A polyester resin for textured powder coating and its preparation method

Abstract

This invention relates to the field of polymer materials technology and discloses a polyester resin for textured powder coatings and its preparation method. The polyester resin for textured powder coatings comprises the following raw materials: soft-segment polyurethane, hard-segment polyester resin, and a silane coupling agent; by mass percentage, the soft-segment polyurethane comprises the following raw materials: 5-20% polyisocyanate and 80-95% oligomeric polyol; the hard-segment polyester resin comprises the following raw materials: 30-45% aliphatic polyol and 60-75% polyacid. The polyester resin for textured powder coatings provided by this invention combines a soft-segment polyurethane structure containing oligomeric polyols with a hard-segment polyester resin structure. The polyester resin has suitable acid value, viscosity, and glass transition temperature, which is beneficial for improving the performance of powder coatings when used as a raw material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a polyester resin for sand-textured powder coatings and its preparation method. Background Technology

[0002] Aluminum profiles are widely used in the construction industry due to their low density, light weight, and excellent mechanical properties. However, untreated aluminum profiles have a monotonous appearance and are prone to corrosion in humid atmospheres, making it difficult to meet the requirements of high decorative appeal and strong weather resistance in building materials. To improve the decorative effect, enhance corrosion resistance, and extend service life, aluminum profiles generally undergo surface treatment. Surface treatment technologies can be divided into three main categories: anodizing, anodizing-electrophoresis, and organic coating. Among these, organic coating includes powder coating and fluorocarbon coating. Powder coating accounts for a large proportion of aluminum profile surface treatments because it is durable, has good resistance to chemical media, and is simple to produce.

[0003] Sand-textured powder coatings scatter light, providing a comfortable visual experience. They also offer advantages such as high film hardness, a smooth feel, scratch resistance, and aging resistance, making them widely used in the architectural aluminum profile industry. Since aluminum profile products are mostly used in outdoor environments, powder coatings in this field require high-performance polyester resins, balancing economic efficiency, weather resistance, and water resistance. Aluminum profiles are easily corroded in humid atmospheres; therefore, the water resistance of powder coatings is the most important performance characteristic for users.

[0004] Currently, the water resistance test for powder coatings typically uses the pressure cooker boiling test method in GB / T 5237.4-2004. The water resistance of the coating is judged by the gloss retention, color difference, and water spot coverage before and after boiling. This is generally referred to as the boiling resistance test. Polyester resins, due to the large number of ester bonds in their structure, are prone to hydrolysis under water, leading to ester bond breakage, decreased coating density, and affecting coating performance. Currently, the color difference ΔE of textured coatings after boiling is generally around 2.0. Discoloration is visually noticeable after boiling, indicating a decline in overall coating performance. Simultaneously, the reduced density of the coating after boiling makes it more susceptible to absorbing and retaining moisture, causing "water spots" on the coating surface, severely affecting the coating's appearance.

[0005] CN 108264828 A discloses a method for preparing a polyester resin for aluminum profile powder coating. This formulation uses special monomers such as p-phenylalanine and silicone oil to improve the coating's water resistance. However, the powder coating prepared by this resin is a leveling type, and aluminum profiles coated with this leveling powder are easily scratched and discolored during handling and use. Therefore, leveling powder for aluminum profiles is increasingly becoming a non-mainstream product. CN 103483988 A discloses a water-resistant sand-textured powder coating suitable for applying to the edges and corners of aluminum profiles and its preparation method. This method improves the water resistance of the sand-textured powder coating on aluminum profiles by adding fumed oxide fillers, such as alumina and silica, during the powder coating preparation process. However, this patent focuses more on the preparation of the powder coating and lacks research and introduction on the polyester resin. CN 114410196 A discloses a water-resistant powder coating, its preparation method, and its application. By adding water-resistant fillers and water-resistant additives to the powder coating, the requirements for water resistance and scratch resistance are met, enabling the wheel hub to adapt to high-temperature and rainy environments. However, the polyester resin is not studied. CN117229485 A discloses a copolymer resin for anti-cratering, anti-frosting, and water-resistant powder coating and its preparation method. An acrylic resin is melt-added to a polyester resin to obtain a copolymer resin. The addition of acrylic resin improves the coating's water resistance and anti-frosting properties, but it does not involve modification of the polyester resin structure. Furthermore, the addition of acrylic resin may affect the mechanical properties of the coating. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide a polyester resin for textured powder coatings; a second objective is to provide a method for preparing such a polyester resin for textured powder coatings; a third objective is to provide a textured powder coating; a fourth objective is to provide a coating layer; and a fifth objective is to provide a polyester resin for textured powder coatings, or the application of textured powder coatings.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A first aspect of the present invention provides a polyester resin for textured powder coatings, comprising the following raw materials: soft-segment polyurethane, hard-segment polyester resin, and silane coupling agent; the soft-segment polyurethane comprises, by mass percentage: 5-20% polyisocyanate and 80-95% oligomeric polyol; the hard-segment polyester resin comprises: 30-45% aliphatic polyol and 60-75% polyacid.

