Thermally conductive high strength polypropylene composite sheet and fabric thereof, polypropylene composite material, and method and application thereof

Abstract

This invention relates to the field of polypropylene materials, and discloses a thermally conductive polypropylene sheet, a thermally conductive polypropylene fabric, a high-strength thermally conductive polypropylene composite material, and their preparation methods and applications. The thermally conductive polypropylene sheet includes a film layer A containing a polypropylene composition A and a film layer B containing a polypropylene composition B. Film layer A... i The two film layers B on both sides may be the same or different; the thermally conductive polypropylene sheet has a BAB layer structure, with film layers B located on both sides of film layer A; wherein polypropylene composition A includes homopolymer polypropylene a, impact-resistant copolymer polypropylene b, and composite thermally conductive filler c; each of the polypropylene compositions B includes random copolymer polypropylene x, thermal bonding enhancer y, and composite thermally conductive filler z. The polypropylene composite material obtained by hot-pressing this thermally conductive polypropylene sheet can simultaneously possess excellent tensile properties, impact resistance, and thermal conductivity, and still exhibits 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 thermally conductive polypropylene sheet, a thermally conductive polypropylene fabric, a high-strength thermally conductive polypropylene composite material, and their preparation methods and applications. Background Technology

[0002] With the miniaturization, miniaturization, and multifunctionality of electronic products, the integration level of electronic components is increasing, and the requirements for their heat dissipation performance are also becoming more stringent. However, the poor thermal conductivity of commonly used polymer materials in electronic components can no longer meet the needs of further development of electronic products.

[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] Self-reinforced polymer composites consist of a matrix and a reinforcing phase composed of different forms of the same polymer. The reinforcing phase is typically highly oriented fibers or ribbons. Most self-reinforced polymer composites are prepared using hot-pressing methods. When the reinforcing phase is hot-pressed under certain pressure and temperature, the surface of the reinforcing phase fibers melts to become the matrix melt. The matrix melt and the surface of the reinforcing phase co-crystallize during melting, thus providing sufficient interfacial bonding strength. For example, in US6312638B1, melt-spun oriented polyolefin fibers are hot-pressed, using specific temperature and pressure to partially melt and bond the polyolefin surface layer to prepare a polyolefin board. This preparation method is not only sensitive to the temperature of hot pressing, but also results in significant deorientation of the oriented fibers after hot pressing, leading to a significant decrease in mechanical strength.

[0005] To broaden the hot-pressing window and reduce the hot-pressing pressure, polyolefins with different melting points can be hot-pressed. For example, US8133537B2 describes the hot-pressing of three layers of polyolefin fibers with different melting points to obtain a polyolefin composite material, wherein 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 hot-pressed composite materials produced by this method are relatively low.

[0006] To enhance the thermal conductivity of polypropylene (PP), Chinese invention patent CN107090129B discloses a mesophase pitch-based graphite fiber / polypropylene composite material and its preparation method. This method uses a twin-screw extruder for melt blending, employing mesophase pitch-based graphite fiber, boron nitride, and magnesium hydroxide as thermally conductive fillers to obtain the mesophase pitch-based graphite fiber / polypropylene composite material. Chinese invention patent CN104277323B discloses a thermally conductive and impact-resistant polypropylene / polyester composite material and its preparation method. This method uses a twin-screw extruder for melt blending, utilizing metal powder and boron carbide powder as thermally conductive fillers to obtain the polypropylene / polyester composite material. Chinese invention patent CN108948417B discloses a compounded thermally conductive powder, a polypropylene composite material, its preparation method, and its application. This method uses melt extrusion granulation, employing aluminum hydroxide, alumina, magnesium oxide, magnesium hydroxide, and zinc oxide as compounded thermally conductive powders to obtain the polypropylene composite material.

[0007] The aforementioned patents each have their own significant shortcomings. The resulting thermally conductive polypropylene composite materials have poor mechanical properties, limiting their processing and application scenarios and making them unsuitable for applications such as thin plates, films, and fabrics. CN107090129B and CN104277323B use highly conductive graphite fibers and metal powder as fillers, respectively, which improves the conductivity of the composite material but makes it unsuitable for electronic components requiring insulation. CN108948417B has a low proportion of composite thermally conductive powder, resulting in poor thermal conductivity of the composite material, which cannot meet the requirements of high thermal conductivity applications. Summary of the Invention

[0008] 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 thermal conductivity. This invention provides thermally conductive, high-strength polypropylene composite sheets and their fabrics, polypropylene composite materials, their manufacturing methods, and applications. Polypropylene composite materials are obtained from the polypropylene sheets of this invention through hot pressing, etc. These polypropylene composite materials possess excellent mechanical and thermal conductivity properties, while also exhibiting good interlaminar peel strength. Even at lower hot-pressing temperatures and within a wide hot-pressing temperature range, the resulting thermally conductive polypropylene composite material still maintains high interlaminar peel strength.

[0009] The first aspect of the present invention is to provide a thermally conductive polypropylene sheet, comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB';

[0010] Layer A contains a polypropylene composition A, which includes homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite thermally 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, thermal bonding enhancer y, and optional composite thermally conductive filler z; and the contents of the corresponding composite thermally conductive fillers c and z in polypropylene compositions A, B, and B' are not all 0 at the same time;

[0011] The melting point of polypropylene composition A is greater than that of polypropylene composition B and polypropylene composition B'.

[0012] According to the present invention, the thin film layers 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 on both sides of the thin film layer A are the same.

[0013] According to a preferred embodiment of the present invention, based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 15-99 wt% homopolymer polypropylene a, 0.3-50 wt% impact copolymer polypropylene b, and 0-70 wt% composite thermally conductive filler c; preferably, the polypropylene composition A comprises 35-81 wt% homopolymer polypropylene a, 5-27 wt% impact copolymer polypropylene b, and 10-50 wt% composite thermally conductive filler c.

[0014] According to a preferred embodiment of the present invention, 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 21-99 wt% random copolymer polypropylene x, 0.3-30 wt% thermal bonding reinforcing agent y, and 0-70 wt% composite thermally conductive filler z; preferably, each of the polypropylene composition B and the polypropylene composition B' comprises 40-81 wt% random copolymer polypropylene x, 5-18 wt% thermal bonding reinforcing agent y, and 10-50 wt% composite thermally conductive filler z.

