An aqueous polyurethane adhesive and its preparation method

Abstract

The present application provides an aqueous polyurethane adhesive and a preparation method thereof, which relates to the technical field of polyurethane adhesives. The aqueous polyurethane adhesive provided by the present application is prepared from the following components in parts by weight: 120-150 parts of polyester diol; 20-50 parts of diisocyanate; 0-0.1 part of dibutyltin dilaurate; 6-10 parts of carboxylic acid hydrophilic chain extender; 2-5 parts of small molecule diol; 3-5 parts of hydrogenated castor oil; 1-3 parts of water-soluble salt nucleating agent or oil-soluble nucleating agent; 40-80 parts of acetone; 3.8-5.5 parts of triethylamine; 200-250 parts of deionized water; 1-3 parts of amine chain extender. It is polymerized by using a polyester diol compound, diisocyanate, hydrogenated castor oil, carboxyl hydrophilic chain extender and small molecule chain extender in combination with a water-soluble salt nucleating agent or an oil-soluble nucleating agent. By using the nucleating agent to change the crystallization behavior of the resin, accelerate the crystallization rate, increase the crystallization density, and promote the refinement of the crystal grain size, the size of the crystallization region tends to be consistent and the distribution is uniform, thereby improving the comprehensive performance of the product.

Description

Technical Field

[0001] This application belongs to the technical field of polyurethane adhesives, and particularly relates to an aqueous polyurethane adhesive and a preparation method thereof. Background Art

[0002] With the continuous development of technology and the significant enhancement of people's environmental awareness, aqueous polyurethane adhesives have replaced solvent-based polyurethane adhesives in many fields due to their advantages such as economy, safety, non-toxicity, no pollution, and low irritating odor. They have excellent adhesion, outstanding oil resistance, impact resistance, wear resistance, low-temperature resistance and other characteristics, and are widely used in various fields such as automobiles, shoes, wood, furniture, etc. The molecular chain structure of polyurethane in aqueous polyurethane adhesives is an important factor affecting the bonding performance. The crystallization performance and crystallization morphology of the molecular chain determine the initial adhesion, activation temperature, heat resistance temperature, and final adhesion of polyurethane adhesives.

[0003] The application process of aqueous polyurethane adhesives is as follows: (1) Spray the aqueous polyurethane adhesive on the surface of the object to be bonded and dry it. The polyurethane adhesive film becomes a milky white film; (2) Place the object to be bonded with the polyurethane adhesive film on the working table of a vacuum thermoforming machine, lay a PVC film, and start heating the PVC film. According to the thickness of the PVC film, the heating time is generally 7 - 15 minutes, and the temperature displayed by the thermocouple is generally 170°C - 220°C. After the PVC film softens, turn on the vacuum to suck the PVC film onto the surface of the object to be bonded. The temperature of the PVC film is the activation temperature of the aqueous polyurethane adhesive. If the activation temperature of the aqueous polyurethane adhesive is relatively high, continuous heating is required after thermoforming, and finally it is cooled to a finished product. Because the PVC film has a certain stress when thermoformed on the surface of the object, the polyurethane adhesive needs to have a relatively high heat resistance temperature for debonding. However, in the existing technology, the activation temperature of the aqueous polyurethane adhesive film is relatively high, the heat resistance temperature for debonding is low, the initial adhesion is relatively low, and the final adhesion is not high, which has become a prominent problem of aqueous polyurethane adhesives and also a research hotspot. Therefore, how to provide an aqueous polyurethane adhesive with a lower activation temperature, a higher heat resistance temperature for debonding, a greater initial adhesion, and a higher final adhesion is a technical problem that urgently needs to be solved in the field of aqueous polyurethane adhesives. Summary of the Invention

[0004] The purpose of this application is to provide an aqueous polyurethane adhesive and a preparation method thereof, aiming to solve the problems of relatively high activation temperature, low heat resistance temperature for debonding, relatively low initial adhesion, and low final adhesion of aqueous polyurethane adhesives in the existing technology.

[0005] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides an aqueous polyurethane adhesive, which is prepared from the following components in parts by weight: 120 - 150 parts of polyester diol; 20 - 50 parts of diisocyanate; 0 - 0.1 part of dibutyltin dilaurate; 6 - 10 parts of carboxylic acid hydrophilic chain extender; 2 - 5 parts of small molecule diol; 3 - 5 parts of hydrogenated castor oil; 1 - 3 parts of water-soluble salt nucleating agent or oil-soluble nucleating agent; 40 - 80 parts of acetone; 3.8 - 5.5 parts of triethylamine; 200 - 250 parts of deionized water; 1 - 3 parts of amine chain extender.

