High-flowability reclaimed material modified PET injection molding material and molding method thereof

Abstract

The invention provides a high-flowability reclaimed material modified PET injection molding material and a molding method thereof. Comprising the following steps: mixing the following components in percentage by weight: 65%-70% of recycled PET, 8%-12% of a PET-BA block copolymer, 2%-4% of a bifunctional polar chain extender, 1%-3% of a nitrogen-doped MXene nanosheet, 3%-6% of a thermally induced reversible Diels-Alder structural monomer, 8%-12% of a plasma modified POE-g-COOH toughening agent, 2%-4% of a polyester-amino silane grafted elastomer and 1%-3% of an efficient phosphate metal salt nucleating agent, by adding the PET-BA block copolymer, the nitrogen-doped MXene nanosheet and the Diels-Alder structural monomer, the melt viscosity of the material is remarkably reduced, the fluidity is improved, and the resistance in the injection molding process is reduced; according to the present invention, the difunctional polar chain extender and the plasma modified POE-g-COOH toughening agent are adopted to enhance the tensile strength, the impact toughness and the bending modulus of the recovered PET so as to make the material meet various molding requirements, and the nitrogen-doped MXene nanosheet and the efficient phosphate metal salt nucleating agent are added to improve the thermal conductivity and the crystallization rate of the material.

Description

Technical Field

[0001] The invention relates to the field of high-fluidity modified materials of recycled polyethylene terephthalate, in particular to a high-fluidity recycled material modified PET injection molding material and a molding method thereof, which are applied to the injection molding process. Background Art

[0002] With rising environmental awareness, the demand for plastic recycling is growing. Recycled PET (rPET) has become a valuable resource, particularly in the recycling of PET (polyethylene terephthalate) bottle flakes and packaging materials. However, rPET often suffers from shortcomings such as poor fluidity, difficulty in molding, and low mechanical properties, which limit its application in injection molding.

[0003] Currently, most recycled PET modification technologies focus on improving its flowability or enhancing its mechanical properties. However, while improving flowability, mechanical properties are often reduced, or comprehensive optimization of different performance requirements cannot be achieved. Therefore, how to further improve the flowability, mechanical properties, and thermal stability of recycled PET while retaining its advantages has become a technical challenge in the industry.

[0004] In order to meet this challenge, the present invention proposes a high-flow recycled material modified PET injection molding material and a molding method thereof. Summary of the Invention

[0005] In view of this, the present invention provides a high-flow recycled material modified PET injection molding material and a molding method thereof. The high-flow modified material based on recycled polyethylene terephthalate (rPET) is applied in the injection molding process, which can significantly improve the fluidity, mechanical properties and thermal stability, reduce the viscosity of the material during the injection molding process, improve production efficiency, and reduce molding defects, so as to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

[0006] The technical solution of the embodiment of the present invention is achieved as follows:

[0007] In the first aspect, the present invention provides a high-flow recycled material modified PET injection molding material, which includes the following components mixed in weight percentage: 65% to 70% recycled PET, 8% to 12% PET-BA block copolymer, 2% to 4% bifunctional polar chain extender, 1% to 3% nitrogen-doped MXene nanosheets, 3% to 6% thermally induced reversible Diels-Alder structure monomer, 8% to 12% plasma-modified POE-g-COOH toughening agent, 2% to 4% polyester-aminosilane grafted elastomer and 1% to 3% high-efficiency phosphate metal salt nucleating agent.

[0008] Further preferably, the bifunctional polar chain extender is a low molecular weight chain extender monomer containing epoxy and carboxyl groups.

[0009] Further preferably, the nitrogen-doped MXene is nitrogen-doped Ti3C2Tx, and its particle size is less than 100 nm.

[0010] Further preferably, the thermally induced reversible Diels-Alder structure monomer is a monomer containing a Diels-Alder reaction functional group, which undergoes a cross-linking reaction when heated to the injection molding temperature.

