Control method for improving anti-cracking performance of thick paste coating

Abstract

The invention discloses a control method for improving the anti-cracking performance of a high-build coating, which comprises the following steps: testing the cracking performance: sequentially applying and maintaining a primer and a high-build coating on a substrate to obtain a test sample; the test sample is tested under the conditions of air supply and heating, the crack condition of the surface of the test sample after the test is completed is obtained, rating is carried out according to the crack condition, and the cracking grade is obtained; according to the cracking grade, adaptive construction conditions and service conditions are obtained; and the thick paste coating is controlled to be constructed and served under the adaptive construction conditions and service conditions. Aiming at the problem that the thick-paste coating is easy to crack in the use process due to large construction thickness, bad outdoor service conditions and the like, the cracking property of the thick-paste coating is tested in advance under the rapid drying conditions of air supply and heating, the cracking risk of a coating system is rapidly identified, and the adaptive application scene of the thick-paste coating is screened out; the anti-cracking performance of the thick paste coating in the actual use process is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and in particular relates to a control method for improving the crack resistance of thick-film coatings. Background Technology

[0002] Thick-film textured coatings, due to their substantial thickness, are susceptible to surface cracking under harsh conditions such as prolonged outdoor exposure to sunlight, wind, rain, and large temperature differences between day and night. This is caused by changes in internal and external stresses within the coating, leading to poor appearance and customer complaints. However, current laboratory testing capabilities cannot detect cracking issues in thick-film textured coatings under conditions like high-temperature exposure, nor can specific solutions be developed.

[0003] Currently, the testing standard for thick-film textured coatings, GB / T 9779-2015 Multi-Layer Architectural Coatings, in Part 6.10, requires that the product exhibit no cracks after 3 hours of drying for initial crack resistance. However, the initial crack resistance test can only characterize the product's initial crack resistance after application under standard conditions. It cannot accurately simulate the product's crack resistance under outdoor high-temperature exposure, and there is no specific testing standard that clearly defines the testing standards and methods for the crack resistance of thick-film coatings under high-temperature conditions. Summary of the Invention

[0004] In order to overcome at least one of the problems existing in the prior art, the purpose of the present invention is to provide a control method for improving the crack resistance of thick-film coatings.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a method for controlling the crack resistance of thick-film coatings, comprising the following steps: Cracking test: Apply and cure primer and thick paint in sequence on the substrate to obtain test sample; test the test sample under air supply and heating conditions, obtain the crack condition on the surface of the test sample after the test, and rate the cracking level according to the crack condition. Process control: Based on the cracking grade, obtain suitable construction and service conditions; control the thick-film coating to be applied and used under suitable construction and service conditions; the construction conditions include at least one of the following: substrate type, primer type, primer application amount, or thick-film coating application amount; the service conditions include air supply velocity, heating temperature, or a combination thereof.

[0006] In some embodiments of the present invention, the crack condition includes the length and number of cracks; in the crack condition, the number of cracks with a length ≤ 5 mm is denoted as M, and the number of cracks with a length > 5 mm is denoted as N; the following criteria are used to rate the crackability in sequence to obtain the cracking grade: 1) Level 0: M=0, N=0; 2) Level 1: M≤2 and N≤1; 3) Level 2: M≤4 and N≤1; 4) Level 3: M≤6 and N≤2; 5) Level 4: M≤6 and N≤3; 6) Level 5: M > 6, or N > 3.

[0007] In some embodiments of the present invention, the adapted construction conditions and service conditions are: the construction conditions and service conditions used for the cracking test when the cracking level is level 0, level 1 or level 2.

[0008] In some embodiments of the present invention, the cracking test is carried out in a drying chamber equipped with a wind tunnel. The test sample is placed in the wind tunnel for testing, and the airflow speed is adjusted by the wind tunnel, while the heating temperature is adjusted by the drying chamber.

[0009] In some embodiments of the present invention, the air velocity of the air supply in the cracking test is 1~10m / s.

[0010] In some embodiments of the present invention, the heating temperature in the cracking test is 30~60°C.

[0011] In some embodiments of the present invention, the curing conditions of the primer in the cracking test are a temperature of 23±2℃, a humidity of 50±5%, and a time of 2 to 4 hours.

[0012] In some embodiments of the present invention, the curing conditions for the thick coating in the cracking test are a temperature of 23±2℃, a humidity of 50±5%, and a time of 24 to 48 hours.

