PET (polyethylene terephthalate) toughening / chain extension aid as well as preparation method and application thereof

Abstract

The invention discloses a PET (polyethylene terephthalate) toughening / chain extension aid and a preparation method and application thereof, and belongs to the technical field of PET material assistants, the preparation method of the PET toughening / chain extension aid comprises the following steps: drying nitrile rubber, adding the nitrile rubber into an internal mixer, stirring for 1-10 minutes, adding glycidyl methacrylate, continuously stirring for 1-5 minutes, adding an initiator, carrying out heat preservation, stirring and mixing for 7-14 minutes, and carrying out extrusion molding to obtain the PET toughening / chain extension aid. The PET toughening / chain extending auxiliary agent is prepared by the following steps: mixing the raw materials, cooling to room temperature after the mixing is finished, putting a reaction product into acetone, stirring and dissolving, filtering, discarding filter residues, removing a small amount of NBR cross-linking products, pouring filtrate into methanol, discarding precipitated solid products, removing GMA self-polymerization products, and finally evaporating the filtrate to dryness, so that the PET toughening / chain extending auxiliary agent is obtained. The method can be applied to processing and modification of recycled PET, and the molecular weight, the melt viscosity, the mechanical property and the impact toughness of the recycled PET can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of PET material additives, and specifically relates to a PET toughening / chain extension additive and a preparation method and application thereof. Background Art

[0002] Polyethylene terephthalate (PET) is an engineering plastic with excellent performance, which is widely used in spinning (polyester fiber), film sheets (such as optical films, packaging materials for various foods and medicines), packaging bottles (such as beverage bottles), electronic appliances (such as TV accessories), automotive accessories (such as motor covers), etc. The high consumption of PET plastics stimulates the continuous increase in its production. In 2023, my country's PET production will increase to about 65.1 million tons. However, PET will produce serious white pollution after being discarded, and recycled PET can be used as a new source of raw materials to alleviate the shortage of PET raw materials. Therefore, whether from the perspective of environmental protection or energy conservation, the recycling and reuse of PET is of great significance.

[0003] Recycled PET plastics are mixed with various additives, and then subjected to processes such as heating, plasticization, and extrusion granulation to obtain PET recycled plastics (i.e., recycled PET), which can be made into PET-related products again. However, recycled PET is mostly used to prepare low-quality products, such as plastic pallets and strapping tapes, rather than directly used to make new plastic bottles. This may be because PET will break and degrade during thermal processing and product use, resulting in problems such as thinning of melt viscosity, making it difficult to melt-spin to make fibers, and serious reduction in mechanical properties, especially poor impact toughness, which limits its application range.

[0004] Therefore, there is an urgent need to develop a toughening / chain extension agent that can simultaneously improve the molecular weight and impact toughness of recycled PET, so as to contribute to the high-value utilization of recycled PET. Summary of the invention

[0005] The purpose of the present invention is to provide a PET toughening / chain extension auxiliary agent and a preparation method and application thereof, so as to solve the problems of low melt viscosity and poor mechanical properties of existing recycled PET.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A PET toughening / chain extension agent, obtained by chemical reaction of nitrile rubber (NBR) and glycidyl methacrylate (GMA), the molecular structure is shown below:

[0008] Where n>0, m>0.

[0009] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0010] The nitrile rubber is dried and then put into an internal mixer. After stirring for 1-10 minutes, glycidyl methacrylate is added, stirring is continued for 1-5 minutes, an initiator is added, and the mixture is stirred and kneaded for 7-14 minutes. After the kneading is completed, the mixture is cooled to room temperature. The reaction product is placed in acetone, stirred and dissolved, and then filtered. The filter residue is discarded, a small amount of NBR cross-linked product is removed, the filtrate is poured into methanol, the precipitated solid product is discarded, the GMA self-polymerization product is removed, and the filtrate is evaporated to dryness to obtain the PET toughening / chain extension additive, i.e., GMA grafted NBR (NBR-g-GMA).

