High-impact-resistance modified polyester for household appliances and preparation method of high-impact-resistance modified polyester

Abstract

The invention belongs to the field of high polymer materials, and discloses high-impact-resistance modified polyester for household appliances and a preparation method thereof.The modified polyester is prepared from PCTG resin, modified glass fibers, modified nano calcium carbonate, a core-shell toughening agent, polyethylene glycol 2000, an antioxidant, ethylene bis stearamide and a nucleating agent; the modified glass fiber is obtained by performing surface modification on glass fiber through a silane coupling agent, grafting PCTG-g-MAH and finally coating a nano ceramic coating in situ; the modified nano calcium carbonate is of a double-shell core-shell structure formed by taking nano calcium carbonate as a core and sequentially coating a POE-g-MAH elastic buffer layer and a phosphorus-nitrogen flame-retardant precursor DOPO-MAL functional layer on the outer layer; according to the invention, the PBT / PET alloy is taken as a matrix, and through synergistic modification of the modified glass fiber and the modified nano calcium carbonate, the resin material has mechanical, flame-retardant, damp-heat-resistant and processability, and can be widely applied to high-damp-heat and high-load scenes of household appliances.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-impact-resistant modified polyester for household appliances and its preparation method. Background Technology

[0002] PCTG resin (poly(1,4-cyclohexanediol)) is a novel copolyester material. Compared to traditional PBT and PET resins, its excellent high transparency, chemical resistance, impact resistance, and ease of molding and processing make it more suitable for the transparent / semi-transparent structural components of high-end home appliances. It has been gradually applied to refrigerator drawers, microwave oven panels, air conditioner vents, and small appliance casings, becoming a polymer matrix material with great development potential in the high-end home appliance manufacturing industry. However, with the rapid development of the home appliance industry towards high-end, lightweight, green, and multi-functional directions, and with consumers' increasing demands for the service life, safety performance, and adaptability to various usage scenarios of home appliances, the basic properties of PCTG resin alone can no longer meet the stringent requirements of home appliance structural components, especially in key performance dimensions such as rigidity, halogen-free flame retardancy, and resistance to damp heat.

[0003] Currently available modified PCTG materials for home appliances generally suffer from problems such as poor rigidity-toughness balance, low flame retardancy efficiency, insufficient resistance to damp heat, poor processability, limited additive functionality and poor interfacial compatibility, and difficulty in industrial application. They cannot simultaneously meet the comprehensive performance requirements of high-end home appliance transparent / non-transparent structural components, which demand high impact resistance, halogen-free flame retardancy, resistance to damp heat, easy processing, high transparency compatibility, and long lifespan. This restricts the widespread application of PCTG materials in the high-end home appliance sector and limits the high-end development of the home appliance industry. Therefore, there is an urgent need to develop a high-impact-resistant modified PCTG material for home appliances that can solve the above-mentioned technical problems, achieve synergistic improvement in multiple properties, and is made from readily available raw materials, compatible with processes, and suitable for industrial production. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a high-impact modified polyester for household appliances and its preparation method. The present invention uses PCTG resin as a matrix and, through the synergistic modification of modified glass fiber and modified nano-calcium carbonate, enables the resin material to take into account mechanical properties, flame retardancy, resistance to damp heat, and processing performance, and can be widely used in high-humidity and high-load scenarios of household appliances.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 60-70 parts PCTG resin, 14-16 parts modified glass fiber, 8-12 parts modified nano-calcium carbonate, 6-10 parts core-shell toughening agent, 1-3 parts polyethylene glycol 2000, 0.3-0.6 parts antioxidant, 0.6-1.0 parts ethylene bis-stearamide, and 0.6-1 part nucleating agent; The modified glass fiber is made by surface modification of glass fiber with silane coupling agent, grafting PCTG-g-MAH onto it, and finally coating it with a nano-ceramic coating in situ. Modified nano-calcium carbonate is a double-shell core-shell structure formed by nano-calcium carbonate as the core and the outer layers sequentially coated with a POE-g-MAH elastic buffer layer and a phosphorus-nitrogen flame retardant precursor DOPO-MAL functional layer. The phosphorus-nitrogen flame retardant precursor DOPO-MAL is obtained by nucleophilic addition of DOPO with maleic anhydride followed by amine dehydration and ring closure.

[0006] Preferably, the core-shell toughening agent is glycidyl methacrylate grafted polyolefin elastomer POE-g-GMA; The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1; The nucleating agent is a mixture of sodium benzoate and ethylene-sodium methacrylate ionomer in a mass ratio of 1:1.

