Modified halloysite nanometer material and synthesis method thereof, MDI composite glue and application of modified halloysite nanometer material in shaving board

Abstract

The invention relates to the technical field of organic modified synthesis, nanometer functional materials and adhesives, in particular to a modified halloysite nanometer material, a synthesis method of the modified halloysite nanometer material, MDI composite glue and application of the modified halloysite nanometer material to shaving boards. Then, carrying out sulfonylation reaction on the halloysite nanotube and alkyl sulfonyl chloride in a solvent system added with an acid-binding agent to generate a stable sulfonate bond, introducing a hydrophobic alkyl chain into the surface of the halloysite nanotube, and further synthesizing the modified halloysite nano material. The synthesis process is simple, the reaction condition is mild and easy to control, the reaction selectivity is high, the hydrophobicity is controllable, the structure of the halloysite nanotube cannot be damaged, and the modified layer in the prepared modified halloysite nano material is firmly combined with the surface of halloysite. The MDI composite glue formed by doping the modified halloysite nano material can improve the bonding strength, mechanical strength and waterproof and moistureproof capabilities of the shaving board.

Description

Technical Field

[0001] This invention relates to the fields of organic modification synthesis, nanomaterials and adhesives, and particularly to the hydrophobic modification of halloysite. Specifically, it relates to a modified halloysite nanomaterial and its synthesis method, MDI composite adhesive and its application in particleboard. Background Technology

[0002] Halloysite nanotubes (HNTs), a natural nanotube clay mineral, possesses a unique hollow tubular structure, excellent mechanical stability, good biocompatibility, and environmental friendliness, showing broad application prospects in composite material reinforcement, drug carriers, adsorption separation, and catalysis. Its chemical composition is mainly aluminosilicate, with the molecular formula Al2Si2O5(OH)4*nH2O. Numerous hydroxyl (-OH) groups are distributed on the outer surface of the tubular structure. These hydroxyl groups impart good hydrophilicity to halloysite through hydrogen bonding, making it prone to aggregation in aqueous solutions or polar systems. Furthermore, its compatibility with non-polar matrices (such as polymers and organic solvents) is poor, severely limiting its performance in non-polar environments.

[0003] In practical applications, the hydrophilicity of halloysite has led to a series of key technical problems. For example, in the preparation of polymer-based composite materials, the weak interfacial bonding between hydrophilic halloysite and the hydrophobic polymer matrix (such as polyethylene, polypropylene, polystyrene, etc.) easily forms interfacial voids, resulting in a significant decrease in the mechanical properties (such as tensile strength, impact strength), thermal stability, and dispersion uniformity of the composite material. In the adsorption or catalytic reactions of nonpolar organic solvent systems, hydrophilic halloysite is difficult to disperse stably, which not only reduces the adsorption capacity or the exposure of catalytic active sites, but may also lead to a decrease in the mass transfer efficiency of the reaction system due to agglomeration, affecting the reaction rate and product purity. In addition, in some scenarios where materials need to have surface hydrophobicity (such as antifouling coatings, oil-water separation membranes, etc.), the hydrophilicity of native halloysite makes it unable to meet the requirements, and hydrophobicity must be controlled through modification.

[0004] To address the hydrophilicity issue of halloysite, various hydrophobic modification methods have been developed in existing technologies, mainly including physical coating, silane coupling agent modification, and surface graft polymerization modification. However, these methods all have certain limitations: physical coating achieves modification by adsorbing or encapsulating hydrophobic substances on the surface, but the modified layer has weak adhesion to the halloysite surface and is prone to detachment during subsequent processing or use, resulting in poor stability; while silane coupling agent modification can bind to the hydroxyl groups on the halloysite surface through silicon-oxygen bonds, the silane coupling agent molecular chain is relatively short, limiting the range of hydrophobicity control, and the reaction requires strictly anhydrous or low-water conditions, making the process highly complex; surface graft polymerization modification can achieve strong hydrophobicity by grafting long-chain hydrophobic polymers, but the reaction process involves multiple reagents such as initiators and monomers, easily introducing impurities, and the polymerization reaction is difficult to precisely control the degree of grafting and the distribution of grafted chains, which may damage the integrity of the tubular structure of halloysite.

[0005] MDI (polyphenyl polymethylene polyisocyanate) adhesive, also known as MDI glue, is a high-performance, low-formaldehyde-emission adhesive widely used in the manufacture of environmentally friendly boards. It exhibits excellent water resistance, weather resistance, and bonding strength. Particleboard, on the other hand, is a type of board made by hot-pressing wood chips or scraps from wood or other non-wood plants with adhesives and other additives. The internal structure of particleboard is a cross-layered, granular structure with largely uniform properties in all directions, providing good sound absorption and insulation. It effectively isolates sound transmission and absorbs environmental noise, thereby reducing indoor noise pollution. Additionally, particleboard also offers some thermal insulation.

