Flame-retardant high-strength high-impact polypropylene sheet and fabrics thereof, flame-retardant polypropylene composites, and methods and applications thereof

Abstract

This invention relates to the field of polypropylene materials, and discloses a flame-retardant, high-strength, and high-impact polypropylene sheet and its fabric, a flame-retardant polypropylene composite material, and its preparation method and application. The flame-retardant polypropylene sheet includes layer A and layers B and B' located on both sides of layer A, with a structure of BAB'; wherein layer B and layer B' may be the same or different, each corresponding to a polypropylene composition B and a polypropylene composition B', wherein the melting point of the polypropylene composition A is greater than the melting points of the polypropylene composition B and the polypropylene composition B', and the contents of flame retardant m and flame retardant n in polypropylene compositions A, B, and B' are not simultaneously 0. By hot-pressing this polypropylene sheet, a polypropylene composite material is obtained, which simultaneously possesses excellent tensile properties, impact resistance, and flame retardant properties, and still exhibits good interlaminar peel strength even when prepared at a relatively low hot-pressing temperature.

Description

Technical Field

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

[0002] Polypropylene (PP) resin has low density, good heat resistance, and good rigidity, hardness, and weldability, which makes it widely used.

[0003] 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.

[0004] 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.

[0005] Polypropylene has poor flame retardancy and a low oxygen index of only 17.0-17.5%, classifying it as a flammable material. During combustion, it releases heat rapidly and has a high calorific value, making it highly susceptible to flame propagation and fires. These factors significantly limit the use of polypropylene film products in industries such as electrical appliances, chemicals, machinery, and military products. Therefore, improving the flame retardant properties of the polymer has attracted widespread attention.

[0006] Currently, commonly used flame retardants for polypropylene include halogenated flame retardants, phosphorus-nitrogen flame retardants, and inorganic flame retardants. Studies have shown that while the addition of large amounts of commercially available flame retardants improves the flame retardant properties of materials, factors such as poor dispersion of additives and matrix materials often compromise the overall mechanical properties of composite materials, especially impact resistance, presenting a technical challenge of the contradiction between flame retardancy and mechanical properties. Existing technologies typically utilize multi-component, multi-functional systems (including flame retardants and toughening agents) to construct high-impact flame-retardant composite material systems. For example, Chinese invention patent CN103724806B discloses a high-impact flame-retardant polypropylene composite material for automotive functional parts and its preparation method. This method uses acrylate rubber powder, polyolefin elastomers, and polar monomer-grafted polyolefin elastomers as composite toughening agents, ensuring that the material achieves a UL94V-0 (1.6 mm) flame retardant rating while significantly improving its impact resistance. CN109776956A describes a high-impact, high-rigidity, flame-retardant, and anti-dripping modified polypropylene material. This material achieves excellent mechanical and flame-retardant properties through a rational formulation of flame retardants, reinforcing fillers, surface-treated whiskers, antioxidants, and compatibilizers. The existing technology uses methods such as adding elastomers or reinforcing fillers to maintain the mechanical properties of flame-retardant polypropylene composites without severe damage; however, this method has limited application scenarios and is not suitable for applications such as thin sheets, films, and fabrics.

[0007] In summary, the key technical problem to be solved is how to provide a flame-retardant polypropylene composite material that simultaneously possesses a wide processing temperature range, strong mechanical properties, high interlaminar peel strength, and flame-retardant properties, while further expanding the application scenarios of flame-retardant polypropylene to make it suitable for applications such as thin sheets, films, and fabrics, while maintaining the mechanical properties of the flame-retardant polypropylene composite material. Summary of the Invention

[0008] The purpose of this invention is to overcome the technical shortcomings of existing flame-retardant polypropylene composite materials, which struggle to simultaneously possess a wide processing temperature range, strong mechanical properties, high interlaminar peel strength, and flame-retardant performance. This invention provides flame-retardant polypropylene sheets, flame-retardant polypropylene fabrics, high-strength and high-impact flame-retardant polypropylene composite materials, their preparation methods, and applications. The flame-retardant polypropylene composite material is obtained from the flame-retardant polypropylene sheet of this invention through hot pressing, etc. This flame-retardant polypropylene composite material exhibits excellent mechanical properties, while also possessing good interlaminar peel strength and flame-retardant performance. Even at relatively low hot-pressing temperatures and within a wide hot-pressing temperature range, the interlaminar peel strength of the obtained flame-retardant polypropylene composite material remains high. Furthermore, the flame-retardant polypropylene sheets, flame-retardant polypropylene fabrics, and high-strength and high-impact flame-retardant polypropylene composite materials of this invention, while maintaining the mechanical properties of flame-retardant polypropylene composite materials, are also suitable for applications in thin sheets, films, and fabrics, thus broadening the application scenarios of flame-retardant polypropylene.

[0009] In a first aspect, the object of the present invention is to provide a flame-retardant polypropylene sheet, comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB';

[0010] Layer B may be the same as or different from layer B', and each contains a polypropylene composition B and a polypropylene composition B', wherein each of the polypropylene compositions B and B' comprises random copolymer polypropylene x, a thermal bonding enhancer y, and an optional flame retardant n; layer A contains a polypropylene composition A, wherein the polypropylene composition A comprises homopolymer polypropylene a, impact copolymer polypropylene b, and an optional flame retardant m.

[0011] Wherein, the melting point of polypropylene composition A is greater than that of polypropylene composition B and polypropylene composition B', and the contents of flame retardant m and flame retardant n in polypropylene composition A, polypropylene composition B, and polypropylene composition B' are not simultaneously 0.

[0012] According to the present invention, the thin film layers B and B' on both sides of the thin film layer A may be the same or different. In a preferred embodiment of the present invention, the thin film layers B and B' on both sides of the thin film layer A are the same.

[0013] According to some preferred embodiments of the present invention, the melting point of homopolymer polypropylene a in polypropylene composition A is greater than the melting point of random copolymer polypropylene x in polypropylene composition B and polypropylene composition B', preferably the temperature difference between the corresponding melting points is greater than or equal to 10°C.

[0014] According to some preferred embodiments of the present invention, based on the total thickness of the flame-retardant polypropylene sheet, the thickness of layer A accounts for 51%-89% of the total thickness, preferably 71%-89%, and more preferably 71%-80%. The thicknesses of film layers B and B' on both sides of film layer A can be the same or different, preferably the same.

[0015] The present invention does not limit the thickness of the polypropylene sheet, and it can be selected within a wide range according to its actual application field. Preferably, the thickness of the polypropylene sheet can be 10-1000μm, more preferably 30-500μm, and even more preferably 50-300μm.