[0007] Preferably, the method for preparing modified glass fiber includes the following steps: (1) Dissolve the silane coupling agent in a mixed solvent of ethanol and water, adjust the pH to 4.5~5.0 with acetic acid, stir for 20~40 min to obtain a silane coupling agent solution, add the dried glass fiber to a high-speed mixer, add the silane coupling agent solution, mix at 60℃ and 800rpm for 15~25 min, after discharge, dry with hot air at 100℃ for 1~3 h, remove the solvent, and obtain silane modified glass fiber; (2) Add silane-modified glass fiber, PCTG-g-MAH and azobisisobutyronitrile to a high-speed mixer, mix at 70°C and 1000 rpm for 10-20 min, then transfer to a sealed reactor, heat to 105°C under nitrogen protection, keep the temperature for 1-3 h, cool and discharge, dry at 100°C for 1-3 h to obtain silane polyester-modified glass fiber; (3) Disperse the nano-ceramic powder in deionized water, add a dispersant, and ultrasonically disperse for 20-40 min to obtain a nano-ceramic suspension. Add silane polyester modified glass fiber to the suspension, stir at 80℃ and 600 rpm for 20-40 min, and dry with hot air at 110℃ for 2-4 h to obtain modified glass fiber.

[0008] Preferably, the silane coupling agent is a mixture of KH-550 and KH-570 in a mass ratio of 7:3; Ethanol and water are mixed in a volume ratio of 95:5; The nano-ceramic powder is a mixture of nano-titanium dioxide and nano-silica in a mass ratio of 1:1. The dispersant is polyethylene glycol 400.

[0009] Preferably, the mass ratio of silane coupling agent, glass fiber, PCTG-g-MAH, azobisisobutyronitrile and nano-ceramic powder is 1.2:100:0.8:0.03:0.5.

[0010] Preferably, the preparation method of modified nano-calcium carbonate includes the following steps: A. Dissolve POE-g-MAH in toluene to prepare a 10wt% solution. Add dried nano-calcium carbonate to a high-speed mixer, add the POE-g-MAH toluene solution, mix at 50℃ and 700rpm for 20~30min, remove toluene by vacuum distillation at 60℃ to obtain polyolefin elastomer-coated nano-calcium carbonate. B. Dissolve the phosphorus-nitrogen flame retardant precursor DOPO-MAL and titanate coupling agent in ethanol, stir for 20-40 minutes until completely dissolved, add polyolefin elastomer-coated nano-calcium carbonate, stir at 65°C and 800 rpm for 30-50 minutes, add anti-hydrolysis agent, continue stirring for 10-20 minutes, dry with hot air at 80°C for 3-5 hours, pulverize and pass through a 200-mesh sieve to obtain modified nano-calcium carbonate.

[0011] Preferably, the titanate coupling agent is titanate coupling agent NDZ-201; The anti-hydrolysis agent is a carbodiimide-based anti-hydrolysis agent; The mass ratio of phosphorus-nitrogen flame retardant precursor, nano-calcium carbonate, DOPO-maleimide, titanate coupling agent, and anti-hydrolysis agent is 25:100:15:1.8:1.2 Preferably, the preparation method of the phosphorus-nitrogen flame retardant precursor DOPO-MAL includes the following steps: a. Add DOPO and maleic anhydride to toluene, stir and dissolve under nitrogen protection, heat to 80°C, keep the reaction at this temperature for 3-5 hours, cool to room temperature and filter, wash the filter cake with toluene 1-3 times, and dry under vacuum at 60°C for 3-5 hours to obtain intermediate DOPO-MA. b. Add intermediate DOPO-MA and diethanolamine to toluene, stir and react at 70°C under nitrogen protection for 2-4 hours, then add p-toluenesulfonic acid, acetic anhydride and triethylamine, heat to 110°C, and reflux to remove water for 4-8 hours; c. Cool to room temperature, remove toluene by vacuum distillation, dissolve the residue in acetone, slowly add it dropwise to rapidly stirred deionized water, a white solid precipitates, filter, wash with deionized water until neutral, dry under vacuum at 60℃ for 4~8h to obtain crude DOPO-MAL, recrystallize with an acetone-water mixture of 8:2 (v / v), filter, and dry under vacuum at 80℃ for 6~10h to obtain the phosphorus-nitrogen flame retardant precursor DOPO-MAL.

