Reversibly crosslinked poss hybrid nanoparticles, methods of making and using the same

Abstract

The application belongs to the technical field of high polymer compounds, and particularly relates to a reversible cross-linking POSS hybrid nanoparticle and a preparation method and application thereof. Vinyl silane and amino silane are stirred uniformly in methanol, hydrochloric acid is added, stirring reaction is carried out, filtration, washing and drying are carried out, and T8-hydrochloride is obtained. T8-hydrochloride is dissolved in methanol to obtain a T8-hydrochloride solution, and then an anion exchange resin is used to obtain a T8-amino solution. Maleic anhydride is added to the T8-amino solution to obtain a reaction liquid I. Furfural is first added to the reaction liquid I, and then an additive and acetic acid are added to obtain a reaction liquid II. A reducing agent is added to the reaction liquid II to obtain a reaction liquid III. The reaction liquid III is dehydrated to obtain a crude reversible cross-linking POSS hybrid nanoparticle. Subsequent post-treatment and drying obtain the reversible cross-linking POSS hybrid nanoparticle. The application has mild reaction conditions, simple reaction operation and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high molecular compounds, and particularly relates to a reversible cross-linking POSS hybrid nanoparticle and a preparation method and application thereof. BACKGROUND

[0002] Polyethylene, as one of polyolefins, is a high molecular material widely used in daily life. However, the molecular chain of polyethylene has poor heat resistance / creep resistance, low mechanical properties, poor environmental stress resistance, easy cracking and insufficient electrical insulation performance, so that the product thereof generally needs to be cross-linked and modified to meet the use requirements. At present, ultraviolet light irradiation, peroxide or silane coupling agent are commonly used in industry to cross-link polyethylene. These methods form a permanent three-dimensional network structure between the molecular chains of polyethylene, improving the use performance of polyethylene products, but cannot impart the recycling processing utilization property to the polyethylene products after damage, causing great environmental pollution and resource waste.

[0003] Among numerous reversible cross-linking technologies, Diels-Alder (DA) reaction has attracted widespread attention due to its mild reaction conditions and excellent reversibility. However, the existing DA reversible cross-linking mostly adopts a separate system of “polymer matrix + small molecule cross-linking agent”, that is, a furan group (or a maleimide group) is first grafted onto a polymer matrix such as polyolefin, and then a small molecule maleimide cross-linking agent (or a furan cross-linking agent) is additionally added to realize cross-linking through physical mixing. However, this separate system has obvious disadvantages: first, the compatibility is poor. The small molecule cross-linking agent mostly contains a polar functional group, which does not match the polarity of the non-polar polymer matrix such as polyolefin, and cannot be uniformly mixed at the molecular level, easily forming agglomerates, resulting in uneven distribution of cross-linking points and fluctuation of the mechanical properties of the product; second, there is a risk of migration and precipitation. The small molecule cross-linking agent is not chemically anchored to the polymer matrix such as polyolefin, but is dispersed by physical action only, which easily causes the collapse of the cross-linking network, the attenuation of the material properties, and even environmental pollution or safety hazards; third, the molar ratio of the groups is unbalanced. The uneven mixing and the migration and loss of the cross-linking agent will cause the ratio of the furan group to the maleimide group to deviate from the ideal value of 1:1, resulting in low density of the cross-linking network, incomplete cross-linking reaction and poor recycling performance of the material.

[0004] Chinese patent CN111454384A discloses a cross-linked polyethylene and its preparation method and application. The cross-linking modification and cyclic processing of polyethylene are realized through the reversibility and cyclic nature of Diels-Alder reaction between furan-modified polyethylene and organic cross-linking agent, hybrid cross-linking agent or inorganic cross-linking agent. The maleimide cross-linking agent in this patent is an inorganic small molecule that is not compatible with the polyethylene body. In the processing process, there are problems such as imbalance of the molar ratio of maleimide groups / furan groups, uneven mixing, or inability to achieve uniform mixing at the molecular level, and migration and precipitation of small molecule cross-linking agents. In addition, the melt viscosity of polyethylene is large, which can easily cause high energy consumption of equipment and rough surface of products in the processing process, and flow modifiers need to be added.

[0005] Cage polysilsesquioxane (POSS) is a kind of nanometer compound with cage structure of siloxane skeleton, which can be divided into two categories: single functional group and multi-functional group. Single functional group POSS can adjust the thermal properties of materials by grafting or end capping, and multi-functional group POSS can be used as a cross-linking agent to prepare thermosetting nanocomposites. When POSS is combined with polymers, the thermal resistance, mechanical properties and flame retardant properties of the polymers can be improved. The cage framework structure of POSS has good dielectric and optical properties. The inorganic core composed of alternating Si-O siloxane skeleton can inhibit the movement of polymer molecular chains and endow hybrid materials with excellent thermal stability, mechanical properties and flame retardance. The three-dimensional size of POSS is in the nanometer range, which is a typical nanometer compound. It has nanometer effects such as small size effect, surface and interface effect, quantum size effect and macroscopic quantum tunneling effect, thus having excellent comprehensive performance. By combining POSS with reversible cross-linking technology, dynamic functional groups can be introduced through surface functionalization modification of POSS, or dynamic cross-linking points can be constructed by using the multi-functional group characteristics of POSS, which is expected to synergistically improve the performance of materials and become an important direction for developing high-performance sustainable hybrid materials.

