A low temperature curing powder coating composition with high flow effect and its low temperature cured coating

Abstract

The application discloses a low-temperature curing powder coating composition with high flow leveling effect and a low-temperature curing coating thereof, and relates to the technical field of powder coating, in particular to a low-temperature curing powder coating composition with high flow leveling effect and a low-temperature curing coating thereof, which comprises a polyester resin, a first epoxy resin and a modified silicone leveling agent as a first leveling agent; wherein the acid value of the polyester resin is not less than 65 mgKOH / g, and the viscosity of the polyester resin at 200 DEG C is not higher than 2500 mPa.s; the epoxy equivalent of the first epoxy resin is not less than 500 g / eq; and after the powder coating is shaped through a curing reaction at a curing temperature of not higher than 150 DEG C, the coating has a PCI flow leveling level of not less than 8 levels, and the basic performance of the coating is excellent.

Description

Technical Field

[0001] This invention belongs to the field of powder coatings, specifically relating to a low-temperature curing powder coating composition with high leveling effect and its low-temperature curing coating. Background Technology

[0002] To meet the corrosion resistance requirements of metal substrate coatings, existing technologies typically employ pure epoxy low-temperature curing powder coating compositions, which are costly to formulate. Although epoxy-polyester hybrid powder coating compositions have a significant cost advantage over pure epoxy low-temperature curing powder coating compositions, their curing temperature usually needs to be above 180℃. If curing is carried out at temperatures below 160℃, not only will the coating performance be poor, but excellent leveling and appearance cannot be achieved.

[0003] Therefore, the applicant hopes to conduct research and development to improve the aforementioned technical problems. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a low-temperature curing powder coating composition with high leveling effect and a low-temperature curing coating thereof. The powder coating is cured at a curing temperature not exceeding 150°C to obtain a coating with a PCI leveling grade of not less than 8, and the coating has excellent basic properties.

[0005] The technical solution adopted in this invention is as follows:

[0006] A low-temperature curing powder coating composition with high leveling effect includes a polyester resin, a first epoxy resin, and a modified silicone leveling agent as a first leveling agent; wherein the acid value of the polyester resin is not less than 65 mg KOH / g, and its viscosity at 200°C is not higher than 2500 mPa·s; the epoxy equivalent of the first epoxy resin is not less than 500 g / eq.

[0007] Preferably, the modified silicone leveling agent comprises a second epoxy resin and a siloxane-modified leveling agent bonded to the second epoxy resin; preferably, the siloxane-modified leveling agent accounts for 0.5-15 wt% of the modified silicone leveling agent by weight, and more preferably 1-10 wt%.

[0008] Preferably, the polyester resin has an acid value range of 70-95 mg KOH / g and a viscosity at 200°C not exceeding 2200 mPa·s; and / or the polyester resin has a glass transition temperature range of 45-60°C; and / or the polyester resin has a softening point temperature range of 90-110°C.

[0009] Preferably, the epoxy equivalent of the first epoxy resin is in the range of 550-700 g / eq; and / or the epoxy equivalent of the modified silicone leveling agent is greater than that of the first epoxy resin.

[0010] Preferably, the softening point temperature of both the first epoxy resin and the modified silicone leveling agent is not higher than 100°C.

[0011] Preferably, the viscosity of the modified silicone leveling agent at 150°C is not higher than 3500 mPa·s.

[0012] Preferably, the polyester resin accounts for no less than 25 wt% of the low-temperature curing powder coating composition; and / or the weight ratio of the polyester resin to the first epoxy resin is in the range of 1:3-3:1; and / or the modified silicone leveling agent accounts for no less than 0.05 wt% of the low-temperature curing powder coating composition, preferably 0.1-2 wt%, more preferably 0.2-1 wt%.

[0013] Preferably, it further includes a low-melting-point degassing agent, wherein the melting point of the low-melting-point degassing agent is not greater than the softening point temperature of the polyester resin.

