CA2072784A1 - Method of producing zinc alloy powder for cell and alkaline cell with the zinc alloy powder - Google Patents
Method of producing zinc alloy powder for cell and alkaline cell with the zinc alloy powderInfo
- Publication number
- CA2072784A1 CA2072784A1 CA002072784A CA2072784A CA2072784A1 CA 2072784 A1 CA2072784 A1 CA 2072784A1 CA 002072784 A CA002072784 A CA 002072784A CA 2072784 A CA2072784 A CA 2072784A CA 2072784 A1 CA2072784 A1 CA 2072784A1
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- Prior art keywords
- zinc alloy
- alloy powder
- cell
- powder
- impurities
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/026—Spray drying of solutions or suspensions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
- B22F1/147—Making a dispersion
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/24—Alkaline accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/42—Alloys based on zinc
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/04—Cells with aqueous electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0002—Aqueous electrolytes
- H01M2300/0014—Alkaline electrolytes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Powder Metallurgy (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In order to clean a zinc alloy powder for an alkaline cell, the zinc ally powder is dispersed in water or an acid or alkaline aqueous solution used as a medium under agitation so that impurities which adhere to the surfaces of the zinc alloy powder are separated and removed as suspended substances. Magnetic impurities mixed in the zinc alloy powder are removed by magnet-ically sorting the powder before or after the treatment using a medium, thereby improving the cleaning circuit.
In order to clean a zinc alloy powder for an alkaline cell, the zinc ally powder is dispersed in water or an acid or alkaline aqueous solution used as a medium under agitation so that impurities which adhere to the surfaces of the zinc alloy powder are separated and removed as suspended substances. Magnetic impurities mixed in the zinc alloy powder are removed by magnet-ically sorting the powder before or after the treatment using a medium, thereby improving the cleaning circuit.
Description
207~78 B i~
The present invention relates to a method of oDe.
producing a zinc alloy powder for the tY~**h~ of an alkaline cell, and particularly to a method of removing impurities which adhere to a zinc allow powder. The zinc alloy po~der obtained by removing the impurities is used in an alkaline cell for improving the leaktightness, decreasing the scattering in cell performance and stabi-~10 lizing the quality of products.
Description of thc ncIatcd Art~
O~
An alkaline cell using zinc as _ active substance has the problem that an increase in the inter-nal pressure of the cell, which is caused by the genera-15 tion of hydrogen gas during storage of the cell, causes . .
the electrolyte to be outwardly e~ected, thereby deteriorating the~leaktightness thereof. In some cases there is~a danger of bringing about the breakage of the .
cell.
~ As a measure against the problem, an amalga-mated ~zinc powder to which mercùry is added for increas-ing;the hydrogen overvoltage of the surface of the zinc used as the ea~hod~ active substance. On the other hand, ;;
in the world-wide concern about the problem of environ-~.
~ .
The present invention relates to a method of oDe.
producing a zinc alloy powder for the tY~**h~ of an alkaline cell, and particularly to a method of removing impurities which adhere to a zinc allow powder. The zinc alloy po~der obtained by removing the impurities is used in an alkaline cell for improving the leaktightness, decreasing the scattering in cell performance and stabi-~10 lizing the quality of products.
Description of thc ncIatcd Art~
O~
An alkaline cell using zinc as _ active substance has the problem that an increase in the inter-nal pressure of the cell, which is caused by the genera-15 tion of hydrogen gas during storage of the cell, causes . .
the electrolyte to be outwardly e~ected, thereby deteriorating the~leaktightness thereof. In some cases there is~a danger of bringing about the breakage of the .
cell.
~ As a measure against the problem, an amalga-mated ~zinc powder to which mercùry is added for increas-ing;the hydrogen overvoltage of the surface of the zinc used as the ea~hod~ active substance. On the other hand, ;;
in the world-wide concern about the problem of environ-~.
~ .
2~72784 1 mental disruption by industrial products, there is strong demand for decreasing the amount of mercury contained in an alkaline cell or developing ~ cell without mercury.
With the social need as background r an approach has been made to decrease the amount of mercury contained in an alkaline cell or to develop a cell without mercury.
In addition, a technique of preventing the corrosion of zlnc alloy composition (JP-A-63-6749) and an inorganic or organic inhibitor having the function to increase an anticorrosion effect (JP-A-2-299150) has been proposed and published. Further, an attempt has been made to restrict the generation of hydrogen gas and to improve the discharge performance by decreasing the content of impurities in zinc ~JP-A-62-123653).
However, the above methods proposed could not obtain an alkaline cell with excellent corrosion resist-ancQ in which the scattering in cell performance is decreased, and the quality of products is stabilized at a high level, by using zinc alloy powder without mercury.
B~ zo~ The present invention hao bccn ne~ievcd to-ool~c thc abo~c pE~lcm~, an~ it-io a* objoat ef tho invcn~io ~ prorido a method of producing a zinc alloy o ~
powder without mercury for the c~thodc of an alkaline cell~in w~hich the corrosion resistance is improved by 2~5 restricting the~generation of hydrogen gas so that the leaktightness is ~mproved, and the scattering in the cell ;~ performance is decreased, whereby the quality o~ alkaline oell products without _ rcury can be stabilized.
