PETS lubricant for engineering plastics and preparation method thereof

Abstract

The invention relates to the technical field of plastic lubricants, and particularly discloses a PETS lubricant for engineering plastics and a preparation method of the PETS lubricant. The PETS lubricant for the engineering plastics is prepared from the following raw materials in parts by weight: 65 to 85 parts of modified PETS, 10 to 15 parts of maleic anhydride grafted ethylene-vinyl acetate, 5 to 15 parts of fluorinated carbon nanotubes, 4 to 7 parts of fluorine-containing ionic liquid and 0.5 to 1 part of antioxidant. The PETS lubricant for the engineering plastics can be used for processing the engineering plastics, has excellent internal and external lubrication performance, and can remarkably improve the mechanical property and the surface quality of engineering plastic products and improve the high-temperature friction resistance of the engineering plastics at the same time.

Description

Technical Field

[0001] This application relates to the technical field of plastic lubricants, and more specifically, it relates to a PETS lubricant for engineering plastics and its preparation method. Background Art

[0002] Engineering plastics, such as polyamide (PA), polycarbonate (PC), polyethylene terephthalate (PET), and polyphenylene sulfide (PPS), etc., have excellent mechanical properties, heat resistance, dimensional stability, and chemical corrosion resistance. With the wide application of engineering plastics in modern industrial fields such as automobiles, mechanical industries, electronics and electrical appliances, and aerospace, higher requirements are put forward for their processing performance and product quality.

[0003] During the processing of engineering plastics, due to their high melt viscosity and poor fluidity, lubricants are often needed to improve their processing performance, reduce equipment wear, and prevent the melt from adhering to the surface of hot processing equipment, thereby improving production efficiency and the surface quality of products and other core indicators.

[0004] In view of the above related technologies, the inventor found that it is often difficult for engineering plastic lubricants in the prior art to achieve synergistic effect of internal and external lubrication. In terms of internal lubrication, although existing lubricants for engineering plastics can, to a certain extent, reduce the melt viscosity and improve its fluidity, they often do so at the expense of the mechanical properties of the engineering plastics themselves. For example, traditional stearate lubricants and polyethylene waxes will cause irreversible mechanical property losses to the engineering plastics themselves. In terms of external lubrication, during high-speed extrusion or injection molding processes, existing lubricants are easily damaged under the action of high shear forces and cannot continuously provide lubrication support for the processing process. For example, silicone lubricants will have their molecular chain structures damaged under high shear, resulting in a decrease in the load-bearing capacity of the lubricant, being unable to effectively separate the friction surfaces, and exacerbating the high-shear friction and adhesion problems.

[0005] Insufficient internal lubrication performance of the lubricant will lead to poor fluidity of the engineering plastic melt during the processing process, increasing the processing difficulty, while insufficient external lubrication performance will prevent an effective lubrication interface from being formed between the plastic surface and the processing equipment, increasing friction and adhesion, affecting the surface quality of the product and the service life of the equipment, and making it difficult to meet the growing high-performance lubrication requirements. Summary of the Invention

[0006] In order to enhance the synergistic effect of internal and external lubrication and high-temperature friction performance of lubricants for engineering plastics, and improve the mechanical properties and surface quality of engineering plastic products, this application provides a PETS lubricant for engineering plastics and its preparation method.

[0007] In the first aspect, this application provides a PETS lubricant for engineering plastics, adopting the following technical solution: A PETS lubricant for engineering plastics, by weight, the raw materials include 65 - 85 parts of modified PETS, 10 - 15 parts of maleic anhydride grafted ethylene - vinyl acetate, 5 - 15 parts of fluorinated carbon nanotubes, 4 - 7 parts of fluorine - containing ionic liquid, and 0.5 - 1 part of antioxidant.

[0008] The inventors found that fluorinated carbon nanotubes and fluorine - containing ionic liquids can form a nano - enhanced and fluorinated synergistic solid - liquid lubrication system inside the modified PETS matrix. The fluorine - containing ionic liquid and the outer wall of the fluorinated carbon nanotubes can form a core - shell structure through fluorine - fluorine interaction.

[0009] Fluorinated carbon nanotubes have a low surface energy and can form an oriented nano - ball structure on the surface of the abrasive tool, converting sliding friction into rolling friction, significantly reducing the friction coefficient of the system, and thus reducing the demolding force. In addition, the fluorine atoms on the surface of F - CNT form hydrogen bonds with polar groups in the engineering plastic matrix, which are dynamically reversible. Under the action of high shear force or high temperature, the hydrogen bonds are preferentially broken to release F - CNT fragments. These fragments fill the micro - cracks through physical adsorption or re - formation of hydrogen bonds, forming a lubricating film with self - repair ability, which significantly improves the ability of the lubricant to inhibit crack propagation under high shear force and high temperature.

