阅读说明：本技术 季铵盐改性碳纳米管、制备方法和一种低密度、低翘曲的软触感聚丙烯改性材料及制备方法 (Quaternary ammonium salt modified carbon nanotube, preparation method thereof, low-density and low-warpage soft-touch polypropylene modified material and preparation method thereof ) 是由 颜晓捷 王绍杰 于 2019-11-01 设计创作，主要内容包括：本发明涉及季铵盐改性碳纳米管、制备方法和一种低密度、低翘曲的软触感聚丙烯改性材料及制备方法。在碳纳米管表面同时接枝N-单/双烷基链,与热塑性弹性体共同用于制备聚丙烯改性材料,降低密度的同时能够消除翘曲,并兼具良好的力学性能。由于季铵盐改性碳纳米管表面接枝的N-烷基链具有内润滑和促进聚丙烯和碳纳米管的结合力的作用,注塑过程中熔体带动改性碳纳米管在膜腔中均匀流动,减少制件的翘曲,适于工业化生产。(The invention relates to a quaternary ammonium salt modified carbon nanotube, a preparation method thereof, a low-density and low-warpage soft-touch polypropylene modified material and a preparation method thereof. N-mono/double alkyl chains are simultaneously grafted on the surface of the carbon nano tube, and the N-mono/double alkyl chains and the thermoplastic elastomer are jointly used for preparing the polypropylene modified material, so that the density is reduced, the warping can be eliminated, and the carbon nano tube has good mechanical properties. Because the N-alkyl chain grafted on the surface of the quaternary ammonium salt modified carbon nano tube has the functions of internal lubrication and promotion of the binding force of polypropylene and the carbon nano tube, the melt drives the modified carbon nano tube to uniformly flow in the film cavity in the injection molding process, the warping of a workpiece is reduced, and the method is suitable for industrial production.)

1. A preparation method of quaternary ammonium salt modified carbon nano-tubes is characterized by comprising the following steps:

(1) adding the carbon nano tube into a nitric acid/hydrogen peroxide mixed solution, ultrasonically stirring for 60-120min, carrying out reflux reaction for 1-3h at the temperature of 80-140 ℃, filtering, washing with water, and drying to obtain the carbon nano tube containing epoxy groups and carboxyl groups;

(2) dispersing the carbon nano tube containing the epoxy group and the carboxyl group prepared in the step (1) into water, ultrasonically stirring for 30-80min at 40-90 ℃, then adding quaternary ammonium salt, wherein the mass ratio of the quaternary ammonium salt to the carbon nano tube is 1:100-100:1, preferably 1:2-1:25, continuously stirring for 30-60min at 40-90 ℃, filtering, washing with water, and drying to obtain the quaternary ammonium salt modified carbon nano tube.

2. The preparation method according to claim 1, wherein in the step (1), the carbon nanotubes are selected from one or a mixture of two of single-walled carbon nanotubes and multi-walled carbon nanotubes;

preferably, the outer diameter of the carbon nanotube is 0.6-80nm, preferably 2-20 nm;

preferably, the carbon content of the carbon nanotubes is 80 to 100 wt%, preferably 90 to 100 wt%; and/or

In the mixed solution of nitric acid and hydrogen peroxide, the concentration of the adopted nitric acid is 60-80 wt%, and the concentration of the adopted hydrogen peroxide is 30-50 wt%; preferably, in the mixed solution of nitric acid and hydrogen peroxide, the volume ratio of nitric acid to hydrogen peroxide is 1:20-20:1, preferably 1:4-4: 1; and/or

The mass ratio of the carbon nano tube to the mixed solution of nitric acid and hydrogen peroxide is 1:100-20:100, preferably 2:100-10: 100.

3. The preparation method according to claim 1 or 2, wherein in the step (1), the ultrasonic agitation is performed at an ultrasonic frequency of 30 to 40 KHz; the stirring temperature is 15-28 ℃; and/or

The filtration is carried out by adopting a microporous filter membrane for suction filtration, and the aperture is 0.1-0.5 mu m; and/or

Washing with water until the pH value is 6-7; and/or

The drying is carried out in a vacuum drying mode at the temperature of 60-100 ℃ for 2-8 h.

