A temperature-resistant high-strength powder coating and a preparation method thereof

Abstract

The application discloses a kind of temperature-resistant high-strength powder coating and its preparation method, belong to the field of coating.A kind of temperature-resistant high-strength powder coating, by comprising the following weight percentage of raw materials is prepared: epoxy resin 40~50%;Polyester resin 20~30%;Curing agent 6~10%;Leveling agent 1~3%;Filler 1~2%;Pigment balance;Polyester resin is obtained by the reaction of aliphatic diisocyanate with polyether polyol, hydroxyl silicone oil polyurethane prepolymer, again by polyurethane prepolymer and vinyl benzylamine, acrylate monomer, acrylic monomer polymerization polyester resin is obtained.The application has the advantages of improving the temperature resistance and strength of powder coating.

Description

Technical Field

[0001] This application relates to the field of coatings, and in particular to a high-temperature resistant, high-strength powder coating and its preparation method. Background Technology

[0002] Powder coatings offer excellent durability, shatter resistance, and abrasion resistance, with low volatile organic compound (VOC) content. Furthermore, because they do not use solvents, they significantly improve efficiency and reduce coating and drying processes, resulting in a smaller environmental impact and good cost-effectiveness.

[0003] Powder coatings are mainly classified into acrylic powder coatings, epoxy resin powder coatings, and fluorocarbon resin powder coatings. All three types exhibit good adhesion, providing stable protection and decoration. However, acrylic powder coatings generally have poor high-temperature resistance, epoxy resin powder coatings have poor weather resistance, and while fluorocarbon resin powder coatings possess good high-temperature and weather resistance, their application is limited due to complex processing conditions and high costs.

[0004] Currently, there are ways to improve the performance of powder coatings by mixing one or more of acrylates, epoxy resins, and fluorocarbon resins. However, due to issues such as resin compatibility, it is difficult for powder coatings to simultaneously meet the requirements of temperature resistance and high strength. Summary of the Invention

[0005] To improve the temperature resistance and strength of powder coatings, this application provides a high-temperature resistant and high-strength powder coating and its preparation method.

[0006] On the one hand, the high-temperature resistant and high-strength powder coating provided in this application adopts the following technical solution:

[0007] A high-strength, heat-resistant powder coating is prepared from raw materials comprising the following weight percentages:

[0008] Epoxy resin 40-50%;

[0009] Polyester resin 20-30%;

[0010] Hardener 6-10%;

[0011] Leveling agent 1-3%;

[0012] 1-2% filler;

[0013] Pigment balance;

[0014] The polyester resin is obtained by reacting aliphatic diisocyanate with polyether polyol and hydroxyl silicone oil to obtain polyurethane prepolymer, and then by polymerizing the polyurethane prepolymer with vinyl benzylamine, acrylate monomer and acrylic monomer to obtain polyester resin.

[0015] By adopting the above technical solution, the temperature resistance and strength of powder coatings are improved by using a mixture of epoxy resin and polyester resin. The flexibility brought by the polyurethane segments in the polyester resin promotes the uniform bonding of polyester resin and epoxy resin. In addition, the addition of hydroxyl silicone oil segments to the polyurethane segments further improves the temperature resistance and weather resistance of the powder coatings.

[0016] By first synthesizing a polyurethane prepolymer and then polymerizing it with acrylate, the polyurethane prepolymer can be reinforced, thereby providing good cohesion to the polyester resin and forming good structural support for the epoxy resin structure. This leverages the strength advantages of the epoxy resin-polyester resin mixture. Vinyl benzylamine acts as a bridge between the polyurethane prepolymer and polyacrylate, and at the same time, it provides a rigid benzene ring structure to the interior of the polyester resin to a certain extent, further improving the strength and wear resistance of the powder coating.

[0017] Optionally, the mass ratio of the aliphatic diisocyanate to the polyether polyol and hydroxyl silicone oil is 1:(0.7-1):(0.4-0.7); the mass ratio of the aliphatic diisocyanate to vinyl benzylamine, acrylate monomer and acrylic monomer is 1:(0.05-0.1):(0.05-0.1):(0.1-0.2).

[0018] By adopting the above technical solution and controlling the ratio of aliphatic diisocyanate to the other raw materials, the polyurethane prepolymer retains isocyanate groups that combine with vinyl benzylamine, and then polymerizes with acrylate monomers and acrylic acid to obtain a carboxyl-terminated polyester resin.

[0019] Optionally, the aliphatic diisocyanate is selected from one or both of L-lysine diisocyanate and hexamethylene diisocyanate.

