Lignin-based non-isocyanate polyurethane foam material and modification method thereof

Abstract

The invention discloses a lignin-based non-isocyanate polyurethane foam material and a modification method thereof. The method comprises the following steps: reacting lignin-based epoxy resin with CO2 under the action of a catalyst to prepare lignin-based cyclic carbonate, and reacting the lignin-based cyclic carbonate with an amine curing agent and water to prepare a non-isocyanate polyurethane (NIPU) foam material; in order to improve the water resistance, the thermal insulation property and the mechanical property of the material, POSS (polyhedral oligomeric silsesquioxane) is introduced through an S-alkylation reaction, and POSS modified NIPU is prepared. The obtained foam has high compression strength, low thermal conductivity (0.0406 W.m <-1 >. K <-1 >), excellent water resistance and recoverable reprocessing performance, and the tensile strength retention rate after hot-pressing recovery is greater than or equal to 87.5%. According to the invention, CO2 fixation and lignin high-value utilization are realized, a green and sustainable high-performance polyurethane foam preparation strategy is provided, and the method is suitable for the fields of heat insulation, structural materials and recoverable macromolecules.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a preparation method of a POSS-reinforced modified lignin-based non-isocyanate polyurethane foam material and its application in the fields of thermal insulation, structural foam and the like. Technical Background

[0002] Polyurethane foam has light weight, high load-bearing capacity, low thermal conductivity, easy processing, and good chemical corrosion resistance and aging resistance. It is widely used in aerospace, automobile manufacturing, building insulation, road transportation, packaging and other fields. Traditional polyurethane foam is mostly made from fossil resources and requires the use of highly toxic and volatile isocyanate monomers, which poses great harm to human health and the environment. At the same time, its thermosetting three-dimensional cross-linked network structure makes it difficult to degrade and recycle, limiting its further promotion and application under sustainable development policies. In recent years, with the advancement of the country's "dual carbon" strategy and the increasing public attention to environmental and health issues, the development of non-isocyanate polyurethane (NIPU) foam materials that do not rely on isocyanates, are renewable, degradable, and recyclable has become a research hotspot in this field.

[0003] Lignin is the most abundant natural aromatic polymer in nature. It is widely available and inexpensive. Its molecular structure is rich in functional groups such as phenolic hydroxyl, alcoholic hydroxyl, and carboxyl groups. It has good reactivity and a rigid carbon skeleton. In theory, it can be used as an ideal biomass raw material for synthesizing NIPU foam materials. In particular, its large molecular rigid skeleton can impart good mechanical properties and thermal stability to the material. However, lignin's complex structure and composition, low reactivity, and poor solubility in most organic solvents have severely limited its application in NIPU synthesis.

[0004] The present invention is take lignin oligomer as raw material, prepares lignin-based epoxy resin by functionalized modification, and further with carbon dioxide cycloaddition reaction under catalyst action, obtains lignin-based cyclic carbonate.Described cyclic carbonate reacts with amine curing agent and appropriate amount of water, prepares self-foaming non-isocyanate polyurethane (NIPU) foam material.For further promoting the mechanical strength, heat-insulating property and water resistance of foam, by S-alkylation reaction, mercapto-functionalized cage type silsesquioxane (POSS-SH) is introduced foam network structure, obtains POSS modified lignin-based NIPU foam material, effectively solves the problems such as prior art lignin substitution rate is low, foam material strength is not high, water resistance is not enough.The foam material structure obtained is dense, has excellent mechanical property, heat-insulating property and recyclable reprocessing performance, is expected to be promoted and applied in the fields such as heat insulation, structural materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and modification method of a lignin-based non-isocyanate polyurethane foam material to solve the problems existing in the prior art such as high raw material toxicity, low lignin utilization, poor foam performance and non-recyclable materials.

[0006] The present invention adopts the following technical solutions:

[0007] The first step is to prepare a lignin-based cyclocarbonate: a lignin-based epoxy resin is reacted with CO2 in the presence of a catalyst to produce a lignin-based cyclocarbonate. The reaction formula is:

[0008]

[0009] The lignin-based epoxy resin is prepared according to the method in Chinese invention patent CN202010672980.5, and the epoxy value is 0.26-0.40 mol / 100g.

[0010] The reaction uses N-methylpyrrolidone or N,N-dimethylformamide (DMF) as solvent, introduces CO2 at a pressure of 0.5-5 MPa into a closed reactor, and reacts at 80-150° C. for 2-24 hours.

[0011] The catalyst is one or a mixture of metal halides such as lithium bromide, lithium chloride, potassium iodide, potassium bromide and zinc bromide, and its usage is 0.1-10% of the mass of the lignin-based epoxy resin.

