Solvent-free low-temperature-resistant polyurethane adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, in particular to a solvent-free low-temperature-resistant polyurethane adhesive and a preparation method thereof. The solvent-free low-temperature-resistant polyurethane adhesive comprises the following components in parts by weight: a component A: 60-70 parts of low-temperature-resistant polyol A, 10-20 parts of bio-based polyol, 1-2 parts of a silane coupling agent and 20-30 parts of a reinforcing filler A; and the component B comprises the following components in parts by weight: 70-80 parts of polyurethane prepolymer and 20-30 parts of reinforcing filler B. The adhesive has excellent comprehensive performance by enhancing physical crosslinking of a polyurethane network, is suitable for a low-temperature environment, and has good development potential in the fields of new energy automobiles, aerospace, traffic and the like.

Description

Technical Field

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

[0002] Polyurethane adhesives are widely used in the automotive, electronics, and packaging industries due to their excellent properties (high strength, abrasion resistance, and applicability to multiple substrates). However, traditional solvent-based polyurethane adhesives release large amounts of volatile organic compounds (VOCs) during production and use, causing environmental pollution and health risks. Increasingly stringent environmental regulations have spurred the development of solvent-free polyurethane adhesives, which employ a 100% solids content system and primarily cure through chemical reactions, eliminating VOCs and making them safer and more environmentally friendly. While solvent-free polyurethane adhesives offer advantages in environmental protection and some performance aspects, their generally insufficient low-temperature resistance remains a bottleneck that urgently needs to be addressed. In low-temperature environments (such as -30°C to -40°C or even lower), the movement of molecular chains in the adhesive layer is restricted, resulting in a significant decrease in flexibility, causing the adhesive layer to harden and become brittle, and a sharp deterioration in impact toughness and peel strength.

[0003] Existing technologies improve low-temperature toughness by adding flexible components, but this often comes at the cost of strength, heat resistance, or durability. Achieving a balance between high solids content, good processability, excellent overall performance, and outstanding low-temperature toughness (maintaining high elasticity and bond strength below -40°C) in a solvent-free system presents significant technical challenges. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a solvent-free, low-temperature resistant polyurethane adhesive and its preparation method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A first aspect of the present invention is to provide a solvent-free, low-temperature resistant polyurethane adhesive, comprising the following components in parts by weight: Component A: 60-70 parts of low-temperature resistant polyol A, 10-20 parts of bio-based polyol, 1-2 parts of silane coupling agent, and 20-30 parts of reinforcing filler A; Component B: 70-80 parts of polyurethane prepolymer, 20-30 parts of reinforcing filler B.

[0006] Based on the above technical solution, the present invention can also be improved as follows: Furthermore, the polyurethane prepolymer is an NCO-terminated polymer, and the molar ratio of isocyanate groups to hydroxyl groups in the polyurethane prepolymer is (2.5-3.0):1; by weight percentage, the polyurethane prepolymer comprises the following raw materials: 35-75% low-temperature resistant polyol B, 5-10% organosilicon polymer, 15-55% diisocyanate, and 10-15 ppm catalyst.

[0007] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By using low-temperature resistant polyol B, organosilicon polymer, and diisocyanate crosslinking polymerization, a large volume of organosilicon polymer is added in the hard segment region to provide flexibility and form a strong physical crosslink. By strictly controlling the amount of each material and the molar ratio of the groups, the resulting polyurethane prepolymer can have excellent low-temperature flexibility and flowability. By limiting the molar ratio of isocyanate groups to hydroxyl groups in the polyurethane prepolymer to (2.5-3.0):1, it is ensured that a prepolymer with almost all active -NCO groups at the end is synthesized, obtaining a prepolymer with moderate and controllable molecular weight and viscosity, which is convenient for subsequent processing and treatment, and provides a basis for forming a high crosslinking density for the final cured product, thereby obtaining excellent mechanical strength, hardness, modulus, solvent resistance, and low compression set.

[0008] Furthermore, the polyurethane prepolymer is prepared by the following method: diisocyanate is mechanically stirred and heated to 75°C under N2 atmosphere by weight percentage; then, low-temperature resistant polyol B and organosilicon polymer are respectively added dropwise to the diisocyanate, and the addition time is controlled at 0.8-1.2h; then, a catalyst is added dropwise, and the reaction is carried out under N2 protection at 80-85°C for 4-6h until the NCO value no longer changes, and then the temperature is lowered to room temperature to obtain the polyurethane prepolymer.