[0007] According to a preferred embodiment, the water-soluble salt nucleating agent includes at least one of organic phosphate nucleating agents, cyclic carboxylate nucleating agents or fatty acid salt nucleating agents.

[0008] According to a preferred embodiment, the oil-soluble nucleating agent includes at least one of dehydroabietic acid nucleating agents, amide nucleating agents or polycyclic compound nucleating agents.

[0009] According to a preferred embodiment, the polyester diol has a high crystallization form, and the polyester diol includes at least one of adipic acid-1,4-butanediol ester with a molecular weight of 3000, adipic acid-1,6-hexanediol ester and polycaprolactone.

[0010] According to a preferred embodiment, the diisocyanate includes at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate.

[0011] According to a preferred embodiment, the small molecule diol includes at least one of 1,4-butanediol, 1,6-hexanediol and diethylene glycol.

[0012] According to a preferred embodiment, the amine chain extender includes at least one of ethylenediamine, butanediamine and hexanediamine.

[0013] In a second aspect, the present application further provides a preparation method of the aqueous polyurethane adhesive, which includes the following steps:

[0014] After dehydrating 120 - 150 parts by weight of polyester diol at 110°C and 0.09 MPa, cool it down to 55°C; add 20 - 50 parts by weight of diisocyanate, 0 - 0.1 part by weight of dibutyltin dilaurate, and keep it at 65 - 80°C for 1 - 2 hours; then add 6 - 10 parts by weight of carboxylic acid hydrophilic chain extender, keep it at 75 - 85°C for 0.5 - 1 hour, then add 2 - 5 parts by weight of small molecule diol and 3 - 5 parts by weight of hydrogenated castor oil, and keep it at 65 - 75°C for 1.5 - 2.5 hours;

[0015] Add 40 - 80 parts by weight of acetone to the product of the above step to adjust the viscosity, cool down to 45 - 50 °C, and add 3.8 - 5.5 parts by weight of triethylamine for salification; then cool down to 40 °C, and add a mixture of 1 - 3 parts by weight of a water-soluble salt nucleating agent and 200 - 250 parts by weight of deionized water under high-speed stirring for emulsification and dispersion; or, add 1 - 3 parts by weight of an oil-soluble nucleating agent to the product of the above step, add 40 - 80 parts by weight of acetone to adjust the viscosity during this period, cool down to 45 - 50 °C, and add 3.8 - 5.5 parts by weight of triethylamine for salification; cool down to 40 °C, and add 200 - 250 parts by weight of deionized water under high-speed stirring for emulsification and dispersion;

[0016] Continue stirring after emulsification and dispersion, then add 1 - 3 parts by weight of an amine chain extender, and remove the residual acetone under vacuum after the reaction ends to obtain an aqueous polyurethane adhesive.

[0017] Based on the above technical solution, the aqueous polyurethane adhesive and its preparation method of the present application at least have the following beneficial technical effects:

[0018] The aqueous polyurethane adhesive provided in the first aspect of the present application is prepared from the following components in parts by weight: 120 - 150 parts of polyester diol; 20 - 50 parts of diisocyanate; 0 - 0.1 part of dibutyltin dilaurate; 6 - 10 parts of carboxylic acid hydrophilic chain extender; 2 - 5 parts of small molecule diol; 3 - 5 parts of hydrogenated castor oil; 1 - 3 parts of water-soluble salt nucleating agent or oil-soluble nucleating agent; 40 - 80 parts of acetone; 3.8 - 5.5 parts of triethylamine; 200 - 250 parts of deionized water; 1 - 3 parts of amine chain extender. It is polymerized by using a bifunctional polyester diol compound with a high crystalline form, diisocyanate, hydrogenated castor oil, a carboxyl hydrophilic chain extender and a small molecule chain extender in combination with a water-soluble salt nucleating agent or an oil-soluble nucleating agent. By changing the crystallization behavior of the resin, accelerating the crystallization rate, increasing the crystallization density, and promoting the refinement of the crystal grain size through the nucleating agent, the size of the crystallization region tends to be consistent and evenly distributed, improving the comprehensive performance of the product, thereby obtaining an aqueous polyurethane adhesive with a lower activation temperature, a higher heat resistance temperature for debonding, a greater initial adhesion and a higher final adhesion. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is the DSC diagram of the WPU film in Example 4 and Comparative Example 1 of the present application;

[0021] Figure 2 It is the time when the WPU film prepared in Example 4 and Comparative Example 1 of this application becomes transparent at the same temperature.