[0006] Chinese patent CN108373579A discloses a POSS / PNIPAM nanocomposite with reversible sol-gel transition and its preparation method and application. A water-soluble polyhedral oligomeric silsesquioxane (POSS) is selected, and N-isopropyl acrylamide is in-situ polymerized in its aqueous solution. Physical crosslinking occurs between POSS and PNIPAM molecular chains through electrostatic or hydrogen bond interaction, and a POSS / PNIPAM nanocomposite is generated. The prepared POSS / PNIPAM nanocomposite has temperature sensitivity, is a flowable sol at room temperature, and is a solid gel at 37℃. The process is reversible, so it has injectability. The addition of POSS can adjust the viscosity and gelation time of the PNIPAM system, and greatly improve the mechanical properties of PNIPAM. However, the reversibility in the patent is based on the electrostatic or hydrogen bond interaction between POSS and PNIPAM. After repeated cold and hot cycles, the crosslinking points are easily broken and difficult to completely reorganize, resulting in a significant decrease in gel strength and sol-gel transition stability, and the composite material cannot withstand long-term stress or temperature fluctuations in industrial scenarios. SUMMARY

[0007] The purpose of the present application is to provide a reversibly crosslinked POSS hybrid nanoparticle with reversible crosslinking properties, which can be used for reversible crosslinking modification of polymers such as polyolefins to obtain a composite material with reversible crosslinking properties. The present application also provides a preparation method and application of the reversibly crosslinked POSS hybrid nanoparticle.

[0008] The reversibly crosslinked POSS hybrid nanoparticle described in the present application is in a crosslinked state when the temperature is < 80℃, and is in a decrosslinked state when the temperature is > 100℃.

[0009] The structural formula of the reversibly crosslinked POSS hybrid nanoparticle described in the present application is as follows:

[0010] ,

[0011] wherein R is one of a vinyl group, a furan group or a maleimide group, and the vinyl group, the furan group and the maleimide group appear at least once in all R;

[0012] The structural formula of the furan group is as follows:

[0013] ;

[0014] The structural formula of the maleimide group is as follows:

[0015] .

[0016] The preparation method of the reversibly crosslinked POSS hybrid nanoparticle described in the present application comprises the following steps:

[0017] (1) adding vinyl silane and amino silane into methanol and stirring uniformly, then adding hydrochloric acid, stirring and reacting, filtering, washing, and drying to obtain T8-hydrochloride;

[0018] (2) dissolving T8-hydrochloride in methanol to obtain T8-hydrochloride solution, and passing the T8-hydrochloride solution through an anion exchange resin to obtain T8-amino solution;

[0019] (3) adding maleic anhydride into the T8-amino solution to obtain reaction liquid I;

[0020] (4) adding furfural into the reaction liquid I, then adding an auxiliary and acetic acid, and reacting to obtain reaction liquid II;

[0021] (5) adding a reducing agent into the reaction liquid II to obtain reaction liquid III;

[0022] (6) dehydrating the reaction liquid III to obtain crude product of reversible cross-linking POSS hybrid nanoparticles;

[0023] (7) post-treating the crude product of reversible cross-linking POSS hybrid nanoparticles and drying to obtain reversible cross-linking POSS hybrid nanoparticles.

[0024] In step (1), the vinyl silane includes one or more of vinyl triethoxysilane (A-151), vinyl trimethoxysilane (A-171), or vinyl tri(β-methoxyethoxy)silane (A-172), the amino silane includes one or more of γ-aminopropyl trimethoxysilane (KH540), γ-aminopropyl triethoxysilane (KH-550), or N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH-792), the stirring and reacting time is 3-10 days, the stirring and reacting temperature is 5-50°C, the washing is washing with methanol, the washing frequency is 2-3 times, and the molar ratio of the vinyl silane to the amino silane is 1:3-7; the ratio among the vinyl silane, methanol, and hydrochloric acid is 1:75-150:2.5-5, wherein the vinyl silane is in mol, and the methanol and hydrochloric acid are both in mL; the concentration of the hydrochloric acid is 36-37 wt.%, the drying temperature is 40-60°C, and the drying time is 4-5 hours.

[0025] The structural formula of T8-hydrochloride is as follows:

[0026] ,

[0027] wherein R1 is vinyl or -CH2CH2CH2NH2•HCl, and vinyl and -CH2CH2CH2NH2•HCl each appear at least once in all R1.

[0028] The ratio of the anion exchange resin in step (2) to the amino silane in step (1) is 16.6-33.4:1, wherein the anion exchange resin is in g and the amino silane is in mol; the ratio of the anion exchange resin to methanol is 1:1.25-1.5, wherein the anion exchange resin is in g and the methanol is in mL; the anion exchange resin needs to be soaked with methanol before use.