[0009] Preferably, the soft segment polyurethane comprises the following raw materials by mass percentage: 5-15% polyisocyanate and 85-95% oligomeric polyol.

[0010] Preferably, the hard-segment polyester resin comprises the following raw materials by mass percentage: 35-40% aliphatic polyol and 60-65% polyacid.

[0011] Preferably, the acid value of the hard-chain polyester resin is 5-25 mgKOH / g; more preferably, the acid value of the hard-chain polyester resin is 7-20 mgKOH / g; and even more preferably, the acid value of the hard-chain polyester resin is 7-5 mgKOH / g.

[0012] Preferably, the viscosity of the hard-chain polyester resin at 200°C is 300-3000 mPa·s; more preferably, the viscosity of the hard-chain polyester resin at 200°C is 500-2500 mPa·s; even more preferably, the viscosity of the hard-chain polyester resin at 200°C is 500-2000 mPa·s.

[0013] Preferably, the polyisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate, and terephthalic diisocyanate.

[0014] Preferably, the molecular weight of the oligomeric polyol is 300-5000 g / mol; more preferably, the molecular weight of the oligomeric polyol is 500-3000 g / mol.

[0015] Preferably, the oligomeric polyol includes at least one of polyester polyol, polyether polyol, and polyolefin polyol.

[0016] Preferably, the polyester polyol includes at least one of polyethylene adipate (PEA), polycarbonate diol (PCDL), and polycaprolactone diol.

[0017] Preferably, the polyether polyol includes at least one of polytetrahydrofuran ether diol (PTMG), polyoxypropylene diol, and polymer polyol.

[0018] Preferably, the polyolefin polyol includes at least one of hydroxyl-terminated polybutadiene styrene (HTBS), hydroxyl-terminated polybutadiene acrylonitrile, and hydroxyl-terminated polybutadiene.

[0019] Preferably, the aliphatic polyol includes at least one of neopentyl glycol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butanediol, hexanediol, diethylene glycol, 1,4-cyclohexanediol, 2-methyl-2,4-pentanediol, ethylbutyric acid, trimethylolpropane, and pentaerythritol.

[0020] Preferably, the polybasic acid includes at least one selected from terephthalic acid, isophthalic acid, trimellitic anhydride, succinic acid, adipic acid, and 1,4-cyclohexanediol.

[0021] Preferably, the silane coupling agent includes at least one of bis[3-(triethoxysilane)propyl]amine and N-[3-(trimethoxysilyl)propyl]ethylenediamine.

[0022] Preferably, the polyester resin for the sand texture powder coating further includes the following raw materials: acid hydrolysate, curing accelerator, and antioxidant.

[0023] Preferably, the acid hydrolysate includes at least one selected from terephthalic acid, isophthalic acid, trimellitic anhydride, succinic acid, adipic acid, and 1,4-cyclohexanediol.

[0024] Preferably, the curing accelerator includes at least one of triphenylethylphosphine bromide and benzyltributylammonium chloride.

[0025] Preferably, the antioxidant includes at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0026] Preferably, the hindered phenolic antioxidant includes at least one of 2,6-di-tert-butyl-p-methylphenol (BHT), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (antioxidant 1076), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine (antioxidant 1098), and triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (antioxidant 245); more preferably, the hindered phenolic antioxidant is antioxidant 1010.

[0027] Preferably, the phosphite antioxidant includes at least one of diphenyl isooctyl phosphite (ODPP), tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168), bisphenol A phosphite, and triphenyl phosphite (TPP); more preferably, the phosphite antioxidant is antioxidant 168.

[0028] Preferably, the mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 1:(0.5-1.5); more preferably, the mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 1:(0.8-1.2).

