Preparation method of hot melt adhesive resin

Abstract

The invention discloses a preparation method of hot melt adhesive resin. The preparation method comprises the following steps: weighing the following raw material components in parts by weight: 60-80 parts of ethylene-vinyl acetate copolymer, 5-10 parts of methyl methacrylate, 0-5 parts of tackifying resin, 3-5 parts of polyethylene wax and 10-20 parts of nano-hydroxyapatite; the tackifying resin is any one of petroleum resin, rosin resin or terpene resin; then taking ethylene-vinyl acetate copolymer, methyl methacrylate and half of nano-hydroxyapatite, stirring and mixing for 20-30 minutes, then sequentially adding the rest of nano-hydroxyapatite, polyethylene wax and / or tackifying resin, and continuously stirring and mixing for 30-45 minutes to obtain the hot melt adhesive resin. According to the preparation method, the nano-hydroxyapatite is prepared by optimizing the process and is added into the hot melt adhesive resin, so that the thermal stability and the bonding strength of the hot melt adhesive resin are effectively improved, and the quality of a hot melt adhesive product is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hot melt adhesives, and in particular relates to a method for preparing a hot melt adhesive resin. Background Art

[0002] Hot melt adhesive is a kind of adhesive that is solid at room temperature, melts into a viscous fluid after heating to a certain temperature, and solidifies rapidly after cooling. It does not use solvents in the bonding process, is environmentally friendly, and solidifies quickly. It is widely used in packaging, wood processing, book binding, shoe materials, automotive interiors and other fields. However, hot melt adhesive also has problems such as poor heat resistance and limited bonding strength, which still need further research and improvement.

[0003] Hot melt adhesive resin is a key component of hot melt adhesive products. It has a decisive influence on the performance of hot melt adhesive, such as the bonding strength, temperature resistance, melt fluidity, durability, curing speed, etc. of hot melt adhesive. It can be seen that the improvement of hot melt adhesive resin is one of the important means to improve the performance of hot melt adhesive. For example, tackifying resin is usually added to hot melt adhesive resin to improve the bonding strength of hot melt adhesive resin. At the same time, researchers have also found that adding a certain amount of inorganic filler can also improve the thermal stability and bonding strength of hot melt adhesive, and the cost of inorganic filler is much lower than that of tackifying resin, which has a good application prospect. However, the compatibility of inorganic fillers with polymer substances is poor. Excessive addition or imbalanced dosage will affect the performance of hot melt adhesive products. In order to improve the compatibility of inorganic fillers with polymer substances, most of them currently adopt the method of adding chemical reagents for modification. The modification process is relatively complicated, and the excessive use of chemical reagents will also increase the difficulty of environmental protection treatment. Therefore, further research on inorganic fillers in hot melt adhesive resins and hot melt adhesive products is still needed. Summary of the invention

[0004] In view of the above shortcomings, the present invention discloses a method for preparing a hot melt adhesive resin, optimizes the process for preparing nano hydroxyapatite and adding it to the hot melt adhesive resin, thereby effectively improving the thermal stability and bonding strength of the hot melt adhesive resin, thereby improving the quality of the hot melt adhesive product.

[0005] The present invention is achieved by adopting the following technical solutions: A method for preparing a hot melt adhesive resin comprises the following steps: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.1-0.2%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is (1-2):100, and then the phosphoric acid solution is slowly added to adjust the pH to 9.5-10.0, and then ultrasonication is performed for 15-20 minutes and the reaction is continued for 30-60 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.0-9.5, and a crystal form control agent is added to continue the reaction for 2-3 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 60-80° C. and then crushed to obtain nano-hydroxyapatite with a particle size of 10-30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; (2) Weigh the raw material components according to the following weight proportions: 60-80 parts of ethylene-vinyl acetate copolymer, 5-10 parts of methyl methacrylate, 0-5 parts of tackifier resin, 3-5 parts of polyethylene wax, and 10-20 parts of nano-hydroxyapatite; the tackifier resin is any one of petroleum resin, rosin resin or terpene resin; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed for 20 to 30 minutes, and then the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin are added in sequence, and the stirring and mixing is continued for 30 to 45 minutes to obtain a hot melt adhesive resin.

[0006] Furthermore, in step (1), the mass fraction of the phosphoric acid solution is 3-6%.

