High-strength anti-freezing vegetable protein adhesive based on multi-scale structure regulation and control and preparation method of high-strength anti-freezing vegetable protein adhesive

Abstract

The invention discloses a high-strength anti-freezing vegetable protein adhesive based on multi-scale structure regulation and a preparation method thereof. The vegetable protein adhesive is mainly prepared from the following raw materials: vegetable protein meal, an anti-freezing modifier, modified cellulose nanocrystals, a chemical cross-linking agent and a dispersion medium. Wherein the components comprise 30 parts of vegetable protein meal, 10-15 parts of an anti-freezing modifier, 0.5-1.2 parts of modified cellulose nanocrystals, 4-6 parts of a chemical cross-linking agent and 70 parts of a dispersion medium. The invention provides a high-strength anti-freezing vegetable protein adhesive based on multi-scale structure regulation and control, which breaks through the bottleneck of low-temperature freezing and brittleness of the traditional adhesive, effectively solves the problem of poor performance of the vegetable protein adhesive in a low-temperature environment, fills up the blank of a bio-based adhesive in the low-temperature field, and has a wide application prospect. The anti-freezing performance, the bonding strength, the environment-friendly performance and the sustainability are excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and specifically provides a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation and a preparation method thereof. Background Art

[0002] China is a major country in the wood-based panel industry, with its volume output exceeding that of steel and plastics. However, 90% of the adhesives used in the preparation of wood-based panels are aldehyde resins, which have problems such as formaldehyde pollution and non-renewable raw materials. As a green and environmentally friendly biomass adhesive, plant protein adhesives have broad application prospects in the fields of wood processing and the like due to their wide raw material sources, low price, renewable nature, and pollution-free properties.

[0003] Therefore, developing high-quality plant protein adhesives to fundamentally solve the problem of formaldehyde pollution in the human living environment is of great significance for realizing the sustainable development of the wood-based panel industry, protecting people's health, and serving the national strategy. However, traditional plant protein adhesives have some defects, which limit their application in some special environments. In a low-temperature environment, the performance of ordinary plant protein adhesives will significantly decline, such as a decrease in bonding strength, a deterioration in flexibility, and even brittle fracture. This is mainly because the water in plant protein molecules freezes, and the formation of ice crystals destroys the intermolecular interactions of protein molecules and the microstructure of the adhesive. Currently, the research on the low-temperature resistance performance of plant protein adhesives is relatively scarce, and some existing improvement methods have limited effects and cannot meet the actual use requirements in cold regions or low-temperature conditions. Therefore, developing a plant protein adhesive with good freeze-resistant performance has important practical significance and market demand. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the existing research, the purpose of the present invention is to provide a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation, which can effectively solve the problem of poor performance of plant protein adhesives in a low-temperature environment, fill the gap in the low-temperature field of bio-based adhesives, and has excellent performance in terms of freeze-resistant performance, bonding strength, environmental protection performance, and sustainability.

[0006] To solve the above technical problems, according to one aspect of the present invention, the following technical solutions are provided:

[0007] A high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation, which comprises the following components in parts by weight: 30 parts of plant protein meal, 10 - 15 parts of antifreeze improver, 0.5 - 1.2 parts of modified cellulose nanocrystals, 4 - 6 parts of chemical cross-linking agent, and 70 parts of dispersion medium.

[0008] As a preferred embodiment of the high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, among them, in the plant protein meal, the protein content is 53%, the carbohydrate content is 33%, and the particle size of the plant protein is greater than 200 mesh.

[0009] As a preferred embodiment of the high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, among them, the particle size of the plant protein is 200 - 250 mesh.

[0010] As a preferred embodiment of the high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, among them, the chemical cross-linking agent is one or more of ethylene glycol glycidyl ether, glycidylamine epoxy resin, or glycerol glycidyl ether.

[0011] As a preferred embodiment of the high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, among them, the dispersion medium is tap water or distilled water.

[0012] A preparation method of a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation, the specific steps are as follows:

[0013] S1. Weigh each component according to the mass ratio, disperse the plant protein meal in the dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion;

[0014] S2. Uniformly disperse the antifreeze improver and modified cellulose nanocrystals in the soybean meal dispersion prepared in step S1, and stir at 60 °C for 0.5 hour;

[0015] S3. Uniformly disperse the chemical cross-linking agent into the solution obtained in step S2, and stir evenly to obtain a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation.

