Rapidly-cured powder coating and preparation method thereof

Abstract

The invention discloses a fast-curing powder coating and a preparation method thereof, and belongs to the field of powder coatings. According to the invention, carboxylated polyester resin and triglycidyl isocyanurate are added for cross-linking reaction to form a network structure. The curing accelerator can activate carboxyl functional groups and effectively promote the functional groups in the carboxylated polyester resin to react, so that the curing speed of the powder coating is increased; the added precipitated barium sulfate can reduce the overall viscosity of the powder system; the modified leveling agent and the wetting accelerant have a synergistic effect, so that the wettability of the powder coating is effectively improved, the internal surface tension of the powder coating in the curing and melting process is reduced, the leveling performance of the powder coating is improved, meanwhile, the carboxylated polyester resin is easier to infiltrate pigments, volatile substances are accelerated to overflow from the surface, and the color fastness of the powder coating is improved. Meanwhile, under the synergistic effect of the degassing agent, bubbles are accelerated to break and overflow, the appearance of a coating film is obviously improved, a flat coating film surface is obtained, and therefore the problem that the coating film surface is rough and uneven due to rapid curing is solved.

Description

Technical Field

[0001] The invention relates to the field of powder coating preparation, in particular to a fast-curing powder coating and a preparation method thereof. Background Art

[0002] Powder coating is a solid powdered synthetic resin coating composed of solid resin, pigment, filler and additives. Powder coating is a solid coating with the advantages of no VOC, high utilization rate, easy coating operation and good comprehensive performance. Powder coating is mainly prepared by melt extrusion, crushing and grinding. As national and local policies have stricter environmental protection requirements, the application of powder coating is becoming more and more extensive, and the market demand is also increasing.

[0003] At present, the curing time of most powder coatings is too long, which not only consumes too much energy resources, but also reduces production efficiency. There are also many fast-curing coatings in the prior art. For example, the invention patent with Chinese patent application number CN201710971232.5 discloses a method for realizing fast curing of powder coatings by using photothermal effect, by mixing and crushing the photothermal conversion filler with the resin, and then evenly placing the crushed powder coating on the substrate, but the coating has the problem of not being able to take into account the performance of the coating film during the molding process; another example is the invention patent with Chinese patent number CN201610993976.2 discloses a high-speed infrared curing leveling powder coating and its preparation method, the components of the powder coating include polyester resin, curing agent, leveling agent, benzoin, inorganic filler, wax powder and pigment, but in the case of fast film formation, there is a problem of difficulty in ensuring the surface performance of the coating film. Therefore, the above-mentioned problems to be solved still exist in the prior art. Summary of the invention

[0004] Based on this, in order to solve the problems of long curing time, low efficiency and poor appearance quality of powder coatings in the prior art, the present invention provides a fast-curing powder coating and a preparation method thereof. The specific technical scheme is as follows:

[0005] A fast-curing powder coating comprises the following raw materials in percentage by mass: 50.0% to 60.0% of carboxylated polyester resin, 4.2% to 5.0% of triglycidyl isocyanurate, 0.2% to 0.3% of curing accelerator, 0.5% to 0.9% of modified leveling agent, 0.5% to 0.9% of wetting accelerator, 0.1% to 0.3% of degassing agent, 0.1% to 0.5% of silane coupling agent, 0.1% to 0.3% of toughening agent, 0.1% to 0.5% of antioxidant, 0.2% to 0.5% of hardening and wear-resistant agent, 10.0% to 30.0% of precipitated barium sulfate and 0% to 5.0% of pigment.

[0006] Furthermore, the acid value of the carboxylated polyester resin is 30 mgKOH / g to 37 mgKOH / g, the viscosity is 3500 mPa·s to 6500 mPa·s at 200°C, and the softening point is 103 to 113°C.

[0007] Furthermore, the curing accelerator is an onium salt compound.

[0008] Furthermore, the wetting promoter is a methacrylate copolymer.

[0009] Furthermore, the degassing agent is a fine amide polymer.

[0010] Furthermore, the antioxidant is pentaerythritol ester.

[0011] Furthermore, the whiteness of the precipitated barium sulfate is greater than 98, and the oil absorption (g / 100g) is 10-20.

[0012] In addition, the present invention also provides a method for preparing a powder coating, the preparation method comprising the following steps:

[0013] Add modified leveling agent, silane coupling agent, wetting promoter and precipitated barium sulfate into the mixing container, and then introduce high-speed airflow to make the powder suspended under the driving effect of the airflow. In this suspension process, the powder particles continuously collide with each other and exchange positions, so that the materials can be evenly bonded together, and finally obtain mixture A;

[0014] Carboxylated polyester resin, triglycidyl isocyanurate, curing accelerator, mixture A modified leveling agent, wetting accelerator, degassing agent, toughening agent, antioxidant, hardening and wear-resistant agent, precipitated barium sulfate and pigment are added to a three-dimensional rotary water-cooled mixer, and mixed at a speed of 400-500r / min for 20-40min. The central axis is water-cooled, which can effectively solve the problem of raw materials sticking to the wall due to the heating of raw materials due to mutual friction during pre-mixing. In the mixing device, after being fully mixed and uniformly, it is subjected to melt extrusion treatment, tablet crushing treatment, grinding treatment and sieving treatment to obtain a fast-curing powder coating.