[0011] Further preferably, the plasma-modified POE-g-COOH toughening agent is treated under argon plasma conditions for 5 minutes.

[0012] A second aspect: A molding method of a high-flow recycled material modified PET injection molding material, comprising the following steps:

[0013] Step 1: crushing, alkaline hot washing and vacuum drying the recovered PET to obtain dry recovered PET raw material;

[0014] Step 2: mixing the components described in PET-BA block copolymer, bifunctional polar chain extender, nitrogen-doped MXene nanosheets, thermally induced reversible Diels-Alder structural monomer, plasma-modified POE-g-COOH toughening agent, polyester-aminosilane grafted elastomer and high-efficiency phosphate metal salt nucleating agent to obtain a premix;

[0015] Step 3: feeding the premix obtained in step 2 into a twin-screw extruder for melt blending, setting the temperature to 180° C. to 235° C. and the shear rate to 300 rpm, performing devolatilization treatment, and cooling and pelletizing the obtained pellets;

[0016] Step 4: Dry the obtained pellets and send them into an injection molding machine for injection molding. The temperature is set to 255°C to 265°C, the mold temperature is 80°C to 95°C, and the molding pressure is 900 to 1200 bar.

[0017] Further preferably, the temperature settings of the twin-screw extruder are: feeding section temperature: 180°C; heating section temperature: 200°C, 220°C, 230°C, 235°C; and the operating temperature of the vacuum devolatilization device is 150°C to 180°C.

[0018] Further preferred: the melt flow rate of the injection molded product is greater than 45g / 10min, the tensile strength is greater than 50MPa, and the notched impact strength is greater than 8kJ / m 2 .

[0019] Further preferably, the recycled PET is crushed, including using recycled PET bottle flakes or films as the main material, and undergoing crushing and washing treatment, and the crushed particle size is 4 to 6 mm.

[0020] Further preferably, the PET-BA block copolymer comprises PET, butadiene and acrylic acid.

[0021] The embodiment of the present invention adopts the above technical solution, which has the following advantages:

[0022] The present invention significantly reduces the melt viscosity of the material, improves fluidity, and reduces resistance during the injection molding process by adding PET-BA block copolymer, nitrogen-doped MXene nanosheets, and Diels-Alder structural monomers;

[0023] The use of bifunctional polar chain extenders and plasma-modified POE-g-COOH toughening agents enhances the tensile strength, impact toughness and flexural modulus of recycled PET, enabling the material to meet various molding requirements;

[0024] The addition of nitrogen-doped MXene nanosheets and high-efficiency phosphate metal salt nucleating agents improves the thermal conductivity and crystallization rate of the material, reduces warping and bubbles during the molding process, and improves the appearance quality of the product.

[0025] Making full use of recycled PET reduces the environmental pressure of plastic waste and conforms to modern environmental protection concepts.

[0026] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 The figure is a flow chart of the molding method of the high-flow recycled material modified PET injection molding material of the present invention. DETAILED DESCRIPTION

[0029] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0030] The following is combined with Figure 1 The embodiments of the present invention are described in detail.

[0031] Preparation Example 1

[0032] Preparation examples of raw materials and intermediates:

[0033] The raw materials for the preparation examples of this application can be obtained from the market:

[0034] PET-BA block copolymer, bifunctional polar chain extender, nitrogen-doped MXene nanosheets, thermally induced reversible Diels-Alder structural monomer, plasma-modified POE-g-COOH toughening agent, polyester-aminosilane grafted elastomer and high-efficiency phosphate metal salt nucleating agent.

[0035] A high-flow recycled material modified PET injection molding material, comprising:

[0036] Recycled PET: 70%, PET-BA block copolymer: 10%, bifunctional polar chain extender: 3%, nitrogen-doped MXene nanosheets: 2%, thermally induced reversible Diels-Alder structural monomer: 5%, plasma-modified POE-g-COOH toughening agent: 10%, polyester-aminosilane grafted elastomer: 3% and high-efficiency phosphate metal salt nucleating agent: 2%.