4. The production method according to any one of claims 1 to 3, wherein in the step (2), the quaternary ammonium salt is a mixture of a monoalkyl chain quaternary ammonium salt and a dialkyl chain quaternary ammonium salt; the molar ratio of the single alkyl chain quaternary ammonium salt to the double alkyl chain quaternary ammonium salt is 1:20-20:1, preferably 1:3-3: 1;

the monoalkyl chain quaternary ammonium salt is selected from one or more of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide and hexadecyl trimethyl ammonium chloride; preferably cetyl trimethylammonium bromide;

the dialkyl chain quaternary ammonium salt is at least one selected from didodecyl dimethyl ammonium bromide and dihexadecyl dimethyl ammonium bromide, and preferably dihexadecyl dimethyl ammonium bromide.

5. The production method according to any one of claims 1 to 4, wherein, in the step (2),

the dispersion concentration of the carbon nano tube in water is 0.1-20 mg/ml; and/or

The ultrasonic frequency is 30-60KHZ, preferably 30-40 KHz; and/or

The filtration is vacuum filtration, the vacuum pressure is 50-2000Pa, and the aperture is 1-10 μm; and/or

And drying at 60-100 deg.C for 2-6 hr.

6. A quaternary ammonium salt modified carbon nanotube prepared by the method of any one of claims 1 to 5.

7. A low-density and low-warpage soft-touch polypropylene modified material, which is characterized in that the quaternary ammonium salt modified carbon nanotube prepared by the method of any one of claims 1 to 5 or the quaternary ammonium salt modified carbon nanotube of claim 6 comprises the following raw material components:

the wt% is based on the total weight of the polypropylene modified material.

8. The polypropylene modification material according to claim 7, wherein the polypropylene is a combination of homo-polypropylene and high impact co-polypropylene, and the mixing ratio of homo-polypropylene and high impact co-polypropylene is 1:19-19:1, preferably 1:4-4: 1;

the homopolymerized polypropylene is the homopolymerized polypropylene with the melt index of 5-80g/10min under the test condition of 230 ℃/2.16kg and the molecular weight of 8-15 ten thousand; preferably homopolypropylene having a molecular weight of 9 to 13 ten thousand and an isotacticity of 96% or more, such as HA5029 available from Polymerle;

the high impact co-polypropylene is one or more of the compositions with the melt index of 0.3-140g/10min under the test condition of 230 ℃/2.16kg, the ethylene monomer content of 5-18 wt%, preferably 7-15 wt%, and the propylene monomer content of 85-93 wt%, such as SP179P of the Chinese petrochemical Qilu petrochemical company Limited and EP540V of And Basel; and/or

The thermoplastic elastomer comprises one or a combination of ethylene-propylene copolymer, ethylene-butylene copolymer and ethylene-octene copolymer, preferably ethylene-propylene copolymer; preferably, the content of the ethylene monomer in the thermoplastic elastomer is 10-30 wt%, the melt index is 0.1-40g/10min under the test condition of 190 ℃/2.16kg, and the Shore hardness is 30-85A; further preferably, the thermoplastic elastomer is an ethylene-propylene copolymer elastomer with the ethylene content of 10-15 wt%, the melt index of 1.0-25g/10min and the Shore hardness of 30-60A; and/or

The antioxidant comprises a main antioxidant and an auxiliary antioxidant, and the mass ratio of the main antioxidant to the auxiliary antioxidant is 1: 5-5: 1, preferably 1: 2-2: 1; the main antioxidant is one or two mixtures of tetra [ beta- (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionic acid ] and beta- (4' -hydroxy-3 ', 5' -di-tert-butylphenyl) propionic acid octadecyl ester; the auxiliary antioxidant is one or a mixture of more than two of tris (2, 4-di-tert-butylphenyl) phosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite, dilauryl thiodipropionate and distearyl thiodipropionate.

9. A method for preparing the low-density and low-warpage soft-touch polypropylene modified material of claim 7 or 8, which comprises the following steps:

(1) preparing quaternary ammonium salt modified carbon nanotube master batch: uniformly mixing polypropylene and quaternary ammonium salt modified carbon nano tube according to the weight ratio of 1:3-10:1, preferably 1:1, and then extruding and granulating at the temperature of 210-;

(2) the polypropylene, the thermoplastic elastomer, the quaternary ammonium salt modified carbon nanotube master batch, the antioxidant and other additives are uniformly mixed, and then extruded, granulated and dried at the temperature of 190-220 ℃ to obtain the low-density and low-warpage soft-touch polypropylene modified material.