[0029] The reaction time in step (3) is 2-6h, the reaction temperature is 0-60℃, and the molar ratio of maleic anhydride to the amino silane in step (1) is 1:1.4-2.

[0030] The reaction time in step (4) is 2-6h, the reaction temperature is 0-60℃, the molar ratio of furfural to the amino silane in step (1) is 1:2-3.5, the auxiliary is one of anhydrous sodium sulfate, anhydrous magnesium sulfate or anhydrous calcium sulfate, and the ratio of furfural, auxiliary and acetic acid is 1:0.1-10:0.1-5, wherein the furfural is in mol, the auxiliary is in g, and the acetic acid is in mL; the reaction time in step (5) is 2-6h, the reaction temperature is 0-5℃, the reducing agent is one of sodium borohydride, lithium aluminum hydride, sodium sulfite or sodium thiosulfate, and the molar ratio of the reducing agent to the vinyl silane in step (1) is 1.5-5:1.

[0031] The dehydration in step (6) is by adding sodium acetate, acetic anhydride and triethylamine to react or by heating to react.

[0032] The reaction time of adding sodium acetate, acetic anhydride and triethylamine to react is 4-8h, the reaction temperature is 25-80℃, the ratio of sodium acetate to the vinyl silane in step (1) is 0.75-1:1, wherein the sodium acetate is in g and the vinyl silane is in mol; the ratio of sodium acetate, acetic anhydride and triethylamine is 1:1-10:0.1-3, wherein the sodium acetate is in g and both the acetic anhydride and the triethylamine are in mL; the heating reaction temperature is 140-170℃, and the heating reaction time is 4-6h.

[0033] The post-treatment in step (7) is by adding to an organic solvent, standing and filtering, the organic solvent includes one of diethyl ether, acetone, toluene, tetrahydrofuran, acetonitrile or ethyl acetate, the temperature of the organic solvent is 30-90℃, and the standing time is 2-8h; the post-treatment is 3-5 times, the drying temperature is 40-60℃, and the drying time is 4-5h.

[0034] In step (1), the T8-hydrochloride uses the silicon-oxygen cage structure of POSS as the backbone, with vinyl and amino hydrochloride on the periphery; in step (3), the addition of maleic anhydride to the T8-amino solution is to add less than the molar number of aminosilanes of maleic anhydride to convert part of the amino group into maleimide acid group, while retaining part of the amino group on the periphery of the silicon-oxygen cage structure of POSS as an active site for subsequent furan group incorporation; in step (4), the addition of furfural first, followed by the addition of auxiliaries and acetic acid, causes the amino group and the aldehyde group of furfural to undergo a Schiff base reaction to generate a C=N double bond, introducing a furan ring; then in step (5), the addition of a reducing agent reduces the C=N double bond to a stable CN bond, forming a stable furan group, thereby incorporating the furan group onto the silicon-oxygen cage structure of POSS; in step (6), the dehydration of reaction solution III is to dehydrate the maleimide acid group and convert it into a maleimide group.

[0035] The methanol in step (2) can also wet the anion exchange resin, serving as a dispersant for the anion exchange resin.

[0036] In this invention, vinylsilane and aminosilane are first mixed in a certain proportion, and under certain conditions, T8 core framework is obtained by de-alcoholization and dehydration condensation. Then, the amino group is successively modified into maleimide acid group and furan group. Finally, the maleimide acid group is dehydrated and converted into maleimide group to obtain reversible crosslinked POSS hybrid nanoparticles.

[0037] The application of the reversible crosslinked POSS hybrid nanoparticles described in this invention involves adding functional additives and reversible crosslinked POSS hybrid nanoparticles to a polymer, mixing them evenly, extruding, water-cooling and stretching, pelletizing, drying, and molding to obtain a reversible crosslinked modified polymer.

[0038] The application of the reversibly crosslinked POSS hybrid nanoparticles described in this invention includes the following steps:

[0039] (A) Functional additives are first added to the polymer, followed by reversible cross-linked POSS hybrid nanoparticles, and the mixture is mixed evenly to obtain a mixture;

[0040] (B) After the twin-screw extruder is turned on and the temperature is stabilized for half an hour, the mixture is added to the hopper of the twin-screw extruder. The mixture is extruded, water-cooled into strips, pelletized, and dried to obtain POSS hybrid nanoparticle modified material.

[0041] (C) The modified material of POSS hybrid nanoparticles is processed to obtain a reversible cross-linked modified polymer.

[0042] The polymer in step (A) comprises one or more of polyethylene, polyolefin elastomer or polypropylene, the functional aid is one or more of flame retardant, lubricant, opening agent, nucleating agent or peroxide, the peroxide comprises one or more of calcium peroxide, di-tert-butyl peroxide, benzoyl peroxide or dicumyl peroxide, the mass of the reversible crosslinking POSS hybrid nanoparticle, the flame retardant, the lubricant, the opening agent, the nucleating agent and the peroxide is respectively 0.1-10%, 0.01-0.2%, 0.01-0.2%, 0.01-0.2%, 0.03-0.3% and 0.05-0.5% of the mass of the polymer.

