KR20030035414A - The Preparation Of Mioropouros Separator - Google Patents

Abstract

PURPOSE: Provided is a method for producing a microporous separator for lead storage battery which shows low electric resistance and rapid absorption without increasing of the content of organic fillers. CONSTITUTION: The method for producing a microporous separator from high density polyolefin, inorganic filler and plasticizer, is characterized in that at least one nonionic surfactant selected from alkylphenol polyethylene oxide or alkyl polyethylene oxide, and at least one anionic surfactant selected from alkylbenzene sulfone soda, sodium dialkyl sulfosuccinate, or alkyl naphthalene sulfonate are used as additives, or coated on the surface of the separator.

Description

The Preparation Of Mioropouros Separator

The present invention relates to a method for manufacturing a microporous separator, and more particularly, to a method for producing a lead-acid battery microporous separator (Separator) made of a thermoplastic elastic material inserted between the positive electrode and the negative electrode plate in the lead-acid battery.

The basic role of the separator is to prevent electric short circuits by depositing the electrode plate and the electrode plate, and to ensure the flow of ions in the electrolyte to allow current to flow. A lead acid battery is composed of a plurality of cells with alternating electrode plates and separators.

The lead-acid battery's membrane must not only have mechanical strength and flexibility to withstand physical shocks, but also have a uniform porosity that prevents the passage of electrode plates that fall out of the electrode grid while ensuring the flow of ions due to its large porosity. . It must also be durable against oxidation and heat that occur in the battery environment. In other words, it should be able to withstand the oxidizing power of the lead dioxide of the anode and the corrosion resistance of sulfuric acid, which is an electrolyte, and at the same time, the heat of the car bonnet. In addition, very high porosity is required with low electrical resistance.

The separator used in lead acid batteries was initially made of thin wood extracted from ligrin, microporous rubber, or various porous materials, but in recent years, many forms of polyolefins and inorganic fillers are used. In order to prepare such a separator, polyolefin, inorganic filler and plasticizer are uniformly mixed and kneaded, and then manufactured into a rib-like sheet through an extrusion process and a calender process, and then the prepared sheet is put into a suitable organic solvent to extract a plasticizer and dried. To form pores to produce a microporous membrane (US Pat. Nos. 3,351,495, 4,024,323, 4,237,08, Japanese Patent Publication Nos. 51-138755, 54-38278, 54-14371, etc.). .

The content of the raw materials shown in the above inventions is 10 to 30% by volume of polyolefin, 30 to 40% by volume of inorganic filler, and 30 to 60% by volume of plasticizer. As an additive, carbon black, graphite, or carbon fiber is added, respectively, or it is characterized by adding. These additives are suitable to have an electrical conductivity of about 500 to 1,000 Ω · cm ^-1 . If a small amount is added, the additive only serves as a colorant, and when an excessive amount is added, the additives are deposited in pores inside the membrane to serve as an electrical conductor, thus combining polyolefin and silica. It is preferable to add in 0.5-10 volume% with respect to quantity.

The higher the electrical resistance of the separator, the lower the electromotive force of the lead acid battery, the lower the efficiency and the lower the starting force at low temperatures has been a major problem to reduce the electrical resistance in the manufacturing of the separator. Particularly in dry lead acid batteries, the electrolyte should have fast absorption into the separator. In order to increase the battery resistance and absorption rate, the desired content can be obtained by increasing the content of the inorganic filler to improve porosity, but it has an adverse effect on mechanical strength and durability. Therefore, there is a need to improve the electrical resistance and absorption rate without increasing the inorganic filling content.

An object of the present invention is to provide a method for manufacturing a lead-acid battery separator having a low electrical resistance and fast absorption without increasing the content of the inorganic filler to solve the problems as described above.

The present invention provides at least one nonionic surfactant selected from alkylphenol polyethylene oxide or alkyl polyethylene oxide and alkylbenzene sulfone soda, sodium dialkyl sulfosuccinate, alkylnaphthalene in preparing the separator with high density polyolefin, inorganic filler and plasticizer. One or more anionic surfactants selected from sulfonates are used as additives or coated on the surface.

Hereinafter, the present invention will be described in detail.

The resin used in the present invention is composed of high density polyethylene having a molecular weight of at least 600,000 and a melt index of 0.04 or less, or polyolefin composed of polyethylene, polypropylene, polybutylene, and the like. In the case of inorganic fillers, carbon black, graphite, microporous Inert materials such as glass particles and silica can be used, but silica is the most effective.

Inorganic fillers have a specific surface area of 90 m ² _/ g or more, oil absorption of 100 to 300 ml / 100 g, and particle size of 25 μm or less. As a plasticizer, petroleum oil containing 30 wt% or more of paraffinic is effective.

After mixing the polyolefin, inorganic filler and plasticizer, the sheet prepared by extrusion and extraction process may be selected from at least one nonionic surfactant selected from alkylphenol polyethylene oxide or alkyl polyethylene oxide, alkylbenzene sulfone soda and sodium dialkyl sulfoxi One or more anionic surfactants selected from nates and alkylnaphthalenesulfonates are deposited in water or organic solvent added at 0.1 to 1.5% by weight to coat the surfactant on the surface or to absorb it into the pores.

