阅读说明：本技术 一种负载催化剂、导电聚烯烃复合材料以及它们的制备方法 (Supported catalyst, conductive polyolefin composite material and preparation methods thereof ) 是由 林伟国 涂志强 荣峻峰 谢婧新 宗明生 于鹏 吴耿煌 余伟发 于 2020-03-27 设计创作，主要内容包括：本发明涉及一种负载催化剂、导电聚烯烃复合材料以及它们的制备方法。该负载催化剂,其包括载体和活性组分,其特征在于,所述载体为三氯化铁改性石墨,所述活性组分为四氯化钛或三氯化钛,其中,所述负载催化剂中钛含量为0.2-6质量％,基于所述负载催化剂的总质量。制备导电聚烯烃复合材料的方法,包括：在本发明负载催化剂和助催化剂存在下,使烯烃进行淤浆聚合,得到导电聚烯烃复合材料前体；向所述导电聚烯烃复合材料前体添加导电碳材料后,进行研磨,得到所述导电聚烯烃复合材料。该复合材料中导电填料含量低,保持了聚烯烃树脂材料性能,且具有良好的导电率,可以应用于导电、防静电、电磁屏蔽等产品。(The invention relates to a supported catalyst, a conductive polyolefin composite material and preparation methods thereof. The supported catalyst comprises a carrier and an active component, and is characterized in that the carrier is ferric trichloride modified graphite, and the active component is titanium tetrachloride or titanium trichloride, wherein the titanium content in the supported catalyst is 0.2-6 mass% based on the total mass of the supported catalyst. A method of making a conductive polyolefin composite comprising: in the presence of the supported catalyst and the cocatalyst, carrying out slurry polymerization on olefin to obtain a conductive polyolefin composite material precursor; and adding a conductive carbon material to the conductive polyolefin composite material precursor, and grinding to obtain the conductive polyolefin composite material. The composite material has low content of conductive filler, keeps the performance of polyolefin resin materials, has good conductivity, and can be applied to products with conductivity, static resistance, electromagnetic shielding and the like.)

1. A supported catalyst comprises a carrier and an active component, and is characterized in that the carrier is ferric trichloride modified graphite, and the active component is titanium tetrachloride or titanium trichloride, wherein the titanium content in the supported catalyst is 0.2-6 mass% based on the total mass of the supported catalyst.

2. The supported catalyst according to claim 1, wherein the supported catalyst has a carbon content of 92 to 98 mass%, an iron content of 0.2 to 2 mass%, an oxygen content of 1 to 4 mass%, a chlorine content of 1 to 3 mass%, and a titanium content of 0.2 to 6 mass%, based on the total mass of the supported catalyst.

3. The supported catalyst according to claim 1 or 2, wherein the iron trichloride-modified graphite is obtained by:

pretreating graphite at 200-400 ℃ in a vacuum state,

carrying out composite modification on the pretreated graphite and anhydrous ferric trichloride at the temperature of 200-500 ℃ to obtain the ferric trichloride modified graphite.

4. The supported catalyst according to claim 3, wherein the pretreated graphite has an oxygen content of 0.1 to 5.0 mass% and a carbon content of 94.0 to 99.0 mass%, based on the total mass of the pretreated graphite.

5. The supported catalyst according to claim 3, wherein the pretreated graphite and the anhydrous ferric trichloride are used in amounts such that the carbon content in the ferric trichloride modified graphite is 95.0 to 99.0% by mass, the oxygen content is 0.1 to 5.0% by mass, and the iron content is 0.1 to 3.0% by mass, based on the total mass of the modified graphite.

6. The supported catalyst according to claim 3, wherein the pretreated graphite and the anhydrous ferric trichloride are used in amounts such that the carbon content in the ferric trichloride-modified graphite is 95.0 to 99.0% by mass, the oxygen content is 0.1 to 2.0% by mass, and the iron content is 0.2 to 2.0% by mass, based on the total mass of the modified graphite.

7. The supported catalyst according to claim 3, wherein the graphite is selected from one or more of natural graphite, expanded graphite, flake graphite and graphite oxide, preferably expanded graphite.

8. A process for preparing the supported catalyst of any one of claims 1 to 7, comprising the steps of:

providing ferric trichloride modified graphite;

and reacting titanium tetrachloride or titanium trichloride with the iron trichloride modified graphite in an inert atmosphere to obtain the supported catalyst.

