Wear-resistant powder coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and provides a wear-resistant powder coating and a preparation method thereof. The wear-resistant powder coating is prepared from the following raw materials in parts by weight: 15 to 25 parts of polyester resin A, 10 to 15 parts of polyester resin A curing agent, 20 to 30 parts of polyester resin B, 1 to 5 parts of polyester resin B curing agent, 1 to 2 parts of hardening wax powder, 50 to 60 parts of ceramic powder and 1 to 2 parts of flatting agent, the acid value of the polyester resin A is smaller than that of the polyester resin B, the polyester resin B is composed of first polyester resin and second polyester resin, the acid values of the first polyester resin and the second polyester resin are the same, and the viscosity of the first polyester resin is lower than that of the second polyester resin. Through the technical scheme, the problem of poor wear resistance of the powder coating in the related technology is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically, to a wear-resistant powder coating and a preparation method thereof. Background Art

[0002] Powder coatings are a new type of solvent-free solid powder coatings, which have the characteristics of environmental protection, high efficiency, durability, etc. During the preparation process, various components are mixed, melted, extruded, and pulverized to form fine powder particles. Different from traditional solvent-based coatings and water-based coatings, powder coatings do not require solvents for dilution during construction. Instead, through methods such as electrostatic spraying or fluidized bed dipping, the powder particles are attached to the surface of the object to be coated, and then through heating and melting, leveling and curing, a uniform and continuous coating film is formed, and it is widely used in the fields of construction, automotive, and furniture and household appliances.

[0003] However, with the continuous improvement of the performance requirements of products in various industries, the performance of ordinary powder coatings has gradually become difficult to meet the needs of some specific application scenarios, especially in terms of wear resistance. For example, in outdoor amusement facilities in parks and playgrounds, such as slides and climbing frames, they have to withstand the use and friction of a large number of children every day. Under the dual action of such high-frequency friction and harsh outdoor environments (such as ultraviolet radiation and rain erosion), the coating of ordinary powder coatings will quickly lose its protective effect. After the coating is worn, the metal structure of the amusement facilities is prone to rust, and the wooden parts may also decay due to the loss of protection, which not only affects the service life of the facilities but also may pose a threat to the safety of children; another example is the frame, handlebars, chains and other components of bicycles. During cycling, they will be subjected to various frictions and impacts. When ordinary powder coating coatings deal with these situations, they often perform poorly and are prone to scratches and wear. For some bicycle enthusiasts who often go mountain biking or long-distance cycling, the coating on the frame surface will wear faster, which not only affects the beauty of the bicycle but also may cause the metal part of the frame to be corroded, reducing the safety and service life of the bicycle.

[0004] Therefore, it is necessary to develop a powder coating with high wear resistance. Summary of the Invention

[0005] The present invention provides a wear-resistant powder coating and a preparation method thereof, which solve the problem of poor wear resistance of powder coatings in related technologies.

[0006] The technical solution of the present invention is as follows: The present invention provides a wear-resistant powder coating, which comprises the following raw materials in parts by weight: 15-25 parts of polyester resin A, 10-15 parts of polyester resin A curing agent, 20-30 parts of polyester resin B, 1-5 parts of polyester resin B curing agent, 1-2 parts of hardening wax powder, 50-60 parts of ceramic powder, and 1-2 parts of leveling agent; the acid value of the polyester resin A is less than that of the polyester resin B, the polyester resin B is composed of a first polyester resin and a second polyester resin, the acid values of the first polyester resin and the second polyester resin are the same, and the viscosity of the first polyester resin is lower than that of the second polyester resin.

[0007] As a further technical solution, the acid value of the first polyester resin is 48-55 mgKOH / g, and the viscosity is 3500-4500 mPa·s; the acid value of the second polyester resin is 48-55 mgKOH / g, and the viscosity is 6000-9000 mPa·s.

