阅读说明：本技术 一种永久抗静电聚丙烯复合材料及其制备方法 (Permanent antistatic polypropylene composite material and preparation method thereof ) 是由 李旭 顾永江 徐卓言 涂永鑫 陆佳伟 杨峰 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种永久抗静电聚丙烯复合材料及其制备方法,通过包含以下组分的原料制备得到：聚丙烯75-91份,碳/硅灰石复合材料5-15份,氧化超导炭黑4-10份,硅烷偶联剂1-2份,抗氧剂0.1-0.5份。本发明通过采用超导炭黑与碳/硅灰石复合材料进行复配以及实现方案,对聚丙烯进行抗静电改性,可以降低超导炭黑的添加量,减少炭黑对材料力学性能的影响。采用该方法所制备的复合材料具有永久抗静电性能,可应用于电子电器周转箱,新能源汽车等多个领域。(The invention discloses a permanent antistatic polypropylene composite material and a preparation method thereof, wherein the permanent antistatic polypropylene composite material is prepared from the following raw materials: 75-91 parts of polypropylene, 5-15 parts of carbon/wollastonite composite material, 4-10 parts of oxidized superconducting carbon black, 1-2 parts of silane coupling agent and 0.1-0.5 part of antioxidant. According to the invention, by adopting the compounding and implementation scheme of the superconducting carbon black and the carbon/wollastonite composite material, the polypropylene is subjected to antistatic modification, so that the addition amount of the superconducting carbon black can be reduced, and the influence of the carbon black on the mechanical property of the material is reduced. The composite material prepared by the method has permanent antistatic performance, and can be applied to a plurality of fields such as electronic and electric appliance turnover boxes, new energy vehicles and the like.)

1. A permanent antistatic polypropylene composite material is prepared from the following raw materials:

75-91 parts of polypropylene, preferably 80-86 parts;

5-15 parts of carbon/wollastonite composite material, preferably 8-12 parts;

4-10 parts of oxidized superconducting carbon black, preferably 6-8 parts;

1-2 parts of silane coupling agent, preferably 1.3-1.7 parts;

0.1-0.5 part of antioxidant; preferably 0.2 to 0.4 parts.

2. The polypropylene composite of claim 1, wherein the carbon/wollastonite composite is prepared by the following method:

(1) mixing wollastonite, water and polyethylene glycol, preferably mixing the wollastonite, 3-4 parts of deionized water and 0.01-0.02 part of polyethylene glycol based on the mass of the wollastonite, and uniformly stirring at the temperature of 80-100 ℃ to obtain a wollastonite suspension;

(2) adding 20 wt% hydrochloric acid solution into the wollastonite suspension, controlling pH to 2-3, reacting for 3-5h, washing with water, and drying to obtain acid-treated wollastonite;

(3) dissolving epoxy resin in acetone, adding acid-treated wollastonite, preferably 30-40 parts of acid-treated wollastonite based on the mass of the epoxy resin, reacting for 2-4h, drying, carbonizing, preferably carbonizing in a tubular furnace at 500-700 ℃ for 3-5h in a nitrogen atmosphere to obtain the carbon/wollastonite composite material.

3. The polypropylene composite material of claim 2, wherein the wollastonite is a wollastonite commercially available for modifying plastics, and has a fibrous morphology and an aspect ratio of 10-20: 1.

4. The polypropylene composite according to any one of claims 1 to 3, wherein the oxidized superconducting carbon black is prepared by a method comprising: mixing and reacting the superconducting carbon black with 5-8 parts of nitric acid based on the mass of the superconducting carbon black for 2-5h, washing and drying to obtain the product, preferably drying in a vacuum oven with the temperature of 100-120 ℃ and the pressure of 0.3-0.5 KPa.

5. The polypropylene composite according to claim 4, wherein the superconducting carbon black is a commercially available nano-sized superconducting carbon black product having an average particle size of < 100 nm.

6. The polypropylene composite material according to any one of claims 1 to 5, wherein the polypropylene is one or a mixture of two of commercially available injection molding grade homo-polypropylene and co-polypropylene, and has a melt index of 10 to 100g/10min and a shrinkage of 1.5 to 2.0%.

7. Polypropylene composite according to any of claims 1-6, whereby the silane coupling agent is a mixture of one or more of the commercially available grades KH550, H560, KH570, preferably the grade KH 560.

8. The polypropylene composite material according to any one of claims 1 to 7, wherein the antioxidant is a mixture of 1: 2-2: 1 antioxidant 1010 and antioxidant 168.

