Biodegradable hot melt adhesive based on castor oil and rosin resin and preparation process thereof

Abstract

The invention relates to the field of hot melt adhesives, and discloses a biodegradable hot melt adhesive based on castor oil and rosin resin and a preparation process thereof, the biodegradable hot melt adhesive comprises EVA resin, modified castor oil, rosin resin, a modified additive, a lubricant and an antioxidant; the modified castor oil is prepared by crosslinking castor oil and isophorone diisocyanate and reacting lignin, 1, 4-butanediol and isocyanate groups; the modified castor oil and the modified additive are added, the modified castor oil and the modified additive are added, the modified castor oil and the modified additive are added, the modified castor oil and the modified additive are added, the modified castor oil and the modified additive are added, the modified castor oil and the modified additive are added, and the modified castor oil and the modified additive are added, so that the modified castor oil and the modified additive are added, and the modified castor oil and the modified additive are added; the tensile property and the adhesive property of the hot melt adhesive are improved, and meanwhile, the flame retardant property and the high and low temperature resistance of the hot melt adhesive can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hot melt adhesives, and in particular relates to a biodegradable hot melt adhesive based on castor oil and rosin resin and a preparation process thereof. Background Art

[0002] Hot melt adhesive refers to an adhesive that is solid at room temperature, becomes liquid after heating and melting, and after coating and wetting the adherend, it is pressed and cooled to complete the bonding within a few seconds. The preparation of hot melt adhesive is usually based on thermoplastic resin, supplemented by smelting with tackifiers, plasticizers, antioxidants and other ingredients. It melts into a viscous flow state when heated and can wet the processing surface. After being separated from the heat source, it cools down and solidifies in a very short time. There is no drying process, low energy consumption, and easy operation. It can be used in high-speed continuous production lines to solve the problem of difficult bonding of certain materials and improve production efficiency. At present, hot melt adhesive, as a convenient type of adhesive, has become a commonly used adhesive in various industries in modern society due to its excellent performance and convenient application.

[0003] EVA hot melt adhesive is known as an environmentally friendly adhesive due to its good processing flowability, non-toxicity, low price, and ease of use. It is widely used in book binding, wood processing, sealants and other fields. Under the background of "dual carbon", the preparation of green, environmentally friendly and high-performance bio-based adhesives with renewable and environmentally friendly biomass raw materials meets the development requirements of economic green transformation and ecological civilization construction. Among them, natural renewable resources represented by vegetable oil esters have the potential advantage of synthesizing bio-based polymer materials. However, due to the performance defect of vegetable oil itself being easily hydrolyzed, the corresponding synthetic materials are insufficient in weather resistance, thermal stability and mechanical properties. In addition, the existing EVA hot melt adhesive has the disadvantages of being flammable, low bonding strength, poor mechanical properties, and poor high and low temperature resistance. It is easy to shrink under low temperature conditions, which makes the bonding strength of EVA-based hot melt adhesive poor at low temperatures. Under high temperature conditions, due to the increase in temperature, the movement of EVA molecular segments in the system is intensified, and there is obvious slip between molecules, which causes the bonding strength of the hot melt adhesive to decrease rapidly, showing poor peel strength, which seriously limits its application range. Summary of the invention

[0004] In order to solve the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide a biodegradable hot melt adhesive based on castor oil and rosin resin and a preparation process thereof, and prepare a biodegradable hot melt adhesive based on castor oil and rosin resin by blending and kneading EVA resin, modified castor oil, rosin resin, modified additives, lubricants and antioxidants in an internal mixer, thereby improving the tensile properties and bonding properties of the hot melt adhesive, and at the same time improving the flame retardant properties and high and low temperature resistance of the hot melt adhesive.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A biodegradable hot melt adhesive based on castor oil and rosin resin, comprising the following raw materials in parts by weight: 30-50 parts of EVA resin, 5-10 parts of modified castor oil, 30-40 parts of rosin resin, 5-10 parts of modified additives, 2-5 parts of lubricants, and 0.1-1 parts of antioxidants; The modified castor oil is prepared by cross-linking castor oil with isophorone diisocyanate by chemical reaction, and reacting lignin and 1,4-butanediol with isocyanate groups; the modified additive is prepared by grafting amino cage-type silsesquioxane with coated aluminum hydroxide by chemical reaction, and further grafting with SBS-g-MAH, wherein the coated aluminum hydroxide is prepared by depositing polydopamine generated by oxidative self-polymerization of dopamine under weak alkaline conditions on the surface of aluminum hydroxide.

