JPS63114060A - Manufacture of paste for anode plate of nickel cadmium alkaline storage battery - Google Patents

Abstract

PURPOSE:To remarkably decrease the dispersion of the viscosity of the paste by kneading CdO powder, Ni powder, and EG, then adding PVA powder to the mixture. CONSTITUTION:The total amount of EG is put into a kneading container, then CdO powder, Ni powder, and CF is mixed, and the mixture is kneaded at the first speed (29rpm) for about 10 minutes. PVA powder is mixed to the kneaded mixture, and the mixture is kneaded at the same speed for about 10 minutes. The mixture is kneaded again at the fourth speed (90rpm) for 4 hours and 40 minutes. The pressure within the container is reduced after one hour kneading to 40-50mmHg. Thereby, the dispersion of the viscosity of the paste obtained is remarkably decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a nickel-cadmium alkaline storage battery using a paste-type cathode plate, and includes cadmium oxide (hereinafter referred to as "cdoJ") powder as an active material and polyvinyl alcohol (hereinafter referred to as "cdoJ") as an adhesive. The present invention relates to an improvement in a method for producing a paste made by kneading powder [hereinafter referred to as "PVAJ"], ethylene glycol (hereinafter referred to as "EGj"), and the like as a solvent.

Conventional Technology There is a strong demand for higher capacity in recent nickel-cadmium alkaline storage batteries, especially sealed cylindrical nickel-cadmium alkaline storage batteries, and to meet this demand, so-called paste-type nickel-cadmium alkaline storage batteries have been developed. being developed. This battery uses a cathode plate made by applying OdO powder, the active material, in a paste form to a core material and drying it, which retains the active material better than the sintered electrode plate that has been widely used in the past. Because it does not have a nickel (hereinafter referred to as JNij) sintered body,
The feature is that even if the thickness, width, and length are the same, the electrode plate can contain a correspondingly larger amount of active material. The paste method is an extremely useful method for cathode plates, which must contain more than twice as much active material (in terms of lightning and air volume) as normal anode plates, and meets the world's need for higher capacity. It can be said that this technology is indispensable to meet these demands.

By the way, in manufacturing a paste type cathode plate, it goes without saying that its composition and crosstalk method are extremely important. We have conducted various studies regarding these points. For example, 100 parts of OdO powder, 15 parts of Ni powder,
part, PVA powder 0.5 part, OF (cut fiber) 0.
7 parts of EG and 24 parts of EG (weight ratio) are used as raw materials, and these are usually put into practical use. Initially, we tried a method in which PVA was pre-dissolved in EG and this was mixed with OdO powder, Ni powder, etc. as a mixing solution, but this method caused gelation of PVA and the resulting paste was difficult to store. I was faced with the problem that the paint solidified inside and could not be applied to the core material, and it was very difficult to find an effective solution. The above-mentioned room temperature process is a technology that solves this problem, and the key point of this technology is that PVA, which is necessary to ensure the strength of the active material layer of the resulting electrode plate, is dissolved in the drying stage after applying the paste. The point is that it should not be dissolved as much as possible during crosstalk. For this reason, kneading is performed at around room temperature, but in reality, a certain amount of P
If VA is not dissolved during mixing, the paste itself may not have sufficient viscosity, so the paste temperature during kneading must be controlled so that it is at least 20°C and the maximum temperature is between 30 and 40"C. ing.

Problems to be Solved by the Invention Although we have manufactured paste-type cathode plates by the above-mentioned room-temperature process, this process is not completely free from problems. One of these problems is that some pastes have an extremely high line viscosity, that is, the viscosity of the paste at the end of kneading. -For example, with the paste composition mentioned above, the standard value of line viscosity is 32000±3000c.
ps or more than 100,000 cps appears once every 20 patches. If such a highly viscous material is used as is, the thickness and weight of the resulting electrode plates will vary, creating a major hindrance in producing batteries of constant quality. In actual work, EG is added and kneaded again for an appropriate period of time, but this kind of work is unfavorable in terms of productivity and work efficiency, and urgent improvements are needed. be.

Now, when kneading the paste using the above-mentioned room temperature process, the raw material powders, namely OdO powder, Ni powder, PVA powder, O
Mix F for a predetermined time without adding EG, leave the powder uniformly dispersed, and add EG to this.
was added to the so-called kneading process. When kneading is carried out in this manner, at the stage when the initial powder is wetted with EG, it becomes extremely elastic, like a rubber ball with sufficient air in it.

Naturally, at this time, the load from the kneading machine side is at its maximum, and the paste in this state is forcibly stirred by the mixer blades, causing the paste itself to deteriorate. causes a rapid rise in temperature. When the paste temperature was continuously monitored during kneading, it was 25-26°C at the start of kneading, but it was 10°C at the start of kneading.
At this time of the year, the temperature reaches 35-38°C. The period during which this rubber ball-like state is exhibited is about 10 to 15 degrees at most, and as the powder becomes sufficiently wet with EG, the state gradually changes, becoming a so-called paste-like state, and the load becomes smaller.