[0029] Preferably, by mass percentage, the polyester resin for the sand texture powder coating comprises the following raw materials: 1-10% soft segment polyurethane, 80-90% hard segment polyester resin, 0.1-2% silane coupling agent, 1-10% acid hydrolysate, 0.01-0.5% curing accelerator, and 0.1-2% antioxidant; more preferably, the polyester resin for the sand texture powder coating comprises the following raw materials: 4-10% soft segment polyurethane, 85-90% hard segment polyester resin, 0.1-1% silane coupling agent, 3-8% acid hydrolysate, 0.01-0.1% curing accelerator, and 0.1-1% antioxidant.

[0030] Preferably, the acid value of the polyester resin used in the sand texture powder coating is 25-40 mg KOH / g; more preferably, the acid value of the polyester resin used in the sand texture powder coating is 30-40 mg KOH / g.

[0031] Preferably, the polyester resin for the sand texture powder coating has a viscosity of 3000-11000 mPa·s at 200°C; more preferably, the polyester resin for the sand texture powder coating has a viscosity of 5000-11000 mPa·s at 200°C; and even more preferably, the polyester resin for the sand texture powder coating has a viscosity of 7000-10000 mPa·s at 200°C.

[0032] A second aspect of the present invention provides a method for preparing the polyester resin for textured powder coatings as described in the first aspect of the present invention, comprising the following steps:

[0033] S1. Polyisocyanate and oligomeric polyol are polymerized to obtain soft segment polyurethane, and aliphatic polyol and polyester are condensed to obtain hard segment polyester resin.

[0034] S2. The soft segment polyurethane and hard segment polyester resin are mixed and reacted, an acid hydrolysate is added, and a vacuum polycondensation reaction is carried out. A curing accelerator, an antioxidant and a silane coupling agent are added to obtain the polyester resin for sand texture powder coating.

[0035] Preferably, in step S1, the process of preparing soft-segment polyurethane and hard-segment polyester resin further includes the use of catalysts respectively.

[0036] Preferably, the catalyst is independently selected from at least one of monobutyltin oxide, dibutyltin dilaurate, monobutyltin triisooctanoate, ethyl titanate, butyl titanate, polytitanate, and titanate chelates.

[0037] Preferably, the polyisocyanate is polymerized with oligomeric polyol to prepare soft segment polyurethane, and the amount of catalyst used is 0.1-0.3% of the total mass of the materials; more preferably, the amount of catalyst used is 0.1-0.2% of the total mass of the materials.

[0038] Preferably, the aliphatic polyol is polycondensed with a polyester to prepare a hard-segment polyester resin, and the amount of catalyst used is 0.05-0.1% of the total mass of the materials; more preferably, the amount of catalyst used is 0.06-0.08% of the total mass of the materials.

[0039] Preferably, in step S1, the polymerization reaction temperature of the soft segment polyurethane is 25-120°C; more preferably, the polymerization reaction temperature of the soft segment polyurethane is 50-110°C; and even more preferably, the polymerization reaction temperature of the soft segment polyurethane is 70-100°C.

[0040] Preferably, in step S1, the polymerization reaction time of the soft segment polyurethane is 0.5-3h; more preferably, the polymerization reaction time of the soft segment polyurethane is 0.5-2h.

[0041] Preferably, in step S1, the esterification polycondensation reaction temperature of the hard segment polyester resin is 25-250°C; more preferably, the esterification polycondensation reaction temperature of the hard segment polyester resin is 130-245°C; and even more preferably, the esterification polycondensation reaction temperature of the hard segment polyester resin is 180-245°C.

[0042] Preferably, in step S1, the esterification polycondensation reaction time of the hard segment polyester resin is 5-16 hours; more preferably, the esterification polycondensation reaction time of the hard segment polyester resin is 10-16 hours.

[0043] Preferably, in step S2, the mixing reaction of the soft segment polyurethane and the hard segment polyester resin further includes the use of a catalyst.

[0044] Preferably, the catalyst comprises at least one of monobutyltin oxide, dibutyltin dilaurate, monobutyltin triisooctanoate, ethyl titanate, butyl titanate, polytitanate, and titanate chelates.

[0045] Preferably, in step S2, the mixing reaction temperature of the soft segment polyurethane and the hard segment polyester resin is 150-200℃; more preferably, the mixing reaction temperature of the soft segment polyurethane and the hard segment polyester resin is 165-200℃.

[0046] Preferably, in step S2, the mixing reaction time of the soft segment polyurethane and the hard segment polyester resin is 0.5-3h; more preferably, the mixing reaction time of the soft segment polyurethane and the hard segment polyester resin is 0.5-2h.