[0008] In the present invention, the acid values of both the first polyester resin and the second polyester resin are controlled within 48-55 mgKOH / g. When the acid value is too high, it means that there are more carboxyl groups on the resin molecular chain, and the reaction rate with the curing agent is too fast, which may cause local overheating, resulting in explosive polymerization, forming an uneven cross-linked structure. Moreover, when the acid value is too high, the polarity of the resin increases, and the compatibility with non-polar or weakly polar components (such as hardening wax powder and ceramic powder) becomes poor, resulting in uneven dispersion of these components in the system, such as agglomeration, which affects the performance of the coating. However, when the acid value is too low, the number of carboxyl groups on the resin molecular chain is small, the reaction with the curing agent is insufficient, the cross-linking density is low, the hardness and wear resistance of the coating will be greatly reduced, and it cannot effectively resist external friction. Moreover, when the polarity is weak, it will also affect the compatibility with additives such as leveling agent. Therefore, maintaining the acid value within a suitable range helps to further improve the wear resistance of the powder coating.

[0009] In the present invention, the first polyester resin with low viscosity has good fluidity and can quickly diffuse in the coating system. When preparing the wear-resistant powder coating, this fluidity enables it to more fully wrap and infiltrate wear-resistant fillers such as hardening wax powder and ceramic powder, and uniformly disperse the fillers in the coating system. The second polyester resin with high viscosity plays a stabilizing role after the fillers are dispersed, preventing the fillers from settling or agglomerating during subsequent processing and storage. The cooperation of the two resins with different viscosities ensures the uniform distribution of the wear-resistant fillers in the coating, so that the fillers can more effectively play their role in enhancing the wear resistance, and further improve the overall wear resistance of the coating.

[0010] As a further technical solution, the mass ratio of the first polyester resin to the second polyester resin is 1-5:2; for example, it can be 1:2, 1:1, 3:2, 2:1, 5:2, and preferably 1-1.5:1.

[0011] In the present invention, by adjusting the mass ratio of the first polyester resin and the second polyester resin, the synergistic effect of the two is exerted to promote the formation of a more sufficient and more uniform crosslinked structure, making the microstructure of the coating more dense, effectively reducing the stress concentration caused by structural defects, enhancing the hardness and integrity of the coating, making it not easy to break and fall off when being rubbed, and further effectively improving the wear resistance.

[0012] As a further technical solution, the hydroxyl value of the polyester resin A is 75 - 85 mgKOH / g, the viscosity is 3000 - 6000 mPa·s, and the acid value is ≤5 mgKOH / g.

[0013] In the present invention, the hydroxyl value of the polyester resin A is 75 - 85 mgKOH / g. The appropriate hydroxyl value enables the polyester resin A and the polyester resin B to combine with each other through chemical bonds or intermolecular forces to form a stable blend system, avoiding the phenomenon of phase separation, ensuring the stability of the coating system, and the appropriate viscosity is conducive to the uniform mixing of the polyester resin A with fillers such as hardening wax powder and ceramic powder, enabling the fillers to be fully dispersed in the resin matrix, enhancing the interfacial bonding force between the fillers and the resin, thereby synergistically improving the wear resistance of the coating.

[0014] As a further technical solution, the curing agent for the polyester resin A includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate, preferably diphenylmethane diisocyanate.

[0015] In the present invention, the curing agent for the polyester resin A contains highly active isocyanate groups, which can react quickly and fully with the hydroxyl groups in the polyester resin A to form urethane bonds, promoting the rapid crosslinking and curing of the coating to form a relatively complex and dense three-dimensional network structure, endowing the coating with excellent hardness and strength, enabling the coating to effectively resist external friction, scratching and abrasion, significantly improving the wear resistance. At the same time, the rapid curing reaction is also beneficial to improving production efficiency and shortening the processing cycle.

[0016] As a further technical solution, the curing agent for the polyester resin B is the curing agent TGIC (triglycidyl isocyanurate).

