CN1023820C - Process for production of expandable graphite - Google Patents

Abstract

The present invention provides a process for the preparation of expandable graphite. In the process, a used apparatus comprises an electrochemical reaction trough; electrochemical solution and an electrode are filled in the trough; a frame prepared from a permeation plate is filled on one side near an anode; graphite to be treated is filled in the frame; a cathode plate and an anode plate are parallel; the rate of plate spacing to the dimension of the short edge lines of the cathode plate and the anode plate is smaller than 0.35. pulse current is led in the process for oxidizing the anode. The present invention simplifies a technology, enhances the quality, and saves electric energy.

Description

Process for production of expandable graphite

The present invention relates to method for making expansible graphite.

Natural graphite is the netted plane of a carbon atom hexagonal overlay structure, a little less than the interlayer bonding force.With manual method can insert foreign atom, ion, molecule in graphite layers, it combines with carbon atom and forms compound between graphite layers.If this intercalation compound belongs to heating and can decompose, moment becomes gas and loss, can produce 10～400 times expansion on graphite crystal C direction of principal axis, so be called expansible black lead.With it is raw material, makes soft graphite, can do sealing material or shielding material etc.

Up to now, the manufacturing of expansible black lead is except that traditional chemical process, also developed electrochemical method, as the Japanese Patent spy open clear 55-62807 number disclose, natural graphite is inserted in the electrolytic bath, by the logical direct current of two electrodes, carry out anodic oxidation treatment, with the reversal of current energising, carry out cathodic reduction and handle then, after repeated multiple times is carried out above-mentioned oxidation-reduction processing, graphite is taken out washing and drying, can obtain expansible black lead.In similar approach, 0.1～100Hz ac process is led in the employing that has, and replaces above-mentioned cathodic reduction to handle, the requirement that has add depress or whipped state under carry out anodic oxidation treatment, what have also will make electrode with the platinum silk screen.

Above-mentioned existing manufacture method has following shortcoming:

(1). need logical reversible circulation carry out cathodic reduction after the anodic oxidation, make the equipment complexity, and also during cathodic reduction, very easy polarization, thereby technology difficulty is big.

(2). increase and stir and pressurizing device, increased the difficulty of cost and technology.

Purpose of the present invention just is, a kind of manufacture method of expansible black lead is provided, and is guaranteeing under the product quality premise that simplified apparatus is simplified technology greatly.

In order to achieve the above object, the method for making expansible graphite that proposes among the present invention comprises the following steps:

1. in filling the electrochemical reaction groove of electrolytic solution, proximal pole anomaly column electrode plate is set, to form in a big way electrochemical field uniformly;

2. natural graphite is put into the permeable barrier frame, made the dividing plate frame be in electrochemical reaction groove anode side;

3. pass to positive pulse electric current or assembled pulse electric current, its frequency is 50-4000HZ, and dutycycle is 10-50%, and the negative pulse proportion is less than 10% in the assembled pulse;

4. graphite is taken out washing, drying.

The expanding graphite made device that uses among the present invention, form by following several parts:

The electrochemical reaction groove of inset solution is housed; Negative electrode, the anode electrode compatible with above-mentioned inset solution are housed in the groove; In anode side the permeable frame of above-mentioned solution is housed, pending natural graphite is housed in the frame, two electrodes are parallel.

Utilize above-mentioned device, mainly be because shortened interpole gap relatively, add the relatively large-area battery lead plate of employing, between two-plate, formed uniform electrochemical field in a big way, in this electrochemical field, make all pending graphite particles all have the reaction conditions that is equal to, speed of response is identical.This just provides good precondition for simplifying technology, for example, there is no need by stirring, and technologies such as pressurization are improved the homogenizing condition of particle reaction.This can not only simplify the difficulty of technology and operation greatly, and can ensure the quality of products, and obtains that quality is good, the uniform expansible black lead of performance.

Utilize method of the present invention, promptly promote blood circulation and graphite is carried out anodic oxidation treatment, be not prone to polarization phenomena towards electric current, this is because in galvanic gaps in the time, impurity can overflow, return molten, so the outer adsorptive capacity of graphite is few, effect in addition of bringing is to make the expansible black lead better quality of making, sulphur and volatile content are lower, because the momentary current of pulsed current is big, electrochemical reaction (insertion) efficient height effectively inserts many, can significantly reduce the content of sulphur and volatile matter, and save electric energy.

Introduce an embodiment below:

In the middle of the electrochemical reaction groove, a planar anode plate of being made by stainless steel is housed, near reactive tank two walls two negative plates of being made by stainless material are arranged in the positive plate both sides, it is parallel relative with above-mentioned positive plate, and the area of each pole plate is 25 * 20cm ², anode and cathode spacing are 5cm.Inject sulphuric acid soln in reactive tank, concentration is higher for well, can adopt 14～18.2 mol.This practicality is executed and is selected 18.2 mol in the example.

1kg puts into the frame of being made by permeable separator with 599 pending natural flake graphites (being the LG50-90 of GB3518-83 regulation), then frame is inserted above-mentioned positive plate both sides, that is to say that positive plate inserts in the above-mentioned frame.Permeable separator is graphite to be isolated in the positive column and the impurity such as gas that produce in solution and the reaction are permeable, is worked out by plastic tape here.After said apparatus is ready, should lead to positive pulse electric current or the assembled pulse electric current of 50～4000HZ to pole plate, in the assembled pulse electric current, the negative pulse proportion is less than 10%.Here be 5%, the stacking factor of pulsed current is 10～50%, is 30% here.Logical in the present embodiment 500HZ pulsed current, peak current density is 35mA/cm ², stacking factor is 30%, handles 2 hours, and quite electric quantity density is 30A.hr/Kg, and the graphite after the processing is through washing, dry getting final product.

The expansible black lead quality of utilizing this method to make is good, as its volatile matter＜10%, S＜2.0%, allowance for expansion is 200ml/g in the time of 950 ℃, in addition, utilize this method Billy about 30% with the power saving of direct current anodic oxidation treatment, if reach and above-mentioned same allowance for expansion, need about 40A.hr/Kg electric quantity density with the direct current anodic oxidation treatment.

Claims (2)

1, a kind of manufacture method of expansible black lead is characterized in that this method comprises the following steps:

(1) in filling the electrochemical reaction groove of electrolytic solution, proximal pole anomaly column electrode plate is set;

(2) natural graphite is put into the permeable barrier frame, again the dividing plate frame is put into electrochemical cell near anode one side;

(3) logical frequency is 50-4000HZ, and pulse duty factor is that the pulsed current of 10-50% carries out anodic oxidation to graphite;

(4) graphite is taken out washing, drying.

2, a kind of manufacture method of expansible black lead is characterized in that this method comprises the following steps:

(1) in filling the electrochemical reaction groove of electrolytic solution, proximal pole anomaly column electrode plate is set;

(2) natural graphite is put into the permeable barrier frame, again the dividing plate frame is put into electrochemical cell near anode one side;

(3) logical assembled pulse electric current carries out anodic oxidation to graphite, and the shared ratio of this assembled pulse electric current negative pulse is less than 10%, and the stacking factor of pulse is 10-50%

(4) graphite is taken out washing, drying.