A self-fluorescent high melt strength modified polypropylene, its preparation method and application

Abstract

This invention discloses a self-fluorescent, high melt strength modified polypropylene, its preparation method, and its applications. The first step involves synthesizing polypropylene-A containing bromophenyl groups in its side chains, followed by the synthesis of polypropylene-B containing styrene groups in its side chains. Finally, polypropylene-A and polypropylene-B undergo a substitution reaction of their side chain groups under the action of a catalyst to generate a modified polypropylene with tetraphenylvinyl groups exhibiting aggregation-induced emission. The synthesized modified polypropylene product not only exhibits fluorescence but also has a significantly higher melt strength than ordinary polypropylene, making it suitable for manufacturing lightweight, heat-insulating polypropylene products such as foamed polypropylene.

Description

Technical Field

[0001] This invention relates to the field of novel polypropylene synthesis, specifically to a self-fluorescent high melt strength modified polypropylene, its preparation method, and its applications. Background Technology

[0002] Polypropylene is increasingly used in household appliances, lighting switches and related electronic products due to its good chemical stability, low price, excellent mechanical properties and strong processability. Some application areas have certain requirements for the fluorescence properties of polypropylene, but at the same time, there are also certain requirements for the environmental protection and food contact safety of the material.

[0003] Chinese patent CN103437210A discloses a fluorescent polypropylene fiber fabric, which is composed of fluorescent powder, polypropylene fiber, polyamide fiber, and plant fiber. The fluorescent powder accounts for 11%-25% of the total amount of the fabric, the polypropylene fiber accounts for 45%-55%, the polyamide fiber accounts for 8%-10%, and the plant fiber accounts for 22%-24%. This invention enables the fabric to have a fluorescent effect while maintaining a soft and smooth texture. However, the fluorescent powder is prone to leaching, which is harmful to human health and the environment.

[0004] Chinese patent CN200810042270.3 relates to a method for preparing fluorescent polypropylene fibers using organic fluorescent compounds, comprising: (1) dissolving salicylaldehyde and its derivatives in anhydrous ethanol, heating in a water bath to 70-100°C, adding an ethanol solution of a diamine compound, refluxing, and allowing to stand to obtain a bright yellow, orange-red, or red precipitate, filtering the precipitate, recrystallizing it with ethanol, filtering it, and drying it to obtain an organic fluorescent compound; (2) mixing polypropylene with the fluorescent compound and fluorescent additives evenly, performing melt blending using a multifilament 400 melt spinning machine, extruding, spinning at a spinning speed of 400 m / min and a spinning temperature of 270°C, and then stretching it by 2.8 times to obtain the product. The preparation method of this invention is simple and has a high yield; the obtained fluorescent compound has good solid-state luminescence properties, is non-toxic and non-radioactive; it is evenly dispersed in polypropylene polymers, has good spinnability, and can achieve a good luminescence effect with an addition amount of less than 1%. However, the process is cumbersome, production is complex, and production costs are high.

[0005] Currently, improving the safety of fluorescent polypropylene products while ensuring fluorescence performance has become a hot research topic. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a self-fluorescent high melt strength modified polypropylene and its preparation method. This material is a chemically bonded homogenized material, resulting in a uniform distribution of self-fluorescent groups, excellent self-fluorescence effect, and no precipitation of fluorescent substances, making it very safe and environmentally friendly. Furthermore, due to the reaction between the substituents on two different polypropylenes, the molecular chains directly entangle to form a spatial network structure. Therefore, the synthesized modified polypropylene product not only exhibits fluorescence but also has a much higher melt strength than ordinary polypropylene, making it suitable for manufacturing lightweight, heat-insulating polypropylene products such as foamed polypropylene.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] This invention provides a method for preparing self-fluorescent high melt strength modified polypropylene, the steps of which include:

[0009] 1) Add an organic solvent to the reactor, then introduce propylene gas, and simultaneously add 4-bromostyrene monomer, metallocene catalyst, and co-catalyst to carry out a polymerization reaction to obtain polypropylene-A with bromobenzene substituents in the side chain.

[0010] 2) Add an organic solvent to the reactor, then introduce propylene gas, and simultaneously add divinylbenzene monomer, metallocene catalyst, and co-catalyst to carry out a polymerization reaction to obtain polypropylene-B with styrene substituents in the side chain.

