Special polypropylene random copolymer soft fiber material and preparation method thereof

Abstract

According to the polypropylene random copolymer soft fiber special material and the preparation method thereof provided by the invention, the modified carbon nano tube obtained by sequentially performing surface modification on the purified carbon nano tube through the coupling agent, the polydopamine and the gelatin is added, so that the compatibility of the carbon nano tube and polypropylene can be remarkably improved; the polypropylene random copolymer resin and other auxiliaries are combined, so that the mechanical property of the special polypropylene material can be remarkably improved, and the application requirements of the special polypropylene material in the fields of high-end hygienic materials, medical ultra-soft materials and the like can be met.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a special material for random copolymerized polypropylene soft fibers and a preparation method thereof. Background Art

[0002] High melt index polypropylene fiber material generally refers to polypropylene with MFR exceeding 20g / min. Since the non-woven fabrics produced by it have the advantages of light weight, softness, breathability, and easy molding, they are widely used in packaging, water purification filter materials, geotextiles, clothing, medical, sanitary products and other fields. Among the fiber raw materials used for non-woven fabrics, chemical fibers account for 99%. Among the chemical fiber raw materials currently used, polypropylene accounts for 63%, polyester accounts for 23%, viscose fiber accounts for 8%, acrylic accounts for 2%, nylon accounts for 1.5%, and other special chemical fibers account for about 3%. It can be seen that polypropylene fiber is the main raw material for non-woven fabrics.

[0003] Non-woven fabric refers to a cloth-like material made without the traditional weaving method. Due to its wide range of raw materials, short process flow, wide product application and low cost, it has attracted the attention of countries around the world, prompting the output of non-woven fabrics to grow year by year. At present, the non-woven fabric industry is in the development stage, and its products involve various sectors of the national economy, partially replacing traditional woven fabrics and knitted fabrics. Hoechst, which produces special resins for polypropylene chemical fibers, has developed and produced a variety of brands of special materials for chemical fibers, such as PPU1780F, PPU1780F2, PPV1080F1 for short filaments, spunbond PPU1080F, PPU1780F1, PPU1780F3, and filaments PPU1080FE, PPU1080FEG, etc. Amoco has newly developed spunbond non-woven fabric special material PPGrade7957, which has the advantages of reducing smoke and eliminating the yellowing phenomenon caused by oxidation of products. In addition, with the development of metallocene catalysts, isotactic polypropylene (m-iPP) has been produced, which greatly improves the spinnability of polypropylene, thereby increasing the spinning speed and reducing the fiber fineness. Exxon's spunbond non-woven fabric material Achieve polypropylene has a low melting point of 148°C and good fluidity. The production line can run at a speed of 4200m / min. The product can be used to produce diapers, sanitary products, surgical gowns, masks and filter materials. Ube Nitto Chemical Co., Ltd. of Japan has developed a high-strength polypropylene fiber, whose breaking strength is twice that of general PP and its elastic modulus is four times that of PP.

[0004] The fiber size is controlled by the take-up rate and the spinneret output. Under the condition of a certain spinneret diameter, the shear rate to which the melt is subjected when flowing in the spinneret is very high. Therefore, for PP resin, the following should be met: (1) The relative molecular mass must be small to make the melt viscosity low. Usually, for spinning thicker filaments, the melt flow rate (MFR) of PP is generally 8.0-12.0 g / 10 min; for spinning fine filaments, the MFR is 30.0-35.0 g / 10 min; for ultrafine filaments, a higher MFR is required, generally above 40.0 g / 10 min. (2) The relative molecular mass distribution should be narrow. Because the relative molecular mass distribution is narrow, the sensitivity of the shear rate to the melt viscosity is reduced, and the viscosity fluctuation is small at high shear rates; at the same time, the melt elasticity is also reduced, which is conducive to keeping the diameter of the filament uniform. After chemical degradation, not only the relative molecular mass of PP decreases, but also the relative molecular mass distribution becomes narrower.

[0005] Japanese scientist Iijima discovered carbon nanotubes in 1991. As the name suggests, carbon nanotubes are tubes formed by graphite sheets curled around the central axis with a certain degree of helicity. The two ends of the tube are generally sealed with a pentagonal hemispherical grid. Each carbon atom in the carbon nanotube is connected to three adjacent carbon atoms to form a hexagonal grid structure, but the hexagonal grid structure in the carbon nanotube generally produces a certain degree of bending to form a spatial topological structure, so it is mainly sp2 hybridization and also contains sp3 hybridization. Carbon nanotubes are generally divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. The length of single-walled carbon nanotubes can reach tens of microns, and the diameter is between a few nanometers and several nanometers. The length of multi-walled carbon nanotubes can reach several millimeters, and the diameter is between a few nanometers and tens of nanometers. The interlayer spacing of graphite remains fixed and is generally about 0.34nm.

