Temperature-resistant high-viscosity adhesive

Abstract

The invention relates to the technical field of adhesives, in particular to a temperature-resistant high-viscosity adhesive. The modified silk fibroin / chitosan nano-whisker / polylimonene composite material is prepared from the following raw materials: modified silk fibroin, chitosan nano-whiskers, polylimonene, lignin-silicon dioxide hybrid aerogel microspheres, a Schiff base dynamic covalent bond cross-linking agent, light-cured bio-based epoxy resin, nano-zinc oxide, a quercetin natural antioxidant, a photoinitiator TPO-L, fluorinated lecithin and deionized water. The preparation method comprises the following steps: S1, pretreatment of bio-based raw materials; s2, preparing lignin-silicon dioxide hybrid aerogel microspheres; s3, preparing a Schiff base dynamic covalent bond cross-linking agent; s4, constructing a reversible cross-linked network; s5, carrying out a light-heat dual-treatment stage; s6, adopting a supercritical CO2 foaming technology for the initial product to generate a microporous structure; and S7, spraying a fluorinated lecithin coating on the surface of the product with the microporous structure to obtain an adhesive layer. And the problems that the adhesive easily pollutes the environment and harms the body health of people during practical application are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly to a high-temperature resistant and high-viscosity adhesive. Background Art

[0002] An adhesive is a substance that generates adhesion at the interface through chemical or physical forces (such as van der Waals forces, hydrogen bonds, chemical bonds, etc.) and connects two or more materials through cohesive forces. Adhesives are widely used in fields such as construction, automotive, electronics, aerospace, etc., and are one of the three major joining technologies (adhesive bonding, welding, mechanical joining).

[0003] Currently, commonly used adhesives often have the problem of being less environmentally friendly in actual applications. For example, solvent-based adhesives contain volatile organic compounds (VOCs), which are easy to pollute the environment and endanger the health of users. In addition, some adhesives (such as traditional urea-formaldehyde resins) release formaldehyde, which does not meet the requirements of green manufacturing and will also pose a potential hazard to the health of users. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature resistant and high-viscosity adhesive to solve the problems of environmental pollution and endangerment to the health of users that commonly used adhesives are prone to in the actual application process.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A high-temperature resistant and high-viscosity adhesive is prepared from the following raw materials by mass percentage: 36-38% of modified silk fibroin, 9-11% of chitin nanowhiskers, 17-21% of poly(limonene); 6-9% of lignin-silica hybrid aerogel microspheres, 2-4% of Schiff base dynamic covalent crosslinking agent, 9-14% of photocurable bio-based epoxy resin, 2-4% of nano-zinc oxide, 0.4-0.8% of quercetin natural antioxidant, 0.6-1.8% of photoinitiator TPO-L, 0.08-0.12% of fluorinated lecithin, and 12-18% of deionized water.

[0006] The preparation method of the adhesive includes the following steps:

[0007] S1. Pretreatment of bio-based raw materials;

[0008] It includes preparing silk fibroin from silkworm cocoons and preparing chitin nanowhiskers from shrimp and crab shells;

[0009] S2. Preparation of lignin-silica hybrid aerogel microspheres;

[0010] First, alkali lignin and tetraethyl orthosilicate are mixed and then subjected to hydrothermal reaction, and then the microspheres are obtained by freeze-drying, and then the microspheres are impregnated with a polydopamine coating to improve the interfacial compatibility to obtain lignin-silica hybrid aerogel microspheres;

[0011] S3. Prepare the Schiff base dynamic covalent bond crosslinking agent;

[0012] React vanillin with hexamethylenediamine in a molar ratio of 1:1 to synthesize a dynamic crosslinking agent containing a Schiff base structure;

[0013] S4. Construct a reversible crosslinking network;

[0014] Add the Schiff base dynamic covalent bond crosslinking agent to the modified silk fibroin for pre-reaction to obtain a pre-reaction product, so as to construct a reversible crosslinking network;

[0015] S5. Carry out the photo-thermal dual-treatment stage;

[0016] First, add chitin nanowhiskers, lignin-silica hybrid aerogel microspheres, poly(limonene), photocurable bio-based epoxy resin, nano-zinc oxide, and quercetin natural antioxidant to the pre-reaction product. After mixing evenly, add the photoinitiator TPO-L to obtain a polymer;

[0017] Second, coat the polymer and irradiate it with UVLED until the surface is dry;

[0018] Third, carry out gradient heating to obtain a primary product;

[0019] S6. Use supercritical CO 2 foaming technology to generate a microporous structure to achieve the purpose of reducing internal stress;

[0020] S7. Spray a fluorinated lecithin coating on the surface of the product with a microporous structure to achieve hydrophobic self-cleaning, so as to obtain an adhesive glue layer.

