Solvent-free polyurethane material based on Diels-Alder dynamic bonds as well as preparation method and application of solvent-free polyurethane material
By synthesizing polyurethane materials under solvent-free conditions through Diels-Alder dynamic bonds, the problems of organic solvent pollution and insufficient performance are solved, achieving self-healing and reprocessable properties, which are suitable for fields such as 3D printing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-29
- Publication Date
- 2026-04-10
AI Technical Summary
Existing polyurethane material synthesis methods suffer from environmental pollution, health hazards, and increased costs due to organic solvents. Furthermore, traditional materials lack self-healing and reprocessable properties.
Polyurethane materials were synthesized under solvent-free conditions using Diels-Alder dynamic bonds. The process involved initial polymerization of polyols and diisocyanates, followed by the addition of conjugated dienes and dienophiles to form a reversible crosslinking network. Finally, curing and crosslinking were performed to prepare polyurethane materials with self-healing and reprocessable properties.
It achieves solvent-free synthesis, avoids environmental pollution, maintains good mechanical properties, and has self-healing and reprocessable properties, making it suitable for fields such as 3D printing.
Smart Images
Figure CN121824915A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials science and engineering technology, and in particular to a solvent-free polyurethane material based on Diels-Alder dynamic bonds, its preparation method and application. Background Technology
[0002] Polyurethane (PU) is a polymer material synthesized by stepwise polymerization of diisocyanate and polyol. Due to its excellent structural designability, mechanical properties, and wear and oil resistance, it has been widely used in elastomers, coatings, adhesives, foam materials, and medical materials. Currently, most polyurethanes are synthesized using solvent methods to reduce system viscosity, control reaction progress, and facilitate processing. This method typically involves prepolymerization and chain extension reactions in organic solvents such as N,N-dimethylformamide (DMF) and tetrahydrofuran (THF). However, this method has significant drawbacks: on the one hand, the use of large amounts of volatile organic solvents not only pollutes the environment and endangers the health of operators but also increases solvent recovery and treatment costs, failing to meet the requirements of green and sustainable development; on the other hand, solvent residues may reduce the thermal stability and mechanical properties of the product, limiting its practical application potential in high-end fields.
[0003] To address these issues, materials scientists have developed various solvent-free / low-solvent polyurethane synthesis techniques in recent years, such as melt prepolymerization and reaction injection molding (RIM). While these techniques reduce dependence on organic solvents to some extent, they generally suffer from high viscosity of the reaction system, uneven mixing, and increased side reactions. Furthermore, the materials prepared are mostly traditional cross-linked structures, lacking functional tunability and making it difficult to achieve intelligent properties such as self-healing and reprocessability. Summary of the Invention
[0004] To address the aforementioned problems, this invention aims to provide a solvent-free polyurethane material based on Diels-Alder dynamic bonds, its preparation method, and its applications.
[0005] The technical solution of the present invention is as follows: On the one hand, a method for preparing solvent-free polyurethane materials based on Diels-Alder dynamic bonds is provided, including the following steps: S1: Polyol and diisocyanate are mixed and then subjected to preliminary polymerization to obtain a prepolymer, which is used as component A; The conjugated diene and dienophile containing Diels-Alder active groups were mixed evenly as component B. S2: Mix component A and component B, and then perform a shear mixing reaction to obtain a polyurethane material with a reversible crosslinked network; S3: Curing and crosslinking the polyurethane material with the reversible crosslinking network to obtain the solvent-free polyurethane material based on Diels-Alder dynamic bonds.
[0006] Preferably, in step S1, the polyol is any one or more of polyether polyol, polycaprolactone polyol, polyester polyol, polycarbonate polyol, aromatic polyester polyol, polysiloxane polyol, and polyester polyether polyol, and the diisocyanate is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophthalic diisocyanate, phenyl dimethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.
[0007] Preferably, in step S1, the initial polymerization is carried out at 80~120℃ for 4~12h.
[0008] Preferably, in step S1, the conjugated diene is any one or more of 1,3-butadiene, isoprene, 1-methoxy-1,3-butadiene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, furan, furfuryl alcohol, 2,5-furandiethanol, and 2,5-furandicarboxylic acid.
