Formula and preparation method of high-temperature-resistant polyurethane hot melt adhesive film

Abstract

The invention discloses a formula of a high-temperature-resistant polyurethane hot melt adhesive film and a preparation method of the high-temperature-resistant polyurethane hot melt adhesive film, and belongs to the technical field of polyurethane hot melt adhesives. The invention provides a formula of a high-temperature-resistant TPU (thermoplastic polyurethane) type hot melt adhesive membrane. The high-temperature-resistant TPU type hot melt adhesive membrane is prepared from the following components in parts by weight: 60-75 parts of polyalcohol, 25-32 parts of diisocyanate, 10-14 parts of a chain extender, 2-4 parts of a catalyst, 12-18 parts of polyhedral oligomeric silsesquioxane, 9-15 parts of diatomite, 0.5-2 parts of a crosslinking additive and 0.3-3 parts of an antioxidant. The polyhydric alcohol is prepared from polycarbonate diol, modified polypropylene oxide diol and epoxypropane-ethylene oxide copolyether triol. According to the invention, the limitation of a traditional TPU type hot melt adhesive in a high-temperature scene is overcome, and the prepared polyurethane hot melt adhesive film has excellent high temperature resistance and final adhesion strength, has a lower application threshold compared with a PUR type hot melt adhesive, and has good market competitiveness.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane hot melt adhesive technology, specifically relating to a formulation and preparation method of a high-temperature resistant polyurethane hot melt adhesive film. Background Technology

[0002] Polyurethane hot melt adhesives form initial tack through melting and application followed by cooling, and then achieve final curing through physical or chemical cross-linking. With its advantages of fast curing speed, high bond strength, and good elasticity and toughness, it is widely used in automotive manufacturing, electronic packaging, textile composites, and furniture assembly. Currently, commercially available products are mainly divided into two categories: thermoplastic polyurethane (TPU) and moisture-reactive polyurethane (PUR). These two types differ fundamentally in their molecular structure design, leading to significant differentiation in performance characteristics and application scenarios.

[0003] PUR-type hot melt adhesives incorporate terminal isocyanate groups, triggering a cross-linking reaction by absorbing ambient moisture to form a three-dimensional network structure. While this chemical curing mechanism endows it with excellent temperature resistance (long-term operating temperature can reach above 140℃), solvent resistance, and high bonding strength, its moisture-induced chemical cross-linking curing is an irreversible process, making rework and repair impossible after application. Furthermore, its complex curing process requires specialized equipment and a closed application system, significantly increasing overall costs and raising the application threshold.

[0004] Unlike PUR-type hot melt adhesives, TPU-type hot melt adhesives, based on a linear molecular chain structure, possess the characteristic of repeated melt-curing. Their core advantages lie in their strong process compatibility (they can be processed using conventional extrusion equipment), reversible curing process (allowing for recycling), significantly reduced raw material and processing costs compared to PUR-type hot melt adhesives, higher initial bond strength, and shorter curing time. However, due to their thermoplastic nature, their heat resistance is generally below 120℃, and they are prone to creep or bond strength decay at high temperatures, posing significant limitations in applications such as engine compartment wiring harness fixing and high-temperature encapsulation of electronic components.

[0005] In view of this, given the current imperfect process performance of PUR-type hot melt adhesive products, which leads to high application barriers, it is still necessary to research a high-temperature resistant TPU-type hot melt adhesive. Summary of the Invention

[0006] In view of the above-mentioned content, the purpose of this invention is to provide a formulation and preparation method for a high-temperature resistant polyurethane hot melt adhesive film. By further optimizing the raw material formulation, this invention overcomes the defects of traditional TPU hot melt adhesives, such as poor high-temperature resistance and low final bond strength, thereby effectively expanding the application range of TPU hot melt adhesives.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution: This invention provides a formulation for a high-temperature resistant polyurethane hot melt adhesive film, comprising the following raw materials by weight: 60-75 parts of polyol 25-32 parts of diisocyanate 10-14 parts of chain extender 2-4 parts of catalyst 12-18 parts of cage-type polysilsesquioxane 9-15 parts diatomaceous earth Crosslinking additive 0.5-2 parts Antioxidant 0.3-3 parts; The polyol is composed of polycarbonate diol, modified polypropylene glycol, and propylene oxide-ethylene oxide copolyether triol.