207278~
--~ `
It was found that when a zinc alloy powder without mercury is used in an alkaline cell, the impuri-ties which adhere to the surfaces of the zinc alloy powder, particularly the iron impurities easily mixed therein in the process of producing the zinc alloy powder, significantly activate the corrosion reaction and increase the generation of hydrogen gas. It is also found that hydrogen gas is continuously generated from portions of the surfaces of the zinc alloy powder where traces of iron impurities are unevenly distributed.
These findings indicate that the generation of hydrogen gas, which is caused by corrosion of the zinc alloy powder, can be restricted by removing the impuri-ties adhering to the surfaces of the zinc alloy powder,thereby improving the corrosion resistance. This led to the achievement of the present invention.
The present invention comprises remowing as suspended substances the impurities which adhere to the surfaces of a zinc alloy powder by dispersing the ~inc alloy powder in water used as a medium under agitation.
A method of producing the zinc alloy powder generally used at the present time is an atomizing method. The method comprises the steps of melting and atomizing a desired zinc alloy to obtain a zinc alloy powder, classifying the resultant zinc alloy powder, and then adjusting the particle size distribution. Each of the steps is under an environment which allows iron 20~78~
1 impurities to adhere to the surfaces of the zinc allow powder. A method is thus generally employed in which the impurities mainly consisting of iron and mixed in the zinc alloy powder are magnetically removed.
However, although this method is effective for an iron metal, the method has the problem that impurities cannot be completely removed by magnetic sorting because some of iron oxides, iron hydroxides and stainless impurities have a low magnetic effect, and because such impurities frequently adhere as fine particles to the surfaces of the zinc alloy powder.
Particularly, in the zinc alloy powder without mercury, iron impurities significantly activate the corrosion reaction because mercury having excellent anticorrosion effect is absent, and the generation of hydrogen gas is increased. Iron oxides, iron hydroxides, stainless impurities and the like are thus also important factors which significantly activate the corrosion : .
reaction of the zinc alloy.
The inventors therefore found that the fine ron~lmpurities~which are easily mixed in a zinc alloy ~ ;
powder~in~the production process and which adhere to the surfaces of the zinc alloy powder can be effectively separated~and removed as suspended substances by a method 25~ (referred to as "decantation" hereinafter) of dispersing : ` :
the zinc alloy powder in water used as a medium under agitation, whereby the corrosion reaction of the zinc ; alloy powder without mercury can be restricted.
`
2 Q~ 2 r~
1 The corrosion resistance of the zinc alloy powder can be further improved by decantation using an acid or alkaline aqueous solution as a medium. It is supposed that this is because the function of the acid or alkaline aqueous solution to chemically polish the surfaces of the zinc alloy powder speeds -~p the separa-tion of impurities from the surfaces of the zinc alloy powder, and improves the removing effect of decantation.
It was also confirmed that magnetic sorting performed before or after the decantation treatment can further restrict the corrosion reaction of the zinc alloy B ~ tio~ b~ scR;leD by ~ e~ t~ ~ R~G~?~
n~I~r c~6e~IrTIo~l or T~Dn~WING3 Fig. 1 is a partially sectional front view ~` 15 showing a principal portion of a flotation apparatus for removing impurities fixed in a zinc alloy powder;
Fig. 2 is a schematic drawings showing a principal portion o~ a magnetic sorting apparatus having a magnetic pulley, and Fig. 3 is a partially sectional side view showing a princlpal portion of an alkaline dry cell.
~he production method of the present invention is described below.
~; 25 A zinc alloy powder used in the present invention is first obtained by a method, for example, 20~278~
1 comprising adding a predetermined metal to a zinc alloy melt and agitating the mixture to form a zinc alloy, atomizing the resultant alloy by compressed air to form a powder and then grading the powder by screening.
: 5 An example of the method of removing impurities mixed in the zinc alloy powder in accordance with the present invention is described below with reference to Fig. 1. The zinc `alloy powder and water in an amount of : 2 to 3 times the apparent volume of the powder are charged in a container 1 of the apparatus shown in Fig.
1. The zinc alloy powder is dispersed in the water in ~: the three-dimensional direction by the rotation of a horizontal ribbon blade 2, and the impurities which adhere to the surfaces of the powder suspended in an :upper:layer in the water in the state of being suspended.
The rotational speed of the ribbon blade 2 is decreased : to a level which causes no sedimentation of the suspended substances, and the container 1 is then inclined so that the suspended substances in the upper layer of the water : 20 : are~discharged through the discharge port 3 provided in -n~upper portion of the container 1. The impurities wwhi~ch adhere to the surfaces of the zinc alloy powder can be removed by repeating the above process according to demand.
::~ 25 ~ The thus-obtained zinc alloy powder is sub~ected to magnetic sorting by the apparatus shown in Fig. 2. The magnetic sorting method is described below.