[0047] Preferably, in step S2, the reaction temperature after adding the acid hydrolysate is 180-240℃; more preferably, the reaction temperature after adding the acid hydrolysate is 200-235℃.

[0048] Preferably, in step S2, the reaction time after adding the acid hydrolysate is 1-5 hours; more preferably, the reaction time after adding the acid hydrolysate is 2-4 hours.

[0049] Preferably, in step S2, the pressure of the vacuum polycondensation reaction is 0.08-0.1 MPa; more preferably, the pressure of the vacuum polycondensation reaction is 0.09-0.1 MPa.

[0050] Preferably, in step S2, the vacuum polycondensation reaction takes 0.5-2 hours; more preferably, the vacuum polycondensation reaction takes 1-2 hours.

[0051] A third aspect of the present invention provides a textured powder coating comprising the polyester resin for textured powder coatings described in the first aspect of the present invention; wherein the polyester resin for textured powder coatings comprises 50-60% by mass.

[0052] Preferably, the polyester resin used in the textured powder coating has a mass percentage of 55-60%.

[0053] Preferably, by mass percentage, the sand-textured powder coating further comprises the following raw materials: 2-8% curing agent, 35-45% inorganic filler, 0.1-1% sand-texturing agent, 0.1-1% bentonite, and 0.3-2% carbon black; more preferably, the sand-textured powder coating further comprises the following raw materials: 2-6% curing agent, 36-42% inorganic filler, 0.1-0.5% sand-texturing agent, 0.1-0.5% bentonite, and 0.3-1% carbon black.

[0054] Preferably, the curing agent includes at least one of triglycidyl isocyanate (TGIC), triglycidyl trimellitate (PT910), triglycidyl pyromellitic acid (Aplus101), and β-hydroxyalkylamide (HAA); more preferably, the curing agent is triglycidyl isocyanate (TGIC).

[0055] Preferably, the inorganic filler comprises barium sulfate.

[0056] Preferably, the sand texture powder coating is prepared by a method comprising the following steps: mixing the raw materials, pressing them into sheets using a twin-screw extruder, freezing and crushing them, and sieving them to obtain the sand texture powder coating.

[0057] A fourth aspect of the present invention provides a coating formed from a textured powder coating as described in the third aspect of the present invention.

[0058] Preferably, during the coating formation process, the curing temperature of the sand texture powder coating is 150-170℃; more preferably, the curing temperature of the sand texture powder coating is 155-165℃.

[0059] Preferably, during the coating formation process, the curing time of the sand texture powder coating is 5-20 minutes; more preferably, the curing time of the sand texture powder coating is 10-20 minutes.

[0060] Preferably, the coating has a 60° gloss of 7-10%; more preferably, the coating has a 60° gloss of 8-9%.

[0061] The fifth aspect of the present invention provides the application of the polyester resin for the sand texture powder coating described in the first aspect of the present invention, or the sand texture powder coating described in the third aspect of the present invention, in the surface treatment of aluminum profiles.

[0062] Compared with the prior art, the beneficial effects of the present invention are:

[0063] 1) The polyester resin for sand texture powder coating provided by the present invention combines a soft segment polyurethane structure containing oligomeric polyols with a hard segment polyester resin structure. The acid value is 25-40 mgKOH / g, the viscosity at 200℃ is 3000-11000 mPa·s, and the glass transition temperature is 65-75℃. The acid value, viscosity and glass transition temperature are suitable, which is beneficial to improving the performance of the coating when used as a raw material for the preparation of powder coating.

[0064] 2) The preparation method of polyester resin for sand texture powder coating provided by the present invention has simple steps and is suitable for industrial application.

[0065] 3) The sand-textured powder coating provided by this invention incorporates the polyester resin for sand-textured powder coatings provided by this invention. Under curing conditions of 160℃ / 15min, the sand-textured powder coating forms a black sand-textured coating with excellent water resistance and a sanding effect. After being boiled in high-pressure water at 120℃ for 2 hours, the coating retains a gloss rate of ≥94%, a color difference ΔE≤2, and virtually no water spots appear on the surface. The coating's 60° gloss is less than 9%, exhibiting low gloss and excellent mechanical properties. When applied to the surface treatment of aluminum profiles, the coating demonstrates good water resistance, is not easily corroded, is not easily scratched, and can maintain excellent performance for a long time without affecting the appearance. Detailed Implementation

[0066] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0067] Example 1

[0068] This embodiment provides a soft segment polyurethane, and the preparation steps are as follows:

