CN110498997B - Polypropylene-based high-voltage direct-current cable material and preparation method thereof - Google Patents
Polypropylene-based high-voltage direct-current cable material and preparation method thereof Download PDFInfo
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Abstract
A polypropylene-based high-voltage direct-current cable material and a preparation method thereof are disclosed, wherein the polypropylene-based high-voltage direct-current cable material comprises, by mass, 10-50 parts of isotactic polypropylene containing a beta nucleating agent, 50-90 parts of ethylene-propylene block copolymer polypropylene and 0.10.5 parts of an antioxidant; wherein the sum of the mass parts of the isotactic polypropylene containing the beta nucleating agent and the ethylene-propylene block copolymerization polypropylene is 100 parts, and the mass fraction of the beta nucleating agent in the isotactic polypropylene containing the beta nucleating agent is 0.3-1%. The invention prepares the blended polypropylene material containing beta crystal by adopting the method of adding beta nucleating agent and blending isotactic polypropylene and block polypropylene, solves the problems of large brittleness, poor low-temperature impact and low dielectric breakdown strength of EPC by blending EPC and beta-iPP, and provides a green recyclable polypropylene-based direct-current high-voltage cable material which has good mechanical and electrical properties and can replace XLPE.
Description
Technical Field
The invention relates to the field of thermoplastic direct current cable materials, in particular to a polypropylene-based high-voltage direct current cable material and a preparation method thereof.
Background
XLPE has excellent mechanical and electrical properties and is the main insulating material of extruded plastic cables. But the side products generated by the cross-linking process have a great influence on the space charge accumulation of the dc cable. The accumulation of space charge can cause the distortion of the electric field in the cable insulation, thereby causing partial discharge and breakdown of the cable insulation and reducing the insulation performance of the material. In addition, the crosslinked polyethylene is a thermosetting material, and the cable cannot be degraded and recycled after decommissioning, and can only be incinerated and buried, so that the environmental pollution is greatly caused. Therefore, the development of thermoplastic cable materials meeting the environmental requirements is urgently needed to replace the crosslinked polyethylene. The polypropylene not only has good electrical performance and heat resistance, but also can be recycled as a thermoplastic material after the service life is ended, and can possibly replace crosslinked polyethylene to be used as a cable material. However, isotactic polypropylene is very brittle and has poor low-temperature impact properties, and the defects limit the application of isotactic polypropylene in high-voltage direct-current cables. Researchers at home and abroad select methods such as blending, copolymerization, crystal form change, chemical modification and the like to improve the brittleness and low-temperature performance of isotactic polypropylene.
Disclosure of Invention
The invention aims to provide a polypropylene-based high-voltage direct-current cable material and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a polypropylene-based high-voltage direct-current cable material comprises, by mass, 10-50 parts of isotactic polypropylene containing a beta nucleating agent, 50-90 parts of ethylene-propylene block copolymer polypropylene and 0.1-0.5 part of an antioxidant; wherein the sum of the mass parts of the isotactic polypropylene containing the beta nucleating agent and the ethylene-propylene block copolymerization polypropylene is 100 parts, and the mass fraction of the beta nucleating agent in the isotactic polypropylene containing the beta nucleating agent is 0.3-1%.
In a further improvement of the invention, the isotactic polypropylene containing a beta nucleating agent is prepared by the following process:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene and a beta nucleating agent into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 5-10% of that of the polypropylene master batch containing the beta nucleating agent;
2) preparing a semi-finished product: adding the polypropylene master batch containing the beta nucleating agent and polypropylene into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.3 to 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass percent.
A further improvement of the present invention is that the isotactic polypropylene has a melt index of 2.9. + -. 0.2g/10 min.
The invention is further improved in that the beta nucleating agent is one or two of 2, 6-cyclohexane diformate, N' -dicyclohexyl-2, 6-naphthalene diamide, TMB-4, TMB-5 and rare earth nucleating agent WBG-II.
The invention has the further improvement that the mass fraction of ethylene segments in the ethylene-propylene block copolymer polypropylene is 10-20%, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min.
The invention is further improved in that the antioxidant is one or more of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tri (2, 4-di-tert-butylphenyl) phosphite and 4, 4' -thiobis (6-tert-butyl-3-methylphenol).