[0006] Currently, MDI adhesives are widely used in the production of formaldehyde-free engineered wood products, especially particleboard. The isocyanate groups (-NCO) and a small amount of urethane groups (-NHCOO) in the molecular chain of MDI adhesives have high polarity and activity. They can react with the hydroxyl groups in wood to form urethane covalent bonds, and at the same time react with the moisture in wood to form polyurea, thereby producing particleboard with high water resistance and high bonding strength.

[0007] However, in the existing technology, the bonding strength, mechanical strength, and waterproof and moisture-proof capabilities of particleboard bonded with MDI glue still need to be further improved. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a method for synthesizing modified halloysite nanomaterials. This method has the advantages of simple process, mild reaction conditions, no introduction of impurities, strong bonding between the modified layer and the halloysite surface, controllable hydrophobicity, and maintenance of the structural integrity of halloysite.

[0009] To overcome the shortcomings of the prior art, the second objective of this invention is to provide a modified halloysite nanomaterial that has the advantages of strong bonding between the modified layer and the halloysite surface, resistance to detachment during subsequent processing or use, excellent stability, and good integrity of the halloysite structure.

[0010] To overcome the shortcomings of the prior art, a third objective of the present invention is to provide an MDI composite adhesive comprising modified halloysite nanomaterials.

[0011] The fourth objective of this invention is to provide an application of MDI composite adhesive in particleboard, which can improve the bonding strength, mechanical strength and waterproof and moisture-proof capabilities of particleboard.

[0012] To achieve the first objective of the invention, the technical solution adopted by the present invention is as follows:

[0013] This invention provides a method for synthesizing modified halloysite nanomaterials, comprising the following steps:

[0014] S1. Activation of halloysite nanotubes: Halloysite nanotubes are placed in an oven for drying and activation, and then cooled to obtain activated halloysite nanotubes.

[0015] S2. Ultrasonic dispersion: The activated halloysite nanotubes are added to the solvent and then ultrasonically dispersed to obtain a dispersion.

[0016] S3. Hydrophobic modification: Alkyl sulfonyl chloride and acid-binding agent are added to the dispersion, and the mixture is heated and refluxed under an inert atmosphere. The solid is then separated by centrifugation, washed, and dried to synthesize the modified halloysite nanomaterial.

[0017] This invention discloses a method for synthesizing modified halloysite nanomaterials. First, halloysite nanotubes are dried and activated to remove polar solvent molecules such as water from their surface, exposing the -OH groups to facilitate reaction. Then, in a solvent system, the highly reactive sulfonyl chloride group (-SO2Cl) in the alkyl sulfonyl chloride (R-SO2Cl) molecule undergoes a nucleophilic substitution reaction (i.e., sulfonation) with the hydroxyl groups (-OH) on the outer wall of the activated halloysite nanotubes, generating a stable sulfonate bond (-O-SO2-R). Simultaneously, a hydrophobic alkyl chain (-R) is introduced into the surface of the halloysite nanotubes, thereby synthesizing the modified halloysite nanomaterials. An acid-binding agent is used to neutralize the hydrogen chloride (HCl) generated during the sulfonation reaction. Furthermore, the acid-binding agent also acts as a catalyst for the sulfonation reaction, improving reaction efficiency and product purity while suppressing side reactions. It is evident that the reaction system of this invention differs from existing modification methods such as physical coating, silane coupling agent modification, and surface graft polymerization modification.

[0018] The sulfonation reaction between alkyl sulfonyl chloride and activated halloysite nanotubes offers several advantages, including mild reaction conditions (it can be carried out at relatively low temperatures), high reaction selectivity (the sulfonyl chloride group only reacts with the hydroxyl group, without destroying the halloysite structure), strong bonding of the modified layer (the sulfonate bond has high bond energy and is not easily broken), and controllable hydrophobicity (the degree of surface hydrophobicity can be adjusted by changing the alkyl chain length). Therefore, the method for synthesizing modified halloysite nanomaterials of this invention effectively addresses the shortcomings of existing modification technologies, providing key technical support for the application of halloysite nanotubes in nonpolar systems and hydrophobic application scenarios.

[0019] One of the methods for synthesizing modified halloysite nanomaterials in this invention involves drying and activating the nanomaterials and then ultrasonically dispersing them to ensure the exposure of hydroxyl groups on the outer wall of the halloysite nanotubes, thereby exposing more active sites and improving reactivity.