[0022] Figure 3 It is the time when the WPU film prepared in Example 4 and Comparative Example 1 of this application becomes transparent at the same temperature. Detailed implementation manners

[0023] In order to make the technical problems to be solved, technical solutions and beneficial effects of this application clearer, the following further details this application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0024] In this application, the term "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may indicate: A exists alone, A and B exist simultaneously, and B exists alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0025] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both indicate: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0026] It should be understood that in various embodiments of this application, the magnitude of the serial numbers of the above processes does not mean the sequence of execution. Some or all steps can be executed in parallel or successively. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0027] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the" and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0028] In the description of the embodiments of the present application, the weights of the relevant components mentioned not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down in proportion, they are within the scope disclosed in the description of the embodiments of the present application. Specifically, the mass described in the description of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0029] The technical solutions of the present application will be described in detail below with reference to specific embodiments.

[0030] Raw materials: Polycaprolactone (PCL), manufacturer: Daicel Chemical Industries, Ltd., Japan. Poly(butylene adipate) (PBA), manufacturer: Hubei Wande Chemical Industry. Poly(hexamethylene adipate) (PHA), manufacturer: Shandong Aolilong Chemical Industry. Polycarbonate diol (PCDL), manufacturer: Shandong Yuanli Technology. Toluene diisocyanate, manufacturer: BASF Shanghai. Isophorone diisocyanate, manufacturer: BASF Shanghai. Hexamethylene diisocyanate, manufacturer: Wanhua Chemical.

[0031] The test methods for testing the prepared waterborne polyurethane adhesive are as follows:

[0032] Preparation method of WPU film: By testing the solid content of WPU waterborne polyurethane, a certain weight portion of the waterborne polyurethane adhesive is weighed and poured into a flat-bottomed PE culture dish box with a diameter of 15 cm, covered with filter paper on top, and gradually dried into a film at room temperature. A flat, opaque film with a uniform thickness can be obtained, which can be used for the DSC, XRD or activation temperature test characterization of the WPU film.

[0033] Activation temperature test: Prepare a film with the same thickness according to the preparation method of the WPU film, put the film into an oven that has been adjusted and has a stable temperature, and observe whether the film can become completely transparent within 300 ± 10 s. If it can become completely transparent, the oven temperature is regarded as the activation temperature. If it becomes transparent below 300 ± 10 s, lower the oven temperature and retest. If it becomes transparent above 300 ± 10 s, raise the oven temperature and retest. Each time the temperature is lowered or raised by 1 °C.

[0034] Adhesion test: The bonding material is a PVC film of the same batch with a thickness of 0.2 mm. It is activated at its activation temperature for 300 ± 10 s, and the specimen is bonded by rolling with a 10 Kg weight for 20 times. Other test conditions are carried out according to GB / T2791-1995.

[0035] Initial delamination temperature test: The bonding materials are PCV film and density board of the same batch. The sample preparation steps are carried out according to the regulations of HG / T2815-1996. The test environment is an oven, the heating rate is 5°C / min, the load is 0.5 Kg. A black marker is used to draw a line at the bonding position of the PCV film and the density board for observation. The temperature at which vitrification starts on the density board is the initial heat resistance temperature.

[0036] Example 1

[0037] Prepare according to the following steps and weight parts ratio:

[0038] After dehydrating 150 parts by weight of polycaprolactone (PCL) at 110°C and 0.09 MPa, cool it down to 55°C; add 27 parts by weight of isophorone diisocyanate and 0.1 part by weight of dibutyltin dilaurate, and then keep it at 80°C for 2 hours; add 7 parts by weight of dimethylolpropionic acid chain extender and keep it at 85°C for 1 hour; then add 4 parts by weight of 1,4-butanediol and 4 parts by weight of hydrogenated castor oil, keep it at 70°C for 2.5 hours. During this period, add 50 parts by weight of acetone to adjust the viscosity, cool it down to 45°C, and add 4.5 parts by weight of triethylamine for salification; then cool it down to 40°C, and add a mixture of 1.8 parts by weight of water-soluble nucleating agent NP508 (organic phosphate nucleating agent) from Luoyang Zhongda Chemical Co., Ltd. and 220 parts by weight of deionized water under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, continue stirring, and then add 3 parts by weight of hexamethylenediamine chain extender; finally, vacuum remove the residual acetone to obtain an environmentally friendly waterborne polyurethane adhesive with adjustable crystal form.