9. Method for the preparation of a permanently antistatic polypropylene composite according to any one of claims 1 to 8 comprising the steps of:

(1) adding the carbon/wollastonite composite material into ethanol and stirring to obtain carbon/wollastonite suspension, adding a silane coupling agent into the suspension and stirring, reacting at the temperature of 60-80 ℃ for 0.5-2h, adding oxidized superconducting carbon black into the system, reacting at the temperature of 60-80 ℃ for 1-3h, and drying at the temperature of 100-120 ℃ to obtain the superconducting carbon black-carbon/wollastonite composite material;

(2) placing the raw materials of polypropylene, superconducting carbon black-carbon/wollastonite composite material and antioxidant in a high-speed stirrer to be mixed for 3-5 minutes at the rotation speed of 500-1500rpm to obtain premix, and adding the premix through a main feeding port of a double-screw extruder;

(3) the premix is melted, extruded, cooled, granulated and dried in an extruder to obtain the polypropylene composite material.

10. The method for preparing according to claim 9, wherein the parameters of the twin-screw extruder are set as follows: the temperature of the first zone is 185-plus-195 ℃, the temperature of the second zone is 190-plus-200 ℃, the temperature of the third zone is 190-plus-200 ℃, the temperature of the fourth zone is 185-plus-195 ℃, and the rotation speed of the screw is 300-plus-500 r/min.

Technical Field

The invention relates to a polypropylene composite material, in particular to a permanent antistatic polypropylene composite material and a preparation method thereof, belonging to the technical field of polypropylene modification.

Background

As a general plastic, polypropylene has the advantages of low price, good heat resistance and the like, and is widely applied to the fields of automobiles, household appliances, office supplies and various electronic and electrical appliances. However, polypropylene is used as a high-insulation material, and the surface resistivity of the polypropylene is as high as 10¹⁶-10¹⁷Omega. The high resistance causes the accumulation of static charges on the surface of the material, and the polypropylene part can cause the accumulation of dust on the surface of the part in the processes of injection molding, transportation and assembly, so that the appearance and the assembly efficiency of the part are influenced; and can cause electrical breakdown, spark discharge, and even serious consequences of combustion or explosion. This limits the application of polypropylene materials in the field of daily production and life, especially in the field of electronic and electrical appliances. In recent years, with the increasing safety awareness, the surface resistivity of polypropylene materials is reduced, and the development of antistatic polypropylene materials is a research and development direction with great attention. The preparation method of the antistatic polypropylene material at present is to carry out blending modification on an antistatic agent and the polypropylene material so as to reduce the surface resistivity of the material. The following are commonly used antistatic agents: (1) the antistatic effect of the material is large in dependence on the humidity of the environment, and the material loses the antistatic effect in a dry or low-humidity working condition; (2) macromolecular permanent/semi-permanent antistatic agent with high addition amount (more than 10%), low antistatic efficiency, high material cost, and high antistatic effect on material mechanicsThe performance influence is obvious, and the material has no great practicability; and (3) conductive fillers such as carbon fibers, carbon nanotubes, graphene, metal sheets and the like are added, and the antistatic agent can endow polypropylene with permanent antistatic performance, but is high in price and not practical. The superconducting carbon black is used as a conductive filler with low price, can endow polypropylene with permanent antistatic performance, but the mechanical property of the material can be obviously reduced when the addition amount is high (more than 15 percent); meanwhile, the relationship between the addition amount of the carbon black and the surface resistivity of the material is nonlinear, the surface resistivity of the material can be reduced in a cliff manner only when the addition amount reaches a percolation threshold, the critical value can be reached only by adding 15-25 parts of the conventional commercially available superconducting carbon black, and a large amount of carbon black is added, so that the fluidity, the strength and the modulus of the material are greatly reduced, the cost of the material is improved, and the material finally cannot meet the use requirement of a finished piece.

Chinese patent publication CN 105924663a provides an antistatic polypropylene foam material, which is prepared by mixing and reacting conductive carbon black and acrylamide in advance, and then coating antistatic adhesive on the surface of a foamed polypropylene sheet, thereby achieving the antistatic effect. Although the method can realize the foaming material with better antistatic effect, the process is complex, and the method is only suitable for extruding sheets and is not suitable for injection molding parts.

According to the mechanism that the superconducting carbon black reduces the surface resistivity of the material: the superconducting carbon black is a conductive material, and in an insulating system such as polypropylene and the like, the addition amount of the superconducting carbon black is high enough to obviously reduce the resistivity of the material and improve the conductivity of the material after a conductive network is formed. Therefore, in order to obtain a modified polypropylene material with a low addition amount of superconducting carbon black, the formation of a conductive network in the material is firstly ensured.

