JP2546240B2 - Storage battery separator and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a storage battery separator and a manufacturing method thereof, and more particularly to a storage battery separator substantially made of glass fibers and a manufacturing method thereof.

[Prior Art] Various types of storage battery separators containing glass fibers have already been proposed and put into practical use, but they are roughly classified into the following three types. That is, those mainly containing short glass fibers, those obtained by mixing and molding short glass fibers and synthetic fibers, and those holding powder in short glass fibers.

Of these, examples of those composed of a mixture of glass fiber and powder include those described in, for example, JP-A-58-206046, which has good liquid absorption,
There is a problem that the powder easily peels off from the separator, and also has a low tensile strength.

On the other hand, as a mixture of short glass fiber and synthetic fiber, Japanese Patent Laid-Open Nos. 49-38126, 54-22531, 56-99968, 53-136632 and Kosho 58-6
Although there are those described in No. 63, these have the advantage that they are easy to perform battery assembly work because they have high mechanical strength (tensile strength and rigidity, etc.), but they are inferior in liquid absorption and liquid retention properties. Battery life is short due to the presence of organic matter inside,
It has the drawback.

On the other hand, as those mainly composed of glass fibers, there are those using a binder such as a liquid adhesive and those not using these binders.

[Problems to be Solved by the Invention] Among separators mainly composed of glass fibers, those not using a binder are capable of free volume expansion due to absorption of a liquid, and have electrolyte retention and liquid absorption properties. It is the best and is suitable in terms of battery characteristics, but on the other hand, this type of separator is shaped only by the water vitrification of the glass fiber surface and the force of entanglement, so the strength and hardness are low, and the machine is used. The battery assembly work described above cannot be sufficiently endured, and the work efficiency is poor.

On the other hand, when a binder is used, its adhesive effect improves the strength and hardness, but the volume expansion due to liquid absorption is hindered by the binder, and the liquid retention and liquid absorption of the separator deteriorate. Moreover, with a liquid-soluble binder,
There is a problem that it dissolves in the electrolytic solution and causes deterioration of battery performance, and it is not preferable from the viewpoint of oxidation resistance.

As a storage battery separator that solves such problems and has excellent strength and hardness as well as excellent liquid retention and liquid absorption properties, the applicant of the present invention has a storage battery separator substantially composed of only glass fibers. A patent application was previously filed for a separator for a storage battery, in which glass fibers are heat-sealed together (Japanese Patent Application No. 61-94083, hereinafter referred to as "first application").

The storage battery separator according to the prior application consists essentially of glass fibers, and since it does not use organic fibers or binders, it is extremely liquid-absorbing and liquid-retaining, and the glass fibers constituting the separator are heat-resistant. Since they are adhered to each other by fusion, their strength and hardness are extremely high.

However, in a separator consisting essentially of glass fibers, a glass fiber forming the separator is melted by heat melting the glass on the surface of the fiber without deteriorating its characteristics, and a heating rate capable of obtaining a desired strength. Since the range of time, etc. is limited to a narrow range, strict control of heat fusion conditions such as heating temperature and time is required, and there is a problem that the heat fusion treatment is difficult.

[Means for Solving Problems] The present invention has been made based on the above-mentioned prior application, and is a separator for a storage battery, which is substantially composed of only glass fiber and is excellent in liquid retention, liquid absorption, strength and the like. Is to provide a separator for a storage battery that can be manufactured extremely easily and a method for manufacturing the same, which is a separator for a storage battery substantially composed of only glass fibers, Than the softening point
A storage battery separator, characterized in that low softening point glass fibers having a low softening point of 50 to 400 ° C. are mixed in an amount of 3 to 20% by weight of all glass fibers, and the glass fibers are heat-sealed. In a method for producing a storage battery separator composed only of glass fibers, a glass fiber as a main component, and a low softening point glass fiber having a softening point lower than the softening point of the main glass fiber by 50 to 400 ° C., The glass fibers are mixed by mixing so that the proportion of the softening point glass fibers is 3 to 20% by weight of the total glass fibers, and heating the intermediate temperature between the softening point of the main glass fibers and the softening point of the low softening point glass fibers. A method for manufacturing a storage battery separator, characterized in that the above is heat-sealed.

 Hereinafter, the present invention will be described in more detail.

The storage battery separator of the present invention is composed of glass fiber as a main component and 3 to 20% by weight of a low softening point glass fiber having a softening point lower by 50 to 400 ° C. than the softening point of the main glass fiber.