[0017] In the present invention, the curing agent TGIC can react with the carboxyl groups in the polyester resin B to form stable chemical bonds, realizing the curing of the coating, making the polyester resin B form a highly crosslinked network structure, and improving the hardness and strength of the coating.

[0018] As a further technical solution, the ceramic powder includes one or more of alumina, silicon carbide, silicon nitride, titanium dioxide, and barium titanate, preferably alumina.

[0019] As a further technical solution, the leveling agent includes one or more of BYK-333, BYK-377, and BYK-381.

[0020] In the present invention, the addition of the leveling agent can not only effectively reduce the surface tension of the coating, enabling the coating to spread more evenly on the surface of the object to be coated during the coating process, reducing the generation of surface defects such as flow marks, shrinkage holes, and orange peel, thereby forming a flat and smooth coating, but also promote the uniform distribution of each component in the coating during the curing process, making the curing reaction more sufficient and uniform, avoiding the situation of incomplete or over-curing in local areas. The uniform curing process helps to form a dense and stable coating structure, improving the hardness, strength, wear resistance and other properties of the coating.

[0021] The present invention also proposes a preparation method of a wear-resistant powder coating for preparing the above-mentioned wear-resistant powder coating, which includes the following steps: S1. Mix the above raw materials to obtain a mixed powder; S2. After extruding and grinding the mixed powder, the wear-resistant powder coating is obtained.

[0022] As a further technical solution, in step S1, the mixing time is 5 - 8 min.

[0023] As a further technical solution, in step S2, the temperature of the first zone for extrusion is 90 °C, and the temperature of the second zone is 120 °C.

[0024] As a further technical solution, the D10 of the wear-resistant powder coating is 13 μm, D50 is 40 μm, and D90 is 85 μm.

[0025] The working principle and beneficial effects of the present invention are as follows: 1. In the present invention, the combination of polyester resin A with polyester resin A curing agent and polyester resin B with polyester resin B curing agent enables the coating to form a denser and more stable cross-linked structure during the curing process. The hardening wax powder can effectively reduce the friction coefficient on the surface of the coating, endow the coating with good slipperiness, and reduce the damage to the coating caused by external friction; while the ceramic powder has extremely high hardness and wear resistance, and after being added to the coating system, it greatly enhances the wear resistance of the coating.

[0026] 2. In the present invention, the first polyester resin and the second polyester resin with the same acid value but different viscosities are used in combination. Since the acid values are the same, the reaction activities of the two polyester resins with the polyester resin B curing agent are basically the same, and they can crosslink more uniformly during the curing process. Compared with a single polyester resin, this combination can form a higher and more uniform crosslinking density. The first polyester resin and the second polyester resin with different viscosities cooperate with each other to form a more complex and orderly microstructure during the coating curing process. The reason is that the high-acid polyester resin with low viscosity has good fluidity and can quickly diffuse in the system to fill the voids inside the coating, while the high-acid polyester resin with high viscosity can provide strong cohesion and support, making the coating structure more compact. This structure helps to disperse and buffer the external frictional stress, reduce the coating wear caused by local stress concentration, and thus effectively improve the wear resistance of the coating. Detailed implementation mode

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present invention.

[0028] In the following examples and comparative examples: Polyester resin A: The hydroxyl value is 75-85 mgKOH / g, the viscosity is 3000-6000 mPa·s, and the model is Hypomer PE9624; The acid value of the first polyester resin is 48-55 mgKOH / g, the viscosity is 3500-4500 mPa·s; the model is YC8000A, purchased from Anhui Yongchang New Materials Technology Co., Ltd.; The acid value of the second polyester resin is 48-55 mgKOH / g, the viscosity is 6000-9000 mPa·s, the model is YC8510, purchased from Anhui Yongchang New Materials Technology Co., Ltd.; Reinforcing wax powder: The model is LANCO TF1788; Aluminum oxide: The average particle size is 500 mesh.