[0043] The conditions of the double-screw extruder in step (B) are as follows: the temperature of each temperature zone is 60-250 DEG C, the feeding amount of the feeding screw is 1-100 kg / h, and the rotating speed of the screw host is 20-400 rpm.

[0044] The forming process in step (C) is one or more of wire drawing, film blowing, vacuum forming, injection molding or foaming.

[0045] The reversible crosslinking POSS hybrid nanoparticle can be used for reversible crosslinking modification of polymers such as polyolefins, so as to obtain a composite material with reversible crosslinking characteristics, which has thermoplasticity during processing and is easy to form, exhibits thermosetting characteristics during actual use, has excellent comprehensive performance, can be recycled after use, and meets the requirements of sustainable development. The composite material with reversible crosslinking characteristics has improved performance, including enhanced tensile strength, improved aging resistance and solvent resistance, improved processing fluidity, enhanced anti-creep ability and anti-ultraviolet radiation ability, and improved elastic modulus, and therefore, the composite material can be used in various fields such as industrial pipes, nuclear power station facilities, hot and cold water conveying pipelines, new energy equipment, various containers and medium and low voltage cable materials.

[0046] The beneficial effects of the present application are as follows:

[0047] (1) In the present application, furan group and maleimide group will undergo Diels-Alder (DA) reaction at low temperature (< 80℃) to form stable six-membered ring crosslinking bond, realizing crosslinking and curing; when the temperature rises to > 100℃, the formed crosslinking bond undergoes reverse DA reaction (rDA), and is decomposed into independent furan group and maleimide group, realizing de-crosslinking; when the temperature gradually decreases to < 80℃, furan group and maleimide group will again undergo DA reaction and re-crosslink. When the material appears microcracks or damage, the crosslinking bonds at the microcracks or damage will break, and the original stable crosslinking bonds near the microcracks or damage will be broken when the temperature rises, the fluidity of the molecular chain is enhanced, and the furan group and maleimide group will spontaneously diffuse and fill into the microcracks or damage; after the temperature decreases, the furan group and maleimide group diffused to the microcracks or damage undergo DA reaction to form new six-membered ring crosslinking bonds, realizing the repair of the material microcracks or damage, thereby greatly prolonging the service life of the material, reducing resource waste and environmental pollution, and meeting the green and environmental protection trend.

[0048] (2) In the present application, the siloxane cage type skeleton of POSS serves as a nano-rigid reinforcing point, which can terminate the microcrack propagation and improve the overall thermal stability, strength and elastic modulus of the material; the vinyl group can form stable chemical bonds with the polymer molecular chain radicals such as polyolefin, realizing firm grafting of the POSS hybrid nanoparticles and the polymer matrix, rather than physical mixing, solving the problem of phase separation when the inorganic nano-phase of POSS is combined with the organic polymer, and avoiding the agglomeration of the POSS hybrid nanoparticles, enhancing the interface load transfer and realizing strong and tough mechanical balance.

[0049] (3) In the present application, the vinyl group, furan group and maleimide group are integrated in the POSS nanoparticles, rather than using a separate system of "polymer matrix + small molecule crosslinking agent", avoiding the problems of poor compatibility of small molecule crosslinking agent and polymer and unbalanced furan group / maleimide group molar ratio in the existing DA reversible crosslinking technology, and the groups are uniformly distributed at the molecular level, the crosslinking reaction is more stable, and the product performance will not be attenuated or the environment will not be polluted due to the migration of the crosslinking agent.

[0050] (4) In the reversible crosslinking POSS hybrid nanoparticles of the present application, the vinyl groups can form stable covalent crosslinking bonds with the POSS nanoparticles through a free radical polymerization reaction, thereby combining multiple POSS nanoparticles together to form a rigid network skeleton, providing the material with basic mechanical strength and structural stability; the furan groups and the maleimide groups can undergo Diels-Alder (DA) / reverse Diels-Alder (rDA) thermal reversible reactions, endowing the material with reversible crosslinking characteristics, and the vinyl groups, the furan groups and the maleimide groups are connected to the siloxane cage skeleton of the POSS, so that the formed reversible crosslinking POSS hybrid nanoparticles have both stable crosslinking sites and dynamic crosslinking sites, thereby making the material have both structural stability and reversible crosslinking characteristics.

[0051] (5) The present application has mild reaction conditions, simple reaction operation and is suitable for large-scale production. By adjusting the ratio between the vinyl groups, the furan groups and the maleimide groups, the crosslinking density of the reversible crosslinking POSS hybrid nanoparticles can be flexibly controlled to adapt to the modification requirements of different polymers. DETAILED DESCRIPTION

[0052] The present application will be further described below in combination with examples.

