Flame-retardant antibacterial modified polypropylene and preparation method thereof

Abstract

The invention discloses flame-retardant antibacterial modified polypropylene and a preparation method thereof, high-temperature trigger release is realized by packaging a liquid flame retardant through a PNIPAM microcapsule, illumination controlled release of Ag is realized by combining spiropyrane modified silver-loaded zeolite (Ag-Zeolite (at) SP), and the problem of component interference is solved by adopting a step-by-step blending and surface coating process. The LOI of the material is greater than or equal to 32%, the antibacterial rate under UV illumination is greater than or equal to 99.9%, and the material is suitable for the field of high-end protection and intelligent packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a polypropylene material with both dynamic flame retardancy and light-controlled antibacterial functions and a preparation method thereof. Background Art

[0002] As a semi-crystalline thermoplastic polymer material, polypropylene (PP) occupies an important position in the fields of automobiles, household appliances and medical treatment by virtue of its unique physical and chemical properties and cost advantages. Polypropylene has the characteristics of low density, low cost, odorless, non-toxic, corrosion-resistant, good electrical insulation, excellent mechanical properties, etc.

[0003] Of course, traditional polypropylene also has some disadvantages, such as poor flame retardancy: the limiting oxygen index (LOI) is only 17-18%, it is flammable and releases a large amount of smoke when burning; single antibacterial function: silver-based antibacterial agents are prone to migration and failure, lacking environmental responsiveness; insufficient functional synergy: the flame retardant and antibacterial components are prone to interfere with each other, resulting in performance attenuation.

[0004] In the prior art, CN118931034A discloses a highly flame-retardant PP material, which uses benzyl chloro chitosan, modified carbon nanotubes and silicon-modified boric acid to react to generate quaternary ammonium salt groups to achieve antibacterial properties, and uses boric acid to achieve flame retardant properties, but it does not have a dynamic regulation function, and the quaternary ammonium salt groups have poor heat resistance; CN119591980A organically bonds inorganic nano-TiO 2 with chitosan quaternary ammonium salt to achieve a composite antibacterial effect, but it does not involve the improvement of flame retardant properties. Therefore, it is urgent to develop a high-performance PP composite material with dynamically adjustable flame retardant / antibacterial functions. Summary of the Invention

[0005] To solve the above technical problems, the present invention adopts the following technical solutions: A flame retardant and antibacterial modified polypropylene, comprising the following components in parts by weight: 70-75 parts of polypropylene, 1-10 parts of thermosensitive microcapsules, 1-5 parts of light-controlled Ag⁺ release agent, 4-6 parts of compatibilizer, 1-5 parts of nano-silica, 0.1-5 parts of antioxidant.

[0006] Preferably, the thermosensitive microcapsules are poly N-isopropylacrylamide (PNIPAM) wrapped liquid flame retardant, and the liquid flame retardant is at least one of triphenyl phosphate, tricresyl phosphate, triethyl phosphate or DOPO derivatives.

[0007] Preferably, the light-controlled Ag⁺ release agent is silver-loaded zeolite (Ag-Zeolite@SP) modified by spiropyran (SP), and the grafting rate ≥80%.

[0008] Preferably, the compatibilizer is polypropylene grafted maleic anhydride (PP-g-MAH), and the grafting rate is ≥1%.

[0009] Preferably, the antioxidant is at least one of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and tris(2,4-di-tert-butylphenyl) phosphite.

[0010] Preferably, the nano-silica has a particle size of 10 - 30 nm and is surface amino-modified.

[0011] The second object of the present invention is to provide a preparation method of flame-retardant and antibacterial modified polypropylene, comprising the following steps: (1) Preparation of thermosensitive microcapsules: Mix the liquid flame retardant and PNIPAM prepolymer, and prepare thermosensitive microcapsules by interfacial polymerization method, and reserve after vacuum drying.

[0012] (2) Preparation of photo-controlled Ag⁺ release agent: React the silver-loaded zeolite in the spiropyran solution, centrifuge, and after vacuum drying, prepare the photo-controlled Ag⁺ release agent.

