polymer materials, specifically to a method for preparing bio-based polyols using lignin as a raw material via solvent displacement. Background Technology

[0002] Polyurethane materials have wide applications in materials, chemical engineering, and pharmaceuticals due to their excellent physical and chemical properties. Green, environmentally friendly, and biodegradable polyurethane materials are gradually becoming a research hotspot. Traditional polyurethane materials mainly rely on petroleum-based polyols, and the use of this non-renewable resource not only leads to resource shortages but also causes serious environmental problems. Currently, bio-based polyols are increasingly considered an ideal alternative to petroleum-based polyols due to their renewable and environmentally friendly properties. Among them, lignin-based polyols are mainly solid products. Lignin originates from agricultural and forestry waste, does not compete with food production, and its aromatic structure endows polyurethane materials with excellent rigidity and intrinsic flame retardancy. At the same time, high carbon content helps increase the bio-based proportion of the product, meeting the requirements of green and sustainable development. However, the limited solubility of lignin in liquid polyol systems restricts its application in polyurethane materials.

[0003] To address the aforementioned issues, researchers have begun exploring new methods for preparing bio-based polyols. Among these, methods using lignin as a raw material, such as etherification-liquefaction and solvent displacement methods, have attracted widespread attention. These methods can not only increase the bio-based content but also reduce costs and improve the degradation performance of the materials. However, how to improve the compatibility and reactivity of lignin with other components while ensuring its solubility remains a key issue limiting the performance of lignin-based polyurethane materials. Therefore, developing a novel method for preparing bio-based polyols that overcomes the shortcomings of existing technologies is of significant research importance.

[0004] CN116554497A discloses a method for preparing polyols and bio-based polymer materials using lignin. This method uses lignin materials, lignin solvent, nucleophiles, and Bronsted acids as raw materials to prepare lignin polyols in a one-pot process. The resulting lignin polyols exhibit strong adjustable functionality, high reactivity, and good compatibility with other polyether polyols. However, there is still room for optimization in controlling the liquefaction conditions and reaction time, which affects the liquefaction efficiency and product quality.

[0005] CN119350650A discloses a bio-based polyol, its preparation method, and its application. This method combines lignin with sugar alcohols and polyols to prepare polyols with high bio-based content. These bio-based polyols are highly renewable at the raw material level, aligning with the principles of green chemistry and a circular economy. However, further optimization of the reaction conditions is needed to improve the yield and purity of the product.

[0006] Meanwhile, CN116554497A and CN119350650A both use renewable resources such as lignin to prepare bio-based polyols. However, in actual processes, a large amount of petroleum-based solvents, catalysts, or low-molecular-weight sugar alcohols are often introduced, resulting in a low carbon content (i.e., bio-based carbon fraction) in the final product. This makes it difficult to meet the green certification standards for high bio-based polyurethane materials (such as ASTM D6866 ≥50%), thus limiting their application in the field of high-end environmentally friendly materials. Summary of the Invention

[0007] To address the problems of high cost, limited solubility, and complex preparation processes of existing bio-based polyols, this application provides a method for preparing bio-based polyols by treating lignocellulose and its components using formic acid and acetic acid organic solvents.

[0008] The specific plan for this application is as follows: 1. A method for preparing a bio-based polyol, wherein the method comprises: Acidic black liquor is obtained by mixing a solid solute with an acidic solvent. A polyol solvent is added to the acidic black liquor, followed by evaporation and filtration to obtain an intermediate. A neutralizing agent is added to the intermediate to obtain a bio-based polyol.

[0009] 2. The method according to item 1, wherein, The acidic solvent includes one or more of formic acid, acetic acid, and water, wherein the total mass ratio of formic acid and acetic acid in the acidic solvent is 80%-100%.

[0010] 3. The method according to claim 1, wherein mixing the solid solute with the acidic solvent to obtain acidic black liquor further comprises: Mix the solid solute with the acidic solvent and stir to dissolve at 50-200℃ for 2-4 hours; The acidic black liquor is filtered and concentrated.

