Electrically conductive high-strength polypropylene sheet and fabric thereof, polypropylene composite material and its manufacturing method and application

Abstract

This invention relates to the field of polypropylene materials, and discloses a conductive polypropylene sheet, fabric, composite material, its preparation method, and applications. The conductive polypropylene sheet has a structure of BAB'; layer A contains a polypropylene composition A comprising homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite conductive filler c; layers B and B' each comprise random copolymer polypropylene x, a thermal bonding reinforcing agent y, and optional composite conductive filler z; wherein the melting point of the polypropylene composition A is greater than the melting points of the polypropylene compositions B and B'; the contents of composite conductive filler c and composite conductive filler z are not simultaneously zero. A conductive polypropylene composite material is obtained by hot-pressing this conductive polypropylene sheet, which simultaneously possesses excellent tensile properties, impact resistance, and conductivity, and maintains good interlaminar peel strength even when prepared at relatively low hot-pressing temperatures.

Description

Technical Field

[0001] This invention relates to the field of polypropylene materials, and more specifically, to a conductive polypropylene sheet, a conductive polypropylene fabric, a high-strength conductive polypropylene composite material, and their preparation methods and applications. Background Technology

[0002] With the development of science and technology and people's pursuit of a convenient life, the demand for wearable electronic products is increasing day by day, especially in the fields of health monitoring, sports behavior tracking, and national defense and military applications, and is receiving increasing attention from academia and industry. Conductive fabrics that combine conductivity and excellent mechanical properties will inevitably be an important component of the future field of flexible wearable electronics.

[0003] Polypropylene (PP) resin has a low density (0.89–0.91 g / cm³). 3 Its excellent heat resistance, rigidity, and hardness make it suitable for a wide range of applications.

[0004] Highly oriented PP fibers or tapes can be obtained through self-reinforcing technology. For example, in US6312638B1, melt-spun oriented polyolefin fibers are hot-pressed. This method uses specific temperature and pressure to partially melt and bond the surface layer of the polyolefin to prepare a polyolefin board. However, this method is not only sensitive to the temperature of the hot pressing (high temperatures are required), but also results in significant deorbiting of the oriented fibers after hot pressing, leading to a marked decrease in mechanical strength. Another example is US8133537B2, which uses hot pressing of three layers of polyolefin fibers with different melting points to obtain a polyolefin composite material. The melting temperature of the first and second polyolefin layers is lower than that of the core layer. However, the impact strength and interlaminar peel strength of the hot-pressed composite material produced by this method are relatively low.

[0005] To make PP conductive, Chinese invention patent CN112409701B discloses a low-density conductive polypropylene composition, comprising the following components by weight: 80-90 parts PP resin, 5-15 parts hollow glass microspheres, 3-8 parts MWCNT, and 0.1-3 parts additives. Chinese invention patent CN113121918B discloses a method for preparing SEBS-modified conductive polypropylene nanocomposite. Using a twin-screw melt extrusion process, nano-CB is used as a conductive filler, and PP is used as the matrix. By filling with SEBS, which has a solubility parameter similar to PP, the flowability of the composite during processing is improved, the processing performance of the composite is enhanced, and the electrical properties of the conductive polypropylene nanocomposite flat filaments are improved.

[0006] However, the above technical solutions cannot produce PP sheets, fabrics, and composite materials that have both excellent mechanical and electrical properties, and therefore cannot meet the application requirements. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical shortcomings of existing polypropylene composite materials, which are difficult to simultaneously possess a wide processing temperature range, strong mechanical properties, high interlaminar peel strength, and good electrical conductivity. This invention provides polypropylene sheets, polypropylene fabrics, high-strength, high-impact polypropylene composite materials, their preparation methods, and applications. The polypropylene composite material obtained from the polypropylene sheets of this invention through hot pressing, etc., possesses excellent mechanical and electrical properties, and also exhibits good interlaminar peel strength. Even at relatively low hot pressing temperatures and within a wide hot pressing temperature range, the resulting conductive polypropylene composite material still maintains high interlaminar peel strength.

[0008] The first objective of this invention is to provide a conductive polypropylene sheet comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB'.

[0009] Layer A contains a polypropylene composition A, which includes homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite conductive filler c; Layer B may be the same as or different from Layer B', and each contains a polypropylene composition B and a polypropylene composition B', which each includes random copolymer polypropylene x, a thermal bonding reinforcing agent y, and optional composite conductive filler z; wherein the melting point of polypropylene composition A is greater than the melting point of polypropylene composition B and polypropylene composition B'; the content of composite conductive filler c and composite conductive filler z is not both 0.

[0010] According to the present invention, the thin film layers B and B' on both sides of the thin film layer A may be the same or different. In a preferred embodiment of the present invention, the thin film layers B and B' on both sides of the thin film layer A are the same.

[0011] In this invention, the content of each component in polypropylene composition A can be selected within a wide range. Preferably, based on the total weight of polypropylene composition A, polypropylene composition A includes 20-95 wt% homopolymer polypropylene a, 1-45 wt% impact copolymer polypropylene b, and 0-60 wt% composite conductive filler c; more preferably, polypropylene composition A includes 30-85 wt% homopolymer polypropylene a, 3-30 wt% impact copolymer polypropylene b, and 5-45 wt% composite conductive filler c.

[0012] According to the present invention, more preferably, based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 30-85 wt% homopolymer polypropylene a, such as 40 wt%, 50 wt%, 60 wt%, 70 wt%, 85 wt%, and any two values ​​or any range of any two values.

[0013] According to the present invention, more preferably, based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 3-30 wt% of impact copolymer polypropylene b, such as 3 wt%, 10 wt%, 20 wt%, 30 wt%, and any two values ​​or any range of any two values.

[0014] According to the present invention, more preferably, based on the total weight of the polypropylene composition A, the polypropylene composition A includes 5-45 wt% of composite conductive filler c, such as 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 45 wt%, and any two values ​​or any range of any two values.

[0015] In this invention, the content of each component of the polypropylene composition B and the polypropylene composition B' can be selected within a wide range. Preferably, based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' includes 20-95 wt% random copolymer polypropylene x, 0.5-35 wt% thermal bonding reinforcing agent y, and 0-60 wt% composite conductive filler z; more preferably, each of the polypropylene composition B and the polypropylene composition B' includes 30-80 wt% random copolymer polypropylene x, 3-25 wt% thermal bonding reinforcing agent y, and 5-45 wt% composite conductive filler z.

[0016] According to the present invention, more preferably, based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 30-80 wt% of random copolymer polypropylene x; for example, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, and any two values ​​or any range of any two values.

[0017] According to the present invention, more preferably, based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 3-25 wt% of a heat-bonding reinforcing agent y, such as 3 wt%, 5 wt%, 10 wt%, 20 wt%, 25 wt%, and any two values ​​or any range of any two values.

[0018] According to the present invention, more preferably, based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 5-45 wt% of composite conductive filler z, such as 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 45 wt%, and any two values ​​or any range of any two values.

[0019] In this invention, the thickness percentage of layer A can be selected within a wide range. Preferably, based on the total thickness of the conductive polypropylene sheet, the thickness of layer A accounts for 51%-89% of the total thickness, more preferably 71%-89%, and even more preferably 71%-80%. The thicknesses of film layers B and B' on both sides of film layer A can be the same or different, preferably the same.

[0020] The present invention does not limit the thickness of the conductive polypropylene sheet, and it can be selected within a wide range according to its actual application field. Preferably, the thickness of the polypropylene sheet can be 10-1000μm, more preferably 30-500μm, and even more preferably 50-300μm.

[0021] According to the present invention, the thickness of film layers A, B, and B' can be controlled by the extruder melt pump during the processing.

[0022] According to some preferred embodiments of the present invention, the melting point of homopolymer polypropylene a in polypropylene composition A is greater than the melting point of random copolymer polypropylene x in polypropylene composition B and polypropylene composition B', preferably the temperature difference between the corresponding melting points is greater than or equal to 10°C.

[0023] According to some preferred embodiments of the present invention, the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B, and the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B', are each greater than or equal to 5°C, preferably greater than or equal to 10°C, and more preferably greater than or equal to 20°C. The inventors of the present invention have surprisingly discovered that the resulting polypropylene sheet, after hot pressing and the like, yields a polypropylene composite material with superior mechanical properties, and also exhibits better interlaminar peel strength. Even at lower hot pressing temperatures and over a wider range of hot pressing temperatures, the resulting polypropylene composite material exhibits higher interlaminar peel strength.

[0024] According to some preferred embodiments of the present invention, the homopolymer polypropylene a has: a melting point of 150-170°C, preferably 160-170°C; and / or a melt flow rate of 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 2.5-18 g / 10 min, at 230°C and a load of 2.16 kg; and / or an isotacticity (mm) of not less than 96%.

[0025] According to some preferred embodiments of the present invention, the impact-resistant copolymer polypropylene b has the following characteristics: the melting point of the impact-resistant copolymer polypropylene b is 150-170°C; and / or, the monomer for copolymerizing the impact-resistant copolymer polypropylene b with propylene is ethylene or butene, preferably butene; and / or, the melt flow rate of the impact-resistant copolymer polypropylene b at 230°C and 2.16 kg load is 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 2.5-18 g / 10 min; and / or, the cantilever beam impact strength of the impact-resistant copolymer polypropylene b is not less than 20 KJ / m. 2 (Tested at 23℃).

[0026] According to the inventors' research, when the melt flow rate and polymer composition ratio of polypropylene composition A are within the above-mentioned preferred range, the high-impact copolymer polypropylene b in the composition can effectively absorb impact energy, meeting the impact performance requirements and giving the sheet good impact performance. Simultaneously, because the macromolecular chain segments in homopolymer polypropylene a are relatively regular, crystallization occurs during the sheet preparation process, thus the sheet also has good tensile properties.

