Preparation method of polypropylene cable insulation resin and polypropylene cable insulation resin

Abstract

The invention discloses a preparation method of polypropylene cable insulation resin and the polypropylene cable insulation resin, belongs to the technical field of cable insulation materials, and solves the problems of poor toughness, poor electrical insulation performance and low melt strength of existing polypropylene. Comprising the following steps: adding a main catalyst, a cocatalyst system, a functional additive, propylene and hydrogen into a first reactor, and carrying out gas-phase polymerization reaction to obtain first polypropylene powder; the first polypropylene powder stays for 0.1-2 hours in the first reactor and then is conveyed to a second reactor, and the first polypropylene powder, propylene, ethylene and hydrogen in the second reactor are subjected to a gas-phase polymerization reaction to obtain the impact-resistant co-polypropylene powder. And the impact-resistant co-polypropylene powder stays for 0.1-2 hours in the second reactor and then is conveyed into a deactivating system for deactivating treatment and devolatilization treatment. And conveying the impact-resistant co-polypropylene powder to an extrusion granulation system, carrying out melt blending on the impact-resistant co-polypropylene powder and a resin additive, and carrying out extrusion granulation. The toughness, the electrical insulation performance and the melt strength of the polypropylene cable insulation resin can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of cable insulation materials, and in particular to a preparation method of a polypropylene cable insulation resin and the polypropylene cable insulation resin. Background Art

[0002] At present, the main insulating material used in power cables is cross-linked polyethylene, which is obtained by cross-linking low-density polyethylene. Although it has excellent mechanical properties, dielectric properties and heat resistance, it has the following shortcomings: (1) The cross-linking process consumes a lot of energy and produces toxic by-products such as methane, cumyl alcohol, acetophenone and methyl styrene; (2) The cable insulation layer is prone to degradation during cable operation; (3) The operating temperature cannot exceed 70°C, and the transmission capacity is limited; (4) It is non-degradable and non-recyclable after use, resulting in waste of resources and environmental pollution.

[0003] Compared with cross-linked polyethylene, polypropylene has become a new generation of environmentally friendly cables that can replace cross-linked polyethylene due to its high rigidity, high melting point, high operating temperature, strong insulation performance, low processing energy consumption and recyclability. However, due to the high modulus, poor toughness and low melt strength of ordinary polypropylene, and the significantly reduced insulation performance of ordinary impact-resistant polypropylene due to the introduction of EPDM, ordinary polypropylene cannot meet the requirements of long-distance continuous and stable extrusion of insulated cables and their electrical insulation performance. Therefore, it is necessary to further improve the polypropylene cable insulation material to improve its toughness, electrical insulation performance and melt processing performance. Summary of the invention

[0004] The embodiments of the present application provide a method for preparing a polypropylene cable insulating resin and a polypropylene cable insulating resin, thereby solving the problems of poor toughness, poor electrical insulation performance and low melt strength of existing polypropylene.

[0005] In a first aspect, an embodiment of the present invention provides a method for preparing a polypropylene cable insulating resin, the method comprising:

[0006] Adding a main catalyst, a co-catalyst system, a functional additive, propylene and hydrogen into a first reactor for gas phase polymerization to obtain a first polypropylene powder, wherein the melt flow rate of the first polypropylene powder is between 0.1 g / 10 min and 50 g / 10 min; the reaction conditions of the first reactor are: a hydrogen concentration of between 0.01 mol% and 15 mol%, a propylene concentration of between 75 mol% and 99.8 mol%, a reaction pressure of between 1 MPa and 3 MPa, and a reaction temperature of between 40° C. and 90° C.;

[0007] After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock and subjected to gas phase polymerization reaction with propylene, ethylene and hydrogen added to the second reactor to obtain impact copolymer polypropylene powder, wherein the melt flow rate of the impact copolymer polypropylene powder is between 0.1g / 10min and 10g / 10min; the reaction conditions of the second reactor are: hydrogen concentration is between 0.01mol% and 10mol%, ethylene concentration is between 0.01mol% and 50mol%, propylene concentration is between 40mol% and 99.8mol%, reaction pressure is between 1Mpa and 3Mpa, and reaction temperature is between 40°C and 90°C;

[0008] The impact copolymer polypropylene powder stays in the second reactor for 0.1h to 2h and then is transported to the deactivation system for deactivation and devolatilization treatment;

[0009] After deactivation and devolatilization, the impact-resistant copolymerized polypropylene powder is transported to an extrusion granulation system for melt blending with resin additives and extrusion granulation to obtain polypropylene cable insulation resin.

