Flexible polypropylene modified material, its preparation method and application

Abstract

The present application belongs to the field of polymers, and relates to a flexible polypropylene modified material and a preparation method and application thereof. The flexible polypropylene modified material comprises a propylene-based continuous phase, and a rubber phase and a graft phase derived from an olefin group-containing functional monomer dispersed in the propylene-based continuous phase; wherein the xylene-soluble content of the flexible polypropylene modified material is 10-55 wt%, based on the total weight of the flexible polypropylene modified material; the content of the structural unit derived from the olefin group-containing functional monomer in the graft state in the flexible polypropylene modified material is 0.4-6 wt%; the flexural modulus of the flexible polypropylene modified material is 200-1000 MPa; and the D50 of the graft phase is less than 300 nm. The flexible polypropylene modified material of the present application can balance mechanical properties and electrical properties at a relatively high working temperature, and is suitable for high-temperature and high-operation-field-strength working conditions.

Description

Technical Field

[0001] This invention belongs to the field of polymers, specifically relating to a flexible polypropylene modified material, a method for preparing the flexible polypropylene modified material, and the application of the flexible polypropylene modified material. Background Technology

[0002] With the sustained and rapid development of my country's economy and the continuous improvement of people's living standards, the demand for electricity is also growing rapidly. Solving the problem of power transmission channels, and delivering large-capacity electrical energy to users, is one of the major issues that urgently needs to be addressed in power development. To address this problem, my country has established the basic development direction of constructing and developing ultra-high voltage and large-capacity AC / DC transmission systems. In the development of extruded plastic insulated cables, the most crucial issue is the development of the cable insulation material. Traditional extruded DC cables generally use cross-linked polyethylene (XLPE) as the cable insulation material.

[0003] The traditional method for disposing of waste XLPE cable insulation is incineration. This method not only wastes energy but also generates greenhouse gases and other environmental problems. Furthermore, the production process of XLPE cables involves cross-linking and degassing, which produce harmful gases and other pollutants, while also wasting significant amounts of energy. Therefore, improving the environmental friendliness and compatibility of power cable insulation materials has become a crucial issue in the development of power cable insulation materials. In recent years, to address this issue and meet the requirements of environmental protection and sustainable development, many institutions and scholars have begun research on novel recyclable non-cross-linked polyolefin cable insulation materials.

[0004] Polypropylene-based materials, as cable insulation, possess inherent advantages such as high operating temperature and high breakdown field strength, along with space charge suppression properties and recyclability, making them a key area of ​​development for non-crosslinked polyolefin insulation materials. Blending polypropylene with polyolefin elastomers and with ethylene-propylene copolymers effectively improves the brittleness of polypropylene while retaining its good thermal and electrical properties. Nanoparticle doping is an effective way to improve the electrical insulation performance of polypropylene materials. However, the tendency of nanoparticles to aggregate, leading to a decrease in insulation performance, limits the widespread application of this method in practical engineering.

[0005] Therefore, it is necessary to find a new type of polypropylene material that is stable in performance and easy to prepare, so as to adapt to applications under higher temperatures and higher field strengths. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flexible polypropylene modified material that can balance mechanical and electrical properties at higher operating temperatures, making it suitable for high-temperature and high-field-strength operating conditions.

[0007] A first aspect of the present invention provides a flexible polypropylene modified material comprising a propylene-based continuous phase, a rubber phase dispersed in the propylene-based continuous phase, and a grafted phase derived from an alkenyl-containing functional monomer; wherein, based on the total weight of the flexible polypropylene modified material, the xylene-soluble content of the flexible polypropylene modified material is 10–55 wt%, preferably 15–45 wt%, more preferably 18–40 wt%; the content of the grafted structural units derived from the alkenyl-containing functional monomer in the flexible polypropylene modified material is 0.4–6 wt%, preferably 1–5 wt%; the flexural modulus of the flexible polypropylene modified material is 200–1000 MPa; and the D50 of the grafted phase is less than 300 nm.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned flexible polypropylene modified material, comprising the following steps: blending polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B) to obtain the flexible polypropylene modified material, wherein the low-modulus polypropylene (B) is unmodified low-modulus polypropylene and / or low-modulus polypropylene grafted with alkenyl functional monomers.

[0009] A third aspect of the present invention provides the application of the above-described flexible polypropylene modified material.

[0010] The flexible polypropylene modified material of this invention can maintain both mechanical and electrical properties at high operating temperatures, making it suitable for high-temperature and high-field-strength operating conditions. Compared to polypropylene materials obtained by in-reactor alloying, mechanically blending polypropylene with low-modulus polypropylene results in products with more diverse structures and greater controllability, thus achieving better performance. Compared to nanodoping technology, the alkenyl-containing functional monomer polymer introduced by dispersion grafting modification can form a uniformly distributed nanoscale dispersed phase in the composite material, i.e., an organic nanoparticle, avoiding the problems of difficulty in adding and dispersing inorganic nanoparticles. Furthermore, compared to materials with added small molecule additives, the grafted modified polypropylene material of this invention avoids performance degradation caused by small molecule migration, thus exhibiting better stability.

[0011] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0012] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0013] Figure 1The image shown is an atomic force microscope photograph of the product in Example 1. The bright white area indicated by the circle is the styrene graft phase, the black area is the rubber phase, and the other areas are the continuous phase.

[0014] Figure 2 The image shows the microstructure of the product in Example 1 under a 10,000x electron microscope, where the spherical dispersed phase is the styrene-grafted phase.

[0015] Figure 3 This is a microscopic image of the product in Example 3 under a 10,000x electron microscope.

[0016] Figure 4 This is a microscopic image of the product in Example 4 under a 10,000x electron microscope.

[0017] Figure 5 This is a microscopic image of the product in Example 5 under a 10,000x electron microscope.

[0018] Figure 6 This is a microscopic image of the product in Comparative Example 3 under a 10,000x electron microscope.

[0019] Figure 7 The image shows the microstructure of the product in Comparative Example 3 after etching under a 10,000x electron microscope. The black area represents the rubber phase.

[0020] Figure 8 This is a microscopic image of the product in Comparative Example 4 under a 10,000x electron microscope.

[0021] Figure 9 This is a microscopic image of the product in Comparative Example 5 under a 10,000x electron microscope. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] This invention provides a flexible polypropylene modified material, comprising a propylene-based continuous phase, a rubber phase dispersed in the propylene-based continuous phase, and a grafted phase derived from alkenyl functional monomers; wherein, based on the total weight of the flexible polypropylene modified material, the xylene-soluble content of the flexible polypropylene modified material is 10-55 wt%, preferably 15-45 wt%, more preferably 18-40 wt%; the content of the grafted structural units derived from alkenyl functional monomers in the flexible polypropylene modified material is 0.4-6 wt%, preferably 1-5 wt%; the flexural modulus of the flexible polypropylene modified material is 200-1000 MPa, preferably 200-700 MPa, more preferably 250-600 MPa; and the D50 of the grafted phase is less than 300 nm, preferably 10-250 nm, more preferably 50-200 nm.

[0024] In this invention, the flexible polypropylene modified material has a phase-separated structure. The term "continuous phase" is known to those skilled in the art and refers to the matrix portion; the "rubber phase" refers to the soft, xylene-soluble portion; and the "grafted phase" is formed from structural units derived from alkenyl-containing functional monomers. These structural units are primarily derived from grafted homopolymer or copolymer polypropylene, and may also partially originate from grafted low-modulus polypropylene. Therefore, structural units "in a grafted state" derived from alkenyl-containing functional monomers refer to structural units covalently linked (grafted) with polypropylene and optionally low-modulus polypropylene. The multiphase structure can be observed using atomic force microscopy (AFM). The black portion observed under AFM is the rubber phase, the bright white portion is the grafted phase, and the other portions are the continuous phase. The grafted phase can also be directly observed using electron microscopy (dispersed phase in the electron micrograph).

[0025] According to the present invention, preferably, the flexible polypropylene modified material has at least one of the following characteristics: a melt flow rate of 0.5 to 15 g / 10 min at 230°C and a load of 2.16 kg, preferably 0.6 to 10 g / 10 min, more preferably 0.8 to 6 g / 10 min; an elongation at break ≥ 200%, preferably ≥ 300%; and a tensile strength greater than 5 MPa, preferably 10 to 25 MPa.

[0026] According to the present invention, preferably, the flexible polypropylene modified material has at least one of the following characteristics:

[0027] - The maximum operating temperature of the flexible polypropylene modified material is ≥90℃, preferably 100~160℃, more preferably 110~140℃;

[0028] The breakdown field strength Eg of the flexible polypropylene modified material at 110°C is ≥290kV / mm, preferably 300~800kV / mm, more preferably 310~750kV / mm; for example, 320kV / mm, 330kV / mm, 340kV / mm, 350kV / mm, 400kV / mm, 450kV / mm, 500kV / mm, 550kV / mm, 600kV / mm, 650kV / mm, 700kV / mm;

[0029] - The DC volume resistivity ρ of the flexible polypropylene modified material at 110℃ and 40kV / mm field strength. vg ≥1.0×10 13 Ω·m, preferably 1.5 × 10 13 Ω·m~1.0×10 20 Ω·m;

[0030] The dielectric constant of the flexible polypropylene modified material at 110°C and 50Hz is greater than 2.0, preferably 2.1 to 2.5.

[0031] The alkenyl groups in the alkenyl-containing functional monomers of the present invention are used for grafting with polypropylene / low-modulus polypropylene. Therefore, any alkenyl-containing functional monomer with an alkenyl group located in a reactive position is applicable to the present invention.

[0032] Specifically, the alkenyl-containing functional monomer is selected from at least one monomer having the structure shown in Formula 1.

