Water vapor skinning resistant PUR edge sealing adhesive modified material and preparation method thereof

Abstract

The invention relates to the technical field of PUR edge sealing adhesives, and discloses a water vapor skinning-resistant PUR edge sealing adhesive modified material and a preparation method thereof.The water vapor skinning-resistant PUR edge sealing adhesive modified material is prepared from crystalline polyester polyol, amorphous polyester polyol, diisocyanate, modified starch, p-toluenesulfonyl isocyanate, a zinc-bismuth composite catalyst and a polymerization inhibitor; the modified starch is prepared from the following raw materials: starch, propionic anhydride, epoxidized soybean oil, a silane coupling agent KH-560, calcium stearate, nano montmorillonite and an antioxidant; the preparation method of the modified starch comprises the following steps: firstly adding starch, nano-montmorillonite and an antioxidant, stirring and dispersing, spraying a silane coupling agent KH-560 and epoxidized soybean oil, then spraying propionic anhydride, finally adding calcium stearate, transferring to a screw extruder, mixing, exhausting in vacuum, and extruding to obtain the modified starch. Through double chemical modification of propionylation and silanization, the modified starch is endowed with hydrophobicity and interface reaction activity, and the problem that the adhesive property is reduced due to the fact that hydrophobic components are added to improve the water vapor resistance of conventional PUR glue is solved.

Description

Technical Field

[0001] This invention relates to the field of PUR edge banding technology, and more particularly to a modified PUR edge banding material resistant to moisture vapor crusting and its preparation method. Background Technology

[0002] Moisture-curing polyurethane hot melt adhesive (PUR) has become the mainstream adhesive material in the furniture edge banding industry due to its excellent bonding strength, heat resistance, and chemical resistance. Existing PUR edge banding adhesives are mainly prepared by reacting petroleum-based polyester polyols with isocyanates.

[0003] However, the edge-sealing process requires PUR to have excellent thermal stability during high-temperature processing at 130℃ to ensure that it does not form a skin or clog nozzles during long-term continuous construction. Because the construction environment inevitably contains humidity, existing PUR is prone to surface cross-linking and skin formation in open melting tanks, and may even produce gel particles. This not only leads to equipment blockage and increased downtime maintenance costs, but also seriously affects the smoothness of the edge-sealing surface and processing efficiency. Therefore, improving resistance to moisture skinning and extending the processing window are the primary technical challenges in the current development of edge-sealing adhesives.

[0004] In existing improvement techniques, adding hydrophobic components can improve the water vapor crust resistance of PUR, but this often leads to a significant decrease in bond strength.

[0005] Building on this, introducing bio-based materials such as starch into PUR formulations has profound environmental significance. On the one hand, starch is inexpensive, readily available, and biodegradable. Introducing such materials can significantly reduce dependence on petrochemical resources, lower the carbon footprint of furniture throughout its entire life cycle, and meet green home furnishing evaluation standards and increasingly stringent environmental regulations. On the other hand, due to the natural properties of starch, it exhibits excellent biodegradability in end products, helping to reduce the pressure of solid waste disposal after furniture disposal and achieving a green transformation of the entire wooden furniture industry chain.

[0006] However, there is a significant contradiction between the introduction of starch and its processing stability and adhesive strength. On the one hand, the polyhydroxy structure and trace moisture in starch can easily induce violent cross-linking of the system at high temperatures, leading to a deterioration in the resistance to moisture crusting and increasing the risk of blockage in the melting equipment. On the other hand, the furniture industry has increasingly higher requirements for peel strength, typically requiring a level of 60 N / cm or higher to reach the substrate failure level, while simply filling with starch often leads to a significant decrease in the cohesive force of the adhesive layer.

[0007] Therefore, how to ensure ultra-long anti-skinning stability while taking into account environmental protection properties and super adhesion strength remains a technical problem that the industry urgently needs to solve. Summary of the Invention

[0008] To address the aforementioned shortcomings, the present invention aims to propose a modified PUR edge sealant material resistant to moisture condensation and its preparation method. This material enhances the resistance to moisture condensation while ensuring the adhesive strength of the PUR edge sealant, thus solving the problem that conventional PUR edge sealants cannot simultaneously achieve both resistance to moisture condensation and adhesive performance.

