Thermosetting polyester powder coating for guardrails and preparation process of thermosetting polyester powder coating

Abstract

The invention discloses a thermosetting polyester powder coating for guardrails and a preparation process of the thermosetting polyester powder coating, and belongs to the technical field of powder coatings. The coating is prepared from the following components in parts by weight: 48 to 55 parts of modified hydroxyl type saturated polyester resin, 6 to 8 parts of modified curing agent, 28 to 32 parts of composite pigment filler and a proper amount of functional additive, wherein the resin is grafted and modified through an epoxy group, the hydroxyl value is 30-40 mgKOH / g, the acid value is smaller than or equal to 5 mgKOH / g, the curing agent is formed by compounding triglycidyl isocyanurate and an imidazole derivative according to the ratio of (9-11): 1, and the composite pigment filler contains modified nano fluorescent carbon fibers with specific sizes. Through synergistic optimization of the components, the coating has excellent mechanical properties (the pencil hardness is greater than or equal to 2H, and the adhesive force grade is less than or equal to 1 grade), weather resistance and corrosion resistance (the salt fog resistance is greater than or equal to 1000h, and the artificial aging resistance is greater than or equal to 800h) and a night fluorescent warning function, is adaptive to the outdoor complex use environment of the guardrail, can prolong the service life of the guardrail, and improves the driving safety; the preparation process is stable and efficient and has high raw material utilization rate.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, specifically to a thermosetting polyester powder coating for guardrails and its preparation process. Background Technology

[0002] As a crucial safety component of infrastructure such as roads and bridges, guardrails are exposed to complex outdoor environments for extended periods, enduring multiple challenges including sunlight, wind and rain erosion, temperature variations, and vehicle exhaust corrosion. Therefore, stringent requirements are placed on the weather resistance, corrosion resistance, mechanical properties, and service life of the surface coating. Thermosetting polyester powder coatings, due to their solvent-free, environmentally friendly, and high-performance characteristics, are widely used for guardrail surface protection.

[0003] However, existing thermosetting polyester powder coatings for guardrails still have many shortcomings: on the one hand, the compatibility between conventional polyester resins and curing agents is poor, resulting in low coating curing efficiency, and the mechanical properties of the cured film, such as hardness and adhesion, are difficult to meet the long-term use requirements of guardrails; on the other hand, guardrail coatings used outdoors are prone to yellowing and aging under ultraviolet radiation, and their resistance to salt spray corrosion is limited, shortening the service life of the guardrails; in addition, traditional guardrail coatings do not have special functions, and their warning effect is insufficient at night or in low-light environments, making it difficult to effectively ensure driving safety.

[0004] To address the aforementioned issues, related technologies have attempted to improve coating performance by optimizing resin formulations and adding anti-aging additives, but the results remain unsatisfactory. For example, some solutions use fluorinated glycidyl ester compound curing agents to replace traditional TGIC to reduce toxicity, but this sacrifices the coating's curing efficiency and mechanical strength. Other solutions introduce carbon nanomaterials to improve the coating's weather resistance, but do not consider the material's dispersibility and the imparting of special functions. Therefore, developing a thermosetting polyester powder coating for guardrails that combines excellent mechanical properties, weather and corrosion resistance, and nighttime warning functionality is of significant practical importance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a thermosetting polyester powder coating for guardrails and its preparation process, aiming to improve the mechanical properties, weather resistance, and corrosion resistance of the coating, while also giving the coating a nighttime fluorescent warning function, extending the service life of the guardrail and improving driving safety.

[0006] The above-mentioned technical objective of the present invention is achieved by the following technical solution:

[0007] A thermosetting polyester powder coating for guardrails, comprising, by weight, the following components: 48-55 parts thermosetting polyester resin, 6-8 parts modified curing agent, 28-32 parts composite pigments and fillers, 1.5-2.5 parts functional leveling agent, 0.8-1.5 parts high-efficiency anti-yellowing agent, 0.8-1.5 parts modified adhesion promoter, and 0.5-0.8 parts nano degassing agent;

[0008] The thermosetting polyester resin is a modified hydroxyl-type saturated polyester resin with a hydroxyl value of 30-40 mgKOH / g, an acid value of ≤5 mgKOH / g, and a glass transition temperature of 55-65℃. The modified hydroxyl-type saturated polyester resin is grafted and modified by introducing 2-5 wt% epoxy groups.

[0009] The modified curing agent is a compound of triglycidyl isocyanurate and epoxy curing accelerator in a weight ratio of (9-11):1, and the epoxy curing accelerator is an imidazole derivative.

[0010] Furthermore, the composite pigment and filler are composed of modified pigment and composite filler in a weight ratio of 1:(2-5);

[0011] The modified pigment is titanium dioxide, iron oxide red, or phthalocyanine blue that has been surface-modified with a silane coupling agent, and the amount of silane coupling agent added is 1-3% of the pigment weight;

[0012] The composite filler is composed of barium sulfate, talc powder and nano fluorescent carbon fiber in a weight ratio of (4-6):(1-3):1. The composite filler is pulverized by airflow to a particle size of 1500-2000 mesh and the surface is coated with stearic acid.