[0006] Carbon nanotubes are made of graphite sheets curled around a central axis. Different curling methods result in different structures and properties. When carbon nanotubes are curled, an angle, i.e. a helical angle, may appear between the nanotube axis and the unchanged hexagonal grid in the graphite sheet (e.g. Figure 1). Carbon nanotubes can show both semiconductor and metallic properties depending on the diameter and helix angle: when (n~m) is an integer multiple of 3, it shows metallic properties, otherwise it shows semiconductor properties. Therefore, carbon nanotubes have excellent properties due to their unique structure. It has ideal elasticity and extremely high mechanical strength. Carbon nanotubes can not only withstand huge axial tension, but also withstand huge radial deformation. The tensile strength reaches 50~200GPa, which is 100 times that of steel. The bending strength can reach 14.2GPa, and the elastic modulus can reach 1.8TPa, which is equivalent to the elastic modulus of diamond, about 5 times that of steel, but the density is only 1 / 6 of that of steel. In addition, carbon nanotubes have high thermal and chemical stability. Their excellent thermal conductivity, superconducting properties and optical properties have also attracted great attention. Their applications have involved composite materials, nanoelectronic devices, catalyst carriers, electrode materials, hydrogen storage materials and many other aspects. Carbon nanotubes can show their elasticity through volume changes, so they can withstand tensile strains greater than 40% without showing plastic deformation, brittle behavior or bond breakage. Therefore, when used in composite materials, carbon nanotubes can be used to greatly absorb energy and increase strength and toughness. These excellent mechanical properties make carbon nanotubes the most promising research hotspot in the field of composite materials. The research on carbon nanotube composites has become an extremely important field and has received widespread attention and research.

[0007] However, since carbon nanotubes are easy to entangle or aggregate into bundles, the surface of carbon nanotubes is relatively "inert" compared with other nanoparticles, and the dispersion in common organic solvents is low, and it is difficult to disperse evenly in polymers, which greatly restricts the research on its application performance. In order to improve the uniformity of the dispersion of carbon nanotubes in polymers, at present, the main methods used at home and abroad to modify carbon nanotubes are surface chemical reaction modification, polymer coating modification, surfactant modification, etc. Surface chemical reaction modification refers to the introduction of some suitable groups on the surface of carbon nanotubes, so that they react chemically on the surface of carbon nanotubes and produce chemical bonds between the surface and the polymer. This method can improve the dispersion and solubility of carbon nanotubes. Modification of the surface of carbon nanotubes has become a research hotspot for polymer / carbon nanotube composites.

[0008] However, how to apply carbon nanotubes to EPDM random copolymer polypropylene soft fiber special material to give full play to the super strong mechanical properties of carbon nanotubes, so as to prepare a random copolymer polypropylene soft fiber special material with high toughness, high rigidity and high fluidity, has become a technical problem to be solved urgently in this field.

[0009] For example, Chinese patent document CN113480802A discloses a high-performance flame-retardant antistatic polypropylene, which includes the following weight fractions: 50-70 parts of raw polypropylene, 10-30 parts of glass fiber, 5-20 parts of carbon nanotubes, 5-15 parts of modified polymer antistatic agent, 3-8 parts of maleic anhydride grafted compatibilizer, 3-10 parts of flame retardant, 1-5 parts of silane coupling agent, and 0.1-3 parts of dispersant. The high-performance flame-retardant antistatic polypropylene enhances the mechanical properties and weather resistance of polypropylene materials, and has high specific strength, light weight, corrosion resistance, good flame retardant effect, less smoke, no toxic gas, and good antistatic performance. However, since carbon nanotubes are easy to entangle or aggregate into bundles, the surface of carbon nanotubes is relatively "inert" compared with other nanoparticles, and it is difficult to disperse evenly in the polymer and is easy to agglomerate in the polymer. Therefore, the brittleness of the polypropylene material increases and the toughness is significantly reduced.

[0010] Chinese patent document CN103408821A discloses a polyethylene / fullerene nanocomposite material and a preparation method thereof, wherein the material is prepared from the following raw materials in parts by weight: 0.05-5 parts by weight of fullerene (carbon nanotube), 95-99.95 parts by weight of polyethylene; the preparation method is to directly add the dried fullerene into high-density polyethylene for melt blending, and the polyethylene nanocomposite material has a higher thermal stability. However, since carbon nanotubes are easily entangled or aggregated into bundles, the surface of carbon nanotubes is relatively "inert" compared with other nanoparticles, and it is difficult to be uniformly dispersed in polymers, and it is easy to agglomerate in polymers, thereby causing the composite material comprehensive performance to not be improved, and the tensile strength decreases instead, which shows that simple mechanical blending is difficult to uniformly disperse carbon nanotubes in a polypropylene matrix.

[0011] Chinese patent document CN103011131A discloses a method for preparing carbon nanotubes modified with a coupling agent, which specifically involves hydrolyzing the coupling agent in alcohol or water to obtain active functional groups, utilizing these active functional groups to react with carbon nanotubes for impregnation, so that the coupling agent migrates from the polymer to the surface of the filler, completing the hydrolysis and condensation reaction, and grafting long-chain alkyl groups on the surface of the carbon nanotubes. Although this solves the problem that the carbon nanotubes are easy to aggregate and entangle, and difficult to disperse, to a certain extent, the chemical inertness of the carbon nanotubes results in that even if the coupling agent modification is first treated with acid, it is difficult to graft groups on the surface of the carbon nanotubes, and it is difficult for the coupling agent and the carbon nanotubes to form a chemical reaction, resulting in the carbon nanotube modification effect not meeting expectations.