[0009] To achieve this objective, the present invention adopts the following technical solution: A modified PUR edge sealant resistant to moisture and skin formation, comprising, by weight: 40-50 parts of crystalline polyester polyol; 12-18 parts of amorphous polyester polyol; 22-26 parts of diisocyanate; 25-35 parts of modified starch; 0.8-1.2 parts of p-toluenesulfonyl isocyanate; 0.1~0.2 parts of zinc-bismuth composite catalyst; Polymerization inhibitor 0.01~0.05 parts; The raw materials for modified starch, by weight, include: 100 parts starch; 18-22 parts of propionic anhydride; 15-20 parts of epoxidized soybean oil; Silane coupling agent KH-560, 2.5~3.5 parts; 0.6-0.8 parts of calcium stearate; 1-2 parts of nano-montmorillonite; Antioxidant 0.2~0.4 parts; The preparation method of modified starch includes the following steps: First, add starch, nano-montmorillonite, and antioxidant, and stir to disperse for 1-3 minutes. While stirring, spray a mixture of silane coupling agent KH-560 and epoxidized soybean oil, and stir for 1-3 minutes. Then, spray in propionic anhydride and stir for 3-5 minutes at a temperature of 50-60°C. Finally, add calcium stearate and stir for at least 3 minutes. Keep warm and transfer to the first screw extruder, where it is sheared and mixed at 120-130°C for 1-5 minutes. Vacuum exhaust is performed at the end of the first screw extruder at a vacuum degree of -0.09-0.095 MPa, and the modified starch is obtained by extrusion.

[0010] Preferably, the crystalline polyester polyol is polyhexamethylene adipate or its homologues, with a molecular weight of 2000-3000, and the amorphous polyester polyol is polypentyl adipate or its homologues, with a molecular weight of 2000-3000.

[0011] Preferably, the diisocyanate is 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate: 4,4'-diphenylmethane diisocyanate: 2,4'-diphenylmethane diisocyanate = 2~4:1.

[0012] Preferably, the zinc-bismuth composite catalyst is a composite catalyst of bismuth isooctanoate and zinc isooctanoate, with the ratio of bismuth isooctanoate to zinc isooctanoate being 1:1~2.

[0013] Preferably, the polymerization inhibitor is benzoyl chloride.

[0014] Preferably, the nano-montmorillonite is quaternary ammonium salt modified nano-organic montmorillonite.

[0015] Preferably, the antioxidants are 1010 and 168, with 1010:168 = 1:1~2.

[0016] Preferably, it also includes 0.01 to 5 parts of other functional additives or fillers.

[0017] A method for preparing a water vapor-resistant modified PUR edge sealant material, used to prepare the aforementioned modified PUR edge sealant material, includes the following steps: crystalline polyester polyol and amorphous polyester polyol are added to a reactor and vacuum dehydrated at 90-100°C for 1-2 hours; a polymerization inhibitor is added and the temperature is lowered to 75-85°C; diisocyanate is added, and the reaction is carried out at 85-95°C for 1-3 hours; after sampling and testing to determine that the free -NCO content of the material in the reactor is 2.3-2.5%, a zinc-bismuth composite catalyst is added and the reaction is continued for 0.5-1 hour, while simultaneously initiating starch modification. After sampling and testing the free NCO content of the material in the reactor to be 1.8~2.2%, the material in the reactor and the modified starch extruded from the first screw extruder are connected in parallel and fed to the second screw extruder for shearing and blending according to the corresponding ratio in the PUR automotive headliner raw material formulation. The blending temperature is 115~125℃, the residence time is 2~5 minutes, and p-toluenesulfonyl isocyanate is injected in the last 1 / 2~3 / 4 range of the stroke of the second screw extruder. Vacuum exhaust is performed at the end of the second screw extruder with a vacuum degree of -0.09~-0.095MPa. After extrusion, the material is sealed and packaged.

[0018] Preferably, the starch is pre-dried to a moisture content of 1-2% by baking at 80-105°C for 1-5 seconds using an airflow dryer.

