Low-temperature-resistant waterborne polyurethane

Abstract

The invention relates to the field of polyurethane, and particularly discloses low-temperature-resistant waterborne polyurethane. Wherein the low-temperature-resistant waterborne polyurethane is prepared from the following raw materials: polyester polyol, polyether polyol, castor oil-based polyol, diisocyanate, hydroxyl-terminated polybutadiene, modified filler, a hydrophilic chain extender, a post-chain extender, an antioxidant and water. Wherein after hydroxyl-terminated polybutadiene serving as a soft segment is added into the waterborne polyurethane, the flexibility of a molecular chain is enhanced, the low-temperature resistance of the waterborne polyurethane is improved, talcum powder is modified by adopting epoxy silane and polyethyleneimine, talcum powder particles are stably dispersed among the molecular chain segments of the polyurethane, agglomeration and collapse among the particles are reduced, and the low-temperature resistance of the waterborne polyurethane is improved. And relative slippage between molecular chain segments is promoted, and a good toughening effect on a polyurethane material is achieved, so that the waterborne polyurethane can still keep excellent flexibility in a low-temperature environment.

Description

Technical Field

[0001] The present invention relates to the field of polyurethane, in particular to a low-temperature resistant water-based polyurethane. Background Art

[0002] Waterborne polyurethane (PU) is an environmentally friendly polymer material using water as its dispersion medium. Its low VOC emissions, non-toxicity, and ease of processing make it widely used in leather finishing, industrial coatings, adhesives, and textile coatings. The performance of PU depends on the microscopic phase separation structure of hard and soft segments. By adjusting the ratio of hard to soft segments in the PU molecular structure, the material's glass transition temperature and mechanical properties can be influenced.

[0003] In existing technologies, improving low-temperature resistance typically requires lowering the glass transition temperature (Tg), meaning increasing the soft segment ratio or introducing flexible segments. However, this approach significantly weakens the material's tensile strength, modulus, and wear resistance. Conversely, enhancing mechanical properties by increasing the hard segment content results in an increase in Tg, making the material less compliant at low temperatures and potentially causing brittle cracking. This contradiction makes it difficult for existing waterborne polyurethanes to achieve a balance between low-temperature performance and mechanical properties, severely limiting their application in low-temperature environments. Summary of the Invention

[0004] In order to improve the problem of cracking and failure of waterborne polyurethane due to increased brittleness in low-temperature environments, the present application provides a low-temperature resistant waterborne polyurethane.

[0005] In the first aspect, the present application provides a low-temperature resistant water-based polyurethane, which adopts the following technical solution: A low-temperature resistant water-based polyurethane is prepared from the following raw materials in parts by weight: 5-10 parts of polyester polyol, 15-20 parts of polyether polyol, 4-8 parts of castor oil-based polyol, 10-14 parts of diisocyanate, 8-12 parts of hydroxyl-terminated polybutadiene, 9-13 parts of modified filler, 0.5-1.5 parts of hydrophilic chain extender, 1.5-2.5 parts of post-chain extender, 0.1-0.3 parts of antioxidant, and 45-65 parts of water; The raw materials for preparing the modified filler include talc powder, epoxy silane, and polyethylene imine, and the weight ratio of the talc powder, epoxy silane, and polyethylene imine is 1: (0.03-0.05): (0.5-0.7).

[0006] By adopting the above technical solution, the waterborne polyurethane molecular chain segments synthesized from polyester polyol, polyether polyol, castor oil-based polyol, and diisocyanate in this application have an appropriate ratio of soft and hard segments. Due to the excellent flexibility of hydroxy-terminated polybutadiene, its addition as a soft segment to the waterborne polyurethane enhances the flexibility of the molecular chain. The increased content of the soft segment in the molecular chain improves the degree of phase separation between the soft and hard segments, thereby lowering the glass transition temperature and improving the low-temperature resistance of the waterborne polyurethane. The addition of modified fillers also provides toughening and reinforcement. Specifically, talc is modified by coupling grafting using epoxysilane and polyethyleneimine. The epoxysilane molecular structure contains alkoxy and epoxy groups. The alkoxy groups are hydrolyzed to generate active silanol groups, which combine with the hydroxyl groups on the surface of the talc. The epoxy groups react with the amino groups in the polyethyleneimine through a ring-opening reaction, and the polyethyleneimine is grafted onto the surface of the talc, so that the talc is evenly dispersed in the polyurethane matrix. In addition, the amino groups in the polyethyleneimine combine with the isocyanate groups, so that the talc particles are stably dispersed between the polyurethane molecular segments, reducing the agglomeration and collapse between the particles and promoting the relative slip between the molecular segments, which has a good toughening effect on the polyurethane material, enhances the material's anti-brittle cracking performance, reduces the generation of cracks, and enables the water-based polyurethane to still maintain excellent mechanical properties under low temperature conditions.