[0020] Furthermore, in step S1, the drying and activation temperature is 90℃~120℃, and the drying and activation time is 2h~6h.

[0021] Further, in step S2, the solvent is an aprotic solvent; and / or, the aprotic solvent is at least one of dichloromethane, tetrahydrofuran, toluene, or N,N-dimethylformamide; wherein, using these aprotic solvents avoids the reaction between protic solvents and alkylsulfonyl chlorides, thereby ensuring reaction selectivity. and / or

[0022] The ultrasonic dispersion time is 5 min to 30 min.

[0023] Furthermore, in step S3, the alkyl group in the alkyl sulfonyl chloride is a C4-C18 straight-chain alkyl group or a branched alkyl group; wherein, the C4-C18 straight-chain alkyl group or branched alkyl group can achieve precise control of the hydrophobicity of the modified halloysite nanomaterials (short-chain alkyl groups achieve weak hydrophobicity, and long-chain alkyl groups achieve strong hydrophobicity), and can ensure the reactivity and product stability. and / or

[0024] The alkyl sulfonyl chloride is at least one selected from butyl sulfonyl chloride, octyl sulfonyl chloride, dodecyl sulfonyl chloride, or octadecyl sulfonyl chloride; and / or

[0025] The acid-binding agent is an organic amine acid-binding agent; and / or, the organic amine acid-binding agent is at least one of triethylamine, pyridine, or 4-dimethylaminopyridine; and / or

[0026] The inert atmosphere is nitrogen.

[0027] Furthermore, in step S3, the temperature of the reflux reaction is 60℃~80℃, and the reflux reaction time is 3h~6h; wherein, in the reflux reaction, the alkyl sulfonyl chloride undergoes a nucleophilic substitution reaction (i.e., sulfonation) with the hydroxyl groups on the outer wall of the activated halloysite nanotubes. The low reaction temperature avoids high-temperature damage to the halloysite tubular structure. And / or

[0028] The washing is performed using ethanol; and / or

[0029] The drying temperature is 80℃~90℃, and the drying time is 40min~60min.

[0030] Furthermore, the mass-to-volume ratio of the halloysite nanotubes to the solvent is (240~260) mg : (6~10) mL; and / or

[0031] The amount of alkyl sulfonyl chloride used is: 1 mmol to 5 mmol of alkyl sulfonyl chloride per gram of halloysite nanotubes; and / or

[0032] The molar ratio of the acid-binding agent to the alkyl sulfonyl chloride is (1~1.5):1.

[0033] To achieve the second objective of the invention, the technical solution adopted by the present invention is as follows:

[0034] This invention provides a modified halloysite nanomaterial, which is prepared by the above-described method for synthesizing a modified halloysite nanomaterial.

[0035] To achieve the third objective of the invention, the technical solution adopted by the present invention is as follows:

[0036] This invention provides an MDI composite adhesive comprising the modified halloysite nanomaterial described above.

[0037] Furthermore, in the MDI composite adhesive, the modified halloysite nanomaterial has a mass percentage content of 0.5% to 1.5%.

[0038] To achieve the fourth objective of the invention, the technical solution adopted by the present invention is as follows:

[0039] This invention provides an application of MDI composite adhesive in particleboard. This application can improve the bonding strength, mechanical strength, and waterproof and moisture-proof capabilities of particleboard.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) A method for synthesizing modified halloysite nanomaterials according to the present invention involves first drying and activating halloysite nanotubes to remove polar solvent molecules such as water from the surface of the halloysite nanotubes, exposing the -OH groups on the surface to facilitate the reaction. Then, in a solvent system, the highly reactive sulfonyl chloride group (-SO2Cl) contained in the alkyl sulfonyl chloride (R-SO2Cl) molecule undergoes a nucleophilic substitution reaction (i.e., sulfonation) with the hydroxyl groups (-OH) on the outer wall of the activated halloysite nanotubes to generate stable sulfonate bonds (-O-SO2-R). At the same time, a hydrophobic alkyl chain (-R) is introduced into the surface of the halloysite nanotubes, thereby synthesizing modified halloysite nanomaterials. An acid-binding agent is used to neutralize the hydrogen chloride (HCl) generated in the sulfonation reaction. In addition, the acid-binding agent can also act as a catalyst for the sulfonation reaction, which can improve the reaction efficiency and product purity, and suppress side reactions.

[0042] (2) A method for synthesizing modified halloysite nanomaterials according to the present invention has the advantages of simple process, mild and easy-to-control reaction conditions, high reaction selectivity, no side reaction interference, no introduction of impurities, strong bonding between the modified layer and the halloysite surface, controllable hydrophobicity and maintenance of the integrity of halloysite structure.