[0033]

[0034] In Equation 1, R b R c R d Each is independently selected from H, substituted or unsubstituted alkyl groups; R a It is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted ester, substituted or unsubstituted carboxyl, substituted or unsubstituted cycloalkyl or heterocyclic, cyano, substituted or unsubstituted silyl.

[0035] According to a preferred embodiment of the present invention, R b R c R d Each is independently selected from H, substituted or unsubstituted C1-C6 alkyl groups; R a Selected from substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C1-C 20 Alkoxy, substituted or unsubstituted C6-C 20 aryl, substituted or unsubstituted C1-C 20Ester group, substituted or unsubstituted C1-C 20 Carboxyl group, substituted or unsubstituted C3-C 20 Cycloalkyl or heterocyclic, cyano, substituted or unsubstituted C3-C 20 Silyl group; the substituted group is halogen, hydroxyl, amino, C1-C 12 Alkyl, C3-C6 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 Acyloxy group.

[0036] According to a more preferred embodiment of the present invention, wherein R b R c R d Each is independently selected from H, substituted or unsubstituted C1-C6 alkyl groups;

[0037] R a Selected from the groups shown in Formula 2, Formula 3, Formula 4, Formula 5, Formula 6, combinations of the groups shown in Formula 6 and Formula 7, and heterocyclic groups;

[0038]

[0039] In Equation 2, R 4 -R 8 Each is independently selected from H, halogen, hydroxyl, amino, phosphate group, sulfonic acid group, substituted or unsubstituted C1-C. 12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; preferably, R 4 -R 8 Each is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy;

[0040]

[0041] In Equation 3, R4-R 10 Each is independently selected from H, halogen, hydroxyl, amino, phosphate group, sulfonic acid group, substituted or unsubstituted C1-C.12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; preferably, R4-R 10 Each of the groups is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, wherein the substituted group is selected from halogen, hydroxyl, amino, C1-C6 alkyl, C1-C6 alkoxy;

[0042]

[0043] In Equation 4, R4'-R 10 Each group is independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C1-C. 12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; preferably, R4'-R 10 Each of the following is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, wherein the substituted group is selected from halogen, hydroxyl, amino, C1-C6 alkyl, C1-C6 alkoxy;

[0044]

[0045] In Equation 5, R', R”, and R”' are each independently selected from substituted or unsubstituted C1-C. 12 Straight-chain alkyl, substituted or unsubstituted C3-C12 Branched alkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 The acyloxy group; preferably, R1 is a C2-C6 alkenyl group, preferably a monounsaturated alkenyl group; R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C6 straight-chain alkyl groups, substituted or unsubstituted C3-C6 branched alkyl groups, substituted or unsubstituted C1-C6 alkoxy groups, and substituted or unsubstituted C1-C6 acyloxy groups;

[0046]

[0047] In Equation 6, R m Selected from the following groups, substituted or unsubstituted: C1-C 20 Straight-chain alkyl, C3-C 20 Branched alkyl, C3-C 12 cycloalkyl, C3-C 12 Epoxyalkyl, C3-C 12 Epoxyalkylalkyl, wherein the substituted group is selected from at least one of halogen, amino and hydroxyl groups;

[0048] The heterocyclic group is selected from imidazole, pyrazol, carbazole, pyrrolidone, pyridinyl, piperidinyl, caprolactam, pyrazinyl, thiazolyl, purine, morpholino, and oxazolino.

[0049] According to a specific embodiment of the present invention, the alkenyl-containing functional monomer is an aromatic olefin monomer, wherein the aromatic olefin monomer is selected from at least one of styrene, α-methylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, monosubstituted or polysubstituted styrene, monosubstituted or polysubstituted α-methylstyrene, monosubstituted or polysubstituted 1-vinylnaphthalene, and monosubstituted or polysubstituted 2-vinylnaphthalene; the substituted group is preferably selected from at least one of halogen, hydroxyl, amino, phosphate group, sulfonic acid group, C1-C8 straight-chain alkyl, C3-C8 branched alkyl or cycloalkyl, C1-C6 straight-chain alkoxy, C3-C8 branched alkoxy or cyclic alkoxy, C1-C8 straight-chain ester group, C3-C8 branched ester group or cyclic ester group, C1-C8 straight-chain amino group, and C3-C8 branched amino group or cyclic amino group; preferably, the aromatic olefin monomer is selected from at least one of styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, and 4-methylstyrene.

[0050] According to a specific embodiment of the present invention, the alkenyl-containing functional monomer is an alkenyl-containing silane monomer, wherein the alkenyl-containing silane monomer is selected from at least one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltritert-butoxysilane, vinyltriacetoxysilane, methylvinyldimethoxysilane, ethylvinyldiethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, allyltriisopropoxysilane, vinyltris(β-methoxyethoxy)silane, allyltris(β-methoxyethoxy)silane, allyltritert-butoxysilane, allyltriacetoxysilane, methylallyldimethoxysilane, and ethylallyldiethoxysilane.

[0051] According to one specific embodiment of the present invention, the alkenyl-containing functional monomer is an acrylate monomer and optionally an acrylic monomer. Preferably, the acrylate monomer is selected from at least one of methyl methacrylate, sec-butyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, dodecyl methacrylate, coconut oleate methacrylate, octadecyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, and glycidyl methacrylate. Preferably, the acrylic monomer is selected from at least one of acrylic acid, methacrylic acid, and 2-ethylacrylic acid.

[0052] In this invention, C3-C 12 Epoxyalkyl refers to an alkyl group that has 3-12 carbon atoms and is substituted with an epoxyalkyl group, such as ethylene oxide methyl.

[0053] In this invention, structural units derived from acrylic monomers may be absent or may coexist with structural units derived from acrylate monomers. Preferably, the molar ratio of structural units derived from acrylate monomers to structural units derived from acrylic monomers is 1:0 to 2, and more preferably 1:0.125 to 1.

[0054] According to a specific embodiment of the present invention, the alkenyl-containing functional monomer is an alkenyl-containing heterocyclic compound. The alkenyl-containing heterocyclic monomer of the present invention can be any alkenyl-containing heterocyclic compound capable of free radical polymerization, and can be selected from at least one of the following: imidazoles containing alkenyl substituents, pyrazoles containing alkenyl substituents, carbazoles containing alkenyl substituents, pyrrolidones containing alkenyl substituents, pyridines or pyridine salts containing alkenyl substituents, piperidines containing alkenyl substituents, caprolactams containing alkenyl substituents, pyrazines containing alkenyl substituents, thiazoles containing alkenyl substituents, purines containing alkenyl substituents, morpholines containing alkenyl substituents, and oxazolines containing alkenyl substituents; preferably, the alkenyl-containing heterocyclic monomer is a monoalkenyl-containing heterocyclic monomer.

[0055] Specifically, the alkenyl-containing heterocyclic monomer may be selected from at least one of the following: 1-vinylimidazolium, 2-methyl-1-vinylimidazolium, N-allylimidazolium, 1-vinylpyrazole, 3-methyl-1-vinylpyrazole, vinylcarbazole, N-vinylpyrrolidone, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, vinylpyridine N-oxide, vinylpyridine salt, vinylpiperidine, N-vinylcaprolactam, 2-vinylpyrazine, N-vinylpiperazine, 4-methyl-5-vinylthiazole, N-vinylpurine, vinylmorpholine, and vinyloxazoline.

[0056] According to a preferred embodiment of the present invention, the flexible polypropylene modified material comprises polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B), wherein the low-modulus polypropylene (B) is unmodified low-modulus polypropylene and / or low-modulus polypropylene grafted with alkenyl functional monomers; preferably, based on the total weight of the flexible polypropylene modified material, the content of the polypropylene (A) grafted with alkenyl functional monomers is 20-80 wt%, preferably 30-70 wt%, more preferably 35-65 wt%, and the content of the low-modulus polypropylene (B) is 20-80 wt%, preferably 30-70 wt%, more preferably 35-65 wt%.

[0057] In the three-phase structure of the flexible polypropylene modified material of the present invention, the polypropylene (A) modified with alkenyl functional monomers provides at least a propylene-based continuous phase and a grafted phase; the low-modulus polypropylene (B) provides a propylene-based continuous phase and a rubber phase, and optionally provides a grafted phase.

[0058] According to the present invention, the flexible polypropylene modified material can be prepared by blending polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B).

[0059] In this invention, the alkenyl functional monomer-grafted modified polypropylene (A) comprises structural units derived from homopolymer or copolymer polypropylene and structural units derived from alkenyl functional monomers; based on the weight of the alkenyl functional monomer-grafted modified polypropylene (A), the content of structural units derived from alkenyl functional monomers and in the grafted state in the alkenyl functional monomer-grafted modified polypropylene (A) is 0.5-20 wt%, preferably 1-15 wt%.

[0060] The term "structural unit" refers to a portion of polypropylene grafted with an alkenyl functional monomer, and its form is not limited. Specifically, "structural unit derived from homopolymer or copolymer polypropylene" refers to a product formed from homopolymer or copolymer polypropylene, which includes both "group" and "polymer" forms. "Structural unit derived from alkenyl functional monomer" refers to a product formed from an alkenyl functional monomer, which includes both "group" and "monomer" forms, as well as "polymer" forms. The "structural unit" can be a repeating unit or a non-repeating independent unit.

[0061] According to a preferred embodiment of the present invention, the homopolymer or copolymer polypropylene has at least one of the following characteristics: a comonomer content of 0-15 mol%, preferably 0-12 mol%, more preferably 0-8 mol%; a melt flow rate of 1-10 g / 10 min at 230°C and 2.16 kg load, preferably 2-5 g / 10 min; a melt temperature Tm of 110-180°C, more preferably 120-170°C; and a weight-average molecular weight of 20 × 10⁻⁶. 4 ~50×10 4 g / mol; flexural modulus of 500–2000 MPa, preferably 600–1700 MPa; elongation at break ≥200%, preferably ≥300%; tensile strength greater than 5 MPa, preferably 10–40 MPa.

