A kind of lignin-based polyurethane material and preparation method thereof

Abstract

The present invention relates to the field of polyurethane materials, and in particular to a lignin-based polyurethane material and a preparation method thereof. The lignin-based polyurethane material is obtained by blending a modified polyurethane elastomer with polylactic acid, wherein the modified polyurethane elastomer is obtained by polymerization and crosslinking of hydroxyl groups in a lignin oligomeric polyol, a chain extender, and polylactic acid diol with isocyanate groups in a diisocyanate, respectively, and the chain extender contains at least two hydroxyl groups in the molecule. A lignin oligomeric polyol is obtained and polymerized with diisocyanate to obtain a prepolymer, and the prepolymer is further polymerized into a polymer by a chain extender, and then polylactic acid diol is introduced and cured to obtain a modified polyurethane elastomer, and a lignin-based polyurethane is obtained by blending with polylactic acid. The lignin-based polyurethane material can reduce the waste of petroleum resources and can maintain a high wear resistance.

Description

Technical Field

[0001] The invention relates to the field of polyurethane materials, and in particular to a lignin-based polyurethane material and a preparation method thereof. Background Art

[0002] Polyurethane is a kind of polymer material with excellent mechanical properties formed by the polycondensation reaction of polyols and polyisocyanates. It has strong plasticity. Its mechanical properties, thermal stability and chemical properties can be adjusted by selecting different polyols, isocyanates and catalysts. It is widely used in the automotive industry, packaging materials, electronic information, furniture and other fields. Traditionally, most of the polyols and isocyanates used to synthesize polyurethane are derived from petroleum, which leads to a large waste of petroleum resources. Therefore, effectively using renewable bio-based raw materials to replace petroleum-based raw materials to produce polyurethane has become a research focus.

[0003] Lignin is the second largest biomass resource in plants after cellulose, and is also the most abundant renewable natural aromatic compound. Lignin has a rich surface functional group (hydroxyl, carbonyl, methoxyl and double bonds, etc.), which has a certain impact on the chemical properties of lignin, making it antibacterial, antioxidant, UV-resistant and hydrophobic. Therefore, lignin has become a popular choice for replacing petroleum-based raw materials in the production of polyurethane in this field. However, lignin has a large molecular weight, low hydroxyl activity in the molecular structure, and is insoluble in organic solvents. These characteristics make it difficult for lignin to effectively cross-link with isocyanate, which in turn leads to low uniformity and poor mechanical properties of the synthesized polyurethane material. Summary of the invention

[0004] The object of the present invention is to provide a lignin-based polyurethane material with good wear resistance and a preparation method thereof.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A lignin-based polyurethane material is obtained by blending a modified polyurethane elastomer with polylactic acid. The modified polyurethane elastomer is obtained by addition reaction, polymerization and cross-linking of hydroxyl groups in lignin oligomeric polyol, chain extender and polylactic acid diol with isocyanate groups in diisocyanate, respectively. The chain extender contains at least two hydroxyl groups in its molecule.

[0007] Optionally, the number average molecular weight of the lignin oligomeric polyol is any value between 500 g / mol and 1500 g / mol.

[0008] Optionally, the chain extender includes one or more of 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol, triethylene glycol, neopentyl glycol, dimethylolbutyric acid and dimethylolpropionic acid;

[0009] The diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0010] In a second aspect, the present invention further provides a method for preparing the above-mentioned lignin-based polyurethane material, comprising:

[0011] preparing the lignin oligomeric polyol;

[0012] reacting the dehydrated lignin oligomeric polyol, the diisocyanate and stannous octoate at a first temperature for a first time to obtain a prepolymer terminated by an isocyanate group;

[0013] Adding the chain extender, reacting at a second temperature for a second time, so that two hydroxyl groups in the chain extender react with two isocyanate groups blocked by the prepolymer to form a polymer;

[0014] Adding the polylactic acid diol to the polymer, reacting at a third temperature for a third time, and curing at a fourth temperature for at least a fourth time to obtain the modified polyurethane elastomer;

[0015] The modified polyurethane elastomer is melt-blended with the polylactic acid to obtain the lignin-based polyurethane material.