[0015] Furthermore, the equipment used in the melt extrusion process is a twin-screw extruder, and the speed of the twin-screw extruder is 120r / min~150r / min, the temperature is 100℃~110℃, and the ratio of the length of the feeding and conveying section to the mixing section in the twin-screw extruder is 1-2:6-8.

[0016] Furthermore, the preparation method of the modified leveling agent is: mixing modified polysiloxane and silicon dioxide in a mass ratio of (6-7): (1-4), stirring for 1h-2h at a rotation speed of 1000r / min-1200r / min and a temperature of 45°C-75°C, and obtaining the modified leveling agent after drying.

[0017] In the above scheme, by optimizing the components and the ratio of the components, the carboxylated polyester resin and triglycidyl isocyanurate undergo a cross-linking reaction to form a network structure. The curing accelerator can effectively promote the reaction of the functional groups in the carboxylated polyester resin to generate more cross-linking bonds, which helps to increase the curing speed of the reaction and greatly shorten the curing time; under the action of high-speed airflow and silane coupling agent, the modified leveling agent and wetting promoter are caused to adhere to the precipitated barium sulfate, so that it is evenly dispersed during the melt extrusion process; the low oil absorption of the added precipitated barium sulfate can also achieve the effect of reducing the overall viscosity of the powder coating; at the same time, the length of the conveying section and the mixing section of the twin-screw extruder is specified, which helps the components in the powder coating system to move more freely and contact each other, so that the components are more evenly dispersed, and the curing speed is further accelerated; the addition of the modified leveling agent can promote the leveling performance of the powder coating, effectively improve the surface tension of the powder coating, and make the powder coating melt and level in a shorter time. And under the synergistic effect of the wetting promoter, the wettability of the powder coating is effectively improved, the surface tension inside the molten coating is reduced, the carboxylated polyester resin is easier to infiltrate the pigment, and the volatile substances such as water generated by the cross-linking reaction are accelerated to overflow from the surface. At the same time, under the synergistic effect of the degassing agent, the bubble bursting and overflowing are accelerated, the appearance of the coating is significantly improved, and a smooth coating surface is obtained, which effectively solves the problem of the rough and uneven coating surface formed by the rapid curing of the powder coating in the prior art. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0020] A fast-curing powder coating in one embodiment of the present invention comprises the following raw materials in percentage by mass: 50.0% to 60.0% of carboxylated polyester resin, 4.2% to 5.0% of triglycidyl isocyanurate, 0.2% to 0.3% of curing accelerator, 0.5% to 0.9% of modified leveling agent, 0.5% to 0.9% of wetting accelerator, 0.1% to 0.3% of degassing agent, 0.1% to 0.5% of silane coupling agent, 0.1% to 0.3% of toughening agent, 0.1% to 0.5% of antioxidant, 0.2% to 0.5% of hardening and wear-resistant agent, 10.0% to 30.0% of precipitated barium sulfate and 0 to 5.0% of pigment.

[0021] In one embodiment, the acid value of the carboxylated polyester resin is 30 mgKOH / g to 37 mgKOH / g, the viscosity is 3500 mPa·s to 6500 mPa·s at 200°C, and the softening point is 103 to 113°C.

[0022] In one embodiment, the melting range of the triglycidyl isocyanurate is 95° C. to 115° C., and the epoxy equivalent (g / eq) is ≤105.

[0023] In one embodiment, the curing accelerator is an onium salt compound.

[0024] In one embodiment, the wetting promoter is a methacrylate copolymer.

[0025] In one embodiment, the degassing agent is a fine amide polymer.

[0026] In one embodiment, the antioxidant is pentaerythritol ester.

[0027] In one embodiment, the melting point of the pentaerythritol ester is 112°C to 129°C.

[0028] In one embodiment, the hardening and wear-resistant agent is polytetrafluoroethylene modified PE wax.

[0029] In one embodiment, the median particle size of the polytetrafluoroethylene modified PE wax is 3 μm to 6 μm.

[0030] In one embodiment, the density of the precipitated barium sulfate is whiteness>98, and the oil absorption (g / 100g) is 10-20.