[0012] Preferably, the molar ratio of DOPO to maleic anhydride is 1:1.05; The molar ratio of intermediate DOPO-MA, diethanolamine, acetic anhydride and triethylamine is 1:1:2:2.

[0013] A method for preparing a high-impact-resistant modified polyester for household appliances includes the following steps: S1. According to the formula ratio, add PCTG resin, modified nano calcium carbonate, core-shell toughening agent, polyethylene glycol 2000, antioxidant, ethylene bis-stearamide and nucleating agent to a high-speed mixer and mix at 60℃ and 1200rpm for 5~15min to make it uniformly dispersed. S2. Add the mixed material from step S1 to the main feed port of a twin-screw extruder, add modified glass fiber from the side feed port, and melt-blend and extrude the mixture through the twin-screw extruder. Cool the melt in a 25°C water cooling tank, pelletize it, and vacuum dry it at 120°C for 2-4 hours to obtain high-impact modified polyester for household appliances.

[0014] The beneficial effects of this invention are: This invention relates to a high-impact modified polyester for household appliances, using PCTG resin as the matrix. Through the synergistic modification of modified glass fiber and modified nano-calcium carbonate, the modified glass fiber provides high strength and high dimensional stability through triple-interface modification, adapting to the requirements of load-bearing structures. The modified nano-calcium carbonate achieves synergistic toughening through double-shell core-shell modification, compensating for the brittleness defects caused by glass fiber reinforcement. The surface modification of both introduces flame-retardant groups and moisture-resistant groups, which, combined with the halogen-free flame-retardant system of the matrix, achieve a dual improvement in flame-retardant efficiency and heat resistance. This allows the resin material to take into account mechanical properties, flame retardancy, moisture resistance, and processing performance, and can be widely used in high-humidity and high-load scenarios of household appliances.

[0015] The modified glass fiber of this invention achieves covalent bonding and physical intercalation between the modified glass fiber and the PCTG resin matrix through a triple interface structure of silane layer, polyester layer and ceramic layer, thereby improving the interfacial shear strength. Under external force, stress can be efficiently transferred to the glass fiber through the interface, significantly improving the tensile strength and flexural modulus of the material, while inhibiting interface debonding and avoiding the brittle defects of glass fiber reinforced polyester. The nano-titanium dioxide and silica ceramic coating on the glass fiber surface can form a dense ceramic barrier layer at high temperatures, isolating oxygen and heat and delaying the thermal decomposition of the polyester matrix. At the same time, the P=O groups in the coating promote the formation of the matrix carbon layer, improve the flame retardant efficiency, achieve V-0 flame retardancy, and raise the glow wire temperature to over 800℃. The dense and non-porous ceramic coating can isolate water molecules in humid and hot environments, preventing water molecules from penetrating to the glass fiber polyester interface, avoiding interface hydrolysis and debonding, significantly improving the retention rate of mechanical properties after humid and hot aging, and solving the problem of poor resistance to humid and hot conditions in traditional glass fiber reinforced polyester. The triple interface modification reduces the surface energy of the glass fiber, eliminates agglomeration, improves melt fluidity, increases the melt flow rate, shortens the molding cycle, and achieves a balance between reinforcement and ease of processing.

[0016] This invention relates to a modified nano-calcium carbonate with nano-calcium carbonate as the core, coated with a POE-g-MAH elastic buffer layer and a DOPO-MAL flame-retardant functional layer, constructing a double-shell core-shell structure. Under impact load, the elastic buffer layer can undergo plastic deformation, absorbing a large amount of impact energy. Simultaneously, the DOPO-MAL flame-retardant layer works synergistically with the elastic layer to avoid a decrease in rigidity due to toughening, achieving toughening without embrittlement and significantly improving notched impact strength. DOPO-MAL is grafted onto the surface of the nano-calcium carbonate, decomposing at high temperatures to generate PO· free radicals, which can capture active free radicals during combustion, promoting the formation of a dense, expanded char layer in the polyester matrix. This layer isolates oxygen and heat, increasing the limiting oxygen index and glow wire temperature, reducing the amount of flame retardant required, lowering costs while improving flame-retardant stability. The modified nano-calcium carbonate surface grafted with carbodiimide anti-hydrolysis agents can capture carboxyl groups generated by polyester hydrolysis, inhibiting the degradation of polyester molecular chains. At the same time, the dense double-shell structure isolates water molecules, significantly improving the retention rate of mechanical properties after humid heat aging, solving the problems of poor resistance to humid heat and easy agglomeration of traditional nano-calcium carbonate. The titanate coupling agent activates the surface of nano-calcium carbonate, reduces the interfacial tension between the filler and the polyester matrix, improves melt fluidity, reduces melt viscosity, and increases melt flow rate. At the same time, it improves filler dispersibility, avoids processing defects, and achieves a balance between toughening and easy processing.

