A polyurethane adhesive and its preparation and application methods

Abstract

This application relates to the field of adhesive technology, and provides a polyurethane adhesive and its preparation and application methods. The polyurethane adhesive includes a first component and a second component. The raw materials of the first component include a polyurethane prepolymer, isocyanate, pigments and fillers, and a thixotropic agent. The raw materials of the second component include a polyol, a dehydrating agent, pigments and fillers, a first catalyst, and a second catalyst. The polyurethane prepolymer is obtained by reacting a low-activity isocyanate monomer and a chain extender. The low-activity isocyanate monomer is selected from at least one of isoflurane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer. The first catalyst is selected from at least one of organotin catalysts and organobismuth catalysts. The second catalyst is selected from at least one of amine catalysts.

Description

Technical Field

[0001] This application relates to the field of adhesive technology, and in particular to a polyurethane adhesive and its preparation and application methods. Background Technology

[0002] Polyurethane adhesives are high-strength, abrasion-resistant, chemical-resistant, and flexible adhesives. They are made from polyurethane polymers, whose molecular chains contain a large number of urethane and isocyanate groups, thus exhibiting excellent shear strength and impact resistance, as well as superior rubber properties, making them suitable for various structural bonding applications.

[0003] Currently, polyurethane adhesives can all cure at room temperature, but the curing time is relatively long. With industrial development and technological advancements, production efficiency has further improved, creating an urgent need for a polyurethane adhesive that can cure quickly. However, rapid curing of polyurethane adhesives often results in a significant reduction in surface drying time and leads to a decrease in the shear strength of the product. Therefore, there is an urgent need to develop a polyurethane adhesive with controllable surface drying time, rapid curing at room temperature, and good shear strength. Summary of the Invention

[0004] The purpose of this application is to provide a polyurethane adhesive, its preparation method, and its application method, which, while ensuring the shear strength of the polyurethane adhesive, solves the problems of difficult-to-control surface drying time and long time to achieve initial solid strength at room temperature, thereby improving production efficiency and reducing energy consumption. The specific technical solution is as follows:

[0005] The first aspect of this application provides a polyurethane adhesive, comprising a first component and a second component; wherein, by weight, the raw materials of the first component include: 20-50 parts of polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent; the raw materials of the second component include: 30-60 parts of polyol, 3-10 parts of dehydrating agent, 30-50 parts of pigments and fillers, 2-5 parts of first catalyst, and 0.5-3 parts of second catalyst. The polyurethane prepolymer is obtained by reacting a low-activity isocyanate monomer with a chain extender, wherein the low-activity isocyanate monomer is selected from at least one of isoflurane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer; the first catalyst is selected from at least one of organotin catalysts and organobismuth catalysts; and the second catalyst is selected from at least one of amine catalysts.

[0006] In some embodiments of this application, the low-activity isocyanate monomer is selected from hexamethylene diisocyanate trimer.

[0007] In some embodiments of this application, the first catalyst is selected from at least one of di(dodecylsulfonium)dibutyltin, dibutyltin mercaptoate, dimethyltin dimercaptoacetate, bismuth tricarboxylate, dibutyltin dilaurate, stannous octanoate, bismuth isooctanoate, bismuth naphthenate, and bismuth laurate; the second catalyst is selected from at least one of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine, 1,8-diazabicycloundec-7-ene, triethylamine, bismorpholinodiethyl ether, N-(dimethylaminopropyl)diisopropanolamine, and N,N-dimethylbenzylamine.

[0008] In some embodiments of this application, the isocyanate group content of the polyurethane prepolymer is between 3 wt% and 10 wt%.

[0009] In some embodiments of this application, the chain extender is selected from at least one of castor oil-modified polyol, dimer acid-modified polyester polyol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, and glycerol. The castor oil-modified polyol has a relative molecular weight of 420-580 and a hydroxyl value of 160-200 mgKOH / g. The dimer acid-modified polyester polyol has a relative molecular weight of 1800-2100 and a hydroxyl value of 50-58 mgKOH / g.

[0010] In some embodiments of this application, the isocyanate is selected from at least one of isoflurone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl isocyanate, and hexamethylene diisocyanate trimer.

[0011] In some embodiments of this application, the pigments and fillers are selected from at least one of wollastonite, alumina, aluminum hydroxide, zinc oxide, talc, mica powder, silica fume and calcium carbonate.

[0012] In some embodiments of this application, the thixotropic agent is selected from at least one of fumed silica, polyamide wax, and organobentonite.

