Natural resin adhesive, production method and application in paper-plastic composite packaging

Abstract

The application discloses a natural resin adhesive, a production method and application in paper-plastic composite packaging, and belongs to the technical field of adhesives. Raw materials mainly include bio-based rosin resin and amber resin, and are supplemented by polyimide resin containing antioxidant modified polysilsesquioxane, meet the requirements of green environmental protection, and have excellent ultraviolet shielding function. In paper-plastic composite packaging, the adhesive can meet the requirements of long-time bonding without aging. The structure contains the rigid structure of polysilsesquioxane and titanium-based MOF, can improve the overall strength of the adhesive, avoid cracking and peeling, and the porosity of polysilsesquioxane and titanium-based MOF can improve the heat dissipation capacity of the adhesive.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically a natural resin adhesive, its production method, and its application in paper-plastic composite packaging. Background Technology

[0002] Paper-plastic composite packaging materials, combining the printability and biodegradability of paper with the moisture-proof and wear-resistant properties of plastic, are widely used in food packaging, book lamination, building materials, and decoration. Currently, mainstream adhesives include solvent-based adhesives, which contain toxic solvents such as toluene and ethyl acetate, releasing volatile organic compounds during production and use, harming operator health and polluting the environment, and easily causing wrinkling and delamination of composite products; water-emulsion synthetic adhesives, while avoiding solvent toxicity, suffer from poor water resistance and aging problems, yellowing and becoming brittle after long-term storage due to insufficient antioxidant groups and UV degradation; and natural-based adhesives, although environmentally friendly and non-toxic, contain hydrophilic groups in their natural polymers, resulting in weak water resistance, swelling and cracking of the adhesive layer in humid and hot environments, and insufficient strength. These methods cannot meet the impact resistance requirements of high-speed packaging lines.

[0003] Although existing technologies attempt to improve performance through modification, they have failed to simultaneously meet the requirements of environmental protection and high strength. With the advancement of global plastic bans, the development of fully bio-based, high-performance natural resin adhesives has become an urgent need for the industry. Summary of the Invention

[0004] The purpose of this invention is to provide a natural resin adhesive, a production method, and its application in paper-plastic composite packaging. The raw materials are mainly bio-based rosin resin and amber resin, supplemented by polyimide resin containing antioxidant-modified polysilsesquioxane, which meets the requirements of green environmental protection and has excellent ultraviolet shielding function. In paper-plastic composite packaging, it can meet the requirement of long-term bonding without aging. Its structure contains a rigid structure of polysilsesquioxane and titanium-based MOF, which can improve the overall strength of the adhesive and prevent cracking and peeling. Furthermore, the porosity of polysilsesquioxane and titanium-based MOF can improve the heat dissipation capacity of the adhesive.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for producing a natural resin adhesive includes the following steps:

[0007] Step 1: Vinyl polysilsesquioxane is obtained by hydrolysis and condensation of vinyltriethoxysilane. Modified polysilsesquioxane is obtained by copolymerization of vinyl groups in 3,3'-(ethylene-1,2-diyl)benzoyl chloride, vinyl polysilsesquioxane, and vinyl groups on the surface of N-methyldiethanolamine dimethacrylate quaternary ammonium salt.

[0008] Step 2: Antioxidant modified polysilsesquioxane is obtained by bonding the acyl chloride groups on the surface of the modified polysilsesquioxane with the hydroxyl groups of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole.

[0009] Step 3: Coating nano-alumina with a titanium-based MOF using 2,5-diaminoterephthalic acid as a monomer to obtain amino-coated nano-alumina. Using 4,4'-oxobisphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene and 3,5-diaminobenzoic acid as raw materials, N-methyl-2-pyrrolidone as solvent, and amino-coated nano-alumina as a crosslinking agent, a modified polyamic acid emulsion is obtained.

[0010] Step 4: Mix the modified polyamic acid emulsion, rosin resin, amber resin, and imidizing agents acetic anhydride and pyridine evenly and cure to obtain a natural resin adhesive.

[0011] Furthermore, the specific preparation method of vinyl polysilsesquioxane is as follows:

[0012] Vinyltriethoxysilane and acetone were added to a reaction vessel and stirred for 20-30 min at 40-50 °C and 400-500 r / min. Then, a 1 mol / L glacial acetic acid solution was added as a catalyst, and the reaction was continued for 70-72 h. The product was recrystallized in a mixed solution of acetone and deionized water (volume ratio 1:1), filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product was then dried under vacuum at 60-70 °C for 1 h to obtain vinyl polysilsesquioxane.

