Low-cost high-performance powder polyester for household appliances and preparation method of low-cost high-performance powder polyester

Abstract

The invention discloses low-cost powder polyester for household appliances and a preparation method of the low-cost powder polyester. The low-cost powder polyester is prepared from ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol, adipic acid, purified terephthalic acid, trimellitic anhydride and monobutyltin oxide. According to the advanced preparation technology provided by the invention, through performance detection, the prepared resin is uniform in product molecular weight, good in compatibility with epoxy resin, high in wettability, high in curing speed and excellent in comprehensive performance after being cured with the epoxy resin, and the cost and performance of the resin are incomparable to those of traditional products in the market; and a very good technical effect is achieved.

Description

Technical Field

[0001] This invention belongs to the field of resin technology, specifically relating to a powdered polyester for household appliances that has uniform molecular weight, good compatibility with resins, strong wettability, fast curing speed, and excellent comprehensive performance after curing with epoxy resin. Background Technology

[0002] Powder coatings are solid powdered synthetic resin coatings composed of solid resin, pigments, fillers, and additives. Unlike ordinary solvent-based and water-based coatings, their dispersion medium is air, not solvent or water. They feature solvent-free production, 100% film formation, and low energy consumption. Powder coatings are broadly classified into thermoplastic and thermosetting types. Thermoplastic powder coatings have poor film appearance (gloss and leveling) and poor adhesion to metal, so they are rarely used in automotive painting. Automotive painting generally uses thermosetting powder coatings. Thermosetting powder coatings use thermosetting synthetic resins as the film-forming substance. During the drying process, the resin first melts, then undergoes chemical cross-linking and solidifies into a smooth and hard film. The appearance, mechanical properties, and corrosion resistance of the film formed by this type of coating meet the requirements of automotive finishing.

[0003] Polyester powder coatings possess unique properties compared to other types of powder coatings. They exhibit superior weather resistance and UV resistance compared to epoxy resins. Furthermore, due to the polar groups present in polyester resins, they have a higher powder application rate than epoxy resins, are less prone to yellowing during baking, and offer high gloss, good leveling, a full film, and light color, resulting in excellent decorative properties. They are commonly used in refrigerators, washing machines, vacuum cleaners, instrument housings, bicycles, furniture, and other applications. Summary of the Invention

[0004] Purpose of the invention: This invention optimizes the feeding ratio and reaction process to produce a product with uniform molecular weight, good compatibility with resin, strong wettability, and fast curing speed. After curing with epoxy resin, it exhibits excellent overall performance, providing a lower-cost, higher-performance polyester resin suitable for powder coatings in household appliances.

[0005] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows: A low-cost, high-performance powdered polyester for household appliances is made from the following raw materials: ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol, adipic acid, purified terephthalic acid, trimellitic anhydride, and monobutyltin oxide.

[0006] As a preferred embodiment, the aforementioned low-cost, high-performance powdered polyester for household appliances is made from the following raw materials in weight percentages: 4-9% ethylene glycol, 10-15% diethylene glycol, 0.5-1% trimethylolpropane, 8-15% neopentyl glycol, 0.3-1% adipic acid, 50-60% purified terephthalic acid, 9-11% trimellitic anhydride, and 0.08-0.1% monobutyltin oxide.

[0007] As a more preferred option, the aforementioned low-cost, high-performance powdered polyester for household appliances is made from the following raw materials in weight percentages: 7-9% ethylene glycol, 12-15% diethylene glycol, 0.6-0.9% trimethylolpropane, 8-10% neopentyl glycol, 0.4-0.8% adipic acid, 50-57% purified terephthalic acid, 9.5-10.5% trimellitic anhydride, and 0.09-0.1% monobutyltin oxide.

[0008] As a particularly preferred embodiment, the aforementioned low-cost, high-performance powdered polyester for household appliances is made from the following raw materials in weight percentages: 8.9% ethylene glycol, 14.1% diethylene glycol, 0.8% trimethylolpropane, 8.9% neopentyl glycol, 0.5% adipic acid, 56.4% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

[0009] The present invention provides a method for preparing low-cost, high-performance powdered polyester for household appliances, comprising the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol, adipic acid, purified terephthalic acid, and monobutyltin oxide to the reaction vessel according to the weight percentage, turn on the stirrer, and heat up; (2) Then, nitrogen gas is introduced to remove oxygen from the reactor. The temperature is then raised at a constant rate to a maximum of 235-245℃ and held for 0.5-1 hour. During the heating process, the distillation head temperature is controlled to be no higher than 101-104℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g. (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 220°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified. (4) After all indicators are tested and qualified, the sheets are cooled and formed into flakes, then crushed, weighed and packaged.

