A low-temperature resistant solvent-free polyurethane adhesive and its preparation method

Abstract

This invention discloses a low-temperature resistant solvent-free polyurethane adhesive and its preparation method, belonging to the technical field of polyurethane adhesives. The adhesive comprises component A and component B. Component A includes the following raw materials in parts by weight: 10-30 parts epoxidized castor oil, 15-35 parts polyether polyol, 5-15 parts bisphenol A type liquid epoxy resin, 20-30 parts epoxy silane-modified nano-hydroxyapatite, and 0.1-0.5 parts catalyst. Component B includes the following raw materials in parts by weight: 30-50 parts isocyanate, 10-20 parts polyether polyol, 5-15 parts terminal aminosiloxane, and 4-10 parts vanillin polyethylene glycol hydrazone. The vanillin polyethylene glycol hydrazone is obtained by the condensation reaction of vanillin and polyethylene glycol dihydrazide. The polyurethane adhesive of this invention introduces multiple flexible chain structures with synergistic effects, enabling the adhesive to possess good toughness under low-temperature conditions.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane adhesive technology, specifically relating to a low-temperature resistant solvent-free polyurethane adhesive and its preparation method. Background Technology

[0002] Polyurethane adhesives are high molecular weight compounds formed by the condensation polymerization of binary or polyisocyanates and hydroxyl-terminated prepolymers. They are characterized by impact resistance, good flexibility, and excellent adhesion. Under the market development trend of energy conservation and environmental protection, solvent-based polyurethane adhesives have the disadvantage of emitting VOCs that harm the environment, while water-based polyurethane adhesives also have the problem of poor adhesion. Therefore, solvent-free polyurethane adhesives are gradually gaining attention.

[0003] Two-component solvent-free polyurethane adhesives possess excellent adhesion, high mechanical properties, and superior chemical resistance. By eliminating the use of organic solvents, they significantly reduce volatile organic compound (VOC) emissions. Composed of polyols and isocyanates or polyurethane prepolymers, their low to medium viscosity and moisture-free curing characteristics make them excellent for laminating flexible packaging films with aluminum foil and metallized materials. Despite their superior performance, the generally insufficient low-temperature resistance of two-component solvent-free polyurethane adhesives remains a bottleneck that urgently needs to be addressed. At low temperatures, the movement of adhesive molecular chains is restricted, resulting in a significant decrease in flexibility, leading to hardening and brittleness of the adhesive layer. Impact toughness and peel strength deteriorate sharply, making delamination or failure more likely. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature resistant solvent-free polyurethane adhesive and its preparation method, which can solve the problem of poor low-temperature resistance of polyurethane adhesives in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions: A low-temperature resistant solvent-free polyurethane adhesive, the adhesive comprising component A and component B; Component A comprises the following raw materials in parts by weight: 10-30 parts of epoxidized castor oil, 15-35 parts of polyether polyol, 5-15 parts of bisphenol A type liquid epoxy resin, 20-30 parts of epoxy silane modified nano hydroxyapatite, and 0.1-0.5 parts of catalyst. Component B comprises the following raw materials in parts by weight: 30-50 parts isocyanate, 10-20 parts polyether polyol, 5-15 parts amino-terminated siloxane, 4-10 parts vanillin polyethylene glycol hydrazone; The vanillin-polyethylene glycol hydrazone is obtained by the condensation reaction of vanillin and polyethylene glycol dihydrazide. The mass ratio of component A to component B is (0.6-1.2):1.

[0006] At low temperatures, the movement of polyurethane molecular chain segments is restricted, causing the material to harden and become brittle. Therefore, the polyurethane molecular structure must incorporate more flexible segments so that the adhesive layer formed by polyurethane adhesives can maintain high elongation at low temperatures. However, when the flexibility of polyurethane is increased, its adhesion strength at low temperatures will decrease.