[0011] 4. The method according to item 1, wherein, In the process of adding polyol solvent to the acidic black liquor, the mass ratio of the solid solute in the acidic black liquor to the mass of the polyol solvent is 1:0.8-1.2.

[0012] 5. The method according to item 1, wherein, The polyol solvent is an alcohol containing at least two hydroxyl groups.

[0013] 6. The method according to claim 5, wherein the polyol solvent is selected from one or more of polyethylene glycol 600, polyethylene glycol 400, polypropylene glycol, diethylene glycol, and mixtures thereof.

[0014] 7. The method according to claim 1, wherein adding a polyol solvent to the acidic black liquor further comprises: Stir the reaction at 65-85℃ for 2-4 hours; The reaction products are subjected to high-vacuum rapid evaporation to remove volatile components.

[0015] 8. The method according to item 1, wherein, When a neutralizing agent is added to the intermediate for neutralization, the neutralizing agent is an organic amine, preferably diethanolamine and / or triethanolamine.

[0016] 9. The method according to item 1, wherein, In the mixture, the mass ratio of the solid solute to the acidic solvent is 1:(0.8-10).

[0017] 10. Application of any one of the methods described in items 1-9 in the field of preparation of polyols.

[0018] The bio-based polyols prepared by the method provided in this application have a viscosity as low as 4.7, which is far superior to the prior art. This shows that the polyols prepared by the method of this application can maintain a high bio-based content while successfully overcoming the problem of high viscosity or solid state caused by the rigid structure of traditional lignin-based polyols. Detailed Implementation

[0019] The present application will now be described in detail. While specific embodiments of the present application are shown below, it should be understood that the present application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0020] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "including but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0021] This application provides a method for preparing bio-based polyols, wherein the method comprises: Acidic black liquor is obtained by mixing a solid solute with an acidic solvent. A polyol solvent is added to the acidic black liquor, followed by evaporation and filtration to obtain an intermediate. A neutralizing agent is added to the intermediate to obtain a bio-based polyol.

[0022] In one embodiment of this application, the solid solute comprises plant biomass.

[0023] In one embodiment of this application, the solid solute comprises lignin; preferably, the solid solute may also comprise cellulose and / or hemicellulose. It should be understood that in this application, the solid solute may comprise one or more of the solid components mentioned above, and these one or more solid components may exist in the solid solute in any amount and by any mass, and should not be considered a limitation of this application.

[0024] In one embodiment of this application, before mixing the solid solute with the acidic solvent, the solid solute is further pretreated, for example, by steps such as component analysis, screening, washing, drying, and crushing.

[0025] For example, when a raw material contains a high proportion of plant biomass, the raw material can be directly used as the solid solute and mixed with an acidic solvent. For example, when a raw material contains a high content of cellulose and / or hemicellulose, it can be considered to mix the raw material with a raw material containing a high content of lignin in a certain proportion to form the solid solute. It should be understood that those skilled in the art can prepare solid solutes according to the type, content and other parameters of the raw materials, and this should not be regarded as a limitation of this application.

[0026] It should be understood that, in this application, plant biomass refers to whole or partial organic materials derived from plants, including plant organs such as roots, stems, leaves, flowers, fruits, and seeds, as well as unrefined plant residues (such as straw, sawdust, fruit shells, fallen leaves, etc.) generated in agricultural production or forestry activities, but does not include single compounds or chemical components (such as lignin, starch, cellulose, essential oils, alkaloids, etc.) obtained by separating or purifying them from plants through chemical or physical methods.

[0027] In one embodiment of this application, the plant source of the plant biomass may be one or more of the following: wheat, rice, soybean, castor bean, rapeseed, jatropha, corn, cassava, sweet potato, sugarcane, reed, sugar beet, switchgrass, miscanthus, bamboo, and straw.

[0028] In one embodiment of this application, the acidic solvent provides an acidic environment that facilitates the chemical process of macromolecular chain breakage in the solid solute.