[0013] Furthermore, the nano-fluorescent carbon fiber has a diameter of 50-100 nm and a length of 5-10 μm, and is surface-modified with a silane coupling agent, with the amount of silane coupling agent added being 2-4% of the weight of the nano-fluorescent carbon fiber.

[0014] Further, the modification process specifically involves: adding nano-fluorescent carbon fibers to an ethanol aqueous solution, ultrasonically dispersing for 30-40 minutes to obtain a dispersion, then adding a silane coupling agent, stirring and reacting at 60-70℃ for 2-3 hours, and after the reaction is completed, centrifuging, washing, and vacuum drying at 80-100℃ for 4-6 hours to obtain modified nano-fluorescent carbon fibers.

[0015] Furthermore, the functional leveling agent is a fluorinated acrylate copolymer leveling agent.

[0016] Furthermore, the highly efficient anti-yellowing agent is a compound of hindered phenolic antioxidants, ultraviolet absorbers and hindered amine light stabilizers, preferably in a weight ratio of 2:1:1.

[0017] Furthermore, the modified adhesion promoter is a compound of an epoxy silane coupling agent and a titanate coupling agent, preferably in a weight ratio of 3:1.

[0018] Furthermore, the nano-degassing agent is a compound of nano-sized benzoin and nano-sized silica, preferably in a weight ratio of 5:1.

[0019] This invention also provides a preparation process for a thermosetting polyester powder coating for guardrails, comprising the following steps:

[0020] S1. Premixing: Add thermosetting polyester resin and modified curing agent to a high-speed mixer and mix at low speed for 2 minutes at a speed of 400 r / min. Then add composite pigments and fillers, functional leveling agent, high-efficiency anti-yellowing agent, modified adhesion promoter and nano degassing agent. Adjust the speed to 1000-1200 r / min and mix at a temperature of 30-35℃ for 6-8 minutes to obtain a uniform premix.

[0021] S2. Melt extrusion: The premixed material obtained in step S1 is fed into a twin-screw extruder. Gradient temperature control is used, with the following temperatures in each section: feeding section 85-90℃, compression section 95-100℃, melting section 105-110℃, and homogenization section 100-105℃. The screw speed is 180-220 r / min. After melting, shearing, and mixing, the material is extruded to obtain strip-shaped material. The material residence time is controlled to be 3-5 minutes during the extrusion process to ensure that the material is fully melted and does not solidify prematurely.

[0022] S3. Cooling and crushing: The strip material obtained in step S2 is fed into a closed-loop cooling conveyor and cooled in stages. First, it is cooled by spraying with 25-30℃ cooling water for 3 minutes, and then cooled to room temperature by blowing with 15-20℃ cold air. After cooling, it is crushed into uniform granular material with a particle size of 2-5mm by a toothed roller crusher.

[0023] S4 Grinding and sieving: The particulate material obtained in step S3 is fed into a classifying airflow pulverizer for grinding, and finally the thermosetting polyester powder coating for guardrail with uniform particle size distribution is obtained.

[0024] Furthermore, in step S4, the grinding pressure is controlled at 0.6-0.8 MPa. After grinding, the material is first screened through a 120-mesh coarse sieve to remove large particles, and then screened through a 160-mesh fine sieve to collect the undersize material. The oversize material is returned to the airflow pulverizer via a screw conveyor for re-grinding, forming a closed-loop production process.

[0025] The present invention has the following advantages:

[0026] 1. This invention uses epoxy group grafted modified hydroxyl-type saturated polyester resin, combined with TGIC and imidazole derivatives as a modified curing agent, which significantly improves the compatibility of the resin and the curing agent, accelerates the curing efficiency, and greatly enhances the hardness, adhesion and other mechanical properties of the paint film, which can effectively resist collision and friction damage during the use of the guardrail.

[0027] 2. This invention uses a combination of hindered phenolic antioxidants, ultraviolet absorbers and hindered amine light stabilizers as highly efficient anti-yellowing agents, which synergistically exert antioxidant and anti-ultraviolet aging effects. Combined with surface-modified composite pigments and fillers, it significantly improves the weather resistance and salt spray corrosion resistance of the coating, making it adaptable to complex and harsh outdoor environments and extending the service life of the guardrail.

[0028] 3. This invention introduces nano-fluorescent carbon fibers of a specific size into the composite filler. After modification with a silane coupling agent, it forms a stable composite filler system with barium sulfate and talc. This not only further enhances the mechanical properties of the coating but also endows the coating with a nighttime fluorescent warning function, which can clearly mark the position of the guardrail in low-light environments and improve driving safety. At the same time, the composite filler is coated with stearic acid, which effectively improves its dispersibility in the resin and avoids agglomeration that affects the coating performance.