[0012] Chinese patent document CN109052370A discloses a method for surface modification of carbon nanotubes, which sequentially uses a composite modification method of high oxidation, polymer coating and coupling agent treatment to treat the surface of carbon nanotubes. The modified carbon nanotubes can be stably dispersed in a solvent and have improved compatibility with the polymer. However, the dispersibility of the surface-modified carbon nanotubes still needs to be improved.

[0013] Chinese patent document CN109749096A discloses a method for preparing a gelatin hydrogel modified with carbon nanotubes, by modifying a carbon nanotube array with a methacrylate polymer having an unsaturated group end, thereby reducing the agglomeration caused by the van der Waals force between the carbon nanotubes. The ester groups on the modified carbon nanotube array are connected to the amino groups or hydroxyl groups in the gelatin through covalent bonds, and the unsaturated bonds in the methacrylate polymer grafted on the carbon nanotubes are cross-linked, thereby obtaining a gelatin hydrogel modified with carbon nanotubes having good mechanical properties. However, the gelatin grafting rate in this scheme is low, and the modification effect of the carbon nanotubes does not meet expectations.

[0014] Therefore, how to apply carbon nanotubes to special polypropylene soft fiber materials to give full play to the super strong mechanical properties of carbon nanotubes, so as to prepare a high toughness, high rigidity and high fluidity ultra-soft random copolymer polypropylene fiber material for high-end sanitary materials and medical use, has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0015] In view of the above defects and improvement needs of the prior art, the present invention provides a special material for random copolymer polypropylene soft fibers and a preparation method thereof. By modifying carbon nanotubes, the compatibility of the carbon nanotubes and the polypropylene resin is improved, and the synergistic effect of the modified carbon nanotubes, the polypropylene resin and the additives is utilized to improve the comprehensive properties of the special polypropylene material, such as mechanical properties, toughness, rigidity and fluidity, so that the special polypropylene material can meet the application requirements in the fields of high-end sanitary materials, medical ultra-soft materials, etc.

[0016] To achieve the above object, the present invention provides a random copolymer polypropylene soft fiber special material, comprising the following components: random copolymer polypropylene resin 90wt%-99wt%, toughening masterbatch 1wt%-10wt%;

[0017] The toughening masterbatch comprises the following components: 65wt%-88.5wt% of random copolymerized polypropylene resin; 0.5wt%-5wt% of modified carbon nanotubes; 5wt%-20wt% of degradation agent and 5wt%-10wt% of antioxidant;

[0018] The modified carbon nanotubes are obtained by sequentially surface-modifying carbon nanotubes purified by oxidation with a coupling agent, polydopamine and gelatin.

[0019] Optionally, in the above two random copolymer polypropylene soft fiber special materials provided by the present invention, when the carbon nanotubes are purified by oxidation, a mixed solution of potassium permanganate and concentrated sulfuric acid is preferably used to purify the carbon nanotubes. By purifying the carbon nanotubes by oxidation, hydroxyl groups can be introduced on the surface of the carbon nanotubes.

[0020] Optionally, in the above two random copolymer polypropylene soft fiber special materials provided by the present invention, the degradation agent is a peroxide degradation agent, such as di-tert-butyl peroxide (DTBP), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (101), 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (301), etc.

[0021] The peroxide degradation method is a process implemented in an extrusion granulator. It does not affect the polymerization process load, does not produce equipment cavitation, is convenient and quick to switch grades, has a short transition time, and uses very little transition material. In addition, the relative molecular mass of the product can be controlled by adjusting the amount of the degradation agent. The product MFR has a wide controllable range and a narrow relative molecular mass distribution. At the same time, other properties remain basically unchanged, making it particularly suitable for fiber production. Therefore, from the perspective of product quality, the degradation method is currently the simplest and most economical way to produce controlled rheology polypropylene fiber materials.

[0022] Preparation of high melt index polypropylene fiber material, the degradation reaction diagram of the degradation agent is as follows Figure 2 As shown, the specific degradation principle is:

[0023] (1) Peroxide decomposes under heat in the mixer to produce peroxide free radicals;

[0024] (2) Peroxide free radicals attack the tertiary carbon atoms on the PP molecular chain, taking away the hydrogen atoms on it, and generating PP free radical molecular chains;

[0025] (3) The tertiary carbon atom of the PP free radical molecular chain breaks at the β position, breaking the long molecular chain into short molecular chains;

[0026] (4) The peroxide is completely consumed, no more peroxide free radicals are generated, and the degradation ends. As the PP molecular chain breaks, the average molecular weight decreases and the MFR increases.

[0027] Optionally, other additives such as weathering agent, acid scavenger, antistatic agent, nucleating agent, etc. may be added to the random copolymer polypropylene soft fiber special material provided by the present invention according to actual needs.

