Propylene-based olefin block copolymer having flame-retardant function, preparation method therefor, and composition comprising recycled plastic

Abstract

Disclosed in the present invention are a propylene-based olefin block copolymer having a flame-retardant function, a preparation method therefor, and a composition comprising recycled plastic. The propylene-based olefin block copolymer having a flame-retardant function comprises a first block and a second block. The first block comprises a polypropylene block, and the second block comprises a copolymer block of propylene, ethylene, and a monomer containing a phosphonic acid group and a carbon-carbon double bond. The composition comprising recycled plastics comprises: recycled polyethylene plastics, recycled polypropylene plastics, and the propylene-based olefin block copolymer having a flame-retardant function. The propylene-based olefin block copolymer having a flame-retardant function of the present invention can be used as a compatibilizer in recycled ethylene-propylene plastics, enabling the recycled ethylene-propylene plastics to have both excellent mechanical properties and flame-retardant performance.

Description

Flame-retardant propylene-based olefin block copolymers, their preparation methods, and compositions containing recycled plastics Technical Field

[0001] This invention relates to the field of flame retardant materials technology, and more specifically, to propylene-based olefin block copolymers with flame retardant function, methods for preparing the same, and compositions containing recycled plastics. Background Technology

[0002] Polyethylene and polypropylene are the most widely used synthetic plastics in society today due to their simple structure, excellent performance, and low cost, accounting for nearly 60% of global plastic production. However, both of these plastics are difficult-to-degrade polymers, and their disposal causes continuous environmental pollution. Therefore, in recent years, the effective recycling and high-value reuse of polyethylene and polypropylene have received widespread attention.

[0003] It is worth noting that polyethylene and polypropylene are often used in the same way, such as using polyethylene for the bottle body and polypropylene for the bottle cap. It is difficult to achieve thorough sorting during recycling. However, the two are thermodynamically incompatible, and recycling and blending will cause severe phase separation, resulting in poor mechanical properties of the recycled plastic, making it difficult to reuse it at high value.

[0004] Existing technologies utilize olefin block copolymers as compatibilizers in the recycling of ethylene-propylene plastics (EPDM), reducing interfacial tension and increasing compatibility, thereby enhancing the impact strength and other mechanical properties of the recycled plastics. However, since polyethylene, polypropylene, and olefin block copolymers are composed of only carbon and hydrogen, they have very low oxygen indices, making them highly flammable. Combustion releases significant amounts of heat, generates molten droplets, accelerates flame propagation, and can even lead to explosions. This severely limits the application prospects of olefin block copolymers as compatibilizers in recycled EPDM.

[0005] In the preparation of flame-retardant materials for polyethylene and polypropylene, flame retardants are typically added. Flame retardants are generally classified as reactive or additive, with additive flame retardants being the most commonly used. Phosphorus-based flame retardants are a very important type of additive flame retardant. However, as reported in CN104693604A, the introduction of phosphorus-based flame retardant particles into the matrix disrupts interfacial bonding, significantly reducing mechanical properties. Therefore, as reported in CN109679203A and CN117866336A, reinforcements are usually added when using this type of additive flame retardant to improve the mechanical properties of the flame-retardant material. Furthermore, while direct use of red phosphorus as a flame retardant yields high flame retardant efficiency, red phosphorus is hygroscopic, and coating technology is typically used to prevent its degradation. However, the use of coating technology increases production costs and complicates the process.

[0006] Therefore, developing compatibilizers for recycled ethylene propylene plastics, enabling them to possess both excellent mechanical and flame-retardant properties, has become one of the urgent problems to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a flame-retardant propylene-based olefin block copolymer, its preparation method, and a composition comprising recycled plastics. The flame-retardant propylene-based olefin block copolymer of the present invention can be used as a compatibilizer in ethylene-propylene recycled plastics, enabling the ethylene-propylene recycled plastics to simultaneously possess excellent mechanical properties and flame-retardant properties.

[0008] To achieve the above objectives, a first aspect of the present invention provides a propylene-based olefin block copolymer with flame-retardant function, comprising: a first block and a second block; the first block comprising a polypropylene block, and the second block comprising a copolymer block of propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds; based on the total molecular weight average of the flame-retardant propylene-based olefin block copolymer being 100%, the content of the first block is 20-30%, and the content of the second block is 70-80%.

[0009] According to a specific embodiment of the present invention, preferably, the number-average molecular weight ratio of the first block and the second block is 1:(3-4).

[0010] According to a specific embodiment of the present invention, preferably, the first block contains an isotactic polypropylene block, wherein the isotacticity of the isotactic polypropylene block is 85-95%.

[0011] According to a specific embodiment of the present invention, preferably, the number-average molecular weight of the first block is 15 to 30 kDa.

[0012] According to a specific embodiment of the present invention, preferably, the molar ratio of the structural unit from propylene, the structural unit from ethylene, and the structural unit from the monomer containing phosphonic acid group and carbon-carbon double bond in the second block is (4-5):(1-2):(0.6-3.5).

[0013] According to a specific embodiment of the present invention, preferably, the monomer containing a phosphonic acid group and a carbon-carbon double bond includes one or more of vinylphosphonic acid and vinylphosphonate compounds. More preferably, the monomer containing a phosphonic acid group and a carbon-carbon double bond includes one or more of vinylphosphonic acid, methyl vinylphosphonate, dimethyl vinylphosphonate, ethyl vinylphosphonate, and diethyl vinylphosphonate.

[0014] According to a specific embodiment of the present invention, preferably, the number-average molecular weight of the second block is 60-90 kDa.

