JP2002117824A - Manufacturing method of separator for lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a separator for a lead-acid battery fully satisfying a separator characteristic and a battery characteristic without reducing productivity and product quality even if inorganic powder to absorb a small amount of oil is used. SOLUTION: In the manufacturing method of the separator for the lead-acid battery wherein after a raw material mixture having three kinds of polyolefinic resin, inorganic powders and mineral oil has been molded as the main raw materials mixture in a sheet-form while kneading in a heating fusion, subsequently a part or all of the mineral oil is removed from the sheet, and the mineral oil is blended at divided times of a preparing time of the raw material mixture before the kneading in the heating fusion and of a kneading time in the heating fusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a separator for a lead-acid battery mainly comprising a polyolefin resin,
The present invention relates to a method for manufacturing a separator for a lead-acid battery manufactured by a method of forming a sheet by heat-melt kneading using a polyolefin-based resin as a main raw material.

[0002]

2. Description of the Related Art Conventionally, as a general method for producing a lead storage battery separator mainly composed of a polyolefin resin, first, a polyolefin resin, which is a main raw material, an inorganic powder and a mineral oil are mixed with a mixer. To make a raw material mixture. In this case, the polyolefin resin and the inorganic powder are mixed in advance, and mineral oil is added later, and the raw materials are uniformly dispersed and mixed until the appearance of the raw material mixture becomes granular. General. Next, the obtained raw material mixture is continuously charged into a temperature-controlled extruder, brought into a molten resin state by heat-melt kneading, and extruded from a T-die into a sheet. Subsequently, pressure is applied by two forming rolls to form a sheet having a predetermined thickness. In this case, usually, a groove having a predetermined shape is engraved on one or both of the forming rolls, and ribs having various shapes can be continuously and / or discontinuously formed on the sheet. Also, as an extruder, usually
From the viewpoint of productivity, one having a cylinder portion provided with a screw that rotates biaxially in the same direction is used. Next, the obtained extruded sheet is immersed in an appropriate organic solvent for a certain period of time to extract and remove a part of the contained mineral oil, and then dried by heating to obtain a lead-acid battery separator.

[0003]

In the above-mentioned conventional method for manufacturing a lead-acid battery separator, the three main raw materials constituting the raw material mixture have the following functions. The polyolefin-based resin has a role of shaping the shape as a separator, and also has a role of securing the mechanical strength of the separator and the oxidation resistance which is greatly related to the battery life. Inorganic powder has the role of retaining the mineral oil in the raw material mixture at the stage of the raw material mixture so as not to be released, and when removing the mineral oil from the extruded sheet to form micropores, It suppresses the shrinkage of the sheet caused by the extraction of the mineral oil, and plays a role in helping to secure micropores. Mineral oil functions as a plasticizer at the time of extrusion molding of the raw material mixture, as a pore forming agent by being extracted with an organic solvent, and as an oxidation resistance imparting agent by remaining in a separator in an amount of 5 to 30% by mass. I do. Therefore, these three
The mixing ratio of the two main raw materials in the raw material mixture is derived as a result of complicatedly overlapping various conditions, and can be said to be based on a delicate balance. Therefore, changing the once-established mixing ratio may affect the quality as a lead storage battery separator and the productivity of the separator, which is difficult and involves risks. In particular, the mixing ratio of the inorganic powder and the mineral oil is important. In both the ratios, if the ratio of the mineral oil is small, the porosity of the separator decreases, and the electrical resistance of the separator increases. Is reduced. On the other hand, when the proportion of the mineral oil is small, the effect as a plasticizer is reduced, the load on the extruder is increased, and the productivity is significantly reduced. On the other hand, if the ratio of mineral oil is large, the inorganic powder exceeds the limit of the ability to absorb and retain mineral oil (oil absorption), so when it is used as a raw material mixture, the inorganic powder absorbs and retains the entire amount of mineral oil. It does not break, and a part of the mineral oil is liberated, and the raw material mixture becomes a lump (dumpling) instead of a good granule. In such a case, when the raw material mixture is injected into the extruder in the next step, it is impossible to stably input the raw material mixture by a fixed amount, which may affect the product quality. This phenomenon includes
Since the relationship (balance) between the oil absorption of the inorganic powder and the mixing ratio (compounding amount) of the mineral oil is affected, when the oil absorption of the inorganic powder is the same as in the above example, the mineral oil May occur when the mixing ratio of the inorganic powder becomes too large, and even when the mixing ratio of the mineral oil is the same, the same phenomenon may occur if the oil absorption of the inorganic powder becomes small. As described above, if the ratio of the mineral oil is small, various problems occur. Therefore, it is necessary to mix the mineral oil at a certain mixing ratio. Generally, an inorganic powder having a larger oil absorption is more expensive, and therefore, it is more advantageous in terms of cost to use an inorganic powder having a smaller oil absorption. However, as described above, the use of an inorganic powder having a small oil absorption has a disadvantage that the raw material mixture has a problem of agglomeration. Inorganic powders with high oil absorption have been used. The present invention
In view of the above problems, even when using an inorganic powder having a small oil absorption, without reducing the productivity and product quality, a lead-acid battery that sufficiently satisfies separator characteristics and battery characteristics. An object of the present invention is to provide a method for manufacturing a separator.