[0027] According to some preferred embodiments of the present invention, the random copolymer polypropylene x has the following characteristics: a melting point of 110-150°C, preferably 120-140°C; and / or a melt flow rate of 0.5-50 g / 10 min at 230°C and a load of 2.16 kg, preferably 1-20 g / 10 min, more preferably 3-18 g / 10 min; and / or a molecular weight distribution Mw / Mn of 5-12, preferably 7-10; and / or a copolymer of propylene with ethylene and / or butene, preferably an ethylene-propylene-butene terpolymer and / or a propylene-ethylene binary copolymer.

[0028] According to some preferred embodiments of the present invention, the thermal bonding reinforcing agent y has: a melting point or viscous flow temperature of 70-110°C; and / or a melt flow rate of 0.5-50 g / 10 min at 190°C and a load of 2.16 kg, preferably 1-20 g / 10 min, more preferably 1-18 g / 10 min; and / or selected from one or more of polyolefin elastomers, ethylene propylene diene monomer (EPDM) rubber, SEBS, SBS, EVA, and petroleum resins; preferably, it is a polyolefin elastomer and / or petroleum resin; more preferably, the polyolefin elastomer is a copolymer elastomer of ethylene and propylene and / or α-olefins, wherein the α-olefin is preferably a C4-C12 α-olefin, more preferably 1-butene and / or 1-octene; and / or, the petroleum resin is a C5 and / or C9 hydrogenated petroleum resin with a softening point of 100-150°C; preferably a cyclopentadiene type resin.

[0029] According to the inventors' research, when the melt flow rate and polymer composition ratio of polypropylene compositions B and B' are within the preferred range, the low-melting-point random copolymer polypropylene x and the heat-bonding reinforcing agent y in the composition can significantly reduce the hot-pressing temperature and widen the hot-pressing temperature window. Furthermore, the heat-bonding reinforcing agent y provides good adhesion performance for the sheet and can further improve the interlayer peel strength.

[0030] According to some preferred embodiments of the present invention, layer A further contains a β-crystal nucleating agent; preferably,

[0031] The β-crystal nucleating agent is selected from at least one of polycyclic aromatic hydrocarbons, group IIA two-component complexes, aromatic diamides, rare earth compounds, and cyclic dicarboxylate nucleating agents.

[0032] In this invention, the content of the β-crystal nucleating agent can be selected over a wide range. Preferably, relative to 100 parts by weight of polypropylene composition A, the content of the β-crystal nucleating agent in layer A is 0.01-0.5 parts by weight. Specifically, for example, the content of the β-crystal nucleating agent can be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5 parts by weight.

[0033] According to the inventors' research, when the melt flow rate, polymer composition ratio, and thickness distribution of film layer A of polypropylene composition A, polypropylene composition B, and polypropylene composition B' are within the preferred range, the sheet preparation process can be made more stable, thereby giving the sheet better uniformity, tensile strength, impact performance, and interlayer peel strength.

[0034] In this invention, the composite conductive filler c and composite conductive filler z have a wide range of options, and can be the same or different, each including a conductive main material, a conductive auxiliary material, and an optional interface modifier; preferably,

[0035] Based on the total weight of the composite conductive filler c and the composite conductive filler z, each of the composite conductive filler c and the composite conductive filler z includes 40-97wt%, more preferably 49.5-95wt%, of conductive main material, 3-60wt%, more preferably 4.5-50wt%, of conductive auxiliary material, and 0-4wt%, more preferably 0.5-3wt%, of interface modifier.

[0036] Preferably, the conductive main material is selected from at least one of metal powder, metal-plated nanoparticles, graphite powder, and carbon black.

[0037] Preferably, the particle size range of the conductive main material is 100nm-100μm.

[0038] Preferably, the conductive auxiliary material is selected from at least one of metal fibers, metal-plated nanofibers, and carbon nanotubes, and / or the particle size range of the conductive auxiliary material is 100nm-100μm.

[0039] Preferably, the interface modifier is selected from one or more of surfactants, maleic anhydride, silane coupling agents, and polyvinylpyrrolidone.

[0040] For illustration, the conductive main material can be commercial metal powder, metal-plated nanoparticles, graphite powder, or carbon black with different particle sizes, ranging from 100nm to 100μm. Preferably, the metal powder includes copper powder, aluminum powder, iron powder, stainless steel powder, nickel powder, cobalt powder, titanium powder, molybdenum powder, tungsten powder, silver powder, gold powder, and platinum powder. Preferably, the metal-plated nanoparticles include gold-plated silicon dioxide, platinum-plated silicon dioxide, gold-plated titanium dioxide, and platinum-plated titanium dioxide. Conductive main materials with different particle sizes have a synergistic filling effect to increase conductivity.

[0041] For illustration, the conductive auxiliary material is a commercial metal fiber, metal-plated nanofiber, or carbon nanotube with different particle sizes, ranging from 100nm to 100μm. Preferably, the metal fiber includes copper fiber, aluminum fiber, iron fiber, stainless steel fiber, nickel fiber, titanium fiber, silver fiber, gold fiber, or platinum fiber. Preferably, the metal-plated nanofiber includes gold-plated calcium sulfate whiskers, platinum-plated calcium sulfate whiskers, gold-plated glass fiber, or platinum-plated glass fiber. The conductive auxiliary material has high conductivity and fibrous microstructure, and can act as a "bridge" between conductive main materials to form a better conductive channel, thereby achieving the production of highly conductive composite materials at low cost.

[0042] As an explanation, the interface modifier is one or more (including two) of surfactants, maleic anhydride, silane coupling agents, titanate coupling agents, and polyvinylpyrrolidone (PVP). The interface modifier has the function of regulating the interfacial compatibility between conductive main materials and conductive auxiliary materials and polypropylene, reducing interfacial voids and interfacial resistance, and can obtain composite materials with higher conductivity.

[0043] According to the inventors' research, when the components of composite conductive filler c and composite conductive filler z are within the above-mentioned preferred range, the conductive auxiliary materials in the composition can form good conductive channels between the conductive main materials, meet higher conductivity requirements, and enable the sheet to have good conductivity.

[0044] In a preferred embodiment of the present invention, the composite conductive filler z is the same as the composite conductive filler c.

[0045] The conductive polypropylene sheet of the present invention can be prepared by means of the following method: the BAB' layer structure of the conductive polypropylene sheet is obtained by co-extruding a layer A raw material containing polypropylene composition A, a layer B raw material containing polypropylene composition B, and a layer B' raw material containing polypropylene composition B'.

[0046] The second objective of this invention is to provide a method for preparing the conductive polypropylene sheet described above, comprising co-extruding, casting or calendering, and stretching a layer A raw material containing a polypropylene composition A, a layer B raw material containing a polypropylene composition B, and a layer B' raw material containing a polypropylene composition B' according to a BAB' structure to obtain the conductive polypropylene sheet.

[0047] Preferably, the preparation of the raw material of layer A includes melt blending of the homopolymer polypropylene a, the impact copolymer polypropylene b, and the optional composite conductive filler c; the melt blending conditions and equipment of the polypropylene composition A adopt the conditions and equipment of polyolefin melt blending in the prior art, preferably, the melting temperature is 150-170℃, and the equipment is preferably a twin-screw extruder.

[0048] Preferably, the preparation of the raw materials for layers B and B' each includes melt blending the components, including the random copolymer polypropylene x, the thermal bonding reinforcing agent y, and the optional composite conductive filler z. The melt blending conditions and equipment for the polypropylene composition B adopt the conditions and equipment for melt blending of polyolefins in the prior art. Preferably, the melting temperature is 110-150°C, and the equipment is preferably a twin-screw extruder.

[0049] The temperature range for co-extrusion molding and casting is relatively wide. In a preferred embodiment of the present invention, the temperatures for co-extrusion and casting are independently selected from 200-240°C.

[0050] In a preferred embodiment of the present invention, the rolling temperature is 50-70°C.

[0051] The range of stretching conditions is relatively wide. In a preferred embodiment of the present invention, the stretching conditions include: the stretching method is free stretching, and / or solid-state stretching, and / or multi-stage stretching; the stretching temperature is 90-165℃, preferably 90-140℃, and more preferably 90-119℃; the stretching ratio is 1-20 times, preferably 2-15 times.

[0052] According to some embodiments of the present invention, polypropylene composition A, polypropylene composition B, and polypropylene composition B' are co-extruded according to a BAB' structure and then cast or calendered to obtain a conductive polypropylene co-extruded sheet. The extrusion calendering process may include passing the conductive polypropylene co-extruded sheet sequentially through calendering rollers and traction rollers, followed by solid-state stretching, edge trimming, and winding to obtain the sheet. The extrusion casting temperature is 200-230°C, and the calendering roller temperature is 50-70°C. The specific process for preparing the film using the extrusion calendering method is a commonly used choice in the art and will not be described in detail here.

[0053] The third objective of this invention is to provide a conductive polypropylene fabric, which is a three-dimensional polypropylene fabric obtained by weaving the conductive polypropylene sheet described above.

[0054] Preferably, the conductive polypropylene fabric is obtained by slitting and weaving the conductive polypropylene sheet; and / or, the conductive polypropylene fabric has a three-dimensional structure of plain weave, twill weave, and / or satin weave.

[0055] To facilitate weaving, it is preferable to cut the conductive polypropylene sheet into a conductive polypropylene sheet flat strip with a width of 2-5mm, and then weave it into a polypropylene fabric.