[0015] According to a specific embodiment of the present invention, preferably, the flame-retardant propylene-based olefin block copolymer has a number-average molecular weight of 75-120 kDa and a molecular weight distribution of 1.9-3.0.

[0016] According to a specific embodiment of the present invention, preferably, the limiting oxygen index of the flame-retardant propylene-olefin block copolymer is 30-40%, and the flame retardant rating of the flame-retardant propylene-olefin block copolymer is UL94 V-0.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned flame-retardant propylene-based olefin block copolymer, comprising the following steps:

[0018] (1) Under anhydrous and oxygen-free conditions, propylene is subjected to a first polymerization reaction in an organic solvent and in the presence of a main catalyst, a co-catalyst and a chain transfer agent to obtain a mixed system after the first polymerization reaction.

[0019] (2) Under anhydrous and oxygen-free conditions, ethylene, propylene and monomers containing phosphonic acid groups and carbon-carbon double bonds are added to the mixture after the first polymerization reaction to carry out a second polymerization reaction, and the mixture after the second polymerization reaction is obtained.

[0020] (3) The mixture after the second polymerization reaction is subjected to at least precipitation and solid-liquid separation to obtain the flame-retardant propylene-based olefin block copolymer;

[0021] The main catalyst comprises a complex of a ligand containing a pyridinyl group and an imine with a group IVB transition metal, the co-catalyst comprises an organoboron compound, and the chain transfer agent comprises an alkylaluminum compound and / or an alkylzinc compound.

[0022] According to a specific embodiment of the present invention, preferably, the temperature of the first polymerization reaction is 25-70°C and the pressure is 0.1-0.5 MPa.

[0023] According to a specific embodiment of the present invention, preferably, the main catalyst comprises a complex having a structure as shown in Formula I and / or Formula II:

[0024] M is selected from one of the transition metals in group IVB;

[0025] R1 and R2 are each independently selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted polycyclic aryl.

[0026] According to a specific embodiment of the present invention, preferably, the molar ratio of the main catalyst to the chain transfer agent is 1:(150-200).

[0027] According to a specific embodiment of the present invention, preferably, the temperature of the second polymerization reaction is 25-70°C and the pressure is 0.1-0.5 MPa.

[0028] A third aspect of the present invention provides a composition comprising recycled plastic, comprising: recycled polyethylene plastic, recycled polypropylene plastic and a compatibilizer, wherein the compatibilizer comprises the above-mentioned propylene-based olefin block copolymer with flame retardant function; wherein the mass ratio of the total amount of the recycled polyethylene plastic and the recycled polypropylene plastic to the mass ratio of the compatibilizer is 8:(1-2).

[0029] The present invention has at least the following beneficial effects:

[0030] The flame-retardant propylene-olefin block copolymer of the present invention comprises a first block and a second block; the first block contains a polypropylene block, which is a hard segment; the second block contains a copolymer block of propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds, which is a soft segment. This propylene-olefin block copolymer simultaneously contains polypropylene segments and copolymer segments containing ethylene structural units. When this propylene-olefin block copolymer is used as a compatibilizer in recycled ethylene-propylene plastics, the polyethylene and polypropylene in the recycled plastics combine with similar segments in the propylene-olefin block copolymer, increasing the compatibility of polyethylene and polypropylene and giving the recycled plastics excellent mechanical properties. Furthermore, compared to random copolymers or graft copolymers formed from propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds, the block copolymer of the present invention has the advantage of highly tunable structure. Compatibility can be improved by adjusting the content or ratio of soft and hard segments according to the ratio of polyethylene and polypropylene in the recycled plastics, significantly increasing the versatility of the block copolymer of the present invention as a compatibilizer. Furthermore, because the second block of this propylene-olefin block copolymer contains structural units from monomers containing phosphonic acid groups and carbon-carbon double bonds, the propylene-olefin block copolymer possesses flame-retardant properties. As a compatibilizer in ethylene-propylene recycled plastics, it imparts excellent flame-retardant performance to the recycled plastics, broadening their application scenarios. In addition, this invention does not employ the prior art method of introducing flame-retardant materials into recycled plastics through blending. Instead, it introduces monomers containing phosphonic acid groups and carbon-carbon double bonds through copolymerization, obtaining a propylene-olefin block copolymer as a compatibilizer. This avoids the adverse effects of introducing flame-retardant materials through blending on the mechanical properties of recycled plastics, resulting in recycled plastics with both excellent flame-retardant and mechanical properties without increasing the complexity of the preparation process for flame-retardant recycled plastics. Attached Figure Description

[0031] Figure 1 is a scanning electron microscope image of the recycled plastic from Example 1.

[0032] Figure 2 is a scanning electron microscope image of the recycled plastic in Example 2.

[0033] Figure 3 is a scanning electron microscope image of the recycled plastic in Example 3.

[0034] Figure 4 is a scanning electron microscope image of the recycled plastic from Example 4.

[0035] Figure 5 is a scanning electron microscope image of the recycled plastic in Example 6.

[0036] Figure 6 is a scanning electron microscope image of the recycled plastic from Comparative Example 1.

[0037] Figure 7 is a scanning electron microscope image of the recycled plastic from Comparative Example 2. Detailed Implementation

[0038] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0039] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0040] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0042] According to a specific embodiment of the first aspect of the present invention, the present invention provides a propylene-based olefin block copolymer with flame retardant function, comprising: a first block and a second block; the first block comprises a polypropylene block, and the second block comprises a copolymer block of propylene, ethylene and monomers containing phosphonic acid groups and carbon-carbon double bonds; based on the total molecular weight average of the propylene-based olefin block copolymer with flame retardant function being 100%, the content of the first block is 20-30%, for example 20%, 25% or 30%, etc., and the content of the second block is 70-80%, for example 70%, 75% or 80%, etc.