[0007] The polyurethane adhesive provided by this invention comprises two components. Component A consists of a mixture of epoxy resin and polyol. Bisphenol A-type liquid epoxy resin provides a rigid structure for the polyol system, avoiding insufficient strength caused by multiple flexible chains. Epoxidized castor oil is a bio-based raw material containing multiple hydroxyl and epoxy groups in its molecular chain, as well as long-chain fatty acid chains. It can react with the isocyanate in component B through hydroxyl groups and condense with the epoxy resin through epoxy groups. This allows the long, flexible chains of castor oil to interweave between the rigid epoxy structure and the hard segments of the polyurethane, effectively improving flexibility and enhancing low-temperature resistance. Epoxysilane-modified nano-hydroxyapatite is added to component A as a filler. The surface of the nano-hydroxyapatite structure contains abundant hydroxyl groups, which can effectively transfer stress when added to the adhesive. To improve its dispersibility, epoxysilane modification is performed. The modified nano-hydroxyapatite, due to the participation of surface epoxy groups and hydroxyl groups in the dual-system curing reaction, tightly binds the organic and inorganic materials, resisting the shrinkage of the polyurethane material at low temperatures, preventing adhesive layer detachment, and improving bonding strength.

[0008] Component B, based on isocyanate, adds polyether polyol. In subsequent preparation, the polyether polyol reacts with the isocyanate to form a polyurethane prepolymer with flexible polyether chains capped with isocyanate. Simultaneously, the terminal aminosiloxane in component B possesses excellent low-temperature resistance. The amino groups can form urea bonds with the isocyanate, and the amino groups can initiate ring-opening reactions of the epoxy groups. This leads to chemical cross-linking between the polyurethane and epoxy chains, promoting curing and enhancing the cohesive strength of the polyurethane adhesive. Furthermore, the polysiloxane segments maintain their mobility even at low temperatures. The introduction of silicone segments into both the epoxy and polyurethane systems significantly improves flexibility, contributing to better adhesion between the adhesive and the substrate.

[0009] This invention designs and synthesizes vanillin-polyethylene glycol acylhydrazone, obtained by the condensation reaction of vanillin and polyethylene glycol dihydrazide. Its molecular chain contains flexible long polyethylene glycol chains, which can be crosslinked with other components using the phenolic hydroxyl groups on vanillin. Building upon the above system's use of flexible ether bonds and organosilicon chains to alleviate the low-temperature brittleness of polyurethane, vanillin-polyethylene glycol acylhydrazone can introduce abundant hydrogen bonding sites through acylhydrazone bonds, exhibiting reversible fracture characteristics under dynamic conditions. At low temperatures, the acylhydrazone bonds can preferentially break, absorbing energy impacts and protecting the main molecular chain from damage under low-temperature shocks.

[0010] Furthermore, the preparation steps of the epoxysilane-modified nano-hydroxyapatite are as follows: Prepare an ethanol-water mixture with a volume ratio of 9:1, add nano-hydroxyapatite, and ultrasonically disperse to form a dispersion. Heat the dispersion in a water bath to 30-50℃, add KH560, stir and react for 0.5-2.5h, centrifuge to collect the precipitate, wash and dry it, and grind it to obtain epoxysilane modified nano-hydroxyapatite.

[0011] Furthermore, the ratio of the nano-hydroxyapatite and the ethanol-water mixture is 10-30g:500mL.

[0012] Furthermore, the mass ratio of KH560 to nano-hydroxyapatite is 0.1-0.5:1.

[0013] Furthermore, the preparation steps of the vanillin-polyethylene glycol hydrazone are as follows: Vanillin was dissolved in methanol, and polyethylene glycol dihydrazide was dissolved in water. Polyethylene glycol dihydrazide solution was added to the vanillin solution, and the mixture was heated to 60-70℃ and stirred for 5-7 hours. After cooling to room temperature, the mixture was filtered, and the precipitate was washed and dried to obtain vanillin polyethylene glycol dihydrazide.

[0014] Furthermore, the mass ratio of vanillin to methanol is 0.10-0.15:1.

[0015] Furthermore, the molecular weight of the polyethylene glycol dihydrazide is 600-2000; The mass ratio of polyethylene glycol dihydrazide to water is 1-2:10.

[0016] Furthermore, the mass ratio of vanillin in the vanillin solution to polyethylene glycol dihydrazide in the polyethylene glycol dihydrazide solution is 0.15-0.55:1.

[0017] Furthermore, the polyether polyol is at least one of polypropylene oxide diol, polytetrahydrofuran diol, and polypropylene oxide triol.

[0018] Furthermore, the catalyst is at least one of bismuth isooctanoate, zinc isooctanoate, and dibutyltin dilaurate.