9. The method of claim 8, wherein the weight ratio of the iron trichloride modified graphite to titanium tetrachloride or titanium trichloride is 20-100: 1; the reaction temperature is 310-500 ℃, the pressure is 10-30 MPa, and the reaction time is 0.5-4 h.

10. A method of making a conductive polyolefin composite comprising:

slurry polymerizing an olefin in the presence of the supported catalyst of any one of claims 1-7 and a cocatalyst to obtain a conductive polyolefin composite precursor;

and adding a conductive carbon material to the conductive polyolefin composite material precursor, and grinding to obtain the conductive polyolefin composite material.

11. The process of claim 10, wherein the cocatalyst is an aluminum alkyl selected from methylaluminoxane, triethylaluminum, triisobutylaluminum, or diethylaluminum monochloride;

the molar ratio of Al to Ti is 25 to 1000, preferably 25 to 500.

12. The method according to claim 10, wherein the amount of the iron trichloride-modified graphite is 1 to 20% by mass, and the amount of the polyolefin material is 80 to 99% by mass, based on the total mass of the conductive polyolefin composite precursor.

13. The method of claim 10, wherein the amount of the ferric trichloride modified graphite is 3 to 10 mass% and the amount of the polyolefin material is 90 to 97 mass% based on the total mass of the conductive polyolefin composite precursor.

14. The method of any one of claims 10-13, wherein the conductive carbon material is selected from one or more of conductive carbon black, graphite, expanded graphite, carbon nanotubes, and graphene.

15. The method according to any one of claims 10 to 13, wherein the conductive carbon material is used in an amount of 1 to 3 mass% of the conductive polyolefin composite precursor.

16. The method according to any one of claims 10-13, wherein milling is performed in a ball mill.

17. The method according to claim 16, wherein the weight ratio of the stainless steel balls to the conductive polyolefin composite precursor in the ball mill is 2-50: 1, the rotation speed is 150-2000 rpm, and the ball milling time is 30 minutes-12 hours.

18. An electrically conductive polyolefin composite obtainable by the process according to any one of claims 10 to 17.

19. The conductive polyolefin composite of claim 18, wherein the conductive polyolefin composite has a volume resistivity of 10 to 1000 Ω -cm.

Technical Field

The invention relates to the field of conductive polyolefin composite materials, in particular to a carbon-supported olefin polymerization catalyst which is prepared by taking expanded graphite as a carrier and modifying a loaded active center, and a conductive polyolefin composite material which is prepared by taking the carbon-supported olefin polymerization catalyst as a main catalyst for polymerization in situ.

Background

The material is characterized by abundant raw materials, low price, easy processing and forming, good chemical resistance, good water resistance, good mechanical strength and the like, and is a high-quality material for films, pipes, plates, various formed products, wires and cables and the like. Polyolefin resins are widely used in the fields of agriculture, packaging, electronics, electrical, automotive, machinery, daily sundry goods, and the like. However, because the polyolefin resin has good insulating property, it also limits its application in the electrical industry, especially in the field of conductive materials, so the development and application of conductive polyolefin resin has become a very active research field in the world in recent years, and it has been developed from the initial pure laboratory research to the application research stage, and is widely applied in the fields of semiconductors, antistatic materials, conductive materials, etc.

Conductive polyolefins can be classified into structural types and filled types. The structural conductive polyolefin is a high polymer or a material which has conductivity after being doped, while the filling type conductive polyolefin is a material which has no conductivity but becomes conductive by adding a conductive filler (conductive filler), and is prepared by mixing and granulating a plastic with better electrical insulating property, a filler with excellent conductivity and other additives, and adopting the methods of injection molding, compression molding, extrusion molding and the like.

The conductive filler is classified into carbon black filled type, graphite filled type, carbon fiber filled type, carbon nanotube filled type, and metal matrix conductive network filled type. Among them, carbon black-filled conductive polymers are most common. At present, research and development in the field of carbon black filled conductive plastics mainly focus on the aspects of carbon black modification, novel conductive carbon black development, nano carbon black application and the like. With the development of nano materials, the preparation of conductive composite materials by compounding nano carbon materials such as nano graphite, carbon nanotubes, graphene and the like with matrix materials becomes a new trend in research and development of filled conductive polymer materials in recent years.