[0007] Furthermore, in step (1), the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, wherein the mass ratio of pepsin: cathepsin: deionized water is (0.2-0.5): (0.1-0.2): 100; then, chlorella protein and deionized water are mixed in a mass ratio of 1: (1-3) to obtain a protein solution, and then a phosphoric acid solution is added to adjust the pH to 4.0-5.0, and then the mixed enzyme solution is added and heated to 65-75° C. under stirring conditions and then kept at a constant temperature for 2-3 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the volume of the protein solution is 1: (8-10). The mixed enzyme solution is prepared by using pepsin and cathepsin to enzymolyze chlorella protein to obtain acidic polypeptides, wherein most of the polypeptides are polypeptides containing amino acid residues such as glutamic acid and aspartic acid. At the same time, the present invention promotes the enzymolysis of chlorella protein by controlling the pH of the enzymolysis solution and the temperature of the enzymolysis process, thereby increasing the yield of acidic polypeptides. Then, the mixed solution containing the acidic peptide is added to the calcium hydroxide solution, and a phosphoric acid solution is added to simulate the biomineralization process, thereby obtaining hydroxyapatite. The added acidic peptide can form coordination with calcium ions by using the oxygen atoms on its carboxyl and carbonyl groups in the early stage of biomineralization, thereby adsorbing calcium ions to become the core of nucleation, thereby inducing mineralization; at the same time, the acidic peptide can change the interface energy between the hydroxyapatite crystal particles and the solution, and drive the linear orderly arrangement of the nano-hydroxyapatite particles through the trend of minimizing the sum of the interface energy, thereby obtaining rod-shaped or plate-shaped nano-hydroxyapatite.

[0008] Furthermore, in step (1), the mass ratio of the crystal form control agent to the calcium hydroxide solution is (0.5-1):100, and the crystal form control agent is obtained by mixing sucrose and sorbitol at a mass ratio of (2-5):1. By adding the crystal form control agent prepared by sucrose and sorbitol, the polar groups existing in the structure of sucrose and sorbitol and having high electronegativity can be coordinated with calcium ions through charge matching, thereby inhibiting the growth of nano-hydroxyapatite particles and controlling the particle size of nano-particles. In addition, sucrose is not easy to react with polypeptides containing amino acid residues to affect their crystal form control effect.

[0009] Furthermore, in step (3), ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 200 to 300 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing is continued at 50 to 80 r / min.

[0010] A hot melt adhesive is prepared using the hot melt adhesive resin. The specific preparation process is to mix the hot melt adhesive resin with an anti-yellowing agent and an anti-hydrolysis agent, add the mixture into a screw extruder for processing, and then water cool and pelletize to obtain a hot melt adhesive product. The working temperature of the screw extruder is 160-180°C.

[0011] Furthermore, the amount of the anti-yellowing agent is 0.1-0.3wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent is 0.2-0.5wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is one of carbodiimide and polycarbodiimide anti-hydrolysis agents.

[0012] Compared with the prior art, this technical solution has the following beneficial effects: 1. The present invention adopts a method of simulating biomineralization to produce and prepare nano-hydroxyapatite materials, wherein a mixed enzyme solution prepared by pepsin and tissue protease is used to promote the formation of nano-hydroxyapatite and control the crystal structure of nano-hydroxyapatite, thereby obtaining a nano-hydroxyapatite material with uniform particle size and regular structure. The nano-hydroxyapatite material has good compatibility with high molecular polymers and is added as a filler to the hot melt adhesive formula, which can effectively improve the thermal stability and bonding strength of the hot melt adhesive resin, thereby improving the quality of the hot melt adhesive product.

[0013] 2. The method of the present invention is simple, easy to operate, and highly stable, and is suitable for large-scale, automated production of hot-melt adhesive resins and hot-melt adhesive products. DETAILED DESCRIPTION

[0014] The present invention is further described by the following examples, but is not intended to be limiting of the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods commonly known to those skilled in the art.