[0015] According to a preferred embodiment of the present invention, based on the total thickness of the thermally conductive polypropylene sheet, the thickness of layer A accounts for 51%-89% of the total thickness, preferably 71%-89%, and more preferably 71%-80%.

[0016] According to a preferred embodiment 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 with a temperature difference of 10°C or greater. In this preferred embodiment, the inventors of the present invention have surprisingly discovered that the resulting polypropylene sheet, after hot pressing, yields a polypropylene composite material with superior mechanical properties and better interlaminar peel strength. Even at lower hot pressing temperatures and over a wider hot pressing temperature range, the resulting polypropylene composite material exhibits higher interlaminar peel strength.

[0017] According to the present invention, the melting point of the polypropylene composition A is greater than that of the polypropylene composition B and the polypropylene composition B'. Preferably, 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, more preferably greater than or equal to 10°C, and more preferably greater than or equal to 20°C.

[0018] According to a preferred embodiment of the present invention, the homopolymer polypropylene a has:

[0019] Melting point is 150-170℃, preferably 160-170℃; and / or,

[0020] The melt flow rate 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,

[0021] The isotacticity (mm) is not less than 96%.

[0022] According to a preferred embodiment of the present invention, the impact-resistant copolymer polypropylene b has at least one of the following characteristics: the melting point of the impact-resistant copolymer polypropylene b is 150-170℃; 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℃ and 2.16kg load is 0.5-50g / 10min, preferably 1-20g / 10min, more preferably 2.5-18g / 10min; and / or, the cantilever beam impact strength of the impact-resistant copolymer polypropylene b is not less than 20KJ / m. 2 (Tested at 23℃).

[0023] 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.

[0024] According to a preferred embodiment of the present invention, the random copolymer polypropylene x has at least one of the following characteristics:

[0025] Melting point is 110-150℃, preferably 120-140℃; and / or,

[0026] The melt flow rate at 230°C and 2.16 kg load is 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 3-18 g / 10 min; and / or,

[0027] The molecular weight distribution Mw / Mn is 5-12, preferably 7-10; and / or,

[0028] It is a copolymer of propylene and ethylene and / or butene, preferably an ethylene-propylene-butene terpolymer and / or a propylene-ethylene binary copolymer.

[0029] According to a preferred embodiment of the present invention, the thermal bonding reinforcing agent y has at least one of the following characteristics:

[0030] Melting point or viscous flow temperature is 70-110℃; and / or,

[0031] The melt flow rate at 190°C and 2.16 kg load is 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 1-18 g / 10 min; and / or,

[0032] It is 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,

[0033] The polyolefin elastomer is a copolymer elastomer of ethylene and propylene and / or α-olefin, 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.

[0034] According to the inventors' research, when the melt flow rate and polymer composition ratio of polypropylene composition 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.

[0035] The composite thermally conductive filler z has a wide range of material selection. In a preferred embodiment of the present invention, the composite thermally conductive filler z is the same as the composite thermally conductive filler c.

[0036] According to a preferred embodiment of the present invention, layer A further contains a β-crystal nucleating agent; preferably,

[0037] 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.

[0038] The content range of the β-crystal nucleating agent is relatively wide. According to a preferred embodiment of the present invention, 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. For example, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 parts by weight, and any two values ​​or any range of any two values.

[0039] According to a preferred embodiment of the present invention, the composite thermally conductive filler c and the composite thermally conductive filler z may be the same or different, and each includes a thermally conductive main material, a thermally conductive auxiliary material and an interface modifier.

[0040] The composite thermally conductive filler c and composite thermally conductive filler z have a wide range of material selection. In a preferred embodiment of the present invention, the composite thermally conductive filler c and composite thermally conductive filler z are each composed of thermally conductive main material, thermally conductive auxiliary material and optional interface modifier. Based on the total weight of the composite thermally conductive filler c, the composite thermally conductive filler c includes 50-99wt% thermally conductive main material, 1-50wt% thermally conductive auxiliary material and 0-3wt% interface modifier.

[0041] The thermally conductive main material is commercial alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon dioxide, and chopped glass fiber with different particle sizes, ranging from 100nm to 100μm. The different particle sizes of the thermally conductive main material synergistically enhance thermal conductivity. Preferably, the weight percentage of the thermally conductive main material is 60-95wt%.

[0042] The thermally conductive auxiliary material is a commercially available boron nitride, silicon carbide, or aluminum nitride with different particle sizes ranging from 100 nm to 100 μm. This auxiliary material has higher thermal conductivity and can form excellent thermal conductivity channels between the main thermally conductive materials, thereby enabling the production of high thermal conductivity composite materials at low cost. Preferably, the weight percentage of the thermally conductive auxiliary material is 5-40 wt%.

[0043] The interface modifier is one or more (including two) selected from maleic anhydride, silane coupling agent, and polyvinylpyrrolidone (PVP). The interface modifier regulates the interfacial compatibility between the thermally conductive main material and the thermally conductive auxiliary material and polypropylene, reduces interfacial porosity and interfacial thermal resistance, and can obtain composite materials with higher thermal conductivity. Preferably, the weight percentage of the interface modifier is 0.5-2 wt%.

[0044] As described above, according to a preferred embodiment of the present invention, based on the total weight of the composite thermally conductive filler c and the composite thermally conductive filler z, each of the composite thermally conductive filler c and the composite thermally conductive filler z comprises 50-99wt%, more preferably 60-95wt%, of a thermally conductive main material, 1-50wt%, more preferably 5-40wt%, of a thermally conductive auxiliary material, and 0-3wt%, more preferably 0.5-2wt%, of an interface modifier.

[0045] According to a preferred embodiment of the present invention, the thermally conductive main material is selected from at least one of alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon dioxide, and chopped glass fiber, and / or the particle size range is 100nm-100μm.