[0004]

Means for Solving the Problems In view of the above points, the present inventors have conducted various studies, and as a result, have derived the following concept. That is, when using an inorganic powder having a small oil absorption, the amount of the inorganic powder absorbed becomes insufficient with respect to the specified amount of the mineral oil to be blended, so that the raw material mixture becomes a lump as it is. . Therefore, in order to avoid this, only mix the mineral oil in the amount appropriate for the oil absorption of the inorganic powder when preparing the raw material mixture, and put the remaining amount into the extruder at the time of heat melting and kneading. It has been found that, by blending, an extruded sheet having the same blending composition as in the case of using a conventional inorganic powder having a large oil absorption is obtained.

That is, according to the method of manufacturing a separator for a lead storage battery of the present invention, as described in claim 1, a raw material mixture mainly composed of a polyolefin resin, an inorganic powder and a mineral oil is melted and kneaded. In a method for producing a separator for a lead-acid battery, after forming into a sheet and then removing a part or all of the mineral oil from the sheet, the mineral oil may be mixed with a raw material mixture before heating and melting and kneading. And being compounded separately.
According to a second aspect of the present invention, there is provided a method of manufacturing a lead storage battery separator according to the first aspect, wherein the inorganic powder has an oil absorption of 220 ml / 100 g or less. The method for producing a separator for a lead storage battery according to claim 3 is the method for producing a lead storage battery according to claim 1 or 2, wherein the heat-melt kneading and sheet forming are performed using an extruder. The compounding of the oil during the heat melting and kneading is performed from any position from the raw material input port provided at the end of the cylinder portion, which is the portion where the heat melting and kneading of the extruder is performed, to the opposite end. In addition, the method for producing a lead storage battery separator according to claim 4 is the production method according to claim 3, wherein the mineral oil is mixed at the time of heat melting and kneading.
Starting from the end of one of the cylinder portions provided with the raw material inlet, the process is performed from any position up to 3/5 of the entire length of the cylinder portion.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The main raw materials used for the lead-acid battery separator of the present invention are a polyolefin resin, an inorganic powder and a mineral oil. As the polyolefin-based resin, polyethylene, polypropylene, polybutene and copolymers thereof, or a mixture thereof can be used, but from the viewpoint of mechanical strength of the separator, ultra-high molecular weight polyethylene having an average molecular weight of 2,000,000 or more is used. It is desirable to use.

As the inorganic powder, one or more of silicic acid, calcium silicate, alumina, calcium carbonate, kaolin clay, talc, diatomaceous earth, glass fiber powder and the like can be used.

As the mineral oil, paraffin oil is mainly used, but it is not limited to this.

The lead storage battery separator of the present invention includes:
A small amount of an antioxidant or a penetrant for improving wettability may be blended.

In the method for producing a separator for a lead storage battery according to the present invention, the mineral oil is separately compounded into a raw material mixture before heat melting and kneading and a heat melting and kneading. That is, when preparing the raw material mixture, only an amount corresponding to the amount of oil absorption of the inorganic powder is added, and the remaining amount is put into an extruder at the time of heating and melting and kneading to mix. The amount of the mineral oil to be blended when preparing the raw material mixture is appropriately determined according to the type of the inorganic powder to be used, that is, the oil absorption characteristics of the powder.

The mineral oil is charged into the extruder at the time of the heat-melt kneading, and the mineral oil is charged at any point from the raw material input port provided at the end of the cylinder portion, which is the portion where the heat-melt kneading of the extruder is performed, to the opposite end. It may be carried out from the position, but more preferably from any position up to 3/5 of the total length of the cylinder part from the end of one cylinder part provided with the raw material inlet. This is because when the mineral oil is injected from the raw material inlet, the injected mineral oil adheres to the surface of the granules of the raw material mixture, so that the granules easily have a binding property. And conversely, 3/5 of the total length of the cylinder part
When the raw material mixture is charged from a position beyond the above, the raw material mixture is completely melted inside the cylinder, so even if the mineral oil is charged, it does not mix well with them, and the charged mineral oil stays in the cylinder in a released state Therefore, slippage occurs between the screw and the extruded material, which hinders extrusion molding.

FIG. 1 shows a schematic diagram of an extrusion molding machine suitably used in the production method of the present invention. The injection of the mineral oil into the extruder 10 during the heat-melt kneading is performed, for example, at any position from the raw material input port 2 provided at the end of the cylinder unit 1 to the opposite end, as shown in FIG. More preferably, a mineral oil input port 3 communicating with the inside of the cylinder portion is provided at any position up to 3/5 of the total length L of the cylinder portion starting from the end of one cylinder portion provided with the raw material input port, Mineral oil may be supplied to the section through a pipe.

[0013]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following description. In addition, the oil absorption of the inorganic powder used below is defined by JIS
It is a numerical value measured based on the oil absorption amount measurement method of K5101.