[0020] By adopting the above technical solution, the polyurethane chain segments formed by the two aliphatic diisocyanates have good flexibility, which promotes the uniform bonding of polyester resin and epoxy resin. Among them, L-lysine diisocyanate is preferred. After L-lysine diisocyanate and hydroxyl silicone oil form chain segments, it can greatly improve the structural stability of the mixed resin system, thereby improving the weather resistance of powder coating.

[0021] Optionally, the polyether polyol may be selected from one or both of polyethylene glycol and polypropylene glycol.

[0022] By adopting the above technical solution, polyethylene glycol and polypropylene glycol have strong ether bond inversion ability, which is suitable for forming highly flexible polyurethane segments, thereby promoting the uniform bonding of polyester resin and epoxy resin.

[0023] Optionally, the hydroxyl silicone oil is a monohydroxyl-terminated silicone oil, wherein the molecular weight of the monohydroxyl-terminated silicone oil is 1500-2500.

[0024] By adopting the above technical solution, the molecular weight of the monohydroxy-terminated silicone oil is controlled, thus ensuring the adhesion of the powder coating.

[0025] Optionally, the epoxy resin is bisphenol A diglycidyl ether.

[0026] By adopting the above technical solution, the structure of bisphenol A diglycidyl ether is stable, which helps to improve the strength of powder coatings.

[0027] Optionally, the filler may be selected from one or both of calcium carbonate and barium sulfate.

[0028] By adopting the above technical solution, calcium carbonate and barium sulfate act as fillers, improving the surface hardness of the powder coating.

[0029] Optionally, the curing agent is a combination of m-phenylenediamine and triglycidyl isocyanurate.

[0030] Optionally, the leveling agent may be one or both of BYK-300 and BYK-333.

[0031] On the other hand, the method for preparing a high-temperature resistant, high-strength powder coating provided in this application adopts the following technical solution: A method for preparing a high-temperature resistant, high-strength powder coating includes the following steps:

[0032] Epoxy resin, polyester resin, curing agent, leveling agent, filler and pigment are premixed, and the resulting mixture is heated and melted, extruded and crushed to obtain a high-temperature resistant and high-strength powder coating.

[0033] Optionally, the method for preparing the polyester resin includes the following steps:

[0034] Under the protection of an inert gas, polyether polyol and aliphatic diisocyanate are heated and reacted for 0.5 to 1 hour. Then, hydroxyl silicone oil is added and the reaction continues for 1 to 1.5 hours. Vinyl benzylamine is added, followed by a chain extender and an organic solvent for dispersion. Then, an initiator, acrylate monomer and acrylic monomer are added and reacted for 1.5 to 2 hours. After cooling and removal of the organic solvent, polyester resin is obtained.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. This application improves the temperature resistance and strength of powder coatings using a mixture of epoxy resin and polyester resin. The flexibility provided by the polyurethane segments in the polyester resin promotes uniform bonding between the polyester and epoxy resins. Furthermore, the incorporation of hydroxyl silicone oil segments into the polyurethane segments further enhances the temperature and weather resistance of the powder coating. The excellent cohesive strength of the polyester resin provides strong structural support for the epoxy resin structure, leveraging the strength advantages of the epoxy-polyester resin mixture. Vinyl benzylamine acts as a bridge between the polyurethane prepolymer and polyacrylate, while also providing a rigid benzene ring structure within the polyester resin to a certain extent, further improving the strength and abrasion resistance of the powder coating.

[0037] 2. In this application, L-lysine diisocyanate is preferred as an aliphatic diisocyanate. After L-lysine diisocyanate forms chain segments with hydroxyl silicone oil, it can greatly improve the structural stability of the mixed resin system, thereby improving the weather resistance of the powder coating. Detailed Implementation

[0038] The following provides a further detailed description of this application.

[0039] Preparation Example 1

[0040] A method for preparing polyester resin includes the following steps:

[0041] Weigh out 1 kg of aliphatic diisocyanate, 0.7 kg of polyether polyol, 0.4 kg of hydroxyl silicone oil, 0.05 kg of vinyl benzylamine, 0.05 kg of acrylate monomer, 0.1 kg of acrylic acid, and 5 g of initiator.

[0042] Specifically, the aliphatic diisocyanate is hexamethylene diisocyanate. The polyether polyol is polyethylene glycol with a molecular weight of 2000. The hydroxyl silicone oil is a monohydroxy-terminated silicone oil with a molecular weight of 1500. The acrylate monomer is methyl methacrylate. The initiator is benzoyl peroxide.

