Waterborne polyurethane adhesive and preparation method thereof

Abstract

The invention provides a waterborne polyurethane adhesive and a preparation method thereof, and relates to the technical field of polyurethane adhesives, and the waterborne polyurethane adhesive provided by the invention is prepared from the following components in parts by weight: 120-150 parts of polyester glycol; 20 to 50 parts of diisocyanate; 0 to 0.1 part of dibutyltin dilaurate; 6-10 parts of a carboxylic acid hydrophilic chain extender; 2-5 parts of small molecular dihydric alcohol; 3-5 parts of hydrogenated castor oil; 1-3 parts of a water-soluble salt nucleating agent or an oil-soluble nucleating agent; 40 to 80 parts of acetone; 3.8 to 5.5 parts of triethylamine; 200 to 250 parts of deionized water; and 1-3 parts of an amine chain extender. The polyester glycol compound, the diisocyanate, the hydrogenated castor oil, the carboxyl hydrophilic chain extender and the small molecule chain extender are matched with the water-soluble salt nucleating agent or the oil-soluble nucleating agent to be polymerized, the crystallization behavior of the resin is changed through the nucleating agent, the crystallization rate is increased, the crystallization density is increased, and the micronization of the grain size is promoted; the size of the crystallization area tends to be consistent, the distribution is uniform, and the comprehensive performance of the product is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of polyurethane adhesives, and in particular relates to a water-based polyurethane adhesive and a preparation method thereof. Background Art

[0002] With the continuous development of technology and the substantial increase in people's awareness of environmental protection, water-based polyurethane adhesives have replaced solvent-based polyurethane adhesives in many fields due to their advantages of being economical, safe, non-toxic, pollution-free, and having little irritating odor. They have excellent adhesion, outstanding oil resistance, impact resistance, wear resistance, and low temperature resistance, and are widely used in various fields such as automobiles, footwear, wood, and furniture. The molecular chain structure of polyurethane in water-based polyurethane adhesives is an important factor affecting the bonding performance. The crystallization performance and crystal morphology of the molecular chain determine the initial bonding force, activation temperature, heat resistance temperature, and final bonding force of the polyurethane adhesive.

[0003] The application process of water-based polyurethane adhesive is as follows: (1) Spray the water-based polyurethane adhesive on the surface of the object to be bonded, let it dry, and the polyurethane adhesive film becomes a milky white film; (2) Place the object to be bonded with the polyurethane adhesive film on the workbench of the vacuum forming machine, spread the PVC film, and start heating the PVC film. The heating time is generally 7 to 15 minutes depending on the thickness of the PVC film. The display temperature of the thermocouple is generally 170°C to 220°C. After the PVC film softens, open the vacuum and 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 water-based polyurethane adhesive. If the activation temperature of the water-based polyurethane adhesive is high, it needs to be continuously heated after forming, and finally cooled to form the finished product. Because the PVC film has a certain stress on the surface of the object during forming, the polyurethane adhesive needs to have a higher heat resistance temperature for opening the glue. However, the activation temperature of the waterborne polyurethane adhesive film in the prior art is relatively high, the heat-resistant temperature of debonding is low, the initial tack is low and the final tack is not high, which has become a prominent problem of waterborne polyurethane adhesives and a research hotspot. Therefore, how to provide a waterborne polyurethane adhesive with a low activation temperature, a high heat-resistant temperature of debonding, a large initial tack and a high final tack is a technical problem that needs to be solved urgently in the field of waterborne polyurethane adhesives. Summary of the invention

[0004] The purpose of the present application is to provide a water-based polyurethane adhesive and a preparation method thereof, aiming to solve the problems of the water-based polyurethane adhesive in the prior art, such as high activation temperature, low heat resistance temperature for debonding, low initial adhesion and low final adhesion.

[0005] In order 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 by the following components in parts by weight: 120 to 150 parts of polyester diol; 20 to 50 parts of diisocyanate; 0 to 0.1 parts of dibutyltin dilaurate; 6 to 10 parts of carboxylic acid hydrophilic chain extender; 2 to 5 parts of small molecule diol; 3 to 5 parts of hydrogenated castor oil; 1 to 3 parts of water-soluble salt nucleating agent or oil-soluble nucleating agent; 40 to 80 parts of acetone; 3.8 to 5.5 parts of triethylamine; 200 to 250 parts of deionized water; and 1 to 3 parts of amine chain extender.

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

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

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

[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 hexamethylenediamine.