[0037] 1. Recycled PET (rPET) main material;

[0038] Source and Processing: We use recycled PET bottle flakes or film as the primary feedstock, which is crushed (to a particle size of approximately 4-6mm) and washed to remove contaminants, ink, and other impurities. This recycled PET undergoes a high-efficiency hot water wash (typically using a 0.5% sodium hydroxide solution) and is vacuum-dried to a moisture content of less than 0.05%.

[0039] Function: As the matrix of the material, it provides good toughness, mechanical properties and structural stability.

[0040] 2.PET-BA block copolymer;

[0041] Name and Structure: PET-BA block copolymer (PET-butadiene-acrylate) is a modifier designed to improve fluidity. Made from PET, butadiene (BA), and acrylic acid (acrylate) blocks, this copolymer possesses a unique segment structure that modifies the material's melt fluidity and enhances its flow properties under low shear conditions.

[0042] Function:

[0043] Improve fluidity: Through the self-assembly of block copolymer segments, the viscosity of the melt is reduced and the fluidity in the molten state is optimized.

[0044] Enhanced toughness: By introducing elastic components such as butadiene, the impact toughness and durability of rPET are improved.

[0045] 3. Bifunctional polar chain extender;

[0046] Name and mechanism of action: This chain extender is a molecule with bifunctional groups (e.g., epoxy and carboxyl groups) that crosslinks with PET chains in the melt, significantly increasing molecular weight. Extenders are typically low-molecular-weight compounds such as epoxy acrylates or difunctional epoxides.

[0047] Function:

[0048] Enhance melt fluidity: By changing the structure of the molecular chain, reducing the interaction between chains, and improving melt fluidity.

[0049] Improve mechanical properties: After the chain extension reaction, the increase in molecular weight helps to improve the tensile strength and flexural modulus of the material.

[0050] 4. Nitrogen-doped MXene nanosheets;

[0051] MXene (Ti3C2Tx) is a two-dimensional material composed of titanium-group metal carbides or nitrides, exhibiting excellent electrical conductivity, thermal stability, and surface modification capabilities. This material is nitrogen-doped to further optimize its dispersibility and fluxing properties.

[0052] Function:

[0053] Reduce melt viscosity: The layered structure of MXene nanosheets can significantly reduce the internal friction of the melt and enhance fluidity.

[0054] Improved thermal conductivity: The addition of nanosheets improves the thermal conductivity of the material, contributing to a more uniform temperature distribution and reducing mold overheating or uneven cooling during the injection molding process.

[0055] Fluxing and interface lubrication: When MXene is blended with other ingredients, it can improve the fluidity between different components and reduce the resistance when the material is melted.

[0056] 5. Thermally induced reversible Diels-Alder structure monomer;

[0057] The Diels-Alder reaction is an organic chemical reaction in which Diels-Alder monomers undergo reversible crosslinking under thermal conditions, forming a stable ring structure. This monomer can be triggered by high temperatures during the injection molding process to participate in the crosslinking-unlinking reaction.

[0058] Function:

[0059] Improve fluidity: In the early stage of injection molding, Diels-Alder monomer increases the structure of the molecular chain through cross-linking reaction, which reduces the melt viscosity and improves fluidity.

[0060] Enhanced mechanical properties: After cooling, the cross-linking reaction is reversed, the chain structure is restored and its mechanical strength is enhanced.

[0061] 6. Plasma modified POE-g-COOH toughening agent;

[0062] POE-g-COOH (chlorinated polyolefin modified) is a common toughening agent. Modified by chlorinated polyolefin, it interacts with PET molecular chains through amino or carboxyl groups, increasing their compatibility. Plasma treatment (argon treatment) imparts active groups to the toughening agent's surface, enhancing its compatibility with the PET matrix.