[0013] In some embodiments of this application, the polyol is selected from at least one of polypropylene oxide polyol, polytetrahydrofuran polyol, bisphenol A modified polyether polyol, castor oil modified polyol, and dimer acid modified polyester polyol. Specifically, the polypropylene oxide polyol has a relative molecular weight of 400-2000 and a hydroxyl value of 56-280 mgKOH / g; the polytetrahydrofuran polyol has a relative molecular weight of 1000-4000 and a hydroxyl value of 28-120 mgKOH / g; the bisphenol A modified polyether polyol has a relative molecular weight of 360-480 and a hydroxyl value of 260-300 mgKOH / g; the castor oil modified polyol has a relative molecular weight of 420-580 and a hydroxyl value of 160-200 mgKOH / g; and the dimer acid modified polyester polyol has a relative molecular weight of 1800-2100 and a hydroxyl value of 50-58 mgKOH / g.

[0014] In some embodiments of this application, the dehydrating agent is selected from type 3A molecular sieve.

[0015] The second aspect of this application provides a method for preparing the polyurethane adhesive described in the first aspect of this application, comprising:

[0016] The low-activity isocyanate monomer and the chain extender are added to the reaction vessel, wherein the weight ratio of the low-activity isocyanate monomer to the chain extender is 100:(31~213), stirred evenly, and the reaction vessel is heated to 45~80℃ and reacted for 4~12h to obtain a polyurethane prepolymer with an isocyanate group weight content of 3wt%~10wt%.

[0017] The first component is obtained by uniformly mixing 20-50 parts of the polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent and then degassing the mixture in a vacuum stirred tank.

[0018] The second component is obtained by mixing 30-60 parts of the polyol, 3-10 parts of the dehydrating agent, 30-50 parts of the pigments and fillers, 2-5 parts of the first catalyst, and 0.5-3 parts of the second catalyst evenly and then degassing the mixture in a vacuum stirred tank.

[0019] A third aspect of this application provides a method of using the polyurethane adhesive described in the first aspect of this application or the polyurethane adhesive prepared in the second aspect of this application, wherein the first component and the second component are mixed evenly at a mass ratio of 1.0:(0.8~1.2) and then used.

[0020] The beneficial effects of this application are:

[0021] This application provides a polyurethane adhesive and its preparation and application methods, comprising a first component and a second component. The first component, by weight, comprises: 20-50 parts of polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent. The second component comprises: 30-60 parts of polyol, 3-10 parts of dehydrating agent, 30-50 parts of pigments and fillers, 2-5 parts of a first catalyst, and 0.5-3 parts of a second catalyst. The polyurethane prepolymer is obtained by reacting a low-activity isocyanate monomer with a chain extender. The low-activity isocyanate monomer is selected from at least one of isoflurane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer. The first catalyst is selected from at least one of organotin catalysts and organobismuth catalysts. The second catalyst is selected from at least one of amine catalysts. The polyurethane prepolymer in this application is obtained by reacting a low-reactivity isocyanate monomer with a chain extender, characterized by low reactive group content and low reactivity. The first catalyst is an organometallic catalyst, which, compared to the second catalyst (amine catalyst), exhibits a strong catalytic effect on the low-reactivity polyurethane prepolymer. This application achieves a controlled curing effect for the polyurethane adhesive through the synergistic effect of the low-reactivity prepolymer and the highly catalytic first catalyst, resulting in a slow-to-fast curing process. This means the surface drying time is relatively long, while the initial curing time is relatively short. The surface drying time can be adjusted by the type and amount of the first catalyst. Because the polyurethane prepolymer has a low content of reactive isocyanate groups, it can rapidly form a cross-linked network after reacting with the polyol, which facilitates faster attainment of high initial bond strength in the polyurethane adhesive and shortens the initial curing time. In this application, the first catalyst can regulate the surface drying time of the polyurethane adhesive, while a large amount of the second catalyst can accelerate the initial curing speed and shorten the initial curing time. The combined use of the second and first catalysts can regulate the reaction balance during the polyurethane curing process, allowing the polyurethane adhesive to fully cure at room temperature after initial curing, ultimately resulting in excellent mechanical and adhesive properties. The polyurethane adhesive prepared using the above settings has a surface drying time controllable between 30 seconds and 10 minutes, an initial curing time controllable between 4 minutes and 30 minutes, and a shear strength greater than 11 MPa, thereby improving production efficiency and reducing energy consumption.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

[0023] The technical solutions of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0024] This application provides a polyurethane adhesive, comprising a first component and a second component. The first component, by weight, comprises: 20-50 parts of polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent. The second component comprises: 30-60 parts of polyol, 3-10 parts of dehydrating agent, 30-50 parts of pigments and fillers, 2-5 parts of a first catalyst, and 0.5-3 parts of a second catalyst. The polyurethane prepolymer is obtained by reacting a low-activity isocyanate monomer with a chain extender. The low-activity isocyanate monomer is selected from at least one of isoflurane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer. The first catalyst is selected from at least one of organotin catalysts and organobismuth catalysts. The second catalyst is selected from at least one of amine catalysts.