[0017] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 A modified glass fiber, wherein the glass fiber is surface modified with a silane coupling agent, grafted with PCTG-g-MAH, and finally coated with a nano-ceramic coating in situ, is prepared by means of the following steps: (1) Dissolve 8.4g KH-550 and 3.6g KH-570 in a mixed solvent of 95mL ethanol and 5mL water, adjust the pH to 4.5~5.0 with acetic acid, stir for 30min to obtain silane coupling agent solution, add 1000g dry glass fiber to a high-speed mixer, add silane coupling agent solution, mix at 60℃ and 800rpm for 20min, after discharge, dry with hot air at 100℃ for 2h, remove solvent to obtain silane modified glass fiber; (2) Add silane-modified glass fiber, 8g PCTG-g-MAH and 0.3g azobisisobutyronitrile to a high-speed mixer, mix at 70℃ and 1000rpm for 15min to allow PCTG-g-MAH to adsorb onto the glass fiber surface, transfer to a sealed reactor, heat to 105℃ under nitrogen protection, keep warm for 2h, azobisisobutyronitrile initiates the amidation reaction of the MAH group of PCTG-g-MAH with the amino group of silane on the glass fiber surface to achieve covalent grafting, cool and discharge, dry at 100℃ for 2h to obtain silane polyester-modified glass fiber; (3) Disperse 2.5g of nano titanium dioxide and 2.5g of nano silica in 1000mL of deionized water, add 1g of polyethylene glycol 400, and ultrasonically disperse for 30min to obtain a nano ceramic suspension. Add silane polyester modified glass fiber to the suspension and stir at 80℃ and 600rpm for 30min. Utilize electrostatic adsorption to uniformly coat the nano ceramic particles on the glass fiber surface. Dry with hot air at 110℃ for 3h to obtain the modified glass fiber.

[0020] Example 2 A modified nano-calcium carbonate, comprising a core of nano-calcium carbonate and an outer layer of POE-g-MAH elastic buffer layer and a phosphorus-nitrogen flame-retardant precursor functional layer, forming a double-shell core-shell structure, is prepared by the following steps: A. Dissolve 25g of POE-g-MAH in 250mL of toluene to prepare a POE-g-MAH toluene solution. Add 100g of dried nano-calcium carbonate to a high-speed mixer, add the POE-g-MAH toluene solution, mix at 50℃ and 700rpm for 25min, and remove toluene by vacuum distillation at 60℃ to obtain nano-calcium carbonate coated with polyolefin elastomer. B. Dissolve 15g of phosphorus-nitrogen flame retardant precursor and 1.8g of titanate coupling agent in 500mL of ethanol, stir for 30min until completely dissolved, add nano-calcium carbonate of polyolefin elastomer, stir at 65℃ and 800rpm for 40min, add 1.2g of carbodiimide anti-hydrolysis agent, continue stirring for 15min, dry with hot air at 80℃ for 4h, pulverize and pass through a 200-mesh sieve to obtain modified nano-calcium carbonate.

[0021] The phosphorus-nitrogen flame retardant precursor DOPO-MAL is obtained by nucleophilic addition of DOPO to maleic anhydride followed by amine dehydration and ring closure. Its preparation method includes the following steps: a. Add 21.6g DOPO and 10.3g maleic anhydride to 200mL toluene, stir and dissolve under nitrogen protection, heat to 80℃, keep the reaction at 80℃ for 4h, cool to room temperature and filter, wash the filter cake twice with toluene, and dry under vacuum at 60℃ for 4h to obtain intermediate DOPO-MA. b. Add 31.9g of intermediate DOPO-MA and 10.5g of diethanolamine to 150mL of toluene, stir and react at 70℃ under nitrogen protection for 3h to open the ring and generate an amide intermediate. Then add 0.04g of p-methylbenzenesulfonic acid, 20.4g of acetic anhydride and 20.2g of triethylamine, heat to 110℃, reflux and separate water for 6h until no water is generated in the water separator; c. Cool to room temperature, remove toluene by vacuum distillation, dissolve the residue in 150 mL of acetone, slowly add to 500 mL of rapidly stirred deionized water, precipitate a white solid, filter, wash with deionized water until neutral, dry under vacuum at 60 °C for 6 h to obtain crude DOPO-MAL, recrystallize with an acetone-water mixture of 8:2 (v / v), filter, and dry under vacuum at 80 °C for 8 h to obtain the phosphorus-nitrogen flame retardant precursor DOPO-MAL.