[0009] Further, the low-temperature resistant polyol B is at least one of polytetrahydrofuran ether diol, polycaprolactone diol, and polycarbonate diol, preferably polytetrahydrofuran ether diol; the diisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate, preferably diphenylmethane diisocyanate; the organosilicon polymer is at least one of polydimethylsiloxane, polymethylphenylsiloxane, polymethylhydrosiloxane, and polydiethylsiloxane, preferably polydimethylsiloxane; the catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate, preferably dibutyltin dilaurate.

[0010] The molecular structure design of low-temperature resistant polyols endows polyurethane soft segments with the ability to maintain chain movement at extremely low temperatures (below -40°C), thus avoiding glass transition brittleness. These low-temperature resistant polyols achieve low-temperature chain mobility through chemical bonds with low rotational barriers (ether bonds are optimal), combined with weak intermolecular forces and long methylene chains. Polytetrahydrofuran ether diol, due to its near-perfect flexible chain structure, has become the preferred choice for extreme environment applications.

[0011] Furthermore, the low-temperature resistant polyol A is selected from at least one of polytetrahydrofuran ether diol, polycaprolactone diol, and polycarbonate diol, preferably polytetrahydrofuran ether diol; the low-temperature resistant polyol A has a hydroxyl value of 50-230 mg KOH / g, an average hydroxyl molecular weight of 500-2000, and an acid value of less than 1.

[0012] The beneficial effects of adopting the above-mentioned further technical solutions are: ensuring that polyols maintain excellent flexibility and elasticity at low temperatures, while guaranteeing their reactivity and storage stability. These have a decisive influence on the low-temperature performance (especially low-temperature brittleness) of polyurethane adhesives.

[0013] Furthermore, the bio-based polyol is at least one of castor oil polyol, palm oil polyol, soybean oil polyol, flaxseed oil polyol, and sunflower seed oil polyol, preferably castor oil polyol.

[0014] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: by adding bio-based polyols, especially castor oil polyols, the sustainability and environmental properties of the product are significantly improved (high bio-based content, low carbon footprint); a unique combination of properties is introduced into the material, especially excellent flexibility, toughness and water resistance; in addition, natural castor oil contains long fatty acid chains (mainly ricinoleic acid), which gives polyurethane adhesives good flexibility and low Tg (about -60℃ to -40℃).

[0015] Furthermore, the silane coupling agent is selected from one of KH-550, KH-560, KH-570, KH-590, and KH-792, with KH-560 being preferred.

[0016] Furthermore, both reinforcing filler A and reinforcing filler B are selected from at least one of calcium carbonate, alumina, aluminum hydroxide, magnesium hydroxide, fumed silica, and silica powder, with calcium carbonate being preferred.