[0006] Preferably, the lubricant is one or more combinations of polyethylene wax, oxidized polyethylene wax, and microcrystalline wax; the antioxidant is one or more combinations of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0007] Preferably, the preparation method of the modified castor oil comprises the following steps: taking castor oil in a reactor, adding ethyl acetate solvent and stirring to dissolve, adding isophorone diisocyanate and a catalyst stannous octoate, reacting at 75-85° C. in a nitrogen atmosphere for 2-3 hours to obtain a prepolymer, taking lignin and 1,4-butanediol, adding ethyl acetate solvent and stirring to mix, and then adding them to the prepolymer, placing at 75-85° C. and continuing to stir and react for 2-3 hours to prepare the modified castor oil.

[0008] Preferably, the mass ratio of castor oil, isophorone diisocyanate, lignin and 1,4-butanediol is 4-5: 3.4-4.8: 0.5-1.5: 0.45-0.75.

[0009] Preferably, the preparation method of the modified additive comprises the following steps: A. Deionized water, propanol, acetonitrile and tetraethylammonium hydroxide are placed in a reactor, stirred and mixed evenly, and then γ-aminopropyltriethoxysilane is added, and the mixture is stirred and reacted at 55-70° C. for 20-24 hours. After the reaction is completed, the mixture is cooled to room temperature, and the product is placed in tetrahydrofuran and cooled and precipitated. The precipitate is filtered and dried to prepare an amino cage-type silsesquioxane; B. Put aluminum hydroxide, deionized water and dopamine hydrochloride in a reactor, then add Tris-HCl, adjust the pH value of the system to 8-8.5 with ammonia water, stir and react for 28-36 hours, and after the reaction is completed, centrifuge, wash and dry to prepare coated aluminum hydroxide; C. Take the coated aluminum hydroxide and the amino cage silsesquioxane in a reactor, add toluene solvent and Tris buffer with a pH value of 8-8.5, place at 70-85°C for reaction for 5-6 hours, and after the reaction is completed, centrifuge, wash and dry to prepare modified aluminum hydroxide; D. Take modified aluminum hydroxide in a reactor, add toluene solvent and disperse it evenly by ultrasonication, take SBS-g-MAH and add toluene solvent, swell it for 20-24 hours at room temperature, then add it to the reactor, place it at 105-120°C for reflux reaction for 1-2 hours, then add triethylamine, reduce the temperature to 80-90°C, and reflux reaction for 2-3 hours. After the reaction is completed, filter, wash and dry to prepare the modified additive.

[0010] Preferably, in step A, the volume ratio of deionized water, propanol, acetonitrile, tetraethylammonium hydroxide and γ-aminopropyltriethoxysilane is 20-25:8-14:2-5:0.5-1:50-60.

[0011] Preferably, in step B, the mass ratio of aluminum hydroxide, deionized water, dopamine hydrochloride and Tris-HCl is 17-20:350-400:1.5-2.5:1.

[0012] Preferably, in step C, the mass ratio of the amino cage silsesquioxane to the coated aluminum hydroxide is 1:3-5.

[0013] Preferably, in step D, the mass ratio of modified aluminum hydroxide to SBS-g-MAH is 0.1-0.5:1.

[0014] The preparation process of the biodegradable hot melt adhesive based on castor oil and rosin resin as described above comprises the following steps: S1, taking parts by weight of EVA resin, modified castor oil, rosin resin and lubricant in a high-speed disperser and fully mixing them, then heating them to 120-130° C. and stirring them until they are completely melted to prepare a mixture; S2. Add parts by weight of the modifying additive to the mixture and continue stirring until it is completely mixed, then add parts by weight of the antioxidant and stir for 5 to 8 minutes, and finally reduce the temperature to 80 to 90° C. and stir at a constant temperature and uniform speed for 20 to 30 minutes to prepare the biodegradable hot melt adhesive based on castor oil and rosin resin.