[0043] (3) The modified halloysite nanomaterial of the present invention has the advantages of strong bonding between the modified layer and the halloysite surface, not easy to fall off during subsequent processing or use, excellent stability and good integrity of halloysite structure.

[0044] (4) An MDI composite adhesive of the present invention is doped with modified halloysite nanomaterials, which can improve the bonding strength of the MDI composite adhesive. When applied to the bonding of boards, it can improve the mechanical strength, waterproof and moisture-proof ability, sound absorption and sound insulation performance, and thermal insulation performance of the boards.

[0045] (5) An application of the MDI composite adhesive of the present invention in particleboard: The particleboard is bonded using the MDI composite adhesive. Because the MDI composite adhesive is doped with modified halloysite nanomaterials, it can improve the bonding strength, mechanical strength, and waterproof and moisture-proof capabilities of the particleboard. Furthermore, because halloysite nanotubes have a unique tubular structure, they can form a network structure in the particleboard, thereby increasing the porosity and elasticity of the particleboard. This structure helps in the absorption and attenuation of sound waves, thus improving the sound absorption and sound insulation performance of the particleboard. In addition, because halloysite nanotubes themselves have a low thermal conductivity, they can also improve the thermal insulation performance of the particleboard. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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.

[0047] Figure 1 This is a schematic diagram illustrating the synthesis of the modified halloysite nanomaterials of the present invention.

[0048] Figure 2 These are comparative images of the appearance of a modified halloysite nanomaterial and an unmodified halloysite nanotube, as shown in Examples 1 and 2.

[0049] Figure 3 These are observation images of the initial and 1-minute static states of the original sample, sample I, and sample II during the hydrophobicity performance test.

[0050] Figure 4 These are observation images of the original sample, sample I, and sample II after standing for 2 minutes and 3 minutes during the hydrophobicity test.

[0051] Figure 5 These are observation images of the original sample, sample I, and sample II after standing for 5 minutes and 10 minutes during the hydrophobicity test.

[0052] Figure 6 These are observation images of the original sample, sample I, and sample II after standing for 20 minutes and 30 minutes during the hydrophobicity test.

[0053] Figure 7 This is a graph showing the particle size distribution test results of the original sample, sample I, and sample II in water. Detailed Implementation

[0054] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0055] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. In this invention, the singular forms “a,” “the,” and “the” as used in the embodiments and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0056] In this embodiment of the invention, a method for synthesizing modified halloysite nanomaterials includes the following steps:

[0057] S1. Activation of halloysite nanotubes: Halloysite nanotubes are placed in an oven for drying and activation, and then cooled to obtain activated halloysite nanotubes.

[0058] S2. Ultrasonic dispersion: The activated halloysite nanotubes are added to the solvent and then ultrasonically dispersed to obtain a dispersion.

[0059] S3. Hydrophobic modification: Alkyl sulfonyl chloride and acid-binding agent are added to the dispersion, and the mixture is heated and refluxed under an inert atmosphere. The solid is then separated by centrifugation, washed, and dried to synthesize the modified halloysite nanomaterial.

[0060] In some embodiments, in step S1, the drying and activation temperature is 90°C to 120°C, and the drying and activation time is 2h to 6h.

[0061] In some embodiments, in step S2, the solvent is an aprotic solvent; and / or, the aprotic solvent is at least one of dichloromethane, tetrahydrofuran, toluene, or N,N-dimethylformamide; and / or

[0062] The ultrasonic dispersion time is 5 min to 30 min.

[0063] In some embodiments, in step S3, the alkyl group in the alkyl sulfonyl chloride is a C4-C18 straight-chain alkyl group or a branched alkyl group; and / or

[0064] The alkyl sulfonyl chloride is at least one selected from butyl sulfonyl chloride, octyl sulfonyl chloride, dodecyl sulfonyl chloride, or octadecyl sulfonyl chloride; and / or

[0065] The acid-binding agent is an organic amine acid-binding agent; and / or, the organic amine acid-binding agent is at least one of triethylamine, pyridine, or 4-dimethylaminopyridine; and / or

[0066] The inert atmosphere is nitrogen.

[0067] In some embodiments, in step S3, the temperature of the reflux reaction is 60°C to 80°C, and the duration of the reflux reaction is 3 hours to 6 hours; and / or

[0068] The washing is performed using ethanol; and / or

[0069] The drying temperature is 80℃~90℃, and the drying time is 40min~60min.