[0010] In combination with the first aspect, in a possible implementation, the dosage of the functional additive is 1 kg / h to 20 kg / h; the functional additive is selected from the general formula R 1 mSiXn(OR 2 )k organosilane, wherein R 1 is a C2-C20 hydrocarbon group and R 1 The end of the olefin contains an α-olefin double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen, R 2 It is a C1-C20 straight chain, branched or isomerized alkyl group, m and n are both integers between 1 and 3, k is an integer between 0 and 2, and m+n+k=4.

[0011] In combination with the first aspect, in a possible implementation, the main catalyst is selected from a Ziegler-Natta catalyst, and its usage is 0.5 Kg / h to 10 Kg / h.

[0012] In combination with the first aspect, in a possible implementation, the co-catalyst system includes alkyl aluminum and an external electron donor, the amount of the alkyl aluminum is 0.1 Kg / h to 10 Kg / h, and the amount of the external electron donor is 0.1 Kg / h to 10 Kg / h.

[0013] In combination with the first aspect, in a possible implementation, the reaction conditions of the first reactor are: hydrogen concentration is between 0.01 mol% and 10 mol%, propylene concentration is between 85 mol% and 99.8 mol%, reaction pressure is between 2 MPa and 2.5 MPa, and reaction temperature is between 55°C and 70°C; the reaction conditions of the second reactor are: hydrogen concentration is between 0.01 mol% and 5 mol%, ethylene concentration is between 10 mol% and 40 mol%, propylene concentration is between 55 mol% and 89.9 mol%, reaction pressure is between 2 MPa and 2.5 MPa, and reaction temperature is between 55°C and 70°C.

[0014] In combination with the first aspect, in a possible implementation, the impact-resistant copolymer polypropylene powder is an ethylene-propylene impact-resistant copolymer with a multi-branched structure; calculated by mass fraction, the content of propylene structural units in the ethylene-propylene impact-resistant copolymer is 70wt% to 99wt%, and the content of ethylene structural units is 1wt% to 30wt%.

[0015] In combination with the first aspect, in a possible implementation, the polypropylene cable insulation resin includes impact-resistant copolymer polypropylene powder and a resin additive; by mass fraction, the content of the impact-resistant copolymer polypropylene powder is 99.5wt% to 99.9wt%, and the content of the resin additive is 0.1wt% to 0.5wt%.

[0016] In a second aspect, an embodiment of the present invention provides a polypropylene cable insulating resin, which is prepared by the above-mentioned method for preparing the polypropylene cable insulating resin.

[0017] In combination with the second aspect, in a possible implementation manner, the melt strength of the polypropylene cable insulation resin is between 5 cN and 30 cN.

[0018] In combination with the second aspect, in a possible implementation manner, the dielectric strength of the polypropylene cable insulation resin is ≥35 kV / mm.