[0025] In some embodiments of this application, the first catalyst is selected from at least one of di(dodecylsulfonium)dibutyltin, dibutyltin mercaptoate, dimethyltin dimercaptoacetate, bismuth tricarboxylate, dibutyltin dilaurate, stannous octanoate, bismuth isooctanoate, bismuth naphthenate, and bismuth laurate; the second catalyst is selected from at least one of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine, 1,8-diazabicycloundec-7-ene, triethylamine, bismorpholinodiethyl ether, N-(dimethylaminopropyl)diisopropanolamine, and N,N-dimethylbenzylamine.

[0026] Curing time and adhesive performance are important parameters for evaluating the performance of polyurethane adhesives. However, rapid curing of polyurethane adhesives often generates significant internal stress and insufficient wetting of the substrate, leading to a decline in the final mechanical and adhesive properties of the product. The inventors have discovered that the polyurethane adhesive of this application uses a low-activity isocyanate monomer and a chain extender in the first component to obtain a polyurethane prepolymer. Compared to highly active aromatic isocyanate monomers, the polyurethane prepolymer prepared using low-activity aliphatic isocyanate monomers can achieve a controllable reaction rate under the strong catalytic action of a large amount of the first catalyst. This allows for adjustment of the surface drying time of the polyurethane adhesive, which is beneficial for its application. Simultaneously, it prolongs the wetting effect of the adhesive on the substrate, resulting in higher shear strength and improved adhesive performance. For example, when the first catalyst is selected from dibutyltin mercaptan and used in an amount of 5 parts, the surface drying time of the polyurethane adhesive is 3 min 25 s; when the first catalyst is selected from bismuth tricarboxylate and used in an amount of 2 parts, the surface drying time of the polyurethane adhesive is 10 min. Simultaneously, prepolymerizing the low-activity isocyanate monomer with the chain extender in advance can reduce the concentration of isocyanate groups in the polyurethane prepolymer. During curing, this allows for rapid reaction to form a cross-linked network, which is beneficial for the polyurethane adhesive to achieve high initial bond strength more quickly and shortens the initial curing time. Furthermore, this application uses a large amount of amine catalyst as a second catalyst, which can accelerate the initial curing speed of the polyurethane adhesive, shorten the initial curing time, and, in combination with the first catalyst, can regulate the reaction balance during polyurethane curing, allowing the polyurethane adhesive to fully cure at room temperature after initial curing, which is beneficial for improving the shear strength of the polyurethane adhesive. Simultaneously using the first and second components described in this application in the polyurethane adhesive, and controlling the weight proportions of each substance in the first and second components within the range described in this application, can control the surface drying time of the polyurethane adhesive to 30s~10min and the initial curing time to 4min~30min, thereby achieving a slow-to-fast curing effect and a shear strength greater than 11MPa. This is beneficial for the construction operation of the polyurethane adhesive, improving production efficiency and reducing energy consumption.

[0027] In some embodiments of this application, the low-reactivity isocyanate monomer is selected from hexamethylene diisocyanate trimer. Using the hexamethylene diisocyanate trimer of this application as the low-reactivity isocyanate monomer allows for rapid reaction and formation of a cross-linked network during the curing process, which facilitates the polyurethane adhesive to achieve high initial bond strength more quickly and further shortens the initial curing time.

[0028] In this application, by weight, the polyurethane prepolymer in the first component can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of these values; the isocyanate in the first component can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any two of these values; the pigments and fillers in the first component can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of these values; the thixotropic agent in the first component can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, or any two of these values; the polyol in the second component can be... The first component can contain 30, 35, 40, 45, 50, 55, or 60 parts, or any two of these values; the second component can contain 3, 4, 5, 6, 7, 8, 9, or 10 parts, or any two of these values; the second component can contain 30, 35, 40, 45, or 50 parts, or any two of these values; the second component can contain 2, 3, 4, or 5 parts, or any two of these values; the amount of the first catalyst within this application range can control the surface drying time of the polyurethane adhesive to allow sufficient time for operation. The second component can contain 0.5, 1, 1.5, 2, 2.5, or 3 parts, or any two of these values; the amount of the second catalyst within this application range can accelerate the initial curing speed of the polyurethane adhesive and shorten the initial curing time. When prepared according to the proportions of this application, the polyurethane adhesive can achieve a surface drying time of 30s to 10min and an initial curing time of 4min to 30min while ensuring its shear strength, thereby improving production efficiency and reducing energy consumption.

