CN103342904A - Method for preparing water-soluble graphene by titanate coupling agent modification process - Google Patents

Abstract

A method for preparing water-soluble graphene by a titanate coupling agent modification method, first heating expandable graphite at a high temperature of 1100°C to obtain worm-like expanded graphite, then obtaining graphite oxide by oxidation of the expanded graphite, and dispersing the graphite oxide into the water solvent and peeled off by means of magnetic stirring to obtain graphene oxide; successively add titanate coupling agent and hydrazine hydrate to the graphene oxide dispersion to obtain a mixed solution; the prepared mixed solution is heated in a water bath The reaction takes place under the conditions to reduce graphene oxide and graft titanate coupling agent molecules at the same time; the obtained mixed solution is repeatedly filtered and washed to remove excess hydrazine hydrate and titanate coupling agent and then vacuum-dried to obtain a powder modified graphene. The invention has the advantages of simple process, high production efficiency, environment-friendly production process and products, high dispersion stability of the prepared graphene in water, long-term storage, and is suitable for the preparation of composite materials and coating materials.

Description

A kind of method for preparing water-soluble graphene by titanate coupling agent modification method

technical field

The invention relates to a method for preparing water-soluble graphene by a titanate coupling agent modification method, and belongs to the technical field of graphene and its preparation.

Background technique

Graphene: Graphene is only one carbon atom thick and is the thinnest material known. Not only is it the thinnest known material, it is also very strong and flexible. It has high mechanical strength, good thermal conductivity and fast carrier mobility, and provides raw materials for the preparation of high-performance devices such as transistors and sensors. In addition, graphene has a very high specific surface area and can be used to prepare nanocomposites. With the announcement of the winner of the Nobel Prize in Physics in 2010, the scientific community has started a new round of discussions about the Nobel Prize, and graphite (Graphene) has also become the focus of discussion.

In recent years, people continue to explore new methods to increase the output of graphene, and the chemical redox method is widely used because it can prepare graphene in large quantities (Songfeng Pei, Hui-Ming Cheng. The reduction of graphene oxide. Carbon.2012, 50(9):1972–2012.). This method first prepares graphite oxide, first disperses the graphite powder in a strong oxidizing mixed acid, such as concentrated nitric acid and concentrated sulfuric acid, then adds a strong oxidant such as potassium permanganate or potassium chlorate to obtain graphite oxide, and then obtains graphite oxide through ultrasonic exfoliation. ene, and finally obtained graphene through reduction reaction. The surface of graphene prepared by this method has only a small amount of oxygen-containing functional groups, so the surface is hydrophobic, making it easy to agglomerate and precipitate in water and common organic solvents. Therefore, effective modification and functionalization are needed to improve their dispersibility in water. The methods reported in the literature for graphene surface chemical modification mainly include amino modification method, surfactant method, silane coupling agent method, polymer grafting method, etc. (Yan Wang, ZiXing Shi', Jie Yin. Kevlar oligomer functionalized graphene for polymer composites. 2011, 52(16):3661–3670.). The scope of application of different modification methods is different. The titanate modification method disclosed in this patent is especially suitable for graphene dispersed in aqueous systems, including the preparation of aqueous solutions of graphene and the preparation of graphene-enhanced aqueous polymer composites. Materials, preparation of graphene-enhanced waterborne coatings, etc.

SUMMARY OF THE INVENTION Aiming at the wide application of graphene in water-based systems in the prior art, the present invention proposes a method for preparing water-soluble graphene by modification with a titanate coupling agent. Titanate coupling agent is a new type of coupling agent, which can act as a molecular bridge between inorganic substances and substrates, and has the characteristics of less dosage, good dispersion effect, low price and wide application range. The modified graphene is still a single layer, on which a titanate acid coupling agent is grafted; the preparation method is simple and effective; and the obtained modified graphene has good anti-sedimentation effect in water.