[0013] In a second aspect, the present application also provides a method for preparing a waterborne polyurethane adhesive, comprising the following steps:

[0014] Dehydrate 120-150 parts by weight of polyester diol at 110° C. and 0.09 MPa, and then cool to 55° C.; add 20-50 parts by weight of diisocyanate and 0-0.1 parts by weight of dibutyltin dilaurate, and keep the temperature at 65-80° C. for 1-2 hours; then add 6-10 parts by weight of carboxylic acid hydrophilic chain extender, and keep the temperature 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 the temperature at 65-75° C. for 1.5-2.5 hours;

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

[0016] After emulsification and dispersion, stirring is continued, and then 1 to 3 parts by weight of an amine chain extender is added. After the reaction is completed, residual acetone is removed in vacuo to obtain a water-based polyurethane adhesive.

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

[0018] The water-based 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 parts 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; and 1-3 parts of amine chain extender. The invention is prepared by polymerizing a highly crystalline bifunctional polyester diol compound, 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. The nucleating agent is used to change the crystallization behavior of the resin, accelerate the crystallization rate, increase the crystallization density, and promote the refinement of the grain size, so that the size of the crystallization region tends to be consistent and the distribution is uniform, thereby improving the comprehensive performance of the product, thereby obtaining a water-based polyurethane adhesive with a lower activation temperature, a higher debonding heat-resistant temperature, a larger initial adhesion and a higher final adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

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

[0021] Figure 2 The time for the WPU films prepared in Example 4 and Comparative Example 1 of the present application to become transparent at the same temperature;

[0022] Figure 3 It is the time for the WPU films prepared in Example 4 and Comparative Example 1 of the present application to become transparent at the same temperature. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0025] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0026] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

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

[0028] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0029] The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0030] Raw materials: Polycaprolactone (PCL), manufacturer: Daicel Chemical Co., Ltd., Japan. 1,4-Butanediol adipate (PBA), manufacturer: Hubei Wande Chemical. 1,6-Hexanediol adipate (PHA), manufacturer: Shandong Orilon Chemical. Polycarbonate diol (PCDL), manufacturer: Shandong Yuanli Technology. Toluene diisocyanate, manufacturer: Shanghai BASF. Isophorone diisocyanate, manufacturer: Shanghai BASF. Hexamethylene diisocyanate, manufacturer: Wanhua Chemical.

[0031] The test method for testing the prepared waterborne polyurethane adhesive is as follows:

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

[0033] Activation temperature test: prepare a film of the same thickness according to the preparation method of WPU film, put the film into an oven with a stable temperature, and observe whether the film can become completely transparent within 300±10s. If it can become completely transparent, the oven temperature is regarded as the activation temperature. If it becomes transparent in less than 300±10s, lower the oven temperature and retest. If it becomes transparent in more than 300±10s, increase the oven temperature and retest. The temperature should be lowered or increased by 1°C each time.

[0034] Adhesion test: The bonding material is PVC film from the same batch with a thickness of 0.2 mm. It is activated at its activation temperature for 300±10s. The bonding of the sample is rolled 20 times with a 10Kg weight. Other test conditions are carried out in accordance with GB / T2791-1995.

[0035] Initial debonding temperature test: The bonding materials are PCV film and density wood board from the same batch. The sample preparation steps are carried out in accordance with HG / T2815-1996. The test environment is an oven, the heating rate is 5℃ / min, the load is 0.5Kg, and a black marker is used to draw a line at the bonding point between the PCV film and the density wood board for observation. The temperature at which vitrification begins on the density board is the initial heat resistance temperature.

[0036] Example 1

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

[0038] 150 parts by weight of polycaprolactone (PCL) were dehydrated at 110°C and 0.09 MPa, then cooled to 55°C; 27 parts by weight of isophorone diisocyanate and 0.1 parts by weight of dibutyltin dilaurate were added, and the mixture was kept at 80°C for 2 hours; 7 parts by weight of dimethylolpropionic acid chain extender was added, and the mixture was kept at 85°C for 1 hour; 4 parts by weight of 1,4-butanediol and 4 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 70°C for 2.5 hours, during which 50 parts by weight of acetone was added. The viscosity was reduced, the temperature was lowered to 45°C, and 4.5 parts by weight of triethylamine was added for salification; the temperature was then lowered to 40°C, and a mixture of 1.8 parts by weight of a water-soluble Luoyang Zhongda Chemical Co., Ltd. NP508 nucleating agent (organic phosphate nucleating agent) and 220 parts by weight of deionized water was added under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, stirring was continued, and 3 parts by weight of hexamethylenediamine chain extender was added; finally, residual acetone was removed under vacuum to obtain an environmentally friendly water-based polyurethane adhesive with adjustable crystal morphology.