[0029] In one aspect of this application, the process of "adding a polyol solvent to the acidic black liquor, followed by evaporation and filtration" described above utilizes the principle of solvent displacement. The components of the solid solute dissolved in the acidic solvent in the previous step are dissolved in the polyol solvent through solvent displacement.

[0030] In one embodiment of this application, "polyol solvent" refers to a class of organic compounds containing two or more hydroxyl (–OH) functional groups.

[0031] In one embodiment of this application, the mass ratio of the solid solute to the acidic solvent is 1:(0.8-10), for example, it can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8. 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0.

[0032] In one embodiment of this application, the acidic solvent comprises one or more of formic acid, acetic acid, and water, wherein the total mass ratio of formic acid and acetic acid in the acidic solvent is 80%-100%.

[0033] For example, the mass ratio of formic acid and acetic acid in the acidic solvent can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%.

[0034] In one embodiment of this application, the total mass ratio of formic acid, acetic acid and water in the acidic solvent can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%.

[0035] In one embodiment of this application, the acidic solvent may contain only formic acid or only acetic acid. In this case, the mass ratio of formic acid and / or acetic acid in the acidic solvent remains 80%-100%. In another embodiment of this application, the mass ratio of formic acid to acetic acid in the acidic solvent is 1:(3-5), for example, it can be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4.0, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, or 1:5.0.

[0036] In one embodiment of this application, the acidic solvent is an acetic acid solution prepared by mixing acetic acid and water. In another embodiment, the total mass ratio of acetic acid and water in the acidic solvent can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. In yet another embodiment, the acidic solvent is an acetic acid solution with a mass concentration of 80%-90%, for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%.

[0037] In one embodiment of this application, the step of mixing the solid solute with an acidic solvent to obtain acidic black liquor further comprises: mixing the solid solute with the acidic solvent and stirring to dissolve at 50-200°C for 2-4 hours; and filtering and concentrating the acidic black liquor. The concentration conditions can be determined according to conditions commonly used by those skilled in the art, for example, concentration can be achieved by heating. For example, the stirring temperature can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C, and the stirring and dissolving time can be 2, 2.5, 3, 3.5, or 4 hours. In one embodiment of this application, the concentrated acidic black liquor contains all solutes at a mass percentage of 30%-60%, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%. It should be understood that the mass percentage of all solutes refers to the mass percentage of the solutes relative to the total mass of the system.

[0038] In one embodiment of this application, when adding a polyol solvent to the acidic black liquor, the mass ratio of the solid solute in the acidic black liquor to the polyol solvent is 1:0.8-1.2. In this application, the mass of the solid solute in the acidic black liquor can be determined by detecting the solid content, for example, according to the German Institute for Standardization standard ISO 638:2019. For example, the mass ratio of the solid solute to the polyol solvent in the acidic black liquor is 1:0.8, 1:0.9, 1:1.0, 1:1.1, or 1:1.2.

[0039] In one embodiment of this application, the addition of polyol solvent to the acidic black liquor can also be done by adding polyol solvent to the concentrated acidic black liquor. This is beneficial for reducing the amount of polyol solvent used and further reducing the cost of the method of this application.

[0040] In one embodiment of this application, the polyol solvent is an alcohol containing at least two hydroxyl groups. Preferably, the polyol solvent comprises one or more of polyethylene glycol 600, polyethylene glycol 400, polypropylene glycol, diethylene glycol, and mixtures thereof. More preferably, the polyol solvent is polyethylene glycol 600 or polyethylene glycol 400. It should be understood that the polyol solvent refers to one or more polyol substances used as solvents in the methods provided in this application. In some embodiments, the state of the polyol at room temperature and pressure is not limited; it can generally be a liquid or a viscous liquid. Those skilled in the art can also dissolve the polyol in conventional solvents for better use. In this case, those skilled in the art can easily calculate the ratio of the polyol to other substances.