In the present invention, the composition of the main glass fiber and the low-melting point glass fiber constituting the separator is not particularly limited, but it is preferable to use alkali-containing silicate glass fiber. That is, when alkali silicate-containing glass fibers are used, water glassy substances are produced on the surface of the glass fibers in the paper making step of the manufacturing process, and the adhesiveness of the water glassy substances allows the fibers to be better bonded together. In the present invention, among alkali-containing silicate glass fibers, those having good acid resistance are preferably used since they are used for storage batteries. It is desirable that the degree of acid resistance is 2% or less in weight loss when measured according to JIS C-2202 in the state of glass fibers having an average fiber diameter of 1 mμ or less. Further, the composition of such glass fiber is 60 to 75% by weight of SiO ₂
And 8 to 20% of R ₂ O (alkali metal oxide such as Na ₂ O and K ₂ O) is mainly contained (provided that SiO ₂ + R ₂ O is 75 to 90).
%) And others such as CaO, MgO, B ₂ O ₃ , Al ₂ O ₃ , ZnO, Fe
Examples include those containing one kind or two or more kinds such as ₂ O ₃ . The alkali-containing silicate glass can easily change its softening point by changing its composition, and can provide a main glass fiber and a low softening point glass fiber. For example, of the components, SiO ₂ is reduced, and CaO and M
The softening point can be lowered by increasing gO, B ₂ O ₃ , Na ₂ O and the like.

Table 1 shows examples of the composition of the main glass fiber and the composition of the low-melting glass fiber of such a preferable alkali silicate.

On the other hand, as the glass fibers constituting the storage battery separator of the present invention, both the main glass fibers and the low softening point glass fibers have a large diameter of 10 to 30 μm.
.About.35% by weight, and an average diameter of more than 2 .mu.m and less than 10 .mu.m, medium to fine glass fibers 0 to 30% by weight, and the balance preferably containing fine diameter glass fibers having an average diameter of 2 .mu.m or less. Such medium-thin diameter, large-diameter glass fibers are less expensive than thin-diameter glass fibers, and in particular, large-diameter glass fibers have the advantage that the tensile strength of the separator can be improved by using them together. is there.

The preferred average diameter of fine glass fibers is 0.5-1.0μ
m, more preferably 0.6 to 0.9 μm. Diameter is 1.0μ
If it exceeds m, the pore size of the separator will increase, and conversely 0.5
If it is smaller than μm, its manufacturing cost becomes high.

The preferable content of the glass fiber having the small diameter is 60% by weight or more, and particularly preferably 65% by weight or more based on the weight of the glass fiber. This is because if the content is less than 60% by weight, the liquid absorbing property and the liquid retaining property tend to be insufficient.

Also, the average length of the glass fibers having a small diameter is preferably 7
It is -50 mm, more preferably 10-40 mm. Average length is 10
If the length is shorter than mm, the strength of the separator will decrease and
If it is longer than mm, it becomes difficult to uniformly disperse it in water during papermaking.

The glass fiber having such a small diameter can be produced by the FA method (flame method), the centrifugal method or other glass short fiber producing methods.

In the present invention, the average diameter of the glass fibers is calculated by taking photographs of three places of the sample with an electron microscope, measuring the diameter of each of the 20 fibers in 0.1 μm units, and taking the average value of these. .

When using medium to small diameter glass fibers, the preferred average diameter is 2.0 to 5.0 μm, especially 3.0 to 4.0 μm. Further, the content is preferably 5.0 to 30.0% by weight, and more preferably 10.0 to 25.0% by weight of the glass fiber weight. By blending medium and small diameter glass fibers, the amount of small diameter glass fibers can be reduced, which is advantageous in terms of cost. The length of the medium-diameter glass fiber is preferably 7 to 50 mm, more preferably 10 to 40 mm.

When using large diameter glass fibers, the preferred average diameter is 10 to 20 μm, especially 12 to 19 μm. The content is 8 to 35% by weight of the glass fiber, especially 10 to 30%.
It is preferably set to wt%. If the average diameter is less than 10 μm or the content is less than 8% by weight, the effect of improving tensile strength becomes small, and if the average diameter exceeds 20 μm or the content exceeds 35% by weight, the separator Liquid absorption and liquid retention are reduced. The length of the large diameter glass fiber is preferably 5 to 80 mm, particularly preferably 6 to 40 mm.