[0012] The second step is to prepare a self-foaming lignin-based non-isocyanate polyurethane foam material: lignin-based cyclic carbonate is reacted with an amine curing agent and water to prepare a self-foaming non-isocyanate polyurethane foam material. The preparation process is as follows:

[0013]

[0014] The process comprises the following steps: mixing lignin-based cyclic carbonate, an amine curing agent, and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) in proportion, adding a certain amount of deionized water and mixing evenly, and performing a curing reaction at 80-180° C. for 1-6 hours.

[0015] The amine curing agent is one or more of polyamide, polyetheramine, alicyclic amine and fatty amine, and the amount of the amine curing agent is such that the molar ratio of amino group to cyclic carbonate group is 0.2:1 to 1:1.

[0016] The molar ratio of water to cyclic carbonate groups is 0.1:1 to 1:1.

[0017] The third step is to prepare a POSS-modified non-isocyanate polyurethane foam material: a lignin-based cyclic carbonate is reacted with an amine curing agent and POSS-SH to prepare a POSS-modified non-isocyanate polyurethane foam material. The preparation process is as follows:

[0018]

[0019] The process comprises the following steps: mixing lignin-based cyclic carbonate, amine curing agent and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) in proportion, adding a certain amount of POSS-SH and mixing evenly, and performing curing reaction at 80-180° C. for 1-6 hours.

[0020] The amine curing agent is one or more of polyamide, polyetheramine, alicyclic amine and fatty amine, and the amount of the amine curing agent is such that the molar ratio of amino group to cyclic carbonate group is 0.2:1 to 1:1.

[0021] The amount of POSS-SH used is such that the molar ratio of the thiol group to the cyclic carbonate group is 0.1:1 to 1:1.

[0022] The POSS modified non-isocyanate polyurethane foam material is characterized in that: the amount of amine curing agent is such that the molar ratio of amino group to cyclic carbonate group is 0.8:1, the amount of POSS-SH is such that the molar ratio of thiol group to cyclic carbonate group is 0.2:1, the curing reaction is carried out at 120° C. for 4 hours and at 160° C. for 4 hours, and the obtained foam material has high compressive strength (4.21 MPa), low thermal conductivity (0.0406 W·m -1 ·K -1 ), excellent water resistance and recyclable reprocessing performance, the tensile strength retention rate after hot pressing recovery is ≥87.5%.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. Using CO2 to participate in the reaction effectively avoids highly toxic and moisture-sensitive isocyanates, achieves carbon fixation and resource utilization, and complies with the principles of green chemistry.

[0025] 2. The prepared NIPU foam material has excellent water resistance, thermal insulation and mechanical properties. Its compressive strength can reach 4.21MPa and its thermal conductivity is as low as 0.0406W·m -1 ·K -1 , and has broad application prospects in the fields of road traffic, building insulation, structural materials, etc.

[0026] 3. The foam has good thermal processing reshaping properties and can still maintain more than 87.5% of its original tensile strength after two rounds of hot pressing and recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : FTIR spectra of lignin-based cyclic carbonate (LCC), non-isocyanate polyurethane (LNIPU) and POSS modified foam (LNIPU / POSS).

[0028] Figure 2 : Physical picture of LNIPU and LNIPU / POSS foam material prepared by the application. DETAILED DESCRIPTION

[0029] A lignin-based non-isocyanate polyurethane foam material and a modification method thereof, which is achieved by the following steps:

[0030] The first step is to prepare a lignin-based cyclocarbonate: a lignin-based epoxy resin is reacted with CO2 in the presence of a catalyst to prepare a lignin-based cyclocarbonate.

[0031] The second step is to prepare a lignin-based non-isocyanate polyurethane foam material: lignin-based cyclic carbonate, amine curing agent, and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) are mixed in proportion, a certain amount of deionized water is added and mixed evenly, and the mixture is cured at 80-180°C for 1-6 hours.

[0032] The third step is to prepare a POSS-modified lignin-based non-isocyanate polyurethane foam material: lignin-based cyclic carbonate, amine curing agent, and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) are mixed in proportion, a certain amount of POSS-SH is added and mixed evenly, and the mixture is cured at 80-180°C for 1-6 hours.

[0033] Example 1

[0034] (1) In a 250 mL autoclave, add 70 g of lignin-based epoxy resin (LEP1, 0.32 mol / 100 g), 1.4 g of lithium bromide, and 50 mL of N-methylpyrrolidone (NMP). Heat to 110°C, introduce CO2 to a certain pressure, check for leaks, and vent. Repeat this operation three times, completely expel the air from the autoclave, introduce CO2 to maintain the pressure at 2 MPa, and stir for 9 h. After the reaction is complete, wash with hot water to remove the catalyst and NMP, and remove water by vacuum distillation to obtain a brown solid, namely, lignin-based cyclocarbonate (LCC1).