[0016] According to the present invention, the thickness of film layers A, B, and B' can be controlled by the extruder melt pump during the processing.

[0017] According to some preferred embodiments of the present invention, the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B, and the difference between the melting point of polypropylene composition A and the melting point of polypropylene composition B', are each greater than or equal to 5°C, preferably greater than or equal to 10°C, and more preferably greater than or equal to 20°C.

[0018] According to some preferred embodiments of the present invention, based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 30-98 wt% homopolymer polypropylene a, 1-50 wt% impact copolymer polypropylene b, and 0-60 wt% flame retardant m; preferably, the polypropylene composition A comprises 40-80 wt% homopolymer polypropylene a, 5-30 wt% impact copolymer polypropylene b, and 2-50 wt% flame retardant m; more preferably, the polypropylene composition A comprises 40-80 wt% homopolymer polypropylene a, 5-30 wt% impact copolymer polypropylene b, and 10-50 wt% flame retardant m.

[0019] More preferably, the polypropylene composition A comprises 40-80 wt% homopolymer polypropylene a, such as 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, and any two values ​​or any range of any two values.

[0020] More preferably, the polypropylene composition A comprises 5-30 wt% of impact copolymer polypropylene b, such as 5 wt%, 10 wt%, 20 wt%, 30 wt%, and any two values ​​or any range of any two values.

[0021] More preferably, the polypropylene composition A includes 10-50 wt% of flame retardant m, such as 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and any two values ​​or any range of any two values.

[0022] According to some preferred embodiments of the present invention, based on the total weight of each of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 30-98 wt% random copolymer polypropylene x, 1-50 wt% heat-bonding reinforcing agent y, and 0-60 wt% flame retardant n; preferably, each of the polypropylene composition B and the polypropylene composition B' comprises 40-80 wt% random copolymer polypropylene x, 5-30 wt% heat-bonding reinforcing agent y, and 2-50 wt% flame retardant n; more preferably, each of the polypropylene composition B and the polypropylene composition B' comprises 40-80 wt% random copolymer polypropylene x, 5-20 wt% heat-bonding reinforcing agent y, and 10-50 wt% flame retardant n.

[0023] More preferably, the polypropylene composition B and the polypropylene composition B' each comprise 40-80 wt% of random copolymer polypropylene x, such as 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, and any two values ​​or any range of any two values.

[0024] More preferably, the polypropylene composition B and the polypropylene composition B' each include 5-20 wt% of a heat-bonding reinforcing agent y, such as 5 wt%, 15 wt%, 20 wt%, and any two values ​​or any range of any two values.

[0025] More preferably, the polypropylene composition B and the polypropylene composition B' each comprise 10-50 wt% of flame retardant n, such as 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and any two values ​​or any range of any two values.

[0026] According to some preferred embodiments of the present invention, the homopolymer polypropylene a has: a melting point of 150-170°C, preferably 160-170°C; and / or a melt flow rate of 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 2.5-18 g / 10 min, at 230°C and a load of 2.16 kg; and / or an isotacticity (mm) of not less than 96%.

[0027] According to some preferred embodiments of the present invention, the impact-resistant copolymer polypropylene b has the following characteristics: the melting point of the impact-resistant copolymer polypropylene b is 150-170°C; and / or, the monomer for copolymerizing the impact-resistant copolymer polypropylene b with propylene is ethylene or butene, preferably butene; and / or, the melt flow rate of the impact-resistant copolymer polypropylene b at 230°C and 2.16 kg load is 0.5-50 g / 10 min, preferably 1-20 g / 10 min, more preferably 2.5-18 g / 10 min; and / or, the cantilever beam impact strength of the impact-resistant copolymer polypropylene b is not less than 20 KJ / m. 2 (Tested at 23℃).

[0028] 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.

[0029] According to some preferred embodiments of the present invention, the random copolymer polypropylene x has the following characteristics: a melting point of 110-150°C, preferably 120-140°C; and / or a melt flow rate of 0.5-50 g / 10 min at 230°C and a load of 2.16 kg, preferably 1-20 g / 10 min, more preferably 3-18 g / 10 min; and / or a molecular weight distribution Mw / Mn of 5-12, preferably 7-10; and / or a copolymer of propylene with ethylene and / or butene, preferably an ethylene-propylene-butene terpolymer and / or a propylene-ethylene binary copolymer.

[0030] According to some preferred embodiments of the present invention, the thermal bonding reinforcing agent y has: a melting point or viscous flow temperature of 70-110°C; and / or a melt flow rate of 0.5-50 g / 10 min at 190°C and a load of 2.16 kg, preferably 1-20 g / 10 min, more preferably 1-18 g / 10 min; and / or selected from one or more of polyolefin elastomers, ethylene propylene diene monomer (EPDM) rubber, SEBS, SBS, EVA, and petroleum resins; preferably, it is a polyolefin elastomer and / or petroleum resin; more preferably, the polyolefin elastomer is a copolymer elastomer of ethylene and propylene and / or α-olefins, wherein the α-olefin is preferably a C4-C12 α-olefin, more preferably 1-butene and / or 1-octene; and / or, the petroleum resin is a C5 and / or C9 hydrogenated petroleum resin with a softening point of 100-150°C; preferably a cyclopentadiene type resin.

[0031] According to the inventors' research, when the melt flow rate and polymer composition ratio of polypropylene compositions B and B' are within the preferred range, the low-melting-point random copolymer polypropylene x and the heat-bonding reinforcing agent y in the composition can significantly reduce the hot-pressing temperature and widen the hot-pressing temperature window. Furthermore, the heat-bonding reinforcing agent y provides good adhesion performance for the sheet and can further improve the interlayer peel strength.

[0032] According to some preferred embodiments of the present invention, layer A further contains a β-crystal nucleating agent; preferably,

[0033] 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.

[0034] According to some preferred embodiments 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.

[0035] According to some preferred embodiments of the present invention, the flame retardant m and the flame retardant n may be the same or different, and each is selected from one or more of the following: organic or inorganic compounds containing flame retardant elements and their polymers, inorganic substances and / or metal hydroxides that are stable at high temperatures; preferably, the flame retardant is selected from at least one of halogen-based flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, boron-based flame retardants, antimony-based flame retardants, biomass flame retardants, intumescent flame retardants, hydroxides, and oxide hydrates.