[0056] In a more preferred embodiment of the present invention, the conductive polypropylene fabric is a plain weave, twill weave, satin weave, or three-dimensional conductive polypropylene fabric obtained by weaving a three-layer co-extruded conductive polypropylene stretch flat strip, and the three-layer co-extruded conductive polypropylene stretch flat strip includes at least one film layer A formed by a high-melting-point polypropylene composition A and at least one film layer B formed by a low-melting-point polypropylene composition B, wherein the polypropylene composition A includes homopolymer polypropylene a, impact copolymer polypropylene b, and composite conductive filler c; the polypropylene composition B includes random copolymer polypropylene x, thermal bonding reinforcing agent y, and composite conductive filler z, and the polymer film layer B is located on both sides of layer A.

[0057] The fourth objective of this invention is to provide a conductive polypropylene composite material, which is prepared by hot pressing together multiple layers of the conductive polypropylene sheets and / or the conductive polypropylene fabrics described above.

[0058] Preferably, the conductive polypropylene composite material is prepared by hot pressing multiple layers of the conductive polypropylene sheets or the conductive polypropylene fabric.

[0059] Preferably, the multilayer conductive polypropylene sheets are stacked from top to bottom at an angle of 0-90° along their respective machine directions.

[0060] Preferably, the multilayer conductive polypropylene fabric is stacked from top to bottom with the warp direction placed at an angle of 0-90° between the warp directions.

[0061] Preferably, the multilayer conductive polypropylene sheet and / or multilayer conductive polypropylene fabric has more than or equal to 2 layers, more preferably 2-200 layers; and most preferably 4-100 layers.

[0062] In some preferred embodiments of the present invention, a conductive polypropylene composite material with a melting point gradient structure is obtained by sequentially stacking the conductive polypropylene sheets described above; preferably, the structure of the conductive polypropylene composite material from bottom to top is B. n A n B n ...B i A i B i ……B2A2B2, B1A1B1, B2A2B2……B i A i B i ...B n A n B n The total number of layers in the conductive polypropylene sheet unit is 2n-1; i and n are both integers not less than 2, and i≤n; the conductive polypropylene sheets are stacked from top to bottom with the warp direction at 0-90° intervals, preferably with more than or equal to 2 layers, more preferably 2-200 layers, and most preferably 4-100 layers. The polypropylene composition A... i The melting point is greater than that of the polypropylene composition B. i .

[0063] Preferably, the polypropylene composition B i The melting point of polypropylene composition B is greater than or equal to that of its adjacent polypropylene composition. i-1 Its melting point.

[0064] In some preferred embodiments of the present invention, the conductive polypropylene composite material comprises a plurality of sequentially stacked polypropylene sheet unit groups; each polypropylene sheet unit group includes at least one identical or different polypropylene sheet unit, and each polypropylene sheet unit includes a core layer A. i and located in core layer A i Outer B on both sides i B' i The structure is B i A i B' i The structure of the conductive polypropylene composite material, from bottom to top, is group n...group i...group 2, group 1, group 2...group i...group n, and the total number of polypropylene sheet unit groups is 2n-1; i and n are both integers not less than 2, and i≤n;

[0065] Among them, the core layer A in the polypropylene sheet unit iComposition A containing polypropylene i Outer layer B i With outer layer B' i Whether the composition is the same or different, each composition corresponds to a polypropylene composition B. i Polypropylene composition B' i ,

[0066] The polypropylene composition A i The melting point is greater than that of the polypropylene composition B. i The polypropylene composition B' i The melting point of the outermost layer in the i-th group is greater than the average melting point of the outermost layer in the (i-1)-th group.

[0067] According to the present invention, in the structure of the polypropylene composite material, the upper i-th group and the lower i-th group may be the same or different.

[0068] In a preferred embodiment of the present invention, polypropylene composition A i The melting point of polypropylene composition B i The difference in melting points, polypropylene composition A i The melting point of polypropylene composition B' i The difference in melting point is greater than or equal to 5°C, preferably greater than or equal to 10°C, more preferably greater than or equal to 20°C; and even more preferably 20-60°C.

[0069] According to the present invention, the core layer in each polypropylene sheet unit can be the same material or different materials. The present invention does not impose any particular limitation on this, as long as A... i The melting point is greater than that of the polypropylene composition B. i Polypropylene composition B' i The melting points of all these factors can achieve better technical results.

[0070] In a preferred embodiment of the present invention, the difference between the average melting point of all outer layers in the i-th group and the average melting point of all outer layers in the (i-1)-th group is the same or different, and is 1-40°C, preferably 1-10°C, and more preferably 1-5°C.

[0071] According to the present invention, the total number of polypropylene sheet unit groups is 2n-1. The present invention has a wide range of options for the total number of polypropylene sheet unit groups. In a preferred embodiment of the present invention, 2≤n≤100, more preferably, 2≤n≤50, and even more preferably, 2≤n≤30.

[0072] According to the present invention, the number of polypropylene sheet units included in each polypropylene sheet unit group can be selected within a wide range. In a preferred embodiment of the present invention, each polypropylene sheet unit group independently includes 1 to 10, preferably 1 to 5, more preferably 1 to 3 identical or different polypropylene sheet units, and even more preferably 1 polypropylene sheet unit. Preferably, the number of polypropylene sheet units included in each polypropylene sheet unit group is the same.

[0073] Preferably, but not necessarily, the melting point of any outer layer in each group is within ±10°C, ±5°C, more preferably within ±3°C, and more preferably within ±1°C of the average melting point of all outer layers in the group.

[0074] In embodiments where each polypropylene sheet unit group comprises only one polypropylene sheet unit, for example, the structure of the polypropylene composite material can be arranged from bottom to top as B n A n B' n ...B i A i B' i ...B2A2B'2, B1A1B'1, B2A2B'2...B i A i B' i ...B n A n B' n The total number of layers in the polypropylene sheet unit is 2n-1; i and n are both integers not less than 2, and i≤n.

[0075] In embodiments where each polypropylene sheet unit group comprises two or more polypropylene sheet units, for example, the structure of the i-th polypropylene sheet unit group is B. i1 A i1 B' i1 B i2 A i2 B' i2 ...B ip A ip B' ip The structure of the polypropylene composite material can be arranged from bottom to top as follows: (B) n1 A n1 B' n1 B n2 A n2 B' n2 ...B nq A nq B' nq )……(B i1 A i1 B' i1 B i2 A i2B' i2 ...B ip A ip B' ip )……(B 21 A 21 B' 21 B 22 A 22 B' 22 ...B 2k A 2k B' 2k (B) 11 A 11 B' 11 B 12 A 12 B' 12 ...B 1j A 1j B' 1j (B) 21 A 21 B' 21 B 22 A 22 B' 22 ...B 2k A 2k B' 2k )……(B i1 A i1 B' i1 B i2 A i2 B' i2 ...B ip A ip B' ip )……(B n1 A n1 B' n1 B n2 A n2 B' n2 ...B nq A nq B' nq The total number of polypropylene sheet units stacked is j+2k+……2p+……2q; j, k, p, and q are each independent integers not less than 2, preferably 2 to 10, more preferably 2 to 5, and even more preferably 2 to 3.

[0076] In a preferred embodiment of the present invention, the polypropylene composite material has at least one of the following characteristics:

[0077] Longitudinal tensile strength ≥100MPa, preferably ≥120MPa;

[0078] Interlayer peel strength ≥1N / mm, preferably ≥1.1N / mm;

[0079] Resistivity ≤100000Ω·cm, preferably ≤10000Ω·cm;

[0080] Tensile strength was determined according to the method specified in GB / T1040.1-2018, interlaminar peel strength was determined according to the method specified in GB / T2358-98, and resistivity was determined according to the method specified in GB / T 15738-2008. The corresponding test specimens for the above tests were the standard test specimens required in the above test standards.

[0081] When the conductive polypropylene composite material is obtained by hot pressing 24 layers of conductive polypropylene fabric and the thickness is about 1.7 mm, the drop hammer impact strength is ≥200 J, preferably ≥220 J.

[0082] The drop hammer impact strength was determined according to the method specified in GB / T14153-1993, and the thickness of the sample was the same as the thickness of the prepared product.

[0083] In a preferred embodiment of the present invention, the areal density of the multilayer conductive polypropylene composite material is greater than or equal to 110 g / m³. 2 More preferably 110g / m 2 -14000g / m 2 The optimal value is 220g / m³. 2 -7000g / m 2 The resistivity of the multilayer conductive polypropylene composite material is less than or equal to 100,000 Ω·cm, more preferably 0.1-100,000 Ω·cm, and most preferably 0.1-10,000 Ω·cm. In a preferred embodiment of the present invention, the conductive polypropylene fabric in each of the stacked layers contains polypropylene composition A. i They can be the same or different, each layer contains polypropylene fabric A i All can be selected independently, with polypropylene composition A being preferred for each layer. i They are the same.

[0084] The fifth objective of this invention is to provide a method for preparing the conductive polypropylene composite material described above. This method includes hot-pressing and fusing the conductive polypropylene sheet and / or the conductive polypropylene fabric into a laminate, and then cooling and shaping it to form the conductive polypropylene composite material.

[0085] Preferably, the temperature of the hot-pressing fusion is 115-170℃, more preferably 115-159℃, and even more preferably 140-159℃.

[0086] Preferably, the pressure of the hot-press fusion is 2-10 MPa.

[0087] Preferably, the preheating time for hot pressing fusion is 5-600s, and the hot pressing time is 1-600s, preferably 10-500s.

[0088] Preferably, the cooling and shaping pressure is 2-8 MPa, and the cooling and shaping time is 30-700 s.

[0089] Preferably, the conductive polypropylene sheet and / or the conductive polypropylene fabric stack has more than or equal to 2 layers, more preferably 2-200 layers; more preferably 4-100 layers.

[0090] Preferably, adjacent layers of the conductive polypropylene fabric stack are placed at an angle of 0-90° between the warp and weft directions.

[0091] Preferably, adjacent layers of the conductive polypropylene sheet stack are placed at 0-90° along their respective machine directions.