[0035] (2) Add 10g LCC1, 3.3g T-403, and 0.22g DBU to a mold, add 0.1g deionized water at 80°C and stir evenly, then cure at 120°C for 4 hours and 160°C for 4 hours to obtain a lignin-based NIPU foam material (LNIPU1). Foam material performance parameters: density 239kg / m 3, pore diameter 0.70mm, thermal conductivity 0.0592W·m -1 ·K -1 , compression strength 1.24MPa, and mechanical properties retained 87.8% after hot pressing recovery.

[0036] Example 2

[0037] (1) In a 250 mL autoclave, add 80 g of lignin-based epoxy resin (LEP2, 0.33 mol / 100 g), 8 g of lithium bromide, and 70 mL of N-methylpyrrolidone (NMP). Heat to 150°C, introduce CO2 to a certain pressure, check for leaks, and vent. Repeat this operation three times, completely expel the air from the autoclave, introduce CO2 to maintain the pressure at 5 MPa, and stir for 2 h. After the reaction is complete, wash with hot water to remove the catalyst and NMP, and remove water by vacuum distillation to obtain a brown solid, namely, lignin-based cyclocarbonate (LCC2).

[0038] (2) Add 10g LCC1, 3.4g T-403, and 0.22g DBU to a mold, add 0.1g deionized water at 80°C and stir evenly, cure at 80°C for 4 hours and 180°C for 4 hours to obtain a lignin-based NIPU foam material (LNIPU2). Foam material performance parameters: density 221kg / m 3 , pore diameter 0.75mm, thermal conductivity 0.0594W·m -1 ·K -1 , compression strength is 0.66MPa, and mechanical properties are retained at 85.2% after hot pressing recovery.

[0039] Example 3

[0040] (1) In a 250 mL autoclave, add 70 g of lignin-based epoxy resin (LEP3, 0.34 mol / 100 g), 0.7 g of lithium bromide, and 70 mL of N,N-dimethylformamide (DMF). Heat to 80°C, introduce CO2 to a certain pressure, check for leaks, and vent. Repeat this operation three times, completely expel the air from the autoclave, introduce CO2 to maintain the pressure at 0.5 MPa, and stir for 24 h. After the reaction is complete, wash with hot water to remove the catalyst and NMP, and remove water by vacuum distillation to obtain a brown solid, namely, lignin-based cyclocarbonate (LCC3).

[0041] (2) Add 10g LCC1, 3.47g T-403, and 0.23g DBU to a mold, add 0.11g deionized water at 80°C and stir evenly, then cure at 120°C for 4 hours and 150°C for 4 hours to obtain a lignin-based NIPU foam material (LNIPU3). Foam material performance parameters: density 210kg / m 3 , pore diameter 0.86mm, thermal conductivity 0.061W·m -1 ·K-1 , compression strength is 0.52MPa, and mechanical properties are retained at 79.3% after hot pressing recovery.

[0042] Example 4

[0043] 10g LCC1, 3.30g T-403, and 0.22g DBU were added to a mold, 0.72g POSS-SH was added at 80°C and stirred evenly, and then cured at 120°C for 4 hours and 150°C for 4 hours to obtain a POSS-modified lignin-based NIPU foam material (LNIPU / POSS1). Foam material performance parameters: density 321kg / m 3 , pore diameter 0.45mm, thermal conductivity 0.0406W·m -1 ·K -1 , compression strength 4.21MPa, and mechanical properties retained 90.1% after hot pressing recovery.

[0044] Example 5

[0045] 10g LCC1, 1.44g isophorone diamine, and 0.22g DBU were added to the mold, and 1.44g POSS-SH was added at 80℃ and stirred evenly. The mixture was cured at 80℃ for 4 hours and 180℃ for 1 hour to obtain POSS-modified lignin-based NIPU foam material (LNIPU / POSS2). Foam material performance parameters: density 296kg / m 3 , pore diameter 0.49mm, thermal conductivity 0.0486W·m -1 ·K -1 , compression strength 2.47MPa, and mechanical properties retained 79.1% after hot pressing recovery.