[0039] Test the prepared waterborne polyurethane adhesive. After testing, the activation temperature of this environmentally friendly waterborne polyurethane adhesive with adjustable crystal form is 48°C, the initial bonding strength is 20 N / mm, the final bonding strength is 25 N / mm, and the initial delamination temperature is 105°C.

[0040] Example 2

[0041] Prepare according to the following steps and weight parts ratio:

[0042] After dehydrating 150 parts by weight of adipic acid-1,4-butanediol ester (PBA) at 110°C and 0.09 Mpa, the temperature was lowered to 55°C; 33 parts by weight of toluene diisocyanate was added, and it was kept at 65°C for 1.5 hours; 8 parts by weight of dimethylolpropionic acid chain extender was added, and it was kept at 75°C for 0.5 hours; then 3 parts by weight of triethylene glycol and 3 parts by weight of hydrogenated castor oil were added, and it was kept at 65°C for 1.5 hours. During this period, 70 parts by weight of acetone was added to adjust the viscosity. The temperature was lowered to 45°C, and 5.0 parts by weight of triethylamine was added for salification; the temperature was lowered to 40°C, and a mixture of 2 parts by weight of a water-soluble nucleating agent (Shanxi Research Institute of Chemical Industry (Co., Ltd.)) TMN-102 (fatty acid salt nucleating agent) and 230 parts by weight of deionized water was emulsified and dispersed under high-speed stirring; after emulsification and dispersion, continuous stirring was carried out, and then 1.3 parts by weight of ethylenediamine chain extender was added; finally, the residual acetone was removed under vacuum to obtain an environmentally friendly waterborne polyurethane adhesive with adjustable crystal form.

[0043] After testing, the activation temperature of this environmentally friendly waterborne polyurethane adhesive with adjustable crystal form was 50°C, the initial adhesion was 23 N / mm, the final adhesion was 26 N / mm, and the initial debonding temperature was 110°C.

[0044] Example 3

[0045] It was prepared according to the following steps and weight ratio:

[0046] After dehydrating 150 parts by weight of adipic acid-1,6-hexanediol ester (PHA) at 110°C and 0.09 Mpa, the temperature was lowered to 55°C; 46 parts by weight of MDI-50 was added, and it was kept at 65°C for 1.5 hours; 10 parts by weight of carboxylic acid hydrophilic chain extender dimethylolbutyric acid was added, and it was kept at 75°C for 0.5 hours; then 2 parts by weight of 1,4-butanediol and 3 parts by weight of hydrogenated castor oil were added, and it was kept at 65°C for 1.5 hours. During this period, 80 parts by weight of acetone was added to adjust the viscosity. The temperature was lowered to 45°C, and 5.5 parts by weight of triethylamine was added for salification; the temperature was lowered to 40°C, and a mixture of 3 parts by weight of a water-soluble nucleating agent (Shanxi Research Institute of Chemical Industry (Co., Ltd.)) GB-120 (cyclic carboxylate nucleating agent) and 250 parts by weight of deionized water was emulsified and dispersed under high-speed stirring; after emulsification and dispersion, continuous stirring was carried out, and then 1.0 part by weight of ethylenediamine chain extender was added; finally, the residual acetone was removed under vacuum to obtain an environmentally friendly waterborne polyurethane adhesive with adjustable crystal form.

[0047] After testing, the activation temperature of this environmentally friendly waterborne polyurethane adhesive with adjustable crystal form was 53°C, the initial adhesion was 24 N / mm, the final adhesion was 26 N / mm, and the initial debonding temperature was 115°C.