[0014] Preferably, it further includes a second leveling agent and / or filler and / or pigment and / or dispersant, wherein when a second leveling agent is included, the second leveling agent preferably includes a polyacrylate leveling agent; and / or when a dispersant is included, the dispersant preferably includes a high molecular weight copolymer adsorbed on silica and having pigment-affinity groups.

[0015] Preferably, a low-temperature curing coating with high leveling effect is obtained by spraying the low-temperature curing powder coating composition as described above onto a substrate, and then forming the coating after a curing reaction; wherein the curing temperature of the coating is not higher than 150°C, and its PCI leveling grade is not lower than 8.

[0016] It should be noted that the acid value testing standard involved in this application is based on ISO 3682-1998; the viscosity value testing standard is based on ASTM D 4287-1994, and the testing equipment used can be a standard commercial cone-plate viscometer (e.g., an ICI cone-plate viscometer (CONE & PLATE), brand name Brookfield CAP 2000 VISCOMETER); the epoxy equivalent data involved are all obtained by testing according to the testing standard GB / T 4612-2008; the melting point temperature and curing temperature data involved are all obtained by testing with a METTLER thermal analyzer of model DSC Q20, and the testing method is differential scanning calorimetry (DSC), with the heating rate parameter set at 20℃ / min; the softening point temperature standard involved is based on ISO 4625-1980.

[0017] This application uses a highly active, low-viscosity polyester resin, combined with a lower equivalent of epoxy resin as the formulation system, resulting in a low melt viscosity. At the same time, a specific modified silicone leveling agent is added to further reduce the melt viscosity of the formulation system. This allows the powder coating to be cured at a temperature not exceeding 150℃ for 15-35 minutes, resulting in a PCI leveling grade of not less than 8 and excellent basic properties. Detailed Implementation

[0018] This application provides a low-temperature curing powder coating composition with high leveling effect, comprising a polyester resin, a first epoxy resin, and a modified silicone leveling agent as a first leveling agent; wherein the acid value of the polyester resin is not less than 65 mg KOH / g, and its viscosity at 200°C is not higher than 2500 mPa.s; the epoxy equivalent of the first epoxy resin is not less than 500 g / eq.

[0019] Preferably, in this embodiment, the modified silicone leveling agent includes a second epoxy resin and a siloxane-modified leveling agent bonded to the second epoxy resin; preferably, in this embodiment, the siloxane-modified leveling agent accounts for 0.5-15 wt% of the modified silicone leveling agent by weight, more preferably 1-10 wt%.

[0020] Preferably, in this embodiment, the acid value of the polyester resin is in the range of 70-95 mgKOH / g, and its viscosity at 200°C is not higher than 2200 mPa·s; and / or preferably, in this embodiment, the glass transition temperature of the polyester resin is in the range of 45-60°C; and / or preferably, in this embodiment, the softening point temperature of the polyester resin is in the range of 90-110°C.

[0021] Preferably, in this embodiment, the epoxy equivalent of the first epoxy resin is in the range of 550-700 g / eq; and / or preferably, in this embodiment, the epoxy equivalent of the modified silicone leveling agent is greater than that of the first epoxy resin; preferably, in this embodiment, the softening point temperature of both the first epoxy resin and the modified silicone leveling agent is not higher than 100°C; preferably, in this embodiment, the viscosity of the modified silicone leveling agent at 150°C is not higher than 3500 mPa·s.

[0022] Preferably, in this embodiment, the polyester resin accounts for no less than 25 wt% of the low-temperature curing powder coating composition; and / or preferably, in this embodiment, the weight ratio of the polyester resin to the first epoxy resin is in the range of 1:3-3:1; and / or preferably, in this embodiment, the modified silicone leveling agent accounts for no less than 0.05 wt% of the low-temperature curing powder coating composition, preferably 0.1-2 wt%, more preferably 0.2-1 wt%.

[0023] Preferably, in order to effectively eliminate pinholes and bubbles in the coating, in this embodiment, the low-temperature curing powder coating composition further includes a low-melting-point degassing agent, the melting point of which is not greater than the softening temperature of the polyester resin.