[0043] In some embodiments, the number-average molecular weight ratio of the first block to the second block is 1:(3-4).

[0044] In some embodiments, the first block contains an isotactic polypropylene block, wherein the isotacticity of the isotactic polypropylene block is 85-95%, such as 85%, 86%, 88%, 90%, 92%, 94%, or 95%, preferably 90-95%.

[0045] In some embodiments, the number-average molecular weight of the first block is 15-30 kDa, preferably 20-25 kDa; the molecular weight distribution of the first block is 1.9-2.1.

[0046] In some embodiments, the molar ratio of the structural unit from propylene, the structural unit from ethylene, and the structural unit from the monomer containing phosphonic acid group and carbon-carbon double bond in the second block is (4-5):(1-2):(0.6-3.5), preferably 5:1:(1-2).

[0047] In some embodiments, the monomer containing a phosphonic acid group and a carbon-carbon double bond includes one or more of vinylphosphonic acid and vinylphosphonate compounds. Specifically, the monomer containing a phosphonic acid group and a carbon-carbon double bond includes one or more of vinylphosphonic acid, methyl vinylphosphonate, dimethyl vinylphosphonate, ethyl vinylphosphonate, and diethyl vinylphosphonate.

[0048] In some embodiments, the number-average molecular weight of the second block is 60-90 kDa, preferably 70-85 kDa; the molecular weight distribution of the second block is 1.9-3.0.

[0049] In some embodiments, the flame-retardant propylene-olefin block copolymer has a number-average molecular weight of 75–120 kDa, preferably 90–110 kDa; and the molecular weight distribution of the flame-retardant propylene-olefin block copolymer is 1.9–3.0.

[0050] In some embodiments, the limiting oxygen index of the flame-retardant propylene-olefin block copolymer is 30-40%, and the flame retardant rating of the flame-retardant propylene-olefin block copolymer is UL94 V-0.

[0051] According to a specific embodiment of the second aspect of the present invention, the present invention provides a method for preparing the above-mentioned flame-retardant propylene-based olefin block copolymer, which includes the following steps:

[0052] (1) Under anhydrous and oxygen-free conditions, propylene is subjected to a first polymerization reaction in an organic solvent and in the presence of a main catalyst, a co-catalyst and a chain transfer agent to obtain a mixed system after the first polymerization reaction.

[0053] (2) Under anhydrous and oxygen-free conditions, ethylene, propylene and monomers containing phosphonic acid groups and carbon-carbon double bonds are added to the mixture after the first polymerization reaction to carry out a second polymerization reaction, and the mixture after the second polymerization reaction is obtained.

[0054] (3) The mixture after the second polymerization reaction is subjected to at least precipitation and solid-liquid separation to obtain the flame-retardant propylene-based olefin block copolymer;

[0055] The main catalyst comprises a complex of a ligand containing a pyridinyl group and an imine with a group IVB transition metal, the co-catalyst comprises an organoboron compound, and the chain transfer agent comprises an alkylaluminum compound and / or an alkylzinc compound.

[0056] In some embodiments, the temperature of the first polymerization reaction is 25–70°C and the pressure is 0.1–0.5 MPa.

[0057] In some embodiments, the main catalyst comprises a complex having a structure as shown in Formula I and / or Formula II:

[0058] M is selected from one of the transition metals in group IVB, specifically, M is selected from one of titanium (Ti), zirconium (Zr), and hafnium (Hf);

[0059] Me stands for methyl;

[0060] R1 and R2 are each independently selected from one of substituted or unsubstituted alkyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, and substituted or unsubstituted polycyclic aryl groups. Specifically, R1 and R2 are each independently selected from C1-C10 substituted or unsubstituted alkyl groups, C3-C10 substituted or unsubstituted cycloalkyl groups, C6-C20 substituted or unsubstituted aryl groups, and C10 or more substituted or unsubstituted polycyclic aryl groups. Polycyclic aryl groups include non-fused-ring polycyclic aryl groups (e.g., biphenyl and bipolyphenyl) and fused-ring aryl groups (e.g., naphthyl, anthracene, phenanthryl, indene, fluorenyl, acenaphthene, pyrene, and myristyl). Preferably, R1 and R2 are each independently selected from one of phenyl and isopropyl-substituted phenyl groups (e.g., 2,6-diisopropylphenyl).

[0061] The main catalyst used in this invention can be prepared by methods disclosed in the prior art, such as the preparation method disclosed in section 2.2.4 of the paper reported by Yin Xiao (Yin Xiao. Preparation of stereoblock polypropylene by chain shuttle polymerization [D]. Tianjin University, 2020.).

[0062] In some embodiments, the co-catalyst comprises one or more of triphenylmethyltetra(pentafluorophenyl)borate, N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate, and tetra-n-butyltetraphenylammonium borate.

[0063] In some embodiments, the chain transfer agent includes one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylzinc, methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

[0064] In some embodiments, the molar ratio of the main catalyst to the chain transfer agent is 1:(150-200), for example 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0065] In some embodiments, the molar ratio of the main catalyst to the co-catalyst is 1:(1-5). Generally, the amount of co-catalyst can be slightly higher than that of the main catalyst, and the molar ratio of the main catalyst to the co-catalyst is, for example, 1:(1.5-2).