[0011] 3) Polypropylene-A and polypropylene-B were dissolved in toluene, and the catalysts tris(4-methoxybenzyl)phosphine and ferric chloride were added to the mixture under elevated temperature to produce fluorescent high melt strength modified polypropylene.

[0012] In this invention, the organic solvents in steps 1) and 2) are each independently selected from one or more of C5-C10 alkanes and C6-C10 aromatic hydrocarbons; the C5-C10 alkanes are selected from one or more of n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, and n-decane; the C6-C10 aromatic hydrocarbons are selected from one or more of benzene, toluene, xylene, ethylbenzene, n-propylbenzene, and isopropylbenzene; in steps 1) and 2), the organic solvents may be the same or different.

[0013] In step 1), the mass ratio of 4-bromostyrene to the organic solvent is 1-5:100, preferably 1-2:100;

[0014] In step 2), the mass ratio of divinylbenzene to organic solvent is 1 to 10:100, preferably 2 to 5:100.

[0015] In this invention, the metallocene catalysts described in steps 1) and 2) are selected from transition metal-π bond compounds with transition metal M as the central atom, wherein M is Ti, Zr, or Hf; preferably, the transition metal-π bond compounds with transition metal M as the central atom are selected from Cp2TiCl2, C2H4(Me4Cp)2MCl2, C2H4(Ind)2MCl2, C2H4(2,4,7-Me3-Ind)2MCl2, Me2Si(Flu)2MCl2, Me2SiCH2(In d) One or more of 2MCl2, Me2Si(2-MeInd)2MCl2, Me2Si(2,5-Me-Cp)2MCl2, Me2Si(4,7-Me2-Ind)2MCl2, and Me2Si(2-Me-4-Naph-Ind)2ZrCl2, wherein Me represents methyl, Ph represents phenyl, Cp represents cyclopentadienyl, Ind represents indene, H4Ind represents 4,5,6,7-tetrahydroindene, Flu represents fluorenyl, and Naph represents naphthyl;

[0016] The cocatalyst is selected from alkylaluminoxane compounds, preferably one or more of methylaluminoxane and isobutylaluminoxane;

[0017] The amount of the co-catalyst added is based on the molar ratio of Al to M in the metallocene catalyst, where Al:M = 10 to 20000:1, preferably 500 to 10000:1.

[0018] In this invention, the amount of metallocene catalyst added in step 1) is, based on the molar amount of M, in a molar ratio of 1 to 1000:10000 with 4-bromostyrene, preferably 1 to 2000:6000.

[0019] The amount of metallocene catalyst added in step 2), based on the molar amount of M, has a molar ratio of 1-4000:15000 to divinylbenzene monomer, preferably 1-5000:11000.

[0020] In this invention, the propylene gas flow rate in step 1) is controlled by the polymerization reaction pressure, which is 0.1–4 MPa, preferably 1–2 MPa;

[0021] The propylene gas flow rate in step 2) is controlled by the polymerization reaction pressure, which is 0.1 to 2 MPa, preferably 1 to 2 MPa.

[0022] In step 1) of the present invention, the polymerization reaction is carried out at a temperature of 30-80°C, preferably 50-60°C, for a time of 0.1-0.5 h, preferably 0.2-0.3 h.

[0023] In step 2) of the present invention, the polymerization reaction is carried out at a temperature of 30-80°C, preferably 50-60°C, for a time of 0.1-0.5h, preferably 0.2-0.3h.

[0024] In step 3) of the present invention, the mass ratio of polypropylene-A to polypropylene-B is 0.5 to 1.5:1, preferably 0.9 to 1.1:1;

[0025] The total mass ratio of polypropylene-A and polypropylene-B to toluene is 10-30:100, preferably 20-25:100.

[0026] In step 3) of the present invention, the total mass ratio of tris(4-methoxyphenyl)phosphine to polypropylene-A and polypropylene-B is 0.05 to 0.1:1, preferably 0.07 to 0.08:1;

[0027] The mass ratio of tris(4-methoxyphenyl)phosphine to ferric chloride is 1:2 to 3, preferably 1:2.5 to 2.6;

[0028] In step 3) of the present invention, the reaction is carried out at a temperature of 80-150°C, preferably 100-120°C, for a time of 20-40 hours, preferably 24-30 hours.

