Bentonite / polyurethane composite material and preparation method thereof

Abstract

The invention discloses a bentonite / polyurethane composite material and a preparation method thereof, and relates to the technical field of composite materials. The preparation method comprises the following steps: adding bentonite into a polyurethane solution, and uniformly stirring to obtain a first solution; adding a mixed solution of a quinone photosensitive cross-linking agent and a flexibilizer into the first solution, and uniformly stirring to obtain a composite solution; the composite solution is tiled, scraped and coated to form a film, dried, hot-pressed and / or subjected to ultraviolet radiation treatment, and the bentonite / polyurethane composite material is obtained. According to the bentonite / polyurethane composite material, through the synergistic effect of nano confinement interface strengthening of bentonite and light-triggered dynamic bonds of the quinone photosensitive cross-linking agent, the bottleneck of toughening imbalance of traditional polyurethane is broken through, the high toughness that the tensile strength is larger than or equal to 15 MPa, the elongation at break is larger than or equal to 1300% and the breaking energy is larger than or equal to 50 kJ / m < 2 > is achieved, and the bentonite / polyurethane composite material has the normal-temperature rapid self-repairing capacity. The method is suitable for flexible electronic devices and intelligent protective coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a bentonite / polyurethane composite material and a preparation method thereof. BACKGROUND

[0002] Polyurethane (PU) as a kind of multi-block copolymer, due to its molecular chain structure adjustability (for example, by adjusting the ratio of soft segment and hard segment, introducing functional functional groups) and excellent elastic performance (elongation at break can reach 500%-800%), has wide application prospect in flexible electronic devices, intelligent protective coating, biomedical materials and other fields. However, the intrinsic mechanical strength of polyurethane is low (tensile strength is usually less than 15MPa), and the crack propagation resistance is weak (fracture toughness is less than 5MPa·m 1 / 2 ), which leads to irreversible damage under dynamic load or high stress environment, seriously limits its application in industrial load-bearing parts, flexible robot driving structure and other fields.

[0003] In order to improve the mechanical properties of polyurethane, the existing technology usually uses inorganic nanoparticles (such as silicon dioxide, carbon nanotube) or short fibers (such as glass fiber, carbon fiber) as reinforcing phase. However, the interface compatibility between such reinforcing body and polyurethane matrix is poor, and interface defects (such as pores, agglomerates) are easy to occur in the process of composite material forming, which causes local stress concentration (the stress level at the interface defect can be increased by 30%-50%), resulting in significant decrease of material toughness. For example, although the addition of 5% mass fraction of carbon nanotube can make the tensile strength of polyurethane increase to about 18MPa, its elongation at break will decrease to below 200%, showing a significant "strong and tough imbalance" problem.

[0004] Therefore, the existing technology still needs to be improved and developed. SUMMARY

[0005] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a bentonite / polyurethane composite material and a preparation method thereof, which aims to solve the problem that the existing polyurethane composite material cannot simultaneously have high strength and toughness and dynamic force response.

[0006] The technical scheme of the present application is as follows:

[0007] In a first aspect, a preparation method of a bentonite / polyurethane composite material is provided, comprising the steps of:

[0008] Adding bentonite into a polyurethane solution and stirring uniformly to obtain a first solution;

[0009] Adding a mixed solution of a quinone photosensitive crosslinking agent and a toughening agent into the first solution and stirring uniformly to obtain a composite solution;

[0010] The composite solution is spread and scraped to form a film, dried, hot-pressed and / or treated by ultraviolet irradiation to obtain the bentonite / polyurethane composite material.

[0011] In a preferred embodiment, the mass ratio of bentonite to polyurethane is (0.1-0.25):1.

[0012] In a preferred embodiment, the mass ratio of the quinone photosensitive crosslinking agent, the toughening agent and the polyurethane is (0.1-0.3):(0.05-0.15):1.

[0013] In a preferred embodiment, the bentonite is natural bentonite and / or bentonite surface-organicized by sodium dodecyl benzene sulfonate.

[0014] In a preferred embodiment, the quinone photosensitive crosslinking agent is anthraquinone and / or benzanthraquinone.

[0015] In a preferred embodiment, the toughening agent is selected from polyethylene glycol and / or polycaprolactone glycol, and the molecular weight of the toughening agent is 2000-10000.