[0007] Preferably, the preparation method of the modified filler comprises the following steps: (1) adding talc powder to a hydroxide solution, heating to 60-80° C., stirring for 4-6 hours, filtering, washing, and drying to obtain pretreated talc powder; (2) dissolving epoxysilane in a solvent to form a hydrolysis solution, adjusting the pH of the solution to 3.0-4.0, adding the treated talc to the hydrolysis solution, ultrasonically dispersing for 30-40 minutes, filtering, washing, and drying to obtain silanized talc; (3) Dispersing polyethyleneimine in a solvent and stirring evenly to obtain a polyethyleneimine solution, dispersing silanized talc in a solvent and stirring evenly to obtain a suspension, slowly dripping the polyethyleneimine solution into the suspension, reacting at room temperature for 6-8 hours, filtering, washing, and drying to obtain a modified filler.

[0008] Preferably, the epoxysilane is selected from one or both of 3-glycidyloxypropyltrimethoxysilane and 3-glycidyloxypropyltriethoxysilane.

[0009] By adopting the above technical solution, talc powder is pretreated in a hydroxide solution to increase the number of hydroxyl groups on the surface of the talc powder. The alkoxy groups in the epoxysilane molecular structure are hydrolyzed to generate active silanol groups. The silanol groups combine with the hydroxyl groups on the surface of the talc powder, thereby coupling-modifying the talc powder. Afterwards, the epoxy groups on the epoxysilane undergo a ring-opening reaction with the amino groups in the polyethyleneimine, and the polyethyleneimine is grafted onto the surface of the talc powder, so that the talc powder can be evenly dispersed in the polyurethane matrix, thereby improving the flexibility of the water-based polyurethane in a low-temperature environment.

[0010] Preferably, the number average molecular weight of the hydroxyl-terminated polybutadiene is 2000-3000.

[0011] By adopting this technical solution, hydroxyl-terminated polybutadiene with a number-average molecular weight of 2,000-3,000 exhibits an appropriate molecular chain length and flexible structure, acting as a "bridge" within the polyurethane molecular structure, ensuring a certain degree of flexibility without excessively weakening the material's cohesion. At low temperatures, the hydroxyl-terminated polybutadiene prevents excessive packing of polyurethane molecular chains, preventing a significant increase in the glass transition temperature and enabling the material to maintain good flexibility, thus preventing brittle cracking.

[0012] Preferably, the hydrophilic chain extender is selected from one or more of dimethylol propionic acid, dimethylol butyric acid, 1,2-propylene glycol-3-sodium sulfonate, and 1,4-butanediol-2-sodium sulfonate.

[0013] Preferably, the post-chain extender is one or more of ethylenediamine, hydrazine hydrate, and isophoronediamine.

[0014] By adopting the above technical solution, hydrophilic chain extenders and post-chain extenders are used to further adjust the ratio of hard segments to soft segments in the molecular structure of waterborne polyurethane. While ensuring the low-temperature resistance of the material, the tensile strength, modulus, etc. of the material are avoided to be significantly weakened by simply increasing the proportion of soft segments or introducing flexible chain segments. The low-temperature performance and mechanical properties of the material are taken into account, making the material better suitable for low-temperature environments.

[0015] Preferably, the antioxidant is one or more of antioxidant 1098, antioxidant 1010, and antioxidant AO-80.

[0016] By adopting the above technical solution, the above antioxidant can capture free radicals generated during the oxidation process, interrupt the chain reaction, effectively resist oxidation, and extend the service life of the low-temperature resistant water-based polyurethane.

[0017] Preferably, the polyester polyol is selected from one or more of polycarbonate diol, polyethylene adipate diol and polyethylene glycol adipate diol; the polyether polyol is compounded by polyoxypropylene diol and polytetramethylene glycol in a weight ratio of (0.6-0.8):1.

[0018] Preferably, the diisocyanate is selected from one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, and cyclohexane dimethylene diisocyanate.