[0046] According to a preferred embodiment of the present invention, the thermally conductive material is selected from at least one of boron nitride, silicon carbide, and aluminum nitride, and / or has a particle size range of 100nm-100μm.

[0047] According to a preferred embodiment of the present invention, the interface modifier is selected from one or more of maleic anhydride, silane coupling agent, and polyvinylpyrrolidone.

[0048] According to the inventors' research, when the components of the composite thermally conductive filler c are within the above-mentioned preferred range, the thermally conductive auxiliary materials in the composition can form good thermally conductive channels between the main thermally conductive materials, meeting higher requirements for thermal conductivity and giving the sheet good thermal conductivity. Simultaneously, the composite thermally conductive filler c is non-conductive, giving the sheet good insulation properties.

[0049] According to the inventors' research, when the melt flow rate, polymer composition ratio, and thickness distribution of film layer A of polypropylene composition A and polypropylene compositions B and 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.

[0050] The BAB' layer structure of the thermally conductive polypropylene sheet can be prepared by various methods. In a preferred embodiment of the present invention, the BAB' layer structure of the thermally conductive polypropylene sheet is obtained by co-extrusion of layer A raw material containing polypropylene composition A, layer B raw material containing polypropylene composition B, and layer B' raw material containing polypropylene composition B'.

[0051] The second aspect of the present invention is to provide a method for preparing the thermally conductive polypropylene sheet described in the first aspect, 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 thermally conductive polypropylene sheet.

[0052] According to a preferred embodiment of the present invention, the preparation of the raw material for layer A includes melt blending of the homopolymer polypropylene a, the impact copolymer polypropylene b, and optionally the composite thermally conductive filler c. The melt blending conditions and equipment for the polypropylene composition A adopt the conditions and equipment for melt blending of polyolefins in the prior art; preferably, the melt temperature is 150-170°C, and the equipment is preferably a twin-screw extruder.

[0053] According to a preferred embodiment of the present invention, the preparation of the raw materials for layers B and B' includes melt blending of each component, including the random copolymer polypropylene x, the thermal bonding reinforcing agent y, and the optional composite thermally conductive filler z. The melt blending conditions and equipment for the polypropylene compositions B and 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.

[0054] According to a preferred embodiment of the present invention, the temperatures of the co-extrusion and casting are each independently selected from 200-240°C.

[0055] According to a preferred embodiment of the present invention, the rolling temperature is 50-70°C.

[0056] According to a preferred embodiment of the present invention, the stretching conditions include: a stretching temperature of 90-165°C, preferably 90-140°C, and more preferably 90-119°C; and a stretching ratio of 1-20 times, preferably 2-15 times.

[0057] In a preferred embodiment of the present invention, the longitudinal tensile strength of the stretched polypropylene sheet is greater than or equal to 30 MPa, more preferably 30 MPa-1 GPa; and most preferably 50-600 MPa.

[0058] 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 thermally conductive polypropylene co-extruded sheet. The extrusion calendering process may include passing the thermally 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 elaborated further here.

[0059] A third aspect of the present invention is to provide a thermally conductive polypropylene fabric, which is a three-dimensional polypropylene fabric obtained by weaving the thermally conductive polypropylene sheet described in the second aspect.

[0060] Preferably, the thermally conductive polypropylene fabric is obtained by slitting and weaving the thermally conductive polypropylene sheet; and / or, the thermally conductive polypropylene fabric has a three-dimensional structure of plain weave, twill weave, and / or satin weave.

[0061] To facilitate weaving, it is preferable to cut the thermally conductive polypropylene sheet into a width of 2-5mm, and then weave it to obtain a thermally conductive polypropylene fabric.

[0062] In a more preferred embodiment of the present invention, the thermally conductive polypropylene fabric is a plain weave, twill weave, satin weave, or three-dimensional thermally conductive polypropylene fabric obtained by weaving a three-layer co-extruded thermally conductive polypropylene stretch flat strip, and the three-layer co-extruded thermally 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, B' formed by low-melting-point polypropylene compositions B, B', wherein the polypropylene composition A includes homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite thermally conductive filler c; the polypropylene compositions B, B' each include random copolymer polypropylene x, thermal bonding reinforcing agent y, and optional composite thermally conductive filler z, and the polymer film layers B, B' are located on both sides of layer A.

[0063] A fourth aspect of the present invention provides a thermally conductive polypropylene composite material, said thermally conductive polypropylene composite material being prepared by hot pressing together multiple layers of thermally conductive polypropylene sheets as described in the first aspect and / or thermally conductive polypropylene fabrics as described in the third aspect; preferably, the structure of the multilayer thermally conductive polypropylene sheet composition, from bottom to top, is B. n A n B' n ...Bi 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 thermally conductive polypropylene sheet unit is 2n-1; i and n are both integers not less than 2, and i≤n; the thermally conductive polypropylene fabric is stacked from top to bottom with the warp direction placed at 0-90° between the warp directions, preferably with more than or equal to 2 layers, more preferably 2-200 layers; and most preferably 4-100 layers.

[0064] Preferably, the thermally conductive polypropylene composite material is prepared by hot pressing multiple layers of the thermally conductive polypropylene sheets or the thermally conductive polypropylene fabric.

[0065] Preferably, the multilayer thermally conductive polypropylene sheets are stacked from top to bottom at an angle of 0-90° along their respective machine directions.

[0066] Preferably, the multilayer thermally conductive polypropylene fabric is stacked from top to bottom with the warp direction placed at an angle of 0-90° between the warp directions.

[0067] Preferably, the multilayer thermally conductive polypropylene sheet and / or multilayer thermally conductive polypropylene fabric has more than or equal to 2 layers, more preferably 2-200 layers; and most preferably 4-100 layers.

[0068] According to a preferred embodiment of the present invention, the thermally 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 thermally conductive polypropylene composite material is arranged from bottom to top as 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;

[0069] 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 ,

[0070] 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 or equal to the average melting point of the outermost layer in the (i-1)-th group.

[0071] As previously stated, preferably, 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.

[0072] 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.