[0009] Preferably, in step S1, the dienophile is any one or more of maleimide, bismaleimide, maleic anhydride and its derivatives, acrylate / acrylamide derivatives, acrolein, acetylene dicarboxylic acid ester, tetracyanoethylene, and nitrobenzene.
[0010] Preferably, in step S2, the shear mixing reaction is carried out at 80~120℃ and 30~100rpm for 0.5~2h.
[0011] Preferably, in step S3, when performing curing and crosslinking, the curing and crosslinking is carried out at 80~120℃ for at least 24 hours.
[0012] Preferably, in step S1, the molar ratio of the polyol to the diisocyanate is 1:1.5~2.5, and the molar ratio of the conjugated diene to the dienophile is 1:0.05~0.5; in step S2, the molar ratio of component A to component B is 1:1.5~3.
[0013] On the other hand, a solvent-free polyurethane material based on Diels-Alder dynamic bonds, prepared by any one of the above-described methods, is provided, along with its application in 3D printing.
[0014] The beneficial effects of this invention are: This invention enables the complete solvent-free synthesis of polyurethane materials, eliminating the environmental pollution problems caused by organic solvents at the source. In a solvent-free system, a polyurethane material with a dynamic reversible cross-linking network is constructed, which can maintain good mechanical properties while possessing efficient self-healing ability and excellent reprocessability. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of the synthesis route of the polyurethane material in Example 1; Figure 2 This is a schematic diagram comparing the infrared curves of polyurethane materials in Example 1 and Comparative Example 1. Figure 3 The tensile stress-strain curve and self-healing stress-strain curve of the polyurethane material in Example 1 are shown. Figure 4 The tensile stress-strain curves and self-healing stress-strain curves of the polyurethane material in Example 2 are shown. Figure 5 The tensile stress-strain curve and self-healing stress-strain curve of polyurethane material are shown in Comparative Example 1. Figure 6 The tensile stress-strain curve of polyurethane material is shown in Comparative Example 2. Detailed Implementation
[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.
[0018] On one hand, the present invention provides a method for preparing a solvent-free polyurethane material based on Diels-Alder dynamic bonds, comprising the following steps: S1: Polyol and diisocyanate are mixed and then subjected to preliminary polymerization to obtain a prepolymer, which is used as component A; The conjugated diene and dienophile containing Diels-Alder active groups were mixed evenly as component B. S2: Mix component A and component B, and then perform a shear mixing reaction to obtain a polyurethane material with a reversible crosslinked network; S3: Curing and crosslinking the polyurethane material with the reversible crosslinking network to obtain the solvent-free polyurethane material based on Diels-Alder dynamic bonds.
[0019] In this invention, no organic solvents are used in any step, thus avoiding the emission of volatile organic compounds (VOCs) and the subsequent solvent recovery costs, which is in line with the basic principles of green chemistry. By introducing Diels-Alder dynamic bonds, the advantages of solvent-free processing can be retained while successfully solving the problems of insufficient mechanical properties, lack of self-healing ability, and lack of reprocessability of traditional materials.
[0020] In a specific embodiment, in step S1, the polyol is any one or more of polyether polyol, polycaprolactone polyol, polyester polyol, polycarbonate polyol, aromatic polyester polyol, polysiloxane polyol, and polyester polyether polyol, and the diisocyanate is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophthalic diisocyanate, phenyl dimethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.
[0021] It should be noted that the polyols and diisocyanates in the above embodiments are only some of the preferred reagents of the present invention. Other polyols and diisocyanates that can be used as raw materials for polyurethane synthesis in the prior art can also be applied to the present invention.
[0022] In one specific embodiment, during step S1, the preliminary polymerization is carried out at 80-120°C for 4-12 hours. It should be noted that the preliminary polymerization of polyols and diisocyanates to obtain prepolymers is prior art. The reaction conditions in this embodiment are merely preferred parameters of the present invention. Other reaction condition parameters in the prior art that enable the preliminary polymerization of polyols and diisocyanates to obtain prepolymers can also be applied to the present invention.
