Random copolymerization transparent polypropylene special material and preparation method thereof

Abstract

According to the two special materials for the random copolymerization transparent polypropylene and the preparation method of the special materials, the modified carbon nano tube obtained by sequentially carrying out surface modification on the purified carbon nano tube by virtue of the coupling agent, the polydopamine and the gelatin is added, so that the compatibility of the carbon nano tube and the polypropylene can be remarkably improved; the polypropylene random copolymer resin and other auxiliaries are combined, so that the transparency, mechanical property and the like 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 transparent polypropylene and a preparation method thereof. Background Art

[0002] In recent years, polypropylene has developed rapidly and has a wide variety of products. People are no longer satisfied with its use as a general material. The market demand for special materials is increasing, and special materials are being used more and more widely. In the face of ever-changing market demand, developing new products to meet market demand, enhancing product profitability, and increasing market share have become the primary tasks of various manufacturers. According to research, transparent polypropylene has developed rapidly in recent years. In 2021, the market demand reached 150 tons / year, increasing at a rate of 5-7% per year, becoming one of the fastest growing varieties of polypropylene products.

[0003] Compared with ordinary polypropylene, transparent polypropylene has higher toughness, rigidity, heat resistance and chemical resistance. Its excellent transparency and glossiness are comparable to those of typical transparent materials, and can be widely used in household products, packaging and medical fields. Transparent polypropylene is mainly divided into high-index, medium-index and low-index transparent PP. This series of products are used in injection molding, hollow molding, thermoforming and injection-stretch-blow molding. The annual demand for medium-index transparent polypropylene is about 100,000 tons, which is widely used in household products, packaging and other fields. At present, domestic high-end sanitary materials and medical ultra-soft random copolymer polypropylene fiber materials mainly rely on imports (such as Basel's RP1669).

[0004] 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.

[0005] 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.

[0006] 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.

[0007] How to apply carbon nanotubes to ethylene-propylene random copolymer transparent polypropylene special material to give full play to the super strong mechanical properties of carbon nanotubes, so as to prepare a high-transparency, high-toughness, high-rigidity random copolymer transparent polypropylene special material, has become a technical problem to be solved in this field.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] Therefore, how to apply carbon nanotubes to polypropylene 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

[0014] In view of the above defects and improvement needs of the prior art, the present invention provides a random copolymer transparent polypropylene special material and a preparation method thereof. By modifying carbon nanotubes, the compatibility of carbon nanotubes and polypropylene resin is improved, and the synergistic effect of the modified carbon nanotubes, polypropylene resin and additives is utilized to improve the comprehensive properties of the polypropylene special material such as mechanical properties, toughness, rigidity and fluidity, so that it can meet the application requirements in the fields of high-end sanitary materials, medical ultra-soft materials, etc.

[0015] To achieve the above object, the present invention provides a random copolymer transparent polypropylene special material, comprising the following components: random copolymer polypropylene resin 95wt%-99.5wt%; modified carbon nanotubes 0.1wt%-1wt%; transparent nucleating agent 0.1wt%-1wt% and composite auxiliary agent 0.2wt%-3wt%;

[0016] The modified carbon nanotubes are obtained by sequentially surface-modifying carbon nanotubes purified by oxidation with a coupling agent, polydopamine and gelatin.

[0017] To achieve the above object, the present invention also provides another random copolymer transparent polypropylene special material, comprising the following components: random copolymer polypropylene resin 90wt%-99wt%, toughening masterbatch 1wt%-10wt%; the toughening masterbatch comprises the following components: random copolymer polypropylene resin 55wt%-96wt%; modified carbon nanotubes 0.5wt%-5wt%; transparent nucleating agent 0.5wt%-10wt% and composite auxiliary agent 3wt%-30wt%;

[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 transparent polypropylene 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 transparent polypropylene special materials provided by the present invention, the composite auxiliary agent is selected from at least one of an antioxidant, an antistatic agent and an acid scavenger.

[0021] Optionally, in the above-mentioned second random copolymer transparent polypropylene special material provided by the present invention, the toughening masterbatch includes the following components: 55wt%-96wt% of random copolymer polypropylene resin; 0.5wt%-5wt% of modified carbon nanotubes; 0.5wt%-10wt% of transparent nucleating agent; 1wt%-10wt% of antistatic agent; 1wt%-10wt% of acid scavenger and 1wt%-10wt% of antioxidant.