[0062] According to a preferred embodiment of the present invention, the comonomer of the copolymerized polypropylene is selected from at least one of C2-C8 α-olefins other than propylene; preferably, the comonomer of the copolymerized polypropylene is selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene; more preferably, the comonomer of the copolymerized polypropylene is ethylene and / or 1-butene; the comonomer content, based on the total molar amount of monomers, is 0.1-15 mol%, preferably 0.1-12 mol%, more preferably 0.1-8 mol%. The copolymerized polypropylene of the present invention is preferably a porous granular or powdered resin.

[0063] The homopolymer or copolymer polypropylene described in this invention can be any commercially available polypropylene powder suitable for this invention, or it can be produced by the polymerization process described in Chinese patents CN102453180B, CN101490096B, CN102816269B, CN102816270B, etc.

[0064] The concept of "low-modulus polypropylene" in this invention is well known to those skilled in the art, and is preferably an ethylene-propylene copolymer with a flexural modulus of less than 300 MPa. Specifically, the ethylene-propylene impact copolymer contains a propylene homopolymer and / or propylene random copolymer matrix component (1) as the matrix phase, and another propylene copolymer component (2) dispersed therein as the dispersed phase, the propylene copolymer component containing one or more ethylene or higher α-olefin comonomers. In the propylene random copolymer, the comonomers are randomly distributed on the main chain of the propylene polymer. Preferably, the propylene copolymer (2) dispersed in the homopolymer or copolymer matrix (1) of the low-modulus polypropylene is substantially amorphous. The term "substantially amorphous" here means that the propylene copolymer (2) has a lower crystallinity than the homopolymer or copolymer matrix (1).

[0065] The low-modulus polypropylene can be an island-type structure or a bicontinuous structure. Preferably, the copolymer polypropylene of the present invention is a multiphase propylene copolymer prepared in situ in a reactor using existing processes.

[0066] According to the present invention, preferably, the low-modulus polypropylene has at least one of the following characteristics: a comonomer content of 8-25 wt%, preferably 10-22 wt%; a xylene-soluble content of 18-75 wt%, preferably 30-70 wt%, more preferably 30-67 wt%; a melt flow rate of 0.1-15 g / 10 min at 230°C and a load of 2.16 kg, preferably 0.2-7 g / 10 min; a melt temperature Tm of 120-165°C, more preferably 125-150°C; a flexural modulus of 10-300 MPa, preferably 15-250 MPa; a xylene-soluble comonomer content of 10-50 wt%, preferably 20-35 wt%; and a xylene-soluble to low-modulus polypropylene intrinsic viscosity ratio of 0.5-3, preferably 0.8-1.3.

[0067] The low-modulus polypropylene described in this invention includes, but is not limited to, any commercially available polypropylene powder and granules suitable for this invention, and can also be produced by the polymerization processes described in Chinese patents CN1069908C, CN1049932C, CN1108315C, CN1117610C, CN1132865C, and CN102020733B. Commonly used polymerization processes include Basell's Spheripol process, Mitsui Chemicals' Hypol process, Borealis' Borstar PP process, Dow Chemical's Unipol process, and INEOSCO's (formerly BP-Amoco) Innovene vapor-phase process, etc.

[0068] In this invention, when the grafting situation is not specified, "low modulus polypropylene" usually refers to ungrafted (i.e., unmodified) low modulus polypropylene.

[0069] According to the present invention, preferably, based on the weight of the low-modulus polypropylene grafted with alkenyl functional monomers, the content of structural units derived from alkenyl functional monomers and in the grafted state in the low-modulus polypropylene grafted with alkenyl functional monomers is 0.1 to 5 wt%, preferably 0.2 to 2.5 wt%.

[0070] The present invention also provides a method for preparing the flexible polypropylene modified material, comprising the following steps: blending polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B) to obtain the flexible polypropylene modified material, wherein the low-modulus polypropylene (B) is unmodified low-modulus polypropylene and / or low-modulus polypropylene grafted with alkenyl functional monomers.

[0071] Preferably, based on the total weight of the flexible polypropylene modified material, the amount of polypropylene (A) is 20-80 wt%, preferably 30-70 wt%, more preferably 35-65 wt%, and the amount of low modulus polypropylene (B) is 20-80 wt%, preferably 30-70 wt%, more preferably 35-65 wt%.

[0072] According to a preferred embodiment of the present invention, the preparation method includes the following steps:

[0073] S1: In the presence of an inert gas, a reaction mixture A, including homopolymer or copolymer polypropylene and an alkenyl functional monomer, is subjected to a grafting reaction to obtain polypropylene grafted with an alkenyl functional monomer.

[0074] Optionally, in the presence of an inert gas, a reaction mixture B comprising low-modulus polypropylene and an alkenyl functional monomer is subjected to a grafting reaction to obtain low-modulus polypropylene grafted with an alkenyl functional monomer.

[0075] S2: The polypropylene grafted with the alkenyl functional monomer is mixed with unmodified low-modulus polypropylene and / or the low-modulus polypropylene grafted with the alkenyl functional monomer, as well as optional additives, and then extruded and granulated to obtain the flexible polypropylene modified material.

[0076] Preferably, the grafting site is initiated by a free radical initiator, and the grafting reaction is further carried out. In this case, reaction mixture A and reaction mixture B also independently include free radical initiators.

[0077] The peroxide radical initiator is preferably selected from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, dodecyl peroxide, tert-butyl peroxide, diisopropyl peroxide, tert-butyl peroxide, and dicyclohexyl peroxide; the azo radical initiator is preferably azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0078] More preferably, the grafting site is initiated by a peroxide-based free radical initiator and the grafting reaction is further carried out.

[0079] Furthermore, the grafting reaction of the present invention can also be carried out by the methods described in CN106543369A, CN104499281A, CN102108112A, CN109251270A, CN1884326A and CN101492517B.

[0080] Under the premise of satisfying the above product characteristics, the present invention does not have a particular limitation on the amount of each component in the grafting reaction. Specifically, the mass ratio of the free radical initiator to the alkenyl functional monomer is 0.01 to 10:100, preferably 0.5 to 5:100. The mass ratio of the alkenyl functional monomer to the homopolymer or copolymer polypropylene is 0.5 to 35:100, preferably 2 to 30:100, more preferably 5 to 25:100; the mass ratio of the alkenyl functional monomer to the low modulus polypropylene is 0.1 to 20:100, preferably 0.2 to 10:100, more preferably 0.5 to 5:100.

[0081] The present invention does not particularly limit the process conditions for the grafting reaction. Preferably, the grafting reaction is a solid-phase grafting reaction. Specifically, the temperature of the grafting reaction is 30-130°C, preferably 60-120°C; and the time is 0.5-10 hours, preferably 1-6 hours.

[0082] In this invention, the "reaction mixture" includes all materials added to the grafting reaction system. The materials can be added all at once or at different stages of the reaction.

[0083] The reaction mixture A and the reaction mixture B of the present invention may each independently include a dispersant, which is preferably an aqueous solution of water or sodium chloride. The mass amount of the dispersant is preferably 50-300% of the mass of polypropylene.

[0084] The reaction mixture A and the reaction mixture B of the present invention may each independently include an interface agent, which is an organic solvent that has a swelling effect on polyolefins, preferably at least one of the following organic solvents that have a swelling effect on polypropylene: ether solvents, ketone solvents, aromatic solvents, alkane solvents; more preferably at least one of the following organic solvents: chlorobenzene, polychlorinated benzene, alkanes or cycloalkanes with more than C6 carbon atoms, benzene, C1-C4 alkyl-substituted benzene, C2-C6 aliphatic ethers, C3-C6 aliphatic ketones, decahydronaphthalene; and even more preferably at least one of the following organic solvents: benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decahydronaphthalene, heptane. The mass content of the interface agent is preferably 1-30% of the mass of polypropylene, and more preferably 10-25%.

[0085] The reaction mixture A and the reaction mixture B of the present invention may each independently include an organic solvent as a solvent for dissolving the solid free radical initiator. The organic solvent preferably includes at least one of C2-C5 alcohols, C2-C4 ethers, and C3-C5 ketones; more preferably, it includes at least one of C2-C4 alcohols, C2-C3 ethers, and C3-C5 ketones; and most preferably, it includes at least one of ethanol, diethyl ether, and acetone. The mass content of the organic solvent is preferably 1-35% of the mass of polypropylene.

[0086] According to a preferred embodiment of the present invention, the preparation method includes the following steps:

[0087] a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas;

[0088] b. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix;

[0089] c. Optionally add an interfacial agent and optionally swell the reaction system;

[0090] d. Optionally add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction;

[0091] e. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain polypropylene grafted with alkenyl functional monomers;

[0092] f. The polypropylene grafted with the alkenyl functional monomer is mixed with ungrafted and / or grafted low-modulus polypropylene and optional additives, and then melt-extruded and granulated to obtain the flexible polypropylene modified material.