[0021] Preferably, the method for preparing the modified silk fibroin in step S1 is as follows:

[0022] First, degum the silkworm cocoons and dissolve them in 9.3M LiBr solution, and dialyze and purify to obtain a regenerated silk fibroin solution;

[0023] Among them, when the degummed silkworm cocoons are dissolved in 9.3M LiBr solution, it lasts for 4h at a temperature of 60°C;

[0024] Third, add transglutaminase and crosslink at a temperature of 50°C for 2h to form a modified silk fibroin with a β-sheet crystal structure, improving the temperature resistance of the finished adhesive.

[0025] Preferably, the method for preparing the chitin nanowhiskers in step S1 is as follows:

[0026] First, sequentially demineralize the shrimp and crab shells with 5% HCl and deproteinize them with 5% NaOH solution;

[0027] Secondly, the demineralized and deproteinized shrimp and crab shells are broken into particles with a particle size of less than 30 nm by high-pressure homogenization;

[0028] Thirdly, 3-aminopropyltriethoxysilane is grafted onto the surface of the shrimp and crab shell particles to obtain chitin nanowhiskers, which can enhance the interfacial bonding with silk fibroin.

[0029] Preferably, when preparing the lignin-silica hybrid aerogel microspheres in step S2, alkali lignin and tetraethyl orthosilicate are mixed at a molar ratio of 1:2, the hydrothermal reaction temperature is 180 °C, and the hydrothermal reaction duration is 8 h.

[0030] Preferably, in step S4, the pre-reaction temperature between the Schiff base dynamic covalent crosslinking agent and the modified silk fibroin is 45 °C and the pre-reaction time is 1 h.

[0031] Preferably, in step S5, the UV main peak wavelength of the UV LED is 365 nm and the power density is 500 mW / cm 2 , and the irradiation time is 20 s.

[0032] Preferably, in the first stage of the gradient heating process in step S5, the temperature is 80 °C and the duration is 30 min; in the second stage, the temperature is 120 °C and the duration is 20 min; in the third stage, the temperature is 150 °C and the duration is 10 min.

[0033] Preferably, in step S6, the temperature for mixing supercritical CO 2 with the initial product is 35 °C and the pressure is 10 MPa.

[0034] Preferably, in step S5 during irradiation, the thickness of the polymer coating is 150 - 200 μm.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. A high-temperature resistant and high-viscosity adhesive involved in the present invention adopts the modified silk fibroin β-sheet crystal + dynamic Schiff base bond mode to construct a high-temperature resistant structure of "rigid skeleton + flexible buffer", greatly enhancing the high-temperature resistance of the adhesive.

[0037] 2. A high-temperature resistant and high-viscosity adhesive involved in the present invention adopts a nano-hierarchical structure, greatly improving the bonding strength.

[0038] 3. A high-temperature resistant and high-viscosity adhesive involved in the present invention is more environmentally friendly through the deep cross of biomacromolecule engineering and nanocomposite technology, avoiding harm to the health of users; in addition, the waste adhesive layer can be degraded in an alkaline solution, which can not only recycle silk fibroin to avoid waste of resources, but also avoid environmental pollution problems. Detailed implementation mode

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment: A high-temperature-resistant and high-viscosity adhesive is prepared from the following raw materials by mass percentage: 36-38% of modified silk fibroin, 9-11% of chitin nanocrystals, 17-21% of poly(limonene); 6-9% of lignin-silica hybrid aerogel microspheres, 2-4% of Schiff base dynamic covalent crosslinking agent, 9-14% of photocurable bio-based epoxy resin, 2-4% of nanozinc oxide, 0.4-0.8% of quercetin natural antioxidant, 0.6-1.8% of photoinitiator TPO-L, 0.08-0.12% of fluorinated lecithin, and 12-18% of deionized water.

[0041] The preparation method of the adhesive includes the following steps:

[0042] S1. Pretreatment of bio-based raw materials;

[0043] It includes preparing silk fibroin from silkworm cocoons and preparing chitin nanocrystals from shrimp and crab shells;

[0044] Among them, the method for preparing modified silk fibroin is as follows:

[0045] First, the degummed silkworm cocoons are dissolved in 9.3M LiBr solution, and dialysis purification is carried out to obtain a regenerated silk fibroin solution;

[0046] Among them, when the degummed silkworm cocoons are dissolved in 9.3M LiBr solution, it lasts for 4h at a temperature of 60°C;

[0047] Secondly, transglutaminase is added and crosslinked at a temperature of 50°C for 2h to form modified silk fibroin with a β-sheet crystal structure.