[0063] Function:

[0064] Improve impact toughness: Tougheners improve the impact strength and impact resistance of materials by introducing a flexible phase.

[0065] Improve fluidity: Improve the interfacial affinity between PET and toughening agent, reduce friction, and help improve melt fluidity.

[0066] 7. Polyester-aminosilane grafted elastomer;

[0067] The grafted elastomer is prepared by grafting silane compounds onto polyester molecules through aminosilane grafting technology to form a highly compatible elastomer structure.

[0068] Function:

[0069] Improve compatibility: Improve the compatibility between the toughening agent and the PET matrix through chemical grafting, making the dispersion more uniform.

[0070] Improve the toughness of the material: enhance the fluidity of PET during high-temperature injection molding while maintaining its good mechanical properties.

[0071] 8. High-efficiency phosphate metal salt nucleating agent;

[0072] Nucleating agents are generally used to enhance the crystallinity of polymers, usually by introducing metal salts or phosphates (such as Na-PPA) to promote the rapid crystallization of polymer materials.

[0073] Function:

[0074] Accelerate crystallization rate: increase the cooling rate of injection molded products, shorten the molding cycle, and improve the molding efficiency of thin-walled parts.

[0075] Optimized molding: helps reduce warping and bubble generation, and improves product surface quality.

[0076] Example 2

[0077] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0078] Step 1: Recycled PET processing and pretreatment;

[0079] Recycled PET material preparation:

[0080] Choose the right recycled PET bottle flakes.

[0081] The PET bottle flakes were crushed to ensure a particle size of 4 mm.

[0082] Cleaning process:

[0083] Wash in an alkaline solution at 90°C (containing 0.5% sodium hydroxide) to remove surface oil and impurities.

[0084] The film was rinsed with deionized water and vacuum dried (temperature 120° C., duration 2 hours).

[0085] Step 2: Preparation of modified formula;

[0086] Premix:

[0087] According to the above formula, rPET, PET-BA block copolymer, chain extender, MXene nanosheets and other components were added into a high-speed mixer in proportion and mixed. The speed was set to 300 rpm and the mixing time was 5 minutes.

[0088] MXene should first be treated using ultrasonic dispersion technology to disperse it in the modifier to form a uniform gel.

[0089] Blending and granulation:

[0090] The pre-mixed material is fed into the twin-screw extruder and the temperature is set to:

[0091] Feeding section: 180℃;

[0092] Heating section: 200℃, 220℃, 230℃, 235℃;

[0093] The screw speed was 300 rpm for melt blending.

[0094] Use vacuum exhaust device to remove moisture and volatile substances to ensure the dryness of the product.

[0095] The mixture was cooled by water-cooling pelletizing technology to obtain pellets.

[0096] Step 3: Injection molding process;

[0097] Drying treatment:

[0098] The pellets were sent to a vacuum drying oven for two-stage drying, with the first stage temperature set at 80°C for 6 hours and the second stage temperature set at 120°C for 4 hours.

[0099] Injection molding machine adjustment:

[0100] The temperature setting of the injection molding machine is:

[0101] Barrel temperature: 255°C (front end), 265°C (back end);

[0102] Mold temperature: 80℃;

[0103] The injection pressure was set to 900 bar and the clamping force to 1000 kN.

[0104] Injection molding operation:

[0105] During the injection molding process, the Diels-Alder reaction is activated by high temperatures as the material enters the mold.

[0106] Use a lower injection speed to ensure that the material can flow evenly and fill the mold.

[0107] Molding cycle and cooling:

[0108] Cooling time: Adjust the mold cooling time according to the thickness of the product, which is 5 minutes.

[0109] After the mold cools down, remove the product to ensure there are no warps, bubbles or defects.

[0110] Example 4

[0111] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0112] Step 1: Recycled PET processing and pretreatment;

[0113] Recycled PET material preparation:

[0114] Select appropriate waste packaging materials.