[0016] In a further preferred embodiment, the specific conditions of the ultrasonic treatment include a power of 500-1000 W and a time of 0.5-1 hour.

[0017] In a further preferred embodiment, the specific conditions of the drying include a temperature of 50-70℃ and a time of 12-24 hours.

[0018] In a preferred embodiment, the method for preparing the polyurethane solution comprises the following steps:

[0019] The polyether polyol, the isocyanate and the alkanolamine catalyst are mixed under an inert atmosphere to perform a polymerization reaction, thereby obtaining the polyurethane solution.

[0020] In a further preferred embodiment, the specific conditions of the polymerization reaction include a temperature of 60-80℃ and a time of 0.5-2 hours.

[0021] In a further preferred embodiment, the molar ratio of the polyether polyol, the isocyanate and the alkanolamine catalyst is 1:(1.2-1.5):(0.005-0.01).

[0022] In a further preferred embodiment, the polyether polyol is selected from one or more of polytetramethylammonium methylene glycol, polytetrahydrofuran glycol and polypropylene glycol, and the molecular weight of the polyether polyol is 2000-3000.

[0023] It is further preferred that the isocyanate is selected from one or more of diphenylmethane diisocyanate, toluene diisocyanate, m-xylylene diisocyanate and trimethylhexane diisocyanate.

[0024] It is further preferred that the alkanolamine catalyst is selected from one or more of triethanolamine, dimethylethanolamine and N,N-dimethylethanolamine.

[0025] It is preferred that the method for preparing the mixed solution of the quinone-based photosensitive crosslinking agent and the toughening agent comprises:

[0026] The quinone-based photosensitive crosslinking agent and the toughening agent are dissolved in an organic solvent to obtain a mixed solution of the quinone-based photosensitive crosslinking agent and the toughening agent.

[0027] The organic solvent is dichloromethane or chloroform.

[0028] It is preferred that the stirring time is 1-2 hours.

[0029] It is preferred that the drying conditions comprise a temperature of 50-70℃ and a time of 12-24 hours.

[0030] It is preferred that the hot-pressing conditions comprise a temperature of 80-100℃, a pressure of 1-2 MPa and a time of 5-30 minutes.

[0031] It is preferred that the ultraviolet irradiation conditions comprise a wavelength of 254-365 nm, an intensity of 10-50 mW / cm 2 and a time of 10-30 min.

[0032] In a second aspect, a bentonite / polyurethane composite material is provided, which is prepared by the method of the first aspect.

[0033] Advantages: Compared with the prior art, the bentonite / polyurethane composite material prepared by the method of the present application breaks through the traditional polyurethane toughening imbalance bottleneck through the synergistic effect of the nano-limited interface strengthening of bentonite and the photo-triggered dynamic bond of the quinone-based photosensitive crosslinking agent, realizes high strength and toughness with a tensile strength ≥ 15 MPa, an elongation at break ≥ 1300% and a breaking energy ≥ 50 kJ / m 2 , and has a room temperature rapid self-repairing capability (repairing time ≤ 10 min, repairing efficiency ≥ 90%). BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Figure 2 is a tensile stress-strain curve of the bentonite / polyurethane composite material of Example 1.

[0035] Figure 2Tensile stress-strain curve for the bentonite / polyurethane composite of Example 1.

[0036] Figure 3 Tensile stress-strain curve for the bentonite / polyurethane composite of Example 3.

[0037] Figure 4 Tensile stress-strain curve for the bentonite / polyurethane composite of Example 4.

[0038] Figure 5 Tensile stress-strain curve for the bentonite / polyurethane composite of Example 5.

[0039] Figure 6 Tensile stress-strain curve for the bentonite / polyurethane composite of Example 6.

[0040] Figure 7 Tensile stress-strain curve for the composite of Comparative Example.

[0041] Figure 8 Surface and cross-section morphology of the bentonite / polyurethane composite of Example 1.

[0042] Figure 9 Shape of the bentonite / polyurethane composite of Example 1 before and after stretching. DETAILED DESCRIPTION

[0043] The present application provides a bentonite / polyurethane composite and a preparation method thereof. To make the purpose, technical scheme and effects of the present application more clear and explicit, the present application is further described in detail as follows.