[0048] The method for preparing chitin nanocrystals is as follows:

[0049] First, the shrimp and crab shells are sequentially demineralized with 5% HCl and deproteinized with 5% NaOH solution;

[0050] Secondly, the demineralized and deproteinized shrimp and crab shells are broken by high-pressure homogenization to particles with a particle size less than 30nm;

[0051] Thirdly, 3-aminopropyltriethoxysilane is grafted on the surface of the shrimp and crab shell particles to obtain chitin nanocrystals.

[0052] S2. Prepare lignin-silica hybrid aerogel microspheres;

[0053] First, mix alkali lignin and tetraethyl orthosilicate and then carry out hydrothermal reaction. After that, obtain microspheres by freeze-drying, and then impregnate the microspheres with a polydopamine coating to obtain lignin-silica hybrid aerogel microspheres;

[0054] Among them, when preparing lignin-silica hybrid aerogel microspheres, alkali lignin and tetraethyl orthosilicate are mixed at a molar ratio of 1:2, the temperature of the hydrothermal reaction is 180 °C, and the duration of the hydrothermal reaction is 8 h.

[0055] S3. Prepare Schiff base dynamic covalent crosslinking agent;

[0056] React vanillin and hexamethylenediamine at a molar ratio of 1:1 to synthesize a dynamic crosslinking agent containing a Schiff base structure.

[0057] S4. Construct a reversible crosslinking network;

[0058] Add the Schiff base dynamic covalent crosslinking agent to the modified silk fibroin for pre-reaction to obtain a pre-reaction product, so as to construct a reversible crosslinking network;

[0059] Among them, the temperature of the pre-reaction between the Schiff base dynamic covalent crosslinking agent and the modified silk fibroin is 45 °C and the pre-reaction time is 1 h.

[0060] S5. Carry out the photo-thermal dual-treatment stage;

[0061] First, add chitin nanowhiskers, lignin-silica hybrid aerogel microspheres, limonene, photocurable bio-based epoxy resin, nano-zinc oxide and quercetin natural antioxidant to the pre-reaction product. After mixing evenly, add the photoinitiator TPO-L to obtain a polymer;

[0062] Secondly, coat the polymer and irradiate it with UVLED until the surface is dry;

[0063] Among them, the UV main peak wavelength of the UVLED is 365 nm and the power density is 500 mW / cm 2 , and the irradiation time is 20 s; during irradiation, the coating thickness of the polymer is 150 - 200 μm.

[0064] Thirdly, carry out gradient heating to obtain a primary product;

[0065] Among them, the temperature of the first stage of the gradient heating process is 80 °C and the duration is 30 min; the temperature of the second stage is 120 °C and the duration is 20 min; the temperature of the third stage is 150 °C and the duration is 10 min.

[0066] S6. Use supercritical CO 2 foaming technology to generate a microporous structure for the initial product;

[0067] Among them, the temperature of the supercritical CO 2 mixed with the initial product is 35°C and the pressure is 10 MPa.

[0068] S7. Spray a coating of fluorinated lecithin on the surface of the product with the microporous structure to obtain the adhesive glue layer.

[0069] Test Example 1: Based on the preparation method of the embodiment, the raw materials are selected by mass percentage as follows: modified silk fibroin 36%, chitin nanowhiskers 9%, poly(limonene) 17%; lignin-silica hybrid aerogel microspheres 6%, Schiff base dynamic covalent crosslinking agent 2%, photocurable bio-based epoxy resin 9%, nanozinc oxide 2%, quercetin natural antioxidant 0.4%, photoinitiator TPO-L 0.6%, fluorinated lecithin 0.08%, deionized water 17.92%.

[0070] Test Example 2: Based on the preparation method of the embodiment, the raw materials are selected by mass percentage as follows: modified silk fibroin 37%, chitin nanowhiskers 10%, poly(limonene) 17%; lignin-silica hybrid aerogel microspheres 7%, Schiff base dynamic covalent crosslinking agent 2%, photocurable bio-based epoxy resin 10%, nanozinc oxide 2%, quercetin natural antioxidant 0.5%, photoinitiator TPO-L 0.9%, fluorinated lecithin 0.1%, deionized water 13.5%.