[0019] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0020] The embodiment of the present invention provides a method for preparing a polypropylene cable insulating resin, the method comprising: adding a main catalyst, a co-catalyst system, a functional additive, propylene and hydrogen to a first reactor for gas phase polymerization to obtain a first polypropylene powder, the melt flow rate of the first polypropylene powder being between 0.1g / 10min and 50g / 10min. The reaction conditions of the first reactor are: a hydrogen concentration between 0.01mol% and 15mol%, a propylene concentration between 75mol% and 99.8mol%, a reaction pressure between 1Mpa and 3Mpa, and a reaction temperature between 40°C and 90°C. After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock, and gas phase polymerization is carried out with propylene, ethylene and hydrogen added to the second reactor to obtain an impact copolymerized polypropylene powder, the melt flow rate of the impact copolymerized polypropylene powder being between 0.1g / 10min and 10g / 10min. The reaction conditions of the second reactor are: hydrogen concentration between 0.01mol% and 10mol%, ethylene concentration between 0.01mol% and 50mol%, propylene concentration between 40mol% and 99.8mol%, reaction pressure between 1Mpa and 3Mpa, and reaction temperature between 40℃ and 90℃. After the impact copolymer polypropylene powder stays in the second reactor for 0.1h to 2h, it is transported to the deactivation system for deactivation and devolatilization. After deactivation and devolatilization, the impact copolymer polypropylene powder is transported to the extrusion granulation system for melt blending and extrusion granulation with resin additives to obtain polypropylene cable insulation resin. The embodiment of the present invention achieves the production of impact copolymer polypropylene powder with high melt strength and tensile strain characteristics by optimizing and controlling the reaction conditions of the first reactor and the second reactor. After deactivation and devolatilization, the impact copolymer polypropylene powder is melt blended and extruded granulated with resin additives to obtain a polypropylene cable insulation resin with a melt flow rate of 0.1g / 10min to 5g / 10min. At the same time, the present invention adjusts the polymer molecular chain structure, crystal size and processing performance by controlling the addition amount of hydrogen, functional additives and resin additives, so that the melt index, melt strength, volume resistivity, dielectric strength and impact strength of the final polypropylene cable insulating resin meet the use requirements of the insulating cable, that is, the present application can improve the toughness, electrical insulation performance and melt strength of the polypropylene cable insulating resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 A production flow chart of a method for preparing a polypropylene cable insulating resin provided in an embodiment of the present application;

[0023] Figure 2 The melt strength test curve of the polypropylene cable insulation resin provided in the embodiment of the present application;

[0024] Figure 3 The tensile rheological properties test of the polypropylene cable insulation resin provided in the embodiment of the present application;

[0025] Figure 4 Scanning electron microscope analysis of the polypropylene cable insulation resin provided in the embodiments of the present application. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the embodiments of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present invention. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to the specific circumstances.

[0028] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a polypropylene cable insulating resin, the method comprising:

[0029] Step 101: Add the main catalyst, the co-catalyst system, the functional additive, propylene and hydrogen into the first reactor for gas phase polymerization to obtain the first polypropylene powder, wherein the melt flow rate of the first polypropylene powder is between 0.1 g / 10 min and 50 g / 10 min. The reaction conditions of the first reactor are: the hydrogen concentration is between 0.01 mol% and 15 mol%, the propylene concentration is between 75 mol% and 99.8 mol%, the reaction pressure is between 1 MPa and 3 MPa, and the reaction temperature is between 40°C and 90°C.

[0030] Step 102: After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock and subjected to gas phase polymerization reaction with propylene, ethylene and hydrogen added to the second reactor to obtain impact copolymer polypropylene powder, and the melt flow rate of the impact copolymer polypropylene powder is between 0.1g / 10min and 10g / 10min. The reaction conditions of the second reactor are: hydrogen concentration between 0.01mol% and 10mol%, ethylene concentration between 0.01mol% and 50mol%, propylene concentration between 40mol% and 99.8mol%, reaction pressure between 1Mpa and 3Mpa, and reaction temperature between 40℃ and 90℃. In practical applications, the main catalyst, co-catalyst system and functional additives will enter the second reactor together with the first polypropylene powder to react.

[0031] Step 103: the impact copolymer polypropylene powder stays in the second reactor for 0.1 h to 2 h and then is transported to a deactivation system for deactivation and devolatilization treatment.

[0032] Step 104: After deactivation and devolatilization, the impact copolymer polypropylene powder is transported to an extrusion granulation system for melt blending with resin additives and extrusion granulation to obtain polypropylene cable insulation resin. Polypropylene cable insulation resin is produced by polymerizing in a gas phase fluidized bed reactor (e.g., two gas phase fluidized bed reactors in series in INEOS), and then melt blending with corresponding resin additives and extrusion granulation. Specifically, wet nitrogen is used to remove residual activity in the impact copolymer polypropylene powder.