[0029] In some embodiments of this application, the isocyanate group weight content of the polyurethane prepolymer is between 3 wt% and 10 wt%, for example, the isocyanate group weight content of the polyurethane prepolymer can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10%, or a range of any two of these values. The isocyanate group weight content is controlled by adjusting the weight ratio of the low-reactivity isocyanate monomer to the chain extender. By controlling the isocyanate group weight content of the polyurethane prepolymer within the above range, it is helpful to obtain higher adhesive strength more quickly after the polyurethane adhesive has initially cured, achieving a fast-curing adhesive effect.

[0030] In some embodiments of this application, the chain extender is selected from at least one of castor oil-modified polyol, dimer acid-modified polyester polyol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, and glycerol. The castor oil-modified polyol has a relative molecular weight of 420-580 and a hydroxyl value of 160-200 mg KOH / g; the dimer acid-modified polyester polyol has a relative molecular weight of 1800-2100 and a hydroxyl value of 50-58 mg KOH / g.

[0031] In some embodiments of this application, the isocyanate is selected from at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl isocyanate, and hexamethylene diisocyanate trimer. The isocyanate selected within the scope of this application can adjust the viscosity of the first component, thereby improving the workability of the polyurethane adhesive.

[0032] In some embodiments of this application, the pigments and fillers are selected from at least one of wollastonite, alumina, aluminum hydroxide, zinc oxide, talc, mica powder, silica fume and calcium carbonate.

[0033] In some embodiments of this application, the thixotropic agent is selected from at least one of fumed silica, polyamide wax, and organobentonite.

[0034] In some embodiments of this application, the polyol is selected from at least one of polypropylene oxide polyol, polytetrahydrofuran polyol, bisphenol A modified polyether polyol, castor oil modified polyol, and dimer acid modified polyester polyol. Specifically, the polypropylene oxide polyol has a relative molecular weight of 400-2000 and a hydroxyl value of 56-280 mgKOH / g; the polytetrahydrofuran polyol has a relative molecular weight of 1000-4000 and a hydroxyl value of 28-120 mgKOH / g; the bisphenol A modified polyether polyol has a relative molecular weight of 360-480 and a hydroxyl value of 260-300 mgKOH / g; the castor oil modified polyol has a relative molecular weight of 420-580 and a hydroxyl value of 160-200 mgKOH / g; and the dimer acid modified polyester polyol has a relative molecular weight of 1800-2100 and a hydroxyl value of 50-58 mgKOH / g. In some embodiments of this application, the dehydrating agent is selected from type 3A molecular sieve.

[0035] In this application, there are no particular limitations on the source of the raw materials used in the first and second components, as long as they can achieve the purpose of this application. For example, the raw materials used in the first and second components can be obtained commercially or prepared.

[0036] The second aspect of this application provides a method for preparing the polyurethane adhesive described in the first aspect of this application, comprising:

[0037] The low-reactivity isocyanate monomer and the chain extender are added to a reaction vessel, wherein the weight ratio of the low-reactivity isocyanate monomer to the chain extender is 100:(31~213). The mixture is stirred until homogeneous, and the reaction vessel is heated to 45~80℃ and reacted for 4~12 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 3wt%~10wt%. The weight ratio of the low-reactivity isocyanate monomer to the chain extender can be 100:31, 100:57, 100:83, 100:109, 100:135, 100:161, 100:187, 100:213, or a range of any two of these values. The weight ratio of the low-activity isocyanate monomer and the chain extender is within the range of this application, so that the prepared polyurethane prepolymer has a low isocyanate group weight content and reactivity, thereby enabling the surface drying time of the polyurethane adhesive described in the first aspect of this application to be controlled between 30s and 10min, the initial curing time to be controlled between 4min and 30min, and the high shear strength.

[0038] The first component is obtained by uniformly mixing 20-50 parts of the polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent and then degassing the mixture in a vacuum stirred tank.

[0039] The second component is obtained by mixing 30-60 parts of the polyol, 3-10 parts of the dehydrating agent, 30-50 parts of the pigments and fillers, 2-5 parts of the first catalyst, and 0.5-3 parts of the second catalyst evenly and then degassing the mixture in a vacuum stirred tank.

[0040] A third aspect of this application provides a method for using the polyurethane adhesive described in the first aspect of this application or the polyurethane adhesive prepared in the second aspect of this application, wherein the first component and the second component are mixed uniformly at a mass ratio of 1.0:(0.8 to 1.2) and then used. The mass ratio of the first component and the second component can be 1.0:0.8, 1.0:0.9, 1.0:1.0, 1.0:1.1, 1.0:1.2, or a range consisting of any two of these values.

