Preparation method of a full-bio-based high softening point block polyamide hot melt adhesive

Abstract

The application relates to a preparation method of a full-bio-based high-softening-point block polyamide hot melt adhesive and belongs to the technical field of polyamide hot melt adhesives. (Hydrogenated) dimer acid and long-chain diacid and diamine are used for melt polycondensation to prepare polyamide prepolymer with different softening points and end amino groups and end carboxyl polyamide prepolymer, and then block copolymerization is carried out to obtain the full-bio-based high-softening-point block polyamide hot melt adhesive. The relatively regular polyamide structure makes the polyamide have high softening point and good peeling strength; the larger hydrophobic group and long aliphatic chain structure in the (hydrogenated) dimer acid and long-chain diacid and diamine make the water absorption rate be greatly lower, and the polyamide is more suitable for precise bonding in the electronic industry and the like; the raw materials are all obtained through microbial fermentation and subsequent conversion of plant oil or glucose, are easy to obtain, are green and environment-friendly on the basis of keeping high performance, and the preparation method is simple and efficient.

Description

Technical Field

[0001] This invention relates to a catalyst-free, high softening point, fully bio-based block polyamide hot melt adhesive preparation method. Specifically, the method involves: first, using (hydrogenated) dimer acid, long-chain diacid, and diamine for melt polycondensation to prepare an amino-terminated dimer acid polyamide prepolymer (tH2N-coDAPA-mn); then, using (hydrogenated) dimer acid, bio-based long-chain diacid, and diamine for polycondensation to prepare a carboxyl-terminated polyamide prepolymer (tHOOC-coDAPA-m'-n'); finally, block copolymerizing the two to obtain a block polyamide copolymer hot melt adhesive. All raw materials are bio-based, and the preparation process does not involve solvents or catalysts. While maintaining high performance, it also meets green and environmentally friendly requirements. The preparation method is simple and efficient, belonging to the field of polyamide hot melt adhesive technology. Background Technology

[0002] Hot melt adhesives have seen rapid development in recent years due to their advantages such as convenient transportation and use, environmental friendliness, and fast bonding speed. They are not only used in packaging and printing, but also play a significant role in automotive interiors, building construction, and ship and aircraft manufacturing. Polyamides, with their good heat resistance, chemical resistance, and excellent mechanical properties, have received widespread attention since their introduction in 1935; they also play a vital role in clothing and textiles, automotive manufacturing, electronic components, and aerospace. Thermoplastic polyamides, due to their good stability and excellent adhesive properties, have become a very important member of the hot melt adhesive family.

[0003] Reports (Polym. Chem., 2021, 12, 1487; J. Adhesion Sci. Technol. 2012, 26, 1267) have investigated the thermomechanical and mechanical properties of polyamide hot melt adhesives. Common polyamide hot melt adhesives, due to their unique amide bond structure, achieve relatively high softening points, but their amide content is usually high, and they contain short carbon chains, resulting in high water absorption. Currently, polyamide hot melt adhesive products that combine high softening point, low water absorption, and good peel strength are not readily available. In the current context of carbon neutrality, achieving the green synthesis of polyamides with high softening point, low water absorption, and good peel strength to fill this technological gap is essential.

[0004] This invention provides a green and efficient method for preparing a fully bio-based high-softening-point block polyamide hot melt adhesive. First, by melt polycondensation of (hydrogenated) dimer acid, long-chain diacid, and diamine, an amino-terminated dimer acid polyamide prepolymer (tH2N-coDAPA-mn) and a carboxyl-terminated polyamide prepolymer (tHOOC-coDAPA-m'-n') are prepared. These two prepolymers are then block copolymerized to obtain the fully bio-based high-softening-point block polyamide hot melt adhesive. The solvent-free and catalyst-free process makes the polyamide hot melt adhesive preparation simple, efficient, and environmentally friendly. Summary of the Invention