[0017] Another aspect of the present invention is to provide a method for preparing the solvent-free, low-temperature resistant polyurethane adhesive provided in the first aspect of the present invention, comprising the following steps: S1. Preparation of polyurethane prepolymer: By weight percentage, 15-55% of diisocyanate is mechanically stirred and heated to 75°C under N2 atmosphere; then, 35-75% of low-temperature resistant polyol B and 5-10% of organosilicon polymer are added dropwise to the diisocyanate, with the addition time controlled at 0.8-1.2h; then 10-15ppm of catalyst is added dropwise, and the reaction is carried out under N2 protection at 80-85°C for 4-6h until the NCO value no longer changes, and then cooled to room temperature to obtain polyurethane prepolymer; S2. Add 60-70 parts of low-temperature resistant polyol A, 10-20 parts of bio-based polyol, 1-2 parts of silane coupling agent, and 20-30 parts of reinforcing filler A into a stirred tank and stir under vacuum for 1-2 hours, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. S3. Add 70-80 parts of polyurethane prepolymer and 20-30 parts of reinforcing filler B into a mixing tank, stir under vacuum for 1-2 hours, control the mixing temperature to ≤50℃ and the vacuum degree to -0.08-0.09 MPa to obtain component B. S4. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0018] Compared with the prior art, the present invention has the following technical effects: The solvent-free, low-temperature resistant polyurethane adhesive prepared by this invention comprises components A and B. Components A and B are combined in a 1:1 volume ratio to prepare an adhesive composition, which has excellent low-temperature flexibility and low-temperature bonding performance, and is suitable for new energy vehicles, aerospace, transportation and other fields. This technical solution innovatively introduces an organosilicon polymer with an ultra-low glass transition temperature and a large-volume structure into the hard segment region of polyurethane. Utilizing its unique mechanism of disrupting hard segment regularity, significantly reducing the self-freezing temperature of hard segment microregions, and providing effective flexible nodes and physical crosslinking points at low temperatures, it combines a specific ratio of low-temperature resistant polyol B to construct a flexible continuous phase. Furthermore, it optimizes the overall crosslinking network and phase separation structure through precise control of diisocyanate dosage and NCO:OH molar ratio, and supplements this with a trace catalyst to ensure controllable reaction and prepolymer flowability. This synergistic approach achieves superior low-temperature flexibility and processing flowability unattainable by existing technologies. This design concept of flexible modification at the hard segment level and the resulting unique low-temperature performance enhancement mechanism constitute the core inventiveness of this invention and its significant distinguishing feature from existing technologies. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0020] Example 1 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: 275 g of diphenylmethane diisocyanate was weighed and placed in a 2000 ml three-necked flask, and heated to 75 °C under N2 atmosphere with mechanical stirring. Subsequently, 493 g of polytetrahydrofuran ether diol and 56 g of polydimethylsiloxane were slowly added dropwise to the flask, with the addition time controlled at 1 h. Then, 10 ppm of dibutyltin dilaurate was slowly added dropwise, and the mixture was reacted at a constant temperature of 80 °C under nitrogen protection for 6 h. When the NCO value showed no change, the mixture was cooled to room temperature, discharged, and placed in a dry nitrogen-sealed container for later use.

[0021] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, control the mixing temperature to ≤50℃, and the vacuum degree to -0.08-0.09 MPa to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0022] Example 2 1. The preparation of the polyurethane prepolymer is the same as in Example 1.

[0023] 2. Preparation of two-component polyurethane adhesives D1. Add 63g of polytetrahydrofuran ether diol, 10g of castor oil polyol, 2g of KH-560, and 25g of calcium carbonate to a mixing tank and stir under vacuum for 1.5h, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. D2. Add 73g of polyurethane prepolymer and 27g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, control the mixing temperature to ≤50℃, and the vacuum degree to -0.08-0.09 MPa to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0024] Example 3 1. The preparation of the polyurethane prepolymer is as described in Example 1; 2. Preparation of two-component polyurethane adhesives D1. Add 67g of polytetrahydrofuran ether diol, 10g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. D2. Add 76g of polyurethane prepolymer and 24g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, control the mixing temperature to ≤50℃, and the vacuum degree to -0.08-0.09 MPa to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0025] Example 4 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: 156 g of diphenylmethane diisocyanate was weighed and placed in a 2000 ml three-necked flask, and heated to 75 °C under N2 atmosphere with mechanical stirring. Subsequently, 335 g of polytetrahydrofuran ether diol and 44 g of polydimethylsiloxane were slowly added dropwise to the flask, with the addition time controlled at 1 h. Then, 10 ppm of dibutyltin dilaurate was slowly added dropwise, and the mixture was reacted at a constant temperature of 80 °C under nitrogen protection for 6 h. When the NCO value showed no change, the mixture was cooled to room temperature, and the product was discharged to obtain a pale yellow transparent polyurethane prepolymer, which was then placed in a dry nitrogen-sealed container for later use.

[0026] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, control the mixing temperature to ≤50℃, and the vacuum degree to -0.08-0.09 MPa to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0027] Example 5 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: 240 g of diphenylmethane diisocyanate was weighed and placed in a 2000 ml three-necked flask, and heated to 75 °C under N2 atmosphere with mechanical stirring. Subsequently, 412 g of polytetrahydrofuran ether diol and 48 g of polydimethylsiloxane were slowly added dropwise to the flask, with the addition time controlled at 1 h. Then, 10 ppm of dibutyltin dilaurate was slowly added dropwise, and the mixture was reacted at a constant temperature of 80 °C under nitrogen protection for 6 h. When the NCO value showed no change, the mixture was cooled to room temperature, discharged, and placed in a dry nitrogen-sealed container for later use.