[0073] According to a preferred embodiment of the present invention, the average melting point of all outer layers in the i-th group is greater than or equal to the average melting point of all outer layers in the (i-1)-th group. More preferably, the inventors of the present invention have discovered that when the melting point gradient structure design of the laminated polypropylene, i.e., when the average melting point of all outer layers in the i-th group is greater than the average melting point of all outer layers in the (i-1)-th group, the resulting polypropylene composite material has superior mechanical properties and better interlaminar peel strength.

[0074] 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.

[0075] More preferably, 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 is 1-40°C, preferably 1-10°C, and more preferably 1-5°C.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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 Ai2 B' 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.

[0081] The areal density of the multilayer thermally 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 2The thermal conductivity of the multilayer thermally conductive polypropylene composite material is greater than or equal to 0.5 W / m. -1 K -1 More preferably, it is 0.5-5.0 W / m. -1 K -1 The optimal value is 0.7-3.0 W / m. -1 K -1 .

[0082] In a preferred embodiment of the present invention, the thermally conductive polypropylene composite material has at least one of the following characteristics:

[0083] Longitudinal tensile strength ≥100MPa, preferably ≥120MPa;

[0084] Interlayer peel strength ≥1N / mm, preferably ≥1.1N / mm;

[0085] Thermal conductivity ≥ 0.5 W / m -1 K -1 Preferred ≥0.7W m -1 K -1 ;

[0086] 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 thermal conductivity was determined according to the method specified in GB / T 10297-2015. The corresponding test specimens for the above tests are the standard test specimens required in the above test standards.

[0087] When the thermally conductive polypropylene composite material is obtained by hot pressing 24 layers of thermally conductive polypropylene fabric and the thickness is about 1.7 mm, the drop hammer impact strength is ≥200 J, preferably ≥220 J.

[0088] 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.

[0089] A fifth aspect of the present invention is to provide a method for preparing the thermally conductive polypropylene composite material described in the fourth aspect, the method comprising hot-pressing and fusing the thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric into a laminate, and then cooling and shaping it to form the thermally conductive polypropylene composite material.

[0090] Preferably, the temperature of the hot-pressing fusion is 115-170℃, more preferably 115-159℃, and even more preferably 140-159℃.

[0091] Preferably, the pressure of the hot-press fusion is 2-10 MPa.

[0092] Preferably, the preheating time for hot pressing fusion is 5-600s, and the hot pressing time is 1-600s, preferably 10-500s.

[0093] Preferably, the cooling and shaping pressure is 2-8 MPa, and the cooling and shaping time is 30-700 s.

[0094] Preferably, the thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric stack has more than or equal to 2 layers, more preferably 2-200 layers; more preferably 4-100 layers.

[0095] Preferably, adjacent layers of the thermally conductive polypropylene fabric stack are placed at 0-90° between the warp and weft directions, i.e., in the stretch direction (MD).

[0096] The adjacent layers of the thermally conductive polypropylene sheet stack are placed at 0-90° along their respective machine directions.

[0097] In a more preferred embodiment of the present invention, the method for preparing the high-strength thermally conductive polypropylene composite material includes the following steps:

[0098] Step a: Mix polypropylene composition A, polypropylene composition B, and B' according to B i A i B' i The structure is co-extruded and cast or calendered to obtain polypropylene co-extruded sheets; preferably, the extrusion casting or calendering temperature is 200-240℃, and the calendering roll temperature is 50-70℃;

[0099] Step b: The thermally conductive polypropylene co-extruded sheet is stretched at a certain temperature to obtain a thermally 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.

[0100] Step c: Cut the thermally conductive polypropylene stretched sheet into polypropylene flat strips, and weave the flat strips into polypropylene fabrics; preferably, the width of the thermally conductive polypropylene flat strips is 2-5mm, and the thermally conductive polypropylene fabrics include plain weave, twill weave, satin weave or other three-dimensional thermally conductive polypropylene fabrics.

[0101] Step d: The thermally conductive polypropylene fabrics are sequentially stacked and hot-pressed together, and then cooled and shaped to form a thermally 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 30-700s; preferably, adjacent thermally conductive polypropylene fabrics in the thermally conductive polypropylene composite material can be placed at 0-90° between the warp and weft directions.

[0102] 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 thermally 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 thermally conductive polypropylene fabrics using a commercial weaving machine according to the designed fabric structure.

[0103] 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.

[0104] In the preparation process, the thermally conductive polypropylene sheets and / or the thermally conductive polypropylene fabrics 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 thermally 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 the aforementioned preparation equipment is used to prepare the thermally conductive polymer composite material, the thermally conductive polymer composite material exhibits better tensile strength, impact resistance, interlaminar peel strength, and thermal conductivity.

[0105] The sixth aspect of the present invention is to provide the application of the thermally conductive polypropylene sheet described in the first aspect, the thermally conductive polypropylene fabric described in the third aspect, the thermally conductive polypropylene composite material described in the fourth aspect, and the thermally conductive polypropylene composite material prepared in the fifth aspect in the fields of heat dissipation of electronic components, communication manufacturing, sports protection, automobile manufacturing, military materials, and consumer products.

[0106] According to specific embodiments of the present invention, the materials field includes the electrical and electronic industry, mobile communications industry, luggage and transportation industry, footwear industry, automobile manufacturing industry, sports equipment manufacturing industry, audio equipment manufacturing industry, and the military field.

[0107] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0108] (1) The thermally conductive polypropylene composite material of the present invention has good tensile strength, impact performance, interlaminar peel strength and thermal conductivity.

[0109] The thermally conductive polypropylene composite material has the following characteristics:

[0110] Longitudinal (MD) tensile strength ≥100MPa, preferably ≥120MPa; interlaminar peel strength ≥1N / mm, preferably ≥1.1N / mm; thermal conductivity ≥0.5W / m. -1 K -1 Preferred ≥0.7W m -1 K -1 When the composite material is made of only 24 layers of polypropylene fabric hot-pressed together and the thickness is about 1.7 mm, the drop hammer impact strength is ≥200 J, preferably ≥220 J.

[0111] (2) The thermally 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 caused by high-temperature operation. At the same time, it still has good interlayer peel strength when prepared at a lower hot-pressing temperature.