[0044] Polyurethane has a wide application prospect in the fields of flexible electronic devices, intelligent protective coatings, biomedical materials, etc. due to its adjustable molecular chain structure and excellent elastic properties. However, the intrinsic mechanical strength of polyurethane is low, and the crack propagation resistance is weak, which leads to irreversible damage when it is subjected to dynamic load or high stress environment, seriously limiting its application in industrial load-bearing parts, flexible robot driving structure, etc.

[0045] Bentonite clay, as a natural layered silicate, has a unique nanolayered structure: 1. Nanometer confined space: the basic structural unit is a silicate nanosheet layer with a thickness of about 1 nm, and there is a controllable nanoscale gap (interlayer spacing) between the sheet layers; 2. High active interface: the surface of the sheet layer is rich in silicon hydroxyl (Si-OH) and exchangeable cations, which provides a basis for interface chemical modification; 3. High specific surface area (≥750 m 2(g): Ensured a huge potential interfacial interaction area. Therefore, bentonite is regarded as a functional component that can create a nano-confinement environment and provide a modifiable interface, rather than a traditional physical reinforcing filler. Its core potential lies in the restriction of polymer chain movement and the induction of ordering through the nano-confinement effect, as well as the realization of efficient stress transfer and energy dissipation through the intensification of interfacial reactions. Despite the recognition of the structural potential of bentonite, existing technologies (such as ion exchange, surfactant intercalation) mainly focus on expanding the interlayer spacing (from ~1.2 nm to 2.0-2.5 nm) to improve the physical compatibility with polymers. However, such methods have fundamental flaws: first, the nano-confinement effect is underutilized: the interlayer spacing after modification is still limited, making it difficult to achieve full exfoliation of the layers to maximize the exposure of the nano-confinement interface, and the confinement constraint on PU molecular chains is insufficient, resulting in limited modulus and strength improvement (the increase in elastic modulus is often <50%); second, the interfacial reaction is weak: after modification, the bentonite layers and PU matrix mainly rely on weak physical adsorption (van der Waals forces, hydrogen bonds), and there is a lack of interfacial chemical bonding. This leads to low interfacial shear strength (<10 MPa), poor stress transfer efficiency, and easy crack initiation and propagation at the interface, making it impossible to synergistically improve strength (target >15 MPa) and toughness (elongation at break target >1300%). The root cause lies in the failure to effectively utilize the active sites on the surface of bentonite to construct a strong and tough chemical interface.

[0046] In terms of material self-repairing function, the prior art mainly realizes repair through external stimulation (such as heat, light, solvent) to trigger the reversible recombination of dynamic chemical bonds (such as Diels-Alder bond, hydrogen bond, ionic bond). However, such methods have obvious limitations: heat-activated repair requires high temperature conditions (usually higher than 120 DEG C), and the repair efficiency is low (tensile strength recovery rate is less than 60%); solvent-assisted repair can be carried out at room temperature, but it needs to rely on a large amount of organic solvents (such as N, N-dimethylformamide, tetrahydrofuran), which has environmental pollution and safety risks; and the system based on dynamic hydrogen bond or ionic bond has certain self-repairing ability, but its mechanical strength is generally low (tensile strength is usually less than 10 MPa), and the repair period is relatively long (more than 24 hours). For example, the self-repairing polyurethane material based on the four hydrogen bonds reported in the prior art can achieve a repair efficiency of 85%, but its tensile strength is only 8 MPa, which is difficult to meet the requirements of mechanical properties for engineering applications. In recent years, quinone photosensitive crosslinking agents (such as anthraquinone) have been explored to construct dynamic covalent networks (such as acylhydrazone bond, disulfide bond) due to the characteristics that the benzenequinone structure can produce active free radicals under the excitation of ultraviolet light (wavelength 365 nm). However, the existing research still has the following technical bottlenecks: first, excessive focus on the mechanical force responsiveness of anthraquinone fails to synergistically design the physical enhancement potential of the rigid aromatic ring structure of anthraquinone, the nano-limiting effect provided by bentonite, and the modifiable interface - the rigid aromatic ring structure of anthraquinone can be used as a physical crosslinking point to improve the modulus of the material, and the bentonite nanosheet can induce stress directional transmission, and the synergistic effect of the two is expected to break through the "strong and tough imbalance" problem caused by traditional reinforcing agents; second, the existing design of anthraquinone-based dynamic network is mostly based on homogeneous dynamic network, which fails to solve the matching problem of "bentonite nano-limiting interface-PU matrix-dynamic covalent bond network". This leads to uneven stress distribution, interface failure and rapid performance decay (such as strength retention rate < 50% after 3 cycles) in the cycle response. Therefore, how to simultaneously realize high strength and toughness (tensile strength ≥ 15 MPa, elongation at break ≥ 1300%), high damage tolerance (fracture energy ≥ 50 kJ / m 2 ) and fast self-repairing performance (repair time ≤ 10 minutes at room temperature, repair efficiency ≥ 90%) through interface design at the molecular scale (for example, grafting anthraquinone responsive groups on the surface of bentonite) and dynamic network regulation at the mesoscale (for example, constructing a gradient crosslinking density distribution) is still a technical problem to be solved in the field.