[0039] The prepared water-based polyurethane adhesive was tested. The test showed that the activation temperature of the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology was 48°C, the initial bonding force was 20N / mm, the final bonding force was 25N / mm, and the initial debonding temperature was 105°C.

[0040] Example 2

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

[0042] 150 parts by weight of 1,4-butylene adipate (PBA) was dehydrated at 110°C and 0.09 MPa, then cooled to 55°C; 33 parts by weight of toluene diisocyanate was added, and the mixture was kept at 65°C for 1.5 hours; 8 parts by weight of dimethylol propionic acid chain extender was added, and the mixture was kept at 75°C for 0.5 hours; 3 parts by weight of triethylene glycol and 3 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 65°C for 1.5 hours, during which 70 parts by weight of acetone was added to adjust the viscosity and reduce the temperature. The mixture was heated to 45°C, and 5.0 parts by weight of triethylamine was added for salification; the mixture was cooled to 40°C, and a mixture of 2 parts by weight of a water-soluble nucleating agent (Shanxi Chemical Research Institute (Co., Ltd.)) TMN-102 (fatty acid salt nucleating agent) and 230 parts by weight of deionized water was added under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, stirring was continued, and 1.3 parts by weight of ethylenediamine chain extender was added; finally, residual acetone was removed under vacuum to obtain an environmentally friendly water-based polyurethane adhesive with adjustable crystal morphology.

[0043] After testing, the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology has an activation temperature of 50°C, an initial bonding force of 23N / mm, a final bonding force of 26N / mm, and an initial debonding temperature of 110°C.

[0044] Example 3

[0045] Prepare according to the following steps and weight proportions:

[0046] 150 parts by weight of 1,6-hexanediol adipate (PHA) was dehydrated at 110°C and 0.09Mpa, then cooled to 55°C; 46 parts by weight of MDI-50 was added, and the mixture was kept at 65°C for 1.5 hours; 10 parts by weight of dimethylolbutyric acid, a carboxylic acid hydrophilic chain extender, was added, and the mixture was kept at 75°C for 0.5 hours; 2 parts by weight of 1,4-butanediol and 3 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 65°C for 1.5 hours, during which 80 parts by weight of acetone was added to adjust the viscosity. , cool to 45°C, add 5.5 parts by weight of triethylamine for salification; cool to 40°C, add 3 parts by weight of a water-soluble nucleating agent (Shanxi Chemical Research Institute (Co., Ltd.)) GB-120 (cyclic carboxylate nucleating agent) and 250 parts by weight of deionized water under high-speed stirring for emulsification and dispersion; continue stirring after emulsification and dispersion, and then add 1.0 part by weight of ethylenediamine chain extender; finally, remove residual acetone in vacuum to obtain an environmentally friendly water-based polyurethane adhesive with adjustable crystal morphology.

[0047] After testing, the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology has an activation temperature of 53°C, an initial bonding force of 24N / mm, a final bonding force of 26N / mm, and an initial debonding temperature of 115°C.

[0048] Example 4

[0049] Prepare according to the following steps and weight proportions:

[0050] 150 parts by weight of polycarbonate diol (PCDL) were dehydrated at 110°C and 0.09 MPa, then cooled to 55°C; 27 parts by weight of hexamethylene diisocyanate and 0.1 parts by weight of dibutyltin dilaurate were added, and the mixture was kept at 80°C for 2 hours; 6 parts by weight of dimethylolbutyric acid chain extender was added, and the mixture was kept at 85°C for 1 hour; 5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 75°C for 2.5 hours, during which 40 parts by weight of acetone were added to adjust the viscosity; the isocyanate content in the above reactants was 1.50 parts by weight. When the theoretical value is reached (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 Chemical Research Institute (Co., Ltd.) TM-3 (water-soluble salt nucleating agent) and 200 parts by weight of deionized water is added under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, stirring is continued, and 2 parts by weight of diaminobutane chain extender are added; finally, residual acetone is removed in vacuum to obtain a water-based polyurethane adhesive with adjustable crystallization state.

[0051] After testing, the activation temperature of the water-based polyurethane adhesive with adjustable crystal state is 45°C, the initial bonding force is 18N / mm, the final bonding force is 24N / mm, and the debonding heat resistance temperature is 100°C.