[0005] The purpose of this invention is to fill the gap in the field of polyamide hot melt adhesives by providing a method for preparing polyamide prepolymers with terminal amino and carboxyl groups of different softening points through melt polycondensation of (hydrogenated) dimer acids with long-chain bio-based aliphatic diacids and diamines, followed by block copolymerization to obtain a fully bio-based high-softening-point block polyamide hot melt adhesive. All monomer raw materials are bio-based, and no solvents or catalysts are used in the preparation process. This achieves green preparation while maintaining excellent adhesive properties, and simultaneously meets the requirements of high softening point and low water absorption. The specific steps are as follows:

[0006] 1) Preparation of amino-terminated dimer acid polyamide prepolymer (tH2N-coDAPA-mn): According to the total acid-amine molar ratio m:(m+1), where the molar fraction of long-chain diacid in the diacid is n%, bio-based (hydrogenated) dimer acid, long-chain diacid, diamine and 0.2% antioxidant are added. Under a nitrogen atmosphere of 0.05MPa, the temperature is raised to 130℃. After the reactants are completely melted, the mixture is stirred to make the reactants uniform. Then the temperature is raised to 160℃ and reacted for 1h. Then the temperature is raised to 190-250℃ and the pressure is adjusted to 0.8MPa and the reaction continues for 2h. Then the temperature is lowered to 220℃ and the reaction is carried out under vacuum for 1h. After cooling, a light yellow solid is obtained.

[0007] 2) Preparation of carboxyl-terminated dimer acid polyamide prepolymer (tHOOC-coDAPA-m'-n'): According to the total acid-amine molar ratio (m'+1):m', where the molar fraction of long-chain diacid in the diacid is n'%, bio-based (hydrogenated) dimer acid, long-chain diacid, diamine, and 0.2% antioxidant are added. The reaction conditions are the same as in step 1). After cooling, a light yellow or white solid is obtained.

[0008] 3) Preparation of bio-based high softening point block polyamide hot melt adhesive: The amino-terminated dimer acid polyamide prepolymer (tH2N-coDAPA-mn) obtained in step 1) and the carboxyl-terminated dimer acid polyamide prepolymer (tHOOC-coDAPA-m'-n') obtained in step 2) are fed in a mass ratio of (5~10):10, reacted at 200~250℃ under normal pressure for 2h, and then under reduced pressure for 2h to obtain a light yellow solid.

[0009] The structure of the amino-terminated dimer acid polyamide prepolymer tH2N-coDAPA-mn synthesized in step 1) is shown in (Ⅰ):

[0010]

[0011]

[0012] Where R1 is -(CH2) q -(q=6~10) and R2 is -(CH2) r -(r=4~8).

[0013] The structure of the carboxyl-terminated dimer polyamide prepolymer tHOOC-coDAPA-m'-n' synthesized in step 2) is shown in (II):

[0014]

[0015] Where R1 is -(CH2) q -(q=6~10) and R2 is -(CH2) r -(r=4~8).

[0016] The structure of the bio-based high softening point block copolyamide synthesized in step 3) is shown in (Ⅲ):

[0017]

[0018] Where A represents structure (Ⅰ) and B represents structure (Ⅱ).

[0019] The long-chain diamines used in steps 1) and 2) are octanediamine, nonanediamine, decanediamine, undecanediamine, and dodecanediamine; the long-chain dicarboxylic acids used are octanoic acid, azelaic acid, sebacic acid, undecanoic acid, and dodecanediic acid.

[0020] The (hydrogenated) dimer acid used in steps 1) and 2) is a dimer acid and a hydrogenated dimer acid, which are...

[0021] The antioxidants used in steps 1) and 2) are preferably one or a mixture of 2-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, antioxidant 1010, antioxidant DLTDP (dilauryl thiodipropionate), p-hydroxyanisole, and sodium hypophosphite.