[0043] Polyether polyol was added to a reactor, nitrogen was introduced into the reactor to replace the internal air, and the mixture was heated to 80°C. Aliphatic diisocyanate was then added and reacted for 0.5 h. Hydroxy silicone oil was then added and the reaction continued for 1 h. Vinyl benzylamine was then added in batches, followed by 1,4-butanediol until the content of -NCO groups in the reaction system was less than 0.5 wt%. 2 L of acetone was then added for dispersion. Initiator and acrylate monomer were then added and the reaction continued for 0.5 h. Acrylic acid was then added and the reaction continued for 1 h. The mixture was cooled and 2 L of acetone was removed to obtain polyester resin.

[0044] Preparation Example 2

[0045] A method for preparing polyester resin includes the following steps:

[0046] Weigh out 1 kg of aliphatic diisocyanate, 1 kg of polyether polyol, 0.7 kg of hydroxyl silicone oil, 0.1 kg of vinyl benzylamine, 0.1 kg of acrylate monomer, 0.2 kg of acrylic acid, and 7 g of initiator.

[0047] Specifically, the aliphatic diisocyanate is hexamethylene diisocyanate. The polyether polyol is polyethylene glycol with a molecular weight of 2000. The hydroxyl silicone oil is a monohydroxy-terminated silicone oil with a molecular weight of 2500. The acrylate monomer is methyl methacrylate. The initiator is benzoyl peroxide.

[0048] Polyether polyol was added to a reactor, nitrogen gas was introduced into the reactor to replace the internal air, and the reactor was heated to 80°C. Aliphatic diisocyanate was added and reacted for 1 hour. Then hydroxyl silicone oil was added and the reaction continued for 1.5 hours. Vinyl benzylamine was added, followed by batches of 1,4-butanediol until the content of -NCO groups in the reaction system was less than 0.5 wt%. Then 2 L of acetone was added for dispersion. Then initiator and acrylate monomer were added and reacted for 0.5 hours. Then acrylic acid was added and reacted for 1.5 hours. The mixture was cooled and 2 L of acetone was removed to obtain polyester resin.

[0049] Preparation Example 3

[0050] The difference between this preparation example and Preparation Example 1 lies in the different aliphatic diisocyanates.

[0051] The aliphatic diisocyanate used in this preparation example is specifically L-lysine diisocyanate, and the amount used is 1.34 kg.

[0052] Comparative Preparation Example 1

[0053] The difference between this comparative preparation example and preparation example 1 lies in the different aliphatic diisocyanates.

[0054] In this comparative preparation example, an equal amount of aromatic diisocyanate was used to replace aliphatic diisocyanate. Specifically, the aromatic diisocyanate was 4,4'-diphenylmethane diisocyanate, and the amount used was 1.49 kg.

[0055] Comparative Preparation Example 2

[0056] The difference between this comparative preparation example and preparation example 1 lies in the different polyether polyols and hydroxyl silicone oils used.

[0057] In this comparative preparation example, an equal amount of polyether polyol was used to replace hydroxyl silicone oil. That is, 1.1 kg of polyether polyol was weighed out, but no hydroxyl silicone oil was weighed out.

[0058] Comparative preparation example 3

[0059] The difference between this comparative preparation example and preparation example 1 lies in the different vinyl benzylamine and acrylate monomers.

[0060] Specifically, in this comparative preparation example, 1 kg of aliphatic diisocyanate, 0.7 kg of polyether polyol, 0.4 kg of hydroxyl silicone oil, 0.043 kg of hydroxyethyl acrylate, 0.086 kg of acrylic acid, and 5 g of initiator were weighed.

[0061] Specifically, the aliphatic diisocyanate is hexamethylene diisocyanate. The polyether polyol is polyethylene glycol with a molecular weight of 2000.

[0062] Polyether polyol was added to a reactor, nitrogen was introduced into the reactor to replace the internal air, and the reactor was heated to 80°C. Aliphatic diisocyanate was added and reacted for 0.5 h. Then hydroxyl silicone oil was added and the reaction continued for 1 h. Hydroxyethyl acrylate was added, and then 1,4-butanediol was added in batches until the content of -NCO groups in the reaction system was less than 0.5 wt%. Then 2 L of acetone was added for dispersion. Then initiator and acrylic acid were added and reacted for 1.5 h. After cooling, 2 L of acetone was removed to obtain polyester resin.

