Waterborne polyurethane adhesive with high thermal stability and preparation method thereof

Abstract

The invention belongs to the technical field of polymer synthesis, and particularly relates to a high-thermal-stability waterborne polyurethane adhesive and a preparation method thereof. Comprising the following raw materials in parts by weight: 100 parts of polycarbonate diol, 30-40 parts of IPDI, 3-6 parts of sulfonic calix [4] arene, 8-15 parts of hydroxyl silicone oil, 0.5-2 parts of N, N '-bis (salicylidene)-1, 3-propane diamine, 5-8 parts of BDO, 2-6 parts of triethylamine and 80-120 parts of deionized water. The material has excellent thermal stability and good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a high thermal stability waterborne polyurethane adhesive and its preparation method. Background Technology

[0002] Waterborne polyurethane (WPU) has attracted much attention due to its environmentally friendly properties, but the inherent poor heat resistance of traditional WPU limits its application in high-temperature environments.

[0003] To improve thermal stability, existing technologies often employ single modification methods, such as organosilicon modification, which can improve heat and water resistance, but single siloxane modification may lead to poor compatibility or loss of mechanical strength. Nanoparticle or epoxy resin blending presents dispersibility and stability issues or complex processes. Adding small molecule ionic chain extenders, such as DMPA, primarily provides hydrophilicity, offering limited improvement in thermal stability.

[0004] These methods often fail to simultaneously achieve high thermal stability, good emulsion stability, and excellent mechanical properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a waterborne polyurethane adhesive with high thermal stability and its preparation method, which has excellent thermal stability and good mechanical properties.

[0006] This invention provides a high thermal stability waterborne polyurethane adhesive, comprising the following raw materials in parts by weight: 100 parts of polycarbonate diol, 30-40 parts of IPDI, 3-6 parts of sulfonic acid calix[4] aromatic hydrocarbon, 8-15 parts of hydroxyl silicone oil, 0.5-2 parts of N,N'-bis(salicylyl)-1,3-propanediamine, 5-8 parts of BDO, 2-6 parts of triethylamine, and 80-120 parts of deionized water.

[0007] Preferably, the raw materials include the following parts by weight: 100 parts of polycarbonate diol, 35-40 parts of IPDI, 4-5 parts of sulfonic acid calix[4] aromatic hydrocarbon, 8-12 parts of hydroxyl silicone oil, 1-2 parts of N,N'-bis(salicylyl)-1,3-propanediamine, 6-7 parts of BDO, 3-5 parts of triethylamine, and 90-110 parts of deionized water.

[0008] Preferably, the raw materials include the following parts by weight: 100 parts of polycarbonate diol, 38 parts of IPDI, 4.2 parts of sulfonic acid calix[4] aromatic hydrocarbon, 10 parts of hydroxyl silicone oil, 1.2 parts of N,N'-bis(salicylyl)-1,3-propanediamine, 6.5 parts of BDO, 4 parts of triethylamine, and 100 parts of deionized water.

[0009] Preferably, the polycarbonate diol has a Mn of 2000 and the hydroxyl silicone oil has a Mn of 4000.

[0010] This invention provides a method for preparing the high thermal stability waterborne polyurethane adhesive, comprising the following steps: 1) Prepolymer: After dehydration, polycarbonate diol is reacted with IPDI at 80-90℃ to obtain the prepolymer; 2) Organosilicon modification: The prepolymer is cooled to 70℃, hydroxyl silicone oil is added, and the reaction is carried out; 3) Chain extension: Then add BDO and sulfonic acid calix[4] aromatics and react at 60-70℃; 4) Schiff base introduction: Cool to 50-60℃, add N,N'-bis(salicylene)-1,3-propanediamine, and react; 5) Neutralization and emulsification: Cool to 30-40℃, add triethylamine for neutralization, and add deionized water for emulsification; 6) Desolventization: Vacuum distillation yields a waterborne polyurethane adhesive with high thermal stability.

[0011] Preferably, acetone is added in batches during the prepolymerization reaction to control the viscosity of the system.

[0012] Preferably, the prepolymerization reaction is carried out at a temperature of 80°C for 2 hours.

[0013] Preferably, the reaction time for organosilicon modification is 1.5 h.

[0014] Preferably, the chain extension reaction temperature is 65°C and the reaction time is 1.5 h.

[0015] Preferably, in step 4), the temperature is lowered to 55°C and the reaction time is 2 hours.

[0016] The beneficial effect of this invention is that it introduces sulfonic acid calixarene as a hydrophilic chain extender into the WPU system for the first time. Its rigid macrocyclic structure not only provides hydrophilic groups but also serves as a strong physical crosslinking point, significantly improving the rigidity and cohesive energy of the molecular chain.

