Bio-based polyol as well as preparation method and application thereof

Abstract

The invention discloses bio-based polyol as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing lignin, sugar alcohol, polyhydric alcohol and concentrated acid, and carrying out liquefaction reaction to obtain the bio-based polyhydric alcohol. According to the preparation method provided by the invention, the lignin is combined with the sugar alcohol and the polyhydric alcohol to prepare the polyhydric alcohol with high bio-based content, and on one hand, the bio-based polyhydric alcohol is highly renewable on the raw material level and conforms to the concepts of green chemistry and circular economy; on the other hand, due to the introduction of sugar alcohol, the flexibility and elasticity of the polyurethane material can be improved, the strength and chemical resistance of the material are improved, and a new path is provided for the development of the polyurethane industry in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-based polymer materials, and specifically relates to a bio-based polyol and a preparation method and application thereof. Background Art

[0002] As global awareness of sustainable development continues to increase, reducing dependence on petrochemical resources and developing environmentally friendly materials have become important research directions in the field of materials science. In this context, bio-based polyols, which can be prepared from renewable resources and have a lower carbon footprint, have gradually replaced traditional petroleum-based polyols and become an important raw material for polymer materials such as polyurethane. By developing polyols with high bio-based content, we can further reduce dependence on petrochemical resources and improve the environmental performance of materials. Bio-based raw materials such as lignin and sugar alcohols show great potential in the development of bio-based polyols.

[0003] Lignin is a complex aromatic polymer that is widely found in the cell walls of wood and other plants. It is the second largest biomass resource in nature after cellulose. The unique structure of lignin gives it good chemical stability and high carbon content, making it suitable as a potential raw material for polyols. Through chemical modifications such as hydroxymethylation and epoxidation, the phenolic hydroxyl groups in lignin can be converted into active polyol groups for the preparation of materials such as polyurethane.

[0004] The bio-based polyols currently prepared by existing technologies have, on the one hand, low bio-based content and low biomass resource utilization rate; on the other hand, the application of bio-based polyols in polyurethane materials requires the polyols to meet certain technical parameters such as hydroxyl value, acid value, viscosity and other performance requirements. However, the hydroxyl value of existing bio-based polyols is generally low or its viscosity and acid value cannot meet the requirements, which limits its application in polymer materials such as polyurethane. Summary of the invention

[0005] The main purpose of the present invention is to provide a bio-based polyol and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] One aspect of the present invention provides a method for preparing a bio-based polyol, which comprises: mixing lignin, sugar alcohol, polyol and concentrated acid to carry out a liquefaction reaction to obtain the bio-based polyol.

[0008] Another aspect of the present invention provides a bio-based polyol prepared by the aforementioned preparation method, wherein the hydroxyl value of the bio-based polyol is 5.0-15.0 mmol / g, the acid value of the bio-based polyol is 0.5-2.0 mmol / g, and the viscosity of the bio-based polyol at 30°C is 0.3-40.52 Pa.s.

[0009] Another aspect of the present invention provides a bio-based polyol, wherein raw materials for preparing the bio-based polyol include the following components: lignin, sugar alcohol, polyol and concentrated acid.

[0010] Another aspect of the present invention also provides the use of the aforementioned bio-based polyol in the preparation of polyurethane materials.

[0011] Compared with the prior art, the technical solution of the present invention has at least the following advantages:

[0012] The present invention combines lignin with sugar alcohol and polyol to prepare polyol with high bio-based content. On the one hand, such polyol is highly renewable at the raw material level, which conforms to the concept of green chemistry and circular economy; on the other hand, sugar alcohol has a high hydroxyl content and excellent biocompatibility. As a soft segment component in polyurethane materials, it can improve the flexibility and elasticity of the material, and the hydroxyl group in the sugar alcohol molecule can cross-link with isocyanate to increase the strength and chemical resistance of the material. The preparation method provided by the present invention has easy-to-obtain reaction raw materials, a simple preparation process, stable product performance, and is easy to industrialize and mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 A schematic diagram of the synthesis process of bio-based polyols in a typical embodiment of the present invention;

[0015] Figure 2 Schematic diagram of the synthesis process of bio-based polyols in Example 1 of the present invention;

[0016] Figure 3 is the bio-based polyol in Example 1 of the present invention 31 P-NMR nuclear magnetic characterization diagram. DETAILED DESCRIPTION

[0017] The present invention will be more fully understood by reading the following specific embodiments. However, it should be understood that the specific embodiments disclosed below are only exemplary of the present invention, and the present invention can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be interpreted as limiting, but only as the basis for the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in any appropriate detailed embodiment.