[0010] On the one hand, the fluorine - containing ionic liquid can cover the areas not contacted by the fluorinated carbon nanotubes, forming a continuous lubricating layer to avoid dry friction and forming a solid - liquid synergistic lubrication system. On the other hand, the anions of the fluorine - containing ionic liquid can form strong hydrogen bonds with the ester groups of the modified PETS, further improving the internal lubrication ability of the lubricant, increasing the melt flow rate of the engineering plastic, and can also be adsorbed on the surface of the metal friction pair through electrostatic adsorption to form a negative charge layer, reducing the direct contact area of the surface friction of the same - polarity engineering plastic, and further improving the external lubrication performance of the lubricant.

[0011] Maleic anhydride grafted ethylene - vinyl acetate, as a polar compatibilizer, forms chemical bonds with the engineering plastic matrix through maleic anhydride groups, promoting the compatibility between the lubricant and the engineering plastic and the uniform distribution in the plastic matrix, preventing the migration of the lubricant. At the same time, a compatibilizing interface layer is formed with the plastic matrix during the processing, reducing the stress concentration phenomenon and ensuring that the engineering plastic has excellent mechanical properties.

[0012] By adopting the above technical scheme, using modified PETS as the matrix to form a fluorinated solid - liquid synergistic lubrication system inside, significantly improves the high - temperature wear resistance and high - shear force resistance of the PETS - based lubricant, endows the PETS - based lubricant with better internal and external lubrication performance, significantly improves the mechanical strength and high - temperature wear resistance of the engineering plastic during the processing, and improves the mechanical properties and surface quality of the engineering plastic products.

[0013] Optionally, by weight, the raw materials of the modified PETS include 8-11 parts of pentaerythritol, 70-85 parts of stearic acid, 10-20 parts of long-chain alkyl mercaptan, and 0.08-0.12 parts of p-toluenesulfonic acid; the long-chain alkyl mercaptan is selected from one or more combinations of dodecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan, octadecyl mercaptan, and docosyl mercaptan.

[0014] The inventors found that the modification of PETS by using long-chain alkyl mercaptan through transesterification introduced thioester bonds and flexible long chains. The introduction of long-chain alkyls increased the flexibility and disorder of the molecular chain, destroyed the crystalline structure of PETS and thus reduced the crystallinity, which further decreased the viscosity of the melt during the processing of engineering plastics and improved the melt flowability better.

[0015] On the one hand, the introduction of thioester bonds enhanced the interfacial adsorption ability between the lubricant and the engineering plastic matrix, making the compatibility between the PETS-based lubricant and the engineering plastic stronger and preventing the migration of the lubricant; on the other hand, thioester bonds could break under high shear to release lubricating molecules and could self-repair through the exchange reaction of mercaptan and disulfide after the shear stopped, which significantly enabled the lubricant to maintain good lubrication effect under long-term and high-load working conditions and significantly improved its high-shear resistance. In addition, the introduction of sulfur element could react with the metal surface to form a ferrous sulfide protective layer, making the lubricant form a more stable boundary lubricating film with the metal surface and improving its anti-wear and extreme pressure properties.

[0016] By adopting the above technical solution, compared with traditional PETS, the modified PETS has further enhanced compatibility with engineering plastics, has excellent internal and external lubrication properties, and also has significantly improved high-shear resistance.

[0017] Optionally, the long-chain alkyl mercaptan is a mixture of dodecyl mercaptan and hexadecyl mercaptan with a mass ratio of 1:(0.5-1).

[0018] By adopting the above technical solution, the inventor found that experiments showed that the modification of PETS with a mixture of dodecyl mercaptan and cetyl mercaptan could obtain a lubricant with optimal performance. This might be because the carbon chain of C12 alkyl mercaptan was relatively short and had higher reactivity, enabling it to react rapidly with the active sites in PETS molecules during the modification reaction to form thioester bonds, reducing the surface energy of the lubricating film and the frictional resistance. While the carbon chain of C16 alkyl mercaptan was relatively long and had slightly lower reactivity, it could continue to participate in the reaction in the later stage of the reaction, providing a longer carbon chain for PETS and further enhancing the flexibility and lubricity of the modified PETS molecules. The alkyl chains of different lengths intertwined and cooperated with each other to form a three-dimensional network structure, further enhancing the thermal stability and chemical stability of the lubricant, enabling it to maintain the performance of the lubricant under harsh working conditions such as high temperature and high shear, and balancing the internal and external lubrication persistence of the lubricant and the interfacial bonding stability with the plastic matrix.

[0019] Optionally, the preparation method of the modified PETS includes the following steps: Under the protection of nitrogen atmosphere, heat stearic acid to 80 - 100 °C, add pentaerythritol and p-toluenesulfonic acid, continue to heat to 160 - 180 °C, stir and react for 2.5 - 4 h, dehydrate under vacuum, then cool to 130 - 140 °C, add long-chain alkyl mercaptan, continue to stir and react for 3.5 - 4.5 h, introduce nitrogen bubbling to assist dehydration, adjust the pH of the system to (6.5 ± 0.3) after cooling to 80 °C, wash while it is hot, then filter and cool, and vacuum dry at 60 - 80 °C for 4 - 6 h to obtain the product.