[0028] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0029] Example 6 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: Weigh 330 g of diphenylmethane diisocyanate into a 2000 ml three-necked flask and heat to 75 °C under N2 atmosphere with mechanical stirring. Then, slowly add 262 g of polytetrahydrofuran ether diol and 38 g of polydimethylsiloxane to the flask, controlling the addition time to 1 h. Then, slowly add 10 ppm of dibutyltin dilaurate and react at 80 °C under nitrogen protection for 6 h. When the NCO value no longer changes, cool to room temperature, discharge, and store in a dry nitrogen-sealed container for later use.

[0030] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0031] Comparative Example 1 1. The preparation of the polyurethane prepolymer is the same as in Example 1; 2. Preparation of two-component polyurethane adhesives D1. Add 55g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 32g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 68g of polyurethane prepolymer and 32g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0032] Comparative Example 2 1. The preparation of the polyurethane prepolymer is as described in Example 1; 2. Preparation of two-component polyurethane adhesives D1. Add 72g of polytetrahydrofuran ether diol, 8g of castor oil polyol, 1g of KH-560, and 19g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 82g of polyurethane prepolymer and 18g of reinforcing filler to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B; D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0033] Comparative Example 3 1. The preparation of the polyurethane prepolymer is the same as in Example 1; 2. Preparation of two-component polyurethane adhesives D1. Add 50g of polytetrahydrofuran ether diol, 21g of castor oil polyol, 2g of KH-560, and 27g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 85g of polyurethane prepolymer and 15g of reinforcing filler to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0034] Comparative Example 4 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: 275 g of diphenylmethane diisocyanate was weighed and placed in a 2000 ml three-necked flask, and heated to 75 °C under N2 atmosphere with mechanical stirring. Subsequently, 549 g of polytetrahydrofuran ether diol was slowly added dropwise to the flask at a rate controlled at 1 h. Then, 10 ppm of dibutyltin dilaurate was slowly added dropwise, and the mixture was reacted at a constant temperature of 80 °C under nitrogen protection for 6 h. When the NCO value showed no change, the mixture was cooled to room temperature, discharged, and a pale yellow transparent polyurethane prepolymer was obtained and placed in a dry nitrogen-sealed container for later use.

[0035] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0036] Comparative Example 5 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: 390 g of diphenylmethane diisocyanate was weighed and placed in a 2000 ml three-necked flask, and heated to 75 °C under N2 atmosphere with mechanical stirring. Subsequently, 105 g of polytetrahydrofuran ether diol and 105 g of polydimethylsiloxane were slowly added dropwise to the above flask, with the dropping rate controlled at 1 h. Then, 10 ppm of dibutyltin dilaurate was slowly added dropwise, and the reaction was carried out at a constant temperature of 80 °C under nitrogen protection for 6 h. When the NCO value showed no change, the temperature was lowered to room temperature, and the product was discharged to obtain a pale yellow transparent polyurethane prepolymer, which was then placed in a dry nitrogen-sealed container for later use.

[0037] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive. Comparative Example 6 1. Preparation of polyurethane prepolymer Preparation of polyurethane prepolymer: Weigh 180g of diphenylmethane diisocyanate into a 2000ml three-necked flask and heat to 75℃ under N2 atmosphere with mechanical stirring. Then, slowly add 270g of polytetrahydrofuran ether diol and 150g of polydimethylsiloxane to the flask, controlling the dropping rate at 1h. Then, slowly add 10ppm of dibutyltin dilaurate and react at 80℃ under nitrogen protection for 6h. When the NCO value no longer changes, cool to room temperature, discharge the material, and obtain a pale yellow transparent polyurethane prepolymer, which is then placed in a dry nitrogen-sealed container for later use.

[0038] 2. Preparation of two-component polyurethane adhesives D1. Add 65g of polytetrahydrofuran ether diol, 12g of castor oil polyol, 1g of KH-560, and 22g of calcium carbonate to a stirred tank and stir under vacuum for 1.5h. The mixing temperature is ≤60℃ and the vacuum degree is -0.08-0.09 MPa to obtain component A. D2. Add 75g of polyurethane prepolymer and 25g of calcium carbonate to a mixing tank, stir under vacuum for 1.5h, with a mixing temperature ≤50℃ and a vacuum degree of -0.08-0.09 MPa, to obtain component B. D3. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

[0039] Performance testing The adhesives prepared in the examples and comparative examples were subjected to the following performance tests: Mechanical property testing GB / T7124-2008 Determination of tensile shear strength of adhesives (-40℃). GB / T7314-2017 Determination of tensile strength and elongation at break of adhesives (-40℃).

[0040] The performance test results are shown in Table 1.