Disclosure of Invention

The invention aims to solve the technical problem of providing a permanent antistatic polypropylene composite material and a preparation method thereof, and solves the problems of environmental dependence, timeliness, poor mechanical properties and high cost of the antistatic property of the existing polypropylene material. The finally prepared antistatic polypropylene material can obtain permanent antistatic performance by adding a small amount of superconducting carbon black, and the mechanical property of the material is obviously improved, so that the material can be applied to a plurality of fields such as electronic and electric appliance transfer boxes, new energy automobiles and the like.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a permanent antistatic polypropylene composite material is prepared from the following raw materials:

75-91 parts of polypropylene, preferably 80-86 parts;

5-15 parts of carbon/wollastonite composite material, preferably 8-12 parts;

4-10 parts of oxidized superconducting carbon black, preferably 6-8 parts;

1-2 parts of silane coupling agent, preferably 1.3-1.7 parts;

0.1-0.5 part of antioxidant; preferably 0.2 to 0.4 parts.

In the invention, the carbon/wollastonite composite material is prepared by the following method:

(1) mixing wollastonite, water and polyethylene glycol, preferably mixing the wollastonite, 3-4 parts of deionized water and 0.01-0.02 part of polyethylene glycol based on the mass of the wollastonite, and uniformly stirring at the temperature of 80-100 ℃ to obtain a wollastonite suspension;

(2) adding 20 wt% hydrochloric acid solution into the wollastonite suspension, controlling pH to 2-3, reacting for 3-5h, washing with water, and drying to obtain acid-treated wollastonite;

(3) dissolving epoxy resin in acetone, adding acid-treated wollastonite, preferably 30-40 parts of acid-treated wollastonite based on the mass of the epoxy resin, reacting for 2-4h, drying, carbonizing, preferably carbonizing in a tubular furnace at 500-700 ℃ for 3-5h in a nitrogen atmosphere to obtain the carbon/wollastonite composite material.

As a preferred scheme, the carbon/wollastonite composite material is prepared by the following method:

(1) mixing wollastonite, 3-4 parts of deionized water based on the mass of the wollastonite and 0.01-0.02 part of polyethylene glycol, and uniformly stirring in a water bath kettle at the constant temperature of 80-100 ℃ to obtain wollastonite suspension for later use;

(2) slowly dripping 20% hydrochloric acid solution into the wollastonite suspension, controlling the pH value to be 2-3, reacting for 3-5h, washing for 3-5 times, and drying at the temperature of 100-120 ℃ to obtain acid-treated wollastonite;

(3) placing epoxy resin and 30-40 parts of acetone based on the epoxy resin in a 50-80 ℃ constant-temperature water bath kettle, uniformly stirring, pouring into a wollastonite beaker containing 30-40 parts of acid-treated wollastonite based on the mass of the epoxy resin, covering wollastonite powder, standing, reacting for 2-4h, drying at 100-120 ℃, and carbonizing for 3-5h in a 500-700 ℃ tube furnace under the nitrogen atmosphere to obtain the carbon/wollastonite composite material.

In the invention, the wollastonite is commercially available wollastonite capable of being used for plastic modification, the shape is fibrous, and the length-diameter ratio is 10-20: 1. Suitable examples include, but are not limited to, Haichard mining W625, Xinda H-1250F, and the like.

In the invention, the oxidized superconducting carbon black is prepared by the following method: mixing and reacting the superconducting carbon black with 5-8 parts of nitric acid based on the mass of the superconducting carbon black for 2-5h, washing and drying to obtain the product, preferably drying in a vacuum oven with the temperature of 100-120 ℃ and the pressure of 0.3-0.5 KPa.

As a preferred scheme, the oxidized superconducting carbon black is prepared by the following method: placing the superconducting carbon black and 5-8 parts of nitric acid with the mass fraction of 35% based on the mass of the superconducting carbon black in a beaker, stirring at room temperature, reacting for 2-5h, and then washing the carbon black with deionized water until the pH value of a washing solution is constant. The carbon black after oxidation treatment is dried in a vacuum oven with the temperature of 100-120 ℃ and the pressure of 0.3-0.5KPa until the quality is constant.

The superconducting carbon black is commercially available nano-scale superconducting carbon black which can be used for plastic modification, and the average particle size is less than 100 nm. Suitable examples include, but are not limited to, ASAHI superconducting carbon black AX-015, BIRLACARBON superconducting carbon black 7093, and the like.

In the invention, the polypropylene is one or a mixture of two of commercially available injection molding grade homopolymerized polypropylene and copolymerization polypropylene, the melt index is 10-100g/10min, and the shrinkage rate is 1.5-2.0%. Suitable examples include, but are not limited to, luoyang petrochemical MN15, korean dadall HJ730, and the like.

In the present invention, the silane coupling agent is a silane coupling agent product that can be used for plastic modification, and suitable examples include, but are not limited to, KH550, KH560, KH570 and the like, which are national medicines.