[0016] As a preferred embodiment of the preparation method of the high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, among them, the specific preparation steps of the antifreeze improver are as follows:

[0017] Add 3.0 mL of acrylic acid, 1.0 g of N-ethylacrylamide, and 45.0 mg of guar gum to 3.0 mL of ammonium persulfate solution (6.6 mg / mL) in sequence, and stir evenly;

[0018] Add 0.7 g of antifreeze protein to the above solution. After stirring for 10 min, add 12.0 mg of FeCl3 and continuously stir evenly to obtain an antifreeze improver.

[0019] As a preferred embodiment of the preparation method of the high-strength antifreeze plant protein adhesive based on multi-scale structure regulation described in the present invention, the specific preparation steps of the modified cellulose nanocrystals are as follows:

[0020] Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and continuously stir. The mixture undergoes four rounds of centrifugation and washing until it turns dark gray in appearance to obtain CNCs@PDA.

[0021] Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 400 rpm at 25 °C for 10 h, and after centrifugal separation, washing, and drying, obtain modified cellulose nanocrystals.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The adhesive of the present invention uses plant protein meal as a raw material, blends the plant protein meal with an antifreeze improver and modified cellulose nanocrystals, and finally crosslinks the plant protein meal with a chemical crosslinking agent such as glycidylamine epoxy resin. Experiments have proved that there is no formaldehyde release problem in the three-ply plywood manufactured by the product of the present invention. The wet bonding strength test of the plywood manufactured by the plant protein adhesive is above 0.7 MPa, and the dry bonding strength is basically above 1.80 MPa, with a significant enhancement effect.

[0024] 2. Antifreeze protein is a protein that can inhibit ice crystal growth and lower the freezing point. Based on the mussel-inspired chemistry principle, dopamine is introduced to increase adhesion and chemical crosslinking points, and zwitterionic proline is modified on the surface of cellulose nanocrystals, which not only enhances the bonding performance of the plant protein adhesive but also further regulates the mechanical properties and antifreeze properties of the plant protein adhesive through the synergistic effect with the antifreeze improver. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in conjunction with the drawings and embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts. Among them:

[0026] Figure 1Schematic diagram of the bonding strength test of the adhesives prepared in Examples 1-4 and Comparative Examples 1-3 provided by the present invention when coated on adhesive veneers;

[0027] Figure 2 Schematic diagram of the shear strength of the adhesives prepared in Examples 1-4 and Comparative Examples 1-3 provided by the present invention after being treated at different freezing temperatures (-10°C, -20°C, -30°C).

[0028] Figure 3 Schematic diagram of the retention rate of the shear strength of the adhesives prepared in Examples 1-4 and Comparative Examples 1-3 provided by the present invention after being treated at different freezing temperatures (-10°C, -20°C, -30°C) relative to room temperature. Detailed implementation manners

[0029] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention will be given in conjunction with the accompanying drawings. It should be understood that the examples given in the embodiments of the present invention are only for the purpose of illustration, and are not used to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention, and all belong to the scope of the present invention.

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0031] The experimental methods used in the embodiments of the present invention are all conventional operation methods unless otherwise specified. The materials, reagents, etc. used in the embodiments of the present invention can be obtained commercially unless otherwise specified.

[0032] The "parts" mentioned in the present invention are all calculated by mass parts unless otherwise specified.

[0033] The present invention provides a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation, which effectively solves the problem of poor performance of plant protein adhesives in low-temperature environments, fills the gap in the low-temperature field of bio-based adhesives, and has excellent performance in terms of freeze resistance, bonding strength, environmental performance and sustainability.

[0034] The high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation comprises the following components in parts by weight: 30 parts of plant protein meal, 10-15 parts of freeze-resistant improver, 0.5-1.2 parts of modified cellulose nanocrystals, 4-6 parts of chemical cross-linking agent and 70 parts of dispersion medium. Among them, in the plant protein meal, the protein content is 53%, the carbohydrate content is 33%, and the particle size of the plant protein is larger than 200 mesh. The chemical cross-linking agent is one or more of ethylene glycol glycidyl ether, glycidylamine epoxy resin or glycerol glycidyl ether, and the dispersion medium is tap water or distilled water.