[0048] Example 4

[0049] It is prepared according to the following steps and weight parts ratio:

[0050] After dehydrating 150 parts by weight of polycarbonate diol (PCDL) at 110 °C and 0.09 Mpa, the temperature is lowered to 55 °C; 27 parts by weight of hexamethylene diisocyanate and 0.1 part by weight of dibutyltin dilaurate are added, and it is kept at 80 °C for 2 hours; 6 parts by weight of dimethylolbutyric acid chain extender is added, and it is kept at 85 °C for 1 hour; then 5 parts by weight of 1,6 - hexanediol and 5 parts by weight of hydrogenated castor oil are added, and it is kept at 75 °C for 2.5 hours. During this period, 40 parts by weight of acetone is added to adjust the viscosity; when the isocyanate group content in the above reactants reaches the theoretical value (the content of isocyanate is generally 2.3 ± 0.3%), the temperature is lowered to 45 °C, and 4.1 parts by weight of triethylamine (TEA) is added for salification; the temperature is lowered to 30 °C, and a mixture of 1.5 parts by weight of nucleating agent Shanxi Research Institute of Chemical Industry (Co., Ltd.) TM - 3 (water - soluble salt nucleating agent) and 200 parts by weight of deionized water is added and emulsified and dispersed under high - speed stirring; after emulsification and dispersion, continuous stirring is carried out, and then 2 parts by weight of butanediamine chain extender is added; finally, the residual acetone is removed under vacuum to obtain a water - borne polyurethane adhesive with adjustable crystallization state.

[0051] After testing, the activation temperature of the water - borne polyurethane adhesive with adjustable crystallization state is 45 °C, the initial bonding strength is 18 N / mm, the final bonding strength is 24 N / mm, and the heat - resistant temperature for debonding is 100 °C.

[0052] Example 5

[0053] It is prepared according to the following steps and weight parts ratio:

[0054] After dehydrating 150 parts by weight of polycaprolactone (PCL) at 110 °C and 0.09 Mpa, the temperature is lowered to 55 °C; 27 parts by weight of hexamethylene diisocyanate and 0.1 part by weight of dibutyltin dilaurate are added, and it is kept at 80 °C for 2 hours; 6 parts by weight of dimethylolpropionic acid chain extender is added, and it is kept at 85 °C for 1 hour; then 5 parts by weight of 1,6 - hexanediol and 5 parts by weight of hydrogenated castor oil are added, and it is kept at 70 °C for 2.5 hours. Then 1.5 parts by weight of nucleating agent DCNDCA of Shin - Nippon Rika Co., Ltd. (amide - type nucleating agent) is added. During this period, 40 parts by weight of acetone is added to adjust the viscosity. The temperature is lowered to 45 °C, and 4.1 parts by weight of triethylamine is added for salification; the temperature is lowered to 40 °C, and a mixture of 200 parts by weight of deionized water is emulsified and dispersed under high - speed stirring; after emulsification and dispersion, continuous stirring is carried out, and then 2 parts by weight of hexanediamine chain extender is added; finally, the residual acetone is removed under vacuum to obtain the environmentally friendly water - borne polyurethane adhesive with adjustable crystallization form.

[0055] After testing, the activation temperature of the environment-friendly waterborne polyurethane adhesive for regulating crystal morphology is 46°C, the initial bonding strength is 19 N / mm, the final bonding strength is 23 N / mm, and the initial debonding temperature is 103°C.

[0056] Example 6

[0057] Prepare according to the following steps and weight ratio:

[0058] After dehydrating 150 parts by weight of polycarbonate diol (PCDL) at 110°C and 0.09 Mpa, cool it down to 55°C; add 27 parts by weight of isophorone diisocyanate and 0.1 part by weight of dibutyltin dilaurate, and keep it at 80°C for 2 hours; add 7 parts by weight of dimethylolbutyric acid chain extender, and keep it at 85°C for 1 hour; then add 4 parts by weight of 1,6-hexanediol and 4 parts by weight of hydrogenated castor oil, and keep it at 70°C for 2.5 hours. Then add 1.8 parts by weight of oil-soluble nucleating agent (Shanxi Research Institute of Chemical Industry (Co., Ltd.)) TMB-5 (condensed ring compound nucleating agent). During this period, add 50 parts by weight of acetone to adjust the viscosity, cool it down to 45°C, and add 4.5 parts by weight of triethylamine for salification; cool it down to 40°C, and add a mixture of 220 parts by weight of deionized water under high-speed stirring for emulsifying and dispersing; continue stirring after emulsifying and dispersing, and then add 3 parts by weight of butanediamine chain extender; finally, vacuum remove the residual acetone to obtain the environment-friendly waterborne polyurethane adhesive for regulating crystal morphology.