[0029] In this invention, after the reactions described in steps 1) and 2) are completed, the polymer solution is transferred to acetone and stirred at room temperature for 2 to 4 hours to inactivate it.

[0030] In this invention, after each reaction step is completed, conventional post-processing operations such as solvent removal, washing, and drying are also included, but no specific requirements are made in this invention.

[0031] The first step of this invention is to synthesize polypropylene-A with bromophenyl side chains, and then to synthesize polypropylene-B with styrene side chains. Finally, polypropylene-A and polypropylene-B are subjected to a substitution reaction of their side chain groups under the action of a catalyst to generate modified polypropylene with tetraphenylvinyl groups exhibiting aggregation-induced emission effect. The reaction process is as follows:

[0032]

[0033] The intensity of the fluorescence effect of this polypropylene material is positively correlated with the number of tetraphenylvinyl groups in the final synthesized polypropylene product. In this invention, the fluorescent effect groups are directly bonded to the polymer. Compared to previously reported polypropylene materials with physically mixed fluorescent substances, the fluorescent groups are more uniformly distributed and do not precipitate to the outside, making it more environmentally friendly and safer. Furthermore, the polypropylene with this structure exhibits higher melt strength.

[0034] The modified polypropylene prepared by the method of this invention has both fluorescence effect and high melt strength, and can be used in household appliances, decoration, toys, takeaway insulated boxes and other fields. It is especially suitable for making lightweight insulating polypropylene products such as foamed polypropylene.

[0035] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0036] This invention first synthesizes polypropylene with bromophenyl groups in the side chain and polypropylene with styrene groups in the side chain. Modified polypropylene products are obtained by substituting two side chain groups on the two types of polypropylene, which have advantages such as self-fluorescence and high melt strength. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments. The embodiments are only for illustration and are not intended to limit the scope of protection of the present invention.

[0038] In the various embodiments and comparative examples of this invention, the main raw materials are sourced as follows; other raw materials and reagents, unless otherwise specified, were obtained through ordinary commercial channels:

[0039] Toluene, brand name Aldrich, manufactured by Sinopharm Chemical Reagent Co., Ltd.

[0040] Methylaluminoxane (10wt toluene solution), Shanghai Maclean Biochemical Technology Co., Ltd.

[0041] bis(cyclopentadiene)zirconium dichloride, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0042] 4-Bromostyrene, Shanghai Aladdin Biotechnology Co., Ltd.;

[0043] p-Divinylbenzene, Shanghai Aladdin Biotechnology Co., Ltd.;

[0044] Tris(4-methoxyphenyl)phosphine, Shanghai Aladdin Biotechnology Co., Ltd.;

[0045] Ferric chloride, Shanghai Aladdin Biotechnology Co., Ltd.;

[0046] Propylene, a bright gas;

[0047] 4-Bromo-1-butene, Shanghai Aladdin Biotechnology Co., Ltd.;

[0048] 1,3-Butadiene, Shanghai Aladdin Biotechnology Co., Ltd.

[0049] The main performance characteristics in this embodiment of the invention were tested using the following methods:

[0050] Monomer insertion rate: liquid NMR;

[0051] Relative fluorescence intensity: fluorophotometer;

[0052] Melt strength: Polymer melt strength tester.

[0053] Example 1

[0054] The steps for preparing self-fluorescent high melt strength modified polypropylene are as follows:

[0055] 1) In a 5L reactor, 1000g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 1MPa, and then 15g (0.082mol) of 4-bromostyrene monomer and 30μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 50℃ for 0.25 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 140g of polypropylene-A product with bromobenzene substituents in the side chain.

[0056] The insertion rate of 4-bromostyrene monomer in polypropylene-A was determined to be 3.5% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 123.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0057] 2) In a 5L reactor, 1000g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 1MPa, and then 20g (0.154mol) of divinylbenzene monomer and 30μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 50℃ for 0.25 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 130g of polypropylene-B product with styrene-substituted side chains.

[0058] The insertion rate of polypropylene-B divinylbenzene monomer was determined to be 4.2% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 137.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0059] 3) Dissolve 20g of polypropylene-A and 20g of polypropylene-B in 200g of toluene, keep the heating temperature at 100℃, add 3g of tris(4-methoxybenzyl)phosphine catalyst and 8g of ferric chloride, react for 24h, collect the product, wash and dry it to obtain 35g of self-fluorescent high melt strength modified polypropylene.