[0019] Further, the isocyanate is at least one of isoflurane diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0020] Furthermore, the terminal aminosiloxane is diaminopropyl polydimethylsiloxane.

[0021] This invention also provides a method for preparing a low-temperature resistant solvent-free polyurethane adhesive, used to prepare the polyurethane adhesive as described above, comprising the following steps: Step 1: Prepare component A raw materials by mixing epoxidized castor oil, bisphenol A type liquid epoxy resin, polyether polyol, epoxy silane modified nano hydroxyapatite and catalyst, and stirring at 50-60℃ for 0.5-1h to obtain component A. Step 2: Prepare the raw materials for component B. Mix isocyanate, polyether polyol, amino-terminated siloxane and vanillin polyethylene glycol hydrazone, and stir at 70-80℃ for 2-4 hours to obtain component B. Step 3: Mix component A and component B in the specified proportions to obtain the adhesive.

[0022] The beneficial effects of this invention are: (1) The polyurethane adhesive provided by the present invention incorporates a variety of flexible chain structures to achieve synergistic effects, enabling the adhesive to have good toughness under low temperature conditions. The long fatty acid chains of epoxidized castor oil in component A, the flexible polyether chains of polyether polyol, and the organosilicon segments of terminal aminosiloxane in component B are interwoven in the polyurethane-epoxy dual system through cross-linking reaction, effectively alleviating low-temperature brittleness.

[0023] (2) In this invention, vanillin polyethylene glycol hydrazone is added to component B of the polyurethane adhesive. On the one hand, the polyethylene glycol chain imparts flexibility, and on the other hand, the dynamic covalent bonds formed by the hydrazone can enhance the cohesive force of the adhesive through hydrogen bonding under normal conditions. When subjected to external force impact at low temperature, the hydrazone bonds can break preferentially, absorb the energy impact, protect the integrity of the main chain structure, and endow the adhesive with potential microcrack self-repair ability, which helps to extend the service life of the material.

[0024] (3) In this invention, while introducing a flexible chain structure into the adhesive system, bisphenol A type liquid epoxy resin is added to component A to provide a rigid benzene ring structure, which forms a microphase separation with the polyurethane soft segment, giving the adhesive high strength. The epoxy silane modified nano hydroxyapatite forms a covalent bond with the epoxy matrix through the epoxy groups on the surface, and crosslinks with the polyurethane matrix through hydroxyl groups. The nano inorganic material is used to transfer stress, which not only plays a nano reinforcement role, but also resists the shrinkage of polyurethane material at low temperature and improves the bonding strength.

[0025] (4) The polyurethane adhesive system provided by the present invention is solvent-free, which can reduce the harm to the environment. Moreover, the raw materials are mostly bio-based and inorganic materials, which have good environmental protection and sustainability. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Preparation Example Preparation Example 1 Preparation of epoxidized castor oil: 100 mL of castor oil, 25 mL of formic acid (88% by mass), and 0.3 g of phosphoric acid (85% by mass) were added to a flask and mixed. The mixture was stirred and heated to 40 °C in a water bath. 60 mL of hydrogen peroxide (30% by mass) was added dropwise. After the addition was complete, the system temperature was adjusted to 65 °C and the mixture was stirred for 5 h. The product was allowed to stand in a separatory funnel to separate into layers. The aqueous layer was removed, and the oil layer was washed with 1% sodium hydroxide solution until the pH reached 6-7. The oil layer was then washed with distilled water until the pH reached 7. The product was dehydrated by vacuum distillation to obtain epoxidized castor oil.

[0028] Preparation Example 2 Preparation of epoxysilane-modified nano-hydroxyapatite: Measure 450 mL of ethanol and 50 mL of distilled water, add them to a beaker and stir well to prepare an ethanol-water mixture with a volume ratio of 9:1. Weigh 20 g of nano-hydroxyapatite (particle size 60-80 nm), add it to the ethanol-water mixture, and place it in an ultrasonic disperser for 30 min to form a dispersion. Transfer it to a water bath and heat it to 40 °C. Weigh 6 g of KH560 and add it to the system. Stir the mixture magnetically for 2 h, centrifuge to collect the precipitate, wash it three times with anhydrous ethanol, place it in an 80 °C oven to dry for 12 h, and then grind it into powder to obtain epoxy silane-modified nano-hydroxyapatite.