[0029] 4. The preparation process of this invention adopts a segmented premixing, gradient melt extrusion, segmented cooling and closed-loop grinding and sieving design, which can ensure that each component is fully mixed and uniform, the material is fully melted and does not solidify prematurely, and finally obtains a powder coating with uniform particle size distribution, ensuring stable coating performance; the closed-loop production mode can also improve the utilization rate of raw materials and reduce production costs. Detailed Implementation

[0031] A thermosetting polyester powder coating for guardrails, comprising, by weight, the following components: 48-55 parts thermosetting polyester resin, 6-8 parts modified curing agent, 28-32 parts composite pigments and fillers, 1.5-2.5 parts functional leveling agent, 0.8-1.5 parts high-efficiency anti-yellowing agent, 0.8-1.5 parts modified adhesion promoter, and 0.5-0.8 parts nano degassing agent;

[0032] The thermosetting polyester resin is a modified hydroxyl-type saturated polyester resin with a hydroxyl value of 30-40 mgKOH / g, an acid value of ≤5 mgKOH / g, and a glass transition temperature of 55-65℃. The modified hydroxyl-type saturated polyester resin is grafted and modified by introducing 2-5 wt% epoxy groups.

[0033] The modified curing agent is a compound of triglycidyl isocyanurate and epoxy curing accelerator in a weight ratio of (9-11):1, and the epoxy curing accelerator is an imidazole derivative.

[0034] The hydroxyl group is a key active group in the crosslinking reaction between polyester resin and modified curing agent (triglycidyl isocyanurate, TGIC), and its content directly determines the curing crosslinking density. In this invention, the modified curing agent is mixed in a ratio of 6-8 parts and compounded with the epoxy curing accelerator at a ratio of (9-11):1. A hydroxyl value of 30-40 mg KOH / g can achieve a precise stoichiometric match with the curing system. If the hydroxyl value is lower than 30 mg KOH / g, insufficient active groups will lead to inadequate crosslinking, resulting in decreased film hardness and corrosion resistance (such as softening and easy scratching). If it is higher than 40 mg KOH / g, excessive hydroxyl groups will lead to excessively high crosslinking density, increased film brittleness, decreased impact resistance, and inability to meet the mechanical requirements of guardrails subjected to vehicle collisions. At the same time, this hydroxyl value range can ensure that the curing reaction rate matches the preparation process (such as melt extrusion without pre-curing), avoiding poor storage stability of the coating due to excessively fast reaction or prolonged construction curing time due to excessively slow reaction.

[0035] Residual carboxyl groups (the source of acid value) in polyester resin can negatively impact the curing reaction. On one hand, carboxyl groups compete with the epoxy groups in TGIC for the reaction, interfering with the normal cross-linking of hydroxyl and epoxy groups and reducing cross-linking efficiency. On the other hand, residual carboxyl groups are hydrophilic, significantly reducing the coating's salt spray resistance and water resistance, leading to blistering and peeling of the coating in humid / corrosive outdoor environments. Controlling the acid value to ≤5mgKOH / g can minimize these adverse effects. Simultaneously, grafting epoxy groups onto the resin (2-5wt%) further improves the compatibility between the resin and the curing agent, ensuring a uniform and dense cross-linked structure in the paint film and enhancing weather resistance and corrosion resistance.

[0036] Furthermore, the modified curing agent can achieve precise activity matching with the epoxy-grafted modified hydroxyl-type saturated polyester resin with specific parameters of this invention. The polyepoxy groups of triglycidyl isocyanurate can fully crosslink with the hydroxyl groups of the resin to form a dense and stable three-dimensional network structure. Meanwhile, imidazole derivatives, as highly efficient promoters, can significantly reduce the activation energy of the curing reaction. This not only solves the drawback of conventional TGIC curing systems requiring high temperature and long curing time, but also allows for precise control of the curing rate through specific compounding ratios to adapt to the preparation process and construction requirements. At the same time, it forms a synergistic effect with the epoxy-grafted structure of the resin, improving compatibility and reducing side reactions. Ultimately, this ensures that the paint film has both excellent mechanical properties and weather resistance and corrosion resistance, making it suitable for outdoor use of guardrails.

[0037] Furthermore, the composite pigment and filler are composed of modified pigment and composite filler in a weight ratio of 1:(2-5);

[0038] The modified pigment is titanium dioxide, iron oxide red, or phthalocyanine blue that has been surface-modified with a silane coupling agent, and the amount of silane coupling agent added is 1-3% of the pigment weight;

[0039] The composite filler is composed of barium sulfate, talc powder and nano fluorescent carbon fiber in a weight ratio of (4-6):(1-3):1. The composite filler is pulverized by airflow to a particle size of 1500-2000 mesh and the surface is coated with stearic acid.

[0040] Furthermore, the nano-fluorescent carbon fiber has a diameter of 50-100 nm and a length of 5-10 μm, and is surface-modified with a silane coupling agent, with the amount of silane coupling agent added being 2-4% of the weight of the nano-fluorescent carbon fiber.