10. The method for preparing the low-density and low-warpage soft-touch polypropylene modified material as claimed in claim 9, wherein in the step 1), the extrusion granulation is performed by using a twin-screw extruder, and the temperature of each temperature zone of the twin-screw extruder is 210 ℃ and 230 ℃; and/or

In the step 2), the raw material mixing process is as follows: mixing and stirring polypropylene, thermoplastic elastomer and quaternary ammonium salt modified carbon nanotube master batch for 3-5min, adding antioxidant and other auxiliary agents for subsequent mixing, and continuously mixing for 5-10min to obtain a mixed raw material; and/or

In the step 2), the extrusion operation is carried out by adopting a double-screw extruder, wherein the temperature of a melting section in the double-screw extrusion process is 190-.

11. Use of the low-density, low-warpage soft-touch polypropylene modification material of claim 7 or 8, or the low-density, low-warpage soft-touch polypropylene modification material prepared by the method of claim 9 or 10, for manufacturing automobile instrument panels, door panels, center channels, home appliances or parts of electronic and electric appliances.

Technical Field

The invention relates to a quaternary ammonium salt modified carbon nanotube and a preparation method thereof, and also relates to a low-density and low-warpage soft-touch polypropylene modified material and a preparation method thereof, which are widely applied to the fields of automobiles, household appliances and electronic and electric appliances.

Background

At present, one of the key development directions of the automotive interior is comfortable soft feeling, the soft feeling is divided into visual sense of touch and hand sense of touch, the visual sense of touch is mainly reflected in that the automotive interior has lower glossiness, and drivers and passengers relieve eye fatigue when in a car and improve driving experience; the hand touch feeling is that when skin touches the surfaces of interior parts such as instrument panels, door panels and the like, good affinity is felt, so that the human body is comfortable.

The automobile interior material formed by injection molding of the polypropylene modified material has higher surface hardness and glossiness, and brings strong plastic feeling to people. The method for attaching a layer of soft skin to a framework is a traditional way for achieving soft feeling of interior parts at present, but the traditional skin is complex in process, serious in environmental pollution and high in cost, and is only suitable for medium-high-end passenger vehicles.

In order to prepare a low-cost soft-touch polypropylene modified material, patent CN20140667370 prepares a soft-touch polypropylene modified material with high mechanical property, strong impact property and low odor by blending polypropylene, ethylene-propylene copolymer, glass fiber and the like, and although the touch of the modified polypropylene material prepared by the method is greatly improved, the polypropylene modified material prepared by the method is easy to warp and deform during injection molding, so that the whole vehicle assembly is affected. In the patent CN201710370631.6, a low-warpage soft-touch polypropylene modified material is prepared by blending and extruding polypropylene, an elastomer, glass fibers, an inorganic filler and fluff powder, but the modified polypropylene material contains the glass fibers, and floating fibers are easy to appear on the surface of an injection molded part and cause damage to the skin of drivers and passengers; and the large amount of glass fiber and inorganic filler can increase the density of the polypropylene modified material, thereby increasing the weight of parts.

With the development trend of light weight of automobiles and the requirement of environmental protection, the development of a soft-touch polypropylene modified material with low density and low warpage is urgently needed.

Disclosure of Invention

The invention aims to provide a quaternary ammonium salt modified carbon nanotube and a preparation method thereof, and a low-density and low-warpage soft-touch polypropylene modified material, wherein an N-mono/dialkyl chain is grafted on the surface of the carbon nanotube simultaneously, and the N-mono/dialkyl chain and a thermoplastic elastomer are used together for preparing the polypropylene modified material, so that the density is reduced, the warpage can be eliminated, and the polypropylene modified material has good mechanical properties.

The invention also provides a preparation method of the low-density and low-warpage soft-touch polypropylene, which takes the polypropylene resin as a matrix, the quaternary ammonium salt modified carbon nanotube as a framework and the elastomer as a soft-touch phase, thereby preparing the low-density and low-warpage soft-touch polypropylene modified material. The method has low energy consumption and simple process, and can realize large-scale production without modifying the existing equipment.