[0036] To better explain the present invention, the flame retardant m and flame retardant n are described as follows: The types of flame retardant m and flame retardant n are not particularly limited; they can be single components or a combination of multiple components. For example, they may include organic or inorganic compounds and their polymers containing flame-retardant elements such as halogens, phosphorus, nitrogen, boron, and antimony. Generally, the weight fraction of the flame-retardant element in the flame retardant is 1-99 wt%, preferably 5-90 wt%; and high-temperature stable inorganic substances, metal hydroxides, etc. Preferably, the flame retardant is selected from at least one of halogen-based flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, boron-based flame retardants, antimony-based flame retardants, biomass flame retardants, intumescent flame retardants, hydroxides, and oxide hydrates. Furthermore, the halogenated flame retardant includes at least one of decabromodiphenyl ethane, brominated epoxy resin, brominated polystyrene, bromotriazine, decabromodiphenyl ether, tetrabromobisphenol A, tetrabromophthalic anhydride, octabromoether, octabromodiphenyl ether, brominated epoxy resin, and brominated styrene-butadiene-styrene copolymer (SBS); the phosphorus-based flame retardant can be at least one of red phosphorus, phosphoric acid, phosphates, hypophosphite, ammonium phosphate, phosphite, pyrophosphate, polyphosphate, phosphate esters, phosphite esters, organophosphates, ammonium polyphosphate, and phosphorus heterocyclic compounds and polymeric phosphonates, preferably aluminum hypophosphite and its alkylation. The flame retardant comprises at least one of the following: modified compounds, pyrophosphates, and ammonium polyphosphates; the nitrogen-based flame retardant includes melamine and its derivatives and related heterocyclic compounds, piperazine and its modified compounds, preferably at least one of melamine and its modified compounds, melamine salts, dicyandiamide, and piperazine and its modified compounds; the boron-based flame retardant can be boric acid and borates, preferably at least one of boric acid, ammonium borate, and zinc borate; the antimony-based flame retardant can be at least one of antimony trioxide, antimony pentoxide, and sodium antimonate; the hydroxide and oxide hydrates can be at least one of aluminum, magnesium, boron, zinc hydroxides and layered bimetallic hydroxides. The flame retardant composed of multiple components may also contain at least one of pentaerythritol and its dimers, trimers, butanethyl alcohol, cyclohexanehexyl alcohol, sorbitol, glucose, maltose, and starch. Preferably, the composite flame retardant also contains an anti-dripping agent.

[0037] According to some preferred embodiments of the present invention, the BAB' layer structure of the flame-retardant 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'.

[0038] 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'. In a preferred embodiment of the present invention, the melting point of the polypropylene composition A is greater than that of the polypropylene compositions B and B'; preferably, the melting point of the homopolymer polypropylene a in the polypropylene composition A is greater than that of the random copolymer polypropylene x in the polypropylene compositions B and B', preferably 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 the polypropylene composition A and the melting point of the polypropylene composition B, and the difference between the melting point of the polypropylene composition A and the melting point of the polypropylene composition B' are each greater than or equal to 5°C, preferably greater than or equal to 10°C, more preferably greater than or equal to 20°C. In such preferred embodiments, the inventors of the present invention have surprisingly discovered that the polypropylene sheet obtained is subjected to hot pressing and the like to obtain a polypropylene composite material, which has superior mechanical properties and better interlaminar peel strength, even at lower hot pressing temperatures and over a wider range of hot pressing temperatures, the obtained polypropylene composite material exhibits higher interlaminar peel strength.

[0039] According to the inventors' research, when the melt flow rate, polymer composition ratio, and thickness distribution of film layers B and B' 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.

[0040] Secondly, the object of the present invention is to provide a method for preparing the flame-retardant 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 flame-retardant polypropylene sheet.

[0041] According to some preferred embodiments of the present invention, the preparation of the raw material for layer A includes melt blending of components including the homopolymer polypropylene a, the impact copolymer polypropylene b, and optionally a flame retardant m. 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.

[0042] According to some preferred embodiments of the present invention, the preparation of the raw materials for layers B and B' each includes melt blending of components including the random copolymer polypropylene x, the thermal bonding reinforcing agent y, and optionally the flame retardant n. The conditions and equipment for melt blending the polypropylene compositions B and B' are those used in the prior art for melt blending of polyolefins; preferably, the melting temperature is 110-150°C, and the equipment is preferably a twin-screw extruder.

[0043] Preferably, the temperatures for co-extrusion and casting are each independently selected from 200-240°C.

[0044] Preferably, the rolling temperature is 50-70°C.

[0045] The range of stretching conditions is relatively wide. In a preferred embodiment of the present invention, the stretching conditions include: the stretching method is free stretching, and / or solid-state stretching, and / or multi-stage stretching; the stretching temperature is 90-165℃, preferably 90-140℃, and more preferably 90-119℃; the stretching ratio is 1-20 times, preferably 2-15 times.

[0046] According to some embodiments of the present invention, polypropylene composition A, polypropylene composition B, and B' are co-extruded according to a BAB' structure and then cast or calendered to obtain a polypropylene co-extruded sheet. The extrusion calendering process may include passing the polypropylene co-extruded sheet sequentially through calendering rollers and traction rollers, followed by solid-state stretching, edge trimming, and winding to obtain the sheet. The extrusion casting temperature is 200-230°C, and the calendering roller temperature is 50-70°C. The specific process for preparing the film using the extrusion calendering method is a commonly used choice in the art and will not be described in detail here.

[0047] Thirdly, the object of the present invention is to provide a flame-retardant polypropylene fabric, which is a three-dimensional polypropylene fabric obtained by weaving the flame-retardant polypropylene sheet described in the first aspect.

[0048] Preferably, the flame-retardant polypropylene fabric is obtained by slitting and weaving the flame-retardant polypropylene sheet; and / or, the flame-retardant polypropylene fabric has a three-dimensional structure of plain weave, twill weave, and / or satin weave.

[0049] To facilitate weaving, it is preferable to cut the polypropylene sheet into polypropylene sheets with a width of 2-5mm, and then weave them into polypropylene fabric.

[0050] Fourthly, the object of the present invention is to provide a flame-retardant polypropylene composite material, which is prepared by hot pressing together multiple layers of flame-retardant polypropylene sheets as described in the first aspect and / or flame-retardant polypropylene fabrics as described in the second aspect.

[0051] Preferably, the flame-retardant polypropylene composite material is prepared by hot pressing multiple layers of the flame-retardant polypropylene sheets or the flame-retardant polypropylene fabric.

[0052] Preferably, the multilayer flame-retardant polypropylene sheets are stacked from top to bottom at an angle of 0-90° along their respective machine directions.