The invention is further improved in that when the antioxidant is two or three of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tris (2, 4-di-tert-butylphenyl) phosphite and 4, 4' -thiobis (6-tert-butyl-3-methylphenol), the mass fraction of each antioxidant is not less than 10% of the total mass of the antioxidant.
The preparation method of the polypropylene-based high-voltage direct-current cable material comprises the following steps:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene and a beta nucleating agent into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 5-10% of that of the polypropylene master batch containing the beta nucleating agent;
2) preparing a semi-finished product: adding the polypropylene master batch containing the beta nucleating agent and polypropylene into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.3 to 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass percent;
3) preparing a finished product material: adding isotactic polypropylene containing beta nucleating agent, ethylene-propylene block copolymer polypropylene and antioxidant into a double-screw mixer, uniformly extruding, cooling, and then feeding into a granulator for granulation to obtain the polypropylene-based high-voltage direct-current cable material.
The further improvement of the invention is that in the step 1), the temperature of each area of the screw is set to be 195-200 ℃, the rotating speed of the feeding port is 8-12 rpm, and the rotating speed of the screw is 150-200 rpm;
in the step 2), the temperature of each area of the screw is set to be 195-200 ℃, the rotating speed of the feeding port is 12-16 rpm, and the rotating speed of the screw is 200-300 rpm.
The further improvement of the invention is that in the step 3), the temperature of each area of the screw is set to be 195-200 ℃, the rotating speed of the feeding port is 12-16 rpm, and the rotating speed of the screw is 200-300 rpm
Compared with the prior art, the invention has the following beneficial effects: the invention adopts the method of adding beta nucleating agent and blending isotactic polypropylene and block polypropylene to prepare the blended polypropylene material containing beta crystal, and has excellent mechanical property, the mechanical tensile elongation at break reaches more than 600 percent, the tensile strength reaches 25MPa, and the low-temperature embrittlement temperature is reduced to below minus 30 ℃. Meanwhile, the electric performance is good, the normal-temperature direct-current breakdown strength reaches 200kV/mm, and no obvious space charge aggregation can be observed after the polarization is carried out for 30min by applying a strong field of 50 kV/mm. And the environment is friendly, and the environment is green and can be recovered.
In the preparation, the method of blending modification and adding the beta nucleating agent is simultaneously used, the material has excellent mechanical property (the normal-temperature impact property is improved by more than 15 times) and electrical property, the environment is friendly, the thermoplastic material can be recycled after the service life is exhausted, the cross-linking is not generated in the manufacturing process, the process is simple, and no cross-linking agent byproduct is generated in the use process. The thermoplastic polypropylene-based high-voltage direct-current cable material provided by the invention is a breakthrough technical product, and the product is prepared by blending ethylene propylene block copolymer polypropylene (EPC) serving as matrix resin with isotactic polypropylene (iPP) containing a nucleating agent, so that the defects of high impact property and brittleness and low breakdown strength of the ethylene propylene block copolymer polypropylene are overcome, and the problem of space charge aggregation caused by a phase interface is avoided because PP serves as a matrix and crystalline states are the same. Meanwhile, the introduction of beta crystals can further improve the mechanical property and the electrical property of the blending material. The cable material has the following characteristics: the material is thermoplastic, environment-friendly and easy to recycle after the service life is exhausted; excellent mechanical and electrical properties, and good processability.
Drawings
FIG. 1 is a metallographic microscopic image of iPP, EPC/iPP and EPC-iPP/nucleating agent. Wherein, (a) is iPP, (b) is EPC, (c) is EPC/iPP, and (d) is EPC-iPP/nucleating agent.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The high-voltage polypropylene-based cable insulation material comprises, by mass, 10-50 parts of isotactic polypropylene containing a nucleating agent, 50-90 parts of ethylene-propylene block copolymer polypropylene and 0.1-0.5 part of an antioxidant. Wherein the sum of the mass parts of the isotactic polypropylene containing the beta nucleating agent and the ethylene-propylene block copolymerization polypropylene is 100 parts, and the mass fraction of the beta nucleating agent in the isotactic polypropylene containing the beta nucleating agent is 0.3-1%.
The melt index of the isotactic polypropylene of the present invention is 2.9 + -0.2 g/10min (measured at 230 + -2 ℃ C. with the application of 2.16 kg).
