Modified curing reaction type PUR hot melt adhesive resin and preparation method thereof

Abstract

The invention relates to the technical field of thermoplastic polyurethane hot melt adhesives, and particularly discloses a modified curing reaction type PUR hot melt adhesive resin and a preparation method thereof. The PUR hot melt adhesive resin is prepared from the following raw materials: a diisocyanate compound, polycarbonate polyol, polyether polyol, glycidyl ether, a catalyst, an antioxidant and a filler, the diisocyanate compound is modified through glycidyl ether, and modified MDI which has an isocyanate group as a terminal group and contains an oxazolidinone structure is obtained; then the modified MDI containing the oxazolidinone structure is introduced into the PUR hot melt adhesive resin, so that the high temperature resistance and the toughness of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane hot melt adhesive technology, and specifically discloses a modified curing reactive PUR hot melt adhesive resin and its preparation method. Background Technology

[0002] Polyurethane reactive hot melt adhesives (PURs) are widely used in various industrial fields such as automotive, electronics, textiles, packaging, and construction due to their excellent bonding properties, good flexibility, and chemical resistance. However, traditional thermoplastic polyurethane (TPU) resins, as the base material for hot melt adhesives, have significant limitations in performance. Typically, TPU has a narrow long-term operating temperature range, generally between 40°C and 100°C. When the ambient temperature exceeds 100°C, the movement of the material's molecular chains intensifies, causing it to soften rapidly, lose mechanical strength, and deform, which greatly limits its application in high-temperature conditions.

[0003] Furthermore, traditional TPU hot melt adhesives exhibit mediocre performance in terms of overall properties such as abrasion resistance, surface hardness, and gloss. In applications requiring high abrasion resistance, high hardness, or specific aesthetic requirements, significant filler additions or post-treatment are often necessary, which can negatively impact bonding and processing properties. While reactive polyurethane hot melt adhesives (PURs) improve heat resistance, solvent resistance, and bonding strength to some extent by introducing terminal isocyanate groups (-NCO) that react with moisture in the air to form a cross-linked network structure after curing, their initial heat resistance still primarily depends on the structure of the polyol and isocyanate used. Conventional polyester or polyether polyol backbones are still prone to thermal degradation or softening at high temperatures, making it difficult to exceed 130°C in their long-term operating temperature range.

[0004] To further improve the overall performance of PUR hot melt adhesives, existing technologies have attempted to introduce heat-resistant fillers (such as nano-silica and carbon fibers) or rigid monomers through physical blending or chemical modification. However, physical blending often suffers from poor compatibility and uneven dispersion, leading to unstable material properties; while simple chemical modification struggles to improve heat resistance while simultaneously maintaining the material's processing flowability, initial tack, and final mechanical properties. In particular, how to significantly improve the high-temperature resistance (e.g., long-term operating temperature ≥150℃) and toughness of the cured adhesive film while ensuring good hot melt processing performance (i.e., moderate melt viscosity and suitable open time) remains a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a modified curing reactive PUR hot melt adhesive resin and its preparation method, which can improve the resin's high temperature resistance and toughness.

[0006] This invention is achieved through the following technical solution: A modified curable reactive PUR hot melt adhesive resin, comprising, by weight, the following raw materials: 20-35 parts of diisocyanate compound, 15-25 parts of polycarbonate polyol, 10-15 parts of polyether polyol, 10-20 parts of glycidyl ether, 0.1-0.3 parts of catalyst, 0.1-0.5 parts of antioxidant, and 5-15 parts of filler.

[0007] Preferably, the diisocyanate compound includes MDI and / or MDI50.

[0008] Preferably, the polycarbonate polyol has a molecular weight of 800-1200 and a hydroxyl value of 112±2 mgKOH / g; the polyether polyol has a molecular weight of 2500-3000 and a hydroxyl value of 38±2 mgKOH / g. More preferably, the polycarbonate polyol is a polycarbonate diol.