[0069] 500g of polycarbonate diol (PCDL2000) was added to a four-necked flask. A stirrer and a vacuum distillation apparatus were set up on the flask. After the vacuum level of the four-necked flask was reduced to -0.99MPa, the oil bath temperature was adjusted to 120℃, and high-temperature desorption was performed for 1 hour. Subsequently, the four-necked flask was cooled to 70℃, and 65g of dicyclohexylmethane diisocyanate (HMDI) and 0.56g of dibutyltin dilaurate were added to the four-necked flask. Nitrogen gas was introduced into the four-necked flask. After HMDI dissolved, the temperature was raised to 85℃ and stirred thoroughly for 1.5 hours to obtain soft-segment polyurethane R1.

[0070] Example 2

[0071] This embodiment provides a soft segment polyurethane, and the preparation steps are as follows:

[0072] 500g of polyethylene adipate (PEA2000) was added to a four-necked flask. A stirrer and a vacuum distillation apparatus were set up on the flask. After the vacuum level of the four-necked flask was reduced to -0.99MPa, the oil bath temperature was adjusted to 120℃, and high-temperature distillation was performed for 1 hour. Subsequently, the four-necked flask was cooled to 70℃, and 65g of dicyclohexylmethane diisocyanate (HMDI) and 0.56g of dibutyltin dilaurate were added to the four-necked flask. Nitrogen gas was introduced into the four-necked flask. After HMDI dissolved, the temperature was raised to 85℃ and stirred thoroughly for 1.5 hours to obtain soft-segment polyurethane R2.

[0073] Example 3

[0074] This embodiment provides a soft segment polyurethane, and the preparation steps are as follows:

[0075] 500g of polytetrahydrofuran ether diol (PTMG2000) was added to a four-necked flask. A stirrer and a vacuum distillation apparatus were set up on the flask. After the vacuum level of the four-necked flask was reduced to -0.99MPa, the oil bath temperature was adjusted to 120℃, and high-temperature desorption was performed for 1 hour. Subsequently, the four-necked flask was cooled to 70℃, and 65g of dicyclohexylmethane diisocyanate (HMDI) and 0.56g of dibutyltin dilaurate were added to the four-necked flask. Nitrogen gas was introduced into the four-necked flask. After HMDI dissolved, the temperature was raised to 85℃ and stirred thoroughly for 1.5 hours to obtain soft-segment polyurethane R3.

[0076] Example 4

[0077] This embodiment provides a soft segment polyurethane, and the preparation steps are as follows:

[0078] 500g of hydroxyl-terminated polybutadiene styrene (HTBS2000) was added to a four-necked flask. A stirring device and a vacuum distillation apparatus were set up on the flask. After the vacuum level of the four-necked flask was reduced to -0.99MPa, the oil bath temperature was adjusted to 120℃, and high-temperature desorption was performed for 1 hour. Subsequently, the four-necked flask was cooled to 70℃, and 65g of dicyclohexylmethane diisocyanate (HMDI) and 0.56g of dibutyltin dilaurate were added to the four-necked flask. Nitrogen gas was introduced into the four-necked flask. After HMDI dissolved, the temperature was raised to 85℃ and stirred thoroughly for 1.5 hours to obtain soft-segment polyurethane R4.

[0079] Example 5

[0080] This embodiment provides a soft segment polyurethane, and the preparation steps are as follows:

[0081] 500g of polycarbonate diol (PCDL2000) was added to a four-necked flask. A stirrer and a vacuum distillation apparatus were then installed on the flask. After the vacuum level of the four-necked flask was reduced to -0.99MPa, the oil bath temperature was adjusted to 120℃, and high-temperature dehydration was carried out for 1 hour. Subsequently, the four-necked flask was cooled to 70℃, and 42g of hexamethylene diisocyanate (HDI) and 0.54g of dibutyltin dilaurate were added to the four-necked flask. Nitrogen gas was then introduced into the four-necked flask. After the HDI dissolved, the temperature was raised to 85℃, and the mixture was stirred thoroughly for 1.5 hours to obtain soft-segment polyurethane R5.

[0082] Example 6

[0083] This embodiment provides a hard-chain polyester resin, and the preparation steps are as follows:

[0084] 271g of neopentyl glycol, 62g of ethylene glycol, 16g of trimethylolpropane, 597g of terephthalic acid, and 0.8g of monobutyltin oxide were added to a four-necked flask. A stirring device, a distillation column, and a condenser column were set up on the four-necked flask. Under a nitrogen atmosphere, the temperature was increased to 240℃ at a programmed heating rate of 5℃ / h. After reaching the set temperature, the temperature was maintained for 4h. The resin sample was clear and transparent, with an acid value of 7.5mgKOH / g and a viscosity of 1200mPa·s, yielding hard-chain polyester resin H1.