[0041] Example

[0042] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0043] Test methods and equipment

[0044] Tests for surface drying time, initial curing time, and shear strength:

[0045] Surface drying time: The surface drying time of polyurethane adhesives is tested by the tack method in GB / T 7123.1-2015 "Determination of workability time of multi-component adhesives", with an application amount of 20g.

[0046] Initial curing time: The curing time required for the polyurethane adhesive to reach a shear strength of 1 MPa is defined as the initial curing time, with a curing temperature of 25°C.

[0047] Shear strength: The shear strength of the polyurethane adhesive was tested according to GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)", with a curing condition of 25℃ / 7d and an aluminum / aluminum substrate.

[0048] Example 1

[0049] Preparation of polyurethane prepolymer: Isoflurane diisocyanate and castor oil modified polyol were added to a reaction vessel at a weight ratio of 100:175, stirred evenly, and heated to 80℃ for 10 h to obtain a polyurethane prepolymer with an isocyanate group weight content of 6 wt%.

[0050] Preparation of the first component: By weight, 25 parts of dicyclohexylmethane diisocyanate, 30 parts of the above polyurethane prepolymer, 44 parts of alumina, and 1 part of fumed silica are mixed evenly and degassed by vacuum stirring.

[0051] Preparation of the second component: By weight, 18 parts of castor oil modified polyol, 15 parts of bisphenol A modified polyether polyol, 15 parts of polyoxypropylene polyol (Mw=400), 43 parts of aluminum hydroxide, 5 parts of type 3A molecular sieve, 3 parts of di(dodecyl sulfide)dibutyltin, and 1 part of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0052] In the embodiments of this application, the castor oil-modified polyol is selected from BY-3126 (Beijing Baiyuan Chemical Co., Ltd.), the bisphenol A-modified polyether polyol is selected from 330HP (Arkema, France), the polyoxypropylene polyol is selected from PPG-400 (Nantong Chenrun Chemical Co., Ltd.), the dimer acid-modified polyester polyol is selected from DA21 (Shanghai Jingri New Material Technology Co., Ltd.), wherein the polymethylene polyphenyl isocyanate is selected from PM-200 (from Wanhua Chemical Group Co., Ltd.), the polytetrahydrofuran polyol (Mw=2000) is selected from PTMG-2000 (Asahi Kasei Chemicals), and the polyoxypropylene polyol (Mw=1000) is selected from PPG-1000 (Nantong Chenrun Chemical Co., Ltd.). The method of using the polyurethane adhesive is as follows: Mix the first component and the second component at a mass ratio of 1.0:1.1 until homogeneous, and then use.

[0053] Example 2

[0054] Preparation of polyurethane prepolymer: Hexamethylene diisocyanate and triethanolamine were added to a reaction vessel at a weight ratio of 100:42, stirred evenly, and heated to 45°C for 4 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 10 wt%.

[0055] Preparation of the first component: By weight, 10 parts of hexamethylene diisocyanate trimer, 5 parts of diphenylmethane diisocyanate, 40 parts of the above polyurethane prepolymer, 44.5 parts of alumina, and 0.5 parts of fumed silica are mixed evenly and degassed in a vacuum stirred tank.

[0056] Preparation of the second component: By weight, 25 parts of castor oil modified polyol, 15 parts of bisphenol A modified polyether polyol, 50 parts of aluminum hydroxide, 4.5 parts of type 3A molecular sieve, 5 parts of dibutyl tin mercaptan, and 0.5 parts of triethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0057] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:1.0 until homogeneous, and then apply.

[0058] Example 3

[0059] Preparation of polyurethane prepolymer: Hexamethylene diisocyanate trimer and dimer acid-modified polyester polyol were added to a reaction vessel at a weight ratio of 100:177, stirred evenly, and heated to 60℃ for 8 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 5 wt%. Preparation of the first component: By weight, 4 parts of polymethylene polyphenyl isocyanate, 15 parts of isoflurane diisocyanate, 50 parts of the above polyurethane prepolymer, 30 parts of alumina, and 1 part of fumed silica were mixed evenly and degassed in a vacuum stirred tank. Preparation of the second component: By weight, 40 parts of polytetrahydrofuran polyol (Mw=2000), 20 parts of bisphenol A-modified polyether polyol, 30 parts of silica powder, 4 parts of type 3A molecular sieve, 4 parts of dimethyltin dimercaptoacetate, and 2 parts of 1,8-diazabicycloundec-7-ene were mixed evenly and degassed in a vacuum stirred tank.

[0060] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:1.2 until homogeneous, and then apply.

[0061] Example 4

[0062] Preparation of polyurethane prepolymer: Hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1,4-butanediol were added to a reaction vessel in a weight ratio of 60:40:31, stirred evenly, and heated to 45°C for 4 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 10wt%.

