JPS63224103A - Manufacture of current collector film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention maintains stable electrical resistance against temperature changes,
The present invention also relates to a method for producing a current collector film that has excellent chemical resistance and low contact resistance on the film surface.

[Prior art]

In general, thermoplastic resins are often used as insulators, and polyolefin resins in particular are used as insulating materials for electrical parts and wires. There are various methods for imparting electrical conductivity to these thermoplastic resins, depending on the electrical conductivity required for the product. Generally, carbon-based fillers are most commonly used because they have little change over time, are resistant to chemicals, and are relatively inexpensive.

On the other hand, as ICs become increasingly highly integrated and highly functional, and electronic equipment becomes smaller, each component built into the device is required to be lighter, thinner, and smaller. Many devices are equipped with built-in batteries as operating power sources, including backup power sources for IC memory elements, but there is also a strong demand for miniaturization of these batteries. but,
Since graphite sheets and conductive rubber sheets are used as collector electrode materials for these battery parts, there is a limit to how thin they can be.

In addition, commonly used carbon black does not have a sufficiently developed carbon structure, and when dispersed in a thermoplastic resin, the conductive path density is low, and the conductive path density decreases due to thermal expansion of the resin matrix due to temperature rise. The so-called PT, in which electrical resistance rapidly increases due to a rapid decrease in
Characteristic C appears. Since this phenomenon has a significant impact on battery performance, there has been a strong desire for a conductive film with stable electrical resistance against temperature changes.

Sheets and films are generally produced using an extrusion calender or a solution casting method, but these methods tend to form a skin layer with good fluidity on the surface of the normally produced sheets or films. Therefore, when sheeting a conductive resin composition highly loaded with conductive filler, the resin layer with extremely little conductive filler forms a skin layer, so even though high conductivity is expected from the composition, it is actually a skin layer. This results in a sheet or film with high contact resistance.

(Object of the invention) The present invention provides a current collector film that maintains stable electrical resistance at temperatures that cannot be reached with conventional current collector films, has excellent chemical resistance, and has low contact resistance on the film surface. As a result of our research, we have found that by selecting the type of carbon black and the type of matrix resin, we can not only obtain a conductive film that maintains stable electrical resistance over temperature, but also use the coextrusion method for film production. Based on this knowledge, we investigated various combinations and conditions for coextrusion. As a result,
The conductive filler can be exposed on the surface of the obtained conductive film, and the present invention has been completed.

[Structure of the invention]

The present invention has a particle size of 5 parts by weight based on 100 parts by weight of thermoplastic resin.
~50 μm, and the specific surface area (by nitrogen adsorption method) is 3
00-2000Td/g, DBP oil absorption 200-4
00ml/1009 carbon black from 20 to 2
A conductive resin composition containing 00 parts by weight is used as an intermediate layer, thermoplastic resin layers with good peelability are coextruded on both sides of the intermediate layer, and after cooling, the thermoplastic resin layers with good peelability on both sides are peeled off. This is a method for manufacturing a current collector film made of a conductive film.

Thermoplastic resins used in the present invention include polypropylene, polyethylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer.
Examples of the resins include polyolefin resins such as propylene copolymers, polystyrene resins, polyamides, polycarbonates, and fluororesins, or mixtures of two or more of them. However, from the viewpoint of chemical resistance and carbon dispersibility, polyolefin resins are preferred.

The carbon black of the present invention is a carbon black with a developed carbon structure that has a large effect of imparting electrical conductivity, and specifically, the particle size is set to 50 μm or less to increase the contact density during filling. Furthermore, in order to increase the conductive path density, carbon black having a specific surface area (nitrogen adsorption method) of 300yf/9 or more and a DBP oil absorption of 200rr11/100g or more is used.

The amount of carbon black added is 20 parts by weight or more. If the weight is less than 20 parts, not only the conductivity level required as a current collector film cannot be obtained, but also the PTC characteristic becomes noticeable.

〔Effect of the invention〕

By using the current collector film of the present invention, it can not only be used in high-temperature regions where conventional batteries cannot be used, but also large-sized batteries, and we are confident that it will greatly contribute to electronic devices. .

[Example] Polypropylene (Noprene Fl-11015 manufactured by Sumitomo Chemical >100 parts by weight) 1-Nesblack (#375
0 A conductive resin composition prepared by Mitsubishi Kasei with a specific surface area of 800 TIi/g and DBP oil absorption maximum of 200 Id/1009) to which 45 parts by weight was added and an anti-aging agent of 1 part by weight was used as the intermediate layer, and polystyrene (9M- 62 (manufactured by Sumitomo Chemical Industries) was coextruded and the polystyrene layer of the amphoteric layer was roughly peeled off to obtain a conductive film with a thickness of 50 μm.

Comparative Example 40 parts by weight of acetylene black (Denka Black Denki Kagaku, industrial product specific surface area 65TIt/g DBP oil absorption ti 250m/100g) and 1 part by weight of anti-aging agent were added to 100 parts by weight of polyethylene (Sumiyukisen F20B-1 manufactured by Sumitomo Chemical). Conductive films with a thickness of 50 μm were obtained from the conductive resin composition prepared in addition in the same manner as in the examples. The volume resistivity was measured by a four-terminal method, and the rate of change with respect to room temperature was determined. Table 1 shows the volume resistance at room temperature and the rate of change at 85°C.

Table 1

Claims (2)

[Claims] (1) Particle size is 5 to 100% by weight of thermoplastic resin
50 μm, and the specific surface area (nitrogen adsorption method) is 300-2
000m^2/g, DBP oil absorption is 200-400m
A conductive resin composition to which 20 to 200 parts by weight of carbon black of l/100g is added is used as an intermediate layer, and thermoplastic resin layers with good releasability are coextruded on both sides of the intermediate layer, and after cooling, a thermoplastic resin layer with good releasability on both sides is formed. A method for producing a current collector film comprising a conductive film obtained by peeling off a thermoplastic resin layer. (2) The method for producing a current collector film according to claim 1, wherein the thermoplastic resin is polyolefin-based.