[0022] Effects of this invention:

[0023] A polyamide prepolymer with terminal amino and carboxyl groups and different softening points was prepared by (hydrogenated) dimer acid, long-chain bio-based aliphatic diacid, and diamine. This prepolymer was then subjected to block copolymerization to obtain a fully bio-based high-softening-point block polyamide hot melt adhesive. This method does not involve solvents or catalysts, and all monomer raw materials are bio-based, making the preparation process green and efficient. The prepared polyamide hot melt adhesive exhibits excellent properties, with a softening point between 170-205℃ and a peel strength of 7.55 N / cm. Due to the large hydrophobic groups and long aliphatic chain structure of its (hydrogenated) dimer acid, long-chain diacid, and diamine, its water absorption rate is significantly low, making it suitable for precision bonding in industries such as electronics. Detailed Implementation

[0024] The synthesis process and steps of the present invention will be described in detail below, but the described embodiments are only a part of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] 1) Preparation of amino-terminated dimer acid polyamide prepolymer (COPA-11-40): First, 11 parts of dodecanediamine were added to a polymerization reactor, followed by 6 parts of hydrogenated dimer acid and 4 parts of dodecanediic acid, with a total acid-amine ratio of 10:11. Then, 0.2% of the antioxidant sodium hypophosphite was added. Under a nitrogen atmosphere of 0.05 MPa, the temperature was raised to 130°C until all the reactants were melted. Stirring was then started to ensure uniform mixing. The temperature was then raised to 160°C and reacted for 1 hour. The temperature was then raised to 190–250°C while simultaneously adjusting the pressure to 0.8 MPa and continuing the reaction for 2 hours. Finally, the temperature was lowered to 220°C and a vacuum was applied for 1 hour to complete the reaction. After cooling, a light yellow solid was obtained. Its softening point was 154°C, viscosity was 5790 mPa·s, and peel strength was 8.57 N / cm.

[0027] 2) Preparation of carboxyl-terminated dimer acid polyamide prepolymer (COPA-9-80): First, add 9 parts of dodecanediamine to the polymerization reactor, then add 2 parts of hydrogenated dimer acid and 8 parts of dodecanediic acid, with a total acid-amine ratio of 10:9. Then add 0.2% of the antioxidant sodium hypophosphite. The reaction conditions are the same as in step 1). After cooling, a light yellow solid is obtained. Its softening point is 175.2℃, its viscosity is 2645 mPa·s, and its peel strength is 2.16 N / cm.

[0028] 3) Preparation of bio-based high softening point block polyamide hot melt adhesive (B-COPA-9-80-1): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) and the carboxyl-terminated dimer acid polyamide prepolymer (COPA-9-80) obtained in step 2) were fed at a mass ratio of 1:2. The mixture was reacted at 220-250℃ under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 176.6℃, its viscosity was 5398 mPa·s, and its peel strength was 5.15 N / cm.

[0029] Example 2:

[0030] Preparation of bio-based high softening point block polyamide hot melt adhesive (B-COPA-9-80-2): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) prepared in step 1) of Example 1 and the carboxyl-terminated dimer acid polyamide prepolymer (COPA-9-80) prepared in step 2) of Example 1 were fed at a mass ratio of 4:5. The mixture was reacted at 220-250°C under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 176°C, its viscosity was 6350 mPa·s, and its peel strength was 11.78 N / cm.

[0031] Example 3:

[0032] 1) Preparation of carboxyl-terminated dimer acid polyamide prepolymer (GG-COPA-9-80): First, 9 parts of decanediamine were added to the polymerization reactor, followed by 2 parts of hydrogenated dimer acid and 8 parts of sebacic acid, with a total acid-amine ratio of 10:9. Then, 0.2% of the antioxidant sodium hypophosphite was added. The reaction conditions were the same as in step 1) of Example 1. After cooling, a white, semi-transparent solid was obtained. Its softening point was 189.8℃, its viscosity was 1567 mPa·s, and its peel strength was 1.96 N / cm.

