Modified polyurethane material and preparation method thereof

Abstract

The invention relates to the technical field of chemical preparation technologies, in particular to a modified polyurethane material and a preparation method thereof.The preparation method comprises the following steps that dynamic covalent bond cross-linked polyether polyol and core-shell nanoparticles are dispersed at the high speed at the temperature of 110-130 DEG C; the preparation method has the beneficial effects that the contradiction between self-repairing and mechanical strength is solved through dynamic covalent bond design, optical-electric-magnetic multifunctional integration is achieved through core-shell particle directional arrangement, the structural uniformity is improved by combining gradient catalysis and a spraying process, and finally the light-weight target is achieved through foaming-printing combination. All technical points support each other to form a complete innovative chain from molecular design to macroscopic performance, so that the application boundary of the polyurethane material is obviously expanded.

Description

Technical Field

[0001] This invention relates to the field of chemical preparation technology, specifically to a modified polyurethane material and its preparation method. Background Technology

[0002] Traditional polyurethane materials are widely used in coatings, elastomers, and foams due to their excellent mechanical properties, wear resistance, and chemical stability. However, the permanent cross-linked structure formed after curing makes it difficult for the material to repair damage, and its limited functionality fails to meet the needs of smart materials (such as self-healing, photoresponsive, and electromagnetic shielding) and lightweight structures. Furthermore, a single catalyst system can easily lead to uneven curing, affecting the stability of the material's performance.

[0003] The introduction of dynamic covalent bonds (such as disulfide bonds and Diels-Alder bonds) endows materials with thermally or optically reversible properties, enabling them to achieve self-repair or structural reorganization under specific conditions. However, in existing technologies, the introduction of dynamic bonds often sacrifices the mechanical strength or response speed of materials, and there is a lack of multi-scale structural control methods.

[0004] Spiropyran derivatives exhibit excellent photochromic properties, but direct doping easily leads to aggregation and photofatigue. Encapsulating these derivatives with silica to form a core-shell structure can improve dispersibility and protect photoresponsive active centers, while also introducing functional interfaces (such as magnetic impurities). However, achieving the directional alignment of core-shell particles to construct anisotropic structures remains a challenge.

[0005] Traditional polyurethane curing uses a single catalyst, resulting in a large difference in curing rate between the substrate and the surface, which can easily lead to internal stress or surface defects. Adding different active catalysts in layers can create a curing rate gradient, but the addition ratio and process conditions must be precisely controlled.

[0006] The aerospace, electronic packaging, and other fields have placed higher demands on the lightweighting (density <0.6g / cm³) and electromagnetic shielding performance (>30dB in the 8-18GHz band) of materials. Supercritical carbon dioxide foaming combined with 3D printing technology can prepare gradient porous structures, but the compatibility issues between the foaming and printing processes need to be resolved. Summary of the Invention

[0007] The purpose of this invention is to provide a modified polyurethane material and its preparation method to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a modified polyurethane material, prepared from the following components in parts by weight: Dynamically covalently crosslinked polyether polyol matrix (70-85 parts), containing disulfide bonds (-SS-) or Diels-Alder bond structures; Crosslinking agent for blending isophorone diisocyanate (IPDI) and methylcyclohexane diisocyanate (HMDI) (15-30 parts); Core-shell structured nanoparticles (3-10 parts), with a core of photochromic spiropyran derivative and an outer shell of silica coating; The gradient catalyst system (0.5-2 parts) is composed of dibutyltin dilaurate (DBTDL) and an organic bismuth catalyst in a mass ratio of 1:2-1:5. The self-repair accelerator (0.1-1 part) is a polyethylene glycol derivative containing thiol groups.

[0009] Preferably, the dynamically covalently crosslinked polyether polyol matrix is ​​prepared by the following method: Polytetrahydrofuran ether glycol (PTMEG) and dithiodipropionic acid (DTDP) were melt-polymerized at 120°C. Adding 5-15% maleic anhydride for graft modification introduces a reversible Diels-Alder bond structure; After vacuum dehydration, a polyol matrix with both thermally reversible and lightly reversible crosslinking points is obtained.

[0010] Preferably, the core-shell structured nanoparticles are prepared using a microemulsion method: Spiropyran derivatives were dissolved in toluene to form an organic phase; It forms a W / O microemulsion with tetraethyl orthosilicate (TEOS) hydrolysate under the action of sodium dodecyl sulfate (SDS); Photoresponsive core-shell particles with a particle size of 50-100 nm were obtained by co-precipitation catalyzed by ammonia water.