[0047] Based on this, the embodiment of the present application provides a preparation method of a bentonite / polyurethane composite material, comprising the following steps:

[0048] The bentonite is added into the polyurethane solution, and stirred uniformly to obtain a first solution;

[0049] adding a mixed solution of a quinone photosensitive crosslinking agent and a toughening agent to the first solution, stirring to obtain a composite solution;

[0050] flatly coating the composite solution to form a film, drying, hot pressing and / or ultraviolet irradiation treatment to obtain a bentonite / polyurethane composite material.

[0051] Specifically, the embodiment is based on a new strategy of bentonite nanometer limited interface functionalization design, using polyurethane as a matrix, using bentonite as a nanometer limited interface reaction template to optimize the interface stress transfer; through chemical bonding to strengthen the interface and integrate a dynamic response unit, using a quinone photosensitive crosslinking agent, activating the free radical crosslinking reaction through hot pressing (mechanical stretching (tensile strain 50%~200%)) or ultraviolet irradiation to construct a dynamic covalent network structure; and further adding a toughening agent to adjust the flexibility of the soft segment, balancing the strength and ductility of the material, and further developing a composite material with high strength, high toughness and repairability.

[0052] In some embodiments, the mass ratio of the bentonite and the polyurethane is (0.1~0.25):1, but is not limited thereto.

[0053] In some embodiments, the mass ratio of the quinone photosensitive crosslinking agent, the toughening agent and the polyurethane is (0.1~0.3):(0.05~0.15):1, but is not limited thereto. The performance of the composite material can be optimized by adjusting the proportion of the quinone photosensitive crosslinking agent, and an appropriate amount of toughening agent can improve the flexibility of the composite material.

[0054] In some embodiments, the bentonite is natural bentonite and / or bentonite organically modified by sodium dodecyl benzene sulfonate, but is not limited thereto, for example, it can be a common commercial bentonite. Other materials with nanometer layered structure (such as montmorillonite-like materials or hydrotalcite-like materials, etc.) can also be used as alternatives.

[0055] In some embodiments, the quinone photosensitive crosslinking agent is anthraquinone and / or benzanthraquinone, but is not limited thereto.

[0056] In some embodiments, the toughening agent is selected from polyethylene glycol and / or polycaprolactone diol, and the molecular weight of the toughening agent is 2000-10000, preferably 2000-4000, but is not limited thereto.

[0057] In some embodiments, before the step of adding the bentonite to the polyurethane solution, the method further comprises: dispersing the bentonite in water, filtering after ultrasonic treatment, and drying to obtain dried bentonite. The bentonite is first dispersed by ultrasonic treatment and then dried, which can achieve nanoscale peeling, so that it can be used as a nanometer limited interface reaction template.

[0058] In some more specific embodiments, the specific conditions of the ultrasonic treatment include a power of 500-1000 W and a time of 0.5-1 hour. The suitable ultrasonic treatment conditions can improve the dispersibility of the bentonite.

[0059] In some more specific embodiments, the specific conditions of the drying include a temperature of 50-70℃ and a time of 12-24 hours, but are not limited thereto. The purpose of the drying is to remove the water in the bentonite so as to enable the bentonite to be uniformly dispersed, and other conditions capable of achieving this effect are also possible.