[0112] (3) This preparation method can reduce the hot pressing operation time, while improving production efficiency and reducing production energy consumption.

[0113] (4) The present invention reduces the hot pressing temperature and expands the hot pressing temperature range to 50°C; effectively reducing equipment energy consumption and damage to composite materials under high temperature operation. Detailed Implementation

[0114] 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.

[0115] In the following embodiments and comparative examples:

[0116] 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.

[0117] The properties of the thermally conductive polypropylene composition and sheet were tested according to the following methods, and the film test results are shown in Table 1:

[0118] (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;

[0119] (2) Density, determined according to the method specified in GB / T 1033.1-2008;

[0120] (3) Melting point, determined according to the method specified in GB / T 28724-2012;

[0121] (4) Tensile strength: determined according to the method specified in GB / T1040.1-2018;

[0122] (5) Drop hammer impact strength: determined according to the method specified in GB / T14153-1993;

[0123] (6) Interlayer peel strength: The test shall be performed in accordance with the method specified in QB / T2358-98.

[0124] (7) Thermal conductivity: The thermal conductivity shall be determined in accordance with the method specified in GB / T 10297-2015.

[0125] 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.

[0126] Example 1

[0127] 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.

[0128] (1) Preparation of polypropylene composition A:

[0129] 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 80 wt% alumina, 19 wt% boron nitride and 1 wt% silane coupling agent, alumina average particle size 20 μm, boron nitride average particle size 10 μm, Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0130] The components obtained above are weighed and mixed according to the proportions, wherein the mass fraction Wa of component a is 40 parts by weight, the mass fraction Wb of component b is 10 parts by weight, and the mass fraction Wc of component c is 50 parts by weight.

[0131] 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 evenly. Then, add the mixed material to the feeder of a twin-screw extruder manufactured by W&P. The material enters the twin screw through the feeder. During the processing, the screw temperature is maintained between 200-230°C. After being melted and mixed evenly by the screw, extruded, granulated and dried, polypropylene composition granules A are obtained. The melting point of polypropylene composition granules A is tested to be 159°C.

[0132] (2) Polypropylene composition B i Preparation:

[0133] Component x1 is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry, Sinopec, 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 the Beijing Research Institute of Chemical Industry, Sinopec, 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 the Beijing Research Institute of Chemical Industry, Sinopec. The random copolymer polypropylene produced by the 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℃. Component y is a polyolefin elastomer of grade 6102, purchased from ExxonMobil, which is an ethylene-propylene copolymer. Component z is composed of 80 wt% alumina, 19 wt% boron nitride, and 1 wt% silane coupling agent. The average particle size of alumina is 20 μm, and the average particle size of boron nitride is 10 μm. It is produced by Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0134] The components obtained above are weighed and mixed according to the specified ratio, wherein the mass fraction of component x is Wx. i The total weight is 42.5 parts by weight, the weight of component y (Wy) is 7.5 parts by weight, the weight of component z (Wz) is 50 parts by weight, and the other steps are the same as in step (1), finally obtaining polypropylene composition B. i Granular material (i.e., x) i+y+z=B i (i = 1, 2, 3), after testing, the melting point of B1 is 130℃, the melting point of B2 is 134℃, and the melting point of B3 is 139℃.

[0135] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0136] 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.

[0137] 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.

[0138] (4) Preparation of polypropylene fabric:

[0139] 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.

[0140] (5) Preparation of polypropylene composite materials:

[0141] The polypropylene fabrics obtained in step (4) were stacked sequentially from bottom to top as 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 410μm.

[0142] Example 2

[0143] 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.

[0144] (1) Preparation of polypropylene composition A:

[0145] The preparation process is the same as step (1) in Example 1.

[0146] (2) Polypropylene composition B i Preparation:

[0147] 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:

[0148] 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.

[0149] 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 112℃, the melting point of B5-B8 is 130℃, and the melting point of B9-B... 12 Its melting point is 149℃.

[0150] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0151] The preparation process is the same as step (3) in Example 1.

[0152] (4) Preparation of thermally conductive polypropylene fabric:

[0153] The preparation process is the same as step (4) of Example 1.

[0154] (5) Preparation of thermally conductive polypropylene composite material:

[0155] 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 AB 12 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 with the warp direction at a 90° angle to each other. 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 1.75mm.

[0156] Example 3

[0157] 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.

[0158] (1) Preparation of polypropylene composition A:

[0159] 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 ℃; component c is composed of 80 wt% alumina, 19 wt% boron nitride and 1 wt% silane coupling agent, with an average particle size of 20 μm for alumina and 10 μm for boron nitride. Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0160] The components obtained above were weighed and mixed according to the specified proportions, wherein component a (Wa) had a mass fraction of 40 parts by weight, component b (Wb) had a mass fraction of 10 parts by weight, and component c (Wc) had a mass fraction of 50 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 3.6 / 10 min; the melting point of polypropylene composition A was 160°C.

[0161] (2) Preparation of polypropylene composition B:

[0162] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec, which 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, which 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% alumina, 19 wt% boron nitride and 1 wt% silane coupling agent, with an average particle size of 20 μm for alumina and 10 μm for boron nitride, and is manufactured by Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0163] The components obtained above were weighed and mixed according to the proportions, wherein the mass fraction of component x, Wx, was 42.5 parts by weight, the mass fraction of component y, Wy, was 7.5 parts by weight, and the mass fraction of component z, Wz, was 50 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 4.5 g / 10 min, and the melting point was 139 °C.

[0164] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0165] 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.

[0166] 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.

[0167] The extrusion casting temperature is 230℃, and the calendering roll temperature is 55℃. During solid-phase stretching, the temperature is 135℃, the stretching rate is 2 m / min, and the stretching ratio is 6 times. After stretching, the film is wound up to form a thermally conductive polypropylene sheet (composite film), which consists of an upper surface layer (film layer B), a core layer (film layer A), and a lower surface layer (film layer B).

[0168] The thickness of the thermally conductive polypropylene sheet (composite film) described above is 85 μm, wherein the thickness of film layer A accounts for 80% of the total thickness of the sheet.