The ethylene-propylene block copolymer polypropylene of the present invention has an ethylene fraction of 10% to 20% and a melt index of 2.1. + -. 0.2g/10min (measured at 230. + -. 2 ℃ C. under a force of 2.16 kg).
The beta nucleating agent can induce polypropylene to generate beta crystals in the crystallization process, and can be one or two of 2, 6-cyclohexane diformate, N, N' -dicyclohexyl-2, 6-naphthalene diamide, TMB-4, TMB-5 and rare earth compounds WBG-II.
The antioxidant is an antioxidant for polypropylene, can resist high temperature in the processing process, such as one or more of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tri (2, 4-di-tert-butylphenyl) phosphite and 4, 4' -thiobis (6-tert-butyl-3-methylphenol), and when multiple antioxidants are used in combination, the content of each antioxidant accounts for not less than 10% of the total weight of the antioxidant.
The iPP has high brittleness, poor low-temperature impact performance and low EPC dielectric strength, can not be directly used as a cable material, and must be modified. The invention improves the low temperature impact performance, brittleness and dielectric strength of the beta-iPP by blending with the iPP in the EPC. The introduction of flower-shaped beta crystals can improve the tensile property and the dielectric strength of the blended material and reduce the aggregation of space charge; the addition of EPC can greatly improve the impact property and low-temperature embrittlement property of the blended material.
The preparation method of the polypropylene-based high-voltage direct-current cable material adopts a master batch method and a step-by-step method to prepare finished materials in order to ensure that a nucleating agent is uniformly and stably dispersed in polypropylene, and specifically comprises the following steps:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene (iPP) and a nucleating agent into a micro double-screw mixer in proportion for melt blending, setting the temperature of each zone of a screw to be within 195-200 ℃, the rotating speed of a feed inlet to be 8-12 rpm and the rotating speed of the screw to be 150-200 rpm, uniformly mixing by using double screws, and extruding to obtain the polypropylene master batch containing 5% of 10% of beta nucleating agent.
2) Preparing a semi-finished product: adding polypropylene master batch containing 5-10% of beta nucleating agent and polypropylene into a miniature double-screw mixer in proportion for melt blending, setting the temperature of each zone of a screw to be between 195-200 ℃, the rotating speed of a feed inlet to be 12-16 rpm and the rotating speed of the screw to be 200-300 rpm, uniformly mixing by using double screws, and extruding to obtain a semi-finished product material beta-iPP containing 0.3-1% of beta nucleating agent.
3) Preparing a finished product material: adding a semi-finished product material beta-iPP containing 0.3-1% of beta nucleating agent, ethylene propylene block copolymer polypropylene (EPC) and an antioxidant into a double-screw mixer in proportion, setting the temperature of each zone of a screw to be (195-200 ℃), the rotating speed of a feed inlet to be (12-16 rpm) and the rotating speed of the screw to be (200-300 rpm), uniformly extruding, cooling, and then feeding into a granulator for granulation to obtain the cable material containing the beta nucleating agent. The cable material comprises, by mass, 10-50 parts of isotactic polypropylene containing a beta nucleating agent, 50-90 parts of ethylene-propylene block copolymer polypropylene and 0.1-0.5 part of an antioxidant.
Comparative examples 1 to 2 and examples 1 to 3 according to the invention have the raw material formulations shown in Table 1.
TABLE 1 formulation of thermoplastic polypropylene-based cable insulation
The examples are as follows:
comparative example 1: according to the mass portion, 10100.1 portions of antioxidant are added into an ethylene propylene block copolymerization polypropylene insulating material k8303 produced by Yanshan petrochemical production.
Comparative example 2: according to the mass portion, isotactic polypropylene T30s for prolonging petrochemical production is adopted, and 1680.2 portions of antioxidant are added.
Example 1: according to the mass parts, 70 parts of ethylene-propylene block copolymer polypropylene, 30 parts of isotactic polypropylene and 3000.1 parts of antioxidant are adopted.
Example 2: according to the mass parts, 60 parts of ethylene propylene block copolymer polypropylene, 40 parts of isotactic polypropylene and 0.12 part of rare earth nucleating agent are adopted, and an antioxidant 1010 (tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester), an antioxidant 168 (tri (2, 4-di-tert-butylphenyl) phosphite) and an antioxidant 300(4, 4' -thiobis (6-tert-butyl-3-methylphenol)) are respectively 0.1 part, 0.2 part and 0.1 part.