[0019] By adopting the above technical solution, the polyurethane synthesized by using the above polyol and diisocyanate has a suitable ratio of soft and hard segments. In addition, the above alicyclic diisocyanate has good yellowing resistance, and the alicyclic structure is a deformable non-planar structure. The synthesized polyurethane has good mechanical properties and flexibility, especially can maintain excellent flexibility in low temperature environment, and has good low temperature resistance.

[0020] In a second aspect, the present application provides a method for preparing a low-temperature resistant waterborne polyurethane, which adopts the following technical solution: A method for preparing a low-temperature resistant waterborne polyurethane, comprising the following steps: S1: Mix polyester polyol, polyether polyol, castor oil-based polyol, and diisocyanate, add a catalyst, introduce nitrogen, and react with stirring at 80-90°C for 2-3 hours. Add a hydrophilic chain extender and acetone, and continue the reaction for 1-2 hours to obtain a polyurethane prepolymer; S2: adding a neutralizing agent to the polyurethane prepolymer for neutralization, adding a portion of water for high-speed dispersion and emulsification, adding terminal hydroxyl polybutadiene, a post-chain extender, and an antioxidant, continuing to stir and react for 40-50 minutes, and removing acetone in vacuo to obtain a polyurethane emulsion; S3: mixing the modified filler with the remaining water, ultrasonically dispersing for 20-30 minutes, adding the dispersion to the polyurethane emulsion, and stirring evenly to obtain a low-temperature resistant water-based polyurethane.

[0021] By adopting the above technical solution, the water-based polyurethane prepared by the above method has good low-temperature resistance and mechanical properties, which can solve the problem of cracking and failure of existing water-based polyurethane materials due to increased brittleness in cold environments, and ensure that the water-based polyurethane materials can still maintain good flexibility in low-temperature environments.

[0022] This application has the following beneficial effects: The waterborne polyurethane molecular chain segments synthesized in the present application using polyester polyols, polyether polyols, castor oil-based polyols, and diisocyanates have a suitable ratio of soft and hard segments. Since the terminal hydroxyl polybutadiene has good flexibility, after it is added to the waterborne polyurethane as a soft segment, the flexibility of the molecular chain is enhanced, and the content of the soft segment in the molecular chain is increased, thereby improving the degree of phase separation between the soft and hard segments. Therefore, the glass transition temperature is reduced, thereby improving the low-temperature resistance of the waterborne polyurethane. The addition of modified fillers plays a role in toughening and strengthening. Epoxysilane and polyethyleneimine are used to couple and graft modify talc. The molecular structure of epoxysilane contains alkoxy and epoxy groups. The alkoxy groups are hydrolyzed to generate active silanol groups, which combine with the hydroxyl groups on the surface of the talc. The epoxy groups react with the amino groups in the polyethyleneimine through ring-opening reaction, and the polyethyleneimine is grafted onto the surface of the talc, so that the talc is evenly dispersed in the polyurethane matrix. In addition, the amino groups in the polyethyleneimine are combined with the isocyanate groups, so that the talc particles are stably dispersed between the polyurethane molecular segments, reducing the agglomeration and collapse between the particles and promoting the relative slip between the molecular segments, which has a good toughening effect on the polyurethane material, enhances the material's anti-brittle cracking performance, reduces the generation of cracks, and enables the water-based polyurethane to maintain excellent mechanical properties even in low temperature environments. DETAILED DESCRIPTION

[0023] Preparation Example Preparation Example 1 Preparation of modified filler: (1) Add 90 g of talc powder to 250 mL of NaOH solution, heat to 60°C, stir and react for 4 h, filter, wash, and dry to obtain pretreated talc powder; (2) dissolving 2.7 g of 3-glycidyloxypropyltrimethoxysilane in 120 mL of n-butanol to form a hydrolysis solution, adjusting the pH of the solution to 3.0, adding the pretreated talc to the hydrolysis solution, ultrasonically dispersing for 30 min, filtering, washing, and drying to obtain silanized talc; (3) Disperse 45 g of polyethyleneimine (Lanabai 9002-98-6) in 120 mL of ethanol and stir evenly to obtain a polyethyleneimine solution. Disperse silanized talc in 250 mL of ethanol and stir evenly to obtain a suspension. Slowly drop the polyethyleneimine solution into the suspension and react at room temperature for 6 h. Filter, wash, and dry to obtain a modified filler.