Technical problem of the present invention is solved by following technical scheme:

A method for preparing water-soluble graphene by titanate coupling agent modification method, obtains graphene oxide by oxidation method, and connects titanate coupling agent while obtaining graphene, the modified graphene obtained can be stable Dispersed in water, and through the bridging effect of titanate coupling agent, it can be combined with different kinds of water-based polymer materials or water-based coatings to obtain various composite materials or composite coatings reinforced by uniformly dispersed modified graphene. It mainly includes the following steps:

A) The expandable graphite is reacted at a high temperature of 1100°C for 15 seconds to obtain worm-like expanded graphite, and then the expanded graphite is oxidized (hummers) to obtain graphite oxide, and the graphite oxide is dispersed in the water solvent, and the dispersion concentration of graphite oxide is 0.2~ 4mg/ml; Graphene oxide is obtained by stripping by magnetic stirring, mechanical vibration, or ultrasonic method;

B) Add titanate coupling agent and hydrazine hydrate successively to the graphene oxide dispersion in step A) to obtain a mixed solution; the addition amount of the titanate coupling agent is 1% to 500% of the mass of graphene oxide %; the amount of hydrazine hydrate added is 10 to 500 times the mass of graphene oxide;

C) Reacting the mixed solution prepared in step B) under the water bath heating method, hydrothermal reaction method or microwave-assisted method, so as to reduce the graphene oxide and graft titanate coupling agent molecules at the same time;

D) The mixed solution obtained in step C) is repeatedly filtered and washed to remove excess hydrazine hydrate and titanate coupling agent, and then dried in vacuum at 60° C. to obtain powdery modified graphene.

The type of titanate coupling agent described in step B) is one of commercially available TM-200S, LD-125, KR-238S or TM-138S.

Preferably, the water-bath heating reaction temperature in step C) is 50°C-90°C, and the water-bath heating reaction time is 10h-48h.

Preferably, the reaction temperature of the hydrothermal reaction in step C) is 100°C-180°C, and the reaction time of the hydrothermal reaction is 8h-24h.

Preferably, step C) the microwave reaction temperature is 80°C-120°C, and the microwave reaction time is 5min-1h.

A kind of modified graphene obtained by the method described in any one of the above, there is a titanate coupling agent chemically grafted on the graphene sheet, and the anti-sedimentation in water is more than one month.

Compared with the prior art, the modified graphene prepared by the present invention has the following advantages:

1. The titanate coupling agent water-soluble modified graphene of the present invention has excellent properties, and the surface resistance value is 26-780kΩ/sq, so adding it to the composite material will improve the conductivity of the composite material.

2. The modified graphene prepared by the method of the present invention has a titanate coupling agent chemically grafted on the surface, so it has high dispersion stability in water and can be stored for a long time without changing its dispersion state.

3. The titanate coupling agent used in the present invention has a variety of unique functions due to the special structure of titanium, and has a wide range of applications in the field of composite materials and coating materials, and the effect is remarkable; therefore, the titanate-modified graphene It is suitable for the preparation of composite materials and coating materials.

4. The present invention is water-soluble modification, so it is more environmentally friendly, and is suitable for environmentally friendly composite materials and coating materials.

5. The present invention adopts water-bath heating reaction, hydrothermal reaction or microwave-assisted reaction, and any kind of reaction can obtain modified graphene, indicating that the range of reaction conditions is wide, and the target product can be obtained through various paths.

6. The invention has simple process, high production efficiency, environment-friendly production process and products, low production cost, good reproducibility of different batches of products, and is suitable for large-scale production.

Detailed ways

The present invention is described in detail below in conjunction with embodiment, but present embodiment can not be used for limiting the present invention, and every similar method and similar variation thereof that adopt the present invention all should be included in protection scope of the present invention.

In the embodiment, the numerical value of Zeta potential is used to quantify the stability of the modified graphene aqueous dispersion. Zeta potential is a measure of the strength of mutual repulsion or attraction between particles. The higher the zeta potential (positive or negative), the more stable the system, that is, the dispersion can resist aggregation. Conversely, the lower the Zeta potential (positive or negative), the more likely it is to coagulate or coagulate, that is, the attractive force exceeds the repulsive force, and the dispersion is destroyed and agglomeration and precipitation occur.

In the following examples, the expandable graphite was reacted at a high temperature of 1100° C. for 15 seconds to obtain worm-like expanded graphite, and then the expanded graphite was oxidized by the hummers method to obtain graphite oxide.