[0066] In some embodiments, the organic solvent is a conventional inert organic solvent in the art, such as one or more of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, toluene, and xylene. The amount of the organic solvent can be conventionally adjusted by those skilled in the art.

[0067] In some embodiments, the temperature of the second polymerization reaction is 25–70°C and the pressure is 0.1–0.5 MPa.

[0068] In some embodiments, in steps (1) and (2), propylene and ethylene are introduced into the reaction system in gaseous form, and the monomer containing phosphonic acid groups and carbon-carbon double bonds is added to the reaction system dropwise. The present invention does not impose any special restrictions on the molar ratio of propylene and ethylene introduced in step (2) and the monomer containing phosphonic acid groups and carbon-carbon double bonds added dropwise; these ratios can be adjusted by those skilled in the art based on the molar ratio of the structural units from the three monomers in the second block described above.

[0069] In some embodiments, in step (3), the precipitated block copolymer can be produced using solvents conventional in the art, such as alcohols. Solid-liquid separation can be performed using conventional methods such as filtration. Furthermore, washing and drying can be performed to obtain the flame-retardant propylene-olefin block copolymer.

[0070] According to a specific embodiment of a third aspect of the present invention, the present invention provides a composition comprising recycled plastic, comprising: recycled polyethylene plastic, recycled polypropylene plastic, and a compatibilizer, wherein the compatibilizer comprises the aforementioned propylene-based olefin block copolymer with flame-retardant function; wherein the mass ratio of the total amount of the recycled polyethylene plastic and the recycled polypropylene plastic to the mass ratio of the compatibilizer is 8:(1-2). The mass ratio of the recycled polyethylene plastic and the recycled polypropylene plastic can be adjusted according to actual needs, for example, it can be 1:1.

[0071] The flame-retardant propylene-based olefin block copolymer of the present invention comprises a first block and a second block; the first block contains a polypropylene block (preferably an isotactic polypropylene block), which is a hard segment; the second block contains a copolymer block of propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds, which is a random copolymer block, and is a soft segment. By controlling the content and ratio of the first and second blocks, and the ratio of structural units from propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds in the second block, the present invention enables the block copolymer to, when used as a compatibilizer in ethylene-propylene recycled plastics, to impart both excellent mechanical properties and significant flame-retardant effects to the recycled plastics, avoiding the high flammability of blends of polyethylene and polypropylene recycled plastics in the prior art. Furthermore, the preparation process of the block copolymer of the present invention is simple and easy to implement, and the flame-retardant propylene-based olefin block copolymer of the present invention has high purity. Furthermore, the composition containing recycled plastic of the present invention, due to the use of this block copolymer, can reduce or even avoid the addition of other flame-retardant materials during blending. This avoids problems such as uneven blending and reduced mechanical properties caused by introducing flame-retardant materials through blending, and does not increase the complexity of the preparation process of the flame-retardant recycled plastic. Therefore, ethylene propylene recycled plastic containing the block copolymer of the present invention has both excellent mechanical properties and flame-retardant properties, breaking through its long-term severely limited application scenarios.

[0072] The technical solutions of the present invention are specifically illustrated below through embodiments, but the present invention is not limited to these embodiments. Of course, various modifications can be made within the scope of the key points of the present invention.

[0073] Test method:

[0074] (1) Purity of propylene-based olefin block copolymers with flame-retardant properties:

[0075] The tests were performed using cross-fractional chromatography (CFC), which combines temperature-eluting fractionation (TREF) and gel permeation chromatography (GPC). A polymer sample (10 mg) (i.e., the product in the examples below) was placed in a disposable vial and automatically injected with 1,2,4-trichlorobenzene containing 0.1 ppm of 2,6-di-tert-butyl-4-methylphenol (BHT) at 150°C. After 1.5 hours, the polymer solution was eluted via a TREF column, crystallizing from 140°C to 25°C at a cooling rate of 0.5°C / min, followed by elution of the fraction at progressively increasing temperatures. The 2D (molecular weight-temperature) and 3D (molecular weight-temperature-percentage) chromatograms of CFC clearly show two components distributed in a high-temperature region (80-130°C) and a low-temperature region (0-40°C). The low-temperature component represents impurities, and the high-temperature component represents the block copolymer content (purity) of the product.

[0076] (2) The molar ratio of structural units from propylene, structural units from ethylene, and structural units from monomers containing phosphonic acid groups and carbon-carbon double bonds in the second block:

[0077] High temperature was measured using a Bruker AVANCE III™ HD 400MHz nuclear magnetic resonance spectrometer. 13 C{ 1 ¹H NMR spectrum. This test was performed at 120 °C with 1,1,2,2-tetrachloroethane-d2 (1,1,2,2-TCE-d2) as the deuterated reagent. The test sample was the high-temperature fraction obtained by elution using a cross-fractional chromatography (CFC) system as described in test (1) above.