[0053] Example 1

[0054] Preparation of the reversible crosslinking POSS hybrid nanoparticles:

[0055] (1) Under the protection of dry nitrogen flow, 150 mL of anhydrous methanol was added to a 250 mL three-necked flask, then 2 mol of vinyl trimethoxysilane and 6 mol of γ-aminopropyl triethoxysilane were added, the mixture was uniformly stirred by magnetic stirring, then 5 mL of hydrochloric acid (concentration of 36.5 wt.%) was added, and the stirring was continuously carried out at 25℃ for 7 days to obtain a white suspension. The white suspension was filtered through a Buchner funnel and washed twice with methanol, and then dried in a vacuum oven at 60℃ for 4 h to obtain T8-hydrochloride;

[0056] (2) The T8-hydrochloride obtained in step (1) was dissolved in 150 mL of methanol to obtain a T8-hydrochloride solution, and the T8-hydrochloride solution was infiltrated into 100 g of anion exchange resin to obtain a T8-amino solution;

[0057] (3) 3 mol of maleic anhydride was added to the T8-amino solution obtained in step (2), and the reaction was carried out at 25℃ for 4 h to obtain reaction liquid I;

[0058] (4) 3 mol of furfural was first added to the reaction liquid I obtained in step (3), then 2 g of anhydrous sodium sulfate and 1.5 mL of acetic acid were added, and the reaction was carried out at 25℃ for 4 h to obtain reaction liquid II;

[0059] (5) The reaction solution II obtained in step (4) is moved to an ice water bath, and 3 mol of sodium borohydride is added in 4 batches, and the reaction is carried out at 0-5°C for 4 h to obtain a reaction solution III;

[0060] (6) 1.5 g of sodium acetate, 15 mL of acetic anhydride and 0.8 mL of triethylamine are added to the reaction solution III obtained in step (5), and the reaction is carried out at 25°C for 6 h to obtain a crude product of reversibly cross-linked POSS hybrid nanoparticles;

[0061] (7) The crude product of reversibly cross-linked POSS hybrid nanoparticles is added to acetone at 60°C and left to stand for 6 h, and then filtered, and the insoluble part is retained; the operation is repeated 3 times according to the above steps to remove organic impurities, and then dried in a vacuum oven at 60°C for 4 h to obtain reversibly cross-linked POSS hybrid nanoparticles.

[0062] Application of reversibly cross-linked POSS hybrid nanoparticles:

[0063] (A) 1000 g of polypropylene is added with 3 g of nano calcium carbonate, 5 g of dicumyl peroxide, 1.5 g of stearamide and 1.5 g of triphenyl phosphate, and then 25 g of reversibly cross-linked POSS hybrid nanoparticles is added, and the mixture is uniformly mixed to obtain a mixture;

[0064] (B) The double-screw extruder is opened, the temperature of each temperature zone (60-250°C), the feeding amount of the feeding screw (8 kg / h) and the rotation speed of the screw host (100 rpm) are set, the temperature is stabilized for half an hour, and then the mixture is added to the hopper of the double-screw extruder, the mixture is extruded, water-cooled, drawn, pelletized, dried to obtain a POSS hybrid nanoparticle modified material;

[0065] (C) The POSS hybrid nanoparticle modified material is subjected to a molding process to obtain reversibly cross-linked modified polypropylene.

[0066] Example 2

[0067] Preparation of reversibly cross-linked POSS hybrid nanoparticles:

[0068] (1) Under the protection of dry nitrogen flow, 150 mL of anhydrous methanol is added to a 250 mL three-necked flask, and then 1 mol of vinyltriethoxysilane and 7 mol of γ-aminopropyltrimethoxysilane are added, and the mixture is uniformly stirred and mixed, and then 5 mL of hydrochloric acid (concentration of 36 wt.%) is added, and the stirring is continued at 5°C for 10 days to obtain a suspension, which is filtered through a Buchner funnel and washed with methanol for 3 times, and then dried in a vacuum oven at 40°C for 5 h to obtain T8-hydrochloride;

[0069] (2) The T8-hydrochloride obtained in step (1) is dissolved in 200 mL of methanol to obtain a T8-hydrochloride solution, and the T8-hydrochloride solution is infiltrated through 150 g of anion exchange resin soaked with methanol to obtain a T8-amino solution;

[0070] (3) 5 moles of maleic anhydride are added to the T8-amino solution obtained in step (2), and the mixture is reacted at 0°C for 6 h to obtain reaction liquid I;

[0071] (4) 2 moles of furfural, 0.2 g of anhydrous magnesium sulfate, and 0.2 mL of acetic acid are added to the reaction liquid I obtained in step (3), and the mixture is reacted at 0°C for 6 h to obtain reaction liquid II;

[0072] (5) The reaction liquid II obtained in step (4) is moved to an ice water bath, and a total of 5 moles of sodium sulfite is added in four equal batches, and the mixture is reacted at 0-5°C for 6 h in an ice water bath to obtain reaction liquid III;

[0073] (6) 1 g of sodium acetate, 5 mL of acetic anhydride, and 3 mL of triethylamine are added to the reaction liquid III obtained in step (5), and the mixture is reacted at 50°C for 8 h to obtain a crude product of reversibly cross-linked POSS hybrid nanoparticles;

[0074] (7) The crude product of reversibly cross-linked POSS hybrid nanoparticles is added to ethyl acetate at 30°C, and after standing for 8 h, the insoluble part is retained by filtration. The operation is repeated 5 times according to the above steps to remove organic impurities, and the mixture is dried in a vacuum oven at 40°C for 5 h to obtain reversibly cross-linked POSS hybrid nanoparticles.