The apparatus shown Ln Fig. 2 comprises a belt 2~72~8~
1 conveyor 12 provided with a magnetic pulley 11 havîng a magnet having strong magnetic force bonded to the surface thereof. When the zinc alloy powder 13 is moved on the belt conveyor 12, ferromagnetic substances 14 such as iron and the like which are mixed in the zinc alloy powder 13 or adhere to the surfaces thereof on the conveyor 12 in contact with the magnetic pulley 11 are moved while adhering to the magnetic pulley 11 through the belt and fall to a position substantially immediately below the magnetic pulley 11, as shown in Fig. 2. On the other hand, the zinc alloy powder 13 which is not ; ; affected by the magnet falls a distant position in the forward direction of the belt conveyor 12. The above principle and mechanism enable separation and division between the ferromagnetic substances such as iron and the like and the zinc alloy powder. The belt conveyor of the apparatus may be used ln a single stage or in combination - of several stages. This method permits the removal the impurities mainly consisting of metal iron mixed in the zinc alloy powder.
Although the decantation alone is of course ` effective for improving the corrosion resistance of the zinc alloy powder, the combination with the magnetic sortin~ is more effect1ve, and the combination of both ~processes may be repeated.
In the thus-obtained zinc alloy powder, the generation of hydrogen gas ls restricted, and the corrosion resistance is improved and stabilized even if ~72~
l it contains no mercury.
I When the zinc alloy powder without mercury is B
used as the 7h~x~active substance for an alkaline cell, iron impurities signficantly activate the corrosion reaction and increase the generation of hydrogen gas, as compared with a zinc alloy powder containing mercury.
However, it was found that the iron impurities which adhere to the surfaces of the zinc alloy powder and which are easily mixed therein in the production process have an adverse effect. In addition, since hydrogen gas is continuously generated from positions of the surfaces of the zinc alloy powder where traces of iron impurities are :: :
distributed, the effective removal of the impurities on the surfaces can restrict the generation of hydrogen gas, lmprove the leaktightness, decrease the scattering in the cell performance and stabilize the quality of alkaline cells without mercury.
Fig. 1 shows a flotatio~l apparatus comprising the container 1 which is charged with water or an acid or ~20 ~ alka;line aqueous solution as a medium for suspending the `g~z~inc~àlloy powder and the impuritLes which adhere to the surf~aces of the zinc alloy powder, the horizontal ribbon blade 2 for agitating the zinc alloy powder and water or an~acid~or alkaline aqueous solutionl and the discharge port 3 for discharging the suspended substances.
Fig. 2 shows a magnetic sorting apparatus comprising the belt conveyor 12 provided with the mag-netic pulley ll having a magnet having strong magnetic ~- 2072 ~8~
l force bonded to the surface thereof.
When the zinc alloy powder 13 moved on the belt conveyor 12 falls, the ferromagnetic substances 14 such as iron and the like which are mixed in the zinc alloy S powder 13 or adhere to the surfaces thereof are moved while adhering the magnetic pulley 11 through the belt and fall to a position substantially immediately below the magnetic pulley 11 shown in Fig. 2. The zinc alloy powder 13 which does not contain the ferromagnetic lO substances such as iron and the like adhering thereto falls to a distant position in the forward direction of the belt conveyor 12.
Fig. 3 is a sectional side view of an alkaline B cell using as oathod~ active substance the zinc alloy lS powder obtained in each of Examples 1 to 4 and Compara-tive Examples 1 and 2. In Fig. 3 reference n~neral ~
Ç~D~
J ~denotes a~_~n~e mix; reference numeral 22, ~ c~thodc~
re erence n~neral 23, a separator; reference numeral 24, 9 ~ 00~ R C~OO~
a ~a~do collector; reference numeral 25, ~n ~no~c 20 terminal cap; reference numeral 26, a metal case;
rèference n~ner~l a 7, an outer package case; reference numeral 28, a polysthylene resln sealing member for ~sealing the opening of the metal case 26; and reference ~; numeral 29, a bottom plate forming the-ea~h~ terminal.
.:
:
EXANPLE
Example 1:
0.05% by weight each of lead, indium and - g_ .
. .
- 20727~
1 bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted. The resultant melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classified by screening so that the particle size range is adjusted to 45 to 150 mesh. 500 Kg of the ~- thus-obtained zinc alloy powder was charged in the apparatus shown in Fig. 1, and was dispersed in water used as a medium for 15 minutes under agitation. After decantation was performed by the above-described process, the suspended substances obtained were filtrated off and then drled to obtain a zinc alloy powder.
~; Example 2:
0.05% by weight each of lead, indium and 15~ bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted. The resultant~
;~ melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classifled by screening so that the particle ~gize range is adjusted to 45 to 150 mesh. 500 Kg of the thus-obtained zinc alloy powder was charged in the appa-ratus shown in Fig. 1, and was dispersed in 2m dqueous hydrochloric acid solution at a concentration of 5~ by weight used as a medium~for lS minutes under agitation.
;~ ~` 25 ~After decantation was performed by the above-described .
process, the suspended substances obtained were subjected to the same water-washing treatment as the treatment 2~72~8~
1 using water as a medium, followed by filtration and drying, to obtain a zinc alloy powder.
Example 3:
A zinc alloy powder was obtained by the same method as that employed in Example 2 with the exception that an aqueous potassium hydroxide solution at a concentration of 10% by weight was used as a medium for decantation.
Example 4:
The zinc alloy powder obtained by the same method as that employed in Example 1 was subjected to . .
magnetic sorting using the apparatus shown in Fig. 2 to obtain a zinc alloy powder.