[0031] In addition, the present invention also provides a method for preparing a powder coating, the preparation method comprising the following steps:

[0032] Add modified leveling agent, silane coupling agent, wetting promoter and precipitated barium sulfate into the mixing container, and then introduce high-speed airflow to make the powder suspended under the driving effect of the airflow. In this suspension process, the powder particles continuously collide with each other and exchange positions, so that the materials can be evenly bonded together, and finally obtain mixture A;

[0033] Carboxylated polyester resin, triglycidyl isocyanurate, curing accelerator, mixture A degassing agent, toughening agent, antioxidant, hardening and wear-resistant agent and pigment are added to a three-dimensional rotary water-cooled mixer and mixed at a speed of 400-500r / min for 20-40min. The central axis is water-cooled, which can effectively solve the problem of raw materials sticking to the wall due to the heating of raw materials due to mutual friction during pre-mixing. After the raw materials are fully mixed, they are melt-extruded, tableted, ground and sieved to obtain a fast-curing powder coating.

[0034] In one embodiment, the equipment used in the melt extrusion process is a twin-screw extruder, and the speed of the twin-screw extruder is 120r / min~150r / min, the temperature is 100℃~110℃, and the ratio of the length of the conveying section and the mixing section in the twin-screw extruder is 1-2:6-8.

[0035] In one of the embodiments, the preparation method of the modified leveling agent is: mixing modified polysiloxane and silicon dioxide in a mass ratio of (6-7): (1-4), stirring for 1h-2h at a rotation speed of 1000r / min-1200r / min and a temperature of 45°C-75°C, and obtaining the modified leveling agent after drying.

[0036] In one embodiment, the modified polysiloxane is one or both of polyether-modified polysiloxane and polyester-modified polysiloxane.

[0037] By optimizing the components and the ratio of the components in the above scheme, a powder coating with fast curing speed, high effect and excellent coating film appearance quality can be obtained.

[0038] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0039] Embodiments 1 to 9:

[0040] The difference between Examples 1 to 9 is that the raw materials for preparing the powder coatings are different, as shown in Table 1;

[0041] The preparation method of the fast-curing powder coating of Examples 1 to 9 comprises the following steps:

[0042] The polyether-modified polysiloxane and silicon dioxide are mixed in a mass ratio of 7:3, stirred at a speed of 1000 r / min and a temperature of 65° C. for 2 h, and dried to obtain a modified leveling agent;

[0043] Add modified leveling agent, silane coupling agent, wetting promoter and precipitated barium sulfate into the mixing container, and then introduce high-speed airflow to make the powder suspended under the driving effect of the airflow. In this suspension process, the powder particles continuously collide with each other and exchange positions, so that the materials can be evenly bonded together, and finally obtain mixture A;

[0044] Carboxylated polyester resin, triglycidyl isocyanurate, curing accelerator, degassing agent of mixture A, toughening agent, antioxidant, hardening and wear-resistant agent and pigment are added to a three-dimensional rotating water-cooled mixer and mixed at a speed of 450r / min for 35min. The central axis is water-cooled, which can effectively solve the problem of raw materials sticking to the wall due to the heating of raw materials due to mutual friction during premixing. After the raw materials are fully mixed, they are melt-extruded and the equipment used in the melt-extrusion process is a twin-screw extruder, and the speed of the twin-screw extruder is 150r / min, the temperature is 100°C, and the ratio of the length of the conveying section to the mixing section in the twin-screw extruder is 1:6. After tableting, grinding and screening, a fast-curing powder coating is obtained.

[0045] Comparative Examples 1 to 3:

[0046] The difference between Comparative Examples 1 to 3 and Example 9 is that the ingredients and proportions of the preparation raw materials are different, and the rest are the same as Example 9. The specific preparation raw materials and raw material proportions are shown in Table 1.

[0047] Comparative Example 4:

[0048] The difference between Comparative Example 4 and Example 9 is that no modified leveling agent is added in Comparative Example 4, and the rest is the same as Example 9.

[0049] Comparative Example 5:

[0050] The difference between Comparative Example 5 and Example 9 is that a conventional leveling agent (acrylate leveling agent) is added to Comparative Example 5, and the rest is the same as Example 9.

[0051] Table 1: Preparation raw materials (%)

[0052]

[0053]

[0054] The powder coating samples prepared in Examples 1 to 9 and the powder coating comparison samples prepared in Comparative Examples 1 to 5 were subjected to performance tests.

[0055] Test Example 1: The roughness of the coating film was tested with reference to the standard GB / T 6062-2009 “Technical Specification for Product Geometric Measurements (GPS) – Nominal Characteristics of Surface Structure Profile Contact (Stylus) Instruments”. The results are shown in Table 2.