[0059] After testing, the activation temperature of the environment-friendly waterborne polyurethane adhesive for regulating crystal morphology is 48°C, the initial bonding strength is 21 N / mm, the final bonding strength is 24 N / mm, and the initial debonding temperature is 110°C.

[0060] Comparative Example 1

[0061] Prepare according to the following steps and weight ratio:

[0062] After dehydrating 150 parts by weight of polycarbonate diol (PCDL) at 110°C and 0.09 Mpa, cool it down to 55°C; add 27 parts by weight of hexamethylene diisocyanate and 0.1 part by weight of dibutyltin dilaurate, and keep it at 80°C for 2 hours; add 6 parts by weight of dimethylolbutyric acid chain extender, and keep it at 85°C for 1 hour; then add 5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil, and keep it at 75°C for 2.5 hours. During this period, add 40 parts by weight of acetone to adjust the viscosity, cool it down to 45°C, and add 4.1 parts by weight of triethylamine for salification; cool it down to 30°C, and add a mixture of 200 parts by weight of deionized water under high-speed stirring for emulsifying and dispersing; continue stirring after emulsifying and dispersing, and then add 2 parts by weight of butanediamine chain extender; finally, vacuum remove the residual acetone to obtain the waterborne polyurethane adhesive.

[0063] After testing, the activation temperature of this waterborne polyurethane adhesive is 64°C, the initial bonding strength is 16 N / mm, the final bonding strength is 19 N / mm, and the heat resistance temperature for debonding is 83°C.

[0064] Comparative Example 2

[0065] It is prepared according to the following steps and weight ratio:

[0066] After dehydrating 150 parts by weight of adipic acid - 1,6 - hexanediol ester (PHA) at 110°C and 0.09 Mpa, the temperature is lowered to 55°C; 46 parts by weight of MDI - 50 is added, and it is kept at 65°C for 1.5 hours; 10 parts by weight of the carboxylic acid hydrophilic chain extender dimethylolbutyric acid is added, and it is kept at 75°C for 0.5 hour; then 2 parts by weight of 1,4 - butanediol and 3 parts by weight of hydrogenated castor oil are added, and it is kept at 65°C for 1.5 hours. During this period, 80 parts by weight of acetone is added to adjust the viscosity. The temperature is lowered to 45°C, and 5.5 parts by weight of triethylamine is added for salification; the temperature is lowered to 40°C, and a mixture of 250 parts by weight of deionized water is emulsified and dispersed under high - speed stirring; after emulsification and dispersion, continuous stirring is carried out, and then 1.0 part by weight of ethylenediamine chain extender is added; finally, the residual acetone is removed under vacuum to obtain the waterborne polyurethane adhesive.

[0067] After testing, the activation temperature of the waterborne polyurethane adhesive is 66°C, the initial bonding strength is 20 N / mm, the final bonding strength is 24 N / mm, and the initial debonding temperature is 92°C.

[0068] Comparative Example 3

[0069] It is prepared according to the following steps and weight ratio:

[0070] After dehydrating 150 parts by weight of polycaprolactone (PCL) at 110°C and 0.09 Mpa, the temperature is lowered to 55°C; 27 parts by weight of hexamethylene diisocyanate and 0.1 part by weight of dibutyltin dilaurate are added, and it is kept at 80°C for 2 hours; 6 parts by weight of the chain extender dimethylolpropionic acid is added, and it is kept at 85°C for 1 hour; then 5 parts by weight of 1,6 - hexanediol and 5 parts by weight of hydrogenated castor oil are added, and it is kept at 70°C for 2.5 hours. During this period, 40 parts by weight of acetone is added to adjust the viscosity. The temperature is lowered to 45°C, and 4.1 parts by weight of triethylamine is added for salification; the temperature is lowered to 40°C, and a mixture of 200 parts by weight of deionized water is emulsified and dispersed under high - speed stirring; after emulsification and dispersion, continuous stirring is carried out, and then 2 parts by weight of hexamethylenediamine chain extender is added; finally, the residual acetone is removed under vacuum to obtain the waterborne polyurethane adhesive.