[0035] In order to verify the performance of the above high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation of the present invention, the following Examples 1-4 and Comparative Examples 1-3 are provided for comparative verification.

[0036] Example 1

[0037] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing and drying, obtain modified cellulose nanocrystals.

[0038] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion.

[0039] S3. Uniformly disperse 10 g of freeze-resistant improver and 0.5 g of the modified cellulose nanocrystals prepared in step S1 in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 h.

[0040] S4. Uniformly disperse 4 g of chemical cross-linking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0041] Example 2

[0042] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing and drying, obtain modified cellulose nanocrystals.

[0043] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion.

[0044] S3. Uniformly disperse 15 g of antifreeze improver and 0.5 g of the modified cellulose nanocrystals prepared in step S1 in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 hour.

[0045] S4. Uniformly disperse 4 g of chemical crosslinking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0046] Example 3

[0047] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing and drying, obtain modified cellulose nanocrystals.

[0048] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion.

[0049] S3. Uniformly disperse 10 g of antifreeze improver and 1.0 g of the modified cellulose nanocrystals prepared in step S1 in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 hour.

[0050] S4. Uniformly disperse 4 g of chemical crosslinking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0051] Example 4

[0052] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing and drying, obtain modified cellulose nanocrystals.

[0053] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion;

[0054] S3. Uniformly disperse 15 g of antifreeze improver and 1.0 g of the modified cellulose nanocrystals prepared in step S1 in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 hour;

[0055] S4. Uniformly disperse 4 g of chemical crosslinking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0056] Comparative Example 1

[0057] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing, and drying, obtain modified cellulose nanocrystals.

[0058] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion;

[0059] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion;

[0059] Comparative Example 2

[0060] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 25 °C at 400 rpm for 10 h, and after centrifugation, separation, washing, and drying, obtain modified cellulose nanocrystals.

[0061] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion;

[0062] S3. Uniformly disperse 10 g of antifreeze improver in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 hour;

[0063] S4. Uniformly disperse 4 g of chemical crosslinking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0064] Comparative Example 3

[0065] S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture is centrifuged and washed four times until it turns dark gray in appearance to obtain CNCs@PDA. Add 0.09 g of zwitterionic proline to 5.0 mL of 0.36 wt% CNCs@PDA, stir at 400 rpm for 10 h at 25 °C, and then perform centrifugation, washing, and drying to obtain modified cellulose nanocrystals.

[0066] S2. Disperse 30 g of plant protein meal in 70 g of dispersion medium, and stir at 20 °C until evenly dispersed to obtain a soybean meal dispersion.

[0067] S3. Uniformly disperse 1.0 g of the modified cellulose nanocrystals prepared in step S1 in the soybean meal dispersion prepared in step S2, and stir at 60 °C for 0.5 h.

[0068] S4. Uniformly disperse 4 g of chemical cross-linking agent into the dispersion obtained in step S3, and then stir for 5 minutes.

[0069] The modified plant protein adhesives prepared in Comparative Examples 1-3 and Examples 1-4 of the present invention were tested for performance according to the following method.

[0070] Adhesive performance evaluation experiment:

[0071] Poplar plywood was sawn according to GB / T9846.7-2004, and the size of the specimen was 100 mm × 25 mm. The process parameters for preparing plywood were as follows: the sizing amount was 300-400 g / m 2 (both sides), and then it was sent to a hot press and hot-pressed at 120 °C under a unit pressure of 1.0-1.2 MPa for 360 s. The bonding strength was tested after the poplar plywood was cooled to room temperature, immersed in warm water at (60 ± 3 °C) for 3 h, cooled at room temperature for 10 min, and the average value was taken from 6 samples in each group. The test results are as Figure 1 shown.

[0072] Poplar plywood was sawn according to GB / T9846.7-2004, and the size of the specimen was 100 mm × 25 mm. The process parameters for preparing plywood were as follows: the sizing amount was 300-400 g / m 2 (both sides), and then it was sent to a hot press and hot-pressed at 120 °C under a unit pressure of 1.0-1.2 MPa for 360 s. Each group had 6 specimens, which were placed in a low-temperature refrigerator, and different freezing temperatures (-10 °C, -20 °C, -30 °C) were set, and the freezing time was 24 h. After the frozen specimens were taken out and thawed at room temperature for 2 h, their shear strength was tested on a mechanical testing machine, and the running rate of the tensile test was set to 10.0 mm / min.