[0063] Preparation of the first component: By weight, 29 parts of hexamethylene diisocyanate trimer, 20 parts of the above polyurethane prepolymer, 50 parts of calcium carbonate, and 1 part of fumed silica are mixed evenly and degassed by vacuum stirring.

[0064] Preparation of the second component: By weight, 30 parts of polyoxypropylene polyol (Mw=1000), 24.5 parts of bisphenol A modified polyether polyol, 30 parts of talc, 10 parts of type 3A molecular sieve, 2 parts of dimethyltin dimercaptoacetic acid, 3 parts of dibutyltin mercaptoate, and 0.5 parts of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0065] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:1.0 until homogeneous, and then apply.

[0066] Example 5

[0067] Preparation of polyurethane prepolymer: Isoflurane diisocyanate, dimer acid modified polyester polyol and glycerol were added to a reaction vessel in a weight ratio of 100:125:10, stirred evenly, and heated to 80℃ for 6 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 8wt%.

[0068] Preparation of the first component: By weight, 5 parts toluene diisocyanate, 5 parts dicyclohexylmethane diisocyanate, 44 parts of the above polyurethane prepolymer, 45 parts calcium carbonate, and 1 part fumed silica are mixed evenly and degassed in a vacuum stirred tank.

[0069] Preparation of the second component: By weight, 40 parts of castor oil modified polyol, 20 parts of dimer acid modified polyester polyol, 15 parts of aluminum hydroxide, 10 parts of zinc oxide, 10 parts of type 3A molecular sieve, 2 parts of bismuth tricarboxylate, and 3 parts of 1,8-diazabicycloundec-7-ene were mixed evenly and degassed in a vacuum stirred tank.

[0070] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:1.2 until homogeneous, and then apply.

[0071] Example 6

[0072] Preparation of polyurethane prepolymer: Hexamethylene diisocyanate trimer and castor oil modified polyol were added to a reaction vessel at a weight ratio of 100:120, stirred evenly, and heated to 80℃ for 4 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 3wt%.

[0073] Preparation of the first component: By weight, 30 parts of hexamethylene diisocyanate trimer, 20 parts of the above polyurethane prepolymer, 49 parts of alumina, and 1 part of fumed silica are mixed evenly and degassed by vacuum stirring.

[0074] Preparation of the second component: By weight, 30 parts castor oil-modified polyol, 25 parts polyoxypropylene polyol (Mw=1000), 35 parts mica powder, 5 parts type 3A molecular sieve, 4 parts di(dodecyl sulfide)dibutyltin, and 1 part 1,8-diazabicycloundec-7-ene are mixed evenly and degassed in a vacuum stirred tank. Application method of the polyurethane adhesive: Mix the first and second components evenly at a mass ratio of 1.0:1.1, and then apply.

[0075] Example 7

[0076] Preparation of polyurethane prepolymer: Isoflurane diisocyanate, 1,4-butanediol and castor oil modified polyol were added to a reaction vessel at a weight ratio of 100:11:128, stirred evenly, and heated to 60℃ for 6 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 5wt%.

[0077] Preparation of the first component: By weight, 10 parts of diphenylmethane diisocyanate, 40 parts of the above polyurethane prepolymer, 49 parts of alumina, and 1 part of fumed silica are mixed evenly and degassed by vacuum stirring.

[0078] Preparation of the second component: By weight, 8 parts of bisphenol A modified polyether polyol, 15 parts of dimer acid modified polyester polyol, 12 parts of polyoxypropylene polyol (Mw=400), 35 parts of calcium carbonate, 15 parts of silica powder, 8 parts of type 3A molecular sieve, 4 parts of di(dodecyl sulfide)dibutyltin, and 3 parts of 1,8-diazabicycloundec-7-ene were mixed evenly and degassed in a vacuum stirred tank.

[0079] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:0.8 until homogeneous, and then apply.

[0080] Example 8

[0081] Preparation of polyurethane prepolymer: Isoflurane diisocyanate, hexamethylene diisocyanate and dimer acid modified polyester polyol were added to a reaction vessel in a weight ratio of 80:20:213, stirred evenly, and heated to 80℃ for 12 h to obtain a polyurethane prepolymer with an isocyanate group weight content of 10wt%.

[0082] Preparation of the first component: By weight, 15 parts hexamethylene diisocyanate, 40 parts of the above polyurethane prepolymer, 44 parts alumina, and 1 part fumed silica are mixed evenly and degassed in a vacuum stirred tank.

[0083] Preparation of the second component: By weight, 40 parts of bisphenol A modified polyether polyol, 20 parts of dimer acid modified polyester polyol, 30 parts of aluminum hydroxide, 5 parts of type 3A molecular sieve, 3 parts of dibutyl tin mercaptan, and 2 parts of N,N-dimethyl (4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed by vacuum stirring.