[0093] The method for preparing the grafted low-modulus polypropylene includes the following steps:

[0094] i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas;

[0095] ii. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix;

[0096] iii. Optionally add an interfacial agent and optionally swell the reaction system;

[0097] iv. Optionally, add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction;

[0098] v. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

[0099] Specifically, the preparation method includes the following steps:

[0100] a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas;

[0101] b. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix;

[0102] c. Add 0-30 parts of interface agent, and optionally allow the reaction system to swell at 20-60°C for 0-24 hours;

[0103] d. Add 0-300 parts of dispersant, heat the system to the graft polymerization temperature of 30-130℃, and react for 0.5-10 hours;

[0104] e. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain polypropylene grafted with alkenyl functional monomers;

[0105] f. Weigh and mix the polypropylene grafted with the alkenyl functional monomer with ungrafted and / or grafted low-modulus polypropylene and optional additives in proportion, and granulate the mixture using a twin-screw extruder at a melt temperature of 180°C to 230°C and a screw speed of 30 to 600 rpm to obtain the flexible polypropylene modified material.

[0106] The method for preparing the grafted low-modulus polypropylene includes the following steps:

[0107] i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas;

[0108] ii. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix;

[0109] iii. Add 0-30 parts of interface agent, and optionally allow the reaction system to swell at 20-60°C for 0-24 hours;

[0110] iv. Add 0-300 parts of dispersant, heat the system to the graft polymerization temperature of 30-130℃, and react for 0.5-10 hours;

[0111] v. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

[0112] According to another preferred embodiment of the present invention, the preparation method includes the following steps:

[0113] a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas;

[0114] b. Mix the organic solvent and the free radical initiator, and add them to the closed reactor;

[0115] c. Remove the organic solvent;

[0116] d. Add an alkenyl-containing functional monomer, optionally add an interfacial agent, and optionally swell the reaction system;

[0117] e. Optionally add a dispersant, raise the temperature of the reaction system to the grafting reaction temperature, and carry out the grafting reaction;

[0118] f. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain polypropylene grafted with alkenyl functional monomers.

[0119] g. The polypropylene grafted with the alkenyl functional monomer is weighed and mixed with ungrafted and / or grafted low-modulus polypropylene and optional additives in proportion, and then melt-extruded and granulated to obtain the flexible polypropylene modified material.

[0120] The method for preparing the grafted low-modulus polypropylene includes the following steps:

[0121] i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas;

[0122] ii. Mix the organic solvent and the free radical initiator and add them to the closed reactor;

[0123] iii. Remove the organic solvent;

[0124] iv. Add an alkenyl-containing functional monomer, optionally add an interfacial agent, and optionally swell the reaction system;

[0125] v. Optionally add a dispersant, heat the reaction system to the grafting reaction temperature, and carry out the grafting reaction;

[0126] vi. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

[0127] Specifically, the preparation method includes the following steps:

[0128] a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas;

[0129] b. Mix the organic solvent and the free radical initiator, and add them to the closed reactor;

[0130] c. Remove the organic solvent;

[0131] d. Add an alkenyl-containing functional monomer, add 0-30 parts of an interfacial agent, and optionally allow the reaction system to swell at 20-60°C for 0-24 hours;

[0132] e. Add 0-300 parts of dispersant, heat the system to the graft polymerization temperature of 30-130℃, and react for 0.5-10 hours;

[0133] f. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain polypropylene grafted with alkenyl functional monomers.

[0134] g. The polypropylene grafted with the alkenyl functional monomer is weighed and mixed with ungrafted and / or grafted low-modulus polypropylene and optional additives in proportion, and then granulated using a twin-screw extruder at a melt temperature of 180°C to 230°C and a screw speed of 30 to 600 rpm to obtain the flexible polypropylene modified material.

[0135] The method for preparing the grafted low-modulus polypropylene includes the following steps:

[0136] i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas;

[0137] ii. Mix the organic solvent and the free radical initiator and add them to the closed reactor;

[0138] iii. Remove the organic solvent;

[0139] iv. Add an alkenyl-containing functional monomer, add 0-30 parts of an interfacial agent, and optionally allow the reaction system to swell at 20-60°C for 0-24 hours;

[0140] v. Add 0-300 parts of dispersant, heat the system to the graft polymerization temperature of 30-130℃, and react for 0.5-10 hours;

[0141] vi. After the reaction is complete, the mixture is optionally filtered (in the case of using an aqueous dispersant) and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

[0142] According to the method of the present invention, if volatile components are present in the system after the reaction, the method preferably includes a step of removing the volatiles, which can be carried out by any conventional method, including vacuum extraction or the use of a stripping agent at the end of the grafting process. Suitable stripping agents include, but are not limited to, inert gases.

[0143] As described above, the "alkenyl functional monomer-grafted modified polypropylene" or "alkenyl functional monomer-grafted modified low-modulus polypropylene" of the present invention includes both the product (crude product) directly obtained from polypropylene / low-modulus polypropylene and alkenyl functional monomer through a grafting reaction, and the grafted modified polypropylene pure product obtained by further purification of the product. Therefore, the preparation method of the present invention may optionally include a step of purifying the crude product. The purification can be carried out using various methods conventional in the art, such as extraction.

[0144] This invention does not impose a particular limitation on the grafting efficiency of the grafting reaction, but a higher grafting efficiency is more advantageous for obtaining the desired alkenyl functional monomer-grafted modified polypropylene material with the desired properties through a one-step grafting reaction. Therefore, it is preferable to control the grafting efficiency of the grafting reaction to be 20-100%, more preferably 25-80%. The concept of grafting efficiency is well known to those skilled in the art, referring to the amount of alkenyl functional monomer on the graft / the total amount of alkenyl functional monomer in the reaction feed.

[0145] The inert gas described in this invention can be any of the inert gases commonly used in the art, including but not limited to nitrogen and argon.

[0146] In the method of this invention, the grafted modified polypropylene is mixed with low-modulus polypropylene and optional additives by mechanical mixing, preferably by twin-screw mechanical blending. The additives are, for example, one or more of antioxidants, stabilizers, and processing aids. The types and amounts of additives used are conventional and known to those skilled in the art.

[0147] The flexible polypropylene modified material of the present invention can be applied in the field of cables, for example, as an insulating material.

[0148] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0149] Test methods

[0150] 1. Determination of copolymer content in polypropylene:

[0151] The content of comonomers was determined by quantitative Fourier transform infrared (FTIR) spectroscopy. The correlation of the determined comonomer content was calibrated by quantitative nuclear magnetic resonance (NMR) spectroscopy. Based on quantitative... 13 The calibration method for the C-NMR spectrometer results was performed according to conventional methods in the art.

[0152] 2. Determination of xylene-soluble content (XS)

[0153] The test shall be conducted according to the method specified in GB / T 24282-2009.

[0154] 3. Determination of xylene-soluble copolymer content (XSC2) and intrinsic viscosity ratio of soluble matter to copolymer polypropylene in low-modulus polypropylene:

[0155] The tests were performed using a Polymer CharCrystal CRYST-EX instrument. Trichlorobenzene solvent was used, and the solution was dissolved at 150°C and held at that temperature for 90 minutes before sampling and testing. The solution was then cooled to 35°C and held at that temperature for 70 minutes before sampling and testing again.

[0156] 4. Weight-average molecular weight of polypropylene (M) w The determination of )

[0157] High-temperature GPC was used for determination using a Polymer Laboratory PL-GPC 220 gel permeation chromatograph. The sample was dissolved in 1,2,4-trichlorobenzene at a concentration of 1.0 mg / mL. The test temperature was 150 °C, and the solution flow rate was 1.0 mL / min. A standard curve was established using the molecular weight of polystyrene as an internal reference, and the molecular weight and molecular weight distribution of the sample were calculated based on the elution time.

[0158] 5. Determination of Melt Flow Rate (MFR):

[0159] The test was performed using a CEAST 7026 melt flow indexer at 230°C and a load of 2.16 kg, according to the method specified in GB / T 3682-2018.

[0160] 6. Determination of melting temperature Tm:

[0161] Differential scanning calorimetry (DSC) was used to analyze the melting and crystallization processes of the material. Specifically, under nitrogen protection, 5–10 mg of sample was heated from 20°C to 200°C using a three-stage temperature rise and fall measurement method. The change in heat flow reflected the melting and crystallization processes, and the melting temperature Tm was calculated.

[0162] 7. Determination of grafting efficiency GE and parameter M1:

[0163] Place 2–4 g of the grafted product into a Soxhlet extractor and extract with an organic solvent (ethyl acetate for aromatic olefin monomers and acrylate monomers; acetone for silane monomers) for 24 hours to remove unreacted monomers and their homopolymers, and obtain pure grafted product. Dry and weigh the product, and calculate the parameters Mn, M1 and grafting efficiency GE.

[0164] The parameter Mn (n = A or B) represents the content of structural units derived from alkenyl functional monomers and in a grafted state in component A or component B, and the parameter M1 represents the content of structural units derived from alkenyl functional monomers and in a grafted state in the composite material. A and M B Calculated. In this invention, the calculation formulas for M1 and Mn are as follows:

[0165]

[0166]

[0167]

[0168] In the above formulas, w0 is the mass of the PP matrix; w1 is the mass of the grafted product before extraction; w2 is the mass of the grafted product after extraction; w3 is the mass of the added alkenyl-containing functional monomer; m A It is the mass of component A in the composite material, m B It is the mass of component B in the composite material, m 产品 It refers to the quality of the composite material.

[0169] 8. Determination of DC volume resistivity:

[0170] The determination shall be carried out in accordance with the method specified in GB / T 1410-2006.

[0171] 9. Determination of breakdown field strength:

[0172] The determination shall be carried out in accordance with the method specified in GB / T 1408-2006.

[0173] 10. Determination of tensile strength:

[0174] The determination shall be carried out in accordance with the method specified in GB / T 1040.2-2006.

[0175] 11. Determination of flexural modulus:

[0176] The determination shall be carried out in accordance with the method specified in GB / T 9341-2008.

[0177] 12. Determination of elongation at break:

[0178] The determination shall be carried out in accordance with the method specified in GB / T 1040-2006.

