Lactose-based covalent organic framework adhesive as well as preparation method and application thereof

Abstract

The application discloses a lactose-based covalent organic framework adhesive as well as a preparation method and application thereof, and belongs to the technical field of adhesives. PN The lactose-based adhesive LHC is prepared through a Schiff base reaction, the problem of insufficient bonding performance of traditional biomass adhesives in a high-temperature and humid environment is overcome, the performance of the adhesive in the high-temperature and humid environment is improved, the covalent organic framework COF is introduced into the lactose-based adhesive LHC, and the lactose-based covalent organic framework adhesive LHC@COF is prepared PN The prepared adhesive has improved flame retardance and further enhanced mechanical strength, the lactose-based covalent organic framework adhesive LHC@COF is prepared PN The dry shear strength of the prepared plywood can reach 1.61 MPa or more, the strength is still 1.49 MPa or more after being soaked in 63 DEG C hot water and 93 DEG C hot water for 3 hours, and the strength and the limiting oxygen index of 37.6 are all higher than those of the plywood prepared by using the lactose-based adhesive LHC, the flame retardance is stronger, and the lactose-based covalent organic framework adhesive LHC is suitable for high-performance application of various wood substrates.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesives, and specifically discloses a lactose-based covalent organic framework adhesive as well as a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of the wood industry, wood plays a vital role in the field of construction. Wood used for structural buildings needs to have excellent mechanical properties and long service life, and these characteristics are closely related to the wood adhesive used. Therefore, the selected wood adhesive must have excellent adhesion, fire resistance and weather resistance, and the existing biomass adhesives cannot meet the requirements in terms of durability, flame retardance and mechanical properties in a high-temperature and humid environment. SUMMARY

[0003] The technical problem to be solved by the application is that the existing biomass adhesives cannot meet the requirements in terms of durability, flame retardance and mechanical properties in a high-temperature and humid environment, and a lactose-based covalent organic framework adhesive as well as a preparation method and application thereof are provided.

[0004] To solve the above technical problem, the application provides a preparation method of a lactose-based covalent organic framework adhesive (LHC@COF PN ), comprising the following steps:

[0005] S1, preparing a citric acid-based hyperbranched polyamine HC: citric acid trimethyl ester and 1,6-hexanediamine are mixed, methanol is added for dissolution, stirring is performed at room temperature until the reaction is completed, the excess methanol in the product is removed, and the citric acid-based hyperbranched polyamine HC is prepared;

[0006] S2, preparing a lactose-based adhesive LHC: the citric acid-based hyperbranched polyamine HC prepared in step S1 is mixed with lactose, and is reacted at 70-90 DEG C for 2-6 hours, and then cooled to room temperature; deionized water is added at 30-50% of the solid content of the lactose-based adhesive LHC to completely dissolve the lactose-based adhesive LHC, and the lactose-based adhesive LHC is prepared;

[0007] S3, preparing a covalent organic framework COF PN : hexachlorocyclotriphosphazene (HCCP) and N,N'-bis(2-aminoethyl) p-phenylenediamine are dissolved in anhydrous tetrahydrofuran (THF) to form a suspension, the suspension is sealed in a high-pressure reaction container and reacted at 90 DEG C for 24 hours, and then cooled to room temperature; filtration, washing and vacuum drying are performed to obtain the covalent organic framework COF PN ;

[0008] S4, preparing a lactose-based covalent organic framework adhesive LHC@COF PN : the lactose-based adhesive LHC prepared in step S2 and the covalent organic framework COF PNMixing at room temperature, 80℃ for 1h, cooling to room temperature, adding deionized water to 50% of its solid content to completely dissolve, to obtain the lactose-based covalent organic framework adhesive LHC@COF PN .

[0009] Specifically, the preparation process of N,N'-bis (2-aminoethyl) p-phenylenediamine in step S3 is as follows: dissolving ethylenediamine in anhydrous ethanol, slowly adding anhydrous ethanol solution of p-xylene aldehyde under stirring, reacting at 60℃ for 24h, pouring the reaction solution into cold water to precipitate solid product, collecting the solid product and washing with cold anhydrous ethanol, and vacuum drying to obtain N,N'-bis (2-aminoethyl) p-phenylenediamine.