[0029] Preparation Example 3 Preparation of vanillin-polyethylene glycol hydrazone: 15.2 g (0.1 mol) of vanillin was weighed and added to 130 g of anhydrous methanol. The mixture was stirred and dissolved to obtain a vanillin solution. 40 g of polyethylene glycol dihydrazide (molecular weight 1000) was weighed and dissolved in 300 mL of distilled water to obtain a polyethylene glycol dihydrazide solution. The vanillin solution prepared above was placed in a flask, and the obtained polyethylene glycol dihydrazide solution was added to the flask. The mass ratio of vanillin in the vanillin solution to polyethylene glycol dihydrazide in the polyethylene glycol dihydrazide solution was 0.38:1. The flask system was stirred and heated to 65 °C for 6 h. After cooling to room temperature, the mixture was filtered. The precipitate was washed three times with distilled water and methanol, respectively. After washing, the precipitate was transferred to an oven and dried at 60 °C for 10 h to obtain vanillin polyethylene glycol hydrazone.

[0030] Example Example 1 A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0031] Component A comprises the following raw materials in parts by weight: Preparation Example 1: 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 10 parts of bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54 eq / 100g), 25 parts of epoxy silane modified nano-hydroxyapatite, and 0.3 parts of dibutyltin dilaurate.

[0032] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of diaminopropyl polydimethylsiloxane, and 7 parts of vanillin polyethylene glycol hydrazone prepared in Preparation Example 3.

[0033] The specific preparation steps are as follows: Step 1: Prepare the raw materials for component A. Mix the epoxidized castor oil prepared in Preparation Example 1, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol, epoxy silane modified nano-hydroxyapatite prepared in Preparation Example 2, and dibutyltin dilaurate. Heat to 55°C, stir at a constant temperature for 40 minutes, and degas under vacuum to obtain component A.

[0034] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, diaminopropyl polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0035] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0036] Example 2 The only difference from Example 1 is that the weight of epoxidized castor oil prepared in Example 1 in component A of the adhesive is reduced to 10 parts, while the other conditions and steps are the same as in Example 1.

[0037] Example 3 The only difference from Example 1 is that the weight of epoxidized castor oil prepared in Example 1 is increased to 30 parts in component A of the adhesive raw material, while the other conditions and steps are the same as in Example 1.

[0038] Example 4 The only difference from Example 1 is that the weight of bisphenol A type liquid epoxy resin in adhesive component A is reduced to 5 parts, while the other conditions and steps are the same as in Example 1.

[0039] Example 5 The only difference from Example 1 is that the weight of bisphenol A type liquid epoxy resin in adhesive component A is increased to 15 parts, while the other conditions and steps are the same as in Example 1.

[0040] Example 6 The only difference from Example 1 is that the weight of the epoxy silane-modified nano-hydroxyapatite prepared in Example 2 is reduced to 20 parts in the raw material of adhesive component A, while the other conditions and steps are the same as in Example 1.

[0041] Example 7 The only difference from Example 1 is that the weight of the epoxy silane-modified nano-hydroxyapatite prepared in Example 2 is increased to 30 parts in component A of the adhesive raw material, while the other conditions and steps are the same as in Example 1.

[0042] Example 8 The only difference from Example 1 is that the weight of diaminopropyl polydimethylsiloxane in component B of the adhesive is reduced to 5 parts, while the other conditions and steps are the same as in Example 1.

[0043] Example 9 The only difference from Example 1 is that the weight of diaminopropyl polydimethylsiloxane in component B of the adhesive is increased to 15 parts, while the other conditions and steps are the same as in Example 1.

[0044] Example 10 The only difference from Example 1 is that the vanillin polyethylene glycol hydrazone prepared in Example 3 is reduced to 4 parts by weight in the raw material of adhesive component B, while the other conditions and steps are the same as in Example 1.

[0045] Example 11 The only difference from Example 1 is that the weight of vanillin polyethylene glycol hydrazone prepared in Example 3 is increased to 10 parts in the raw material of adhesive component B, while the other conditions and steps are the same as in Example 1.