[0060] The tetraphenyl fluorescent group of this invention can be clearly characterized by the characteristic peaks at 140 (characteristic peak of the carbon atom in the benzene ring connected to the double bond) and 141 (characteristic peak of the carbon atom in the double bond connected to the benzene ring) in the high-temperature carbon spectrum.

[0061] The modified polypropylene was tested for its relative fluorescence intensity and melt strength, and the results are shown in Table 1.

[0062] Example 2

[0063] The steps for preparing self-fluorescent high melt strength modified polypropylene are as follows:

[0064] 1) In a 5L reactor, 1500g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 2MPa, and then 30g (0.163mol) of 4-bromostyrene monomer and 30μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 60℃ for 0.3 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 145g of polypropylene-A product with bromobenzene substituents in the side chain.

[0065] The insertion rate of 4-bromostyrene monomer in polypropylene-A was determined to be 6.5% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 123.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0066] 2) In a 5L reactor, 1500g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 2MPa, and then 40g (0.307mol) of divinylbenzene monomer and 30μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 60℃ for 0.3 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 132g of polypropylene-B product with styrene substituents in the side chains.

[0067] The insertion rate of polypropylene-B divinylbenzene monomer was determined to be 7.1% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 137.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0068] 3) Dissolve 10g of polypropylene-A and 20g of polypropylene-B in 120g of toluene, keep the heating temperature at 120℃, add 3g of tris(4-methoxybenzyl)phosphine catalyst and 8g of ferric chloride, react for 24h, collect the product, wash and dry it to obtain 28g of self-fluorescent high melt strength modified polypropylene.

[0069] The modified polypropylene was tested for its relative fluorescence intensity and melt strength, and the results are shown in Table 1.

[0070] Example 3

[0071] The steps for preparing self-fluorescent high melt strength modified polypropylene are as follows:

[0072] 1) In a 5L reactor, 1000g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 1MPa, and then 15g (0.082mol) of 4-bromostyrene monomer and 20μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 55℃ for 0.2 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 160g of polypropylene-A product with bromobenzene substituents in the side chain.

[0073] The insertion rate of 4-bromostyrene monomer in polypropylene-A was determined to be 4.8% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 123.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0074] 2) In a 5L reactor, 1000g of toluene was added, followed by 40mL of methylaluminoxane (1.0mol / L) under stirring. Propylene gas was introduced to 1MPa, and then 20g (0.154mol) of divinylbenzene monomer and 30μmol of metallocene bis(cyclopentadiene)zirconium chloride were added. The polymerization reaction was carried out at 55℃ for 0.2 hours. After the reaction was completed, the polymer solution was transferred to acetone and stirred at room temperature for 2 hours to fully deactivate the catalyst. The product was collected, washed, and dried to obtain 130g of polypropylene-B product with styrene-substituted side chains.

[0075] The insertion rate of polypropylene-B divinylbenzene monomer was determined to be 5.4% (molar ratio) by analyzing the peak area of ​​the characteristic peak (peak value 137.1) of the benzene ring carbon linked to bromine in the high-temperature carbon NMR spectrum.

[0076] 3) Dissolve 20g of polypropylene-A and 20g of polypropylene-B in 200g of toluene, keep the heating temperature at 80℃, add 3g of tris(4-methoxybenzyl)phosphine catalyst and 8g of ferric chloride, react for 40h, collect the product, wash and dry it to obtain 36g of self-fluorescent high melt strength modified polypropylene.

[0077] The modified polypropylene was tested for its relative fluorescence intensity and melt strength, and the results are shown in Table 1.

[0078] Comparative Example 1

[0079] The preparation method of Example 1 was followed, except that in step 1), 4-bromostyrene monomer was replaced with 4-bromo-1-butene monomer, and other operations remained unchanged. Modified polypropylene was obtained, and its relative fluorescence intensity and melt strength were tested. The results are shown in Table 1.

[0080] Comparative Example 2

[0081] The preparation method of Example 1 was followed, except that in step 2), the divinylbenzene monomer was replaced with 1,3-butadiene monomer, while other operations remained unchanged. Modified polypropylene was obtained, and its relative fluorescence intensity and melt strength were tested. The results are shown in Table 1.

