A method for bonding PVC substrate surface to waterproof coating

Abstract

This invention relates to the field of PVC bonding technology, and discloses a method for bonding a PVC substrate surface to a waterproof coating, comprising the steps of: wiping the PVC substrate and immersing it in a toluene solution of cobalt acetylacetonate, removing it and applying a waterproof coating; applying a base material and curing it, then applying a second layer of waterproof coating and allowing it to stand at room temperature. In this invention, it was unexpectedly discovered that using cobalt acetylacetonate(II) as an adhesive, immersing the PVC substrate in a toluene solution of cobalt acetylacetonate, and then curing it at high temperature allows cobalt acetylacetonate(II) to be effectively grafted onto the PVC surface. Characteristic absorption peaks of cobalt acetylacetonate(II) are found on the modified PVC surface, while the other side interacts with the waterproof coating, achieving non-covalent interfacial adhesion. This effectively combines the PVC and the waterproof coating, enabling resistance to various humid and high-salt environments.

Description

Technical Field

[0001] This invention relates to the field of PVC bonding technology, and more specifically to a method for bonding a PVC substrate surface to a waterproof coating. Background Technology

[0002] Polyvinyl chloride (PVC) is a general-purpose thermoplastic material. Due to its excellent weather resistance and chemical resistance, it is commonly used in the manufacture of windshield system components, window frames, and sewage and water pipes. Among these, the largest consumer of PVC is the building and industrial piping installation industry. Because of the wide range of applications for PVC building materials, the sealing construction between PVC and other building materials such as cement has become an essential research topic.

[0003] Over the past few decades, researchers have focused on modifying PVC surfaces to increase their surface energy. High free surface energy combined with suitable roughness indicates increased wettability and improved adhesion of PVC substrates. Therefore, the improvement of adhesive strength between PVC and other materials (e.g., bitumen-based waterproof coatings) largely depends on PVC surface treatment techniques. Currently, methods for PVC surface modification are mainly divided into two categories: chemical treatment and physical treatment. Physical treatment includes flame treatment, corona treatment, and low-temperature plasma treatment technologies.

[0004] PVC surface chemical treatments include: reagent treatment, organic solvent treatment, primer treatment, and surfactant treatment. Primer treatment is one of the simplest and easiest surface modification methods used to improve the surface properties of PVC. This process involves only brushing a primer onto the PVC plastic sheet. Primers include various types of cobalt complexes, amine primers, polyurethane, polyethyleneimine, and chlorinated polypropylene, etc.

[0005] CN113773704A discloses a PVC water-based primer and its preparation method, comprising a latex and an acrylic resin cross-linked with the latex. The acrylic resin is formed by emulsion polymerization of butyl acrylate, methyl methacrylate, hydroxyethyl acrylate, and methacrylic acid in water. The solid content of the acrylic resin is 45-50%. This primer has the characteristic that its tackifying effect does not fail at high temperatures.

[0006] CN113402695A discloses a waterborne polyurethane resin, comprising, by weight: 15-20 parts isophorone diisocyanate, 5-15 parts hydroxyl-terminated polybutadiene, 5-18 parts organic solvent, 5-12 parts castor oil-modified polyester polyol, 2-8 parts hydrophilic chain extender, 2-6 parts neutralizer, 0.4-5 parts post-chain extender, 0.01-0.25 parts catalyst, and 50-65 parts deionized water. It exhibits good low-temperature and high-humidity resistance. The hydroxyl-terminated polybutadiene possesses excellent high adhesion and low-temperature resistance, while the castor oil-modified polyester polyol exhibits strong crystallinity and excellent high-temperature and high-humidity resistance. The two react with isophorone diisocyanate to form an interpenetrating network structure resin, which, after film formation, exhibits good low-temperature and high-humidity resistance, resulting in good adhesion under low-temperature and high-humidity conditions.