[0063] Example 1

[0064] A method for preparing a high-temperature resistant, high-strength powder coating includes the following steps:

[0065] 4 kg of epoxy resin, 3 kg of polyester resin, 0.6 kg of curing agent, 0.1 kg of leveling agent, 0.1 kg of filler and 2.2 kg of pigment were premixed. The resulting mixture was heated to 125°C to melt, extruded and cooled, crushed into powder, and sieved to obtain a high-temperature resistant and high-strength powder coating.

[0066] Specifically, the epoxy resin is bisphenol A diglycidyl ether. The polyester resin is prepared according to Preparation Example 1. The curing agent is 0.4 kg of m-phenylenediamine and 0.2 kg of triglycidyl isocyanate. The leveling agent is BYK-300. The filler is barium sulfate. The pigment is titanium dioxide.

[0067] Example 2

[0068] A method for preparing a high-temperature resistant, high-strength powder coating includes the following steps:

[0069] 5 kg of epoxy resin, 2 kg of polyester resin, 1 kg of curing agent, 0.3 kg of leveling agent, 0.2 kg of filler and 1.5 kg of pigment were premixed. The resulting mixture was heated to 125°C to melt, extruded and cooled, crushed into powder, and sieved to obtain a high-temperature resistant and high-strength powder coating.

[0070] Specifically, the epoxy resin is bisphenol A diglycidyl ether. The polyester resin is prepared according to Preparation Example 1. The curing agent is 0.6 kg of m-phenylenediamine and 0.4 kg of triglycidyl isocyanate. The leveling agent is BYK-300. The filler is barium sulfate. The pigment is titanium dioxide.

[0071] Example 3

[0072] A method for preparing a high-temperature resistant, high-strength powder coating includes the following steps:

[0073] 4.5 kg of epoxy resin, 2.7 kg of polyester resin, 0.8 kg of curing agent, 0.2 kg of leveling agent, 0.15 kg of filler and 1.65 kg of pigment were premixed. The resulting mixture was heated to 125°C to melt, extruded and cooled, crushed into powder, and sieved to obtain a high-temperature resistant and high-strength powder coating.

[0074] Specifically, the epoxy resin is bisphenol A diglycidyl ether. The polyester resin is prepared according to Preparation Example 1. The curing agent is 0.5 kg of m-phenylenediamine and 0.3 kg of triglycidyl isocyanate. The leveling agent is BYK-300. The filler is barium sulfate. The pigment is titanium dioxide.

[0075] Example 4

[0076] A method for preparing a high-temperature resistant and high-strength powder coating, the difference between this embodiment and Example 3 lies in the different polyester resins.

[0077] The polyester resin in this embodiment was specifically prepared using Preparation Example 2.

[0078] Example 5

[0079] A method for preparing a high-temperature resistant and high-strength powder coating, the difference between this embodiment and Example 3 lies in the different polyester resins.

[0080] The polyester resin in this embodiment was specifically prepared using Preparation Example 3.

[0081] Comparative Example 1

[0082] A method for preparing powder coating, the difference between this comparative example and Example 3 lies in the different polyester resins.

[0083] The polyester resin in this embodiment is a commercially available carboxyl-terminated polyester resin.

[0084] Comparative Example 2

[0085] A method for preparing powder coating, the difference between this comparative example and Example 3 lies in the different polyester resins.

[0086] The polyester resin in this embodiment was specifically prepared from Comparative Preparation Example 1.

[0087] Comparative Example 3

[0088] A method for preparing powder coating, the difference between this comparative example and Example 3 lies in the different polyester resins.

[0089] The polyester resin in this embodiment was specifically prepared from Comparative Preparation Example 2.

[0090] Comparative Example 4

[0091] A method for preparing powder coating, the difference between this comparative example and Example 3 lies in the different polyester resins.

[0092] The polyester resin in this embodiment was specifically prepared from Comparative Preparation Example 3.

[0093] Performance testing

[0094] Powder coatings prepared in different embodiments and comparative examples were used as test materials. The test materials were sprayed onto the surface of steel plates by electrostatic spraying and cured at 220°C for 15 minutes to form a coating with a thickness of 60 μm on the surface of the steel plates. The following tests were then performed.

[0095] 1. Referring to GB / T 9286-1998 "Cross-cut test of paint and varnish film", the coating peeling situation was counted after the coating was cut to test the adhesion of the coating. The affected area of ​​the coating was less than 5% as Grade 1, 5% to 15% as Grade 2, 15% to 35% as Grade 3, 35% to 65% as Grade 4, and the worst as Grade 5. The results are shown in Table 1.