[0020] Optionally, the fluorinated ionic liquid is selected from any one of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0021] By adopting the above technical solution, the above fluorinated ionic liquids can all maintain good thermal stability and low viscosity at high temperature and high shear rate, ensuring that a continuous lubricating film can be formed at high temperature and significantly improving the lubrication performance of the lubricant under high temperature and high shear.

[0022] Optionally, the antioxidant is antioxidant 1076 and antioxidant 168 with a mass ratio of 1:(0.2 - 0.5).

[0023] By adopting the above technical solution, the dual antioxidant mechanism extends the service life of the lubricant and inhibits the oxidation and yellowing phenomenon of plastics.

[0024] In a second aspect, the present application provides a method for preparing a PETS lubricant for engineering plastics, adopting the following technical solution: A method for preparing a PETS lubricant for engineering plastics, comprising the following steps: Mix carbon fluoride nanotubes and a fluorine-containing ionic liquid and stir evenly to form a pre-dispersed slurry; Mix modified PETS, maleic anhydride grafted ethylene-vinyl acetate, the pre-dispersed slurry and an antioxidant, and then obtain the product after melt extrusion granulation.

[0025] Optionally, the carbon fluoride nanotubes are pretreated as follows before being mixed with the fluorine-containing ionic liquid: Immerse the carbon fluoride nanotubes in a concentrated acid solution, perform ultrasonic treatment at 50-60 °C for 45-60 min, then wash and dry to obtain surface-modified carbon fluoride nanotubes; Immerse the surface-modified carbon fluoride nanotubes in a 3-6 wt% silane coupling agent solution, perform ultrasonic treatment at 55-65 °C for 2-3 h, centrifuge, wash and dry to obtain pretreated carbon fluoride nanotubes.

[0026] By adopting the above technical solution, the carbon fluoride nanotubes pretreated by surface modification can be better dispersed in the lubricant system after being mixed with the fluorine-containing ionic liquid, and a more stable lubrication network system is formed between the carbon fluoride nanotubes and the modified PETS matrix, synergistically improving the high-temperature and high-shear friction performance and the interfacial strength.

[0027] Optionally, the silane coupling agent is an amino silane coupling agent, selected from any one of γ-aminopropyltriethoxysilane coupling agent (KH550) and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (KH792).

[0028] By adopting the above technical solution, compared with other types of surface modifiers, the amino group of the amino silane coupling agent can act as a bridge to enhance the interaction between the carbon fluoride nanotubes and the methylimidazole bis(trifluoromethanesulfonyl)imide salt ionic solution, and at the same time enhance the compatibility between the carbon fluoride nanotubes and the PETS matrix.

[0029] In summary, the present application has the following beneficial effects: 1. Since the lubricant of the present application is prepared with long-chain alkyl mercaptan-modified PETS as the matrix, thioester bonds and alkyl flexible long chains are introduced, increasing the flexibility and disorder of the lubricant molecular chains, reducing the overall crystallinity, significantly enhancing the internal lubricity, further decreasing the melt viscosity during the processing of engineering plastics, and better improving the fluidity. The introduction of thioester bonds enhances the compatibility between the modified PETS and the engineering plastic matrix, significantly improving the external lubrication performance. The thioester bonds can achieve the self-repair ability of the lubricant under high-temperature and high-shear conditions, maintaining a long-term good lubrication effect. The introduction of sulfur elements can also react on the metal surface to form an iron sulfide protective layer, enabling the lubricant to form a more stable boundary lubricating film with the metal surface and enhancing its anti-friction performance.

[0030] 2. The present application introduces fluorinated carbon nanotubes and fluorinated ionic liquids into the modified PETS matrix to form a solid-liquid synergistic lubrication system. The fluorinated ionic liquid and the outer wall of the fluorinated carbon nanotubes can form a core-shell structure through fluorine-fluorine interactions. The fluorinated carbon nanotubes convert sliding friction into rolling friction, and the fluorinated ionic liquid further covers the areas not in contact with the fluorinated carbon nanotubes, significantly reducing the friction coefficient of the lubrication system, forming a continuous and stable lubricating layer, significantly enhancing the internal and external lubrication performance of the lubricant, and improving the mechanical properties and surface quality of engineering plastic products.

[0031] 3. The present application prepares the lubricant by surface-modifying and pre-treating the fluorinated carbon nanotubes with an amino coupling agent and then mixing them with other raw materials. The amino group can act as a bridge to enhance the interaction between the fluorinated carbon nanotubes and the methylimidazole bis(trifluoromethanesulfonyl)imide salt ionic solution, as well as the compatibility between the fluorinated carbon nanotubes and the PETS matrix, enabling them to disperse better in the modified PETS matrix after mixing to form a more stable lubrication network system, synergistically enhancing the high-temperature and high-shear friction resistance and interface strength. Detailed implementation manners

[0032] The following examples further illustrate the present application in detail.