[0010] Specifically, in step S1, the molar ratio of trimethyl citrate to 1,6-hexanediamine is 1:3.

[0011] Specifically, in step S2, the mass ratio of citric acid-based hyperbranched polyamine HC to lactose is 1:(2-6), preferably 1:3.

[0012] Specifically, in step S3, the molar ratio of hexachlorocyclotriphosphazene (HCCP) to N,N'-bis (2-aminoethyl) p-phenylenediamine is 1:3.

[0013] Specifically, in step S4, the mass ratio of covalent organic framework COF PN to lactose-based adhesive LHC is (0.01-0.1):1, preferably 0.3:1.

[0014] To solve the above technical problems, the application further provides a lactose-based covalent organic framework adhesive LHC@COF PN , which is prepared according to the preparation method.

[0015] To solve the above technical problems, the application further provides such a lactose-based covalent organic framework adhesive LHC@COF PN for use in preparing laminated plywood.

[0016] Further, the plywood is three-layered, and the preparation process is as follows:

[0017] SS1, drying: drying the single board to be pressed to a water content of less than 10%;

[0018] SS2, sizing: brushing the lactose-based covalent organic framework adhesive LHC@COF PN on both sides of the dried single board. PN The total brushing amount of the lactose-based covalent organic framework adhesive LHC@COF 2 is 320 g / m

[0019] SS3, group blank: arrange and combine the single boards coated with the lactose-based covalent organic framework adhesive in a vertical texture manner to form a blank body with a predetermined shape and size;

[0020] SS4, hot pressing; hot pressing the blank body after the group blank under the condition of 180-220 DEG C, 1.0-1.5 MPa for 5-8 min to obtain the laminated board.

[0021] Due to the adoption of the above technical solutions, the application has the following beneficial effects:

[0022] (1) The lactose-based adhesive prepared by the Schiff base reaction overcomes the problem of insufficient bonding performance of the traditional biomass adhesive in high-temperature and humid environments, improves the performance of the adhesive in high-temperature and humid environments, and makes it exhibit more excellent stability and reliability in harsh conditions;

[0023] (2) By introducing the covalent organic framework COF containing phosphorus (P) and nitrogen (N) elements, PN the flame retardant performance of the adhesive is significantly improved, which is a function that the traditional biomass adhesive cannot achieve, so that it is more suitable for application occasions with high safety requirements;

[0024] (3) By combining the covalent organic framework COF PN with the lactose-based adhesive LHC, the mechanical strength of the adhesive is further enhanced while the flame retardant performance is improved, thereby widening the application range of the adhesive in higher load occasions;

[0025] (4) The lactose-based adhesive is prepared by using citric acid-based hyperbranched polyamine HC and lactose as raw materials for the Schiff base reaction, which provides a new idea for optimizing the performance of biomass adhesives.

[0026] In general, the preparation method of the lactose-based covalent organic framework adhesive LHC@COF PN of the application is a new strategy based on the Schiff base reaction, which not only improves the performance of the adhesive in high-temperature and humid environments, but also improves the flame retardant performance and mechanical strength of the adhesive by introducing the covalent organic framework COF containing phosphorus and nitrogen elements, PN while improving the heat resistance and moisture resistance of the adhesive; and the reaction conditions are mild and the reaction equipment requirements are not high; at the same time, the main raw materials used are derived from biomass, avoiding the use of formaldehyde, which reduces the production cost, improves the environmental performance of the board, reduces environmental pollution, and promotes the rational development and utilization of renewable resources. Therefore, the application greatly improves the applicability of biomass adhesives in high-performance applications, especially in the field of wood-based boards. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1Schematic diagram of the reaction principle of HC for citrate-based hyperbranched polyamines;

[0028] Figure 2 A schematic diagram illustrating the reaction principle and preparation process of lactose-based adhesive LHC;