The preparation method for compounding carbon materials such as graphite and the like with polyolefin materials mainly comprises two methods: physical blending methods and in situ polymerization methods. The physical blending method can be divided into a solution blending method and a melt blending method. The modified carbon material is well compatible with a matrix by mechanical means (such as shearing force, magnetic stirring, ultrasound and the like) and fully utilizing the affinity or steric hindrance effect between the modified carbon material and a polymer. The blending method is simple and easy to implement, and is convenient for controlling factors such as volume fraction of the carbon material in the polyolefin matrix. In the in-situ polymerization method, an olefin polymerization catalyst is loaded on a carbon material, and the composite material is prepared by in-situ polymerization.

The Chinese patent CN101275036B adopts the melting and mixing of the expanded graphite and the polymer at the expansion temperature of the expanded graphite to prepare the polymer conductive nano composite material, or firstly mixes the expandable graphite with the polymer, the polymer solution, the low molecular organic assistant or the low molecular organic assistant solution at the expansion temperature of the expandable graphite to prepare the nano graphite conductive composite material, and then compounds the nano graphite conductive composite material with the polymer to prepare the polymer conductive nano composite material. The polymer adopted by the method is polyolefin or polycarbonate, and the graphite content in the composite material is 4-18 mass%.

Chinese patent CN108117684A prepares polyolefin conductive composite material from high-density polyethylene, polypropylene, modified carbon nanotube, graphene and other carbon materials in the presence of lubricant, compatilizer and antioxidant, and the volume resistivity of the composite material reaches 10²Omega cm. According to the process, cobalt chloride, nickel chloride, sodium borohydride and the like are adopted to modify a carbon material, the process flow is complex, and the prepared composite material of polyethylene, polypropylene and carbon is used for eliminating the electrostatic influence of a polyolefin material.

Chinese patent CN109535529A4 mixes polyethylene, ethylene propylene copolymer, conductive carbon black and graphene, and then carries out melt extrusion to obtain conductive polyethylene, which is used for chemical raw material barrel inner containers to reduce static electricity and pollution. The surface resistivity of the conductive polyethylene can reach 10³Omega cm, the surface resistivity of the prepared liner section can reach 10⁵Ω·cm。

Chinese patent CN1252416A provides a method for preparing conductive polyolefin composite material by filling method, which adopts pretreated high-dispersibility conductive filler graphite or superconducting carbon black activated by ziegler-natta catalyst, then olefin monomer polymerization is carried out on the surface to prepare conductive filler/polymer composite material with adjustable conductive range. The composite material comprises 5-90 wt% of conductive filler and 10-95 wt% of polyolefin polymer.

Disclosure of Invention

In order to realize the purpose of obtaining conductive polyolefin by compounding polyolefin and expanded graphite, the invention provides a modification method of expanded graphite and a method for preparing an olefin polymerization catalyst by using the modified graphite as a carrier to prepare a carbon polyolefin composite material by olefin polymerization.

In one aspect, the invention provides a supported catalyst, which comprises a carrier and an active component, and is characterized in that the carrier is iron trichloride modified graphite, and the active component is titanium tetrachloride or titanium trichloride, wherein the titanium content in the supported catalyst is 0.2-6% by mass based on the total mass of the supported catalyst.

In one embodiment, the supported catalyst has a carbon content of 92 to 98 mass%, an iron content of 0.2 to 2 mass%, an oxygen content of 1 to 4 mass%, a chlorine content of 1 to 3 mass%, and a titanium content of 0.2 to 6 mass%, based on the total mass of the supported catalyst.

In one embodiment, the iron trichloride-modified graphite is obtained by:

pretreating graphite at 200-400 ℃ in a vacuum state,

carrying out composite modification on the pretreated graphite and anhydrous ferric trichloride at the temperature of 200-500 ℃ to obtain the ferric trichloride modified graphite.

In one embodiment, the pretreated graphite has an oxygen content of 0.1 to 5.0 mass% and carbon of 94.0 to 99.0 mass% based on the total mass of the pretreated graphite.

In one embodiment, the pretreated graphite and the anhydrous ferric chloride are used in amounts such that the carbon content of the ferric chloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 2.0 mass%, based on the total mass of the modified graphite.