[0092] In a more preferred embodiment of the present invention, the method for preparing the high-strength conductive polypropylene composite material includes the following steps:

[0093] Step a: Take polypropylene composition A i Polypropylene composition B i Polypropylene composition B' i According to B i A i B' i The structure is co-extruded and then cast or calendered to obtain a conductive polypropylene co-extruded sheet; preferably, the extrusion casting or calendering temperature is 200-240℃, and the calendering roll temperature is 50-70℃.

[0094] Step b: The conductive polypropylene co-extruded sheet is stretched at a certain temperature to obtain a conductive polypropylene stretched sheet; the stretching method is free stretching, and / or solid-phase stretching, and / or multi-stage stretching; the stretching temperature is preferably 90-165℃, more preferably 90-140℃, and even more preferably 90-119℃; the stretching ratio is 1-20 times, preferably 2-15 times.

[0095] Step c: Cut the conductive polypropylene stretched sheet into conductive polypropylene flat strips, and weave the flat strips into polypropylene fabrics; preferably, the width of the conductive polypropylene flat strips is 2-5mm, and the conductive polypropylene fabrics include plain weave, twill weave, satin weave or other three-dimensional conductive polypropylene fabrics.

[0096] Step d: The conductive polypropylene fabrics are sequentially stacked and hot-pressed together, and then cooled and shaped to form a conductive polypropylene composite material; preferably, in step d, the hot-pressing conditions are: hot-pressing temperature 115-170℃, preferably 115-159℃, more preferably 140-159℃; hot-pressing pressure 2-10MPa, preheating time 5-600s, hot-pressing time 1-600s, preferably 10-500s, cooling pressure 2-8MPa, cooling time 30s-700s; preferably, adjacent polypropylene fabrics in the polypropylene composite material can be placed at 0-90° between the warp and weft directions.

[0097] According to some embodiments of the present invention, in step c, a high-speed slitting machine with multiple blades can be used to cut the oriented conductive polypropylene flat strip with a width of 2-5 mm; the oriented flat strip is then woven into plain weave, twill weave, satin weave or other three-dimensional conductive polypropylene fabrics using a commercial weaving machine according to the designed fabric structure.

[0098] According to a preferred embodiment of the present invention, the pressure is preferably maintained continuously during the hot pressing and cooling process without any decrease. The hot pressing process is continuous, and preferably a continuous hot pressing composite material molding equipment is adopted, consisting of a preheating machine, a crawler-type continuous planar hot press, a crawler-type continuous planar cooling press, a sheet cutting machine, and a sheet stacking machine arranged in sequence. Preferably, the crawler-type continuous planar hot press has a preheating unit, an independent heating and pressurizing unit, an air cooling unit, and a lifting mechanism.

[0099] In the preparation process, the conductive polypropylene sheets and / or the conductive polypropylene fabric are sequentially stacked and preheated in a preheating machine. The preheated samples are then sequentially hot-pressed and fused using a tracked flatbed hot press, followed by cooling and shaping using a tracked continuous flatbed cooling press to produce a conductive polypropylene composite material, i.e., a stacked hot-pressed product. Afterwards, the product is sliced ​​as needed using a sheet cutter, and then stacked and arranged using a sheet stacking machine. The hot-pressing temperature is controlled by the preheating unit, independent heating and pressurizing unit, and air-cooling unit in the tracked flatbed hot press, while the hot-pressing pressure is controlled by a lifting mechanism. According to the inventors' research, when the preparation process parameters are within the preferred range, and when the aforementioned preparation equipment is used to prepare the conductive polymer composite material, the conductive polymer composite material exhibits better tensile strength, impact resistance, interlaminar peel strength, and electrical conductivity.

[0100] The sixth objective of this invention is to provide an application of the conductive polypropylene sheet, the conductive polypropylene fabric, the conductive polypropylene composite material, and the conductive polypropylene composite material prepared by the preparation method described above in the fields of flexible wearable devices, heating fabrics, heating films, electromagnetic shielding, sports protection, automobile manufacturing, military materials, and consumer products.

[0101] According to specific embodiments of the present invention, the materials field includes the electrical and electronic industry, the apparel industry, the building materials and decoration industry, the automobile manufacturing industry, the sports equipment manufacturing industry, the audio equipment manufacturing industry, and the military field.

[0102] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0103] (1) The conductive polypropylene composite material of the present invention has good tensile strength, impact performance and interlaminar peel strength.

[0104] The conductive polypropylene composite material has the following characteristics:

[0105] Longitudinal (MD) tensile strength ≥100MPa, preferably ≥120MPa; interlaminar peel strength ≥1N / mm, preferably ≥1.1N / mm; resistivity ≤100000Ω·cm, preferably ≤10000Ω·cm; when the composite material is made of only 24 layers of polypropylene fabric hot-pressed together and the thickness is about 1.7mm, the drop hammer impact strength ≥200J, preferably ≥220J.

[0106] (2) The conductive polypropylene composite material of the present invention is suitable for preparation at a lower hot pressing temperature and a wider hot pressing temperature range, which effectively reduces the energy consumption of equipment and the damage to the composite material under high temperature operation. At the same time, it still has good interlayer peel strength when prepared at a lower hot pressing temperature.

[0107] (3) The present invention reduces the hot pressing temperature and widens the hot pressing temperature range to 50°C; effectively reducing equipment energy consumption and damage to composite materials under high temperature operation;

[0108] (4) This preparation method can reduce the hot pressing operation time, while improving production efficiency and reducing production energy consumption. Detailed Implementation

[0109] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0110] In the following embodiments and comparative examples:

[0111] The extrusion calender and solid phase stretching equipment were purchased from Tianjin Hengrui Company, and the model is HRPC-800 three-layer co-extrusion plastic stretching sheet production line.

[0112] The properties of the conductive polypropylene composition and sheet were tested according to the following methods, and the film test results are shown in Table 1:

[0113] (1) Melt mass flow rate (MFR): The test shall be performed in accordance with the method specified in GB / T 3682-2000, wherein the test temperature is 230℃ and the load is 2.16kg;

[0114] (2) Density, determined according to the method specified in GB / T 1033.1-2008;

[0115] (3) Melting point, determined according to the method specified in GB / T 28724-2012;

[0116] (4) Tensile strength: determined according to the method specified in GB / T1040.1-2018;

[0117] (5) Drop hammer impact strength: determined according to the method specified in GB / T14153-1993;

[0118] (6) Interlayer peel strength: The test shall be performed in accordance with the method specified in QB / T2358-98.

[0119] (7) Resistivity: The resistivity shall be determined in accordance with the method specified in GB / T 15738-2008.

[0120] In the following examples, the β-crystal nucleating agent with the brand name VP101B was sourced from the Beijing Research Institute of Chemical Industry, China Petroleum & Chemical Corporation; the sources of some raw materials are described in the examples, and the remaining raw materials are commercially available unless otherwise specified.

[0121] Example 1

[0122] This embodiment illustrates the preparation of the thermally conductive polypropylene composition, the three-layer co-extruded thermally conductive polypropylene sheet, the thermally conductive polypropylene fabric, and the thermally conductive polypropylene composite material provided by the present invention.

[0123] (1) Preparation of polypropylene composition A:

[0124] Component a is a homopolymer polypropylene self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with a melting point of 160℃, a melt flow rate (melt mass flow rate) of 3.2 g / 10 min, and an isotacticity of 97%; component b is a polypropylene impact copolymer self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with an ethylene content of 11 wt%, a melting point of 155℃, and a cantilever beam impact strength of 23 KJ / m. 2 (23℃), melt flow rate is 2.0 g / 10 min; component c is composed of 95 wt% conductive carbon black, 4 wt% carbon nanotubes and 1 wt% silane coupling agent KH550, the conductive carbon black particle size is 100-200 nm and the carbon nanotube diameter is 10-50 nm.

[0125] The components obtained above are weighed and mixed according to the proportions, wherein the mass fraction Wa of component a is 60 parts by weight, the mass fraction Wb of component b is 15 parts by weight, and the mass fraction Wc of component c is 25 parts by weight.

[0126] Add 0.05 parts by weight of β-crystal nucleating agent of grade VP101B. Then, add the mixture to a high-speed mixer and mix thoroughly. Next, add the mixed material to the feeder of a twin-screw extruder manufactured by W&P. The material enters the twin screws through the feeder. During processing, the screw temperature is maintained between 200-230℃. After uniform melting and mixing in the screws, extrusion, granulation, and drying, polypropylene composition granules are obtained. The melt flow rate (MFRA) was tested to be 3.3 / 10min. Polypropylene composition A i Its melting point is 162℃.

[0127] (2) Polypropylene composition B i Preparation:

[0128] Component x1 is a random copolymer polypropylene produced by Sinopec Beijing Research Institute of Chemical Industry, which is an ethylene-propylene-butene terpolymer with a molecular weight distribution (Mw / Mn) of 8.9, a melt flow rate of 8.1 g / 10 min, and a melting point of 130℃; Component x2 is a random copolymer polypropylene produced by Sinopec Beijing Research Institute of Chemical Industry, which is an ethylene-propylene-butene terpolymer with a molecular weight distribution (Mw / Mn) of 7.6, a melt flow rate of 7.2 g / 10 min, and a melting point of 135℃; Component x3 is a random copolymer polypropylene produced by Sinopec Beijing Research Institute of Chemical Industry. The random copolymer polypropylene produced by the Industrial Research Institute is an ethylene-propylene-butene terpolymer with a molecular weight distribution Mw / Mn of 7.3, a melt flow rate of 6.6 g / 10 min, and a melting point of 140 °C. Component y is a polyolefin elastomer of grade 6102, purchased from ExxonMobil, which is an ethylene-propylene copolymer. Component z is composed of 95 wt% conductive carbon black, 4 wt% carbon nanotubes, and 1 wt% silane coupling agent KH550. The conductive carbon black has a particle size of 100-200 nm, and the carbon nanotubes have a diameter of 5-10 μm.