[0013] (3) Compounding and molding: Premix polypropylene, compatibilizer, and antioxidant to form a polypropylene matrix, and then compound the polypropylene matrix, thermosensitive microcapsules, and nano-silica through a twin-screw extruder and injection mold.

[0014] (4) Surface loading: Fix the photo-controlled Ag⁺ release agent on the material surface through a solution impregnation - hot pressing process to obtain the modified polypropylene material.

[0015] Preferably, the thermosensitive microcapsules have a particle size of 1 - 10 μm and a rupture temperature of 70 - 90 °C.

[0016] Preferably, in step (2), the reaction temperature of the silver-loaded zeolite and spiropyran is 50 - 70 °C, and the reflux reaction is carried out for 10 - 12 hours.

[0017] Preferably, in step (3), the extrusion temperature of the twin-screw extruder is ≤170 °C; the injection molding temperature is 175 - 190 °C, and the pressure is 40 - 60 MPa.

[0018] Preferably, in step (4), for the solution impregnation - hot pressing process, the impregnation time is 5 - 15 min, the hot pressing temperature is 110 - 130 °C, the pressure is 1 - 10 MPa, and the time is 1 - 10 minutes.

[0019] Beneficial effects Through the design of a temperature-sensitive microcapsule and a light-controlled Ag⁺ release system, the present invention realizes the on-demand dynamic regulation of flame retardancy and antibacterial functions. Using a PNIPAM temperature-sensitive polymer as the coating shell and a liquid flame retardant inside, they jointly form a temperature-sensitive microcapsule. As the temperature rises, the microcapsule ruptures, releasing the liquid flame retardant, which decomposes at high temperature to generate phosphoric acid, promoting dehydration and carbonization to form a dense carbon layer, thus achieving the flame retardant effect. Zeolite is a porous aluminosilicate framework that is loaded with Ag⁺ (silver loading of 3-4%) through ion exchange, providing a high specific surface area and a slow-release channel. Spiropyran is grafted on the surface, and its molecules undergo a ring-opening reaction under ultraviolet light, enhancing polarity and promoting the release of Ag⁺. Under UV irradiation, the ring-opening of spiropyran causes a change in the surface electrostatic potential of the zeolite, and Ag⁺ detaches from the zeolite pores and enters the environment. After stopping the light irradiation, spiropyran resumes its closed-ring structure, reducing the surface polarity and inhibiting the further release of Ag⁺, realizing the intelligent response of antibacterial. The step-by-step blending and surface coating processes are used to solve the problem of component interference. The two form a smart response system with spatio-temporal separation but functional synergy in the material. This design breaks through the static limitations of traditional functional materials and provides an innovative paradigm for the dynamic functionalization of polymer materials. Detailed implementation mode

[0020] The following will clearly and completely describe the technical solutions in the present invention in combination with the examples and comparative examples in the present invention.

[0021] Example 1 A flame retardant and antibacterial modified polypropylene, the preparation method comprising the following steps: 1. Preparation of temperature-sensitive microcapsules: Mix 10 g of triphenyl phosphate (TPP) with a PNIPAM prepolymer (95% NIPAM, 5 g of cross-linking agent), and perform interfacial polymerization in a cyclohexane / SDS system, and cure at 60°C for 6 hours to obtain microcapsules with a particle size of 1-3 μm.

[0022] 2. Preparation of a light-controlled Ag⁺ release agent: Immerse silver-loaded zeolite (Ag content 3%) in a toluene solution containing 1 wt% spiropyran, reflux at 60°C for 12 hours, and after centrifugation and drying, the SP grafting rate is 92%.