[0023] In a specific embodiment, in step S1, the conjugated diene is any one or more of 1,3-butadiene, isoprene, 1-methoxy-1,3-butadiene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, furan, furfuryl alcohol, 2,5-furandiethanol, and 2,5-furandicarboxylic acid, and the dienophile is any one or more of maleimide, bismaleimide, maleic anhydride and its derivatives, acrylate / acrylamide derivatives, acrolein, acetylene dicarboxylic acid ester, tetracyanoethylene, and nitrobenzene.
[0024] In one specific embodiment, during step S2, the shear mixing reaction is carried out at 80-120°C and 30-100 rpm for 0.5-2 hours. It should be noted that the purpose of this step is to introduce the Diels-Alder active groups of component B into the prepolymer, thereby forming a polyurethane material with a reversible crosslinked network. The reaction conditions in this embodiment are merely preferred parameters of the present invention; other reaction condition parameters capable of achieving this purpose are also applicable to the present invention.
[0025] In one specific embodiment, during step S3, the curing and crosslinking are performed at 80°C for at least 24 hours. It should be noted that the purpose of this step is to cure and crosslink the polyurethane material with the reversible crosslinking network. The reaction conditions in this embodiment are merely preferred parameters of the present invention; other reaction condition parameters that can achieve this purpose are also applicable to the present invention.
[0026] In a specific embodiment, in step S1, the molar ratio of the polyol and the diisocyanate is 1:1.5~2.5, and the molar ratio of the conjugated diene and the dienophile is 1:0.05~0.5; in step S2, the molar ratio of component A and component B is 1:1.5~3.
[0027] On the other hand, the present invention also provides a solvent-free polyurethane material based on Diels-Alder dynamic bonds prepared by the preparation method of solvent-free polyurethane material based on Diels-Alder dynamic bonds as described in any one of the above-mentioned methods, and its application in 3D printing.
[0028] In this invention, the solvent-free polyurethane material based on Diels-Alder dynamic bonds can be directly powdered for 3D printing (such as selective laser sintering (SLS), high-speed sintering (HSS), etc.), which can significantly shorten the production cycle and reduce costs.
[0029] Example 1 A solvent-free polyurethane material based on Diels-Alder dynamic bonds, such as Figure 1 As shown, it is prepared through the following steps: (1) Polytetrahydrofuran ether diol (PTMEG, 10.0 g, 0.005 mol) with a molecular weight of 2000 g / mol and diphenylmethane diisocyanate (MDI, 2.50 g, 0.01 mol) were placed in a reactor and stirred in an oil bath at 80°C for 12 h to obtain a polyurethane prepolymer with NCO-terminated ends, which was used as component A; (2) Mix 2,5-furandiethanol (0.64 g, 0.005 mol) and bismaleimide (BMI, 0.716 g, 0.002 mol) evenly as component B; (3) Place component A and component B in a mixer and perform a shear mixing reaction at 80°C and 60 rpm for 2 hours. Construct a dynamic covalent crosslinking network through the Diels-Alder [4+2] cycloaddition reaction between 2,5-furandimethylol / bismaleimide to obtain a polyurethane material with a reversible crosslinking network. (4) The polyurethane material with reversible crosslinking network is cured and crosslinked at 80°C for 24 hours. After natural cooling, a yellow material is obtained. This material is the solvent-free polyurethane material based on Diels-Alder dynamic bonds, denoted as PUDA.
[0030] In this embodiment, step (3) is carried out in a mixer. Even under high viscosity or local gelation conditions, efficient mixing and uniform cross-linking of the reaction components can still be achieved, effectively solving the mass transfer limitation problem caused by the sharp increase in viscosity in solvent-free systems. It has good process scalability and industrialization potential.
[0031] Example 2 Unlike Example 1, the temperature for the shear mixing reaction in step (3) of this example is 120°C.
[0032] Example 3 Unlike Example 1, the shear mixing reaction time in step (3) of this example is 30 min.
[0033] Example 4 Unlike Example 1, the polyol in step (1) of this example is polycarbonate diol (PCDL, Mn = 2000 g / mol).
