JPS624826B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in the sealing part of alkaline batteries such as silver batteries, mercury batteries, nickel cadmium batteries, alkaline manganese batteries, etc., and an object of the present invention is to improve leakage resistance. Conventionally, in this type of battery, the space between the gasket and the sealing plate is filled with a sealant such as asphalt pitch, fatty polyamide resin, low polymerization degree fluororesin, or polyisobutylene to prevent liquid from leaking from the contact surfaces mentioned above. It is proposed that. However, with the sealant mentioned above, deterioration occurs due to long-term contact with alkaline electrolyte under pressure or repeated thermal history from low to high temperatures, resulting in a decrease in the elasticity and water repellency of the sealant. Therefore, the effect of using a sealant was not sufficiently exerted, resulting in leakage. The present invention provides an alkaline battery that has a stable liquid-tight effect over a long period of time by filling the space between the gasket and the sealing plate with a sealant made of a mixture of high molecular weight polyfluoroalkoxyphosphazene and low molecular weight polyfluoroalkoxyphosphazene. It is something. Phosphazene is a compound in which nitrogen and phosphorus bonds are arranged alternately as a backbone. Phosphazene is a compound in which phosphorus pentachloride is dissolved in an organic solvent such as tetrachloroethane, chlorobenzole, or nitrobenzole.
A crystalline substance obtained by reacting this with ammonium chloride, represented by (PNCl ₂ ) _n (where m
is an integer of 3 or 4), if m is 3, use the following (1)
It has a cyclic structure as shown in . This easily undergoes ring-opening polymerization by heating, resulting in the following (2)
It is a polymer compound as shown in the formula and has rubber elasticity, but the bond between phosphorus and chlorine in the formula is extremely unstable, and because it absorbs moisture in the air and hydrolyzes it, it is used as a sealant for alkaline batteries. is inappropriate. Therefore, in the present invention, the polymer compound (2) includes, for example, CF ₃ ONa, CF ₃ CH ₂ ONa, HC ₂ F ₄ CH ₂ ONa,
A polyfluoroalkoxyphosphazene obtained by reacting one or more fluoroalkoxides such as HC ₃ F ₆ CH ₂ ONa, C ₆ H ₄ FOK, and C ₆ H ₄ CF ₃ OK was used as a sealant. Examples of their structural formulas are as follows, and they are a type of phosphazene polymer having a fluorinated hydrocarbon in the side chain. This polyfluoroalkoxyphosphazene is
For example, the phosphazene represented by the structural formula (1) is introduced into a glass tube, the tube is evacuated and sealed, and the polymer compound (2) is converted into one or two fluoroalkoxides by heating and polymerizing the tube. It is obtained by reacting the above and substituting the Cl group and fluoroalkoxide group of the polymer compound (2). The molecular weight of polyfluoroalkoxyphosphazene can be adjusted by the polymerization temperature at which the polymer compound (2) is produced by subjecting phosphazene to a heating polymerization reaction, and polyfluoroalkoxyphosphazene has a high molecular weight of about 3 x 10 ⁴ to 3 x 10 ⁶ . The polymerization temperature is about 230°C to 280°C, and the polymerization temperature is about 200°C to about 200°C for low molecular weight ones with a molecular weight of up to about 4 x ¹⁰³ .
Obtained at a temperature of 220°C. In this way, depending on the manufacturing conditions, the molecular weight is approximately 3×
A variety of compounds can be obtained, ranging from those with a high molecular weight of about 10 ⁴ to 3×10 ⁶ to those with a low molecular weight of about 4×10 ³ . High-molecular-weight polyfluoroalkoxyphosphazenes do not lose their water repellency even after repeated thermal cycles from low to high temperatures, and they do not deteriorate at all even when immersed in high-concentration alkaline solutions under pressure for long periods of time. Although it is chemically extremely stable, it does not have sufficient flexibility or elongation. On the other hand, low molecular weight polyfluoroalkoxyphosphazenes exhibit high elastic modulus and elongation, and adhere well to minute irregularities formed on the surfaces of gaskets and sealing plates. In comparison, it has the disadvantage that water repellency slightly decreases