[0029] Example 1 A preparation method of wear-resistant powder coating, comprising the following steps: S1. Mix 15 parts of polyester resin A, 10 parts of diphenylmethane diisocyanate, 20 parts of polyester resin B, 1 part of curing agent TGIC, 1 part of hardening wax powder, 50 parts of alumina, and 1 part of BYK-333 for 5 minutes to obtain a mixed powder. Polyester resin B is composed of a first polyester resin YC8000A and a second polyester resin YC8510 with a mass ratio of 1:1. S2. Extrude the mixed powder through a screw extruder at a temperature of 90°C in the first zone and 120°C in the second zone, and grind it to D10 of 13 μm, D50 of 40 μm, and D90 of 85 μm to obtain the wear-resistant powder coating.

[0030] Example 2 A preparation method of a wear-resistant powder coating includes the following steps: S1. Mix 20 parts of polyester resin A, 12 parts of diphenylmethane diisocyanate, 25 parts of polyester resin B, 3 parts of curing agent TGIC, 1.5 parts of hardening wax powder, 55 parts of alumina, and 1.5 parts of BYK-377 for 6 minutes to obtain a mixed powder. Polyester resin B is composed of a first polyester resin YC8000A and a second polyester resin YC8510 with a mass ratio of 1:1. S2. Extrude the mixed powder through a screw extruder at a temperature of 90°C in the first zone and 120°C in the second zone, and grind it to D10 of 13 μm, D50 of 40 μm, and D90 of 85 μm to obtain the wear-resistant powder coating.

[0031] Example 3 A preparation method of a wear-resistant powder coating includes the following steps: S1. Mix 25 parts of polyester resin A, 15 parts of diphenylmethane diisocyanate, 30 parts of polyester resin B, 5 parts of curing agent TGIC, 2 parts of hardening wax powder, 60 parts of alumina, and 2 parts of BYK-381 for 8 minutes to obtain a mixed powder. Polyester resin B is composed of a first polyester resin YC8000A and a second polyester resin YC8510 with a mass ratio of 1:1. S2. Extrude the mixed powder through a screw extruder at a temperature of 90°C in the first zone and 120°C in the second zone, and grind it to D10 of 13 μm, D50 of 40 μm, and D90 of 85 μm to obtain the wear-resistant powder coating.

[0032] Example 4 Compared with Example 1, the difference in Example 4 is that polyester resin B is composed of a first polyester resin YC8000A and a second polyester resin YC8510 with a mass ratio of 3:2.

[0033] Comparative Example 1 Compared with Example 1, the difference in Comparative Example 1 is that the polyester resin B is only the first polyester resin YC8000A.

[0034] Comparative Example 2 Compared with Example 1, the difference in Comparative Example 2 is that the polyester resin B is only the second polyester resin YC8510.

[0035] Comparative Example 3 Compared with Example 1, the difference in Comparative Example 3 is that the second polyester resin is replaced with a polyester resin of model YC8600, with an acid value of 33 - 38 mgKOH / g and a viscosity of 6000 - 8000 mPa·s, purchased from Anhui Yongchang New Materials Technology Co., Ltd.

[0036] Comparative Example 4 Compared with Example 1, the difference in Comparative Example 4 is that the polyester resin B is only a polyester resin of model YC8502, with an acid value of 48 - 53 mgKOH / g and a viscosity of 4000 - 5500 mPa·s, purchased from Anhui Yongchang New Materials Technology Co., Ltd.

[0037] Experimental Example 1 For the wear-resistant powder coatings prepared in Examples 1 - 4 and Comparative Examples 1 - 4, according to the test method specified in GB / T 6739-2022 "Determination of film hardness by pencil method for paints and varnishes", the hardness of the samples was tested. The wear-resistant powder coatings prepared in Examples 1 - 4 and Comparative Examples 1 - 4 were electrostatically sprayed onto a 0.8 mm thick cold-rolled steel plate that had been derusted and degreased. The curing temperature was 230 °C, the curing time was 20 min, and the coating thickness was 70 μm. The coatings were then tested.