[0075] Application of reversibly cross-linked POSS hybrid nanoparticles:

[0076] (A) 1000 g of polypropylene is added with 3 g of nano calcium carbonate, 5 g of dicumyl peroxide, 2 g of stearamide, and 2 g of triphenyl phosphate, and then 45 g of reversibly cross-linked POSS hybrid nanoparticles are added, and the mixture is uniformly mixed to obtain a mixture;

[0077] (B) The double-screw extruder is opened, the temperature of each temperature zone (60-250°C), the feeding amount of the feeding screw (5 kg / h), and the rotation speed of the screw host (100 rpm) are set, and after the temperature is stabilized for half an hour, the mixture is added to the hopper of the double-screw extruder. The mixture is extruded, water-cooled, drawn, granulated, and dried to obtain a POSS hybrid nanoparticle modified material;

[0078] (C) The POSS hybrid nanoparticle modified material is subjected to a molding process to obtain reversibly cross-linked modified polypropylene.

[0079] Example 3

[0080] Preparation of reversibly cross-linked POSS hybrid nanoparticles:

[0081] (1) Under the protection of dry nitrogen flow, 100 mL of anhydrous methanol was added into a 250 mL three-necked flask, then 1 mol of vinyl tri (β-methoxyethoxy) silane and 6 mol of N- (β-aminoethyl) -γ-aminopropyl trimethoxysilane were added, and after the mixture was stirred and mixed uniformly, 3 mL of hydrochloric acid (concentration of 37 wt.%) was added, and the stirring was continued at 50°C for 3 days to obtain a suspension, which was filtered through a Buchner funnel and washed twice with methanol, and then dried in a vacuum oven at 50°C for 4.5 h to obtain T8-hydrochloride;

[0082] (2) The T8-hydrochloride obtained in step (1) was dissolved in 250 mL of methanol to obtain a T8-hydrochloride solution, and the T8-hydrochloride solution was infiltrated through 200 g of anion exchange resin soaked with methanol to obtain a T8-amino solution;

[0083] (3) 4 mol of maleic anhydride was added to the T8-amino solution obtained in step (2), and the reaction was carried out at 60°C for 2 h to obtain reaction liquid I;

[0084] (4) 2 mol of furfural was first added to the reaction liquid I obtained in step (3), and then 20 g of anhydrous calcium sulfate and 10 mL of acetic acid were added, and the reaction was carried out at 60°C for 2 h to obtain reaction liquid II;

[0085] (5) The reaction liquid II obtained in step (4) was moved to an ice water bath, and a total of 3 mol of sodium thiosulfate was added in 4 equal batches, and the reaction was carried out at 0-5°C for 2 h in an ice water bath to obtain reaction liquid III;

[0086] (6) 0.9 g of sodium acetate, 0.9 mL of acetic anhydride and 0.09 mL of triethylamine were added to the reaction liquid III obtained in step (5), and the reaction was carried out at 80°C for 4 h to obtain a crude product of reversibly cross-linked POSS hybrid nanoparticles;

[0087] (7) The crude product of reversibly cross-linked POSS hybrid nanoparticles was added to acetonitrile at 90°C and left to stand for 2 hours, then filtered, and the insoluble part was retained; the above steps were operated 4 times to remove organic impurities, and the product was dried in a vacuum oven at 50°C for 4.5 h to obtain reversibly cross-linked POSS hybrid nanoparticles.

[0088] Application of reversibly cross-linked POSS hybrid nanoparticles:

[0089] (A) 1000 g of polypropylene was added with 2 g of nano calcium carbonate, 4 g of dicumyl peroxide, 1.5 g of stearamide and 1.5 g of triphenyl phosphate, and then 50 g of reversibly cross-linked POSS hybrid nanoparticles was added, and the mixture was uniformly mixed to obtain a mixture;

[0090] (B) open the twin-screw extruder, set the temperature of each temperature zone (60-250℃), the feeding amount of the feeding screw (7 kg / h) and the rotating speed of the screw host (100 rpm), after the temperature is stable for half an hour, add the mixture into the hopper of the twin-screw extruder, the mixture is extruded, water-cooled, drawn, granulated, dried, and the POSS hybrid nanoparticle modified material is obtained;

[0091] (C) the POSS hybrid nanoparticle modified material is subjected to a molding process, and the reversibly crosslinked modified polypropylene is obtained.

[0092] Comparative Example 1

[0093] Without adding maleic anhydride, the other steps are the same as those in Example 1, and the POSS hybrid nanoparticle and the modified polypropylene are obtained.