In the present invention, the antioxidant is an antioxidant product which can be used for plastic modification, and suitable examples include but are not limited to basf 1010, 168, etc., and the preferred weight ratio is 1: 2-2: 1 antioxidant 1010 and antioxidant 168.

A preparation method of a permanent antistatic polypropylene composite material comprises the following steps:

(1) adding the carbon/wollastonite composite material into ethanol and stirring to obtain carbon/wollastonite turbid liquid, adding a silane coupling agent into the turbid liquid and fully stirring, reacting at the temperature of 60-80 ℃ for 0.5-2h, adding oxidized superconducting carbon black into the system, fully stirring, further reacting at the temperature of 60-80 ℃ for 1-3h, and drying at the temperature of 100-120 ℃ to obtain a superconducting carbon black/wollastonite composite material mixture;

(2) placing the raw materials of polypropylene, superconducting carbon black-carbon/wollastonite composite material and antioxidant in a high-speed stirrer to be mixed for 3-5 minutes at the rotation speed of 500-1500rpm to obtain premix, and adding the premix through a main feeding port of a double-screw extruder;

(3) and melting, extruding, cooling, granulating and drying the premixed raw materials in an extruder to obtain the polypropylene composite material. Preferably, the parameters of the twin screws are set as follows: the temperature of the first zone is 185-plus-195 ℃, the temperature of the second zone is 190-plus-200 ℃, the temperature of the third zone is 190-plus-200 ℃, the temperature of the fourth zone is 185-plus-195 ℃, and the rotation speed of the screw is 300-plus-500 r/min; generally, the product is extruded from a double screw, cooled by cooling water, granulated by a granulator and dried in an oven at 90 ℃ for 2 hours.

Compared with the prior art, the invention has the beneficial effects that:

(1) compared with granular superconducting carbon black, the fibrous carbon/wollastonite composite material has larger length-diameter ratio and is easier to be connected with each other in the material to form a conductive network.

(2) Compared with the carbon/wollastonite composite material, the superconducting carbon black has excellent conductive performance, and is used as a charge transmission pivot in a conductive network to ensure that charges are smooth and unimpeded in the conductive network.

(3) The polypropylene is subjected to antistatic modification by compounding the superconducting carbon black and the carbon/wollastonite composite material, wherein the addition amount of the superconducting carbon black can be reduced by the synergistic effect of the granular superconducting carbon black and the fibrous carbon/wollastonite, so that the influence of the carbon black on the mechanical property of the material is reduced. The carbon/wollastonite composite material is carbonized only on the surface layer of the wollastonite, the crystal structure and the performance of the wollastonite are still kept inside the carbon/wollastonite composite material, and the tensile strength and the flexural modulus of the carbon/wollastonite composite material can be obviously improved in a polypropylene system, so that the mechanical property of the carbon/wollastonite composite material meets the requirements of actual use.

(4) In order to facilitate the compounding effect of the superconducting carbon black and the carbon/wollastonite composite material, the carbon/wollastonite composite material is subjected to surface modification by using a silane coupling agent, and two hydroxyl groups connected with a silicon element in the modified silane coupling agent are exposed in the air without further reaction. By adding the super-conductive carbon black subjected to the oxidation treatment into the system, the carboxyl on the surface of the carbon black is further reacted with the hydroxyl in the silane coupling agent, and finally one end of a silicon element in the silane coupling agent is connected with the carbon/wollastonite composite material, and the other two ends of the silicon element are connected with the super-conductive carbon black. The processing method enables the superconducting carbon black and carbon/wollastonite composite material to have better compounding effect in a final material system, and simultaneously can greatly improve the compatibility of the inorganic filler and the polypropylene matrix and ensure the formation of a final conductive network.

The antistatic polypropylene material finally obtained is added with a small amount of superconducting carbon black, so that the permanent antistatic performance can be obtained, the mechanical property of the material is improved, the material can be recycled, and the environment-friendly property is realized. The finally prepared material can be applied to a plurality of fields such as electronic and electric appliance turnover boxes, new energy automobiles and the like.

Detailed Description

The present invention is further illustrated by the following examples, which are provided only for the purpose of illustration and are not intended to limit the scope of the present invention.

The polypropylene is Loyang petrochemical homopolymerized polypropylene MN15, the material melt index is 15g/10min, and the shrinkage rate is 1.8%.

The superconducting carbon black is ASAHI superconducting carbon black AX-015, and the average grain diameter of the product is 19 nm.

The length-diameter ratio of the adopted wollastonite is Haicheng mining wollastonite W625, and is 11: 1.

The antioxidant is Pasteur antioxidant 1010, 168, and the product ratio is 1: 1. (ii) a

The silane coupling agent is a Chinese medicament KH 560;