[0084] Instructions for using polyurethane adhesive: Mix the first component and the second component at a mass ratio of 1.0:1.1 until homogeneous, and then apply.

[0085] Example 9

[0086] Preparation of polyurethane prepolymer: Hexamethylene diisocyanate trimer and castor oil modified polyol were added to a reaction vessel at a weight ratio of 100:80, stirred evenly, and heated to 80℃ for 10 h to obtain a polyurethane prepolymer with an isocyanate group weight content of 6 wt%.

[0087] Except for replacing the polyurethane prepolymer in the first component with the polyurethane prepolymer described above, the rest is the same as in Example 1.

[0088] Comparative Example 1

[0089] Except for adjusting the weight of talc in the second component to 35 parts and omitting dimethyltin dimercaptoacetate and dibutyltin dithioate, the rest is the same as in Example 4.

[0090] Comparative Example 2

[0091] Except for adjusting the weight of talc in the second component to 30.5 parts and not using N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine, the rest is the same as in Example 4.

[0092] Comparative Example 3

[0093] Except for not preparing and using a polyurethane prepolymer and adjusting the weight percentage of hexamethylene diisocyanate trimer in the first component to 39 parts and the weight percentage of calcium carbonate to 60 parts, the rest is the same as in Example 4.

[0094] Comparative Example 4

[0095] Preparation of polyurethane prepolymer: Diphenylmethane diisocyanate and castor oil modified polyol were added to a reaction vessel at a weight ratio of 100:86, stirred evenly, and heated to 80℃ for 4 hours to obtain a polyurethane prepolymer with an isocyanate group weight content of 10wt%.

[0096] Except for replacing the polyurethane prepolymer in the first component with the polyurethane prepolymer described above, the rest is the same as in Example 4. Comparative Example 5

[0097] Preparation of the second component: By weight, 30 parts of polyoxypropylene polyol (Mw=1000), 24.5 parts of bisphenol A modified polyether polyol, 33.5 parts of talc, 10 parts of type 3A molecular sieve, 0.5 parts of dimethyltin dimercaptoacetic acid, 1 part of dibutyltin mercaptoate, and 0.5 parts of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0098] Except for changing the proportion of raw materials in the second component, everything else is the same as in Example 4.

[0099] Comparative Example 6

[0100] Preparation of the second component: By weight, 30 parts of polyoxypropylene polyol (Mw=1000), 24.5 parts of bisphenol A modified polyether polyol, 28 parts of talc, 10 parts of type 3A molecular sieve, 3 parts of dimethyltin dimercaptoacetate, 4 parts of dibutyltin mercaptothiol, and 0.5 parts of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0101] Except for changing the proportion of raw materials in the second component, everything else is the same as in Example 4.

[0102] Comparative Example 7

[0103] Preparation of the second component: By weight, 30 parts of polyoxypropylene polyol (Mw=1000), 24.5 parts of bisphenol A modified polyether polyol, 30.3 parts of talc, 10 parts of type 3A molecular sieve, 2 parts of dimethyltin dimercaptoacetate, 3 parts of dibutyltin mercaptoate, and 0.2 parts of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0104] Except for changing the proportion of raw materials in the second component, everything else is the same as in Example 4.

[0105] Comparative Example 8

[0106] Preparation of the second component: By weight, 30 parts of polyoxypropylene polyol (Mw=1000), 24.5 parts of bisphenol A modified polyether polyol, 28 parts of talc, 10 parts of type 3A molecular sieve, 2 parts of dimethyltin dimercaptoacetic acid, 3 parts of dibutyltin mercaptoate, and 5 parts of N,N-dimethyl(4-methyl-1-piperazinyl)ethylamine were mixed evenly and degassed in a vacuum stirred tank.

[0107] Except for changing the proportion of raw materials in the second component, everything else is the same as in Example 4.

[0108] Table 1 shows the test results for each embodiment and comparative example.