[0017] This invention designs a synergistic structure of aromatic heterocyclic rings (calixarenes) and organosilicon segments. By utilizing the rigidity of calixarenes and the flexibility and low surface energy of siloxanes, a balance of rigidity and flexibility is achieved, simultaneously improving heat resistance, mechanical properties, and water resistance.

[0018] This invention introduces Schiff base groups as thermally triggered crosslinking points, enabling chemical crosslinking to occur during the film forming process, forming a three-dimensional network, which significantly improves dimensional stability and strength at high temperatures.

[0019] The WPU adhesive of the present invention has a significantly higher thermal decomposition temperature of the adhesive film than conventional WPU and single modified WPU, while maintaining excellent mechanical properties and emulsion stability. Attached Figure Description

[0020] Figure 1 This is the DSC test chart for Example 1. Detailed Implementation

[0021] Example 1 A high thermal stability waterborne polyurethane adhesive, comprising the following raw materials: 100g of polycarbonate diol (PCDL, Mn=2000), CAS number of polycarbonate diol is 29862-10-0, molecular formula C 19 H 24 O5, molecular weight 332.39, IPDI 38g, IPDI is isophorone diisocyanate, chemical formula C 12 H 18 N2O2, with a molecular weight of 222.29, 4.2 g of sulfonic acid calix[4]arene (C4AS). Sulfonic acid calix[4]arene (C4AS) is a calixarene derivative modified with sulfonic acid groups. Its molecular structure consists of a benzene ring connected by a methylene bridge to form a cup-shaped cavity. Some hydrogen atoms are replaced by sulfonic acid groups (-SO3H). The CAS number of this compound is 137407-62-6. Hydroxy-terminated silicone oil (Mn=4000) 10g. Hydroxy-terminated silicone oil is a hydroxyl-terminated polydimethylsiloxane with the chemical formula HO[(CH3)2SiO]. n H, CAS number 70131-67-8 N,N'-bis(salicylene)-1,3-propanediamine 1.2g, CAS number 120-70-7, BDO (1,4-butanediol) 6.5g, Triethylamine (neutralizing agent) 4g, 100g of deionized water.

[0022] A high thermal stability waterborne polyurethane adhesive and its preparation method, comprising the following steps: 1) Prepolymer: After PCDL is dehydrated, it is reacted with IPDI at 80℃ for 2 hours. During the reaction, 100g of acetone is added in batches to control the viscosity of the system, and the prepolymer is obtained.

[0023] 2) Organosilicon modification: The prepolymer is cooled to 70°C, hydroxyl silicone oil is added, and the reaction is carried out for 1.5 hours.

[0024] 3) Chain extension: Then add BDO and sulfonic acid calix[4] aromatics and react at 65℃ for 1.5h.

[0025] 4) Schiff base introduction: Cool to 55℃, add N,N'-bis(salicylyl)-1,3-propanediamine, and react for 2 hours.

[0026] 5) Neutralization and emulsification: Cool to 35°C, add triethylamine for neutralization, and emulsify with deionized water under high-speed shear.

[0027] 6) Desolventization: Remove acetone by vacuum distillation to obtain a water-based adhesive product with a solid content of 40%.

[0028] Test results: Thermal stability was tested using DSC, with a maximum decomposition temperature of 370℃; the mechanical properties of the film were tested using a tensile testing machine, showing a tensile strength of 55.7 MPa and an elongation at break of 430%. The DSC test results are shown below. Figure 1 As shown.

[0029] Comparative Example 1 Compared with Comparative Example 1, the difference is that the sulfonic acid calix[4] aromatic hydrocarbon is replaced with dimethylolpropionic acid (DMPA).

[0030] The rest is the same as in Example 1.

[0031] Test results: The thermal stability was tested by DSC, and the maximum decomposition temperature was 325℃; the mechanical properties of the film were tested by tensile testing machine, and the tensile strength was 43MPa and the elongation at break was 361%.

[0032] It can be seen that C4AS's unique rigid macroring structure is irreplaceable in improving thermal stability and mechanical strength. DMPA can only provide hydrophilicity, but cannot introduce a rigid framework and physical cross-linking points.

[0033] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in that the hydroxyl silicone oil is replaced with polyether polyol (PPG, Mn=2000). The rest is the same as Example 1.

[0034] Test results: The thermal stability was tested by DSC, and the maximum decomposition temperature was 335℃; the mechanical properties of the film were tested by a tensile testing machine, and the tensile strength was 46.5MPa and the elongation at break was 410%.

[0035] It can be seen that organosilicon segments play a key role in improving the hydrophobicity, flexibility, and heat resistance of the film. Polyether polyols cannot provide the low surface energy and excellent thermal stability of siloxanes.

[0036] Comparative Example 3 Compared with Example 1, Comparative Example 3 is the same as Example 1 except that it does not contain N,N'-bis(salicylyl)-1,3-propanediamine (Schiff base crosslinking agent).