[0070] In some embodiments, the mass-to-volume ratio of the halloysite nanotubes to the solvent is (240~260) mg : (6~10) mL; and / or

[0071] The amount of alkyl sulfonyl chloride used is: 1 mmol to 5 mmol of alkyl sulfonyl chloride per gram of halloysite nanotubes; and / or

[0072] The molar ratio of the acid-binding agent to the alkyl sulfonyl chloride is (1~1.5):1.

[0073] In this embodiment of the invention, a modified halloysite nanomaterial is prepared by the above-described method for synthesizing a modified halloysite nanomaterial.

[0074] In this embodiment of the invention, an MDI composite adhesive includes the modified halloysite nanomaterial described above.

[0075] In some embodiments, an MDI composite adhesive contains modified halloysite nanomaterials at a mass percentage content of 0.5% to 1.5%.

[0076] In this embodiment of the invention, an MDI composite adhesive is used in particleboard.

[0077] The following description is based on specific embodiments. Example 1

[0078] A method for synthesizing modified halloysite nanomaterials (synthesis schematic diagram shown) Figure 1 (As shown), including the following steps:

[0079] S1. Activation of halloysite nanotubes: Halloysite nanotubes were dried and activated in an oven at 120℃ for 2 hours, and then cooled to obtain activated halloysite nanotubes.

[0080] S2. Ultrasonic dispersion: The activated halloysite nanotubes were added to tetrahydrofuran and then ultrasonically dispersed for 20 min to obtain a dispersion.

[0081] S3. Hydrophobic modification: Octylsulfonyl chloride and triethylamine, an acid-binding agent, were added to the dispersion. The mixture was heated to reflux at 70°C for 4 hours under nitrogen protection. The solid was then separated by centrifugation, washed with ethanol, and dried in an oven at 85°C for 50 minutes to obtain the modified halloysite nanomaterial.

[0082] In this embodiment, the mass-to-volume ratio of halloysite nanotubes to tetrahydrofuran is 250 mg: 8 mL; the amount of octylsulfonyl chloride is 1 mmol per gram of halloysite nanotubes; and the molar ratio of triethylamine to octylsulfonyl chloride is 1:1. Example 2

[0083] A method for synthesizing modified halloysite nanomaterials is disclosed. The difference between this embodiment and Example 1 is that the alkyl sulfonyl chloride in this embodiment is dodecyl sulfonyl chloride. The remaining synthesis methods in this embodiment are the same as those in Example 1. Example 3

[0084] A method for synthesizing modified halloysite nanomaterials (synthesis schematic diagram shown) Figure 1 (As shown), including the following steps:

[0085] S1. Activation of halloysite nanotubes: Halloysite nanotubes were dried and activated in a 90℃ oven for 6 hours, and then cooled to obtain activated halloysite nanotubes.

[0086] S2, Ultrasonic dispersion: The activated halloysite nanotubes were added to dichloromethane and then ultrasonically dispersed for 5 minutes to obtain a dispersion.

[0087] S3. Hydrophobic modification: Butyl sulfonyl chloride and acid-binding agent pyridine are added to the dispersion, and the mixture is heated to reflux at 60°C for 6 hours under nitrogen protection. The solid is then separated by centrifugation, washed with ethanol, and dried in an oven at 80°C for 60 minutes to obtain the modified halloysite nanomaterial.

[0088] In this embodiment, the mass-to-volume ratio of halloysite nanotubes to tetrahydrofuran is 240 mg: 6 mL; the amount of butyl sulfonyl chloride is 5 mmol per gram of halloysite nanotubes; and the molar ratio of pyridine to butyl sulfonyl chloride is 1.5:1. Example 4

[0089] A method for synthesizing modified halloysite nanomaterials (synthesis schematic diagram shown) Figure 1 (As shown), including the following steps:

[0090] S1. Activation of halloysite nanotubes: Halloysite nanotubes were dried and activated in an oven at 100℃ for 5 hours, and then cooled to obtain activated halloysite nanotubes.

[0091] S2. Ultrasonic dispersion: The activated halloysite nanotubes were added to toluene and then ultrasonically dispersed for 30 min to obtain a dispersion.

[0092] S3. Hydrophobic modification: Octadecyl sulfonyl chloride and acid-binding agent 4-dimethylaminopyridine were added to the dispersion and the mixture was heated to reflux at 80°C for 3 hours under nitrogen protection. The solid was then separated by centrifugation, washed with ethanol, and dried in an oven at 90°C for 40 minutes to obtain the modified halloysite nanomaterial.