[0060] In some embodiments, the method for preparing the polyurethane solution specifically includes:

[0061] The polyether polyol, the isocyanate and the alkanolamine catalyst are mixed under an inert atmosphere to perform a polymerization reaction, thereby obtaining a polyurethane solution.

[0062] During the reaction, the isocyanate groups and the hydroxyl groups undergo a nucleophilic addition reaction to form urethane bonds (-NH-COO-), thereby constructing the polyurethane. The alkanolamine catalyst can accelerate the reaction.

[0063] In some more specific embodiments, the specific conditions of the polymerization reaction include a temperature of 60-80℃ and a time of 0.5-2 hours, but are not limited thereto, and can be adjusted according to the types of the reactants of the polymerization reaction and the performance requirements of the product.

[0064] In some more specific embodiments, the molar ratio of the polyether polyol, the isocyanate and the alkanolamine catalyst is 1:(1.2-1.5):(0.005-0.01), but is not limited thereto. The excess isocyanate is conducive to the full performance of the polymerization reaction, and the proportion of the isocyanate can be adjusted as needed to control the hardness of the polyurethane.

[0065] In some more specific embodiments, the polyether polyol is selected from one or more of polytetramethylendiamine glycol, polytetrahydrofuran glycol and polypropylene glycol, but is not limited thereto; and the molecular weight of the polyether polyol is 2000-3000.

[0066] In some more specific embodiments, the isocyanate is selected from one or more of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), m-xylylene diisocyanate (XDI) and trimethylhexane diisocyanate (TMXDI), but is not limited thereto.

[0067] In some more specific embodiments, the alkanolamine catalyst is selected from one or more of triethanolamine, dimethylethanolamine and N,N-dimethylethanolamine, but is not limited thereto.

[0068] In some embodiments, the method for preparing the mixed solution of the quinone photosensitive crosslinking agent and the toughening agent comprises:

[0069] dissolving the quinone photosensitive crosslinking agent and the toughening agent in an organic solvent to obtain a mixed solution of the quinone photosensitive crosslinking agent and the toughening agent;

[0070] The organic solvent is dichloromethane or chloroform.

[0071] In some embodiments, the stirring time is 1-2 hours, but is not limited thereto. The stirring is performed until the substances in the solution are uniformly mixed.

[0072] In some embodiments, the specific drying conditions include a temperature of 50-70°C and a time of 12-24 hours, but are not limited thereto. The drying is performed until the solution in the composite film is removed.

[0073] In some embodiments, the specific hot-pressing conditions include a temperature of 80-100°C, a pressure of 1-2 MPa, and a time of 5-30 minutes, but are not limited thereto. The hot-pressing can further improve the compactness and crosslinking degree of the composite film.

[0074] In some embodiments, the specific ultraviolet irradiation conditions include a wavelength of 254-365 nm, an intensity of 10-50 mW / cm 2 , and a time of 10-30 minutes, but are not limited thereto. The ultraviolet irradiation can activate the quinone photosensitive crosslinking agent to construct a dynamic covalent network, thereby obtaining a flexible composite film.

[0075] In some embodiments, in the step of spreading and blade-coating the composite solution to form a film, the thickness of the film is 0.3-1 cm, but is not limited thereto. The specific thickness of the film depends on the size of the mold and has little effect on the performance of the material.

[0076] Based on the same inventive concept, a bentonite / polyurethane composite material is provided, which is prepared by the preparation method described above.

[0077] The application will be further described below through specific examples.

[0078] Example 1

[0079] (1) 1 g of natural bentonite and 2.75 g of MDI were dispersed in 20 mL of DMF, ultrasonically treated for 40 min, and dried at 60°C for 12 h.

[0080] (2) 1 g of anthraquinone (CAS 84-65-1) was dissolved in 30 mL of dichloromethane, and after stirring until completely dissolved, 1.5 g of PEG (molecular weight 4000) was added and continued to be stirred until completely dissolved, to obtain a mixed solution of anthraquinone and PEG.

[0081] (3) Under the protection of nitrogen, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80°C for 1 h to obtain a polyurethane solution.

[0082] (4) 3 g of bentonite treated in step (1) was added to the polyurethane solution, and a mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added after high-shear stirring for 1.5 h, and the stirring was continued for 45 min to obtain a composite solution.