[0011] Preferably, the gradient catalyst system is achieved through layered addition: DBTDL is added to the bottom layer (near the substrate side) to promote rapid gelation; An organic bismuth catalyst is added to the surface (air contact side) to delay surface curing; A curing rate gradient difference of ≥30% is formed from the substrate to the surface.

[0012] A method for preparing a modified polyurethane material, comprising the following steps: (1) Dynamically covalently cross-linked polyether polyols and core-shell nanoparticles are dispersed at high speed at 110-130℃; (2) After cooling to 50-70℃, add the gradient catalyst system and self-healing promoter, and then perform vacuum degassing; (3) A two-component spraying process is adopted: Component A (containing IPDI / HMDI crosslinking agent) and component B (the mixture in step (2)) are passed through a static mixer; the spraying pressure is 0.2-0.5MPa and the atomizing air pressure is 0.3-0.6MPa; (4) Exposed to ultraviolet light (365nm, 50mW / cm) 2 Irradiation for 5-15 minutes initiates photocuring.

[0013] Preferably, after step (3), a magnetic field-assisted orientation process is added: a uniform magnetic field of 0.1-0.5T is applied; the magnetic impurities (Fe3O4, content ≤2%) in the core-shell nanoparticles are aligned along the direction of the magnetic field; an anisotropic conductive path is formed, and the surface resistivity difference rate is ≥40%.

[0014] Preferably, in the two-component spraying process, component A further contains 0.5-3% of fluorinated polyether siloxane leveling agent, so that the contact angle of the material surface is ≥120°.

[0015] Preferably, the modified polyurethane material has the following properties: Self-healing efficiency: Crack width repaired ≤50μm after 24 hours at 60℃; Photoresponsive color change: Color difference ΔE ≥ 30 after 10 minutes of ultraviolet light irradiation; Electromagnetic shielding effectiveness: 30-50dB in the 8-18GHz frequency band.

[0016] Preferably, after step (4), a supercritical carbon dioxide (scCO2) foaming-3D printing combined process is added: foaming temperature 130-150℃, pressure 10-20MPa; printing nozzle temperature 170-190℃, layer thickness 0.1-0.3mm; to obtain a lightweight material with a honeycomb gradient pore structure (pore size 10-200μm) and a density of 0.3-0.6g / cm³. 3 .

[0017] Compared with the prior art, the beneficial effects of the present invention are: The modified polyurethane material and its preparation method proposed in this invention resolve the contradiction between self-healing and mechanical strength through dynamic covalent bond design, achieve multifunctional integration of optoelectronic and magnetic properties by utilizing the directional arrangement of core-shell particles, improve structural uniformity by combining gradient catalysis and spraying processes, and finally achieve the goal of lightweighting through foaming-printing. These technologies support each other, forming a complete innovation chain from molecular design to macroscopic properties, significantly expanding the application boundaries of polyurethane materials. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: The invention provides a technical solution: a modified polyurethane material for intelligent dimming window film. 1. Material formula (parts by weight) Dynamically covalently crosslinked polyether polyol matrix: 80 parts (PTMEG:DTDP=85:15, containing 5% maleic anhydride grafting) Crosslinking agent: 20 parts of IPDI / HMDI = 70:30 blend; Core-shell nanoparticles: 5 parts of spiropyran@SiO2 (particle size 80nm); Gradient catalyst: 0.3 parts DBTDL (bottom layer) + 0.7 parts organic bismuth (top layer); Self-repair accelerator: 0.5 parts of mercapto polyethylene glycol (MW=1000); 2. Preparation process (1) Matrix synthesis: PTMEG and DTDP were melt-condensed at 120℃ for 4h, maleic anhydride was added and grafted at 140℃ for 2h, and vacuum dehydrated to a water content of <0.05%.

[0021] (2) Nanoparticle dispersion: Spiropyran was dissolved in toluene (concentration 10wt%) and mixed with TEOS hydrolysate (pH=9) at a volume ratio of 1:3. After SDS emulsification, ammonia water was used for co-precipitation. The mixture was stirred at 80℃ for 6h to obtain core-shell particles.

[0022] (3) Two-component spraying: Component B: Matrix + nanoparticles are dispersed at 120℃ at high speed (3000 rpm, 30 min), cooled to 60℃, catalyst and accelerator are added, and vacuum degassing is performed for 20 min.