[0024] Preferably, in order to further improve the leveling performance of the coating, in this embodiment, the low-temperature curing powder coating composition further includes a second leveling agent and / or a dispersant, wherein, when the second leveling agent is included, the second leveling agent preferably includes a polyacrylate leveling agent; and / or preferably, in this embodiment, when the low-temperature curing powder coating composition includes a dispersant, the dispersant preferably includes a high molecular weight copolymer adsorbed on silica and having pigment-affinity groups, which can reduce the viscosity of the system and further improve the leveling performance of the coating.

[0025] Preferably, this application embodiment also proposes a low-temperature curing coating with high leveling effect, wherein the low-temperature curing powder coating composition as described above is sprayed onto the substrate, and the coating is formed after curing reaction; wherein the curing temperature of the coating is not higher than 150°C, the curing time is recommended to be 15-35 minutes, and its PCI leveling grade is not lower than 8; in this embodiment, the substrate is preferably a metal substrate, such as steel, iron or aluminum.

[0026] All the raw materials involved in this application can be purchased directly on the market, and the source of raw materials is easy to obtain.

[0027] In specific implementations of this application, it is also possible to further add known antioxidants, stabilizers, curing accelerators, functional additives, pigments, fillers, or other additives to the low-temperature curing powder coating composition. These are all conventional technical choices for those skilled in the art.

[0028] When preparing the low-temperature curing powder coating composition of this application, any known preparation process can be used. Preferably, it is prepared by mixing the raw materials, melt extrusion and crushing, etc., according to known processes. Of course, other known preparation processes can also be used to obtain the low-temperature curing powder coating composition of this embodiment. This application does not have any particular limitation on its preparation process.

[0029] To verify the technical effects of this application, the following sets of embodiments and comparative examples were specifically implemented, and the performance of each embodiment and comparative example was compared and tested:

[0030] Example 1: A powder coating composition, the raw material formula of which is as follows:

[0031] 35wt% polyester resin, the grade of which is polyester resin TM5013 provided by Zhejiang Chuanhua Tiansong, has an acid value range of 75-85mgKOH / g, a viscosity of 500-2000mPa.s at 200℃, a glass transition temperature of 51±3℃, and a softening point temperature of 90-110℃.

[0032] 35wt% of the first epoxy resin, brand name CHANG CHUN PLASTICS CO.,LTD BE-502, with an epoxy equivalent of 600-650g / eq and a softening point temperature of 82-92℃;

[0033] 0.5wt% of modified silicone leveling agent, brand name Dow Plastics DER8230-W5, with an epoxy equivalent of 770-860 g / eq, a softening point temperature of 82-92℃, and a viscosity of 800-3000 mPa.s at 150℃.

[0034] 1 wt% polyacrylate leveling agent, brand name BYK-3933P;

[0035] 1 wt% of dispersant, specifically a high molecular weight copolymer adsorbed on silica and having pigment-loving groups, with the brand name BYK-3951P;

[0036] 1.5 wt% of a low-melting-point degassing agent, BYK's CERAFLOUR 964, with a melting point of 75°C;

[0037] 26wt% filler, specifically barium sulfate.

[0038] Example 2: The remaining technical solutions of Example 2 are the same as those of Example 1, except that Example 2 provides a powder coating composition with the following raw material formula:

[0039] 25wt% polyester resin;

[0040] 45wt% of the first epoxy resin;

[0041] 0.5 wt% modified silicone leveling agent;

[0042] 1 wt% polyacrylate leveling agent;

[0043] 1 wt% dispersant;

[0044] 1.5 wt% low melting point degassing agent;

[0045] 26 wt% filler.

[0046] Example 3: The remaining technical solutions of Example 3 are the same as those of Example 1, except that Example 3 provides a powder coating composition with the following raw material formula:

[0047] 30wt% polyester resin;

[0048] 40wt% of the first epoxy resin;

[0049] 0.5 wt% modified silicone leveling agent;

[0050] 1 wt% polyacrylate leveling agent;

[0051] 1 wt% dispersant;

[0052] 1.5 wt% low melting point degassing agent;

[0053] 26 wt% filler.