[0037] Test results: The thermal stability was tested by DSC, and the maximum decomposition temperature was 345℃; the mechanical properties of the film were tested by a tensile testing machine, and the tensile strength was 50.2MPa and the elongation at break was 395%.

[0038] This demonstrates the importance of Schiff base groups in the formation of thermally triggered dynamic crosslinking networks. Without this component, the network structure and strength retention of the film at high temperatures will significantly decrease.

[0039] Comparative Example 4 Compared with Example 1, Comparative Example 4 differs in that the sulfonic acid calix[4] aromatic hydrocarbon is replaced with hydroquinone bis(hydroxyethyl) ether-5-sulfonate sodium.

[0040] The rest is the same as in Example 1.

[0041] Test results: The thermal stability was tested by DSC, and the maximum decomposition temperature was 330℃; the mechanical properties of the film were tested by a tensile testing machine, and the tensile strength was 44.9MPa and the elongation at break was 370%.

[0042] It can be seen that the special macrocyclic cavity structure of sulfonic acid calix[4] aromatics is the core of performance improvement, rather than a simple acid group. General linearizing agents cannot provide the same rigid support and cavity effect.

[0043] The performance of the adhesives in Example 1 and Comparative Examples 1-4 is shown in Table 1.

[0044] Table 1 Comparison of basic properties of adhesives

[0045] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0046] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A high-heat-stable waterborne polyurethane adhesive, characterized by, The polyurethane adhesive comprises the following raw materials by weight: Polycarbonate diol 100 parts, IPDI 30-40 parts, sulfonic acid-based calix[4]arene 3-6 parts, hydroxyl silicone oil 8-15 parts, N,N'-bis(salicylidene)-1,3-propanediamine 0.5-2 parts, BDO 5-8 parts, triethylamine 2-6 parts, and deionized water 80-120 parts.

2. The high thermal stability waterborne polyurethane adhesive as described in claim 1, characterized in that, The polyurethane adhesive comprises the following raw materials by weight: Polycarbonate diol 100 parts, IPDI 35-40 parts, sulfonic acid-based calix[4]arene 4-5 parts, hydroxyl silicone oil 8-12 parts, N,N'-bis(salicylidene)-1,3-propanediamine 1-2 parts, BDO 6-7 parts, triethylamine 3-5 parts, and deionized water 90-110 parts.

3. The high-heat-stable waterborne polyurethane adhesive according to claim 2, wherein the polyol component comprises a polyol having a hydroxyl group content of 2.0 to 5.0 mol / kg. The polyurethane adhesive comprises the following raw materials by weight: Polycarbonate diol 100 parts, IPDI 38 parts, sulfonic acid-based calix[4]arene 4.2 parts, hydroxyl silicone oil 10 parts, N,N'-bis(salicylidene)-1,3-propanediamine 1.2 parts, BDO 6.5 parts, triethylamine 4 parts, and deionized water 100 parts.

4. The high-heat-stable waterborne polyurethane adhesive according to any one of claims 1 to 3, characterized in that, The Mn of the polycarbonate diol is 2000, and the Mn of the hydroxyl silicone oil is 4000.

5. A process for preparing a high-heat-stable waterborne polyurethane adhesive according to any one of claims 1 to 4, characterized by, The polyurethane adhesive comprises the following steps: 1) Pre-polymerization: after dehydration of the polycarbonate diol, the polycarbonate diol is reacted with IPDI at 80-90°C to obtain a pre-polymer; 2) Silicone modification: the pre-polymer is cooled to 70°C, and the hydroxyl silicone oil is added and reacted; 3) Chain extension: then, BDO and sulfonic acid-based calix[4]arene are added and reacted at 60-70°C; 4) Schiff base introduction: the temperature is lowered to 50-60°C, N,N'-bis(salicylidene)-1,3-propanediamine is added, and the reaction is carried out; 5) Neutralization and emulsification: the temperature is lowered to 30-40°C, triethylamine is added for neutralization, and deionized water is added for emulsification; 6) Desolvation: vacuum distillation is carried out to obtain a high-heat-stable water-based polyurethane adhesive.

6. The production method according to claim 5, wherein In the pre-polymerization reaction, acetone is added in batches to control the viscosity of the system.

7. The production method according to claim 5, wherein the production method is characterized by, The temperature of the pre-polymerization reaction is 80°C, and the time is 2h.

8. The production method according to claim 5, wherein The reaction time of the silicone modification is 1.5h.

9. The production method according to claim 5, wherein the production method is characterized by, The reaction temperature of the chain extension is 65°C, and the time is 1.5h.

10. The production method according to claim 5, wherein In step 4), the temperature is lowered to 55°C, and the reaction time is 2h.

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