[0016] Optionally, the preparation of the lignin oligomeric polyol comprises:

[0017] A mixture containing lignin, a solid catalyst and a solvent is subjected to hydrogenation catalytic degradation under a high pressure of a first pressure to obtain lignin oligomers, wherein the solid catalyst is one or more of Ni / ZrO2, Ni / Hβ, and Ni / ZrO2 / Hβ, and the solvent is one or more of methanol, ethanol, isopropanol, and ethylene glycol;

[0018] The lignin oligomer is reacted with n-butyl glycidyl ether and N,N-dimethylbenzylamine at a fifth temperature for a fifth time to obtain the lignin oligomer polyol.

[0019] Optionally, the first pressure is any value between 2MPa and 6MPa;

[0020] The content of the solid catalyst in the mixture is any value within a range of 0.5% to 3.0% of the content of the lignin, and the mass of the solvent is 2 to 2.5 times the mass of the lignin.

[0021] Optionally, the fifth temperature is any value between 100° C. and 120° C., and the fifth time is any value between 4 h and 6 h;

[0022] The mass ratio of the lignin oligomer to the n-butyl glycidyl ether and the N,N-dimethylbenzylamine is (50-80): (35-60): (1.5-2.5).

[0023] Optionally, the molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the lignin oligomeric polyol is any value between (1:1) and (5:1), and the mass of the stannous octoate is any value between 0.1% and 1.0% of the mass of the lignin oligomeric polyol;

[0024] When the chain extender is dimethylol propionic acid, the mass of the chain extender is any value between 10% and 20% of the mass of the lignin oligomeric polyol;

[0025] The first temperature is any value between 90°C and 130°C, and the first time is any value between 2h and 4h;

[0026] The second temperature is any value between 80° C. and 120° C., and the second time is any value between 3 h and 5 h.

[0027] Optionally, the number average molecular weight of the polylactic acid diol is any value between 1500 g / mol and 2500 g / mol, and the mass of the polylactic acid diol is any value between 20% and 40% of the mass of the lignin oligomeric polyol;

[0028] The third temperature is any value between 70°C and 90°C, and the third time is any value between 1h and 3h;

[0029] The fourth temperature is any value between 150° C. and 170° C., and the fourth time is 2 hours.

[0030] Optionally, the mass ratio of the modified polyurethane elastomer to the polylactic acid is any value between (90:10) and (60:40);

[0031] The blending temperature is any value between 170° C. and 220° C., the rotation speed is any value between 50 r / min and 100 r / min, and the blending time is any value between 5 min and 15 min.

[0032] According to the first aspect of the present invention, lignin is degraded into lignin oligomers, which can effectively retain the rigidity characteristics of the lignin aromatic structural units while increasing the content of active functional groups therein, increasing their solubility and reactivity in organic solvent systems, and facilitating the preparation of lignin-based polymer materials. Lignin oligomers are modified into lignin oligomer polyols and applied to polyurethane synthesis, which can not only reduce the consumption of petroleum resources, but also improve the mechanical properties of polyurethanes, giving the products special properties such as wear resistance, flame retardancy, and UV resistance. The modified polyurethane elastomer is mixed with polylactic acid by melt blending to obtain a lignin-based polyurethane material, which helps to improve the wear resistance of the material. The modified polyurethane elastomer is obtained by copolymerizing polylactic acid diol with lignin oligomeric polyol, chain extender and diisocyanate, so that the polyurethane molecular chain includes a lactic acid component, which can improve the compatibility and interfacial interaction between the modified polyurethane elastomer and the polylactic acid material, and at the same time help to improve the dispersion of polylactic acid in the lignin-based polyurethane elastomer, thereby significantly improving the wear resistance and mechanical strength of the lignin-based polyurethane material obtained by blending the modified polyurethane elastomer and polylactic acid.

[0033] Furthermore, too high a number average molecular weight of lignin oligomeric polyol is not conducive to increasing the content of active functional groups in lignin oligomeric polyols of equal mass, and is not conducive to increasing its solubility and reactivity in organic solvent systems, and is thus not conducive to copolymerization of lignin oligomeric polyols with chain extenders, polylactic acid diols and diisocyanates. Too low a number average molecular weight of lignin oligomeric polyols is not conducive to maintaining the rigidity of lignin aromatic structural units, and will result in the mechanical properties of the modified polyurethane elastomer being difficult to meet the requirements.