[0018] As one aspect of the technical solution of the present invention, a method for preparing a bio-based polyol involves: mixing lignin, sugar alcohol, polyol and concentrated acid to carry out a liquefaction reaction to obtain a bio-based polyol.

[0019] Specifically, the reaction mechanism of the present invention can be found in Figure 1 The schematic diagram of the bio-based polyol synthesis process shown in the figure is a reaction of dehydration between alcohol molecules. Under the action of concentrated acid, the phenolic hydroxyl group and alcohol hydroxyl group in lignin and the hydroxyl group of sugar alcohol and polyol can be dehydrated to form ethers. It mainly includes two reaction mechanisms. One is the dehydration between the molecules of primary alcohol, mainly through S N 2 Reaction mechanism: First, the alcohol hydroxyl group is protonated, so that the carbon atom in the alkyl group has a partial positive charge and combines with the oxygen in another alcohol. At the same time, the protonated hydroxyl group leaves in the form of water, and then loses the proton to obtain ether. The other is the intermolecular dehydration of secondary alcohols, mainly through S N 1 Reaction mechanism: Under the action of protonation, the alcohol first loses a part of water to form a stable carbon cation, then reacts rapidly with another alcohol molecule, and then loses a proton to obtain an ether. Among them, lignin, sugar alcohol and polyol can fully provide primary alcohol and secondary alcohol to the entire reaction, and polyols with different hydroxyl contents can be obtained by controlling the reaction time, reaction speed and catalyst content. These two reaction mechanisms can not only further convert the phenolic hydroxyl groups in lignin into alcohol hydroxyl groups, thereby improving the reaction efficiency, but also further provide the flexibility and elasticity of the polyurethane material through the generated ether bonds.

[0020] In the present invention, the polyol plays two roles in the overall reaction: one is to serve as a good solvent for lignin and sugar alcohol to accelerate the reaction; the other is to provide hydroxyl groups to participate in the reaction.

[0021] In some embodiments, the mass ratio of lignin, sugar alcohol, polyol and concentrated acid is (10-50):(1-50):(60-100):(2-7).

[0022] In some embodiments, the lignin includes but is not limited to any one or a combination of two or more of woody plant lignin, microbial lignin, alkali lignin, organic solvent lignin, Kraft lignin, steam foam lignin, lignin sulfonate, enzymatic lignin, and herbaceous plant lignin.

[0023] Lignin can be divided into woody lignin and herbaceous lignin based on its source. Compared with woody plant lignin, herbaceous lignin has significant advantages in environmental protection. First, herbaceous plants have a shorter growth cycle and a higher annual output. Especially in large agricultural countries, herbaceous plant lignin is easier to obtain and has a lower cost. Secondly, the collection and processing of herbaceous plants have less impact on the environment, and the extraction process of their lignin requires less energy and chemicals, which helps to reduce carbon emissions and environmental pollution. In addition, herbaceous lignin is simpler in structure and has a higher chemical reactivity, making it easier to modify and utilize in the synthesis of bio-based polyols. These characteristics make herbaceous lignin a more environmentally friendly and economical raw material.

[0024] In some embodiments, the sugar alcohol includes but is not limited to any one or a combination of two or more of sorbitol, mannitol, erythritol, maltitol, lactitol, and xylitol. Sugar alcohol is also an important source of bio-based polyols, and common sugar alcohols include sorbitol, xylitol, and maltitol. Sugar alcohol is usually prepared by hydrolysis of starch or cellulose, and then through fermentation, hydrogenation and other processes. Sugar alcohol has a higher hydroxyl content and excellent biocompatibility. As a soft segment component in polyurethane materials, it can improve the flexibility and elasticity of materials. In addition, the hydroxyl group in the sugar alcohol molecule can cross-link with isocyanate to increase the strength and chemical resistance of the material. The introduction of sugar alcohol not only improves the bio-based content of polyols, but also gives the material good processing properties and physical properties.