[0019] The technical solution provided by this invention may include the following beneficial effects: 1. Through dual chemical modification of propionylation and silanization, modified starch is endowed with high hydrophobicity and interfacial reactivity. Combined with the internal plasticizing effect of epoxidized soybean oil, utilizing its strong hydrophobicity and excellent compatibility with the PUR system, a dense hydrophobic barrier is constructed within the system while improving processing fluidity. This significantly enhances the system's resistance to moisture and skinning while ensuring the adhesive strength of the PUR edge banding adhesive, solving the problem of decreased adhesive performance caused by adding hydrophobic components to conventional PUR adhesives to improve moisture resistance. Furthermore, the use of a high proportion of bio-based materials greatly improves the biodegradability and environmental value of the edge banding adhesive, providing a high-performance and eco-friendly solution for the furniture edge banding industry.

[0020] 2. The epoxy group at one end of the silane coupling agent KH-560 exhibits excellent compatibility and reactivity with the polyurethane system, while the alkoxy group at the other end can firmly bind starch. More importantly, through the in-situ hydrolytic condensation of its alkoxy groups, KH-560 constructs a dense siloxane network upon encountering moisture. This further passivates the hydrophilic activity of starch, significantly enhances the overall water vapor penetration resistance of the system, and achieves strong interfacial anchoring through chemical bonding. This improves the peel strength and impact resistance of the adhesive layer, solving the problem of decreased adhesion performance of PUR edge-sealing adhesives caused by the addition of starch.

[0021] 3. The starch modification method employs a combination of room-temperature in-situ modification and high-temperature shear-blending. First, silane coupling agent KH-560 and epoxidized soybean oil are sprayed in. The permeability of soybean oil allows KH-560 to wet the starch interface. Then, propionic anhydride is sprayed in. Propionic anhydride not only esterifies the starch but also catalyzes the hydrolysis of the KH-560 already wetted on the starch surface. Subsequently, a high-shear process at 130°C in the first twin-screw extruder thoroughly breaks down and plasticizes the starch particles, triggering propionylation and further hydrolysis and condensation of the silane. Simultaneously, nano-montmorillonite is uniformly dispersed throughout the process. After the reaction in the first screw extruder, reaction byproducts and moisture are completely removed through a vacuum exhaust port at the end of the first screw extruder, preventing byproducts and residual moisture from affecting the subsequent stable blending with the PUR system. Finally, calcium stearate is added to adjust the extrusion torque and prevent localized scorching of the material, while also preventing its coating effect from affecting the starch modification reaction.

[0022] 4. A polyurethane backbone was constructed using the addition polymerization reaction of diisocyanate and polyester polyol. By controlling the blending ratio of crystalline and amorphous segments, a balance between rapid initial tack and long-lasting flexibility was achieved at the molecular level. Based on this, a high proportion of bio-based components was stably introduced into the moisture-curing system through chemical grafting and interfacial anchoring of dual-modified starch particles, ultimately yielding a modified PUR edge-sealing adhesive material that combines high initial tack strength, excellent water resistance, and eco-friendliness.

[0023] 5. As a crosslinking agent, diisocyanate reacts with polyester polyols to construct an elastomer skeleton with high cohesive strength, and forms strong chemical bonds with the active groups on the surface of modified starch particles and the fiber of the board, thereby achieving integrated chemical locking of the interface between the adhesive layer, modified starch and the adhesive substrate.

[0024] 6. Toluenesulfonyl isocyanate, as a highly efficient dehydrating agent, captures trace amounts of residual moisture in the system, inhibiting moisture crusting and can swelling. The zinc-bismuth composite catalyst ensures the open time of the adhesive during edge sealing through the low induction activity of zinc salts, and utilizes bismuth salt catalysis to ensure curing and improved cohesive strength after pressing. Antioxidants inhibit thermal degradation and yellowing during high-temperature processing and long-term storage, while polymerization inhibitors inhibit the self-polymerization reaction of -NCO groups; both work synergistically to ensure the stability of the edge sealing adhesive during production and storage. Calcium stearate's lubricating and neutralizing effect significantly improves the overall processing fluidity of the system. The layered barrier effect of nano-montmorillonite effectively blocks moisture penetration and enhances resistance to moisture.

[0025] 7. The long carbon chain structure of polyhexanediol adipate not only endows the system with excellent mechanical strength, but its low polarity and hydrophobicity further reduce the water absorption rate of the adhesive layer; the side methyl structure of the polyhexanediol adipate in combination with it produces a steric hindrance effect, which not only breaks the brittleness caused by excessive crystallization, but also effectively reduces the free volume of water molecules by increasing the arrangement density of polymer chains.

[0026] The combination of polyhexyl adipate and polyhexyl adipate forms a hydrophobic barrier inside the adhesive layer, inhibiting premature erosion of the internal active isocyanate groups by external moisture, and further enhancing the moisture resistance and long-term stability of the PUR edge sealant. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0028] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0029] 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 to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] A modified PUR edge sealant resistant to moisture and skin formation, comprising, by weight: 40-50 parts of crystalline polyester polyol; 12-18 parts of amorphous polyester polyol; 22-26 parts of diisocyanate; 25-35 parts of modified starch; 0.8-1.2 parts of p-toluenesulfonyl isocyanate; 0.1~0.2 parts of zinc-bismuth composite catalyst; Polymerization inhibitor 0.01~0.05 parts; The raw materials for modified starch, by weight, include: 100 parts starch; 18-22 parts of propionic anhydride; 15-20 parts of epoxidized soybean oil; Silane coupling agent KH-560, 2.5~3.5 parts; 0.6-0.8 parts of calcium stearate; 1-2 parts of nano-montmorillonite; Antioxidant 0.2~0.4 parts; The preparation method of modified starch includes the following steps: The starch is pre-dried to a moisture content of 1-2% by baking at 100°C for 4 seconds using an airflow dryer. First, add dried starch, nano-montmorillonite, and antioxidant, and stir to disperse for 1-3 minutes. While stirring, spray a mixture of silane coupling agent KH-560 and epoxidized soybean oil, and stir for 1-3 minutes. Then, spray in propionic anhydride and stir for 3-5 minutes at a temperature of 50-60°C. Finally, add calcium stearate and stir for at least 3 minutes. Keep warm and transfer to the first screw extruder, where it is sheared and mixed at 120-130°C for 1-5 minutes. Vacuum exhaust is performed at the end of the first screw extruder at a vacuum degree of -0.09-0.095 MPa, and the modified starch is obtained by extrusion.

[0031] Through dual chemical modification via propionylation and silanization, the modified starch is endowed with high hydrophobicity and interfacial reactivity. Combined with the internal plasticizing effect of epoxidized soybean oil, utilizing its strong hydrophobicity and excellent compatibility with the PUR system, a dense hydrophobic barrier is constructed within the system while improving processing fluidity. This significantly enhances the system's resistance to moisture and skinning while ensuring the adhesive strength of the PUR edge banding adhesive, solving the problem of decreased adhesive performance caused by adding hydrophobic components to conventional PUR adhesives to improve moisture resistance. Furthermore, the use of a high proportion of bio-based materials greatly improves the biodegradability and environmental value of the edge banding adhesive, providing a high-performance and eco-friendly solution for the furniture edge banding industry.

[0032] The epoxy group at one end of the silane coupling agent KH-560 exhibits excellent compatibility and reactivity with the polyurethane system, while the alkoxy group at the other end can firmly bind starch. More importantly, through the in-situ hydrolytic condensation of its alkoxy groups, KH-560 constructs a dense siloxane network upon encountering moisture. This further passivates the hydrophilic activity of starch, significantly enhances the overall water vapor penetration resistance of the system, and achieves strong interfacial anchoring through chemical bonding. This improves the peel strength and impact resistance of the adhesive layer, solving the problem of decreased adhesion performance of PUR edge-sealing adhesives caused by the addition of starch.

[0033] The starch modification method employs a combination of room-temperature in-situ modification and high-temperature shear-blending. First, silane coupling agent KH-560 and epoxidized soybean oil are sprayed in. The permeability of soybean oil allows KH-560 to wet the starch interface. Then, propionic anhydride is sprayed in. Propionic anhydride not only esterifies the starch but also catalyzes the hydrolysis of the KH-560 already wetted on the starch surface. Subsequently, a high-shear process at 130°C in the first twin-screw extruder thoroughly breaks down and plasticizes the starch particles, triggering propionylation and further hydrolysis and condensation of the silane. Simultaneously, nano-montmorillonite is uniformly dispersed throughout the process. After the reaction in the first screw extruder, reaction byproducts and moisture are completely removed through a vacuum exhaust port at the end of the extruder, preventing byproducts and residual moisture from affecting the stable blending with the PUR system. Finally, calcium stearate is added to adjust the extrusion torque and prevent localized scorching of the material, while also preventing its coating effect from affecting the starch modification reaction.

[0034] A polyurethane backbone was constructed using the addition polymerization reaction of diisocyanate and polyester polyol. By controlling the blending ratio of crystalline and amorphous segments, a balance between rapid initial tack and long-lasting flexibility was achieved at the molecular level. Based on this, a high proportion of bio-based components was stably introduced into the moisture-curing system through chemical grafting and interfacial anchoring of dual-modified starch particles, ultimately yielding a modified PUR edge-sealing adhesive material that combines high initial tack strength, excellent water resistance, and eco-friendliness.

[0035] As a crosslinking agent, diisocyanate reacts with polyester polyols to construct an elastomer skeleton with high cohesive strength, and forms strong chemical bonds with the active groups on the surface of modified starch particles and the fiber of the board, thereby achieving integrated chemical locking of the interface between the adhesive layer, modified starch and the adhesive substrate.

[0036] p-Toluenesulfonyl isocyanate is a highly efficient dehydrating agent that captures trace amounts of residual moisture in the system, inhibiting water vapor crusting and tank bulging.

[0037] The zinc-bismuth composite catalyst ensures the open time of the adhesive during edge sealing construction through the low induction activity of zinc salt, and uses bismuth salt catalysis to ensure the curing and cohesive strength improvement after pressing.

[0038] Antioxidants inhibit thermal degradation and yellowing during high-temperature processing and long-term storage, while polymerization inhibitors inhibit the self-polymerization reaction of -NCO groups. Together, they ensure the stability of the sealing adhesive during production and storage.

[0039] Furthermore, the lubricating and neutralizing effect of calcium stearate significantly improves the overall processing fluidity of the system. The layered barrier effect of nano-montmorillonite effectively blocks moisture penetration and enhances resistance to water vapor.

[0040] Preferably, the crystalline polyester polyol is polyhexamethylene adipate or its homologues, with a molecular weight of 2000-3000, and the amorphous polyester polyol is polypentyl adipate or its homologues, with a molecular weight of 2000-3000.

[0041] The long carbon chain structure of polyhexanediol adipate not only endows the system with excellent mechanical strength, but its low polarity and hydrophobicity further reduce the water absorption rate of the adhesive layer. The side methyl structure of the polyhexanediol adipate in combination with it produces a steric hindrance effect, which not only breaks the brittleness caused by excessive crystallization, but also effectively reduces the free volume of water molecules by increasing the arrangement density of polymer chains.

[0042] The combination of polyhexyl adipate and polyhexyl adipate forms a hydrophobic barrier inside the adhesive layer, inhibiting premature erosion of the internal active isocyanate groups by external moisture, and further enhancing the moisture resistance and long-term stability of the PUR edge sealant.

[0043] Preferably, the diisocyanate is 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate: 4,4'-diphenylmethane diisocyanate: 2,4'-diphenylmethane diisocyanate = 2~4:1.

[0044] 4,4'-Diphenylmethane diisocyanate exhibits high reactivity. Its regular molecular structure allows it to form a dense network with high cross-linking density during curing, providing excellent cohesive strength and further inhibiting the penetration of external moisture. An appropriate amount of 2,4'-diphenylmethane diisocyanate can further delay the skinning process. The open time can be adjusted according to construction requirements by modifying the proportion of 2,4'-diphenylmethane diisocyanate used.

[0045] Preferably, the zinc-bismuth composite catalyst is a composite catalyst of bismuth isooctanoate and zinc isooctanoate, with the ratio of bismuth isooctanoate to zinc isooctanoate being 1:1~2.

[0046] The proportion of zinc isooctanoate is higher. By utilizing its highly selective catalytic effect on the reaction between isocyanate groups and hydroxyl groups, it can effectively delay the initial surface cross-linking while ensuring the internal strength construction, thereby preventing the instantaneous skin formation on the surface induced by moisture.

[0047] Preferably, the polymerization inhibitor is benzoyl chloride.

[0048] Benzoyl chloride exhibits good compatibility with the system and moderate volatility. It not only effectively neutralizes the system's alkalinity to inhibit the uncontrolled self-polymerization of -NCO groups, but also reacts with trace amounts of moisture to generate benzoic acid and hydrogen chloride, thus providing a chemical drying effect and eliminating the potential for surface crusting at its source. Most of the generated benzoic acid and hydrogen chloride are removed under vacuum, with the trace residue providing a slightly acidic stabilizing condition for the system.

[0049] Preferably, the nano-montmorillonite is quaternary ammonium salt modified nano-organic montmorillonite.

[0050] Quaternary ammonium salt modified nano-organic montmorillonite has better compatibility with epoxidized soybean oil and polyester polyols, improving dispersion efficiency and overall protective performance.

[0051] Preferably, the antioxidants are 1010 and 168, with 1010:168 = 1:1~2.

[0052] By combining hindered phenolic antioxidant 1010 with phosphite antioxidant 168, the high synergistic effect of the two is utilized to ensure antioxidant effect throughout the entire process from processing modification to finished product storage and use.

[0053] Preferably, it also includes 0.01 to 5 parts of other functional additives or fillers.

[0054] In one embodiment, the addition of 0.01 parts of fluorescent whitening agent and 0.05 parts of titanium dioxide significantly improves the whiteness of the sealing adhesive.

[0055] In another embodiment, 0.1 to 5 parts of carbon black are added as a colorant to produce gray, dark gray to black PUR edge sealing adhesive.

[0056] In another embodiment, 0.1 parts of 2-n-octyl-4-isothiazolin-3-one were added as a fungicide.

[0057] A method for preparing a water vapor-resistant modified PUR edge sealant material, used to prepare the aforementioned modified PUR edge sealant material, includes the following steps: crystalline polyester polyol and amorphous polyester polyol are added to a reactor and vacuum dehydrated at 90-100°C for 1-2 hours; a polymerization inhibitor is added and the temperature is lowered to 75-85°C; diisocyanate is added, and the reaction is carried out at 85-95°C for 1-3 hours; after sampling and testing to determine that the free -NCO content of the material in the reactor is 2.3-2.5%, a zinc-bismuth composite catalyst is added and the reaction is continued for 0.5-1 hour, while simultaneously initiating starch modification. After sampling and testing the free NCO content of the material in the reactor to be 1.8~2.2%, the material in the reactor and the modified starch extruded from the first screw extruder are connected in parallel and fed to the second screw extruder for shearing and blending according to the corresponding ratio in the PUR automotive headliner raw material formulation. The blending temperature is 115~125℃, the residence time is 2~5 minutes, and p-toluenesulfonyl isocyanate is injected in the last 1 / 2~3 / 4 range of the stroke of the second screw extruder. Vacuum exhaust is performed at the end of the second screw extruder with a vacuum degree of -0.09~-0.095MPa. After extrusion, the material is sealed and packaged.

[0058] If the free NCO content is too low, the density of active groups that can reach the interface and complete chemical locking before the adhesive cools and solidifies is too small. After long-term use, the sealing strip is very prone to delamination due to environmental stress. If the content is too high, it is easy to form a skin and overflow adhesive.

[0059] Preferably, the starch is pre-dried to a moisture content of 1-2% by baking at 80-105°C for 1-5 seconds using an airflow dryer.

[0060] By exchanging airflow at high temperatures, the physically adsorbed water and some bound water on the surface of starch granules are removed in a very short time. This not only curbs the violent side reaction between water and isocyanate groups -NCO from the source, but also avoids foaming and viscosity runaway in the system, laying a solid foundation for the preparation of high-quality, zero-bubble moisture-curing PUR sealing adhesive.

[0061] Example 1 By weight, the raw materials include: 45 parts of polyhexyl adipate; 15 parts of polypentyl adipate; 25 parts of diisocyanate, 4,4'-diphenylmethane diisocyanate: 2,4'-diphenylmethane diisocyanate = 4:1; 30 parts modified starch; 1 part of p-toluenesulfonyl isocyanate; 0.15 parts of zinc-bismuth composite catalyst, bismuth isooctanoate: zinc isooctanoate = 1:2; Benzoyl chloride 0.03 parts; The raw materials for modified starch, by weight, include: 100 parts starch; 20 parts propionic anhydride; 15 parts of epoxidized soybean oil; Silane coupling agent KH-560, 3 parts; 0.8 parts calcium stearate; 1.5 parts of quaternary ammonium salt modified nano-organic montmorillonite; Antioxidant 0.3 parts, 1010:168=1:2; The steps for starch modification are as follows: First, add starch, nano-montmorillonite, and antioxidant, and stir to disperse for 3 minutes. While stirring, spray a mixture of silane coupling agent KH-560 and epoxidized soybean oil, and stir for 3 minutes. Then, spray in propionic anhydride and stir for 5 minutes at 60°C. Finally, add calcium stearate, stir, and keep warm for later use. After the free NCO content of the material in the reactor is detected to be 1.8~2.2% during the above-mentioned simultaneous process, it is sent to the first screw extruder, sheared and mixed at 120~130°C, with a residence time of 4 minutes. Vacuum exhaust is performed at the end of the first screw extruder with a vacuum degree of -0.095MPa, and the mixture is extruded to the second screw extruder in proportion.

[0062] The preparation steps for PUR edge sealing adhesive are as follows: Crystalline and amorphous polyester polyols were added to a reactor and vacuum dehydrated at 95°C for 2 hours. An inhibitor was added and the temperature was lowered to 80°C. Diisocyanate was added, and the mixture was reacted at 90°C for 1-3 hours. After sampling and testing the free NCO content of the material in the reactor (which was 2.3-2.5%), a zinc-bismuth composite catalyst was added, and the mixture was reacted for another 0.5-1 hour. Simultaneously, starch modification was initiated. After sampling and testing the free NCO content of the material in the reactor (which was 1.8-2.2%), the material in the reactor was combined with the modified starch extruded from the first screw extruder in the corresponding proportions specified in the PUR automotive headliner raw material formulation and then sheared and blended in parallel with the material in the second screw extruder. The blending temperature was 120°C, and the residence time was 3 minutes. P-Toluenesulfonyl isocyanate was injected near the end 3 / 4 of the stroke of the second screw extruder. Vacuum degassing was performed at the end of the second screw extruder at a vacuum degree of -0.095 MPa. After extrusion, the mixture was sealed and packaged to obtain PUR edge-sealing adhesive.

[0063] Example 2 The difference from Example 1 is that the amount of modified starch used is 25 parts.

[0064] Example 3 The difference from Example 1 is that the amount of modified starch used is 35 parts.

[0065] Comparative Example The difference from Example 1 is that modified starch is not added, and the antioxidant is added to the reactor simultaneously with crystalline polyester polyol and amorphous polyester polyol.

[0066] The bond strength after 7 days was measured according to GB / T 2790-2014 "Adhesives - 180° Peel Strength Test Method - Flexible Materials vs. Rigid Materials". The skinning time was also measured at 130℃ and 50%RH in an open environment. The results are shown in the table below: Table 1 Test Results

[0067] As can be seen from the test results in Table 1, the 7-day bond strength and skinning time of the comparative examples are already at a relatively high level among existing commercially available products. Based on this, Examples 1-3, with different amounts of modified starch added, all exhibited better 7-day bond strength and significantly improved resistance to moisture-induced skinning. Although the 7-day bond strength of Example 3 was significantly lower than that of Examples 1 and 2 after the amount of modified starch was increased, it still showed better 7-day bond strength than the comparative examples, while also achieving better resistance to moisture-induced skinning.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A modified PUR edge-sealing adhesive material resistant to moisture vapor crusting, characterized in that: By weight, the raw materials include: 40-50 parts of crystalline polyester polyol; 12-18 parts of amorphous polyester polyol; 22-26 parts of diisocyanate; 25-35 parts of modified starch; 0.8-1.2 parts of p-toluenesulfonyl isocyanate; 0.1~0.2 parts of zinc-bismuth composite catalyst; Polymerization inhibitor 0.01~0.05 parts; The raw materials for modified starch, by weight, include: 100 parts starch; 18-22 parts of propionic anhydride; 15-20 parts of epoxidized soybean oil; Silane coupling agent KH-560, 2.5~3.5 parts; 0.6-0.8 parts of calcium stearate; 1-2 parts of nano-montmorillonite; Antioxidant 0.2~0.4 parts; The preparation method of modified starch includes the following steps: First, add starch, nano-montmorillonite, and antioxidant, and stir to disperse for 1-3 minutes. While stirring, spray a mixture of silane coupling agent KH-560 and epoxidized soybean oil, and stir for 1-3 minutes. Then, spray in propionic anhydride and stir for 3-5 minutes at a temperature of 50-60°C. Finally, add calcium stearate and stir for at least 3 minutes. Keep warm and transfer to the first screw extruder, where it is sheared and mixed at 120-130°C for 1-5 minutes. Vacuum exhaust is performed at the end of the first screw extruder at a vacuum degree of -0.09-0.095 MPa, and the modified starch is obtained by extrusion.

2. The PUR edge-sealing modified material resistant to moisture vapor crusting according to claim 1, characterized in that: Crystalline polyester polyols are polyhexamethylene adipate and its homologues, with a molecular weight of 2000-3000. Amorphous polyester polyols are polypentyl adipate and its homologues, with a molecular weight of 2000-3000.

3. The PUR edge-sealing adhesive modified material resistant to moisture vapor crusting according to claim 1, characterized in that: The diisocyanate is 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate: 4,4'-diphenylmethane diisocyanate: 2,4'-diphenylmethane diisocyanate = 2~4:

1.

4. The PUR edge-sealing adhesive modified material resistant to moisture vapor crusting according to claim 1, characterized in that: The zinc-bismuth composite catalyst is a composite catalyst of bismuth isooctanoate and zinc isooctanoate, with the ratio of bismuth isooctanoate to zinc isooctanoate being 1:1~2.

5. The PUR edge-sealing adhesive modified material resistant to moisture vapor crusting according to claim 1, characterized in that: The polymerization inhibitor is benzoyl chloride.

6. The PUR edge-sealing modified material resistant to moisture vapor crusting according to claim 1, characterized in that: Nano-montmorillonite is a quaternary ammonium salt modified nano-organic montmorillonite.

7. The PUR edge-sealing modified material resistant to moisture vapor crusting according to claim 1, characterized in that: The antioxidants are 1010 and 168, with a ratio of 1:1 to 2.

8. The PUR edge-sealing modified material resistant to moisture vapor crusting according to claim 1, characterized in that: It also includes 0.01 to 5 parts of other functional additives or fillers.

9. A method for preparing a PUR edge-sealing adhesive modified material resistant to water vapor crusting, characterized in that, The preparation of the PUR edge-sealing adhesive modified material according to any one of claims 1-8 comprises the following steps: crystalline polyester polyol and amorphous polyester polyol are added to a reactor and vacuum dehydrated at 90-100°C for 1-2 hours; a polymerization inhibitor is added and the temperature is lowered to 75-85°C; diisocyanate is added and reacted at 85-95°C for 1-3 hours; after sampling and testing the free -NCO content of the material in the reactor to ensure it is 2.3-2.5%, a zinc-bismuth composite catalyst is added and the reaction continues for 0.5-1 hour, while simultaneously starting starch modification; and the material in the reactor is sampled and tested. After the free NCO content of the material is 1.8~2.2%, the material in the reactor and the modified starch extruded by the first screw extruder are fed in parallel to the second screw extruder for shearing and blending according to the corresponding ratio in the PUR automotive headliner raw material formula. The blending temperature is 115~125℃, the residence time is 2~5 minutes, and p-toluenesulfonyl isocyanate is injected in the last 1 / 2~3 / 4 range of the stroke of the second screw extruder. Vacuum degassing is performed at the end of the second screw extruder with a vacuum degree of -0.09~-0.095MPa. After extrusion, the material is sealed and packaged.

10. The preparation method according to claim 9, characterized in that: The starch is pre-dried to a moisture content of 1-2% by baking at 80-105℃ for 1-5 seconds using an airflow dryer.

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