Now, to touch on the relationship between the linear viscosity and the amount of PVA dissolved in EG, when EG is extracted from a paste whose linear viscosity is within the standard value and the PVA concentration in EG is found to be 0. It is about .024. On the other hand, those exhibiting a significantly high viscosity as described above had a viscosity of 0.5 to 0.6, which clearly indicates that a large amount of PVA was dissolved. According to the results of investigating the relationship between the temperature of EG and the amount of PVA dissolved, it has been found that the solubility increases rapidly at temperatures above 50 to 60°C, and these results indicate that the line viscosity is abnormal. The reason for the increase in temperature is thought to be that the paste reached a higher temperature than normal for some reason during crosstalk, and as a result, a large amount of PVA melted.

It has been mentioned that in the room temperature process, it is important not to dissolve PVA more than necessary during kneading, but from this point of view, the above-mentioned kneading methods are problematic. The reason that there is always a period when the temperature rises rapidly during crosstalk is due to some reason; for example, a slight difference in the time after the EG is turned on until the crosstalk starts will affect the way the temperature rises, causing the PVA to become abnormal. This is because it is thought that there is inevitably an inherent opportunity for dissolution.

Means for Solving the Problems It has been found that the following kneading method is effective as a means for analyzing the above-mentioned problems. Needless to say, the point is to reduce the load during kneading as much as possible, and the specific means for doing so is: (1) Adding powder to the liquid.

■Components that have the effect of increasing viscosity, that is, P
VA or OF is not added from the beginning of crosstalk, but is added once a paste has been formed to some extent. ■Temperature control during kneading (
For example, the temperature and flow rate of the cooling water can be adjusted more precisely. Among these, the most effective one is (2), and when OdO powder and Ni powder are added to EG and kneaded, the EG wets these powders very well and forms a paste very easily. Even if PVA powder and OF, which are binders, are added to this, there is almost no region where the load increases significantly, which was observed in the conventional cross-wire method. Therefore, the paste temperature should not rise suddenly, and in fact, the result of monitoring the paste temperature shows that the temperature of the cooling water flowing into the water jacket of the kneading vessel is plus 6 to 7 degrees, as shown in Figure 1. It only goes up to C. (In the conventional method, the temperature rises by 10 to 12° C.) Effect: Variations in the viscosity of the finished paste can be suppressed, and electrode plates of stable quality can be produced.

Example Next, one embodiment of the present invention will be described.

Container volume is 110! A kneading machine (manufactured by Shinayo Seisakusho 110)
DMA-rr type), OdOura 50ky, Ni powder 7
．． 5kp, PVA powder 2501, CF 350 f%EG
A composition of 13.5 kg force was kneaded by the method according to the invention, and the variation in linear viscosity was compared with that of the conventional one. Details of the kneading according to the present invention are as follows. First, put the entire amount of EG into a kneading container, add OdO powder, Ni powder,
Inject the entire amount of OF and turn it to 10 in 1st gear (rotation speed 29 rpm).
Kneaded for a minute. Next, the entire amount of PVA powder was added thereto, and kneaded for 10 minutes at the first speed.

After this, change the crosstalk speed to 4th gear (90 rpm) for 4 hours 40 minutes.
Kneaded for a minute. During this time, the pressure inside the kneading container was reduced to 40 to 50 oaHg from 1 hour after the start of the mixing. On the other hand, to describe the conventional method of cross-talk, first put all the powder of the above weight into a container, mix for 30 minutes, then add EG, and mix at first speed (29 rpm) for 3 minutes.
Subsequently, the mixture was kneaded for 10 minutes at the third speed (6 lrpm), and then increased to the fourth speed (90 rpm) and kneaded for 4 hours and 47 minutes. From 20 minutes after the start of kneading, the pressure inside the mixed line container is 40 to 50.
■Reduce the pressure to Hg. The temperature of the cooling water is 2.
Control at 5±1°C.

Table 1 shows the variation in line viscosity when 50 batches of crosstalk were performed using the method described above.

Table 1 Effects of the Invention As is clear from Table 1 (by adopting the crosstalk method according to the present invention, the variation in line rise viscosity is significantly smaller than that of the conventional method, and the effect is extremely You can see that it's big.

[Brief explanation of the drawing]

FIG. 1 is a comparative curve diagram showing changes in paste temperature during kneading according to the method of the present invention and the conventional method.

Claims (1)

[Claims] When kneading cadmium oxide powder, nickel powder, polyvinyl alcohol powder, etc. and ethylene glycol to make a paste, the cadmium oxide powder, nickel powder, etc. and ethylene glycol are kneaded in advance, and then the binder polyvinyl alcohol is mixed. A method for producing a paste for a cathode plate of a nickel-cadmium alkaline storage battery, which comprises adding powder.