[0007] PVC, as a representative of plastic substrates, possesses a non-porous surface with chemical inertness and low surface energy. Modification materials applied to the PVC surface can increase the surface energy and surface polarity of the PVC substrate through surface wetting. A prerequisite for good adhesion between the PVC substrate and asphalt-based waterproof coatings is a wetted PVC surface. The more effectively the surface modification material wets the PVC substrate, the larger the covered surface area, allowing for more interaction of active groups, thus forming a stronger bond with the overlying waterproof coating.

[0008] However, in humid and high-salt environments, PVC substrates and asphalt-based waterproof coatings are prone to delamination, resulting in decreased adhesion. Summary of the Invention

[0009] This invention addresses the problem of poor adhesion between water-emulsion rubber asphalt compounds and PVC substrates in humid and high-salt environments by providing a method for bonding PVC substrate surfaces to waterproof coatings. This method utilizes cobalt acetylacetone to achieve effective chemical bonding between PVC and the waterproof coating, has a simple composition, and is more suitable for building waterproofing applications in humid and high-salt environments.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for bonding a PVC substrate surface to a waterproof coating includes the following steps: wiping the PVC substrate and immersing it in a toluene solution of cobalt(II) acetylacetonate, removing it and applying the waterproof coating; applying a base material and curing it, then applying a second layer of waterproof coating and allowing it to stand at room temperature.

[0012] In this invention, it was unexpectedly discovered that using cobalt(II) acetylacetonate as an adhesive, PVC substrate is immersed in a toluene solution of cobalt(II) acetylacetonate and then cured at high temperature to effectively graft cobalt(II) acetylacetonate onto the PVC surface. Characteristic absorption peaks of cobalt(II) acetylacetonate are found on the modified PVC surface. At the same time, the other side interacts with the waterproof coating to obtain non-covalent interfacial adhesion, thereby combining PVC and waterproof coating in a way that can resist various humid and high-salt environments.

[0013] The cobalt acetylacetonate solution in toluene has a cobalt acetylacetonate mass concentration of 0.3-0.7 wt%. Preferably.

[0014] When the PVC substrate is immersed in a toluene solution of cobalt acetylacetone and allowed to stand and stretch, the cobalt acetylacetone is evenly adhered to the PVC surface through this static stretching method. This reduces the generation of air bubbles in the solution, fills the peaks and troughs of the plastic surface, allows more active groups to interact, and facilitates good contact with the waterproof coating above.

[0015] The PVC substrate is immersed in a toluene solution of cobalt acetylacetone for 10-20 seconds. In this invention, the PVC surface is loaded with cobalt acetylacetone using only a very short immersion time, and then the PVC and waterproof coating are bonded together by heating and curing. The process is extremely simple and efficient.

[0016] The curing temperature is 50-70℃, and the treatment time is 3-5 hours. Through heating, cobalt acetylacetone catalyzes the cracking or breaking of the polymer chains in the asphalt-based waterproofing adhesive, promoting the formation of a wettable and tight bond between the low molecular weight hydrocarbon compounds in the asphalt and the PVC substrate, and slowing down the penetration of water from the external environment at the interface between the two.

[0017] Allow the layers to stand at room temperature for 12-24 hours to ensure a stronger bond.

[0018] Wiping PVC substrates uses water or a 10-35% sodium hydroxide solution. This removes impurities and grease from the PVC surface. After wiping, allow the surface to dry for 30 minutes until no moisture remains.

[0019] The waterproof coating is a water-emulsion type rubber asphalt waterproof coating.

[0020] The thickness of the waterproof coating is 0.5-3mm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The PVC substrate surface pretreatment construction method of the present invention includes primer preparation and high-temperature curing. To address the damage to the adhesion between the PVC substrate and the waterproof coating caused by water damage and salt corrosion, a cobalt(II) acetylacetonate toluene solution is selected as the primer. Cobalt(II) acetylacetonate improves the low surface energy and non-wetting properties of the PVC substrate surface. Through the wetting of the cobalt(II) acetylacetonate toluene solution, the surface area covered by the cobalt(II) acetylacetonate increases, which can enhance the interaction of more active groups, thereby making the waterproof coating and the PVC substrate form a stronger bond.

