Two-component polyurethane adhesive for anodic aluminum oxide base material and preparation method of two-component polyurethane adhesive

Abstract

The invention provides a two-component polyurethane adhesive for an anodic aluminum oxide substrate and a preparation method thereof, the two-component polyurethane adhesive comprises a component A and a component B. When the two-component polyurethane adhesive is used, the mass ratio of the component A to the component B is 10: 3; the component A comprises the following components in percentage by mass: 35-45 wt% of castor oil, 5-10 wt% of vegetable oil, 2-5 wt% of bisphenol A polyether polyol, 0.1-0.5 wt% of a catalyst and an auxiliary agent; and the component B comprises isocyanate. The polyurethane adhesive disclosed by the invention has relatively good toughness and strength, can adapt to anodized aluminum oxide base materials with different film thicknesses, and is particularly excellent in damp-heat aging resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane adhesives for anodized honeycomb aluminum panels, and in particular relates to a two-component polyurethane adhesive for anodized aluminum substrates and a preparation method thereof. Background Art

[0002] The molecular structure of polyurethane contains a variety of polar groups such as carbamate groups, ester groups and ether groups, which can form hydrogen bonds with the polar groups on the bonded materials, making the polyurethane adhesive have very strong bonding properties. In addition, polyurethane has a large number of raw materials and flexible formula adjustment. It is one of the three most widely used synthetic materials and has been widely used in construction, filters, electronics, rail transportation and other fields.

[0003] Common surface treatments for aluminum alloys include mechanical grinding, sandblasting, brushing, and anodizing. Anodizing can meet a wide variety of needs and is currently the most extensively researched and developed technology, as well as the most widely used and successful. Anodized aluminum sheets have increased hardness and wear resistance, excellent heat resistance, and superior insulation properties. They also offer a breakdown voltage of up to 2000V and enhanced corrosion resistance, with resistance to corrosion for thousands of hours in high-intensity salt spray.

[0004] However, the anodized film of aluminum alloy has high hardness but is very brittle. The adhesive needs to have high toughness to cushion the impact of aluminum profile deformation (such as bending and vibration) on the bonding layer and prevent the film from cracking. In addition, the adhesive must also match the thickness of the anodized film. Therefore, it is necessary to provide a polyurethane adhesive that is suitable for anodized aluminum substrates. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a two-component polyurethane adhesive for anodized aluminum substrates and a preparation method thereof. The polyurethane adhesive of the present invention has good toughness and strength, can adapt to anodized aluminum substrates of different film thicknesses, and is particularly excellent in resistance to moisture and heat aging.

[0006] To achieve the above object, the technical solution of the present invention is: In one aspect, the present invention provides a two-component polyurethane adhesive for anodized aluminum substrates, comprising component A and component B. When used, the mass ratio of component A to component B is 10:3; The component A comprises, by mass, 35-45 wt% castor oil, 5-10 wt% vegetable oil, 2-5 wt% bisphenol A polyether polyol, and 0.1-0.5 wt% catalyst and additives; The B component includes isocyanate.

[0007] Preferably, the mass fraction of castor oil in component A is 42.75wt%, 40.25wt%, 37.75wt%, 35.25wt%, preferably 37.75wt%, the mass fraction of bisphenol A polyether polyol is 2.5wt%, 5wt%, 7.5wt%, the mass fraction of vegetable oil polyol is 5.9wt%, and the mass fraction of catalyst is 0.1wt%, 0.2wt%, 0.3wt%. The catalyst can be homemade AUCAT-AS11, CUCAT-RM21, KOSMOS16 or Polycat SA-101.

[0008] Preferably, based on the additives as the calculation base, the additives include 5-8 wt% of a dewatering agent, 40-60 wt% of a filler, 0.1-0.2 wt% of a dust suppressant, and 0-0.3 wt% of a rheological additive.

[0009] Preferably, the dehydrating agent is 3A molecular sieve.

[0010] Preferably, the filler is calcite powder.

[0011] Preferably, the dust suppressant is fumed silica.

[0012] Preferably, the rheological additive can be selected from any one of CAB-O-SIL TS720, AEROSIL 200, BETONE SD-2, ASA T-550F or CRAYVALLAC ULTRA or a mixture thereof.