[0094] Comparative Example 2

[0095] Without adding furfural, the other steps are the same as those in Example 1, and the POSS hybrid nanoparticle and the modified polypropylene are obtained.

[0096] Take 15 g of the reversibly crosslinked POSS hybrid nanoparticle prepared in Examples 1-3 and 15 g of the POSS hybrid nanoparticle prepared in Comparative Examples 1-2 respectively, and then add 75 g of N,N-dimethylformamide (DMF) with a temperature of 60℃ into each of the 15 g of the nanoparticle, and stir to obtain a mixture a, and then observe the morphology of the POSS hybrid nanoparticle in the mixture a; heat the mixture a to 110℃, and stir to obtain a mixture b, and then observe the morphology of the POSS hybrid nanoparticle in the mixture b; place the mixture b in an oven at 60℃ for 2 hours to obtain a mixture c, and then observe the morphology of the POSS hybrid nanoparticle in the mixture c; and the results are shown in Table 1.

[0097] Table 1 Test results of the reversibly crosslinked POSS hybrid nanoparticle prepared in Examples 1-3 and the POSS hybrid nanoparticle prepared in Comparative Examples 1-2

[0098]

[0099] The reversibly crosslinked POSS hybrid nanoparticle in Examples 1-3 is not dissolved in DMF at 60℃, when the temperature is heated to 110℃, the POSS hybrid nanoparticle in the mixture b can be dissolved in DMF, and the POSS hybrid nanoparticle in the mixture c forms a gel, which indicates that the crosslinking of the reversibly crosslinked POSS hybrid nanoparticle in Examples 1-3 is reversible. The reversibly crosslinked POSS hybrid nanoparticle in Comparative Examples 1-2 can be dissolved in DMF at 60℃ and 110℃, and no gel appears after being placed in a 60℃ oven for 2 hours, which indicates that the reversibly crosslinked POSS hybrid nanoparticle in Comparative Examples 1-2 does not form a reversible crosslinking structure.

[0100] The tensile strength, elongation at break and elastic modulus of the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 and the modified polypropylenes prepared in Comparative Examples 1-2 were tested, and the test results are shown in Table 2.

[0101] Table 2 Tensile strength, elongation at break and elastic modulus of the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 and the modified polypropylenes prepared in Comparative Examples 1-2

[0102]

[0103] As can be seen from the data in Table 2, the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 have higher tensile strength and elastic modulus but lower elongation at break than the modified polypropylenes prepared in Comparative Examples 1-2, indicating that the modified polypropylenes prepared in Examples 1-3 form crosslinked structures.

[0104] Each 20 g of the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 and the modified polypropylenes prepared in Comparative Examples 1-2 was added into 100 g of decalin at 60°C, and stirred to obtain mixture 1, and the morphology of the modified polypropylenes in mixture 1 was observed; mixture 1 was heated to 130°C and stirred to obtain mixture 2, and the morphology of the modified polypropylenes in mixture 2 was observed; mixture 2 was placed in an oven at 60°C for 2 hours to obtain mixture 3, and the morphology of the modified polypropylenes in mixture 3 was observed; mixture 3 was heated to 130°C and stirred to obtain mixture 4, and the morphology of the modified polypropylenes in mixture 4 was observed; mixture 4 was placed in an oven at 60°C for 2 hours to obtain mixture 5, and the morphology of the modified polypropylenes in mixture 5 was observed; and the results are shown in Table 3.

[0105] Table 3 Test results of the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 and the modified polypropylenes prepared in Comparative Examples 1-2

[0106]

[0107] The reversibly crosslinked modified polypropylenes in Examples 1-3 were in crosslinked state at 60℃ and insoluble in decalin; when the temperature was raised to 130℃, the DA bonds in the modified polypropylenes were broken and the modified polypropylenes could be dissolved in decalin; the decalin containing the modified polypropylenes was placed in an oven at 60℃ for 2h and it was found that a gel was formed in the decalin containing the modified polypropylenes, at this time the broken DA bonds in the modified polypropylenes were crosslinked again, indicating that the crosslinking of the modified polypropylenes in Examples 1-3 was reversible, at low temperature (e.g. 60℃) the modified polypropylenes were in crosslinked state and at high temperature (e.g. 130℃) the modified polypropylenes were in uncrosslinked state; while in mixture 4 it was observed that the formed gel could be dissolved in decalin and in mixture 5 the gel appeared again, indicating that from mixture 3 to mixture 4 and then to mixture 5, the modified polypropylenes again realized the process of crosslinking-uncrosslinking-re-crosslinking, indicating that the reversibly crosslinked modified polypropylenes prepared in Examples 1-3 had good reversibly crosslinked properties. The modified polypropylenes in Comparative Examples 1-2 could be dissolved in decalin at 60℃ and 130℃, and after being placed in an oven at 60℃ for 2h, mixture 3 was still clear and no gel appeared, and no gel appeared in mixture 4 and mixture 5, indicating that the modified polypropylenes in Comparative Examples 1-2 did not form reversibly crosslinked structure and could not realize the process of crosslinking-uncrosslinking-re-crosslinking.