[0022] Example 3 A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 70 parts PCTG resin, 14 parts modified glass fiber, 12 parts modified nano-calcium carbonate, 6 parts POE-g-GMA, 1 part polyethylene glycol 2000, 0.4 parts antioxidant 1010, 0.2 parts antioxidant 168, 0.6 parts ethylene bis-stearamide, 0.5 parts sodium benzoate, and 0.5 parts ethylene-sodium methacrylate ionomer; the modified glass fiber is prepared in Example 1; the modified nano-calcium carbonate is prepared in Example 2.

[0023] The preparation method of the above-mentioned high impact-resistant modified polyester for household appliances is characterized by comprising the following steps: S1. According to the formula ratio, add PCTG resin, modified nano calcium carbonate, POE-g-GMA, polyethylene glycol 2000, antioxidant 1010, antioxidant 168, ethylene bis-stearamide, sodium benzoate and ethylene-sodium methacrylate ion polymer into a high-speed mixer and mix at 60℃ and 1200rpm for 5 minutes to make it uniformly dispersed. S2. Add the mixed material from step S1 to the main feed port of a twin-screw extruder, add modified glass fiber from the side feed port, and melt-blend and extrude the mixture through the twin-screw extruder. Cool the melt in a 25°C water cooling tank, pelletize it, and vacuum dry it at 120°C for 4 hours to obtain the high-impact-resistant modified polyester for household appliances.

[0024] Example 4 A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 60 parts PCTG resin, 16 parts modified glass fiber, 8 parts modified nano-calcium carbonate, 10 parts POE-g-GMA, 3 parts polyethylene glycol 2000, 0.2 parts antioxidant 1010, 0.1 parts antioxidant 168, 1.0 part ethylene bis-stearamide, 0.3 parts sodium benzoate, and 0.3 parts ethylene-sodium methacrylate ionomer; the modified glass fiber is prepared in Example 1; the modified nano-calcium carbonate is prepared in Example 2.

[0025] The preparation method of the above-mentioned high impact-resistant modified polyester for household appliances is characterized by comprising the following steps: S1. According to the formula ratio, add PCTG resin, modified nano calcium carbonate, POE-g-GMA, polyethylene glycol 2000, antioxidant 1010, antioxidant 168, ethylene bis-stearamide, sodium benzoate and ethylene-sodium methacrylate ionomer to a high-speed mixer and mix at 60℃ and 1200rpm for 15min to make it uniformly dispersed. S2. Add the mixed material from step S1 to the main feed port of a twin-screw extruder, add modified glass fiber from the side feed port, and melt-blend and extrude the mixture through the twin-screw extruder. Cool the melt in a 25°C water cooling tank, pelletize it, and vacuum dry it at 120°C for 2 hours to obtain the high impact-resistant modified polyester for household appliances.

[0026] Example 5 A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 65 parts PCTG resin, 20 parts PET resin, 15 parts modified glass fiber, 10 parts modified nano-calcium carbonate, 8 parts POE-g-GMA, 2 parts polyethylene glycol 2000, 0.3 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.8 parts ethylene bis-stearamide, 0.4 parts sodium benzoate, and 0.4 parts ethylene-sodium methacrylate ionomer; the modified glass fiber is prepared in Example 1; and the modified nano-calcium carbonate is prepared in Example 2.

[0027] The preparation method of the above-mentioned high impact-resistant modified polyester for household appliances is characterized by comprising the following steps: S1. According to the formula ratio, add PCTG resin, modified nano calcium carbonate, POE-g-GMA, polyethylene glycol 2000, antioxidant 1010, antioxidant 168, ethylene bis-stearamide, sodium benzoate and ethylene-sodium methacrylate ionomer to a high-speed mixer and mix at 60℃ and 1200rpm for 5~15min to make it uniformly dispersed; S2. Add the mixed material from step S1 to the main feed port of a twin-screw extruder, add modified glass fiber from the side feed port, and melt-blend and extrude the mixture through the twin-screw extruder. Cool the melt in a 25°C water cooling tank, pelletize it, and vacuum dry it at 120°C for 2-4 hours to obtain the high impact-resistant modified polyester for household appliances.