[0024] Preparation Example 2 Preparation of modified filler: (1) Add 110 g of talc powder to 250 mL of NaOH solution, heat to 70°C, stir and react for 5 h, filter, wash, and dry to obtain pretreated talc powder; (2) dissolving 4.4 g of 3-glycidyloxypropyltrimethoxysilane in 140 mL of n-butanol to form a hydrolysis solution, adjusting the pH of the solution to 3.5, adding the pretreated talc to the hydrolysis solution, ultrasonically dispersing for 35 min, filtering, washing, and drying to obtain silanized talc; (3) Disperse 66 g of polyethyleneimine (Lanabai 9002-98-6) in 140 mL of ethanol and stir evenly to obtain a polyethyleneimine solution. Disperse silanized talc in 250 mL of ethanol and stir evenly to obtain a suspension. Slowly drop the polyethyleneimine solution into the suspension and react at room temperature for 7 h. Filter, wash, and dry to obtain a modified filler.

[0025] Preparation Example 3 Preparation of modified filler: (1) Add 130 g of talc powder to 250 mL of NaOH solution, heat to 80°C, stir and react for 6 h, filter, wash, and dry to obtain pretreated talc powder; (2) dissolving 6.5 g of 3-glycidyloxypropyltriethoxysilane in 160 mL of n-butanol to form a hydrolysis solution, adjusting the pH of the solution to 4.0, adding the pretreated talc to the hydrolysis solution, ultrasonically dispersing for 40 min, filtering, washing, and drying to obtain silanized talc; (3) Disperse 91 g of polyethyleneimine (Lanabai 9002-98-6) in 160 mL of ethanol and stir evenly to obtain a polyethyleneimine solution. Disperse silanized talc in 250 mL of ethanol and stir evenly to obtain a suspension. Slowly drop the polyethyleneimine solution into the suspension and react at room temperature for 8 h. Filter, wash, and dry to obtain a modified filler.

[0026] Preparation Example 4 The difference between this Preparation Example and Preparation Example 2 is that an equal amount of 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane is used instead of 3-glycidyloxypropyltrimethoxysilane.

[0027] Preparation Example 5 The difference between this preparation example and preparation example 2 is that 3-glycidyloxypropyltrimethoxysilane is not added, that is, the preparation method of the modified filler is: (1) Add 110 g of talc powder to 250 mL of NaOH solution, heat to 70°C, stir and react for 5 h, filter, wash, and dry to obtain pretreated talc powder; (2) Disperse 66 g of polyethyleneimine (Lanabai 9002-98-6) in 140 mL of ethanol and stir evenly to obtain a polyethyleneimine solution. Disperse the pretreated talc in 250 mL of ethanol and stir evenly to obtain a suspension. Slowly drop the polyethyleneimine solution into the suspension and react at room temperature for 7 h. Filter, wash, and dry to obtain a modified filler.

[0028] Preparation Example 6 The difference between this preparation example and preparation example 2 is that no polyethyleneimine is added, that is, the preparation method of the modified filler is: (1) Add 110 g of talc powder to 250 mL of NaOH solution, heat to 70°C, stir and react for 5 h, filter, wash, and dry to obtain pretreated talc powder; (2) 4.4 g of 3-glycidyloxypropyltrimethoxysilane was dissolved in 140 mL of n-butanol to form a hydrolysis solution. The pH of the solution was adjusted to 3.5. The pretreated talc was added to the hydrolysis solution and ultrasonically dispersed for 35 min. The modified filler was filtered, washed, and dried to obtain the modified filler.

[0029] Preparation Example 7 The difference between this preparation example and preparation example 2 is that an equal amount of 3-aminopropyltrimethoxysilane is used instead of 3-glycidyloxypropyltrimethoxysilane.

[0030] Preparation Example 8 The difference between this Preparation Example and Preparation Example 2 is that an equal amount of vinyltrimethoxysilane is used instead of 3-glycidyloxypropyltrimethoxysilane. Example

[0031] Example 1 A low-temperature resistant water-based polyurethane is prepared from the following raw materials: 50g of polycarbonate diol (Lanabai 29862-10-0), 56g of polyoxypropylene glycol (Maikerui 25322-69-4), 94g of polytetramethylene ether glycol (Deyitai 25190-06-1), 40g of castor oil-based polyol (Langbowan), 100g of dicyclohexylmethane diisocyanate, 80g of terminal hydroxyl polybutadiene (number average molecular weight of 2000), 90g of modified filler (prepared in Preparation Example 1), 5g of dihydroxymethylbutyric acid, 15g of hydrazine hydrate (concentration 65%), 1g of antioxidant 1098, and 450g of water.