[0041] The 50-100nm diameter and 5-10μm length of the nano-fluorescent carbon fibers allow them to form a uniform three-dimensional dispersion network within the composite filler. This avoids agglomeration and loss of fluorescent warning function due to excessively small size, while also preventing damage to the coating's density due to excessive size. Simultaneously, it enhances the coating's mechanical strength and wear resistance. Secondly, silane coupling agent modification effectively improves the surface polarity of the nano-fluorescent carbon fibers, enhancing their compatibility and interfacial bonding with polyester resin and other fillers. This prevents delamination and precipitation during coating preparation and curing, ensuring stable coating performance. Thirdly, a modifier addition of 2-4% allows for precise control of the modification effect. This ensures sufficient coverage of the active sites on the nano-fluorescent carbon fiber surface without excessive addition leading to resource waste or affecting the coating's fluorescent performance. Ultimately, this synergistic improvement in both the fluorescent warning function of the nano-fluorescent carbon fibers and the protective performance of the coating is achieved.

[0042] Further, the modification process specifically involves: adding nano-fluorescent carbon fibers to an ethanol aqueous solution, ultrasonically dispersing for 30-40 minutes to obtain a dispersion, then adding a silane coupling agent, stirring and reacting at 60-70℃ for 2-3 hours, and after the reaction is completed, centrifuging, washing, and vacuum drying at 80-100℃ for 4-6 hours to obtain modified nano-fluorescent carbon fibers.

[0043] Furthermore, the functional leveling agent is a fluorinated acrylate copolymer leveling agent.

[0044] Furthermore, the highly efficient anti-yellowing agent is a compound of hindered phenolic antioxidant, ultraviolet absorber and hindered amine light stabilizer in a weight ratio of 2:1:1.

[0045] The synergistic effect of the three components can comprehensively resist the aging and yellowing problems faced by the guardrail coating during outdoor use. Among them, the hindered phenolic antioxidant can preferentially capture free radicals generated during the aging process of the coating, inhibit the initiation and propagation of oxidation chain reaction, and delay the oxidative degradation of the coating from the root. The ultraviolet absorber can selectively absorb ultraviolet rays that are extremely harmful to the coating and convert them into harmless heat energy release, avoiding the direct damage of ultraviolet rays to the resin molecular structure. The hindered amine light stabilizer can regenerate the consumed ultraviolet absorber, and at the same time further terminate the free radical chain reaction, extending the service life of the anti-aging system.

[0046] Furthermore, the modified adhesion promoter is a compound of epoxy silane coupling agent and titanate coupling agent in a weight ratio of 3:1.

[0047] Furthermore, the nano-degassing agent is a compound of nano-sized benzoin and nano-sized silica in a weight ratio of 5:1.

[0048] This invention also provides a preparation process for a thermosetting polyester powder coating for guardrails, comprising the following steps:

[0049] S1. Premixing: Add thermosetting polyester resin and modified curing agent to a high-speed mixer and mix at low speed for 2 minutes at a speed of 400 r / min. Then add composite pigments and fillers, functional leveling agent, high-efficiency anti-yellowing agent, modified adhesion promoter and nano degassing agent. Adjust the speed to 1000-1200 r / min and mix at a temperature of 30-35℃ for 6-8 minutes to obtain a uniform premix.

[0050] S2. Melt extrusion: The premixed material obtained in step S1 is fed into a twin-screw extruder. Gradient temperature control is used, with the following temperatures in each section: feeding section 85-90℃, compression section 95-100℃, melting section 105-110℃, and homogenization section 100-105℃. The screw speed is 180-220 r / min. After melting, shearing, and mixing, the material is extruded to obtain strip-shaped material. The material residence time is controlled to be 3-5 minutes during the extrusion process to ensure that the material is fully melted and does not solidify prematurely.

[0051] S3. Cooling and crushing: The strip material obtained in step S2 is fed into a closed-loop cooling conveyor and cooled in stages. First, it is cooled by spraying with 25-30℃ cooling water for 3 minutes, and then cooled to room temperature by blowing with 15-20℃ cold air. After cooling, it is crushed into uniform granular material with a particle size of 2-5mm by a toothed roller crusher.

[0052] S4 Grinding and sieving: The particulate material obtained in step S3 is fed into a classifying airflow pulverizer for grinding, and finally the thermosetting polyester powder coating for guardrail with uniform particle size distribution is obtained.

[0053] Furthermore, in step S4, the grinding pressure is controlled at 0.6-0.8 MPa. After grinding, the material is first screened through a 120-mesh coarse sieve to remove large particles, and then screened through a 160-mesh fine sieve to collect the undersize material. The oversize material is returned to the airflow pulverizer via a screw conveyor for re-grinding, forming a closed-loop production process.

[0054] Example 1

[0055] A thermosetting polyester powder coating for guardrails, comprising the following components by weight: 48 parts modified hydroxyl-type saturated polyester resin, 6 parts modified curing agent, 28 parts composite pigments and fillers, 1.5 parts fluorinated acrylate copolymer leveling agent, 0.8 parts high-efficiency anti-yellowing agent, 0.8 parts modified adhesion promoter, and 0.5 parts nano degassing agent;

[0056] The modified hydroxyl-type saturated polyester resin has a hydroxyl value of 30 mgKOH / g, an acid value of 4 mgKOH / g, a glass transition temperature of 55℃, and an epoxy group grafting amount of 2wt%. The modified curing agent is a mixture of TGIC and imidazole derivatives in a weight ratio of 10:1.