[0010] As a preferred embodiment, the preparation method of the low-cost, high-performance powdered polyester for household appliances described above includes the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol by weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide, and purified terephthalic acid. (2) Then, heat the resin at a constant rate to a maximum of 245℃ and hold it at that temperature for 0.5 to 1 hour. During the heating process, the temperature of the distillation head should be controlled to be no higher than 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. After the acid value is lower than 20 mg KOH / g, start the vacuum pump and gradually adjust the vacuum degree in the reactor to -0.085 MPa to continue polycondensation. Take samples regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g. (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 210°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified. (4) After all indicators are tested and qualified, the sheets are cooled and formed into flakes, then crushed, weighed and packaged.

[0011] In step (3), the qualified acid value means an acid value of 72-78 mgKOH / g and a melt viscosity of 70-110 mPa·S / 175. o C; The qualified indicators mentioned in step (4) refer to a softening point of 100-115. o C.

[0012] Compared with the prior art, the present invention has the following advantages: This invention obtained the optimal raw material composition through extensive experimental screening. During the experiments, it was discovered that the amounts of neopentyl glycol and purified terephthalic acid are crucial. Insufficient neopentyl glycol did not significantly improve weather resistance, while excessive amounts increased costs. Insufficient purified terephthalic acid resulted in poor resin flexibility, while excessive amounts negatively impacted the hardness of the powdered resin. Therefore, this invention obtained the optimal composition and dosage ratio of each raw material through extensive experimental screening.

[0013] Performance testing results show that the powdered polyester resin prepared by the invention has excellent flexibility, hardness, and adhesion properties, but its cost performance is better than that of existing powdered polyester, achieving very good technical results. Detailed Implementation

[0014] Example 1

[0015] A low-cost, high-performance powdered polyester for household appliances is made from the following raw materials in weight percentages: 8.9% ethylene glycol, 14.1% diethylene glycol, 0.8% trimethylolpropane, 8.9% neopentyl glycol, 0.5% adipic acid, 56.4% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

[0016] 2. A method for preparing low-cost, high-performance powdered polyester for household appliances, comprising the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol by weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide, and purified terephthalic acid. (2) The temperature is then raised at a constant rate to a maximum of 245℃ and held for 0.5 to 1 hour. During the heating process, the temperature of the distillation head is controlled not to exceed 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g.

[0017] (3) Maintain a vacuum of -0.085MPa, control the temperature of the reactor to reduce the reactants to 210℃, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192℃ until the acid value and melt viscosity are qualified. (4) Various indicators (acid value 72-78 mgKOH / g, melt viscosity 70-110 mPa·S / 175) o C, softening point 100-115 o C) After passing the inspection, the sheets are cooled and solidified, then crushed, weighed, and packaged.

[0018] Example 2

[0019] 1. A low-cost, high-performance powdered polyester for household appliances, which is made from the following raw materials in weight percentages: 8.9% ethylene glycol, 10% diethylene glycol, 0.8% trimethylolpropane, 13% neopentyl glycol, 0.5% adipic acid, 56.4% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

[0020] 2. A method for preparing low-cost, high-performance powdered polyester for household appliances, comprising the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol by weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide, and purified terephthalic acid. (2) The temperature is then raised at a constant rate to a maximum of 245℃ and held for 0.5 to 1 hour. During the heating process, the temperature of the distillation head is controlled not to exceed 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g.

[0021] (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 210°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified.

[0022] (4) Various indicators (acid value 72-78 mgKOH / g, melt viscosity 70-110 mPa·S / 175) o C, softening point 100-115 o C) After passing the inspection, the sheets are cooled and solidified, then crushed, weighed, and packaged.