[0046] Comparative Example 1 The only difference from Example 1 is that bisphenol A type liquid epoxy resin is not added to the raw materials of adhesive component A.

[0047] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0048] Component A comprises the following raw materials in parts by weight: Preparation Example 1: 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 25 parts of epoxysilane-modified nano-hydroxyapatite, and 0.3 parts of dibutyltin dilaurate.

[0049] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of diaminopropyl polydimethylsiloxane, and 7 parts of vanillin polyethylene glycol hydrazone prepared in Preparation Example 3.

[0050] The specific preparation steps are as follows: Step 1: Prepare the raw materials for component A. Mix the epoxidized castor oil prepared in Preparation Example 1, polytetrahydrofuran diol, epoxysilane-modified nano-hydroxyapatite prepared in Preparation Example 2, and dibutyltin dilaurate. Heat to 55°C, stir at a constant temperature for 40 minutes, and degas under vacuum to obtain component A.

[0051] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, diaminopropyl polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0052] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0053] Comparative Example 2 The only difference from Example 1 is that castor oil is used instead of epoxidized castor oil in the raw material of adhesive component A.

[0054] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0055] Component A comprises the following raw materials in parts by weight: 20 parts castor oil, 25 parts polytetrahydrofuran diol, 10 parts bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54 eq / 100g), 25 parts epoxy silane modified nano-hydroxyapatite prepared in Preparation Example 2, and 0.3 parts dibutyltin dilaurate.

[0056] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of diaminopropyl polydimethylsiloxane, and 7 parts of vanillin polyethylene glycol hydrazone prepared in Preparation Example 3.

[0057] The specific preparation steps are as follows: Step 1: Prepare component A raw materials by mixing castor oil, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol, epoxy silane modified nano-hydroxyapatite prepared in Preparation Example 2, and dibutyltin dilaurate. Heat to 55°C, stir at a constant temperature for 40 minutes, and degas under vacuum to obtain component A.

[0058] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, diaminopropyl polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0059] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0060] Comparative Example 3 The only difference from Example 1 is that epoxy silane-modified nano-hydroxyapatite is not added to the raw material of adhesive component A.

[0061] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0062] Component A comprises the following raw materials in parts by weight: Preparation Example 1 prepared 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 10 parts of bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54eq / 100g), and 0.3 parts of dibutyltin dilaurate.

[0063] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of diaminopropyl polydimethylsiloxane, and 7 parts of vanillin polyethylene glycol hydrazone prepared in Preparation Example 3.

[0064] The specific preparation steps are as follows: Step 1: Prepare component A raw materials. Mix the epoxidized castor oil prepared in Preparation Example 1, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol and dibutyltin dilaurate, heat to 55°C, stir at a constant temperature for 40 min, and degas under vacuum to obtain component A.

[0065] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, diaminopropyl polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0066] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0067] Comparative Example 4 The only difference from Example 1 is that nano-hydroxyapatite is used instead of epoxy silane-modified nano-hydroxyapatite in the raw material of adhesive component A.

[0068] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0069] Component A comprises the following raw materials in parts by weight: Preparation Example 1 prepared 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 10 parts of bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54eq / 100g), 25 parts of nano hydroxyapatite (particle size 60-80nm), and 0.3 parts of dibutyltin dilaurate.

[0070] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of diaminopropyl polydimethylsiloxane, and 7 parts of vanillin polyethylene glycol hydrazone prepared in Preparation Example 3.

[0071] The specific preparation steps are as follows: Step 1: Prepare component A raw materials. Mix the epoxidized castor oil prepared in Example 1, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol, nano hydroxyapatite and dibutyltin dilaurate, heat to 55°C, stir at a constant temperature for 40 min, and degas under vacuum to obtain component A.

[0072] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, diaminopropyl polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0073] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0074] Comparative Example 5 The only difference from Example 1 is that polydimethylsiloxane is used instead of diaminopropyl polydimethylsiloxane in the raw material of adhesive component B.

[0075] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0076] Component A comprises the following raw materials in parts by weight: Preparation Example 1: 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 10 parts of bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54 eq / 100g), 25 parts of epoxy silane modified nano-hydroxyapatite, and 0.3 parts of dibutyltin dilaurate.