The invention is realized by the following technical scheme:

the invention provides a preparation method of quaternary ammonium salt modified carbon nano tubes, which comprises the following steps:

(1) adding the carbon nano tube into a nitric acid/hydrogen peroxide mixed solution, ultrasonically stirring for 60-120min, carrying out reflux reaction for 1-3h at the temperature of 80-140 ℃, filtering, washing with water, and drying to obtain the carbon nano tube containing epoxy groups and carboxyl groups;

(2) dispersing the carbon nano tube containing the epoxy group and the carboxyl group prepared in the step (1) into water, ultrasonically stirring for 30-80min at 40-90 ℃, then adding quaternary ammonium salt, wherein the mass ratio of the quaternary ammonium salt to the carbon nano tube is 1:100-100:1, preferably 1:2-1:25, continuously stirring for 30-60min at 40-90 ℃, filtering, washing with water, and drying to obtain the quaternary ammonium salt modified carbon nano tube.

In the step (1), the carbon nanotube is selected from one or a mixture of a single-walled carbon nanotube and a multi-walled carbon nanotube, and the preparation method thereof is not particularly limited and may be selected from one or more of an arc discharge method, a laser ablation method, a chemical vapor deposition method, a solid phase pyrolysis method, an ion and laser sputtering method, a polymerization method and a catalytic pyrolysis method.

Preferably, the carbon nanotubes have an outer diameter of 0.6 to 80nm, preferably 2 to 20 nm.

Preferably, the carbon content of the carbon nanotubes is 80 to 100 wt%, preferably 90 to 100 wt%.

In the step (1), the concentration of the adopted nitric acid in the mixed solution of nitric acid and hydrogen peroxide is 60-80 wt%, and the concentration of the adopted hydrogen peroxide is 30-50 wt%; further preferably, in the mixed solution of nitric acid and hydrogen peroxide, the volume ratio of nitric acid to hydrogen peroxide is 1:20-20:1, preferably 1:4-4:1, and most preferably 1: 3.

In the step (1), the carbon nano tube is added into the mixed solution of nitric acid and hydrogen peroxide in a mass ratio of 1:100-20:100, preferably 2:100-10: 100.

In the step (1), the ultrasonic stirring is carried out, wherein the ultrasonic frequency is 30-40 KHZ; the stirring temperature is normal temperature (15-28 ℃).

In the step (1), the filtration and the suction filtration are preferably carried out by adopting a microporous membrane, and the aperture is 0.1-0.5 um.

In the step (1), the washing is preferably performed by using deionized water until the pH value is 6-7; the number of washing with water is not limited, but is preferably 2 to 8.

In the step (1), drying is carried out in a vacuum drying mode at the temperature of 60-100 ℃ for 2-8h, and the preferable range of drying pressure is 10Pa-2000Pa absolute.

In the step (2), the dispersion concentration of the carbon nano tube in water is 0.1-20mg/ml, and deionized water is preferably adopted.

In the step (2), the quaternary ammonium salt is a mixture of a single alkyl chain quaternary ammonium salt and a double alkyl chain quaternary ammonium salt; the molar ratio of the single alkyl chain quaternary ammonium salt to the double alkyl chain quaternary ammonium salt is 1:20-20:1, preferably 1:3-3: 1.

The monoalkyl chain quaternary ammonium salt is selected from one or more of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide and hexadecyl trimethyl ammonium chloride; cetyl trimethylammonium bromide is preferred.

The dialkyl chain quaternary ammonium salt is at least one selected from didodecyl dimethyl ammonium bromide and dihexadecyl dimethyl ammonium bromide, and preferably dihexadecyl dimethyl ammonium bromide.

The quaternary ammonium salt is preferably added with a quaternary ammonium salt aqueous solution, the water temperature is controlled at 40-90 ℃ in the dissolving process, and the concentration of the quaternary ammonium salt aqueous solution is 0.1-0.3 g/ml; the quaternary ammonium salt has no specific requirement on the charging time, and can be stably charged.

In the step (2), the ultrasonic agitation is carried out, wherein the ultrasonic frequency is 30-60KHz, and preferably 30-40 KHz.

In the step (2), the filtration is vacuum filtration, the vacuum pressure is 50-2000Pa, and the aperture of the filter paper is 1-10 μm.

In the step (2), deionized water is preferably adopted for water washing, and the number of water washing is not limited, preferably 2-5.