[0015] Embodiment 1: A method for preparing a hot melt adhesive resin, comprising the following steps: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.12%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is 1.2:100, and then the phosphoric acid solution is slowly added to adjust the pH to 9.6, and then ultrasonication is continued for 16 minutes and the reaction is continued for 40 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.2, and a crystal form control agent is added to continue the reaction for 2.5 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 70°C and then crushed to obtain nano-hydroxyapatite with a particle size of 10 to 30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; the phosphoric acid solution The mass fraction is 4%; the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, and the mass ratio of pepsin: cathepsin: deionized water is 0.3:0.12:100; then, chlorella protein and deionized water are mixed in a mass ratio of 1:2 to obtain a protein solution, and then a phosphoric acid solution is added to adjust the pH to 4.5, and then the mixed enzyme solution is added and heated to 68°C under stirring conditions and kept at a constant temperature for 2.5 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the protein solution is 1:9; the mass ratio of the crystal form control agent to the calcium hydroxide solution is 0.65:100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of 3:1; (2) Weigh the following raw material components in parts by weight: 65 parts of ethylene-vinyl acetate copolymer, 6 parts of methyl methacrylate, 2 parts of tackifying resin, 4 parts of polyethylene wax, and 14 parts of nano-hydroxyapatite; the tackifying resin is rosin resin; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 250 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing are continued at 60 r / min for 40 minutes to obtain a hot melt adhesive resin.

[0016] A hot melt adhesive is prepared using the hot melt adhesive resin described in this embodiment. The specific preparation process is to mix the hot melt adhesive resin with an anti-yellowing agent and an anti-hydrolysis agent, add the mixture to a screw extruder for processing, and then water cool and pelletize to obtain a hot melt adhesive product. The working temperature of the screw extruder is 170°C; the amount of the anti-yellowing agent is 0.2wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent is 0.3wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is carbodiimide.

[0017] Embodiment 2: A method for preparing a hot melt adhesive resin, comprising the following steps: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.1%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is 1:100, and then the phosphoric acid solution is slowly added to adjust the pH to 9.5, and then the reaction is continued for 30 minutes after ultrasonic treatment for 15 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.0, and a crystal form control agent is added to continue the reaction for 2 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 60°C and then crushed to obtain nano-hydroxyapatite with a particle size of 10 to 30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; the phosphoric acid solution The mass fraction is 3%; the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, and the mass ratio of pepsin: cathepsin: deionized water is 0.2:0.1:100; then, chlorella protein and deionized water are mixed in a mass ratio of 1:1 to obtain a protein solution, and then a phosphoric acid solution is added to adjust the pH to 4.0, and then the mixed enzyme solution is added and heated to 65°C under stirring conditions and kept at a constant temperature for 3 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the protein solution is 1:8; the mass ratio of the crystal form control agent to the calcium hydroxide solution is 0.5:100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of 2:1; (2) Weigh the raw material components according to the following weight proportions: 60 parts of ethylene-vinyl acetate copolymer, 5 parts of methyl methacrylate, 3 parts of polyethylene wax, and 10 parts of nano-hydroxyapatite; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 200 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing is continued at 50 r / min for 30 minutes to obtain a hot melt adhesive resin.

[0018] A hot melt adhesive is prepared using the hot melt adhesive resin described in this embodiment. The specific preparation process is to mix the hot melt adhesive resin with an anti-yellowing agent and an anti-hydrolysis agent, add the mixture to a screw extruder for processing, and then water cool and pelletize to obtain a hot melt adhesive product. The working temperature of the screw extruder is 160°C; the amount of the anti-yellowing agent is 0.1wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent is 0.2wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is carbodiimide.

[0019] Embodiment 3: A method for preparing a hot melt adhesive resin, comprising the following steps: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.18%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is 1.6:100, and then the phosphoric acid solution is slowly added to adjust the pH to 9.8, and then the reaction is continued for 50 minutes after ultrasonic treatment for 18 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.2, and a crystal form control agent is added to continue the reaction for 2.5 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 75°C and then crushed to obtain nano-hydroxyapatite with a particle size of 10 to 30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; the mass of the phosphoric acid solution is The amount fraction is 56%; the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, and the mass ratio of pepsin: cathepsin: deionized water is 0.4:0.18:100; then take chlorella protein and deionized water in a mass ratio of 1:2 and mix them evenly to obtain a protein solution, then add a phosphoric acid solution to adjust the pH to 4.5, and then add the mixed enzyme solution and heat it to 72°C under stirring conditions and keep the temperature constant for 2.5 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the volume of the protein solution is 1:9.5; the mass ratio of the crystal form control agent to the calcium hydroxide solution is 0.8:100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of 4:1; (2) Weigh the raw material components according to the following weight proportions: 75 parts of ethylene-vinyl acetate copolymer, 8 parts of methyl methacrylate, 4 parts of tackifying resin, 4 parts of polyethylene wax, and 18 parts of nano-hydroxyapatite; the tackifying resin is a terpene resin; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 250 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing are continued at 60 r / min for 40 minutes to obtain a hot melt adhesive resin.

