JP2015115102A - Recovery method of powder in paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of powders in a paste in which an active material alloy is separated and recovered in a powder state in an active material paste from the active material paste discharged as a waste in a battery manufacturing step.SOLUTION: The recovery method of powders by filtration and separation from a battery paste containing powders and an organic polymer thickener includes a step of reducing molecular weight of the organic polymer thickener before the filtration and separation step.

Description

  The present invention relates to recycling of battery materials and the like containing rare metals, and a method for recovering powder in paste by recovering powder by filtration separation of battery paste containing powder and organic polymer thickener. It is about.

  Recent mass production, mass consumption, and mass disposal economic activities have caused environmental problems on a global scale such as resource depletion or global warming. Among them, industrial waste, which is one of the causes of environmental destruction, contains a variety of rare metals. Recycling these rare metals for recycling is not only environmental conservation but also economical. This is also very meaningful from the viewpoint of.

  Nickel metal hydride secondary batteries are used in batteries for electric vehicles, mobile phones, and the like, and the demand has rapidly increased. Since nickel-metal hydride secondary batteries contain rare metals such as neodymium as the negative electrode active material, it is not possible to collect waste metal from nickel-metal hydride secondary batteries, separate rare metal materials such as neodymium, and reuse them. Very important.

  In the manufacturing process of nickel-metal hydride secondary batteries, a large amount of waste of active material paste is generated in the source process for manufacturing the electrode plate. In particular, the separation and recovery of active material alloys containing rare metals, Reuse of secondary batteries as raw materials is indispensable both in terms of environment and economy.

  Patent Document 1 proposes a method of separating and recovering an active material alloy from an active material paste discharged as waste in a battery manufacturing process. This Patent Document 1 proposes a method in which an inorganic flocculant is mixed with an active material paste discharged as a waste to make an active material alloy into an agglomerate, followed by filtration and separation.

JP 2013-41698 A

  In the method of separating and recovering the active material alloy from the active material paste discharged as waste in the conventional battery manufacturing process of Patent Document 1, an inorganic flocculant is mixed, and the active material alloy is aggregated for filtration separation. By doing so, the active material alloy and the thickener can be separated efficiently.

  However, since the inorganic flocculant is mixed as a foreign substance in the recovered active material alloy, a refining process is required to reuse the recovered active material alloy as the raw material of the battery, which is sufficient for both environmental and economic reasons. The effect is not obtained.

  In view of the above circumstances, the present invention provides a powder recovery method in a paste in which an active material alloy is separated and recovered in a powder state in the active material paste from the active material paste discharged as waste in the battery manufacturing process. The purpose is to provide.

  In order to achieve the above object, the present invention is configured as follows.

According to the method for recovering powder in the paste according to the first aspect of the present invention, the organic polymer system increase of the battery paste is performed by stirring the battery paste containing the powder and the organic polymer system thickener. Reduce the molecular weight of the adhesive,
Next, the battery paste having a reduced molecular weight of the organic polymer thickener is filtered to separate the powder from the organic polymer thickener.

  According to the method for recovering powder in the paste according to the second aspect of the present invention, in the first aspect, in the step of reducing the molecular weight of the organic polymer thickener, the organic polymer increase after the stirring is performed. The battery paste is agitated so that the molecular weight of the adhesive decreases to ½ or less of the molecular weight before agitation.

  According to the method for recovering powder in the paste according to the third aspect of the present invention, in the first or second aspect, in the step of reducing the molecular weight of the organic polymer thickener, And the battery paste is stirred by rotating the stirring blade at a linear velocity of 6 m / sec or more at the tip of the stirring blade.

  According to the method for recovering powder in the paste according to the fourth aspect of the present invention, in the first or second aspect, in the step of reducing the molecular weight of the organic polymer thickener, the stirrer with the stirring blades The stirring time for stirring the battery paste by rotating the stirring blades using is 15 minutes or more.

  According to the method for recovering powder in the paste according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the organic polymer thickener is a water-soluble cellulose material. It is characterized by.

  According to the method for recovering powder in the paste according to the sixth aspect of the present invention, in any one of the first to fifth aspects, the powder includes at least a metal material.

  According to the above aspect of the present invention, the powder from the battery paste containing the powder and the organic polymer thickener is reduced by reducing the molecular weight of the organic polymer thickener before the filtration separation step. Can be separated by filtration. As a result, the collected powder can be reused as a raw material of the battery simply by performing a simple post-treatment such as washing or drying after the filtration and separation.