[0083] (5) The composite solution was coated into a film, and a flexible composite film, i.e., a bentonite / polyurethane composite material, was obtained after hot pressing at 80°C (1.5 MPa) and ultraviolet irradiation for 20 min.

[0084] Example 2

[0085] (1) 1 g of natural bentonite was dispersed in 20 mL of DMF with 2.75 g of MDI, ultrasonic treatment was performed for 40 min, and drying was performed at 60°C for 12 h.

[0086] (2) 1 g of anthraquinone (CAS 84-65-1) was dissolved in 30 mL of dichloromethane, 1.5 g of PEG (molecular weight 10000) was added after stirring until complete dissolution, and the stirring was continued until complete dissolution to obtain a mixed solution of anthraquinone and PEG.

[0087] (3) Under the protection of nitrogen, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80°C for 1 h to obtain a polyurethane solution.

[0088] (4) 3 g of bentonite treated in step (1) was added to the polyurethane solution, and a mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added after high-shear stirring for 1.5 h, and the stirring was continued for 45 min to obtain a composite solution.

[0089] (5) The composite solution was coated into a film, and a flexible composite film, i.e., a bentonite / polyurethane composite material, was obtained after hot pressing at 80°C (1.5 MPa) and ultraviolet irradiation for 20 min.

[0090] Example 3

[0091] (1) 1 g of natural bentonite was dispersed in 20 mL of DMF with 5.56 g of MDI, ultrasonic treatment was performed for 40 min, and drying was performed at 60°C for 12 h.

[0092] (2) 1 g of anthraquinone (CAS 84-65-1) was dissolved in 30 mL of dichloromethane, 1.5 g of PEG (molecular weight 4000) was added after stirring until complete dissolution, and the stirring was continued until complete dissolution to obtain a mixed solution of anthraquinone and PEG.

[0093] (3) Under the protection of nitrogen, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80°C for 1 h to obtain a polyurethane solution.

[0094] (4) 3 g of bentonite treated in step (1) was added to the polyurethane solution, and a mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added after high-shear stirring for 1.5 h, and the stirring was continued for 45 min to obtain a composite solution.

[0095] (5) The composite solution was coated into a film, and a flexible composite film, i.e., a bentonite / polyurethane composite material, was obtained after hot pressing at 80°C (1.5 MPa) and ultraviolet irradiation for 20 min.

[0096] Example 4

[0097] (1) 1 g of natural bentonite was dispersed in 20 mL of DMF with 8.33 g of MDI, ultrasonic treatment was performed for 40 min, and drying was performed at 60°C for 12 h.

[0098] (2) 1 g of anthraquinone (CAS 84-65-1) was dissolved in 30 mL of dichloromethane, 1.5 g of PEG (molecular weight 4000) was added after stirring to complete dissolution, and the stirring was continued until complete dissolution to obtain a mixed solution of anthraquinone and PEG.

[0099] (3) Under the protection of nitrogen, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80°C for 1 h to obtain a polyurethane solution.

[0100] (4) 3 g of bentonite treated in step (1) was added to the polyurethane solution, and a mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added after high-shear stirring for 1.5 h, and the stirring was continued for 45 min to obtain a composite solution.

[0101] (5) The composite solution was coated into a film, and a flexible composite film, i.e., a bentonite / polyurethane composite material, was obtained after hot pressing at 80°C (1.5 MPa) and ultraviolet irradiation for 20 min.

[0102] Example 5

[0103] (1) 1 g of natural bentonite was dispersed in 20 mL of DMF with 11.13 g of MDI, ultrasonic treatment was performed for 40 min, and drying was performed at 60°C for 12 h.

[0104] (2) 1 g anthraquinone (CAS 84-65-1) was dissolved in 30 mL dichloromethane, and after stirring until completely dissolved, 1.5 g PEG (molecular weight 4000) was added and continued to be stirred until completely dissolved, to obtain a mixed solution of anthraquinone and PEG.

[0105] (3) 5 g polyether polyol (molecular weight 2000) was mixed with 2 g MDI under nitrogen protection, 0.05 g triethanolamine was added, and reacted at 80°C for 1 h to obtain a polyurethane solution.