[0054] Example 4: The remaining technical solutions of Example 4 are the same as those of Example 1, except that Example 4 provides a powder coating composition with the following raw material formula:

[0055] 40wt% polyester resin;

[0056] 30wt% of the first epoxy resin;

[0057] 0.5 wt% modified silicone leveling agent;

[0058] 1 wt% polyacrylate leveling agent;

[0059] 1 wt% dispersant;

[0060] 1.5 wt% low melting point degassing agent;

[0061] 26 wt% filler.

[0062] Example 5: The remaining technical solutions of Example 5 are the same as those of Example 1, except that Example 5 provides a powder coating composition with the following raw material formula:

[0063] 45wt% polyester resin;

[0064] 25wt% of the first epoxy resin;

[0065] 0.5 wt% modified silicone leveling agent;

[0066] 1 wt% polyacrylate leveling agent;

[0067] 1 wt% dispersant;

[0068] 1.5 wt% low melting point degassing agent;

[0069] 26 wt% filler.

[0070] Example 6: The remaining technical solutions of Example 6 are the same as those of Example 1, except that Example 6 provides a powder coating composition with the following raw material formula:

[0071] 35wt% polyester resin;

[0072] 35wt% of the first epoxy resin;

[0073] 0.5 wt% modified silicone leveling agent;

[0074] 1 wt% dispersant;

[0075] 1.5 wt% low melting point degassing agent;

[0076] 27wt% filler.

[0077] Example 7: The remaining technical solutions of Example 7 are the same as those of Example 1, except that Example 7 provides a powder coating composition with the following raw material formula:

[0078] 35wt% polyester resin;

[0079] 35wt% of the first epoxy resin;

[0080] 0.5 wt% modified silicone leveling agent;

[0081] 1 wt% polyacrylate leveling agent;

[0082] 1.5 wt% low melting point degassing agent;

[0083] 27wt% filler.

[0084] Example 8: The remaining technical solutions of Example 8 are the same as those of Example 1, except that Example 8 provides a powder coating composition with the following raw material formula:

[0085] 35wt% polyester resin;

[0086] 35wt% of the first epoxy resin;

[0087] 0.5 wt% modified silicone leveling agent;

[0088] 1 wt% polyacrylate leveling agent;

[0089] 1 wt% dispersant;

[0090] 27.5 wt% of filler.

[0091] Comparative Example 1: The remaining technical solutions of Comparative Example 1 are the same as those of Example 1, except that: Comparative Example 1 provides a powder coating composition, the raw material formula of which is as follows:

[0092] 35wt% polyester resin;

[0093] 35wt% of the first epoxy resin;

[0094] 1 wt% polyacrylate leveling agent;

[0095] 1 wt% dispersant;

[0096] 1.5 wt% low melting point degassing agent;

[0097] 26.5 wt% of filler.

[0098] Comparative Example 2: The remaining technical solutions of Comparative Example 2 are the same as those of Example 1, except that: Comparative Example 2 provides a powder coating composition, the raw material formula of which is as follows:

[0099] 35 wt% polyester resin, brand name CYTEC 4420-0, acid value 49-54 mgKOH / g, viscosity at 200℃ is 4500-6600 mPa.s, glass transition temperature is about 64℃;

[0100] 35wt% of the first epoxy resin;

[0101] 0.5 wt% modified silicone leveling agent;

[0102] 1 wt% polyacrylate leveling agent;

[0103] 1 wt% dispersant;

[0104] 1.5 wt% low melting point degassing agent;

[0105] 26 wt% filler.

[0106] Comparative Example 3: The remaining technical solutions of Comparative Example 3 are the same as those of Example 1, except that: Comparative Example 3 provides a powder coating composition, the raw material formula of which is as follows:

[0107] 35wt% polyester resin;

[0108] 35wt% GMA acrylic resin, with the brand name Ningbo Nanhai Chemical's GMA1618, has an epoxy equivalent of 400-430 g / eq and a softening point temperature of 92-97℃.