[0033] The invention uses propylene as the main raw material, ethylene as the comonomer, and hydrogen as the molecular weight regulator, and changes the original resin molecular chain structure by introducing functional additives to polymerize and generate impact-resistant copolymerized polypropylene powder. The impact-resistant copolymerized polypropylene powder is melt-blended with a resin additive after deactivation and devolatilization treatment, and extruded into granules to obtain a polypropylene cable insulating resin.

[0034] The embodiment of the present invention provides a method for preparing a polypropylene cable insulating resin, the method comprising: adding a main catalyst, a co-catalyst system, a functional additive, propylene and hydrogen to a first reactor for gas phase polymerization to obtain a first polypropylene powder, the melt flow rate of the first polypropylene powder being between 0.1g / 10min and 50g / 10min. The reaction conditions of the first reactor are: a hydrogen concentration between 0.01mol% and 15mol%, a propylene concentration between 75mol% and 99.8mol%, a reaction pressure between 1Mpa and 3Mpa, and a reaction temperature between 40°C and 90°C. After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock, and gas phase polymerization is carried out with propylene, ethylene and hydrogen added to the second reactor to obtain an impact copolymerized polypropylene powder, the melt flow rate of the impact copolymerized polypropylene powder being between 0.1g / 10min and 10g / 10min. The reaction conditions of the second reactor are: hydrogen concentration between 0.01mol% and 10mol%, ethylene concentration between 0.01mol% and 50mol%, propylene concentration between 40mol% and 99.8mol%, reaction pressure between 1Mpa and 3Mpa, and reaction temperature between 40℃ and 90℃. After the impact copolymer polypropylene powder stays in the second reactor for 0.1h to 2h, it is transported to the deactivation system for deactivation and devolatilization. After deactivation and devolatilization, the impact copolymer polypropylene powder is transported to the extrusion granulation system for melt blending and extrusion granulation with resin additives to obtain polypropylene cable insulation resin. The embodiment of the present invention achieves the production of impact copolymer polypropylene powder with high melt strength and tensile strain characteristics by optimizing and controlling the reaction conditions of the first reactor and the second reactor. After deactivation and devolatilization, the impact copolymer polypropylene powder is melt blended and extruded granulated with resin additives to obtain a polypropylene cable insulation resin with a melt flow rate of 0.1g / 10min to 5g / 10min. At the same time, the present invention adjusts the polymer molecular chain structure, crystal size and processing performance by controlling the addition amount of hydrogen, functional additives and resin additives, so that the melt index, melt strength, volume resistivity, dielectric strength and impact strength of the final polypropylene cable insulating resin meet the use requirements of the insulating cable, that is, the present application can improve the toughness, electrical insulation performance and melt strength of the polypropylene cable insulating resin.

[0035] In the embodiment of the present application, the dosage of the functional additive is 1 kg / h to 20 kg / h. The functional additive is selected from the general formula R 1 mSiXn(OR 2 )k organosilane (e.g., 7-octenyltrichlorosilane), wherein R 1 is a C2-C20 hydrocarbon group and R 1The end of the olefin contains an α-olefin double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen, R 2 It is a C1-C20 straight chain, branched or isomerized alkyl group, m and n are both integers between 1 and 3, k is an integer between 0 and 2, and m+n+k=4.

[0036] Specifically, the main catalyst is selected from Ziegler-Natta catalyst, and its dosage is 0.5Kg / h to 10Kg / h. Ziegler-Natta catalyst, translated into Chinese as Ziegler-Natta catalyst, is an important directional polymerization catalyst. Specifically, the main catalyst is a titanium catalyst.

[0037] In the embodiment of the present application, the co-catalyst system includes an alkyl aluminum and an external electron donor, the amount of the alkyl aluminum is 0.1 Kg / h to 10 Kg / h, and the amount of the external electron donor is 0.1 Kg / h to 10 Kg / h. Preferably, the alkyl aluminum is triethyl aluminum. Specifically, the external electron donor is selected from at least one of carboxylic acids, organophosphorus compounds and organosilicon compounds. More specifically, the external electron donor is selected from at least one of diisobutyldimethoxysilane (DIBDMS), diisopropyldimethoxysilane (DIPDMS), isobutylisopropyldimethoxysilane (IBMDMS) and tetraethyl silicate (TEOS).