[0023] 3. Preparation of modified polypropylene: Weigh according to the mass ratio: 72% PP, 4% PNIPAM microcapsules, 5% PP-g-MAH, 2.5% nano-SiO 2 2.5%, 0.3% antioxidant. Dry polypropylene, PP-g-MAH, and antioxidant at 80°C for 12 hours to form a polypropylene matrix; perform twin-screw extrusion (temperature 170°C, rotation speed 200 rpm) to blend the polypropylene matrix, microcapsules, and nano-SiO 2, injection molding; placing the formed polypropylene matrix material in a suspension of a light-controlled Ag⁺ release agent, impregnating for 10 min, placing the dried sample piece between the upper and lower templates of a hot press, covering with a polytetrafluoroethylene (PTFE) separator film. After heating to 120 °C, pressurize to 5 MPa and hold the pressure for 5 minutes. After naturally cooling to below 60 °C, release the pressure and take out the sample piece, and place it in a vacuum drying oven (60 °C, -0.1 MPa) for 2 hours to completely remove the solvent residue.

[0024] Example 2 A flame-retardant and antibacterial modified polypropylene, the preparation method comprising the following steps: 1. Preparation of thermosensitive microcapsules: Mix 10 g of DOPO with a PNIPAM prepolymer (95% NIPAM, 5 g of crosslinking agent), carry out interfacial polymerization in a cyclohexane / SDS system, and cure at 60 °C for 6 hours to obtain microcapsules with a particle size of 1-3 μm.

[0025] 2. Preparation of a light-controlled Ag⁺ release agent: Immerse silver-loaded zeolite (Ag content 3%) in a toluene solution containing 1 wt% spiropyran, reflux at 60 °C for 12 hours, and after centrifugal drying, the SP grafting rate is 92%.

[0026] 3. Preparation of modified polypropylene: Weigh according to the mass ratio: 72% PP, 4% PNIPAM microcapsules, 5% PP-g-MAH, nano-SiO 2 2.5%, 0.3% antioxidant; dry polypropylene, PP-g-MAH, and antioxidant at 80 °C for 12 hours to form a polypropylene matrix; twin-screw extrusion (temperature 170 °C, rotation speed 200 rpm) to blend the polypropylene matrix, microcapsules and nano-SiO 2 , injection molding; placing the formed polypropylene matrix material in a suspension of a light-controlled Ag⁺ release agent, impregnating for 10 min, placing the dried sample piece between the upper and lower templates of a hot press, covering with a polytetrafluoroethylene (PTFE) separator film. After heating to 120 °C, pressurize to 5 MPa and hold the pressure for 5 minutes. After naturally cooling to below 60 °C, release the pressure and take out the sample piece, and place it in a vacuum drying oven (60 °C, -0.1 MPa) for 2 hours to completely remove the solvent residue.

[0027] Example 3 A flame-retardant and antibacterial modified polypropylene, the preparation method comprising the following steps: 1. Preparation of thermosensitive microcapsules: Mix 10 g of triphenyl phosphate (TPP) with a PNIPAM prepolymer (95% NIPAM, 5 g of crosslinking agent), carry out interfacial polymerization in a cyclohexane / SDS system, and cure at 60 °C for 6 hours to obtain microcapsules with a particle size of 1-3 μm.

[0028] 2. Preparation of photocontrolled Ag⁺ release agent: Immerse silver-loaded zeolite (Ag content 4%) into toluene solution containing 1 wt% spiropyran, reflux at 60 °C for 12 hours, and after centrifugation and drying, the grafting rate of SP is 92%.

[0029] 3. Preparation of modified polypropylene: Weigh according to the mass ratio: 72% of PP, 4% of PNIPAM microcapsules, 5% of PP-g-MAH, 2.5% of nano-SiO 2 0.3% of antioxidant; dry polypropylene, PP-g-MAH, and antioxidant at 80 °C for 12 hours to form a polypropylene matrix; co-mix the polypropylene matrix, microcapsules and nano-SiO by twin-screw extrusion (temperature 170 °C, rotation speed 200 rpm) 2 , and then injection mold; place the formed polypropylene matrix material in the suspension of the photocontrolled Ag⁺ release agent, immerse for 10 min, place the dried sample between the upper and lower templates of a hot press, and cover with a polytetrafluoroethylene (PTFE) isolation film. After heating to 120 °C, apply pressure to 5 MPa, hold the pressure for 5 minutes. After natural cooling to below 60 °C, release the pressure and take out the sample, and place it in a vacuum drying oven (60 °C, -0.1 MPa) for 2 hours to completely remove the solvent residue.