[0023] Example 3

[0024] 1. A low-cost, high-performance powdered polyester for household appliances, made from the following raw materials in weight percentages: 13.3% ethylene glycol, 14.1% diethylene glycol, 0.8% trimethylolpropane, 8.9% neopentyl glycol, 0.5% adipic acid, 52% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

[0025] 2. A method for preparing low-cost, high-performance powdered polyester for household appliances, comprising the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol by weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide, and purified terephthalic acid. (2) The temperature is then raised at a constant rate to a maximum of 245℃ and held for 0.5 to 1 hour. During the heating process, the temperature of the distillation head is controlled not to exceed 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g.

[0026] (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 210°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified. (4) Various indicators (acid value 72-78 mgKOH / g, melt viscosity 70-110 mPa·S / 175) o C, softening point 100-115 o C) After passing the inspection, the sheets are cooled and solidified, then crushed, weighed, and packaged.

[0027] Example 4

[0028] 1. A low-cost, high-performance powdered polyester for household appliances, which is made from the following raw materials in weight percentages: 5.3% ethylene glycol, 14.1% diethylene glycol, 0.8% trimethylolpropane, 8.9% neopentyl glycol, 0.5% adipic acid, 60% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

[0029] 2. A method for preparing low-cost, high-performance powdered polyester for household appliances, comprising the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol by weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide, and purified terephthalic acid. (2) The temperature is then raised at a constant rate to a maximum of 245℃ and held for 0.5 to 1 hour. During the heating process, the temperature of the distillation head is controlled not to exceed 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g.

[0030] (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 210°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified. (4) Various indicators (acid value 72-78 mgKOH / g, melt viscosity 70-110 mPa·S / 175) o C, softening point 100-115 o C) After passing the inspection, the sheets are cooled and solidified, then crushed, weighed, and packaged.

[0031] Performance Test 1 (1) According to the mass percentage, take 30% of the resin prepared in Examples 1-3, 30% of epoxy resin 604 (produced by Jiangsu Sanmu Chemical Co., Ltd.), 20% of titanium dioxide, 17.7% of filler barium sulfate, 0.3% of benzoin, 1% of leveling agent 701, and 1% of accelerator 588, stir and disperse evenly, and then bake on an electrostatic spray plate. The following performance tests were conducted for comparison. The specific experimental results are shown in Table 1: Table 1. Coating film performance tests of different embodiments Example 1 Example 2 Example 3 Example 4 Impact resistance 50 front and back 50 front and back 50 front and back 50 front and back Pencil hardness H H H HB flexibility 2mm 2mm 3mm 2mm Adhesion Level 1 Level 1 Level 2 Level 1 luster 93 91 92 92 Impact resistance was assessed using a drop hammer impact test. A weight of a certain mass was dropped freely from a specified height onto the sample, and the paint film was observed to determine whether it cracked or peeled, thus evaluating its impact resistance. Refer to GB / T 20624.2-2006.

[0032] Pencil hardness is determined using a pencil hardness test. A set of drawing pencils of known hardness (from softest to hardest) are used to scratch the paint film surface at a specific angle and with pressure. The hardness rating of the hardest pencil that will not scratch the paint film is then determined. Refer to GB / T 6739-2022.

[0033] Flexibility was assessed using a shaft bending test. The painted test panel was bent across shafts of varying diameters, and the paint film was inspected for cracking or peeling. Flexibility was evaluated based on the smallest shaft diameter (e.g., 2 mm) that the panel could pass through. Refer to GB / T 1731-2020.

[0034] Adhesion is usually assessed using a cross-cut test. A grid of squares with a specified spacing is cut into the paint film with a knife, tape is applied and then quickly peeled off, and the grade is determined based on the area of ​​paint film that has peeled off from the squares (e.g., grade 1 is the best).

[0035] Refer to GB / T 9286-2021.

[0036] Gloss is measured using a gloss meter. At a specified incident angle (e.g., 60°), the amount of light reflected from the paint film surface is measured and compared with the amount of light reflected from a standard panel, expressed as a percentage (%). Refer to GB / T 9754-2007.

[0037] The above performance test results show that the powdered polyester resin obtained by this invention through extensive experimental screening and advanced preparation process exhibits excellent flexibility, hardness, adhesion, impact strength, and gloss properties. Furthermore, comparisons show that when the purified terephthalic acid content in Example 3 decreases, the resin's flexibility and adhesion decrease; conversely, when the purified terephthalic acid content in Example 4 increases, the resin's hardness decreases. Overall, under the same cost, the powdered polyester resin accelerator prepared in Example 1 of this invention demonstrates the best performance in all aspects, achieving excellent technical results.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-cost, high-performance powdered polyester for household appliances, characterized in that, It is made from the following raw materials: ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol, adipic acid, purified terephthalic acid, trimellitic anhydride, and monobutyltin oxide.