In the step (2), the drying is carried out at the temperature of 60-100 ℃ for 2-6 hours.

The quaternary ammonium salt modified carbon nano tube prepared by the method has the advantages that N- (single/double) alkyl chains are introduced by quaternary ammonium salts, part of quaternary ammonium salts and epoxy groups on the surface of the carbon nano tube are subjected to ring-opening reaction, and N-alkane chains are grafted on the surface of the carbon nano tube in a covalent bond mode; in addition, because the quaternary ammonium salt and the carboxyl on the surface of the carbon nano tube can generate electrostatic adsorption, the residual quaternary ammonium salt is grafted with N-alkane chains on the surface of the carbon nano tube through electrostatic adsorption.

The invention provides a quaternary ammonium salt modified carbon nanotube prepared by the method, wherein the surface of the quaternary ammonium salt modified carbon nanotube is grafted with an N-alkyl chain, and the N-alkyl chain comprises an N-monoalkyl chain and an N-dialkyl chain, wherein the N-monoalkyl chain is introduced by monoalkyl chain quaternary ammonium salt, and the N-dialkyl chain is introduced by dialkyl chain quaternary ammonium salt.

The invention also provides a low-density and low-warpage soft-touch polypropylene modified material, which adopts the quaternary ammonium salt modified carbon nano tube and comprises the following raw materials:

the wt% is based on the total weight of the polypropylene modified material.

In the polypropylene modified material, the quaternary ammonium salt modified carbon nano tube (with a small addition amount) is added, so that the flexural modulus and tensile strength of the polypropylene modified material can be greatly increased, the density of the polypropylene resin is not increased after a small amount of quaternary ammonium salt modified carbon nano tube is added, good fluidity of the polypropylene material can be maintained, and the problem of material warping is solved. In the prepared modified material, the N-alkyl chain grafted on the surface of the quaternary ammonium salt modified carbon nano tube can generate chain winding with a polypropylene molecular chain, so that the binding force is enhanced, the mechanical property is greatly improved, and the warping problem is favorably solved. The N-alkyl chain grafted in a covalent bond mode can also obviously enhance the interaction force with polypropylene, and the N-alkyl chain grafted in an electrostatic adsorption mode can enable the carbon nano tube to have higher reaction activity. In addition, the N-monoalkyl chain grafted on the surface of the carbon nano tube can obviously enhance the dispersibility of the carbon nano tube in the polypropylene resin matrix, and meanwhile, the grafted N-dialkyl chain can also eliminate the internal loss of a PP (polypropylene) molecular chain and further eliminate the warping problem of an injection molding part.

In the polypropylene modified material, the polypropylene is a composition of homo-polypropylene and high impact co-polypropylene, and the mixing ratio of the homo-polypropylene and the high impact co-polypropylene is 1:19-19:1, preferably 1:4-4: 1.

The homopolymerized polypropylene is the homopolymerized polypropylene with the melt index of 5-80g/10min under the test condition of 230 ℃/2.16kg and the molecular weight of 8-15 ten thousand; homopolypropylene having a molecular weight of 9 to 13 ten thousand and an isotacticity of 96% or more is preferable, and HA5029 available from Polymeria corporation can be used. The homopolymerized polypropylene is a polymer of a single propylene monomer, and the homopolymerized polypropylene has a regular three-dimensional structure and high crystallinity, so that the selection of the homopolymerized polypropylene is favorable for increasing the rigidity of the polypropylene modified material.

The high impact co-polypropylene is one or more of the compositions of SP179P from Zhongpetrochemical Qilu petrochemical company Limited and EP540V from Liangdebasel, wherein the high impact co-polypropylene has a melt index of 0.3-140g/10min at 230 ℃/2.16kg test condition, a content of ethylene monomer of 5-18 wt%, preferably 7-15 wt%, and a content of propylene monomer of 85-93 wt%. The high impact co-polypropylene is a polypropylene blend generated by stepwise in-situ polymerization of propylene and ethylene, and the combination of the high impact co-polypropylene and the homo-polypropylene can generate a synergistic effect, so that the polypropylene forms fine microcrystals in the cooling process, and the defect of high polypropylene molding shrinkage is improved; moreover, the combination of the homopolymerized polypropylene and the high impact copolymerization polypropylene can increase the winding points of two polypropylene molecular chains, so that the performance of the polypropylene modified material is more balanced, and the performance of the overall performance of the polypropylene material is favorably exerted.