[0053] Preferably, the multilayer flame-retardant polypropylene fabric is stacked from top to bottom with the warp direction placed at an angle of 0-90° between the warp directions.

[0054] Preferably, the multilayer flame-retardant polypropylene sheet and / or multilayer flame-retardant polypropylene fabric has more than or equal to 2 layers, more preferably 2-200 layers; and most preferably 4-100 layers.

[0055] According to some preferred embodiments of the present invention, the flame-retardant 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 flame-retardant 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;

[0056] 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 ,

[0057] The polypropylene composition A i The melting point is greater than that of the polypropylene composition B. i The polypropylene composition B' i The melting point of the outermost layer in the i-th group is greater than the average melting point of the outermost layer in the (i-1)-th group.

[0058] 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.

[0059] According to some preferred embodiments of the present invention, polypropylene composition Ai 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, and more preferably greater than or equal to 20°C.

[0060] 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.

[0061] According to some preferred embodiments of the present invention, the difference between the average melting point of all outer layers in the i-th group and the average melting point of all outer layers in the (i-1)-th group is the same or different, and is 1-40°C, preferably 1-10°C, and more preferably 1-5°C.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 Ai 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.

[0066] In embodiments where each polypropylene sheet unit group comprises two or more polypropylene sheet units, for example, the structure of the i-th polypropylene sheet unit group is B. i1 A i1 B' i1 B i2 A i2 B' i2 ...B ip A ip B' ip The structure of the polypropylene composite material can be arranged from bottom to top as follows: (B) n1 A n1 B' n1 B n2 A n2 B' n2 ...B nq A nq B' nq )……(B i1 A i1 B' i1 B i2 A i2 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.

[0067] In a preferred embodiment of the present invention, the flame-retardant polypropylene composite material has at least one of the following characteristics:

[0068] Longitudinal tensile strength ≥110MPa, preferably ≥130MPa;

[0069] Interlayer peel strength ≥1N / mm, preferably ≥1.2N / mm;

[0070] Tensile strength was determined according to the method specified in GB / T1040.1-2018, and interlaminar peel strength was determined according to the method specified in GB / T2358-98. The corresponding specimens for the above two tests were the standard specimens required in the above testing standards.

[0071] When the polypropylene composite material is obtained by hot pressing 24 layers of polypropylene fabric and the thickness is about 1.6 mm, the drop hammer impact strength is ≥200 J, preferably ≥220 J.

[0072] 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.

[0073] Fifthly, the object of the present invention is to provide a method for preparing the flame-retardant polypropylene composite material described in the fourth aspect, the method comprising hot-pressing and fusing the flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric together, and then cooling and shaping to form the flame-retardant polypropylene composite material. Preferably,

[0074] Preferably, the preparation method of the flame-retardant polypropylene composite material includes the following conditions: the hot-pressing fusion temperature is 115-170℃, preferably 115-159℃, more preferably 140-159℃; and / or, the hot-pressing fusion pressure is 2-10MPa; and / or, the preheating time of the hot-pressing fusion is 5-600s, and the hot-pressing time is 1-600s, preferably 10-500s; and / or, the cooling and setting pressure is 2-8MPa, and the cooling and setting time is 30-700s; and / or, the number of layers of the flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric stack is greater than or equal to 2 layers, preferably 2-200 layers; more preferably 4-100 layers; and / or, adjacent layers of the flame-retardant polypropylene fabric stack are placed at 0-90° between the warp directions; and / or, adjacent layers of the flame-retardant polypropylene sheet stack are placed at 0-90° along their respective machine directions.

[0075] As an example, in some preferred embodiments of the present invention, the method for preparing the high-strength, high-impact polypropylene composite material includes the following steps:

[0076] Step a: Polypropylene composition A, polypropylene composition B, and B' are co-extruded according to the BAB' structure and then cast or calendered to obtain a polypropylene co-extruded sheet; preferably, the extrusion casting or calendering temperature is 200-240°C, and the temperature of the calendering roll is 50-70°C.

[0077] Step b: The polypropylene co-extruded sheet is stretched at a certain temperature to obtain a 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.

[0078] Step c: Cut the polypropylene stretched sheet into polypropylene flat strips, and weave the flat strips into polypropylene fabrics; preferably, the width of the polypropylene flat strips is 2-5 mm, and the polypropylene fabrics include plain weave, twill weave, satin weave or other three-dimensional polypropylene fabrics.

[0079] Step d: The polypropylene fabrics are sequentially stacked and hot-pressed together, and then cooled and shaped to form a 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 polypropylene fabrics in the polypropylene composite material can be placed at 0-90° between the warp and weft directions.

[0080] 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 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 polypropylene fabrics using a commercial weaving machine according to the designed fabric structure.

[0081] 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.

[0082] In the preparation process, the polypropylene sheets and / or 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 polypropylene composite material, i.e., a stacked hot-pressed product. Afterwards, the product is sliced ​​as needed using a sheet cutter, and then stacked and arranged using a sheet stacking machine. The hot-pressing temperature is controlled by the preheating unit, independent heating and pressurizing unit, and air-cooling unit in the tracked flatbed hot press, while the hot-pressing pressure is controlled by a lifting mechanism. According to the inventors' research, when the preparation process parameters are within the preferred range, and when the aforementioned preparation equipment is used to prepare the polymer composite material, the polymer composite material exhibits better tensile strength, impact performance, and interlaminar peel strength.

[0083] Sixthly, the object of the present invention is to provide an application of the flame-retardant polypropylene sheet described in the first aspect, the flame-retardant polypropylene fabric described in the third aspect, the flame-retardant polypropylene composite material described in the fourth aspect, and the flame-retardant polypropylene composite material prepared by the preparation method described in the fifth aspect in the fields of electrical component packaging, automobile manufacturing, military materials, and consumer products.

[0084] According to specific embodiments of the present invention, the materials field includes the electrical and electronic industry, the luggage and transportation industry, the footwear industry, the automobile manufacturing industry, the sports equipment manufacturing industry, the audio equipment manufacturing industry, and the military field.

[0085] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0086] (1) The flame-retardant polypropylene composite material of the present invention has good tensile strength, impact performance and interlaminar peel strength.

[0087] The flame-retardant polypropylene composite material has the following characteristics:

[0088] Longitudinal (MD) tensile strength ≥110MPa, preferably ≥130MPa; interlaminar peel strength ≥1N / mm, preferably ≥1.2N / mm; oxygen index ≥26%, preferably ≥28%; UL94 vertical burning rating V-1, preferably V-0; when the composite material is made of only 24 layers of polypropylene fabric hot-pressed together and the thickness is about 1.6mm, the drop hammer impact strength ≥200J, preferably ≥220J.