[0023] (2) In this invention, the addition amount of cobalt(II) acetylacetonate is low, the improvement effect is excellent, the durability is good, and it can maintain good mechanical strength. To better resist the influence of water damage and salt corrosion on interfacial adhesion, high-temperature curing (heat treatment) is used to raise the surface temperature of the cement substrate. This facilitates the interaction between more PVC surface groups active by cobalt(II) acetylacetonate and the groups contained in the waterproof coating above, forming a tighter bond. This invention makes a breakthrough in construction technology performance and has great advantages in water-based coatings and PVC interface modification systems.

[0024] (3) The preparation method of the present invention is simple to operate, easy to control, and has high production efficiency, making it suitable for industrial production. Attached Figure Description

[0025] Figure 1 The diagram shows the water contact angles of the PVC surface before and after modification in Example 1.

[0026] Figure 2 The images show the total reflectance infrared spectra of the PVC surface before and after modification in Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0028] The raw materials used in the following specific embodiments were all purchased commercially: purified water, sodium hydroxide solution, and PVC sheets. The water used was common purified water, and the sodium hydroxide solution used was sodium hydroxide with an AR content of over 90% and a mass concentration of 30%. The PVC base layer used was 70×70×10 mm. 3 The experimental conditions were: temperature (23±2)℃ and relative humidity (50±10)%.

[0029] Example 1

[0030] PVC substrate surface pretreatment methods and waterproof coating construction process:

[0031] (1) Dissolve cobalt(II) acetylacetonate in toluene to form a mixed solution; then stir it evenly to obtain a cobalt(II) acetylacetonate toluene solution with a concentration of 0.3 wt%.

[0032] (2) Wipe the PVC base surface to remove surface grease and stains.

[0033] (3) After the PVC surface is dried, the PVC substrate is completely immersed in the acetylacetone cobalt toluene solution and held in place for 12 seconds.

[0034] (4) Apply the waterproof coating to the PVC surface, cover it with the base material, and then place it in an oven at 60℃ for high-temperature curing for 2 hours. Then apply a second layer of waterproof coating and leave it at room temperature for 120 hours. Note: In subsequent examples, sodium hydroxide with an AR content of over 90% and a mass concentration of 30% was used. The PVC base layer used was 70×70×10 (mm). 3 )board,

[0035] Example 2

[0036] PVC substrate surface pretreatment methods and waterproof coating construction process:

[0037] (1) Dissolve cobalt(II) acetylacetonate in toluene to form a mixed solution; then stir it evenly to obtain a cobalt(II) acetylacetonate toluene solution with a concentration of 0.5 wt%.

[0038] (2) Wipe the PVC base surface to remove surface grease and stains.

[0039] (3) After the PVC surface is dried, the PVC substrate is completely immersed in the acetylacetone cobalt toluene solution and held in place for 12 seconds.

[0040] (4) Apply waterproof coating to the PVC surface, attach the base material, and then place it in an oven at 60°C for high-temperature curing for 2 hours. Then attach the second layer of waterproof coating and place it at room temperature for 120 hours.

[0041] Water immersion test: The entire bonded specimen was placed in a constant temperature (25℃) water environment for 7 days, and then placed at room temperature for more than 24 hours to conduct a water immersion test.

[0042] Salt resistance test: The integrally bonded sample is placed in a 10wt% NaCl solution (salt solution), with the liquid level at least 10mm above the sample, and continuously immersed for 48 hours. After rinsing thoroughly with water, it is dried. After immersion and drying, it is placed in an electric heating oven at (50±2)℃ for 6 hours±15 minutes, and then placed under standard test conditions for (18±2) hours.