In one embodiment, the pretreated graphite and the anhydrous ferric chloride are used in amounts such that the carbon content of the ferric chloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 2.0 mass%, and the iron content is 0.2 to 2.0 mass%, based on the total mass of the modified graphite.

In one embodiment, the graphite is selected from one or more of natural graphite, expanded graphite, flake graphite, and graphite oxide, preferably expanded graphite.

The invention also relates to a process for preparing the supported catalyst of the invention, comprising the steps of:

providing ferric trichloride modified graphite;

and reacting titanium tetrachloride or titanium trichloride with the iron trichloride modified graphite in an inert atmosphere to obtain the supported catalyst.

In one embodiment, the weight ratio of the iron trichloride modified graphite to titanium tetrachloride or titanium trichloride is 20-100: 1; the reaction temperature is 310-500 ℃, the pressure is 10-30 MPa, and the reaction time is 0.5-4 h.

The present invention also relates to a method of preparing a conductive polyolefin composite comprising:

in the presence of the supported catalyst and the cocatalyst, carrying out slurry polymerization on olefin to obtain a conductive polyolefin composite material precursor;

and adding a conductive carbon material to the conductive polyolefin composite material precursor, and grinding to obtain the conductive polyolefin composite material.

In one embodiment, wherein the cocatalyst is an aluminum alkyl selected from methylaluminoxane, triethylaluminum, triisobutylaluminum, or diethylaluminum monochloride;

the molar ratio of Al to Ti is 25 to 1000, preferably 25 to 500.

In one embodiment, the amount of the iron trichloride-modified graphite is 1 to 20% by mass, and the amount of the polyolefin material is 80 to 99% by mass based on the total mass of the conductive polyolefin composite precursor.

In one embodiment, the amount of the iron trichloride-modified graphite is 3 to 10 mass%, and the amount of the polyolefin material is 90 to 97 mass%, based on the total mass of the conductive polyolefin composite precursor.

In one embodiment, the conductive carbon material is selected from one or more of conductive carbon black, graphite, expanded graphite, carbon nanotubes, and graphene.

In one embodiment, the conductive carbon material is used in an amount of 1 to 3% by mass of the conductive polyolefin composite precursor.

In one embodiment, the milling is performed in a ball mill.

In one embodiment, in the ball mill, the weight ratio of the stainless steel balls to the conductive polyolefin composite precursor in the ball mill is 2 to 50: 1, the rotation speed is 150 to 2000 r/min, and the ball milling time is 30 minutes to 12 hours.

The invention also relates to the conductive polyolefin composite material obtained by the method. In one embodiment, the volume resistivity of the conductive polyolefin composite is 10 to 1000 Ω · cm.

Firstly, modifying graphite by anhydrous ferric chloride by adopting a high-temperature high-pressure method; then loading titanium tetrachloride or titanium trichloride as a polymerization active component to prepare an olefin polymerization catalyst, preparing a modified graphite polyethylene composite material by slurry polymerization in the presence of an alkyl aluminum cocatalyst, and further grinding and compounding the modified graphite polyethylene composite material with a conductive carbon material to obtain the conductive polyolefin composite material. The composite material has low content of conductive filler, keeps the performance of polyolefin resin materials, has good conductivity, and can be applied to products with conductivity, static resistance, electromagnetic shielding and the like.

Drawings

FIG. 1 is an X-ray diffraction pattern (XRD pattern) of the catalyst before and after modification and preparation of the expanded graphite used in the examples.

Fig. 2A, 2B and 2C are transmission electron microscope images (TEM images) of the expanded graphite, the modified expanded graphite and the supported catalyst used in the examples, respectively.

Fig. 3 is an X-ray photoelectron spectrum (XPS spectrum) of the supported catalyst of the present example.

Detailed Description

The technical solution of the present invention is further explained below according to specific embodiments. The scope of protection of the invention is not limited to the following examples, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.

The invention provides a supported catalyst, which comprises a carrier and an active component, and is characterized in that the carrier is ferric trichloride modified graphite, and the active component is titanium tetrachloride or titanium trichloride, wherein the titanium content in the supported catalyst is 0.2-6% by mass based on the total mass of the supported catalyst.

The supported catalyst provided by the invention takes ferric trichloride modified graphite as a carrier. By modifying the graphite, the graphite is easier to load polymerization active centers and strip, so that polymerization monomers are polymerized on the graphite interlayer and the surface. The supported catalyst has good activity of catalyzing olefin polymerization, and can be used as an olefin polymerization catalyst.