[0028] Comparative Example 1 A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 65 parts PCTG resin, 15 parts modified glass fiber, 10 parts modified nano-calcium carbonate, 8 parts POE-g-GMA, 2 parts polyethylene glycol 2000, 0.3 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.8 parts ethylene bis-stearamide, 0.4 parts sodium benzoate, and 0.4 parts ethylene-sodium methacrylate ionomer; wherein the modified nano-calcium carbonate is prepared in Example 2.

[0029] The preparation method of the above-mentioned high impact-resistant modified polyester for home appliances is the same as that in Example 5, except that modified glass fiber is not added from the side feed port in step S2.

[0030] Comparative Example 2 A high-impact modified polyester for household appliances comprises the following raw materials in parts by weight: 65 parts PCTG resin, 15 parts modified glass fiber, 10 parts modified nano-calcium carbonate, 8 parts POE-g-GMA, 2 parts polyethylene glycol 2000, 0.3 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.8 parts ethylene bis-stearamide, 0.4 parts sodium benzoate, and 0.4 parts ethylene-sodium methacrylate ionomer; the modified glass fiber is from Example 1.

[0031] The preparation method of the above-mentioned high impact-resistant modified polyester for home appliances is the same as that in Example 5, except that modified nano-calcium carbonate is not added during the mixing process in step S1.

[0032] Performance testing The high impact-resistant modified polyesters for household appliances prepared in Example 5, Comparative Example 1, and Comparative Example 2 were tested for mechanical properties, flame retardant properties, damp heat resistance, and processing properties.

[0033] (1) Mechanical property testing Notched impact strength was tested according to GB / T 1043.1-2018, tensile strength and elongation at break were tested according to GB / T 1040.2-2018, and flexural modulus was tested according to GB / T 9341-2008. The results are shown in Table 1 below.

[0034] Table 1. Test results of mechanical properties of high-impact modified polyester for household appliances

[0035] As can be seen from the data in Table 1, the notched impact strength of Example 5 reached 19.2 kJ / m. 2 The performance of this material far exceeds the minimum requirements for home appliances, showing a significant improvement over Comparative Example 1 and Comparative Example 2. Its tensile and flexural moduli meet the rigidity requirements of high-end home appliance structural components, and its elongation at break is excellent, achieving a balance between rigidity and toughness. Comparative Example 1, without modified glass fiber, exhibits significantly reduced mechanical properties, with impact strength failing to meet home appliance standards and insufficient rigidity, making it only suitable for low-load non-structural components, highlighting the core reinforcing role of modified glass fiber. Comparative Example 2, without modified nano-calcium carbonate, has an impact strength of only 12.3 kJ / m². 2 The result is still significantly different from Example 5, indicating that modified nano-calcium carbonate is the key to synergistic toughening.

[0036] (2) Flame retardant performance test The vertical burning test was conducted according to UL94-2019 to determine the UL94 rating. The glow wire temperature was tested according to IEC60695-2-10:2013, and the limiting oxygen index was tested according to GB / T2406.2-2022. The results are shown in Table 2 below.

[0037] Table 2. Test results of flame retardant properties of high impact-resistant modified polyester for household appliances

[0038] As can be seen from the data in Table 2, the UL94 ratings of Example 5, Comparative Example 1, and Comparative Example 2 all reached the V-0 level. However, the glow wire temperature of Example 5 reached 810℃, which far exceeded the safety standard for household appliances, and its flame retardant performance was the best. The glow wire temperature of Comparative Example 1 was only 740℃, which was close to the lower limit of the standard. Its heat resistance was poor and its adaptability was poor. Comparative Example 3 also had insufficient flame retardant synergy, which shows the flame retardant synergistic effect of modified nano-calcium carbonate.

[0039] (3) Testing of resistance to damp heat Referring to GB / T2573-2008, the samples were placed in a damp heat aging chamber with a set temperature of 85℃ and relative humidity of 85% for 1000 hours. After aging, the samples were removed and equilibrated at 23℃ / 50%RH for 24 hours. The tensile strength and notched impact strength were tested, and the tensile strength retention rate and impact strength retention rate were calculated. The dimensional changes of the samples before and after aging were tested according to GB / T10316-2008. The results are shown in Table 3 below.