[0038] Specifically, the reaction conditions of the first reactor are: hydrogen concentration between 0.01 mol% and 10 mol%, propylene concentration between 85 mol% and 99.8 mol%, reaction pressure between 2 MPa and 2.5 MPa, and reaction temperature between 55°C and 70°C; the reaction conditions of the second reactor are: hydrogen concentration between 0.01 mol% and 5 mol%, ethylene concentration between 10 mol% and 40 mol%, propylene concentration between 55 mol% and 89.9 mol%, reaction pressure between 2 MPa and 2.5 MPa, and reaction temperature between 55°C and 70°C.

[0039] Specifically, the impact-resistant copolymer polypropylene powder is an ethylene-propylene impact-resistant copolymer with a multi-branched structure. In terms of mass fraction, the content of propylene structural units in the ethylene-propylene impact-resistant copolymer is 70wt% to 99wt%, and the content of ethylene structural units is 1wt% to 30wt%.

[0040] In the embodiment of the present application, the polypropylene cable insulation resin includes impact-resistant copolymerized polypropylene powder and resin additives. According to the mass fraction, the content of the impact-resistant copolymerized polypropylene powder is 99.5wt% to 99.9wt%, and the content of the resin additive is 0.1wt% to 0.5wt%. The resin additive includes hindered phenol antioxidants, phosphite antioxidants, thioester antioxidants, acid scavengers (such as hydrotalcite, calcium stearate, zinc oxide) and nucleating agents. Specifically, the specific ratio of the resin additive is: antioxidant (70wt% to 90wt%), acid scavenger (5wt% to 15wt%), and nucleating agent (5wt% to 15wt%).

[0041] The embodiment of the present invention realizes the production of impact-resistant copolymerized polypropylene powder with high melt strength and tensile strain characteristics by optimizing and controlling the reaction conditions of the first reactor and the second reactor. The impact-resistant copolymerized polypropylene powder is melt-blended and extruded and granulated with a resin additive after deactivation and devolatilization treatment to obtain a polypropylene cable insulating resin with a melt flow rate of 0.1g / 10min to 5g / 10min. At the same time, the present invention adjusts the polymer molecular chain structure, crystal size and processing performance by controlling the addition amount of hydrogen, functional additives and resin additives, so that the melt index, melt strength, volume resistivity, dielectric strength and impact strength of the final polypropylene cable insulating resin meet the use requirements of the insulating cable, that is, the present application can improve the toughness, electrical insulation performance and melt strength of the polypropylene cable insulating resin.

[0042] In addition, the present application adopts the INEOS gas-phase fluidized bed polymerization process, uses a Ziegler-Natta titanium catalyst and a functional additive that can achieve a multi-branched structure of the polypropylene molecular chain, and is achieved by operating two reactors in series. The production process is simple to operate and can be produced over a long period of time.

[0043] At the same time, the present invention controls the product molecular weight by adjusting the amount of hydrogen added, introduces functional additives to adjust the polymer molecular structure and crystal size, and generates an ethylene propylene rubber component in the second reactor to improve the impact toughness of the polymer, so as to meet the long-distance stable extrusion processing and application requirements of the insulated cable.

[0044] The embodiment of the present invention provides a polypropylene cable insulating resin, which is prepared by the above-mentioned preparation method of the polypropylene cable insulating resin.

[0045] Specifically, the melt strength of the polypropylene cable insulation resin is between 5 cN and 30 cN.

[0046] Specifically, the dielectric strength of polypropylene cable insulation resin is ≥35kV / mm.

[0047] In the embodiment of the present application, the melt flow rate of the polypropylene cable insulation resin is between 0.1 g / 10 min and 5 g / 10 min.

[0048] In the embodiment of the present application, the volume resistivity of the polypropylene cable insulation resin is ≥1×10 14 Ω·m.

[0049] (I) Example of industrial preparation of polypropylene cable insulation resin:

[0050] The polymerization reaction was carried out on an INEOS Innovene gas phase fluidized bed process.

[0051] Remove trace impurities such as water, oxygen and carbonyl sulfide from the raw materials propylene and ethylene.