[0093] In this embodiment, the mass-to-volume ratio of halloysite nanotubes to tetrahydrofuran is 260 mg: 10 mL; the amount of octadecyl sulfonyl chloride is 2 mmol of octadecyl sulfonyl chloride per gram of halloysite nanotubes; and the molar ratio of 4-dimethylaminopyridine to octadecyl sulfonyl chloride is 1.1:1. Example 5

[0094] A method for synthesizing modified halloysite nanomaterials (synthesis schematic diagram shown) Figure 1 (As shown), including the following steps:

[0095] S1. Activation of halloysite nanotubes: Halloysite nanotubes were dried and activated in an oven at 110℃ for 3 hours, and then cooled to obtain activated halloysite nanotubes.

[0096] S2. Ultrasonic dispersion: The activated halloysite nanotubes were added to N,N-dimethylformamide and then ultrasonically dispersed for 10 min to obtain a dispersion.

[0097] S3. Hydrophobic modification: Octylsulfonyl chloride and triethylamine, an acid-binding agent, were added to the dispersion. The mixture was heated to reflux at 65°C for 5 hours under nitrogen protection. The solid was then separated by centrifugation, washed with ethanol, and dried in an oven at 82°C for 55 minutes to obtain the modified halloysite nanomaterial.

[0098] In this embodiment, the mass-to-volume ratio of halloysite nanotubes to tetrahydrofuran is 245 mg: 7 mL; the amount of octylsulfonyl chloride is 3 mmol per gram of halloysite nanotubes; and the molar ratio of triethylamine to octylsulfonyl chloride is 1.2:1. Example 6

[0099] A method for synthesizing modified halloysite nanomaterials (synthesis schematic diagram shown) Figure 1 (As shown), including the following steps:

[0100] S1. Activation of halloysite nanotubes: Halloysite nanotubes were dried and activated in a 95℃ oven for 4 hours, and then cooled to obtain activated halloysite nanotubes.

[0101] S2. Ultrasonic dispersion: The activated halloysite nanotubes were added to tetrahydrofuran and then ultrasonically dispersed for 15 min to obtain a dispersion.

[0102] S3. Hydrophobic modification: Dodecyl sulfonyl chloride and acid-binding agent pyridine are added to the dispersion, and the mixture is heated to reflux at 75°C for 4 hours under nitrogen protection. The solid is then separated by centrifugation, washed with ethanol, and dried in an oven at 87°C for 45 minutes to obtain the modified halloysite nanomaterial.

[0103] In this embodiment, the mass-to-volume ratio of halloysite nanotubes to tetrahydrofuran is 255 mg: 9 mL; the amount of dodecyl sulfonyl chloride is 4 mmol per gram of halloysite nanotubes; and the molar ratio of pyridine to dodecyl sulfonyl chloride is 1.3:1. Example 7

[0104] An MDI composite adhesive comprising any one of the modified halloysite nanomaterials from Examples 1 to 6. Example 8

[0105] An MDI composite adhesive includes a modified halloysite nanomaterial from Example 1. The modified halloysite nanomaterial comprises 0.5% by mass in the MDI composite adhesive. Example 9

[0106] An MDI composite adhesive includes a modified halloysite nanomaterial from Example 1. The modified halloysite nanomaterial comprises 1.0% by mass in the MDI composite adhesive. Example 10

[0107] An MDI composite adhesive includes a modified halloysite nanomaterial from Example 1. The modified halloysite nanomaterial comprises 1.5% by mass in the MDI composite adhesive. Example 11

[0108] An application of MDI composite adhesive in particleboard is described. In this embodiment, the MDI composite adhesive of Example 8 is applied to the bonding of particleboard of type P2 (standard raw particleboard). In this embodiment, the application amount of MDI composite adhesive is 3.5 wt%. Example 12

[0109] An application of MDI composite adhesive in particleboard is described. In this embodiment, the MDI composite adhesive of Example 9 is applied to the bonding of particleboard of type P2 (standard raw particleboard). In this embodiment, the application amount of MDI composite adhesive is 3.5 wt%. Example 13

[0110] An application of MDI composite adhesive in particleboard is described. In this embodiment, the MDI composite adhesive of Example 10 is applied to the bonding of particleboard of type P2 (standard raw particleboard). In this embodiment, the application amount of MDI composite adhesive is 3.5 wt%.

[0111] Appearance and morphology comparison

[0112] The modified halloysite nanomaterial prepared in Example 1 (referred to as Sample I), the modified halloysite nanomaterial prepared in Example 2 (referred to as Sample II), and the unmodified halloysite nanotubes (referred to as the original sample) were compared in appearance. Please refer to [link to sample I]. Figure 2 .

[0113] Depend on Figure 2 It can be seen that the morphology of Sample I, Sample II and the original sample are all white powdery solids, but the original sample shows more obvious clumping.

