Single-component polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of polyurethane hot melt adhesives, and particularly relates to a single-component polyurethane hot melt adhesive and a preparation method thereof, the single-component polyurethane hot melt adhesive comprises the following raw materials by mass: 20-70 parts of polyether polyol; 1 to 50 parts of polyester polyol; 1 to 20 parts of polyisocyanate; 10 to 20 parts of tackifying resin; 5 to 20 parts of hollow microbeads; 0.5 to 1 part of a leveling agent; 1-3 parts of a coupling agent I; 0.01 to 1 part of a catalyst; wherein the particle size of the hollow microbeads is 20-125 [mu] m. Through optimized raw material combination and proportion, the hot melt adhesive simultaneously shows low elastic modulus, high rebound resilience, high bonding strength and excellent fatigue resistance after being cured, an adhesive layer can adapt to large interface deformation due to the combination characteristic, the shape can be rapidly recovered after stress, and the anti-fatigue performance of the hot melt adhesive is improved. And meanwhile, the adhesive still keeps firm adhesion under long-term dynamic load, and is particularly suitable for application occasions with higher requirements on flexibility and durability.

Description

Technical Field

[0001] This invention relates to a single-component polyurethane hot melt adhesive and its preparation method, belonging to the field of polyurethane hot melt adhesive technology. Background Technology

[0002] With the continuous improvement of industrial development, higher requirements are being placed on the comprehensive performance of adhesives. In various application scenarios such as bonding flexible screens and frames in electronic products and fixing interior parts in automobiles, adhesives are required not only to have high bonding strength to ensure reliable connection of the bonded parts, but also to have a low modulus so that they can adapt to certain deformations under external forces or thermal stress, avoiding cracking of the adhesive layer or delamination of the interface due to stress concentration; at the same time, excellent weather resistance and resistance to damp heat are also important indicators in practical applications.

[0003] However, traditional polyurethane hot melt adhesives often fall short in balancing modulus and strength. Specifically, to achieve higher bond strength, high-modulus raw materials are typically required, but this results in excessive rigidity and reduced flexibility of the adhesive layer, making it prone to cracking or delamination when subjected to impact or thermal expansion and contraction caused by environmental temperature changes. Conversely, if the modulus is reduced to improve flexibility through formulation adjustments, the bond strength often decreases significantly, failing to meet application requirements. Furthermore, some existing polyurethane hot melt adhesives also suffer from slow curing speeds and poor resistance to damp heat, further limiting their application expansion in high-end industrial fields. Summary of the Invention

[0004] In view of the above-mentioned technical problems in the prior art, the present invention provides a single-component polyurethane hot melt adhesive and its preparation method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: One objective of this invention is to provide a one-component polyurethane hot melt adhesive, comprising the following raw materials in parts by weight: 20-70 parts of polyether polyol, wherein the molecular weight of the polyether polyol is 400-4000; 1 to 50 parts of polyester polyol, wherein the molecular weight of the polyester polyol is 2000 to 4000; 1-20 parts of polyisocyanate; 10-20 parts of tackifying resin; 5-20 parts of hollow microspheres; Leveling agent 0.5 to 1 part; Coupling agent 1-3 parts; Catalyst 0.01 to 1 part; The hollow microspheres have a particle size of 20–125 μm.

[0006] The beneficial effects of this invention are as follows: This invention, through optimized raw material combination and ratio, enables the hot melt adhesive to exhibit low elastic modulus, high resilience, high adhesive strength, and excellent fatigue resistance after curing. This combination of characteristics allows the adhesive layer to adapt to large interfacial deformation and quickly recover its shape after being subjected to stress, while maintaining a firm bond under long-term dynamic loads. It is especially suitable for applications that require high flexibility and durability.

[0007] This invention significantly reduces the colloidal modulus and improves resilience by introducing hollow microspheres and using tackifying resins to meet deformation requirements.

[0008] The present invention combines polyester polyol and polyether polyol to enhance cohesive strength; the tackifying resin improves interfacial adhesion, enabling the colloid to maintain high strength and fatigue resistance even at low modulus.

[0009] The hot melt adhesive of this invention is suitable for a variety of harsh environments such as electronics, automobiles, and construction, and performs particularly well in high-end applications such as narrow bezels and flexible screens.

[0010] Based on the above technical solution, the present invention can also be improved as follows: Furthermore, the hollow microparticles are selected from one or more of hollow glass microspheres, hollow plastic microspheres, and hollow rubber microspheres.

[0011] Furthermore, the hollow microspheres undergo pretreatment, which involves mixing hollow microparticles with a particle size of 30–200 μm with an organosilane coupling agent at 50–100 °C, drying, and sieving to obtain hollow microspheres; the particle size of the hollow microspheres is 50–90 μm.

[0012] The addition of hollow microspheres can reduce the density of hot melt adhesive, thereby reducing the modulus while maintaining strength, and improving the flexibility and impact resistance of the adhesive layer.