:: The zinc alloy powder obtained in each of 15~ Examples 1 to 4 and the suspended substances separated therefrom were sub~ected to analysis of the iron content :;: and a test of generation of hydrogen gas. The results : : .
: :obtained are shown in Table 1. The generation of h~ydrogen gas:was:tested by measuring the gas generation 20: speed (~l/g~day) at 60C using 10 g of each of the samples and as an electrolyte 5 ml bf 40~ by weight : potassium hydroxide aqueous solution which is saturated with zinc oxide.
.
, ~ .
;' - 11 -:
~ 2~7~7~
., ~ ~~ ~1~ 1 ~,,~,, ~1 ¦ H ¦ P ¦ N ~ I I ~ ~1 ., ~a ~
~ s~ Z Z Z ~ Z P~
u~ _ .
__ ~ ~:
.~ ~ _, ~m a) æ æ
O~ ~ I ~ ~ _ ~ ~ O U~ O U~ In O
~--_ _ ~ ~ :
~o ~ L i _ ,.~ , ' ,' : .
~ 20727~
1 Comparative Example 1:
0.05% by weight each of lead, indium and bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted in the same way as in Example 1. The resultant melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classified by screening so that the particle size range is adjusted to 45 to 150 mesh to obtain a sample.
Comparative Example 2:
The zinc alloy powder obtained by the same method as that employed in Comparative Example 1 was subjected to magnetic sorting using the apparatus shown in Fig~ 2 to obtain a zinc alloy powder.
; 15 The zinc alloy powders obtained in Comparative Examples 1 and 2 were subjected to analysis of the iron content and a test of generation of hydrogen gas. The .
~ results obtained are shown in Table 1.
.:
The results shown in Table 1 re~eal that the 20~ iron contents of all samples of the present invention obtained in Examples 1 to 4 are low, and the iron contents o~ the suspended substances sep~rated are high, as ~compared with those~of;the samples of Comparative Examples. This confirms the effect of decantation. The ~ : :
~ 25 use of an acid or alkaline aqueous solution in place of .: : :
water as a medium produces good results.
The results of Example 4 show that magnetic 2~7~7~
1 sorting performed after decantation produces good results, as compared with decantation only. On the other hand, as seen from the results of Comparative Example 2, magnetic sorting only does not produce good results, as compared with Examples of the invention. In Example 4, magnetic sorting treatment performed before decantation also produces the same effects.
The zinc alloy powder obtained in each of Examples 1 to 4 and Comparative Examples 1 and 2 was used as ~ active substance of the alkaline-manganese cell shown in Fig. 3, and the gas generation speed of the , the leaktightness of the cell and the open-circuit voltage characteristics were evaluated.
In the measurement of the gas generation speed of the clthod~ of each cell, partial discharge was per-formed to 25% at a discharge temperature of 20C and a constant resistance of 1 Q for a discharge duration to the final voltage of 0.9 V, and the gas generation speed t~l/Cell-day) during storage at 60C was measured. The results obtained are shown in Table 2.
The leaktightness of the cell was evaluated by a~method in which partial discharge was performed in the~
same way as that described above, and the number of leaks produced after storage at 60C for 2 months was visually 25 observed. The results obtained are shown in Table 2.
~: :
~ .
~7278 ~oo _ C" __ _ _ __ o ~ ~ O 0 O O ~ a~
o~ ~o~
~, _ a~ ~ ~ ~ :
. :
~_ I
~, ~ .,~c~P
o ~ ~ _ _ _ _ :
, ~ ~: p ~
~ ~ ~ P Z; H ~
__ __ _ ~
: â) ~ a~ ~ : ~ ~
3 ~ o; ~ ~ :
~ ~C~
_ ;~ ~ :~ _ .r _~
2~2~8~
1 In regard to the open-circuit voltage of each cell, the number of cells at a voltage of ~average - lO
mV) or less was measured in the initial stage and after storage at 20C for 3 months and shown as an index representing the degree of scattering in Table 2.
As is understood from the results shown in B P~~S
Table 2, the gas generation speeds of the ~K~ku~of the cells respectively using as e~athodc active substances the powders treated in Examples l to 4 of the invention are lower than those of Comparative Examples. The results of the leaktightness test show that all the samples of Examples 1 to 4 produce no leak after storage at 60C for 2 months and maintain practical leaktightness properties.
~While the samples of Comparative Example produce leak and 15~ cannot maintain practical leaktightness properties.
In regard to the open-circuit voltage of a cell, the numbers of cells at a voltage of (average - lO
mV~ or less which respectively use the powders of .
Examples and Comparative Examples are zero in the initial 20 ~stage. However, after storage at 20C for 3 months, the numbers in Comparative Examples 1 and 2 are 12 and 9, respectively, and~show~large scattering, while the numbers in Examples are zero. This indicates that the ;cells of Examples have small scattering and stable ~25 ~quality.
As described above, in the present invention, the impurities which adhere to the surfaces of the zinc alloy powder are removed by dispersing the powder in .
1 water used as a medium under agitation. It is thus possible to attempt to restrict the generation of hydrogen gas, improve the corrosion resistance and the leaktightness, decrease the scattering in performance of cells and stabilize the product quality even by using the ~ 0~
1~ zinc alloy powder without mercury as ~~ ~ active substance of an alkaline cell.