Example 1 20 parts by mass of a high-density polyethylene resin powder having a weight average molecular weight of 2,000,000 and an oil absorption of 16
30 parts by mass of fine silica powder of 9 ml / 100 g was mixed for 2 minutes using a Henschel mixer. In the obtained mixture, the specified amount of paraffin oil is 3 /
30 parts by mass corresponding to 5 were added and mixed again. After 840 seconds, the mixing was terminated when the mixture of the three became granular. Next, a twin-screw co-rotating extruder equipped with a T-die controlled at a predetermined temperature is prepared, and the obtained raw material mixture is supplied through a raw material inlet provided at an end of a cylinder portion of the extruder. Mineral that is continuously charged at a rate of 440 kg / h and communicates with a cylinder provided at a position about 2/5 of the entire length of the cylinder starting from the end of one cylinder provided with the raw material inlet. From the oil inlet, a paraffin-based oil is continuously fed at a rate of 110 kg / h, extruded into a sheet shape, and pressed and formed between two forming rolls to obtain an extruded sheet having a thickness of 0.25 mm. Was. Next, the obtained extruded sheet was immersed in a trichloroethylene solution for 3 minutes to extract and remove a part of the mineral oil in the sheet, and then heated and dried to obtain a lead storage battery separator. In this example, the extrudability and the product quality of the raw material mixture were good.

Comparative Example 1 20 parts by mass of a high-density polyethylene resin powder having a weight average molecular weight of 2,000,000 and an oil absorption of 16
30 parts by mass of fine silica powder of 9 ml / 100 g was mixed for 2 minutes using a Henschel mixer. To the obtained mixture, 50 parts by mass corresponding to the total amount of the specified amount of the paraffin-based oil to be originally blended was added and mixed again. After 5 seconds, 3
The mixture of the sampler became a lump (dumpling) and a significant load was applied to the mixer, so that the mixing was terminated. Because the raw materials of the three parties are not evenly mixed because they are mixed only for 5 seconds after the mineral oil is injected, and because they have become lump, they cannot be quantitatively injected into the extruder. Extrusion molding was judged impossible.

(Conventional Example 1) 20 parts by mass of a high-density polyethylene resin powder having a weight average molecular weight of 2,000,000 and an oil absorption of 24
30 parts by mass of 1 ml / 100 g of silica fine powder was mixed for 2 minutes using a Henschel mixer. To the obtained mixture, 50 parts by mass corresponding to the total amount of the specified amount of the paraffin-based oil to be originally blended was added and mixed again. After 720 seconds, the mixing was terminated when the mixture of the three became granular. Next, a twin-screw co-rotating extruder equipped with a T-die controlled at a predetermined temperature is prepared, and 550 kg of the obtained raw material mixture is fed from a raw material inlet provided at an end of a cylinder portion of the extruder. / H, continuously extruded at a rate of / h, extruded into a sheet shape, and formed under pressure through two forming rolls to obtain an extruded sheet having a thickness of 0.25 mm. Next, the obtained extruded sheet was immersed in a trichloroethylene solution for 3 minutes to extract and remove a part of the mineral oil in the sheet, and then heated and dried to obtain a lead storage battery separator. In this conventional example, the extrudability and product quality of the raw material mixture were good.

[0017]

According to the method for producing a separator for a lead storage battery of the present invention, a raw material mixture mainly composed of a polyolefin resin, an inorganic powder and a mineral oil is formed into a sheet while being melted and kneaded. Then, in the method for producing a lead storage battery separator for removing part or all of the mineral oil from the sheet, the mineral oil is divided into a raw material mixture before heat melting and kneading and a heat melting and kneading. By blending, even when using an inorganic powder having a small oil absorption, a separator for a lead-acid battery that sufficiently satisfies separator characteristics and battery characteristics can be obtained without lowering productivity or quality. In addition, the cost of the separator can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an extrusion molding machine suitably used in the production method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder part (the part heated and melted with a screw) 2 Raw material input port 3 Mineral oil input port 4 T die 5 Forming roll 6 Extruded sheet manufactured from molten resin 10 Extruder L Length of cylinder section

Claims (4)

[Claims] 1. A material mixture mainly composed of a polyolefin resin, an inorganic powder and a mineral oil is formed into a sheet while being heated, melt-kneaded, and then a part or all of the mineral oil is removed from the sheet. A method for manufacturing a separator for a lead-acid battery, wherein the mineral oil is divided and mixed at the time of preparing a raw material mixture before heat-melting and kneading and at the time of heating-melting and kneading. . 2. The inorganic powder has an oil absorption of 220 ml /
The method for producing a lead storage battery separator according to claim 1, wherein the weight is 100 g or less. 3. The heat-melt kneading and sheet forming are performed by using an extruder, and the blending of the mineral oil at the time of heat-melt kneading is a portion where the heat-melt kneading of the extruder is performed. The method for producing a separator for a lead storage battery according to claim 1, wherein the method is performed from any position from a raw material inlet provided at an end of the cylinder portion to an opposite end. 4. Mixing of said mineral oil during heat melting and kneading is carried out from any position up to 3/5 of the total length of the cylinder part, starting from the end of one cylinder part provided with a raw material inlet. A method for producing a separator for a lead storage battery according to claim 3, characterized in that: