KR20060134155A - Aramid tissue material and electric/electronic component employing it - Google Patents

Abstract

An aramid tissue material composed of two components, aramid short fibers and fibrillated aramid, or these two components and aramid hybrid, characterized in that the following expressions (1) and (2)/are satisfied; [Internal resistance] (mum)=0.5 (sec/100 cm3) expression (2), wherein the [internal resistance] is a resistance being calculated according to the following expression (3) ; [Internal resistance] (mum)=[electric conductivity of electrolyte] /[electric conductivity when electrolyte is injected into tissue material] x [thickness of tissue material] (mum) formula (3).

Description

Aramid Leaf Material and Electric Electronic Component Employing It {Aramid Tissue Material and Electric / Electronic Component Employing It}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aramid leaf material useful as a separator for isolating conductive members in electrical and electronic parts and allowing ionic species such as electrolytes or ions to pass through, and electrical and electronic parts using the same. In particular, it is related with the aramid leaf material useful as a separator between electrodes, such as a capacitor, a capacitor, and a battery which uses lithium ion, sodium ion, ammonium ion, hydrogen ion, etc. as a carrier of an electric current.

As symbolized by recent advances in portable communication devices, high-speed information processing devices, and the like, small size, light weight, and high performance of electronic devices have shown remarkable developments. Among them, small-size, light-weight, high-capacity, high-performance batteries and capacitors that withstand long-term storage are expected to be high. In order to cope with this, the necessity of technology and quality development is increasing also with respect to a member which is a partition material between electrodes, for example.

Among the various characteristics required for the separator, it is recognized that the following three characteristic items are particularly important.

1) Good conductivity in the state of holding electrolyte,

2) high interelectrode shielding,

3) having mechanical strength.

Conventionally, a porous sheet formed by using a polyolefin-based polymer such as polyethylene or polypropylene (see Japanese Patent Laid-Open No. 63-273651), and a nonwoven fabric sheeted using polyolefin-based polymer fibers such as polyethylene and polypropylene (See Japanese Patent Laid-Open No. 2001-11761), nonwoven fabric sheeted with nylon fibers (see Japanese Patent Laid-Open No. 58-147956), and the like are widely used for the separator. Such a separator is wound up in one layer, multiple layers, or roll shape, and is used in a battery.

In addition, the member used for an electrode,

1) In the aluminum electrolytic capacitor, the aluminum foil electrode is etched,

2) In the electric double layer capacitor, a method such as using activated carbon as an electrode

High pores are achieved by producing fine pores in the surface and increasing the surface area.

These porous sheets and nonwoven fabrics have good physical properties as separators, but they are not necessarily sufficient to cope with the high capacity and high output required for electric vehicle capacitors, capacitors, and batteries.

In separators in electrical and electronic parts such as capacitors, capacitors, and batteries that require high capacity and high power,

1) Good conductivity in the state of holding electrolyte,

2) high interelectrode shielding,

3) having mechanical strength,

4) Chemically and electrochemically stable (heat resistance),

5) able to withstand high temperature drying (heat resistance)

It is necessary to simultaneously meet the five characteristics of.

In particular, shielding between electrodes, heat resistance,

1) Prevents short circuits between conductive members in electrical / electronic parts such as capacitors, capacitors, and batteries as driving power sources for electric vehicles, for example, using a large current in high capacity electrodes charged at high density,

2) It is considered to be very important in the sense of sufficiently drying the moisture in the fine pores of the electrode such as aluminum foil and activated carbon during the manufacturing process of the electrical and electronic components.

In view of such a situation, the present inventors have made intensive studies to develop a material for high heat-resistant separators that can withstand high currents due to high capacity and high output and withstand high temperature drying during the manufacturing process. As a result, the present invention has been completed. .

Thus, the present invention comprises two components of aramid short fibers and fibrillated aramid, or two components and aramid fibrids, which are useful as separators between conductive members of electrical and electronic components such as capacitors, capacitors, and batteries. It provides an aramid leaf material characterized in that.

In addition, the present invention provides the above-mentioned aramid leaf material, characterized in that to satisfy both the following equations (1) and (2).

[Internal Resistance] (µm) ≤ 250 (µm)

[Okenen type air permeability] (second / 100 cm ³ ) ≥0.5 (second / 100 cm ³ )

In the formula, [internal resistance value] is a resistance value calculated by the following equation (3).

[Internal Resistance] (µm) = [Electric Conductivity of Electrolyte] / [Electric Conductivity when Electrolyte is injected into the Foil Sheet] × [Thickness of Foil Sheet] (µm)

However, [the electrical conductivity when the electrolyte solution is injected into a foil material] is the electrical conductivity computed from the alternating current impedance measured between two electrodes in the state which injected electrolyte solution into the foil material.

The present invention also provides an electrical and electronic component such as a capacitor, a capacitor and a battery, wherein the aramid leaf material of the present invention is used as a separator between conductive members.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

(Aramid)

In the present invention, aramid means a linear polymer compound in which 60% or more of the amide bonds are directly bonded to an aromatic ring. As such aramid, for example, polymethaphenylene isophthalamide and copolymers thereof, polyparaphenylene terephthalamide and copolymers thereof, poly (paraphenylene) -copoly (3,4-diphenyl ether) terephthal Amides and the like. These aramids are industrially manufactured by the conventionally well-known interfacial polymerization method, solution polymerization method, etc. which used isophthalic acid chloride and metaphenylenediamine, for example, Although it can obtain as a commercial item, it is not limited to these. Of these aramids, polymethetylene isophthalamide is preferably used in view of having good molding processability, heat adhesiveness, flame retardancy, heat resistance and the like.

(Aramid Fibrid)

In the present invention, aramid fibrids are film-like aramid particles having papermaking properties and are also called aramid pulp (see Japanese Patent Publication No. 35-11851, Japanese Patent Publication No. 37-5752, and the like). .

It is widely known that aramid fibrids can be used as a raw material for papermaking by carrying out fiber defibration and beating treatment, similar to conventional wood pulp, and so-called beating treatment can be performed for the purpose of maintaining the quality suitable for papermaking. The beating treatment can be performed by a papermaking raw material processing device having a disc refiner, a beater, and other mechanical cutting action. In this operation, the shape change of the fibrid can be monitored by the degree of freedom test method (prinis) prescribed in Japanese Industrial Standard P8121.

In the present invention, the degree of freedom of the aramid fibrid after the beating treatment is preferably in the range of 10 to 300 cm ³ , particularly 10 to 80 cm ³ (Canadian Prinis). In fibrids having a degree of freedom greater than this range, there is a possibility that the strength of the aramid leaf material molded therefrom may decrease. On the other hand, in order to obtain a degree of freedom of less than 10 cm ³ , the utilization efficiency of the mechanical power to be input becomes small, the throughput per unit time is often small, and the micronization of fibrids proceeds excessively, so that the so-called binder function It is easy to cause degradation. Therefore, even if you want to obtain a degree of freedom of less than 10 cm ^{3 in} this way no particular advantage is confirmed.

About the use of this invention, it is preferable that the aramid fibrid exists in the range of 1.2 mm or less, especially 1.2-0.6 mm in weight average fiber length when it measures with the optical fiber length measuring apparatus after beating treatment. Here, as an optical fiber length measuring apparatus, measuring instruments, such as a fiber quality analyzer (OpTest Equipment Co., Ltd. make) and a Kayani-type measuring apparatus (Kaani Company make), can be used. In such an instrument, the fiber length and shape of the aramid fibrids passing through a certain optical path are individually observed and the measured fiber lengths are statistically processed, if the weight average fiber length of the aramid fibrids used exceeds 1 mm, Deterioration of the electrolyte absorbency, generation of partial non-impregnation of the electrolyte, and increase of internal resistance of electrical and electronic parts are likely to occur.

(Aramid short fiber)

Aramid short fibers are obtained by cutting fibers made of aramid as a raw material, and such fibers include, for example, "Teijin Conex (registered trademark)", "Technora (registered trademark)", and UNICHIKA of Teijin. In brand names such as "APEL (registered trademark)" of DuPont, "Nomex (registered trademark)" "Kevler (registered trademark)" of DuPont, "Towaron (registered trademark)" of Teijin Towaron Corporation Although what can be obtained is mentioned, it is not limited to these.

The short aramid fibers may preferably have a fineness in the range from 0.05 dtex to less than 25 dtex, in particular from 0.1 to 2 dtex. Here, fineness is defined as fiber weight in grams per 1000 m. Fibers having a fineness of less than 0.05 dtex are not preferable because they tend to cause agglomeration in the production by the wet method (to be described later), and fibers of 25 dtex or more are, for example, in the form of a round shape because of their excessively large fiber diameter. If it is 1.4 g / cm <^3> , when diameter is 45 microns or more, there exists a possibility that problems, such as a decrease of an aspect ratio, a reduction of a mechanical reinforcement effect, and the uniformity of an aramid leaf material, may arise. Here, poor uniformity of the aramid leaf material means that the distribution of the pore size is widened, and nonuniformity occurs in the mobility of the ionic species as described above.

The length of the aramid short fibers can be selected within the range of 1 mm or more and less than 50 mm, especially 2 to 10 mm. If the length of the short fiber is less than 1 mm, the mechanical properties of the aramid thin material is lowered, while for the 50 mm or more, "entanglement", "cohesion", etc. are liable to occur during the production of the aramid thin material in the wet method described later, and cause of defects. It is easy to be.

(Fibrillated Aramid)

Fibrillated aramid is fibrillated by applying shear force to aramid fibers, aramid fibrids, and the like, and the degree of freedom is 10 to 800 cm ³ , in particular 30 to 700 cm ³ (Canadian Prinis). It is preferable to be in a range. In fibrillated aramid having a degree of freedom greater than this range, there is a possibility that sufficient shielding between electrodes cannot be ensured. On the other hand, if it is desired to obtain a degree of freedom smaller than 10 cm ³ , since the miniaturization of the fibrillated aramid proceeds excessively, it is easy to cause a so-called deterioration of the binder function. Therefore, even if you want to obtain a degree of freedom of less than 10 cm ^{3 in} this way no particular advantage is confirmed.

The specific surface area of the fibrillated aramid is preferably at least 5 g / m ² , in particular from 6 to 20 g / m ² . If it is smaller than 5 g / m ² , the binder function is likely to be degraded. Further, the weight average fiber length can be selected within the range of 0.01 mm or more and less than 7 mm, in particular 0.3 to 3 mm. Fibrillated aramid having a weight average fiber length larger than this range may be poor in dispersibility at the time of initial wetting and may cause local defects such as fiber mass of aramid thin paper. On the other hand, if it is desired to obtain a weight average fiber length smaller than 0.01 mm, since the miniaturization of the fibrillated aramid proceeds too much, it is easy to cause a so-called deterioration of the binder function.

Specific examples of the fibrillated aramid include those available under trade names such as "Kevler Pulp" of DuPont, "Towaron Pulp" of Teijin Towaron, but are not limited to these.

(Aramid leaf material)

The aramid leaf material of the present invention is an aramid leaf material comprising two components of the aramid short fibers described above and fibrillated aramid, or the two components and aramid fibrid, wherein the leaf material is the following formula 1 And within the range that satisfies all 2, any aramid short fiber content, fibrillated aramid content, aramid fibrid content, basis weight and density (base weight / thickness), the content of the aramid short fibers Generally, it is preferable to exist in 20 to 80%, especially 30 to 70% of range. In the case where the thin leaf material contains more aramid short fibers than the above range, there is a possibility that the annealing becomes difficult because the binder component is insufficient. On the other hand, when it is less than 20%, the electrolyte absorption liquid absorptivity decreases, the partial non-electrolyte impregnation part arises, and also the internal resistance of an electrical / electronic component rises easily.

<Equation 1>

[Internal Resistance] (µm) ≤ 250 (µm)

<Equation 2>

[Okenen type air permeability] (second / 100 cm ³ ) ≥0.5 (second / 100 cm ³ )

Preferably

<Equation 1a>

[Internal Resistance] (µm) ≤ 230 (µm)

<Equation 2a>

[Ooken-style spectacle] (sec / 100 cm ³ ) ≥ 1 (sec / 100 cm ³ )

In the formula, [internal resistance value] is a resistance value calculated by the following equation (3).

<Equation 3>

[Internal Resistance] (µm) = [Electric Conductivity of Electrolyte] / [Electric Conductivity when Electrolyte is injected into the Foil Sheet] × [Thickness of Foil Sheet] (µm)

However, [the electrical conductivity when the electrolyte solution is injected into a foil material] is the electrical conductivity computed from the alternating current impedance measured between two electrodes in the state which injected electrolyte solution into the foil material.

About the content rate of components other than aramid short fiber, it is generally preferable to make content of fibrillated aramid more than content of aramid fibrid. When the content of aramid fibrid increases, it becomes easy to generate | occur | produce the electrolyte solution liquid absorptivity, the partial unimpregnation of electrolyte, and also raise the internal resistance of an electrical / electronic component.

It is also preferred that the aramid leaf material generally has a thickness in the range of 5 μm to 150 μm, in particular 5 μm to 60 μm. When the thickness is smaller than 5 mu m, the mechanical properties deteriorate, and the handleability such as shape maintenance as a separator or conveyance in the manufacturing process is likely to occur, while when it exceeds 150 mu m, it is easy to cause an increase in internal resistance. It becomes difficult to manufacture smaller, high-performance electrical and electronic components.

In addition, the aramid thin material may generally have a basis weight in the range of 5 to 150 g / m ² , in particular 5 to 50 g / m ² . When the basis weight is less than 5 g / m ² , the mechanical strength is insufficient to easily cause breakage during various handling in the parts manufacturing process such as electrolyte impregnation treatment or winding, while the base weight aramid thin leaf is larger than 150 g / m ^2. The ash tends to increase in thickness and decrease in impregnation and penetration of the electrolyte.

The density of the aramid thin material is a value calculated from the basis weight / thickness, and can usually take a value within the range of 0.1 to 1.2 g / m ³ , in particular 0.1 to 1.0 g / m ³ .

In addition, the aramid leaf material that does not satisfy the conditions of the formula (1) and 2,

(1) The internal resistance of electrical and electronic components becomes excessively high, which causes the operation of electrical and electronic components to be disturbed. (2) The problem of short-circuit and failure of shielding between electrodes is prevented when they are inserted and compressed between densely charged electrodes. There is a possibility to generate.

(Method for producing aramid leaf material)

In general, the aramid thin material of the present invention having the characteristics as described above is a mixture of the aramid short fibers and fibrillated aramid, or the aramid short fibers and fibrillated aramid and aramid fibrid in a desired ratio. It can manufacture by the method of post-sheeting. Specifically, for example, a method of dry blending the aramid short fibers and fibrillated aramid or the aramid short fibers and fibrillated aramid and aramid fibrid, and then forming a sheet using airflow; Aramid short fibers and fibrillated aramid or aramid short fibers and fibrillated aramid and aramid fibrid are dispersed and mixed in a liquid medium, and then discharged onto a liquid permeable support such as a net or a belt to form a sheet. Although the method of removing a liquid and drying etc. can be applied, the so-called wet-wetting method which uses water especially as a medium is especially preferable among these.

As a wet evaporation method, an aqueous slurry of a single, two or three component mixture containing at least aramid short fibers and fibrillated aramids, or aramid short fibers and fibrillated aramids and aramid fibrids, respectively, is fed to a paper machine. The method of winding up as a sheet | seat by performing dehydration, water squeeze, and a drying operation after dispersion is common. As the paper machine, a long paper machine, a long paper machine, an inclined paper machine, a composite paper machine combining them, and the like can be used. In the case of production in a composite paper machine, a composite sheet including a plurality of paper layers can be obtained by sheet molding and unifying slurry having different blending ratios. At the time of annealing, additives, such as a dispersibility improving agent, an antifoamer, and an intelligence enhancer, can be used as needed. In addition, other fibrous components (for example, polyphenylene sulfide fibers, polyether ether ketone fibers, cellulose fibers, PVA fibers, polyester fibers, acrylate fibers, liquid crystal polyester fibers, polyethylene naphthalate fibers, etc.) Organic fibers; inorganic fibers such as glass fibers, rock wool, asbestos, and boron fibers). When adding these other fibrous components, it is preferable that the compounding quantity shall be 10% or less based on the total weight of all the fiber components.

The aramid leaf material thus obtained can be improved in density and mechanical strength by, for example, hot pressing at high temperature and high pressure between a pair of flat plates or between metal rolls. The conditions of the hot pressure can be exemplified in the range of the temperature of 100 to 400 ° C and the linear pressure of 50 to 400 kg / cm, for example, when using a metal roll, but are not limited to these. It is also possible to simply pressurize at room temperature without applying a heating operation. A plurality of thin leaves may be laminated at the time of hot pressing. Said hot-pressure processing can also be performed in arbitrary order in multiple times.

In order to further increase the strength of the aramid leaf material of the present invention, it may be used in a state in which it is laminated with another known separator (for example, a polyolefin microporous membrane) and a known method (for example, the above-mentioned hot-pressure working).

The aramid leaf material of the present invention is (1) having excellent properties such as heat resistance and flame retardancy, (2) excellent in the holding function of the electrolyte derived from the pore structure, (3) specific gravity of the aramid is small and lightweight about 1.4 It can be used suitably as a separator between electrically conductive members of an electrical / electronic component for the reason of being.

In this way, electrical and electronic components such as capacitors, capacitors, and batteries produced by using the aramid leaf material of the present invention as a separator between conductive members have high shielding properties between electrodes and maintain safety, and are inherently hybrid due to high heat resistance. It is effective to withstand the use in high current environments of cars and electric vehicles.

(Internal resistance)

[Internal resistance value] that characterizes the aramid leaf material of the present invention is a resistance value calculated by the following equation (3).

<Equation 3>

[Internal Resistance] (µm) = [Electric Conductivity of Electrolyte] / [Electric Conductivity when Electrolyte is injected into the Foil Sheet] × [Thickness of Foil Sheet] (µm)

However, [the electrical conductivity when the electrolyte solution is injected into a foil material] is the electrical conductivity computed from the alternating current impedance measured between two electrodes in the state which injected electrolyte solution into the foil material.

Here, the electrolyte means a liquid in which an electrolyte is dissolved in a solvent.

In the present invention, there are no particular restrictions on the solvent used for the electrolyte, the type of electrolyte, the concentration of the electrolyte, and the like, for example, as the solvent, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate. Ethylmethyl carbonate, butylene carbonate, glutaronitrile, adiponitrile, acetonitrile, methoxyacetonitrile, 3-methoxypropionitrile, r-butyrolactone, r-valerolactone, sulfolane , 3-methyl sulfolane, nitroethane, nitromethane, trimethyl phosphate, N-methyloxazolidinone, N, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N, N'-dimethylimida Zolidinone, amidine, water, and mixtures of two or more thereof.

Moreover, an ionic substance is contained as an electrolyte, for example, The combination of the following cations and an anion is mentioned as an ionic component of the said substance, for example.

1) Cation: quaternary ammonium ions, quaternary phosphonium ions, lithium ions, sodium ions, ammonium ions, hydrogen ions or mixtures thereof and the like.

2) Anions: perchlorate ions, boron fluoride ions, hexafluorophosphate ions, sulfate ions, hydroxide ions or mixtures thereof.

In addition, in this invention, (electrical conductivity at the time of injecting electrolyte solution into a foil material) means the electrical conductivity computed from the alternating current impedance measured by sandwiching two electrodes in the state which injected the said electrolyte solution into the foil material. Although there is no restriction | limiting in particular about the measurement frequency of AC impedance, The inside of the range of 1 kHz-100 kHz is generally preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, these Examples are only illustrations and do not limit the content of this invention.

(How to measure)

(1) Measurement of the basic weight and thickness of the sheet

It carried out according to JIS C2111.

(2) measuring electrical conductivity

The thin leaf material was cut into a circle having a diameter of 20 mm and inserted into two SUS electrodes and calculated from an AC impedance at 60 kHz. At this time, the measurement temperature was 25 degreeC. 1 M lithium boron fluoride ethylene carbonate / propylene carbonate (1/1 weight ratio) was used for the measurement.

(3) speculation

Measurements were made using an Oucken air permeability meter. As for a series of thin leaves, it can be said that the shorter the time, the more porous.

(Raw material manufacturing)

Fibrids of polymetaphenyleneisophthalamide were produced by using a wet settler composed of a combination of stators and rotors described in Japanese Patent Application Laid-open No. 52-151624. This was treated with a fiber separator and a beaker to adjust the weight average fiber length to 0.9 mm.

On the other hand, 0.8 denier single fiber fineness of the meta-aramid fiber (Teijin Connex (registered trademark) made by Teijin Corporation) is cut | disconnected to length 5mm, and Towaron pulp (Towaron (registration) made by Teijin Towaron Corporation Trademark)) to a specific surface area of 14 m ² / g and 85 ml of Yeosu, and to cut polyester short fibers (Tetron (registered trademark), short fiber fineness of 0.1 denier) manufactured by Teijin Co., Ltd. It was made into the raw material for fat.

<Examples 1 and 2>

(Manufacture of Aramid Leaf Material)

Slurries were prepared by dispersing the prepared aramid fibrids, short aramid fibers, and fibrillated aramids in respective waters. These slurries were mixed so that the aramid fibrids, short aramid fibers, and fibrillated aramids became the blending ratios of each of the examples shown in Table 1 below, and a sheet-like material was prepared by a tapping manual paper machine (cross section 325 cm ² ). Subsequently, this was hot-pressed at a temperature of 330 ° C. and a linear pressure of 100 kg / cm with a metal calender roll to obtain a thin leaf material.

The main characteristic values of the aramid leaf material thus obtained are shown in Table 1.

However, the electrical conductivity of electrolyte solution was 5.0 (mS / cm).

Since the aramid leaf material of each example is considered to have sufficiently low internal resistance, sufficient permeability of ionic species, high air permeability, and sufficient shielding between electrodes, the electrical conductivity in electrical and electronic components such as capacitors, capacitors, and batteries is considered. It is useful as an inter-member separator.

Comparative Example 1

(Manufacture of Foil Leaf)

Slurries were prepared by dispersing the prepared aramid fibrids, short aramid fibers, and short tetron fibers in water. These slurries were mixed so that the fibrids and short aramid fibers were in the blending ratios shown in Table 2 below to prepare a sheet-like material by the wet evaporation method.

Subsequently, this was hot-pressed at a temperature of 230 ° C. and a linear pressure of 300 kg / cm with a metal calender roll to obtain a thin leaf material.

The main characteristic values of the thus obtained leaf material are shown in Table 2.

However, the electrical conductivity of electrolyte solution was 5.0 (mS / cm).

It is thought that the thin leaf material of the comparative example has high internal resistance, the permeability of ionic species is not enough, and since polyester short fiber is used, it is difficult to endure high temperature drying.

The aramid leaf material of the present invention is useful as a separator between conductive members in electrical and electronic parts such as capacitors, capacitors, batteries, etc., because the aramid leaf material of the present invention maintains sufficient shielding between electrodes and also has sufficient permeability of ionic species. In addition, electrical and electronic components such as capacitors, capacitors, and batteries using the aramid leaf material of the present invention can be dried at a high temperature together with electrodes such as aluminum foil and activated carbon containing fine pores during the production process. It exhibits the effect of not exhibiting adverse effects on the electrical properties of electrical and electronic components such as capacitors, capacitors, and batteries caused by moisture.

Claims (3)

An aramid leaf material comprising two components of aramid short fibers and fibrillated aramid, or two components and aramid fibrids. The aramid leaf material according to claim 1, wherein all of the following Equations 1 and 2 are satisfied. <Equation 1> [Internal Resistance] (µm) ≤ 250 (µm) <Equation 2> [Okenen type air permeability] (second / 100 cm ³ ) ≥0.5 (second / 100 cm ³ ) In the formula, [internal resistance value] is a resistance value calculated by the following equation (3). <Equation 3> [Internal Resistance] (µm) = [Electric Conductivity of Electrolyte] / [Electric Conductivity when Electrolyte is injected into the Foil Sheet] × [Thickness of Foil Sheet] (µm) However, [the electrical conductivity when the electrolyte solution is injected into a foil material] is the electrical conductivity computed from the alternating current impedance measured between two electrodes in the state which injected electrolyte solution into the foil material. The aramid leaf material of Claim 1 or 2 is used as a separator between electrically conductive members, The electrical and electronic component characterized by the above-mentioned.