[0046] Example 6

[0047] 10g LCC1, 0.66g hexamethylenediamine, and 0.22g DBU were added to a mold, 2.16g POSS-SH was added at 80°C and stirred evenly, and then cured at 120°C for 4 hours and 160°C for 1 hour to obtain POSS-modified lignin-based NIPU foam material (LNIPU / POSS3). Foam material performance parameters: density 288kg / m 3 , pore diameter 0.69mm, thermal conductivity 0.0530W·m -1 ·K -1 , compression strength 1.22MPa, and mechanical properties retained 77.8% after hot pressing recovery.

[0048] Example 7

[0049] 10g LCC1, 1.1g polyamide Y330, and 0.22g DBU were added to a mold, 2.88g POSS-SH was added at 80°C and stirred evenly, and then cured at 120°C for 4 hours and 160°C for 1 hour to obtain POSS-modified lignin-based NIPU foam material (LNIPU / POSS4). Foam material performance parameters: density 291kg / m 3 , pore diameter 0.86mm, thermal conductivity 0.0552W·m -1 ·K -1 , compression strength is 0.79MPa, and mechanical properties are retained at 76.7% after hot pressing recovery.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A lignin-based non-isocyanate polyurethane foam material and a modification method thereof. Characterized in that: The following steps are involved: In the first step, lignin-based epoxy resin and CO2 are reacted with a cycloaddition reaction under the action of a catalyst to prepare lignin-based cyclic carbonate; in the second step, lignin-based cyclic carbonate is reacted with an amine curing agent and water to prepare a self-foaming non-isocyanate polyurethane foam material; in the third step, lignin-based cyclic carbonate is reacted with an amine curing agent and a mercapto-functionalized cage-type silsesquioxane (POSS-SH) to prepare a POSS-modified non-isocyanate polyurethane foam material with a dense structure and excellent performance.

2. The method for preparing the first step of lignin-based cyclic carbonate according to claim 1, characterized in that: The reaction uses N-methylpyrrolidone or N,N-dimethylformamide (DMF) as a solvent, introduces CO2 at a pressure of 0.5-5 MPa in a closed reactor, and reacts at 80-150°C for 2-24 hours; the lignin-based epoxy resin is prepared according to the method in Chinese invention patent CN202010672980.5, and the epoxy value is 0.26-0.40 mol / 100g.

3. The method for preparing the first step of lignin-based cyclic carbonate according to claim 1, characterized in that: The catalyst is one or a mixture of metal halides such as lithium bromide, lithium chloride, potassium iodide, potassium bromide and zinc bromide, and its usage is 0.1-10% of the mass of the lignin-based epoxy resin.

4. The method for preparing the second step lignin-based non-isocyanate polyurethane foam material according to claim 1, characterized in that: The following steps are involved: Lignin-based cyclic carbonate, amine curing agent, and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) are mixed in proportion, a certain amount of deionized water is added and mixed evenly, and the mixture is cured at 80-180° C. for 1-6 hours.

5. The method for preparing the lignin-based non-isocyanate polyurethane foam material according to claim 4, wherein: The amine curing agent is one or more of polyamide, polyetheramine, alicyclic amine and fatty amine, and the amount of the amine curing agent is such that the molar ratio of amino group to cyclic carbonate group is 0.2:1 to 1:1; the molar ratio of water to cyclic carbonate group is 0.1:1 to 1:

1.

6. the preparation method of the 3rd step POSS modified non-isocyanate polyurethane foam material as claimed in claim 1, is characterized in that, The following steps are involved: Lignin-based cyclic carbonate, amine curing agent, and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) are mixed in proportion, a certain amount of POSS-SH is added and mixed evenly, and the mixture is cured at 80-180° C. for 1-6 hours.

7. the preparation method of POSS modified non-isocyanate polyurethane foam material as claimed in claim 6, is characterized in that: The amine curing agent is one or more of polyamide, polyetheramine, alicyclic amine and fatty amine, and the amount of the amine curing agent is such that the molar ratio of amino group to cyclic carbonate group is 0.2:1-1:1; the amount of the POSS-SH is such that the molar ratio of thiol group to cyclic carbonate group is 0.1:1-1:

1.

8. the preparation method of POSS modified non-isocyanate polyurethane foam material as claimed in claim 6, is characterized in that: The amount of amine curing agent was such that the molar ratio of amino group to cyclocarbonate group was 0.8:1, and the amount of POSS-SH was such that the molar ratio of thiol group to cyclocarbonate group was 0.2:

1. The curing reaction was carried out at 120℃ for 4h and at 160℃ for 4h. The obtained foam material had high compressive strength (4.21MPa), low thermal conductivity (0.0406W·m -1 ·K -1 ), excellent water resistance and recyclable reprocessing performance, the tensile strength retention rate after hot pressing recovery is ≥87.5%.

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