' ~ ~ '
With the social need as background r an approach has been made to decrease the amount of mercury contained in an alkaline cell or to develop a cell without mercury.
In addition, a technique of preventing the corrosion of zlnc alloy composition (JP-A-63-6749) and an inorganic or organic inhibitor having the function to increase an anticorrosion effect (JP-A-2-299150) has been proposed and published. Further, an attempt has been made to restrict the generation of hydrogen gas and to improve the discharge performance by decreasing the content of impurities in zinc ~JP-A-62-123653).
However, the above methods proposed could not obtain an alkaline cell with excellent corrosion resist-ancQ in which the scattering in cell performance is decreased, and the quality of products is stabilized at a high level, by using zinc alloy powder without mercury.
B~ zo~ The present invention hao bccn ne~ievcd to-ool~c thc abo~c pE~lcm~, an~ it-io a* objoat ef tho invcn~io ~ prorido a method of producing a zinc alloy o ~
powder without mercury for the c~thodc of an alkaline cell~in w~hich the corrosion resistance is improved by 2~5 restricting the~generation of hydrogen gas so that the leaktightness is ~mproved, and the scattering in the cell ;~ performance is decreased, whereby the quality o~ alkaline oell products without _ rcury can be stabilized.
207278~
--~ `
It was found that when a zinc alloy powder without mercury is used in an alkaline cell, the impuri-ties which adhere to the surfaces of the zinc alloy powder, particularly the iron impurities easily mixed therein in the process of producing the zinc alloy powder, significantly activate the corrosion reaction and increase the generation of hydrogen gas. It is also found that hydrogen gas is continuously generated from portions of the surfaces of the zinc alloy powder where traces of iron impurities are unevenly distributed.
These findings indicate that the generation of hydrogen gas, which is caused by corrosion of the zinc alloy powder, can be restricted by removing the impuri-ties adhering to the surfaces of the zinc alloy powder,thereby improving the corrosion resistance. This led to the achievement of the present invention.
The present invention comprises remowing as suspended substances the impurities which adhere to the surfaces of a zinc alloy powder by dispersing the ~inc alloy powder in water used as a medium under agitation.
A method of producing the zinc alloy powder generally used at the present time is an atomizing method. The method comprises the steps of melting and atomizing a desired zinc alloy to obtain a zinc alloy powder, classifying the resultant zinc alloy powder, and then adjusting the particle size distribution. Each of the steps is under an environment which allows iron 20~78~
1 impurities to adhere to the surfaces of the zinc allow powder. A method is thus generally employed in which the impurities mainly consisting of iron and mixed in the zinc alloy powder are magnetically removed.
However, although this method is effective for an iron metal, the method has the problem that impurities cannot be completely removed by magnetic sorting because some of iron oxides, iron hydroxides and stainless impurities have a low magnetic effect, and because such impurities frequently adhere as fine particles to the surfaces of the zinc alloy powder.
Particularly, in the zinc alloy powder without mercury, iron impurities significantly activate the corrosion reaction because mercury having excellent anticorrosion effect is absent, and the generation of hydrogen gas is increased. Iron oxides, iron hydroxides, stainless impurities and the like are thus also important factors which significantly activate the corrosion : .
reaction of the zinc alloy.
The inventors therefore found that the fine ron~lmpurities~which are easily mixed in a zinc alloy ~ ;
powder~in~the production process and which adhere to the surfaces of the zinc alloy powder can be effectively separated~and removed as suspended substances by a method 25~ (referred to as "decantation" hereinafter) of dispersing : ` :
the zinc alloy powder in water used as a medium under agitation, whereby the corrosion reaction of the zinc ; alloy powder without mercury can be restricted.
`
2 Q~ 2 r~
1 The corrosion resistance of the zinc alloy powder can be further improved by decantation using an acid or alkaline aqueous solution as a medium. It is supposed that this is because the function of the acid or alkaline aqueous solution to chemically polish the surfaces of the zinc alloy powder speeds -~p the separa-tion of impurities from the surfaces of the zinc alloy powder, and improves the removing effect of decantation.
It was also confirmed that magnetic sorting performed before or after the decantation treatment can further restrict the corrosion reaction of the zinc alloy B ~ tio~ b~ scR;leD by ~ e~ t~ ~ R~G~?~
n~I~r c~6e~IrTIo~l or T~Dn~WING3 Fig. 1 is a partially sectional front view ~` 15 showing a principal portion of a flotation apparatus for removing impurities fixed in a zinc alloy powder;
Fig. 2 is a schematic drawings showing a principal portion o~ a magnetic sorting apparatus having a magnetic pulley, and Fig. 3 is a partially sectional side view showing a princlpal portion of an alkaline dry cell.
~he production method of the present invention is described below.
~; 25 A zinc alloy powder used in the present invention is first obtained by a method, for example, 20~278~
1 comprising adding a predetermined metal to a zinc alloy melt and agitating the mixture to form a zinc alloy, atomizing the resultant alloy by compressed air to form a powder and then grading the powder by screening.
: 5 An example of the method of removing impurities mixed in the zinc alloy powder in accordance with the present invention is described below with reference to Fig. 1. The zinc `alloy powder and water in an amount of : 2 to 3 times the apparent volume of the powder are charged in a container 1 of the apparatus shown in Fig.