[0057] The composite pigment and filler are composed of modified titanium dioxide (modified with silane coupling agent, the amount of modifier added is 1% of the weight of titanium dioxide) and composite filler in a weight ratio of 1:3; the composite filler is composed of barium sulfate, talc powder and nano fluorescent carbon fiber in a weight ratio of 5:2:1, with a particle size of 1500 mesh and a surface coated with stearic acid; the nano fluorescent carbon fiber has a diameter of 50nm and a length of 5μm, and is modified with silane coupling agent (the amount of modifier added is 2%).

[0058] The high-efficiency anti-yellowing agent is a mixture of hindered phenolic antioxidant, ultraviolet absorber and hindered amine light stabilizer in a weight ratio of 2:1:1; the modified adhesion promoter is a mixture of epoxy silane coupling agent and titanate coupling agent in a weight ratio of 3:1; the nano degassing agent is a mixture of nano-sized benzoin and nano-silica in a weight ratio of 5:1.

[0059] The preparation process is as follows:

[0060] S1. Premixing: Weigh each component according to the weight parts. First, put the modified hydroxyl-type saturated polyester resin and the modified curing agent into a high-speed mixer and mix at a low speed of 400 r / min for 2 min. Then add the remaining components, adjust the speed to 1000 r / min and the temperature to 30℃, and mix for 6 min to obtain the premix.

[0061] S2. Melt extrusion: The premix is ​​fed into a twin-screw extruder with gradient temperature control: 85°C in the feeding section, 95°C in the compression section, 105°C in the melting section, and 100°C in the homogenization section. The screw speed is 180 r / min, and the material residence time is 3 min. Strip-shaped material is extruded.

[0062] S3. Cooling and crushing: The strip material is fed into a closed-loop cooling conveyor, first cooled by 25°C cooling water spray for 3 minutes, then blew with 15°C cold air to room temperature, and then crushed into 2-5mm particles by a toothed roller crusher.

[0063] S4. Grinding and sieving: The particles are fed into a classifying airflow pulverizer with a grinding pressure of 0.6 MPa. After grinding, the particles pass through a 120-mesh coarse sieve and a 160-mesh fine sieve. The material passing through the sieve is the finished product, while the material passing through the sieve is returned for re-grinding.

[0064] Tests showed that after curing at 180℃ for 20 minutes, the paint film had a pencil hardness of 2H, an adhesion grade of 1, a salt spray resistance of 1000h, an artificial aging resistance of 800h, a gloss (60°) of 30 gloss units, and a significant nighttime fluorescent warning effect.

[0065] Example 2

[0066] A thermosetting polyester powder coating for guardrails, comprising the following components by weight: 52 parts modified hydroxyl-type saturated polyester resin, 7 parts modified curing agent, 30 parts composite pigments and fillers, 2 parts fluorinated acrylate copolymer leveling agent, 1.2 parts high-efficiency anti-yellowing agent, 1.2 parts modified adhesion promoter, and 0.6 parts nano degassing agent;

[0067] The modified hydroxyl-type saturated polyester resin has a hydroxyl value of 35 mgKOH / g, an acid value of 3 mgKOH / g, a glass transition temperature of 60℃, and an epoxy group grafting amount of 3.5 wt%. The modified curing agent is a mixture of TGIC and imidazole derivatives in a weight ratio of 10:1.

[0068] The composite pigment and filler are composed of modified iron oxide red (modified with silane coupling agent, the modifier being added at 2% of the weight of iron oxide red) and composite filler in a weight ratio of 1:3; the composite filler is composed of barium sulfate, talc powder, and nano-fluorescent carbon fiber in a weight ratio of 5:2:1, with a particle size of 1800 mesh and a surface treated with stearic acid; the nano-fluorescent carbon fiber has a diameter of 80 nm and a length of 8 μm, and is modified with silane coupling agent (modifier being added at 3%).

[0069] The high-efficiency anti-yellowing agent, modified adhesion promoter, and nano degassing agent are the same as in Example 1.

[0070] The preparation process is as follows:

[0071] S1. Premixing: Weigh each component according to the weight parts. First, put the modified hydroxyl-type saturated polyester resin and the modified curing agent into a high-speed mixer and mix at a low speed of 400 r / min for 2 min. Then add the remaining components, adjust the speed to 1100 r / min and the temperature to 32℃, and mix for 7 min to obtain the premix.

[0072] S2. Melt extrusion: The premix is ​​fed into a twin-screw extruder with gradient temperature control: 88°C in the feeding section, 98°C in the compression section, 108°C in the melting section, and 102°C in the homogenization section. The screw speed is 200 r / min, and the material residence time is 4 min. Strip-shaped material is obtained by extrusion.

[0073] S3. Cooling and crushing: The strip material is fed into a closed-loop cooling conveyor, first sprayed with 28°C cooling water for 3 minutes, then blown with 18°C ​​cold air to room temperature, and then crushed into 2-5mm particles by a toothed roller crusher.

[0074] S4. Grinding and sieving: The particles are fed into a classifying airflow pulverizer with a grinding pressure of 0.7MPa. After grinding, the particles pass through a 120-mesh coarse sieve and a 160-mesh fine sieve. The material that passes through the sieve is the finished product, and the material that passes through the sieve is returned for re-grinding.