[0028] Optionally, in the random copolymer polypropylene soft fiber special material provided by the present invention, the antioxidant, the antistatic agent, the acid scavenger and the nucleating agent are not specifically limited, and conventional ones in the industry can be used. The antioxidant recommended by the present invention is a phenolic antioxidant; for example, 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, β-(4-hydroxy-3,5-di-tert-butylphenyl) propionate, 4,4'-dihydroxybiphenyl, butylated styrenated cresol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol) ), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4-methyl-6-(α-methylcyclohexyl)phenol), 4,4'-butylidenebis(3-methyl-6-butyl-tert-phenol), 4,4'-methylenebis(2,6-di-tert-butylphenol) and at least one of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 164, etc.;

[0029] The antistatic agent can be selected from at least one of alcohol ether phosphate monoester, alkyl phosphate diethanol ammonium salt, stearamidopropyl-β-hydroxyethyl quaternary ammonium nitrate, (3-laurylamidopropyl)trimethylammonium methylsulfate, Antistat68, SGK-03 antistatic agent, ASA-10, octylphenol polyoxyethylene ether, polyoxyethylene stearate and monoglyceride;

[0030] The acid scavenger may be selected from at least one of calcium stearate, hydrotalcite, zinc oxide, etc.;

[0031] The nucleating agent can be selected from at least one of aromatic phosphate transparent nucleating agents, sorbitol transparent nucleating agents, carboxylic acid metal salt transparent nucleating agents, dehydrogenated polar acids and their salts transparent nucleating agents, branched acid amine transparent nucleating agents, and the like.

[0032] Optionally, in the random copolymer polypropylene soft fiber special material provided by the present invention, the random copolymer polypropylene resin is an ethylene-propylene copolymer resin; preferably, the melt index of the ethylene-propylene copolymer resin is 6-11 g / 10 min, and the ethylene content is 2wt%-5wt%; more preferably, the melt index of the ethylene-propylene copolymer resin is 7-9 g / 10 min, and the ethylene content is 2wt%-3wt%.

[0033] Optionally, in the random copolymer polypropylene soft fiber special material provided by the present invention, the coupling agent is selected from a silane coupling agent or a titanate coupling agent, such as vinyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane (KH-550), methylethyl silane, 1,1,2,-trimethylpropyl trichlorosilane, vinyl trimethoxysilane, vinyl tri(β-methoxyethoxy) silane, isopropyl dioleyloxy (dioctyl phosphate acyloxy), isopropyl dioleyloxy (dioctyl phosphate acyloxy) titanate, etc.

[0034] Optionally, the preparation method of the random copolymer polypropylene soft fiber special material provided by the present invention is not specifically limited, and a conventional method in the industry can be used.

[0035] The random copolymerized polypropylene resin, modified carbon nanotubes, degradation agent and antioxidant are mixed in a high-speed mixer (e.g., mixed at room temperature for 3-5 minutes), and then put into a twin-screw extruder for melt extrusion to obtain a toughening masterbatch; preferably, the extrusion temperature is 160-190° C. and the screw speed is 55-150 rpm;

[0036] The random copolymer polypropylene resin and the toughening masterbatch are mixed in a low-speed mixer, and then put into a twin-screw extruder for melt extrusion. The extruded material is cooled, air-dried, and pelletized to obtain the random copolymer polypropylene soft fiber special material; preferably, the extrusion temperature is 200-210° C., and the screw speed is 200-300 rpm.

[0037] Optionally, in the method for preparing the random copolymer polypropylene soft fiber special material provided by the present invention, the preparation of the modified carbon nanotubes comprises the following steps:

[0038] Purification: dispersing carbon nanotubes in an oxidant for reflux reaction, and after the reaction is completed, separating, washing to neutrality, and vacuum drying to obtain purified carbon nanotubes;

[0039] Coupling agent modification: dispersing the coupling agent and the purified carbon nanotubes in ethanol for reflux reaction, and after the reaction is completed, removing the ethanol to obtain the coupling agent-modified carbon nanotubes;

[0040] Polydopamine modification: reacting the carbon nanotubes modified with the coupling agent and polydopamine in a tris-buffered solution, and after the reaction, washing with deionized water to neutrality to obtain carbon nanotubes modified with the coupling agent and polydopamine;

[0041] Gelatin modification: the coupling agent and the carbon nanotubes modified with polydopamine are dispersed in deionized water, and then mixed with the gelatin aqueous solution for reaction. After the reaction is completed, the separated solid is washed with deionized water and dried to obtain the modified carbon nanotubes.

[0042] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, the mass volume ratio of the carbon nanotubes to the oxidant is 25 mg:(1-10) mL; preferably, the oxidant is a mixed solution of potassium permanganate and concentrated sulfuric acid in a mass ratio of (1-2):(1-2).

[0043] Optionally, in the preparation process of modified carbon nanotubes provided by the present invention, in the purification step, the carbon nanotubes are placed in an oxidant, and then ultrasonically treated at room temperature for 2-3 hours until they are evenly dispersed, refluxed at 120-130°C for 3-5 hours, and then filtered, washed with deionized water until neutral, and dried under vacuum conditions to constant weight to obtain purified carbon nanotubes.

[0044] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, the outer diameter of the carbon nanotubes is 20-30 nm, the length is 10-30 μm, and the density is 2-3 g / m 3 , surface area greater than 110m 2 / g.

[0045] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, in the coupling agent modification step, the mass ratio of the purified carbon nanotubes to the coupling agent is 5:(1-10).

[0046] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, in the coupling agent modification step, the coupling agent and the purified carbon nanotubes are added to ethanol, ultrasonically treated at room temperature for 1-2 hours, refluxed at 70-80°C for 2-3 hours, and then the ethanol is removed to obtain the coupling agent-modified carbon nanotubes.