[0011] As a preferred technical solution of the present invention, the drying temperature of the nitrile rubber is 80-100° C., and the drying time is 6-10 hours.

[0012] As a preferred technical solution of the present invention, the drying temperature of the nitrile rubber is 80° C. and the drying time is 6 hours.

[0013] As a preferred technical solution of the present invention, the temperature of the internal mixer is 165-180° C., and the rotation speed is 40-100 rpm.

[0014] The reaction temperature and time used in the present invention are determined based on the melting point of NBR, the decomposition rate of the initiator and the production cost. The above reaction conditions are the optimal conditions verified by experiments.

[0015] As a preferred technical solution of the present invention, the internal mixer is of XSS-300 type with a working capacity of 60 mL.

[0016] As a preferred technical solution of the present invention, the initiator is at least one of dicumyl peroxide (DCP), dicumyl hydroperoxide and dibenzoyl peroxide. More preferably, the initiator is dicumyl peroxide.

[0017] As a preferred technical solution of the present invention, the usage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g:1.5-5g:0.2-0.4g, and more preferably, the usage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g:3g:0.3g.

[0018] A PET toughening / chain extension aid is used to improve the melt viscosity and mechanical properties of recycled PET.

[0019] As a preferred technical solution of the present invention, the amount of the PET toughening / chain extension agent is 5-15% of the mass of the recycled PET, and more preferably, the amount of the PET toughening / chain extension agent is 10% of the mass of the recycled PET.

[0020] As a preferred technical solution of the present invention, the amount of the PET toughening / chain extension agent prepared by the present invention must be moderate. Too little addition will not achieve the expected effect, and too much addition will cause the strength of the recycled PET modified material to decrease too much, affecting its effect. The above addition amount is a better condition verified by experiments.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention provides a PET toughening / chain extension auxiliary agent, which is obtained by chemical reaction of nitrile rubber and glycidyl methacrylate (GMA), wherein the NBR structure in the molecular chain can improve the impact toughness of recycled PET; and the GMA structure in the molecular chain can extend the chain of recycled PET, thereby improving the molecular weight and melt viscosity of the recycled PET; and the epoxy group on the GMA structure can react with -OH or -COOH on the PET macromolecular chain, thereby improving the interface adhesion between the NBR rubber phase and the PET matrix resin phase, making the NBR rubber phase uniformly dispersed in the PET matrix resin phase, thereby further improving the impact toughness of the recycled PET; and the effect is better than adding a single NBR toughening agent, a single GMA chain extender or a physical compound of the two, and the technical scheme can effectively solve the problems existing in the prior art, and provides a simple and feasible way for the processing and modification of recycled PET, and has a low production cost, has a wide application prospect and is beneficial to environmental protection.

[0023] 2. The present invention limits the amount of PET toughening / chain extension additive added to the recycled PET. Too little addition will not achieve the expected effect, while too much addition will cause the strength of the recycled PET modified material to decrease too much, affecting its effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 This is the infrared spectrum of the PET toughening / chain extension agent prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, a~b (i.e. a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple, respectively.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific implementation rules, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the implementation rules of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0029] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0030] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0031] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0033] Since the recycled PET will break and degrade during the thermal processing and product use, it will cause the melt viscosity to become thinner and difficult to melt-spin to make fibers and the mechanical properties to be seriously reduced, especially the impact toughness is too poor, which leads to its limited application range. In order to solve the above problems to a certain extent, the first aspect of the embodiment of the present application provides a PET toughening / chain extension auxiliary agent, which is obtained by chemical reaction of nitrile rubber (NBR) and glycidyl methacrylate (GMA), and the molecular structure is as follows:

[0034] Where n>0, m>0.