[0013] Furthermore, the organosilane coupling agent is γ-mercaptopropyltrimethoxysilane.

[0014] Furthermore, the tackifying resin comprises at least one of hydroxyl-terminated rubber and modified hydroxyl-terminated acrylate, and the tackifying resin accounts for 10% or more of the total mass of the raw materials. The modified hydroxyl-terminated acrylate has a molecular weight of 1500 to 2500, and its side chain comprises at least one of benzene ring, ester group or hydroxyl group.

[0015] Tackifying resins can significantly improve the surface adhesion of hot melt adhesives to various substrates, improve initial tack, and enhance the adhesion between the adhesive layer and the adhered objects.

[0016] Furthermore, the polyether polyol is selected from at least one of polypropylene glycol, polyethylene glycol, and polytetrahydrofuran glycol.

[0017] The molecular structure of polyether polyols endows hot melt adhesives with good flexibility, which can effectively reduce the modulus and provide space for molecular chains to move, thus improving the elastic recovery ability of the adhesive layer.

[0018] Furthermore, the polyester polyol is selected from at least one of diacid-based polyester diol, polycarbonate diol, polyethylene terephthalate, and phthalic anhydride polyester polyol.

[0019] Polyester polyols can enhance the cohesive strength of hot melt adhesives. They work synergistically with polyether polyols to improve overall bond strength and chemical resistance while maintaining low modulus.

[0020] Furthermore, the polyisocyanate is selected from at least one of diphenylmethane diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate.

[0021] Polyisocyanates act as crosslinking agents in the reaction, reacting with the hydroxyl groups of polyether polyols and polyester polyols to form a three-dimensional network structure, which plays a key role in the strength and curing performance of hot melt adhesives.

[0022] Furthermore, the catalyst is selected from one or more organotin or amine catalysts.

[0023] Furthermore, the leveling agent is selected from one or more of acrylic, silicone, and fluorinated leveling agents; the leveling agent can improve the flowability and leveling properties of hot melt adhesive during the coating process, so that the adhesive layer is evenly distributed, and improve the bonding quality and appearance.

[0024] Furthermore, the coupling agent is a silane coupling agent; the coupling agent can enhance the interfacial bonding force between different raw materials, improve the overall performance of the hot melt adhesive, and promote the synergistic effect between the components.

[0025] A second objective of this invention is to provide a method for preparing the single-component polyurethane hot melt adhesive as described above, comprising the following steps: (1) Add polyether polyol, polyester polyol, tackifying resin and hollow microspheres into the reactor, heat to 110-140°C, and dehydrate under vacuum for 2-3 hours; (2) Cool down to 60-70℃, add polyisocyanate under nitrogen protection, and react at 80-140℃ for 0.5-2 hours to generate isocyanate-terminated prepolymer; (3) Add catalyst, leveling agent and coupling agent one under nitrogen protection, and stir under vacuum at 80-140°C for 0.5-1.5 hours, then discharge.

[0026] The preparation method of the present invention has mild process conditions, simple operation and control, and requires no special equipment, which is conducive to achieving stable industrial production, reducing production costs, and has good economic and practical value. Detailed Implementation

[0027] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1 1. Raw material preparation: 40 parts of polyether polyol (polypropylene glycol, molecular weight 2000), 20 parts of polyester polyol (polycarbonate diol, molecular weight 3000), 8 parts of polyisocyanate (diphenylmethane diisocyanate), 15 parts of tackifying resin (hydroxyl-terminated polybutadiene), 10 parts of hollow microspheres (made by mixing hollow glass microspheres with organosilane coupling agent diluted with solvent, heating and drying, and the particle size after treatment is 50μm), 0.8 parts of leveling agent (organosilicon), 2 parts of coupling agent one (silane coupling agent), and 0.05 parts of catalyst (organotin). 2. Preparation process: Polyether polyol, polyester polyol, tackifying resin and hollow microspheres were added to a reactor, heated to 120°C, and stirred and dehydrated under vacuum for 2.5 hours.

[0029] The temperature was lowered to 65°C, and polyisocyanate was added under N2 protection. The mixture was stirred at 100°C for 1.5 hours to generate isocyanate-terminated polyurethane prepolymer.

[0030] Under N2 protection, add catalyst, leveling agent, and coupling agent one, and stir under vacuum at 100°C for 1 hour before discharging. Tests showed that the adhesive performance of the hot melt adhesive did not decrease significantly after 1,000 fatigue tests.