[0047] Optionally, in the preparation process of modified carbon nanotubes provided by the present invention, in the polydopamine modification step, the carbon nanotubes modified with the coupling agent are dispersed in a tris-buffer by ultrasound at room temperature, and then polydopamine is added and reacted under stirring for 3-5 hours, and the solid obtained by centrifugation is washed 2-5 times with deionized water until it is neutral, thereby obtaining carbon nanotubes modified with the coupling agent and polydopamine.

[0048] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, in the polydopamine modification step, the mass ratio of the carbon nanotubes modified with the coupling agent to polydopamine is 5:(1-10); the mass volume ratio of the carbon nanotubes modified with the coupling agent to the tris-buffer is 5 mg:(1-10) mL.

[0049] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, in the gelatin modification step, gelatin is dissolved in deionized water to obtain a gelatin aqueous solution; the coupling agent and the carbon nanotubes modified with polydopamine are added to deionized water, and then mixed with the gelatin aqueous solution under stirring for 20-26 hours, and the solid obtained by centrifugation is washed with deionized water and freeze-dried for 20-26 hours to obtain the modified carbon nanotubes.

[0050] Optionally, in the preparation process of the modified carbon nanotubes provided by the present invention, in the gelatin modification step, the mass volume ratio of the coupling agent and the carbon nanotubes modified with polydopamine to deionized water, and the mass volume ratio of the gelatin to deionized water in the gelatin aqueous solution are not specifically limited, and can be adjusted according to actual conditions, as long as the coupling agent and the carbon nanotubes modified with polydopamine can be evenly dispersed in the deionized water and the gelatin can be dissolved in the deionized water. The mass ratio of the coupling agent and the carbon nanotubes modified with polydopamine to the gelatin is 5:(1-10).

[0051] In the preparation process of the modified carbon nanotubes provided by the present invention, the reaction time of each step can be adjusted according to the actual reaction conditions (such as feed amount, reaction temperature, etc.). The above-mentioned dispersion method is not specifically limited, and conventional methods in the industry, such as ultrasound, stirring, etc., can be used.

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] Beneficial effect 1: The random copolymer polypropylene soft fiber special material provided by the present invention is prepared by first mixing the modified carbon nanotubes, which are surface-modified by coupling agent, polydopamine and gelatin in sequence, with antioxidants and degradation agents to form a toughening masterbatch, and then mixing it with the random copolymer polypropylene resin; that is, first making the modified carbon nanotubes into a toughening masterbatch, and then mixing it into the random copolymer polypropylene resin for secondary dispersion, which can significantly improve the compatibility of the carbon nanotubes with the random copolymer polypropylene resin, so that the mechanical properties of the carbon nanotubes can be fully exerted, and the obtained polypropylene special material has excellent mechanical properties, toughness, rigidity and high fluidity and other comprehensive properties, which can meet its application requirements in the fields of high-end health materials, medical ultra-soft and the like. Compared with the existing polypropylene special material, the impact strength and flexural modulus of the random copolymer polypropylene soft fiber special material provided by the present invention have been significantly improved.

[0054] Beneficial effect 2: In the modified carbon nanotubes provided by the present invention, the purified carbon nanotubes are first modified with a coupling agent, and then modified with polydopamine so that polydopamine is combined with the carbon nanotubes, and finally gelatin is grafted onto the surface of the carbon nanotubes through polydopamine; one end of the coupling agent is firmly combined with the carbon nanotubes, and the other end is combined with the random copolymer polypropylene resin. This modification method will not damage the structure of the carbon nanotubes themselves, so that a modified carbon nanotube with a complete structure can be obtained. The modified carbon nanotubes are added to the random copolymer polypropylene resin matrix, which improves the compatibility of the carbon nanotubes and the random copolymer polypropylene, and the steric hindrance effect of the introduced long carbon chain can avoid the agglomeration of the carbon nanotubes. At the same time, the carbon nanotubes have excellent mechanical properties and act as physical crosslinking points, thereby playing a role in strengthening and toughening. Combined with other additives, the comprehensive performance of the random copolymer polypropylene soft fiber special material can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the curled structure of carbon nanotubes;

[0056] Figure 2 Schematic diagram of the degradation reaction when preparing high melt index polypropylene fiber material. DETAILED DESCRIPTION

[0057] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0058] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0059] Example 1

[0060] This embodiment provides a random copolymer polypropylene soft fiber special material, and the preparation method thereof is as follows:

[0061] (I) Preparation of modified carbon nanotubes

[0062] Purification: Disperse 250 mg of carbon nanotubes in 10 mL of oxidant, treat with ultrasound at room temperature for 2 hours, reflux at 120-130°C for 4 hours until the reaction is complete, filter, wash the obtained solid with deionized water until neutral, and vacuum dry to constant weight to obtain purified carbon nanotubes. The oxidant is a mixed solution of potassium permanganate and concentrated sulfuric acid in a mass ratio of 1:1;

[0063] Coupling agent modification: 50 mg of silane coupling agent (KH-570) and 250 mg of the purified carbon nanotubes were added to ethanol, and ultrasonic dispersion was performed for 2 h. After the reaction was refluxed at 70-80° C. for 3 h, the ethanol was distilled off to obtain coupling agent-modified carbon nanotubes.