[0035] The second aspect of the embodiment of the present application provides a method for preparing the above-mentioned PET toughening / chain extension agent, comprising the following steps:

[0036] The nitrile rubber is dried and then put into an internal mixer. After stirring for 1-10 minutes, glycidyl methacrylate is added, stirring is continued for 1-5 minutes, an initiator is added, and the mixture is stirred and kneaded for 7-14 minutes. After kneading, the mixture is cooled to room temperature. The reaction product is placed in acetone, stirred and dissolved, and then filtered. The filter residue is discarded, a small amount of NBR cross-linked product is removed, the filtrate is poured into methanol, the precipitated solid product is discarded, the GMA self-polymerization product is removed, and the filtrate is evaporated to dryness to obtain the PET toughening / chain extension additive, i.e., GMA grafted NBR.

[0037] In some embodiments, the drying temperature of the nitrile rubber is 80-100°C. In the exemplary embodiment, it can be a typical but non-limiting temperature such as 80°C, 85°C, 90°C, 95°C, 100°C, or a range between any two temperatures. Within this temperature range, the nitrile rubber is easy to dry, which is beneficial to the subsequent mixing step.

[0038] In some embodiments, the drying time of the nitrile rubber is 6-10 hours. In the exemplary embodiment, it can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., typical but non-limiting times or a range between any two times. Within this time range, the nitrile rubber is easy to dry, which is beneficial to the subsequent mixing step.

[0039] In some embodiments, the temperature of the internal mixer is 165-180°C. In the exemplary embodiment, it can be a typical but non-limiting temperature such as 165°C, 170°C, 175°C, 180°C, or a range between any two temperatures. Within this temperature range, nitrile rubber is easily grafted with glycidyl methacrylate, which is beneficial to obtain the above-mentioned PET toughening / chain extension agent.

[0040] In some embodiments, the speed of the internal mixer is 40-100 rpm. In the exemplary embodiment, it can be 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, etc., typical but non-limiting speeds or a range between any two speeds. Within this speed range, nitrile rubber is easily grafted with glycidyl methacrylate, which is beneficial to obtain the above-mentioned PET toughening / chain extension additive.

[0041] In some embodiments, the internal mixer is of XSS-300 type with a working capacity of 60 mL.

[0042] In some embodiments, the initiator is at least one of dicumyl peroxide, dicumyl hydroperoxide and dibenzoyl peroxide. Preferably, the initiator is dicumyl peroxide.

[0043] In some embodiments, the usage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g:1.5-5g:0.2-0.4g. Preferably, the usage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g:3g:0.3g.

[0044] The third aspect of the embodiments of the present application provides the use of the above-mentioned PET toughening / chain extension agent in improving the melt viscosity and mechanical properties of recycled PET.

[0045] In some embodiments, the amount of the PET toughening / chain extension agent is 5-15% of the mass of the recycled PET. More preferably, the amount of the PET toughening / chain extension agent is 10% of the mass of the recycled PET.

[0046] The technical solution of the present application is illustrated below by specific embodiments and comparative examples. In the following embodiments and comparative examples, the nitrile rubber is selected from Lanzhou Petrochemical Nitrile Rubber, with a brand name of NBR3304.

[0047] Example 1

[0048] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0049] 50g of nitrile rubber was dried at 80°C for 6h, and then put into an internal mixer with a temperature of 165°C and a rotation speed of 40rpm. After stirring for 1min, 1.5g of glycidyl methacrylate was added, and stirring was continued for 1min. 0.2g of diisopropylbenzene peroxide was added, and the mixture was stirred and mixed for 7min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered. The residue was discarded, and a small amount of NBR cross-linked product was removed. The filtrate was poured into 500mL of methanol, and the precipitated solid product was discarded, and the GMA self-polymerization product was removed. Finally, the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0050] Example 2

