Molecular chain woven composite product formed by in-situ compounding of one-dimensional and two-dimensional polymers based on mechanochemistry and preparation method of molecular chain woven composite product

Abstract

The invention provides a molecular chain woven composite product formed by in-situ compounding of one-dimensional and two-dimensional polymers based on mechanochemistry and a preparation method of the molecular chain woven composite product. The preparation method comprises the following steps: firstly, pre-mixing p-toluenesulfonic acid and thermoplastic plastic containing polar groups, and then adding the mixture into a millstone-shaped solid-phase mechanochemical reactor for co-milling; then co-grinding the collected solid product and p-phenylenediamine, co-grinding the collected solid product and trialdehyde phloroglucinol, collecting to obtain composite powder, and preparing composite granules through a vacuum devolatilization extrusion granulation process; and finally preparing the molecular chain woven composite product from the composite granules based on a conventional injection molding process. According to the preparation method, an in-situ intercalation scheme adopted when a conventional two-dimensional inorganic material and a polymer matrix are blended is broken through, and a novel two-dimensional and one-dimensional compounding method is realized. According to the invention, one-dimensional and two-dimensional polymer molecular chain woven composite products are successfully expanded to public application terminals in a low-cost processing mode.

Description

Technical Field

[0001] This invention belongs to the field of composite products of one-dimensional and two-dimensional polymers, and relates to a molecular chain braided composite product formed by in-situ composite of one-dimensional and two-dimensional polymers based on mechanochemistry, and its preparation method. Specifically, it involves using solid-phase shearing and milling technology to achieve in-situ mechanochemical synthesis of two-dimensional polymers in one-dimensional linear polymers, and using the two-dimensional polymers to restrict the linear molecular chains of the one-dimensional polymers, thereby realizing the molecular chain braiding function during the processing, and finally preparing a molecular chain braided composite product. In particular, it is aimed at using an industrial grinding disc-shaped solid-phase mechanochemical reactor disclosed in Chinese invention patent CN114534660B for preparation. Background Technology

[0002] General-purpose and engineering plastics, from a geometrical topological perspective, belong to the random coil structure and are classified as one-dimensional linear materials. Cross-linked rubber materials, thermosetting plastics, and gels belong to three-dimensional network materials, with a history of at least a century. One-dimensional random coil materials cover various fields of civil engineering, while three-dimensional polymer materials, with their unique cross-linked network structure (and rigid chains) providing structural stability, are widely used in aerospace and other fields. Two-dimensional polymers, namely covalent organic frameworks (COFs), were not reported until 2005. COFs possess unique characteristics that surpass those of one-dimensional and three-dimensional polymer materials, such as artificially controllable polymerization, ultra-high cross-linking degree, porosity, and high temperature resistance. Since their inception, two-dimensional polymers have developed extremely rapidly, with many scholars utilizing their ultra-high porosity and structural stability to achieve remarkable results in fields such as chemical separation, catalysis, and energy.

[0003] Whether it's one-dimensional linear polymer materials, or two-dimensional and three-dimensional polymer materials, they are all combined with various inorganic zero-dimensional particles, one-dimensional nanotubes, two-dimensional graphene-like materials, and three-dimensional spherical irregular particles to prepare various functional structural materials. The combination of organic and inorganic materials greatly enriches the application scenarios of polymer-based materials.

[0004] Organic-to-organic composites are often combinations of one-dimensional linear polymers, such as PVC / ABS composites; one-dimensional and three-dimensional composites, such as NBR / PVC rubber-plastic composites and PP / EPDM thermoplastic elastomers; three-dimensional polymer combinations, such as the incorporation of a three-dimensional network polymer prepolymer into a resin system; and two-dimensional covalent organic framework (COF) composites also exist. However, among the above composite systems, only three-dimensional and two-dimensional material composites achieve a high degree of molecular chain-level composites. Composites combining one-dimensional and two-dimensional polymers are rarely reported, and research on related technologies and processes is extremely rare, focusing only on the preparation of cutting-edge materials and requiring complex preparation processes.

[0005] Therefore, if a highly efficient method is found to achieve a high degree of inter-molecular chain interaction between conventional one-dimensional linear polymers such as general-purpose and engineering plastics and two-dimensional polymers, a novel one-dimensional and two-dimensional polymer composite material can be obtained. This is expected to further broaden polymer processing technology and expand the application of geometric topological composite materials to the mass market. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a molecular chain braided composite product and its preparation method based on mechanochemistry-based in-situ composite of one-dimensional and two-dimensional polymers. This composite product utilizes a strong and continuous external force field provided by solid-state shear milling technology to achieve in-situ synthesis of a β-keto-enamine covalent organic framework in a thermoplastic matrix. Subsequently, a twin-screw extruder is used to achieve complete cyclization of the mechanochemically pre-synthesized covalent organic framework, resulting in strong composite with the thermoplastic molecular chains. Finally, using conventional injection molding, based on different shear force fields, different regions of the one-dimensional molecular chains and the two-dimensional COF with varying degrees of bonding in the composite material are induced to produce different responses, thereby achieving molecular chain braiding. This invention breaks through the conventional in-situ intercalation scheme used in blending two-dimensional inorganic materials with polymer matrices, realizing a novel method for two-dimensional and one-dimensional composites. This invention successfully expands the application of one-dimensional and two-dimensional polymer molecular chain braided composite products to mass-market applications with a low-cost processing method.