[0022] Optionally, in the above-mentioned first random copolymer transparent polypropylene special material provided by the present invention, the random copolymer transparent polypropylene special material includes the following components: random copolymer polypropylene resin 95wt%-99.5wt%; modified carbon nanotubes 0.1wt%-1wt%; transparent nucleating agent 0.1wt%-1wt%; antistatic agent 0.1wt%-0.5wt%; acid scavenger 0.1wt%-0.5wt% and antioxidant 0.1wt%-2wt%.

[0023] Optionally, in the above two random copolymer transparent polypropylene special materials provided by the present invention, the antioxidant, the antistatic agent, the acid scavenger and the transparent 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-butylphenyl)propionate, 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.;

[0024] 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;

[0025] The acid scavenger may be selected from at least one of calcium stearate, hydrotalcite, zinc oxide, etc.;

[0026] The transparent 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.

[0027] Optionally, in the above two random copolymer transparent polypropylene special materials 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%.

[0028] Optionally, in the above two random copolymer transparent polypropylene special materials 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.

[0029] The preparation methods of the two random copolymer transparent polypropylene special materials provided by the present invention are not specifically limited, and conventional methods in the industry can be used. For example, the first random copolymer transparent polypropylene special material can be prepared by the following method:

[0030] The random copolymer polypropylene resin, modified carbon nanotubes, transparent nucleating agent and composite auxiliary agent are mixed in a low-speed mixer (such as mixing at 20-30° C. for 3-5 minutes), added into a twin-screw extruder for melt extrusion, and the extruded material is cooled, air-dried and pelletized to obtain the random copolymer transparent polypropylene special material; preferably, the extrusion temperature is 200-210° C. and the screw speed is 200-300 rpm.

[0031] The second random copolymer transparent polypropylene special material provided by the present invention can be prepared by the following method:

[0032] The random copolymer polypropylene resin, modified carbon nanotubes, transparent nucleating agent and composite auxiliary agent are mixed in a high-speed mixer (such as mixing 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;

[0033] 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 transparent polypropylene special material; preferably, the extrusion temperature is 200-210° C., and the screw speed is 200-300 rpm.

[0034] Optionally, in the preparation methods of the above two random copolymer transparent polypropylene special materials provided by the present invention, the preparation of the modified carbon nanotubes comprises the following steps:

[0035] 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;

[0036] 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;

[0037] 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;

[0038] 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.

[0039] 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).

[0040] Optionally, in the preparation process of the 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.

[0041] 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.

[0042] 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).

[0043] 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.

[0044] Optionally, in the preparation process of the 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] In the modified carbon nanotube preparation process 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.

[0049] Compared with the prior art, the present invention has the following advantages:

[0050] Beneficial effect 1: The first random copolymer transparent polypropylene special material provided by the present invention can significantly improve the compatibility of carbon nanotubes with random copolymer polypropylene resin by adding modified carbon nanotubes whose surface is modified by coupling agent, polydopamine and gelatin in sequence from purified carbon nanotubes, so that the mechanical properties of carbon nanotubes can be fully exerted. Combined with the synergistic effect of other additives, 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 supersoft, etc. The second random copolymer transparent polypropylene special material provided by the present invention can further significantly improve the compatibility of carbon nanotubes with polypropylene and enhance the comprehensive performance of polypropylene special materials by adding a toughening masterbatch formed by partially random copolymer polypropylene resin, modified carbon nanotubes whose surface is modified by coupling agent, polydopamine and gelatin in sequence from purified carbon nanotubes and additives. Compared with the existing polypropylene special materials, the impact strength and flexural modulus of the two random copolymer transparent polypropylene special materials provided by the present invention have been significantly improved.

[0051] 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 transparent polypropylene special material can be significantly improved.

[0052] Beneficial effect 3: The second random copolymer transparent polypropylene special material provided by the present invention first prepares the modified carbon nanotubes into toughened masterbatch, and then mixes it into the random copolymer polypropylene resin for secondary dispersion, which can further improve the compatibility of the carbon nanotubes and the polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Schematic diagram of the curled structure of carbon nanotubes. DETAILED DESCRIPTION

[0054] 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.

[0055] 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.

[0056] Example 1

[0057] This embodiment provides a random copolymer transparent polypropylene special material, and the preparation method thereof is as follows:

[0058] (I) Preparation of modified carbon nanotubes

[0059] 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;

[0060] 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.

[0061] 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;

[0062] 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.