【Example 1】

Ultrasonically disperse graphite oxide into water at a concentration of 0.2 mg/ml; first add titanate coupling agent LD-125 into the graphene oxide dispersion, the amount added is 100% of the mass of graphene oxide; then add hydrazine hydrate, add The amount is 500 times of the mass of graphene oxide; then react in a water bath at 60°C for 10h; after the reaction, wash with deionized water to pH=7; dry at 60°C in vacuum to obtain modified graphene powder; modify graphene powder to 1mg/ml dispersed in deionized water.

Anti-sedimentation results: stable dispersion in water for more than one week.

Surface resistance: 321kΩ/sq;

Zeta potential: -32mV.

[Example 2]

Ultrasonic disperse graphene oxide into water at a concentration of 2 mg/ml; add titanate coupling agent LD-125 into the graphene oxide dispersion, the amount added is 400% of the mass of graphene oxide; add hydrazine hydrate, the amount It is 500 times the mass of graphene oxide; and then reacted at 80°C for 30min under the assistance of microwave;

Anti-sedimentation results: stable dispersion in water for more than one month;

Surface resistance value: 513kΩ/sq;

Zeta potential: -41mV.

[Example 3]

Disperse graphite oxide into water with magnetic stirring at a concentration of 4mg/ml; add titanate coupling agent TM-200S into the graphene oxide dispersion, the amount added is 200% of the mass of graphene oxide; add hydrazine hydrate, the amount 10 times the mass of graphene oxide; then react in a hydrothermal kettle at 180°C for 24h;

Anti-sedimentation results: stable dispersion in water for more than one month;

Surface resistance value: 712kΩ/sq;

Zeta potential: -42mV.

【Example 4】

Graphite oxide was ultrasonically dispersed into water at a concentration of 2 mg/ml; titanate coupling agent TM-138S was added to the graphene oxide dispersion in an amount of 1% of the mass of graphene oxide; hydrazine hydrate was added in an amount of 300 times the mass of graphene oxide; then react at 120°C for 1 hour under the assistance of microwave;

Anti-sedimentation results: stable dispersion in water for more than one week;

Surface resistance value: 26kΩ/sq;

Zeta potential: -31mV.

【Example 5】

Disperse graphite oxide into water with mechanical vibration at a concentration of 1 mg/ml; add titanate coupling agent TM-200S into the graphene oxide dispersion, the amount added is 500% of the mass of graphene oxide; add hydrazine hydrate, the amount It is 300 times the mass of graphene oxide; then reacted at 70°C for 40min under heating in a water bath;

Anti-sedimentation results: stable dispersion in water for more than one month;

Surface resistance value: 103kΩ/sq;

Zeta potential: -37mV.

[Example 6]

Graphite oxide is ultrasonically dispersed into water at a concentration of 2 mg/ml; titanate coupling agent TM-138S is added to the graphene oxide dispersion in an amount of 100% of the mass of graphene oxide; hydrazine hydrate is added in an amount of 500 times the mass of graphene oxide; then react in a hydrothermal kettle at 180°C for 8 hours;

Anti-sedimentation results: stable dispersion in water for more than one week;

Surface resistance value: 42kΩ/sq;

Zeta potential: -32mV.

[Example 7]

Disperse graphite oxide into water with mechanical vibration at a concentration of 1 mg/ml; add titanate coupling agent LD-125 into the graphene oxide dispersion, the amount added is 500% of the mass of graphene oxide; add hydrazine hydrate, the amount It is 500 times the mass of graphene oxide; then reacted at 120°C for 50min under the assistance of microwave;

Anti-sedimentation results: stable dispersion in water for more than one month;

Surface resistance value: 529kΩ/sq;

Zeta potential: -43mV.

[Embodiment 8]

Disperse graphite oxide into water with magnetic stirring at a concentration of 1 mg/ml; add titanate coupling agent KR-238S into the graphene oxide dispersion, the amount added is 200% of the mass of graphene oxide; add hydrazine hydrate, the amount It is 300 times the mass of graphene oxide; then reacted at 120°C for 40min under the assistance of microwave;

Anti-sedimentation results: stable dispersion in water for more than one week;

Surface resistance value: 519kΩ/sq;

Zeta potential: -38mV.