[0033] Raw materials Unless otherwise specified, the raw materials used in the preparation examples, examples, and comparative examples of the present application are all commercially available products, specifically: Pentaerythritol, C 5 H 12 O 4 , CAS: 115 - 77 - 5; Stearic acid, C 18 H 36 O 2 , CAS: 57 - 11 - 4; Fluorinated carbon nanotubes, selected from Jiangsu Xianfeng Nano Materials Technology Co., Ltd., 101909, with a particle size of 20 - 30 nm; Ordinary carbon nanotubes, with a particle size of 20 - 40 nm; Dodecyl mercaptan, C 12 H 26 S, tert-dodecyl mercaptan, CAS: 25103 - 58 - 6; Tetradecyl mercaptan, C 14 H 30 S, CAS: 2079 - 95 - 0; Hexadecyl mercaptan, C 16 H 34 S, n-hexadecyl mercaptan, CAS: 2917 - 26 - 2; Octadecyl mercaptan, C 18 H 38 S, n-octadecyl mercaptan, CAS: 2885 - 00 - 9; Docosyl mercaptan, C 22 H 46 S, 1-docosyl mercaptan, CAS: 7773 - 83 - 3; Antioxidant 1076, selected from BASF, Antioxidant 1076; Antioxidant 168, selected from BASF, Antioxidant 168.

[0034] Preparation examples of modified PETS Preparation example 1 Modified PETS, with the raw materials and dosages shown in Table 1, where the long-chain alkyl mercaptan is a mixture of dodecyl mercaptan and hexadecyl mercaptan with a mass ratio of 1:0.8.

[0035] Table 1 The preparation method of the above-mentioned modified PETS includes the following steps: S1: Under the protection of nitrogen atmosphere, add stearic acid to the reaction kettle, heat to 90 °C, then add pentaerythritol and p-toluenesulfonic acid, stir at a speed of 500 rpm, continue to heat to 180 °C, stir and react for 4 h, and obtain the intermediate crude ester after vacuum dehydration; S2: Cool the intermediate crude ester to 140 °C, add long-chain alkyl mercaptan, continue to stir and react for 4.5 h, introduce nitrogen bubbling to assist dehydration, cool to 80 °C, add sodium bicarbonate buffer solution to adjust the system pH to (6.5 ± 0.3), wash while it is hot, filter, cool, and vacuum dry at 70 °C for 5 h to obtain the product.

[0036] Preparation example 2 Modified PETS, different from Preparation Example 1 in that the raw materials and their dosages are shown in Table 1, wherein the long-chain alkyl mercaptan is dodecyl mercaptan and cetyl mercaptan with a mass ratio of 1:0.5; The preparation method of the above-mentioned modified PETS includes the following steps: S1: Add stearic acid to the reaction kettle under the protection of nitrogen atmosphere, heat to 80 °C, then add pentaerythritol and p-toluenesulfonic acid, stir at a speed of 500 rpm, continue to heat to 160 °C, stir and react for 4 h, and obtain the intermediate crude ester after vacuum dehydration; S2: Cool the intermediate crude ester to 130 °C, then add the long-chain alkyl mercaptan, continue to stir and react for 4.5 h, introduce nitrogen bubbling to assist dehydration, cool to 80 °C, add sodium bicarbonate buffer solution to adjust the pH of the system to (6.5 ± 0.3), wash while it is hot, filter, cool, and vacuum dry at 60 °C for 6 h to obtain the product.

[0037] Preparation Example 3 Modified PETS, different from Preparation Example 1 in that the raw materials and their dosages are shown in Table 1, wherein the long-chain alkyl mercaptan is dodecyl mercaptan and cetyl mercaptan with a mass ratio of 1:1; The preparation method of the above-mentioned modified PETS includes the following steps: S1: Add stearic acid to the reaction kettle under the protection of nitrogen atmosphere, heat to 100 °C, then add pentaerythritol and p-toluenesulfonic acid, stir at a speed of 500 rpm, continue to heat to 180 °C, stir and react for 2.5 h, and obtain the intermediate crude ester after vacuum dehydration; S2: Cool the intermediate crude ester to 140 °C, then add the long-chain alkyl mercaptan, continue to stir and react for 3.5 h, introduce nitrogen bubbling to assist dehydration, cool to 80 °C, add sodium bicarbonate buffer solution to adjust the pH of the system to (6.5 ± 0.3), wash while it is hot, filter, cool, and vacuum dry at 80 °C for 4 h to obtain the product.

[0038] Preparation Example 4 Modified PETS, different from Preparation Example 1 in that the raw materials and their dosages are shown in Table 1, wherein the long-chain alkyl mercaptan is tetradecyl mercaptan and octadecyl mercaptan with a mass ratio of 1:0.8; The preparation method of the above-mentioned modified PETS includes the following steps: S1: Add stearic acid to the reaction kettle under the protection of nitrogen atmosphere, heat to 90 °C, then add pentaerythritol and p-toluenesulfonic acid, stir at a speed of 500 rpm, continue to heat to 170 °C, stir and react for 3.5 h, and obtain the intermediate crude ester after vacuum dehydration; S2: Cool the intermediate crude ester to 140 °C, add long-chain alkyl mercaptan, continue stirring and reacting for 4 h, introduce nitrogen gas for bubbling to assist dehydration, cool to 80 °C, add sodium bicarbonate buffer solution to adjust the pH of the system to (6.5 ± 0.3), wash while it is hot, then filter and cool, and dry under vacuum at 70 °C for 5 h to obtain the product.