[0025] In some embodiments, the polyol includes but is not limited to any one of glycerol, ethylene glycol, propylene glycol, pentaerythritol, butylene glycol, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 2000, polycaprolactone diol 800, and polycaprolactone 2000, or a combination of two or more thereof.

[0026] In some embodiments, the concentrated acid includes, but is not limited to, any one or a combination of two or more of concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated phosphoric acid.

[0027] In some preferred embodiments, the lignin is an organic solvent lignin, and the polyol is a mixture of polyethylene glycol 400, glycerol and sugar alcohol.

[0028] In some more preferred embodiments, the polyol is preferably a mixture of polyethylene glycol 400, glycerol and sorbitol in a mass ratio of 4:1:1. Organic solvent lignin has a relatively complete lignin structure and a good surface hydroxyl content, and is easy to modify; the combination of polyethylene glycol 400, glycerol and sorbitol has both high reactivity with lignin and high compatibility with lignin.

[0029] In some embodiments, the liquefaction reaction is carried out at a temperature of 100-170° C. and for a time of 0.5-2 h.

[0030] In some preferred embodiments, the temperature of the liquefaction reaction is 130-150°C and the time is 0.7-1.3h. If the reaction temperature is low, the degree of modification is low, and the phenolic hydroxyl group of lignin does not react completely. If the reaction temperature is high, the polyol undergoes a recondensation reaction, and lumps appear in the polyol. If the time is short, the degree of modification is low, and the phenolic hydroxyl group of lignin does not react completely. If the time is long, a recondensation reaction occurs, and lumps appear in the polyol.

[0031] In some more preferred embodiments, the liquefaction reaction is carried out at a temperature of 140° C. and for a time of 1 hour.

[0032] In some embodiments, the preparation method includes: mixing the lignin, sugar alcohol, polyol and concentrated acid to form a mixed reaction system, and performing a liquefaction reaction under a protective atmosphere to obtain a bio-based polyol.

[0033] In some preferred embodiments, the protective atmosphere includes, but is not limited to, a nitrogen atmosphere or an argon atmosphere.

[0034] In some embodiments, the preparation method further comprises: after the liquefaction reaction is completed, adjusting the pH value of the mixed reaction system to 6-7 with an alkaline substance, and then dehydrating for 2-6 hours to obtain the bio-based polyol.

[0035] In some preferred embodiments, the alkaline substance includes but is not limited to sodium hydroxide.

[0036] As another aspect of the technical solution of the present invention, it also relates to a bio-based polyol prepared by the aforementioned preparation method, wherein the hydroxyl value of the bio-based polyol is 5.0-15.0 mmol / g, the acid value of the bio-based polyol is 0.5-2.0 mmol / g, and the viscosity of the bio-based polyol at 30°C is 0.3-40.52 Pa.s.

[0037] As another aspect of the technical solution of the present invention, a raw material for preparing a bio-based polyol includes the following components: lignin, sugar alcohol, polyol and concentrated acid.

[0038] In some embodiments, the raw materials for preparing the bio-based polyol include, by weight: 10-50 parts of lignin, 1-50 parts of sugar alcohol, 60-100 parts of polyol and 2-7 parts of concentrated acid.

[0039] In some embodiments, the lignin includes but is not limited to any one or a combination of two or more of woody plant lignin, microbial lignin, alkali lignin, organic solvent lignin, Kraft lignin, steam foam lignin, lignin sulfonate, enzymatic lignin, and herbaceous plant lignin.

[0040] In some embodiments, the sugar alcohol includes, but is not limited to, any one or a combination of two or more of sorbitol, mannitol, erythritol, maltitol, lactitol, and xylitol.

[0041] In some embodiments, the polyol includes but is not limited to any one of glycerol, ethylene glycol, propylene glycol, pentaerythritol, butylene glycol, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 2000, polycaprolactone diol 800, and polycaprolactone 2000, or a combination of two or more thereof.