[0063] (II) Preparation of random copolymer transparent polypropylene special material

[0064] Weigh each material according to the following weight content:

[0065] Random copolymer polypropylene resin 95wt%

[0066] Modified carbon nanotubes 1wt%

[0067] Transparent nucleating agent 1wt%

[0068] The composite auxiliary agent is 3wt% (1wt% antistatic agent, 1wt% acid scavenger, 0.5wt% primary antioxidant and 0.5wt% secondary antioxidant).

[0069] 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 transparent polypropylene special material.

[0070] Embodiment 2-10

[0071] 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.

[0072] Table 1 Preparation parameters of modified carbon nanotubes

[0073]

[0074] Note: Methylethylsilane is marked as A, 1,1,2-trimethylpropyltrichlorosilane is marked as B.

[0075] Table 2 Preparation parameters of random copolymer transparent polypropylene special material

[0076]

[0077]

[0078] Note: The ratio of primary antioxidant to secondary antioxidant is the same in each example.

[0079] Embodiment 11

[0080] This embodiment provides a random copolymer transparent polypropylene special material, and the preparation method thereof is as follows:

[0081] (I) Preparation of modified carbon nanotubes

[0082] Same as Example 1.

[0083] (II) Preparation of toughening masterbatch

[0084] Weigh each material according to the following weight content:

[0085] Random copolymer polypropylene resin 95.5wt%

[0086] Modified carbon nanotubes 0.5wt%

[0087] Transparent nucleating agent 1wt%

[0088] Antistatic agent 1wt%

[0089] Acid scavenger 1wt%

[0090] Antioxidant 1wt% (primary antioxidant 0.5wt% and secondary antioxidant 0.5wt%)

[0091] Among them, the transparent nucleating agent is NA-21; the antistatic agent is monoglyceride; the acid scavenger is calcium stearate; the main antioxidant is 1010, and the auxiliary antioxidant is 168.

[0092] 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 toughened masterbatch.

[0093] (III) Preparation of random copolymer transparent polypropylene special material

[0094] Weigh each material according to the following weight content:

[0095] Random copolymer polypropylene resin 90wt%

[0096] Toughening masterbatch 10wt%

[0097] 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%.

[0098] 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 transparent polypropylene special material.

[0099] Examples 12-20

[0100] Examples 12-20 are similar to Example 11, except that some parameters and raw materials are different, as shown in Table 3 below.

[0101] Table 3

[0102]

[0103]

[0104] Note: The properties of the ethylene-propylene copolymer resin involved in Examples 11-20, as well as the modified carbon nanotubes, transparent nucleating agent, antistatic agent, acid scavenger and antioxidant are the same as those in Examples 1-10, respectively.

[0105] Comparative Example 1

[0106] 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:

[0107] 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;

[0108] 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.

[0109] Comparative Example 2

[0110] This comparative example is similar to Example 15, the only difference being that different modified carbon nanotubes are used. The preparation method of the modified carbon nanotubes used in this comparative example is the same as the preparation method of the modified carbon nanotubes in Comparative Example 1.

[0111] Comparative Example 3

[0112] This comparative example provides a random copolymer transparent polypropylene special material, and its preparation method is as follows:

[0113] Weigh each material according to the following weight content:

[0114] Random copolymer polypropylene resin 95wt%

[0115] Carbon nanotubes 1wt%

[0116] Transparent nucleating agent 1wt%

[0117] The composite auxiliary agent is 3wt% (1wt% antistatic agent, 1wt% acid scavenger, 0.5wt% primary antioxidant and 0.5wt% secondary antioxidant).

[0118] 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 transparent nucleating agent is NA-21, the antistatic agent is monoglyceride; the acid scavenger is calcium stearate; the main antioxidant is 1010, and the auxiliary 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.

[0119] 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 transparent polypropylene special material.

[0120] Comparative Example 4

[0121] This comparative example provides a random copolymer transparent polypropylene special material, and its preparation method is as follows:

[0122] (I) Preparation of modified carbon nanotubes

[0123] 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;

[0124] 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;

[0125] 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.

[0126] 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.

[0127] (II) Preparation of random copolymer transparent polypropylene special material

[0128] Weigh each material according to the following weight content:

[0129] Random copolymer polypropylene resin 95wt%

[0130] Modified carbon nanotubes 1wt%

[0131] Transparent nucleating agent 1wt%

[0132] The composite auxiliary agent is 3wt% (1wt% antistatic agent, 1wt% acid scavenger, 0.5wt% primary antioxidant and 0.5wt% secondary antioxidant).