[0109] Table 1

[0110]

[0111] As can be seen from Examples 1 to 9 and Comparative Examples 1 to 8, by selecting the first and second components within the scope of this application and adjusting the weight proportions of each substance in the first and second components within the scope of this application, the obtained polyurethane adhesive can achieve a surface drying time of 30s to 10min and an initial curing time of 4min to 30min while ensuring its shear strength, thus improving production efficiency and reducing energy consumption. In Comparative Example 1, the second component did not use the first catalyst within the scope of this application, resulting in a polyurethane adhesive with a surface drying time of 6 hours and an initial curing time greater than 1 day, significantly reducing production efficiency and also decreasing shear strength. In Comparative Example 2, the second component did not use the second catalyst within the scope of this application, resulting in a polyurethane adhesive with a surface drying time of 3min15s, slightly increased, but an initial curing time of 16min, somewhat delayed, and a decrease in shear strength after curing. In Comparative Example 3, the first component did not prepare a polyurethane prepolymer, only using isocyanate monomers, resulting in a slightly increased surface drying time, but a significantly increased initial curing time and a significantly decreased shear strength. In Comparative Example 4, the first component used aromatic isocyanate to synthesize a polyurethane prepolymer. Its reactivity was significantly higher than that of the polyurethane prepolymer synthesized from low-activity isocyanate monomers in Example 4, resulting in a substantial reduction in surface drying time and initial curing time, leading to a very short workable time. Furthermore, the polyurethane adhesive could not fully wet the substrate, resulting in a significant decrease in shear strength. In Comparative Examples 5 and 6, the amount of the first catalyst in the second component was outside the scope of this application. The shear strength of the prepared polyurethane adhesives decreased in both cases. Moreover, when the amount of the first catalyst was below the lower limit of the scope of this application, the surface drying time was 40 minutes, reducing production efficiency; when the amount of the first catalyst exceeded the upper limit of the scope of this application, the surface drying time was less than 15 seconds, which was too short for operation. In Comparative Examples 7 and 8, the amount of the second catalyst in the second component of the raw materials was not within the scope of this application. The shear strength of the polyurethane adhesive prepared was reduced. Furthermore, when the amount of the second catalyst was lower than the lower limit of the scope of this application, the initial solidification time increased, reducing production efficiency. When the amount of the second catalyst was higher than the upper limit of the scope of this application, although the initial solidification time was slightly shortened, the shear strength decreased significantly.

[0112] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A polyurethane adhesive, comprising a first component and a second component; wherein, By weight, the raw materials of the first component include: 20-50 parts of polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent; the raw materials of the second component include: 30-60 parts of polyol, 3-10 parts of dehydrating agent, 30-50 parts of pigments and fillers, 2-5 parts of first catalyst, and 0.5-3 parts of second catalyst; the first component and the second component are mixed evenly at a mass ratio of 1.0:(0.8-1.2) and used. The polyurethane prepolymer is obtained by reacting a low-activity isocyanate monomer with a chain extender. The low-activity isocyanate monomer is selected from at least one of isoflurane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer. The isocyanate group content of the polyurethane prepolymer is between 3 wt% and 10 wt%. The chain extender is selected from at least one of castor oil modified polyol, dimer acid modified polyester polyol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, and glycerol. The first catalyst is selected from at least one of organotin catalysts and organobismuth catalysts; The second catalyst is selected from at least one of amine catalysts; The isocyanate is selected from at least one of isoflurone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl isocyanate, and hexamethylene diisocyanate trimer; The polyol is selected from at least one of polyoxypropylene polyol, polytetrahydrofuran polyol, bisphenol A modified polyether polyol, castor oil modified polyol, and dimer acid modified polyester polyol.

2. The polyurethane adhesive according to claim 1, wherein, The low-activity isocyanate monomer is selected from hexamethylene diisocyanate trimer.

3. The polyurethane adhesive according to claim 1, wherein, The pigments and fillers are selected from at least one of wollastonite, alumina, aluminum hydroxide, zinc oxide, talc, mica powder, silica powder, and calcium carbonate.

4. The polyurethane adhesive according to claim 1, wherein, The thixotropic agent is selected from at least one of fumed silica, polyamide wax, and organobentonite.

5. The polyurethane adhesive according to claim 1, wherein, The dehydrating agent is selected from type 3A molecular sieve.

6. A method for preparing a polyurethane adhesive according to any one of claims 1 to 5, comprising: The low-activity isocyanate monomer and the chain extender are added to the reaction vessel, wherein the weight ratio of the low-activity isocyanate monomer to the chain extender is 100:(31~213), stirred evenly, and the reaction vessel is heated to 45~80℃ and reacted for 4~12h to obtain a polyurethane prepolymer with an isocyanate group weight content of 3wt%~10wt%. The first component is obtained by uniformly mixing 20-50 parts of the polyurethane prepolymer, 10-30 parts of isocyanate, 30-50 parts of pigments and fillers, and 0.5-1 parts of thixotropic agent and then degassing the mixture in a vacuum stirred tank. The second component is obtained by mixing 30-60 parts of the polyol, 3-10 parts of the dehydrating agent, 30-50 parts of the pigments and fillers, 2-5 parts of the first catalyst, and 0.5-3 parts of the second catalyst evenly and then degassing the mixture in a vacuum stirred tank.

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