[0051] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0052] 50g of nitrile rubber was dried at 80°C for 6h, and then put into an internal mixer with a temperature of 175°C and a rotation speed of 60rpm. After stirring for 1min, 3g of glycidyl methacrylate was added, and stirring was continued for 1min. 0.3g of diisopropylbenzene peroxide was added, and the mixture was kept warm, stirred and mixed for 7min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered, the filter residue was discarded, a small amount of NBR cross-linked product was removed, and the filtrate was poured into 500mL of methanol, the precipitated solid product was discarded, the GMA self-polymerization product was removed, and the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0053] The PET toughening / chain extension agent obtained in Example 2 was tested by infrared spectroscopy. The test results are as follows: Figure 1 As shown, from Figure 1 It can be seen that 2242cm -1 The characteristic absorption peak at 1725cm is attributed to -CN on NBR, while -1 With 1450cm -1 The peaks at the two ends belong to the carbonyl stretching vibration peak and -CH2 bending vibration peak on GMA, respectively, indicating that GMA was successfully grafted onto NBR.

[0054] Example 3

[0055] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0056] 50g of nitrile rubber was dried at 100°C for 10h, and then put into an internal mixer with a temperature of 180°C and a rotation speed of 100rpm. After stirring for 10min, 5g of glycidyl methacrylate was added, and stirring was continued for 5min. 0.4g of diisopropylbenzene peroxide was added, and the mixture was kept warm, stirred and mixed for 14min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered. The residue was discarded, and a small amount of NBR cross-linked product was removed. The filtrate was poured into 500mL of methanol, the precipitated solid product was discarded, and the GMA self-polymerization product was removed. Finally, the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0057] Example 4

[0058] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0059] 50g of nitrile rubber was dried at 80°C for 8h, and then put into an internal mixer with a temperature of 170°C and a rotation speed of 60rpm. After stirring for 3min, 2g of glycidyl methacrylate was added, and stirring was continued for 3min. 0.3g of diisopropylbenzene hydroperoxide was added, and the mixture was stirred and mixed for 10min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered. The filter residue was discarded, and a small amount of NBR cross-linked product was removed. The filtrate was poured into 500mL of methanol, and the precipitated solid product was discarded, and the GMA self-polymerization product was removed. Finally, the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0060] Example 5

[0061] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0062] 50g of nitrile rubber was dried at 100°C for 6h, and then put into an internal mixer with a temperature of 165°C and a rotation speed of 100rpm. After stirring for 10min, 5g of glycidyl methacrylate was added, stirring was continued for 5min, 0.4g of dibenzoyl peroxide was added, and the mixture was stirred and mixed for 14min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered, the filter residue was discarded, a small amount of NBR cross-linked product was removed, and the filtrate was poured into 500mL of methanol, the precipitated solid product was discarded, the GMA self-polymerization product was removed, and the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0063] Example 6

[0064] A method for preparing a PET toughening / chain extension agent comprises the following steps:

[0065] 50g of nitrile rubber was dried at 98°C for 7h, and then put into an internal mixer with a temperature of 178°C and a rotation speed of 80rpm. After stirring for 8min, 3.5g of glycidyl methacrylate was added, stirring was continued for 5min, 0.4g of dibenzoyl peroxide was added, and the mixture was stirred and mixed for 14min. After mixing, the mixture was cooled to room temperature, and the reaction product was placed in 500mL of acetone, stirred and dissolved, and then filtered, the filter residue was discarded, a small amount of NBR cross-linked product was removed, and the filtrate was poured into 500mL of methanol, the precipitated solid product was discarded, the GMA self-polymerization product was removed, and the filtrate was evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

[0066] Example 7

[0067] A method for preparing recycled PET material comprises the following steps:

[0068] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 1 were conventionally mixed in a high-speed mixer at a mass ratio of 95:5, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through a conventional process.

[0069] Example 8

[0070] A method for preparing recycled PET material comprises the following steps:

[0071] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 2 were conventionally mixed in a high-speed mixer at a mass ratio of 95:5, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through conventional processes.

[0072] Example 9

[0073] A method for preparing recycled PET material comprises the following steps:

[0074] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 2 were conventionally mixed in a high-speed mixer at a mass ratio of 90:10, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through conventional processes.