[0129] The components obtained above were weighed and mixed according to the specified proportions, wherein the mass fraction of component x, Wx, was 63.75 parts by weight, the mass fraction of component y, Wy, was 11.25 parts by weight, and the mass fraction of component z, Wz, was 25 parts by weight. Other steps were the same as in step (1), and the final polypropylene composition B was obtained. i Granular material (i.e., x) i +y+z=B i (i = 1, 2, 3), after testing, the melting point of B1 is 131℃, the melting point of B2 is 136℃, and the melting point of B3 is 141℃.

[0130] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0131] The polypropylene composition A and polypropylene composition B obtained in steps (1) and (2) above are used. i The granules are dried, and then polypropylene composition A is added to the core layer extruder of a multilayer extrusion calender, and polypropylene composition B is added. i The granules are fed into the upper and lower surface extruders of a multi-layer extrusion casting machine. After being co-extruded and compounded through the extruder die, the granules pass sequentially through calendering rolls and traction rolls, followed by solid-phase stretching, edge trimming, and winding to produce sheets B1AB1, B2AB2, and B3AB3, respectively. The extrusion casting temperature is 230℃, and the calendering roll temperature is 58℃. The solid-phase stretching process is carried out at 140℃, with a stretching rate of 2 m / min and a stretching ratio of 6.

[0132] A composite film (polypropylene sheet) made by stretching and then winding consists of an upper surface layer (outer film B). i ), core layer (film A) and lower surface layer (outer film B) i The composite film is composed of layers A and B. The composite film is 85 μm thick, with layer A accounting for 80% of the total thickness of the sheet.

[0133] (4) Preparation of polypropylene fabric:

[0134] The three-layer co-extruded polypropylene sheet obtained in step (3) above is cut with a high-speed slitting machine with multiple blades to obtain oriented polypropylene flat strips with a width of 3mm; the oriented flat strips are woven with commercial weaving machines according to the designed fabric structure to obtain plain weave polypropylene fabrics B1AB1, B2AB2, and B3AB3.

[0135] (5) Preparation of polypropylene composite materials:

[0136] The polypropylene fabrics obtained in step (4) were stacked sequentially from bottom to top as follows: B3A3B3, B2A2B2, B1A1B1, B2A2B2, and B3A3B3, for a total of 5 layers. The stacked polypropylene fabrics were then hot-pressed together and cooled to form a polypropylene composite material. The polypropylene fabrics were placed at a 90° angle between the warp and weft directions. The hot-pressing conditions were: temperature 145℃, hot-pressing pressure 5MPa, preheating time 90s, hot-pressing time 90s, and cooling time 300s. The thickness of the prepared polypropylene composite material was 413μm.

[0137] Example 2

[0138] This embodiment illustrates the preparation of the thermally conductive polypropylene composition, the three-layer co-extruded thermally conductive polypropylene sheet, the thermally conductive polypropylene fabric, and the thermally conductive polypropylene composite material provided by the present invention.

[0139] (1) Preparation of polypropylene composition A:

[0140] The preparation process is the same as step (1) in Example 1.

[0141] (2) Polypropylene composition B i Preparation:

[0142] The main preparation process is the same as step (2) in Example 1. The difference is that component B... i and x i The materials selected are as follows:

[0143] Components x1-x4 are random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry, Sinopec, which is an ethylene-propylene-butene terpolymer with a melting point of 110℃; components x5-x8 are random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry, Sinopec, which is an ethylene-propylene-butene terpolymer with a melting point of 130℃; components x9-x 12 This is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec. It is an ethylene-propylene-butene terpolymer with a melting point of 150℃; wherein, components x1-x 12 The molecular weight distribution Mw / Mn is between 7 and 10, and the components x1-x 12 The melt flow rates are all between 1 and 20 g / 10 min.

[0144] Finally, polypropylene composition B was obtained. i Granular material (i.e., x) i +y+z=B i (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12), after testing, the melting point of B1-B4 is 113℃, the melting point of B5-B8 is 131℃, and the melting point of B9-B... 12 Its melting point is 151℃.

[0145] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0146] The preparation process is the same as step (3) in Example 1.

[0147] (4) Preparation of thermally conductive polypropylene fabric:

[0148] The preparation process is the same as step (4) of Example 1.

[0149] (5) Preparation of thermally conductive polypropylene composite material:

[0150] The polypropylene fabrics obtained in step (4) above are stacked sequentially, from bottom to top as B. 12 AB 12… B3AB3, B2AB2, B1AB1, B1AB1, B2AB2, B3AB3,…B 12 AB12 The total number of layers is 24. The laminated polypropylene fabrics are hot-pressed and fused together, then cooled and shaped to form a polypropylene composite material. The polypropylene fabrics are placed at a 90° angle between the warp and weft directions. The hot-pressing conditions are: temperature 150℃, hot-pressing pressure 5MPa, preheating time 300s, hot-pressing time 180s, and cooling time 600s. The prepared polypropylene composite material has a thickness of 1.74mm.

[0151] Example 3

[0152] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0153] (1) Preparation of polypropylene composition A:

[0154] Component a is a homopolymer polypropylene self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with a melting point of 160℃, a melt flow rate of 3.2 g / 10 min, and an isotacticity of 97%; component b is a polypropylene impact copolymer self-produced by the Beijing Research Institute of Chemical Industry of Sinopec (impact strength 23 KJ / m under 23℃ testing conditions). 2 The ethylene content is 11wt%, the melt flow rate is 2.0g / 10min, and the melting point is 155℃; component c is composed of 95wt% conductive carbon black, 4wt% carbon nanotubes and 1wt% silane coupling agent KH550, the conductive carbon black particle size is 100-200nm, and the carbon nanotube diameter is 10-50nm.

[0155] The components obtained above were weighed and mixed according to the specified proportions, wherein component a (Wa) had a mass fraction of 60 parts by weight, component b (Wb) had a mass fraction of 15 parts by weight, and component c (Wc) had a mass fraction of 25 parts by weight. 0.05 parts by weight of β-crystal nucleating agent (VP101B) were added. The mixture was then added to a high-speed mixer and mixed thoroughly. The mixed material was then fed into the feeder of a twin-screw extruder manufactured by W&P. The material entered the twin screws through the feeder. During processing, the screw temperature was maintained between 200-230°C. After being melted and mixed evenly by the screws, extruded, granulated, and dried, polypropylene composition granules were obtained. The melt flow rate (MFRA) was measured to be 3.3 / 10 min; the melting point of polypropylene composition A was 162°C.

[0156] (2) Preparation of polypropylene composition B:

[0157] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec. It is an ethylene-propylene-butene terpolymer with a melting point of 140℃ and a melt flow rate of 6.6 g / 10 min. Component y is a polyolefin elastomer of grade 6102 purchased from Exxon. It is an ethylene-propylene copolymer with an ethylene content of 16 wt% and a melt flow rate of 1.4 g / 10 min at 230℃ and 2.16 kg load. Component z is composed of 95 wt% conductive carbon black, 4 wt% carbon nanotubes and 1 wt% silane coupling agent KH550. The conductive carbon black has a particle size of 100-200 nm and the carbon nanotubes have a diameter of 5-10 μm.

[0158] The components obtained above were weighed and mixed according to the proportions, wherein the mass fraction of component x, Wx, was 63.75 parts by weight, the mass fraction of component y, Wy, was 11.25 parts by weight, and the mass fraction of component z, Wz, was 25 parts by weight. Other steps were the same as in step (1). Finally, polypropylene composition B granules were obtained. The melt flow rate MFRB was tested to be 4.4 g / 10 min, and the melting point was 143 °C.

[0159] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0160] The polypropylene composition A and polypropylene composition B granules obtained in steps (1) and (2) above are dried. Then, polypropylene composition A is added to the core extruder of a multilayer extrusion calender, and polypropylene composition B is added to the upper and lower surface extruders of a multilayer extrusion casting machine.

[0161] After the granules are co-extruded and compounded through the die of an extruder, they pass through calendering rollers and traction rollers in sequence, and then undergo solid-phase stretching, edge trimming and winding to obtain the sheet material.

[0162] The extrusion casting temperature is 230℃, and the calendering roll temperature is 55℃. The solid-phase stretching process is carried out at a temperature of 135℃, a stretching rate of 2 m / min, and a stretching ratio of 6 times. After stretching, the film is wound up to form a conductive polypropylene sheet (composite film), which consists of an upper surface layer (film layer A), a core layer (film layer A), and a lower surface layer (film layer B).

[0163] The thickness of the conductive polypropylene sheet (composite film) described above is 82 μm, wherein the thickness of film layer A accounts for 80% of the total thickness of the sheet.

[0164] (4) Preparation of conductive polypropylene fabric:

[0165] The three-layer co-extruded conductive polypropylene sheet obtained in step (3) above is cut with a high-speed slitting machine with multiple blades to obtain an oriented polypropylene flat strip with a width of 3mm; the oriented flat strip is woven with a commercial weaving machine according to the designed fabric structure to obtain a plain weave conductive polypropylene fabric.

[0166] (5) Preparation of conductive polypropylene composite material:

[0167] The conductive polypropylene fabrics obtained in step (4) were sequentially stacked and hot-pressed to form a laminated conductive polypropylene sheet. The laminated conductive polypropylene sheet comprises 24 layers of conductive polypropylene fabric, with the fabrics positioned at 90° angles between the warp and weft directions. The hot-pressing conditions were: temperature 150℃, hot-pressing pressure 5MPa, preheating time 180s, hot-pressing time 180s, and cooling time 600s. The thickness of the prepared conductive polypropylene composite material was 1.73mm.