[0032] The method for preparing the low-temperature resistant waterborne polyurethane of this embodiment comprises the following steps: S1: polycarbonate diol, polyoxypropylene diol, polytetramethylene glycol, castor oil-based polyol, and dicyclohexylmethane diisocyanate were mixed, 3 mL of dibutyltin dilaurate was added, nitrogen was introduced, and the mixture was stirred and reacted at 80°C for 2 h. Dimethylolbutyric acid and acetone were added and the reaction was continued for 1 h to obtain a polyurethane prepolymer; S2: triethylamine was added to the polyurethane prepolymer for neutralization, 200 mL of water was added for high-speed dispersion and emulsification, terminal hydroxyl polybutadiene, hydrazine hydrate, and antioxidant 1098 were added, and the stirring reaction was continued for 40 minutes. The acetone was removed in vacuo to obtain a polyurethane emulsion; S3: the modified filler was mixed with the remaining 250 mL of water, ultrasonically dispersed for 20 minutes, the dispersion was added to the polyurethane emulsion, and stirred evenly to obtain a low-temperature resistant water-based polyurethane.

[0033] Example 2 A low-temperature resistant water-based polyurethane, prepared from the following raw materials: 70g of polyethylene adipate glycol, 74g of polyoxypropylene glycol (Mikerui 25322-69-4), 106g of polytetramethylene ether glycol (Deyitai 25190-06-1), 60g of castor oil-based polyol (Langbowan), 120g of isophorone diisocyanate, 100g of terminal hydroxyl polybutadiene (number average molecular weight of 2700), 110g of modified filler (prepared in Preparation Example 2), 10g of dihydroxymethylpropionic acid, 20g of ethylenediamine, 2g of antioxidant AO-80 (Japan ADEKA), and 550g of water.

[0034] The method for preparing the low-temperature resistant waterborne polyurethane of this embodiment comprises the following steps: S1: Polyethylene adipate glycol, polyoxypropylene glycol, polytetramethylene ether glycol, castor oil-based polyol, and isophorone diisocyanate were mixed, 4 mL of dibutyltin dilaurate was added, nitrogen was introduced, and the mixture was stirred and reacted at 85°C for 2.5 h. Dimethylolpropionic acid and acetone were added, and the reaction was continued for 1.5 h to obtain a polyurethane prepolymer; S2: triethylamine was added to the polyurethane prepolymer for neutralization, 250 mL of water was added for high-speed dispersion and emulsification, terminal hydroxyl polybutadiene, ethylenediamine, and antioxidant AO-80 were added, and the stirring reaction was continued for 45 minutes. The acetone was removed in vacuo to obtain a polyurethane emulsion; S3: the modified filler was mixed with the remaining 300 mL of water, ultrasonically dispersed for 25 minutes, the dispersion was added to the polyurethane emulsion, and stirred evenly to obtain a low-temperature resistant water-based polyurethane.

[0035] Example 3 A low-temperature resistant water-based polyurethane is prepared from the following raw materials: 100g of polyneopentyl adipate (Xinyuhong 27925-07-1), 89g of polyoxypropylene glycol (Maikerui 25322-69-4), 111g of polytetramethylene ether glycol (Deyitai 25190-06-1), 80g of castor oil-based polyol, 140g of cyclohexane dimethylene diisocyanate, 120g of hydroxy-terminated polybutadiene (number average molecular weight of 3000), 130g of modified filler (prepared in Preparation Example 3), 15g of sodium 1,2-propylene glycol-3-sulfonate, 25g of isophorone diamine, 3g of antioxidant 1010, and 650g of water.

[0036] The method for preparing the low-temperature resistant waterborne polyurethane of this embodiment comprises the following steps: S1: Poly (neopentyl adipate), polyoxypropylene glycol, polytetramethylene glycol, castor oil-based polyol, and cyclohexane dimethylene diisocyanate were mixed, 5 mL of dibutyltin dilaurate was added, nitrogen was introduced, and the mixture was stirred and reacted at 90°C for 3 h. Sodium 1,2-propylene glycol-3-sulfonate and acetone were added, and the reaction was continued for 2 h to obtain a polyurethane prepolymer; S2: triethylamine was added to the polyurethane prepolymer for neutralization, 300 mL of water was added for high-speed dispersion and emulsification, hydroxy-terminated polybutadiene, isophorone diamine, and antioxidant 1010 were added, and the reaction was continued with stirring for 50 min. The acetone was removed under vacuum to obtain a polyurethane emulsion; S3: The modified filler was mixed with the remaining 350 mL of water, and ultrasonically dispersed for 30 min. The dispersion was added to the polyurethane emulsion and stirred evenly to obtain a low-temperature resistant water-based polyurethane.