[0056] Table 2: Roughness

[0057] Group Roughness / μm Example 1 0.8 Example 2 0.7 Example 3 0.7 Example 4 0.6 Example 5 0.9 Example 6 0.7 Example 7 0.7 Example 8 0.8 Example 9 0.8 Comparative Example 1 2.1 Comparative Example 2 2.9 Comparative Example 3 2.4 Comparative Example 4 3.4 Comparative Example 5 1.4

[0058] From the data analysis of Table 2, it can be seen that the present application can obtain a coating film with a smooth surface by optimizing the preparation of raw materials and proportions, which is beneficial to its application.

[0059] Test Example 2: Reference standard GB / T 5237.4-2017 Aluminum Alloy Building Profiles Part 4 Powder Spraying Profiles. The results are shown in Table 3.

[0060] Table 3: Test results

[0061]

[0062] From the data analysis of Table 3, it can be seen that after optimizing the preparation of raw materials and raw material ratios, the present application has excellent bending resistance and stability, and the overall comprehensive performance of the coating film is remarkable.

[0063] Test Example 3: Curing by heating, recording the curing time, the results are shown in Table 4 below.

[0064] Table 4: Curing time

[0065] Group Curing temperature / ℃ Curing time / min Example 1 180 4 Example 2 180 6 Example 3 180 5 Example 4 180 4 Example 5 180 6 Example 6 180 4 Example 7 180 4 Example 8 180 6 Example 9 180 5 Comparative Example 1 180 10 Comparative Example 2 180 9 Comparative Example 3 180 10 Comparative Example 4 180 11 Comparative Example 5 180 9

[0066] From the data analysis of Table 4, it can be seen that the present application helps to shorten the curing time of the powder coating by optimizing the preparation of raw materials and proportions. While ensuring the comprehensive performance of the coating film, it can achieve a balance between the degree of curing and the curing time, which helps to improve production efficiency.

[0067] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fast-curing powder coating, characterized in that: The powder coating comprises the following raw materials in percentage by mass: 50.0% to 60.0% of carboxylated polyester resin, 4.2% to 5.0% of triglycidyl isocyanurate, 0.2% to 0.3% of curing accelerator, 0.5% to 0.9% of modified leveling agent, 0.5% to 0.9% of wetting accelerator, 0.1% to 0.3% of degassing agent, 0.1% to 0.5% of silane coupling agent, 0.1% to 0.3% of toughening agent, 0.1% to 0.5% of antioxidant, 0.2% to 0.5% of hardening and wear-resistant agent, 10.0% to 30.0% of precipitated barium sulfate and 0% to 5.0% of pigment.

2. The powder coating according to claim 1, characterized in that The carboxylated polyester resin has an acid value of 30 mgKOH / g to 37 mgKOH / g, a viscosity of 3500 mPa·s to 6500 mPa·s at 200°C, and a softening point of 103 to 113°C.

3. The powder coating according to claim 1, characterized in that The curing accelerator is an onium salt compound.

4. The powder coating according to claim 1, characterized in that The wetting promoter is a methacrylate copolymer.

5. The powder coating according to claim 1, characterized in that: The degassing agent is a fine amide polymer.

6. The powder coating according to claim 1, characterized in that The antioxidant is pentaerythritol ester.

7. The powder coating according to claim 1, characterized in that The whiteness of the precipitated barium sulfate is greater than 98, and the oil absorption (g / 100g) is 10-20.

8. A method for preparing a powder coating, characterized in that: The preparation method is used to prepare the powder coating according to any one of claims 1 to 7, and the preparation method comprises the following steps: Add modified leveling agent, silane coupling agent, wetting promoter and precipitated barium sulfate into the mixing container, and then introduce high-speed airflow to make the powder suspended under the driving effect of the airflow. In this suspension process, the powder particles continuously collide with each other and exchange positions, so that the materials can be evenly bonded together, and finally obtain mixture A; Carboxylated polyester resin, triglycidyl isocyanurate, curing accelerator, mixture A degassing agent, toughening agent, antioxidant, hardening and wear-resistant agent and pigment are added to a three-dimensional rotary water-cooled mixer and mixed at a speed of 400-500r / min for 20-40min. The central axis is water-cooled, which can effectively solve the problem of raw materials sticking to the wall due to the heating of raw materials due to mutual friction during pre-mixing. After the raw materials are fully mixed, they are melt-extruded, tableted, ground and sieved to obtain a fast-curing powder coating.

9. The preparation method according to claim 8, characterized in that: The equipment used in the melt extrusion process is a twin-screw extruder, and the speed of the twin-screw extruder is 120r / min-150r / min, the temperature is 100℃-110℃, and the ratio of the length of the conveying section to the mixing section in the twin-screw extruder is 1-2:6-8.

10. The preparation method according to claim 8, characterized in that: The preparation method of the modified leveling agent is as follows: modifying polysiloxane and silicon dioxide in a mass ratio of (6-7): (1-4) are mixed, stirring for 1h-2h at a rotation speed of 1000r / min-1200r / min and a temperature of 45°C-75°C, and drying to obtain the modified leveling agent.

Images