[0071] Perform performance tests on the adhesives prepared from the two components in Test Example 1 and Test Example 2. The test items include heat resistance, shear strength, peel strength, resistance to damp heat aging, and VOCs content. The test results are shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] The above is only the implementation mode of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A heat-resistant high-viscosity adhesive, characterized in that: According to mass percentage, it is prepared from the following raw materials: Modified silk protein 36-38%, chitin nano whiskers 9-11%, polylimonene 17-21%, lignin-silica hybrid aerogel microspheres 6-9%, Schiff base dynamic covalent bond crosslinker 2-4%, photocurable bio-based epoxy resin 9-14%, nano zinc oxide 2-4%, quercetin natural antioxidant 0.4-0.8%, photoinitiator TPO-L 0.6-1.8%, fluorinated lecithin 0.08-0.12%, and deionized water 12-18%.

2. A heat-resistant high-viscosity adhesive according to claim 1, characterized in that: The preparation method of the adhesive comprises the following steps: S1, bio-based raw material pretreatment; Including using silk cocoons to prepare silk fibroin and using shrimp and crab shells to prepare chitin nano whiskers; S2, preparing lignin-silica hybrid aerogel microspheres; Firstly, alkali lignin and tetraethyl orthosilicate are mixed and then subjected to hydrothermal reaction, and then freeze-dried to obtain microspheres, and then the microspheres are impregnated with a polydopamine coating to obtain lignin-silica hybrid aerogel microspheres; S3, preparing a Schiff base dynamic covalent bond cross-linking agent; Vanillin and hexamethylenediamine were reacted in a 1:1 molar ratio to synthesize a dynamic cross-linking agent containing a Schiff base structure; S4, constructing a reversible cross-linking network; The Schiff base dynamic covalent bond cross-linking agent is added into the modified silk fibroin for pre-reaction to obtain a pre-reaction product, so as to construct a reversible cross-linking network; S5, performing light-heat dual treatment stage; Firstly, chitosan nano whiskers, lignin-silica hybrid aerogel microspheres, polylimonene, light-cured bio-based epoxy resin, nano zinc oxide and quercetin natural antioxidant are added to the pre-reaction product, mixed evenly, and then a photoinitiator TPO-L is added to obtain a polymer; Secondly, the polymer is coated and then irradiated with UVLED until the surface is dry; Again, the temperature is increased in a gradient manner to obtain the initial product; S6, using supercritical CO2 foaming technology to generate a microporous structure on the primary product; S7. Spray a fluorinated lecithin coating on the surface of the product having the microporous structure to obtain an adhesive layer.

3. A heat-resistant high-viscosity adhesive according to claim 2, characterized in that: The method for preparing the modified silk fibroin in step S1 is: First, the silkworm cocoons were degummed and dissolved in 9.3M LiBr solution, and then dialyzed and purified to obtain the regenerated silk fibroin solution; Among them, the degummed silkworm cocoons were dissolved in 9.3 M LiBr solution at 60 °C for 4 h; Again, glutamine aminotransferase was added and cross-linked at 50°C for 2 hours to form a modified silk fibroin with a β-pleated crystal structure.

4. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: The method for preparing chitosan nano whiskers in step S1 is: First, shrimp and crab shells were decalcified with 5% HCl and deproteinized with 5% NaOH solution; Secondly, the decalcified and deproteinized shrimp and crab shells are crushed into particles with a size of less than 30 nm by high-pressure homogenization; Thirdly, 3-aminopropyltriethoxysilane was grafted onto the surface of shrimp and crab shell particles to obtain chitosan nanowhiskers.

5. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: When preparing the lignin-silica hybrid aerogel microspheres in step S2, alkali lignin and tetraethyl orthosilicate are mixed in a molar ratio of 1:2, the temperature of the hydrothermal reaction is 180° C., and the duration of the hydrothermal reaction is 8 hours.

6. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: In the step S4, the temperature for the pre-reaction between the Schiff base dynamic covalent bond cross-linking agent and the modified silk fibroin is 45° C. and the pre-reaction time is 1 hour.

7. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: In step S5, the UV main peak wavelength of the UVLED is 365nm and the power density is 500mW / cm 2 , the irradiation time is 20s.

8. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: In the step S5, the temperature of the first stage of the gradient heating process is 80° C. and lasts for 30 minutes; the temperature of the second stage is 120° C. and lasts for 20 minutes; the temperature of the third stage is 150° C. and lasts for 10 minutes.

9. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: In step S6, the temperature of the mixture of supercritical CO2 and the primary product is 35°C and the pressure is 10 MPa.

10. The heat-resistant high-viscosity adhesive according to claim 2, characterized in that: During the irradiation in step S5, the thickness of the polymer coating is 150-200 μm.

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