[0040] Table 3. Test results of damp heat resistance of high impact-resistant modified polyester for household appliances

[0041] As can be seen from the data in Table 3, after damp heat aging, the mechanical properties of Example 5 retained more than 95%, and the dimensional change rate was only 0.08%, showing the best damp heat resistance and making it suitable for high-humidity and high-heat household appliance scenarios such as kitchens and bathrooms. In contrast, the interface between glass fiber and polyester in Comparative Example 1 had poor damp heat resistance, and the interface debonded after aging, with a performance retention rate of only 82.5%, large dimensional deformation, and easy failure after long-term use. Comparative Example 2 had no modified nano-calcium carbonate, and its hydrolysis resistance decreased, with a performance retention rate lower than that of Example 5, demonstrating the damp heat protection effect of modified nano-calcium carbonate.

[0042] (4) Processing performance testing Melt flow rate (MFR) was tested according to GB / T 3682.1-2018, and the molding cycle was recorded in real time by the injection molding machine. Melt viscosity was tested by capillary rheometer according to GB / T 3683-2011. The results are shown in Table 4 below.

[0043] Table 4. Test results of processing performance of high impact-resistant modified polyester for household appliances

[0044] As can be seen from the data in Table 4, Example 5 has a melt flow rate of 15.8 g / 10 min and a molding cycle of only 58 s. It has low melt viscosity, optimal processability, and is suitable for high-speed injection molding production lines, thus improving production efficiency. Comparative Example 1 has high melt viscosity, poor fluidity, and a molding cycle that is more than 15% longer, resulting in low production efficiency and a tendency to produce defects such as incomplete filling and silver streaks. Comparative Example 2 has lower fluidity than Example 5 and a slightly longer molding cycle, demonstrating the effect of modified nano-calcium carbonate on improving processing fluidity.

[0045] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A high-impact-resistant modified polyester for household appliances, characterized in that, The raw materials include the following parts by weight: 60-70 parts PCTG resin, 14-16 parts modified glass fiber, 8-12 parts modified nano calcium carbonate, 6-10 parts core-shell toughening agent, 1-3 parts polyethylene glycol 2000, 0.3-0.6 parts antioxidant, 0.6-1.0 parts ethylene bis-stearamide, and 0.6-1 part nucleating agent; The modified glass fiber is made by surface modification of glass fiber with silane coupling agent followed by grafting PCTG-g-MAH, and finally in-situ coating with nano-ceramic coating. The modified nano-calcium carbonate is a double-shell core-shell structure formed by nano-calcium carbonate as the core and an outer layer of POE-g-MAH elastic buffer layer and phosphorus-nitrogen flame retardant precursor DOPO-MAL functional layer. The phosphorus-nitrogen flame retardant precursor DOPO-MAL is obtained by nucleophilic addition of DOPO with maleic anhydride followed by amine dehydration and ring closure.

2. The high impact-resistant modified polyester for household appliances according to claim 1, characterized in that, The core-shell toughening agent is glycidyl methacrylate grafted polyolefin elastomer POE-g-GMA. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1; The nucleating agent is a mixture of sodium benzoate and ethylene-sodium methacrylate ionomer in a mass ratio of 1:

1.

3. The high impact-resistant modified polyester for household appliances according to claim 1, characterized in that, The method for preparing the modified glass fiber includes the following steps: (1) Dissolve the silane coupling agent in a mixed solvent of ethanol and water, adjust the pH to 4.5~5.0 with acetic acid, stir for 20~40 min to obtain a silane coupling agent solution, add the dried glass fiber to a high-speed mixer, add the silane coupling agent solution, mix at 60℃ and 800rpm for 15~25 min, after discharge, dry with hot air at 100℃ for 1~3 h, remove the solvent, and obtain silane modified glass fiber; (2) Add silane-modified glass fiber, PCTG-g-MAH and azobisisobutyronitrile to a high-speed mixer, mix at 70°C and 1000 rpm for 10-20 min, then transfer to a sealed reactor, heat to 105°C under nitrogen protection, keep the temperature for 1-3 h, cool and discharge, dry at 100°C for 1-3 h to obtain silane polyester-modified glass fiber; (3) Disperse the nano-ceramic powder in deionized water, add a dispersant, and ultrasonically disperse for 20-40 min to obtain a nano-ceramic suspension. Add silane polyester modified glass fiber to the suspension, stir at 80°C and 600 rpm for 20-40 min, and dry with hot air at 110°C for 2-4 h to obtain the modified glass fiber.