[0013] In some embodiments of the present invention, the amount of primer applied in the cracking test is 80~120 g / m³. 2 .

[0014] In some embodiments of the present invention, the amount of the thick-film coating applied in the cracking test is 600~1000 g / m². 2 .

[0015] In some embodiments of the present invention, the substrate in the cracking test includes at least one of asbestos-free fiber cement substrate, metal substrate, ceramic tile substrate, substrate coated with exterior wall putty, substrate coated with a coating, concrete substrate, or brick masonry substrate.

[0016] In some embodiments of the present invention, the primer in the cracking test includes a film-forming primer or a penetrating primer.

[0017] In some specific embodiments of the present invention, the primer conforms to the requirements of JG / T 210-2018 standard.

[0018] In some embodiments of the present invention, the thick paste coating conforms to the requirements of GB / T 9779-2015 standard.

[0019] In some embodiments of the present invention, the thick coating is an exterior wall type III composite coating that meets the requirements of GB / T 9779-2015 standard.

[0020] The beneficial effects of this invention are: This invention addresses the problem that thick-film coatings are prone to cracking during use due to their thick application thickness and harsh outdoor service conditions. It conducts a cracking test on the coating under rapid drying conditions of air supply and heating in advance, quickly identifies the cracking risk of the coating system, and screens out suitable application scenarios for thick-film coatings, effectively improving the crack resistance of thick-film coatings in actual use. Detailed Implementation

[0021] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0022] In the following examples and comparative examples, the thick-film coating used is a thick-film textured coating, specifically an exterior wall type III composite coating that conforms to GB / T9779-2015 Multi-Layer Building Coatings.

[0023] In the following examples and comparative examples, the standard laboratory conditions were a temperature of 23±2℃ and a humidity of 50±5%.

[0024] Example 1 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 asbestos-free fiber cement boards and roll-coat them with a film-forming primer conforming to "JG / T 210-2018 Primers for Interior and Exterior Walls". The primer consumption is 100g / m². 2 Primer curing time: 2 hours; S2: After the primer curing is completed, use a textured roller to apply a coating to the sample with a consumption of 800 / m. 2The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard laboratory conditions; S3: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 3 m / s and a drying chamber temperature of 60℃ for 24 hours. S4: Take out 3 test samples, observe the crack conditions on the sample surfaces, and rate the samples to obtain a cracking level. The specific rating method is as follows: establish a cracking level assessment based on the degree of cracking, crack length, and number of cracks on the sample surface, specifically in units of dm. 2 The length and number of crack streaks in the coating are used as the criteria to classify the degree of cracking of thick-film textured coatings into 0-5 levels. The evaluation level increases from 0 to 5, with 0 indicating no cracking and 5 indicating the most severe cracking. The ratings are conducted in the order shown in Table 1.

[0025] Table 1. Cracking resistance levels and corresponding evaluation criteria

[0026] S5: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0027] Example 2 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 asbestos-free fiber cement boards and roll-coat them with a penetrating primer conforming to "JG / T 210-2018 Primers for Interior and Exterior Walls". The primer consumption is 80g / m². 2 Primer curing time: 2 hours; S2: After the primer curing is completed, apply a roughening roller to the sample with a consumption of 600g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S3: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 3 m / s and a drying chamber temperature of 60℃ for 24 hours. S4: Take out 3 test samples, observe the cracks on the sample surfaces, and rate the samples to obtain the crackability level. The specific rating method is the same as in Example 1.

[0028] S5: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0029] Example 3 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 pieces of asbestos-free fiber cement board and apply ordinary type P putty that conforms to "JG / T 157-2009 Putty for Building Exterior Walls" to the boards; S2: Apply a penetrating primer conforming to "JG / T 210-2018 Primers for Interior and Exterior Walls" to the board by roller coating, with a primer consumption of 100g / m². 2 Primer curing time: 2 hours; S3: After the primer has cured, apply a roughening roller to the sample with a coating rate of 1000g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S4: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 3m / s and a drying chamber temperature of 60℃ for 24 hours. S5: Take out 3 test samples, observe the cracks on the sample surfaces, rate the samples, and obtain the crackability level. The specific rating method is the same as in Example 1.