[0077] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, 10 parts of polydimethylsiloxane, and 7 parts of vanillin-polyethylene glycol hydrazone prepared in Preparation Example 3.

[0078] The specific preparation steps are as follows: Step 1: Prepare the raw materials for component A. Mix the epoxidized castor oil prepared in Preparation Example 1, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol, epoxy silane modified nano-hydroxyapatite prepared in Preparation Example 2, and dibutyltin dilaurate. Heat to 55°C, stir at a constant temperature for 40 minutes, and degas under vacuum to obtain component A.

[0079] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofurandiol, polydimethylsiloxane, and vanillin polyethylene glycol hydrazone prepared in Preparation Example 3. Heat to 80°C, stir at a constant temperature for 3 hours, and degas under vacuum to obtain component B.

[0080] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0081] Comparative Example 6 The only difference from Example 1 is that vanillin polyethylene glycol hydrazone is not added to the raw material of adhesive component B.

[0082] A low-temperature resistant solvent-free polyurethane adhesive, comprising component A and component B.

[0083] Component A comprises the following raw materials in parts by weight: Preparation Example 1: 20 parts of epoxidized castor oil, 25 parts of polytetrahydrofuran diol, 10 parts of bisphenol A type liquid epoxy resin (E51 type, epoxy value 0.51-0.54 eq / 100g), 25 parts of epoxy silane modified nano-hydroxyapatite, and 0.3 parts of dibutyltin dilaurate.

[0084] Component B comprises the following raw materials in parts by weight: 40 parts of isoflurane diisocyanate, 15 parts of polytetrahydrofuran diol, and 10 parts of diaminopropyl polydimethylsiloxane.

[0085] The specific preparation steps are as follows: Step 1: Prepare the raw materials for component A. Mix the epoxidized castor oil prepared in Preparation Example 1, bisphenol A type liquid epoxy resin, polytetrahydrofuran diol, epoxy silane modified nano-hydroxyapatite prepared in Preparation Example 2, and dibutyltin dilaurate. Heat to 55°C, stir at a constant temperature for 40 minutes, and degas under vacuum to obtain component A.

[0086] Step 2: Prepare the raw materials for component B. Mix isoflurane diisocyanate, polytetrahydrofuran diol, and diaminopropyl polydimethylsiloxane, heat to 80°C, stir at a constant temperature for 3 hours, and then degas under vacuum to obtain component B.

[0087] Step 3: Mix component A and component B at a mass ratio of 0.8:1 to obtain the adhesive.

[0088] The adhesives prepared in Examples 1-11 and Comparative Examples 1-6 were subjected to performance tests, and the results are shown in Table 1.

[0089] Shear strength: In accordance with the standard GB / T 7124-2008 Determination of tensile shear strength of adhesives (rigid material to rigid material), aluminum-aluminum test samples were prepared using adhesives. After curing, the adhesive layer thickness was 10 μm, and the shear strength was tested.

[0090] Tensile strength and elongation at break: The adhesive was coated on a polytetrafluoroethylene plate and left at room temperature for 12 hours. Then it was transferred to an oven and cured at 50°C for 24 hours. The cured adhesive layer was cut with a cutter to obtain dumbbell-shaped specimens. The tensile strength and elongation at break were tested on a universal testing machine at a tensile rate of 100 mm / min.

[0091] Low-temperature resistance: The aluminum-aluminum test sample for shear strength testing was placed at -196℃ for 1 hour, and the shear strength was tested after returning to room temperature; dumbbell-shaped samples were prepared according to the above tensile strength and elongation at break test, and the tensile strength and elongation at break were tested after being placed at -40℃ for 24 hours.

[0092] Table 1

[0093] As can be seen from Table 1, the shear strength and low-temperature resistance of the adhesive in Example 1 of this invention are significantly better than those of the comparative example. By optimizing the formulation, a variety of flexible chain structures are introduced into the prepared polyurethane adhesive. The interwoven structure of epoxy crosslinking network and polyurethane crosslinking network enables the adhesive to maintain high strength. Simultaneously, epoxy silane-modified nano-hydroxyapatite is added to disperse stress, and the acylhydrazone dynamic bonds of vanillin polyethylene glycol acylhydrazone absorb impact energy, giving the adhesive good toughness under low-temperature conditions.