[0168] Example 4

[0169] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0170] (1) Preparation of polypropylene composition A:

[0171] The preparation process is the same as step (1) in Example 3.

[0172] (2) Preparation of polypropylene composition B:

[0173] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec. It is an ethylene-propylene-butene terpolymer with a melting point of 140℃ and a melt flow rate of 6.6 g / 10 min. Component y is a polyolefin elastomer of grade 6102 purchased from Exxon. It is an ethylene-propylene copolymer with an ethylene content of 16 wt% and a melt flow rate of 1.4 g / 10 min at 230℃ and a load of 2.16 kg. Component z is not added.

[0174] The components prepared above were weighed and mixed according to the ratio, wherein the mass part of component x, Wx, was 85 parts by weight, the mass part of component y, Wy, was 15 parts by weight, and the other steps were the same as in step (1). Finally, polypropylene composition B granules were obtained. The melt flow rate MFRB was tested to be 5.2 g / 10 min, and the melting point was 138 °C.

[0175] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0176] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0177] (4) Preparation of conductive polypropylene fabric:

[0178] The preparation process is the same as step (4) in Example 3.

[0179] (5) Preparation of conductive polypropylene composite material:

[0180] The preparation process is the same as step (5) in Example 3.

[0181] The thickness of the prepared conductive polypropylene composite material is similar to that of Example 3.

[0182] Example 5

[0183] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0184] (1) Preparation of polypropylene composition A:

[0185] Component a is a homopolymer polypropylene self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with a melting point of 160℃, a melt flow rate of 3.2 g / 10 min, and an isotacticity of 97%; component b is a polypropylene impact copolymer self-produced by the Beijing Research Institute of Chemical Industry of Sinopec (impact strength 23 KJ / m under 23℃ testing conditions). 2 The ethylene content is 11 wt%, the melt flow rate is 2.0 g / 10 min, and the melting point is 155 °C; no component c is added.

[0186] The components obtained above were weighed and mixed according to the specified proportions, wherein component a (Wa) had a mass fraction of 80 parts by weight and component b (Wb) had a mass fraction of 20 parts by weight. 0.05 parts by weight of β-crystal nucleating agent (VP101B) were added. The mixture was then added to a high-speed mixer and mixed thoroughly. The mixed material was then fed into the feeder of a twin-screw extruder manufactured by W&P. The material entered the twin screws through the feeder. During processing, the screw temperature was maintained between 200-230°C. After being melted and mixed evenly by the screws, extruded, granulated, and dried, polypropylene composition granules were obtained. The melt flow rate (MFRA) was measured to be 4.6 / 10 min; the melting point of polypropylene composition A was 157°C.

[0187] (2) Preparation of polypropylene composition B:

[0188] The preparation process is the same as step (2) in Example 3.

[0189] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0190] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0191] (4) Preparation of conductive polypropylene fabric:

[0192] The preparation process is the same as step (4) in Example 3.

[0193] (5) Preparation of conductive polypropylene composite material:

[0194] The preparation process is the same as step (5) in Example 3.

[0195] The thickness of the prepared conductive polypropylene composite material is similar to that of Example 3.

[0196] Example 6

[0197] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0198] (1) Preparation of polypropylene composition A:

[0199] Component a is a homopolymer polypropylene self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with a melting point of 160℃, a melt flow rate of 3.2 g / 10 min, and an isotacticity of 97%; component b is a polypropylene impact copolymer self-produced by the Beijing Research Institute of Chemical Industry of Sinopec (impact strength 23 KJ / m under 23℃ testing conditions). 2 The ethylene content is 11wt%, the melt flow rate is 2.0g / 10min, and the melting point is 155℃; component c is composed of 80wt% conductive carbon black, 19wt% stainless steel fiber and 1wt% silane coupling agent KH550, the conductive carbon black particle size is 100-200nm, and the stainless steel fiber diameter is 1-5μm.

[0200] The components obtained above were weighed and mixed according to the specified proportions, wherein component a (Wa) had a mass fraction of 60 parts by weight, component b (Wb) had a mass fraction of 15 parts by weight, and component c (Wc) had a mass fraction of 25 parts by weight. 0.05 parts by weight of β-crystal nucleating agent (VP101B) were added. The mixture was then added to a high-speed mixer and mixed thoroughly. The mixed material was then fed into the feeder of a twin-screw extruder manufactured by W&P. The material entered the twin screws through the feeder. During processing, the screw temperature was maintained between 200-230°C. After being melted and mixed evenly by the screws, extruded, granulated, and dried, polypropylene composition granules were obtained. The melt flow rate (MFRA) was measured to be 4.0 / 10 min; the melting point of polypropylene composition A was 161°C.

[0201] (2) Preparation of polypropylene composition B:

[0202] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec. It is an ethylene-propylene-butene terpolymer with a melting point of 140℃ and a melt flow rate of 6.6 g / 10 min. Component y is a polyolefin elastomer of grade 6102 purchased from Exxon. It is an ethylene-propylene copolymer with an ethylene content of 16 wt% and a melt flow rate of 1.4 g / 10 min at 230℃ and 2.16 kg load. Component z is composed of 80 wt% conductive carbon black, 19 wt% stainless steel fiber and 1 wt% silane coupling agent KH550. The conductive carbon black has a particle size of 100-200 nm and the stainless steel fiber has a diameter of 1-5 μm.

[0203] The components obtained above were weighed and mixed according to the proportions, wherein the mass fraction of component x, Wx, was 63.75 parts by weight, the mass fraction of component y, Wy, was 11.25 parts by weight, and the mass fraction of component z, Wz, was 25 parts by weight. Other steps were the same as in step (1). Finally, polypropylene composition B granules were obtained. The melt flow rate MFRB was tested to be 4.6 g / 10 min, and the melting point was 140 °C.

[0204] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0205] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0206] (4) Preparation of conductive polypropylene fabric:

[0207] The preparation process is the same as step (4) in Example 3.

[0208] (5) Preparation of conductive polypropylene composite material:

[0209] The preparation process is the same as step (5) in Example 3.

[0210] The thickness of the prepared conductive polypropylene composite material is similar to that of Example 3.

[0211] Example 7

[0212] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0213] (1) Preparation of polypropylene composition A:

[0214] The preparation process is the same as step (1) in Example 6.

[0215] (2) Preparation of polypropylene composition B:

[0216] The preparation process is the same as step (2) in Example 4.

[0217] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0218] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0219] (4) Preparation of conductive polypropylene fabric:

[0220] The preparation process is the same as step (4) in Example 3.

[0221] (5) Preparation of conductive polypropylene composite material:

[0222] The preparation process is the same as step (5) in Example 3.

[0223] The thickness of the prepared conductive polypropylene composite material is similar to that of Example 3.

[0224] Example 8

[0225] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0226] (1) Preparation of polypropylene composition A:

[0227] The preparation process is the same as step (1) in Example 5.

[0228] (2) Preparation of polypropylene composition B:

[0229] The preparation process is the same as step (2) of Example 6.

[0230] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0231] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0232] (4) Preparation of conductive polypropylene fabric:

[0233] The preparation process is the same as step (4) in Example 3.

[0234] (5) Preparation of conductive polypropylene composite material:

[0235] The preparation process is the same as step (5) in Example 3.

[0236] The thickness of the prepared conductive polypropylene composite material is similar to that of Example 3.

[0237] Example 9

[0238] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0239] (1) Preparation of polypropylene composition A:

[0240] The preparation process is the same as step (1) in Example 3.

[0241] (2) Preparation of polypropylene composition B:

[0242] The preparation process is the same as step (2) in Example 3.

[0243] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0244] The preparation process is the same as step (3) in Example 3.

[0245] (4) Preparation of conductive polypropylene fabric:

[0246] The preparation process is the same as step (4) in Example 3.

[0247] (5) Preparation of conductive polypropylene composite material:

[0248] The main steps are the same as in Example 3. The laminated conductive polypropylene sheet includes two layers of conductive polypropylene fabric. The hot-pressing conditions used are: temperature 140℃, hot-pressing pressure 2MPa, preheating time 120s, hot-pressing time 10s, and cooling time 300s. The thickness of the prepared conductive polypropylene composite material is 144μm.

[0249] Example 10

[0250] This embodiment illustrates the preparation of the conductive polypropylene composition, the three-layer co-extruded conductive polypropylene sheet, the conductive polypropylene fabric, and the conductive polypropylene composite material provided by the present invention.

[0251] (1) Preparation of polypropylene composition A:

[0252] The preparation process is the same as step (1) in Example 3.

[0253] (2) Preparation of polypropylene composition B:

[0254] The preparation process is the same as step (2) in Example 3.

[0255] (3) Preparation of three-layer co-extruded conductive polypropylene sheets:

[0256] The preparation process is the same as step (3) in Example 3.

[0257] (4) Preparation of conductive polypropylene fabric:

[0258] The preparation process is the same as step (4) in Example 3.

[0259] (5) Preparation of conductive polypropylene composite material:

[0260] The main steps are the same as in Example 3. The laminated conductive polypropylene sheet includes 100 layers of conductive polypropylene fabric. The hot-pressing conditions used are: 159°C, hot-pressing pressure of 10 MPa, preheating time of 300 s, hot-pressing time of 300 s, and cooling time of 700 s. The thickness of the prepared conductive polypropylene composite material is 7.53 mm.

[0261] Comparative Example 1

[0262] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 3. However, only polypropylene composition A was used for extrusion casting into a single-layer film with a thickness of 82 μm.

[0263] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0264] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0265] Comparative Example 2

[0266] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 3. However, only polypropylene composition B was used for extrusion casting into a single-layer film with a thickness of 82 μm.