[0034] Furthermore, the two hydroxyl groups of the chain extender react with the isocyanate groups in different molecules to achieve the purpose of chain extension. Therefore, the chain extender needs to be a substance with two hydroxyl groups in the molecule, among which dimethylol propionic acid is a commonly used chain extender in the preparation of polyurethane. The diisocyanate needs to include two isocyanate groups so as to react with the hydroxyl groups in two different molecules to achieve copolymerization and crosslinking.

[0035] According to a second aspect of the present invention, a hydroxyl group in a lignin oligomeric polyol and an isocyanate group in a diisocyanate undergo an addition reaction under the catalysis of stannous octoate, so that the lignin oligomeric polyol and the diisocyanate are polymerized to obtain a prepolymer, and the prepolymer is terminated by an isocyanate group. The terminal isocyanate group of the prepolymer reacts with the hydroxyl group of the chain extender to form a polymer. The isocyanate group in the polymer reacts with the hydroxyl group of the polylactic acid diol, thereby introducing a lactic acid component into the polymer. During the curing process, the polymer chains inside the material are further cross-linked and cured to obtain a modified polyurethane elastomer. When the modified polyurethane elastomer is melt-blended with polylactic acid, the lactic acid component in the modified polyurethane elastomer makes the modified polyurethane elastomer have good compatibility with the polylactic acid, thereby obtaining a lignin-based polyurethane material with higher wear resistance.

[0036] Furthermore, lignin is hydrogenated and catalytically degraded into lignin oligomers with a small molecular weight under the action of a solid catalyst suitable for catalytic hydrogenation reaction. The obtained lignin oligomers are fully dissolved in the solvent. Under the catalysis of N,N-dimethylbenzylamine, n-butyl glycidyl ether undergoes a ring-opening reaction and dehydrates and de-alcoholizes the hydroxyl groups of the lignin oligomers to form a stable ether bond, thereby obtaining lignin oligomer polyols, which are convenient for polymerization to obtain lignin-based polyurethane materials.

[0037] Furthermore, by limiting the reaction conditions and raw material ratios, the number average molecular weight of lignin is within a preset range, and the number average molecular weight of lignin oligomeric polyols is thereby made to meet the reaction requirements, thereby ensuring the mechanical properties of the modified polyurethane elastomer while ensuring that the lignin oligomeric polyols are easy to react.

[0038] Furthermore, by limiting the reaction conditions and the raw material ratio, the lignin can be fully converted into lignin oligomeric polyols, which helps to improve the purity of the obtained lignin oligomeric polyols.

[0039] Furthermore, by limiting the amount of diisocyanate and chain extender, adjusting the amount of each component in the polymer helps to adjust the mechanical properties of the polymer, thereby improving the wear resistance of the material.

[0040] Furthermore, by limiting the number average molecular weight and addition amount of polylactic acid diol, the content of polylactic acid segments in the modified polyurethane elastomer is adjusted, thereby adjusting the compatibility and interfacial force between the modified polyurethane elastomer and polylactic acid, preventing the modified polyurethane elastomer and polylactic acid from being incompatible, which helps to improve the mechanical properties of the material, ensures that the modified polyurethane elastomer contains lignin-based polyurethane as the main component, and prevents the modified polyurethane elastomer from being doped with a large amount of polylactic acid diol that does not participate in the reaction and affects the mechanical properties of the material.

[0041] Furthermore, by adjusting the blending parameters and the amount of polylactic acid added, the material can obtain better mechanical properties and higher wear resistance while maintaining the characteristics of the polyurethane itself.

[0042] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of the method for preparing the lignin-based polyurethane material shown in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] The lignin-based polyurethane material protected by the present invention is obtained by blending a modified polyurethane elastomer with polylactic acid, wherein the modified polyurethane elastomer is obtained by polymerization and cross-linking of the hydroxyl groups in the lignin oligomeric polyol, the chain extender and the polylactic acid diol with the isocyanate groups in the diisocyanate through addition reaction, and the chain extender contains at least two hydroxyl groups in the molecule.