[0013] Preferably, the open time of the two-component polyurethane adhesive is 15-18 minutes.

[0014] On the other hand, the present invention also provides a method for preparing a two-component polyurethane adhesive for anodized aluminum substrates, comprising the following preparation method: Preparation of component A: According to the formula, part of the castor oil and bisphenol A polyether polyol are mixed evenly and then dehydrated, and then the measured amount of isocyanate is added and mixed evenly to obtain a hydroxyl-terminated PU prepolymer. The hydroxyl-terminated prepolymer is then mixed evenly with the remaining castor oil, vegetable oil, catalyst and additives.

[0015] Preferably, when preparing component A, 50% castor oil and bisphenol A polyether polyol are stirred and mixed at a temperature of 80-85°C. After all the solids are dissolved, the temperature is raised to 105-110°C for vacuum distillation and dehydration. After dehydration, the temperature is lowered to below 50°C, and isocyanate is added. The temperature is raised to 80-85°C while stirring, and the reaction is kept warm. After the reaction is completed, the mixture is naturally cooled to obtain a terminal hydroxyl PU prepolymer.

[0016] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The two-component polyurethane adhesive of the present application can be used for anodized aluminum substrates and has excellent toughness, resistance to moisture and heat aging, and temperature difference performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram showing the bonding state of the honeycomb structure with an open time of 8-12 minutes in Sample 5 in Example 2; Figure 2 This is a diagram showing the bonding state of the honeycomb structure with an open time of 15-18 minutes in Sample 6 in Example 2; Figure 3 This is a diagram showing the bonding state of the honeycomb structure with an open time of 27-30 minutes in Sample 7 in Example 2; Figure 4 This is a diagram of the wet heat aging test in Example 4; Figure 5 This is a test diagram of the temperature difference resistance performance in Example 4. DETAILED DESCRIPTION

[0018] The following is a further detailed description of a two-component polyurethane adhesive for anodized aluminum substrates and its preparation method proposed by the present invention, with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description.

[0019] The performance test conditions in the following examples are: Shear strength was measured according to GB / T7124-2008. The bonded substrate was an anodized aluminum specimen. Cured at 80°C for 15 minutes, the specimen was then cooled to room temperature in the furnace and allowed to stand at room temperature for 24 hours before testing. Planar tensile strength and roller peel strength were measured according to GB / T 1452-2005. The substrate was an anodized aluminum specimen with a thickness of 1mm, an oxide film thickness of 18µm, and a honeycomb core with specifications of 6*6*0.076*8mm (side length*side length*wall thickness*height). The specimen was pressed in a hot press at 80°C for 15 minutes, cooled to room temperature, and allowed to stand at room temperature for 24 hours before testing. Planar compressive strength was determined according to GB / T 1453-2005. The substrate was anodized aluminum with a thickness of 1 mm, the oxide film thickness was 18 µm, and the honeycomb core specifications were 6 x 6 x 0.076 x 8 mm (side length * side length * wall thickness * height). The honeycomb was held in a hot press at 80°C for 15 minutes, cooled to room temperature, and then left at room temperature for 24 hours before testing.

[0020] Example 1 The sources and mass ratios of raw materials for component A are detailed in Table 1: Component B: Polymethylene polyphenyl isocyanate Preparation of component A: Partially refined first-grade castor oil and bisphenol A polyether polyol D33 are stirred and mixed at a temperature of 80-85°C. After all the solids are dissolved, the mixture is heated to 105-110°C and dehydrated by vacuum distillation. After dehydration, the mixture is cooled to below 50°C, and a portion of vegetable oil polyol FH4320 is added. The mixture is heated to 80-85°C while stirring, and the mixture is kept warm for reaction. After the reaction is completed, the mixture is naturally cooled to obtain a hydroxyl-terminated PU prepolymer. The hydroxyl-terminated PU prepolymer is then uniformly mixed with the remaining refined first-grade castor oil, vegetable oil polyol FH4320, catalyst, 3A molecular sieve activation powder, SUPRASEC 3051, hydrophobic fumed silica, and catalyst. The mixture is stirred and vacuumized, and the material is discharged after the process parameters are met.