[0013] Furthermore, the ratio of vinyltriethoxysilane, acetone, and glacial acetic acid solution is 150-160g: 800-900mL: 1-2mL.

[0014] Furthermore, the specific preparation method of modified polysilsesquioxane is as follows:

[0015] Deionized water, 3,3'-(ethylene-1,2-diyl)benzoyl chloride, and N-methyldiethanolamine dimethacrylate quaternary ammonium salt were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then, vinyl polysilsesquioxane and ammonium persulfate were added, and the mixture was heated to 70-80℃. Under a nitrogen atmosphere, the mixture was stirred and reacted for 6-7 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and deionized water, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 h to obtain modified polysilsesquioxane.

[0016] Furthermore, the ratio of deionized water, 3,3'-(ethylene-1,2-diyl)benzoyl chloride, N-methyldiethanolamine dimethacrylate quaternary ammonium salt, vinyl polysilsesquioxane, and ammonium persulfate is 800-900mL: 100-120g: 40-50g: 80-100g: 12-14g.

[0017] Furthermore, the specific preparation method of antioxidant modified polysilsesquioxane is as follows:

[0018] 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, toluene, and modified polysilsesquioxane were added to a reaction vessel and stirred at 90-100℃ and 500-600 r / min for 6-7 h. After natural cooling, the mixture was filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 h to obtain antioxidant modified polysilsesquioxane.

[0019] Furthermore, the ratio of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, toluene, and modified polysilsesquioxane is 100-120g:100-120mL:12-14mL.

[0020] Furthermore, the specific preparation method of amino-coated nano-alumina is as follows:

[0021] Nano-alumina, 2,5-diaminoterephthalic acid, and N,N-dimethylformamide were added to a polytetrafluoroethylene-lined reactor and stirred for 20-30 min at 20-25℃ and 50-6000 r / min. Then, the mixture was heated to 80-90℃, triethylamine was added, and stirring was continued for 1-2 h. Titanium tetrachloride was then added, and the mixture was heated to 120-130℃ and stirred for 24-26 h. The mixture was then allowed to cool naturally to room temperature, centrifuged at 10000-12000 r / min for 5-7 min, filtered, and the filter cake was washed 2-4 times with N,N-dimethylformamide and methanol, respectively. The cake was then vacuum dried at 60-70℃ for 1-2 h to obtain amino-coated nano-alumina.

[0022] Furthermore, the ratio of nano-alumina, 2,5-diaminoterephthalic acid, N,N-dimethylformamide, triethylamine, and titanium tetrachloride is 140-150g: 150-170g: 2-3L: 4-6mL: 80-90g.

[0023] Furthermore, the specific preparation method of natural resin adhesive is as follows:

[0024] Modified polyamic acid emulsion, rosin resin, and amber resin are added to a reaction vessel and stirred for 20-30 minutes at 20-25℃ and 500-600 r / min. Then, acetic anhydride and pyridine are added and stirring is continued for 15-16 hours. Next, antioxidant modified polysilsesquioxane is added and stirring is continued for 10-12 hours. The product is transferred to a mold and evaporated at 50-60℃ for 12-14 hours. Then, it is cured at 100-110℃ for 2-4 hours and then cured again at 150-160℃ for 2-3 hours to obtain a natural resin adhesive.

[0025] Furthermore, the ratio of modified polyamic acid emulsion, rosin resin, amber resin, acetic anhydride, pyridine, and antioxidant modified polysilsesquioxane is 40-50 mL: 120-140 g: 200-240 g: 20-25 g: 15-20 g: 80-90 g.

[0026] Furthermore, the specific preparation method of the modified polyamic acid emulsion is as follows:

[0027] 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 0-4℃ and 500-600 r / min under nitrogen protection. Then, amino-coated nano-alumina was added, and stirring was continued for 1-2 h. The mixture was then heated to 20-25℃ and stirred for 4-5 h. Unreacted monomers were removed by rotary evaporation to obtain a modified polyamic acid emulsion.

[0028] Furthermore, the ratio of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, N-methyl-2-pyrrolidone and amino-coated nano-alumina is 130-140g: 120-130g: 50-60g: 800-900mL: 40-60g.

[0029] This invention also provides an application of natural resin adhesives in paper-plastic composite packaging.