In the polypropylene modified material, the thermoplastic elastomer comprises one or a combination of ethylene-propylene copolymer, ethylene-butene copolymer and ethylene-octene copolymer, and preferably ethylene-propylene copolymer. Preferably, the content of the ethylene monomer in the thermoplastic elastomer is 10-30 wt%, the melt index is 0.1-40g/10min under the test condition of 190 ℃/2.16kg, and the Shore hardness is 30-85A. Further preferably, the thermoplastic elastomer is an ethylene-propylene copolymer elastomer with the ethylene content of 10-15 wt%, the melt index of 1.0-25g/10min and the Shore hardness of 30-60A. The ethylene-propylene copolymer elastomer is a copolymer of ethylene and propylene, has low surface hardness and good soft touch, contains a large amount of propylene, has good compatibility with a polypropylene matrix, has good bonding force with the polypropylene, and is more beneficial to the embodiment of the soft touch effect.

In the polypropylene modified material, the antioxidant comprises a main antioxidant and an auxiliary antioxidant, and the mass ratio of the main antioxidant to the auxiliary antioxidant is 1: 5-5: 1, preferably 1: 2-2: 1. the main antioxidant is one or two mixtures of tetra [ beta- (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionic acid ] and beta- (4' -hydroxy-3 ', 5' -di-tert-butylphenyl) propionic acid octadecyl ester; the auxiliary antioxidant is one or a mixture of more than two of tris (2, 4-di-tert-butylphenyl) phosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite, dilauryl thiodipropionate and distearyl thiodipropionate.

In the polypropylene modified material of the invention, the other auxiliary agent is one or a mixture of more than two of the following components: toner, ultraviolet absorber, light stabilizer, scratch-resistant agent, lubricant, nucleating agent, antibacterial agent and antistatic agent.

The invention further provides a preparation method of the low-density and low-warpage soft-touch polypropylene modified material, which comprises the following steps:

1) preparing quaternary ammonium salt modified carbon nanotube master batch: uniformly mixing polypropylene and quaternary ammonium salt modified carbon nano tube according to the weight ratio of 1:3-10:1, preferably 1:1, and then extruding and granulating at the temperature of 210-;

2) the polypropylene, the thermoplastic elastomer, the quaternary ammonium salt modified carbon nanotube master batch, the antioxidant and other additives are uniformly mixed, and then extruded, granulated and dried at the temperature of 190-220 ℃ to obtain the low-density and low-warpage soft-touch polypropylene modified material.

In the step 1), the extrusion granulation is carried out by adopting a double-screw extruder, and the temperature of each temperature zone of the double-screw extruder is 210-.

In the step 2), the raw material mixing process is preferably as follows: mixing and stirring polypropylene, thermoplastic elastomer and quaternary ammonium salt modified carbon nanotube master batch for 3-5min, adding antioxidant and other auxiliary agents for subsequent mixing, and continuously mixing for 5-10min to obtain a mixed raw material;

the extrusion operation adopts a double-screw extruder, the temperature of the melting section is 190-; the granules are long cylindrical uniform granules of 2-8mm, preferably 2-6 mm.

The drying operation is carried out at the drying temperature of 70-120 ℃, and the most preferable temperature is 90 ℃; the drying time is 1-5h, most preferably 2 h.

According to the preparation method of the low-density and low-warpage soft-touch polypropylene modified material, the quaternary ammonium salt modified carbon nano tube and the polypropylene are prefabricated into the master batch, so that dust pollution in the use process of the carbon nano tube is eliminated, and the modified carbon nano tube can be dispersed in a polypropylene matrix more uniformly by prefabricating the master batch, so that the carbon nano tube can play a role of a framework in the polypropylene resin matrix more favorably.

The low-density and low-warpage soft-touch polypropylene modified material can be used for manufacturing parts such as automobile instrument panels, door panels, central channels, household appliances or electronic appliances.

By means of the technical scheme, the invention has the advantages that:

(1) the preparation method of the quaternary ammonium salt modified carbon nano tube has simple and environment-friendly process, does not use organic solvent, can graft N- (mono/bi) alkyl chains on the surface of the carbon nano tube simultaneously, and has high grafting rate, good fluidity and stronger interface bonding force with polypropylene resin.