[0007] To achieve the above objectives, the present invention employs a technical solution consisting of the following technical measures.

[0008] This invention provides a method for preparing molecular chain braided composite products composed of one-dimensional and two-dimensional polymers through in-situ composite based on mechanochemistry, mainly including the following steps:

[0009] (1) Weigh p-toluenesulfonic acid (PTSA), p-phenylenediamine (Pa), and trialdehyde phloroglucinol (Tp) in a molar ratio of 2.5:(0.43~0.47):(0.28~0.32, and prepare them as monomers for COF synthesis;

[0010] Thermoplastic plastic containing polar groups is prepared, and the mass of the COF synthetic monomer is 1 to 10 wt% of the total mass of the thermoplastic plastic containing polar groups and the COF synthetic monomer.

[0011] (2) The p-toluenesulfonic acid prepared in step (1) and the thermoplastic plastic containing polar groups are premixed and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 3 to 8. After milling, the collected solid product A is premixed with p-phenylenediamine and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 5 to 10. After milling again, the collected solid product B is premixed with trialdehyde phloroglucinol and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 10 to 25. The composite powder of β-ketoenamine covalent organic framework synthesized in situ in thermoplastic plastic matrix is ​​collected.

[0012] (3) The composite powder obtained in step (2) is used in conjunction with a twin-screw extruder and a vacuum negative pressure device to prepare composite granules based on the vacuum devouring extrusion granulation process;

[0013] The process parameters involved include: twin-screw extruder speed of 150-250 rpm, temperature of 200-260℃, and vacuum pressure of 0.3-1 MPa.

[0014] (4) The composite granules obtained in step (3) are used to prepare molecular chain braided composite products using conventional injection molding processes. It should be noted that different shear force fields can be constructed based on different injection pressures and injection speeds in the injection molding process, and composite products with different molecular braiding behaviors can be prepared in the end.

[0015] In this article, the thermoplastic plastic containing polar groups mentioned in step (1) refers to thermoplastic plastics with polar groups in their molecular chains, such as nylon, thermoplastic polyurethane elastomers, etc.

[0016] It should be noted that the reason for using thermoplastic plastics containing polar groups as raw materials in step (1) is that in the actual experimental process of this invention, it was found that when polyethylene, which is also a thermoplastic plastic, is selected, there is no interaction between its matrix molecular chain and COF, thus forming obvious phase separation characterization, and therefore effective molecular chain weaving cannot be achieved.

[0017] It should be noted that p-toluenesulfonic acid (PTSA) was selected as one of the monomers for COF synthesis in step (1). As a template agent for subsequent monomer reactions, it has the characteristic of low melting point. During co-milling, it can highly coat thermoplastic powder and form hydrogen bond interactions with thermoplastics containing polar groups, thus constructing more active template sites for COF reactions on the surface of the thermoplastic powder. In addition, it should also meet the characteristic of being removable in the subsequent vacuum devolatilization extrusion granulation process. After comparison, p-toluenesulfonic acid (PTSA) was selected as the preferred monomer.

[0018] In this paper, the millstone-shaped solid-phase mechanochemical reactor mentioned in step (2) is the industrial millstone-shaped solid-phase mechanochemical reactor disclosed in the prior invention patent CN114534660B of the applicant of this invention.

[0019] It should be noted that this industrial millstone-shaped solid-phase mechanochemical reactor is an industrial device that is an improvement on the mechanochemical reactor disclosed in the prior authorized patent ZL95111258.9. It is significantly different from the structure of the laboratory prototype machine when ZL95111258.9 was applied for. It has designed a brand-new millstone structure for industrial high-efficiency mechanochemical grinding, which has been improved from the previous vertical millstone setting to a horizontal setting, and the size of the millstone has been greatly increased. Based on the horizontal setting and large size of the millstone, related fixed millstone components and hydraulic lifting system have been innovatively designed, which greatly improves its three-dimensional shear force.

[0020] Typically, the number of grinding times in step (2) is 3 to 8. When the number of grinding times is 2 or more, the actual process is to grind the material in a disc-shaped solid-state chemical reactor, collect the product at the discharge end, and then place it in a disc-shaped solid-state chemical reactor for grinding again. The above process is considered as 2 grinding times.

[0021] Typically, the process parameters of the disc-shaped solid-state chemical reactor in step (2), except for the number of milling cycles, can be the conventional settings for thermoplastic plastics, or the conventional settings based on the thermoplastic plastic specifically selected in step (1). To better illustrate the present invention and provide a technical solution for reference, the process parameters of the disc-shaped solid-state chemical reactor in step (2) are as follows: milling pressure of 2-8 MPa, disc surface temperature controlled by circulating cooling liquid at 15-35°C, and disc rotation speed of 50-200 rpm; the cooling liquid is water, ethylene glycol, or glycerol.

[0022] In this paper, the composite granules described in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding processes. The injection molding machines used in the injection molding process include injection molding machines commonly used in the market / processing field as well as micro injection molding machines.