[0015] Beneficial effects of the present invention: The present invention utilizes EVA resin, modified castor oil, rosin resin, modified additive, lubricant and antioxidant to be mixed and kneaded in an internal mixer to prepare a biodegradable hot melt adhesive based on castor oil and rosin resin, thereby improving the tensile properties and bonding properties of the hot melt adhesive, and simultaneously improving the flame retardant properties and high and low temperature resistance of the hot melt adhesive. The present invention utilizes castor oil as a high-functionality polyol to cross-link with isophorone diisocyanate, and utilizes active groups such as phenolic hydroxyl group and alcoholic hydroxyl group in the lignin structure to react with isocyanate groups. Lignin is the second largest biomass resource in the plant kingdom after cellulose in terms of reserves, and has the characteristics of low cost, biodegradability and non-toxicity. Its phenolic structure has the scavenging effect on oxygen-containing active free radicals, so that it has antioxidant activity. The introduction of lignin not only reduces the cost, but also improves the biodegradability. When preparing the modified castor oil, the cross-linking density can also be enhanced, thereby combining the dual advantages of lignin and castor oil to improve the comprehensive performance of the hot melt adhesive.

[0016] The invention utilizes the hydrolysis condensation reaction of γ-aminopropyltriethoxysilane to synthesize the aminated cage silsesquioxane. Meanwhile, the invention utilizes the oxidative self-polymerization of dopamine under weak alkaline conditions to generate polydopamine. The polyphenol structure of polydopamine is not only a good carbon-forming agent, but also its catechol has a good free radical scavenging effect during the combustion process. The polydopamine is deposited on the surface of aluminum hydroxide, and then the environmentally friendly bio-based raw material dopamine is used as a bridge to connect the coated aluminum hydroxide and the aminated cage silsesquioxane. The self-polymerization advantage of dopamine enables the coated aluminum hydroxide surface to have abundant carbonyl groups. Then, the aminated cage silsesquioxane with a three-dimensional Si-O-Si skeleton structure and the coated aluminum hydroxide are subjected to Schiff base reaction to prepare modified aluminum hydroxide, and further the amino group in the modified aluminum hydroxide structure is grafted with the anhydride group in the SBS-g-MAH structure to prepare the modified additive. The modified aluminum hydroxide and SBS-g-MAH are combined through a strong chemical bond, which can improve the polarity of SBS-g-MAH and prevent SBS-g-MAH from migrating to the surface or bonding interface of the hot melt adhesive, thereby avoiding the formation of a weak bonding layer at the bonding interface and causing a decrease in peel strength. The interface strength between the modified aluminum hydroxide and SBS is also improved, thereby improving the mechanical properties of the hot melt adhesive. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1 A method for preparing modified castor oil comprises the following steps: Take 4g of castor oil in a reactor, add 15mL of ethyl acetate solvent and stir to dissolve, add 3.5g of isophorone diisocyanate and 100μL of catalyst stannous octoate, and react at 85°C in a nitrogen atmosphere for 2h to obtain a prepolymer, take 0.7g of lignin and 0.55g of 1,4-butanediol, add 5mL of ethyl acetate solvent and stir to mix, then add to the prepolymer, place at 85°C and continue stirring to react for 2h to prepare modified castor oil.

[0019] Example 2 A method for preparing a modified additive comprises the following steps: A. Take 24 mL of deionized water, 12 mL of propanol, 3 mL of acetonitrile and 1 mL of tetraethylammonium hydroxide in a reactor, stir and mix evenly, then add 55 mL of γ-aminopropyltriethoxysilane, stir and react at 60 ° C for 24 hours, cool to room temperature after the reaction is completed, place the product in tetrahydrofuran and cool and precipitate, filter and dry the precipitate to prepare an amino cage silsesquioxane; B. Take 20g of aluminum hydroxide, 400mL of deionized water and 2g of dopamine hydrochloride in a reactor, then add 1g of Tris-HCl, adjust the pH value of the system to 8.5 with ammonia water, stir and react for 36h, and after the reaction is completed, centrifuge, wash and dry to prepare coated aluminum hydroxide; C. Weigh 0.5 g of tris(hydroxymethyl)aminomethane hydrochloride and dissolve it in 450 mL of deionized water. Use 0.1 mol / L sodium hydroxide solution to adjust the pH value to 8.5 to obtain Tris buffer. Put 5 g of coated aluminum hydroxide and 1 g of amino cage silsesquioxane in a reactor. Add 200 mL of toluene solvent and 60 mL of Tris buffer. Place the reactor at 80° C. to react for 5 h. After the reaction is completed, centrifuge, wash and dry to obtain modified aluminum hydroxide. D. Take 1g of modified aluminum hydroxide in a reactor, add 100mL of toluene solvent and disperse it evenly by ultrasonication, take 5g of SBS-g-MAH and add 450mL of toluene solvent, swell for 24h at room temperature and then add it to the reactor, place it at 110℃ for reflux reaction for 1h, then add 2mL of triethylamine, reduce the temperature to 85℃, and reflux reaction for 2h. After the reaction is completed, filter, wash and dry to prepare the modified additive.