[0064] Polydopamine modification: 250 mg of the carbon nanotubes modified with the coupling agent were ultrasonically dispersed in 50 mL of tris-buffered solution, and then 50 mg of polydopamine PODA was added. After reacting for 4 h under stirring, the solid obtained by centrifugation was washed with deionized water until neutral, thereby obtaining carbon nanotubes modified with the coupling agent and polydopamine;

[0065] Gelatin modification: 50 mg of gelatin was dissolved in 50 mL of deionized water to obtain a gelatin solution; 250 mg of the above-mentioned coupling agent and polydopamine-modified carbon nanotubes were dispersed in 100 mL of deionized water, and then stirred and mixed with the gelatin solution for 24 hours until the reaction was completed, centrifuged, and the obtained solid was washed 3 times with deionized water, and then freeze-dried to obtain modified carbon nanotubes.

[0066] (II) Preparation of toughened masterbatch

[0067] Weigh each material according to the following weight content:

[0068] Random copolymer polypropylene resin 74.5wt%

[0069] Modified carbon nanotubes 0.5wt%

[0070] Degradation agent 15wt%

[0071] Antioxidant 10wt% (primary antioxidant 0.5wt% and secondary antioxidant 0.5wt%)

[0072] Among them, the degradation agent is 101; the main antioxidant is 1010, and the auxiliary antioxidant is 168.

[0073] The above materials were mixed in a high-speed mixer for 4 minutes, and then put into a twin-screw extruder for extrusion granulation. The screw speed of the twin-screw extruder was 100 rpm and the temperature was 160-190° C. to obtain a toughened masterbatch.

[0074] (III) Preparation of random copolymer polypropylene soft fiber special material

[0075] Weigh each material according to the following weight content:

[0076] Random copolymer polypropylene resin 90wt%

[0077] Toughening masterbatch 10wt%

[0078] The random copolymer polypropylene resins in the above steps (ii) and (iii) are all ethylene-propylene copolymer resins, with a melt index of 6 g / 10 min and an ethylene content of 2 wt%.

[0079] The above materials are mixed in a low-speed mixer at 20°C for 3 minutes, and then added into a twin-screw extruder for melt extrusion. The extrusion temperature is between 200 and 210°C, and the screw speed is 250 rpm. The extruded material is then cooled, air-dried, and pelletized to obtain a random copolymer polypropylene soft fiber special material.

[0080] Embodiment 2-10

[0081] Examples 2-10 are similar to Example 1, except that some parameters and raw materials are different, as shown in Tables 1 and 2 below.

[0082] Table 1 Preparation parameters of modified carbon nanotubes

[0083]

[0084] Note: Methylethylsilane is marked as A, 1,1,2-trimethylpropyltrichlorosilane is marked as B.

[0085] Table 2 Preparation parameters of random copolymer polypropylene soft fiber special material

[0086]

[0087]

[0088] Note: The ratio of primary antioxidant to secondary antioxidant is the same in each example.

[0089] Comparative Example 1

[0090] This comparative example is similar to Example 5, except that different modified carbon nanotubes are used. The preparation method of the modified carbon nanotubes used in this comparative example is as follows:

[0091] Purification: Disperse 250 mg of carbon nanotubes in 50 mL of oxidant, treat with ultrasound at room temperature for 2 hours, reflux at 120-130°C for 4 hours until the reaction is complete, filter, wash the obtained solid with deionized water until neutral, and vacuum dry to constant weight to obtain purified carbon nanotubes. The oxidant is a mixed solution of potassium permanganate and concentrated sulfuric acid in a mass ratio of 1:1;

[0092] Coupling agent modification: 250 mg of silane coupling agent (1,1,2-trimethylpropyltrichlorosilane) and 250 mg of the above-purified carbon nanotubes were added to ethanol, and after ultrasonic dispersion treatment for 2 hours, reflux reaction was carried out at 70-80°C for 2 hours until the reaction was completed, and ethanol was distilled off to obtain modified carbon nanotubes.

[0093] Comparative Example 2

[0094] This comparative example provides a random copolymer polypropylene soft fiber special material, and its preparation method is as follows:

[0095] Weigh each material according to the following weight content:

[0096] Random copolymer polypropylene resin 74.95wt%

[0097] Carbon nanotubes 0.05wt%

[0098] Degradation agent 15wt%

[0099] Antioxidant 10wt% (primary antioxidant 5wt% and secondary antioxidant 5wt%).

[0100] The random copolymer polypropylene resin is an ethylene-propylene copolymer resin, with a melt index of 6 g / 10 min and an ethylene content of 2 wt %; the degradation agent is 101; the primary antioxidant is 1010, and the secondary antioxidant is 168; the outer diameter of the carbon nanotube is 20 nm, the length is 10 μm, and the density is 2 g / m 3 , with a surface area of ​​150m 2 / g.

[0101] The above materials are mixed in a low-speed mixer at 20°C for 3 minutes, and then added into a twin-screw extruder for melt extrusion. The extrusion temperature is between 200 and 210°C, and the screw speed is 250 rpm. The extruded material is then cooled, air-dried, and pelletized to obtain a random copolymer polypropylene soft fiber special material.