[0052] Example 5

[0053] Prepare according to the following steps and weight proportions:

[0054] 150 parts by weight of polycaprolactone (PCL) were dehydrated at 110°C and 0.09 MPa, then cooled to 55°C; 27 parts by weight of hexamethylene diisocyanate and 0.1 parts by weight of dibutyltin dilaurate were added, and the mixture was kept at 80°C for 2 hours; 6 parts by weight of dimethylolpropionic acid chain extender was added, and the mixture was kept at 85°C for 1 hour; 5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 70°C for 2.5 hours, and 1.5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 70°C for 2.5 hours. The nucleating agent is DCNDCA (amide nucleating agent) from Shin Nippon Chemical Co., Ltd., during which 40 parts by weight of acetone are added to adjust the viscosity, the temperature is lowered to 45°C, and 4.1 parts by weight of triethylamine are 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, stirring is continued, and 2 parts by weight of hexamethylenediamine chain extender are added; finally, residual acetone is removed in vacuum to obtain the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology.

[0055] After testing, the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology has an activation temperature of 46°C, an initial bonding force of 19N / mm, a final bonding force of 23N / mm, and an initial debonding temperature of 103°C.

[0056] Example 6

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

[0058] 150 parts by weight of polycarbonate diol (PCDL) were dehydrated at 110°C and 0.09 MPa, then cooled to 55°C; 27 parts by weight of isophorone diisocyanate and 0.1 parts by weight of dibutyltin dilaurate were added, and the mixture was kept at 80°C for 2 hours; 7 parts by weight of dimethylolbutyric acid chain extender was added, and the mixture was kept at 85°C for 1 hour; 4 parts by weight of 1,6-hexanediol and 4 parts by weight of hydrogenated castor oil were added, and the mixture was kept at 70°C for 2.5 hours, and 1.8 parts by weight of oil-soluble nucleating agent was added. agent (Shanxi Chemical Research Institute (Co., Ltd.)) TMB-5 (condensed ring compound nucleating agent), during which 50 parts by weight of acetone were added to adjust the viscosity, the temperature was lowered to 45°C, and 4.5 parts by weight of triethylamine were added for salification; the temperature was lowered to 40°C, and 220 parts by weight of deionized water were added to the mixture under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, stirring was continued, and 3 parts by weight of diaminobutane chain extender were added; finally, residual acetone was removed in vacuo to obtain the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology.

[0059] After testing, the environmentally friendly water-based polyurethane adhesive with adjusted crystal morphology has an activation temperature of 48°C, an initial bonding force of 21N / mm, a final bonding force of 24N / mm, and an initial debonding temperature of 110°C.

[0060] Comparative Example 1

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

[0062] 150 parts by weight of polycarbonate diol (PCDL) are dehydrated at 110° C. and 0.09 Mpa, and then cooled to 55° C.; 27 parts by weight of hexamethylene diisocyanate and 0.1 parts by weight of dibutyltin dilaurate are added, and the mixture is kept at 80° C. for 2 hours; 6 parts by weight of dimethylolbutyric acid chain extender is added, and the mixture is kept at 85° C. for 1 hour; 5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil are added, and the mixture is kept at 75° C. for 2.5 hours, during which 40 parts by weight of acetone are added to adjust the viscosity, the mixture is cooled to 45° C., and 4.1 parts by weight of triethylamine are added for salification; the mixture is cooled to 30° C., and 200 parts by weight of deionized water are added to the mixture under high-speed stirring for emulsification and dispersion; after emulsification and dispersion, the mixture is continuously stirred, and then 2 parts by weight of dibutylene diamine chain extender is added; and finally, residual acetone is removed under vacuum to obtain the waterborne polyurethane adhesive.

[0063] After testing, the activation temperature of the water-based polyurethane adhesive was 64°C, the initial bonding strength was 16N / mm, the final bonding strength was 19N / mm, and the debonding heat resistance temperature was 83°C.

[0064] Comparative Example 2

[0065] Prepare according to the following steps and weight proportions:

[0066] 150 parts by weight of 1,6-hexanediol adipate (PHA) are dehydrated at 110° C. and 0.09 Mpa, and then cooled to 55° C.; 46 parts by weight of MDI-50 are added, and the mixture is kept at 65° C. for 1.5 hours; 10 parts by weight of dimethylolbutyric acid, a carboxylic acid hydrophilic chain extender, are added, and the mixture is kept at 75° C. for 0.5 hours; 2 parts by weight of 1,4-butanediol and 3 parts by weight of hydrogenated castor oil are added, and the mixture is kept at 65° C. for 1.5 hours, during which 80 parts by weight of acetone are added to adjust the viscosity, the mixture is cooled to 45° C., and 5.5 parts by weight of triethylamine are added for salification; the mixture is cooled 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, stirring is continued, and then 1.0 parts by weight of ethylenediamine chain extender is added; and finally, residual acetone is removed under vacuum to obtain a waterborne polyurethane adhesive.