[0041] In one embodiment of this application, the polypropylene glycol is selected from oxypropyl sucrose polyether 4110, oxypropyl sucrose polyether 560, oxypropyl sucrose polyether 7340, etc. As is well known to those skilled in the art, the polyether described in this application is essentially a polyether polyol, and those skilled in the art can also understand that it is also an alcohol containing at least two hydroxyl groups. Therefore, the polypropylene glycol can also be selected from sucrose polyether, glycerol polyether, EO-terminated polyether, etc.

[0042] In one embodiment of this application, adding a polyol solvent to the acidic black liquor further comprises: The reaction mixture was stirred at 65-85°C for 2-4 hours; the reaction product was then subjected to high-vacuum rapid evaporation to remove volatile components, yielding the intermediate.

[0043] For example, the stirring temperature can be 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, or 85℃, and the stirring reaction time can be 2, 2.5, 3, 3.5, or 4 hours. In one embodiment of this application, "high vacuum rapid evaporation" refers to evaporation under high vacuum conditions (usually referring to pressures far below atmospheric pressure, such as <10℃). -1 ~10 -3 Vacuum evaporation (VBA) is a technique that utilizes the principle of lowering the boiling point of a liquid to achieve rapid, low-temperature removal of solvents or volatile components; it can also be called vacuum evaporation. For example, it can be achieved using high-vacuum distillation systems such as rotary evaporators, multi-effect evaporators, and thin-film evaporators. In one embodiment of this application, the water content of the residue after evaporation can be 0% to 5%, for example, 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%.

[0044] In one embodiment of this application, when a neutralizing agent is added to the intermediate, the neutralizing agent is an organic amine. In this application, the organic amine is a hydrocarbon derivative of ammonia, that is, an organic compound formed by the partial or complete substitution of hydrogen atoms in an ammonia (NH3) molecule by hydrocarbon groups. In one embodiment of this application, the neutralizing agent is preferably diethanolamine and / or triethanolamine. It should be understood that in one embodiment of this application, the neutralizing agent is used to neutralize acidic substances in acidic black liquor. In some cases, the neutralizing agent can also act as a catalyst to promote the reaction, a chain extender participating in the reaction, a performance modifier, etc. The neutralizing agent can be used to adjust the pH value of the above intermediate and participate in the reaction.

[0045] In one embodiment of this application, the pH value of the intermediate is adjusted to 5-8 by a neutralizing agent, for example, it can be 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, or 8.0.

[0046] Those skilled in the art can measure the above-mentioned parameters such as ratio and temperature using conventional methods, and this should not be considered a limitation of this application.

[0047] This application also provides the application of any of the methods described above in the field of preparing polyols.

[0048] Example Specific embodiments of this application will now be described in more detail. While specific embodiments of this application are shown herein, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0049] This application provides a general and / or specific description of the materials and methods used in the experiments, as shown in the examples below. Unless otherwise specified, all reagents and instruments used are commercially available conventional products.

[0050] This application provides a method for preparing bio-based polyols, comprising the following steps: Step 1: Raw material pretreatment Lignin and hemicellulose (solid solutes) are mixed with an acidic solvent to undergo acidic depolymerization and dissolution. Specifically, First, lignin and hemicellulose in a mass ratio of 2:1 are mixed to form a solid solute. Then, the solid solute is mixed with an acidic solvent in a mass ratio of 1:5. The mixture is stirred at 55°C for 3 hours to obtain acidic black liquor. After filtering the acidic black liquor to remove insoluble substances, it is subjected to vacuum evaporation to remove most of the volatile components until the solid solute content in the remaining mixture increases to 50%.

[0051] Step 2 Solvent replacement Add polyol solvent to the filtered and evaporated acidic black liquor obtained in step 1, stir and mix well, and perform solvent replacement. The mixture was stirred under reduced pressure at 85°C for 3 hours to remove volatile components until the moisture content of the remaining mixture dropped to below 1.0%, thus obtaining the intermediate.

[0052] Step 3 Neutralization treatment Neutralizing agent is continuously added to the intermediate obtained in step 2 to adjust the pH value. Stir at 30°C for 30 minutes, and continuously measure the pH value of the intermediate; The product is then filtered to obtain a liquid final product, namely bio-based polyols. Performance testing of bio-based polyols.