Example 3: according to the mass parts, 80 parts of ethylene propylene block copolymer polypropylene, 20 parts of isotactic polypropylene and 0.06 part of rare earth nucleating agent are adopted, and 0.1 part and 0.2 part of antioxidant 1010 (tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester) and antioxidant 168 (tri (2.4-di-tert-butylphenyl) phosphite) are added respectively.
In comparative examples 1-2 in Table 1, the preparation method of 3 cable materials in example 1 is the same, and the granules are uniformly mixed and then subjected to melt blending extrusion by a micro double screw (the screw temperature is 195-200 ℃, the screw rotating speed is 200-300 rpm, and the rotating speed of a feeding port is 12-16 rpm).
The preparation methods of the 2 cable materials of the embodiments 2 and 3 are the same, and comprise the following process steps:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene (iPP) and a nucleating agent into a micro double-screw mixer in proportion for melt blending, setting the temperature of each zone of a screw to be within 195-200 ℃, the rotating speed of a feed inlet to be 8-12 rpm and the rotating speed of the screw to be 150-200 rpm, uniformly mixing by using double screws, and extruding to obtain the iPP master batch containing 5% -10% of the beta nucleating agent.
2) Preparing a semi-finished product: adding iPP master batch containing 5-10% of beta nucleating agent and pure iPP into a miniature double-screw mixer in proportion for melt blending, setting the temperature of each zone of a screw to be (195-200 ℃), the rotating speed of a feed inlet to be (12-16 rpm) and the rotating speed of the screw to be (200-300 rpm), uniformly mixing by using double screws, and extruding to obtain a semi-finished product beta-iPP containing 0.3-1% of beta nucleating agent.
3) Preparing a finished product material: adding a semi-finished product material beta-iPP containing 0.3-1% of beta nucleating agent, ethylene propylene block copolymer polypropylene (EPC) and an antioxidant into a double-screw mixer in proportion, setting the temperature of each zone of a screw to be (195-200 ℃), the rotating speed of a feed inlet to be (12-16 rpm) and the rotating speed of the screw to be (200-300 rpm), uniformly extruding, cooling, and then feeding into a granulator for granulation to obtain 10-50 parts of isotactic polypropylene containing the beta nucleating agent, 50-90 parts of ethylene propylene block copolymer polypropylene and 0.1-0.5 part of the antioxidant.
The combination of properties of the cable materials of the examples is shown in Table 2.
TABLE 2 combination of properties of the cable materials of the different examples
As shown in fig. 1, fig. 1 is a polarization microscope image of the crystal form of the polypropylene-based insulating material, with a magnification of 400 times. FIG. 1(a) is a crystal polarization microscope image of iPP, in which alpha spherulites in iPP are in cross extinction and grow radially from the center to the periphery, the crystal size is large and reaches about 200 μm, and obvious boundaries exist between spherulites. Fig. 1(b) is a crystal polarization micrograph of EPC, and α spherulites generated in EPC are small in size, around 60 μm, denser than iPP, and the boundaries between spherulites are not obvious. FIG. 1(c) is a crystal polarization microscope image of EPC/iPP, in which the size of α crystal generated in EPC/iPP is about 100 μm and a boundary exists between spherulites. FIG. 1(d) is a crystal polarization microscope image of EPC/iPP-nucleating agent, after the nucleating agent is added, the beta crystal grows in flower shape, and the size of the beta crystal reaches about 300 μm.
Example 4
1) Preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene with the melt index of 2.9 +/-0.2 g/10min and a beta nucleating agent into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 195 ℃, the rotating speed of a feed inlet at 8rpm and the rotating speed of the screw at 150rpm, uniformly mixing by using double screws, and extruding to obtain polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 10 percent of the mass of the polypropylene master batch containing the beta nucleating agent; the beta nucleating agent is 2, 6-phthalic acid cyclohexylamide.