[0078] A peak at approximately 21.94 ppm can be considered a pentatonic isotactic polypropylene signal (PPPPP), a peak at approximately 46.6 ppm can be considered a tetratonic isotactic polypropylene signal (PPPPP), and a peak at approximately 28.97 ppm can be considered a tritonic isotactic polypropylene signal (PPP). It is assumed that these three signals belong to the first block, and the remaining signals belong to the second block. The sum of the peak area integrals of the remaining signals is calculated and denoted as S. A peak at approximately 11.98 ppm can be considered a signal from a carbon atom linked to vinylphosphonic acid or vinylphosphonate. The area integral of this peak is calculated and denoted as S1. The molar ratio of the structural units from ethylene and propylene in the second block was calculated according to the method described on pages 237-256 of J. Polym. Sci., Part C: Polym. Rev. 1989, 29, 201-317. For example, peaks at 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm can be considered as signals from the random copolymerization of ethylene and propylene, such as EPEPE+EPEPE, EPEE+EEPE, PPEE+EEPP, PEEP, PEEE+EEEP, and EEE. The sum of the peak area integrals corresponding to the structural units from ethylene and propylene is S-S1. Based on the molar ratio and S-S1, the peak area integral of the structural unit from ethylene is calculated as S2, and the peak area integral of the structural unit from propylene is calculated as S3. S3:S2:S1 is the molar ratio of structural units from propylene, structural units from ethylene, and structural units from monomers containing phosphonic acid groups and carbon-carbon double bonds.

[0079] (3) Number-average molecular weight and molecular weight distribution of the first block, the second block, and the flame-retardant propylene olefin block copolymers:

[0080] Number-average molecular weight and molecular weight distribution (PDI) were determined by high-temperature gel permeation chromatography (high-temperature GPC). The chromatographic column was a PLgel Olexis 300 mm × 7.5 mm × 13 μm column (3 columns in series). The mobile phase was 1,2,4-trichlorobenzene (1,2,4-TCB) containing 2,6-di-tert-butyl-4-methylphenol (BHT, 200 mg / L) as a stabilizer, with a flow rate of 1.0 mL / min. The test temperature was 150 °C. The test sample was a polymer solution with a mass concentration of 50 mg / mL prepared using the mobile phase as a solvent, with an injection volume of 10 μL. The polymer tested was the high-temperature fraction obtained by elution using a cross-fractional chromatography (CFC) system as described in test (1) above. The obtained molecular weight was calibrated against the polystyrene standard Easi-Cal PS-1 (PL Corporation).

[0081] The number-average molecular weight of the first block was determined using the method described above for the product obtained from the first polymerization reaction. The number-average molecular weight of the second block was obtained by subtracting the number-average molecular weight of the first block from the number-average molecular weight of the final block copolymer. The product obtained from the first polymerization reaction was prepared by precipitation, solid-liquid separation, washing, and drying of the mixed system after the first polymerization reaction.

[0082] (4) Content of the first and second blocks:

[0083] The contents of the first block and the second block are the percentages of the number-average molecular weight of the first block and the number-average molecular weight of the second block to the number-average molecular weight of the block copolymer, respectively.

[0084] (5) Isotacticity of isotactic polypropylene blocks:

[0085] isostatus 13 C10 NMR spectroscopy was used for determination. A Bruker 600MHz high-temperature NMR spectrometer was employed. 50 mg of sample was added to an NMR tube, followed by 0.6 mL of deuterated o-dichlorobenzene. The mixture was dissolved using a hot air gun, thoroughly mixed, and then tested at 120 °C. The sample was the product obtained from the first polymerization reaction.

[0086] (6) Limiting oxygen index:

[0087] The limiting oxygen index (LOI) should be tested according to the method described in GB 2406.2-2009. The limiting oxygen index is the lowest oxygen concentration required for a sample to maintain stable combustion in a mixture of oxygen and nitrogen under specified test conditions. Specifically, the test procedure includes: vertically fixing the sample in a glass combustion chamber, with its base connected to a device that generates a nitrogen-oxygen mixture; igniting the top of the sample, where the oxygen concentration in the mixture will continuously decrease until the flame extinguishes; the oxygen concentration at which the flame just extinguishes is the limiting oxygen index. Five samples should be tested for each material, and the average value should be taken. Each sample should be flat, smooth, and free of air bubbles. The sample dimensions are: length 120 mm, width 10.0 mm, and thickness 4 mm.

[0088] (7) Flame retardant rating:

[0089] The flame retardancy rating is tested according to the method described in the vertical burning test in UL94-2018. Specifically, the test steps include: test sample preparation, sample pretreatment, flame rating assessment, and test apparatus. This test classifies materials into V-0, V-1, V-2, and NR levels, with V-0 representing the highest flame retardancy rating and NR representing no flame retardancy rating.

[0090] (8) Tensile strength and elongation at break:

[0091] Tensile strength and elongation at break were tested using an Instron 3367 universal testing machine. The test was performed according to the method described in ASTM D1708-13. Dumbbell-shaped specimens with a width of 5 mm and a thickness of 0.5 mm were used. Each specimen was subjected to at least five repeated tensile tests, and the average value was taken. The tensile speed was 10 mm / min.

[0092] Example 1

[0093] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0094] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 0.6 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0095] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0096] The structure of the pyridineimine hafnium is shown below:

[0097] The pyridineimide hafnium can be prepared using methods disclosed in the prior art, such as the preparation method disclosed in section 2.2.4 of the paper reported by Yin Xiao (Yin Xiao. Preparation of stereoblock polypropylene by chain shuttle polymerization [D]. Tianjin University, 2020.).

[0098] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; the total mass of the prepared product is 12.2 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 24.1%, and the content of the second block is 75.9%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid monomers in the second block is 5:1.8:0.6. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 69.3 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 91.3 kDa, and the molecular weight distribution is 2.65.

[0099] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment had a mass content (purity) of 91.4%. Nuclear magnetic resonance spectroscopy, as described in test method (2) above, showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0100] The flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 32% and a flame retardancy rating of UL94 V-0. It should be noted that the limiting oxygen index and flame retardancy rating tested here are for the product obtained in the examples (unpurified), and the same applies to the following examples and comparative examples.