[0115] The PET bottle flakes were crushed to ensure a particle size of 6 mm.

[0116] Cleaning process:

[0117] Wash in an alkaline solution at 90°C (containing 0.5% sodium hydroxide) to remove surface oil and impurities.

[0118] The film was rinsed with deionized water and vacuum dried (temperature 120° C., duration 2 hours).

[0119] Step 2: Preparation of modified formula;

[0120] Premix:

[0121] According to the above formula, rPET, PET-BA block copolymer, chain extender, MXene nanosheets and other components were added into a high-speed mixer in proportion and mixed. The speed was set to 300 rpm and the mixing time was 5 minutes.

[0122] MXene should first be treated using ultrasonic dispersion technology to disperse it in the modifier to form a uniform gel.

[0123] Blending and granulation:

[0124] The pre-mixed material is fed into the twin-screw extruder and the temperature is set to:

[0125] Feeding section: 180℃;

[0126] Heating section: 200℃, 220℃, 230℃, 235℃;

[0127] The screw speed was 300 rpm for melt blending.

[0128] Use vacuum exhaust device to remove moisture and volatile substances to ensure the dryness of the product.

[0129] The mixture was cooled by water-cooling pelletizing technology to obtain pellets.

[0130] Step 3: Injection Molding Process

[0131] Drying treatment:

[0132] The pellets were sent to a vacuum drying oven for two-stage drying, with the first stage temperature set at 80°C for 6 hours and the second stage temperature set at 120°C for 4 hours.

[0133] Injection molding machine adjustment:

[0134] The temperature setting of the injection molding machine is:

[0135] Barrel temperature: 255°C (front end), 265°C (back end);

[0136] Mold temperature: 95°C;

[0137] The injection pressure was set to 1200 bar and the clamping force was 1000 kN.

[0138] Injection molding operation:

[0139] During the injection molding process, the Diels-Alder reaction is activated by high temperatures as the material enters the mold.

[0140] Use a lower injection speed to ensure that the material can flow evenly and fill the mold.

[0141] Molding cycle and cooling:

[0142] Cooling time: Adjust the mold cooling time by 10 minutes according to the thickness of the product.

[0143] After the mold cools down, remove the product to ensure there are no warps, bubbles or defects.

[0144] Example 5

[0145] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0146] Step 1: Grind the recycled PET into 6mm particle size, then wash and dry it to ensure the moisture content is less than 0.05%.

[0147] Step 2: Add all components in proportion to the high-speed mixer and mix them to ensure uniform dispersion. Then send the mixture into a twin-screw extruder for melt blending at a set temperature of 235°C and a shear rate of 300 rpm for devolatilization.

[0148] Step 3: The pellets were cooled, cut into pellets, and then dried in a vacuum drying oven in two stages. The first drying stage was at 80°C for 6 hours, and the second drying stage was at 120°C for 4 hours.

[0149] Step 4: The dried pellets are fed into an injection molding machine for injection molding. The injection temperature is set to 265°C, the mold temperature is 95°C, and the injection pressure is 1200 bar.

[0150] Example 6

[0151] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0152] Step 1: Grind the recycled PET into 4mm particle size, then wash and dry it to ensure the moisture content is less than 0.05%.

[0153] Step 2: Add all components in proportion to the high-speed mixer and mix them to ensure uniform dispersion. Then send the mixture into a twin-screw extruder for melt blending at a set temperature of 180°C and a shear rate of 300 rpm for devolatilization.

[0154] Step 3: The pellets were cooled, cut into pellets, and then dried in a vacuum drying oven in two stages. The first drying stage was at 80°C for 6 hours, and the second drying stage was at 120°C for 4 hours.

[0155] Step 4: The dried pellets are fed into an injection molding machine for injection molding. The injection temperature is set to 250°C, the mold temperature is 80°C, and the injection pressure is 900 bar.