[0042] In some embodiments, the concentrated acid includes, but is not limited to, any one or a combination of two or more of concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated phosphoric acid.

[0043] As another aspect of the technical solution of the present invention, it also involves the use of the aforementioned bio-based polyols in the preparation of polyurethane materials.

[0044] In summary, the present invention can prepare polyols with high bio-based content by combining lignin with sugar alcohols. This type of polyol is not only highly renewable at the raw material level, in line with the concepts of green chemistry and circular economy, but also can provide excellent performance for polyurethane materials. The introduction of lignin enhances the strength, heat resistance and chemical resistance of the material, while the addition of sugar alcohol improves the flexibility and processability of the material. In addition, the environmental advantage of herbal lignin, which is easier to obtain than woody lignin raw materials, further improves the environmental friendliness and sustainability of the final material.

[0045] The invention develops high bio-based polyols based on lignin (especially herbal lignin) and sugar alcohols, which has important environmental significance and application prospects. This not only conforms to the current concept of green chemistry and circular economy, but also provides a new path for the development of the future polyurethane industry.

[0046] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The reagents and raw materials used in the following examples are commercially available, and the experimental methods without specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0047] Example 1

[0048] According to weight, 70 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of sorbitol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The viscosity of the obtained bio-based polyol was tested, and the viscosity was 4.74 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was mmol / g, the acid value was 0.9 mmol / g, and the pH = 7. The schematic diagram of the synthesis process of the bio-based polyol in this embodiment is shown in the figure. Figure 2 As shown, 31 P-NMR characterization Figure 3 shown.

[0049] Example 2

[0050] According to the weight, 70 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of erythritol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 3.24 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 5.8 mmol / g and the acid value was 0.8 mmol / g; pH = 7.

[0051] Example 3

[0052] According to the weight, 70 parts of polyethylene glycol 400, 20 parts of propylene glycol, and 10 parts of mannitol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 3.07 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 6.2 mmol / g and the acid value was 0.87 mmol / g; pH = 7.

[0053] Example 4

[0054] According to the weight, 70 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of sorbitol were weighed, and then 40 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 36.87 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 6.09 mmol / g and the acid value was 0.5 mmol / g; pH = 7. The increase in lignin content and molecular weight leads to an increase in viscosity.

[0055] Example 5

[0056] According to the weight, 70 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of sorbitol were weighed, and then 15 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 36.87 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 6.89 mmol / g and the acid value was 0.65 mmol / g; pH = 7.

[0057] Example 6

[0058] According to the weight, 70 parts of ethylene glycol, 20 parts of propylene glycol, and 10 parts of sorbitol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 0.42 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 5.4 mmol / g and the acid value was 0.6 mmol / g; pH = 7.

[0059] Example 7

[0060] According to the weight, 70 parts of ethylene glycol, 20 parts of propylene glycol, and 10 parts of erythritol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 0.58 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 5.7 mmol / g and the acid value was 0.5 mmol / g; pH = 7.

[0061] Example 8

[0062] According to the weight, 70 parts of ethylene glycol, 20 parts of propylene glycol, and 10 parts of mannitol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 0.61Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 5.6mmol / g and the acid value was 0.8mmol / g; pH = 7.

[0063] Example 9

[0064] According to the weight, 60 parts of polyethylene glycol 400, 20 parts of glycerol, and 25 parts of sorbitol were weighed, and then 30 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 5.22 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 7.2 mmol / g and the acid value was 0.8 mmol / g; pH = 7.

[0065] Example 10

[0066] According to the weight ratio, 70 parts of polyethylene glycol 400, 30 parts of propylene glycol, and 50 parts of sorbitol were weighed, and then 50 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 7 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 170°C for 120 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, dehydrated on a rotary evaporator for 4 hours to obtain brown bio-based polyols. The obtained bio-based polyols were tested for viscosity, which was 30.74 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 5.2 mmol / g, the acid value was 0.8 mmol / g, and the pH was 7.