[0267] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0268] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0269] Comparative Example 3

[0270] A three-layer co-extruded polypropylene sheet was prepared according to the method of Example 6. However, only polypropylene composition A was used for extrusion casting into a single-layer film with a thickness of 82 μm.

[0271] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0272] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0273] Comparative Example 4

[0274] A three-layer co-extruded polypropylene sheet was prepared according to the method of Example 6. However, only polypropylene composition B was used for extrusion casting into a single-layer film with a thickness of 82 μm.

[0275] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0276] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0277] Comparative Example 5

[0278] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 3. The only difference was that polypropylene composition A did not contain composition c, and polypropylene composition B did not contain composition z; the film thickness was 85 μm.

[0279] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0280] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0281] Comparative Example 6

[0282] Three-layer co-extruded polypropylene sheets and polypropylene fabrics were prepared according to the method in Example 1. The difference lies in the preparation of the polypropylene composite material. The prepared polypropylene fabrics were stacked sequentially from bottom to top as B1A1B1, B2A2B2, B3A3B3, B2A2B2, and B1A1B1, with a total of 5 layers. The stacked polypropylene fabrics were then hot-pressed and fused together, and then cooled and shaped to form the polypropylene composite material.

[0283] Example

[0284] The conductive polypropylene composite materials obtained in the above examples and comparative examples were tested according to the following methods, and the test results are shown in Table 1.

[0285] (1) Tensile strength: Samples were prepared and tested according to the methods specified in GB / T1040.1-2018;

[0286] (2) Interlayer peel strength: Samples were prepared and measured in accordance with the method specified in QB / T2358-98.

[0287] (3) Drop hammer impact strength: The test shall be conducted in accordance with the method specified in GB / T14153-1993.

[0288] (4) Resistivity: The resistivity was measured according to the method specified in GB / T 15738-2008. Among them, the thickness of the polypropylene composite materials obtained in Examples 2-8 and Comparative Examples 1-5 were all similar, around 1.7 mm, and all within the range of 1.7 mm ± 0.1 mm.

[0289] Table 1

[0290]

[0291]

[0292] The results from the examples in Table 1 show that the conductive polypropylene composite material prepared according to the present invention possesses excellent tensile properties, impact resistance, and electrical conductivity, while also exhibiting good interlaminar peel strength at relatively low hot-pressing temperatures. The conductive polypropylene composite sheet of the present invention has a longitudinal (MD) tensile strength ≥120 MPa, an interlaminar peel strength ≥1 N / mm, and a resistivity ≤100000 Ω·cm. When the conductive polypropylene composite material is made of 24 layers of conductive polypropylene fabric hot-pressed together with a thickness of approximately 1.7 mm, its drop hammer impact strength ≥200 J.

[0293] As can be seen from the preferred embodiments 3, 6, and 10, the conductive polypropylene composite material prepared by the present invention has a longitudinal (MD) tensile strength ≥120MPa, an interlayer peel strength ≥1.2N / mm, and a resistivity ≤1000Ω·cm; when the conductive polypropylene composite material is made of 24 layers of conductive polypropylene fabric hot-pressed together and the thickness is about 1.7mm, the drop hammer impact strength is ≥200J.

[0294] As can be seen from Comparative Examples 1-6, using only a single-layer sheet structure or using interlayer ratios outside the scope of the examples will lead to a decrease in the performance of the laminated polypropylene sheets or fabrics. Using process conditions outside the scope of the examples will significantly reduce the tensile strength, impact performance, interlayer peel strength, or electrical conductivity of the resulting polypropylene composite material.

[0295] A comparison of Examples 1-2 and Comparative Example 6 shows that, compared with conventional non-gradient melting point polypropylene composites, the polypropylene composites of the present invention with a melting point gradient structure exhibit higher tensile strength, impact properties, and interlaminar peel strength. Compared with conventional non-gradient melting point polypropylene composites, the polypropylene composites of the present invention with a melting point gradient structure require shorter hot-pressing times or lower hot-pressing temperatures during processing. It is believed that reducing the hot-pressing time or temperature can reduce the damage to mechanical properties caused by molecular chain disorientation. Furthermore, reducing the hot-pressing time or temperature can also achieve the beneficial effect of cost reduction and efficiency improvement.

[0296] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0297] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A conductive polypropylene sheet, comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB'; Layer A contains a polypropylene composition A, which includes homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite conductive filler c; layer B may be the same as or different from layer B', and each contains a polypropylene composition B and a polypropylene composition B', which each include random copolymer polypropylene x, thermal bonding reinforcing agent y, and optional composite conductive filler z. in, The melting point of the polypropylene composition A is greater than that of the polypropylene composition B and the polypropylene composition B'; the contents of the composite conductive filler c and the composite conductive filler z are not both 0; Based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 20-95 wt% homopolymer polypropylene a, 1-45 wt% impact copolymer polypropylene b, and 0-60 wt% composite conductive filler c. Based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 20-95 wt% random copolymer polypropylene x, 0.5-35 wt% thermal bonding reinforcing agent y, and 0-60 wt% composite conductive filler z.

2. The conductive polypropylene sheet according to claim 1, characterized in that: Based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 30-85 wt% homopolymer polypropylene a, 3-30 wt% impact copolymer polypropylene b, and 5-45 wt% composite conductive filler c; and / or, Based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 30-80 wt% random copolymer polypropylene x, 3-25 wt% thermal bonding reinforcing agent y, and 5-45 wt% composite conductive filler z.

3. The conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the conductive polypropylene sheet, the thickness of layer A accounts for 51%-89% of the total thickness; and / or, The melting point of homopolymer polypropylene a in polypropylene composition A is greater than the melting point of random copolymer polypropylene x in polypropylene composition B and polypropylene composition B'; and / or, The difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B, and the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B', are each greater than or equal to 5°C.

4. The conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the conductive polypropylene sheet, the thickness of layer A accounts for 71%-89% of the total thickness; and / or, The melting point of homopolymer polypropylene a in polypropylene composition A is greater than the melting point of random copolymer polypropylene x in polypropylene composition B and polypropylene composition B', and the temperature difference between the corresponding melting points is greater than or equal to 10°C; and / or, The difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B, and the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B', are each greater than or equal to 10°C.

5. The conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the conductive polypropylene sheet, the thickness of layer A accounts for 71%-80% of the total thickness; and / or, The difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B, and the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B', are each greater than or equal to 20°C.

6. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The homopolymer polypropylene a has: Melting point is 150-170℃; and / or, The melt flow rate at 230℃ and 2.16kg load is 0.5-50g / 10min; and / or, The isomechanics is not less than 96%.

7. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The homopolymer polypropylene a has: Melting point is 160-170℃; and / or, The melt flow rate at 230℃ and 2.16kg load is 1-20g / 10min.

8. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The homopolymer polypropylene a has: The melt flow rate at 230℃ and 2.16kg load is 2.5-18g / 10min.

9. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The impact-resistant copolymer polypropylene b has a melting point of 150-170℃: and / or, The monomer for the copolymerization of the impact-resistant polypropylene b with propylene is ethylene or butene; and / or, The impact-resistant copolymer polypropylene b has a melt flow rate of 0.5-50 g / 10 min at 230°C and a load of 2.16 kg; and / or, The cantilever beam impact strength of the impact-resistant copolymer polypropylene b is not less than 20 KJ / m. 2 .

10. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The monomer for the copolymerization of the impact-resistant polypropylene b and propylene is butene; and / or, The impact-resistant copolymer polypropylene b has a melt flow rate of 1-20 g / 10 min at 230°C and 2.16 kg load.

11. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The impact-resistant copolymer polypropylene b has a melt flow rate of 2.5-18 g / 10 min at 230°C and 2.16 kg load.

12. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The random copolymer polypropylene x has: Melting point is 110-150℃; and / or, The melt flow rate at 230℃ and 2.16kg load is 0.5-50g / 10min; and / or, The molecular weight distribution Mw / Mn is 5-12; and / or, The random copolymer polypropylene x is a copolymer of propylene with ethylene and / or butene.

13. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The random copolymer polypropylene x has: The melting point is 120-140℃; and / or, The melt flow rate at 230℃ and 2.16kg load is 1-20g / 10min; and / or, The molecular weight distribution Mw / Mn is 7-10; and / or, The random copolymer polypropylene x is an ethylene-propylene-butene terpolymer and / or a propylene-ethylene binary copolymer.

14. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The random copolymer polypropylene x has: The melt flow rate at 230℃ and 2.16kg load is 3-18g / 10min.

15. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The thermal bonding enhancer y has the following characteristics: Melting point or viscous flow temperature is 70-110℃; and / or, The melt flow rate at 190℃ and 2.16kg load is 0.5-50g / 10min.

16. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The thermal bonding enhancer y has the following characteristics: The melt flow rate at 190℃ and 2.16kg load is 1-20g / 10min.

17. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The thermal bonding enhancer y has the following characteristics: The melt flow rate at 190℃ and 2.16kg load is 1-18g / 10min.

18. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The heat-adhesive reinforcing agent y is selected from one or more of polyolefin elastomers, ethylene propylene diene monomer (EPDM) rubber, SEBS, SBS, EVA, and petroleum resin.

19. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The heat-adhesive reinforcing agent y is a polyolefin elastomer and / or petroleum resin.

20. The conductive polypropylene sheet according to claim 18, characterized in that: The polyolefin elastomer is a copolymer elastomer of ethylene with propylene and / or α-olefins.

21. The conductive polypropylene sheet according to claim 20, characterized in that: The α-olefin is a C4-C12 α-olefin.

22. The conductive polypropylene sheet according to claim 20, characterized in that: The α-olefin is 1-butene and / or 1-octene.

23. The conductive polypropylene sheet according to claim 18, characterized in that: The petroleum resin is a C5 and / or C9 hydrogenated petroleum resin with a softening point of 100-150℃.