[0023] In one of the technical solutions, the composite granules in step (4) are used to prepare molecular chain woven composite products based on conventional injection molding processes. The injection molding machine used in the injection molding process adopts a single screw or plunger feeding device, which is not easy to damage the composite between COF and thermoplastic.

[0024] During the research and investigation process for this invention, the inventors found that existing literature on covalent organic framework (COF) materials as two-dimensional polymer materials, when combined with other dimensional materials, can basically only be prepared by fine chemical synthesis, and cannot be done using traditional polymer processing equipment. Furthermore, the selection of other dimensional materials is also very limited.

[0025] The inventive point of this invention lies in the in-situ synthesis of β-ketoenamine covalent organic frameworks (COFs) within a thermoplastic matrix using solid-phase shear milling combined with twin-screw extrusion. Then, the controlled shear flow field of an injection molding machine is utilized to achieve the behavior of COF weaving the matrix molecular chains. This invention represents the first successful in-situ synthesis of COFs within a one-dimensional polymer matrix using polymer matrix processing as a medium. It breaks through the conventional in-situ intercalation scheme used when blending two-dimensional inorganic materials with polymer matrices, realizing a novel method for two-dimensional and one-dimensional composites. This invention successfully extends the low-cost, high-efficiency application of chemically synthesized novel materials to mass-market applications through polymer processing.

[0026] The principle of this invention is that in step (2), thermoplastic plastic and PTSA are first co-milled. The strong external force field of solid-phase shear milling promotes the melting of PTSA by frictional heat on the one hand, and shear mixing promotes the high degree of surface modification of the plastic matrix by PTSA on the other hand, which plays the role of building hydrogen bond templates. Then, Pa is added for co-milling to complete the assembly of two-dimensional hydrogen bond templates between hydroxyl and amino groups. Finally, Tp is added for the final co-milling mechanochemical COF synthesis. The aldehyde group replaces the hydroxyl group to form a two-dimensional hydrogen bond template on the amino group, and a Schiff base reaction occurs to prepare COF particles in situ. In step (3), based on the strong shear force field and high temperature plasticizing ability of the twin-screw extruder, the glassy thermoplastic plastic is converted into a viscous flow state to realize the complete movement of the molecular chain. The high temperature promotes the complete cyclization of COF and the vacuum negative pressure condition removes the volatiles. Under high temperature, the viscous flow state of the matrix molecular chain and the COF cyclization process occur simultaneously, which can realize the encapsulation of one-dimensional linear matrix molecular chains during the two-dimensional COF cyclization process, and complete the composite of one-dimensional and two-dimensional polymer materials. In step (4), by adjusting the injection pressure or injection speed of the injection molding machine, especially when using a micro injection molding machine, the flow of the composite melt can be controlled to achieve molecular chain orientation. The different degrees of bonding between COF and the plastic matrix molecular chains result in different molecular chain motion responses, presenting spherical agglomeration areas or transforming into fiber agglomeration areas under shear flow fields, and presenting fibrous structures across the entire cross section, thereby realizing the molecular chain weaving function using traditional polymer processing.

[0027] Based on the above principle explanation, in one preferred technical solution, the composite granules in step (4) are used to prepare molecular chain woven composite products based on conventional injection molding process. When the injection molding process is to use a conventional industrial injection molding machine, the injection pressure is 40-60 MPa and the temperature is set to 230-250℃.

[0028] Based on the above principle explanation, in one preferred technical solution, the composite granules in step (4) are used to prepare molecular chain woven composite products based on conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 50-400 mm / s and the pressure is selected as 1500-2000 bar.

[0029] More preferably, in order to obtain a molecular chain woven composite product with a fibrous cross section, the composite granules in step (4) are prepared into a molecular chain woven composite product based on a conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 50-100 mm / s and the pressure is selected as 1500-2000 bar.

[0030] More preferably, in order to obtain a molecular chain braided composite product with a flat cross-section, the composite granules in step (4) are prepared into a molecular chain braided composite product based on a conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 150-300 mm / s and the pressure is selected as 1500-2000 bar.

[0031] The present invention has the following beneficial effects:

[0032] (1) This invention provides a molecular chain braided composite product and its preparation method based on mechanochemistry to realize the in-situ composite of one-dimensional and two-dimensional polymers. It utilizes reactive extrusion to construct a two-dimensional COF and one-dimensional linear polymer composite bonding phase region in situ in a polymer matrix, and can realize the weaving effect of traditional polymer processing methods on molecular chains by micro-injection molding.

[0033] (2) The present invention can directly realize the in-situ synthesis of β-keto-enamine covalent organic framework in thermoplastic matrix based on solid-phase shear milling technology, without the need to add catalyst or synthesize in solvent system, and has the basic conditions for continuous production preparation.

[0034] (3) This invention can directly utilize conventional polymer-based material processing conditions, has a simple production process, is easy to operate, can be mass-produced and continuously produced, and can transform chemically synthesized new materials to large-scale end-use products, thus having obvious commercial promotion advantages. Attached Figure Description

[0035] Figure 1The images shown are photographs and SEM images of the raw material PA12 used in Example 1 of this invention and the composite powder obtained in step (2). Figure (a) is a photograph of the PA12 raw material used in Example 1; Figure (b) is a photograph of the composite powder obtained in step (2) of Example 1; Figure (c) is an SEM microscopic morphology image of the composite powder obtained in step (2) of Example 1; and Figure (d) is a magnified view of the PA12 surface area in the composite powder obtained in step (2) of Example 1.