[0030] Comparative Example 1 A flame-retardant and antibacterial modified polypropylene, the preparation method includes the following steps (only omitting the thermosensitive microcapsules compared with Example 1) 1. Preparation of photocontrolled Ag⁺ release agent: Immerse silver-loaded zeolite (Ag content 3%) into toluene solution containing 1 wt% spiropyran, reflux at 60 °C for 12 hours, and after centrifugation and drying, the grafting rate of SP is 92%.

[0031] 2 Preparation of modified polypropylene: Weigh according to the mass ratio: 72% of PP, 5% of PP-g-MAH, 2.5% of nano-SiO 2 0.3% of antioxidant; dry polypropylene, PP-g-MAH, and antioxidant at 80 °C for 12 hours to form a polypropylene matrix; co-mix the polypropylene matrix and nano-SiO by twin-screw extrusion (temperature 170 °C, rotation speed 200 rpm) 2 , and then injection mold; place the formed polypropylene matrix material in the suspension of the photocontrolled Ag⁺ release agent, immerse for 10 min, place the dried sample between the upper and lower templates of a hot press, and cover with a polytetrafluoroethylene (PTFE) isolation film. After heating to 120 °C, apply pressure to 5 MPa, hold the pressure for 5 minutes. After natural cooling to below 60 °C, release the pressure and take out the sample, and place it in a vacuum drying oven (60 °C, -0.1 MPa) for 2 hours to completely remove the solvent residue.

[0032] Comparative Example 2 A flame-retardant and antibacterial modified polypropylene, the preparation method comprising the following steps (replacing the photo-controlled Ag⁺ releasing agent with ordinary silver-loaded zeolite compared with Example 1) 1. Preparation of thermosensitive microcapsules: Mix 10 g of triphenyl phosphate (TPP) with PNIPAM prepolymer (95% NIPAM, 5 g of crosslinking agent), and carry out interfacial polymerization in a cyclohexane / SDS system, and cure at 60°C for 6 hours to obtain microcapsules with a particle size of 1-3 μm.

[0033] 2. Preparation of modified polypropylene: Weigh according to the mass ratio: 72% PP, 5% PP-g-MAH, nano-SiO 2 2.5%, 0.3% antioxidant; dry polypropylene, PP-g-MAH, and antioxidant at 80°C for 12 hours to form a polypropylene matrix; co-extrude (temperature 170°C, rotation speed 200 rpm) the polypropylene matrix, microcapsules and nano-SiO 2 , and injection mold; place the molded polypropylene matrix material in a suspension of silver-loaded zeolite (Ag content 3%), immerse for 10 min, place the dried sample piece between the upper and lower templates of a hot press, and cover with a polytetrafluoroethylene (PTFE) isolation film. After heating to 120°C, pressurize to 5 MPa, hold the pressure for 5 minutes. After naturally cooling to below 60°C, release the pressure and take out the sample piece, and place it in a vacuum drying oven (60°C, -0.1 MPa) for 2 hours to completely remove the solvent residue.

[0034] Perform performance tests on the polypropylene materials prepared in Examples 1-3 and Comparative Examples 1-2, and the results are shown in the following table.

[0035] Among them, Flame retardancy test: LOI, UL-94 test (ASTM standard) Antibacterial performance test: Contact the sample with the bacterial solution for 24 hours, and test the antibacterial rate (ISO 22196); Ag⁺ release kinetics: Detect the Ag⁺ concentration under light by ICP-MS.