[0179] 13. Determination of dielectric constant:

[0180] The determination shall be carried out in accordance with the method specified in GB / T 1409-2006.

[0181] 14. Characterization of the rubber phase

[0182] During twin-screw extrusion granulation, one to two composite material samples, each 5–10 cm long, were taken. The samples were immersed in liquid nitrogen for 15 minutes until they became brittle. The fracture surface was then immersed in xylene at room temperature for 24 hours, followed by immersion in water and sonication for 15 minutes. Finally, the fracture surface was rinsed with alcohol and air-dried. The fracture surface was then sputter-coated with gold, and the material was characterized using a scanning electron microscope.

[0183] 15. Characterization of grafted phases and calculation of D50

[0184] The composite material specimens were immersed in liquid nitrogen for 15 minutes and then fractured. The fracture surface was sputter-coated with gold, and the cross-section was characterized by scanning electron microscopy to obtain microscopic morphology images. Using analytical software, 200 dispersed phases from each sample were taken and their diameters measured. The D50 was calculated using data processing software. D50 represents the median particle size, which is the particle size corresponding to a cumulative particle size distribution percentage of 50% for a sample.

[0185] 16. Characterization of three-phase structure

[0186] Composite material samples were cooled to -50°C with liquid nitrogen and then sliced. The microstructure of the composite material was characterized using a Bruker Dimension rapid scanning atomic force microscope (RFF).

[0187] Example

[0188] The raw materials and their properties used in the examples are described in Tables A, B, and C.

[0189] Table A

[0190] PP 1* Self-made according to the method described in CN110305400A PP 2* Self-made according to the method described in CN102453180A PP 3* Self-made according to the method described in CN102816269A b-PP 1* Self-made according to the method described in CN101679557A b-PP 2* Self-made according to the method described in CN109153831A b-PP 3* Self-made according to the method described in CN101679557A Benzoyl peroxide J&K Chemicals lauroyl peroxide J&K Chemicals tert-butyl peroxide (2-ethylhexanoate) Adamas Reagents Ltd. (adamas-beta) styrene J&K Chemicals Vinyltriethoxysilane J&K Chemicals Methyl methacrylate J&K Chemicals Polystyrene GPPS-123 Shanghai SECCO Petrochemical Co., Ltd.

[0191] *PP 1: Homopolymer polypropylene used in Examples 1 and 4, and Comparative Examples 1 and 5.

[0192] *PP 2: The copolymer polypropylene used in Examples 2 and 3, and Comparative Examples 3 and 4.

[0193] *PP 3: Copolymer polypropylene used in Example 5.

[0194] *b-PP 1: Low-modulus polypropylene used in Examples 1, 2, 4, and Comparative Examples 3, 4, 5.

[0195] *b-PP 2: Example 3, the low-modulus polypropylene used in Comparative Example 2.

[0196] *b-PP 3: Low-modulus polypropylene used in Example 5.

[0197] Table B

[0198]

[0199] Table C

[0200]

[0201] Example 1

[0202] 2.0 kg of PP1 powder (after sieving to remove fine powder smaller than 40 mesh) was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 4.83 g of tert-butyl peroxide (2-ethylhexanoate) and 322 g of styrene were added, and the mixture was stirred for 30 minutes. 2 kg of water (as a dispersant) was added, and the mixture was allowed to swell at 50 °C for 2 hours. The temperature was then raised to 90 °C, and the reaction was continued for 4 hours. After the reaction was completed, the mixture was cooled, filtered to remove the water (as a dispersant), and vacuum dried at 70 °C for 10 hours to obtain polypropylene-g-styrene powder, whose M... A =7.2%.

[0203] Weigh 1.2 kg of polypropylene-g-styrene powder and b-PP1 in a mass ratio of 36:64, add 3000 ppm of antioxidant 1010 / 168 (mass ratio 1:1), and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 400 rpm to obtain composite material C1. The performance parameters of the obtained product are shown in Table 1.

[0204] Figure 1 The image shows an atomic force microscope (AFM) image (modulus diagram) of the material product in Example 1. The bright white areas represent the styrene-grafted phase, the black areas represent the rubber phase, and the other areas represent the continuous phase.

[0205] Figure 2 The image shows the microstructure of the material product in Example 1 under a 10,000x electron microscope, where the spherical dispersed phase is the styrene-grafted phase. It can be seen that the styrene-grafted phase has a small particle size and a regular morphology.

[0206] Example 2

[0207] 2.0 kg of PP2 powder (after sieving to remove fine powder smaller than 40 mesh) was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 2.4 g of benzoyl peroxide and 240 g of styrene were added, and the mixture was stirred and mixed for 30 minutes. The mixture was then swelled at 40 °C for 2 hours, and the temperature was raised to 100 °C, and the reaction was continued for 3 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-styrene powder, whose M... A =7.0%.

[0208] Weigh out 1.2 kg of polypropylene-g-styrene powder and b-PP1 in a mass ratio of 60:40, add 3000 ppm antioxidant 1035 and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 450 rpm to obtain composite material C2. The performance parameters of the obtained product are shown in Table 1.

[0209] Example 3

[0210] 2.0 kg of PP2 powder (after sieving to remove fine powder smaller than 40 mesh) was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 2.2 g of benzoyl peroxide and 100 g of methyl methacrylate were added, and the mixture was stirred for 20 minutes. The temperature was raised to 95 °C, and the reaction was carried out for 5 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-methyl methacrylate powder, whose M... A =2.5%.

[0211] Weigh out 1.2 kg of polypropylene-g-methyl methacrylate powder and b-PP2 in a mass ratio of 60:40, add 3000 ppm antioxidant 1035 and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 200-210-220-230-230-230-220-220-210℃ and a screw speed of 350 rpm to obtain composite material C3. The performance parameters of the obtained product are shown in Table 1.

[0212] Figure 3The image shows the microstructure of the material product in Example 3 under a 10,000x electron microscope, where the spherical dispersed phase is the methyl methacrylate grafted phase. It can be seen that the methyl methacrylate grafted phase has a small particle size and a regular morphology.

[0213] Example 4

[0214] 2.0 kg of PP1 powder, after sieving to remove fine powder smaller than 40 mesh, was added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 3.4 g of benzoyl peroxide and 226 g of styrene were added, and the mixture was stirred for 30 minutes. 2 L of deionized water was added as a dispersant, and the mixture was heated to 90 °C and reacted for 6 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-styrene powder 1, whose M... A =6.2%.

[0215] 2.0 kg of b-PP1 powder was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 0.28 g of benzoyl peroxide and 28.0 g of styrene were added, and the mixture was stirred for 20 minutes. 2 L of deionized water was added as a dispersant, and the mixture was heated to 90 °C and reacted for 5 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-styrene powder 2, whose M... B =0.8%.

[0216] Weigh out 1.2 kg of polypropylene-g-styrene powder 1 and polypropylene-g-styrene powder 2 at a mass ratio of 36:64, add 3000 ppm of antioxidant 1010 / 168 (mass ratio 1:1) and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 400 rpm to obtain composite material C4. The performance parameters of the obtained product are shown in Table 1.

[0217] Figure 4 The image shows the microstructure of the material product in Example 4 under a 10,000x electron microscope, where the spherical dispersed phase is the styrene-grafted phase. It can be seen that the styrene-grafted phase has a small particle size and a regular morphology.

[0218] Example 5

[0219] 2.0 kg of PP3 powder, after sieving to remove fine powder smaller than 40 mesh, was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 7.5 g of lauroyl peroxide, 150 g of vinyltriethoxysilane, and 100 ml of xylene were mixed until homogeneous. This mixture was added to the reactor and stirred for 20 minutes. The temperature was raised to 105 °C, and the reaction was carried out for 4 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-vinyltriethoxysilane powder, whose M... A =1.8%.

[0220] 1.2 kg of polypropylene-g-vinyltriethoxysilane powder and b-PP3 were weighed according to a mass ratio of 40:60, and 2000 ppm of antioxidant 1024 was added and mixed in a high-speed mixer. The mixture was then granulated using a twin-screw extruder at a zone temperature of 200-210-220-230-230-230-220-220-210℃ and a screw speed of 400 rpm to obtain composite material C5. The performance parameters of the obtained product were tested, and the results are shown in Table 1.

[0221] Figure 5 The image shows the microstructure of the material product in Example 5 under a 10,000x electron microscope, where the spherical dispersed phase is the vinyltriethoxysilane grafted phase. It can be seen that the vinyltriethoxysilane grafted phase has a small particle size and a regular morphology.

[0222] Comparative Example 1

[0223] 2.0 kg of PP1 powder (after sieving to remove fine powder smaller than 40 mesh) was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used to purge oxygen. 2 g of benzoyl peroxide and 100 g of styrene were added, and the mixture was stirred for 60 minutes. The mixture was then allowed to swell at 40 °C for 4 hours, and the temperature was raised to 95 °C, where it was reacted for another 4 hours. After the reaction was complete, the mixture was purged with nitrogen to cool it down, yielding polypropylene-g-styrene powder.

[0224] 1.2 kg of polypropylene-g-styrene powder was weighed and mixed with 3000 ppm of antioxidant 1010 / 168 (mass ratio 1:1) in a high-speed mixer. The mixture was then granulated using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 400 rpm to obtain product D1. The performance parameters of the obtained product were tested, and the results are shown in Table 1.

[0225] Comparative Example 2

[0226] Polypropylene powder with the following characteristics was selected: ethylene content of comonomer 20.2 mol%, xylene-soluble content 44.2 wt%, and weight average molecular weight 35.3 × 10⁻⁶.4 The MFR (Mean Flow Rate) at 230℃ and 2.16kg load is 1.55g / 10min, and Tm = 143.6℃. 1.2kg of the above polypropylene powder was weighed and mixed with 3000ppm antioxidant 1010 / 168 (mass ratio 1:1) in a high-speed mixer. The mixture was then granulated using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 400rpm to obtain product D2. The performance parameters of the obtained product were tested, and the results are shown in Table 1.