[0082] Comparative Example 3

[0083] The preparation method of Example 1 was followed, except that tris(4-methoxybenzyl)phosphine and ferric chloride were not added to the catalyst in step 3), while other operations remained unchanged. Modified polypropylene was obtained, and its relative fluorescence intensity and melt strength were tested. The results are shown in Table 1.

[0084] Comparative Example 4

[0085] Referring to the preparation method of polypropylene-A in step 1) of Example 1, the only difference is that the 4-bromostyrene monomer is replaced with a mixture of 4-bromostyrene monomer and p-divinylbenzene monomer (mixing mass ratio of 1:1), and other operations remain unchanged. Modified polypropylene is obtained, and its relative fluorescence intensity and melt strength are tested. The results are shown in Table 1.

[0086] Table 1. Fluorescence intensity and melt strength under UV lamp in Examples 1-2 and Comparative Example 1.

[0087] Relative fluorescence intensity Melt strength (F / Mn) Example 1 348 167 Example 2 552 232 Example 3 438 201 Comparative Example 1 68 155 Comparative Example 2 72 178 Comparative Example 3 69 87 Comparative Example 4 110 135

Claims

1. A method for preparing self-fluorescent high melt strength modified polypropylene, characterized in that the steps include... include: 1) Add an organic solvent to the reactor, then introduce propylene gas, and simultaneously add 4-bromostyrene monomer, metallocene catalyst, and co-catalyst to carry out a polymerization reaction to obtain polypropylene-A with bromobenzene substituents in the side chain. 2) Add an organic solvent to the reactor, then introduce propylene gas, and simultaneously add divinylbenzene monomer, metallocene catalyst, and co-catalyst to carry out a polymerization reaction to obtain polypropylene-B with styrene substituents in the side chain. 3) Polypropylene-A and polypropylene-B were dissolved in toluene, and the catalysts tris(4-methoxybenzyl)phosphine and ferric chloride were added to the mixture at elevated temperature to produce fluorescent high melt strength modified polypropylene.

2. The preparation method according to claim 1, characterized in that, The organic solvents used in steps 1) and 2) are each independently selected from one or more of C5-C10 alkanes and C6-C10 aromatic hydrocarbons; the organic solvents used in steps 1) and 2) may be the same or different. In step 1), the mass ratio of 4-bromostyrene to the organic solvent is 1-5:100; In step 2), the mass ratio of divinylbenzene to organic solvent is 1 to 10:

100.

3. The preparation method according to claim 2, characterized in that, The C5-C10 alkanes are selected from one or more of n-pentane, n-hexane, cyclohexane, n-heptane, n-octane, and n-decane, and the C6-C10 aromatics are selected from one or more of benzene, toluene, xylene, ethylbenzene, n-propylbenzene, and isopropylbenzene.

4. The preparation method according to claim 2, characterized in that, The mass ratio of 4-bromostyrene to the organic solvent is 1 to 2:

100.

5. The preparation method according to claim 2, characterized in that, The mass ratio of p-divinylbenzene to organic solvent is 2-5:

100.

6. The preparation method according to claim 1, characterized in that, The metallocene catalysts described in steps 1) and 2) are selected from transition metal-π bond compounds with transition metal M as the central atom, wherein M is Ti, Zr, or Hf; The cocatalyst is selected from alkylaluminoxane compounds; The amount of the co-catalyst added is based on the molar ratio of Al to M in the metallocene catalyst, where Al:M = 10 to 20000:

1.

7. The preparation method according to claim 6, characterized in that, The transition metal-π bonded compound with transition metal M as the central atom is selected from one or more of Cp2TiCl2, Cp2ZrCl2, C2H4(Me4Cp)2MCl2, C2H4(Ind)2MCl2, C2H4(2,4,7-Me3-Ind)2MCl2, Me2Si(Flu)2MCl2, Me2SiCH2(Ind)2MCl2, Me2Si(2-MeInd)2MCl2, Me2Si(2,5-Me-Cp)2MCl2, Me2Si(4,7-Me2-Ind)2MCl2, and Me2Si(2-Me-4-Naph-Ind)2ZrCl2, wherein Me represents methyl, Ph represents phenyl, Cp represents cyclopentadienyl, Ind represents indyl, Flu represents fluorenyl, and Naph represents naphthyl.

8. The preparation method according to claim 6, characterized in that, The co-catalyst is selected from one or more of methylaluminoxane and isobutylaluminoxane.