2) Preparing a semi-finished product: adding polypropylene master batch containing the beta nucleating agent and polypropylene into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 200 ℃, the rotating speed of a feeding port at 13rpm and the rotating speed of the screw at 250rpm, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass;
3) preparing a finished product material: adding isotactic polypropylene containing a beta nucleating agent, ethylene-propylene block copolymer polypropylene and an antioxidant into a double-screw mixer, setting the temperature of each region of a screw at 195 ℃, the rotating speed of a feed inlet at 12rpm and the rotating speed of the screw at 200rpm, uniformly extruding, cooling, feeding into a granulator, and granulating to obtain the polypropylene-based high-voltage direct-current cable material, wherein the cable material comprises 10 parts by mass of the isotactic polypropylene containing the beta nucleating agent, 90 parts by mass of the ethylene-propylene block copolymer polypropylene and 0.1 part by mass of the antioxidant. The mass fraction of the ethylene segment in the ethylene-propylene block copolymer polypropylene is 10 percent, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min. The antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester.
Example 5
1) Preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene with the melt index of 2.9 +/-0.2 g/10min and a beta nucleating agent into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 200 ℃, the rotating speed of a feed inlet at 12rpm and the rotating speed of the screw at 170rpm, uniformly mixing by using double screws, and extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 7 percent of that of the polypropylene master batch containing the beta nucleating agent; the beta nucleating agent is a mixture of 2, 6-cyclohexane dicarboxamide and N, N' -dicyclohexyl-2, 6-naphthalene diamide.
2) Preparing a semi-finished product: adding polypropylene master batch containing the beta nucleating agent and polypropylene into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 200 ℃, the rotating speed of a feeding port at 14rpm, and the rotating speed of the screw at 220rpm, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.7 percent of the mass of the isotactic polypropylene containing the beta nucleating agent;
3) preparing a finished product material: adding isotactic polypropylene containing a beta nucleating agent, ethylene-propylene block copolymer polypropylene and an antioxidant into a double-screw mixer, setting the temperature of each zone of a screw at 197 ℃, the rotating speed of a feed inlet at 13rpm and the rotating speed of the screw at 270rpm, uniformly extruding, cooling, feeding into a granulator, and granulating to obtain the polypropylene-based high-voltage direct-current cable material, wherein the cable material comprises 50 parts by mass of the isotactic polypropylene containing the beta nucleating agent, 50 parts by mass of the ethylene-propylene block copolymer polypropylene and 0.2 part by mass of the antioxidant. The mass fraction of the ethylene segment in the ethylene-propylene block copolymer polypropylene is 15 percent, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min. The antioxidant is tris (2, 4-di-tert-butylphenyl) phosphite.
Example 6
1) Preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene with the melt index of 2.9 +/-0.2 g/10min and a beta nucleating agent into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 198 ℃, setting the rotating speed of a feeding port at 10rpm and the rotating speed of the screw at 180rpm, uniformly mixing by using double screws, and extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 8 percent of that of the polypropylene master batch containing the beta nucleating agent; the beta nucleating agent is a mixture of TMB-4 and TMB-5.
2) Preparing a semi-finished product: adding polypropylene master batch containing the beta nucleating agent and polypropylene into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 195 ℃, the rotating speed of a feeding port at 16rpm and the rotating speed of the screw at 200rpm, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.5 percent of the mass of the isotactic polypropylene containing the beta nucleating agent;
3) preparing a finished product material: adding isotactic polypropylene containing a beta nucleating agent, ethylene-propylene block copolymer polypropylene and an antioxidant into a double-screw mixer, setting the temperature of each region of a screw at 200 ℃, the rotating speed of a feed inlet at 16rpm and the rotating speed of the screw at 240rpm, uniformly extruding, cooling, feeding into a granulator, and granulating to obtain the polypropylene-based high-voltage direct-current cable material, wherein the cable material comprises 20 parts by mass of the isotactic polypropylene containing the beta nucleating agent, 80 parts by mass of the ethylene-propylene block copolymer polypropylene and 0.3 part by mass of the antioxidant. The mass fraction of the ethylene segment in the ethylene-propylene block copolymer polypropylene is 20 percent, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min. The antioxidant is a mixture of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester and tris (2, 4-di-tert-butylphenyl) phosphite, and the mass ratio of the tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester to the tris (2, 4-di-tert-butylphenyl) phosphite is 1: 9.