[0020] Example 3 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 33 parts of EVA resin, 5 parts of modified castor oil prepared in Example 1, 30 parts of rosin resin, 5 parts of modified additive prepared in Example 2, 2 parts of lubricant polyethylene wax, and 0.2 parts of antioxidant 1010.

[0021] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following steps: S1, taking parts by weight of EVA resin, modified castor oil, rosin resin and lubricant in a high-speed disperser and fully mixing them, then heating to 125° C. and stirring until completely melted to prepare a mixture; S2, adding parts by weight of a modifying additive to the mixture and continuing to stir until completely mixed, then adding parts by weight of an antioxidant and stirring for 5 minutes, and finally lowering the temperature to 80° C. and stirring at a constant temperature and uniform speed for 20 minutes to prepare the biodegradable hot melt adhesive based on castor oil and rosin resin.

[0022] Example 4 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 45 parts of EVA resin, 7 parts of modified castor oil prepared in Example 1, 35 parts of rosin resin, 8 parts of modified additive prepared in Example 2, 3 parts of lubricant oxidized polyethylene wax, and 0.5 parts of antioxidant 168.

[0023] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0024] Example 5 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 48 parts of EVA resin, 9 parts of modified castor oil prepared in Example 1, 37 parts of rosin resin, 10 parts of modified additive prepared in Example 2, 5 parts of lubricant microcrystalline wax, and 0.9 parts of antioxidant 1076.

[0025] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0026] Comparative Example 1 A method for preparing modified castor oil comprises the following steps: Take 4g of castor oil in a reactor, add 15mL of ethyl acetate solvent and stir to dissolve, add 3.5g of isophorone diisocyanate and 100μL of catalyst stannous octoate, and react at 85°C in a nitrogen atmosphere for 2h to obtain a prepolymer, take 0.55g of 1,4-butanediol, add 5mL of ethyl acetate solvent and stir to mix, then add to the prepolymer, place at 85°C and continue stirring to react for 2h to prepare modified castor oil.

[0027] Comparative Example 2 A method for preparing a modified additive comprises the following steps: A. Take 24 mL of deionized water, 12 mL of propanol, 3 mL of acetonitrile and 1 mL of tetraethylammonium hydroxide in a reactor, stir and mix evenly, then add 55 mL of γ-aminopropyltriethoxysilane, stir and react at 60 ° C for 24 hours, cool to room temperature after the reaction is completed, place the product in tetrahydrofuran and cool and precipitate, filter and dry the precipitate to prepare an amino cage silsesquioxane; B. Take 1g of amino cage silsesquioxane in a reactor, add 100mL of toluene solvent and disperse it evenly by ultrasonication, take 5g of SBS-g-MAH and add 450mL of toluene solvent, swell for 24h at room temperature and then add it to the reactor, place it at 110℃ for reflux reaction for 1h, then add 2mL of triethylamine, reduce the temperature to 85℃, and reflux reaction for 2h. After the reaction is completed, filter, wash and dry to prepare the modified additive.

[0028] Comparative Example 3 A method for preparing a modified additive comprises the following steps: A. Take 20g aluminum hydroxide, 400mL deionized water and 2g dopamine hydrochloride in a reactor, then add 1g Tris-HCl, adjust the pH value of the system to 8.5 with ammonia water, stir and react for 36h, and after the reaction is completed, centrifuge, wash and dry to prepare coated aluminum hydroxide; B. Take 1g of coated aluminum hydroxide in a reactor, add 100mL of toluene solvent and disperse it evenly by ultrasonication, take 5g of SBS-g-MAH and add 450mL of toluene solvent, swell for 24h at room temperature and then add it to the reactor, place it at 110°C for reflux reaction for 1h, then add 2mL of triethylamine, reduce the temperature to 85°C, and reflux reaction for 2h. After the reaction is completed, filter, wash and dry to prepare the modified additive.

[0029] Comparative Example 4 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 48 parts of EVA resin, 9 parts of castor oil prepared in Comparative Example 1, 37 parts of rosin resin, 10 parts of the modified additive prepared in Example 2, 5 parts of lubricant microcrystalline wax, and 0.9 parts of antioxidant 1076.