[0073] Calculate the retention rate of the shear strength at different freezing temperatures relative to the room temperature control group:

[0074] Retention rate (%) = (X n / X0) × 100%, where X n is the shear strength at different freezing temperatures, and X0 is the shear strength of the room temperature control group. The frost resistance of the plant protein wood adhesive is evaluated by analyzing the retention rate. The higher the retention rate, the better the frost resistance.

[0075] The experimental results show that the formaldehyde emission of the three-layer plywood made of the formaldehyde-free plant protein adhesive of the present invention is not detected, and Figure 1 as shown, the wet state bonding strength of the plywood made of the plant protein adhesive in the examples is above 0.70 MPa, and the dry state bonding strength is basically above 1.80 MPa. As Figure 2 and Figure 3 shown, the shear strength retention rate of the plant protein adhesive added with the antifreeze improver and modified cellulose nanocrystals can still be maintained above 62% at -30°C. These results all indicate that the adhesive has good frost resistance.

[0076] Although the present invention has been described above with reference to the embodiments, various modifications can be made to it and components thereof can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention can be combined with each other in any way. The exhaustive description of these combinations is not given in this specification only for the sake of saving space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation, characterized in that, include: Plant protein meal, antifreeze improver, modified cellulose nanocrystals, chemical cross-linking agent, dispersion medium; The composition includes 30 parts of plant protein meal, 10 to 15 parts of antifreeze improver, 0.5 to 1.2 parts of modified cellulose nanocrystals, 4 to 6 parts of chemical cross-linking agent and 70 parts of dispersion medium.

2. The high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation according to claim 1, wherein The plant protein meal has a protein content of 53% and a carbohydrate content of 33%, and the particle size of the plant protein is greater than 200 meshes.

3. The high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation according to claim 1, wherein, The chemical cross-linking agent is one or more of ethylene glycol glycidyl ether, glycidylamine epoxy resin or glycerol glycidyl ether.

4. A high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation according to claim 1, characterized in that, The dispersion medium is tap water or distilled water.

5. A preparation method of a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation as described in any one of claims 1-4, characterized in that, The specific steps are as follows: S1. Weigh each component according to the mass ratio, disperse the plant protein meal in the dispersion medium, and stir at 20°C until uniformly dispersed to obtain a soybean meal dispersion; S2, uniformly dispersing the antifreeze improver and modified cellulose nanocrystals in the soybean meal dispersion prepared in step S1, and stirring at 60° C. for 0.5 hour; S3. Evenly disperse the chemical cross-linking agent into the solution obtained in step S2, and stir evenly to obtain a high-strength antifreeze plant protein adhesive based on multi-scale structure regulation.

6. The preparation method of a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation according to claim 5, characterized in that, The specific preparation steps of the antifreeze improver are as follows: S1. Add 3.0 mL of acrylic acid, 1.0 g of N-ethylacrylamide, and 45.0 mg of guar gum to 3.0 mL of ammonium persulfate solution (6.6 mg / mL) in sequence and stir well. S2. Add 0.7 g of antifreeze protein to the above solution, stir for 10 min, then add 12.0 mg of FeCl3 and continue stirring to obtain an antifreeze improver.

7. The preparation method of a high-strength and freeze-resistant plant protein adhesive based on multi-scale structure regulation according to claim 5, characterized in that, The specific preparation steps of the modified cellulose nanocrystals are as follows: S1. Dissolve 100.0 mg of cellulose nanocrystals in deionized water, add Tris-HCl buffer solution to adjust the pH to 8.5, add 100.0 mg of dopamine powder and stir continuously. The mixture undergoes four rounds of centrifugation and washing until it becomes dark gray in appearance to obtain CNCs@PDA. S2. 0.09 g of zwitterionic proline was added to 5.0 mL of 0.36 wt% CNCs@PDA, and the mixture was stirred at 400 rpm at 25° C. for 10 h. Modified cellulose nanocrystals were obtained after centrifugal separation, washing, and drying.

8. An application of a high-strength antifreeze plant protein adhesive based on multi-scale structural regulation as described in claims 1-7 in wood processing and antifreeze and cold-resistant artificial boards.

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