[0036] Figure 2 Figures 5, 8, 11, and 12 show SEM images and TEM phase separation images of the samples prepared in Examples 5, 8, 11, and 12 of this invention. Specifically, Figure (a) is an SEM image of the sample prepared in Example 11, clearly showing spherical phase separation regions in the quenched fracture surface; Figure (b) is an SEM image of the sample prepared in Example 5, showing a fibrous fracture surface; Figure (c) is an SEM image of the sample prepared in Example 8, showing a fibrous fracture surface different from Figure (b); Figures (d) and (e) are TEM phase separation images of the sample prepared in Example 12 after cryosectioning.

[0037] Figure 3 Figure 1 presents a summary of the photoelectric properties of the samples prepared in Examples 9-12 and Comparative Example 2, as well as the influence of COF on the molecular chain mobility and arrangement of PA12. Specifically, Figure 1(a) shows the UV-DRS comparison spectrum of COF in the PA12 matrix during the preparation process of Examples 10-12, with Comparative Example 2 as a comparison; Figure 2(b) shows the photoelectric property test results of the samples prepared in Examples 10-12; Figure 2(c) shows the DMA test results of the samples prepared in Examples 9-12; and Figure 2(d) shows the SAXS porod test results of the samples prepared in Examples 10, 11, and Comparative Example 2, illustrating the relationship between electron density changes and the uniformity of the composite product system.

[0038] Figure 4 The figures show the mechanical property test results of the samples prepared in Examples 2-8 and Comparative Example 1 of this invention.

[0039] Figure (a) is a bar graph comparing the yield strength of the samples prepared in Examples 2-8 and Comparative Example 1; Figure (b) is a line graph comparing the elongation of the samples prepared in Examples 2-8 and Comparative Example 1. Detailed Implementation

[0040] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. Those skilled in the art can refer to the content of this document to appropriately improve the process parameters. In particular, it should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention. Although it is believed that those skilled in the art will fully understand the following terms, the following definitions are set forth to help illustrate the subject matter disclosed in the present invention.

[0041] This invention provides a method for preparing molecular chain braided composite products composed of one-dimensional and two-dimensional polymers through in-situ composite based on mechanochemistry, mainly including the following steps:

[0042] (1) Weigh p-toluenesulfonic acid (PTSA), p-phenylenediamine (Pa), and trialdehyde phloroglucinol (Tp) in a molar ratio of 2.5:(0.43~0.47):(0.28~0.32, and prepare them as monomers for COF synthesis;

[0043] Thermoplastic plastic containing polar groups is prepared, and the mass of the COF synthetic monomer is 1 to 10 wt% of the total mass of the thermoplastic plastic containing polar groups and the COF synthetic monomer.

[0044] (2) The p-toluenesulfonic acid prepared in step (1) and the thermoplastic plastic containing polar groups are premixed and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 3 to 8. After milling, the collected solid product A is premixed with p-phenylenediamine and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 5 to 10. After milling again, the collected solid product B is premixed with trialdehyde phloroglucinol and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 10 to 25. The composite powder of β-ketoenamine covalent organic framework synthesized in situ in thermoplastic plastic matrix is ​​collected.

[0045] (3) The composite powder obtained in step (2) is used in conjunction with a twin-screw extruder and a vacuum negative pressure device to prepare composite granules based on the vacuum devouring extrusion granulation process;

[0046] The process parameters involved include: twin-screw extruder speed of 150-250 rpm, temperature of 200-260℃, and vacuum pressure of 0.3-1 MPa.

[0047] (4) The composite granules obtained in step (3) are used to prepare molecular chain braided composite products using conventional injection molding processes. It should be noted that different shear force fields can be constructed based on different injection pressures and injection speeds in the injection molding process, and composite products with different molecular braiding behaviors can be prepared in the end.

[0048] In this document, the thermoplastic plastic containing polar groups mentioned in step (1) refers to a thermoplastic plastic with polar groups in its molecular chain, such as nylon, thermoplastic polyurethane elastomer, etc. in one embodiment.

[0049] It should be noted that the reason for using thermoplastic plastics containing polar groups as raw materials in step (1) is that in the actual experimental process of this invention, it was found that when polyethylene, which is also a thermoplastic plastic, is selected, there is no interaction between its matrix molecular chain and COF, thus forming obvious phase separation characterization, and therefore effective molecular chain weaving cannot be achieved.

[0050] It should be noted that p-toluenesulfonic acid (PTSA) was selected as one of the monomers for COF synthesis in step (1). As a template agent for subsequent monomer reactions, it has the characteristic of low melting point. During co-milling, it can highly coat thermoplastic powder and form hydrogen bond interactions with thermoplastics containing polar groups, thus constructing more active template sites for COF reactions on the surface of the thermoplastic powder. In addition, it should also meet the characteristic of being removable in the subsequent vacuum devolatilization extrusion granulation process. After comparison, p-toluenesulfonic acid (PTSA) was selected as the preferred monomer.