[0021] Then, component A and component B were mixed in a ratio of 10:3 to make adhesive samples for testing hardness, shear strength, 180° roller peel strength, and residue on aluminum profiles. The test results are shown in Table 2: From the results in Table 2, it can be seen that with the increase in the amount of D33, the crosslinking density of the adhesive system increases accordingly, the tensile shear strength of the system increases linearly, and the roller peel strength first increases and then decreases, indicating that the system undergoes a transformation from flexibility to toughness to rigidity, which is more obvious in the roller peel performance.

[0022] This is primarily because castor oil systems fall into the category of low-modulus systems. The aromatic rings and carbon-oxygen chain structures in the bisphenol A polyether polyol molecule impart specific rigidity and toughness to the material, effectively improving the structure and properties of the polymer, making the synthesized resin more stable and providing superior performance. This suggests that adding bisphenol A polyether polyol to component A can increase the toughness of the adhesive.

[0023] Example 2 Test the effect of different opening times on the composite performance of honeycomb panels: The sources and mass ratios of raw materials for component A are detailed in Table 3: Component B: Polymethylene polyphenyl isocyanate Preparation of component A: Partially refined first-grade castor oil and bisphenol A polyether polyol D33 are stirred and mixed at a temperature of 80-85°C. After all the solids are dissolved, the mixture is heated to 105-110°C and dehydrated by vacuum distillation. After dehydration, the mixture is cooled to below 50°C, and a portion of vegetable oil polyol FH4320 is added. The mixture is heated to 80-85°C while stirring, and the mixture is kept warm for reaction. After the reaction is completed, the mixture is naturally cooled to obtain a hydroxyl-terminated PU prepolymer. The hydroxyl-terminated PU prepolymer is then uniformly mixed with the remaining refined first-grade castor oil, vegetable oil polyol FH4320, catalyst, 3A molecular sieve activation powder, SUPRASEC 3051, hydrophobic fumed silica, and catalyst. The mixture is stirred and vacuumized, and the material is discharged after the process parameters are met.

[0024] Then, component A and component B were mixed in a ratio of 10:3 to prepare adhesive. The open time of sample 5 was 8-12 mins, the open time of sample 6 was 15-18 mins, and the open time of sample 7 was 27-30 mins. Then, honeycomb aluminum panels were prepared according to the gluing steps, and the roller peeling of the honeycomb aluminum panels was tested and the bonding state of the honeycomb structure was observed. The results are shown in Table 4 and Figure 1-3 .

[0025] Table 4 Effect of open time on the roller peeling performance of honeycomb panels in samples 5-7 Open time refers to the maximum amount of time, after applying the mixed resin and curing agent, that the substrate can remain open before bonding. Generally, this refers to the time after application, when bonding is performed, at least 80% of the tensile strength immediately after application is retained. For two-component polyurethane systems using a coating process, the open time of the adhesive is a critical parameter. Excessive open time can easily cause adhesive runoff during programmed production line operation, ultimately leading to a sharp drop in bond strength or even failure. Too short an open time can cause the adhesive to nearly cure before the workpieces are laminated, resulting in a false bond. With current mainstream adhesive dispensing equipment, the process from dispensing glue to workpiece placement, laying the honeycomb core, and then the composite panel generally takes about 25 minutes, so a reasonable open time is required. The performance results in Table 4 indicate that a reasonable open time is 15-18 minutes.

[0026] Example 3 Sample 3 was used to test the effect of aluminum substrates with different oxide film thicknesses on the performance of polyurethane adhesive. The results are shown in Table 5.

[0027] It can be seen from the data in Table 5 that the shear strength and roller peeling of the two-component polyurethane adhesive of this embodiment stabilize at a certain value as the thickness of the oxide film gradually increases. This shows that the two-component adhesive of this embodiment has good adaptability to anodized aluminum substrates with different film thicknesses after sealing.

[0028] Example 4 Comprehensive performance test of the sample of Example 3 1. According to the test standard of JG / T334-2012 for aluminum honeycomb composite panels for building exterior walls, the main properties of the adhesive product on sulfuric acid anodized aluminum substrate were tested, see Table 6 Table 6 Mechanical properties of adhesives The results in Table 6 show that the requirements of aluminum honeycomb composite panels are met.