[0075] Example 10

[0076] A method for preparing recycled PET material comprises the following steps:

[0077] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 2 were conventionally mixed in a high-speed mixer at a mass ratio of 85:15, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through conventional processes.

[0078] Embodiment 11

[0079] A method for preparing a recycled PET material, compared with Example 8, the only difference is that the PET toughening / chain extension aid in Example 8 is replaced by the product prepared in Example 3.

[0080] Example 12

[0081] A method for preparing a recycled PET material, compared with Example 8, the only difference is that the PET toughening / chain extension aid in Example 8 is replaced by the product prepared in Example 4.

[0082] Example 13

[0083] A method for preparing a recycled PET material, compared with Example 8, the only difference is that the PET toughening / chain extension aid in Example 8 is replaced by the product prepared in Example 5.

[0084] Embodiment 14

[0085] A method for preparing a recycled PET material, compared with Example 8, the only difference is that the PET toughening / chain extension aid in Example 8 is replaced by the product prepared in Example 6.

[0086] Comparative Example 1

[0087] A method for preparing recycled PET material, compared with Example 8, the only difference is that no PET toughening / chain extension agent is added, and only recycled PET raw materials (recycled mineral water bottle materials) are used to prepare recycled PET particles.

[0088] Comparative Example 2

[0089] A method for preparing a recycled PET material, compared with Example 9, the only difference is that an equal mass of nitrile rubber (NBR) is used to replace an equal mass of the PET toughening / chain extending agent in Example 9.

[0090] Comparative Example 3

[0091] A method for preparing a recycled PET material, compared with Example 8, the only difference is that an equal mass of glycidyl methacrylate (GMA) is used to replace an equal mass of the PET toughening / chain extending agent in Example 8.

[0092] Comparative Example 4

[0093] A method for preparing recycled PET material comprises the following steps:

[0094] The recycled PET raw material (recycled mineral water bottle material), nitrile rubber (NBR), and glycidyl methacrylate (GMA) were conventionally mixed in a high-speed mixer at a mass ratio of 90:1.1:0.9, with a mixing speed of 4000 rpm and a mixing time of 10 min. After mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through a conventional process.

[0095] Comparative Example 5

[0096] A method for preparing recycled PET material comprises the following steps:

[0097] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 2 were conventionally mixed in a high-speed mixer at a mass ratio of 80:20, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through conventional processes.

[0098] Comparative Example 6

[0099] A method for preparing recycled PET material comprises the following steps:

[0100] The recycled PET raw material (recycled mineral water bottle material) and the PET toughening / chain extension agent prepared in Example 2 were conventionally mixed in a high-speed mixer at a mass ratio of 99:1, the mixing speed was 4000 rpm, the mixing time was 10 min, and after mixing evenly, the recycled PET particles were obtained by extrusion granulation through a twin-screw extruder through a conventional process.

[0101] The recycled PET particles obtained in Examples 7 to 14 and Comparative Examples 1 to 6 were injection molded on an injection molding machine to obtain standard specimens, and performance tests were performed, wherein the tensile strength and elongation at break were tested according to ASTM D638, with a tensile rate of 10 mm / min; the notched cantilever beam impact strength was tested according to ASTM D790; and the melt viscosity was tested according to ASTM D256. The test results are shown in Table 1:

[0102] Table 1

[0103]

[0104]

[0105] According to the experimental results in Table 1, the tensile strength, elongation at break, notched cantilever impact strength and melt viscosity of the recycled PET added with the PET toughening / chain extension additive prepared by the present invention in Examples 7 to 14 are relatively high. Among them, the comprehensive performance of Example 9 with an addition amount of 10wt% is the best, which is much higher than the pure recycled PET in Comparative Example 1, indicating that the additive prepared by the present invention has the effect of significantly improving the impact toughness and melt viscosity of the recycled PET. In addition, it can be seen from the test results of Examples 8, 9 and 10 that the mechanical properties and impact toughness of the recycled PET will decrease with the further increase in the amount of additive added.