4. The high impact-resistant modified polyester for household appliances according to claim 3, characterized in that, The silane coupling agent is a mixture of KH-550 and KH-570 in a mass ratio of 7:3; The ethanol and water are mixed at a volume ratio of 95:5; The nano-ceramic powder is a mixture of nano-titanium dioxide and nano-silicon dioxide in a mass ratio of 1:

1. The dispersant is polyethylene glycol 400.

5. The high impact-resistant modified polyester for household appliances according to claim 3, characterized in that, The mass ratio of the silane coupling agent, glass fiber, PCTG-g-MAH, azobisisobutyronitrile, and nano-ceramic powder is 1.2:100:0.8:0.03:0.

5.

6. The high impact-resistant modified polyester for household appliances according to claim 1, characterized in that, The preparation method of the modified nano-calcium carbonate includes the following steps: A. Dissolve POE-g-MAH in toluene to prepare a 10wt% solution. Add dried nano-calcium carbonate to a high-speed mixer, add the POE-g-MAH toluene solution, mix at 50℃ and 700rpm for 20~30min, remove toluene by vacuum distillation at 60℃ to obtain polyolefin elastomer-coated nano-calcium carbonate. B. Dissolve the phosphorus-nitrogen flame retardant precursor DOPO-MAL and titanate coupling agent in ethanol, stir for 20-40 minutes until completely dissolved, add polyolefin elastomer-coated nano-calcium carbonate, stir at 65°C and 800 rpm for 30-50 minutes, add anti-hydrolysis agent, continue stirring for 10-20 minutes, dry with hot air at 80°C for 3-5 hours, pulverize and pass through a 200-mesh sieve to obtain modified nano-calcium carbonate.

7. The high impact-resistant modified polyester for household appliances according to claim 6, characterized in that, The titanate coupling agent is titanate coupling agent NDZ-201; The anti-hydrolysis agent is a carbodiimide-based anti-hydrolysis agent; The mass ratio of the phosphorus-nitrogen flame retardant precursor, nano-calcium carbonate, DOPO-maleimide, titanate coupling agent, and anti-hydrolysis agent is 25:100:15:1.8:1.

2.

8. The high impact-resistant modified polyester for household appliances according to claim 6, characterized in that, The preparation method of the phosphorus nitrogen flame retardant precursor DOPO-MAL includes the following steps: a. Add DOPO and maleic anhydride to toluene, stir and dissolve under nitrogen protection, heat to 80°C, keep the reaction at this temperature for 3-5 hours, cool to room temperature and filter, wash the filter cake with toluene 1-3 times, and dry under vacuum at 60°C for 3-5 hours to obtain intermediate DOPO-MA. b. Add intermediate DOPO-MA and diethanolamine to toluene, stir and react at 70°C under nitrogen protection for 2-4 hours, then add p-toluenesulfonic acid, acetic anhydride and triethylamine, heat to 110°C, and reflux to remove water for 4-8 hours; c. Cool to room temperature, remove toluene by vacuum distillation, dissolve the residue in acetone, slowly add it dropwise to rapidly stirred deionized water, a white solid precipitates, filter, wash with deionized water until neutral, dry under vacuum at 60℃ for 4~8h to obtain crude DOPO-MAL, recrystallize with an acetone-water mixture of 8:2 (v / v), filter, and dry under vacuum at 80℃ for 6~10h to obtain the phosphorus-nitrogen flame retardant precursor DOPO-MAL.

9. The high impact-resistant modified polyester for household appliances according to claim 8, characterized in that, The molar ratio of DOPO to maleic anhydride is 1:1.05; The molar ratio of the intermediate DOPO-MA, diethanolamine, acetic anhydride, and triethylamine is 1:1:2:

2.

10. The method for preparing the high impact-resistant modified polyester for household appliances according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. According to the formula ratio, add PCTG resin, modified nano calcium carbonate, core-shell toughening agent, polyethylene glycol 2000, antioxidant, ethylene bis-stearamide and nucleating agent to a high-speed mixer and mix at 60℃ and 1200rpm for 5~15min to make it uniformly dispersed. S2. Add the mixed material from step S1 to the main feed port of a twin-screw extruder, add modified glass fiber from the side feed port, and melt-blend and extrude the mixture through the twin-screw extruder. Cool the melt in a 25°C water cooling tank, pelletize it, and vacuum dry it at 120°C for 2-4 hours to obtain the high impact-resistant modified polyester for household appliances.

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