[0052] Hydrogen, propylene, main catalyst (Ziegler-Natta catalyst), co-catalyst system (triethylaluminum and diisopropyldimethoxysilane) and functional additive (7-octenyltrichlorosilane) are injected into the first reactor in the form of flushing through a feed pump, and a gas phase polymerization reaction is carried out in the first reactor to obtain a first polypropylene powder with a melt flow rate between 0.1g / 10min and 50g / 10min. The reaction conditions of the first reactor are: hydrogen concentration between 0.01mol% and 15mol%, propylene concentration between 75mol% and 99.8mol%, reaction pressure between 1Mpa and 3Mpa, and reaction temperature between 40°C and 90°C.

[0053] After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock and reacts with propylene, ethylene and hydrogen added to the second reactor in a gas phase to obtain an impact copolymer polypropylene powder with a melt flow rate of 0.1g / 10min to 10g / 10min. The reaction conditions of the second reactor are: hydrogen concentration between 0.01mol% and 10mol%, ethylene concentration between 0.01mol% and 50mol%, propylene concentration between 40mol% and 99.8mol%, reaction pressure between 1Mpa and 3Mpa, and reaction temperature between 40℃ and 90℃.

[0054] The impact copolymer polypropylene powder stays in the second reactor for 0.1h to 2h and then is transported to the deactivation system for deactivation and devolatilization treatment.

[0055] After deactivation and devolatilization, the impact copolymer polypropylene powder is conveyed to the extrusion granulation system.

[0056] 99 wt% of deactivated impact copolymer polypropylene powder and 1 wt% of resin additive are melt-blended and extruded into granules through a twin-screw extruder to obtain polypropylene cable insulating resin.

[0057] In the production process of the above-mentioned impact-resistant copolymer polypropylene powder, the process control parameters are shown in Table 1.

[0058] Table 1. Process control parameters of impact copolymer polypropylene powder

[0059] project First Reactor Second Reactor Reaction temperature, °C 63.5 66.5 Reaction pressure, Mpa 2.25 2.35 Triethylaluminum feed, Kg / h 3.5 -- DIBDMS feed, Kg / h 3 -- Hydrogen concentration, mol% 2.13 0.08 Functional additives, Kg / h 8.2 -- Main catalyst, Kg / h 2.6 --

[0060] Note: In the first reactor and the second reactor, the melt index (2.16Kg / 230℃) of the polymer is 13.1g / 10min and 0.20g / 10min respectively.

[0061] When the hydrogen concentration of the first reactor is between 0.1mol% and 3.5mol%, the hydrogen concentration of the second reactor is between 0.01mol% and 1mol%, and the ethylene concentration is between 20mol% and 30mol%, an impact-resistant copolymerized polypropylene powder with a melt flow rate close to 0.25g / 10min can be obtained. In the production process of the impact-resistant copolymerized polypropylene powder, the introduction of functional additives introduces multiple branched structures into propylene during the copolymerization reaction, reduces the size of polypropylene spherulites, increases the grain density, inhibits the aggregation of ethylene-propylene rubber phases, and enhances the interphase interface force, so that the dispersed phase size of ethylene-propylene rubber phase is small, uniformly dispersed and stable, thereby giving the polymer excellent processing performance, mechanical properties (tensile properties, impact properties) and high dielectric strength and other characteristics. The addition of corresponding resin additives (including antioxidant system and calcium stearate) during the extrusion granulation process can make the polypropylene resin have better antioxidant properties, prevent aging, and extend the service life.

[0062] (ii) The prepared polypropylene cable insulating resin is then tested for its performance by the following steps:

[0063] (1) Preparation of polypropylene cable insulation resin samples: According to 4.3 of GB / T 2546.2-2022, the sample injection molding conditions are selected according to the following contents:

[0064] a) Melt temperature: adjusted according to the melt mass flow rate of the material;

[0065] b) Injection pressure: Adjust the pressure to ensure that the specimen is intact and does not produce flash, shrinkage marks or bubbles;

[0066] c) Mould temperature: 40℃±1℃.

[0067] The preparation process of injection molding specimens was carried out in accordance with GB / T 17037.1.