[0227] Comparative Example 3

[0228] Weigh 1.2 kg of PP2 powder and b-PP1 in a 50:50 mass ratio, add 3000 ppm of antioxidant 1035, and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 450 rpm to obtain composite material D3. The performance parameters of the obtained product are shown in Table 1.

[0229] Figure 6 This is a microscopic image of the product in Comparative Example 3 under a 10,000x electron microscope. Figure 7 This is a microscopic image of the etched structure of the product in Comparative Example 3 under a 10,000x electron microscope; the black areas represent the rubber phase. Figure 6 and Figure 7 It can be seen that the ungrafted product includes a rubber phase but does not contain a grafted phase. The grafted product of this invention has a three-phase structure that includes both a rubber phase and a grafted phase.

[0230] Comparative Example 4

[0231] 2.0 kg of PP2 powder (after sieving to remove fine powder smaller than 40 mesh) was weighed and added to a 10 L reactor equipped with a mechanical stirrer. The reaction system was sealed, and nitrogen was used for purging to remove oxygen. 10 g of benzoyl peroxide and 566.7 g of styrene were added, and the mixture was stirred for 30 minutes. 2 L of deionized water was added, and the mixture was allowed to swell at 40 °C for 2 hours. The temperature was then raised to 90 °C, and the reaction was continued for 6 hours. After the reaction was completed, the mixture was cooled and dried under vacuum at 70 °C for 10 hours to obtain polypropylene-g-styrene powder, whose M... A =12.7%.

[0232] Weigh out 1.2 kg of polypropylene-g-styrene powder and b-PP1 in a 50:50 mass ratio, add 3000 ppm antioxidant 1035, and mix thoroughly in a high-speed mixer. Granulate the mixture using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 450 rpm to obtain composite material D4. The performance parameters of the obtained product are shown in Table 1.

[0233] Figure 8 This is a microscopic image of the product in Comparative Example 4 under a 10,000x electron microscope.

[0234] Comparative Example 5

[0235] 1.2 kg of PP1, b-PP1, and polystyrene GPPS-123 were weighed according to a mass ratio of 31:64:5, and 3000 ppm of antioxidant 1010 / 168 (mass ratio 1:1) was added and mixed thoroughly in a high-speed mixer. The mixture was then granulated using a twin-screw extruder at zone temperatures of 190-200-210-220-220-220-220-210-200℃ and a screw speed of 400 rpm to obtain composite material D5. The performance parameters of the obtained product were tested, and the results are shown in Table 1.

[0236] Figure 9 The image shows the microstructure of the product in Comparative Example 5 under a 10,000x electron microscope. Due to poor compatibility, the dispersed phase size is uneven, with obvious large-sized dispersed phases.

[0237]

[0238] Comparing the data of Example 1 and Comparative Example 1, it can be seen that when T30S powder is used as the base powder, the resulting polypropylene-g-styrene material product has an excessively high flexural modulus and poor mechanical properties, which cannot meet the processing and use requirements of insulating materials.

[0239] Comparing the data of Example 1 and Comparative Example 2, it can be seen that the mechanical properties of the product obtained by the present invention are no less than those of polypropylene prepared by the direct alloying method in the autoclave, while the electrical properties are superior.

[0240] Comparing the data of Example 1 and Comparative Example 3, it can be seen that the mechanical properties of the flexible polypropylene modified material are almost the same as those of the material without grafted phase, while the breakdown field strength and DC volume resistivity are improved, indicating that the flexible polypropylene modified material of the present invention has good electrical properties.

[0241] Comparing the data of Example 1 and Comparative Example 4, it can be seen that an excessively large graft phase D50 will lead to a decrease in the breakdown field strength and volume resistivity of the obtained flexible polypropylene modified material product, thus affecting the electrical properties of the material.

[0242] Comparing the data of Example 1 and Comparative Example 5, it can be seen that using the method of blending alkenyl functional monomer polymers results in an excessively large dispersed phase size of alkenyl functional monomers, leading to a significant decrease in the breakdown field strength and volume resistivity of the material, which greatly affects the electrical properties of the material.

[0243] In summary, as can be seen from the data in Table 1, the flexible polypropylene modified material obtained by this invention not only has excellent electrical insulation properties, but also good mechanical properties.

[0244] Furthermore, the dielectric constant data shows that the material of this invention meets the necessary conditions for insulation.

[0245] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0246] The endpoints and any values ​​of the ranges disclosed herein 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 herein.

Claims

1. A flexible polypropylene modified material, comprising a propylene-based continuous phase, a rubber phase dispersed in the propylene-based continuous phase, and a grafted phase derived from an alkenyl-containing functional monomer; wherein, Based on the total weight of the flexible polypropylene modified material, the xylene-soluble content of the flexible polypropylene modified material is 10~55 wt%; the content of structural units derived from alkenyl functional monomers in the grafted state in the flexible polypropylene modified material is 0.4~6 wt%; the flexural modulus of the flexible polypropylene modified material is 200~700 MPa; and the D50 of the grafted phase is less than 300 nm. The alkenyl-containing functional monomer is selected from at least one monomer having the structure shown in Formula 1. Formula 1 In Equation 1, R b R c R d Each is independently selected from H, substituted or unsubstituted alkyl groups; R a Selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted ester, substituted or unsubstituted carboxyl, substituted or unsubstituted cycloalkyl or heterocyclic, cyano, substituted or unsubstituted silyl; The flexible polypropylene modified material includes polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B), wherein the low-modulus polypropylene (B) is unmodified low-modulus polypropylene and / or low-modulus polypropylene grafted with alkenyl functional monomers; wherein the polypropylene (A) grafted with alkenyl functional monomers provides at least a propylene-based continuous phase and a grafted phase; the low-modulus polypropylene (B) provides a propylene-based continuous phase and a rubber phase, and optionally provides a grafted phase; Based on the total weight of the flexible polypropylene modified material, the content of the alkenyl functional monomer-grafted modified polypropylene (A) is 20-80 wt%, and the content of the low-modulus polypropylene (B) is 20-80 wt%. The low-modulus polypropylene is an ethylene-propylene copolymer with a flexural modulus of less than 300 MPa. The ethylene-propylene copolymer contains a propylene homopolymer and / or a propylene random copolymer matrix component (1), and another propylene copolymer component (2) dispersed therein. The ethylene-propylene copolymer has the following characteristics: the comonomer content is 8~25 wt%; the xylene-soluble content is 18~75 wt%; the melt flow rate at 230 °C and 2.16 kg load is 0.1~15 g / 10min; the melt temperature Tm is 120~165 °C; the flexural modulus is 10~300 MPa; the comonomer content in the xylene-soluble component is 10~50 wt%; and the intrinsic viscosity ratio of the xylene-soluble component to the low-modulus polypropylene is 0.5~3.

2. The flexible polypropylene modified material according to claim 1, wherein, The xylene-soluble content of the flexible polypropylene modified material is 15-45 wt% based on the total weight of the modified material.

3. The flexible polypropylene modified material according to claim 2, wherein, The xylene-soluble content of the flexible polypropylene modified material is 18-40 wt% based on the total weight of the modified material.

4. The flexible polypropylene modified material according to claim 1, wherein, The content of the structural units derived from alkenyl functional monomers in the grafted state in the flexible polypropylene modified material is 1~5 wt%.

5. The flexible polypropylene modified material according to claim 1, wherein, The D50 of the grafted phase is 10~250 nm.

6. The flexible polypropylene modified material according to claim 5, wherein, The D50 of the grafted phase is 50~200 nm.

7. The flexible polypropylene modified material according to claim 1, wherein, The flexural modulus of the flexible polypropylene modified material is 250~600 MPa.

8. The flexible polypropylene modified material according to claim 1, wherein, The flexible polypropylene modified material has at least one of the following characteristics: a melt flow rate of 0.5~15 g / 10min at 230 °C and 2.16 kg load; an elongation at break ≥200%; and a tensile strength greater than 5 MPa.

9. The flexible polypropylene modified material according to claim 8, wherein, The flexible polypropylene modified material has a melt flow rate of 0.6~10 g / 10min at 230℃ and 2.16 kg load.

10. The flexible polypropylene modified material according to claim 9, wherein, The flexible polypropylene modified material has a melt flow rate of 0.8~6 g / 10min at 230℃ and 2.16 kg load.

11. The flexible polypropylene modified material according to claim 8, wherein, The elongation at break of the flexible polypropylene modified material is ≥300%.

12. The flexible polypropylene modified material according to claim 8, wherein, The tensile strength of the flexible polypropylene modified material is 10~25 MPa.

13. The flexible polypropylene modified material according to claim 1, wherein, The flexible polypropylene modified material has at least one of the following characteristics: - The maximum operating temperature of the flexible polypropylene modified material is ≥90 ℃; - The breakdown field strength Eg of the flexible polypropylene modified material at 110 °C is ≥290 kV / mm; - The DC volume resistivity ρ of the flexible polypropylene modified material at 110 ℃ and 40 kV / mm field strength. vg ≥1.0×10 13 Ω m; The dielectric constant of the flexible polypropylene modified material is greater than 2.0 at 110 °C and 50 Hz.

14. The flexible polypropylene modified material according to claim 13, wherein, The maximum operating temperature of the flexible polypropylene modified material is 100~160 ℃.

15. The flexible polypropylene modified material according to claim 14, wherein, The maximum operating temperature of the flexible polypropylene modified material is 110~140 ℃.