[0101] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. The mixture was stirred for 7 minutes at 200°C and 100 rpm. The resulting copolymer was extruded and cooled in air to obtain recycled ethylene-propylene plastic with a flame-retardant compatibilizer. It should be noted that the flame-retardant propylene-olefin block copolymer added here is the product obtained in the examples (unpurified), and the same applies to the following examples and comparative examples.

[0102] The scanning electron microscope image of the recycled plastic is shown in Figure 1.

[0103] Example 2

[0104] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0105] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 0.7 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0106] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0107] The structure of the pyridineimine hafnium is shown below:

[0108] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.5%; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; the total mass of the prepared product is 12.4 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 23.7%, and the content of the second block is 76.3%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid in the second block is 5:1.5:0.88. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 70.8 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 92.8 kDa, and the molecular weight distribution is 2.8.

[0109] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 90.2% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0110] This flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 33% and a flame retardant rating of UL94 V-0.

[0111] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0112] The scanning electron microscope image of the recycled plastic is shown in Figure 2.

[0113] Example 3

[0114] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0115] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 0.8 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0116] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0117] The structure of the pyridineimine hafnium is shown below:

[0118] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; the total mass of the prepared product is 12.8 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 23.0%, and the content of the second block is 77.0%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid in the second block is 5:1:1.06. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 73.7 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 95.7 kDa, and the molecular weight distribution is 2.74.

[0119] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 88.6% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0120] The flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 34.5% and a flame retardant rating of UL94 V-0.

[0121] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0122] The scanning electron microscope image of the recycled plastic is shown in Figure 3.

[0123] Example 4

[0124] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0125] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 1.0 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0126] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0127] The structure of the pyridineimine hafnium is shown below:

[0128] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.5%; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; the total mass of the prepared product is 13.6 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 21.6%, and the content of the second block is 78.4%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid in the second block is 5:1:1.98. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 79.9 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 101.9 kDa, and the molecular weight distribution is 2.91.

[0129] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 85.7% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0130] This flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 37% and a flame retardant rating of UL94 V-0.

[0131] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0132] The scanning electron microscope image of the recycled plastic is shown in Figure 4.

[0133] Example 5

[0134] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 2.0 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0135] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 1.0 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0136] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0137] The structure of the pyridineimine hafnium is shown below:

[0138] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; the total mass of the prepared product is 13.8 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 21.7%, and the content of the second block is 78.3%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid in the second block is 5:1:1.86. The number-average molecular weight of the first block is 17.3 kDa. The number-average molecular weight of the second block is 62.6 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 79.9 kDa, and the molecular weight distribution is 2.5.

[0139] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 86.0% by mass. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0140] The flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 36.5% and a flame retardant rating of UL94 V-0.

[0141] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0142] Example 6

[0143] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0144] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and vinylphosphonic acid was added dropwise at a rate of 1.2 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0145] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0146] The structure of the pyridineimine hafnium is shown below:

[0147] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the total mass of the prepared product is 14.4 g; the second block contains random copolymer blocks of propylene, ethylene, and vinylphosphonic acid; based on a total number-average molecular weight of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 20.4%, and the content of the second block is 79.6%. The molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid in the second block is 4:1:3.12. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 85.8 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 107.8 kDa, and the molecular weight distribution is 2.82.

[0148] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 85.0% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0149] This flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 39% and a flame retardant rating of UL94 V-0.

[0150] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0151] The scanning electron microscope image of the recycled plastic is shown in Figure 5.

[0152] Example 7

[0153] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0154] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and dimethyl vinylphosphonate was added dropwise at a rate of 1.26 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of dimethyl vinylphosphonate was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0155] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0156] The structure of the pyridineimine hafnium is shown below:

[0157] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the second block contains random copolymer blocks of propylene, ethylene, and dimethyl vinylphosphonate; the total mass of the prepared product is 13.1 g; based on the total number average molecular weight of the flame-retardant propylene-based olefin block copolymer being 100%, the content of the first block is 22.6%, and the content of the second block is 77.4%. The molar ratio of structural units from propylene, ethylene, and dimethyl vinylphosphonate in the second block is 5:1:1.76. The number average molecular weight of the first block is 22 kDa. The number average molecular weight of the second block is 75.2 kDa. The number average molecular weight of the flame-retardant propylene-based olefin block copolymer is 97.2 kDa, and the molecular weight distribution is 3.02.

[0158] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 83.3% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0159] The flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 35.5% and a flame retardant rating of UL94 V-0.

[0160] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0161] Example 8

[0162] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0163] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture obtained after the first polymerization reaction in step (1). The pressure of the reactor was maintained at 0.2 MPa, and diethyl vinylphosphonate was added dropwise at a rate of 1.55 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 10 minutes of reaction, the addition of diethyl vinylphosphonate was stopped, and the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture after the second polymerization reaction.

[0164] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0165] The structure of the pyridineimine hafnium is shown below:

[0166] The product of this embodiment contains a flame-retardant propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.2%; the second block contains random copolymer blocks of propylene, ethylene, and diethyl vinylphosphonate; the total mass of the prepared product is 13.4 g; based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 22.6%, and the content of the second block is 77.4%. The molar ratio of structural units from propylene, ethylene, and diethyl vinylphosphonate in the second block is 5:1:1.58. The number-average molecular weight of the first block is 22 kDa. The number-average molecular weight of the second block is 73.8 kDa. The number-average molecular weight of the flame-retardant propylene-based olefin block copolymer is 95.8 kDa, and the molecular weight distribution is 2.85.