[0030] The beneficial effects of this invention are:

[0031] 1. The natural resin adhesive prepared by this invention, when applied in paper-plastic composite packaging, possesses excellent mechanical properties, heat resistance, bonding strength, and aging resistance.

[0032] 2. The natural resin adhesive prepared in this invention is obtained by synthesizing vinyl polysilsesquioxane containing vinyl groups and copolymerizing it with 3,3'-(ethylene-1,2-diyl)dibenzoyl chloride monomer containing double bonds to obtain modified polysilsesquioxane containing acyl chloride groups. By using the acyl chloride groups to bond with 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, an antioxidant modified polysilsesquioxane is obtained. Benzotriazole oxidants will volatilize and migrate during the use of polymer materials, resulting in a decrease in their concentration and thus affecting the ultraviolet absorption performance. On the one hand, grafting onto the surface of polysilsesquioxane can increase the fixation effect of benzotriazole, avoiding the volatilization and migration caused by traditional direct addition. Moreover, the anti-ultraviolet effect of benzotriazole is not completely reversible, and the antioxidant effect will decay. The introduced titanium-based MOF utilizes the amino groups in the titanium-based MOF to participate in the crosslinking of polyimide. In addition, the titanium in the titanium-based MOF can make up for the lack of anti-ultraviolet effect of benzotriazole. The two work synergistically.

[0033] 3. The natural resin adhesive prepared by this invention uses bio-based rosin resin and amber resin as the main raw materials, and polyimide resin containing antioxidant modified polysilsesquioxane as the auxiliary material. It completely avoids the VOCs release problems such as toluene and ethyl acetate in traditional solvent-based adhesives, meets the requirements of green environmental protection, and has excellent ultraviolet shielding function. In paper-plastic composite packaging, it can meet the requirements of long-term bonding without aging. Its structure contains the rigid structure of polysilsesquioxane and titanium-based MOF, which can improve the overall strength of the adhesive and prevent cracking and peeling. Furthermore, the porosity of polysilsesquioxane and titanium-based MOF can improve the heat dissipation capacity of the adhesive. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: A method for producing a natural resin adhesive, comprising the following steps:

[0036] S1: Add 150g of vinyltriethoxysilane and 800mL of acetone to a reaction vessel, stir for 20min at 40℃ and 400r / min, then add 1mL of 1mol / L glacial acetic acid solution as a catalyst, and continue the reaction for 70h. Recrystallize the product in a mixed solution of acetone and deionized water (volume ratio 1:1), filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry it under vacuum at 60℃ for 1h to obtain vinyl polysilsesquioxane.

[0037] S2: Add 800 mL of deionized water, 100 g of 3,3'-(ethylene-1,2-diyl)benzoyl chloride and 40 g of N-methyldiethanolamine dimethacrylate quaternary ammonium salt to a reaction vessel, stir for 20 min at 20 °C and 500 r / min, then add 80 g of vinyl polysilsesquioxane and 12 g of ammonium persulfate, heat to 70 °C, and continue stirring for 6 h under a nitrogen atmosphere. Filter, wash the filter cake twice with deionized water and deionized water respectively, and dry under vacuum at 60 °C for 1 h to obtain modified polysilsesquioxane.

[0038] S3: Add 100g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 100mL of toluene and 12mL of modified polysilsesquioxane to a reaction vessel, stir for 6h at 90℃ and 500r / min, cool naturally, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry under vacuum at 60℃ for 1h to obtain antioxidant modified polysilsesquioxane.

[0039] S4: 140g of nano-alumina, 150g of 2,5-diaminoterephthalic acid and 2L of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined reactor. The mixture was stirred at 20℃ and 50r / min for 20min, then heated to 80℃, 4mL of triethylamine was added, and stirring was continued for 1h. Then 80g of titanium tetrachloride was added, and the mixture was heated to 120℃ and stirred for 24h. The mixture was allowed to cool naturally to room temperature, centrifuged at 10000r / min for 5min, filtered, and the filter cake was washed twice with N,N-dimethylformamide and methanol, respectively. The mixture was then vacuum dried at 60℃ for 1h to obtain amino-coated nano-alumina.

[0040] S5: 130g of 4,4'-oxophthalic anhydride, 120g of 1,3-bis(4'-aminophenoxy)benzene, 50g of 3,5-diaminobenzoic acid and 800mL of N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20min at 0℃ and 500r / min under nitrogen protection. Then 40g of amino-coated nano-alumina was added and stirring was continued for 1h. The mixture was then heated to 20℃ and stirred for 4h. Unreacted monomers were removed by rotary evaporation to obtain a modified polyamic acid emulsion.