[0085] Example 7

[0086] This embodiment provides a hard-chain polyester resin, and the preparation steps are as follows:

[0087] 290g neopentyl glycol, 62g ethylene glycol, 597g terephthalic acid, and 0.8g monobutyltin oxide were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 240℃ at a programmed rate of 5℃ / h. After reaching the set temperature, it was held for 4 hours. The resin sample was clear and transparent, with an acid value of 6.4 mg KOH / g and a viscosity of 900 mPa·s, yielding hard-chain polyester resin H2.

[0088] Example 8

[0089] This embodiment provides a polyester resin for sand-textured powder coatings. The raw materials and dosages are shown in Table 1.

[0090] Table 1. Raw materials and dosage of polyester resin used in the preparation of textured powder coating in Example 8.

[0091]

[0092] The preparation steps are as follows:

[0093] Soft-segment polyurethane R1 and hard-segment polyester resin H2 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for sand-textured powder coatings.

[0094] Example 9

[0095] This embodiment provides a polyester resin for sand-textured powder coatings. The raw materials and dosages are shown in Table 2.

[0096] Table 2 shows the raw materials and dosage of polyester resin used in the preparation of the sand texture powder coating in Example 9.

[0097]

[0098] The preparation steps are as follows:

[0099] Soft segment polyurethane R1 and hard segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the four-necked flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for textured powder coating.

[0100] Example 10

[0101] This embodiment provides a polyester resin for sand texture powder coating. The raw materials and dosages are shown in Table 3.

[0102] Table 3 shows the raw materials and dosage of polyester resin used in the preparation of the sand texture powder coating in Example 10.

[0103]

[0104] The preparation steps are as follows:

[0105] Soft segment polyurethane R2 and hard segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for textured powder coatings.

[0106] Example 11

[0107] This embodiment provides a polyester resin for sand texture powder coating. The raw materials and dosages are shown in Table 4.

[0108] Table 4 shows the raw materials and dosage of polyester resin used in the preparation of the sand texture powder coating in Example 11.

[0109]

[0110] The preparation steps are as follows:

[0111] Soft-segment polyurethane R3 and hard-segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for textured powder coatings.

[0112] Example 12

[0113] This embodiment provides a polyester resin for sand-textured powder coatings. The raw materials and dosages are shown in Table 5.

[0114] Table 5. Raw materials and dosage of polyester resin used in Example 12 for sand texture powder coating.

[0115]

[0116]

[0117] The preparation steps are as follows:

[0118] Soft-segment polyurethane R4 and hard-segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum was applied at -0.09 MPa for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for textured powder coatings.

[0119] Example 13

[0120] This embodiment provides a polyester resin for sand texture powder coating. The raw materials and dosages are shown in Table 6.

[0121] Table 6 shows the raw materials and dosage of polyester resin used in the preparation of the sand texture powder coating in Example 13.

[0122]

[0123] The preparation steps are as follows:

[0124] Soft-segment polyurethane R5 and hard-segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum was applied at -0.09 MPa for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin for textured powder coatings.

[0125] Comparative Example 1

[0126] This comparative example provides a polyester resin, and the raw materials and amounts used are shown in Table 7:

[0127] Table 7 shows the raw materials and dosages used in the preparation of polyester resin in Comparative Example 1.

[0128]

[0129] The preparation steps are as follows:

[0130] Soft-segment polyurethane R1 and hard-segment polyester resin H1 were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, a curing accelerator and an antioxidant were added, and the mixture was stirred for 0.5 hours before being discharged to obtain the polyester resin.

[0131] Comparative Example 2

[0132] This comparative example provides a polyester resin, and the raw materials and amounts used are shown in Table 8:

[0133] Table 8 shows the raw materials and dosages used in the preparation of polyester resin in Comparative Example 2.

[0134]

[0135] The preparation steps are as follows:

[0136] Hard-chain polyester resin H1 was added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 180°C at a programmed heating rate of 5°C / h and stirred for 1 hour. Then, an acid hydrolysate was added to initiate the reaction, and the temperature was increased to 230°C at a programmed heating rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain the polyester resin.