[0068] (2) Sample condition adjustment: According to the provisions of GB / T 2918, the standard environment temperature is 23±2℃ and the relative humidity is 50%±10%.

[0069] (3) Particle appearance: According to the method specified in SH / T 1541.1.

[0070] (4) Melt mass flow rate: carried out according to the method specified in GB / T 3682.1.

[0071] (5) Ash content: It is carried out in accordance with the method specified in GB / T 9345.1. Direct calcination method (A) is adopted, and the calcination temperature is 850℃±50℃.

[0072] (6) Tensile properties: The test was carried out according to the method specified in GB / T 1040.1, with a specimen gauge length of 75 mm. The specimen selection was carried out according to the provisions of GB / T 1040.2.

[0073] (7) Flexural modulus: According to GB / T 9341, the test speed is 2 mm / min and the test specimen size is 80 mm × 10 mm × 4 mm.

[0074] (8) Simply supported beam notched impact strength: The specimen is a 80 mm × 10 mm × 4 mm long strip specimen. The strip should be notched within 1 to 4 hours after forming, and the notch type is Type A in GB / T 1043.1.

[0075] (9) Volume resistivity: Measured in accordance with the provisions of GB / T 31838.2.

[0076] (10) Oxidation induction time: The sample preparation shall be carried out in accordance with the provisions of 6.2 of GB / T 19466.6-2009, and the sample thickness shall be 650 μm ± 100 μm.

[0077] (11) Melt strength: The melt strength was tested using a Rheoten melt strength tester manufactured by Geottfert Werkstoff Pruefmaschinen, Germany.

[0078] According to the above test results, the performance indicators of polypropylene cable insulation resin are shown in Table 2, and the breakdown strength test results of polypropylene cable insulation resin are shown in Table 3.

[0079] Table 2. Performance indicators of polypropylene cable insulation resin

[0080] project unit Test value Melt mass flow rate (2.16kg / 230℃) g / 10min 0.20 Tensile yield stress Mpa 11.0 Flexural modulus MPa 337 Simple supported beam notched impact strength 23℃ kJ / m2 98.5P* Simple supported beam notched impact strength -20℃ kJ / m2 107.6P* Volume resistivity Ω <![CDATA[7.13×10 14 ]]> Oxidation Induction Time OIT (200℃, Al) min ＞60

[0081] Table 3. Test results of the breakdown strength of polypropylene cable insulation resin

[0082]

[0083] like Figure 2As shown, the melt strength of the polypropylene cable insulation resin is measured to be up to 24.2 cN, reflecting that the prepared polypropylene cable insulation resin has a higher melt strength.

[0084] like Figure 3 As shown, at different stretching rates (0.01s -1 , 0.1s -1 and 1.0s -1 ) was tested for tensile rheological properties of polypropylene cable insulation resin. Due to the presence of multiple long chain branches in the resin molecular structure, it exhibits obvious tensile strain hardening characteristics during melt stretching, which can ensure the stability of the cable during extrusion and avoid the occurrence of sag.

[0085] like Figure 4 As shown, scanning electron microscope analysis was performed on the polypropylene cable insulation resin. Through the pore analysis on the sample surface, it was found that the average size of the soluble rubber phase was 0.42μm, and there were a large number of larger rubber phase particles (>1.0μm). The presence of rubber phase particles can make the polypropylene cable insulation resin have higher processing toughness.

[0086] The polypropylene cable insulating resin prepared by the invention has higher melt strength and significant tensile strain hardening characteristics, and can effectively improve processing performance.