(2) The quaternary ammonium salt modified carbon nano tube can greatly increase the fluidity, tensile strength, flexural modulus and impact resistance of polypropylene resin, has stronger binding force with a PP matrix, can better play a synergistic effect after introducing a thermoplastic elastomer on the basis, further increases the soft touch and scratch resistance of the polypropylene modified material, reduces the glossiness, reduces the density, eliminates the warpage and has good mechanical property.

(3) Because the N-alkyl chain grafted on the surface of the quaternary ammonium salt modified carbon nano tube has the functions of internal lubrication and promotion of the binding force of PP resin and the carbon nano tube, the melt drives the modified carbon nano tube to uniformly flow in the film cavity in the injection molding process, the warping of a workpiece is reduced, the low-density and low-warping soft-touch polypropylene modified material can be prepared without modifying the existing equipment, and the method is suitable for industrial production. The weight of the automobile parts injection-molded by the polypropylene modified material prepared by the invention can be reduced by more than 19% compared with the automobile parts injection-molded by the traditional polypropylene modified material.

Drawings

FIG. 1 shows the IR spectra of epoxy and carboxylated carbon nanotubes and various quaternary ammonium salt modified carbon nanotubes.

Detailed Description

The features, benefits and advantages of the present invention will become apparent to those skilled in the art from a reading of the present disclosure.

All formulations and tests herein occurred at 23 ℃ environment, unless otherwise indicated.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following examples are intended to further describe and demonstrate embodiments within the scope of the present invention. The examples are therefore to be understood as merely illustrative of the invention in more detail and not as limiting the content of the invention in any way.

The following examples further illustrate preferred embodiments within the scope of the present invention. These examples are merely illustrative and not intended to limit the scope of the invention, as many variations of the invention are possible without departing from the spirit and scope thereof.

Performance test method

Melt index testing was performed according to ISO1133 standard.

The density was measured according to ISO1183 standard.

The feel was scored according to K3A dermatoglyph, with the scoring criteria shown in Table 1.

TABLE 1 tactile Scale description

Grade	Description of the invention
		1	Strong hard plastic feeling
2	Slightly stronger hard plastic feeling
		3	Slightly soft touch feeling
4	Good soft touch
		5	Comfortable soft touch

Warpage testing was compared visually to the molded part.

Scratch resistance was tested according to PV3952, and the leather grain board model was K3A.

The mechanical properties are measured after a mechanical sample strip obtained after the injection molding of the granules prepared by the invention is regulated in a standard environment (23 ℃, 50 percent relative humidity) for 24 hours. Wherein the tensile, bending and notched Izod impact test bars have the dimensional requirements as shown in Table 2

TABLE 2 mechanical spline size requirements

Spline name	Sample size (mm)
		Tensile sample strip	150 (length) 10 (width) 4 (thickness)
Curved spline	80 (length) 10 (width) 4 (thickness)
		Notched impact bar for cantilever beam	80 (length) × 10 (width) × 4 (thickness) notch of A type

Tensile strength, tensile modulus and elongation at break were performed according to ISO527 standard; flexural strength and flexural modulus were performed according to ISO178 standard; notched izod impact strength was performed according to ISO180 standards.

Polypropylene

HA5029, available commercially from Polymerle corporation, melt finger (230 ℃/2.16kg)60g/10 min.

EP540V, Liandrebasel, melt index (230 ℃/2.16kg)100g/10min, commercially available.

SP179P, Zhongpetrochemical Qilu petrochemical Co., Ltd., melt index (230 ℃/2.16kg)9g/10min, commercially available.

Thermoplastic elastomer

Vistamaxx 6202, ethylene content 15 wt%, melt index (190 ℃/2.16kg)9.1g/10min, Shore hardness 60A, Exon Mobil chemical company, commercially available.

Carbon nanotube

IM897P, Chinese academy of sciences, GmbH, diameter 30-80nm, specific surface area 80-110m²Per g, multi-wall, 98% carbon, commercially available.

Auxiliary agent

Antioxidant Irganox 1010, New Basff materials, Inc., commercially available.

Antioxidant Irgafos 168, available from Pasteur materials, Inc.

The invention is further illustrated by the following examples.

First, examples 1-2 and comparative examples 1-3: preparation of quaternary ammonium salt modified carbon nanotubes