In one embodiment, the carbon content of the iron trichloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 3.0 mass%, based on the total mass of the modified graphite. Preferably, the carbon content of the iron trichloride modified graphite is 95.0-99.0 mass%, the oxygen content is 0.1-3.0 mass%, and the iron content is 0.1-2.0 mass%, based on the total mass of the modified graphite. In one embodiment, the carbon content of the iron trichloride modified graphite is 98.0 to 99.8 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 3.0 mass%, based on the total mass of the modified graphite. In another embodiment, the carbon content of the iron trichloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 2.0 mass%, based on the total mass of the modified graphite.

In one embodiment, the iron trichloride modified graphite of the present application can be obtained by:

pretreating graphite at 200-400 ℃ in a vacuum state,

carrying out composite modification on the pretreated graphite and anhydrous ferric trichloride at the temperature of 200-500 ℃ to obtain the ferric trichloride modified graphite.

In the process of preparing the ferric trichloride modified graphite, the graphite is pretreated at the temperature of 200-400 ℃ in a vacuum state, so that the influence of impurities and bound water on the surface of the graphite can be removed. The pretreated graphite contains 0.1 to 5.0 mass% of oxygen and 95.0 to 99.9 mass% of carbon, and can be determined by photoelectron spectroscopy.

In the process of preparing the ferric trichloride modified graphite, the pretreated graphite and anhydrous ferric trichloride can be compositely modified in a high-temperature high-pressure reaction kettle, the vacuum degree is reduced to be below 0.09MPa, the reaction temperature is 200-500 ℃, and the reaction time is 0.5-4 h. The properties of the resulting iron trichloride-modified graphite can be controlled by adjusting the amounts of the pretreated graphite and the anhydrous iron trichloride. In one embodiment, the pretreated graphite and the anhydrous ferric chloride are used in amounts such that the carbon content of the ferric chloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 3.0% by weight, based on the total mass of the modified graphite; preferably, the carbon content of the iron trichloride modified graphite is 95.0-99.0 mass%, the oxygen content is 0.1-2.0 mass%, and the iron content is 0.2-2.0 mass%, based on the total mass of the modified graphite. In one embodiment, the pretreated graphite and the anhydrous ferric chloride are used in amounts such that the carbon content of the ferric chloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 0.1 to 5.0 mass%, and the iron content is 0.1 to 3.0 mass%, based on the total mass of the modified graphite. In another embodiment, the pretreated graphite and the anhydrous ferric chloride are used in amounts such that the carbon content of the ferric chloride modified graphite is 95.0 to 99.0 mass%, the oxygen content is 2.0 to 5.0 mass%, and the iron content is 0.2 to 2.0 mass%, based on the total mass of the modified graphite.

In the present application, the graphite is selected from one or more of natural graphite, expanded graphite, flake graphite, and graphite oxide. Preferably, the graphite is expanded graphite, because the expanded graphite is a vermicular product obtained by oxidizing, acidifying intercalation, washing, drying and expanding natural crystalline flake graphite, the vermicular graphite reserves the lamellar structure of the natural graphite, has the characteristics of high temperature resistance, corrosion resistance, electric conduction, heat conduction, self lubrication and the like, has the characteristics of reduced specific gravity, enlarged specific surface, enlarged compression shape, easy rebound and the like caused by expansion, and is an ideal functional material such as a lubricant, an adsorbent, an additive and the like. In addition, because the expanded graphite is prepared from natural graphite through processes of oxidation, acidification intercalation and the like in the preparation process, compared with the natural graphite, the oxygen content in the graphite is increased, so that the conductivity of the graphite is reduced, and the application of the expanded graphite in conductive materials is limited. In one embodiment, the expanded graphite is selected from the group consisting of flake expanded graphite having a multiple expansion of 300 or more and a particle size of 1 μm or more, and has a volume resistivity of less than 1 Ω · cm. The expanded graphite with small volume resistivity is beneficial to obtaining the conductive composite material with more excellent conductivity.