[0030] S6: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0031] Example 4 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 pieces of asbestos-free fiber cement board and apply ordinary type P putty that conforms to "JG / T 157-2009 Putty for Building Exterior Walls" to the boards; S2: Apply a penetrating primer conforming to "JG / T 210-2018 Primers for Interior and Exterior Walls" to the board by roller coating, with a primer consumption of 100g / m². 2 Primer curing time: 2 hours; S3: After the primer has cured, apply a roughening roller to the sample with a coating rate of 1000g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S4: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 6 m / s and a drying chamber temperature of 50℃ for 24 hours. S5: Take out 3 test samples, observe the cracks on the sample surfaces, rate the samples, and obtain the crackability level. The specific rating method is the same as in Example 1.

[0032] S6: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0033] Example 5 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 pieces of tinplate and roll-coat them with a film-forming primer conforming to "JG / T 210-2018 Primer for Interior and Exterior Walls". The primer consumption is 80g / m². 2 Primer curing time: 2 hours; S2: After the primer curing is completed, apply a roughening roller to the sample with a consumption of 800g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S3: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 6 m / s and a drying chamber temperature of 50℃ for 24 hours. S4: Take out 3 test samples, observe the cracks on the sample surfaces, and rate the samples to obtain the crackability level. The specific rating method is the same as in Example 1.

[0034] S5: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0035] Comparative Example 1 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 asbestos-free fiber cement boards and roll-coat them with a penetrating primer conforming to "JG / T 210-2018 Primers for Interior and Exterior Walls". The primer consumption is 100g / m². 2 Primer curing time: 2 hours; S2: After the primer has cured, apply a roughening roller to the sample with a coating rate of 1000g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S3: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 3 m / s and a drying chamber temperature of 60℃ for 24 hours. S4: Take out 3 test samples, observe the cracks on the sample surfaces, and rate the samples to obtain the crackability level. The specific rating method is the same as in Example 1.

[0036] S5: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0037] Comparative Example 2 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Take 3 pieces of tinplate and roll-coat a penetrating primer conforming to "JG / T 210-2018 Primer for Interior and Exterior Walls of Buildings" onto the plates. The primer consumption is 80g / m². 2 Primer curing time: 2 hours; S2: After the primer curing is completed, apply a roughening roller to the sample with a consumption of 800g / m². 2 The coating conforms to the Type III composite coating for exterior walls in GB / T9779-2015 Multi-Layer Architectural Coatings, and is cured for 24 hours under standard conditions; S3: After the test sample has completed its curing period, it is placed in a wind tunnel with a wind speed of 6 m / s and a drying chamber temperature of 50℃ for 24 hours. S4: Take out 3 test samples, observe the cracks on the sample surfaces, and rate the samples to obtain the crackability level. The specific rating method is the same as in Example 1.

[0038] S5: Based on the cracking grade, obtain the construction and service conditions during the test; control the construction and service of the thick-film coating under these construction and service conditions.

[0039] Comparative Example 3 A method for improving the crack resistance of thick-film coatings includes the following steps: S1: Cracking test shall be conducted in accordance with Part 6.10 of GB / T 9779-2015 Multi-Layer Architectural Coatings. Specifically, the primer shall be applied to an asbestos-free fiber cement plate and dried for 1-2 hours. Then, a thick coating shall be applied on top of the primer and immediately placed on a test frame in a wind tunnel with the length of the test plate parallel to the airflow. The test temperature shall be 23±2℃ and the wind speed shall be fixed at 3±0.3m / s. The test plate shall be removed after 3 hours. The test plate shall be removed and the surface of the test plate shall be observed. If no cracks are found on two out of the three test plates, the test plate shall be evaluated as "no cracks".

[0040] S2: Based on the construction and service conditions at the time of testing, control the application and service of the thick-film coating under those conditions.

[0041] Because the test method in GB / T 9779-2015 requires an experimental temperature of 23±2℃ and a wind speed of 3±0.3m / s, it is difficult to effectively characterize the actual field application of thick-film coatings. This makes it impossible to reproduce many product application scenarios and identify the cracking risk of thick-film coatings. In actual application, cracking problems are prone to occur under high temperature and wind conditions.

[0042] The cracking rating results of Examples 1-5 and Comparative Examples 1-2 are shown in Table 2.