[0043] Example 3

[0044] PVC substrate surface pretreatment methods and waterproof coating construction process:

[0045] (1) Dissolve cobalt(II) acetylacetonate in toluene to form a mixed solution; then stir it evenly to obtain a cobalt(II) acetylacetonate toluene solution with a concentration of 0.7 wt%.

[0046] (2) Wipe the PVC base surface to remove surface grease and stains.

[0047] (3) After the PVC surface is dried, the PVC substrate is completely immersed in the acetylacetone cobalt toluene solution and held in place for 12 seconds.

[0048] (4) Apply waterproof coating to the PVC surface, attach the base material, and then place it in an oven at 60°C for high-temperature curing for 2 hours. Then attach the second layer of waterproof coating and place it at room temperature for 120 hours.

[0049] Comparative Example 1

[0050] Construction process of PVC substrate and waterproof coating:

[0051] (1) Wipe the PVC base surface to remove surface grease and stains.

[0052] (2) After the PVC surface is dry and free of moisture, apply the first layer of waterproof coating, then cover it with the base material, leave it for 12-24 hours, then apply the second layer of waterproof coating and leave it at room temperature for 120 hours.

[0053] Water immersion test:

[0054] The entire bonded specimen was placed in a constant temperature (25℃) water environment for 7 days, and then placed at room temperature for more than 24 hours.

[0055] Salt tolerance test:

[0056] The overall bonded sample was placed in a 10wt% NaCl solution (salt solution), with the liquid level at least 10mm above the sample, and continuously immersed for 24 hours. After rinsing thoroughly with water, the sample was dried. After immersion and drying, the sample was placed in an electric heating oven at (50±2)℃ for 6 hours±15 minutes, and then placed under standard test conditions for (18±2) hours.

[0057] Comparative Example 2

[0058] PVC substrate surface pretreatment methods and waterproof coating construction process:

[0059] (1) Dissolve cobalt(II) acetylacetonate in toluene to form a mixed solution; then stir it evenly to obtain a cobalt(II) acetylacetonate toluene solution with a concentration of 0.1 wt%.

[0060] (2) Wipe the PVC base surface to remove surface grease and stains.

[0061] (3) After the PVC surface is dried, the PVC substrate is completely immersed in the acetylacetone cobalt toluene solution and held in place for 12 seconds.

[0062] (4) Apply waterproof coating to the PVC surface, attach the base material, and then place it in an oven at 60°C for high-temperature curing for 2 hours. Then attach the second layer of waterproof coating and place it at room temperature for 120 hours.

[0063] Comparative Example 3

[0064] PVC substrate surface pretreatment methods and waterproof coating construction process:

[0065] (1) Dissolve cobalt(II) acetylacetonate in toluene to form a mixed solution; then stir it evenly to obtain a 1 wt% cobalt(II) acetylacetonate toluene solution.

[0066] (2) Wipe the PVC base surface to remove surface grease and stains.

[0067] (3) After the PVC surface is dried, the PVC substrate is completely immersed in the acetylacetone cobalt toluene solution and held in place for 12 seconds.

[0068] (4) Apply waterproof coating to the PVC surface, attach the base material, and then place it in an oven at 60°C for high-temperature curing for 2 hours. Then attach the second layer of waterproof coating and place it at room temperature for 120 hours.

[0069] Comparative Example 4

[0070] Construction process of PVC substrate and waterproof coating:

[0071] (1) Wipe the PVC base surface to remove surface grease and stains.

[0072] (2) After the PVC surface is dry and free of moisture, apply the first layer of waterproof coating, then attach the base material, place it in a 60℃ oven for high-temperature curing for 2 hours, then apply the second layer of waterproof coating, and place it at room temperature for 120 hours.

[0073] Waterproof specimens prepared using pretreatment with cobalt acetylacetone toluene solutions of different concentrations in Examples 1-3, and waterproof specimens obtained in Comparative Examples 1 and 2, were subjected to water immersion and salt resistance environment simulation tests to compare their bonding strength. The testing standard was based on GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings". The prepared waterproof specimens should be placed under standard test conditions for at least 24 hours before the test. The specimens were stretched at a speed of (5±1) mm / min until failure, and the test temperature was (23±2)℃. The test results are shown in Table 1.