Compared with an intercalated graphite compound, the ferric trichloride modified graphite obtained by the method has the advantages that the reaction temperature is low, the reaction time is short, the ferric trichloride is almost free of intercalated graphite interlayers, the ferric trichloride is combined with the oxygen functional groups at the edge of the graphite or fills partial graphite structure defects, so that the material resistance caused by partial oxygen functional groups or defects is increased, the graphite is easier to load a polymerization active center due to the change of the graphite edge functional groups and the influence of iron elements, the bonding energy of the graphite and a resin material is improved, the sheets are easier to peel off in the process of mixing and grinding with the graphite, and can be mutually overlapped and occluded in the material to form a conductive network, so that the composite material with higher conductivity can be obtained under the condition of adding less expanded graphite materials.

In one embodiment, the supported catalyst has a carbon content of 92 to 98 mass%, an iron content of 0.2 to 2 mass%, an oxygen content of 1 to 4 mass%, a chlorine content of 1 to 3 mass%, and a titanium content of 0.2 to 6 mass%, based on the total mass of the supported catalyst.

The invention also provides a method for preparing the supported catalyst, which comprises the following steps:

providing ferric trichloride modified graphite;

and reacting titanium tetrachloride or titanium trichloride with the iron trichloride modified graphite in an inert atmosphere to obtain the supported catalyst.

The step of providing the iron trichloride modified graphite is as described above and will not be described herein.

In one embodiment, the preparation of the supported catalyst may be carried out as follows:

placing ferric trichloride modified graphite in a reaction kettle, introducing inert gas nitrogen for replacement, removing air in the reaction kettle, adding titanium tetrachloride or titanium trichloride, wherein the weight ratio of the modified graphite to the titanium tetrachloride or the titanium trichloride is 20-100: and 1, continuously introducing nitrogen to keep a certain pressure, raising the temperature for reaction, reducing the reaction temperature to 310-500 ℃, the pressure to 1-30 MPa, and the reaction time to 0.5-4 h, reducing the temperature to normal temperature after the reaction is finished, adding an inert solvent to wash and remove unreacted titanium tetrachloride or titanium trichloride components on the surface of the carrier, wherein the inert solvent is preferably selected from toluene, xylene and hexane, and drying to obtain the supported catalyst.

In yet another aspect, the present invention provides a method for preparing an electrically conductive polyolefin composite comprising

In the presence of the supported catalyst and the cocatalyst, carrying out slurry polymerization on olefin to obtain a conductive polyolefin composite material precursor;

and adding a conductive carbon material to the conductive polyolefin composite material precursor, and grinding to obtain the conductive polyolefin composite material.

In one embodiment, the cocatalyst is an aluminum alkyl selected from methylaluminoxane, triethylaluminum, triisobutylaluminum, or diethylaluminum monochloride. In the above reaction, the molar ratio of Al/Ti is 25 to 1000, preferably 25 to 500.

The olefins that may be used in the process of the present invention include one or more alpha-olefins, for example, one or more alpha-olefins having from 2 to 10 carbon atoms. Examples of the α -olefin may include ethylene, propylene, butene, hexene, octene, and the like. Thus, a conductive polyolefin composite based on a homopolymer or copolymer of polyethylene, a conductive polyolefin composite based on a homopolymer or copolymer of polypropylene, a conductive polyolefin composite based on a homopolymer or copolymer of polybutene, a conductive polyolefin composite based on a homopolymer or copolymer of polyhexene, a conductive polyolefin composite based on a homopolymer or copolymer of polyoctene, and the like can be obtained.

The process of the present invention employs an in situ polymerization process, such as an in situ slurry polymerization process, to effect polymerization of the polyolefin. In this in situ slurry polymerization process, various solvents known in the art, such as hexane, may be used. The temperature and pressure in the reaction process can be selected according to needs, for example, the reaction temperature can be 50-100 ℃, and the reaction pressure can be 0.4-1.0 MPa. The time for the polymerization reaction may be selected as needed, and may be, for example, 0.2 to 2 hours.

In one embodiment, the amount of the supported catalyst is controlled such that the amount of the iron trichloride-modified graphite is 3 to 10% by mass and the amount of the polyolefin material is 90 to 97% by mass based on the total mass of the conductive polyolefin composite precursor. Preferably, the amount of the iron trichloride-modified graphite is 3 to 10% by mass, and the amount of the polyolefin material is 90 to 97% by mass, based on the total mass of the conductive polyolefin composite precursor.