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

[0068] Comparative Example 3

[0069] Prepare according to the following steps and weight proportions:

[0070] 150 parts by weight of polycaprolactone (PCL) are dehydrated at 110°C and 0.09Mpa, and then cooled to 55°C; 27 parts by weight of hexamethylene diisocyanate and 0.1 parts by weight of dibutyltin dilaurate are added, and the mixture is kept at 80°C for 2 hours; 6 parts by weight of dimethylolpropionic acid chain extender is added, and the mixture is kept at 85°C for 1 hour; 5 parts by weight of 1,6-hexanediol and 5 parts by weight of hydrogenated castor oil are added, and the mixture is kept at 70°C for 2.5 hours, during which 40 parts by weight of acetone are added to adjust the viscosity, the mixture is cooled to 45°C, and 4.1 parts by weight of triethylamine are added for salification; the mixture is cooled 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, stirring is continued, and 2 parts by weight of hexamethylenediamine chain extender are added; and the residual acetone is removed by vacuum to obtain a waterborne polyurethane adhesive.

[0071] After testing, the activation temperature of the water-based polyurethane adhesive is 62°C, the initial bonding strength is 22N / mm, the final bonding strength is 25N / mm, and the debonding heat resistance temperature 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 formula, the activation temperature, initial bonding force, final bonding force and initial debonding temperature of the waterborne polyurethane adhesive after adding the nucleating agent are shown in Table 1, wherein the activation temperature of the waterborne polyurethane adhesive is between 45 and 53°C, the initial bonding force is between 18 and 24 N / mm, the final bonding force is between 23 and 26 N / mm, and the initial debonding temperature is between 100 and 115°C. Compared with Comparative Example 1, Example 3 and Comparative Example 2, and Example 5 and Comparative Example 3 in Table 1, the activation temperature of the water-based polyurethane adhesive to which a nucleating agent is added during the preparation process is lower than the activation temperature of the water-based polyurethane adhesive without a nucleating agent, the initial bonding force of the water-based polyurethane adhesive to which a nucleating agent is added during the preparation process is higher than the initial bonding force of the water-based polyurethane adhesive without a nucleating agent, the final bonding force of the water-based polyurethane adhesive to which a nucleating agent is added during the preparation process is higher than the final bonding force of the water-based polyurethane adhesive without a nucleating agent, and the initial debonding temperature of the water-based polyurethane adhesive to which a nucleating agent is added during the preparation process is higher than the initial debonding temperature of the water-based polyurethane adhesive without a nucleating agent.

[0076] Figure 1 The DSC graphs of the WPU films of Example 4 and Comparative Example 1 of the present application are shown. Figure 1 It can be seen that the crystalline state of the WPU film prepared in Example 4 with the addition of a nucleating agent undergoes an endothermic transition at about 45°C, which is about 19°C lower than the endothermic transition temperature of the WPU film prepared in Comparative Example 1 at about 64°C, indicating that the addition of a nucleating agent does play a role in changing the crystal morphology and lowering the activation temperature of the film.

[0077] To further prove the effect of adding nucleating agent on the transformation of WPU film crystal state (i.e., at a certain temperature, the crystal state gradually transforms into glass state and amorphous state), the WPU film of Example 4 and the WPU film of Comparative Example 1 (Comparative Example 4 without adding nucleating agent) were placed in an oven at a constant temperature of 50°C, and the time for the film to become completely transparent was observed. Figure 2 , Figure 3 .from Figure 2 , Figure 3It can be seen that the WPU film prepared in Example 4 with the addition of nucleating agent has become completely transparent in 4 minutes and 16 seconds, while the WPU film prepared in Comparative Example 1 has become completely transparent only in 10 minutes and 33 seconds, indicating that the addition of nucleating agent can change the crystal form of WPU film in a shorter time and requires less heat, proving that the nucleating agent does change the crystallization behavior of the resin, accelerates the crystallization rate, increases the crystal density, promotes the refinement of the grain size, promotes the uniformity of the size of the crystallization region, and evenly distributes it, making the material easier to crystallize, thereby reducing the activation temperature of the product. The heating temperature of the polyurethane adhesive can be reduced during use, thereby reducing energy consumption.