[0167] The cross-fractional chromatography (CFC) method described in test method (1) above showed that the flame-retardant propylene-based olefin block copolymer of this embodiment contained 85.1% by mass in the product. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above showed peaks at 21.94 ppm, 46.6 ppm, 28.97 ppm, 11.98 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the flame-retardant propylene-based olefin block copolymer of this embodiment contains the aforementioned first and second blocks.

[0168] The flame-retardant propylene-based olefin block copolymer has a limiting oxygen index of 34.5% and a flame retardant rating of UL94 V-0.

[0169] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the flame-retardant propylene-based olefin block copolymer of this embodiment were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0170] Comparative Example 1

[0171] This comparative example is basically the same as Example 1, except that vinylphosphonic acid was not added.

[0172] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimine hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Propylene gas was introduced into the reactor, and the polymerization reaction was carried out at 50 °C and 0.2 MPa. After 5 minutes of reaction, the propylene gas was rapidly released to obtain the mixed system after the first polymerization reaction.

[0173] (2) Under anhydrous and oxygen-free conditions, ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the mixture system after the first polymerization reaction obtained in step (1), and the pressure of the reactor was maintained at 0.2 MPa. The polymerization reaction was carried out at 50°C and 0.2 MPa. After the reaction was carried out for 10 minutes, the introduction of ethylene gas and propylene gas was stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixture system after the second polymerization reaction.

[0174] (3) After transferring the mixture obtained from the second polymerization reaction in step (2) out of the reactor, add ethanol to precipitate it, and then filter, wash and dry the precipitate to obtain the product;

[0175] The structure of the pyridineimine hafnium is the same as that in Example 1.

[0176] The product of this comparative example contains a propylene-based olefin block copolymer, which comprises: a first block and a second block; the first block contains isotactic polypropylene blocks with an isotacticity of 94.8%; the second block contains copolymer blocks of propylene and ethylene; the total mass of the prepared product is 11.9 g; based on the total number average molecular weight of the propylene-based olefin block copolymer being 100%, the content of the first block is 24.7%, and the content of the second block is 75.3%. The molar ratio of propylene structural units to ethylene structural units in the second block is 5:2. The number average molecular weight of the first block is 22 kDa. The number average molecular weight of the second block is 67 kDa. The number average molecular weight of the propylene-based olefin block copolymer is 89 kDa.

[0177] The cross-fractional chromatography (CFC) method described in test method (1) above was used to test the product, and the mass content of the propylene-based olefin block copolymer in this comparative example was found to be 95.1%. Nuclear magnetic resonance spectroscopy (NMR) as described in test method (2) above was used to test the product, and peaks were observed at 21.94 ppm, 46.6 ppm, 28.97 ppm, 37.94 ppm, 37.58 ppm, 37.50 ppm, 30.76 ppm, 30.38 ppm, and 29.98 ppm, confirming that the propylene-based olefin block copolymer in this comparative example contains the aforementioned first and second blocks.

[0178] The limiting oxygen index of this propylene-based olefin block copolymer is 15%, and its flame retardancy rating is UL94 NR.

[0179] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and the propylene-based olefin block copolymer of this comparative example were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic with a compatibilizer.

[0180] The scanning electron microscope image of the recycled plastic is shown in Figure 6.

[0181] Comparative Example 2

[0182] No compatibilizer was added to the recycled plastics in this comparative example.

[0183] High-density polyethylene (Sabic B4660) and isotactic polypropylene (Dow Chemical H314-02Z) were added to an extruder at a mass ratio of 40:40. After mixing for 7 minutes at 200°C and 100 rpm, the mixture was extruded and cooled in air to obtain recycled ethylene propylene plastic.

[0184] The scanning electron microscope image of the recycled plastic is shown in Figure 7.

[0185] Comparative Example 3

[0186] This comparative example uses a random copolymer of propylene, ethylene, and vinylphosphonic acid as a compatibilizer.

[0187] (1) Under anhydrous and oxygen-free conditions, 250 ml of toluene was added to the reactor, followed by 1.5 mmol of triisobutylaluminum, 10 μmol of pyridineimide hafnium and 20 μmol of triphenylmethyltetra(pentafluorophenyl)borate. Ethylene gas and propylene gas with a molar ratio of 1:1 were introduced into the reactor, while vinylphosphonic acid was added dropwise at a rate of 0.67 g / min. The polymerization reaction was carried out at 50 °C and 0.2 MPa. After 15 minutes of reaction, the addition of vinylphosphonic acid was stopped, and the introduction of ethylene gas and propylene gas was also stopped. Subsequently, the pressure of the reactor was reduced to atmospheric pressure to obtain the mixed system after the polymerization reaction.

[0188] (2) After the polymerization reaction mixture obtained in step (1) is transferred out of the reactor, ethanol is added to precipitate it. The precipitate is then filtered, washed and dried to obtain the product.

[0189] The structure of the pyridineimine hafnium is the same as that in Example 1.

[0190] The product of this comparative example contains a random copolymer of propylene, ethylene, and vinylphosphonic acid, wherein the molar ratio of structural units from propylene, ethylene, and vinylphosphonic acid is 5:1:2.05. The number average molecular weight of this random copolymer of propylene, ethylene, and vinylphosphonic acid is 103 kDa.

[0191] The random copolymer of propylene, ethylene and vinylphosphonic acid has a limiting oxygen index of 37% and a flame retardant rating of UL94 V-0.