[0075] Tests showed that after curing at 180℃ for 20 minutes, the paint film had a pencil hardness of 3H, an adhesion grade of 0, a salt spray resistance of 1200h, an artificial aging resistance of 900h, a gloss (60°) of 45 gloss units, and excellent nighttime fluorescent warning effect.

[0076] Example 2

[0077] A thermosetting polyester powder coating for guardrails, comprising the following components by weight: 52 parts modified hydroxyl-type saturated polyester resin, 7 parts modified curing agent, 30 parts composite pigments and fillers, 2 parts fluorinated acrylate copolymer leveling agent, 1.2 parts high-efficiency anti-yellowing agent, 1.2 parts modified adhesion promoter, and 0.6 parts nano degassing agent;

[0078] The modified hydroxyl-type saturated polyester resin has a hydroxyl value of 35 mgKOH / g, an acid value of 3 mgKOH / g, a glass transition temperature of 60℃, and an epoxy group grafting amount of 3.5 wt%. The modified curing agent is a mixture of TGIC and imidazole derivatives in a weight ratio of 10:1.

[0079] The composite pigment and filler are composed of modified iron oxide red (modified with silane coupling agent, the modifier being added at 2% of the weight of iron oxide red) and composite filler in a weight ratio of 1:3; the composite filler is composed of barium sulfate, talc powder, and nano-fluorescent carbon fiber in a weight ratio of 5:2:1, with a particle size of 1800 mesh and a surface treated with stearic acid; the nano-fluorescent carbon fiber has a diameter of 80 nm and a length of 8 μm, and is modified with silane coupling agent (modifier being added at 3%).

[0080] The high-efficiency anti-yellowing agent, modified adhesion promoter, and nano degassing agent are the same as in Example 1.

[0081] The preparation process is as follows:

[0082] S1. Premixing: Weigh each component according to the weight parts. First, put the modified hydroxyl-type saturated polyester resin and the modified curing agent into a high-speed mixer and mix at a low speed of 400 r / min for 2 min. Then add the remaining components, adjust the speed to 1100 r / min and the temperature to 32℃, and mix for 7 min to obtain the premix.

[0083] S2. Melt extrusion: The premix is ​​fed into a twin-screw extruder with gradient temperature control: 88°C in the feeding section, 98°C in the compression section, 108°C in the melting section, and 102°C in the homogenization section. The screw speed is 200 r / min, and the material residence time is 4 min. Strip-shaped material is obtained by extrusion.

[0084] S3. Cooling and crushing: The strip material is fed into a closed-loop cooling conveyor, first sprayed with 28°C cooling water for 3 minutes, then blown with 18°C ​​cold air to room temperature, and then crushed into 2-5mm particles by a toothed roller crusher.

[0085] S4. Grinding and sieving: The particles are fed into a classifying airflow pulverizer with a grinding pressure of 0.7MPa. After grinding, the particles pass through a 120-mesh coarse sieve and a 160-mesh fine sieve. The material that passes through the sieve is the finished product, and the material that passes through the sieve is returned for re-grinding.

[0086] Tests showed that after curing at 180℃ for 20 minutes, the paint film had a pencil hardness of 3H, an adhesion grade of 0, a salt spray resistance of 1200h, an artificial aging resistance of 900h, a gloss (60°) of 45 gloss units, and excellent nighttime fluorescent warning effect.

[0087] Example 3

[0088] A thermosetting polyester powder coating for guardrails, comprising the following components by weight: 55 parts modified hydroxyl-type saturated polyester resin, 8 parts modified curing agent, 32 parts composite pigments and fillers, 2.5 parts fluorinated acrylate copolymer leveling agent, 1.5 parts high-efficiency anti-yellowing agent, 1.5 parts modified adhesion promoter, and 0.8 parts nano degassing agent;

[0089] The modified hydroxyl-type saturated polyester resin has a hydroxyl value of 40 mgKOH / g, an acid value of 5 mgKOH / g, a glass transition temperature of 65℃, and an epoxy group grafting amount of 5 wt%. The modified curing agent is a mixture of TGIC and imidazole derivatives in a weight ratio of 10:1.

[0090] The composite pigment and filler are composed of modified phthalocyanine blue (modified with silane coupling agent, the modifier being added at 3% of the weight of phthalocyanine blue) and composite filler in a weight ratio of 1:3; the composite filler is composed of barium sulfate, talc powder, and nano-fluorescent carbon fiber in a weight ratio of 5:2:1, with a particle size of 2000 mesh and a surface treated with stearic acid; the nano-fluorescent carbon fiber has a diameter of 100 nm and a length of 10 μm, and is modified with silane coupling agent (modifier being added at 4%).

[0091] The high-efficiency anti-yellowing agent, modified adhesion promoter, and nano degassing agent are the same as in Example 1.

[0092] The preparation process is as follows:

[0093] S1. Premixing: Weigh each component according to the weight proportions. First, put the modified hydroxyl-type saturated polyester resin and the modified curing agent into a high-speed mixer and mix at a low speed of 400 r / min for 2 min. Then add the remaining components, adjust the speed to 1200 r / min and the temperature to 35℃, and mix for 8 min to obtain the premix.