[0049] By degrading lignin into lignin oligomers, the rigidity of the lignin aromatic structural unit is effectively retained, while the content of active functional groups in the system is increased, the solubility and reactivity of the system in the organic solvent system are increased, and it is convenient to prepare bio-based polymer materials with lignin. Modifying lignin oligomers into lignin oligomer polyols and applying them to polyurethane synthesis can not only reduce the consumption of petroleum resources, but also improve the mechanical properties of polyurethane, giving the product special properties such as wear resistance, flame retardancy, and UV resistance. The modified polyurethane elastomer is mixed with polylactic acid by melt blending to obtain a lignin-based polyurethane material, which helps to improve the wear resistance of the material. The polylactic acid diol is copolymerized with lignin oligomer polyols, chain extenders and diisocyanates to obtain a modified polyurethane elastomer, so that the polyurethane molecular chain contains lactic acid components, which can improve the compatibility and interfacial interaction between the modified polyurethane elastomer and the polylactic acid material, and at the same time help to improve the dispersion of polylactic acid in the lignin-based polyurethane elastomer, so that the wear resistance and mechanical strength of the lignin-based polyurethane material obtained by blending the modified polyurethane elastomer with polylactic acid are significantly improved.

[0050] In some embodiments, the number average molecular weight of the lignin oligomeric polyol is any value between 500 g / mol and 1500 g / mol, for example, any value between 500 g / mol, 700 g / mol, 900 g / mol, 1100 g / mol, 1300 g / mol and 1500 g / mol.

[0051] See also Figure 1 In some embodiments, the method for preparing the lignin-based polyurethane material claimed in the present invention comprises:

[0052] S1, preparing lignin oligomeric polyols;

[0053] S2, reacting the dehydrated lignin oligomeric polyol, diisocyanate and stannous octoate at a first temperature for a first time to obtain a prepolymer terminated by an isocyanate group;

[0054] S3, adding a chain extender, reacting at a second temperature for a second time, so that two hydroxyl groups in the chain extender react with two isocyanate groups blocked by the prepolymer to form a polymer;

[0055] S4, adding polylactic acid diol to the polymer, reacting at a third temperature for a third time, and curing at a fourth temperature for at least a fourth time to obtain a modified polyurethane elastomer;

[0056] S5. Melt-blending the modified polyurethane elastomer and polylactic acid to obtain a lignin-based polyurethane material.

[0057] A hydroxyl group in a lignin oligomeric polyol and an isocyanate group in a diisocyanate undergo an addition reaction under the catalysis of stannous octoate, so that the lignin oligomeric polyol and the diisocyanate are polymerized to obtain a prepolymer, and the prepolymer is terminated by an isocyanate group. The terminal isocyanate group of the prepolymer reacts with the hydroxyl group of the chain extender to form a polymer. The isocyanate group in the polymer reacts with the hydroxyl group of the polylactic acid diol, thereby introducing a lactic acid component into the polymer. During the curing process, the polymer chains inside the material are further cross-linked and cured to obtain a modified polyurethane elastomer. When the modified polyurethane elastomer is melt-blended with polylactic acid, the lactic acid component in the modified polyurethane elastomer makes the modified polyurethane elastomer and the polylactic acid have good compatibility, thereby obtaining a lignin-based polyurethane material with high wear resistance.

[0058] In some embodiments, the molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the lignin oligomeric polyol is any value from (1:1) to (5:1), for example, any ratio from (1:1), (2:1), (3:1), (4:1) and (5:1).

[0059] The mass of stannous octoate may be any value in the range of 0.1% to 1.0% of the mass of the lignin oligomeric polyol, for example, any value in the range of 0.1%, 0.3%, 0.5%, 0.7%, 0.9% and 1.0%.

[0060] When dimethylol propionic acid is selected as the chain extender, the mass of the chain extender is any value between 10% and 20% of the mass of the lignin oligomeric polyol, for example, any value between 10%, 13%, 15%, 17%, 19% and 20%.