9. The preparation method according to claim 6, characterized in that, The amount of the co-catalyst added is based on the molar ratio of Al to M in the metallocene catalyst, where Al:M = 500 to 10000:

1.

10. The preparation method according to claim 1, characterized in that, The amount of metallocene catalyst added in step 1), based on the molar amount of M, has a molar ratio of 1 to 1000:10000 with 4-bromostyrene. The amount of metallocene catalyst added in step 2), calculated by the molar amount of M, has a molar ratio of 1 to 4000:15000 with respect to divinylbenzene monomer.

11. The preparation method according to claim 10, characterized in that, The amount of metallocene catalyst added in step 1), calculated by the molar amount of M, has a molar ratio of 1 to 2000:6000 with 4-bromostyrene.

12. The preparation method according to claim 10, characterized in that, The amount of metallocene catalyst added in step 2), calculated by the molar amount of M, has a molar ratio of 1 to 5000:11000 with respect to divinylbenzene monomer.

13. The preparation method according to claim 1, characterized in that, The propylene gas flow rate in step 1) is controlled by the polymerization reaction pressure, which is 0.1–4 MPa. The propylene gas flow rate in step 2) is controlled by the polymerization reaction pressure, which is 0.1–2 MPa.

14. The preparation method according to claim 13, characterized in that, The propylene gas flow rate in step 1) is controlled by the polymerization reaction pressure, which is 1-2 MPa.

15. The preparation method according to claim 13, characterized in that, The propylene gas flow rate in step 2) is controlled by the polymerization reaction pressure, which is 1-2 MPa.

16. The preparation method according to claim 1, characterized in that, In step 1), the polymerization reaction is carried out at a temperature of 30–80°C for a time of 0.1–0.5 h. In step 2), the polymerization reaction is carried out at a temperature of 30–80°C for a time of 0.1–0.5 h.

17. The preparation method according to claim 16, characterized in that, In step 1), the polymerization reaction is carried out at a temperature of 50–60°C for a time of 0.2–0.3 h.

18. The preparation method according to claim 16, characterized in that, In step 2), the polymerization reaction is carried out at a temperature of 50–60°C for a time of 0.2–0.3 h.

19. The preparation method according to claim 1, characterized in that, In step 3), the mass ratio of polypropylene-A to polypropylene-B is 0.5 to 1.5:1; The total mass ratio of polypropylene-A and polypropylene-B to toluene is 10-30:100; In step 3), the total mass ratio of tris(4-methoxyphenyl)phosphine to polypropylene-A and polypropylene-B is 0.05 to 0.1:1; The mass ratio of tris(4-methoxybenzyl)phosphine to ferric chloride is 1:2-3.

20. The preparation method according to claim 19, characterized in that, The mass ratio of polypropylene-A to polypropylene-B is 0.9 to 1.1:

1.

21. The preparation method according to claim 19, characterized in that, The total mass ratio of polypropylene-A and polypropylene-B to toluene is 20-25:

100.

22. The preparation method according to claim 19, characterized in that, The total mass ratio of the tris(4-methoxybenzyl)phosphine to polypropylene-A and polypropylene-B is 0.07 to 0.08:

1.

23. The preparation method according to claim 19, characterized in that, The mass ratio of tris(4-methoxybenzyl)phosphine to ferric chloride is 1:2.5-2.

6.

24. The preparation method according to claim 1, characterized in that, In step 3), the reaction is carried out at a temperature of 80–150°C for 20–40 hours. After the reactions described in steps 1) and 2) are completed, the polymer solution is transferred to acetone and inactivated by stirring at room temperature for 2 to 4 hours.

25. The preparation method according to claim 23, characterized in that, In step 3), the reaction is carried out at a temperature of 100–120°C for 24–30 hours.

26. A self-fluorescent high melt strength modified polypropylene prepared by the preparation method according to any one of claims 1-25.

27. The application of self-fluorescent high melt strength modified polypropylene prepared by the preparation method according to any one of claims 1-25 in the fields of household appliances, decoration, toys, and takeaway insulated boxes.

28. The application of the self-fluorescent high melt strength modified polypropylene prepared by the preparation method according to any one of claims 1-25 in the manufacture of lightweight and heat-insulating polypropylene products.

29. The application according to claim 28, characterized in that, The lightweight, heat-insulating polypropylene product is foamed polypropylene.

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