[0156] The melt flow rate (MFR) of the molded product is greater than 45g / 10min, the tensile strength is greater than 50MPa, and the impact strength is greater than 8kJ / m 2 , with smooth surface, no warping, no bubbles, and excellent mechanical properties and fluidity.

[0157] Example 7

[0158] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0159] Step 1: Pre-treatment of recycled PET;

[0160] The recycled PET bottle flakes are crushed into 6mm particles.

[0161] Alkaline hot washing (water temperature 90°C, alkali solution content 0.5% NaOH) is used to remove surface impurities and ink.

[0162] Use a vacuum drying oven for two-stage drying:

[0163] Stage 1: 80°C, 8 hours (initial dehydration);

[0164] The second stage: 120℃, 2 hours (deep devolatilization);

[0165] Step 2: Preparation of modified blending premix;

[0166] All ingredients were premixed in a high-speed mixer (300 rpm, 5 minutes) according to the proportions. Note that the nanoflux (MXene) should be ultrasonically dispersed in the blend to form a gel before addition.

[0167] The premixed material is fed into a twin-screw extruder for granulation:

[0168] Screw temperature range setting: 180℃, 200℃, 220℃, 230℃, 235℃;

[0169] The screw shear rate was controlled at 300 rpm to avoid excessive degradation of rPET.

[0170] The vacuum devolatilization port was maintained at -0.09 MPa to remove trace amounts of water and volatiles.

[0171] After discharging, the material is water-cooled, granulated, and dried for later use.

[0172] Step 3: high flow injection molding step;

[0173] The granulated material was dried (temperature 120°C, time 6 hours) and then added to the hopper of the injection molding machine.

[0174] Injection molding machine parameter setting:

[0175] Injection temperature: 265℃;

[0176] Mold temperature: 95°C;

[0177] Injection speed: rapid injection (>90% injection speed);

[0178] Injection holding pressure: 80 MPa, holding time: 5 seconds; cooling time: 15 seconds (because the nucleating agent increases the crystallization speed).

[0179] Example 8

[0180] A molding method of a high-flow recycled material modified PET injection molding material comprises the following steps:

[0181] Step 1: Pre-treatment of recycled PET;

[0182] The recycled PET bottle flakes are crushed into 5mm particles.

[0183] Alkaline hot washing (water temperature 90°C, alkali solution content 0.5% NaOH) is used to remove surface impurities and ink.

[0184] Use a vacuum drying oven for two-stage drying:

[0185] Stage 1: 80°C, 8 hours (initial dehydration);

[0186] The second stage: 120℃, 2 hours (deep devolatilization);

[0187] Step 2: Preparation of modified blending premix;

[0188] All ingredients were premixed in a high-speed mixer (300 rpm, 5 minutes) according to the proportions. Note that the nanoflux (MXene) should be ultrasonically dispersed in the blend to form a gel before addition.

[0189] The premixed material is fed into a twin-screw extruder for granulation:

[0190] Screw temperature range setting: 180℃, 200℃, 220℃, 230℃, 235℃;

[0191] The screw shear rate was controlled at 300 rpm to avoid excessive degradation of rPET.

[0192] The vacuum devolatilization port was maintained at -0.09 MPa to remove trace amounts of water and volatiles.

[0193] After discharging, the material is water-cooled, granulated, and dried for later use.

[0194] Step 3: high flow injection molding step;

[0195] The granulated material was dried (temperature 120°C, time 6 hours) and then added to the hopper of the injection molding machine.

[0196] Injection molding machine parameter setting:

[0197] Injection temperature: 260℃;

[0198] Mold temperature: 90℃;

[0199] Injection speed: rapid injection (>90% injection speed);

[0200] Injection holding pressure: 80MPa, holding time: 5 seconds;

[0201] Cooling time: 12 seconds (because the nucleating agent increases the crystallization speed).