[0102] Comparative Example 3

[0103] This comparative example provides a random copolymer polypropylene soft fiber special material, and its preparation method is as follows:

[0104] Weigh each material according to the following weight content:

[0105] Random copolymer polypropylene resin 75wt%

[0106] Degradation agent 15wt%

[0107] Antioxidant 10wt% (primary antioxidant 5wt% and secondary antioxidant 5wt%).

[0108] The random copolymer polypropylene resin is an ethylene-propylene copolymer resin, with a melt index of 6 g / 10 min and an ethylene content of 2 wt %; the degradation agent is 101; the primary antioxidant is 1010, and the secondary antioxidant is 168.

[0109] The above materials are mixed in a low-speed mixer at 20°C for 3 minutes, and then added into a twin-screw extruder for melt extrusion. The extrusion temperature is between 200 and 210°C, and the screw speed is 250 rpm. The extruded material is then cooled, air-dried, and pelletized to obtain a random copolymer polypropylene soft fiber special material.

[0110] Comparative Example 4

[0111] This comparative example provides a random copolymer polypropylene soft fiber special material, and its preparation method is as follows:

[0112] (I) Preparation of modified carbon nanotubes

[0113] Purification: Disperse 250 mg of carbon nanotubes in 10 mL of oxidant, ultrasonically treat at room temperature for 2 hours, reflux at 120-130°C for 4 hours until the reaction is complete, filter, wash the obtained solid with deionized water until neutral, and vacuum dry to constant weight to obtain purified carbon nanotubes. The oxidant is a mixed solution of potassium permanganate and concentrated sulfuric acid in a mass ratio of 1:1; the outer diameter, length, density and surface area of ​​the carbon nanotubes are the same as those in Example 1;

[0114] Polydopamine modification: 250 mg of the carbon nanotubes modified with the coupling agent were ultrasonically dispersed in 50 mL of tris-buffered solution, and then 50 mg of polydopamine PODA was added. After reacting for 4 h under stirring, the solid obtained by centrifugation was washed with deionized water until neutral to obtain polydopamine-modified carbon nanotubes;

[0115] Gelatin modification: 50 mg of gelatin was dissolved in 50 mL of deionized water to obtain a gelatin solution; 250 mg of the above-mentioned polydopamine-modified carbon nanotubes were dispersed in 100 mL of deionized water, and then stirred and mixed with the gelatin solution for 24 hours until the reaction was completed, centrifuged, and the obtained solid was washed 3 times with deionized water, and then freeze-dried to obtain polydopamine and gelatin-modified carbon nanotubes.

[0116] Coupling agent modification: 50 mg of silane coupling agent (KH-570) and 250 mg of the carbon nanotubes modified with polydopamine and gelatin were added to ethanol, and ultrasonic dispersion was performed for 2 h. After the reaction was refluxed at 70-80° C. for 3 h, the ethanol was removed by distillation to obtain modified carbon nanotubes.

[0117] (II) Preparation of toughened masterbatch

[0118] Weigh each material according to the following weight content:

[0119] Random copolymer polypropylene resin 74.5wt%

[0120] Modified carbon nanotubes 0.5wt%

[0121] Degradation agent 15wt%

[0122] Antioxidant 10wt% (primary antioxidant 0.5wt% and secondary antioxidant 0.5wt%)

[0123] Among them, the degradation agent is 101; the main antioxidant is 1010, and the auxiliary antioxidant is 168.

[0124] The above materials were mixed in a high-speed mixer for 4 minutes, and then put into a twin-screw extruder for extrusion granulation. The screw speed of the twin-screw extruder was 100 rpm and the temperature was 160-190° C. to obtain a toughened masterbatch.

[0125] (III) Preparation of random copolymer polypropylene soft fiber special material

[0126] Weigh each material according to the following weight content:

[0127] Random copolymer polypropylene resin 90wt%

[0128] Toughening masterbatch 10wt%

[0129] The random copolymer polypropylene resins in the above steps (ii) and (iii) are both ethylene-propylene copolymer resins, with a melt index of 6 g / 10 min and an ethylene content of 2 wt%.

[0130] The above materials are mixed in a low-speed mixer at 20°C for 3 minutes, and then added into a twin-screw extruder for melt extrusion. The extrusion temperature is between 200 and 210°C, and the screw speed is 250 rpm. The extruded material is then cooled, air-dried, and pelletized to obtain a random copolymer polypropylene soft fiber special material.

[0131] Experimental example

[0132] The special polypropylene materials prepared in each embodiment and comparative example were tested for mechanical properties, melt flow rate and molecular weight distribution, wherein the impact strength was tested using GB / T1843-2008, the flexural modulus was tested using GB / T9341-2008, the melt flow rate was tested using GB / T3682-2000, and the gel permeation chromatography was tested using GB / T 21863-2008; the specific test results are shown in the table below.