[0039] Preparation Example 5 Modified PETS, different from Preparation Example 1 in that the long-chain alkyl mercaptan in the raw materials is cetyl mercaptan and docosyl mercaptan with a mass ratio of 1:0.8, and other steps are the same as those in Preparation Example 1.

[0040] Preparation Example 6 Modified PETS, different from Preparation Example 1 in that the long-chain alkyl mercaptan in the raw materials is dodecyl mercaptan, and other steps are the same as those in Preparation Example 1.

[0041] Preparation Example 7 Modified PETS, different from Preparation Example 1 in that the long-chain alkyl mercaptan in the raw materials is cetyl mercaptan, and other steps are the same as those in Preparation Example 1.

[0042] Preparation Example 8 Modified PETS, different from Preparation Example 1 in that the long-chain alkyl mercaptan in the raw materials is dodecyl mercaptan and cetyl mercaptan with a mass ratio of 1:2, and other steps are the same as those in Preparation Example 1.

[0043] Preparation Example 9 Modified PETS, different from Preparation Example 1 in that its preparation method includes the following steps: Under the protection of nitrogen atmosphere, add stearic acid to the reaction kettle, heat to 90 °C, add pentaerythritol and p-toluenesulfonic acid, stir at a speed of 500 rpm, continue heating to 180 °C, stir and react for 4 h, dehydrate under vacuum, then cool to 80 °C, add sodium bicarbonate buffer solution to adjust the pH of the system to (6.5 ± 0.3), wash while it is hot, then filter and cool, and dry under vacuum at 70 °C for 5 h to obtain the product. Example

[0044] Example 1 A PETS lubricant for engineering plastics, the raw materials and their dosages are shown in Table 2, wherein the modified PETS is obtained from Preparation Example 1, the fluorinated ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the antioxidant is antioxidant 1076 and antioxidant 168 with a mass ratio of 1:0.4.

[0045] Table 2 The preparation method of the above PETS lubricant for engineering plastics includes the following steps: S1: Immerse the fluorinated carbon nanotubes in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, ultrasonically treat for 45 min at 60 °C, then wash and dry to obtain surface-modified fluorinated carbon nanotubes; S2: Immerse the surface-modified fluorinated carbon nanotubes in a 5 wt% γ-aminopropyltriethoxysilane (KH550) coupling agent solution, ultrasonically treat for 3 h at 60 °C, centrifuge, wash, and dry to obtain pretreated fluorinated carbon nanotubes; S3: Ultrasonically stir the pretreated fluorinated carbon nanotubes and the fluorinated ionic liquid for 30 min to mix evenly and form a pre-dispersed slurry; S4: Mix the modified PETS, maleic anhydride-grafted ethylene-vinyl acetate, the pre-dispersed slurry, and the antioxidant, stir and mix at 2500 rpm for 15 min, then add to a screw extruder, and obtain the product after melt extrusion and pelletization.

[0046] Example 2 A PETS lubricant for engineering plastics, different from Example 1 in that the raw materials and dosages are as shown in Table 2, wherein the fluorinated ionic liquid is 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the antioxidant is antioxidant 1076 and antioxidant 168 with a mass ratio of 1:0.2; The preparation method of the above PETS lubricant for engineering plastics includes the following steps: S1: Immerse the fluorinated carbon nanotubes in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, ultrasonically treat for 60 min at 50 °C, then wash and dry to obtain surface-modified fluorinated carbon nanotubes; S2: Immerse the surface-modified fluorinated carbon nanotubes in a 3 wt% N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) coupling agent solution, ultrasonically treat for 3 h at 65 °C, centrifuge, wash, and dry to obtain pretreated fluorinated carbon nanotubes; S3: Ultrasonically stir the pretreated fluorinated carbon nanotubes and the fluorinated ionic liquid for 30 min to mix evenly and form a pre-dispersed slurry; S4: Mix the modified PETS, maleic anhydride-grafted ethylene-vinyl acetate, the pre-dispersed slurry, and the antioxidant, stir and mix at 2500 rpm for 15 min, then add to a screw extruder, and obtain the product after melt extrusion and pelletization.

[0047] Example 3 A PETS lubricant for engineering plastics, different from Example 1 in that the raw materials and dosages are as shown in Table 2, wherein the fluorinated ionic liquid is 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the antioxidant is antioxidant 1076 and antioxidant 168 with a mass ratio of 1:0.5; The preparation method of the above PETS lubricant for engineering plastics includes the following steps: S1: Immerse the fluorinated carbon nanotubes in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, ultrasonically treat for 45 min at 60 °C, then wash and dry to obtain surface-modified fluorinated carbon nanotubes; S2: Immerse the surface-modified fluorinated carbon nanotubes in a 6 wt% solution of γ-aminopropyltriethoxysilane coupling agent (KH550), ultrasonically treat for 2 h at 55 °C, centrifuge, wash, and dry to obtain pretreated fluorinated carbon nanotubes; S3: Ultrasonically stir and mix the pretreated fluorinated carbon nanotubes and the fluorinated ionic liquid for 30 min to form a pre-dispersed slurry; S4: Mix the modified PETS, maleic anhydride-grafted ethylene-vinyl acetate, the pre-dispersed slurry, and the antioxidant, stir and mix at 2500 rpm for 15 min, then add to a screw extruder, and obtain the product after melt extrusion and pelletization.

[0048] Example 4 A PETS lubricant for engineering plastics, which is different from Example 1 in that the raw materials and their dosages are shown in Table 2, wherein the fluorinated ionic liquid is 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the other steps are the same as those in Example 1.

[0049] Examples 5 - 11 A PETS lubricant for engineering plastics, the difference between Examples 5 - 11 and Example 1 is that the source of the modified PETS in the raw materials is shown in Table 3, and the other steps are the same as those in Example 1.

[0050] Table 3 Example 12 A PETS lubricant for engineering plastics, which is different from Example 1 in that the fluorinated carbon nanotubes are not pretreated, and its preparation method includes the following steps: S1: Ultrasonically stir and mix the fluorinated carbon nanotubes and the fluorinated ionic liquid for 30 min to form a pre-dispersed slurry; S2: Mix the modified PETS, maleic anhydride-grafted ethylene-vinyl acetate, the pre-dispersed slurry, and the antioxidant, stir and mix at 2500 rpm for 15 min, then add to a screw extruder, and obtain the product after melt extrusion and pelletization, and the other steps are the same as those in Example 1.

[0051] Comparative Example Comparative Example 1 A PETS lubricant for engineering plastics, which is different from Example 1 in that carbon fluoride nanotubes are not added, and the carbon fluoride nanotubes in the raw materials are replaced with an equal mass of modified PETS. Its preparation method is as follows: Mix modified PETS, maleic anhydride grafted ethylene-vinyl acetate, fluorine-containing ionic liquid and antioxidant, stir and mix at 2500 rpm for 15 min, then add them into a screw extruder, and obtain the product after melt extrusion and granulation. Other steps are the same as those in Example 1.

[0052] Comparative Example 2 A PETS lubricant for engineering plastics, which is different from Example 1 in that the carbon fluoride nanotubes in the raw materials are replaced with an equal mass of unfluorinated ordinary carbon nanotubes. Other steps are the same as those in Example 1.

[0053] Comparative Example 3 A PETS lubricant for engineering plastics, which is different from Example 1 in that the fluorine-containing ionic liquid is not added, and the fluorine-containing ionic liquid in the raw materials is replaced with an equal mass of modified PETS. Its specific preparation method is as follows: S1: Immerse carbon fluoride nanotubes in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, perform ultrasonic treatment at 60 °C for 45 min, then wash and dry to obtain surface-modified carbon fluoride nanotubes; S2: Immerse the surface-modified carbon fluoride nanotubes in a 5 wt% γ-aminopropyltriethoxysilane (KH550) coupling agent solution, perform ultrasonic treatment at 60 °C for 3 h, centrifuge, wash and dry to obtain pretreated carbon fluoride nanotubes; S4: Mix modified PETS, maleic anhydride grafted ethylene-vinyl acetate, pretreated carbon fluoride nanotubes and antioxidant, stir and mix at 2500 rpm for 15 min, then add them into a screw extruder, and obtain the product after melt extrusion and granulation.

[0054] Comparative Example 4 A PETS lubricant for engineering plastics, which is different from Example 1 in that the modified PETS is obtained from Preparation Example 9. Other steps are the same as those in Example 1.

[0055] Performance detection test Set up an experimental group: Use PA (selected from Sinopec Baling PA6YH-800) as the matrix, add 0.4 wt% of a PETS lubricant for engineering plastics obtained in Examples 1-12 and Comparative Examples 1-4 of the present application and 10 wt% of 1000-mesh light calcium carbonate, mix them evenly to obtain a mixture, and perform melt extrusion and granulation through a screw extruder to obtain PA engineering plastic particles; Set up Control Group 1: The difference from the experimental group is that the PETS lubricant for engineering plastics obtained in Examples 1-12 and Comparative Examples 1-4 of the present application is not added; Set control group 2: The difference from the experimental group is that the lubricant used is pentaerythritol stearate (selected from KOKYO Alcohol, KAKPTI of Japan).

[0056] Detect and evaluate the relevant performance parameters during the processing of the mixture and PA for the lubricating performance of a PETS lubricant for engineering plastics obtained in Examples 1-12 and Comparative Examples 1-4. Each group of tests was carried out 3 times, and the average value of the 3 tests was taken as the final result and the final result was recorded in Table 3.