[0078] When the waterborne polyurethane adhesive prepared in the present application is used, the crystalline state gradually changes to the glassy state and the amorphous state at a certain temperature, and the temperature at this time is the activation temperature of the product. Due to the effect of the nucleating agent, the crystallization behavior of the resin is changed, the crystallization rate is accelerated, the crystal density is increased, the grain size is refined, and the size of the crystal region is promoted to be consistent and evenly distributed, making the material easier to crystallize, thereby reducing the activation temperature of the product.

[0079] On the other hand, when the water-based polyurethane adhesive prepared in the present application is recrystallized in the glassy and amorphous states, the nucleating agent promotes the formation of a fine and dense microcrystalline structure, so that the molecular chain has a faster crystallization rate at a slightly higher temperature, and the crystal region can grow more regularly into spherulite particles with uniform size and uniform distribution, thereby increasing the cohesive force and thus improving the initial adhesion and final adhesion of the product.

[0080] On the other hand, after bonding, the waterborne polyurethane adhesive product prepared in the present application has an increase in its contact interface due to the change in the crystalline region and the non-crystalline region after recrystallization, making it more difficult to convert into the glassy state and 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 to the water-based polyurethane adhesive prepared in the present application during the product synthesis process, which can give the water-based polyurethane adhesive a certain amount of thixotropy, which can not only ensure the wettability of the substrate during bonding, but also reduce the excessive penetration of the adhesive into the substrate.

[0082] The environmentally friendly water-based polyurethane adhesive prepared by the method of the 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, and good storage stability, and the industrial production process is stable.

[0083] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A water-based polyurethane adhesive, characterized in that: The invention is prepared by comprising the following components in parts by weight: 120-150 parts of polyester diol; 20-50 parts of diisocyanate; 0-0.1 parts 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; and 1-3 parts of amine chain extender.

2. The water-based polyurethane adhesive according to claim 1, characterized in that: The water-soluble salt nucleating agent includes at least one of an organic phosphate nucleating agent, a cyclic carboxylate nucleating agent or a fatty acid salt nucleating agent.

3. The water-based polyurethane adhesive according to claim 1, characterized in that: The oil-soluble nucleating agent includes at least one of a dehydroabietic acid nucleating agent, an amide nucleating agent or a condensed ring compound nucleating agent.

4. The water-based polyurethane adhesive according to claim 1, characterized in that: The polyester diol has a high crystalline form, and the polyester diol includes at least one of 1,4-butanediol adipate, 1,6-hexanediol adipate and polycaprolactone with a molecular weight of 3000.

5. The water-based 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.

6. The water-based 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.

7. The water-based polyurethane adhesive according to claim 1, characterized in that: The amine chain extender includes at least one of ethylenediamine, butanediamine and hexamethylenediamine.

8. A method for preparing a water-based polyurethane adhesive, characterized in that: The steps include: Dehydrate 120-150 parts by weight of polyester diol at 110° C. and 0.09 MPa, and then cool to 55° C.; add 20-50 parts by weight of diisocyanate and 0-0.1 parts by weight of dibutyltin dilaurate, and keep the temperature at 65-80° C. for 1-2 hours; then add 6-10 parts by weight of carboxylic acid hydrophilic chain extender, and keep the temperature 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 the temperature at 65-75° C. for 1.5-2.5 hours; Add 40 to 80 parts by weight of acetone to the product of the above step to adjust the viscosity, cool it to 45 to 50° C., and add 3.8 to 5.5 parts by weight of triethylamine for salification; then cool it to 40° C., and add 1 to 3 parts by weight of a water-soluble salt nucleating agent and 200 to 250 parts by weight of deionized water under high-speed stirring for emulsification and dispersion; or, add 1 to 3 parts by weight of an oil-soluble nucleating agent to the product of the above step, during which 40 to 80 parts by weight of acetone are added to adjust the viscosity, cool it to 45 to 50° C., and add 3.8 to 5.5 parts by weight of triethylamine for salification; cool it to 40° C., and add 200 to 250 parts by weight of deionized water under high-speed stirring for emulsification and dispersion; After emulsification and dispersion, stirring is continued, and then 1 to 3 parts by weight of an amine chain extender is added. After the reaction is completed, residual acetone is removed in vacuo to obtain a water-based polyurethane adhesive.

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