[0023] Component A: Crosslinking agent + 1% fluorinated polyether siloxane leveling agent.

[0024] Spraying parameters: pressure 0.3MPa, atomization pressure 0.5MPa, static mixer speed 1500rpm.

[0025] (4) Post-treatment: UV irradiation (365nm, 50mW / cm) 2After 10 min of magnetic field orientation (0.3T, 10 min), scCO2 foaming (140℃, 15MPa) was performed, followed by 3D printing (layer thickness 0.2mm).

[0026] 3. Performance Verification Self-healing: Repairs 50μm cracks at 60℃ for 24 hours with a repair rate of 92%.

[0027] Light response: After 10 min of UV irradiation, ΔE=35, and visible light transmittance decreased from 85% to 18%.

[0028] Electromagnetic shielding: Average effectiveness of 42dB in the 8-18GHz frequency band.

[0029] Example 2, based on Example 1, proposes a highly conductive electromagnetic shielding material. 1. Material formula (parts by weight) Dynamic covalent matrix: 75 parts (PTMEG:DTDP=80:20, containing 10% maleic anhydride); Crosslinking agent: 25 parts of IPDI / HMDI = 60:40 blend; Core-shell nanoparticles: 8 parts of spiropyran@SiO2 (containing 1.5% Fe3O4); Gradient catalyst: 0.4 parts DBTDL + 1.2 parts organic bismuth; Self-repair accelerator: 0.8 parts of mercapto polyethylene glycol; 2. Preparation process (1) Matrix synthesis: Same as in Example 1, but the grafting temperature is increased to 150°C to enhance the stability of the DA bond.

[0030] (2) Nanoparticle preparation: Adjust the amount of TEOS to increase the shell thickness to 20nm and improve insulation.

[0031] (3) Spraying process: Component A contains 2% fluorinated leveling agent, and the spraying pressure is 0.4 MPa.

[0032] The magnetic field orientation time was extended to 15 min (0.4 T), forming a surface resistivity gradient (bottom layer 5 × 10⁻⁶). 3 Ω·cm, surface layer 2×10 5 Ω·cm).

[0033] (4) Foaming printing: The scCO2 pressure is increased to 18MPa and the printing nozzle temperature is 180℃ to obtain a honeycomb structure with a porosity of 65%.

[0034] 3. Performance Verification Conductivity anisotropy: The conductivity along the magnetic field direction is 2.8 times higher than that perpendicular to the magnetic field direction.

[0035] Electromagnetic shielding: Effectiveness reaches 48dB in the 8-18GHz frequency band, with a density of 0.45g / cm³. 3 .

[0036] Mechanical properties: tensile strength 48MPa, elongation at break 320%.

[0037] Example 3, based on Example 2, proposes a self-healing flexible sensor substrate. 1. Material formula (parts by weight) Dynamic covalent matrix: 82 parts (PTMEG:DTDP=90:10, containing 8% maleic anhydride); Crosslinking agent: 18 parts of a blend of IPDI / HMDI = 75:25; Core-shell nanoparticles: 4 parts of spiropyran@SiO2 (particle size 60nm); Gradient catalyst: 0.2 parts DBTDL + 0.6 parts organic bismuth; Self-repair accelerator: 0.3 parts of mercapto polyethylene glycol; 2. Preparation process (1) Matrix optimization: 0.5% nano calcium carbonate was added as a nucleating agent to increase crystallinity to 40%.

[0038] (2) Functionalization of nanoparticles: amino groups are grafted onto the surface of the shell to form chemical bonds with the matrix.

[0039] (3) Spraying parameters: The dispersion temperature of component B is reduced to 110℃ to prevent the thermal decomposition of spiropyran.

[0040] Immediately after spraying, UV curing (8 min) and magnetic field orientation (0.2T, 8 min) are performed.

[0041] (4) Foaming adjustment: scCO2 temperature 135℃, pressure 12MPa, printing layer thickness 0.15mm, to obtain a lightweight structure with a closed-cell rate of 90%.

[0042] 3. Performance Verification Self-healing efficiency: Repairing 30μm cracks at 60℃ for 24 hours with a repair rate of 95%, and the tensile strength after repair recovers to 90% of the original value.

[0043] Photochromic: ΔE=32, color-changing performance decays by <5% after 100 cycles.