[0202] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

[0203] Experimental data: as shown in Table 1:

[0204]

[0205] Table 1

[0206] The high-flow recycled PET injection molding material proposed in this invention effectively improves the fluidity, mechanical properties, and thermal stability of recycled PET, resolving the poor fluidity and molding difficulties of existing recycled PET materials. This material not only meets the dual requirements of fluidity and strength during injection molding, but also offers high environmental friendliness and sustainability, making it suitable for a wide range of injection molded products and promising application prospects.

[0207] The high-flow recycled-material-modified PET injection molding material of the present invention successfully achieves a significant improvement in the melt flowability of recycled PET (rPET) while maintaining excellent mechanical properties through precise proportions and an innovative combination of modifiers. This breakthrough, achieved through the introduction of PET-BA block copolymers, nitrogen-doped MXene nanosheets, and thermally induced reversible Diels-Alder monomers, represents a qualitative leap over traditional modification methods. Conventional rPET materials typically sacrifice mechanical properties when improving flowability, but the material of the present invention achieves an excellent balance between flowability and mechanical properties, resolving this technical challenge.

[0208] This invention, for the first time, incorporates heat-induced reversible Diels-Alder structural monomers into rPET modification. Leveraging the reversibility of the Diels-Alder reaction, this crosslinking reaction is activated by heating during the injection molding process. This reaction improves the material's fluidity during injection molding while simultaneously restoring its mechanical strength and thermal stability during cooling. This innovative solution ensures excellent fluidity during molding while retaining outstanding mechanical properties and thermal stability in the final product, representing an unprecedented solution.

[0209] This invention utilizes nitrogen-doped MXene nanosheets. The application of this high-performance nanomaterial in a rPET matrix represents a groundbreaking innovation. MXene nanosheets not only act as a filler to improve the material's thermal conductivity and thermal stability, but also, through nitrogen doping, enhance interfacial compatibility with the PET matrix, significantly increasing the material's crystallization rate and reducing defects such as warping and bubbles during molding. The introduction of this material represents a novel approach to rPET modification both domestically and internationally.

[0210] In this invention, the plasma-modified POE-g-COOH toughening agent is treated with argon plasma, improving its compatibility with the PET matrix and enhancing the material's toughness and impact strength. Compared to traditional toughening agents, the plasma-modified toughening agent used in this invention has stronger interfacial bonding ability, significantly improving the material's impact strength and tensile properties, resolving the application bottleneck of recycled PET materials with high impact strength requirements.

[0211] This invention innovatively utilizes a high-efficiency phosphate metal salt nucleating agent, which not only increases the crystallization rate of rPET but also effectively reduces warping during the molding process. This nucleating agent not only increases the crystallization rate but also improves the appearance of the product, resulting in a smoother and flatter surface for the injection-molded product, further enhancing the material's processability and appearance.

[0212] This invention efficiently modifies recycled PET using a variety of environmentally friendly modified materials, optimizing its fluidity and mechanical properties while avoiding the use of large quantities of new raw materials. This material not only reduces the environmental impact of plastic waste, aligning with the concept of sustainable development, but also, due to its excellent performance, effectively reduces scrap rates and energy consumption during the injection molding process, further improving production efficiency and environmental friendliness.

[0213] The preparation method provided by the present invention not only optimizes material properties by precisely controlling the proportions of the various ingredients, but also employs a multi-stage temperature control and mixing process. Blending and vacuum drying in a twin-screw extruder ensure uniformity and consistency among the various material components. Furthermore, efficient injection molding technology is employed to ensure that the high-flow recycled material-modified PET injection molding material achieves good fluidity and molding quality at relatively low temperatures, reducing production costs and energy consumption.

[0214] The advantages of the present invention are:

[0215] Through the precise ratio of PET-BA block copolymer, nitrogen-doped MXene nanosheets and thermally induced reversible Diels-Alder structural monomers, the fluidity, mechanical properties and thermal stability of rPET are optimized, solving the contradiction between fluidity and strength.