Example 7
1) Preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene with the melt index of 2.9 +/-0.2 g/10min and a beta nucleating agent into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 200 ℃, the rotating speed of a feed inlet at 11rpm and the rotating speed of the screw at 200rpm, uniformly mixing by using double screws, and extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 5 percent of that of the polypropylene master batch containing the beta nucleating agent; the beta nucleating agent is a rare earth nucleating agent WBG-II.
2) Preparing a semi-finished product: adding polypropylene master batch containing the beta nucleating agent and polypropylene into a miniature double-screw mixer for melt blending, setting the temperature of each zone of a screw at 195 ℃, the rotating speed of a feeding port at 12rpm and the rotating speed of the screw at 300rpm, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass;
3) preparing a finished product material: adding isotactic polypropylene containing a beta nucleating agent, ethylene-propylene block copolymer polypropylene and an antioxidant into a double-screw mixer, setting the temperature of each region of a screw at 200 ℃, the rotating speed of a feed inlet at 14rpm and the rotating speed of the screw at 300rpm, uniformly extruding, cooling, feeding into a granulator, and granulating to obtain the polypropylene-based high-voltage direct-current cable material, wherein the cable material comprises 30 parts by mass of the isotactic polypropylene containing the beta nucleating agent, 70 parts by mass of the ethylene-propylene block copolymer polypropylene and 0.5 part by mass of the antioxidant. The mass fraction of the ethylene segment in the ethylene-propylene block copolymer polypropylene is 13 percent, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min. The antioxidant is a mixture of tris (2, 4-di-tert-butylphenyl) phosphite and 4, 4 '-thiobis (6-tert-butyl-3-methylphenol), and the mass ratio of tris (2, 4-di-tert-butylphenyl) phosphite to 4, 4' -thiobis (6-tert-butyl-3-methylphenol) is 1: 1.
The preparation method of the cable material comprises the process steps of preparing a master batch of the cable material, and carrying out melt blending on the master batch, EPC and iPP; the cable master batch consists of iPP and beta nucleating agent. Compared with the prior art, the invention has the following advantages: the thermoplastic blending polypropylene cable insulating material containing beta crystals and having excellent performance is obtained by double-screw mixing. The preparation of the master batch ensures the uniform and stable dispersion of the nucleating agent and induces the generation of beta crystals in polypropylene. Meanwhile, the introduction of beta crystals and the blending of two polypropylene matrixes ensure that the polypropylene composite material has both electrical performance (the direct current breakdown strength is improved by more than 15% compared with EPC, no obvious space charge is observed after pressurization of 50kv/mm 300 min) and mechanical performance (the fracture growth rate is improved by more than 30% compared with pure iPP, the normal-temperature impact strength is improved by more than 10 times compared with iPP, and the low-temperature embrittlement temperature point reaches below-30 ℃).
Claims (7)
1. The polypropylene-based high-voltage direct-current cable material is characterized by comprising, by mass, 10-50 parts of isotactic polypropylene containing a beta nucleating agent, 50-90 parts of ethylene-propylene block copolymer polypropylene and 0.1-0.5 part of an antioxidant; wherein the sum of the mass parts of the isotactic polypropylene containing the beta nucleating agent and the ethylene-propylene block copolymer polypropylene is 100 parts, and the mass fraction of the beta nucleating agent in the isotactic polypropylene containing the beta nucleating agent is 0.3-1%;
the isotactic polypropylene containing the beta nucleating agent is prepared by the following processes:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene and a beta nucleating agent into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 5-10% of that of the polypropylene master batch containing the beta nucleating agent;
2) preparing a semi-finished product: adding the polypropylene master batch containing the beta nucleating agent and polypropylene into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.3 to 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass percent;
the mass fraction of ethylene segments in the ethylene-propylene block copolymer polypropylene is 10-20%, and the melt index of the ethylene-propylene block copolymer polypropylene is 2.1 +/-0.2 g/10 min;
the beta nucleating agent is a rare earth nucleating agent WBG-II.
2. The polypropylene-based high voltage direct current cable material according to claim 1, wherein the isotactic polypropylene has a melt index of 2.9 ± 0.2g/10 min.