[0087] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0088] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for preparing a polypropylene cable insulating resin, characterized in that: include: Adding a main catalyst, a co-catalyst system, a functional additive, propylene and hydrogen into a first reactor for gas phase polymerization to obtain a first polypropylene powder, wherein the melt flow rate of the first polypropylene powder is between 0.1 g / 10 min and 50 g / 10 min; the reaction conditions of the first reactor are: a hydrogen concentration of between 0.01 mol% and 15 mol%, a propylene concentration of between 75 mol% and 99.8 mol%, a reaction pressure of between 1 MPa and 3 MPa, and a reaction temperature of between 40° C. and 90° C.; After the first polypropylene powder stays in the first reactor for 0.1h to 2h, it is transported to the second reactor through an air lock and subjected to gas phase polymerization reaction with propylene, ethylene and hydrogen added to the second reactor to obtain impact copolymer polypropylene powder, wherein the melt flow rate of the impact copolymer polypropylene powder is between 0.1g / 10min and 10g / 10min; the reaction conditions of the second reactor are: hydrogen concentration is between 0.01mol% and 10mol%, ethylene concentration is between 0.01mol% and 50mol%, propylene concentration is between 40mol% and 99.8mol%, reaction pressure is between 1Mpa and 3Mpa, and reaction temperature is between 40°C and 90°C; The impact copolymer polypropylene powder stays in the second reactor for 0.1h to 2h and then is transported to the deactivation system for deactivation and devolatilization treatment; After deactivation and devolatilization, the impact-resistant copolymerized polypropylene powder is transported to an extrusion granulation system for melt blending with resin additives and extrusion granulation to obtain polypropylene cable insulation resin.

2. The method for preparing a polypropylene cable insulating resin according to claim 1, characterized in that: The dosage of the functional auxiliary agent is 1Kg / h~20Kg / h; the functional auxiliary agent is selected from an organic silane with the general formula R1mSiXn(OR2)k, wherein R1 is a C2~C20 hydrocarbon group and the end of R1 contains an α-olefin double bond, a norbornene group, a cycloolefin group or a dicyclopentadiene group, X is a halogen, R2 is a C1~C20 straight chain, branched or isomerized alkyl group, m and n are both integers between 1 and 3, k is an integer between 0 and 2, and m+n+k=4.

3. The method for preparing a polypropylene cable insulating resin according to claim 1, characterized in that: The main catalyst is selected from Ziegler-Natta catalyst, and its usage is 0.5Kg / h to 10Kg / h.

4. The method for preparing a polypropylene cable insulating resin according to claim 1, characterized in that: The co-catalyst system comprises alkyl aluminum and an external electron donor. The usage amount of the alkyl aluminum is 0.1 Kg / h to 10 Kg / h, and the usage amount of the external electron donor is 0.1 Kg / h to 10 Kg / h.

5. The method for preparing polypropylene cable insulating resin according to claim 1, characterized in that: The reaction conditions of the first reactor are: hydrogen concentration between 0.01mol% and 10mol%, propylene concentration between 85mol% and 99.8mol%, reaction pressure between 2Mpa and 2.5Mpa, and reaction temperature between 55°C and 70°C; the reaction conditions of the second reactor are: hydrogen concentration between 0.01mol% and 5mol%, ethylene concentration between 10mol% and 40mol%, propylene concentration between 55mol% and 89.9mol%, reaction pressure between 2Mpa and 2.5Mpa, and reaction temperature between 55°C and 70°C.

6. The method for preparing polypropylene cable insulating resin according to claim 1, characterized in that: The impact-resistant copolymer polypropylene powder is an ethylene-propylene impact-resistant copolymer with a multi-branched structure; in terms of mass fraction, the content of propylene structural units in the ethylene-propylene impact-resistant copolymer is 70wt% to 99wt%, and the content of ethylene structural units is 1wt% to 30wt%.

7. The method for preparing a polypropylene cable insulating resin according to claim 1, characterized in that: The polypropylene cable insulation resin comprises impact-resistant copolymer polypropylene powder and resin additives; Calculated by mass fraction, the content of the impact-resistant copolymer polypropylene powder is 99.5wt% to 99.9wt%, and the content of the resin additive is 0.1wt% to 0.5wt%.

8. A polypropylene cable insulating resin, characterized in that: The polypropylene cable insulating resin is prepared by the preparation method of the polypropylene cable insulating resin according to any one of claims 1 to 7.

9. The polypropylene cable insulating resin according to claim 8, characterized in that: The melt strength of the polypropylene cable insulation resin is between 5cN and 30cN.

10. The polypropylene cable insulating resin according to claim 8, characterized in that: The dielectric strength of the polypropylene cable insulation resin is ≥35kV / mm.

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