[0041] S6: Add 40 mL of modified polyamic acid emulsion, 120 g of rosin resin, and 200 g of amber resin to a reaction vessel and stir for 20 min at 20 °C and 500 r / min. Then add 20 g of acetic anhydride and 15 g of pyridine to the reaction vessel and continue stirring for 15 h. Then add 80 g of antioxidant modified polysilsesquioxane and continue stirring for 10 h. Transfer the product to a mold, evaporate at 50 °C for 12 h, then cure at 100 °C for 2 h, and then cure again at 150 °C for 2 h to obtain a natural resin adhesive.

[0042] Example 2: A method for producing a natural resin adhesive, comprising the following steps:

[0043] S1: Add 155g of vinyltriethoxysilane and 850mL of acetone to a reaction vessel and stir for 25min at 45℃ and 450r / min. Then add 1.5mL of 1mol / L glacial acetic acid solution as a catalyst and continue the reaction for 71h. Recrystallize the product in a mixed solution of acetone and deionized water (volume ratio 1:1), filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and dry it under vacuum at 65℃ for 1h to obtain vinyl polysilsesquioxane.

[0044] S2: Add 850 mL of deionized water, 110 g of 3,3'-(ethylene-1,2-diyl)benzoyl chloride and 45 g of N-methyldiethanolamine dimethacrylate quaternary ammonium salt to a reaction vessel, stir for 25 min at 22.5 °C and 550 r / min, then add 90 g of vinyl polysilsesquioxane and 13 g of ammonium persulfate, heat to 75 °C, and continue stirring for 6.5 h under a nitrogen atmosphere. Filter, wash the filter cake three times with deionized water and three times with deionized water, and dry under vacuum at 65 °C for 1.5 h to obtain modified polysilsesquioxane.

[0045] S3: Add 110g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 110mL of toluene and 13mL of modified polysilsesquioxane to a reaction vessel, stir at 95℃ and 550r / min for 6.5h, cool naturally, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 65℃ for 1.5h to obtain antioxidant modified polysilsesquioxane.

[0046] S4: 145g of nano-alumina, 160g of 2,5-diaminoterephthalic acid, and 2.5L of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined reactor. The mixture was stirred for 25 min at 22.5℃ and 3025r / min, then heated to 85℃, and 5mL of triethylamine was added. The mixture was stirred for another 1.5 h, then 85g of titanium tetrachloride was added, and the mixture was heated to 125℃. The mixture was stirred for another 25 h, then allowed to cool naturally to room temperature. The mixture was centrifuged at 11000r / min for 6 min, filtered, and the filter cake was washed three times each with N,N-dimethylformamide and methanol. The cake was then vacuum dried at 65℃ for 1.5 h to obtain amino-coated nano-alumina.

[0047] S5: 135g of 4,4'-oxophthalic anhydride, 125g of 1,3-bis(4'-aminophenoxy)benzene, 55g of 3,5-diaminobenzoic acid, and 850mL of N-methyl-2-pyrrolidone were added to a reaction vessel. Under nitrogen protection, the mixture was stirred at 2℃ and 550r / min for 25min. Then, 50g of amino-coated nano-alumina was added, and stirring was continued for 1.5h. The mixture was then heated to 22.5℃ and stirred for 4.5h. Unreacted monomers were removed by rotary evaporation to obtain the modified polyamic acid emulsion.

[0048] S6: Add 450 mL of modified polyamic acid emulsion, 130 g of rosin resin, and 230 g of amber resin to a reaction vessel and stir for 25 min at 23 °C and 550 r / min. Then add 22.5 g of acetic anhydride and 17.5 g of pyridine to the reaction vessel and continue stirring for 15.5 h. Then add 85 g of antioxidant modified polysilsesquioxane and continue stirring for 11 h. Transfer the product to a mold and evaporate at 55 °C for 13 h, then cure at 105 °C for 3 h, and then cure at 155 °C for 2.5 h to obtain a natural resin adhesive.

[0049] Example 3: A method for producing a natural resin adhesive, comprising the following steps:

[0050] S1: Add 160g of vinyltriethoxysilane and 900mL of acetone to a reaction vessel, stir for 30min at 50℃ and 500r / min, then add 2mL of 1mol / L glacial acetic acid solution as a catalyst, and continue the reaction for 72h. Recrystallize the product in a mixed solution of acetone and deionized water (volume ratio 1:1), filter, wash the filter cake four times with deionized water and anhydrous ethanol respectively, and dry it under vacuum at 70℃ for 1h to obtain vinyl polysilsesquioxane.

[0051] S2: Add 900 mL of deionized water, 120 g of 3,3'-(ethylene-1,2-diyl)benzoyl chloride and 50 g of N-methyldiethanolamine dimethacrylate quaternary ammonium salt to a reaction vessel, stir for 30 min at 25 °C and 600 r / min, then add 100 g of vinyl polysilsesquioxane and 14 g of ammonium persulfate, heat to 80 °C, and continue stirring for 7 h under a nitrogen atmosphere. Filter, wash the filter cake four times with deionized water and deionized water respectively, and dry under vacuum at 70 °C for 2 h to obtain modified polysilsesquioxane.

[0052] S3: Add 120g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 120mL of toluene and 14mL of modified polysilsesquioxane to a reaction vessel, stir for 7h at 100℃ and 600r / min, cool naturally, filter, wash the filter cake 4 times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 70℃ for 2h to obtain antioxidant modified polysilsesquioxane.

[0053] S4: 150g of nano-alumina, 170g of 2,5-diaminoterephthalic acid and 3L of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined reactor. The mixture was stirred at 25℃ and 6000r / min for 30min, then heated to 90℃, 6mL of triethylamine was added, and stirring was continued for 2h. Then 90g of titanium tetrachloride was added, and the mixture was heated to 130℃ and stirred for 26h. The mixture was allowed to cool naturally to room temperature, centrifuged at 12000r / min for 7min, filtered, and the filter cake was washed 4 times with N,N-dimethylformamide and methanol, respectively. The mixture was then vacuum dried at 70℃ for 2h to obtain amino-coated nano-alumina.

[0054] S5: 140g of 4,4'-oxophthalic anhydride, 130g of 1,3-bis(4'-aminophenoxy)benzene, 60g of 3,5-diaminobenzoic acid and 900mL of N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 30min at 4℃ and 600r / min under nitrogen protection. Then 60g of amino-coated nano-alumina was added and stirring was continued for 2h. The mixture was then heated to 25℃ and stirred for 5h. Unreacted monomers were removed by rotary evaporation to obtain a modified polyamic acid emulsion.

[0055] S6: Add 50 mL of modified polyamic acid emulsion, 140 g of rosin resin, and 240 g of amber resin to a reaction vessel and stir for 30 min at 25 °C and 600 r / min. Then add 25 g of acetic anhydride and 20 g of pyridine to the reaction vessel and continue stirring for 16 h. Then add 90 g of antioxidant modified polysilsesquioxane and continue stirring for 12 h. Transfer the product to a mold and evaporate at 60 °C for 14 h. Then cure at 110 °C for 4 h and then cure at 160 °C for another 3 h to obtain a natural resin adhesive.

[0056] Comparative Example 1: Based on Example 3, the modified polysilsesquioxane in step S3 was replaced with the vinyl polysilsesquioxane in step S2.

[0057] Comparative Example 2: Based on Example 3, the antioxidant modified polysilsesquioxane in step S6 was replaced with the modified polysilsesquioxane in step S2.

[0058] Comparative Example 3: Based on Example 3, the amino-coated nano-alumina in step S5 was replaced with nano-alumina.

[0059] The performance of the natural resin adhesives prepared in Examples 1-3 and Comparative Examples 1-3 was tested. First, the natural resin adhesive was uniformly coated on the surface of PET and CPP films, and the coating amount of solid components was adjusted to 4 g / m. 2 Subsequently, PET and CPP films coated with natural resin adhesive were dried at 80°C for 10 minutes to obtain adhesive-coated PET and CPP films. Then, the dark side of aluminum foil was placed over the surface of the adhesive-coated PET film, and the bright side of aluminum foil was placed over the surface of the adhesive-coated CPP film. The two films were then pressed together for 30 minutes at 50°C and a closing pressure of 1.0 MPa using a flat press device. The pressed film was then aged at 50°C for 3 days to obtain the final paper-plastic composite packaging sample. Samples prepared with different natural resin adhesives were cut into 15 mm wide samples and placed in an oven at 60°C for aging treatment for 48 hours. A blank group was also set up. In the blank group, 140 g of rosin resin and 240 g of amber resin were stirred and mixed, heated to 80°C and stirred until melted. After being mixed evenly, the mixture was transferred to a clean mold for curing to obtain the natural resin adhesive.

[0060] The results are shown in Table 1:

[0061]

[0062] As can be seen from Table 1, the tensile shear strength, impact strength, heat resistance and bonding strength of the natural resin adhesives prepared in Examples 1-3 are significantly better than those of the comparative examples, indicating that the natural resin adhesives prepared in this invention have excellent mechanical properties, heat resistance, bonding strength and aging resistance when applied in paper-plastic composite packaging.

[0063] In Comparative Example 1, the modified polysilsesquioxane was replaced with vinyl polysilsesquioxane. The absence of acyl chloride groups and quaternary ammonium salt cationic structures resulted in the material lacking reactive sites and hydrophilic-hydrophobic adjustment capabilities. Acyl chloride groups are key sites for subsequent bonding with benzotriazole antioxidants. Their absence prevents the antioxidants from being effectively grafted, weakening the anti-aging ability. The absence of quaternary ammonium salt groups reduces compatibility with polar resins (such as rosin and amber resins), making phase separation more likely. The uniformity of the adhesive deteriorates, and the synergistic reinforcing effect of the inorganic Si-O-Si skeleton and organic groups in the copolymer is weakened.

[0064] In Comparative Example 2, the antioxidant modified polysilsesquioxane was replaced with modified polysilsesquioxane. The benzotriazole UV-absorbing groups were not attached, resulting in the loss of molecular-level immobilized UV-resistant function. The introduction of titanium-based MOF could not form a synergistic anti-aging mechanism with benzotriazole. The unfixed benzotriazole volatilized or migrated to the interface during the curing process.

[0065] In Comparative Example 3, the amino-coated nano-alumina was replaced with nano-alumina. The nano-alumina surface was not modified with amino, and it lost its chemical bonding ability with the polyimide precursor. It did not form a titanium-based MOF porous structure, and the specific surface area was reduced. The unmodified nano-alumina was severely agglomerated in the polyimide emulsion, becoming a stress concentration point, which reduced the tensile strength. The lack of MOF pore structure led to a weakening of heat dissipation capacity. The amino coating layer could originally participate in the curing and crosslinking of polyimide, but its absence reduced the crosslinking density.

[0066] The blank group used rosin resin and amber resin directly as natural resin adhesives. As shown in Table 1, all the performance test data were lower than those of Examples 1-3 and Comparative Examples 1-3, indicating that the natural resin adhesive prepared by the present invention is superior to the traditional single-component natural resin adhesive.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for producing a natural resin adhesive, characterized in that, Includes the following steps: Step 1: Vinyl polysilsesquioxane is obtained by hydrolysis and polycondensation of vinyltriethoxysilane, and then modified polysilsesquioxane is obtained by copolymerization of vinyl groups in 3,3'-(ethylene-1,2-diyl)benzoyl chloride, vinyl polysilsesquioxane, and vinyl groups on the surface of N-methyldiethanolamine dimethacrylate quaternary ammonium salt. Step 2: Antioxidant modified polysilsesquioxane is obtained by bonding the acyl chloride groups on the surface of the modified polysilsesquioxane with the hydroxyl groups of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole. Step 3: Coating nano-alumina with a titanium-based MOF using 2,5-diaminoterephthalic acid as a monomer to obtain amino-coated nano-alumina. Using 4,4'-oxobisphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene and 3,5-diaminobenzoic acid as raw materials, N-methyl-2-pyrrolidone as solvent, and amino-coated nano-alumina as a crosslinking agent, a modified polyamic acid emulsion is obtained. Step 4: Add the modified polyamic acid emulsion, rosin resin, and amber resin to the reactor and stir for 20-30 minutes at 20-25℃ and 50-6000 r / min. Then add acetic anhydride and pyridine and continue stirring for 15-16 hours. Next, add the antioxidant-modified polysilsesquioxane and continue stirring for 10-12 hours. Transfer the product to a mold and evaporate at 50-60℃ for 12-14 hours. Then cure at 100-110℃ for 2-4 hours and then cure again at 150-160℃ for 2-3 hours to obtain a natural resin adhesive.

2. The method for producing a natural resin adhesive according to claim 1, characterized in that, The specific preparation method of the vinyl polysilsesquioxane is as follows: Vinyltriethoxysilane and acetone were added to a reaction vessel and stirred at 40-50℃ and 400-500 r / min for 20-30 min. Then, a 1 mol / L glacial acetic acid solution was added and the reaction was continued for 70-72 h. The product was recrystallized in a mixed solution of acetone and deionized water (volume ratio 1:1), filtered, washed, and vacuum dried to obtain vinyl polysilsesquioxane.

3. The method for producing a natural resin adhesive according to claim 2, characterized in that, The ratio of vinyltriethoxysilane, acetone and glacial acetic acid solution is 150-160g: 800-900mL: 1-2mL.

4. The method for producing a natural resin adhesive according to claim 1, characterized in that, The specific preparation method of the modified polysilsesquioxane is as follows: Deionized water, 3,3'-(ethylene-1,2-diyl)benzoyl chloride and N-methyldiethanolamine dimethacrylate quaternary ammonium salt were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 20-30 min. Then, vinyl polysilsesquioxane and ammonium persulfate were added, and the mixture was heated to 70-80℃. Under a nitrogen atmosphere, the mixture was stirred and reacted for 6-7 h. The mixture was then filtered, washed, and vacuum dried to obtain modified polysilsesquioxane. The ratio of deionized water, 3,3'-(ethylene-1,2-diyl)benzoyl chloride, N-methyldiethanolamine dimethacrylate quaternary ammonium salt, vinyl polysilsesquioxane, and ammonium persulfate is 800-900mL: 100-120g: 40-50g: 80-100g: 12-14g.

5. The method for producing a natural resin adhesive according to claim 1, characterized in that, The specific preparation method of the antioxidant modified polysilsesquioxane is as follows: 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, toluene, and modified polysilsesquioxane were added to a reaction vessel and stirred at 90-100℃ and 500-600r / min for 6-7h. After natural cooling, the mixture was filtered, washed, and vacuum dried to obtain antioxidant modified polysilsesquioxane. The ratio of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, toluene, and modified polysilsesquioxane is 100-120g:100-120mL:12-14mL.

6. The method for producing a natural resin adhesive according to claim 1, characterized in that, The specific preparation method of the amino-coated nano-alumina is as follows: Nano-alumina, 2,5-diaminoterephthalic acid, and N,N-dimethylformamide were added to a polytetrafluoroethylene-lined reactor and stirred for 20-30 minutes at 20-25°C and 500-600 r / min. Then, the mixture was heated to 80-90°C, triethylamine was added, and stirring was continued for 1-2 hours. Titanium tetrachloride was then added, and the mixture was heated to 120-130°C and stirred for 24-26 hours. After natural cooling, the mixture was centrifuged at 10000-12000 r / min for 5-7 minutes, filtered, washed, and vacuum dried to obtain amino-coated nano-alumina. The ratio of nano-alumina, 2,5-diaminoterephthalic acid, N,N-dimethylformamide, triethylamine, and titanium tetrachloride is 140-150g: 150-170g: 2-3L: 4-6mL: 80-90g.

7. The method for producing a natural resin adhesive according to claim 1, characterized in that, The ratio of the modified polyamic acid emulsion, rosin resin, amber resin, acetic anhydride, pyridine, and antioxidant modified polysilsesquioxane is 40-50 mL: 120-140 g: 200-240 g: 20-25 g: 15-20 g: 80-90 g.

8. The method for producing a natural resin adhesive according to claim 1, characterized in that, The specific preparation method of the modified polyamic acid emulsion is as follows: 4,4'-O-diphthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid and N-methyl-2-pyrrolidone were added to a reaction vessel and stirred for 20-30 min at 0-4℃ and 500-600 r / min under nitrogen protection. Then, amino-coated nano-alumina was added and stirring was continued for 1-2 h. The mixture was then heated to 20-25℃ and stirred for 4-5 h. Unreacted monomers were removed by rotary evaporation to obtain a modified polyamic acid emulsion. The ratio of the amounts of 4,4'-oxophthalic anhydride, 1,3-bis(4'-aminophenoxy)benzene, 3,5-diaminobenzoic acid, N-methyl-2-pyrrolidone, and amino-coated nano-alumina is 130-140g: 120-130g: 50-60g: 800-900mL: 40-60g.

9. A natural resin adhesive, characterized in that, It is produced by the production method described in any one of claims 1-8.

10. The application of the natural resin adhesive of claim 9 in paper-plastic composite packaging.

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