3. The polypropylene-based high-voltage direct-current cable material as claimed in claim 1, wherein the antioxidant is one or more of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tris (2, 4-di-tert-butylphenyl) phosphite and 4, 4' -thiobis (6-tert-butyl-3-methylphenol).
4. The polypropylene-based high-voltage direct current cable material as claimed in claim 3, wherein when the antioxidant is two or three of tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tris (2, 4-di-tert-butylphenyl) phosphite and 4, 4' -thiobis (6-tert-butyl-3-methylphenol), the mass fraction of each antioxidant in the total mass of the antioxidant is not less than 10%.
5. A method for preparing a polypropylene based high voltage direct current cable material according to any one of claims 1 to 4, comprising the steps of:
1) preparation of polypropylene master batch containing beta nucleating agent: adding isotactic polypropylene and a beta nucleating agent into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain a polypropylene master batch containing the beta nucleating agent; wherein the mass of the beta nucleating agent is 5-10% of that of the polypropylene master batch containing the beta nucleating agent;
2) preparing a semi-finished product: adding the polypropylene master batch containing the beta nucleating agent and polypropylene into a double-screw mixer for melt blending, uniformly mixing by using double screws, and then extruding to obtain isotactic polypropylene containing the beta nucleating agent; wherein the beta nucleating agent accounts for 0.3 to 1 percent of the isotactic polypropylene containing the beta nucleating agent by mass percent;
3) preparing a finished product material: adding isotactic polypropylene containing beta nucleating agent, ethylene-propylene block copolymer polypropylene and antioxidant into a double-screw mixer, uniformly extruding, cooling, and then feeding into a granulator for granulation to obtain the polypropylene-based high-voltage direct-current cable material.
6. The preparation method of the polypropylene-based high-voltage direct current cable material according to claim 5, wherein in the step 1), the temperature of each region of the screw is set to be 195-200 ℃, the rotation speed of the feeding port is 8-12 rpm, and the rotation speed of the screw is 150-200 rpm;
in the step 2), the temperature of each area of the screw is set to be 195-200 ℃, the rotating speed of the feeding port is 12-16 rpm, and the rotating speed of the screw is 200-300 rpm.
7. The preparation method of the polypropylene-based high-voltage direct current cable material according to claim 5, wherein in the step 3), the temperature of each region of the screw is set to be 195-200 ℃, the rotation speed of the feeding port is 12-16 rpm, and the rotation speed of the screw is 200-300 rpm.
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| CN111560136A (en) * | 2020-04-09 | 2020-08-21 | 天津大学 | Polypropylene-based high-voltage direct-current cable material and modification and crystallization temperature regulation and control method |
| CN111423658A (en) * | 2020-04-10 | 2020-07-17 | 天津大学 | Polypropylene cable material under polarity reversal working condition, and preparation method and application thereof |
| KR102695877B1 (en) * | 2020-11-19 | 2024-08-14 | 롯데케미칼 주식회사 | Resin composition for insulation of eco-friendly power cables |
| CN113248832A (en) * | 2021-02-03 | 2021-08-13 | 中国电力科学研究院有限公司 | High-voltage direct-current polypropylene cable material |
| CN114106504A (en) * | 2021-09-06 | 2022-03-01 | 中国电力科学研究院有限公司 | Thermoplastic medium-voltage cable insulating material and preparation method thereof |
| KR102595967B1 (en) * | 2021-09-14 | 2023-10-30 | 한화토탈에너지스 주식회사 | Soft Polyolefin Resin Composition for Power Cables with Excellent Insulation Characteristics and Article Molded Therefrom |
| CN113845734B (en) * | 2021-10-22 | 2023-09-19 | 万华化学（宁波）有限公司 | Thermoplastic polypropylene cable insulating material for high voltage and preparation method thereof |
| CN114015154B (en) * | 2021-11-09 | 2023-08-18 | 南方电网科学研究院有限责任公司 | Preparation method of environment-friendly high-voltage cable polypropylene insulating material |
| CN114806029B (en) * | 2022-05-30 | 2023-07-21 | 宜兴汉光高新石化有限公司 | Environment-friendly high-voltage cable polypropylene special material and preparation method thereof |
| CN115651317B (en) * | 2022-11-30 | 2024-02-13 | 南方电网科学研究院有限责任公司 | Environment-friendly polypropylene insulating material, preparation method and application thereof, and cable |
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