[0051] In this paper, the millstone-shaped solid-phase mechanochemical reactor mentioned in step (2) is the industrial millstone-shaped solid-phase mechanochemical reactor disclosed in the prior invention patent CN114534660B of the applicant of this invention.

[0052] It should be noted that this industrial millstone-shaped solid-phase mechanochemical reactor is an industrial device that is an improvement on the mechanochemical reactor disclosed in the prior authorized patent ZL95111258.9. It is significantly different from the structure of the laboratory prototype machine when ZL95111258.9 was applied for. It has designed a brand-new millstone structure for industrial high-efficiency mechanochemical grinding, which has been improved from the previous vertical millstone setting to a horizontal setting, and the size of the millstone has been greatly increased. Based on the horizontal setting and large size of the millstone, related fixed millstone components and hydraulic lifting system have been innovatively designed, which greatly improves its three-dimensional shear force.

[0053] Typically, the number of grinding times in step (2) is 3 to 8. When the number of grinding times is 2 or more, the actual process is to grind the material in a disc-shaped solid-state chemical reactor, collect the product at the discharge end, and then place it in a disc-shaped solid-state chemical reactor for grinding again. The above process is considered as 2 grinding times.

[0054] Typically, the process parameters of the disc-shaped solid-state chemical reactor in step (2), except for the number of milling cycles, can be the conventional settings for thermoplastics, or the conventional settings based on the thermoplastic specifically selected in step (1). To better illustrate the present invention and provide a reference embodiment, the process parameters of the disc-shaped solid-state chemical reactor in step (2) are as follows: milling pressure of 2–8 MPa, disc surface temperature controlled by circulating cooling liquid at 15–35°C, and disc rotation speed of 50–200 rpm; the cooling liquid is water, ethylene glycol, or glycerol.

[0055] In one embodiment, in step (2), the p-toluenesulfonic acid prepared in step (1) is premixed with a thermoplastic plastic containing polar groups and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling cycles is 3 to 8, for example, 3, 4, 5, 6, 7, or 8. After milling, the collected solid product A is premixed with p-phenylenediamine and then added to the disc-shaped solid-state chemical reactor for co-milling. The number of milling cycles is 5 to 8. 10 times, for example, 5 times, 6 times, 7 times, 8 times, 9 times or 10 times; after the grinding is completed again, the collected solid product B is premixed with trialdehyde phloroglucinol and added to a disc-shaped solid-phase mechanochemical reactor for co-grinding, the grinding number is 10 to 25 times, for example 10 times, 11 times, 12 times, 13 times, 14 times, 15 times, 16 times, 17 times, 18 times, 19 times, 20 times, 21 times, 22 times, 23 times, 24 times or 25 times.

[0056] In one embodiment, the process parameters in step (3) include: a twin-screw extruder speed of 150-250 rpm, such as 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm or any range or point value between them; a temperature of 200-260°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or any range or point value between them; and a vacuum negative pressure value of 0.3-1 MPa, such as 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa or any range or point value between them.

[0057] In this paper, the composite granules described in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding processes. The injection molding machines used in the injection molding process include injection molding machines commonly used in the market / processing field as well as micro injection molding machines.

[0058] In one embodiment, the composite granules in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding processes. The injection molding machine used in the injection molding process adopts a single screw or plunger feeding device, which is not easy to damage the composite between COF and thermoplastic.

[0059] During the research and investigation process for this invention, the inventors found that existing literature on covalent organic framework (COF) materials as two-dimensional polymer materials, when combined with other dimensional materials, can basically only be prepared by fine chemical synthesis, and cannot be done using traditional polymer processing equipment. Furthermore, the selection of other dimensional materials is also very limited.

[0060] The inventive point of this invention lies in the in-situ synthesis of β-ketoenamine covalent organic frameworks (COFs) within a thermoplastic matrix using solid-phase shear milling combined with twin-screw extrusion. Then, the controlled shear flow field of an injection molding machine is utilized to achieve the behavior of COF weaving the matrix molecular chains. This invention represents the first successful in-situ synthesis of COFs within a one-dimensional polymer matrix using polymer matrix processing as a medium. It breaks through the conventional in-situ intercalation scheme used when blending two-dimensional inorganic materials with polymer matrices, realizing a novel method for two-dimensional and one-dimensional composites. This invention successfully extends the low-cost, high-efficiency application of chemically synthesized novel materials to mass-market applications through polymer processing.