[0009] Preferably, the glycidyl ether comprises one or more of 1,4-butanediol glycidyl ether, 1,6-hexanediol glycidyl ether, and neopentyl glycol glycidyl ether.

[0010] Preferably, the catalyst comprises one or more of 2,4,6-tris(dimethylaminomethyl)phenol and dibutyltin dilaurate.

[0011] Preferably, the antioxidant includes one or more of 2,6-di-tert-butyl-p-phenol and triphenyl phosphite.

[0012] Preferably, the filler comprises one or more of calcium carbonate, talc, and fumed silica.

[0013] A method for preparing a modified, curable reactive PUR hot melt adhesive resin includes the following steps: Step 1: Modify diisocyanate compounds with glycidyl ether to obtain modified MDI with an oxazolidinone structure containing isocyanate groups at the end; Step 2: Heat polycarbonate polyol, polyether polyol and filler to 120℃, dehydrate under vacuum, add modified MDI and catalyst, heat to 100-110℃ for reaction until NCO value is 0, add diisocyanate compound and continue reaction at 100-110℃ until NCO value is 1.0-2.0%, cool to 90-100℃, add antioxidant, degas under vacuum, discharge to obtain cured reactive PUR hot melt adhesive resin.

[0014] Preferably, in step one, the diisocyanate compound and glycidyl ether are mixed, a catalyst is added, and the mixture is heated to 110-120°C and reacted for 2-3 hours until the NCO value is 10-11%, then cooled for later use.

[0015] Preferably, vacuum dehydration is carried out for 1-2 hours under a negative pressure of 0.0975 MPa.

[0016] The technical solution of the present invention has at least the following advantages and beneficial effects: The curing reactive PUR hot melt adhesive of this invention is produced under solvent-free conditions. First, a diisocyanate compound is modified with a diepoxy-containing glycidyl ether to obtain a modified MDI containing an oxazolidinone structure with isocyanate end groups, thereby introducing the oxazolidinone structure into the PUR hot melt adhesive resin. The oxazolidinone structure itself possesses high thermal stability. When introduced into the polymer backbone, it acts as a rigid structural unit, effectively restricting the movement of polymer chain segments, thus increasing the glass transition temperature of the material and allowing it to maintain its mechanical properties at higher temperatures. The rigid oxazolidinone domains, acting as the "hard phase," provide the material's strength and stiffness, while the inherent flexible segments in polyurethane form the "soft phase" or rubber phase, responsible for absorbing impact energy and preventing crack propagation. When the material is subjected to external impact, these dispersed rubber phases can induce crazes and shear bands, effectively terminating cracks and absorbing a large amount of impact energy. Simultaneously, the oxazolidinone ring itself can integrate into the polymer crosslinking network, optimizing the density and uniformity of the crosslinking network and contributing to overall strength. This synergistic effect of combining rigidity and flexibility allows the material to achieve a significant increase in strength while also substantially improving its toughness. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0018] Example 1 A method for preparing a modified, curable reactive PUR hot melt adhesive resin includes the following steps: Step 1: Mix 30 parts of MDI50 and 15 parts of 1,4-butanediol glycidyl ether in a reaction vessel, add 0.1 parts of 2,4,6-tris(dimethylaminomethyl)phenol, heat to 120℃ and react for 2.5 h until the NCO value is 10-11%, then cool down for later use to obtain modified MDI with an oxazolidinone structure at the end of isocyanate groups; Step 2: Heat 15 parts of polycarbonate diol, 10 parts of polyether polyol, and 5 parts of talc to 120°C and dehydrate under vacuum for 2 hours under a negative pressure of 0.0975 MPa. Add 0.1 parts of modified MDI and dibutyltin dilaurate and heat to 110°C for 1.5 hours until the NCO value is 0. Add 5 parts of MDI and continue to react at 110°C for 1.5 hours until the NCO value is 1.0-2.0%. Cool to 100°C and add 0.2 parts of 2,6-di-tert-butyl-p-phenol. Degas under vacuum and discharge to obtain a reactive PUR hot melt adhesive resin with isocyanate end groups and an NCO value of 1.0-2.0%.