[0169] (4) Preparation of thermally conductive polypropylene fabric:

[0170] The three-layer co-extruded thermally 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 thermally conductive polypropylene fabric.

[0171] (5) Preparation of thermally conductive polypropylene composite material:

[0172] The thermally conductive polypropylene fabrics obtained in step (4) were sequentially stacked and hot-pressed to form a laminated thermally conductive polypropylene sheet. The laminated thermally conductive polypropylene sheet comprises 24 layers of thermally conductive polypropylene fabrics, placed at a 90° angle 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 thermally conductive polypropylene composite material was 1.76mm.

[0173] Example 4

[0174] 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.

[0175] (1) Preparation of polypropylene composition A:

[0176] The preparation process is the same as step (1) in Example 3.

[0177] (2) Preparation of polypropylene composition B:

[0178] 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.

[0179] 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.

[0180] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0181] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0182] (4) Preparation of thermally conductive polypropylene fabric:

[0183] The preparation process is the same as step (4) in Example 3.

[0184] (5) Preparation of thermally conductive polypropylene composite material:

[0185] The preparation process is the same as step (5) in Example 3.

[0186] The thickness of the prepared thermally conductive polypropylene composite material is similar to that of Example 3.

[0187] Example 5

[0188] 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.

[0189] (1) Preparation of polypropylene composition A:

[0190] 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.

[0191] 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.

[0192] (2) Preparation of polypropylene composition B:

[0193] The preparation process is the same as step (2) in Example 3.

[0194] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0195] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0196] (4) Preparation of thermally conductive polypropylene fabric:

[0197] The preparation process is the same as step (4) in Example 3.

[0198] (5) Preparation of thermally conductive polypropylene composite material:

[0199] The preparation process is the same as step (5) in Example 3.

[0200] The thickness of the prepared thermally conductive polypropylene composite material is similar to that of Example 3.

[0201] Example 6

[0202] 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.

[0203] (1) Preparation of polypropylene composition A:

[0204] 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 ℃; component c is composed of 80 wt% magnesium oxide, 19 wt% silicon carbide and 1 wt% silane coupling agent, with an average particle size of 4 μm for magnesium oxide and 10 μm for silicon carbide. Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0205] 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 4.2 / 10 min; the melting point of polypropylene composition A was 158°C.

[0206] (2) Preparation of polypropylene composition B:

[0207] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry of Sinopec, which 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, which 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 composed of 80 wt% magnesium oxide, 19 wt% silicon carbide and 1 wt% silane coupling agent, with an average particle size of 4 μm for magnesium oxide and 10 μm for silicon carbide, and is produced by Shanghai Baitu High-Tech Materials Technology Co., Ltd.

[0208] The components prepared above were weighed and mixed according to the ratio, wherein the mass part of component x, Wx, was 63.75 parts by weight, the mass part of component y, Wy, was 11.25 parts by weight, and the mass part 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 5.0 g / 10 min, and the melting point was 138 °C.

[0209] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0210] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0211] (4) Preparation of thermally conductive polypropylene fabric:

[0212] The preparation process is the same as step (4) in Example 3.

[0213] (5) Preparation of thermally conductive polypropylene composite material:

[0214] The preparation process is the same as step (5) in Example 3.

[0215] The thickness of the prepared thermally conductive polypropylene composite material is similar to that of Example 3.

[0216] Example 7

[0217] 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.

[0218] (1) Preparation of polypropylene composition A:

[0219] The preparation process is the same as step (1) in Example 6.

[0220] (2) Preparation of polypropylene composition B:

[0221] The preparation process is the same as step (2) in Example 3.

[0222] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0223] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0224] (4) Preparation of thermally conductive polypropylene fabric:

[0225] The preparation process is the same as step (4) in Example 3.

[0226] (5) Preparation of thermally conductive polypropylene composite material:

[0227] The preparation process is the same as step (5) in Example 3.

[0228] The thickness of the prepared thermally conductive polypropylene composite material is similar to that of Example 3.

[0229] Example 8

[0230] 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.

[0231] (1) Preparation of polypropylene composition A:

[0232] The preparation process is the same as step (1) in Example 5.

[0233] (2) Preparation of polypropylene composition B:

[0234] The preparation process is the same as step (2) of Example 6.

[0235] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0236] The main steps are the same as in Example 3. The preparation process is the same as step (3) of Example 3.

[0237] (4) Preparation of thermally conductive polypropylene fabric:

[0238] The preparation process is the same as step (4) in Example 3.

[0239] (5) Preparation of thermally conductive polypropylene composite material:

[0240] The preparation process is the same as step (5) in Example 3.

[0241] The thickness of the prepared thermally conductive polypropylene composite material is similar to that of Example 3.

[0242] Example 9

[0243] 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.

[0244] (1) Preparation of polypropylene composition A:

[0245] The preparation process is the same as step (1) in Example 3.

[0246] (2) Preparation of polypropylene composition B:

[0247] The preparation process is the same as step (2) in Example 3.

[0248] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0249] The preparation process is the same as step (3) in Example 3.

[0250] (4) Preparation of thermally conductive polypropylene fabric:

[0251] The preparation process is the same as step (4) in Example 3.

[0252] (5) Preparation of thermally conductive polypropylene composite material:

[0253] The main steps are the same as in Example 3. The laminated thermally conductive polypropylene sheet includes two layers of thermally 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 thermally conductive polypropylene composite material is 149μm.

[0254] Example 10

[0255] 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.

[0256] (1) Preparation of polypropylene composition A:

[0257] The preparation process is the same as step (1) in Example 3.

[0258] (2) Preparation of polypropylene composition B:

[0259] The preparation process is the same as step (2) in Example 3.

[0260] (3) Preparation of three-layer co-extruded thermally conductive polypropylene sheets:

[0261] The preparation process is the same as step (3) in Example 3.

[0262] (4) Preparation of thermally conductive polypropylene fabric:

[0263] The preparation process is the same as step (4) in Example 3.

[0264] (5) Preparation of thermally conductive polypropylene composite material:

[0265] The main steps are the same as in Example 3. The laminated thermally conductive polypropylene sheet includes 100 layers of thermally 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 thermally conductive polypropylene composite material is 7.68 mm.