[0020] A hot melt adhesive is prepared using the hot melt adhesive resin described in this embodiment. The specific preparation process is to mix the hot melt adhesive resin with an anti-yellowing agent and an anti-hydrolysis agent, add the mixture to a screw extruder for processing, and then water cool and pelletize to obtain a hot melt adhesive product. The working temperature of the screw extruder is 175°C; the amount of the anti-yellowing agent is 0.25wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent is 0.35wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is a polycarbodiimide anti-hydrolysis agent.

[0021] Embodiment 4: A method for preparing a hot melt adhesive resin, comprising the following steps: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.2%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is 2:100, and then the phosphoric acid solution is slowly added to adjust the pH to 10.0, and then the reaction is continued for 60 minutes after ultrasonic treatment for 20 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.5, and a crystal form control agent is added to continue the reaction for 3 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 80°C and then crushed to obtain nano-hydroxyapatite with a particle size of 10 to 30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; the phosphoric acid solution The mass fraction of the enzyme solution is 6%; the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, and the mass ratio of pepsin: cathepsin: deionized water is 0.5:0.2:100; then, chlorella protein and deionized water are mixed in a mass ratio of 1:3 to obtain a protein solution, and then a phosphoric acid solution is added to adjust the pH to 5.0, and then the mixed enzyme solution is added and heated to 75°C under stirring conditions and kept at a constant temperature for 2 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the volume of the protein solution is 1:10; the mass ratio of the crystal form control agent to the calcium hydroxide solution is 1:100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of 5:1; (2) Weigh the following raw material components in parts by weight: 80 parts of ethylene-vinyl acetate copolymer, 10 parts of methyl methacrylate, 5 parts of tackifying resin, 5 parts of polyethylene wax, and 20 parts of nano-hydroxyapatite; the tackifying resin is rosin resin; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 300 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing is continued at 80 r / min for 45 minutes to obtain a hot melt adhesive resin.

[0022] A hot melt adhesive is prepared using the hot melt adhesive resin described in this embodiment. The specific preparation process is to mix the hot melt adhesive resin with an anti-yellowing agent and an anti-hydrolysis agent, add the mixture to a screw extruder for processing, and then water cool and pelletize to obtain a hot melt adhesive product. The working temperature of the screw extruder is 180°C; the amount of the anti-yellowing agent is 0.3wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent is 0.5wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is carbodiimide.

[0023] Comparative Example 1: The method for preparing the hot melt adhesive resin in this comparative example differs from the method described in Example 1 only in that step (1) is omitted and nano-hydroxyapatite is not added to the formula of the hot melt adhesive resin.

[0024] Comparative Example 2: The preparation method of the hot melt adhesive resin described in this comparative example is different from the method described in Example 1 only in that in step (1), no mixed enzyme solution is used, and only nano calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.1%, and the phosphoric acid solution is slowly added to adjust the pH to 9.5, and then ultrasonication is continued for 15 minutes and the reaction is continued for 30 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.0, and a crystal form control agent is added to continue the reaction for 2 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 60°C and crushed to obtain nano hydroxyapatite with a particle size of 10 to 30 nm; the mass ratio of the crystal form control agent to the calcium hydroxide solution is 0.5:100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of 2:1.

[0025] Experimental Example: Hot melt adhesive was prepared according to the method described in Examples 1 to 4 and Comparative Examples 1 to 2, and then the performance was tested according to the following method. The test results are shown in Table 1: (1) Refer to HG / T 3660-1999 "Determination of melt viscosity of hot melt adhesives" for melt viscosity test; (2) Melt the obtained hot melt adhesive and apply it between two pine boards. The amount of adhesive applied is 10g / m 2 , press for 5 minutes to obtain a bonded wood board, then soak the bonded wood board in peanut oil for 1 minute, and then place it in -40℃, 20℃ and 60℃ environments for 72 hours, then peel it off along 90° until the bonded wood board is completely separated; if the bonded wood board is damaged and the opening is in the two pine boards, it is qualified; if the bonded wood board can be completely separated and the opening is at the interface of the glue or the interface between the glue and the board, it is unqualified.