[0109] 0.5 wt% modified silicone leveling agent;

[0110] 1 wt% polyacrylate leveling agent;

[0111] 1 wt% dispersant;

[0112] 1.5 wt% low melting point degassing agent;

[0113] 26 wt% filler.

[0114] The powder coating compositions of each embodiment and comparative example are obtained by weighing, premixing, melt extrusion, grinding, and cyclone separation according to the above raw material formula (known process preparation technology).

[0115] In this application, powder coating compositions were prepared for Examples 1-8 and Comparative Examples 1-3, respectively. These compositions were then sprayed onto aluminum substrates of the same type and cured (curing conditions were uniformly selected as 150℃@15min) to obtain cured coatings. The film thickness of each cured coating was 60-120μm. The performance of each cured coating was compared and tested as shown in Table 1 below.

[0116] Table 1. Performance Test Comparison Table of Various Embodiments and Comparative Examples of this Application

[0117]

[0118]

[0119] It should be noted that the performance tests involved in this embodiment or comparative example were conducted in accordance with the test standards or conditions described in Table 2 below.

[0120] Table 2 Test Items and Test Standards or Conditions

[0121]

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low-temperature curing powder coating composition with high leveling effect, characterized in that, The composition includes a polyester resin, a first epoxy resin, and a modified silicone leveling agent as a first leveling agent; wherein the polyester resin has an acid value of not less than 65 mg KOH / g and a viscosity at 200°C not higher than 2500 mPa·s; the first epoxy resin has an epoxy equivalent of not less than 500 g / eq; the modified silicone leveling agent includes a second epoxy resin and a siloxane-modified leveling agent bonded to the second epoxy resin; the epoxy equivalent of the modified silicone leveling agent is greater than that of the first epoxy resin; the siloxane-modified leveling agent accounts for 0.5-15 wt% of the modified silicone leveling agent by weight; the modified silicone leveling agent accounts for 0.1-2 wt% of the low-temperature curing powder coating composition by weight; the viscosity of the modified silicone leveling agent at 150°C is not higher than 3500 mPa·s; and the softening point temperature of both the first epoxy resin and the modified silicone leveling agent is not higher than 100°C. The low-temperature curing powder coating composition is sprayed onto a substrate and then cured to form a coating; wherein the curing temperature of the coating is not higher than 150°C and its PCI leveling grade is not lower than 8.

2. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, The siloxane-modified leveling agent accounts for 1-10 wt% of the modified organosilicon leveling agent.

3. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, The polyester resin has an acid value range of 70-95 mgKOH / g and a viscosity at 200°C not exceeding 2200 mPa·s; and / or the polyester resin has a glass transition temperature range of 45-60°C; and / or the polyester resin has a softening point temperature range of 90-110°C.

4. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, The epoxy equivalent of the first epoxy resin is in the range of 550-700 g / eq.

5. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, The polyester resin accounts for no less than 25 wt% of the weight of the low-temperature curing powder coating composition; and / or the weight ratio of the polyester resin to the first epoxy resin is in the range of 1:3-3:1; and / or the modified silicone leveling agent accounts for 0.2-1 wt% of the weight of the low-temperature curing powder coating composition.

6. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, It also includes a low-melting-point degassing agent, wherein the melting point of the low-melting-point degassing agent is not greater than the softening point temperature of the polyester resin.

7. The low-temperature curing powder coating composition with high leveling effect according to claim 1, characterized in that, It also includes a second leveling agent and / or filler and / or pigment and / or dispersant, wherein, when a second leveling agent is included, the second leveling agent comprises a polyacrylate leveling agent; and / or when a dispersant is included, the dispersant comprises a high molecular weight copolymer adsorbed on silica and having pigment-affinity groups.

8. A low-temperature curing coating with high leveling effect, characterized in that, The low-temperature curing powder coating composition as described in any one of claims 1-7 is sprayed onto a substrate, and the coating is formed after a curing reaction; wherein the curing temperature of the coating is not higher than 150°C, and its PCI leveling grade is not lower than 8.

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