1. The zinc alloy powder is dispersed in the water in ~: the three-dimensional direction by the rotation of a horizontal ribbon blade 2, and the impurities which adhere to the surfaces of the powder suspended in an :upper:layer in the water in the state of being suspended.
The rotational speed of the ribbon blade 2 is decreased : to a level which causes no sedimentation of the suspended substances, and the container 1 is then inclined so that the suspended substances in the upper layer of the water : 20 : are~discharged through the discharge port 3 provided in -n~upper portion of the container 1. The impurities wwhi~ch adhere to the surfaces of the zinc alloy powder can be removed by repeating the above process according to demand.
::~ 25 ~ The thus-obtained zinc alloy powder is sub~ected to magnetic sorting by the apparatus shown in Fig. 2. The magnetic sorting method is described below.
The apparatus shown Ln Fig. 2 comprises a belt 2~72~8~
1 conveyor 12 provided with a magnetic pulley 11 havîng a magnet having strong magnetic force bonded to the surface thereof. When the zinc alloy powder 13 is moved on the belt conveyor 12, ferromagnetic substances 14 such as iron and the like which are mixed in the zinc alloy powder 13 or adhere to the surfaces thereof on the conveyor 12 in contact with the magnetic pulley 11 are moved while adhering to the magnetic pulley 11 through the belt and fall to a position substantially immediately below the magnetic pulley 11, as shown in Fig. 2. On the other hand, the zinc alloy powder 13 which is not ; ; affected by the magnet falls a distant position in the forward direction of the belt conveyor 12. The above principle and mechanism enable separation and division between the ferromagnetic substances such as iron and the like and the zinc alloy powder. The belt conveyor of the apparatus may be used ln a single stage or in combination - of several stages. This method permits the removal the impurities mainly consisting of metal iron mixed in the zinc alloy powder.
Although the decantation alone is of course ` effective for improving the corrosion resistance of the zinc alloy powder, the combination with the magnetic sortin~ is more effect1ve, and the combination of both ~processes may be repeated.
In the thus-obtained zinc alloy powder, the generation of hydrogen gas ls restricted, and the corrosion resistance is improved and stabilized even if ~72~
l it contains no mercury.
I When the zinc alloy powder without mercury is B
used as the 7h~x~active substance for an alkaline cell, iron impurities signficantly activate the corrosion reaction and increase the generation of hydrogen gas, as compared with a zinc alloy powder containing mercury.
However, it was found that the iron impurities which adhere to the surfaces of the zinc alloy powder and which are easily mixed therein in the production process have an adverse effect. In addition, since hydrogen gas is continuously generated from positions of the surfaces of the zinc alloy powder where traces of iron impurities are :: :
distributed, the effective removal of the impurities on the surfaces can restrict the generation of hydrogen gas, lmprove the leaktightness, decrease the scattering in the cell performance and stabilize the quality of alkaline cells without mercury.
Fig. 1 shows a flotatio~l apparatus comprising the container 1 which is charged with water or an acid or ~20 ~ alka;line aqueous solution as a medium for suspending the `g~z~inc~àlloy powder and the impuritLes which adhere to the surf~aces of the zinc alloy powder, the horizontal ribbon blade 2 for agitating the zinc alloy powder and water or an~acid~or alkaline aqueous solutionl and the discharge port 3 for discharging the suspended substances.
Fig. 2 shows a magnetic sorting apparatus comprising the belt conveyor 12 provided with the mag-netic pulley ll having a magnet having strong magnetic ~- 2072 ~8~
l force bonded to the surface thereof.
When the zinc alloy powder 13 moved on the belt conveyor 12 falls, the ferromagnetic substances 14 such as iron and the like which are mixed in the zinc alloy S powder 13 or adhere to the surfaces thereof are moved while adhering the magnetic pulley 11 through the belt and fall to a position substantially immediately below the magnetic pulley 11 shown in Fig. 2. The zinc alloy powder 13 which does not contain the ferromagnetic lO substances such as iron and the like adhering thereto falls to a distant position in the forward direction of the belt conveyor 12.
Fig. 3 is a sectional side view of an alkaline B cell using as oathod~ active substance the zinc alloy lS powder obtained in each of Examples 1 to 4 and Compara-tive Examples 1 and 2. In Fig. 3 reference n~neral ~
Ç~D~
J ~denotes a~_~n~e mix; reference numeral 22, ~ c~thodc~
re erence n~neral 23, a separator; reference numeral 24, 9 ~ 00~ R C~OO~
a ~a~do collector; reference numeral 25, ~n ~no~c 20 terminal cap; reference numeral 26, a metal case;
rèference n~ner~l a 7, an outer package case; reference numeral 28, a polysthylene resln sealing member for ~sealing the opening of the metal case 26; and reference ~; numeral 29, a bottom plate forming the-ea~h~ terminal.
.:
:
EXANPLE
Example 1:
0.05% by weight each of lead, indium and - g_ .
. .
- 20727~
1 bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted. The resultant melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classified by screening so that the particle size range is adjusted to 45 to 150 mesh. 500 Kg of the ~- thus-obtained zinc alloy powder was charged in the apparatus shown in Fig. 1, and was dispersed in water used as a medium for 15 minutes under agitation. After decantation was performed by the above-described process, the suspended substances obtained were filtrated off and then drled to obtain a zinc alloy powder.