[0034] Example 5 Unlike Example 1, the diisocyanate in step (1) of this example is a mixture of diphenylmethane diisocyanate (MDI) and isophthalic dimethyl diisocyanate (TMXDI) (molar ratio of 4:1).
[0035] Comparative Example 1 A polyurethane material is prepared by the following steps: (1) Polytetrahydrofuran ether diol (PTMEG, 10.0 g, 0.005 mol) with a molecular weight of 2000 g / mol and diphenylmethane diisocyanate (MDI, 2.50 g, 0.01 mol) were added to a reaction vessel containing 5 mL of dioxane and stirred in an oil bath at 80 °C for 12 h to obtain a polyurethane prepolymer with NCO-terminated ends; (2) Add 8 mL of dioxane to the reaction system to prevent gelation, and add furan diethanol (0.64 g, 0.005 mol) and 1 drop of catalyst dibutyltin dilaurate. Continue stirring the reaction at 80 °C for 3 h. (3) Add bismaleimide (BMI, 0.716 g, 0.002 mol), and add an appropriate amount of solvent if necessary. Continue the reaction at 80℃ for 1 h to allow the Diels–Alder [4+2] cycloaddition reaction to occur, forming a three-dimensional cross-linked network. (4) Transfer the reaction solution to a mold and dry it in a vacuum drying oven at 80°C for at least 72 hours to obtain a yellow material, which is the polyurethane material.
[0036] Comparative Example 2 A polyurethane material is prepared by the following steps: (1) Polytetrahydrofuran ether diol (PTMEG, 10.0 g, 0.005 mol) with a molecular weight of 2000 g / mol and diphenylmethane diisocyanate (MDI, 2.50 g, 0.01 mol) were placed in a reaction flask and stirred in an oil bath at 80°C for 12 h to obtain a polyurethane prepolymer with terminal -NCO groups, which was used as component A; (2) Mix 1,6-hexanediol (0.4506 g, 0.005 mol) with the crosslinking agent trimer hexamethylene diisocyanate (tri-HDI, 0.673 g, 0.0013 mol) evenly as component B; (3) Place component A and component B in a mixer and perform a shear mixing reaction at 80°C and 60 rpm for 2 hours; (4) The product obtained in step (3) is cured at 80°C for 24 hours and then naturally cooled to room temperature to obtain the polyurethane material.
[0037] Test Example 1 Standard samples were prepared from the polyurethane materials obtained in each embodiment and comparative example by hot pressing (120°C, 15MPa, 20min). Performance tests were then conducted on these standard samples, and the test results are as follows: Figures 2-6 As shown.
[0038] from Figure 2 It can be seen that the polyurethane material prepared by the solvent-free method in Example 1 and the polyurethane material prepared by the solvent method in Comparative Example 1 have no structural difference and have the same structure.
[0039] from Figure 3 As can be seen, the polyurethane material in Example 1 has a tensile strength of 38 MPa (average) and an elongation at break of 922%. The dumbbell-shaped specimens were pre-notched (notch depth > 90% of specimen thickness) and then heat-treated at 120°C for 1 hour. After repair, the tensile strength of the specimen recovered to 31 MPa (self-healing efficiency 81.5%), and the elongation at break recovered to 822% (self-healing efficiency 89%).
[0040] from Figure 4 As can be seen, the tensile strength of the polyurethane material in Example 2 is 22 MPa, and the elongation at break can reach 882%. After 1 hour at 120°C, the strength recovers to 23 MPa (self-healing efficiency 104%), and the elongation at break recovers to 896% (self-healing efficiency 101%). Further treatment at 120°C further promotes the full reaction, resulting in a repair and enhancement phenomenon.
[0041] from Figure 5 It can be seen that the tensile strength of the polyurethane material in Comparative Example 1 is 38 MPa (average value), and the elongation at break is 696%. After being treated at 120℃ for 1 hour, its tensile strength recovered to 36 MPa (self-healing efficiency 94.7%), and its elongation at break recovered to 825% (self-healing efficiency 118%).