[0019] Example 2 A method for preparing a modified, curable reactive PUR hot melt adhesive resin includes the following steps: Step 1: Mix 20 parts of MDI50 and 25 parts of 1,6-hexanediol glycidyl ether and add them to a reaction vessel. Add 0.2 parts of 2,4,6-tris(dimethylaminomethyl)phenol, heat to 110℃ and react for 2 hours until the NCO value is 10-11%. Cool down and set aside to obtain modified MDI with an oxazolidinone structure containing isocyanate groups at the end. Step 2: Heat 20 parts of polycarbonate diol, 15 parts of polyether polyol, and 10 parts of calcium carbonate to 120°C, and dehydrate under vacuum for 1 hour under a negative pressure of 0.0975 MPa. Add 0.1 parts of modified MDI and dibutyltin dilaurate, and heat to 110°C to react for 1.5 hours until the NCO value is 0. Add 5 parts of MDI and continue to react at 110°C for 1.5 hours until the NCO value is 1.0-2.0%. Cool to 100°C, add 0.1 parts of triphenyl phosphite, degas under vacuum, and discharge to obtain a reactive PUR hot melt adhesive resin with isocyanate end groups and an NCO value of 1.0-2.0%.

[0020] Example 3 A method for preparing a modified, curable reactive PUR hot melt adhesive resin includes the following steps: Step 1: Mix 10 parts of MDI50 and 20 parts of neopentyl glycol glycidyl ether and add them to a reaction vessel. Add 0.15 parts of 2,4,6-tris(dimethylaminomethyl)phenol, heat to 120℃ and react for 2.5 h until the NCO value is 10-11%. Cool down and set aside to obtain modified MDI with an oxazolidinone structure containing isocyanate groups at the end. Step 2: Heat 25 parts of polycarbonate diol, 12 parts of polyether polyol, and 15 parts of fumed silica to 120°C and dehydrate under vacuum at a negative pressure of 0.0975 MPa for 1.5 hours. Add 0.15 parts of modified MDI and dibutyltin dilaurate and heat to 105°C for 2 hours until the NCO value is 0. Add 5 parts of MDI and continue to react at 105°C for 2 hours until the NCO value is 1.0-2.0%. Cool down to 95°C and add 0.5 parts of 2,6-di-tert-butyl-p-phenol. Degas under vacuum and discharge to obtain a reactive PUR hot melt adhesive resin with isocyanate end groups and an NCO value of 1.0-2.0%.

[0021] Comparative Example 1 The difference between this comparative example and Example 1 is that the MDI is not modified, and the resin is prepared as follows: Add 15 parts of polycarbonate diol, 10 parts of polyether polyol, and 5 parts of talc to a reactor. Heat to 120℃ and dehydrate under vacuum at a negative pressure of 0.0975 MPa for two hours. Cool to 110℃ and add 30 parts of MDI and 0.3 parts of dibutyltin dilaurate. React for 2.5 hours, and check the NCO value to be 1.0-2.0%. Cool to 100℃ and add 0.2 parts of 2,6-di-tert-butyl-p-phenol. Degas under vacuum and package the product.