[0106] The PET toughening / chain extension aid prepared by the present invention is prepared by grafting reaction, which can play a synergistic role in improving the mechanical properties, impact toughness, melt viscosity and compatibility of recycled PET. However, in Comparative Examples 2-4, only a single toughening agent, a chain extender or a simple physical compound of the two is added, and no chemical reaction is performed, so the above effects cannot be fully exerted. Among them, the toughening agent NBR rubber added in Comparative Example 2 can play a certain toughening and viscosity-increasing effect, but the strength decreases significantly. The chain extender GMA added in Comparative Example 3 can increase the molecular weight of recycled PET, and then moderately improve the mechanical properties, impact toughness and melt viscosity of recycled PET. The toughening effect is not as good as NBR, but the viscosity-increasing effect is better than NBR.

[0107] In comparison, in Comparative Example 4, toughening agent NBR and chain extender GMA are added at the same time, and the strength is improved compared with Comparative Example 2. The impact toughness and melt viscosity are higher than those of Comparative Example 2-3 in which NBR and GMA are added separately, showing a certain synergistic effect. This may be because the added GMA plays a role in compatibilizing PET and NBR, but the synergistic effect is still far behind that of Example 9.

[0108] It can be seen from the test results in Example 10 and Comparative Example 5 that the content of PET toughening / chain extension aid in the recycled PET is too high, resulting in excessive decrease in the strength of the recycled PET modified material, affecting its effect. It can be seen from the test results in Comparative Example 6 and Example 8 that the content of PET toughening / chain extension aid in the recycled PET is too low and the expected effect cannot be achieved. Excessive addition will cause the strength of the recycled PET modified material to decrease too much, affecting its effect.

[0109] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0110] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A PET toughening / chain extension agent, characterized in that: The molecular structure is shown below: Where n>0, m>0.

2. The method for preparing a PET toughening / chain extension agent according to claim 1, characterized in that: The following steps are involved: The nitrile rubber is dried and then put into an internal mixer. After stirring for 1-10 minutes, glycidyl methacrylate is added, stirring is continued for 1-5 minutes, an initiator is added, and the mixture is stirred and kneaded for 7-14 minutes. After the kneading is completed, the mixture is cooled to room temperature. The reaction product is placed in acetone, stirred and dissolved, and then filtered, the filter residue is discarded, the filtrate is poured into methanol, the precipitated solid product is discarded, and the filtrate is evaporated to dryness to obtain the PET toughening / chain extension auxiliary agent.

3. The method for preparing a PET toughening / chain extension agent according to claim 2, characterized in that: The drying temperature of the nitrile rubber is 80° C. and the drying time is 6 hours.

4. The method for preparing a PET toughening / chain extension auxiliary agent according to claim 2, characterized in that: The temperature of the internal mixer is 165-180° C., and the rotation speed is 40-100 rpm.

5. The method for preparing a PET toughening / chain extension agent according to claim 2, characterized in that: The initiator is at least one of dicumyl peroxide, dicumyl hydroperoxide and dibenzoyl peroxide.

6. The method for preparing a PET toughening / chain extension agent according to claim 2, characterized in that: The usage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g:1.5-5g:0.2-0.4g.

7. The method for preparing a PET toughening / chain extension agent according to claim 2 or 6, characterized in that: The dosage ratio of nitrile rubber, glycidyl methacrylate and initiator is 50g: 3g:0.3g.

8. Use of the PET toughening / chain extension agent according to claim 1 or the PET toughening / chain extension agent obtained by the preparation method according to any one of claims 2 to 7 in improving the melt viscosity and mechanical properties of recycled PET.

9. The use according to claim 8, characterized in that: The dosage of the PET toughening / chain extension auxiliary agent is 5-15% of the mass of the recycled PET.

10. The use according to claim 8 or 9, characterized in that: The dosage of the PET toughening / chain extension auxiliary agent is 10% of the mass of the recycled PET.

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