In one embodiment, the polymerization reaction may be carried out as follows:

adding hexane as a solvent into a polymerization reaction kettle, taking the supported catalyst of the invention as a main catalyst and alkyl aluminum as a cocatalyst, wherein the molar ratio of Al to Ti is 25-500, the reaction temperature is 50-100 ℃, the reaction pressure is 0.4-1.0 MPa, the addition amount is 2-10 volume percent of the hexane solvent, and the polymerization reaction time is 0.2-2 h. And after the reaction is finished, cooling to normal temperature, taking out the polymer slurry, filtering, washing with deionized water, and drying to obtain the composite material precursor.

And after the reaction is finished, cooling to normal temperature, taking out the polymer slurry, filtering, washing with deionized water, and drying to obtain the composite material precursor.

The method of the present invention also requires milling the composite precursor. The conductive carbon material may also be added to the composite material precursor prior to milling thereof. In one embodiment, the conductive carbon material is selected from one or more of conductive carbon black, graphite, expanded graphite, carbon nanotubes, and graphene; preferably, the conductive carbon material is ferric trichloride modified graphite, in particular ferric trichloride modified expanded graphite. In one embodiment, the conductive carbon material is used in an amount of 1 to 3% by mass of the conductive polyolefin composite precursor.

The composite material precursor and the conductive carbon material are ground and compounded, so that carbon materials wrapped in polyolefin material particles are exposed in a tunneling mode and compounded with the added conductive carbon material to form a conductive network, and the conductive polyolefin composite material with good conductivity is obtained.

The grinding may be performed by ball milling, roll milling or the like. Preferably, the grinding compounding is performed in a ball mill. The compatibility of the graphite material and the polyolefin resin can be further improved by modifying the graphite, the graphite material can be more easily peeled off by ball milling to form a conductive network, so that the conductive polyolefin composite material is obtained, and meanwhile, the prepared conductive polyolefin composite material keeps the resin performance of the polyolefin resin. In the ball mill, the weight ratio of the stainless steel balls to the composite material precursor in the ball mill is 2-50: 1, preferably 2-10: 1; the rotating speed is 150-2000 r/min, preferably 150-800 r/min; the ball milling time is 30 minutes to 12 hours, or 30 minutes to 4 hours.

The invention also relates to the conductive polyolefin composite material obtained by the invention. The conductive polyolefin composite material with good conductivity can be applied to conductive, antistatic and electromagnetic shielding products. In one embodiment, the volume resistivity of the conductive polyolefin composite is 10 to 1000 Ω · cm.

The present invention will be described in detail below by way of examples for illustrating the conductive polyolefin composite material of the present invention and the method for preparing the same.

Example 1

(1) Adding 20g of expanded graphite (the expansion multiple is 300-400 times, the average particle size is 1 mu m, and the resistivity is 1.78m omega cm) into a 500mL high-temperature high-pressure reaction kettle, vacuumizing to below 0.09MPa, raising the temperature to 300 ℃ at the heating rate of 10 ℃/min, keeping the temperature for 2 hours, and then reducing the temperature to the normal temperature, wherein the oxygen content and the carbon content in the treated expanded graphite are respectively 2.08 mass% and 97.92 mass%.

(2) Adding 4g of anhydrous ferric trichloride into the pretreated expanded graphite, continuously carrying out reaction modification in a high-temperature high-pressure reaction kettle, vacuumizing to be below 0.09MPa, raising the temperature to 320 ℃ at the heating rate of 10 ℃/min, keeping the temperature for 2 hours, then reducing the temperature to the normal temperature, introducing nitrogen for protection for later use, wherein the iron content, the oxygen content and the carbon content in the modified expanded graphite are respectively 1.01 mass%, 2.06 mass% and 96.93 mass%.

(3) Introducing nitrogen into a reaction kettle containing 5g of modified expanded graphite for replacement, adding 0.2mL of titanium tetrachloride, heating to 310 ℃, continuously introducing nitrogen to keep the pressure at 10MPa, reacting for 4 hours, cooling to normal temperature, adding 90mL of hexane for washing for three times, removing an inactive titanium tetrachloride component attached to the surface of the modified graphite, and drying and evaporating a solvent to obtain the modified graphite carrier olefin polymerization catalyst, wherein the catalyst contains 2.14 mass percent of titanium, 1.08 mass percent of iron, 2.04 mass percent of oxygen and 94.74 mass percent of carbon.