[0133] Table 4

[0134] sample <![CDATA[Impact KJ / m 2 > Flexural modulus MPa Melt flow rate g / 10min Molecular weight distribution Example 1 3.05 705 35.0 2.81 Example 2 3.1 710 35.4 2.85 Example 3 3.21 720 35.7 2.79 Example 4 3.25 725 36.1 2.76 Example 5 3.27 727 36.2 2.70 Example 6 3.21 721 35.9 2.81 Example 7 3.1 710 35.7 2.88 Example 8 2.98 706 34.1 2.89 Example 9 2.95 698 33.2 2.90 Example 10 2.93 699 32.9 2.95 Comparative Example 1 2.98 706 34.1 2.89 Comparative Example 2 2.95 698 33.2 2.90 Comparative Example 3 2.93 699 32.9 2.95 Comparative Example 4 2.85 653 31.8 2.98

[0135] It can be seen from the data in the above table that compared with the prior art, the impact strength and bending modulus of the random copolymer polypropylene soft fiber special material provided by the present invention are significantly improved, indicating that the modified carbon nanotubes provided by the present invention, which are obtained by surface modification of the purified carbon nanotubes with coupling agents, polydopamine and gelatin in sequence, will not damage the structure of the carbon nanotubes themselves, so that the modified carbon nanotubes with complete structure can be obtained, and then added to the random copolymer polypropylene matrix to improve the compatibility of the random copolymer polypropylene resin and the carbon nanotubes. After the modified carbon nanotubes and part of the random copolymer polypropylene resin, antioxidants and degradation agents are first formed into a toughening masterbatch, and then mixed into the random copolymer polypropylene resin for secondary dispersion to further improve the dispersion uniformity of the carbon nanotubes, the agglomeration of the carbon nanotubes is effectively avoided, so that the mechanical properties of the carbon nanotubes are fully exerted, and at the same time, the carbon nanotubes can play the role of physical crosslinking points, with the effects of strengthening and toughening.

[0136] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A random copolymer polypropylene soft fiber special material, characterized in that: The composition comprises the following contents: 90wt%-99wt% of random copolymerized polypropylene resin and 1wt%-10wt% of toughening masterbatch; The toughening masterbatch comprises the following components: 65wt%-88.5wt% of random copolymerized polypropylene resin; 0.5wt%-5wt% of modified carbon nanotubes; 5wt%-20wt% of degradation agent and 5wt%-10wt% of antioxidant; The modified carbon nanotubes are obtained by sequentially surface-modifying carbon nanotubes purified by oxidation with a coupling agent, polydopamine and gelatin.

2. The random copolymer polypropylene soft fiber special material according to claim 1, characterized in that: When the carbon nanotubes are purified by oxidation, a mixed solution of potassium permanganate and concentrated sulfuric acid is used to purify the carbon nanotubes.

3. The random copolymer polypropylene soft fiber special material according to claim 1, characterized in that: The degradation agent is a peroxide degradation agent.

4. A method for preparing the random copolymer polypropylene soft fiber special material according to any one of claims 1 to 3, characterized in that: The steps include: The random copolymerized polypropylene resin, modified carbon nanotubes, a degradation agent and an antioxidant are mixed uniformly, and then put into a twin-screw extruder for melt extrusion to obtain a toughening masterbatch; The random copolymer polypropylene resin and the toughening masterbatch are mixed evenly and then put into a twin-screw extruder for melt extrusion to obtain the random copolymer polypropylene soft fiber special material.

5. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 4, characterized in that: The preparation of the modified carbon nanotubes comprises the following steps: Purification: dispersing carbon nanotubes in an oxidant for reflux reaction, and after the reaction is completed, separating, washing to neutrality, and vacuum drying to obtain purified carbon nanotubes; Coupling agent modification: dispersing the coupling agent and the purified carbon nanotubes in ethanol for reflux reaction, and after the reaction is completed, removing the ethanol to obtain the coupling agent-modified carbon nanotubes; Polydopamine modification: reacting the carbon nanotubes modified with the coupling agent and polydopamine in a tris-buffer, and after the reaction, washing to neutrality to obtain carbon nanotubes modified with the coupling agent and polydopamine; Gelatin modification: the coupling agent and the carbon nanotubes modified with polydopamine are dispersed in deionized water, and then mixed with the gelatin aqueous solution for reaction. After the reaction is completed, the separated solid is washed with deionized water and dried to obtain the modified carbon nanotubes.

6. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 5, characterized in that: In the purification step, the mass volume ratio of the carbon nanotubes to the oxidant is 25 mg:(1-10) mL; the oxidant is a mixed solution of potassium permanganate and concentrated sulfuric acid in a mass ratio of (1-2):(1-2).

7. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 5, characterized in that: In the purification step, the carbon nanotubes have an outer diameter of 20-30 nm, a length of 10-30 μm, and a density of 2-3 g / m 3 , surface area greater than 110m 2 / g.

8. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 5, characterized in that: In the coupling agent modification step, the mass ratio of the purified carbon nanotubes to the coupling agent is 5:(1-10).

9. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 5, characterized in that: In the polydopamine modification step, the mass ratio of the carbon nanotubes modified with the coupling agent to polydopamine is 5:(1-10); the mass volume ratio of the carbon nanotubes modified with the coupling agent to the tris-buffer is 5 mg:(1-10) mL.

10. The method for preparing the random copolymer polypropylene soft fiber special material according to claim 5, characterized in that: In the gelatin modification step, the mass ratio of the coupling agent and the carbon nanotubes modified with polydopamine to the gelatin is 5:(1-10).

Images