[0067] Embodiment 11

[0068] Weigh 80 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of sorbitol by weight, then add 10 parts of enzymatic lignin, stir for 10 minutes until it is evenly dispersed, add 2 parts of concentrated sulfuric acid, and then react under nitrogen protection at 100°C for 30 minutes. After the reaction, add sodium hydroxide aqueous solution to neutralize the mixture to a pH value of about 7. After liquefaction, dehydrate on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 4.25 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, with a hydroxyl value of 14.9 mmol / g and an acid value of 0.9 mmol / g; pH = 7.

[0069] Example 12

[0070] According to the weight ratio, 50 parts of polyethylene glycol 400, 10 parts of glycerol, and 1 part of sorbitol were weighed, and then 10 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 5 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 100°C for 30 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 1.57 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 6.0 mmol / g and the acid value was 0.93 mmol / g; pH = 7.

[0071] Comparative Example 1

[0072] According to the weight, 70 parts of polyethylene glycol 400, 20 parts of glycerol, and 10 parts of sorbitol were weighed, and then 70 parts of enzymatic lignin were added, stirred for 10 minutes until it was evenly dispersed, and 2 parts of concentrated sulfuric acid were added, and then nitrogen protection was reacted at 150°C for 60 minutes. After the reaction, sodium hydroxide aqueous solution was added to neutralize the mixture to a pH value of about 7. After liquefaction, it was dehydrated on a rotary evaporator for 4 hours to obtain a brown bio-based polyol. The obtained bio-based polyol was tested for viscosity, which was 50.5 Pa.s at 30 degrees Celsius; the hydroxyl value and acid value were analyzed by titration, and the hydroxyl value was 4.0 mmol / g, and the acid value was 1.3 mmol / g; pH = 7. The bio-based polyol in this comparative example has too much lignin content, resulting in too high viscosity, and due to the large steric hindrance of lignin, the reaction efficiency of the entire reaction process is further affected, and the hydroxyl value content decreases. The bio-based polyol prepared due to its excessive viscosity cannot be further used.

[0073] Comparative Example 2

[0074] Compared with Example 1, difference is, wherein polyethylene glycol 400 is replaced by polytetrahydrofuran diol.In the process of dewatering and mixing with lignin, because polytetrahydrofuran has stronger hydrophobicity and rigidity, poor compatibility with lignin, the phenomenon of stratification occurs, can not normally carry out the synthesis experiment of homogeneous phase.Therefore long-chain diol of the present invention should select flexible long-chain diol, should not select the diol that contains too many rigid groups in structure.

[0075] Comparative Example 3

[0076] Compared with Example 1, the difference is that the amount of sorbitol added is 0. The hydroxyl value of the obtained product is only 4.8 mmol / g. Therefore, the sugar alcohol introduced in the present invention can increase the hydroxyl value of the bio-based polyol.

[0077] Comparative Example 4

[0078] Compared with Example 1, the difference is that the amount of sorbitol added is 60 parts. The viscosity of the obtained product is 45 Pa.s. Therefore, once the amount of sugar alcohol added is excessive and the reaction time and temperature are not changed, the viscosity will increase, which seriously restricts its application in chemical synthesis experiments.

[0079] Comparative Example 5

[0080] Compared with Example 1, the difference is that the amount of polyethylene glycol 400 and glycerol added is 0. Lignin and sugar alcohol are almost incompatible, and after the temperature is lowered, the product appears as a black solid and cannot be used at all. Therefore, polyols must be introduced as a compatibilizer for sugar alcohol and lignin.

[0081] Comparative Example 6

[0082] Compared with Example 1, the difference is that the reaction temperature is 180° C. The hydroxyl value of the obtained product is 2.0 mmol / g and the viscosity is 54.7 Pa.s; the reason is that due to the increase in reaction temperature, the reaction is relatively violent, resulting in more hydroxyl groups undergoing intermolecular dehydration, thereby resulting in increased viscosity and decreased hydroxyl value.

[0083] Comparative Example 7

[0084] Compared with Example 1, the difference is that the reaction temperature is 90° C. In the process of removing water, a large amount of lignin is precipitated, which is because the reaction temperature is not enough, so the reaction cannot proceed, resulting in the precipitation of lignin.