[0089] (2) The flame-retardant 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.

[0090] (3) This preparation method can reduce the hot pressing operation time, while improving production efficiency and reducing production energy consumption.

[0091] (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.

[0092] (5) The flame-retardant polypropylene sheets, flame-retardant polypropylene fabrics, and high-strength, high-impact flame-retardant polypropylene composite materials of the present invention are suitable for use in thin sheets, films, and fabrics while maintaining the mechanical properties of flame-retardant polypropylene composite materials, thus broadening the application scenarios of flame-retardant polypropylene. Detailed Implementation

[0093] 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.

[0094] In the following embodiments and comparative examples:

[0095] 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.

[0096] The properties of the polypropylene composition and sheet were tested according to the following methods, and the film test results are shown in Table 1:

[0097] (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;

[0098] (2) Melting point, determined according to the method specified in GB / T 28724-2012;

[0099] (3) Tensile strength: determined according to the method specified in GB / T1040.1-2018;

[0100] (4) Drop hammer impact strength: determined according to the method specified in GB / T14153-1993;

[0101] (5) Interlayer peel strength: determined according to the method specified in QB / T2358-98;

[0102] (6) Vertical combustion: The test shall be conducted in accordance with the method specified in GN / T 2408-2008;

[0103] (7) Limiting oxygen index: determined according to the method specified in GB / T 2406.1-2008.

[0104] 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.

[0105] Example 1

[0106] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0107] (1) Preparation of polypropylene composition A:

[0108] 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℃; the flame retardant m is a composition of ammonium polyphosphate and pentaerythritol, purchased from Jinan Haobang Chemical Co., Ltd. The weight ratio of ammonium polyphosphate to pentaerythritol in component m is 2:1.

[0109] The components obtained above were weighed and mixed according to the specified proportions, where component a (Wa) had a mass fraction of 64 parts by weight, component b (Wb) had a mass fraction of 16 parts by weight, and component m (Wm) had a mass fraction of 20 parts by weight. 0.05 parts by weight of β-crystal nucleating agent (VP101B) and 0.3 parts by weight of blendex 6530 anti-dripping agent 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 A were obtained. The melting point of polypropylene composition A was determined to be 158°C.

[0110] (2) Preparation of polypropylene composition B:

[0111] Component x is a 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 140℃ and a melt flow rate of 6.6 g / 10 min; component y is a polyolefin elastomer of grade 6102, purchased from ExxonMobil, 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; flame retardant n is a composition of ammonium polyphosphate and pentaerythritol. The weight ratio of ammonium polyphosphate to pentaerythritol in component n is 2:1.

[0112] The components prepared above are weighed and mixed according to the ratio, wherein the mass part of component x, Wx, is 60 parts by weight, the mass part of component y, Wy, is 10 parts by weight, and the mass part of component n, Wn, is 30 parts by weight. Other steps are the same as in step (1). Finally, polypropylene composition B granules are obtained, and its melting point is tested to be 138℃.

[0113] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0114] 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.

[0115] 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.

[0116] The extrusion casting temperature is 230℃, and the calendering roll temperature is 55℃. The solid-phase stretching process is carried out at a temperature of 135℃, a stretching rate of 2 m / min, and a stretching ratio of 6 times. After stretching, the film is wound up to form a polypropylene sheet (composite film), which consists of an upper surface layer (film layer A), a core layer (film layer A), and a lower surface layer (film layer B).

[0117] The thickness of the polypropylene sheet (composite film) mentioned above is 80 μm, wherein the thickness of film layer A accounts for 80% of the total thickness of the sheet.

[0118] (4) Preparation of polypropylene fabric:

[0119] The three-layer co-extruded polypropylene sheet obtained in step (3) above is cut into 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 into a plain weave polypropylene fabric according to the designed fabric structure using a commercial weaving machine.

[0120] (5) Preparation of polypropylene composite materials:

[0121] The polypropylene fabrics obtained in step (4) were sequentially stacked and hot-pressed to form a laminated polypropylene sheet. The laminated polypropylene sheet consisted of 24 layers of polypropylene fabric, with the warp and weft directions arranged at 90° angles. 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 polypropylene composite material was 1.67mm.

[0122] Example 2

[0123] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0124] (1) Preparation of polypropylene composition A:

[0125] Component a is a homopolymer polypropylene self-produced by the Beijing Research Institute of Chemical Industry of Sinopec, with a melting point of 165℃, a melt flow rate of 8.1 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 impact strength of 25 kJ / m under a test condition of 23℃. 2 The ethylene content is 8% wt, the melt flow rate is 3.2 g / 10 min, and the melting point is 155℃. Flame retardant m is a composition of ammonium polyphosphate and pentaerythritol. The weight ratio of ammonium polyphosphate to pentaerythritol in component m is 2:1.

[0126] The components obtained above were weighed and mixed according to the specified proportions, where component a (Wa) had 56 parts by weight, component b (Wb) had 24 parts by weight, and component m (Wm) had 20 parts by weight. 0.05 parts by weight of β-crystal nucleating agent (VP101B) and 0.3 parts by weight of blendex 6530 anti-dripping agent 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 A were obtained. The melting point of polypropylene composition A was determined to be 162°C.

[0127] (2) Preparation of polypropylene composition B:

[0128] Component x is a random copolymer polypropylene produced by the Beijing Research Institute of Chemical Industry, Sinopec, with a melting point of 134℃. It is an ethylene-propylene-butene terpolymer with a melt flow rate of 5.2 g / 10 min. Component y is a polyolefin elastomer produced by the Beijing Research Institute of Chemical Industry, Sinopec, which is an ethylene-propylene copolymer with an ethylene content of 15% wt. It has a melting point of 105℃ and a melt flow rate of 9 g / 10 min at 230℃ and a load of 2.16 kg. Flame retardant n is a composition of ammonium polyphosphate and pentaerythritol. The weight ratio of ammonium polyphosphate to pentaerythritol in component n is 2:1.

[0129] The components obtained above are weighed and mixed according to the ratio, wherein the mass part of component x, Wx, is 60 parts by weight, the mass part of component y, Wy, is 10 parts by weight, and the mass part of component n, Wn, is 30 parts by weight. Other steps are the same as in step (1). Finally, polypropylene composition B granules are obtained. The melting point of polypropylene composition B is tested to be 132℃.

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

[0131] The preparation process is the same as step (3) in Example 1.