[0033] 2) Preparation of bio-based high softening point block polyamide hot melt adhesive (B-GG-COPA-9-80-1): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) of Example 1 and the carboxyl-terminated dimer acid polyamide prepolymer (GG-COPA-9-80) obtained in step 1) of Example 3 were fed at a mass ratio of 1:2. The mixture was reacted at 220-250℃ under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 192.2℃, its viscosity was 7920 mPa·s, and its peel strength was 6.43 N / cm.

[0034] Example 4:

[0035] 1) Preparation of carboxyl-terminated dimer acid polyamide prepolymer (G-COPA-9-80): First, 9 parts of dodecanediamine were added to the polymerization reactor, then 2 parts of hydrogenated dimer acid and 8 parts of sebacic acid were added, with a total acid-amine ratio of 10:9. Then, 0.2% of the antioxidant sodium hypophosphite was added. The reaction conditions were the same as in step 1) of Example 1. After cooling, a white, semi-transparent solid was obtained. Its softening point was 183℃, its viscosity was 2173 mPa·s, and its peel strength was 2.91 N / cm.

[0036] 2) Preparation of bio-based high softening point block polyamide hot melt adhesive (BG-COPA-9-80): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) of Example 1 and the carboxyl-terminated dimer acid polyamide prepolymer (G-COPA-9-80) obtained in step 1) of Example 4 were fed at a mass ratio of 1:2. The mixture was reacted at 220-250℃ under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 184.9℃, its viscosity was 5099 mPa·s, and its peel strength was 7.33 N / cm.

[0037] Example 5:

[0038] Preparation of bio-based high softening point block polyamide hot melt adhesive (B-GG-COPA-9-80-2): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) of Example 1 and the carboxyl-terminated dimer acid polyamide prepolymer (GG-COPA-9-80) obtained in step 1) of Example 3 were fed at a mass ratio of 2:3. The mixture was reacted at 220-250°C under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 192.2°C, its viscosity was 5491 mPa·s, and its peel strength was 6.50 N / cm.

[0039] Example 6:

[0040] 1) Preparation of carboxyl-terminated dimer acid polyamide prepolymer (GG-COPA-9-90): First, 9 parts of decanediamine were added to the polymerization reactor, followed by 1 part of hydrogenated dimer acid and 9 parts of sebacic acid, with a total acid-amine ratio of 10:9. Then, 0.2% of the antioxidant sodium hypophosphite was added, and the reaction conditions were the same as in step 1) of Example 1. After cooling, a white, semi-transparent solid was obtained. Its softening point was 196.1℃, its viscosity was 2186 mPa·s, and its peel strength was 2.14 N / cm.

[0041] 2) Preparation of bio-based high softening point block polyamide hot melt adhesive (B-GG-COPA-9-90): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) of Example 1 and the carboxyl-terminated dimer acid polyamide prepolymer (GG-COPA-9-90) obtained in step 1) of Example 6 were fed at a mass ratio of 1:2. The mixture was reacted at 220-250°C under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 197.1°C, its viscosity was 4109 mPa·s, and its peel strength was 7.86 N / cm.

[0042] Example 7:

[0043] 1) Preparation of carboxyl-terminated polyamide prepolymer (GG-COPA-9-100): First, 9 parts of decanediamine were added to the polymerization reactor, followed by 10 parts of sebacic acid, resulting in a total acid-amine ratio of 10:9. Then, 0.2% of the antioxidant sodium hypophosphite was added, and the reaction conditions were the same as in step 1) of Example 1. After cooling, a white, semi-transparent solid was obtained. Its softening point was 202.8℃, its viscosity was 3235 mPa·s, and its peel strength was 1.54 N / cm.