[0133] 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 transparent nucleating agent is NA-21, the antistatic agent is monoglyceride; the acid scavenger is calcium stearate; the main antioxidant is 1010, and the auxiliary 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.

[0134] 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 transparent polypropylene special material.

[0135] Experimental example

[0136] The special polypropylene materials prepared in each embodiment and comparative example were tested for mechanical properties, transparency, etc., wherein the impact strength was tested using GB / T1843-2008, the flexural modulus was tested using GB / T9341-2008, the yellowness index was tested using GB / T 2409, and the haze was tested using GB / T 2410; the specific test results are shown in the table below.

[0137] Table 4

[0138]

[0139]

[0140] 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 transparent polypropylene special material provided by the present invention are significantly improved, indicating that the modified carbon nanotubes obtained by surface modification of the purified carbon nanotubes by coupling agent, polydopamine and gelatin in turn have good compatibility with the random copolymer polypropylene resin, effectively avoiding the agglomeration of the carbon nanotubes, so that the mechanical properties of the carbon nanotubes are fully exerted, and the carbon nanotubes can play the role of physical crosslinking points, with the effect of strengthening and toughening. Among them, the effect of Examples 11-20 is better than that of Examples 1-10, because in Examples 11-20, the modified carbon nanotubes and part of the random copolymer polypropylene resin and the auxiliary agent 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.

[0141] 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 transparent polypropylene special material, characterized in that: The invention comprises the following components: 95wt% to 99.5wt% of random copolymerized polypropylene resin; 0.1wt% to 1wt% of modified carbon nanotubes; 0.1wt% to 1wt% of transparent nucleating agent and 0.2wt% to 3wt% of composite auxiliary agent; The modified carbon nanotubes are obtained by sequentially surface-modifying carbon nanotubes purified by oxidation with a coupling agent, polydopamine and gelatin.

2. A random copolymer transparent polypropylene 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: 55wt%-96wt% of random copolymerized polypropylene resin; 0.5wt%-5wt% of modified carbon nanotubes; 0.5wt%-10wt% of transparent nucleating agent and 3wt%-30wt% of composite auxiliary agent; The modified carbon nanotubes are obtained by sequentially surface-modifying carbon nanotubes purified by oxidation with a coupling agent, polydopamine and gelatin.

3. The random copolymer transparent polypropylene special material as claimed in claim 1 or 2, 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.

4. The random copolymer transparent polypropylene special material as claimed in claim 1 or 2, characterized in that: The composite auxiliary agent is selected from at least one of an antioxidant, an antistatic agent and an acid scavenger.

5. The random copolymer transparent polypropylene special material as claimed in claim 4, characterized in that: The toughening masterbatch comprises the following components: 55wt%-96wt% of random copolymer polypropylene resin; 0.5wt%-5wt% of modified carbon nanotubes; 0.5wt%-10wt% of transparent nucleating agent; 1wt%-10wt% of antistatic agent; 1wt%-10wt% of acid scavenger and 1wt%-10wt% of antioxidant.

6. The random copolymer transparent polypropylene special material as claimed in claim 4, characterized in that: The random copolymer transparent polypropylene special material comprises the following components: random copolymer polypropylene resin 95wt%-99.5wt%; modified carbon nanotubes 0.1wt%-1wt%; transparent nucleating agent 0.1wt%-1wt%; antistatic agent 0.1wt%-0.5wt%; Acid scavenger 0.1wt%-0.5wt% and antioxidant 0.1wt%-2wt%.

7. A method for preparing the random copolymer transparent polypropylene special material according to any one of claims 1, 3, 4, and 6, characterized in that: The steps include: The random copolymerized polypropylene resin, modified carbon nanotubes, transparent nucleating agent and composite auxiliary agent are mixed at room temperature, and then put into a twin-screw extruder for melt extrusion to obtain the random copolymerized transparent polypropylene special material.

8. A method for preparing the random copolymer transparent polypropylene special material according to any one of claims 2 to 5, characterized in that: The steps include: After uniformly mixing the random copolymer polypropylene resin, modified carbon nanotubes, transparent nucleating agent and composite additive, the mixture is 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 transparent polypropylene special material.

9. The method for preparing the random copolymer transparent polypropylene special material according to claim 7 or 8, 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 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.

10. The method for preparing the random copolymer transparent polypropylene special material according to claim 9, 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); and / or 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; and / or In the coupling agent modification step, the mass ratio of the purified carbon nanotubes to the coupling agent is 5:(1-10); and / or 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; and / or 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).

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