[0106] (4) 3 g bentonite treated in step (1) was added to the polyurethane solution, and after high shear stirring for 1.5 h, the mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added, and continued to be stirred for 45 min to obtain a composite solution.

[0107] (5) The composite solution was coated into a film, and after hot pressing (1.5 MPa) at 80°C and ultraviolet irradiation for 20 min, a flexible composite film, i.e. bentonite / polyurethane composite material, was obtained.

[0108] Example 6

[0109] (1) 1 g natural bentonite was dispersed in 20 mL DMF with 27.78 g MDI, ultrasonic treatment for 40 min, and dried at 60°C for 12 h.

[0110] (2) 1 g anthraquinone (CAS 84-65-1) was dissolved in 30 mL dichloromethane, and after stirring until completely dissolved, 1.5 g PEG (molecular weight 10000) was added and continued to be stirred until completely dissolved, to obtain a mixed solution of anthraquinone and PEG.

[0111] (3) 5 g polyether polyol (molecular weight 2000) was mixed with 2 g MDI under nitrogen protection, 0.05 g triethanolamine was added, and reacted at 80°C for 1 h to obtain a polyurethane solution.

[0112] (4) 3 g bentonite treated in step (1) was added to the polyurethane solution, and after high shear stirring for 1.5 h, the mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane 0.2:1) was added, and continued to be stirred for 45 min to obtain a composite solution.

[0113] (5) The composite solution was coated into a film, and after hot pressing (1.5 MPa) at 80°C and ultraviolet irradiation for 20 min, a flexible composite film, i.e. bentonite / polyurethane composite material, was obtained.

[0114] Comparative Example 1

[0115] (1) 1 g natural bentonite was dispersed in 20 mL DMF with 2.75 g MDI, ultrasonic treatment for 40 min, and dried at 60°C for 12 h.

[0116] (2) Under nitrogen protection, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80 °C for 1 h to obtain a polyurethane solution.

[0117] (3) 3 g of the bentonite treated in step (1) was added to the polyurethane solution and stirred under high shear for 1.5 h to fully react to obtain a composite solution.

[0118] (4) The composite solution was coated into a film, hot-pressed at 80°C (1.5 MPa), and then irradiated with ultraviolet light for 20 min to obtain a flexible composite film, i.e., a composite material.

[0119] Comparative Example 2

[0120] (1) Dissolve 1 g of anthraquinone (CAS 84-65-1) in 30 mL of dichloromethane, stir until completely dissolved, then add 1.5 g of PEG (molecular weight 4000) and continue stirring until completely dissolved to obtain a mixed solution of anthraquinone and PEG.

[0121] (2) Under nitrogen protection, 5 g of polyether polyol (molecular weight 2000) was mixed with 2 g of MDI, 0.05 g of triethanolamine was added, and the mixture was reacted at 80 °C for 1 h to obtain a polyurethane solution.

[0122] (3) After the polyurethane solution was stirred under high shear for 1.5 h, a mixed solution of anthraquinone and PEG (mass ratio of anthraquinone to polyurethane was 0.2:1) was added and stirred for 45 min to obtain a composite solution.

[0123] (4) The composite solution was coated into a film, hot-pressed at 80°C (1.5 MPa), and then irradiated with ultraviolet light for 20 min to obtain a flexible composite film, i.e., a composite material.

[0124] Tensile strength test

[0125] The tensile strength of the membrane material was tested using a universal testing machine (Instron 3400) with dumbbell-shaped membrane material, test temperature: 27°C, test fixture: double-clamp tensile fixture, and tensile rate of 50 mm / min. The results are as follows Figures 1-7 shown.

[0126] Comparative test results of the bentonite / polyurethane composite material of Example 1 and the composite materials of Comparative Examples 1 to 2 ( Figure 7 ), the bentonite / polyurethane composite material of the embodiment of the present invention has excellent mechanical properties, with a tensile strength of 17 MPa, which is 12 times that of the composite material without bentonite and 4 times that of the composite material without anthraquinone, and an elongation at break of 1357%, which is 15 times that of the composite material without bentonite and 6.6 times that of the composite material without anthraquinone.