[0043] Table 2. Crack resistance rating results of Examples 1-5 and Comparative Examples 1-2

[0044] Table 2 shows that the cracking properties of thick-film textured coatings vary significantly under different substrates, primers, and testing environments. Under the cracking test conditions of Comparative Examples 1-2, the thick-film textured coatings exhibited severe cracking. Therefore, if the control methods described in this invention are not applied to identify the cracking risk of the coating system, and thick-film coatings are directly applied under the construction and service conditions tested in Comparative Examples 1-2, the thick-film coatings may experience problems such as coating cracking, poor appearance, and customer complaints under harsh environments such as long-term outdoor exposure, wind and rain, and large diurnal temperature variations.

[0045] The embodiments of the present invention comprehensively consider various construction conditions such as substrate type, primer type, primer application amount or thick paste coating application amount, as well as various service conditions such as air supply speed and heating temperature. Cracking tests are conducted on the coating system in advance under rapid drying conditions of air supply and heating, which can quickly identify the cracking risk of the coating system and screen suitable application scenarios for thick paste coatings. Process control of thick paste textured coatings can effectively improve the crack resistance of thick paste coatings in actual use.

[0046] Using the control method provided in the embodiments of the present invention, suitable application environments for thick-film textured coatings can be obtained. Some suitable application environments obtained by some embodiments of the present invention are shown in Table 3. Based on the matching system solutions shown in Table 3, a better coating matching system can be selected and adjusted to avoid cracking problems in the coating during subsequent delivery.

[0047] Table 3 Suitable Application Environments for Thick-Film Textured Coatings

[0048] In summary, this invention addresses the problem of cracking in thick-film coatings due to their thick application thickness and harsh outdoor service conditions. By conducting pre-cracking tests on the coatings under rapid drying conditions involving air supply and heating, the cracking risk of the coating system can be quickly identified, and suitable application scenarios for thick-film coatings can be selected, effectively improving the crack resistance of thick-film coatings in actual use.

Claims

1. A method for controlling the crack resistance of thick-film coatings, characterized in that, Includes the following steps: Cracking test: Apply and cure primer and thick paint in sequence on the substrate to obtain test sample; test the test sample under air supply and heating conditions, obtain the crack condition on the surface of the test sample after the test, and rate the cracking level according to the crack condition. Process control: Based on the cracking grade, obtain suitable construction and service conditions; control the thick-film coating to be applied and used under suitable construction and service conditions; the construction conditions include at least one of the following: substrate type, primer type, primer application amount, or thick-film coating application amount; the service conditions include air supply velocity, heating temperature, or a combination thereof.

2. The control method according to claim 1, characterized in that, The crack condition includes the length and number of cracks; in the crack condition, each dm 2 The number of cracks ≤ 5 mm in length on the surface of the test sample is denoted as M, and the number of cracks > 5 mm in length is denoted as N; the following standards are used to rate the crackability in sequence to obtain the cracking grade: 1) Level 0: M=0, N=0; 2) Level 1: M≤2 and N≤1; 3) Level 2: M≤4 and N≤1; 4) Level 3: M≤6 and N≤2; 5) Level 4: M≤6 and N≤3; 6) Level 5: M > 6, or N > 3.

3. The control method according to claim 2, characterized in that, The appropriate construction and service conditions are: the construction and service conditions used for the cracking test when the cracking level is 0, 1 or 2.

4. The control method according to claim 1, characterized in that, In the cracking test, the air velocity of the supplied air is 1~10m / s.

5. The control method according to claim 1, characterized in that, In the cracking test, the heating temperature is 30~60℃.

6. The control method according to claim 1, characterized in that, In the cracking test, the curing conditions for the primer are a temperature of 23±2℃, a humidity of 50±5%, and a time of 2 to 4 hours.

7. The control method according to claim 1, characterized in that, In the cracking test, the curing conditions for the thick coating are a temperature of 23±2℃, a humidity of 50±5%, and a time of 24~48 hours.

8. The control method according to claim 1, characterized in that, In the cracking test, the amount of primer applied is 80~120 g / m³. 2 .

9. The control method according to claim 1, characterized in that, In the cracking test, the application rate of the thick-film coating is 600~1000 g / m². 2 .

10. The control method according to claim 1, characterized in that, In the cracking test, the substrate includes at least one of the following: asbestos-free fiber cement substrate, metal substrate, ceramic tile substrate, substrate coated with exterior wall putty, substrate coated with a coating, concrete substrate, or brick masonry substrate. And / or, in the cracking test, the primer includes a film-forming primer or a penetrating primer.

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