[0029] Figure 3 It is a covalent organic framework (COF) containing phosphorus and nitrogen. PN A schematic diagram illustrating the reaction principle and preparation process;

[0030] Figure 4 LHC@COF is a lactose-based covalent organic framework adhesive. PN A schematic diagram illustrating the reaction principle and preparation process;

[0031] Figure 5 LHC@COF is a lactose-based covalent organic framework adhesive. PN The flame retardant mechanism diagram. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] The reaction principle of the citrate-based hyperbranched polyamine HC used in the following examples is as follows: Figure 1 As shown, its preparation method is as follows:

[0034] Trimethyl citrate and 1,6-hexanediamine were mixed at a molar ratio of 1:3, dissolved in methanol, and stirred at room temperature for 48 hours. After the reaction was completed, excess methanol was removed from the product by rotary evaporator to obtain citrate-based hyperbranched polyamine HC. Example 1

[0035] This embodiment provides a method for preparing lactose-based adhesive LHC, the reaction principle and preparation process of which are as follows: Figure 2 As shown, specifically:

[0036] 2g of citrate-based hyperbranched polyamine HC and 4g of lactose were mixed and reacted at 80℃ for 3h. After the reaction was completed, the product was cooled to room temperature and 50% of its solid content was added to deionized water to completely dissolve it, thus obtaining lactose-based adhesive LHC.

[0037] Examples 2-14 are all methods for preparing lactose-based adhesives (LHC), with different reaction conditions. The specific reaction conditions are shown in Table 1 and will not be repeated here.

[0038] The covalent organic framework COF used in the following examples PN The reaction principle and preparation process are as follows: Figure 3 As shown, its preparation method is as follows:

[0039] A solution of 1.34 g of terephthaldehyde was prepared by dissolving it in 10 mL of anhydrous ethanol, and then 1.20 g of ethylenediamine was added to a reaction bottle with 10 mL of anhydrous ethanol and stirring was started, and then the terephthaldehyde solution was slowly added to the ethylenediamine solution, stirring was continued and the reaction was carried out in a sand bath at 60°C for 24 h, and the solution turned yellow, indicating the formation of the intermediate N,N'-bis(2-aminoethyl) p-phenylenediamine imine, after the reaction was completed, the mixture was poured into 100 mL of cold water to precipitate the solid product, which was collected by vacuum filtration and washed with a small amount of cold anhydrous ethanol, and finally dried in a vacuum drying oven at 70°C for 24 h to obtain purified N,N'-bis(2-aminoethyl) p-phenylenediamine imine;

[0040] Hexachlorocyclotriphosphazene (HCCP) and N,N'-bis(2-aminoethyl) p-phenylenediamine imine were dissolved in 50 mL of anhydrous tetrahydrofuran (THF) at a molar ratio of 1:3 to form a suspension, which was then transferred to a high-pressure reaction vessel, sealed and reacted at 90°C for 24 h, after the reaction was completed, it was cooled to room temperature, and the orange powder was collected by filtration, washed with deionized water and ethanol until the filtrate was colorless, and dried at 70°C for 24 h to obtain a light yellow covalent organic framework COF PN .

[0041] Example 15

[0042] This example provides a preparation method of a lactose-based covalent organic framework adhesive LHC@COF PN , the reaction principle and preparation process of which are shown in Figure 4 , and specifically, 10 g of the lactose-based adhesive LHC prepared in Example 7 and 0.1 g of the covalent organic framework (COF PN ) prepared in Example 16 were mixed at room temperature, and stirred at 80°C for 1 h, and the product obtained after the reaction was cooled to room temperature, deionized water was added at 50% of the solid content to completely dissolve it, and thus a lactose-based covalent organic framework adhesive LHC@COF PN .

[0043] Examples 16-18 are all preparation methods of a lactose-based covalent organic framework adhesive LHC@COF PN , and the specific reaction conditions are shown in Table 2, which will not be repeated here.