[0031] Example 2 1. Raw material preparation: 50 parts of polyether polyol (polyethylene glycol, molecular weight 3000), 15 parts of polyester polyol (adipic acid-based polyester glycol, molecular weight 2500), 6 parts of polyisocyanate (hexamethylene diisocyanate), 12 parts of tackifying resin (modified hydroxyl-terminated acrylate, side chain containing benzene ring, molecular weight 2000), 8 parts of hollow microspheres (hollow plastic microspheres with a particle size of 80μm after treatment), 0.6 parts of leveling agent (acrylic), 1.5 parts of coupling agent one (silane coupling agent), and 0.08 parts of catalyst (amine). 2. Preparation process: Polyether polyol, polyester polyol, tackifying resin and hollow microspheres are added to a reactor, heated to 130°C, and stirred and dehydrated under vacuum for 2 hours.

[0032] The temperature was lowered to 70°C, and polyisocyanate was added under N2 protection. The mixture was stirred at 120°C for 1 hour to generate isocyanate-terminated polyurethane prepolymer.

[0033] Under N2 protection, the catalyst, leveling agent, and coupling agent 1 are added, and the mixture is vacuumed at 120°C and stirred for 0.8 hours before being discharged. Tests showed that the hot melt adhesive maintained good bonding performance after being placed in an environment of 80℃ and 90% humidity for 7 days. Comparative Example 1 Polyurethane hot melt adhesive was prepared using a conventional formulation and preparation method. The raw materials included 30 parts of polyether polyol (molecular weight 2000), 30 parts of polyester polyol (molecular weight 3000), 10 parts of polyisocyanate (diphenylmethane diisocyanate), 10 parts of tackifying resin (ordinary acrylic resin), no hollow microspheres added, 0.5 parts of leveling agent (organosilicon), 1 part of coupling agent (ordinary coupling agent), and 0.03 parts of catalyst (organotin).

[0034] The preparation process involves mixing the raw materials and heating them to 100°C for 2 hours, without any special protection or post-treatment steps.

[0035] Tests showed that the adhesive properties of the hot melt adhesive decreased significantly after 500 fatigue cycles.

[0036] The performance of the hot melt adhesives in the examples and comparative examples was tested, and the results are shown in Table 1.

[0037] Table 1 Performance Test Table of Examples and Comparative Examples

[0038] By comparing the examples and comparative examples, it can be seen that the single-component polyurethane hot melt adhesive prepared by the present invention has significant advantages in various properties. By optimizing the raw material combination and process conditions, the present invention has successfully prepared a polyurethane hot melt adhesive with low modulus, high strength, high resilience and excellent durability, which has broad application prospects.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A one-component polyurethane hot melt adhesive, characterized in that, By weight, it includes the following raw materials: 20-70 parts of polyether polyol; 1-50 parts of polyester polyol; 1-20 parts of polyisocyanate; 10-20 parts of tackifying resin; 5-20 parts of hollow microspheres; Leveling agent 0.5 to 1 part; Coupling agent 1-3 parts; Catalyst 0.01 to 1 part; The hollow microspheres have a particle size of 20–125 μm.

2. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The hollow microparticles are selected from one or more of hollow glass microspheres, hollow plastic microspheres, and hollow rubber microspheres.

3. The single-component polyurethane hot melt adhesive according to claim 2, characterized in that, The hollow microspheres are pretreated by mixing hollow microparticles with a particle size of 30-200 μm with an organosilane coupling agent at 50-100°C, drying, and sieving to obtain hollow microspheres; the particle size of the hollow microspheres is 50-90 μm.

4. The single-component polyurethane hot melt adhesive according to claim 3, characterized in that, The organosilane coupling agent is γ-mercaptopropyltrimethoxysilane.

5. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The tackifying resin comprises at least one of hydroxyl-terminated rubber and modified hydroxyl-terminated acrylate, and the tackifying resin accounts for 10% or more of the total mass of the raw materials. The modified hydroxyl-terminated acrylate has a molecular weight of 1500 to 2500, and its side chain comprises at least one of benzene ring, ester group or hydroxyl group.

6. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The polyether polyol is selected from at least one of polypropylene glycol, polyethylene glycol, and polytetrahydrofuran glycol.

7. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The polyester polyol is selected from at least one of the following: bisacrylic acid polyester diol, polycarbonate diol, polyethylene terephthalate, and phthalic anhydride polyester polyol.

8. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The polyisocyanate is selected from at least one of diphenylmethane diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate.

9. The single-component polyurethane hot melt adhesive according to claim 1, characterized in that, The catalyst is selected from one or more of organotin or amine catalysts; the leveling agent is selected from one or more of acrylic, organosilicon, and fluorine leveling agents; and the coupling agent is a silane coupling agent.

10. A method for preparing a single-component polyurethane hot melt adhesive as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Add polyether polyol, polyester polyol, tackifying resin and hollow microspheres into the reactor, heat to 110-140°C, and dehydrate under vacuum for 2-3 hours; (2) Cool down to 60-70℃, add polyisocyanate under nitrogen protection, and react at 80-140℃ for 0.5-2 hours to generate isocyanate-terminated prepolymer; (3) Add catalyst, leveling agent and coupling agent one under nitrogen protection, and stir under vacuum at 80-140°C for 0.5-1.5 hours, then discharge.

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