[0137] Comparative Example 3

[0138] This comparative example provides a polyester resin, and the raw materials and amounts used are shown in Table 9:

[0139] Table 9 shows the raw materials and dosages used in the preparation of polyester resin in Comparative Example 3.

[0140]

[0141] The preparation steps are as follows:

[0142] Polyols, polyacids, oligomeric polyols, and catalysts were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 240°C at a programmed rate of 5°C / h and held for 4 hours after reaching the set temperature. Then, the temperature was lowered to 180°C, and an acid hydrolysate was added to initiate the reaction. After stirring for 1 hour, the temperature was increased to 230°C at a programmed rate of 5°C / h and held for 2 hours after reaching the set temperature. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and a curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain polyester resin.

[0143] Comparative Example 4

[0144] This comparative example provides a polyester resin, and the raw materials and amounts used are shown in Table 10:

[0145] Table 10 shows the raw materials and dosages used in the preparation of polyester resin in Comparative Example 4.

[0146]

[0147]

[0148] The preparation steps are as follows:

[0149] Polyol, polyacid, and catalyst monobutyltin oxide were added to a four-necked flask. A stirring device, distillation column, and condenser were set up on the flask. Under a nitrogen atmosphere, the temperature was increased to 240°C at a programmed rate of 5°C / h and held for 4 hours. Then, the temperature was lowered to 180°C, and polyisocyanate, acid hydrolysate, and catalyst dibutyltin dilaurate were added to react. After stirring for 1 hour, the temperature was increased to 230°C at a programmed rate of 5°C / h and held for 2 hours. Subsequently, a vacuum of -0.09 MPa was applied for 2 hours. Finally, the temperature was lowered to 190°C, and curing accelerator, antioxidant, and silane coupling agent were added. After stirring for 0.5 hours, the product was discharged to obtain polyester resin.

[0150] Application Example 1

[0151] Textured powder coatings were prepared using the polyester resins from Examples 8-13 and Comparative Examples 1-4 as raw materials. The composition of the textured powder coatings is shown in Table 11 below:

[0152] Table 11 Application Example 1: Components and Content (g) of Sand Texture Powder Coating

[0153]

[0154]

[0155] The preparation steps are as follows:

[0156] The raw materials are mixed, pressed into sheets using a twin-screw extruder, frozen and crushed, and sieved to obtain sand texture powder coating 1-10.

[0157] Application Example 2

[0158] The sand-textured powder coating 1-10 prepared in Application Example 1 was applied to the surface of an aluminum profile by electrostatic spraying and cured at 160°C for 15 minutes to obtain a black sand-textured coating 1-10.

[0159] Performance testing

[0160] 1. The acid value, viscosity and glass transition temperature of the polyester resins in Examples 8-13 and Comparative Examples 1-4 were tested in accordance with T / GDTL 004-2019. The test results are shown in Table 12.

[0161] Table 12 shows the test results of acid value, viscosity, and glass transition temperature of the polyester resins in Examples 8-13 and Comparative Examples 1-4.

[0162]

[0163]

[0164] Table 12 shows the test results of acid value, viscosity and glass transition temperature of polyester resin in Examples 8-13 and Comparative Examples 1-4. As can be seen from Table 12, the acid value of polyester resin used in the sand texture powder coating in Examples 8-13 is 30-40 mg KOH / g, the viscosity at 200℃ is 7000-10000 mPa·s, and the glass transition temperature is 65-75℃. The polyester resin has suitable acid value, viscosity and glass transition temperature, which is beneficial to improving the performance of powder coating.

[0165] 2. The coatings 1-10 in Application Example 2 were tested for 60° gloss, impact resistance, horizontal flowability, gloss retention after boiling in water at 120℃ for 2 hours, color difference ΔE, and surface water stain severity. Gloss testing was conducted according to GB / T 9754-2007, impact resistance testing according to T / GDTL004-2019, horizontal flowability according to GB 6554-1986, and water resistance testing using the pressure cooker boiling method in GB 5237.4-2004. The area of ​​water stains on the coating surface after boiling was determined visually. The test results are shown in Table 13.

[0166] Table 13 shows the performance test results of coatings 1-10 in Application Example 2.