[0061] The principle of this invention is that in step (2), thermoplastic plastic and PTSA are first co-milled. The strong external force field of solid-phase shear milling promotes the melting of PTSA by frictional heat on the one hand, and shear mixing promotes the high degree of surface modification of the plastic matrix by PTSA on the other hand, which plays the role of building hydrogen bond templates. Then, Pa is added for co-milling to complete the assembly of two-dimensional hydrogen bond templates between hydroxyl and amino groups. Finally, Tp is added for the final co-milling mechanochemical COF synthesis. The aldehyde group replaces the hydroxyl group to form a two-dimensional hydrogen bond template on the amino group, and a Schiff base reaction occurs to prepare COF particles in situ. In step (3), based on the strong shear force field and high temperature plasticizing ability of the twin-screw extruder, the glassy thermoplastic plastic is converted into a viscous flow state to realize the complete movement of the molecular chain. The high temperature promotes the complete cyclization of COF and the vacuum negative pressure condition removes the volatiles. Under high temperature, the viscous flow state of the matrix molecular chain and the COF cyclization process occur simultaneously, which can realize the encapsulation of one-dimensional linear matrix molecular chains during the two-dimensional COF cyclization process, and complete the composite of one-dimensional and two-dimensional polymer materials. In step (4), by adjusting the injection pressure or injection speed of the injection molding machine, especially when using a micro injection molding machine, the flow of the composite melt can be controlled to achieve molecular chain orientation. The different degrees of bonding between COF and the plastic matrix molecular chains result in different molecular chain motion responses, presenting spherical agglomeration areas or transforming into fiber agglomeration areas under shear flow fields, and presenting fibrous structures across the entire cross section, thereby realizing the molecular chain weaving function using traditional polymer processing.

[0062] Based on the above principle, in one preferred embodiment, the composite granules in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding process. When the injection molding process is to use a conventional industrial injection molding machine, the injection pressure is 40-60 MPa and the temperature is set to 230-250℃.

[0063] Based on the above principle, in one preferred embodiment, the composite granules in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 50-400 mm / s and the pressure is 1500-2000 bar.

[0064] More preferably, in order to obtain a molecular chain woven composite product with a fibrous cross section, the composite granules in step (4) are prepared into a molecular chain woven composite product based on a conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 50-100 mm / s and the pressure is selected as 1500-2000 bar.

[0065] More preferably, in order to obtain a molecular chain braided composite product with a flat cross-section, the composite granules in step (4) are prepared into a molecular chain braided composite product based on a conventional injection molding process. When the injection molding process is a micro injection molding machine, the injection speed is 150-300 mm / s and the pressure is selected as 1500-2000 bar.

[0066] The present application will be further explained in detail below with reference to embodiments. However, those skilled in the art should understand that these embodiments are provided for illustrative purposes only and are not intended to limit the present application.

[0067] Example

[0068] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the scope of this application. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all commercially available conventional products. This application should not be construed as being limited to the specific embodiments described.

[0069] 1. Raw materials

[0070] PA12 powder was purchased from Farsoon Technologies (Wuhan, China).

[0071] Trialdehyde phloroglucinol (Tp), p-toluenesulfonic acid (monohydrate) (PTSA), and p-phenylenediamine (Pa) were all purchased from Chengdu Dingsheng Technology Co., Ltd.

[0072] 2. Preparation method

[0073] (1) Weigh p-toluenesulfonic acid (PTSA), p-phenylenediamine (Pa), and trialdehyde phloroglucinol (Tp) in a molar ratio of 2.5:0.45:0.3 and prepare them as monomers for COF synthesis.

[0074] Prepare PA12, wherein the mass of the COF synthesis monomer is 1 to 10 wt% of the total mass of PA12 and the COF synthesis monomer;

[0075] (2) The p-toluenesulfonic acid prepared in step (1) and PA12 are premixed and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 5. After milling, the collected solid product A is premixed with p-phenylenediamine and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 5. After milling again, the collected solid product B is premixed with trialdehyde phloroglucinol and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 10. The composite powder synthesized in situ in the PA12 matrix by the β-ketoenamine covalent organic framework is collected.

[0076] Other process parameters of the milling disc-shaped solid-phase mechanochemical reactor include: a milling pressure of 2 MPa, a milling disc surface temperature controlled at 15°C by circulating cooling liquid, and a milling disc rotation speed of 50 rpm.

[0077] (3) The composite powder obtained in step (2) is used in conjunction with a twin-screw extruder and a vacuum negative pressure device to prepare composite granules based on the vacuum devouring extrusion granulation process;

[0078] The process parameters involved include: twin-screw extruder speed of 220 rpm, temperature of each zone of 200-260℃, and negative pressure value of vacuum negative pressure equipment of 0.5 MPa;

[0079] (4) The composite granules obtained in step (3) are used to prepare molecular chain braided composite products using conventional injection molding process;

[0080] The injection molding process uses a micro injection molding machine (MicroPower15, Wittmann Battenfeld GmbH, Austria), with an injection speed of 50–250 mm / s and a pressure of 1500–2000 bar.

[0081] Or,

[0082] The injection molding process uses a large industrial injection molding machine with an injection pressure of 60 MPa and a temperature of 230–250 °C.

[0083] 3. Testing Methods

[0084] In the examples, scanning electron microscopy (SEM) was used to examine the one-dimensional molecular chain aggregation region of COF complex in the samples.

[0085] Thermomechanical analysis (DMA) is used to determine the glass transition temperature of a sample.

[0086] Ultraviolet (UV) spectra can be used to detect the synthesis of COF in a sample.

[0087] An electrochemical workstation was used to test the photoelectric properties of the samples.

[0088] Mechanical performance testing was conducted in accordance with ASTM D 412, with the chuck running at a speed of 50 mm / min.