(4) And (2) pumping and replacing a 1L high-pressure kettle with nitrogen for three times, replacing with hydrogen for one time, then sequentially adding 500mL of dried hexane, 17mL of hexane solution (1mol/L) of triethylaluminum and 60mg of the solid catalyst prepared in the step (3), stirring and heating to 80 ℃, introducing hydrogen to raise the pressure to 0.2MPa, introducing ethylene to raise the pressure to 0.8MPa, carrying out polymerization reaction for 1h, cooling to normal temperature, taking out and filtering, removing the hexane solution, washing and filtering with 100mL of deionized water for three times, washing an alkyl aluminum component in the material, and vacuumizing and drying at 60 ℃ in a vacuum oven for 2h to obtain 30g of a blackish brown carbon polymer composite material, wherein the content of expanded graphite in the composite material is 0.19 mass%.

(5) And (3) taking 20g of the dried carbon polymer composite material prepared in the step (4) and 0.40g of the modified expanded graphite prepared in the step (2), placing the materials in a 500mL stainless steel ball milling tank, and ball milling the materials for 2 hours at 300 r/min by using 100g of stainless steel balls to obtain black brown carbon polymer powder, wherein the carbon content in the composite material is 2.19 mass%. Melt index MI of composite materials_2.16The volume resistivity of the prepared carbon polymer was measured to be 24 Ω · cm using a four-probe resistivity tester at 1.96g/10 min.

FIG. 1 is an X-ray diffraction pattern (XRD pattern) of the catalyst before and after modification and preparation of the expanded graphite used in the examples. Fig. 2A, 2B and 2C are transmission electron microscope images (TEM images) of the expanded graphite, the modified expanded graphite and the supported catalyst used in the examples, respectively. Fig. 3 is an X-ray photoelectron spectrum (XPS spectrum) of the supported catalyst of the present example.

Example 2

According to the method of the embodiment 1, except that in the step (2), the addition amount of anhydrous ferric trichloride is 2g, and the temperature is raised to 350 ℃;

in the step (4), the addition amount of the modified expanded graphite is 2g, and 24g of the blackish brown carbon polymer composite material is obtained.

Adding 0.2g of the expanded graphite treated in the step (1) into the mixture obtained in the step (5), and performing ball milling for 4 hours to obtain black brown carbon polymer powder and the melt index MI of the composite material_2.162.04g/10min, and the volume resistivity of the prepared carbon polymer was 31. omega. cm as measured using a four-probe resistivity tester.

Example 3

The method of example 1 was followed except that the carbon material used in the step (5) was natural graphite (resistivity of 9.0 m.OMEGA.cm), which was ball-milled for 4 hours, to obtain a dark brown carbon polymer powder, and the melt index MI of the composite material was_2.162.06g/10min, and the volume resistivity of the prepared carbon polymer can be measured to be 76 omega cm by using a four-probe resistivity tester.

Example 4

The method of example 1, except that the expanded graphite used was vermicular graphite (resistivity 15.6m Ω. cm, expansion factor 150-400 times, average particle diameter 1-2 μm) to give a blackish brown carbon polymer powder, melt index MI of the composite material_2.162.08g/10min, and the volume resistivity of the prepared carbon polymer can be measured to be 55 omega cm by using a four-probe resistivity tester.

Comparative example 1

The process of example 1 was followed except that the carbon material used was expanded graphite and was modified without adding anhydrous ferric chloride, i.e., without the step (2) process. 19g of a carbon polymer composite are obtained, the melt index MI of the composite being_2.161.76g/10min, adding 0.40g of expanded graphite in the step (5), and ball-milling to obtain a bodyA carbon polymer composite material having a volume resistivity of 372k Ω · cm.

Comparative example 2

According to the method described in example 1, except that the carbon material used was natural graphite (resistivity of 9.0 m.OMEGA.. multidot.cm), modified without adding anhydrous ferric trichloride, that is, without the step (2) process. The polyolefin catalyst thus prepared gave 1.8g of a composite material having a melt index MI_2.16At 0.37g/10min, the polymer could not be used directly as a conductive polyolefin composite.

The experimental results show that the carbon polymer composite material has certain conductivity, and can be used as a conductive material for conductive, antistatic and electromagnetic shielding products.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.