when the thermal history is repeated from low to high temperatures, and furthermore, when immersed in a high concentration alkaline solution under pressure for a long period of time, some deterioration occurs. Therefore, by using a mixture of high molecular weight polyfluoroalkoxyphosphazene and low molecular weight polyfluoroalkoxyphosphazene as a sealant, the drawbacks of each can be compensated for and the excellent properties of both can be selectively exhibited. can do. Note that organic liquids such as ketones, esters, and tetrahydrofuran are used as the solvent for the polyfluoroalkoxyphosphazene according to the present invention. Next, an embodiment of the present invention will be described with reference to FIG. A circle is formed by pressure molding a mixed powder of anode active material such as silver oxide or mercury oxide and a conductive agent such as phosphorous graphite or acetylene black, and a metal pedestal 1 having an L-shaped cross section is integrally attached to the periphery. A plate-shaped anode 2 is inserted into the bottom of a battery container 3, which is made of a nickel-plated iron can and also serves as an anode terminal. A predetermined amount of alkaline electrolyte is injected into the bottom of the battery container 3 in advance, and when the anode 2 is inserted, the electrolyte permeates into the pores of the anode 2 and wets the entire anode. On the anode 2 are a blocking membrane 4 made of a microporous polyolefin film graft-polymerized with acrylic acid or methacrylic acid, a semipermeable membrane 5 made of cellophane or polyvinyl alcohol film, and a nonwoven fabric of polypropylene fiber, vinylon fiber, and viscose rayon. Absorbent papers 6 made of fiber-mixed paper or the like are placed one after another. A hanging part 8 having a U-shaped or V-shaped cross section is formed at the periphery of the sealing plate 7 which also serves as a cathode terminal. A mixture of a high molecular weight polyfluoroalkoxyphosphazene having a molecular weight of ×10 ⁴ to 3 × 10 ⁶ and a low molecular weight polyfluoroalkoxyphosphazene having a molecular weight of up to about 4 × 10 ³ dissolved in an organic solvent is applied and dried. A continuous sealant coating 9 is formed. A gasket 10 made of synthetic resin such as polyethylene, polypropylene, polyamide, etc. and having an L-shaped cross section is fitted on the outside of the hanging part 8, and amalgamated zinc powder and polyacrylic acid salt are fitted on the inside of the sealing plate 7. The cathode material 11 is filled with a mixture of an alkaline electrolyte gelled with a gelling agent such as the following. The sealing plate 7 and gasket 10 are fitted into the open end 12 of the battery container 3, and the open end 12 is squeezed inward to compress the gasket 10 and exert a high contact pressure. The edge edge 13 of the sealing plate 7 facing upward so as to face the sealing plate 12 is bitten into the gasket 10 through the sealant coating 9 to assemble the button-type alkaline battery. The alkaline battery of the present invention shown in Figure 1 and the same type of alkaline battery using a conventional sealant were tested at 35
The following table shows the leakage rate when stored at ℃ and 80% relative humidity. The battery shown in the table was applied to a battery having the structure shown in FIG. 1, in which the space between the gasket and the sealing plate was filled with a sealant.

【table】

[Table] As is clear from this table, the alkaline battery according to the present invention has excellent leakage resistance. A preferred mixing ratio of low molecular weight polyfluoroalkoxyphosphazenes is about 5-60% by weight, more preferably about 10-30% by weight. It is also conceivable to use a composite membrane sealant instead of the mixed sealant, but this is not preferable since it requires at least two membrane formation steps to form a composite membrane, making the work complicated.

[Brief explanation of the drawing]

FIG. 1 is an overall sectional view of a button-type alkaline battery according to an embodiment of the present invention. 3...Battery container, 7...Sealing plate, 9...Sealant, 1
0...Gasket.

Claims (1)

[Claims] 1. An alkaline battery characterized in that the space between the gasket and the sealing plate is filled with a sealant made of a mixture of high molecular weight polyfluoroalkoxyphosphazene and low molecular weight polyfluoroalkoxyphosphazene.