[0089] Example 1

[0090] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 1 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 250 mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0091] Example 2

[0092] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 3wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 250mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0093] Example 3

[0094] In this embodiment, the preparation method is prepared according to the steps in “2” above. In step (1), the mass of the COF synthetic monomer is 5 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 250 mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0095] Example 4

[0096] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 10wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 250mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0097] Example 5

[0098] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 5wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 50mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0099] Example 6

[0100] In this embodiment, the preparation method is prepared according to the steps in “2” above. In step (1), the mass of the COF synthetic monomer is 5 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 100 mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0101] Example 7

[0102] In this embodiment, the preparation method is prepared according to the steps in “2” above. In step (1), the mass of the COF synthetic monomer is 5 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 150 mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0103] Example 8

[0104] In this embodiment, the preparation method is prepared according to the steps in “2” above. In step (1), the mass of the COF synthetic monomer is 5 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by a micro injection molding machine with an injection speed of 200 mm / s. Finally, a molecular chain braided composite product is prepared as a sample.

[0105] Example 9

[0106] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 1 wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by using a large industrial injection molding machine with an injection pressure of 60 MPa and a temperature of 230-250°C. Finally, a molecular chain braided composite product is prepared as a sample.

[0107] Example 10

[0108] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 3wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by using a large industrial injection molding machine with an injection pressure of 60MPa and a temperature of 230-250℃. Finally, a molecular chain braided composite product is prepared as a sample.

[0109] Example 11

[0110] In this embodiment, the preparation method is prepared according to the steps in “2. Preparation method” above. In step (1), the mass of the COF synthetic monomer is 5wt% of the total mass of PA12 and COF synthetic monomer. In step (4), the injection molding process is carried out by using a large industrial injection molding machine with an injection pressure of 60MPa and a temperature of 230-250℃. Finally, a molecular chain braided composite product is prepared as a sample.

[0111] Example 12

[0112] In this embodiment, the preparation method is prepared according to the steps in "2. Preparation method" above. In step (1), the mass of the COF synthetic monomer is 10wt% of the total mass of PA12 and COF synthetic monomer. The injection molding process is to use a large industrial injection molding machine with an injection pressure of 60MPa and a temperature of 230-250℃. Finally, a molecular chain braided composite product is prepared as a sample.

[0113] Comparative Example 1

[0114] Comparative Example 1 is a PA12 product prepared using PA12 as raw material and based on conventional injection molding process, which serves as a comparative sample. The injection molding process uses a micro injection molding machine (MicroPower15, Wittmann Battenfeld GmbH, Austria), with an injection speed of 250 mm / s and a pressure of 1500–2000 bar.

[0115] Comparative Example 2

[0116] Comparative Example 2 is a PA12 product prepared using PA12 as raw material and based on conventional injection molding process, which serves as a comparison sample. The injection molding process uses a large industrial injection molding machine with an injection pressure of 60 MPa and a temperature of 230–250 °C.

[0117] 4. Test Result Analysis

[0118] In this invention, the strong polarity of PA12, based on the principle of similar compatibility, ensures good compatibility with the three reactive monomers, guaranteeing wettability during co-milling. Under the strong destructive force field of solid-phase milling, PA12 particles can be broken down to create new surfaces. During co-milling, PTSA, due to its low melting point, experiences high instantaneous frictional heat during the solid-phase shear milling process. PTSA will fully wet the PA12 surface, providing a template for the subsequent construction of a two-dimensional hydrogen bond structure with p-phenylenediamine. Simultaneously, PA12 itself contains abundant carbonyl and amino groups, which can also form a certain hydrogen bond structure when co-milled with p-toluenesulfonic acid, jointly participating in the subsequent synthesis of the amino-hydroxy two-dimensional hydrogen bond template. The introduction of trialdehyde phloroglucinol, under the catalysis of external force, undergoes a Schiff base reaction with the amino group, displacing the amino group in the two-dimensional hydrogen bond structure. Part of this phloroglucinol undergoes a cyclization reaction with the amino group of p-phenylenediamine to synthesize COF, while another part forms hydrogen bonds with the amino group in the PA12 matrix, ultimately yielding the mechanochemically synthesized PA12@COF composite powder (see attached specification). Figure 1 ).

[0119] After processing with a twin-screw reactive extrusion process, the composite powder changes directly from yellowish-brown to reddish-brown granules. Due to its powerful shearing force field, the twin-screw extruder, based on its limited screw speed design, controls the degree of complete COF reaction and the degree of polymerization-induced phase separation of the one-dimensional linear molecular chains during COF cyclization. The negative pressure vacuum process efficiently removes small molecule byproducts such as water, reducing the degradation effect of water vapor on polar polymer chains. In the subsequent injection molding process, although large injection molding machines have high injection pressure and a wide adjustable range, the large thickness of the product means the shearing force field has a weaker influence on the melt. The COF-composite PA12 molecular chain agglomeration region will appear spherical, indicating that the COF-composite molecular chains cause regions of different viscosities within the PA12 matrix (see instruction manual). Figure 2 This further implies a strong physicochemical interaction between COF and PA12. Micro-injection molding machines possess a more powerful injection shear field, which can induce deformation of the COF-PA12 molecular chain regions with the shear flow field, resulting in a fibrous shape, or the entire composite product may exhibit a fibrous cross-section due to the physicochemical interaction between COF and PA12 (see instruction manual). Figure 2 ).