[0114] Hydrophobicity test

[0115] The hydrophobic properties of a modified halloysite nanomaterial prepared in Example 1 (referred to as Sample I), a modified halloysite nanomaterial prepared in Example 2 (referred to as Sample II), and an unmodified halloysite nanotube (referred to as the original sample) were tested.

[0116] The test method is as follows: Take 250 mg of the unmodified original sample, Sample I, and Sample II, and place them in separate test tubes. Add 5 mL of purified water, shake, and then sonicate for 1 min. Observe the initial state, state after 1 min, 2 min, 3 min, 5 min, 10 min, 20 min, and 30 min of standing time, respectively. Figures 3 to 6 As shown.

[0117] Depend on Figure 3 As can be seen, after ultrasonic dispersion and standing for 1 minute, sample II showed obvious interfacial stratification, while the unmodified original sample and sample I did not show obvious interfacial stratification. Figure 4 As can be seen, after standing for 2 minutes, sample I showed obvious interfacial stratification, and the stratification phenomenon was even more obvious in sample II, while the unmodified original sample did not show obvious interfacial stratification; after standing for 3 minutes, samples I and II showed obvious interfacial stratification, while the unmodified original sample did not show obvious interfacial stratification. Figure 5 It is evident that after standing for 5 minutes and 10 minutes, compared to standing for 3 minutes, the rate of interfacial delamination slowed down, and no obvious interfacial delamination was observed in the unmodified original sample. Figure 6It can be seen that after standing for 20 minutes, the stratification state of the interface between sample I and sample II tends to be stable, and the unmodified original sample did not show obvious interface stratification after standing for 20 minutes and 30 minutes.

[0118] The hydrophobic performance test results show that, due to the large number of hydroxyl groups (hydrophilic) on the surface of the unmodified halloysite nanotubes, they can form hydrogen bonds with water molecules. Due to electrostatic repulsion and the protection of the hydration film, the particles can be stably dispersed in water, forming fine monodisperse particles with slow sedimentation. Furthermore, the modified halloysite nanomaterial of this invention, due to its better hydrophobicity, leads to particle aggregation through hydrophobic interactions, resulting in aggregates with a particle size much larger than individual particles. With the increased particle size, gravity far exceeds the resistance of water molecules, significantly accelerating the sedimentation rate. Therefore, the modified halloysite nanotubes exhibit significantly enhanced hydrophobicity due to the introduction of alkyl chains (from alkyl sulfonyl chlorides). Specifically, compared to the modified halloysite nanomaterial of Example 1 (Sample I), the modified halloysite nanomaterial of Example 2 (Sample II) exhibits faster stratification sedimentation speed because the added alkyl sulfonyl chlorides are octyl sulfonyl chloride and dodecyl sulfonyl chloride. The dodecyl group has a greater hydrophobic effect than the octyl group.

[0119] Particle size testing and analysis

[0120] The modified halloysite nanomaterial prepared in Example 1 (denoted as Sample I), the modified halloysite nanomaterial prepared in Example 2 (denoted as Sample II), and the unmodified halloysite nanotubes (denoted as the original sample) were subjected to particle size analysis. The test method is as follows: using water as the dispersion system, the particle size distribution of the unmodified halloysite original sample, Sample I, and Sample II in water was measured using a laser particle size analyzer. The test results are as follows. Figure 7 As shown.

[0121] Depend on Figure 7 The particle size distribution results showed that the average diameter of the original sample was 7.54 μm, the average diameter of sample I was 13.59 μm, and the average diameter of sample II was 15.06 μm. The particle size analysis results were consistent with the stratification and sedimentation results in the hydrophobicity test. The enhanced hydrophobicity of the halloysite nanotubes modified in this invention disrupts their dispersion stability in water, promotes particle aggregation, increases particle size, and thus accelerates sedimentation and stratification.

[0122] Particleboard performance testing

[0123] Particleboards prepared by bonding with the MDI composite adhesive of the present invention in Examples 11 to 13 (referred to as Sample 1, Sample 2, and Sample 3, respectively), and particleboard prepared by bonding with MDI adhesive without modified halloysite nanomaterials (referred to as the control sample) were tested for bonding strength, static bending strength, elastic modulus, and 2-hour thickness expansion rate. The percentage improvement in bonding strength, static bending strength, elastic modulus, and 2-hour thickness expansion rate of Sample 1, Sample 2, and Sample 3 compared to the control sample is shown in Table 1.

[0124] Table 1. Performance improvements of Sample 1, Sample 2, and Sample 3 compared to the control sample.