[0192] High-density polyethylene (Sabic B4660), isotactic polypropylene (Dow Chemical H314-02Z), and a random copolymer of propylene, ethylene, and vinylphosphonic acid in this comparative example were added to an extruder at a mass ratio of 40:40:20. After mixing for 7 minutes at 200°C and 100 rpm, the resulting eutectic was extruded and cooled in air to obtain recycled ethylene propylene plastic with a flame-retardant compatibilizer.

[0193] Comparative Example 4

[0194] This comparative example is essentially the same as Example 1, except that the main catalyst, pyridinium imine hafnium, in Example 1 is replaced with a metallocene catalyst, and the amount used is the same as in Example 1. This metallocene catalyst is dimethylsilyl bis(2-methyl-4-phenylindenidyl)zirconia dichloride, and its structure is shown below:

[0195] The product prepared in this comparative example is different from that in Example 1. Only the first block, namely the polypropylene block, can be prepared, with a mass of 2g and a number-average molecular weight of 15kDa. It is not possible to prepare the flame-retardant propylene-based olefin block copolymer of Example 1.

[0196] Mechanical properties, vertical burning and limiting oxygen index tests were conducted on the recycled plastic samples obtained in Examples 1-8 and Comparative Examples 1-3. The test results are shown in Table 1.

[0197] Table 1

[0198] As can be seen from Table 1, when the flame-retardant propylene-based olefin block copolymers of the various embodiments of the present invention are used as compatibilizers in ethylene-propylene recycled plastics, the recycled plastics simultaneously possess excellent mechanical properties and flame-retardant properties.

[0199] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the present invention are still within the protection scope of the present invention.

Claims

1. A flame-retardant propylene-based olefin block copolymer, comprising: a first block and a second block; the first block comprising a polypropylene block, and the second block comprising a copolymer block of propylene, ethylene, and monomers containing phosphonic acid groups and carbon-carbon double bonds; wherein, based on a total molecular weight average of 100% for the flame-retardant propylene-based olefin block copolymer, the content of the first block is 20-30%, and the content of the second block is 70-80%.

2. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The number-average molecular weight ratio of the first block to the second block is 1:(3-4).

3. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The first block contains isotactic polypropylene blocks, and the isotacticity of the isotactic polypropylene blocks is 85-95%.

4. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The number-average molecular weight of the first block is 15–30 kDa.

5. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The molar ratio of the structural units from propylene, the structural units from ethylene, and the structural units from monomers containing phosphonic acid groups and carbon-carbon double bonds in the second block is (4-5):(1-2):(0.6-3.5).

6. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The monomers containing phosphonic acid groups and carbon-carbon double bonds include one or more of vinylphosphonic acid and vinylphosphonate compounds.

7. The flame-retardant propylene-based olefin block copolymer according to claim 6, wherein, The monomers containing phosphonic acid groups and carbon-carbon double bonds include one or more of vinylphosphonic acid, methyl vinylphosphonate, dimethyl vinylphosphonate, ethyl vinylphosphonate, and diethyl vinylphosphonate.

8. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The number-average molecular weight of the second block is 60–90 kDa.

9. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The flame-retardant propylene-based olefin block copolymer has a number-average molecular weight of 75–120 kDa and a molecular weight distribution of 1.9–3.

0.

10. The propylene-based olefin block copolymer with flame-retardant function according to claim 1, wherein, The limiting oxygen index of the flame-retardant propylene-olefin block copolymer is 30-40%, and the flame retardancy rating of the flame-retardant propylene-olefin block copolymer is UL94 V-0.

11. A method for preparing a flame-retardant propylene-based olefin block copolymer according to any one of claims 1-10, comprising the following steps: (1) Under anhydrous and oxygen-free conditions, propylene is subjected to a first polymerization reaction in an organic solvent and in the presence of a main catalyst, a co-catalyst and a chain transfer agent to obtain a mixed system after the first polymerization reaction. (2) Under anhydrous and oxygen-free conditions, ethylene, propylene and monomers containing phosphonic acid groups and carbon-carbon double bonds are added to the mixture after the first polymerization reaction to carry out a second polymerization reaction, and the mixture after the second polymerization reaction is obtained. (3) The mixture after the second polymerization reaction is subjected to at least precipitation and solid-liquid separation to obtain the flame-retardant propylene-based olefin block copolymer; The main catalyst comprises a complex of a ligand containing a pyridinyl group and an imine with a group IVB transition metal, the co-catalyst comprises an organoboron compound, and the chain transfer agent comprises an alkylaluminum compound and / or an alkylzinc compound.

12. The preparation method according to claim 11, wherein, The temperature of the first polymerization reaction is 25–70°C, and the pressure is 0.1–0.5 MPa.

13. The preparation method according to claim 11, wherein, The main catalyst comprises a complex having a structure as shown in Formula I and / or Formula II: M is selected from one of the transition metals in group IVB; R1 and R2 are each independently selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted polycyclic aryl.

14. The preparation method according to claim 11, wherein, The molar ratio of the main catalyst to the chain transfer agent is 1:(150-200).

15. The preparation method according to claim 11, wherein, The second polymerization reaction is carried out at a temperature of 25–70°C and a pressure of 0.1–0.5 MPa.

16. A composition comprising recycled plastic, comprising: The invention comprises recycled polyethylene plastic, recycled polypropylene plastic, and a compatibilizer, wherein the compatibilizer includes a propylene-based olefin block copolymer with flame-retardant function as described in any one of claims 1-10; wherein the mass ratio of the total amount of the recycled polyethylene plastic and the recycled polypropylene plastic to the mass ratio of the compatibilizer is 8:(1-2).

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