[0044]

[0045] Example 19 Performance Test:

[0046] 1. Adhesive strength test:

[0047] In order to test the lactose-based adhesive LHC and the lactose-based covalent organic framework adhesive LHC@COF prepared by the present application PN The performance of the prepared laminated plywood was tested by using the lactose-based adhesive LHC prepared by Examples 1-14 and the lactose-based covalent organic framework adhesive LHC@COF prepared by Examples 15-18, respectively. PN Eighteen pieces of three-layer laminated plywood were prepared, and the specific preparation process was as follows:

[0048] The single boards to be pressed were dried to a moisture content of less than 10%; the lactose-based adhesive LHC or the lactose-based covalent organic framework adhesive LHC@COF was brushed on both sides of the dried single boards PN , and the total brushing amount was 320 g / m 2 ; then the single boards were arranged and combined in a vertical texture manner to form a blank body with a predetermined shape and size; and the blank body after the blanking was hot-pressed at 200℃ and 1.5MPa for 6min to obtain eighteen pieces of laminated plywood.

[0049] Adhesion strength test: the evaluation of the adhesion strength was carried out according to the national standard GB / T17657-2013. First, the sample was cut into the same size (100mm×25mm), and then the slot processing was carried out so that the area of the bonding part was 25mm×25mm. Next, the sample was immersed in a water bath at 63±3℃ and 93±3℃, respectively, for 3h. After taking out, it was placed at room temperature for 10min, and then the adhesion strength test was carried out using an electronic universal mechanical testing machine, and the test results are shown in Tables 3 and 4.

[0050] Result analysis: from the data in Tables 3 and 4, it can be seen that the dry shear strength of the laminated plywood prepared by using the lactose-based adhesive LHC is 0.72-1.68MPa, while the dry shear strength of the laminated plywood prepared by using the lactose-based covalent organic framework adhesive LHC@COF PN is greater than 1.61MPa, and the maximum can reach 1.88MPa, which is much higher than the dry shear strength of the laminated plywood prepared by using the lactose-based adhesive LHC. The wet strength of the laminated plywood prepared by using the lactose-based adhesive LHC after 3h hot water immersion at 63℃ is 0.68-1.47MPa, while the wet strength of the laminated plywood prepared by using the lactose-based covalent organic framework adhesive LHC@COF PN after 3h hot water immersion at 63℃ is greater than 1.49MPa, and the maximum can reach 2.28MPa; the wet strength of the laminated plywood prepared by using the lactose-based adhesive LHC after 3h hot water immersion at 93℃ is 0.77-1.50MPa; while the wet strength of the laminated plywood prepared by using the lactose-based covalent organic framework adhesive (LHC@COF PNThe wet strength of the laminated plywood prepared by soaking in hot water at 93°C for 3 hours was greater than 1.57 MPa, with a maximum of 2.20 MPa, which was also higher than the wet strength of the laminated plywood prepared with lactose-based adhesive LHC.

[0051] Conclusion: The above performance test data demonstrate that the introduction of a covalent organic framework (COF) containing P and N elements into the lactose-based adhesive LHC is effective. PN This improves the heat resistance, moisture resistance and mechanical strength of the adhesive.

[0052]

[0053]

[0054] 2. Flame retardancy test:

[0055] The laminated plywood prepared with lactose-based adhesive LHC (prepared in Example 7) was cut into three equal-length (80mm × 10mm) control samples, and then coated with lactose-based covalent organic framework adhesive LHC@COF. PN The laminated plywood prepared in Example 16 was cut into three experimental samples of equal length (80mm × 10mm). The limiting oxygen index (LOI) of the two groups of samples was then tested. The test results are shown in Table 5. As can be seen from Table 5, the LOI of the experimental group samples is much higher than that of the control group samples, indicating that the experimental group samples have stronger flame retardancy.

[0056] from Figure 5 Lactose-based covalent organic framework adhesive LHC@COF PN The flame retardant mechanism shows that the lactose-based covalent organic framework adhesive LHC@COF PN During combustion, NH3 / N2 and PO may be generated. * / P * It reacts with H2O to form an insulating film on the surface, isolating oxygen, reducing the surface's oxidative heat, and preventing combustion.