[0061] The first temperature is any value between 90°C and 130°C, for example, it can be any value between 90°C, 100°C, 110°C, 120°C and 130°C. The first time is any value between 2h and 4h, for example, it can be any value between 2h, 3h and 4h.

[0062] The second temperature is any value between 80°C and 120°C, for example, it can be any value between 80°C, 90°C, 100°C, 110°C and 120°C. The second time is any value between 3h and 5h, for example, it can be any value between 3h, 4h and 5h.

[0063] In some embodiments, the number average molecular weight of the polylactic acid diol is any value between 1500 g / mol and 2500 g / mol, for example, any value between 1500 g / mol, 1700 g / mol, 1900 g / mol, 2100 g / mol, 2300 g / mol and 2500 g / mol.

[0064] The mass of the polylactic acid diol is any value in the range of 20% to 40% of the mass of the lignin oligomeric polyol, for example, any value in the range of 20%, 25%, 30%, 35% and 40%.

[0065] The third temperature is any value between 70°C and 90°C, for example, it can be any value between 70°C, 75°C, 80°C, 85°C and 90°C. The third time is any value between 1h and 3h, for example, it can be any value between 1h, 2h and 3h.

[0066] The fourth temperature is any value between 150° C. and 170° C., for example, it may be any value between 150° C., 155° C., 160° C., 165° C. and 170° C., and the fourth time is 2 hours.

[0067] In some embodiments, the mass ratio of the modified polyurethane elastomer to the polylactic acid is any value between (90:10) and (60:40), for example, any value between (85:15), (75:25) and (65:35).

[0068] The blending temperature is any value in the range of 170°C to 220°C, for example, any value in the range of 170°C, 190°C, 210°C and 220°C. The speed is any value in the range of 50 r / min to 100 r / min, for example, any value in the range of 50 r / min, 60 r / min, 70 r / min, 80 r / min, 90 r / min and 100 r / min. The time is any value in the range of 5 min to 15 min, for example, any value in the range of 5 min, 7 min, 9 min, 11 min, 13 min and 15 min.

[0069] In some embodiments, preparing lignin oligomeric polyols comprises:

[0070] S101, subjecting a mixture containing lignin, a solid catalyst and a solvent to hydrogenation catalytic degradation under a high pressure of a first pressure to obtain lignin oligomers, wherein the solid catalyst is one or more of Ni / ZrO2, Ni / Hβ, and Ni / ZrO2 / Hβ, and the solvent is one or more of methanol, ethanol, isopropanol, and ethylene glycol;

[0071] S102, reacting the lignin oligomer with n-butyl glycidyl ether and N,N-dimethylbenzylamine at a fifth temperature for a fifth time to obtain a lignin oligomer polyol.

[0072] In some embodiments, the first pressure is any value between 2 MPa and 6 MPa, for example, it can be any value between 2 MPa, 3 MPa, 4 MPa, 5 MPa and 6 MPa.

[0073] The content of the solid catalyst in the mixture is any value in the range of 0.5% to 3.0% of the content of lignin, for example, any value in the range of 0.5%, 1.0%, 2.0% and 3.0%. The mass of the solvent is 2 to 2.5 times the mass of lignin, for example, 2 times, 2.1 times, 2.3 times, 2.4 times or 2.5 times.

[0074] In some embodiments, the fifth temperature is any value between 100°C and 120°C, for example, it can be any value between 100°C, 105°C, 110°C, 115°C and 120°C, and the fifth time is any value between 4h and 6h, for example, it can be any value between 4h, 5h and 6h.

[0075] The mass ratio of lignin oligomer to n-butyl glycidyl ether and N,N-dimethylbenzylamine is (50-80):(35-60):(1.5-2.5), for example, it can be (50:50:2.0), (50:40:1.5), (70:40:2.5), (60:60:1.5) or (80:35:1.5).

[0076] Please see the following examples and comparative examples for details.