[0037] Example 4 The difference between this embodiment and embodiment 2 is that the modified filler prepared in preparation example 4 is used.

[0038] Comparative Example Comparative Example 1 A low-temperature resistant water-based polyurethane, which differs from Example 2 in that the modified filler prepared in Preparation Example 5 is used.

[0039] Comparative Example 2 A low-temperature resistant water-based polyurethane, which differs from Example 2 in that the modified filler prepared in Preparation Example 6 is used.

[0040] Comparative Example 3 A low-temperature resistant water-based polyurethane, which differs from Example 2 in that the modified filler prepared in Preparation Example 7 is used.

[0041] Comparative Example 4 A low-temperature resistant water-based polyurethane is different from Example 2 in that the modified filler prepared in Preparation Example 8 is used.

[0042] Comparative Example 5 A low-temperature resistant water-based polyurethane is different from Example 2 in that an equal amount of talc is used instead of the modified filler.

[0043] Comparative Example 6 A low-temperature resistant water-based polyurethane, which differs from Example 2 in that no modified filler is added.

[0044] Comparative Example 7 A low-temperature resistant water-based polyurethane, which differs from Example 2 in that no hydroxyl-terminated polybutadiene is added.

[0045] Performance testing 1. Glass transition temperature: Use DSC test and measure according to the DSC test method specified in IPC-TM-6502.4.25.

[0046] 2. Low-Temperature Resistance Test: Static stiffness β1 at -40°C and static stiffness β0 at 23°C were measured according to TB / T 3395-2015. Low-temperature stiffness change rate = (β1 - β0) / β0 × 100%. The lower the low-temperature stiffness change rate, the better the low-temperature resistance. The test results are recorded in Table 1.

[0047] 3. Low-Temperature Flexibility Test: The low-temperature-resistant water-based polyurethanes prepared in Examples 1-4 and Comparative Examples 1-7 were coated on tinplate and dried at 100°C for 30 min to form a film with a thickness of 25±1 μm. The film was tested according to the method of GB / T 1731-2020 to observe whether there were any reticulations, cracks, or peeling. The test results are recorded in Table 1.

[0048] Table 1 According to the comparison between Example 2 and Comparative Examples 1-2 and the data in Table 1, it can be seen that in Comparative Example 1, only polyethyleneimine was used to graft-modify talc, and in Comparative Example 2, only epoxysilane was used to couple-modify talc. Although these two modification methods can improve the dispersibility of talc to a certain extent, some agglomerates still exist in the waterborne polyurethane matrix, affecting the mechanical properties of the material. In contrast, the present application uses epoxysilane and polyethyleneimine to couple-graft-modify talc, so that the talc particles are evenly and stably dispersed between the polyurethane molecular segments, reducing agglomeration and collapse between the particles, playing a good toughening role on the polyurethane material, reducing the generation of cracks, and enabling the waterborne polyurethane to maintain excellent mechanical properties even in low-temperature environments.

[0049] According to the comparison between Example 2 and Comparative Examples 3-4 and the data in Table 1, it can be seen that compared with amino groups and unsaturated double bonds, the amino groups in polyethyleneimine are more easily combined with epoxy groups, thereby grafting polyethyleneimine on the surface of talc, improving the surface activity of talc, and making it uniformly dispersed in the aqueous polyurethane matrix, which has a good toughening effect on the polyurethane material, enhances the material's anti-brittle cracking performance, and reduces the occurrence of cracks.

[0050] Comparison of Example 2 with Comparative Examples 5-6 and the data in Table 1 shows that the talc added in Comparative Example 5 is unmodified and easily agglomerates in the polyurethane matrix, forming stress concentration points that easily induce cracks when subjected to external forces, thereby reducing the toughness of the material. In Comparative Example 6, no modified filler is added, and the waterborne polyurethane material is prone to brittle cracking in low-temperature environments. The present application adds talc, modifies the talc with epoxysilane and polyethyleneimine, and uniformly disperses it in the polyurethane matrix to improve the flexibility of the waterborne polyurethane in low-temperature environments and reduce the occurrence of brittle cracking.