[0044] Flexibility: Resistance change rate is <8% when bending radius is 2mm, suitable for wearable devices.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modified polyurethane material, characterized in that: It is prepared from the following components in parts by weight: Dynamically covalently crosslinked polyether polyol matrix (70-85 parts), containing disulfide bonds (-SS-) or Diels-Alder bond structures; Crosslinking agent for blending isophorone diisocyanate (IPDI) and methylcyclohexane diisocyanate (HMDI) (15-30 parts); Core-shell structured nanoparticles (3-10 parts), with a core of photochromic spiropyran derivative and an outer shell of silica coating; The gradient catalyst system (0.5-2 parts) is composed of dibutyltin dilaurate (DBTDL) and an organic bismuth catalyst in a mass ratio of 1:2-1:

5. The self-repair accelerator (0.1-1 part) is a polyethylene glycol derivative containing thiol groups.

2. The modified polyurethane material according to claim 1, characterized in that: The dynamically covalently crosslinked polyether polyol matrix was prepared by the following method: Polytetrahydrofuran ether glycol (PTMEG) and dithiodipropionic acid (DTDP) were melt-polymerized at 120°C. Adding 5-15% maleic anhydride for graft modification introduces a reversible Diels-Alder bond structure; After vacuum dehydration, a polyol matrix with both thermally reversible and lightly reversible crosslinking points is obtained.

3. The modified polyurethane material according to claim 1, characterized in that: Core-shell structured nanoparticles were prepared using a microemulsion method: Spiropyran derivatives were dissolved in toluene to form an organic phase; It forms a W / O microemulsion with tetraethyl orthosilicate (TEOS) hydrolysate under the action of sodium dodecyl sulfate (SDS); Photoresponsive core-shell particles with a particle size of 50-100 nm were obtained by co-precipitation catalyzed by ammonia water.

4. The modified polyurethane material according to claim 1, characterized in that: The gradient catalyst system is achieved through layered addition: DBTDL is added to the bottom layer (near the substrate side) to promote rapid gelation; An organic bismuth catalyst is added to the surface (air contact side) to delay surface curing; A curing rate gradient difference of ≥30% is formed from the substrate to the surface.

5. A method for preparing a modified polyurethane material, used to prepare the modified polyurethane material according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Dynamically covalently cross-linked polyether polyols and core-shell nanoparticles are dispersed at high speed at 110-130℃; (2) After cooling to 50-70℃, add the gradient catalyst system and self-healing promoter, and then perform vacuum degassing; (3) A two-component spraying process is adopted: Component A (containing IPDI / HMDI crosslinking agent) and component B (the mixture in step (2)) are passed through a static mixer; the spraying pressure is 0.2-0.5MPa and the atomizing air pressure is 0.3-0.6MPa; (4) Exposed to ultraviolet light (365nm, 50mW / cm) 2 Irradiation for 5-15 minutes initiates photocuring.

6. The method for preparing a modified polyurethane material according to claim 5, characterized in that: After step (3), a magnetic field-assisted orientation process is added: a uniform magnetic field of 0.1-0.5T is applied; the magnetic impurities (Fe3O4, content ≤2%) in the core-shell nanoparticles are aligned along the direction of the magnetic field; an anisotropic conductive path is formed, and the surface resistivity difference rate is ≥40%.

7. The method for preparing a modified polyurethane material according to claim 5, characterized in that: In the two-component spraying process, component A also contains 0.5-3% of fluorinated polyether siloxane leveling agent, which makes the contact angle of the material surface ≥120°.

8. The method for preparing a modified polyurethane material according to claim 5, characterized in that: Modified polyurethane materials have the following properties: Self-healing efficiency: Crack width repaired ≤50μm after 24 hours at 60℃; Photoresponsive color change: Color difference ΔE ≥ 30 after 10 minutes of ultraviolet light irradiation; Electromagnetic shielding effectiveness: 30-50dB in the 8-18GHz frequency band.

9. The method for preparing a modified polyurethane material according to claim 5, characterized in that: Following step (4), a supercritical carbon dioxide (scCO2) foaming-3D printing combined process is added: foaming temperature 130-150℃, pressure 10-20MPa; printing nozzle temperature 170-190℃, layer thickness 0.1-0.3mm; resulting in a lightweight material with a honeycomb gradient pore structure (pore size 10-200μm) and a density of 0.3-0.6g / cm³. 3 .

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