~; Example 2:
0.05% by weight each of lead, indium and 15~ bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted. The resultant~
;~ melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classifled by screening so that the particle ~gize range is adjusted to 45 to 150 mesh. 500 Kg of the thus-obtained zinc alloy powder was charged in the appa-ratus shown in Fig. 1, and was dispersed in 2m dqueous hydrochloric acid solution at a concentration of 5~ by weight used as a medium~for lS minutes under agitation.
;~ ~` 25 ~After decantation was performed by the above-described .
process, the suspended substances obtained were subjected to the same water-washing treatment as the treatment 2~72~8~
1 using water as a medium, followed by filtration and drying, to obtain a zinc alloy powder.
Example 3:
A zinc alloy powder was obtained by the same method as that employed in Example 2 with the exception that an aqueous potassium hydroxide solution at a concentration of 10% by weight was used as a medium for decantation.
Example 4:
The zinc alloy powder obtained by the same method as that employed in Example 1 was subjected to . .
magnetic sorting using the apparatus shown in Fig. 2 to obtain a zinc alloy powder.
:: The zinc alloy powder obtained in each of 15~ Examples 1 to 4 and the suspended substances separated therefrom were sub~ected to analysis of the iron content :;: and a test of generation of hydrogen gas. The results : : .
: :obtained are shown in Table 1. The generation of h~ydrogen gas:was:tested by measuring the gas generation 20: speed (~l/g~day) at 60C using 10 g of each of the samples and as an electrolyte 5 ml bf 40~ by weight : potassium hydroxide aqueous solution which is saturated with zinc oxide.
.
, ~ .
;' - 11 -:
~ 2~7~7~
., ~ ~~ ~1~ 1 ~,,~,, ~1 ¦ H ¦ P ¦ N ~ I I ~ ~1 ., ~a ~
~ s~ Z Z Z ~ Z P~
u~ _ .
__ ~ ~:
.~ ~ _, ~m a) æ æ
O~ ~ I ~ ~ _ ~ ~ O U~ O U~ In O
~--_ _ ~ ~ :
~o ~ L i _ ,.~ , ' ,' : .
~ 20727~
1 Comparative Example 1:
0.05% by weight each of lead, indium and bismuth were added to a zinc base metal having purity of at least 99.97% and then uniformly melted in the same way as in Example 1. The resultant melt was atomized by compressed air, i.e., by a so-called atomizing method, to form a powder. The thus-obtained powder was classified by screening so that the particle size range is adjusted to 45 to 150 mesh to obtain a sample.
Comparative Example 2:
The zinc alloy powder obtained by the same method as that employed in Comparative Example 1 was subjected to magnetic sorting using the apparatus shown in Fig~ 2 to obtain a zinc alloy powder.
; 15 The zinc alloy powders obtained in Comparative Examples 1 and 2 were subjected to analysis of the iron content and a test of generation of hydrogen gas. The .
~ results obtained are shown in Table 1.
.:
The results shown in Table 1 re~eal that the 20~ iron contents of all samples of the present invention obtained in Examples 1 to 4 are low, and the iron contents o~ the suspended substances sep~rated are high, as ~compared with those~of;the samples of Comparative Examples. This confirms the effect of decantation. The ~ : :
~ 25 use of an acid or alkaline aqueous solution in place of .: : :
water as a medium produces good results.
The results of Example 4 show that magnetic 2~7~7~
1 sorting performed after decantation produces good results, as compared with decantation only. On the other hand, as seen from the results of Comparative Example 2, magnetic sorting only does not produce good results, as compared with Examples of the invention. In Example 4, magnetic sorting treatment performed before decantation also produces the same effects.
The zinc alloy powder obtained in each of Examples 1 to 4 and Comparative Examples 1 and 2 was used as ~ active substance of the alkaline-manganese cell shown in Fig. 3, and the gas generation speed of the , the leaktightness of the cell and the open-circuit voltage characteristics were evaluated.
In the measurement of the gas generation speed of the clthod~ of each cell, partial discharge was per-formed to 25% at a discharge temperature of 20C and a constant resistance of 1 Q for a discharge duration to the final voltage of 0.9 V, and the gas generation speed t~l/Cell-day) during storage at 60C was measured. The results obtained are shown in Table 2.
The leaktightness of the cell was evaluated by a~method in which partial discharge was performed in the~
same way as that described above, and the number of leaks produced after storage at 60C for 2 months was visually 25 observed. The results obtained are shown in Table 2.
~: :
~ .
~7278 ~oo _ C" __ _ _ __ o ~ ~ O 0 O O ~ a~
o~ ~o~
~, _ a~ ~ ~ ~ :
. :
~_ I
~, ~ .,~c~P
o ~ ~ _ _ _ _ :
, ~ ~: p ~
~ ~ ~ P Z; H ~
__ __ _ ~
: â) ~ a~ ~ : ~ ~
3 ~ o; ~ ~ :
~ ~C~
_ ;~ ~ :~ _ .r _~
2~2~8~
1 In regard to the open-circuit voltage of each cell, the number of cells at a voltage of ~average - lO
mV) or less was measured in the initial stage and after storage at 20C for 3 months and shown as an index representing the degree of scattering in Table 2.