[0132] (4) Preparation of polypropylene fabric:

[0133] The preparation process is the same as step (4) of Example 1.

[0134] (5) Preparation of polypropylene composite materials:

[0135] The preparation process is the same as step (5) in Example 1.

[0136] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0137] Example 3

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

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

[0140] Similar to Example 1, except that the flame retardant m is a composition of decabromodiphenyl ethane and antimony trioxide, purchased from Jinan Taixing Fine Chemical Co., Ltd. The weight ratio of decabromodiphenyl ethane to antimony trioxide in component m is 5:1. 0.05 parts by weight of β-crystal nucleating agent (VP101B) and 0.3 parts by weight of blendex 6530 anti-dripping agent were added. Polypropylene composition A granules were obtained, and the melting point of polypropylene composition A was determined to be 159°C.

[0141] (2) Preparation of polypropylene composition B:

[0142] Similar to Example 1, except that the flame retardant n is a composition of decabromodiphenyl ethane and antimony trioxide, purchased from Jinan Taixing Fine Chemical Co., Ltd. The weight ratio of decabromodiphenyl ethane to antimony trioxide in component n is 5:1, ultimately yielding polypropylene composition B granules. The melting point of polypropylene composition B was tested to be 140℃.

[0143] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0144] The preparation process is the same as step (3) in Example 1.

[0145] (4) Preparation of polypropylene fabric:

[0146] The preparation process is the same as step (4) of Example 1.

[0147] (5) Preparation of polypropylene composite materials:

[0148] The preparation process is the same as step (5) in Example 1.

[0149] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0150] Example 4

[0151] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0152] (1) Preparation of polypropylene composition A:

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

[0154] (2) Preparation of polypropylene composition B:

[0155] The preparation process is the same as step (2) of Example 1. The difference is that in the preparation of polypropylene composition B, the mass fraction of component x, Wx, is 85 parts by weight, and the mass fraction of component y, Wy, is 15 parts by weight, wherein flame retardant n is not added.

[0156] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0157] The main steps are the same as in Example 1. The thickness of the polypropylene sheet is 80 μm, wherein the thickness of the film layer A accounts for 90% of the total thickness of the sheet.

[0158] (4) Preparation of polypropylene fabric:

[0159] The preparation process is the same as step (4) of Example 1.

[0160] (5) Preparation of polypropylene composite materials:

[0161] The preparation process is the same as step (5) in Example 1.

[0162] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0163] Example 5

[0164] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0165] (1) Preparation of polypropylene composition A:

[0166] The preparation process is the same as step (1) in Example 1.

[0167] (2) Preparation of polypropylene composition B:

[0168] The preparation process is the same as step (2) of Example 1.

[0169] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0170] The main steps are the same as in Example 1. The thickness of the polypropylene sheet is 80 μm, wherein the thickness of the film layer A accounts for 70% of the total thickness of the sheet.

[0171] (4) Preparation of polypropylene fabric:

[0172] The preparation process is the same as step (4) of Example 1.

[0173] (5) Preparation of polypropylene composite materials:

[0174] The preparation process is the same as step (5) in Example 1.

[0175] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0176] Example 6

[0177] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0178] (1) Preparation of polypropylene composition A:

[0179] The preparation process is the same as step (1) in Example 1.

[0180] (2) Preparation of polypropylene composition B:

[0181] The preparation process is the same as step (2) of Example 1.

[0182] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0183] The preparation process is the same as step (3) in Example 1.

[0184] (4) Preparation of polypropylene fabric:

[0185] The preparation process is the same as step (4) of Example 1.

[0186] (5) Preparation of polypropylene composite materials:

[0187] The main steps are the same as in Example 1. The laminated polypropylene sheet includes two layers of 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 polypropylene composite material is 129μm.

[0188] Example 7

[0189] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0190] (1) Preparation of polypropylene composition A:

[0191] The preparation process is the same as step (1) in Example 1.

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

[0193] The preparation process is the same as step (2) of Example 1.

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

[0195] The preparation process is the same as step (3) in Example 1.

[0196] (4) Preparation of polypropylene fabric:

[0197] The preparation process is the same as step (4) of Example 1.

[0198] (5) Preparation of polypropylene composite materials:

[0199] The main steps are the same as in Example 1. The laminated polypropylene sheet includes 100 layers of 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 polypropylene composite material is 7.23 mm.

[0200] Example 8

[0201] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0202] (1) Polypropylene composition A i Preparation:

[0203] The preparation process is the same as step (1) in Example 1.

[0204] (2) Polypropylene composition B i Preparation:

[0205] 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:

[0206] Component x1 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 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 of 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 of Sinopec, which 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.

[0207] Finally, polypropylene composition B was obtained. i Granular material (i.e., x) i +y+n=B i(i = 1, 2, 3), after testing, the melting point of B1 is 128℃, the melting point of B2 is 134℃, and the melting point of B3 is 138℃.

[0208] (3) Preparation of three-layer co-extruded polypropylene sheets:

[0209] The preparation process is the same as step (3) of Example 1. Sheets B1AB1, B2AB2, and B3AB3 were prepared respectively.

[0210] (4) Preparation of polypropylene fabric:

[0211] The preparation process is the same as step (4) in Example 1. Plain weave polypropylene fabrics B1AB1, B2AB2, and B3AB3 were obtained.

[0212] (5) Preparation of polypropylene composite materials:

[0213] 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.

[0214] Example 9

[0215] This embodiment illustrates the preparation of the polypropylene composition, three-layer co-extruded polypropylene sheet, polypropylene fabric, and polypropylene composite material provided by the present invention.

[0216] (1) Polypropylene composition A i Preparation:

[0217] The preparation process is the same as step (1) in Example 1.

[0218] (2) Polypropylene composition B i Preparation:

[0219] 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:

[0220] Components x1-x4 are 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 128℃; components x5-x8 are 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 135℃; 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 142℃; 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.

[0221] Finally, polypropylene composition B was obtained. i Granular material (i.e., x) i +y+n=B i (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12), after testing, the melting point of B1-B4 is 126℃, the melting point of B5-B8 is 133℃, and the melting point of B9-B... 12 Its melting point is 140℃.

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

[0223] The preparation process is the same as step (3) in Example 1.

[0224] (4) Preparation of polypropylene fabric:

[0225] The preparation process is the same as step (4) of Example 1.