[0022] Comparative Example 2 The difference between this comparative example and Example 1 is that the polycarbonate diol content is increased, and the resin preparation method is as follows: 30 parts of MDI50 and 15 parts of 1,4-butanediol glycidyl ether were mixed and added to a reaction vessel. 0.1 parts of 2,4,6-tris(dimethylaminomethyl)phenol were added, and the mixture was heated to 120°C and reacted for 2.5 h. The NCO value was 10-11%, and modified MDI with an isocyanate end group containing an oxazolidinone structure was obtained. 30 parts of polycarbonate diol, 10 parts of polyether polyol, and 5 parts of talc were heated to 120°C and vacuum-dehydrated for 2 hours under a negative pressure of 0.0975 MPa. Modified MDI and 0.1 parts of dibutyltin dilaurate were added, and the temperature was raised to 110°C for 1.5 hours. Then, 5 more parts of MDI were added, and the reaction was continued at 110°C for another 1.5 hours. Finally, 0.2 parts of 2,6-di-tert-butyl-p-phenol were added, and the mixture was degassed under vacuum. The product was then discharged. Because the increased polycarbonate diol content resulted in insufficient NCO content, no NCO residue was found after the addition of MDI. The resulting product was a PUR hot melt adhesive that could not be wet-cured.

[0023] Comparison of resin performance parameters: Tensile strength and breaking strength: Refer to ASTM D638; Shear strength: Refer to GB7124-86; Curing speed and strength after 24 hours of application: Refer to GB7124-86; Table 1

[0024] As can be seen from Table 1, the resin in Example 1, due to its oxazolidinone structure, exhibits better high-temperature resistance, higher cured strength, and better resistance to salt spray and aging. In contrast, the conventional hot melt adhesive in Comparative Example 1 clearly cannot withstand high temperatures, and in Comparative Example 2, the addition of too much polycarbonate diol and incorrect parameters resulted in insufficient NCO participation in the wet curing process, leading to a significant decrease in the adhesive's aging resistance and strength.

[0025] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified, curing reactive PUR hot melt adhesive resin, characterized in that, By weight, it includes the following raw materials: 20-35 parts of diisocyanate compounds, 15-25 parts of polycarbonate polyol, 10-15 parts of polyether polyol, 10-20 parts of glycidyl ether, 0.1-0.3 parts of catalyst, 0.1-0.5 parts of antioxidant and 5-15 parts of filler.

2. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The diisocyanate compounds include MDI and / or MDI50.

3. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The polycarbonate polyol has a molecular weight of 800-1200 and a hydroxyl value of 112±2 mgKOH / g; the polyether polyol has a molecular weight of 2500-3000 and a hydroxyl value of 38±2 mgKOH / g.

4. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The glycidyl ethers include one or more of 1,4-butanediol glycidyl ether, 1,6-hexanediol glycidyl ether, and neopentyl glycol glycidyl ether.

5. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The catalyst comprises one or more of 2,4,6-tris(dimethylaminomethyl)phenol and dibutyltin dilaurate.

6. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The antioxidant includes one or more of 2,6-di-tert-butyl-p-phenol and triphenyl phosphite.

7. The modified curing reactive PUR hot melt adhesive resin according to claim 1, characterized in that, The filler includes one or more of calcium carbonate, talc, and fumed silica.

8. The method for preparing the modified curable reactive PUR hot melt adhesive resin according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Modify diisocyanate compounds with glycidyl ether to obtain modified MDI with an oxazolidinone structure containing isocyanate groups at the end; Step 2: Heat polycarbonate polyol, polyether polyol and filler to 120℃, dehydrate under vacuum, add modified MDI and catalyst, heat to 100-110℃ for reaction until NCO value is 0, add diisocyanate compound and continue reaction at 100-110℃ until NCO value is 1.0-2.0%, cool to 90-100℃, add antioxidant, degas under vacuum, discharge to obtain cured reactive PUR hot melt adhesive resin.

9. The method for preparing the modified, curing reactive PUR hot melt adhesive resin according to claim 8, characterized in that, In step one, diisocyanate compounds and glycidyl ether are mixed, a catalyst is added, and the mixture is heated to 110-120℃ and reacted for 2-3 hours until the NCO value is 10-11%. The mixture is then cooled and stored for later use.

10. The method for preparing the modified, curing reactive PUR hot melt adhesive resin according to claim 8, characterized in that, Vacuum dehydration was carried out for 1-2 hours under a negative pressure of 0.0975 MPa.

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