[0036] Mechanical property test: Test with a universal material testing machine (ASTM D638) Comparing Example 1 with Comparative Example 1, the addition of thermosensitive microcapsules increased the LOI from 25% to 33%, and the UL-94 rating was improved from not rated to V-0, indicating that the thermosensitive microcapsules can trigger flame retardancy at high temperatures and have efficient high-temperature flame retardant performance; Comparing Example 1 with Comparative Example 2, it can be found that the antibacterial rate of Example 1 under light increased from 75% to 99.95%, and the Ag⁺ release amount increased from 0.9 ppm to 3.2 ppm; while in Comparative Example 2, the antibacterial rate and Ag⁺ release amount of the ordinary silver-loaded zeolite added did not change significantly under both light and dark conditions, indicating that the modification of the silver-loaded zeolite by spiropyran can achieve a controlled release effect.

[0037] From the above examples and comparative examples, it can be seen that the modified polypropylene obtained by the preparation method provided by the present invention has excellent high-temperature flame retardant performance and efficient light-controlled antibacterial performance.

[0038] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0039] The above is only the best implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several modifications or equivalent replacements can be made to the technical solution of the present invention, and the same technical effects can also be achieved, which should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A flame retardant and antibacterial modified polypropylene material, characterized in that: The following components are included in weight: polypropylene 70-75 parts, 1-10 parts of thermosensitive microcapsules, 1-5 parts of light-controlled Ag⁺ release agent, 4-6 parts of compatibilizer, 1-5 parts of nano-silicon dioxide, and 0.1-5 parts of antioxidant.

2. The flame retardant and antibacterial modified polypropylene material according to claim 1, characterized in that: Thermosensitive microgel The capsule is poly N-isopropylacrylamide (PNIPAM) encapsulating a liquid flame retardant, wherein the liquid flame retardant is at least one of triphenyl phosphate, tricresyl phosphate, triethyl phosphate or a DOPO derivative.

3. The flame retardant and antibacterial modified polypropylene material according to claim 1, characterized in that: The photo-controlled Ag⁺ The release agent is spiropyran-modified silver-loaded zeolite (Ag-Zeolite@SP) with a grafting rate of ≥80%.

4. The flame retardant and antibacterial modified polypropylene material according to claim 1, characterized in that: The compatibilizer is Polypropylene grafted maleic anhydride (PP-g-MAH), the grafting rate is ≥1%; the antioxidant is at least one of pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) and tris (2,4-di-tert-butylphenyl) phosphite.

5. The flame retardant and antibacterial modified polypropylene material according to claim 1, characterized in that: The nanometer dioxide The particle size of silicon dioxide is 10-30nm, and the surface is amino-modified.

6. A method for preparing flame retardant and antibacterial modified polypropylene, characterized in that: The following steps are involved: (1) Preparation of thermosensitive microcapsules: Mix the liquid flame retardant and PNIPAM prepolymer, prepare thermosensitive microcapsules by interfacial polymerization, and vacuum dry them for later use; (2) Preparation of light-controlled Ag⁺ release agent: silver-loaded zeolite is placed in a spiropyran solution for reaction, centrifuged, and vacuum dried to obtain a light-controlled Ag⁺ release agent; (3) Blending molding: premix polypropylene, compatibilizer, and antioxidant to form a polypropylene matrix, and then blend the polypropylene matrix, temperature-sensitive microcapsules, and nano-silica through a twin-screw extruder and injection mold; (4) Surface loading: The photocontrolled Ag⁺ releaser is fixed on the material surface through a solution impregnation-hot pressing process to obtain a modified polypropylene material.

7. The preparation method according to claim 6, characterized in that: The thermosensitive microcapsule described in step (1) The particle size is 1-10μm and the rupture temperature is 70-90℃.

8. The preparation method according to claim 6, characterized in that: The silver-loaded zeolite and the spiro The reaction temperature of pyran is 50-70°C, and the reflux reaction is performed for 10-12 hours.

9. The preparation method according to claim 6, characterized in that: Twin screw extrusion as described in step (3) The extrusion temperature of the machine is ≤170℃; the injection temperature is 175-190℃, and the pressure is 40-60 MPa.

10. The preparation method according to claim 6, characterized in that: The solution impregnation described in step (4) - Hot pressing process, dipping time 5-15min; hot pressing temperature: 110-130℃; pressure: 1-10 MPa; hot pressing time: 1-10 minutes.

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