[0216] The Diels-Alder reaction technology was applied to rPET modification for the first time, providing an innovative solution for reversible cross-linking.

[0217] The use of advanced materials such as nitrogen-doped MXene nanosheets, plasma-modified POE-g-COOH toughening agents and high-efficiency phosphate metal salt nucleating agents has significantly improved the comprehensive performance and production stability of the materials.

[0218] The use of environmentally friendly modification technology is in line with the concept of green and sustainable development.

[0219] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various modifications and substitutions within the technical scope disclosed in the present invention, and such modifications and substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A high-flow recycled material modified PET injection molding material, characterized in that: The invention comprises the following components mixed in weight percentage: 65% to 70% of recycled PET, 8% to 12% of PET-BA block copolymer, 2% to 4% of bifunctional polar chain extender, 1% to 3% of nitrogen-doped MXene nanosheets, 3% to 6% of thermally induced reversible Diels-Alder structural monomer, 8% to 12% of plasma-modified POE-g-COOH toughening agent, 2% to 4% of polyester-aminosilane grafted elastomer and 1% to 3% of high-efficiency phosphate metal salt nucleating agent.

2. The high-flow recycled material modified PET injection molding material according to claim 1, characterized in that: The bifunctional polar chain extender is a low molecular weight chain extender monomer containing epoxy and carboxyl groups.

3. The high-flow recycled material modified PET injection molding material according to claim 1, characterized in that: The nitrogen-doped MXene is nitrogen-doped Ti3C2Tx, and its particle size is less than 100 nm.

4. The high-flow recycled material modified PET injection molding material according to claim 1, characterized in that: The thermally induced reversible Diels-Alder structure monomer is a monomer containing a Diels-Alder reaction functional group, and a cross-linking reaction occurs when heated to the injection molding temperature.

5. The high-flow recycled material modified PET injection molding material according to claim 1, characterized in that: The plasma-modified POE-g-COOH toughening agent is treated under argon plasma conditions for 5 minutes.

6. A method for molding a high-flow recycled material modified PET injection molding material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: crushing, alkaline hot washing and vacuum drying the recovered PET to obtain dry recovered PET raw material; Step 2: mixing the components described in PET-BA block copolymer, bifunctional polar chain extender, nitrogen-doped MXene nanosheets, thermally induced reversible Diels-Alder structural monomer, plasma-modified POE-g-COOH toughening agent, polyester-aminosilane grafted elastomer and high-efficiency phosphate metal salt nucleating agent to obtain a premix; Step 3: feeding the premix obtained in step 2 into a twin-screw extruder for melt blending, setting the temperature to 180° C. to 235° C. and the shear rate to 300 rpm, performing devolatilization treatment, and cooling and pelletizing the obtained pellets; Step 4: Dry the obtained pellets and send them into an injection molding machine for injection molding. The temperature is set to 255°C to 265°C, the mold temperature is 80°C to 95°C, and the molding pressure is 900 to 1200 bar.

7. The molding method of the high-flow recycled material modified PET injection molding material according to claim 6, characterized in that: The temperature settings of the twin-screw extruder are as follows: feeding section temperature: 180°C; heating section temperature: 200°C, 220°C, 230°C, 235°C; and the operating temperature of the vacuum devolatilization device is 150°C to 180°C.

8. The molding method of the high-flow recycled material modified PET injection molding material according to claim 6, characterized in that: The injection molded product has a melt flow rate greater than 45g / 10min, a tensile strength greater than 50MPa, and a notched impact strength greater than 8kJ / m 2 .

9. The molding method of the high-flow recycled material modified PET injection molding material according to claim 6, characterized in that: The recycled PET is crushed, including using recycled PET bottle flakes or films as the main material, and undergoing crushing and washing treatment, and the crushed particle size is 4-6 mm.

10. The molding method of the high-flow recycled material modified PET injection molding material according to claim 6, characterized in that: The PET-BA block copolymer includes PET, butadiene and acrylic acid.

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