[Example 9]

Ultrasonically disperse graphite oxide into water at a concentration of 0.2 mg/ml; first add titanate coupling agent TM-138S into the graphene oxide dispersion, the amount added is 100% of the mass of graphene oxide; then add hydrazine hydrate, add The amount is 500 times the mass of graphene oxide; then reacted at 50°C for 48h under heating in a water bath;

Anti-sedimentation results: stable dispersion in water for more than a week.

Surface resistance: 326kΩ/sq;

Zeta potential: -35mV.

【Example 10】

Ultrasonically disperse graphite oxide into water at a concentration of 3 mg/ml; first add titanate coupling agent KR-238S into the graphene oxide dispersion, the amount added is 10% of the mass of graphene oxide; then add hydrazine hydrate, the amount 500 times the mass of graphene oxide; then heated in a water bath at 90°C for 10 hours; after the reaction, washed with deionized water until pH = 7; dried in vacuum at 60°C to obtain modified graphene powder; modified graphene powder in 1mg /ml dispersed in deionized water.

Anti-sedimentation results: stable dispersion in water for more than a week.

Surface resistance: 331kΩ/sq;

Zeta potential: -39mV.

[Example 11]

Ultrasonically disperse graphite oxide into water at a concentration of 2 mg/ml; first add titanate coupling agent LD-125 into the graphene oxide dispersion, the amount added is 200% of the mass of graphene oxide; then add hydrazine hydrate, the amount 500 times the mass of graphene oxide; then react in a hydrothermal kettle at 100°C for 16h.

Anti-sedimentation results: stable dispersion in water for more than one month.

Surface resistance: 327kΩ/sq;

Zeta potential: -41mV.

Claims (5)

1. a titanate coupling agent modification method prepares the method for water-soluble Graphene, it is characterized in that: obtain graphene oxide by oxidation style, reduction connects titanate coupling agent when obtaining Graphene, the modified graphene that obtains can be stable be dispersed in the water, and the bridging effect by titanate coupling agent, combine with aqueous high molecular material or water-borne coatings, obtain various matrix materials or composite coating that finely dispersed modified graphene strengthens; Specifically may further comprise the steps:

A) expansible black lead is heated 15s under 1100 ℃ of high temperature and obtain vermiform expanded graphite, expanded graphite obtains graphite oxide by oxidation style then, and graphite oxide is distributed in the water solvent, and it is 0.2～4mg/ml that graphite oxide disperses concentration; Peel off by magnetic agitation, mechanical vibration or ultrasonic method, obtain graphene oxide;

B) in steps A) the graphene oxide dispersion liquid in successively add titanate coupling agent and hydrazine hydrate, obtain mixed solution; Described titanate coupling agent add-on is 1%～500% of graphene oxide quality; The hydrazine hydrate add-on is 10～500 times of graphene oxide quality;

C) with step B) mixed solution that makes reacts under heating in water bath method, hydro-thermal reaction method or microwave assisting method, makes graphene oxide reduction and the titanate coupling agent of grafting simultaneously molecule;

D) to step C) mixed solution that obtains filters repeatedly and cleans, and removes excessive hydrazine hydrate and titanate coupling agent 60 ℃ of dryings of vacuum then, obtains Powdered modified graphene.

2. a kind of titanate coupling agent modification method according to claim 1 prepares the method for water-soluble Graphene, it is characterized in that: step B) described titanate coupling agent kind is a kind of among commercially available TM-200S, LD-125, KR-238S or the TM-138S.

3. a kind of titanate coupling agent modification method according to claim 1 prepares the method for water-soluble Graphene, it is characterized in that: step C) described heating in water bath for reaction temperature is 50 ℃～90 ℃, and the heating in water bath for reaction time is 10h～48h.

4. a kind of titanate coupling agent modification method according to claim 1 prepares the method for water-soluble Graphene, it is characterized in that: step C) temperature of reaction of described hydro-thermal reaction is 100 ℃～180 ℃, and the reaction times of hydro-thermal reaction is 8h～24h.

5. a kind of titanate coupling agent modification method according to claim 1 prepares the method for water-soluble Graphene, it is characterized in that: step C) described microwave reaction temperature is 80 ℃～120 ℃, and the microwave reaction time is 5min～1h.