[0008] Furthermore, the polypolyol is composed of polycarbonate diol, modified polypropylene oxide diol, and propylene oxide-ethylene oxide copolyether triol in a mass ratio of 10:(3.2-4.5):(3-6).

[0009] Furthermore, the preparation method of the modified polypropylene glycol is as follows: polypropylene glycol is preheated in a protective gas to remove water, and then a polymerization inhibitor, a catalyst and a solvent are added in sequence. Glycidyl methacrylate is slowly added under constant temperature and stirring. After the reaction is completed, the modified polypropylene glycol is obtained.

[0010] Further, the polymerization inhibitor is 4-methoxyphenol and the catalyst is tetrabutylammonium bromide; the mass ratio of polypropylene glycol, 4-methoxyphenol, tetrabutylammonium bromide and glycidyl methacrylate is 100:(0.1-0.2):(0.05-0.3):(6-11).

[0011] Further, the diisocyanate is at least one of 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0012] Furthermore, the chain extender is hydroquinone dihydroxyethyl ether.

[0013] Furthermore, the catalyst is dibutyltin dilaurate.

[0014] Furthermore, the cage-like polysilsesquioxane is a vinylheptaoctyl cage-like polysilsesquioxane.

[0015] Furthermore, the crosslinking additive is trimethylolpropane.

[0016] The present invention also provides a method for preparing the above-mentioned high-temperature resistant polyurethane hot melt adhesive film, comprising the following steps: Step 1: Weigh out each raw material according to the formula and set aside. Mix the polyol, diisocyanate, catalyst and cage-type polysilsesquioxane, and stir and react in a protective atmosphere at 90-100℃ for 1-2 hours. Degas under vacuum to obtain the prepolymer. Step 2: Mix the prepolymer obtained in Step 1 with chain extender, diatomaceous earth, crosslinking additive and antioxidant, and stir and react in a protective atmosphere at 85-90℃ for 1.5-3 h. After the reaction is completed, cast and cure, and cool to obtain high temperature resistant polyurethane hot melt adhesive film.

[0017] Traditional TPU hot melt adhesives are formed by the physical cross-linking network of soft segments (polyester polyols / polyether polyols) and hard segments (diisocyanates and chain extenders) through microphase separation. However, the glass transition temperature of the soft segments is relatively low. At high temperatures, the mobility of the soft segment chains is enhanced and the molecular chain slippage is intensified, leading to material creep failure. Hydrogen bonds between hard segments are the main force in the physical cross-linking network, but their bond energy is low, and the storage modulus decreases sharply as the temperature rises. Based on this, addressing the limitations of traditional TPU hot melt adhesives in terms of soft / hard segment performance, this invention employs glycidyl methacrylate graft modification of polypropylene glycol, followed by its combination with polycarbonate glycol and propylene oxide-ethylene oxide copolyether triol in a specific ratio to form a polyol. Simultaneously, this invention further adjusts the soft / hard segment ratio, designing molecular chains to construct a matrix molecular framework more suitable for cage-like polysilsesquioxanes. This promotes the subsequent embedding of vinylheptaoctyl cage-like polysilsesquioxanes as molecular reefs, more deeply restricting the thermal motion of molecular chains at high temperatures. This significantly improves the overall molecular framework stability and the thermal stability of the physical crosslinking network, resulting in a significant improvement in the high-temperature resistance of the obtained TPU hot melt adhesive. Furthermore, diatomaceous earth possesses a natural porous structure, capable of forming internal mechanical meshing structures, further enhancing mechanical and temperature resistance properties. The addition of a small amount of trimethylolpropane as a crosslinking additive controls weak crosslinking and inhibits high-temperature flow, also improving the high-temperature resistance of the TPU hot melt adhesive.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention precisely designs molecular chains through optimized raw material formulations to construct a matrix molecular framework more suitable for vinylheptaoctyl cage-like polysilsesquioxane, effectively promoting deeper embedding of vinylheptaoctyl cage-like polysilsesquioxane as a molecular reef. By constructing a moderately cross-linked network, the material can be endowed with superior thermal stability under high temperature conditions, ensuring reliable bonding performance of the prepared TPU hot melt adhesive under a wider range of high temperature conditions. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Example 1 A method for preparing a high-temperature resistant polyurethane hot melt adhesive film, comprising the following steps: 1. Vacuum the reactor and replace it with nitrogen. Repeat this process three times. Then add 100 parts by weight of polypropylene glycol (molecular weight 2000). Preheat the reactor to 80°C for 50 min. Then add 0.15 parts of 4-methoxyphenol, 0.2 parts of tetrabutylammonium bromide and 18 parts of toluene in sequence and stir until homogeneous. Heat the reactor to 92°C and maintain the temperature. Continue stirring and slowly add 8 parts of glycidyl methacrylate (control the addition to be completed within 75 min). Continue stirring until the epoxy groups are consumed by FTIR detection to more than 95%. Stop heating and remove the solvent and unreacted substances to obtain glycidyl methacrylate grafted modified polypropylene glycol.