The block diagram of the filtration apparatus in one Embodiment of this invention The figure which shows the relationship between the linear velocity of the stirring blade front-end | tip of the filtration apparatus of the said embodiment of this invention, and the average molecular weight of carboxymethylcellulose. The figure which shows the relationship between the stirring processing time of the said embodiment of this invention, and the average molecular weight of carboxymethylcellulose. Figure showing the results of tabulating the waste paste under various conditions by stirring, producing waste pastes with different CMC molecular weights, and filtration separation FIG. 1 is a tabular view showing the relationship between the processing time in the stirrer of the filtration device of FIG. 1 and the rate of change in the current value of the torque measuring device, the viscosity of waste paste, and the average molecular weight of CMC.

  The powder recovery method in the paste concerning one embodiment of the present invention is explained below.

  Generally, an active material paste for a battery is a slurry in which a solution containing an active material powder as a main component and a thickener is uniformly mixed and slurried, and a small amount of a binder or a conductive auxiliary agent is present. It has been added. For example, the active material powder includes misch metal, cobalt alloy, or graphite. As an example of the thickener, a water-soluble cellulose material or the like is used. Examples of the binder include styrene butadiene copolymer rubber. As an example of the conductive aid, carbon black or the like is used.

  Among these, the thickener is a water-soluble cellulosic material having an average molecular weight of about 100,000 for the purpose of uniformly dispersing the solid content in the paste and ensuring thixotropy and fluidity of the paste, for example, Carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or the like is used. Carboxymethylcellulose is a cellulose derivative and is a cellulose ether in which a carboxyl group is introduced into a hydroxyl group of cellulose. Similarly, methyl cellulose is a cellulose ether in which a methoxy group is introduced into a hydroxyl group of cellulose, and hydroxypropyl cellulose is a cellulose ether in which a hydroxypropyl group is introduced into a hydroxyl group of cellulose. These cellulose derivatives are structures in which the molecular skeleton is composed of cellulose and only some of the functional groups are different.

  As a method for separating and recovering active material powder from the active material paste discharged as waste in the battery manufacturing process, a filtration separation method can be easily devised. However, when a general-purpose filtration / separation filter is used, since the structure of the water-soluble cellulose material having an average molecular weight of about 100,000 is long, the separation filter is blocked and the active material powder cannot be separated and recovered. Further, in a coarse separation filter that is not clogged with a water-soluble cellulose material having an average molecular weight of about 100,000, the active material powder cannot pass through the separation filter because the active material powder passes through the separation filter.

  As a method for improving the separability of the active material powder from the active material paste, a method of reducing the average molecular weight of the thickener used during the production of the active material paste and preventing the separation filter from clogging can be conceived. However, this method cannot be employed because the desired thixotropy and fluidity of the active material paste cannot be ensured.

  Accordingly, as a result of various concepts and examinations of methods for separating and recovering active material powder from active material paste discharged as waste in the battery manufacturing process, water-soluble cellulose in the active material paste discharged as waste The inventor has conceived of reducing the molecular weight of the material. However, as conventional means for reducing the molecular weight of the water-soluble cellulosic material, hydrolysis with strong alkaline substances and degradation with enzymes such as cellulase are known. However, with these means, the recovered active material powder Since impurities are mixed into the body, it is not suitable for the purpose of reusing it as a raw material for batteries.

  Therefore, the present inventor has conducted various studies on means for reducing the molecular weight of the water-soluble cellulose-based material in which impurities are not mixed into the recovered active material powder.

  As a result, the present inventors have found that the molecular weight of the cellulosic material can be reduced by applying a strong shearing force to the active material paste discharged as waste in the battery manufacturing process. Then, after applying a strong shearing force to the active material paste discharged as waste in the battery manufacturing process and performing filtration separation using a general-purpose filtration filter, the active material powder does not clog the separation filter. The body could be separated and recovered.

  FIG. 1 shows the structure of a filtration device 1 used in a method for recovering powder in a paste according to an embodiment of the present invention.

  The filtration device 1 is attached to the tank 1a, the stirrer 3 for reducing the molecular weight of the thickener contained in the waste paste 2 in the tank 1a, and the rotating shaft 3a of the stirrer 3 to measure the viscosity of the waste paste 2 And a torque measuring device 4 that performs the same. A filtration filter unit 6 is connected to the lower end of the tank 1 a via an electromagnetic valve 7.