[0077] Embodiment 1:

[0078] See also Figure 1 The preparation method of the lignin-based polyurethane material shown in a preferred embodiment of the present application includes:

[0079] S1, preparing lignin oligomeric polyols;

[0080] S2, reacting the dehydrated lignin oligomeric polyol, diisocyanate and stannous octoate at a first temperature for a first time to obtain a prepolymer terminated by an isocyanate group;

[0081] S3, adding a chain extender, reacting at a second temperature for a second time, so that two hydroxyl groups in the chain extender react with two isocyanate groups blocked by the prepolymer to form a polymer;

[0082] S4, adding polylactic acid diol to the polymer, reacting at a third temperature for a third time, and curing at a fourth temperature for at least a fourth time to obtain a modified polyurethane elastomer;

[0083] S5. Melt-blending the modified polyurethane elastomer and polylactic acid to obtain a lignin-based polyurethane material.

[0084] Wherein, step S1 comprises:

[0085] S101, lignin, Ni / ZrO2 / Hβ solid catalyst and solvent ethanol are sealed in a high pressure reactor at a mass ratio of 50:1:100, the pressure in the reactor is 4MPa, and the reaction is stirred at 270°C for 8 hours, and then the lignin oligomers are obtained by reduced pressure distillation. Lignin is degraded by catalytic hydrogenation reaction under suitable conditions, and the number average molecular weight of the obtained lignin oligomers is detected by gel permeation chromatography, and the number average molecular weight of the lignin oligomers is about 1000g / mol.

[0086] S102, reacting lignin oligomers with n-butyl glycidyl ether and N,N-dimethylbenzylamine at a mass ratio of 50:35:1.5 at 120° C. for 5 hours to obtain lignin oligomer polyols. In this step, n-butyl glycidyl ether combines with the hydroxyl group of the lignin oligomer under the catalysis of N,N-dimethylbenzylamine to form a side chain with a hydroxyl group. The reaction route is as follows:

[0087] ;

[0088] Wherein, the R1 group and the R2 group are both lignin groups.

[0089] Step S2 includes:

[0090] Lignin oligomeric polyol, toluene diisocyanate and stannous octoate are mixed evenly in a mass ratio of 60:75:1 after vacuum dehydration, and the temperature is raised to 90°C for 4 hours to generate a prepolymer terminated by an isocyanate group in the reaction system. The hydroxyl group of the lignin oligomeric polyol and the isocyanate group of toluene diisocyanate undergo an addition reaction under the catalysis of stannous octoate to generate a carbamate group, thereby connecting and polymerizing the lignin oligomeric polyol and toluene diisocyanate to form a prepolymer. In this step, the excess toluene diisocyanate helps the lignin oligomeric polyol to fully react, and the remaining unreacted toluene diisocyanate is used for the formation of a polymer in a subsequent step.

[0091] Step S3 includes:

[0092] Add dimethylol propionic acid as a chain extender to the reaction system, the mass of the chain extender being 10% of the lignin oligomeric polyol. After reacting at 100°C for 2 hours, a reaction solution including a polymer terminated by an isocyanate group is obtained. The hydroxyl group of the chain extender continues to react with the isocyanate group of toluene diisocyanate, so that the prepolymer continues to react and polymerize into a polymer.

[0093] Step S4 includes:

[0094] Add polylactic acid diol to the reaction solution, and the mass of polylactic acid diol is 25% of that of lignin oligomer polyol. After reacting at 80°C for 2 hours, pour into a mold at 160°C and cure for 2 hours before taking out to obtain a modified polyurethane elastomer containing polylactic acid. The hydroxyl group of polylactic acid diol continues to react with the isocyanate group of toluene diisocyanate to introduce polylactic acid segments into the polymer. During the curing process, the hydroxyl group in the molecule is further cross-linked with the isocyanate group to form a modified polyurethane elastomer with good mechanical properties.

[0095] In this embodiment, the polylactic acid diol was purchased from Fengyuan Group with the specification of PLA 2000 and a molecular weight of 2000±200.

[0096] Step S5 includes:

[0097] The modified polyurethane elastomer containing polylactic acid and polylactic acid were put into an internal mixer in a mass ratio of 90:10 for melt blending at a temperature of 180°C, a rotation speed of 60 r / min, and a time of 10 min to obtain a lignin-based polyurethane material with further enhanced mechanical properties and wear resistance.

[0098] In this embodiment, the polylactic acid is also purchased from Fengyuan Group.

[0099] Embodiment 2:

[0100] The only difference between this embodiment and the first embodiment is that in step S5, the mass ratio of the modified polyurethane elastomer to the polylactic acid is 80:20.

[0101] Embodiment three:

[0102] The only difference between this embodiment and the first embodiment is that in step S5, the mass ratio of the modified polyurethane elastomer to the polylactic acid is 70:30.

[0103] Embodiment 4:

[0104] The only difference between this embodiment and the third embodiment is that the mass of the polylactic acid diol in step S4 is 30% of the lignin oligomeric polyol.

[0105] Embodiment five:

[0106] The only difference between this embodiment and the third embodiment is that the mass of the polylactic acid diol in step S4 is 40% of the lignin oligomeric polyol.

[0107] Embodiment six:

[0108] The only difference between this embodiment and the fifth embodiment is that in step S5, the mass ratio of the modified polyurethane elastomer to the polylactic acid is 60:40.

[0109] Comparative Example 1:

[0110] The only difference between this embodiment and the fifth embodiment is that polylactic acid is not added in step S5.

[0111] The mechanical properties and wear resistance of the above embodiments and comparative examples were tested. The obtained lignin-based polyurethane material was molded into 1 mm thick tensile bars, 4 mm thick impact bars and 4 mm thick wear-resistant bars by a flat vulcanizer. The molding conditions were: temperature 180°C, pressure 15 MPa, and time 8 min. A WDW-5 microcomputer-controlled electronic universal testing machine was used to perform tensile tests on each tensile bar at a temperature of 25°C, and the tensile rate was set to 50 mm / min. An RH-6050 pendulum impact tester was used to perform impact tests on each impact bar with reference to the national standard "GB / T 1843-2008 Determination of the impact strength of plastic cantilever beams". A multifunctional friction and wear testing machine UMT-TriboLab was used to perform wear resistance tests on each wear-resistant bar at a rotation rate of 200 r / min under a load of 30 N, and the experimental time was 60 min.

[0112] The main mechanical properties and wear resistance data of Examples 1 to 6 of the present invention and Comparative Example 1 are shown in Table 1 below:

[0113]

[0114] In combination with the above embodiments and the data in Table 1, Examples 1 to 3 and Examples 5 to 6 are compared respectively. In the blending modification process of Examples 1 to 3, the addition amount of polylactic acid is increased from 10% to 30%, so that the tensile strength of the obtained lignin-based polyurethane material is gradually increased, the elongation at break and the notched impact strength are slightly decreased, and the wear amount of the blend is gradually reduced. Similarly, in the blending modification process of Examples 5 to 6, the addition amount of polylactic acid is increased from 30% to 40%, and the performance of the obtained lignin-based polyurethane material changes in the same trend.

[0115] In combination with the above embodiments and the data in Table 1, in Examples 3 to 5, by adjusting the mass of polylactic acid diol from 25% to 40% of the lignin oligomer polyol, the content of polylactic acid segments in the modified polyurethane elastomer was increased, the tensile strength and notched impact strength of the blend were gradually increased, the wear amount was significantly reduced, and the elongation at break also showed an overall increasing trend.

[0116] In comparative example 1, polylactic acid was not added to the modified polyurethane elastomer. From the mechanical test and wear test results of the embodiment and the comparative example, it can be seen that the obtained material has a low tensile strength and a large wear amount. It can be seen that increasing the content of polylactic acid in the blending modification process and the content of polylactic acid in the lignin-based polyurethane segment can effectively improve the tensile strength and wear resistance of the lignin-based polyurethane material.