As is understood from the results shown in B P~~S
Table 2, the gas generation speeds of the ~K~ku~of the cells respectively using as e~athodc active substances the powders treated in Examples l to 4 of the invention are lower than those of Comparative Examples. The results of the leaktightness test show that all the samples of Examples 1 to 4 produce no leak after storage at 60C for 2 months and maintain practical leaktightness properties.
~While the samples of Comparative Example produce leak and 15~ cannot maintain practical leaktightness properties.
In regard to the open-circuit voltage of a cell, the numbers of cells at a voltage of (average - lO
mV~ or less which respectively use the powders of .
Examples and Comparative Examples are zero in the initial 20 ~stage. However, after storage at 20C for 3 months, the numbers in Comparative Examples 1 and 2 are 12 and 9, respectively, and~show~large scattering, while the numbers in Examples are zero. This indicates that the ;cells of Examples have small scattering and stable ~25 ~quality.
As described above, in the present invention, the impurities which adhere to the surfaces of the zinc alloy powder are removed by dispersing the powder in .
1 water used as a medium under agitation. It is thus possible to attempt to restrict the generation of hydrogen gas, improve the corrosion resistance and the leaktightness, decrease the scattering in performance of cells and stabilize the product quality even by using the ~ 0~
1~ zinc alloy powder without mercury as ~~ ~ active substance of an alkaline cell.
' ~ ~ '
Claims (5)
1. A method of producing a zinc alloy powder for a cell comprising removing as suspended substances impuri-ties which adhere to the surfaces of a powder by dispers-ing said zinc alloy powder in water used as a medium under agitation.
2. A method of producing a zinc alloy powder for a cell comprising removing as suspended substances impuri-ties which adhere to the surfaces of a powder by dispers-ing said zinc alloy powder in an acid or alkaline aqueous solution used as a medium under agitation.
3. A method of producing a zinc alloy powder for a cell comprising removing magnetic impurities mixed in a zinc alloy powder by magnetic sorting, and then removing impurities which adhere to the surfaces of said zinc alloy powder by dispersing said powder in a dispersion medium under agitation.
4. A method of producing a zinc alloy powder for a cell comprising removing impurities which adhere to the surfaces of said zinc alloy powder by dispersing said powder in a dispersion medium under agitation, and then removing magnetic impurities mixed in said zinc alloy powder by magnetic sorting.
5. An alkaline cell comprising a zinc alloy powder for a cell according to any one of Claims 1 to 4.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3162657A JPH0513079A (en) | 1991-07-03 | 1991-07-03 | Method for producing zinc alloy powder for battery and alkaline battery using the zinc alloy powder |
| JP03-162657 | 1991-07-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2072784A1 true CA2072784A1 (en) | 1993-01-06 |
Family
ID=15758799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002072784A Abandoned CA2072784A1 (en) | 1991-07-03 | 1992-06-30 | Method of producing zinc alloy powder for cell and alkaline cell with the zinc alloy powder |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0521508A3 (en) |
| JP (1) | JPH0513079A (en) |
| KR (1) | KR960005809B1 (en) |
| AU (1) | AU639184B2 (en) |
| CA (1) | CA2072784A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2742927B1 (en) * | 1995-12-21 | 1998-03-06 | Leclanche Sa | WATERPROOF MINIATURE ALKALINE NON-MERCURY BATTERIES AND METHOD OF MANUFACTURE THEREOF |
| CN110434117A (en) * | 2019-08-06 | 2019-11-12 | 陈岩 | A kind of solid waste processing method for scrap iron recycling |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR525566A (en) * | 1919-10-24 | 1921-09-24 | Electrolyt Zinc Australasia | Finely Divided Zinc Processing Improvements |
| FR529905A (en) * | 1920-11-22 | 1921-12-09 | Rheinisch Nassauische Bergwerk | Process for producing zinc dust with a high metal zinc content |
| SE350770B (en) * | 1971-05-14 | 1972-11-06 | Hoeganaes Ab | |
| ZA886696B (en) * | 1987-09-11 | 1989-04-26 | Alcan Int Ltd | Method of separating metal alloy particles |
| KR950009282B1 (en) * | 1992-07-14 | 1995-08-18 | 현대전자산업주식회사 | Metal contact forming method |
-
1991
- 1991-07-03 JP JP3162657A patent/JPH0513079A/en active Pending
-
1992
- 1992-06-29 AU AU18657/92A patent/AU639184B2/en not_active Ceased
- 1992-06-30 CA CA002072784A patent/CA2072784A1/en not_active Abandoned
- 1992-07-02 KR KR1019920011741A patent/KR960005809B1/en not_active Expired - Fee Related
- 1992-07-02 EP EP19920111237 patent/EP0521508A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0521508A3 (en) | 1993-04-14 |
| KR930003455A (en) | 1993-02-24 |
| AU639184B2 (en) | 1993-07-15 |
| EP0521508A2 (en) | 1993-01-07 |
| AU1865792A (en) | 1993-01-07 |
| JPH0513079A (en) | 1993-01-22 |
| KR960005809B1 (en) | 1996-05-01 |
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| EEER | Examination request | ||
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