[0226] (5) Preparation of polypropylene composite materials:

[0227] The polypropylene fabrics obtained in step (4) above are stacked sequentially, from bottom to top as B. 12 AB 12… B3AB3, B2AB2, B1AB1, B2AB2, B3AB3,…B 12 AB 12 The total number of layers is 23. The laminated polypropylene fabrics are hot-pressed and fused together, then cooled and shaped to form a polypropylene composite material. The polypropylene fabrics are placed at a 90° angle between the warp and weft directions. The hot-pressing conditions are: temperature 150℃, hot-pressing pressure 5MPa, preheating time 160s, hot-pressing time 160s, and cooling time 600s. The prepared polypropylene composite material has a thickness of 1.57mm.

[0228] Comparative Example 1

[0229] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 1. However, only polypropylene composition A was used for extrusion casting into a single-layer film with a thickness of 80 μm. Polypropylene fabrics and polypropylene composites were also prepared according to the method of Example 1.

[0230] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0231] Comparative Example 2

[0232] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 1. However, only polypropylene composition B was used for extrusion casting into a single-layer film with a thickness of 80 μm. Polypropylene fabrics and polypropylene composites were also prepared according to the method of Example 1.

[0233] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0234] Comparative Example 3

[0235] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 3. However, the polypropylene composition A contained only component b and component m, with component b having a mass fraction (Wb) of 75 parts by weight and component m having a mass fraction (Wm) of 25 parts by weight. Polypropylene fabrics and polypropylene composites were prepared according to the method of Example 1.

[0236] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0237] Comparative Example 4

[0238] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 3. However, the polypropylene composition B contained only component y and component n, with component y (Wy) comprising 75 parts by weight and component n (Wn) comprising 25 parts by weight. Polypropylene fabrics and polypropylene composite materials were prepared according to the method of Example 1.

[0239] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0240] Comparative Example 5

[0241] Three-layer co-extruded polypropylene sheets were prepared according to the method of Example 1. However, polypropylene composition A did not contain component m, and polypropylene composition B did not contain component n. Polypropylene fabrics and polypropylene composites were also prepared according to the method of Example 1.

[0242] The thickness of the prepared polypropylene composite material is similar to that of Example 1.

[0243] Comparative Example 6

[0244] Three-layer co-extruded polypropylene sheets and polypropylene fabrics were prepared according to the method in Example 8.

[0245] The difference lies in the preparation of the polypropylene composite material. Polypropylene fabrics are layered sequentially in the following order from bottom to top: B1A1B1, B2A2B2, B3A3B3, B2A2B2, B1A1B1 (i.e., B1 has a melting point of 128℃, B2 has a melting point of 134℃, and B3 has a melting point of 138℃), for a total of 5 layers. The laminated polypropylene fabrics are then hot-pressed together and cooled to set the composite material. The polypropylene fabrics are placed at a 90° angle between the warp and weft directions. The hot-pressing conditions are: temperature 145℃, hot-pressing pressure 5MPa, preheating time 110s, hot-pressing time 110s, and cooling time 300s. The thickness of the prepared polypropylene composite material is 418μm.

[0246] Experimental Example

[0247] The 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.

[0248] (1) Tensile strength: Samples were prepared and tested in accordance with the methods specified in GB / T1040.1-2018.

[0249] (2) Interlayer peel strength: Samples were prepared and measured in accordance with the method specified in QB / T2358-98.

[0250] (3) Drop hammer impact strength: The test was conducted according to the method specified in GB / T14153-1993. Among them, the thickness of the polypropylene composite materials obtained in Examples 1-5, Example 9, and Comparative Examples 1-5 were all similar, around 1.6 mm, and all within the range of 1.6 mm ± 1 mm.

[0251] (4) Vertical combustion: The test was conducted according to the method specified in GN / T 2408-2008. Among them, the thickness of the polypropylene composite materials obtained in Examples 1-5, Example 9, and Comparative Examples 1-5 was similar, around 1.6 mm; 12 samples of Example 6 were stacked and hot-pressed to obtain samples with a thickness of about 1.6 mm; 4 samples of Example 8 and Comparative Example 6 were stacked and hot-pressed to obtain samples with a thickness of about 1.6 mm; the sample of Example 7 was cut into 1.6 mm samples.

[0252] (5) Limiting oxygen index: determined according to the method specified in GB / T 2406.1-2008.

[0253] Table 1

[0254]

[0255]

[0256] The results from the examples in Table 1 show that the flame-retardant polypropylene composite material prepared according to the present invention possesses excellent tensile properties, impact resistance, and flame retardancy, while also exhibiting good interlaminar peel strength at relatively low hot-pressing temperatures. The longitudinal (MD) tensile strength of the polypropylene composite sheet of the present invention is ≥110 MPa, and the interlaminar peel strength is ≥1 N / mm. When the polypropylene composite material is made of 24 layers of polypropylene fabric hot-pressed together with a thickness of approximately 1.6 mm, the drop hammer impact strength is ≥200 J, reaching V-1 level, and more preferably V-0 level.

[0257] As can be seen from the preferred embodiments 1-3, the longitudinal (MD) tensile strength of the polypropylene composite material prepared by the present invention is ≥130MPa, the interlaminar peel strength is ≥1.2N / mm; when the polypropylene composite material is made of 24 layers of polypropylene fabric hot-pressed together and the thickness is about 1.6mm, the drop hammer impact strength is ≥220J, and the UL-94 reaches V-1 level.

[0258] As can be seen from Comparative Examples 1-5, using only a single-layer sheet structure or using interlayer ratios outside the scope of this invention will lead to a decrease in the performance of laminated polypropylene sheets or fabrics. Using conditions outside the scope of this invention will significantly reduce the tensile strength, impact performance, interlayer peel strength, or flame retardant properties of the resulting polypropylene composite material.

[0259] 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.

[0260] 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 flame-retardant polypropylene sheet, comprising layer A and layers B and B' located on both sides of layer A, having a structure of BAB'; Layer B may be the same as or different from layer B', and each contains a polypropylene composition B and a polypropylene composition B', wherein each of the polypropylene compositions B and B' comprises random copolymer polypropylene x, a thermal bonding enhancer y, and an optional flame retardant n; layer A contains a polypropylene composition A, wherein the polypropylene composition A comprises homopolymer polypropylene a, impact copolymer polypropylene b, and an optional flame retardant m. in, The melting point of the polypropylene composition A is greater than that of the polypropylene composition B and the polypropylene composition B', and the contents of flame retardant m and flame retardant n in the polypropylene compositions A, B, and B' are not all 0 at the same time. Based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 30-98 wt% homopolymer polypropylene a, 1-50 wt% impact copolymer polypropylene b, and 0-60 wt% flame retardant m. Based on the total weight of the polypropylene composition B and the polypropylene composition B', each of the polypropylene composition B and the polypropylene composition B' comprises 30-98 wt% random copolymer polypropylene x, 1-50 wt% thermal bonding enhancer y, and 0-60 wt% flame retardant n.