  In the stirrer 3, a plurality of stirring blades 5 are fixed to the lower part of the rotating shaft 3a inserted into the tank 1a. The rotary shaft 3a is connected to a driving device 3b such as a motor. The molecular weight of the thickener in the waste paste 2 in the tank 1a can be reduced by driving the driving device 3b and rotating the stirring blade 5 at a high speed integrally with the rotating shaft 3a. By reducing the molecular weight of the thickener in the waste paste 2, the tank 1a filtration filter unit 6 can separate and recover the powder. By opening the electromagnetic valve 7, the waste paste 2 moves from the tank 1a to the filtration filter unit 6 by its own weight.

  Examples of the embodiment of the present invention will be described below in detail with reference to the drawings.

(Example)
The misch metal powder was separated and recovered from the negative electrode paste (hereinafter referred to as “waste paste”) that remained in the piping or container of the negative electrode plate manufacturing process of the nickel metal hydride battery and was discharged as waste. In addition, the compounding ratio at the time of manufacture of a negative electrode paste is 70.7 weight% for misch metal powder (average particle diameter of 25 microns), and 0.6 weight% for carboxymethylcellulose (Daiichi Kogyo Seiyaku WS-A). Water is 28.3%, styrene butadiene copolymer rubber (JSR 2108) is 0.2%, and carbon black (Lion's carbon ECP600JD) is 0.2%.

  Using a stirrer with a stirring blade (manufactured by PRIMIX: model number RM), 1 L (liter ) About 500 cc of the waste paste placed in the resin beaker was stirred. The relationship between the linear velocity at the tip of the stirring blade at this time and the average molecular weight of the carboxymethyl cellulose (hereinafter referred to as “CMC”) is shown in FIG. The stirring time was 20 minutes. The average molecular weight of CMC is measured by diluting the waste paste to 2 volumes with pure water, and then removing a part of the liquid phase by centrifugation and using a dynamic light scattering photometer (DSL-8000 manufactured by Otsuka Electronics). The measurement was performed by the laser static scattering method. The subsequent measurement of the average molecular weight of CMC was carried out in the same manner.

  As shown in FIG. 2, the CMC molecular weight decreased as the linear velocity increased. Moreover, the influence of the outer diameter of the stirring blade was not recognized. Further, it was found that the molecular weight of CMC becomes 1/2 or less at a linear velocity of 6 m / sec or more.

  Next, using the stirrer with a stirring blade, about 500 cc of waste paste placed in a 1 L (liter) resin beaker was stirred at 2000 rpm, and the relationship between the processing time and the average molecular weight of the CMC Is shown in FIG.

  As shown in FIG. 3, the molecular weight of CMC is reduced by stirring treatment and becomes 1/2 in about 10 minutes. For 15 minutes or more, there is no sudden change in molecular weight even if the treatment time is extended, and in the case of 20 minutes or more Was confirmed to be almost constant.

  FIG. 4 is a diagram showing, in a tabular form, the results of stirring and treating a waste paste under various conditions to produce a waste paste having a different CMC molecular weight and performing a filtration and separation process. In addition, after the stirring treatment, the waste paste was diluted to 2 times volume with pure water to obtain a sample for filtration separation treatment. For comparison, a similar test was also performed on a comparative sample that was diluted to a double volume without stirring. As the filtration / separation apparatus, a PP double filter press (120 mm / 1 chamber type) manufactured by Nippon Filtration Equipment was used. In addition, 1 L of the sample was used in one test, and various air-permeable filters were replaced each time to check the clogging condition and separability of the filter, and evaluation was performed according to the following criteria.

  The filter clogging was evaluated as acceptable when a sample of about 1 L was completed in less than 5 minutes, and “◯” was shown in FIG. Further, the case where it took 5 minutes or more to complete the processing or the case where the separation was not completed due to the blockage was regarded as unacceptable, and “x” was shown in FIG. Regarding the separability, the filtrate was visually confirmed, and the case where the filtrate was transparent was regarded as acceptable, and “◯” was shown in FIG. The case where the filtrate was not changed from that before the treatment was regarded as unacceptable, and “XX” was shown in FIG. Further, the filtrate was changed from that before the treatment, but it was also rejected when it was still cloudy, and “x” was shown in FIG.

  As shown in FIG. 4, regarding the separability, it was found that the filter could not pass unless the air permeability of the filter was 108 cc / square cm or less per minute. In addition, in the case of a comparative sample not subjected to a stirring treatment and a sample having an average molecular weight of CMC of 81,000, clogging was rejected at 108 cc / square cm or less, and it was confirmed that good separation was not possible. In addition, it was confirmed that no clogging occurred in a sample having a CMC average molecular weight of 54,000 or less even when the air permeability of the filter was 108 cc / square cm or less per minute. For this reason, in order to surely achieve good separation, it is preferable to reduce the molecular weight of CMC to ½ or less of the comparative sample. In other words, this means that it is preferable to stir the molecular weight of CMC so that the molecular weight after stirring is reduced to 1/2 or less compared to the molecular weight before stirring.