If less than 0.1% by weight can not see the effect of the surfactant, 1.5% by weight or more absorption time is faster, but the electrical resistance is increased due to the generation of bubbles there is a problem that the effect of the surfactant is lowered.

Alternatively, the silica is placed in a high speed stirrer and mixed with a solution containing 0.5 to 10% by weight of a surfactant with silica weight while rotating at 1,000 rpm or more, followed by mixing polyolefin and plasticizer, followed by extrusion, extraction, and drying. The separator is prepared through.

To be described in detail by the following examples, the present invention is not limited by the following examples.

The electrical resistance, water absorption rate, and absorption rate of the separator prepared in the following Examples were measured by the following method.

① electrical resistance

According to the Korean Industrial Standard (KS C 2202), when the current flows 1A in sulfuric acid solution with a specific gravity of 1.260, the electric resistance difference is measured and calculated as follows.

(m / cm ² / piece)

n: number of specimens

R ': electrical resistance after specimen insertion

R: resistance only solution without specimen

② Absorption rate

Distilled water was prepared (maintained at 25 ° C.), the sheet was cut to 10 cm × 10 cm in size, weighed, and the sheet was immersed in distilled water. After 1 hour, the surface water was removed, and then weighed.

Weight After Absorption-Weight Before Absorption

--------------------------------- × 100

Weight before absorption

③ Absorption rate

After 0.5 ml of sulfuric acid aqueous solution having a specific gravity of 1.260 was added dropwise to the surface of the separator, the time (minutes) until the moisture was not seen on the surface was measured.

<Example 1-4>

Silica (Hi-sil SBG specific surface area 170m ² / g, oil absorption 200ml / 100g) and carbon black was put into a high speed stirrer and mixed for 3 minutes at 2000rpm. Subsequently, the amount of silica was 35% by volume, 20% by volume of high density polyethylene (XL-1800, melting index of 0.01 or less), and 45% by volume of plasticizer (Shell412, boiling point 234 ° C) at 1,000 rpm under high speed stirring. Mixing for a uniform composition.

The mixed raw materials were placed in an extruder and extruded to obtain a sheet shape (temperature 190-220 ° C.), which was then extracted with a plasticizer using trichloroethylene under a temperature of 60 ° C. The sheet from which the plasticizer was extracted was again immersed or passed through distilled water at 75 ° C to 95 ° C containing 0.1 to 1.5% by weight of alkyl polyethylene oxide for 5 minutes to remove trichloroethylene and dried to prepare a separator.

Physical properties of the obtained separator was shown in Table 1 below.

Changes in Electrical Resistance and Absorption Rate with Changes in Surfactant Content Distilled water content of surfactant (%) Electric resistance (mΩcm ² ) Absorption rate (min) Absorption rate (% by weight) Example 1 0.1 122 115 83 Example 2 0.5 89 96 99 Example 3 1.0 85 93 101 Example 4 1.5 96 82 102

<Comparative Examples 1-3>

Unlike the above example, the content of the high density polyethylene was changed and the physical properties of the prepared polymer without surfactant were measured. [Table 2].

Electrical Resistance and Absorption Rate When Untreated Surfactant Composition (% by volume) Electric resistance (mΩcm ² ) Absorption rate (min) Absorption rate (% by weight) HDPE Silica Oil Comparative Example 1 20 35 45 175 210 75 Comparative Example 2 15 40 45 132 175 85 Comparative Example 3 10 45 45 98 103 98

<Examples 5-7>

Table 3 shows the results of measuring physical properties prepared by treating the surfactant differently while making the same composition and method as in Example 3.

Electrical Resistance and Absorption Rate According to the Change of Surfactant Surfactants Electric resistance (mΩcm ² ) Absorption rate (min) Absorption rate (% by weight) Example 5 A 88 97 98 Example 6 B 90 100 100 Example 7 C 83 92 101

A: alkylbenzene sulfone soda

B: sodium dialkyl sulfosuccinate

C: 2.4,7, -tetramethyl-5-deken-4,7-diol

The separator produced by the present invention has excellent electrical properties with low electrical resistance of 83-122 mPa · cm ² , absorption rate of 82-115 minutes, and absorption rate of 83-102% by weight. Therefore, since it is not necessary to increase the content of the inorganic material to improve the electrical properties of the separator, it is possible to produce a separator having excellent mechanical properties and durability with excellent electrical properties.

Claims (2)

From at least one nonionic surfactant selected from alkylphenol polyethylene oxide or alkyl polyethylene oxide and alkylbenzene sulfone soda, sodium dialkyl sulfosuccinate, alkylnaphthalenesulfonate in preparing the separator with high density polyolefins, inorganic fillers and plasticizers Method for producing a microporous separator, characterized in that at least one anionic surfactant selected is used as an additive or coated on the surface The method of claim 1, wherein the surfactant is coated with a solution of 0.1 to 1.5% by weight based on 100 parts by weight of distilled water or absorbed into internal pores.