[0038] The test results are shown in Table 1: Table 1 Performance test results of the wear-resistant powder coatings prepared in Examples 1 - 4 and Comparative Examples 1 - 4

[0039] As can be seen from Table 1, when the polyester resin B consists of the first polyester resin and the second polyester, the wear resistance of the powder coating can be improved.

[0040] Experimental Example 2 1. Impact resistance: For the wear-resistant powder coating prepared in Example 1, according to the test method specified in GB / T 1732-2020 "Determination of impact resistance of films", the impact resistance of the sample was tested. The wear-resistant powder coating prepared in Example 1 was electrostatically sprayed onto a 0.8 mm thick cold-rolled steel plate that had been derusted and degreased. The curing temperature was 230 °C, the curing time was 20 min, and the coating thickness was 70 μm. The coating was then tested.

[0041] 2. Adhesion (Cross - hatch method) grade: According to the test method specified in ISO 2409, test the adhesion of the sample with a cutting spacing of 2 mm.

[0042] 3. Scratch resistance: According to the test method specified in DIN 68861 - 4, test the scratch resistance of the sample.

[0043] 4. Light resistance: According to the test method specified in prEN 15187, test the light resistance of the sample.

[0044] The test results are shown in Table 2: Table 2 Performance test results of the wear - resistant powder coating prepared in Example 1

[0045] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A wear-resistant powder coating, characterized in that: The invention comprises the following raw materials in parts by weight: 15-25 parts of polyester resin A, 10-15 parts of polyester resin A curing agent, 20-30 parts of polyester resin B, 1-5 parts of polyester resin B curing agent, 1-2 parts of hardening wax powder, 50-60 parts of ceramic powder and 1-2 parts of leveling agent; the acid value of the polyester resin A is less than that of the polyester resin B, the polyester resin B is composed of a first polyester resin and a second polyester resin, the acid values ​​of the first polyester resin and the second polyester resin are the same and the viscosity of the first polyester resin is lower than that of the second polyester resin.

2. A wear-resistant powder coating according to claim 1, characterized in that: The acid value of the first polyester resin is 48-55 mgKOH / g, and the viscosity is 3500-4500 mPa·s; the acid value of the second polyester resin is 48-55 mgKOH / g, and the viscosity is 6000-9000 mPa·s.

3. A wear-resistant powder coating according to claim 1, characterized in that: The mass ratio of the first polyester resin to the second polyester resin is 1-5:

2.

4. A wear-resistant powder coating according to claim 1, characterized in that: The polyester resin A has a hydroxyl value of 75-85 mgKOH / g, a viscosity of 3000-6000 mPa·s, and an acid value of ≤5 mgKOH / g.

5. The wear-resistant powder coating according to claim 1, characterized in that: The polyester resin A curing agent includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

6. A wear-resistant powder coating according to claim 1, characterized in that: The polyester resin B curing agent is curing agent TGIC.

7. The wear-resistant powder coating according to claim 1, characterized in that: The leveling agent includes one or more of BYK-333, BYK-377, and BYK-381.

8. A method for preparing a wear-resistant powder coating, for preparing a wear-resistant powder coating as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1, mixing the raw materials to obtain a mixed powder; S2. The mixed powder is extruded and ground to obtain a wear-resistant powder coating.

9. The method for preparing a wear-resistant powder coating according to claim 8, characterized in that: In step S2, the temperature of the first extrusion zone is 90°C, and the temperature of the second extrusion zone is 120°C.

10. The method for preparing a wear-resistant powder coating according to claim 8, characterized in that: The wear-resistant powder coating has a D10 of 13 μm, a D50 of 40 μm and a D90 of 85 μm.

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