[0094] S2. Melt extrusion: The premix is ​​fed into a twin-screw extruder with gradient temperature control: 90°C in the feeding section, 100°C in the compression section, 110°C in the melting section, and 105°C in the homogenization section. The screw speed is 220 r / min, and the material residence time is 5 min. Strip-shaped material is extruded.

[0095] S3. Cooling and crushing: The strip material is fed into a closed-loop cooling conveyor, first sprayed with 30°C cooling water for 3 minutes, then blown with 20°C cold air to room temperature, and then crushed into 2-5mm particles by a toothed roller crusher.

[0096] S4. Grinding and sieving: The particles are fed into a classifying airflow pulverizer with a grinding pressure of 0.8MPa. After grinding, the particles pass through a 120-mesh coarse sieve and a 160-mesh fine sieve. The material that passes through the sieve is the finished product, and the material that passes through the sieve is returned for re-grinding.

[0097] Tests showed that after curing at 180℃ for 20 minutes, the paint film had a pencil hardness of 3H, an adhesion grade of 0, a salt spray resistance of 1300h, an artificial aging resistance of 1000h, a gloss (60°) of 60 gloss units, and a stable nighttime fluorescent warning effect.

[0098] Comparative Example 1

[0099] Conventional hydroxyl-type saturated polyester resin (unmodified) was used, and the remaining components and preparation process were the same as in Example 2. Tests showed that the paint film had a pencil hardness of 1H, an adhesion grade of 2, salt spray resistance of 600 hours, artificial aging resistance of 500 hours, and no fluorescent warning function.

[0100] Comparative Example 2

[0101] Nano-fluorescent carbon fibers were not added to the composite filler; the remaining components and preparation process were the same as in Example 2. Testing showed that the paint film had a pencil hardness of 2H, an adhesion grade of 1, salt spray resistance of 800 hours, artificial aging resistance of 700 hours, and no fluorescent warning function.

[0102] Comparative Example 3

[0103] The high-efficiency anti-yellowing agent is only a hindered phenolic antioxidant; the remaining components and preparation process are the same as in Example 2. Testing showed that the paint film had a pencil hardness of 3H, an adhesion grade of 0, salt spray resistance of 900 hours, artificial aging resistance of 600 hours, and good fluorescent warning effect, but poor aging resistance.

[0104] The test methods and standards for each performance indicator are as follows:

[0105] 1. Pencil hardness: The test was conducted according to GB / T6739-2006 "Determination of paint film hardness by pencil method for paints and varnishes". A Zhonghua brand 101 drawing pencil was used to scratch the paint film at a uniform speed under a load of 750g. The results were observed to see if scratches appeared on the paint film. The highest pencil hardness grade that did not show scratches was taken as the test result.

[0106] 2. Adhesion rating: The test shall be conducted in accordance with GB / T9286-1998 "Cross-cut test for paint and varnish film". A cross-cut tester shall be used to cut 10×10 1mm² squares on the paint film surface. After removing the debris from the cut area, pressure-sensitive adhesive tape shall be applied and quickly peeled off. The adhesion rating shall be determined according to the area of ​​paint film peeling off within the squares. Rating 0 is no peeling, and Rating 1 is peeling area ≤5%.

[0107] 3. Salt spray resistance: The test was conducted in accordance with GB / T1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes". The test conditions were 5% NaCl aqueous solution, temperature 35℃, and continuous spraying. The blistering, rusting, and peeling of the paint film were observed during the test. The longest time without obvious corrosion was taken as the result of salt spray resistance.

[0108] 4. Artificial aging resistance: Tested according to GB / T1865-2009 "Artificial climate aging and artificial radiation exposure of paints and varnishes", using a xenon lamp aging test chamber with an irradiance of 0.51W / (m²·nm) (340nm), a blackboard temperature of 65℃, and a relative humidity of 50%. Water was sprayed periodically, and the yellowing, chalking, cracking and other aging phenomena of the paint film were observed. The longest time without obvious aging phenomena was taken as the result of artificial aging resistance.

[0109] 5. Fluorescent warning effect: The test was conducted in accordance with the relevant requirements for reflective / fluorescent performance in GB / T24725-2009 "Highway Traffic Sign Boards and Supports". In a dark room environment, the sample was pre-irradiated with a D65 standard light source for 1 hour. The fluorescence brightness value of the sample was measured at a 0° observation angle and a 5° incident angle using a fluorescence luminance meter. A brightness value ≥10 cd / m² indicates a significant fluorescent warning effect, and a brightness value ≥15 cd / m² indicates an excellent fluorescent warning effect.

[0110] As can be seen from the test results of the examples and comparative examples, the present invention significantly improves the overall performance of the coating through the synergistic optimization of each component and a specific preparation process. It has excellent mechanical properties, weather resistance and corrosion resistance, and nighttime fluorescent warning function, which is superior to existing conventional coatings.