2. The low-cost, high-performance powdered polyester for household appliances according to claim 1, characterized in that, It is made from the following raw materials in weight percentage: 4-9% ethylene glycol, 10-15% diethylene glycol, 0.5-1% trimethylolpropane, 8-15% neopentyl glycol, 0.3-1% adipic acid, 50-60% purified terephthalic acid, 9-11% trimellitic anhydride, and 0.08-0.1% monobutyltin oxide.

3. The low-cost, high-performance powdered polyester for household appliances according to claim 2, characterized in that, It is made from the following raw materials in weight percentage: 7-9% ethylene glycol, 12-15% diethylene glycol, 0.6-0.9% trimethylolpropane, 8-10% neopentyl glycol, 0.4-0.8% adipic acid, 50-57% purified terephthalic acid, 9.5-10.5% trimellitic anhydride, and 0.09-0.1% monobutyltin oxide.

4. The low-cost, high-performance powdered polyester for household appliances according to claim 3, characterized in that, It is made from the following raw materials in weight percentage: 8.9% ethylene glycol, 14.1% diethylene glycol, 0.8% trimethylolpropane, 8.9% neopentyl glycol, 0.5% adipic acid, 56.4% purified terephthalic acid, 10.3% trimellitic anhydride, and 0.1% monobutyltin oxide.

5. The method for preparing low-cost, high-performance powdered polyester for household appliances according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane, neopentyl glycol, adipic acid, purified terephthalic acid, and monobutyltin oxide to the reaction vessel according to the weight percentage, turn on the stirrer, and heat up; (2) Then nitrogen gas is introduced to remove oxygen in the reactor. The temperature is raised to 235~245℃ at a constant rate and kept at that temperature for 0.5~1 hour. During the heating process, the temperature of the distillation head is controlled not to exceed 101~104℃. After the resin is clear and transparent, the acid value and melt viscosity are measured. When the acid value is lower than 20mgKOH / g, the vacuum pump is started and the vacuum degree in the reactor is gradually adjusted to -0.085MPa to continue polycondensation. Samples are taken periodically to measure the acid value and melt viscosity until the acid value is lower than 5mgKOH / g. (3) Maintain a vacuum of -0.085 MPa, control the temperature of the reactor to reduce the reactants to 220°C, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192°C until the acid value and melt viscosity are qualified. (4) After the index test is qualified, the product is cooled and formed into flakes, then crushed, weighed and packaged.

6. The method for preparing low-cost, high-performance powdered polyester for household appliances according to claim 5, characterized in that, Includes the following steps: (1) Add ethylene glycol, diethylene glycol, trimethylolpropane and neopentyl glycol according to weight percentage, purge with nitrogen, turn on stirring, heat up, and then add adipic acid, monobutyltin oxide and purified terephthalic acid. (2) The temperature is then uniformly increased to a maximum of 245℃ and held for 0.5 to 1 hour. During the heating process, the head temperature is controlled to be no higher than 102℃. After the resin sample is clear and transparent, the acid value and melt viscosity should be measured regularly during this period. When the acid value is lower than 20 mg KOH / g, the vacuum pump is started, and the vacuum degree in the reactor is gradually adjusted to -0.085 MPa to continue polycondensation. Samples are taken regularly to measure the acid value and melt viscosity until the acid value is lower than 5 mg KOH / g. (3) Maintain a vacuum of -0.085MPa, control the temperature of the reactor to reduce the reactants to 210℃, add trimellitic anhydride to the reactor, and control the reaction temperature at 188~192℃ until the acid value and melt viscosity are qualified. (4) After the index test is qualified, the product is cooled and formed into flakes, then crushed, weighed and packaged.

7. The method for preparing low-cost, high-performance powdered polyester for household appliances according to claim 5 or 6, characterized in that, The acceptable acid value in step (3) refers to an acid value of 72-78 mgKOH / g and a melt viscosity of 70-110 mPa·S / 175. o C; The qualified index mentioned in step (4) refers to a softening point of 100-115. o C.