[0120] Research has found that the formation of COF in the PA12 matrix endows PA12 composites with unprecedented ultraviolet reflection arcs and photoelectric properties (see attached instruction manual). Figure 3 Various tests revealed that the combination of two-dimensional COF and one-dimensional COF leads to changes in the molecular chain behavior of the one-dimensional PA12 matrix: molecular chain mobility, ordered molecular chain stacking behavior, and the presence of the COF-PA12 molecular chain composite region results in a large number of internal inhomogeneous regions in the PA12 composite product, increasing the fluctuation of the electron density of the entire composite product. After micro-injection molding, different shear fields induce different response characteristics in the PA12 molecular chains affected by COF, thus exhibiting different matrix cross-sectional morphology characteristics. Simultaneously, it affects the arrangement of one-dimensional linear PA12 molecular chains without affecting their mobility. This means that during the gradual straightening of the one-dimensional PA12 molecular chains under shear flow, the two-dimensional COF sheets are not arranged along the flow direction but are deflected, providing additional free volume space, while not eliminating the physicochemical confinement between COF and PA12 (see instruction manual). Figure 4 ).

[0121] Based on the above conditions, the technical solution of this invention can successfully achieve a high degree of molecular chain composite between one-dimensional linear polymer materials and two-dimensional COF polymer materials. The prepared PA12@COF composite products exhibit interesting molecular chain weaving behavior due to the physicochemical restriction of the PA12 molecular chains by the COF. Different degrees of molecular chain weaving and different mechanical properties can be achieved depending on the shear force field during injection molding, successfully extending the synthesis of this new material to mass-market applications.

[0122] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing molecular chain braided composite products based on mechanochemistry to achieve in-situ composite of one-dimensional and two-dimensional polymers, characterized in that... The main steps include: (1) Weigh p-toluenesulfonic acid, p-phenylenediamine, and trialdehyde phloroglucinol in a molar ratio of 2.5:(0.43~0.47):(0.28~0.32, and prepare them as monomers for COF synthesis; Thermoplastic plastic containing polar groups is prepared, and the mass of the COF synthetic monomer is 1 to 10 wt% of the total mass of the thermoplastic plastic containing polar groups and the COF synthetic monomer. (2) The p-toluenesulfonic acid prepared in step (1) and the thermoplastic plastic containing polar groups are premixed and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 3 to 8. After milling, the collected solid product A is premixed with p-phenylenediamine and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 5 to 10. After milling again, the collected solid product B is premixed with trialdehyde phloroglucinol and then added to a disc-shaped solid-state chemical reactor for co-milling. The number of milling times is 10 to 25. The composite powder of β-ketoenamine covalent organic framework synthesized in situ in thermoplastic plastic matrix is ​​collected. (3) The composite powder obtained in step (2) is used in conjunction with a twin-screw extruder and a vacuum negative pressure device to prepare composite granules based on the vacuum devouring extrusion granulation process; The process parameters involved include: twin-screw extruder speed of 150-250 rpm, temperature of 200-260℃, and vacuum pressure of 0.3-1 MPa. (4) The composite granules obtained in step (3) are used to prepare molecular chain braided composite products using conventional injection molding processes.

2. The preparation method according to claim 1, characterized in that: The thermoplastic containing polar groups mentioned in step (1) includes nylon or thermoplastic polyurethane elastomer.

3. The preparation method according to claim 1, characterized in that: The process parameters of the milling disc solid-phase mechanochemical reactor in step (2) are as follows: the milling pressure is 2-8 MPa, the temperature of the milling disc surface is controlled by circulating cooling liquid to be 15-35℃, and the milling disc rotation speed is 50-200 rpm; the cooling liquid is water, ethylene glycol or glycerol.

4. The preparation method according to claim 1, characterized in that: The composite granules described in step (4) are used to prepare molecular chain braided composite products based on conventional injection molding processes, wherein the injection molding machine used in the injection molding process adopts a single screw or plunger feeding device.

5. The preparation method according to claim 1, characterized in that: In step (4), the composite granules are used to prepare molecular chain braided composite products based on conventional injection molding processes. When the injection molding process uses a conventional industrial injection molding machine, the injection pressure is 40-60 MPa and the temperature is set to 230-250°C.

6. The preparation method according to claim 1, characterized in that: In step (4), the composite granules are used to prepare molecular chain braided composite products based on conventional injection molding processes. When the injection molding process is a micro injection molding machine, the injection speed is 50-400 mm / s and the pressure is 1500-2000 bar.

7. The preparation method according to claim 1, characterized in that: In step (4), the composite granules are used to prepare molecular chain braided composite products based on conventional injection molding processes. When the injection molding process is a micro injection molding machine, the injection speed is 50-100 mm / s and the pressure is 1500-2000 bar.

8. The preparation method according to claim 1, characterized in that: In step (4), the composite granules are used to prepare molecular chain braided composite products based on conventional injection molding processes. When the injection molding process is a micro injection molding machine, the injection speed is 150-300 mm / s and the pressure is 1500-2000 bar.

9. The molecular chain braided composite product prepared by the method for preparing a molecular chain braided composite product composed of one-dimensional and two-dimensional polymers in situ based on mechanochemistry as described in claim 1.

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