[0026] Table 1 Performance test results of hot melt adhesives prepared by different methods

[0027] It can be seen from the data in Table 1 that the hot melt adhesive resin and hot melt adhesive product prepared according to the method of the present invention have good bonding strength and temperature resistance.

[0028] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a hot melt adhesive resin, Features: The following steps are involved: (1) Preparation of nano-hydroxyapatite: nano-calcium hydroxide and deionized water are mixed to obtain a calcium hydroxide solution with a mass fraction of 0.1-0.2%, and then an enzyme solution is added and mixed evenly under stirring conditions, wherein the mass ratio of the enzyme solution to the calcium hydroxide solution is (1-2):100, and then the phosphoric acid solution is slowly added to adjust the pH to 9.5-10.0, and then ultrasonication is performed for 15-20 minutes and the reaction is continued for 30-60 minutes, and then the phosphoric acid solution is slowly added to adjust the pH to 9.0-9.5, and a crystal form control agent is added to continue the reaction for 2-3 hours, and then the mixture is sent to a filter press for filtration to obtain a precipitate, and the precipitate is dried at 60-80° C. and then crushed to obtain nano-hydroxyapatite with a particle size of 10-30 nm; the enzyme solution is obtained by adding pepsin and cathepsin to deionized water; (2) Weigh the raw material components according to the following weight proportions: 60-80 parts of ethylene-vinyl acetate copolymer, 5-10 parts of methyl methacrylate, 0-5 parts of tackifier resin, 3-5 parts of polyethylene wax, and 10-20 parts of nano-hydroxyapatite; the tackifier resin is any one of petroleum resin, rosin resin or terpene resin; (3) Ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed for 20 to 30 minutes, and then the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin are added in sequence, and the stirring and mixing is continued for 30 to 45 minutes to obtain a hot melt adhesive resin.

2. The method for preparing the hot melt adhesive resin according to claim 1, Features: In step (1), the mass fraction of the phosphoric acid solution is 3-6%.

3. The method for preparing the hot melt adhesive resin according to claim 1, Features: In step (1), the preparation method of the enzyme solution is to add pepsin and cathepsin to deionized water to obtain a mixed enzyme solution, wherein the mass ratio of pepsin: cathepsin: deionized water is (0.2-0.5): (0.1-0.2): 100; then, chlorella protein and deionized water are mixed in a mass ratio of 1: (1-3) to obtain a protein solution, and then a phosphoric acid solution is added to adjust the pH to 4.0-5.0, and then the mixed enzyme solution is added and heated to 65-75° C. under stirring conditions and then kept at a constant temperature for 2-3 hours to obtain an enzyme solution, and the volume ratio of the added mixed enzyme solution to the protein solution is 1: (8-10).

4. The method for preparing the hot melt adhesive resin according to claim 3, Features: In step (1), the mass ratio of the crystal form control agent to the calcium hydroxide solution is (0.5-1):100, and the crystal form control agent is obtained by mixing sucrose and sorbitol in a mass ratio of (2-5):

1.

5. The method for preparing the hot melt adhesive resin according to claim 1, Features: In step (3), ethylene-vinyl acetate copolymer, methyl methacrylate and half of the nano-hydroxyapatite are stirred and mixed at a speed of 200 to 300 r / min; after adding the remaining nano-hydroxyapatite, polyethylene wax and / or tackifying resin, the stirring and mixing are continued at a speed of 50 to 80 r / min.

6. A hot melt adhesive, Features: The hot melt adhesive is prepared by using the hot melt adhesive resin as claimed in any one of claims 1 to 5.

7. A hot melt adhesive according to claim 6, Features: The preparation process of the hot melt adhesive is to mix the hot melt adhesive resin with the anti-yellowing agent and the anti-hydrolysis agent, add the mixture into a screw extruder for processing, and then water cool and pelletize to obtain the hot melt adhesive product. The working temperature of the screw extruder is 160-180°C.

8. A hot melt adhesive according to claim 7, Features: The amount of the anti-yellowing agent used is 0.1-0.3wt% of the hot melt adhesive resin, and the anti-yellowing agent is a hindered phenol ultraviolet absorber; the amount of the anti-hydrolysis agent used is 0.2-0.5wt% of the hot melt adhesive resin, and the anti-hydrolysis agent is one of carbodiimide and polycarbodiimide anti-hydrolysis agents.

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