[0051] According to the comparison between Example 2 and Comparative Example 7 and the data in Table 1, it can be seen that: in Comparative Example 7, no terminal hydroxyl polybutadiene is added, and the low-temperature resistance of the water-based polyurethane is poor. However, the present application uses terminal hydroxyl polybutadiene to enhance the flexibility of the polyurethane molecular chain segment, so that the content of the soft segment in the molecular chain is increased, thereby improving the phase separation degree of the soft and hard segments, and synergizing with the modified filler to improve the flexibility of the water-based polyurethane in a low-temperature environment.

[0052] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low-temperature resistant water-based polyurethane, characterized in that: The invention is prepared from the following raw materials in parts by weight: 5-10 parts of polyester polyol, 15-20 parts of polyether polyol, 4-8 parts of castor oil-based polyol, 10-14 parts of diisocyanate, 8-12 parts of hydroxyl-terminated polybutadiene, 9-13 parts of modified filler, 0.5-1.5 parts of hydrophilic chain extender, 1.5-2.5 parts of post-chain extender, 0.1-0.3 parts of antioxidant, and 45-65 parts of water; The raw materials for preparing the modified filler include talc powder, epoxy silane and polyethylene imine, and the weight ratio of the talc powder, epoxy silane and polyethylene imine is 1: (0.03-0.05): (0.5-0.7).

2. A low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The preparation method of the modified filler comprises the following steps: (1) Add talc powder to a hydroxide solution, heat to 60-80°C, stir and react for 4-6 hours, filter, wash, and dry to obtain pretreated talc powder; (2) dissolving epoxysilane in a solvent to form a hydrolysis solution, adjusting the pH of the solution to 3.0-4.0, adding the treated talc powder to the hydrolysis solution, ultrasonically dispersing for 30-40 minutes, filtering, washing, and drying to obtain silanized talc powder; (3) Disperse polyethyleneimine in a solvent and stir evenly to obtain a polyethyleneimine solution; disperse silanized talc in a solvent and stir evenly to obtain a suspension; slowly drip the polyethyleneimine solution into the suspension; react at room temperature for 6-8 hours; filter, wash, and dry to obtain a modified filler.

3. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The epoxysilane is selected from one or both of 3-glycidyloxypropyltrimethoxysilane and 3-glycidyloxypropyltriethoxysilane.

4. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The number average molecular weight of the hydroxyl-terminated polybutadiene is 2000-3000.

5. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The hydrophilic chain extender is selected from one or more of dimethylol propionic acid, dimethylol butyric acid, 1,2-propylene glycol-3-sodium sulfonate, and 1,4-butanediol-2-sodium sulfonate.

6. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The post-chain extender is selected from one or more of ethylenediamine, hydrazine hydrate, and isophoronediamine.

7. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The antioxidant is selected from one or more of antioxidant 1098, antioxidant 1010, and antioxidant AO-80.

8. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The polyester polyol is selected from one or more of polycarbonate diol, polyneopentyl adipate diol, and polyethylene adipate diol; the polyether polyol is compounded by polyoxypropylene diol and polytetramethylene ether diol in a weight ratio of (0.6-0.8):

1.

9. The low-temperature resistant waterborne polyurethane according to claim 1, characterized in that: The diisocyanate is selected from one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, and cyclohexane dimethylene diisocyanate.

10. The method for preparing a low-temperature resistant waterborne polyurethane according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Mix polyester polyol, polyether polyol, castor oil-based polyol, and diisocyanate, add a catalyst, introduce nitrogen, and react with stirring at 80-90°C for 2-3 hours. Add a hydrophilic chain extender and acetone, and continue the reaction for 1-2 hours to obtain a polyurethane prepolymer; S2: adding a neutralizing agent to the polyurethane prepolymer for neutralization, adding a portion of water for high-speed dispersion and emulsification, adding hydroxy-terminated polybutadiene, a post-chain extender, and an antioxidant, continuing to stir and react for 40-50 minutes, and removing acetone in vacuo to obtain a polyurethane emulsion; S3: Mix the modified filler with the remaining water, and ultrasonically disperse for 20-30 minutes. Add the dispersion into the polyurethane emulsion, and stir evenly to obtain a low-temperature resistant water-based polyurethane.

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