[0094] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-temperature resistant solvent-free polyurethane adhesive, characterized in that, The adhesive comprises component A and component B; Component A comprises the following raw materials in parts by weight: 10-30 parts of epoxidized castor oil, 15-35 parts of polyether polyol, 5-15 parts of bisphenol A type liquid epoxy resin, 20-30 parts of epoxy silane modified nano hydroxyapatite, and 0.1-0.5 parts of catalyst. Component B comprises the following raw materials in parts by weight: 30-50 parts isocyanate, 10-20 parts polyether polyol, 5-15 parts amino-terminated siloxane, 4-10 parts vanillin polyethylene glycol hydrazone; The vanillin-polyethylene glycol hydrazone is obtained by the condensation reaction of vanillin and polyethylene glycol dihydrazide. The mass ratio of component A to component B is (0.6-1.2):

1.

2. The low-temperature resistant solvent-free polyurethane adhesive according to claim 1, characterized in that, The preparation steps of the epoxy silane modified nano-hydroxyapatite are as follows: Prepare an ethanol-water mixture with a volume ratio of 9:1, add nano-hydroxyapatite, and ultrasonically disperse to form a dispersion. Heat the dispersion in a water bath to 30-50℃, add KH560, stir and react for 0.5-2.5h, centrifuge to collect the precipitate, wash and dry it, and grind it to obtain epoxysilane modified nano-hydroxyapatite.

3. The low-temperature resistant solvent-free polyurethane adhesive according to claim 2, characterized in that, The ratio of the nano-hydroxyapatite and ethanol-water mixture is 10-30g:500mL.

4. The low-temperature resistant solvent-free polyurethane adhesive according to claim 2, characterized in that, Furthermore, the mass ratio of KH560 to nano-hydroxyapatite is 0.1-0.5:

1.

5. The low-temperature resistant solvent-free polyurethane adhesive according to claim 1, characterized in that, The preparation steps of the vanillin-polyethylene glycol hydrazone are as follows: Vanillin was dissolved in methanol, and polyethylene glycol dihydrazide was dissolved in water. Polyethylene glycol dihydrazide solution was added to the vanillin solution, and the mixture was heated to 60-70℃ and stirred for 5-7 hours. After cooling to room temperature, the mixture was filtered, and the precipitate was washed and dried to obtain vanillin polyethylene glycol dihydrazide.

6. The low-temperature resistant solvent-free polyurethane adhesive according to claim 5, characterized in that, The mass ratio of vanillin to methanol is 0.10-0.15:

1.

7. The low-temperature resistant solvent-free polyurethane adhesive according to claim 5, characterized in that, The molecular weight of the polyethylene glycol dihydrazide is 600-2000; The mass ratio of polyethylene glycol dihydrazide to water is 1-2:

10.

8. The low-temperature resistant solvent-free polyurethane adhesive according to claim 5, characterized in that, The mass ratio of vanillin in the vanillin solution to polyethylene glycol dihydrazide in the polyethylene glycol dihydrazide solution is 0.15-0.55:

1.

9. The low-temperature resistant solvent-free polyurethane adhesive according to claim 1, characterized in that, The polyether polyol is at least one of polyoxypropylene diol, polytetrahydrofuran diol, and polyoxypropylene triol; The catalyst is at least one of bismuth isooctanoate, zinc isooctanoate, and dibutyltin dilaurate; The isocyanate is at least one of isoflurone diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; The terminal aminosiloxane is diaminopropyl polydimethylsiloxane.

10. A method for preparing a low-temperature resistant solvent-free polyurethane adhesive, characterized in that, The preparation of the low-temperature resistant solvent-free polyurethane adhesive as described in any one of claims 1-9 comprises the following steps: Step 1: Prepare component A raw materials by mixing epoxidized castor oil, bisphenol A type liquid epoxy resin, polyether polyol, epoxy silane modified nano hydroxyapatite and catalyst, and stirring at 50-60℃ for 0.5-1h to obtain component A. Step 2: Prepare the raw materials for component B. Mix isocyanate, polyether polyol, amino-terminated siloxane and vanillin polyethylene glycol hydrazone, and stir at 70-80℃ for 2-4 hours to obtain component B. Step 3: Mix component A and component B in the specified proportions to obtain the adhesive.

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