[0030] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0031] Comparative Example 5 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 48 parts of EVA resin, 9 parts of modified castor oil prepared in Example 1, 37 parts of rosin resin, 10 parts of the modified additive prepared in Comparative Example 2, 5 parts of lubricant microcrystalline wax, and 0.9 parts of antioxidant 1076.

[0032] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0033] Comparative Example 6 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 48 parts of EVA resin, 9 parts of modified castor oil prepared in Example 1, 37 parts of rosin resin, 10 parts of the modified additive prepared in Comparative Example 3, 5 parts of lubricant microcrystalline wax, and 0.9 parts of antioxidant 1076.

[0034] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0035] Comparative Example 7 A biodegradable hot melt adhesive based on castor oil and rosin resin comprises the following raw materials in parts by weight: 48 parts of EVA resin, 9 parts of modified castor oil prepared in Example 1, 37 parts of rosin resin, 2 parts of modified aluminum hydroxide prepared in Example 2, 8 parts of SBS-g-MAH, 5 parts of lubricant microcrystalline wax, and 0.9 parts of antioxidant 1076.

[0036] The preparation process of the above-mentioned biodegradable hot melt adhesive based on castor oil and rosin resin is the same as that in Example 3.

[0037] Performance Testing The hot melt adhesives prepared in Examples 3-5 and Comparative Examples 4-7 were subjected to performance testing: a. According to GB / T 528-2009 standard, the tensile strength and elongation at break of the hot melt adhesive were tested using a universal tensile testing machine; samples were prepared according to GB / T 2790-1995 standard, and the 180° peel strength was measured using a universal tensile testing machine; according to GB / T 15332-1994 standard, the softening point test was performed using the ring and ball method; according to GB / T 10707-2008, the limiting oxygen index and vertical burning tests were performed, and the data results are shown in Table 1.

[0038] b. Biodegradability test: Biodegradability refers to the ability of a sample to be degraded into small molecules by microorganisms in the natural environment. Usually, the soil burial method is used to test the sample. 2 A square thin film sample was weighed m1, buried in moist soil, taken out after one month, washed, dried and weighed m2. Its degradation performance was characterized by its mass change rate. The monthly degradation rate α = (m1-m2) / m1×100%. The data results are shown in Table 1.

[0039] Table 1 Test results of sample performance

[0040] From the data in Table 1, it can be seen that the hot melt adhesive prepared in Examples 3-5 of the present invention has good bonding properties, flame retardant properties, mechanical properties and high and low temperature resistance. Among them, the modified castor oil added in Comparative Example 4 does not contain lignin components, and its measured tensile strength is significantly lower than that of Examples 3-5. The reason is that the introduction of lignin increases the intramolecular crosslinking density, which significantly enhances the tensile strength, but the addition of lignin reduces the toughness of the hot melt adhesive, so the elongation at break will be reduced. The modified additive added in Comparative Example 5 does not contain coated aluminum hydroxide components, and its measured limiting oxygen index and UL-94 grade are lower than those of Examples 3-5, indicating that the addition of coated aluminum hydroxide can improve the flame retardant properties of the hot melt adhesive. The addition of coated aluminum hydroxide in Comparative Example 6 The modified additive does not contain an amino cage silsesquioxane component, and its measured tensile strength, elongation at break, softening point and peel strength are lower than those of Examples 3-5, indicating that the introduction of amino cage silsesquioxane can improve the mechanical properties of the material, improve its high and low temperature resistance and bonding properties. In Comparative Example 7, the modified aluminum hydroxide and SBS-g-MAH are simply mixed, and its measured tensile strength, elongation at break and peel strength are lower than those of Examples 3-5, indicating that the grafting reaction of modified aluminum hydroxide and SBS-g-MAH can improve the mechanical properties and bonding properties of the material.

[0041] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A biodegradable hot melt adhesive based on castor oil and rosin resin, characterized in that: The invention comprises the following raw materials in parts by weight: 30-50 parts of EVA resin, 5-10 parts of modified castor oil, 30-40 parts of rosin resin, 5-10 parts of modified additive, 2-5 parts of lubricant, and 0.1-1 part of antioxidant; The modified castor oil is prepared by cross-linking castor oil with isophorone diisocyanate by chemical reaction, and reacting lignin and 1,4-butanediol with isocyanate groups; the modified additive is prepared by grafting amino cage-type silsesquioxane with coated aluminum hydroxide by chemical reaction, and further grafting with SBS-g-MAH, wherein the coated aluminum hydroxide is prepared by depositing polydopamine generated by oxidative self-polymerization of dopamine under weak alkaline conditions on the surface of aluminum hydroxide.

2. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 1, characterized in that: The lubricant is one or more combinations of polyethylene wax, oxidized polyethylene wax, and microcrystalline wax; the antioxidant is one or more combinations of antioxidant 1010, antioxidant 168, and antioxidant 1076.

3. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 1, characterized in that: The preparation method of the modified castor oil comprises the following steps: taking castor oil in a reactor, adding ethyl acetate solvent to stir and dissolve, adding isophorone diisocyanate and stannous octoate as a catalyst, reacting at 75-85° C. for 2-3 hours in a nitrogen atmosphere to obtain a prepolymer, taking lignin and 1,4-butanediol, adding ethyl acetate solvent to stir and mix, then adding the mixture to the prepolymer, placing the mixture at 75-85° C. for continuous stirring and reaction for 2-3 hours to prepare the modified castor oil.

4. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 3, characterized in that: The mass ratio of the castor oil, isophorone diisocyanate, lignin and 1,4-butanediol is 4-5:3.4-4.8:0.5-1.5:0.45-0.

75.

5. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 1, characterized in that: The preparation method of the modified additive comprises the following steps: A. Deionized water, propanol, acetonitrile and tetraethylammonium hydroxide are placed in a reactor, stirred and mixed evenly, and then γ-aminopropyltriethoxysilane is added, and the mixture is stirred and reacted at 55-70° C. for 20-24 hours. After the reaction is completed, the mixture is cooled to room temperature, and the product is placed in tetrahydrofuran and cooled and precipitated. The precipitate is filtered and dried to prepare an amino cage-type silsesquioxane; B. Put aluminum hydroxide, deionized water and dopamine hydrochloride in a reactor, then add Tris-HCl, adjust the pH value of the system to 8-8.5 with ammonia water, stir and react for 28-36 hours, and after the reaction is completed, centrifuge, wash and dry to prepare coated aluminum hydroxide; C. Take the coated aluminum hydroxide and the amino cage silsesquioxane in a reactor, add toluene solvent and Tris buffer with a pH value of 8-8.5, place at 70-85°C for reaction for 5-6 hours, and after the reaction is completed, centrifuge, wash and dry to prepare modified aluminum hydroxide; D. Take modified aluminum hydroxide in a reactor, add toluene solvent and disperse it evenly by ultrasonication, take SBS-g-MAH and add toluene solvent, swell it for 20-24 hours at room temperature, then add it to the reactor, place it at 105-120°C for reflux reaction for 1-2 hours, then add triethylamine, reduce the temperature to 80-90°C, and reflux reaction for 2-3 hours. After the reaction is completed, filter, wash and dry to prepare the modified additive.

6. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 5, characterized in that: In the step A, the volume ratio of deionized water, propanol, acetonitrile, tetraethylammonium hydroxide and γ-aminopropyltriethoxysilane is 20-25:8-14:2-5:0.5-1:50-60.

7. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 5, characterized in that: In the step B, the mass ratio of aluminum hydroxide, deionized water, dopamine hydrochloride and Tris-HCl is 17-20:350-400:1.5-2.5:

1.

8. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 5, characterized in that: In the step C, the mass ratio of the amino cage-type silsesquioxane to the coated aluminum hydroxide is 1:3-5.

9. The biodegradable hot melt adhesive based on castor oil and rosin resin according to claim 5, characterized in that: In the step D, the mass ratio of the modified aluminum hydroxide to SBS-g-MAH is 0.1-0.5:

1.

10. A process for preparing a biodegradable hot melt adhesive based on castor oil and rosin resin according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, taking parts by weight of EVA resin, modified castor oil, rosin resin and lubricant in a high-speed disperser and fully mixing them, then heating them to 120-130° C. and stirring them until they are completely melted to prepare a mixture; S2. Add parts by weight of the modifying additive to the mixture and continue stirring until it is completely mixed, then add parts by weight of the antioxidant and stir for 5 to 8 minutes, and finally reduce the temperature to 80 to 90° C. and stir at a constant temperature and uniform speed for 20 to 30 minutes to prepare the biodegradable hot melt adhesive based on castor oil and rosin resin.

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