[0167]

[0168] Table 13 shows the performance test results of coatings 1-10 in Application Example 2. As can be seen from Table 13, the sand texture powder coatings prepared with polyester resin in Examples 8-13, after electrostatic spraying and curing, form coatings 1-6 with a 60° gloss of less than 9%, which is low gloss. The coatings have good impact resistance. After being boiled in high-pressure water at 120℃ for 2 hours, the gloss retention rate is ≥94%, and can reach more than 99%. The color difference ΔE≤2, and water spots basically do not appear on the surface. This indicates that the polyester resin for sand texture powder coatings provided by the present invention is used to prepare sand texture powder coatings. The coating has excellent sanding effect, water resistance and mechanical properties. When used for surface treatment, the coating is not easily corroded or scratched, and can maintain excellent performance for a long time without affecting the appearance.

[0169] Comparative Example 1 did not contain a silane coupling agent, Comparative Example 2 did not contain a soft-segment polyurethane, and Comparative Examples 3 and 4 were conventional polyester resin formulations, none of which contained hard-segment polyester resin or soft-segment polyurethane. It is evident that when Comparative Example 1 was used to prepare a textured powder coating, after coating 7 was boiled in high-pressure water at 120℃ for 2 hours, the gloss retention rate was 92.2%, the color difference ΔE was 1.30, and there were numerous water spots on the surface, indicating poor water resistance. When Comparative Example 2 was used to prepare a textured powder coating, after coating 8 was boiled in high-pressure water at 120℃ for 2 hours, the gloss retention rate was 88.2%, the color difference ΔE was 1.95, and there were many water spots on the surface, indicating a significant decrease in water resistance. The textured powder coatings prepared using Comparative Examples 3 and 4 can be considered as textured powder coatings in the prior art, and their water resistance is significantly worse than that of this invention.

Claims

1. A polyester resin for textured powder coatings, characterized in that, The preparation materials include: soft-segment polyurethane, hard-segment polyester resin, and silane coupling agent; by mass percentage, the soft-segment polyurethane includes the following preparation materials: 5-20% polyisocyanate and 80-95% oligomeric polyol; the hard-segment polyester resin includes the following preparation materials: 30-45% aliphatic polyol and 60-75% polyacid. The silane coupling agent includes at least one of bis[3-(triethoxysilane)propyl]amine and N-[3-(trimethoxysilyl)propyl]ethylenediamine; The polyester resin used in the sand texture powder coating has an acid value of 25-40 mgKOH / g, a viscosity of 3000-11000 mPa·s at 200℃, and a glass transition temperature of 65-75℃.

2. The polyester resin for textured powder coating according to claim 1, characterized in that, The polyisocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and terephthalic diisocyanate; And / or, the molecular weight of the oligomeric polyol is 300-5000 g / mol.

3. The polyester resin for textured powder coating according to claim 1, characterized in that, The aliphatic polyols include at least one of neopentyl glycol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butanediol, hexanediol, diethylene glycol, 1,4-cyclohexanediol, 2-methyl-2,4-pentanediol, ethylbutylpropanediol, trimethylolpropane, and pentaerythritol. And / or, the polyacid includes at least one of terephthalic acid, isophthalic acid, trimellitic anhydride, succinic acid, adipic acid, and 1,4-cyclohexanediol.

4. The polyester resin according to any one of claims 1-3, characterized in that, The polyester resin also includes the following raw materials: acid hydrolysate, curing accelerator, and antioxidant.

5. The polyester resin for textured powder coating according to claim 4, characterized in that, The polyester resin comprises, by weight percentage, the following raw materials: 1-10% soft segment polyurethane, 80-90% hard segment polyester resin, 0.1-2% silane coupling agent, 1-10% acid hydrolysate, 0.01-0.5% curing accelerator, and 0.1-2% antioxidant.

6. The method for preparing the polyester resin for textured powder coating according to claim 5, characterized in that, Includes the following steps: S1. Polyisocyanate and oligomeric polyol are polymerized to obtain soft segment polyurethane, and aliphatic polyol and polyester are condensed to obtain hard segment polyester resin. S2. The soft segment polyurethane and hard segment polyester resin are mixed and reacted, an acid hydrolysate is added, and a vacuum polycondensation reaction is carried out. A curing accelerator, an antioxidant and a silane coupling agent are added to obtain the polyester resin for sand texture powder coating.

7. A textured powder coating, characterized in that, Includes the polyester resin for textured powder coatings as described in any one of claims 1-5; The polyester resin used in the textured powder coating has a mass percentage of 50-60%.

8. A coating, characterized in that, It is formed by the sand texture powder coating as described in claim 7.

9. The polyester resin for textured powder coating according to any one of claims 1-5, or the application of textured powder coating according to claim 7 in the surface treatment of aluminum profiles.

Images