[0029] 2. Adhesive's resistance to moisture and heat aging Immerse the specimen in 98℃ ± 2℃ distilled water at a constant temperature for 2h, 4h, 6h, 8h, 10h, and 12h, avoiding the specimens from moving around during the test. Then let the specimens cool naturally to room temperature in the distilled water, remove the specimens and wipe them dry, and inspect the specimens for abnormal changes in appearance such as bubbling, degumming, peeling, and cracking. Then conduct a peel strength test according to GB / T 1452-2005. The results are shown in the table below. Figure 4 .

[0030] pass Figure 4 It can be seen that it has excellent resistance to moisture and heat.

[0031] 3. Adhesive temperature resistance Keep the specimen at -40℃±2℃ for at least 2 hours, take it out and immediately place it at 80℃±2℃ for at least 2 hours. This is one cycle, and a total of 50 cycles are performed. Then visually inspect the specimen for abnormal changes in appearance such as bubbling, debonding, peeling, cracking, etc., and then perform a peel strength test according to GB / T 1452-2005. The results are shown in the table. Figure 5 .from Figure 5 It can be seen that the blank control is the peel strength directly tested without temperature difference cycling. The peel strength of the blank control is 88, and the peel strength after aging is 86. The difference between the two is not large, indicating that it has excellent temperature difference performance.

[0032] The present invention converts the adhesive system from a low-modulus flexible system to a medium-modulus tough system by adding bisphenol A-modified polyol to component A, and the shear strength and roller peeling are optimal when the addition amount is 5wt%.

[0033] Open time is a crucial parameter for adhesives used in large-area composite systems. Based on the actual production line process, this invention determines an open time of 15-18 minutes. This ensures both line operability and sufficient viscosity before entering the press, preventing runaway. Furthermore, this two-component polyurethane adhesive exhibits excellent resistance to moisture, heat, and temperature differences, especially for bonding anodized films 8-25μm thick.

[0034] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the scope of protection of the present invention.

Claims

1. A two-component polyurethane adhesive for anodized aluminum substrates, characterized in that: The invention comprises component A and component B. When used, the mass ratio of component A to component B is 10:

3. The component A comprises, by mass, 35-45 wt% castor oil, 5-10 wt% vegetable oil, 2-5 wt% bisphenol A polyether polyol, 30-45 wt% filler, 0.1-0.5 wt% catalyst and rheological additive; The B component includes isocyanate.

2. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 1, characterized in that: Taking the additive as the calculation base, the additive includes 5-8 wt% of dehydrating agent, 30-45 wt% of filler, 0.1-0.2 wt% of catalyst and 0-0.3 wt% of rheological additive.

3. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 2, characterized in that: The dehydrating agent is 3A molecular sieve.

4. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 2, characterized in that: The filler is calcite powder.

5. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 2, characterized in that: The dust suppressant is fumed silica.

6. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 2, characterized in that: The rheological additive is selected from any one of CAB-O-SIL TS720, AEROSIL 200, BETONE SD-2, ASA T-550F or CRAYVALLAC ULTRA or a mixture thereof.

7. The two-component polyurethane adhesive for anodized aluminum substrate according to claim 1, characterized in that: The open time of the two-component polyurethane adhesive is 15-18 minutes.

8. A method for preparing a two-component polyurethane adhesive for anodized aluminum substrates, characterized in that: The invention comprises the following preparation methods: According to the formula, part of castor oil and bisphenol A polyether polyol are mixed evenly and then dehydrated, and then a measured amount of isocyanate is added and mixed evenly to react to obtain a terminal hydroxyl PU prepolymer. The terminal hydroxyl prepolymer is then mixed evenly with the remaining castor oil, vegetable oil, catalyst and additives.

9. The method for preparing a two-component polyurethane adhesive for anodized aluminum substrates according to claim 8, characterized in that: Mix 50% castor oil and bisphenol A polyether polyol at 80-85°C, and after all the solids are dissolved, heat to 105-110°C and perform vacuum distillation for dehydration. After dehydration, cool to below 50°C, add isocyanate, and heat to 80-85°C while stirring. Keep the mixture warm for reaction, and cool naturally after the reaction is completed to obtain a hydroxyl-terminated PU prepolymer.

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