[0096] 2. Referring to GB / T 1723-1993 "Test Method for Impact Resistance of Coating Film", the maximum height of the hammer that does not cause damage to the coating was counted to test the impact resistance of the coating. The results are shown in Table 1.

[0097] 3. Referring to GB / T1771-1991 "Determination of resistance to neutral salt spray of paints and varnishes", continuous spraying with neutral salt spray at 35℃ and 95%RH was performed, and the time required for unilateral rusting was recorded to test the weather resistance of the coating. The results are shown in Table 1.

[0098] 4. Referring to GB / T1735-2009 "Determination of heat resistance of paints and varnishes", different temperatures were continuously heated for 5 hours. The maximum heating temperature at which the coating remained intact and did not peel off was counted to test the heat resistance of the coating. The results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] According to the test results in Table 1, Examples 1-3 all exhibited good properties in terms of adhesion, impact resistance, weather resistance and heat resistance, and can be applied to various high-temperature and harsh working environments.

[0103] The powder coating resin system formed by ordinary carboxyl-terminated polyester resin and epoxy resin, namely Comparative Example 1, is weaker than Example 3 in terms of adhesion, impact resistance, weather resistance and heat resistance. This proves that the polyester resin synthesized in Example 3 has good compatibility with epoxy resin, and the resulting resin system is stable and meets the requirements of temperature resistance and high strength of powder coatings.

[0104] Compared with Comparative Examples 2-4, Example 3 also showed good performance in terms of adhesion, impact resistance, weather resistance and heat resistance. It can be found that the choice of diisocyanate, the introduction of hydroxyl silicone oil and the composition of polyacrylate all affect the properties of polyester resin, and thus affect the overall performance of powder coating.

[0105] Compared with Example 3, Example 5 showed stronger weather resistance, indicating that L-lysine diisocyanate is more helpful in improving the structural stability of the resin system of powder coatings, thereby improving weather resistance.

[0106] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A temperature resistant high strength powder coating, characterized in that: Prepared from raw materials comprising the following weight percentages: epoxy resin 40~50%; polyurethane resin 20~30%; curing agent 6~10%; leveling agent 1~3%; filler 1~2%; pigment balance; The polyurethane resin is obtained by reacting aliphatic diisocyanate with polyether polyol and hydroxyl silicone oil to obtain a polyurethane prepolymer, and then polymerizing the polyurethane prepolymer with vinyl benzylamine, acrylic ester monomer, and acrylic monomer to obtain the polyurethane resin. The mass ratio of the aliphatic diisocyanate to the polyether polyol and the hydroxyl silicone oil is 1:(0.7~1):(0.4~0.7), and the mass ratio of the aliphatic diisocyanate to the vinyl benzylamine, the acrylic ester monomer, and the acrylic monomer is 1:(0.05~0.1):(0.05~0.1):(0.1~0.2). The hydroxyl silicone oil is a monohydroxyl-terminated silicone oil, and the molecular weight of the monohydroxyl-terminated silicone oil is 1500~2500.

2. The temperature resistant high strength powder coating according to claim 1, characterized in that: The aliphatic diisocyanate is selected from one or both of L-lysine diisocyanate and hexamethylene diisocyanate.

3. The temperature resistant high strength powder coating according to claim 1, characterized in that: The polyether polyol is selected from one or both of polyethylene glycol and polypropylene glycol.

4. The temperature resistant high strength powder coating according to claim 1, characterized in that: The epoxy resin is selected from bisphenol A diglycidyl ether.

5. The temperature resistant high strength powder coating according to claim 1, characterized in that: The filler is selected from one or both of calcium carbonate and barium sulfate.

6. A process for the production of a temperature resistant high strength powder coating, characterized in that: A method for preparing the temperature-resistant high-strength powder coating of any one of claims 1~5, comprising the following steps: Pre-mixing the epoxy resin, the polyurethane resin, the curing agent, the leveling agent, the filler, and the pigment, heating and melting the obtained mixture together, extruding, breaking, and obtaining the temperature-resistant high-strength powder coating.

7. The method according to claim 6, wherein the method is characterized by: A method for preparing the polyurethane resin, comprising the following steps: Under the protection of inert gas, the polyether polyol and the aliphatic diisocyanate are heated and reacted for 0.5~1h, then the hydroxyl silicone oil is added, and the reaction is continued for 1~1.5h, then the vinyl benzylamine is added, then the chain extender is added, then the organic solvent is added for dispersion, then the initiator, the acrylic ester monomer, and the acrylic monomer are added and reacted for 1.5~2h, the temperature is lowered, the organic solvent is removed, and the polyurethane resin is obtained.

Images