[0053] Performance testing methods: Determination method for bio-based carbon content of bio-based polyols: GB / T 39715.2-2021 Bio-based content of plastics - Part 2: Determination of bio-based carbon content; Method for determining the hydroxyl value of bio-based polyols: GB / T 31412-2015 Determination of hydroxyl value of paints and varnishes by titration. Method for determining the viscosity of bio-based polyols: GB / T 22235-2008 Determination of viscosity of liquids.

[0054] Example 1 Example 1-1 Bio-based polyols were prepared according to the methods described in steps 1 to 3 above, and their performance was tested.

[0055] In step 1, the solid solute is 100g, and the acidic solvent is 500g. The acidic solvent contains 90% formic acid (i.e., a formic acid solution) and 100% acetic acid. The 500g of acidic solvent comprises 90g formic acid solution, 320g acetic acid, and 90g water. In step 2, the polyol solvent is polyethylene glycol 600. The mass ratio of the solid solute to the polyol solvent in the acidic black liquor is 1:1.

[0056] In step 3, diethanolamine, a neutralizing agent, is added to adjust the pH of the mixture to 6.5.

[0057] The results of the performance tests are summarized in Table 1.

[0058] Those skilled in the art can determine the above ratios using conventional methods.

[0059] Examples 1-2 The operation is the same as in Example 1-1, except that in step 2, the mass ratio of the solid solute in the acidic black liquor to the polyol solvent is 1:0.8.

[0060] Examples 1-3 The operation is the same as in Example 1-1, except that in step 2, the mass ratio of the solid solute in the acidic black liquor to the polyol solvent is 1:1.2.

[0061] Examples 1-4 The operation is the same as in Example 1-1, except that in step 2, the mass ratio of the solid solute in the acidic black liquor to the polyol solvent is 1:1.5.

[0062] Examples 1-5 The procedure was the same as in Example 1-1, except that in step 2, the polyol solvent was replaced with polyethylene glycol 400. The performance test results are summarized in Table 1.

[0063] Examples 1-6 The procedure was the same as in Example 1-1, except that in step 2, the polyol solvent was replaced with oxypropyl sucrose polyether 4110. The results of the performance tests are summarized in Table 1.

[0064] Examples 1-7 The procedure was the same as in Example 1-1, except that in step 2, the polyol solvent was replaced with diethylene glycol. The performance test results are summarized in Table 1.

[0065] Examples 1-8 The procedure was the same as in Example 1-1, except that in step 3, the neutralizing agent was changed to triethanolamine. The results of the performance tests are summarized in Table 1.

[0066] Examples 1-9 The procedure was the same as in Example 1-1, except that the neutralizing agent was not added in step 3. The results of the performance tests are summarized in Table 1.

[0067] Examples 1-10 The operation is the same as in Example 1-1, except that in step 3, the diethanolamine neutralizer is replaced with sodium hydroxide. The results of the performance test are summarized in Table 1.

[0068] Examples 1-11 The procedure is the same as in Example 1-1, except that in step 1, the mass ratio of the solid solute to the acidic solvent is 1:0.8. The results of the performance tests are summarized in Table 1.

[0069] Examples 1-12 The procedure is the same as in Example 1-1, except that in step 1, the mass ratio of the solid solute to the acidic solvent is 1:10. The results of the performance tests are summarized in Table 1.

[0070] Examples 1-13 The procedure is the same as in Example 1-1, except that in step 1, the mass ratio of the solid solute to the acidic solvent is 1:12. The results of the performance tests are summarized in Table 1.

[0071] Examples 1-14 The procedure was the same as in Example 1-1, except that in step 1, lignin and hemicellulose were replaced with an equal mass of plant biomass (the plant biomass consisted of the stems and leaves of agricultural straw). The results of the performance tests are summarized in Table 1.

[0072] Examples 1-15 The procedure was the same as in Example 1-1, except that in step 1, lignin and hemicellulose were replaced with an equal mass of lignin. The results of the performance tests are summarized in Table 1.