16. The flexible polypropylene modified material according to claim 13, wherein, The breakdown field strength Eg of the flexible polypropylene modified material at 110 °C is 300~800 kV / mm.

17. The flexible polypropylene modified material according to claim 16, wherein, The breakdown field strength Eg of the flexible polypropylene modified material at 110 °C is 310~750 kV / mm.

18. The flexible polypropylene modified material according to claim 13, wherein, The flexible polypropylene modified material has a DC volume resistivity ρ at 110 °C and a field strength of 40 kV / mm. vg 1.5×10 13 Ω m~1.0×10 20 Ω m.

19. The flexible polypropylene modified material according to claim 13, wherein, The dielectric constant of the flexible polypropylene modified material is 2.1~2.5 at 110 °C and 50 Hz.

20. The flexible polypropylene modified material according to claim 1, wherein, R b R c R d Each is independently selected from H, substituted or unsubstituted C1-C6 alkyl groups; R a Selected from substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C1-C 20 Alkoxy, substituted or unsubstituted C6-C 20 aryl, substituted or unsubstituted C1-C 20 Ester group, substituted or unsubstituted C1-C 20 Carboxyl, substituted or unsubstituted C3-C 20 Cycloalkyl or heterocyclic, cyano, substituted or unsubstituted C3-C 20 Silyl group; the substituted group is halogen, hydroxyl, amino, C1-C 12 Alkyl, C3-C6 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 Acyloxy group.

21. The flexible polypropylene modified material according to claim 20, wherein, R b R c R d Each is independently selected from H, substituted or unsubstituted C1-C6 alkyl groups; R a Selected from the groups shown in Formula 2, Formula 3, Formula 4, Formula 5, Formula 6, combinations of the groups shown in Formula 6 and Formula 7, and heterocyclic groups; Formula 2 In Equation 2, R 4 -R 8 Each is independently selected from H, halogen, hydroxyl, amino, phosphate group, sulfonic acid group, substituted or unsubstituted C1-C. 12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; Formula 3 In Equation 3, R4-R 10 Each is independently selected from H, halogen, hydroxyl, amino, phosphate group, sulfonic acid group, substituted or unsubstituted C1-C. 12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; Formula 4 In Equation 4, R4'-R 10 Each group is independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C1-C. 12 Alkyl, substituted or unsubstituted C3-C 12 cycloalkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 ester group, substituted or unsubstituted C1-C 12 The substituted amino group, wherein the substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C1-C 12 alkoxy groups, C1-C 12 ester group, C1-C 12 The amino group; Formula 5 In Equation 5, R', R'', and R''' are each independently selected from substituted or unsubstituted C1-C. 12 Straight-chain alkyl, substituted or unsubstituted C3-C 12 Branched alkyl, substituted or unsubstituted C1-C 12 alkoxy, substituted or unsubstituted C1-C 12 Acyloxy group; Formula 6 Formula 7 In Equation 6, R m Selected from the following groups, substituted or unsubstituted: C1-C 20 Straight-chain alkyl, C3-C 20 Branched alkyl, C3-C 12 cycloalkyl, C3-C 12 Epoxyalkyl, C3-C 12 Epoxyalkylalkyl, wherein the substituted group is selected from at least one of halogen, amino and hydroxyl groups; The heterocyclic group is selected from imidazole, pyrazol, carbazole, pyrrolidone, pyridinyl, piperidinyl, caprolactam, pyrazinyl, thiazolyl, purine, morpholino, and oxazolino.

22. The flexible polypropylene modified material according to claim 21, wherein, In Equation 2, R 4 -R 8 Each is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy.

23. The flexible polypropylene modified material according to claim 21, wherein, In Equation 3, R4-R 10 Each of the groups is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, wherein the substituted group is selected from halogen, hydroxyl, amino, C1-C6 alkyl, C1-C6 alkoxy.

24. The flexible polypropylene modified material according to claim 21, wherein, In Equation 4, R4'-R 10 Each of the groups is independently selected from H, halogen, hydroxyl, amino, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, wherein the substituted group is selected from halogen, hydroxyl, amino, C1-C6 alkyl, C1-C6 alkoxy.

25. The flexible polypropylene modified material according to claim 1, wherein, The alkenyl-containing functional monomer is an aromatic olefin monomer, wherein the aromatic olefin monomer is selected from at least one of styrene, α-methylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, monosubstituted or polysubstituted styrene, monosubstituted or polysubstituted α-methylstyrene, monosubstituted or polysubstituted 1-vinylnaphthalene, and monosubstituted or polysubstituted 2-vinylnaphthalene; and / or The alkenyl-containing functional monomer is an alkenyl-containing silane monomer, wherein the alkenyl-containing silane monomer is selected from at least one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltritert-butoxysilane, vinyltriacetoxysilane, methylvinyldimethoxysilane, ethylvinyldiethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, allyltriisopropoxysilane, vinyltris(β-methoxyethoxy)silane, allyltris(β-methoxyethoxy)silane, allyltritert-butoxysilane, allyltriacetoxysilane, methylallyldimethoxysilane, and ethylallyldiethoxysilane; and / or The alkenyl-containing functional monomer is an acrylate monomer or an optional acrylic monomer.

26. The flexible polypropylene modified material according to claim 25, wherein, The substituted group is selected from at least one of halogen, hydroxyl, amino, phosphate, sulfonic acid, C1-C8 straight-chain alkyl, C3-C8 branched alkyl or cycloalkyl, C1-C6 straight-chain alkoxy, C3-C8 branched alkoxy or cycloalkoxy, C1-C8 straight-chain ester, C3-C8 branched ester or cycloester, C1-C8 straight-chain amino, and C3-C8 branched amino or cycloamino.

27. The flexible polypropylene modified material according to claim 25, wherein, The aromatic olefin monomer is selected from at least one of styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, and 4-methylstyrene.

28. The flexible polypropylene modified material according to claim 25, wherein, The acrylate monomers are selected from at least one of methyl methacrylate, sec-butyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isooctyl methacrylate, dodecyl methacrylate, coconut oil ester methacrylate, octadecyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, and glycidyl methacrylate; the acrylic monomers are selected from at least one of acrylic acid, methacrylic acid, and 2-ethylacrylic acid.

29. The flexible polypropylene modified material according to claim 25, wherein, The molar ratio of structural units derived from acrylate monomers to structural units derived from acrylic monomers is 1:0~2.

30. The flexible polypropylene modified material according to claim 29, wherein, The molar ratio of structural units derived from acrylate monomers to structural units derived from acrylic monomers is 1:0.125~1.

31. The flexible polypropylene modified material according to claim 1, wherein, Based on the total weight of the flexible polypropylene modified material, the content of the polypropylene (A) grafted with alkenyl functional monomers is 30-70 wt%, and the content of the low-modulus polypropylene (B) is 30-70 wt%.

32. The flexible polypropylene modified material according to claim 31, wherein, Based on the total weight of the flexible polypropylene modified material, the content of the polypropylene (A) grafted with alkenyl functional monomers is 35-65 wt%, and the content of the low-modulus polypropylene (B) is 35-65 wt%.

33. The flexible polypropylene modified material according to claim 1, wherein, The flexible polypropylene modified material is prepared by blending polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B).

34. The flexible polypropylene modified material according to claim 1, wherein, The alkenyl functional monomer-grafted modified polypropylene (A) comprises structural units derived from homopolymer or copolymer polypropylene and structural units derived from alkenyl functional monomers; based on the weight of the alkenyl functional monomer-grafted modified polypropylene (A), the content of structural units derived from alkenyl functional monomers and in the grafted state in the alkenyl functional monomer-grafted modified polypropylene (A) is 0.5~20 wt.

35. The flexible polypropylene modified material according to claim 34, wherein, Based on the weight of the polypropylene (A) grafted with alkenyl functional monomers, the content of structural units derived from alkenyl functional monomers and in the grafted state in the polypropylene (A) grafted with alkenyl functional monomers is 1~15 wt.

36. The flexible polypropylene modified material according to claim 34, wherein, The homopolymer or copolymer polypropylene has at least one of the following characteristics: comonomer content of 0-15 mol%; melt flow rate of 1-10 g / 10 min at 230 °C and 2.16 kg load; melt temperature Tm of 110-180 °C; and weight-average molecular weight of 20 × 10⁻⁶. 4 ~50×10 4 g / mol; flexural modulus of 500~2000 MPa; elongation at break ≥200%; tensile strength greater than 5 MPa.

37. The flexible polypropylene modified material according to claim 36, wherein, The homopolymer or copolymer polypropylene contains 0-12 mol of comonomer.

38. The flexible polypropylene modified material according to claim 37, wherein, The homopolymer or copolymer polypropylene contains 0-8 mol of comonomer.

39. The flexible polypropylene modified material according to claim 36, wherein, The homopolymer or copolymer polypropylene has a melt flow rate of 2~5 g / 10 min at 230°C and 2.16 kg load.

40. The flexible polypropylene modified material according to claim 36, wherein, The melting temperature Tm of the homopolymer or copolymer polypropylene is 120~170 ℃.

41. The flexible polypropylene modified material according to claim 36, wherein, The flexural modulus of the homopolymer or copolymer polypropylene is 600~1700 MPa.

42. The flexible polypropylene modified material according to claim 36, wherein, The homopolymer or copolymer polypropylene has an elongation at break of ≥300%.

43. The flexible polypropylene modified material according to claim 36, wherein, The tensile strength of the homopolymer or copolymer polypropylene is 10~40 MPa.

44. The flexible polypropylene modified material according to claim 34, wherein, The comonomer of the copolymerized polypropylene is selected from at least one of the C2-C8 α-olefins other than propylene; the comonomer content is 0.1~15 mol based on the total molar amount of the monomers.