[0042] contrast Figure 3 and Figure 5 As can be seen, the polyurethane material prepared by the solvent-free method in Example 1 maintains high tensile strength (38 MPa) comparable to that of the solvent-based method in Comparative Example 1, and excellent elongation at break (>900%) compared to the solvent-based method in Comparative Example 1, while also possessing good self-healing properties. More importantly, the method of this invention completely avoids the use of organic solvents, and has outstanding advantages such as being green and environmentally friendly, safe in the process, and easy to scale up for production. It achieves a clean and sustainable preparation process while ensuring performance.
[0043] from Figure 6 It can be seen that the tensile strength of the polyurethane material in Comparative Example 2 is 14 MPa, the elongation at break is 803%, and it does not have self-healing properties.
[0044] It should be noted that the above embodiments are only some embodiments of the present invention. Changing the type and amount of reagents of polyol, diisocyanate, conjugated diene, and dienophile, as well as changing the reaction temperature and time, can all produce the solvent-free polyurethane material based on Diels-Alder dynamic bonds described in the present invention. Moreover, they all have similar properties, can achieve high tensile strength comparable to that of the solvent method, and have a higher elongation at break than the solvent method. At the same time, the reduction in self-healing performance is not significant.
[0045] In summary, this invention enables the preparation of self-healing polyurethane materials under solvent-free conditions, and the tensile strength of these materials is comparable to that of materials prepared by solvent methods, while exhibiting superior elongation at break. Compared to existing technologies, this invention represents a significant advancement.
[0046] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing a solvent-free polyurethane material based on Diels-Alder dynamic bonds, characterized in that, Includes the following steps: S1: Polyol and diisocyanate are mixed and then subjected to preliminary polymerization to obtain a prepolymer, which is used as component A; The conjugated diene and dienophile containing Diels-Alder active groups were mixed evenly as component B. S2: Mix component A and component B, and then perform a shear mixing reaction to obtain a polyurethane material with a reversible crosslinked network; S3: Curing and crosslinking the polyurethane material with the reversible crosslinking network to obtain the solvent-free polyurethane material based on Diels-Alder dynamic bonds.
2. The method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S1, the polyol is any one or more of polyether polyol, polycaprolactone polyol, polyester polyol, polycarbonate polyol, aromatic polyester polyol, polysiloxane polyol, and polyester polyether polyol, and the diisocyanate is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophthalic diisocyanate, phenyl dimethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.
3. The method for preparing solvent-free polyurethane materials based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S1, the initial polymerization is carried out at 80~120℃ for 4~12h.
4. The method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S1, the conjugated diene is any one or more of 1,3-butadiene, isoprene, 1-methoxy-1,3-butadiene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, furan, furfuryl alcohol, 2,5-furandiethanol, and 2,5-furandicarboxylic acid.
5. The method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S1, the dienophile is any one or more of maleimide, bismaleimide, maleic anhydride and its derivatives, acrylate / acrylamide derivatives, acrolein, acetylene dicarboxylic acid ester, tetracyanoethylene, and nitrobenzene.
6. The method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S2, the shear mixing reaction is carried out at 80~120℃ and 30~100rpm for 0.5~2h.
7. The method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds according to claim 1, characterized in that, In step S3, when performing curing and crosslinking, the curing and crosslinking shall be carried out at 80~120℃ for at least 24 hours.
8. The method for preparing solvent-free polyurethane materials based on Diels-Alder dynamic bonds according to any one of claims 1-7, characterized in that, In step S1, the molar ratio of the polyol and the diisocyanate is 1:1.5~2.5, and the molar ratio of the conjugated diene and the dienophile is 1:0.05~0.5; in step S2, the molar ratio of component A and component B is 1:1.5~3.
9. A solvent-free polyurethane material based on Diels-Alder dynamic bonds, characterized in that, It is prepared by the method for preparing solvent-free polyurethane material based on Diels-Alder dynamic bonds as described in any one of claims 1-8.
10. The application of the solvent-free polyurethane material based on Diels-Alder dynamic bonds as described in claim 9 in 3D printing.