[0044] 2) Preparation of bio-based high softening point block polyamide hot melt adhesive (B-GG-COPA-9-100): The amino-terminated dimer acid polyamide prepolymer (COPA-11-40) obtained in step 1) of Example 1 and the carboxyl-terminated polyamide prepolymer (GG-COPA-9-100) obtained in step 1) of Example 7 were fed at a mass ratio of 1:1. The mixture was reacted at 220-250℃ under normal pressure for 2 hours, followed by a reduced pressure reaction for 2 hours to obtain a block copolymer polyamide, which appeared as a light yellow solid. Its softening point was 204.5℃, its viscosity was 13050 mPa·s, and its peel strength was 6.75 N / cm.

Claims

1. A method for preparing a fully bio-based high softening point block polyamide hot melt adhesive, characterized in that, Includes the following steps: 1) Preparation of amino-terminated dimer acid polyamide prepolymer tH2N-coDAPA-mn: According to the total acid-amine molar ratio m:(m+1), where the molar fraction of long-chain diacid in the diacid is n, bio-based dimer acid or bio-based hydrogenated dimer acid, long-chain diacid, long-chain diamine and 0.2% antioxidant are added. Under a nitrogen atmosphere of 0.05MPa, the temperature is raised to 130℃. After the reactants are completely melted, the mixture is stirred to make the reactants uniform. Then the temperature is raised to 160℃ and reacted for 1h. Then the temperature is raised to 190~250℃ and the pressure is adjusted to 0.8MPa and the reaction is continued for 2h. Then the temperature is lowered to 220℃ and the reaction is carried out under vacuum for 1h. After cooling, a light yellow solid is obtained. 2) Preparation of carboxyl-terminated dimer acid polyamide prepolymer tHOOC-coDAPA-m'-n': According to the total acid-amine molar ratio (m'+1):m', where the molar fraction of long-chain diacid in the diacid is n', add bio-based dimer acid or bio-based hydrogenated dimer acid, long-chain diacid and long-chain diamine and 0.2% antioxidant. The reaction conditions are the same as in step 1). After cooling, a light yellow or white solid is obtained. 3) Preparation of bio-based high softening point block polyamide hot melt adhesive: The amino-terminated dimer acid polyamide prepolymer tH2N-coDAPA-mn obtained in step 1) and the carboxyl-terminated dimer acid polyamide prepolymer tHOOC-coDAPA-m'-n' obtained in step 2) were fed in a mass ratio of (5~10):10, reacted at 200~250℃ under normal pressure for 2 h, and then under reduced pressure for 2 h to obtain a light yellow solid; The softening point can reach 175-205℃; The structure of the amino-terminated dimer acid polyamide prepolymer tH2N-coDAPA-mn synthesized in step 1) is shown in (Ⅰ): or ； （Ⅰ） Where R1 is -(CH2) q -, q=6~10; R2 is -(CH2) r -, r=4~8; The structure of the carboxyl-terminated dimer polyamide prepolymer tHOOC-coDAPA-m'-n' synthesized in step 2) is shown in (II): or ； （Ⅱ） Where R1 is -(CH2) q -, q=6~10; R2 is -(CH2) r -, r=4~8.

2. The method according to claim 1, characterized in that, The structure of the bio-based high softening point block copolyamide synthesized in step 3) is shown in (Ⅲ): ； （Ⅲ） Where A is structure (Ⅰ) and B is structure (Ⅱ).

3. The method according to claim 1, characterized in that, The long-chain diamines used in steps 1) and 2) are octanediamine, nonanediamine, decanediamine, undecanediamine, or dodecanediamine; the long-chain diacids used are octanoic acid, azelaic acid, sebacic acid, undecanoic acid, or dodecanediic acid.

4. The method according to claim 1, characterized in that, The bio-based dimer acid or bio-based hydrogenated dimer acid used in steps 1) and 2) is... .

5. The method according to claim 1, characterized in that, The antioxidants used in steps 1) and 2) are selected from one or a mixture of several of the following: 2-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, antioxidant 1010, antioxidant DLTDP (dilauryl thiodipropionate), p-hydroxyanisole, and sodium hypophosphite.

6. The fully bio-based high softening point block polyamide hot melt adhesive prepared according to any one of claims 1-5.

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