[0057]

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A method for preparing a lactose-based covalent organic framework adhesive, characterized by, The method comprises the following steps: S1, preparing a citric acid-based hyperbranched polyamine: mixing trimethyl citrate and 1,6-hexanediamine, dissolving in methanol, stirring at room temperature until the reaction is completed, removing the excess methanol in the product, and obtaining the citric acid-based hyperbranched polyamine; S2, preparing a lactose-based adhesive: mixing the citric acid-based hyperbranched polyamine prepared in step S1 with lactose, reacting at 70-90°C for 2-6 hours, cooling to room temperature, and adding deionized water at 40-60% of the solid content to completely dissolve the mixture, and obtaining the lactose-based adhesive; S3, preparing a covalent organic framework: dissolving hexachlorocyclotriphosphazene and N,N'-bis(2-aminoethyl) p-phenylenediamine in anhydrous tetrahydrofuran to form a suspension, sealing the suspension in a high-pressure reaction container, and reacting at 90°C for 24 hours, cooling to room temperature, filtering, washing, and vacuum drying to obtain the covalent organic framework; S4, preparing a lactose-based covalent organic framework adhesive: mixing the lactose-based adhesive prepared in step S2 and the covalent organic framework prepared in step S3 at room temperature, reacting at 80°C for 1 hour, cooling to room temperature, and adding deionized water at 50% of the solid content to completely dissolve the mixture, and obtaining the lactose-based covalent organic framework adhesive.

2. The method for preparing the lactose-based covalent organic framework adhesive as described in claim 1, characterized in that, The preparation process of the N,N'-bis(2-aminoethyl) p-phenylenediamine in step S3 is as follows: dissolving ethylenediamine in anhydrous ethanol, slowly adding a p-xylene formaldehyde anhydrous ethanol solution under stirring, reacting at 60°C for 24 hours, pouring the reaction solution into cold water to precipitate the solid product, collecting the solid product and washing with cold anhydrous ethanol, and vacuum drying to obtain the N,N'-bis(2-aminoethyl) p-phenylenediamine.

3. The method for preparing the lactose-based covalent organic framework adhesive as described in claim 1, characterized in that: In step S1, the molar ratio of trimethyl citrate to 1,6-hexanediamine is 1:

3.

4. The method for preparing the lactose-based covalent organic framework adhesive as described in claim 1, characterized in that: In step S2, the mass ratio of the citric acid-based hyperbranched polyamine to lactose is 1:(2-6).

5. The method for preparing the lactose-based covalent organic framework adhesive as described in claim 1, characterized in that: In step S3, the molar ratio of hexachlorocyclotriphosphazene to N,N'-bis(2-aminoethyl) p-phenylenediamine is 1:

3.

6. The method for preparing the lactose-based covalent organic framework adhesive as described in claim 1, characterized in that: In step S4, the mass ratio of the covalent organic framework to the lactose-based adhesive is (0.01-0.1):

1.

7. A lactose-based covalent organic framework adhesive, characterized by: Prepared according to any one of claims 1-6.

8. The use of the lactose-based covalent organic framework adhesive of claim 7 in the preparation of laminated plywood.

9. Use of the lactose-based covalent organic framework adhesive according to claim 8 for the preparation of a laminated board, characterized in that, The plywood is three-layered, and the preparation process is as follows: SS1, drying: drying the single board to be pressed to a water content of less than 10%; SS2, sizing: after drying, the veneer is coated on both sides with the lactose-based covalent organic framework adhesive of claim 7, and the total coating amount of the lactose-based covalent organic framework adhesive is 320 g / m 2 ; SS3, assembling: arranging and combining the single boards coated with the lactose-based covalent organic framework adhesive in a vertical texture manner to form a blank body with a predetermined shape and size; SS4, hot pressing: hot pressing the blank body after assembling at 180-220°C and 1.0-1.5 MPa for 5-8 min to obtain the laminated plywood.

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