[0022] 2. Polycarbonate diol (molecular weight 1800), modified polypropylene glycol prepared in step 1, and propylene oxide-ethylene oxide copolyether triol CHE-330N were weighed in a mass ratio of 10:3.8:4.5 to form a polypolyol. 68 parts by weight of the polypolyol, 28 parts by weight of diisocyanate (4,4'-diphenylmethane diisocyanate), 12 parts by weight of chain extender (hydroquinone dihydroxyethyl ether), 3 parts by weight of catalyst (dibutyltin dilaurate), 16 parts by weight of vinylheptaoctyl cage-like polysilsesquioxane, 12 parts by weight of diatomaceous earth, 1.2 parts by weight of trimethylolpropane, and 1.5 parts by weight of antioxidant 1010.

[0023] 3. Mix polyol, diisocyanate, catalyst, and vinylheptaoctyl cage-like polysilsesquioxane, and stir at 95°C for 1.5 h under nitrogen atmosphere. Vacuum degassing is then performed to obtain a prepolymer. The obtained prepolymer is then mixed with chain extender, diatomaceous earth, trimethylolpropane, and antioxidant, and stirred at 88°C for 2.5 h under nitrogen atmosphere. After the reaction is completed, the mixture is cast and cured. Cooling yields a high-temperature resistant polyurethane hot melt adhesive film (90 mm wide, 0.2 mm thick, 100 yards / roll).

[0024] Example 2 A method for preparing a high-temperature resistant polyurethane hot melt adhesive film, comprising the following steps: 1. Vacuum the reactor and replace it with nitrogen. Repeat this process three times. Then add 100 parts by weight of polypropylene glycol (molecular weight 2000). Preheat the reactor to 80°C for 50 min. Then add 0.1 parts of 4-methoxyphenol, 0.05 parts of tetrabutylammonium bromide and 18 parts of toluene in sequence and stir until homogeneous. Heat the reactor to 92°C and maintain the temperature. Continue stirring and slowly add 6 parts of glycidyl methacrylate (control the addition to be completed within 60 min). Continue stirring until the epoxy groups are consumed by FTIR detection to more than 95%. Stop heating and remove the solvent and unreacted substances to obtain glycidyl methacrylate grafted modified polypropylene glycol.

[0025] 2. Polycarbonate diol (molecular weight 1800), modified polypropylene glycol prepared in step 1, and propylene oxide-ethylene oxide copolyether triol CHE-330N were weighed in a mass ratio of 10:3.2:6 to form a polypolyol. 60 parts by weight of the polypolyol, 25 parts by weight of diisocyanate (4,4'-diphenylmethane diisocyanate), 10 parts by weight of chain extender (hydroquinone dihydroxyethyl ether), 2 parts by weight of catalyst (dibutyltin dilaurate), 12 parts by weight of vinylheptaoctyl cage-like polysilsesquioxane, 9 parts by weight of diatomaceous earth, 0.5 parts by weight of trimethylolpropane, and 0.3 parts by weight of antioxidant 1010.

[0026] 3. Mix polyol, diisocyanate, catalyst, and vinylheptaoctyl cage-like polysilsesquioxane, and stir and react at 90°C for 2 h under nitrogen atmosphere. Vacuum degassing is then performed to obtain a prepolymer. The obtained prepolymer is then mixed with chain extender, diatomaceous earth, trimethylolpropane, and antioxidant, and stirred and reacted at 85°C for 3 h under nitrogen atmosphere. After the reaction is completed, the mixture is cast and cured. Cooling yields a high-temperature resistant polyurethane hot melt adhesive film (90 mm wide, 0.2 mm thick, 100 yards / roll).

[0027] Example 3 A method for preparing a high-temperature resistant polyurethane hot melt adhesive film, comprising the following steps: 1. Vacuum the reactor and replace it with nitrogen three times. Then add 100 parts by weight of polypropylene glycol (molecular weight 2000), preheat at 80°C for 50 min, and then add 0.2 parts of 4-methoxyphenol, 0.3 parts of tetrabutylammonium bromide and 18 parts of toluene in sequence and stir evenly. Raise the temperature to 92°C and keep it constant. Continue stirring and slowly add 11 parts of glycidyl methacrylate (control the addition to be completed within 90 min). Continue stirring until the epoxy group consumption reaches more than 95% as detected by FTIR. Stop heating and remove the solvent and unreacted substances to obtain glycidyl methacrylate grafted modified polypropylene glycol.

[0028] 2. Polycarbonate diol (molecular weight 1800), modified polypropylene glycol prepared in step 1, and propylene oxide-ethylene oxide copolyether triol CHE-330N were weighed in a mass ratio of 10:4.5:3 to form a polypolyol. 75 parts of the polypolyol, 32 parts of diisocyanate (4,4'-diphenylmethane diisocyanate), 14 parts of chain extender (hydroquinone dihydroxyethyl ether), 4 parts of catalyst (dibutyltin dilaurate), 18 parts of vinylheptaoctyl cage-like polysilsesquioxane, 15 parts of diatomaceous earth, 2 parts of trimethylolpropane, and 3 parts of antioxidant 1010 were weighed according to the following weight proportions.

[0029] 3. Mix polyol, diisocyanate, catalyst, and vinylheptaoctyl cage-like polysilsesquioxane, and stir and react at 100°C for 1 h under nitrogen atmosphere. Vacuum degassing is then performed to obtain a prepolymer. The obtained prepolymer is then mixed with chain extender, diatomaceous earth, trimethylolpropane, and antioxidant, and stirred and reacted at 90°C for 1.5 h under nitrogen atmosphere. After the reaction is completed, the mixture is cast and cured. Cooling yields a high-temperature resistant polyurethane hot melt adhesive film (90 mm wide, 0.2 mm thick, 100 yards / roll).

[0030] Comparative Example 1 Referring to the steps and parameters of Example 1 of this invention, the only difference is that the polyol system is adjusted, and the polyoxypropylene glycol is not modified.

[0031] Comparative Example 2 Referring to the steps and parameters of Example 1 of this invention, the only difference is that the polyol system is adjusted, and propylene oxide-ethylene oxide copolyether triol CHE-330N is not added. That is, the polyol is composed of polycarbonate diol and modified polyoxypropylene diolamine in a mass ratio of 10:3.8.

[0032] Comparative Example 3 Referring to the steps and parameters of Example 1 of this invention, the only difference is that the mass ratio of polycarbonate diol, modified polypropylene glycol, and propylene oxide-ethylene oxide copolyether triol is adjusted to 1:1:1.

[0033] Comparative Example 4 Referring to the steps and parameters of Example 1 of this invention, the only difference is the adjustment of the ratio of soft and hard segments, that is, the amount of polyol is adjusted to 80 parts, and the amount of diisocyanate / chain extender is adjusted to 20 parts / 8.5 parts.