[0085] Comparative Example 8

[0086] Compared with Example 1, the difference is that the reaction time is 180 min. The hydroxyl value of the obtained product is 1.7 mmol / g and the viscosity is 60.2 Pa.s; the reason is that the extension of the reaction time causes more hydroxyl groups to undergo intermolecular dehydration, thereby increasing the viscosity and decreasing the hydroxyl value.

[0087] Comparative Example 9

[0088] Compared with Example 1, the difference is that the reaction time is 20 minutes. In the process of removing water, a large amount of lignin is precipitated, which is due to insufficient reaction time, so that the reaction cannot proceed, resulting in the precipitation of lignin.

[0089] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0090] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a bio-based polyol, characterized in that: include: Lignin, sugar alcohol, polyol and concentrated acid are mixed to carry out liquefaction reaction to obtain bio-based polyol.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the lignin, sugar alcohol, polyol and concentrated acid is (10-50): (1-50): (60-100): (2-7).

3. The preparation method according to claim 1, characterized in that: The lignin includes any one or a combination of two or more of woody plant lignin, microbial lignin, alkali lignin, organic solvent lignin, Kraft lignin, steam foam lignin, lignin sulfonate, enzymatic lignin, and herbaceous plant lignin; And / or, the sugar alcohol includes any one or a combination of two or more of sorbitol, mannitol, erythritol, maltitol, lactitol, and xylitol; And / or, the polyol includes any one or a combination of two or more of glycerol, ethylene glycol, propylene glycol, pentaerythritol, butylene glycol, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 2000, polycaprolactone diol 800, and polycaprolactone 2000; And / or, the concentrated acid includes any one or a combination of two or more of concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated phosphoric acid; And / or, the liquefaction reaction is carried out at a temperature of 100-170° C. and for a time of 30-120 min.

4. The preparation method according to claim 2, characterized in that: The temperature of the liquefaction reaction is 130-150° C. and the time is 0.7-1.3 h.

5. The preparation method according to claim 1, characterized in that: include: The lignin, sugar alcohol, and polyol are mixed with concentrated acid to form a mixed reaction system, and a liquefaction reaction is performed under a protective atmosphere to obtain a bio-based polyol; The protective atmosphere includes a nitrogen atmosphere or an argon atmosphere; And / or, the preparation method further comprises: after the liquefaction reaction is completed, adjusting the pH value of the mixed reaction system to 6-7 with an alkaline substance, and then dehydrating for 2-6 hours to obtain the bio-based polyol.

6. The preparation method according to claim 5, characterized in that: The alkaline substance includes sodium hydroxide.

7. A bio-based polyol prepared by the preparation method according to any one of claims 1 to 6, wherein the hydroxyl value of the bio-based polyol is 5.0-15.0 mmol / g, the acid value of the bio-based polyol is 0.5-2.0 mmol / g, and the viscosity of the bio-based polyol at 30° C. is 0.3-40.52 Pa.s.

8. A bio-based polyol, characterized in that The raw materials for preparing the bio-based polyol include the following components: lignin, sugar alcohol, polyol and concentrated acid.

9. The bio-based polyol according to claim 8, characterized in that The raw materials for preparing the bio-based polyol include, by weight: 10-50 parts of lignin, 1-50 parts of sugar alcohol, 60-100 parts of polyol and 2-7 parts of concentrated acid; And / or, the lignin includes any one or a combination of two or more of woody plant lignin, microbial lignin, alkali lignin, organic solvent lignin, Kraft lignin, steam foam lignin, lignin sulfonate, enzymatic lignin, and herbaceous plant lignin; And / or, the sugar alcohol includes any one or a combination of two or more of sorbitol, mannitol, erythritol, maltitol, lactitol, and xylitol; And / or, the polyol includes any one or a combination of two or more of glycerol, ethylene glycol, propylene glycol, pentaerythritol, butylene glycol, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 2000, polycaprolactone diol 800, and polycaprolactone 2000; And / or, the concentrated acid includes any one or a combination of two or more of concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated phosphoric acid.

10. Use of the bio-based polyol according to claim 8 or 9 in the preparation of polyurethane materials.

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