24. The conductive polypropylene sheet according to claim 18, characterized in that: The petroleum resin is a cyclopentadiene type resin.

25. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The BAB' layer structure of the conductive polypropylene sheet is obtained by co-extruding a layer A raw material containing polypropylene composition A, a layer B raw material containing polypropylene composition B, and a layer B' raw material containing polypropylene composition B'.

26. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: Layer A also contains a β-crystal nucleating agent.

27. The conductive polypropylene sheet according to claim 26, characterized in that: The β-crystal nucleating agent is selected from at least one of polycyclic aromatic hydrocarbons, group IIA binary complexes, aromatic diamides, rare earth compounds, and cyclic dicarboxylate nucleating agents; and / or, The content of the β-crystal nucleating agent in layer A is 0.01-0.5 parts by weight relative to 100 parts by weight of polypropylene composition A.

28. The conductive polypropylene sheet according to any one of claims 1-5, characterized in that: The composite conductive filler c and the composite conductive filler z may be the same or different, and each includes a conductive main material, a conductive auxiliary material and an optional interface modifier.

29. The conductive polypropylene sheet according to claim 28, characterized in that: Based on the total weight of the composite conductive filler c and the composite conductive filler z, each of the composite conductive filler c and the composite conductive filler z includes 40-97wt% conductive main material, 3-60wt% conductive auxiliary material, and 0-4wt% interface modifier.

30. The conductive polypropylene sheet according to claim 28, characterized in that: Based on the total weight of the composite conductive filler c and the composite conductive filler z, each of the composite conductive filler c and the composite conductive filler z includes 49.5-95wt% of conductive main material, 4.5-50wt% of conductive auxiliary material, and 0.5-3wt% of interface modifier.

31. The conductive polypropylene sheet according to claim 28, characterized in that: The conductive main material is selected from at least one of metal powder, metal-plated nanoparticles, graphite powder, and carbon black, and / or has a particle size range of 100nm-100μm; and / or, The conductive auxiliary material is selected from at least one of metal fibers, metal-plated nanofibers, and carbon nanotubes, and / or has a particle size range of 100 nm to 100 μm; and / or, The interface modifier is selected from one or more of surfactants, maleic anhydride, silane coupling agents, and polyvinylpyrrolidone.

32. A method for preparing the conductive polypropylene sheet according to any one of claims 1-31, comprising co-extruding, casting or calendering, and stretching a layer A raw material containing a polypropylene composition A, a layer B raw material containing a polypropylene composition B, and a layer B' raw material containing a polypropylene composition B' according to a BAB' structure to obtain the conductive polypropylene sheet.

33. The method for preparing the conductive polypropylene sheet according to claim 32, characterized in that, The preparation of the raw material for layer A includes melt blending of the components, including the homopolymer polypropylene a, the impact copolymer polypropylene b, and the optional composite conductive filler c; and / or, The preparation of the raw materials for layers B and B' each includes melt blending the components, including the random copolymer polypropylene x, the thermal bonding reinforcing agent y, and the optional composite conductive filler z; and / or, The temperatures for co-extrusion and casting are each independently selected from 200-240°C; and / or, The rolling temperature is 50-70℃; and / or, The stretching conditions include: a stretching temperature of 90-165℃; and a stretching ratio of 1-20 times.

34. The method for preparing the conductive polypropylene sheet according to claim 32, characterized in that, The stretching conditions include: a stretching temperature of 90-140℃ and a stretching ratio of 1-20 times.

35. The method for preparing the conductive polypropylene sheet according to claim 32, characterized in that, The stretching conditions include: a stretching temperature of 90-119℃ and a stretching ratio of 1-20 times.

36. A conductive polypropylene fabric, a three-dimensional polypropylene fabric obtained by weaving the conductive polypropylene sheet according to any one of claims 1-31.

37. The conductive polypropylene fabric according to claim 36, characterized in that: The conductive polypropylene fabric is obtained by slitting and weaving the conductive polypropylene sheet; and / or, the conductive polypropylene fabric has a three-dimensional structure of plain weave, twill weave and / or satin weave.

38. A conductive polypropylene composite material, wherein the conductive polypropylene composite material is prepared by hot pressing together multiple layers of conductive polypropylene sheets according to any one of claims 1-31 and / or conductive polypropylene fabrics according to claims 36 or 37.

39. The conductive polypropylene composite material according to claim 38, characterized in that: The conductive polypropylene composite material is prepared by hot pressing multiple layers of the conductive polypropylene sheets or the conductive polypropylene fabric; and / or Multilayer conductive polypropylene sheets are stacked from top to bottom at 0-90° angles along their respective machine directions; and / or, The multilayer conductive polypropylene fabric consists of layers stacked from top to bottom with warp directions at 0-90° intervals; and / or, The number of layers in the multilayer conductive polypropylene sheet and / or multilayer conductive polypropylene fabric is greater than or equal to 2.

40. The conductive polypropylene composite material according to claim 38, characterized in that: The number of layers in the multilayer conductive polypropylene sheet and / or multilayer conductive polypropylene fabric is 2-200.

41. The conductive polypropylene composite material according to claim 38, characterized in that: The number of layers in the multilayer conductive polypropylene sheet and / or multilayer conductive polypropylene fabric is 4-100.

42. The conductive polypropylene composite material according to any one of claims 38-41, characterized in that: The conductive polypropylene composite material comprises multiple sequentially stacked polypropylene sheet unit groups; each polypropylene sheet unit group includes at least one identical or different polypropylene sheet unit, and each polypropylene sheet unit includes a core layer A. i and located in core layer A i Outer B on both sides i B' i The structure is B i A i B' i The structure of the conductive polypropylene composite material, from bottom to top, is group n...group i...group 2, group 1, group 2...group i...group n, and the total number of polypropylene sheet unit groups is 2n-1. Both i and n are integers not less than 2, and i ≤ n; Among them, the core layer A in the polypropylene sheet unit i Composition A containing polypropylene i Outer layer B i With outer layer B' i Whether the composition is the same or different, each composition corresponds to a polypropylene composition B. i Polypropylene composition B' i , The polypropylene composition A i The melting point is greater than that of the polypropylene composition B. i The polypropylene composition B' i The melting point of the outermost layer in the i-th group is greater than the average melting point of the outermost layer in the (i-1)-th group.

43. The conductive polypropylene composite material according to claim 42, characterized in that: Polypropylene Composition A i The melting point of polypropylene composition B i The difference in melting points, polypropylene composition A i The melting point of polypropylene composition B' i The difference in their melting points is greater than or equal to 5°C; and / or, The difference between the average melting point of all outer layers in group i and the average melting point of all outer layers in group (i-1) is the same or different, and each is between 1 and 40°C; and / or, 2≤n≤100; and / or, Each polypropylene sheet unit group, independently, comprises 1 to 10 identical or different polypropylene sheet units.

44. The conductive polypropylene composite material according to claim 42, characterized in that: Polypropylene Composition A i The melting point of polypropylene composition B i The difference in melting points, polypropylene composition A i The melting point of polypropylene composition B' i The difference in their melting points is greater than or equal to 10°C; and / or, The difference between the average melting point of all outer layers in group i and the average melting point of all outer layers in group (i-1) is the same or different, each ranging from 1 to 10 °C; and / or, 2≤n≤50; and / or, Each polypropylene sheet unit group, independently, comprises 1 to 5 identical or different polypropylene sheet units.

45. The conductive polypropylene composite material according to claim 42, characterized in that: Polypropylene Composition A i The melting point of polypropylene composition B i The difference in melting points, polypropylene composition A i The melting point of polypropylene composition B' i The difference in their melting points is greater than or equal to 20°C; and / or, The difference between the average melting point of all outer layers in group i and the average melting point of all outer layers in group i-1, whether the difference is the same or different, is 1-5℃.

46. ​​A method for preparing the conductive polypropylene composite material according to any one of claims 38-45, the method comprising hot-pressing and fusing the conductive polypropylene sheet and / or the conductive polypropylene fabric together, and then cooling and shaping it to form the conductive polypropylene composite material.

47. The method for preparing the conductive polypropylene composite material according to claim 46 The hot-pressing fusion temperature is 115-170℃; and / or, The pressure for hot-pressing fusion is 2-10 MPa; and / or, The preheating time for the hot-pressing fusion is 5-600s, and the hot-pressing time is 1-600s; and / or, The cooling and setting pressure is 2-8 MPa, and the cooling and setting time is 30-700 s; and / or, The conductive polypropylene sheet and / or the conductive polypropylene fabric laminate has at least two layers; and / or Adjacent layers of the conductive polypropylene fabric stack are positioned at 0-90° angles between each other along the warp direction; and / or, The adjacent layers of the conductive polypropylene sheet stack are placed at 0-90° along their respective machine directions.

48. The method for preparing the conductive polypropylene composite material according to claim 46 The hot-pressing fusion temperature is 115-159℃; and / or, The preheating time for the hot-pressing fusion is 5-600s, and the hot-pressing time is 10-500s; and / or, The conductive polypropylene sheet and / or the conductive polypropylene fabric stack has 2-200 layers.

49. The method for preparing the conductive polypropylene composite material according to claim 46 The hot-pressing fusion temperature is 140-159℃; and / or, The conductive polypropylene sheet and / or the conductive polypropylene fabric stack has 4-100 layers.

50. The applications of the conductive polypropylene sheet according to any one of claims 1-31, the conductive polypropylene fabric according to claim 36 or 37, the conductive polypropylene composite material according to any one of claims 38-45, and the conductive polypropylene composite material prepared by the preparation method according to any one of claims 46-49 in the fields of flexible wearable devices, heating fabrics, heating films, electromagnetic shielding, automobile manufacturing, military materials, and consumer products.

51. The application according to claim 50, characterized in that: The consumer products mentioned are for sports protection.

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