[0034] Comparative Example 5 Referring to the steps and parameters of Embodiment 1 of the present invention, the only difference is that methacrylate-based cage-like silsesquioxane is used instead of vinyl heptaoctyl cage-like polysilsesquioxane.

[0035] Comparative Example 6 The steps and parameters are the same as in Example 1 of this invention, except that the formulation does not contain cross-linking additives.

[0036] Test case The performance of the TPU hot melt adhesive film samples obtained in Examples 1-3 and Comparative Examples 1-6 above was tested, and the results are shown in Table 1 (melting point test according to GB / T 15332-1994, elongation at break test using a universal testing machine, and bond strength test according to GB / T 7124-2008).

[0037] Table 1 Performance test results of TPU hot melt adhesive film

[0038] The test results above show that the TPU-type hot melt adhesive prepared by this invention has a softening point of 125-135℃, which is significantly higher than that of traditional TPU-type hot melt adhesives, and also exhibits excellent tensile properties. Through formula optimization, this invention not only maintains the high initial tack strength inherent in TPU-type hot melt adhesives, but also significantly improves their final tack strength and high-temperature resistance, approaching the weather resistance of PUR-type hot melt adhesives. While maintaining reliable bonding strength, it also has a low application threshold, effectively expanding the application range of TPU-type hot melt adhesives.

[0039] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they are not intended to limit the present invention. It should be noted that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A formulation for a high-temperature resistant polyurethane hot melt adhesive film, characterized in that, The ingredients, by weight, include the following: 60-75 parts of polyol 25-32 parts of diisocyanate 10-14 parts of chain extender 2-4 parts of catalyst 12-18 parts of cage-type polysilsesquioxane 9-15 parts diatomaceous earth Crosslinking additive 0.5-2 parts Antioxidant 0.3-3 parts; The polyol is composed of polycarbonate diol, modified polypropylene glycol, and propylene oxide-ethylene oxide copolyether triol.

2. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The polyol is composed of polycarbonate diol, modified polypropylene glycol, and propylene oxide-ethylene oxide copolyether triol in a mass ratio of 10:(3.2-4.5):(3-6).

3. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 2, characterized in that, The modified polypropylene glycol is prepared by preheating polypropylene glycol in a protective atmosphere to remove water, then adding polymerization inhibitor, catalyst and solvent in sequence, and slowly adding glycidyl methacrylate under constant temperature and stirring. After the reaction is completed, the modified polypropylene glycol is obtained.

4. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 3, characterized in that, The polymerization inhibitor is 4-methoxyphenol, and the catalyst is tetrabutylammonium bromide; the mass ratio of polypropylene glycol, 4-methoxyphenol, tetrabutylammonium bromide, and glycidyl methacrylate is 100:(0.1-0.2):(0.05-0.3):(6-11).

5. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The diisocyanate is at least one of 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

6. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The chain extender is hydroquinone dihydroxyethyl ether.

7. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The catalyst is dibutyltin dilaurate.

8. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The cage-like polysilsesquioxane is vinylheptaoctyl cage-like polysilsesquioxane.

9. The formulation of the high-temperature resistant polyurethane hot melt adhesive film according to claim 1, characterized in that, The crosslinking additive is trimethylolpropane.

10. A method for preparing the high-temperature resistant polyurethane hot melt adhesive film according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Weigh out each raw material according to the formula and set aside. Mix the polyol, diisocyanate, catalyst and cage-type polysilsesquioxane, and stir and react in a protective atmosphere at 90-100℃ for 1-2 hours. Degas under vacuum to obtain the prepolymer. Step 2: Mix the prepolymer obtained in Step 1 with chain extender, diatomaceous earth, crosslinking additive and antioxidant, and stir and react in a protective atmosphere at 85-90℃ for 1.5-3 h. After the reaction is completed, cast and cure, and cool to obtain high temperature resistant polyurethane hot melt adhesive film.

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