Claims

1. A reversibly cross-linked POSS hybrid nanoparticle, characterized in that... The structure is as follows: ， Wherein, R is one of vinyl, furanyl, or maleimide, and all of R's vinyl, furanyl, and maleimide groups appear at least once.

2. A method for preparing the reversibly crosslinked POSS hybrid nanoparticles according to claim 1, characterized in that... Includes the following steps: (1) Add vinylsilane and aminosilane to methanol and stir until homogeneous. Then add hydrochloric acid, stir to react, filter, wash and dry to obtain T8-hydrochloride. (2) T8-hydrochloride is dissolved in methanol to obtain T8-hydrochloride solution. The T8-hydrochloride solution is passed through an anion exchange resin to obtain T8-amino solution. (3) Maleic anhydride was added to the T8-amino solution and reacted to obtain reaction solution I; (4) Furfural is added to reaction solution I first, followed by the auxiliary agent and acetic acid. The reaction is carried out to obtain reaction solution II. (5) A reducing agent is added to reaction solution II to react and obtain reaction solution III; (6) The reaction solution III was dehydrated to obtain crude reversibly cross-linked POSS hybrid nanoparticles; (7) The crude reversible cross-linked POSS hybrid nanoparticles were post-treated and dried to obtain reversible cross-linked POSS hybrid nanoparticles.

3. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 2, characterized in that... In step (1), the vinyl silane includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltri(β-methoxyethoxy)silane, and the amino silane includes one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. The stirring reaction time is 3-10 days, the stirring reaction temperature is 5-50℃, the washing is with methanol, and the number of washings is 2-3 times. The molar ratio of vinyl silane to amino silane is 1:3-7. The ratio between vinyl silane, methanol, and hydrochloric acid is 1:75-150:2.5-5, wherein vinyl silane is expressed in mol, and methanol and hydrochloric acid are expressed in mL. The concentration of hydrochloric acid is 36-37 wt.%, the drying temperature is 40-60℃, and the drying time is 4-5 hours.

4. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 2, characterized in that... In step (2), the ratio of anion exchange resin to aminosilane in step (1) is 16.6-33.4:1, where the anion exchange resin is in g and the aminosilane is in mol; the ratio of anion exchange resin to methanol is 1:1.25-1.5, where the anion exchange resin is in g and the methanol is in mL.

5. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 2, characterized in that... The reaction time in step (3) is 2-6 h, the reaction temperature is 0-60 °C, and the molar ratio of maleic anhydride to aminosilane in step (1) is 1:1.4-2.

6. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 2, characterized in that... In step (4), the reaction time is 2-6 h, the reaction temperature is 0-60 °C, the molar ratio of furfural to aminosilane in step (1) is 1:2-3.5, the auxiliary agent is one of anhydrous sodium sulfate, anhydrous magnesium sulfate or anhydrous calcium sulfate, and the ratio of furfural, auxiliary agent and acetic acid is 1:0.1-10:0.1-5, wherein furfural is in mol, auxiliary agent is in g, and acetic acid is in mL; in step (5), the reaction time is 2-6 h, the reaction temperature is 0-5 °C, the reducing agent is one of sodium borohydride, lithium aluminum hydride, sodium sulfite or sodium thiosulfate, and the molar ratio of reducing agent to vinylsilane in step (1) is 1.5-5:

1.

7. The method for preparing reversibly cross-linked POSS hybrid nanoparticles according to claim 2, characterized in that... In step (6), dehydration is achieved by reacting sodium acetate, acetic anhydride, and triethylamine, or by heating.

8. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 7, characterized in that... The reaction time for adding sodium acetate, acetic anhydride and triethylamine is 4-8 h, and the reaction temperature is 25-80 °C. The ratio of sodium acetate to vinylsilane in step (1) is 0.75-1:1, where sodium acetate is in g and vinylsilane is in mol. The ratio of sodium acetate, acetic anhydride and triethylamine is 1:1-10:0.1-3, where sodium acetate is in g and acetic anhydride and triethylamine are in mL.

9. The method for preparing reversibly crosslinked POSS hybrid nanoparticles according to claim 2, characterized in that... In step (7), the post-treatment involves adding the product to an organic solvent, allowing it to stand, and then filtering it. The organic solvent includes one of the following: diethyl ether, acetone, toluene, tetrahydrofuran, acetonitrile, or ethyl acetate. The temperature of the organic solvent is 30-90℃, and the standing time is 2-8 hours. The number of post-treatments is 3-5 times, the drying temperature is 40-60℃, and the drying time is 4-5 hours.

10. An application of the reversibly crosslinked POSS hybrid nanoparticles according to claim 1, characterized in that... Functional additives and reversibly crosslinked POSS hybrid nanoparticles were added to the polymer, mixed evenly, extruded, water-cooled into strips, granulated, dried, and shaped to obtain a reversibly crosslinked modified polymer.

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