[0057] 1. Melt flow rate: Refer to the relevant regulations of ISO 1133-2005, and detect the melt flow rate of the compound at 275 °C and 2.16 kg conditions; 2. Torque: Refer to the relevant regulations of ISO 11443, and use a Haake torque rheometer to detect the equilibrium torque of the mixture melt; 3. Coefficient of friction: Refer to the relevant regulations of ISO 8295, and measure the dynamic coefficient of friction of PA engineering plastic particles through a sliding friction testing machine; 4. High shear resistance: Refer to ASTM D3835, and determine the melt viscosity at a shear rate of 280 °C and 1000 s -1 by capillary rheometry; 5. Mechanical properties: Refer to the relevant regulations of ISO 527-2 (1996) and ISO 179-2000 respectively, and test the tensile strength and notched impact strength of PA engineering plastic particles.

[0058] Table 3 It can be seen from the performance test results of the experimental group and the two control groups in Table 3 that a PETS lubricant for engineering plastics of the present application has excellent internal and external lubricating properties when processing engineering plastics, can increase the fluidity of the system by 37.4-52.2%, and significantly improve the processing performance of engineering plastics; has a low coefficient of friction, can form an effective lubricating interface between the plastic surface and the processing equipment, reduce friction and adhesion; compared with the existing PETS lubricants, the PETS lubricant of the present application can improve the adverse effects of the lubricant itself on the mechanical properties of engineering plastics, has the ability to withstand high shear, can maintain good self-stability without damage under the action of high shear force, maintain the effectiveness and durability of the lubricating effect, and effectively improve the mechanical properties and surface quality of engineering plastic products.

[0059] From the performance test results of Examples 1-11 and Comparative Example 4, it can be seen that the modification of PETS using long-chain alkyl mercaptan through transesterification reaction significantly improves the internal and external lubrication performance of PETS lubricant, enhances the stability of PETS lubricant under high temperature and high shear force, can effectively reduce the melt viscosity of engineering plastics under complex working conditions, improve its melt flow rate, and effectively improves the processing of engineering plastics.

[0060] This is because the modification of PETS using long-chain alkyl mercaptan through transesterification reaction introduces thioester bonds and flexible long chains into the PETS molecule, improving both the flexibility and disorder of the molecular chain. This damages the crystalline structure of PETS itself, reduces the crystallinity, further reduces the melt viscosity of engineering plastics, and the introduction of thioester bonds enhances the compatibility between the PETS lubricant and the engineering plastic matrix, preventing the migration of the lubricant. The lubricant can release lubricating molecules under the action of high shear and then achieve self-repair through the exchange reaction of mercaptan and disulfide, thus enhancing the lubrication effect of the lubricant under complex and high-load working conditions. In addition, the introduction of sulfur elements can react with the metal surface to form an iron sulfide protective layer, making the lubricant form a more stable boundary lubricating film with the metal surface, enhancing its internal and external lubrication and high-temperature friction resistance.

[0061] From the performance test results of Examples 1-6 and Examples 7-11, it can be seen that the mixture of dodecyl mercaptan and hexadecyl mercaptan can obtain a lubricant with the best performance when modifying PETS compared to the compound or single use of other alkyl mercaptans. The dosage of dodecyl mercaptan should be less than that of hexadecyl mercaptan. This may be because the carbon chain of C12 alkyl mercaptan is relatively short and the reaction activity is higher, enabling it to react quickly with the active sites in the PETS molecule during the modification reaction to form thioester bonds, reducing the surface energy of the lubricating film and the frictional resistance. While the carbon chain of C16 alkyl mercaptan is relatively long and the reaction activity is slightly lower, it can continue to participate in the reaction in the later stage of the reaction, providing a longer carbon chain for PETS, further enhancing the flexibility and lubricity of the modified PETS molecule. The alkyl chains of different lengths are intertwined and cooperate with each other to form a three-dimensional network structure, further enhancing the thermal stability and chemical stability of the lubricant, enabling it to maintain the performance of the lubricant under harsh working conditions such as high temperature and high shear, and balancing the internal and external lubrication persistence of the lubricant and the interfacial bonding stability with the plastic matrix.

[0062] From the performance test results of Example 1 and Comparative Examples 1-3, it can be seen that fluorinated carbon nanotubes and fluorine-containing ionic liquids can form a nano-enhanced and fluorinated synergistic solid-liquid lubrication system inside the modified PETS matrix. The two cooperate with each other, achieving the maximum improvement in the lubrication effect of the lubricant compared to their single use.

[0063] This is because the fluorine-containing ionic liquid and the outer wall of the fluorinated carbon nanotubes can form a core-shell structure through fluorine-fluorine interactions. The use of fluorinated carbon nanotubes forms an oriented nano-ball structure on the surface of the abrasive tool, converting sliding friction into rolling friction and significantly reducing the friction coefficient of the system. The fluorine-containing ionic liquid can cover the areas not in contact with the fluorinated carbon nanotubes, forming a continuous lubricating layer to avoid dry friction and further enhancing the internal and external lubrication effects of the lubricant.