[0041] Table 1. Comparison of test data between the examples and comparative examples

[0042] As can be seen from the test results in Table 1, the two-component polyurethane adhesive in the embodiments of the present invention has excellent low-temperature flexibility and low-temperature bonding performance, and is suitable for new energy vehicles, aerospace, transportation and other fields.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solvent-free, low-temperature resistant polyurethane adhesive, characterized in that, The components include the following parts by weight: Component A: Low-temperature resistant polyol A 60-70 parts, bio-based polyol 10-20 parts, silane coupling agent 1-2 parts, reinforcing filler A 20-30 parts; Component B: 70-80 parts of polyurethane prepolymer, 20-30 parts of reinforcing filler B.

2. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 1, characterized in that, The polyurethane prepolymer is an NCO-terminated polymer, and the molar ratio of isocyanate groups to hydroxyl groups in the polyurethane prepolymer is (2.5-3.0):

1. By weight percentage, the polyurethane prepolymer comprises the following raw materials: 35-75% low-temperature resistant polyol B, 5-10% organosilicon polymer, 15-55% diisocyanate, and 10-15 ppm catalyst.

3. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 2, characterized in that, The polyurethane prepolymer was prepared by the following method: diisocyanate was heated to 75°C under N2 atmosphere by mechanical stirring according to weight percentage; then, low-temperature resistant polyol B and organosilicon polymer were added dropwise to the diisocyanate, with the addition time controlled at 0.8-1.2h; then, a catalyst was added dropwise, and the reaction was carried out under N2 protection at 80-85°C for 4-6h until the NCO value did not change, and then the temperature was lowered to room temperature to obtain the polyurethane prepolymer.

4. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 2 or 3, characterized in that, The low-temperature resistant polyol B is at least one of polytetrahydrofuran ether diol, polycaprolactone diol, and polycarbonate diol; the diisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate; the organosilicon polymer is at least one of polydimethylsiloxane, polymethylphenylsiloxane, polymethylhydrosiloxane, and polydiethylsiloxane; and the catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.

5. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 1, characterized in that, The low-temperature resistant polyol A is selected from at least one of polytetrahydrofuran ether diol, polycaprolactone diol, and polycarbonate diol; the hydroxyl value of the low-temperature resistant polyol A is 50-230 mg KOH / g, the average molecular weight of the hydroxyl group is 500-2000, and the acid value is less than 1.

6. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 1, characterized in that, The bio-based polyol is at least one of castor oil polyol, palm oil polyol, soybean oil polyol, flaxseed oil polyol, and sunflower seed oil polyol.

7. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 1, characterized in that, The silane coupling agent is selected from one of KH-550, KH-560, KH-570, KH-590, and KH-792.

8. The solvent-free, low-temperature resistant polyurethane adhesive according to claim 1, characterized in that, The reinforcing filler A and reinforcing filler B are both selected from at least one of calcium carbonate, alumina, aluminum hydroxide, magnesium hydroxide, fumed silica, and silica powder.

9. A method for preparing the solvent-free, low-temperature resistant polyurethane adhesive according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Preparation of polyurethane prepolymer: By weight percentage, 15-55% of diisocyanate is mechanically stirred and heated to 75°C under N2 atmosphere; then, 35-75% of low-temperature resistant polyol B and 5-10% of organosilicon polymer are added dropwise to the diisocyanate, with the addition time controlled at 0.8-1.2h; then 10-15ppm of catalyst is added dropwise, and the reaction is carried out under N2 protection at 80-85°C for 4-6h until the NCO value no longer changes, and then cooled to room temperature to obtain polyurethane prepolymer; S2. Add 60-70 parts of low-temperature resistant polyol A, 10-20 parts of bio-based polyol, 1-2 parts of silane coupling agent, and 20-30 parts of reinforcing filler A into a stirred tank and stir under vacuum for 1-2 hours, controlling the mixing temperature to ≤60℃ and the vacuum degree to -0.08-0.09 MPa to obtain component A. S3. Add 70-80 parts of polyurethane prepolymer and 20-30 parts of reinforcing filler B into a mixing tank, stir under vacuum for 1-2 hours, control the mixing temperature to ≤50℃ and the vacuum degree to -0.08-0.09 MPa to obtain component B. S4. Mix component A and component B at a volume ratio of 1:1 to obtain a solvent-free, low-temperature resistant polyurethane adhesive.

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