[0125]

[0126] As shown in Table 1, compared with the control sample, the particleboard bonded with MDI composite adhesive doped with the modified halloysite nanomaterial prepared in this invention exhibits varying degrees of percentage improvement in parameters such as bond strength, static bending strength, elastic modulus, and 2-hour thickness expansion rate. Specifically, when doped with 0.5% modified halloysite nanomaterial, the bond strength is increased by 22%, static bending strength by 33%, elastic modulus by 12%, and 2-hour thickness expansion rate increases by 4% compared with the control sample; when doped with 1.0% modified halloysite nanomaterial, the bond strength is increased by 24%, static bending strength by 30%, elastic modulus by 8%, and 2-hour thickness expansion rate remains essentially unchanged compared with the control sample; when doped with 1.5% modified halloysite nanomaterial, the bond strength is increased by 35%, static bending strength by 25%, elastic modulus by 4%, and 2-hour thickness expansion rate decreases by 13% compared with the control sample. Therefore, it can be seen that when the MDI composite adhesive of the present invention is doped with 0.5~1.5% modified halloysite nanomaterials, it significantly improves the bonding strength and static bending strength of particleboard (greater than 22%), and also improves the elastic modulus of particleboard to a certain extent (greater than 4%). This indicates that the MDI composite adhesive doped with modified halloysite nanomaterials is beneficial to improving the mechanical strength during the application of particleboard. When the MDI composite adhesive is doped with 1.5% modified halloysite nanomaterials, the thickness expansion rate is reduced by 13% after 2 hours, indicating that when an appropriate amount of modified halloysite nanomaterials is added, the water absorption of particleboard can be reduced, the hydrophobicity can be enhanced, and the waterproof and moisture-proof capabilities can be improved.

[0127] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for synthesizing modified halloysite nanomaterials, characterized in that, Includes the following steps: S1. Activation of halloysite nanotubes: Halloysite nanotubes are placed in an oven for drying and activation, and then cooled to obtain activated halloysite nanotubes. S2. Ultrasonic dispersion: The activated halloysite nanotubes are added to the solvent and then ultrasonically dispersed to obtain a dispersion. S3. Hydrophobic modification: Alkyl sulfonyl chloride and acid-binding agent are added to the dispersion, and the mixture is heated and refluxed under an inert atmosphere. The solid is then separated by centrifugation, washed, and dried to synthesize the modified halloysite nanomaterial.

2. The method for synthesizing modified halloysite nanomaterials as described in claim 1, characterized in that, In step S1, the drying and activation temperature is 90℃~120℃, and the drying and activation time is 2h~6h.

3. The method for synthesizing a modified halloysite nanomaterial as described in claim 1, characterized in that, In step S2, the solvent is an aprotic solvent; and / or, the aprotic solvent is at least one of dichloromethane, tetrahydrofuran, toluene, or N,N-dimethylformamide; and / or The ultrasonic dispersion time is 5 min to 30 min.

4. The method for synthesizing modified halloysite nanomaterials as described in claim 1, characterized in that, In step S3, the alkyl group in the alkyl sulfonyl chloride is a C4-C18 straight-chain alkyl group or a branched alkyl group; and / or The alkyl sulfonyl chloride is at least one selected from butyl sulfonyl chloride, octyl sulfonyl chloride, dodecyl sulfonyl chloride, or octadecyl sulfonyl chloride; and / or The acid-binding agent is an organic amine acid-binding agent; and / or, the organic amine acid-binding agent is at least one of triethylamine, pyridine, or 4-dimethylaminopyridine; and / or The inert atmosphere is nitrogen.

5. The method for synthesizing a modified halloysite nanomaterial as described in claim 1, characterized in that, In step S3, the temperature of the reflux reaction is 60℃~80℃, and the reflux reaction time is 3h~6h; and / or The washing is performed using ethanol; and / or The drying temperature is 80℃~90℃, and the drying time is 40min~60min.

6. The method for synthesizing a modified halloysite nanomaterial as described in claim 1, characterized in that, The mass-to-volume ratio of the halloysite nanotubes to the solvent is (240~260) mg : (6~10) mL; and / or The amount of alkyl sulfonyl chloride used is: 1 mmol to 5 mmol of alkyl sulfonyl chloride per gram of halloysite nanotubes; and / or The molar ratio of the acid-binding agent to the alkyl sulfonyl chloride is (1~1.5):

1.

7. A modified halloysite nanomaterial, characterized in that, It is prepared by the synthesis method of the modified halloysite nanomaterial according to any one of claims 1 to 6.

8. An MDI composite adhesive, characterized in that, Including the modified halloysite nanomaterial as described in claim 7.

9. The MDI composite adhesive as described in claim 8, characterized in that, The modified halloysite nanomaterial has a mass percentage content of 0.5% to 1.5%.

10. The application of the MDI composite adhesive as described in claim 8 or 9 in particleboard.

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