[0117] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] 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 lignin-based polyurethane material, characterized in that: The modified polyurethane elastomer is obtained by melt blending with polylactic acid, wherein the mass ratio of the modified polyurethane elastomer to the polylactic acid is any value between (90:10) and (60:40); The preparation method of the modified polyurethane elastomer comprises: A mixture containing lignin, a solid catalyst and a solvent is subjected to hydrogenation catalytic degradation under a high pressure of a first pressure to obtain lignin oligomers; The lignin oligomer is reacted with n-butyl glycidyl ether and N,N-dimethylbenzylamine to obtain a lignin oligomer polyol, wherein the number average molecular weight of the lignin oligomer polyol is any value between 500 g / mol and 1500 g / mol; The dehydrated lignin oligomeric polyol, diisocyanate and stannous octoate are reacted to obtain a prepolymer terminated by an isocyanate group, and the prepolymer is reacted with a chain extender to form a polymer, wherein the chain extender has at least two hydroxyl groups in its molecule; Polylactic acid diol is added to the polymer, and the modified polyurethane elastomer is obtained after reaction and curing.

2. The lignin-based polyurethane material according to claim 1, characterized in that The chain extender includes one or more of 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol, triethylene glycol, neopentyl glycol, dimethylolbutyric acid and dimethylolpropionic acid; The diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

3. A method for preparing a lignin-based polyurethane material according to any one of claims 1 or 2, characterized in that: include: preparing the lignin oligomeric polyol; reacting the dehydrated lignin oligomeric polyol, the diisocyanate and stannous octoate at a first temperature for a first time to obtain a prepolymer terminated by an isocyanate group; Adding the chain extender, reacting at a second temperature for a second time, so that two hydroxyl groups in the chain extender react with two isocyanate groups blocked by the prepolymer to form a polymer; Adding the polylactic acid diol to the polymer, reacting at a third temperature for a third time, and curing at a fourth temperature for at least a fourth time to obtain the modified polyurethane elastomer; The modified polyurethane elastomer is melt-blended with the polylactic acid to obtain the lignin-based polyurethane material.

4. The preparation method according to claim 3, characterized in that: The preparation of the lignin oligomeric polyol comprises: A mixture containing lignin, a solid catalyst and a solvent is subjected to hydrogenation catalytic degradation under a high pressure of a first pressure to obtain lignin oligomers, wherein the solid catalyst is one or more of Ni / ZrO2, Ni / Hβ, and Ni / ZrO2 / Hβ, and the solvent is one or more of methanol, ethanol, isopropanol, and ethylene glycol; The lignin oligomer is reacted with n-butyl glycidyl ether and N,N-dimethylbenzylamine at a fifth temperature for a fifth time to obtain the lignin oligomer polyol.

5. The preparation method according to claim 4, characterized in that: The first pressure is any value between 2MPa and 6MPa; The content of the solid catalyst in the mixture is any value within a range of 0.5% to 3.0% of the content of the lignin, and the mass of the solvent is 2 to 2.5 times the mass of the lignin.

6. The preparation method according to claim 4, characterized in that: The fifth temperature is any value between 100° C. and 120° C., and the fifth time is any value between 4 h and 6 h; The mass ratio of the lignin oligomer to the n-butyl glycidyl ether and the N,N-dimethylbenzylamine is (50-80):(35-60):(1.5-2.5).

7. The preparation method according to claim 3, characterized in that: The molar ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the lignin oligomeric polyol is any value between (1:1) and (5:1), and the mass of the stannous octoate is any value between 0.1% and 1.0% of the mass of the lignin oligomeric polyol; When the chain extender is dimethylol propionic acid, the mass of the chain extender is any value between 10% and 20% of the mass of the lignin oligomeric polyol; The first temperature is any value between 90°C and 130°C, and the first time is any value between 2h and 4h; The second temperature is any value between 80° C. and 120° C., and the second time is any value between 3 h and 5 h.

8. The preparation method according to claim 3, characterized in that: The number average molecular weight of the polylactic acid diol is any value between 1500 g / mol and 2500 g / mol, and the mass of the polylactic acid diol is any value between 20% and 40% of the mass of the lignin oligomeric polyol; The third temperature is any value between 70°C and 90°C, and the third time is any value between 1h and 3h; The fourth temperature is any value between 150° C. and 170° C., and the fourth time is 2 hours.

9. The preparation method according to claim 3, characterized in that: The blending temperature is any value between 170° C. and 220° C., the rotation speed is any value between 50 r / min and 100 r / min, and the blending time is any value between 5 min and 15 min.

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