[0073] Examples 1-16 The procedure was the same as in Example 1-1, except that in step 1, lignin and hemicellulose were replaced with an equal mass of cellulose. The results of the performance tests are summarized in Table 1.

[0074] Examples 1-17 The procedure was the same as in Example 1-1, except that in step 1, lignin and hemicellulose were replaced with equal masses of hemicellulose. The results of the performance tests are summarized in Table 1.

[0075] Comparative Example 1-1 Bio-based polyols were prepared according to the method in Example 5 of patent CN119350650A, and the performance tests described above were performed on the prepared bio-based polyols. The results of the performance tests are summarized in Table 1.

[0076] Comparative Examples 1-2 Bio-based polyols were prepared according to the method in Example 2 of patent CN120081703A, and the performance tests described above were performed on the prepared bio-based polyols. The results of the performance tests are summarized in Table 1.

[0077] Comparative Examples 1-3 Bio-based polyols were prepared according to the method in Example 2 of patent US12195491B2, and the performance tests described above were performed on the prepared bio-based polyols. The results of the performance tests are summarized in Table 1.

[0078] Comparative Examples 1-4 Bio-based polyols were prepared according to the method described in patent EP4305028A4, and the performance tests described above were performed on the prepared bio-based polyols. The results of the performance tests are summarized in Table 1.

[0079] Table 1

[0080] In the table above, Examples 1-14 to 1-17 did not change the mass ratio of solid solute to acidic solvent. However, it should be understood that the solid solute used therein is as described in the corresponding text and should not be regarded as a limitation of this application.

[0081] As shown in Table 1, Examples 1-1 to 1-5 illustrate that when the mass ratio of solid solute to polyol solvent in acidic black liquor is adjusted from 1:1.2 to 1:1.5, the bio-based content in the bio-based polyol product decreases significantly. This indicates that the polyol solvent content is excessive, and the proportion of petroleum-based components from the polyol solvent is too high. When the solid solute content is too high, the polyol is loaded with too many effective components, resulting in excessive product viscosity. It is speculated that the reduction of polyol makes it easier for solid components such as lignin in the black liquor to aggregate and entangle through hydrogen bonds, crossing the critical point of a sharp increase in viscosity, thereby triggering a nonlinear rheological response.

[0082] When polyethylene glycol 600 and polyethylene glycol 400 are used as polyol solvents, the product exhibits good bio-based carbon content, hydroxyl value, and viscosity. However, when oxypropyl sucrose polyether 4110 is used as the polyol solvent, the product achieves the optimal bio-based content, but the viscosity is too high, limiting its application scenarios. For example, it can be used in cast polyurethane elastomers (such as stamping dies and forklift tires), solvent-free polyurethane coatings (such as floor coatings), and some polyurethane adhesives (such as automotive structural adhesives). Diethylene glycol, as a polyol solvent, ensures a viscosity below 10, making the product applicable to multiple scenarios. However, its high hydroxyl value usually necessitates blending with other components to avoid producing hard and brittle polyurethane foam when used alone. In this case, polyethylene glycol 600 and polyethylene glycol 400 are preferred polyol solvents, while oxypropyl sucrose polyether 4110 and diethylene glycol can be used to prepare bio-based polyol products with specific properties.

[0083] As can be seen from Examples 1-1, 1-8 to 1-10, a neutralizing agent must be added during the neutralization process, preferably an organic base with hydroxyl groups. Acidic substances in the system affect the reaction rate and the material strength of the final product. The addition of diethanolamine and triethanolamine, when used properly, does not significantly change the bio-based content of the final product. Using sodium hydroxide will result in excessive viscosity of the final product because the ratio of macromolecular hemicellulose and lignin to the solvent is relatively large. Compared to diethanolamine and triethanolamine, sodium hydroxide cannot improve the system's fluidity as a solvent. Both diethanolamine and triethanolamine can be used as neutralizing agents with comparable results; however, triethanolamine is slightly more expensive than diethanolamine.