[0064] Compared with the use of ordinary carbon nanotubes without fluorination modification, the fluorine atoms on the surface of the fluorinated carbon nanotubes form hydrogen bonds with polar groups in the engineering plastic matrix, which are dynamically reversible. Under the action of high shear force or high temperature, the hydrogen bonds are preferentially broken to release F-CNT fragments. These fragments fill the microcracks through physical adsorption or reformation of hydrogen bonds, forming a lubricating film with self-healing ability, which significantly enhances the ability of the lubricant to inhibit crack propagation under the action of high shear force and high temperature, ensuring the lubrication effect under the action of high temperature and high shear force.

[0065] According to the performance test results of Example 1 and Example 12, it can be seen that after the surface modification of fluorinated carbon nanotubes with amino silane coupling agent as the surface modifier, the amino group can act as a bridge to enhance the interaction between the fluorinated carbon nanotubes and the methylimidazole bis(trifluoromethanesulfonyl)imide salt ionic solution, and at the same time enhance the compatibility between the fluorinated carbon nanotubes and the PETS matrix. Compared with the fluorinated carbon nanotubes without coupling agent modification, the lubricant can be better dispersed in the modified PETS matrix to form a more stable lubricating network system after being mixed with the engineering plastic matrix, synergistically enhancing the high-temperature high-shear friction and interface strength.

[0066] This specific embodiment is only an explanation of the present application and does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to their needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A PETS lubricant for engineering plastics, characterized in that: In terms of weight, the raw materials include 65-85 parts of modified PETS, 10-15 parts of maleic anhydride grafted ethylene-vinyl acetate, 5-15 parts of fluorinated carbon nanotubes, 4-7 parts of fluorine-containing ionic liquid and 0.5-1 part of antioxidant.

2. The PETS lubricant for engineering plastics according to claim 1, characterized in that In parts by weight, the raw materials of the modified PETS include 8-11 parts of pentaerythritol, 70-85 parts of stearic acid, 10-20 parts of long-chain alkyl mercaptan and 0.08-0.12 parts of p-toluenesulfonic acid; the long-chain alkyl mercaptan is selected from one or more combinations of dodecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan, octadecyl mercaptan and docosyl mercaptan.

3. PETS lubricant for engineering plastics according to claim 2, characterized in that, The long-chain alkyl mercaptan is dodecyl mercaptan and hexadecyl mercaptan in a mass ratio of 1:(0.5-1).

4. The PETS lubricant for engineering plastics according to claim 2, characterized in that: The preparation method of the modified PETS comprises the following steps: Heat stearic acid to 80-100° C. under a nitrogen atmosphere, add pentaerythritol and p-toluenesulfonic acid, continue to heat to 160-180° C., react with stirring for 2.5-4 h, dehydrate under vacuum, cool to 130-140° C., add long-chain alkyl thiol, continue to react with stirring for 3.5-4.5 h, introduce nitrogen bubbling to assist dehydration, cool to 80° C., adjust the system pH to (6.5±0.3), wash while hot, filter, cool, and vacuum dry at 60-80° C. for 4-6 h to obtain the product.

5. The PETS lubricant for engineering plastics according to claim 1, characterized in that: The fluorine-containing ionic liquid is selected from any one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

6. The PETS lubricant for engineering plastics according to claim 1, characterized in that: The antioxidants are antioxidant 1076 and antioxidant 168 in a mass ratio of 1:(0.2-0.5).

7. The method for preparing the PETS lubricant for engineering plastics according to any one of claims 1 to 6, characterized in that: The following steps are involved: Mixing and stirring the fluorinated carbon nanotubes and the fluorine-containing ionic liquid uniformly to form a pre-dispersed slurry; The modified PETS, maleic anhydride grafted ethylene-vinyl acetate, pre-dispersed slurry and antioxidant are mixed and stirred, and then melt-extruded and granulated to obtain the product.

8. The method for preparing a PETS lubricant for engineering plastics according to claim 7, wherein: The fluorinated carbon nanotubes are pretreated as follows before being mixed with the fluorine-containing ionic liquid: The fluorinated carbon nanotubes are ultrasonically treated in a concentrated acid solution at 50-60° C. for 45-60 minutes, and then washed and dried to obtain surface-modified fluorinated carbon nanotubes; The surface-modified fluorinated carbon nanotubes are immersed in a 3-6wt% silane coupling agent solution, ultrasonically treated at 55-65°C for 2-3h, and centrifuged, washed and dried to obtain pretreated fluorinated carbon nanotubes.

9. The method for preparing a PETS lubricant for engineering plastics according to claim 8, wherein: The silane coupling agent is an aminosilane coupling agent, selected from any one of γ-aminopropyltriethoxysilane coupling agent (KH550) and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (KH792).

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