[0266] Comparative Example 1

[0267] 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 85 μm.

[0268] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0269] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0270] Comparative Example 2

[0271] 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 85 μm.

[0272] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0273] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0274] Comparative Example 3

[0275] Three-layer co-extruded polypropylene sheets were 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 85 μm.

[0276] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0277] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0278] Comparative Example 4

[0279] 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 85 μm.

[0280] Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 3.

[0281] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0282] Comparative Example 5

[0283] 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. Polypropylene fabrics and polypropylene composites were also prepared according to the method of Example 3.

[0284] The thickness of the prepared polypropylene composite material is similar to that of Example 3.

[0285] Comparative Example 6

[0286] Three-layer co-extruded polypropylene sheets and polypropylene fabrics were prepared according to the method in Example 1.

[0287] The difference lies in the preparation of the polypropylene composite material. The prepared polypropylene fabric is stacked in sequence, from bottom to top, as B1A1B1, B2A2B2, B3A3B3, B2A2B2, and B1A1B1, with a total of 5 layers. The stacked polypropylene fabrics are then hot-pressed and fused together, and then cooled and shaped to form the polypropylene composite material.

[0288] Experimental Example

[0289] The thermally 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.

[0290] (1) Tensile strength: Samples were prepared and tested according to the methods specified in GB / T1040.1-2018;

[0291] (2) Interlayer peel strength: Samples were prepared and measured in accordance with the method specified in QB / T2358-98.

[0292] (3) Drop hammer impact strength: The test shall be conducted in accordance with the method specified in GB / T14153-1993.

[0293] (4) Thermal conductivity: The thermal conductivity was measured according to the method specified in GB / T 10297-2015. Among them, the thickness of the polypropylene composite materials obtained in Examples 3-10 and Comparative Examples 1-5 were all similar, around 1.7 mm, and all within the range of 1.7 mm ± 0.1 mm.

[0294] Table 1

[0295]

[0296] The results from the examples in Table 1 show that the thermally conductive polypropylene composite material prepared according to the present invention possesses excellent tensile properties, impact resistance, and thermal conductivity, while also exhibiting good interlaminar peel strength at relatively low hot-pressing temperatures. The thermally 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 thermal conductivity ≥0.5 W / m. -1 K -1 When the thermally conductive polypropylene composite material is made of 24 layers of thermally conductive polypropylene fabric hot-pressed together with a thickness of about 1.7 mm, the drop hammer impact strength is ≥200 J.

[0297] As can be seen from preferred embodiments 2, 3, 6, 9, and 10, the thermally conductive polypropylene composite material prepared by the present invention has a longitudinal (MD) tensile strength ≥130 MPa, an interlaminar peel strength ≥1.2 N / mm, and a thermal conductivity ≥0.9 W / m. -1 K -1 When the thermally conductive polypropylene composite material is made of 24 layers of thermally conductive polypropylene fabric hot-pressed together with a thickness of about 1.7 mm, the drop hammer impact strength is ≥200 J.

[0298] 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 properties, interlayer peel strength, or thermal conductivity of the resulting polypropylene composite material.

[0299] A comparison of Example 1 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.

[0300] 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.

[0301] 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 thermally conductive polypropylene sheet, comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB'; wherein layer A contains a polypropylene composition A, the polypropylene composition A comprising homopolymer polypropylene a, impact copolymer polypropylene b, and optional composite thermally conductive filler c; layer B may be the same as or different from layer B', each correspondingly containing polypropylene composition B and polypropylene composition B', the polypropylene composition B and the polypropylene composition B' each comprising random copolymer polypropylene x, thermal bonding reinforcing agent y, and optional composite thermally conductive filler z; and the content of the corresponding composite thermally conductive filler c and composite thermally conductive filler z in the polypropylene composition A, the polypropylene composition B, and the polypropylene composition B' is not simultaneously 0; in, The melting point of polypropylene composition A is greater than that of polypropylene composition B and polypropylene composition B'. The composite thermally conductive filler c and the composite thermally conductive filler z may be the same or different, and each includes a thermally conductive main material, a thermally conductive auxiliary material and an optional interface modifier. Based on the total weight of the composite thermally conductive filler c and the composite thermally conductive filler z, each of the composite thermally conductive filler c and the composite thermally conductive filler z includes 50-99 wt% of thermally conductive main material, 1-50 wt% of thermally conductive auxiliary material, and 0-3 wt% of interface modifier, which is not 0 wt%. The thermally conductive material is selected from at least one of alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon dioxide, and chopped glass fiber. The thermally conductive material is selected from at least one of boron nitride, silicon carbide, and aluminum nitride. The interface modifier is selected from one or more of maleic anhydride, silane coupling agent, and polyvinylpyrrolidone.

2. The thermally 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 15-99 wt% homopolymer polypropylene a, 0.3-50 wt% impact copolymer polypropylene b, 0-70 wt% composite thermally 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 21-99 wt% random copolymer polypropylene x, 0.3-30 wt% thermal bonding reinforcing agent y, and 0-70 wt% composite thermally conductive filler z.

3. The thermally 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 35-81 wt% homopolymer polypropylene a, 5-27 wt% impact copolymer polypropylene b, and 10-50 wt% composite thermally 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 40-81 wt% random copolymer polypropylene x, 5-18 wt% thermal bonding reinforcing agent y, and 10-50 wt% composite thermally conductive filler z.

4. The thermally conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the thermally 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.

5. The thermally conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the thermally 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.

6. The thermally conductive polypropylene sheet according to claim 1, characterized in that: Based on the total thickness of the thermally 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.

7. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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%.

8. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

9. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The homopolymer polypropylene a has: The melt flow rate at 230℃ and 2.16kg load is 2.5-18g / 10min.

10. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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 and 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 .

11. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

12. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

13. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

14. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The random copolymer polypropylene x has: 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.

15. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The random copolymer polypropylene x has: The melt flow rate at 230℃ and 2.16kg load is 3-18g / 10min.

16. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

17. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

18. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

19. The thermally conductive polypropylene sheet according to any one of claims 1-6, 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.

20. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The heat-adhesive reinforcing agent y is a polyolefin elastomer and / or petroleum resin.

21. The thermally conductive polypropylene sheet according to claim 20, characterized in that: The polyolefin elastomer is a copolymer elastomer of ethylene with propylene and / or α-olefin; and / or, the petroleum resin is a C5 and / or C9 hydrogenated petroleum resin with a softening point of 100-150°C.

22. The thermally conductive polypropylene sheet according to claim 20, characterized in that: The polyolefin elastomer is a copolymer elastomer of ethylene and propylene and / or α-olefin, wherein the α-olefin is a C4-C12 α-olefin; and / or, the petroleum resin is a cyclopentadiene type resin.

23. The thermally conductive polypropylene sheet according to claim 20, characterized in that: The polyolefin elastomer is a copolymer elastomer of ethylene and propylene and / or α-olefin, wherein the α-olefin is 1-butene and / or 1-octene.

24. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The BAB' layer structure of the thermally 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'.

25. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: Layer A also contains a β-crystal nucleating agent.

26. The thermally conductive polypropylene sheet according to claim 25, 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.

27. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: Based on the total weight of the composite thermally conductive filler c and the composite thermally conductive filler z, each of the composite thermally conductive filler c and the composite thermally conductive filler z includes 60-95wt% of thermally conductive main material, 5-40wt% of thermally conductive auxiliary material, and 0.5-2wt% of interface modifier.

28. The thermally conductive polypropylene sheet according to any one of claims 1-6, characterized in that: The particle size range of the thermally conductive main material is 100nm-100μm; and / or, The particle size range of the thermally conductive auxiliary material is 100nm-100μm.

29. A method for preparing the thermally conductive polypropylene sheet according to any one of claims 1-28, 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 thermally conductive polypropylene sheet.

30. The method for preparing the thermally conductive polypropylene sheet according to claim 29, 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 thermally conductive filler c; and / or, The preparation of the raw materials for layers B and B' includes the melt blending of each component, including the random copolymer polypropylene x, the thermal bonding reinforcing agent y, and the optional composite thermally 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.

31. The method for preparing the thermally conductive polypropylene sheet according to claim 29, characterized in that, The stretching conditions include: a stretching temperature of 90-140℃ and a stretching ratio of 1-20 times.

32. The method for preparing the thermally conductive polypropylene sheet according to claim 29, characterized in that, The stretching conditions include: a stretching temperature of 90-119℃ and a stretching ratio of 1-20 times.

33. A thermally conductive polypropylene fabric, a three-dimensional polypropylene fabric obtained by weaving the thermally conductive polypropylene sheet according to any one of claims 1-28.

34. The thermally conductive polypropylene fabric according to claim 33, characterized in that: The thermally conductive polypropylene fabric is obtained by slitting and weaving the thermally conductive polypropylene sheet; and / or, the thermally conductive polypropylene fabric has a three-dimensional structure of plain weave, twill weave and / or satin weave.

35. A thermally conductive polypropylene composite material, wherein the thermally conductive polypropylene composite material is prepared by hot pressing together multiple layers of thermally conductive polypropylene sheets according to any one of claims 1-28 and / or thermally conductive polypropylene fabrics according to claims 33 or 34.

36. The thermally conductive polypropylene composite material according to claim 35, characterized in that: The thermally conductive polypropylene composite material is prepared by hot pressing multiple layers of the thermally conductive polypropylene sheets or the thermally conductive polypropylene fabric; and / or Multilayer thermally conductive polypropylene sheets are stacked from top to bottom at 0-90° angles along their respective machine directions; and / or, The multilayer thermally conductive polypropylene fabric is arranged in layers from top to bottom with the warp directions placed at 0-90° intervals; and / or, The number of layers in the multilayer thermally conductive polypropylene sheet and / or multilayer thermally conductive polypropylene fabric is greater than or equal to 2.

37. The thermally conductive polypropylene composite material according to claim 35, characterized in that: The number of layers in the multilayer thermally conductive polypropylene sheet and / or multilayer thermally conductive polypropylene fabric is 2-200.

38. The thermally conductive polypropylene composite material according to claim 35, characterized in that: The number of layers in the multilayer thermally conductive polypropylene sheet and / or multilayer thermally conductive polypropylene fabric is 4-100.

39. The thermally conductive polypropylene composite material according to any one of claims 35-38, characterized in that: The thermally 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 thermally 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 or equal to the average melting point of the outermost layer in the (i-1)-th group.

40. The thermally conductive polypropylene composite material according to claim 39, 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.

41. The thermally conductive polypropylene composite material according to claim 39, 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.

42. The thermally conductive polypropylene composite material according to claim 39, 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℃.

43. A method for preparing the thermally conductive polypropylene composite material according to any one of claims 39-42, comprising hot-pressing and fusing the thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric together, and then cooling and shaping it to form the thermally conductive polypropylene composite material.

44. The method for preparing the thermally conductive polypropylene composite material according to claim 43, characterized in that: 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 thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric stack has a greater than or equal to 2 layers; And / or, Adjacent layers of the thermally conductive polypropylene fabric stack are positioned at 0-90° angles between each other along the warp direction; and / or, The adjacent layers of the thermally conductive polypropylene sheet stack are placed at 0-90° along their respective machine directions.

45. The method for preparing the thermally conductive polypropylene composite material according to claim 43, characterized in that: 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 thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric stack has 2-200 layers.

46. ​​The method for preparing the thermally conductive polypropylene composite material according to claim 43, characterized in that: The thermally conductive polypropylene sheet and / or the thermally conductive polypropylene fabric stack has 4-100 layers.

47. The thermally conductive polypropylene sheet according to any one of claims 1-28, the thermally conductive polypropylene fabric according to claim 33 or 34, the thermally conductive polypropylene composite material according to any one of claims 39-42, and the thermally conductive polypropylene composite material prepared by the preparation method according to any one of claims 43-46 are used in the fields of heat dissipation of electronic components, communication manufacturing, automobile manufacturing, military materials, and consumer products.

48. The application according to claim 47, characterized in that: The consumer products mentioned are for sports protection.

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