[0127] Morphology test

[0128] The surface and cross-sectional morphology of the bentonite / polyurethane composite of Example 1 were tested, and the results are shown in Figure 8 .

[0129] The shape of the bentonite / polyurethane composite of Example 1 before and after stretching was observed, and the results are shown in Figure 9 .

[0130] It should be understood that the application of the present application is not limited to the above examples, and those of ordinary skill in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for preparing a bentonite / polyurethane composite, characterized by, The method comprises the steps of: adding bentonite into a polyurethane solution, stirring uniformly to obtain a first solution; adding a mixed solution of a quinone photosensitive crosslinking agent and a toughening agent into the first solution, stirring uniformly to obtain a composite solution; paving and doctor-blading the composite solution to form a film, drying, hot pressing and / or ultraviolet irradiation treatment to obtain a bentonite / polyurethane composite material.

2. The method for preparing a bentonite / polyurethane composite according to claim 1, characterized by, The mass ratio of the bentonite and the polyurethane is (0.1-0.25):1; The mass ratio of the quinone photosensitive crosslinking agent, the toughening agent and the polyurethane is (0.1-0.3):(0.05-0.15):1; The bentonite is natural bentonite and / or bentonite which is surface-organically modified by sodium dodecyl benzene sulfonate; The quinone photosensitive crosslinking agent is anthraquinone and / or benzanthraquinone; The toughening agent is selected from polyethylene glycol and / or polycaprolactone glycol, and the molecular weight of the toughening agent is 2000-10000.

3. The method of claim 1, wherein the bentonite / polyurethane composite is prepared by the steps of: Before the step of adding bentonite into a polyurethane solution, the method further comprises the steps of:

4. The method of preparing a bentonite / polyurethane composite according to claim 3, characterized in that, dispersing the bentonite in water, ultrasonic treatment, filtration, and drying to obtain dried bentonite. The specific conditions of the ultrasonic treatment include a power of 500-1000 W and a time of 0.5-1 hour.

5. The method of claim 1, wherein the bentonite / polyurethane composite is prepared by the steps of: The specific conditions of the drying include a temperature of 50-70℃ and a time of 12-24 hours. The method for preparing the polyurethane solution specifically comprises the steps of:

6. The method of claim 5, wherein the bentonite / polyurethane composite is prepared by the steps of: mixing polyether polyol, isocyanate and alkanolamine catalyst under an inert atmosphere, and performing polymerization reaction to obtain the polyurethane solution. The specific conditions of the polymerization reaction include a temperature of 60-80℃ and a time of 0.5-2 hours.

7. The method for preparing the bentonite / polyurethane composite material according to claim 5, characterized in that: The molar ratio of the polyether polyol, the isocyanate and the alkanolamine catalyst is 1:(1.2-1.5):(0.005-0.01). The polyether polyol is selected from one or more of polytetramethylaminediamine glycol, polytetrahydrofuran glycol and polypropylene glycol, and the molecular weight of the polyether polyol is 2000-3000. The isocyanate is selected from one or more of diphenylmethane diisocyanate, toluene diisocyanate, m-xylylene diisocyanate and trimethylhexane diisocyanate.

8. The method of claim 1, wherein the bentonite / polyurethane composite is prepared by the steps of: The alkanolamine catalyst is selected from one or more of triethanolamine, dimethylethanolamine and N,N-dimethylethanolamine. The method for preparing the mixed solution of the quinone photosensitive crosslinking agent and the toughening agent comprises the steps of: dissolving the quinone photosensitive crosslinking agent and the toughening agent in an organic solvent to obtain the mixed solution of the quinone photosensitive crosslinking agent and the toughening agent; 9. The method of claim 1, wherein the bentonite / polyurethane composite is prepared by the steps of: The organic solvent is dichloromethane or chloroform. The stirring time is 1-2 hours. The specific conditions of the drying include a temperature of 50-70℃ and a time of 12-24 hours. The specific conditions of the ultraviolet irradiation include: wavelength of 254-365 nm, intensity of 10-50 mW / cm 2 , time of 10-30 min.

10. A bentonite / polyurethane composite, characterized by, The specific conditions of the hot pressing include a temperature of 80-100℃, a pressure of 1-2 MPa and a time of 5-30 minutes. The method is prepared by the preparation method in any one of claims 1-9.

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