[0071] After testing, the activation temperature of this waterborne polyurethane adhesive is 62°C, the initial bonding strength is 22 N / mm, the final bonding strength is 25 N / mm, and the heat resistance temperature for debonding is 94°C.

[0072] Table 1 Test Data Results of Examples 1 to 6 and Comparative Examples 1 to 3

[0073]

[0074]

[0075] The experimental results are shown in Table 1. It can be seen from Examples 1 to 6 and Comparative Examples 1 to 3 that under the same process, raw materials, and formulation, after adding a nucleating agent, the activation temperature, initial adhesion, final adhesion, and initial debonding temperature of the waterborne polyurethane adhesive are shown in Table 1. Among them, the activation temperature of the waterborne polyurethane adhesive is between 45 and 53 °C, the initial adhesion is between 18 and 24 N / mm, the final adhesion is between 23 and 26 N / mm, and the initial debonding temperature is between 100 and 115 °C. Comparing Example 4 with Comparative Example 1, Example 3 with Comparative Example 2, and Example 5 with Comparative Example 3 in Table 1, the activation temperature of the waterborne polyurethane adhesive with a nucleating agent added during the preparation process is lower than that of the waterborne polyurethane adhesive without a nucleating agent, the initial adhesion of the waterborne polyurethane adhesive with a nucleating agent added during the preparation process is higher than that of the waterborne polyurethane adhesive without a nucleating agent, the final adhesion of the waterborne polyurethane adhesive with a nucleating agent added during the preparation process is higher than that of the waterborne polyurethane adhesive without a nucleating agent, and the initial debonding temperature of the waterborne polyurethane adhesive with a nucleating agent added during the preparation process is higher than that of the waterborne polyurethane adhesive without a nucleating agent.

[0076] Figure 1 The DSC diagrams of the WPU films of Example 4 and Comparative Example 1 of the present application are shown. From Figure 1 it can be seen that the crystal state of the WPU film prepared in Example 4 with a nucleating agent added undergoes a transformation with endothermic absorption at about 45 °C, which is about 19 °C lower than the temperature of about 64 °C at which the WPU film prepared in Comparative Example 1 without a nucleating agent added undergoes endothermic absorption, indicating that adding a nucleating agent does play a role in changing the crystal morphology and reducing the activation temperature of the film.

[0077] To further prove the transformation of the crystal state of the WPU film by adding a nucleating agent (i.e., at a certain temperature, the crystalline state gradually transforms into the glassy state and the amorphous state), the WPU film of Example 4 and the WPU film of Comparative Example 1 (comparing Example 4 without a nucleating agent added) were placed in an oven with a constant temperature of 50 °C, and the time for the film to become completely transparent was observed. See Figure 2 、 Figure 3 。From Figure 2 、 Figure 3It can be seen that the WPU film prepared in Example 4 with the addition of a nucleating agent became completely transparent at 4 minutes and 16 seconds, while the WPU film prepared in Comparative Example 1 became completely transparent at 10 minutes and 33 seconds. This shows that after adding the nucleating agent, the WPU film can change its crystal form in a shorter time and requires less heat, proving that the nucleating agent has indeed changed the crystallization behavior of the resin, accelerated the crystallization rate, increased the crystallization density, promoted the refinement of the crystal grain size, made the size of the crystallization regions tend to be consistent and evenly distributed, making the material more prone to crystallization, thereby reducing the activation temperature of the product. The heating temperature during the use of the polyurethane adhesive can be reduced, thus reducing energy consumption.

[0078] When the waterborne polyurethane adhesive prepared in this application is used, at a certain temperature, the crystalline state gradually transforms into the glassy state and the amorphous state, and the temperature at this time is the activation temperature of the product. Due to the action of the nucleating agent, the crystallization behavior of the resin has been changed, the crystallization rate has been accelerated, the crystallization density has been increased, the refinement of the crystal grain size has been promoted, the size of the crystallization regions has been made to tend to be consistent and evenly distributed, making the material more prone to crystallization, thereby reducing the activation temperature of the product.

[0079] On the other hand, when the waterborne polyurethane adhesive prepared in this application recrystallizes in the glassy state and the amorphous state, due to the action of the nucleating agent, it promotes the formation of a fine and dense microcrystalline structure, enabling the molecular chains to have a faster crystallization rate at a slightly higher temperature, and can make the crystal regions grow more regularly into spherulite particles with uniform size and even distribution, increasing the cohesive force, thereby improving the initial adhesion and final adhesion of the product.