[0074] Table 1. Bond strength (MPa) of the examples and comparative examples

[0075] Serial Number No-environment simulation experiment Water immersion experiment Salt tolerance test Example 1 1.50 - - Example 2 1.62 1.17 1.50 Example 3 1.56 - - Comparative Example 1 1.40 0.9 1.39 Comparative Example 2 1.42 - - Comparative Example 3 1.44 - - Comparative Example 4 1.47 - -

[0076] The contact angle between liquids and solids was measured using a DSA-100 contact angle meter. Due to the different interfacial tensions between liquids and solids, the shape of the resulting spherical cap at the contact angle varies. When the adhesion between the liquid and solid is strong, the contact area is larger, and the spherical cap is more even. When the adhesion between the liquid and solid is weak, the contact area is smaller. The contact angle test for each sample and reagent was repeated five times, and the average value was taken as the final contact angle.

[0077] The water contact angle diagrams for the PVC substrate before and after modification in Example 1 show that the average water contact angle of the unmodified PVC was 91.2° (a), and the average water contact angle of the modified PVC surface was 66.5° (b). Figure 1 It can be seen that cobalt(II) acetylacetonate “wets” the PVC substrate, increasing its surface area and filling the crests and troughs of the plastic surface, allowing for better mechanical interlocking. It also allows more active groups to interact, resulting in stronger adhesion and facilitating subsequent bonding with the waterproof coating above.

[0078] The effective grafting of cobalt(II) acetylacetonate onto PVC surfaces was demonstrated using total reflectance infrared characterization. Figure 2 The images show the total reflectance infrared spectra of the PVC substrate before and after modification in Example 1. It can be seen that the PVC surface and the modified PVC surface share many characteristic peaks, such as... Figure 2 As shown, it is located at 1431cm. -1 The deformation vibration absorption peak of -CH2Cl at 1244 cm⁻¹, and the absorption peak at 1244 cm⁻¹. -1 The absorption vibration peak of CH-Cl appears at 611 cm⁻¹, while the absorption vibration peak of C-Cl appears at 611 cm⁻¹.-1 The difference between its spectrum and that of modified PVC lies in the intensity of the bands, which may be due to the coverage of cobalt(II) acetylacetonate on its surface, resulting in a weakened absorption peak. The characteristic absorption peak of cobalt(II) acetylacetonate was found at 1589 cm⁻¹ on the modified PVC substrate. -1 1507cm -1 Because the anion in cobalt(II) acetylacetonate coordinates with cobalt(II) to form two large bonds, the C=O bond is weakened, and the stretching vibration peak shifts to the right (lower frequency). It is located at 757 cm⁻¹. -1 649cm -1 The vibrations involved are stretching vibrations of the Co-O bond and deformation vibrations of the chelate ring. These results verify the effective grafting of cobalt(II) acetylacetonate onto the PVC surface.

[0079] Observing the performance test results obtained in Table 1, the bond strength between the unmodified PVC substrate and the asphalt-based waterproof coating in Comparative Example 1 was 1.40 MPa, while the bond strength between the modified PVC and the asphalt-based waterproof coating (M-PVC) in Example 2 was 1.62 MPa. The results indicate that although the bond strength between the asphalt-based waterproof coating and the PVC substrate itself is high, the bond strength is further improved when cobalt(II) acetylacetonate is added to the PVC surface. This suggests that cobalt(II) acetylacetonate may interact with the waterproof coating above, resulting in non-covalent interfacial adhesion. Observing Examples 1-3, it can be seen that when the concentration of the cobalt(II) acetylacetonate toluene solution is 0.3-0.7 wt%, its bond strength is higher than that of Comparative Example 1, but the optimal concentration of the cobalt(II) acetylacetonate toluene solution is 0.5 wt%.