[0084] As can be seen from the table, the mass ratio of solid solute to acidic solvent has little effect. However, excessive acidic solvent requires more neutralizing agent for subsequent treatment, resulting in wasted costs. Furthermore, evaporating and removing excess acidic solvent can lead to excessive condensation of lignin components, reducing the performance of polyols. It can also be seen that in the products prepared in Examples 1-12 and 1-13, the bio-based carbon content remains unchanged, but the hydroxyl value decreases with increasing acid content. Therefore, it can be inferred that a mass ratio of solid solute to acidic solvent of 1:10 or less yields better results.

[0085] When changing the type of biomass, plant biomass can achieve better results when used alone. Lignin is preferably used in conjunction with hemicellulose. Using cellulose or hemicellulose alone results in excessively high viscosity. The viscosity is slightly lower when using cellulose because cellulose is less compatible with the overall system, leading to lower reactivity. Therefore, before using the method provided in this application, the solid solute can be analyzed for composition. It is preferable to use plant biomass or lignin alone, and more preferably to add cellulose and / or hemicellulose to lignin.

[0086] The bio-based polyols prepared by the method provided in this application have a stable hydroxyl value between 400 and 500, and a minimum viscosity of 4.7, which is far superior to existing technologies. This indicates that the polyols prepared by the method of this application successfully overcome the high viscosity or solid state problem caused by the rigid structure of traditional lignin-based polyols while maintaining a high bio-based content. In contrast, existing technologies cannot achieve a balanced development of bio-based carbon content, hydroxyl value, and viscosity. Furthermore, comparative examples 1-1 to 1-4 use methods such as acid-catalyzed dehydration etherification modification, propylene oxide-catalyzed ring-opening modification, and cyclic carbonate grafting modification. The method of this application is significantly lower in cost than existing technologies. Compared with the comparative examples, the method provided in this application does not use hazardous reagents such as propylene oxide and concentrated sulfuric acid, making it safer than existing technologies.

[0087] Although the embodiments of this application have been described above, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A method for preparing a bio-based polyol, wherein, The method includes: Acidic black liquor is obtained by mixing a solid solute with an acidic solvent. A polyol solvent is added to the acidic black liquor, followed by evaporation and filtration to obtain an intermediate. A neutralizing agent is added to the intermediate to obtain a bio-based polyol.

2. The method according to claim 1, wherein, The acidic solvent includes one or more of formic acid, acetic acid, and water, wherein the total mass ratio of formic acid and acetic acid in the acidic solvent is 80%-100%.

3. The method according to claim 1, wherein, The process of mixing a solid solute with an acidic solvent to obtain acidic black liquor further comprises: Mix the solid solute with the acidic solvent and stir to dissolve at 50-200℃ for 2-4 hours; The acidic black liquor is filtered and concentrated.

4. The method according to claim 1, wherein, In the process of adding polyol solvent to the acidic black liquor, the mass ratio of the solid solute in the acidic black liquor to the mass of the polyol solvent is 1:0.8-1.

2.

5. The method according to claim 1, wherein, The polyol solvent is an alcohol containing at least two hydroxyl groups.

6. The method according to claim 5, wherein, The polyol solvent is selected from one or more of polyethylene glycol 600, polyethylene glycol 400, polypropylene glycol, diethylene glycol, and mixtures thereof.

7. The method according to claim 1, wherein, Adding a polyol solvent to the acidic black liquor further comprises: Stir the reaction at 65-85℃ for 2-4 hours; The reaction products are subjected to high-vacuum rapid evaporation to remove volatile components.

8. The method according to claim 1, wherein, When a neutralizing agent is added to the intermediate for neutralization, the neutralizing agent is an organic amine, preferably diethanolamine and / or triethanolamine.

9. The method according to claim 1, wherein, In the mixture, the mass ratio of the solid solute to the acidic solvent is 1:(0.8-10).

10. The application of any one of the methods according to claims 1-9 in the field of polyol preparation.

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