[0080] On the other hand, after the product of the waterborne polyurethane adhesive prepared in this application is bonded, due to the changes in the crystalline regions and non-crystalline regions after recrystallization, the contact interface is increased, and it becomes more difficult to transform back into the glassy state and the amorphous state again, thereby increasing the initial debonding temperature of the material.

[0081] On the other hand, a small amount of hydrogenated castor oil is added during the synthesis of the waterborne polyurethane adhesive prepared in this application, which can endow the waterborne polyurethane adhesive with a certain amount of thixotropy, ensuring both the wetting flatness of the substrate during bonding and reducing the excessive penetration of the adhesive into the substrate.

[0082] The environmentally friendly waterborne polyurethane adhesive prepared by the method of the present invention can adjust the crystal form, has a fast drying rate, a large initial adhesion, a high final adhesion, a low activation temperature, an initial debonding temperature, good storage stability, and a stable industrial production process.

[0083] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. An aqueous polyurethane adhesive, characterized in that, It is prepared from the following components in parts by weight: 120 - 150 parts of polyester diol; 20 - 50 parts of diisocyanate; 0 - 0.1 part of dibutyltin dilaurate; 6 - 10 parts of carboxylic acid hydrophilic chain extender; 2 - 5 parts of small molecule diol; 3 - 5 parts of hydrogenated castor oil; 1 - 3 parts of water-soluble salt nucleating agent or oil-soluble nucleating agent; 40 - 80 parts of acetone; 3.8 - 5.5 parts of triethylamine; 200 - 250 parts of deionized water; 1 - 3 parts of amine chain extender. Among them, the water-soluble salt nucleating agent includes at least one of organic phosphate nucleating agent, fatty acid salt nucleating agent or nucleating agent TM-3, and the oil-soluble nucleating agent includes amide nucleating agent.

2. The aqueous polyurethane adhesive according to claim 1, characterized in that, The polyester diol has a high crystallization form, and the polyester diol includes at least one of adipic acid-1,4-butanediol ester with a molecular weight of 3000, adipic acid-1,6-hexanediol ester and polycaprolactone.

3. The aqueous polyurethane adhesive according to claim 1, characterized in that, The diisocyanate includes at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate.

4. The aqueous polyurethane adhesive according to claim 1, characterized in that, The small molecule diol includes at least one of 1,4-butanediol, 1,6-hexanediol and diethylene glycol.

5. The aqueous polyurethane adhesive according to claim 1, characterized in that, The amine chain extender includes at least one of ethylenediamine, butanediamine and hexanediamine.

6. A preparation method of an aqueous polyurethane adhesive, characterized in that, It includes the following steps: After dehydrating 120 - 150 parts by weight of polyester diol at 110°C and 0.09 MPa, cool it down to 55°C; add 20 - 50 parts by weight of diisocyanate and 0 - 0.1 part by weight of dibutyltin dilaurate, keep it warm at 65 - 80°C for 1 - 2 hours; then add 6 - 10 parts by weight of carboxylic acid hydrophilic chain extender, keep it warm at 75 - 85°C for 0.5 - 1 hour, then add 2 - 5 parts by weight of small molecule diol and 3 - 5 parts by weight of hydrogenated castor oil, keep it warm at 65 - 75°C for 1.5 - 2.5 hours; Add 40 - 80 parts by weight of acetone to the product of the above step to adjust the viscosity, cool it down to 45 - 50°C, add 3.8 - 5.5 parts by weight of triethylamine for salification; then cool it down to 40°C, and emulsify and disperse the mixture of 1 - 3 parts by weight of water-soluble salt nucleating agent and 200 - 250 parts by weight of deionized water under high-speed stirring; or, add 1 - 3 parts by weight of oil-soluble nucleating agent to the product of the above step, add 40 - 80 parts by weight of acetone to adjust the viscosity during this period, cool it down to 45 - 50°C, add 3.8 - 5.5 parts by weight of triethylamine for salification; cool it down to 40°C, and emulsify and disperse 200 - 250 parts by weight of deionized water under high-speed stirring; Keep stirring after emulsification and dispersion, then add 1 - 3 parts by weight of amine chain extender, and remove the residual acetone by vacuum after the reaction ends to obtain the waterborne polyurethane adhesive.

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