  Also, from the results of FIG. 2 and FIG. 4, regarding the stirring conditions, when the linear velocity at the tip of the stirring blade is 6 m / sec or more, the molecular weight of CMC becomes ½ or less. Is preferably 6 m / sec or more.

  Further, from the results of FIG. 3, the stirring time is preferably 15 minutes or longer, which eliminates a rapid change in molecular weight.

  Furthermore, separation work was performed using the filtration device 1 for the waste paste. The stirring blade 5 of the stirrer 3 was processed at a rotational speed of 2000 rpm using a 50 mmφ one.

  Further, in FIG. 5, the relationship between the processing time (stirring time) in the stirrer 3, the rate of change of the current value of the torque measuring device 4, the viscosity of the waste paste, and the average molecular weight of CMC is shown in a tabular form. Indicated. The change rate (%) of the current value was (current value before processing−current value after processing) × 100 / (current value before processing).

  As the treatment time increased, the rate of change of the current value of the torque measuring device 4 increased, and the viscosity of the waste paste and the average molecular weight of CMC both decreased. Further, the rate of change of the current value of the torque measuring device 4, the viscosity of the waste paste and the average molecular weight of CMC are correlated, and the average molecular weight of CMC can be grasped by measuring the current value of the torque measuring device 4. I understood.

  In this embodiment, since the rate of change of the current value of the torque measuring device 4 becomes −53% 10 minutes after the start of the treatment, the stirrer 3 is stopped, the electromagnetic valve 7 is opened, and the waste paste is removed from the filtration filter unit. 6 for separation. At this time, a filter having an air permeability of 84 cc / square cm per minute was used. As a result, the separability was good and clogging did not occur. The molecular weight of CMC contained in the filtrate was 49,000.

  In this embodiment, detailed examples of nickel-metal hydride batteries have been described, but the present invention can also be applied to waste paste generated in the manufacturing process of other products such as fuel cells.

  In addition, it can be made to show the effect which each has by combining arbitrary embodiment or modification of the said various embodiment or modification suitably.

  According to the method for recovering powder in the paste according to the present invention, the powder can be separated from the battery paste containing the powder and the organic polymer thickener. As a result, the recovered powder can be reused as a raw material for batteries simply by applying simple post-treatment such as washing or drying after filtration separation, and the manufacturing process of other products such as fuel cells, not limited to nickel metal hydride batteries It can also be applied to waste paste generated in In addition, according to the method for recovering powder in the paste according to the present invention, a stirrer for reducing the molecular weight of the organic polymer thickener and a torque measuring device for measuring the viscosity of the battery paste are provided. A filtration device can be provided.

DESCRIPTION OF SYMBOLS 1 Filtration apparatus 1a Tank 2 Waste paste 3 Stirrer 3a Rotating shaft 3b Drive apparatus 4 Torque measuring instrument 5 Stirring blade 6 Filtration filter unit 7 Electromagnetic valve

Claims (6)

The molecular weight of the organic polymer thickener of the battery paste is reduced by stirring the battery paste containing the powder and the organic polymer thickener,
Next, a method for recovering a powder in a paste, wherein the battery paste having a reduced molecular weight of the organic polymer thickener is filtered to separate the powder and the organic polymer thickener.   In the step of reducing the molecular weight of the organic polymer thickener, the battery paste is adjusted so that the molecular weight of the organic polymer thickener after the stirring is reduced to ½ or less of the molecular weight before the stirring. The method for recovering powder in a paste according to claim 1, wherein stirring is performed.   In the step of reducing the molecular weight of the organic polymer thickener, the stirrer is rotated by using a stirrer with a stirrer blade and the linear velocity at the tip of the stirrer blade is 6 m / second or more. The method for recovering powder in a paste according to claim 1 or 2, wherein the paste is stirred.   In the step of reducing the molecular weight of the organic polymer thickener, the stirring time for stirring the battery paste by rotating the stirring blade using the stirrer with the stirring blade is 15 minutes or more, Item 4. A method for recovering powder in a paste according to Item 3.   The powder recovery method in the paste according to any one of claims 1 to 4, wherein the organic polymer thickener is a water-soluble cellulose material.   The powder recovery method in the paste according to any one of claims 1 to 5, wherein the powder includes at least a metal material.

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