[0111] The above embodiments are provided for those skilled in the art to implement or use the present invention. Those skilled in the art can make various modifications or changes to the above embodiments without departing from the inventive concept of the present invention. Therefore, the protection scope of the present invention is not limited to the above embodiments, but should be the maximum scope that conforms to the innovative features mentioned in the claims.

Claims

1. A thermosetting polyester powder coating for guardrails, characterized in that, By weight, it consists of the following components: 48-55 parts thermosetting polyester resin, 6-8 parts modified curing agent, 28-32 parts composite pigments and fillers, 1.5-2.5 parts functional leveling agent, 0.8-1.5 parts high-efficiency anti-yellowing agent, 0.8-1.5 parts modified adhesion promoter, and 0.5-0.8 parts nano degassing agent; The thermosetting polyester resin is a modified hydroxyl-type saturated polyester resin with a hydroxyl value of 30-40 mgKOH / g, an acid value of ≤5 mgKOH / g, and a glass transition temperature of 55-65℃. The modified hydroxyl-type saturated polyester resin is grafted and modified by introducing 2-5 wt% epoxy groups. The modified curing agent is a compound of triglycidyl isocyanurate and epoxy curing accelerator in a weight ratio of (9-11):1, and the epoxy curing accelerator is an imidazole derivative.

2. The thermosetting polyester powder coating for guardrails according to claim 1, characterized in that, The composite pigment and filler are composed of modified pigments and composite fillers in a weight ratio of 1:(2-5); The modified pigment is titanium dioxide, iron oxide red, or phthalocyanine blue that has been surface-modified with a silane coupling agent, and the amount of silane coupling agent added is 1-3% of the pigment weight; The composite filler is composed of barium sulfate, talc powder and nano fluorescent carbon fiber in a weight ratio of (4-6):(1-3):

1. The composite filler is pulverized by airflow to a particle size of 1500-2000 mesh and the surface is coated with stearic acid.

3. The thermosetting polyester powder coating for guardrails according to claim 2, characterized in that, The nano-fluorescent carbon fiber has a diameter of 50-100 nm and a length of 5-10 μm, and is surface modified with a silane coupling agent, with the amount of silane coupling agent added being 2-4% of the weight of the nano-fluorescent carbon fiber.

4. The thermosetting polyester powder coating for guardrails according to claim 3, characterized in that, The modification process is as follows: nano-fluorescent carbon fibers are added to an ethanol aqueous solution and ultrasonically dispersed for 30-40 minutes to obtain a dispersion. Then, a silane coupling agent is added and the mixture is stirred and reacted at 60-70℃ for 2-3 hours. After the reaction is completed, the mixture is centrifuged, washed, and vacuum dried at 80-100℃ for 4-6 hours to obtain modified nano-fluorescent carbon fibers.

5. The thermosetting polyester powder coating for guardrails according to claim 1, characterized in that, The functional leveling agent is a fluorinated acrylate copolymer leveling agent.

6. The thermosetting polyester powder coating for guardrails according to claim 1, characterized in that, The highly effective anti-yellowing agent is a compound of hindered phenolic antioxidants, ultraviolet absorbers and hindered amine light stabilizers.

7. The thermosetting polyester powder coating for guardrails according to claim 1, characterized in that, The modified adhesion promoter is a compound of epoxy silane coupling agent and titanate coupling agent.

8. The thermosetting polyester powder coating for guardrails according to claim 1, characterized in that, The nano-degassing agent is a compound of nano-sized benzoin and nano-sized silica.

9. The preparation process of the thermosetting polyester powder coating for guardrails according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Premixing: Thermosetting polyester resin and modified curing agent are put into a high-speed mixer and mixed at low speed. Then, composite pigments and fillers, functional leveling agent, high-efficiency anti-yellowing agent, modified adhesion promoter and nano degassing agent are added. The speed is adjusted to 1000-1200 r / min and mixed at 30-35℃ for 6-8 min to obtain a uniform premix. S2. Melt extrusion: The premixed material obtained in step S1 is fed into a twin-screw extruder. Gradient temperature control mode is adopted, with the following temperatures in sequence: feeding section 85-90℃, compression section 95-100℃, melting section 105-110℃, homogenization section 100-105℃, and screw speed 180-220 r / min. After melting, shearing, and mixing, the material is extruded to obtain strip-shaped material. S3. Cooling and crushing: The strip material obtained in step S2 is fed into a closed-loop cooling conveyor and cooled in stages. First, it is cooled by spraying with cooling water at 25-30℃, and then cooled to room temperature by blowing with cold air at 15-20℃. After cooling, it is crushed into uniform granular material with a particle size of 2-5mm by a toothed roller crusher. S4 Grinding and sieving: The particulate material obtained in step S3 is fed into a classifying airflow pulverizer for grinding, and finally the thermosetting polyester powder coating for guardrail is obtained.

10. The preparation process of the thermosetting polyester powder coating for guardrails according to claim 9, characterized in that, In step S4, the grinding pressure is controlled at 0.6-0.8 MPa. After grinding, the material is first screened through a 120-mesh coarse sieve to remove large particles, and then screened through a 160-mesh fine sieve to collect the undersize material. The oversize material is returned to the airflow pulverizer via a screw conveyor for re-grinding, forming a closed-loop production process.