45. The flexible polypropylene modified material according to claim 44, wherein, The comonomer of the copolymerized polypropylene is selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

46. ​​The flexible polypropylene modified material according to claim 45, wherein, The comonomer of the copolymerized polypropylene is ethylene and / or 1-butene.

47. The flexible polypropylene modified material according to claim 44, wherein, The comonomer content is 0.1~12 mol based on the total molar amount of monomers.

48. The flexible polypropylene modified material according to claim 47, wherein, The comonomer content is 0.1~8 mol based on the total molar amount of monomers.

49. The flexible polypropylene modified material according to claim 1, wherein, The low-modulus polypropylene has an island structure or a bicontinuous structure.

50. The flexible polypropylene modified material according to claim 1, wherein, The low-modulus polypropylene is prepared in situ within the reactor.

51. The flexible polypropylene modified material according to claim 1, wherein, The comonomer content of the low-modulus polypropylene is 10~22 wt%.

52. The flexible polypropylene modified material according to claim 1, wherein, The xylene-soluble content of the low-modulus polypropylene is 30-70 wt%.

53. The flexible polypropylene modified material according to claim 52, wherein, The xylene-soluble content of the low-modulus polypropylene is 30-67 wt%.

54. The flexible polypropylene modified material according to claim 1, wherein, The low-modulus polypropylene has a melt flow rate of 0.2~7 g / 10min at 230 °C and 2.16 kg load.

55. The flexible polypropylene modified material according to claim 1, wherein, The melting temperature Tm of the low-modulus polypropylene is 125~150 ℃.

56. The flexible polypropylene modified material according to claim 1, wherein, The flexural modulus of the low-modulus polypropylene is 15~250 MPa.

57. The flexible polypropylene modified material according to claim 1, wherein, The xylene-soluble copolymer content of the low-modulus polypropylene is 20-35 wt%.

58. The flexible polypropylene modified material according to claim 1, wherein, The ratio of xylene-soluble component to intrinsic viscosity of the low-modulus polypropylene is 0.8 to 1.

3.

59. The flexible polypropylene modified material according to claim 1, wherein, Based on the weight of the low-modulus polypropylene grafted with alkenyl functional monomers, the content of structural units derived from alkenyl functional monomers and in the grafted state in the low-modulus polypropylene grafted with alkenyl functional monomers is 0.1~5 wt%.

60. The flexible polypropylene modified material according to claim 59, wherein, Based on the weight of the low-modulus polypropylene grafted with alkenyl functional monomers, the content of structural units derived from alkenyl functional monomers and in the grafted state in the low-modulus polypropylene grafted with alkenyl functional monomers is 0.2~2.5 wt%.

61. A method for preparing the flexible polypropylene modified material according to any one of claims 1-60, comprising the following steps: The flexible polypropylene modified material is prepared by blending polypropylene (A) grafted with alkenyl functional monomers and low-modulus polypropylene (B), wherein the low-modulus polypropylene (B) is unmodified low-modulus polypropylene and / or low-modulus polypropylene grafted with alkenyl functional monomers. Based on the total weight of the flexible polypropylene modified material, the amount of the polypropylene (A) grafted with the alkenyl functional monomer is 20-80 wt%, and the amount of the low-modulus polypropylene (B) is 20-80 wt%.

62. The preparation method according to claim 61, wherein, Based on the total weight of the flexible polypropylene modified material, the amount of the polypropylene (A) grafted with alkenyl functional monomers is 30-70 wt%, and the amount of the low-modulus polypropylene (B) is 30-70 wt%.

63. The preparation method according to claim 62, wherein, Based on the total weight of the flexible polypropylene modified material, the amount of the polypropylene (A) grafted with the alkenyl functional monomer is 35-65 wt%, and the amount of the low-modulus polypropylene (B) is 35-65 wt%.

64. The preparation method according to claim 61, wherein, The preparation method includes the following steps: S1: In the presence of an inert gas, a reaction mixture A, including homopolymer or copolymer polypropylene and an alkenyl functional monomer, is subjected to a grafting reaction to obtain polypropylene grafted with an alkenyl functional monomer. Optionally, in the presence of an inert gas, a reaction mixture B comprising low-modulus polypropylene and an alkenyl functional monomer is subjected to a grafting reaction to obtain low-modulus polypropylene grafted with an alkenyl functional monomer. S2: The polypropylene grafted with the alkenyl functional monomer is mixed with unmodified low-modulus polypropylene and / or the low-modulus polypropylene grafted with the alkenyl functional monomer, as well as optional additives, and then extruded and granulated to obtain the flexible polypropylene modified material.

65. The preparation method according to claim 64, wherein, The reaction mixture A and the reaction mixture B each independently comprise a free radical initiator; the free radical initiator is selected from peroxide free radical initiators and / or azo free radical initiators.

66. The preparation method according to claim 65, wherein, The peroxide radical initiator is selected from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, tert-butyl peroxide, diisopropyl peroxide, tert-butyl peroxide, and dicyclohexyl peroxide; the azo radical initiator is azobisisobutyronitrile and / or azobisisoheptanenitrile.

67. The preparation method according to claim 65, wherein, The mass ratio of the free radical initiator to the alkenyl-containing functional monomer is 0.01~10:

100.

68. The preparation method according to claim 67, wherein, The mass ratio of the free radical initiator to the alkenyl-containing functional monomer is 0.5~5:

100.

69. The preparation method according to claim 64, wherein, The mass ratio of the alkenyl-containing functional monomer to the homopolymer or copolymer polypropylene is 0.5~35:100; the mass ratio of the alkenyl-containing functional monomer to the low-modulus polypropylene is 0.1~20:

100.

70. The preparation method according to claim 69, wherein, The mass ratio of the alkenyl-containing functional monomer to the homopolymer or copolymer polypropylene is 2~30:

100.

71. The preparation method according to claim 70, wherein, The mass ratio of the alkenyl-containing functional monomer to the homopolymer or copolymer polypropylene is 5~25:

100.

72. The preparation method according to claim 69, wherein, The mass ratio of the alkenyl-containing functional monomer to the low-modulus polypropylene is 0.2~10:

100.

73. The preparation method according to claim 72, wherein, The mass ratio of the alkenyl-containing functional monomer to the low-modulus polypropylene is 0.5~5:

100.

74. The preparation method according to claim 64, wherein, The grafting reaction is carried out at a temperature of 30~130 ℃ for 0.5~10 hours.

75. The preparation method according to claim 74, wherein, The grafting reaction is carried out at a temperature of 60~120℃.

76. The preparation method according to claim 74, wherein, The grafting reaction takes 1 to 6 hours.

77. The preparation method according to claim 64, wherein, The reaction mixture A and the reaction mixture B each independently comprise at least one of the following components: a dispersant, an interface agent, and an organic solvent, wherein the mass content of the dispersant is 50-300% of the mass of homopolymer or copolymer polypropylene / low modulus polypropylene, the mass content of the interface agent is 1-30% of the mass of homopolymer or copolymer polypropylene / low modulus polypropylene, and the mass content of the organic solvent is 1-35% of the mass of homopolymer or copolymer polypropylene / low modulus polypropylene.

78. The preparation method according to claim 77, wherein, The preparation method includes the following steps: a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas; b. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix; c. Optionally add an interfacial agent and optionally swell the reaction system; d. Optionally add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction; e. After the reaction is complete, the mixture is optionally filtered and dried to obtain polypropylene grafted with alkenyl functional monomers. f. The polypropylene grafted with the alkenyl functional monomer is mixed with ungrafted and / or grafted low-modulus polypropylene and optional additives, and then melt-extruded and granulated to obtain the flexible polypropylene modified material. The method for preparing the grafted low-modulus polypropylene includes the following steps: i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas; ii. Add the free radical initiator and the alkenyl-containing functional monomer to the closed reactor and stir to mix; iii. Optionally add an interfacial agent and optionally swell the reaction system; iv. Optionally, add a dispersant to raise the temperature of the reaction system to the grafting reaction temperature and carry out the grafting reaction; v. After the reaction is complete, the mixture is optionally filtered and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

79. The preparation method according to claim 77, wherein, The preparation method includes the following steps: a. Place homopolymer or copolymer polypropylene in a closed reactor and replace it with an inert gas; b. Mix the organic solvent and the free radical initiator, and add them to the closed reactor; c. Remove the organic solvent; d. Add an alkenyl-containing functional monomer, optionally add an interfacial agent, and optionally swell the reaction system; e. Optionally add a dispersant, heat the reaction system to the grafting reaction temperature, and carry out the grafting reaction; f. After the reaction is complete, the mixture is optionally filtered and dried to obtain polypropylene grafted with alkenyl functional monomers. g. The polypropylene grafted with the alkenyl functional monomer is weighed and mixed with ungrafted and / or grafted low-modulus polypropylene and optional additives in proportion, and then melt-extruded and granulated to obtain the flexible polypropylene modified material. The method for preparing the grafted low-modulus polypropylene includes the following steps: i. Place the low-modulus polypropylene in a closed reactor and replace it with an inert gas; ii. Mix the organic solvent and the free radical initiator and add them to the closed reactor; iii. Remove the organic solvent; iv. Add an alkenyl-containing functional monomer, optionally add an interfacial agent, and optionally swell the reaction system; v. Optionally add a dispersant, raise the temperature of the reaction system to the grafting reaction temperature, and carry out the grafting reaction; vi. After the reaction is complete, the mixture is optionally filtered and dried to obtain low-modulus polypropylene grafted with alkenyl functional monomers.

80. The application of the flexible polypropylene modified material according to any one of claims 1-60.

81. The application according to claim 80, wherein, The flexible polypropylene modified material is used in the cable industry.

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