[0080] After the specimens in Example 2 and Comparative Example 1 underwent the same salt resistance test, it was observed that the bond strength between the modified PVC substrate and the asphalt waterproof coating decreased in the salt resistance test, but it was still higher than the bond strength between the untreated PVC substrate and the waterproof coating in Comparative Example 1. This indicates that the pre-treated primer, cobalt acetylacetonate (II), effectively blocked some of the salt erosion at the interface, maintaining a high bonding performance.

[0081] After immersion in water for 7 days, the bond strength between the PVC substrate modified with cobalt(II) acetylacetone and the asphalt-based waterproof coating in Example 2 and Comparative Example 1 remained above 1.0 MPa. The bond strength between the unmodified PVC substrate and the asphalt-based waterproof coating changed by -35.81% after the 7-day water immersion test. The unmodified waterproof specimen showed a greater decrease in bond strength, indicating that it suffered more water damage, leading to a decrease in adhesion. However, the high-temperature curing process used during construction of the PVC substrate modified with cobalt(II) acetylacetone and the asphalt-based waterproof coating promoted the reaction between the asphalt-based waterproof coating and the underlying cobalt(II) acetylacetone, resulting in a strong bond with the PVC substrate, thus resisting the debonding caused by water damage.

[0082] Observations of Comparative Examples 1 and 4 show that when the waterproof coating is applied to a PVC substrate, the application of a high-temperature curing process for 2 hours can improve the overall bonding strength of the waterproof specimens. This indicates that high-temperature conditions can promote effective bonding between the waterproof coating and the PVC substrate.

[0083] In summary, both the addition of cobalt(II) acetylacetone as a primer and the high-temperature curing process of the waterproof specimens play a crucial role in the overall adhesion performance of the waterproof specimens under humid and salt-corrosion conditions. Improper component addition or incorrect construction techniques will lead to a decrease in the product's adhesion performance. Table 1 shows that the waterproof specimens obtained in Examples 1-3 exhibit high adhesion strength and maintain a relatively stable and excellent adhesion strength even after water immersion and salt resistance environment simulation tests.

[0084] In this invention, the combination of components in the primer within the dosage range defined by this invention can achieve good results. For example, variations in the concentration of cobalt(II) acetylacetonate from different manufacturers, as well as variations in toluene, can all yield primers with excellent performance. During the preparation process, some parameters, such as stirring speed, are not strictly controlled; the stirring speed is chosen to ensure uniform mixing of the components. The waterproof coating applied to the PVC substrate surface can be any type of water-emulsion asphalt-based waterproof coating. Therefore, any combination within the dosage range defined by this invention is applicable to this invention. Further details will not be elaborated here.

Claims

1. A method for bonding a PVC substrate surface to a waterproof coating, characterized in that, The steps include: wiping the PVC substrate and immersing it in a toluene solution of cobalt acetylacetonate, then removing it and applying a waterproof coating; applying the base material and allowing it to cure, then applying a second layer of waterproof coating and letting it stand at room temperature; The cobalt acetylacetonate solution in toluene has a cobalt acetylacetonate mass concentration of 0.3-0.7 wt%.

2. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, The PVC substrate is immersed in a toluene solution of cobalt acetylacetonate and then allowed to stand for stretching.

3. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, The PVC substrate is immersed in a toluene solution of cobalt acetylacetonate for 10-20 seconds.

4. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, The curing temperature is 50-70℃, and the treatment time is 3-5 hours.

5. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, Let stand at room temperature for 12-24 hours.

6. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, For PVC substrates, use water or a sodium hydroxide solution with a mass concentration of 10-35% to wipe them.

7. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, The waterproof coating is a water-emulsion type rubber asphalt waterproof coating.

8. The method for bonding a PVC substrate surface to a waterproof coating according to claim 1, characterized in that, The thickness of the waterproof coating is 0.5-3mm.

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