2. The flame-retardant polypropylene sheet according to claim 1, characterized in that: 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, Based on the total thickness of the flame-retardant polypropylene sheet, the thickness of layer A accounts for 51%-89% 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 5°C.

3. The flame-retardant polypropylene sheet according to claim 1, characterized in that: 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, Based on the total thickness of the flame-retardant polypropylene sheet, the thickness of layer A accounts for 71%-89% 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 10°C.

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

5. The flame-retardant polypropylene sheet according to claim 1, characterized in that: Based on the total weight of the polypropylene composition A, the polypropylene composition A comprises 40-80 wt% homopolymer polypropylene a, 5-30 wt% impact copolymer polypropylene b, 2-50 wt% flame retardant m; 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 40-80 wt% random copolymer polypropylene x, 5-30 wt% thermal bonding enhancer y, and 2-50 wt% flame retardant n.

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

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

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

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

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

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

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

13. The flame-retardant polypropylene sheet according to any one of claims 1-5, 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.

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

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

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

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

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

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

20. The flame-retardant polypropylene sheet according to claim 19, characterized in that: The polyolefin elastomer is a copolymer elastomer of ethylene with propylene and / or α-olefins.

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

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

23. The flame-retardant polypropylene sheet according to claim 19, characterized in that: The petroleum resin is a C5 and / or C9 hydrogenated petroleum resin with a softening point of 100-150℃.

24. The flame-retardant polypropylene sheet according to claim 19, characterized in that: The petroleum resin is a cyclopentadiene type resin.

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

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

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

28. The flame-retardant polypropylene sheet according to any one of claims 1-5, characterized in that: The flame retardant m and flame retardant n may be the same or different, and each is selected from one or more of the following: organic or inorganic compounds containing flame retardant elements and their polymers, inorganic substances that are stable at high temperatures and / or metal hydroxides.

29. The flame-retardant polypropylene sheet according to any one of claims 1-5, characterized in that: The flame retardant m and flame retardant n may be the same or different, and each is selected from one or more of the following: halogenated flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, boron-based flame retardants, antimony-based flame retardants, biomass flame retardants, intumescent flame retardants, hydroxides, and oxide hydrates.

30. A method for preparing a flame-retardant polypropylene sheet according to any one of claims 1-29, 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 flame-retardant polypropylene sheet.

31. The method for preparing flame-retardant polypropylene sheets according to claim 30, characterized in that, The preparation of the raw material for layer A includes melt blending of the homopolymer polypropylene a, the impact copolymer polypropylene b, and an optional flame retardant m; and / or, The preparation of the raw materials for layers B and B' each includes melt blending the components, including the random copolymer polypropylene x, the thermal bonding enhancer y, and the optional flame retardant n; 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.

32. The method for preparing flame-retardant polypropylene sheets according to claim 30, characterized in that, The stretching conditions include: a stretching temperature of 90-140℃ and a stretching ratio of 1-20 times.

33. The method for preparing flame-retardant polypropylene sheets according to claim 30, characterized in that, The stretching conditions include: a stretching temperature of 90-119℃ and a stretching ratio of 1-20 times.

34. A flame-retardant polypropylene fabric, a three-dimensional polypropylene fabric obtained by weaving the flame-retardant polypropylene sheet according to any one of claims 1-29.

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

36. A flame-retardant polypropylene composite material, wherein the flame-retardant polypropylene composite material is prepared by hot pressing together multiple layers of flame-retardant polypropylene sheets as described in any one of claims 1-29 and / or flame-retardant polypropylene fabrics as described in claims 34 or 35.

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

38. The flame-retardant polypropylene composite material according to claim 36, characterized in that: The number of layers in multilayer flame-retardant polypropylene sheets and / or multilayer flame-retardant polypropylene fabrics ranges from 2 to 200.

39. The flame-retardant polypropylene composite material according to claim 36, characterized in that: The number of layers in multilayer flame-retardant polypropylene sheets and / or multilayer flame-retardant polypropylene fabrics ranges from 4 to 100.

40. The flame-retardant polypropylene composite material according to any one of claims 36-39, characterized in that: The flame-retardant 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 flame-retardant polypropylene composite material, from bottom to top, is group n...group i...group 2, group 1, group 2...group i...group n, and the total number of polypropylene sheet unit groups is 2n-1. Both i and n are integers not less than 2, and i ≤ n; Among them, the core layer A in the polypropylene sheet unit i Composition A containing polypropylene i Outer layer B i With outer layer B' i Whether the composition is the same or different, each composition corresponds to a polypropylene composition B. i Polypropylene composition B' i , The polypropylene composition A i The melting point is greater than that of the polypropylene composition B. i The polypropylene composition B' i The melting point of the outermost layer in the i-th group is greater than the average melting point of the outermost layer in the (i-1)-th group.

41. The flame-retardant polypropylene composite material according to claim 40, 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.

42. The flame-retardant polypropylene composite material according to claim 40, 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.

43. The flame-retardant polypropylene composite material according to claim 40, 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℃.

44. A method for preparing a flame-retardant polypropylene composite material according to any one of claims 36-43, the method comprising hot-pressing and fusing the flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric together, and then cooling and shaping it to form a flame-retardant polypropylene composite material.

45. The method for preparing the flame-retardant polypropylene composite material according to claim 44, 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 flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric laminate has at least two layers; and / or Adjacent layers of the flame-retardant polypropylene fabric laminate are placed at an angle of 0-90° between warp directions; and / or, The adjacent layers of the flame-retardant polypropylene sheet stack are placed at 0-90° along their respective machine directions.

46. ​​The method for preparing the flame-retardant polypropylene composite material according to claim 44, 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 flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric stack has 2-200 layers.

47. The method for preparing the flame-retardant polypropylene composite material according to claim 44, characterized in that: The flame-retardant polypropylene sheet and / or the flame-retardant polypropylene fabric stack has 4-100 layers.

48. The applications of the flame-retardant polypropylene sheet according to any one of claims 1-29, the flame-retardant polypropylene fabric according to claim 34 or 35, the flame-retardant polypropylene composite material according to any one of claims 36-43, and the flame-retardant polypropylene composite material prepared by the preparation method according to claims 44-47 in the fields of electrical component packaging, automobile manufacturing, military materials, and consumer products.

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