The storage battery separator of the present invention is preferably a thin-diameter, medium-diameter, and large-diameter alkali-containing silicate glass fiber having the above-described composition, which is entangled by wet papermaking, and preferably has a low softening point glass fiber. Only the glass fibers are substantially fused to each other by being softened or melted by heating so that they are heat-sealed to each other without any special adhesive.

That is, in the present invention, preferably, by heat fusion by heating, the main glass fiber is hardly softened or melted, only the low softening point glass fiber is softened or melted, and the softened or melted low softening point glass fiber is preferably used. Adhere glass fiber comrades together.

In the method of the present invention, in order to manufacture such a storage battery separator, the heating temperature at the time of heat fusion is set to an intermediate temperature between the main glass fiber and the low softening point glass fiber. From the viewpoint of controlling the heating temperature, it is disadvantageous if the difference in softening point between the main glass fiber and the low softening point glass fiber is too small. Further, if the difference in softening point between both glass fibers is too large, the difference in composition, physical properties, etc. of both glass fibers may be too wide open, which may adversely affect the obtained separator. Therefore, in the present invention,
The low softening point glass fiber is 50 than the softening point of the main glass fiber.
It has a softening point of about 400 to 400 ° C, preferably about 60 to 200 ° C.

Further, if the proportion of the low softening point glass fiber that is softened or melted by the heat fusion treatment by heating is too small,
Sufficient strength cannot be obtained in the obtained separator, and conversely, if it is too large, it causes a decrease in liquid retention and liquid absorption. Therefore, in the present invention, the proportion of the low softening point glass fiber is 3 to 20% by weight, preferably 7 to 18% by weight of the total glass fiber.
And

In order to manufacture such a storage battery separator of the present invention, the main glass fiber and the low softening point glass fiber may be mixed in a desired ratio and mixed and manufactured.

The glass fiber is paper-made on the net. At that time, the pH in the disintegrator and / or the pH in the paper-making tank is
Is preferably less than about 3, for example about 2.5. By defibration and / or wet papermaking in such an acidic region, an adhesive layer of water glass is formed on the surface of the glass fiber, and then the glass fiber is heated to a predetermined temperature, for example, 80 to 160 ° C. It becomes possible to adhere to each other by the water glass of.

That is, if the glass fiber constituting the separator has an alkali silicate glass composition, the alkali component and the silica component in the glass fiber react with water for dispersion in an acidic region of about pH 2.5, and water. A glass layer is formed on the glass fiber surface, and this water glass layer acts as an adhesive to firmly bond the glass fibers to each other.

Usually, the glass fiber papermaking product thus wet-processed is dried along the drum dryer to be a product, but in the production of the separator of the present invention, after the obtained papermaking product is dried, the main glass By heating at a temperature between the softening point of the fiber and the softening point of the low-softening point glass fiber at a high temperature, only the low-softening point glass fiber is melted and the glass fibers are heat-sealed. This heat treatment time varies depending on the glass fiber composition and the like, but if it is too long, it causes the liquid absorption of the separator to decrease, and if it is too short, heat fusion becomes insufficient. Usually, the heating time is about 1 to 5 minutes, preferably about 2 to 3 minutes. The heating is performed to such an extent that the glass fibers are heat-sealed and firmly bonded to each other, and the hardness and strength of the separator are significantly improved, but the liquid absorbency is not deteriorated.

In the production of the separator of the present invention, the above-mentioned heating for drying may be combined with the high-temperature heating for this heat fusion, and the drying treatment may be omitted. Alternatively, the heat treatment may be performed after the drying treatment in advance. You may process.

In addition, a dispersant may be used in dispersing the fibers in water for papermaking.

The thickness of the separator of the present invention itself varies depending on the storage battery used, but is generally preferably 0.3 to 3 mm.

The storage battery separator of the present invention thus obtained has a density of 0.16 ± 0.03 g / cm ³ and a tensile strength of 400 g / 15 mm.
It is preferable that the width is 1 mm or more and the buckling strength is 30 g / 10 mm width 1 mm or more.

[Operation] The separator for a storage battery of the present invention is substantially made of only glass fibers, and since it uses organic fibers and a binder, it is extremely excellent in liquid absorption and liquid retention. Further, while organic fibers and other adhesives that are usually used for improving the strength of the separator may weaken the acid resistance of the separator, the separator made of glass fiber as in the present invention is extremely excellent. It has acid resistance.

Further, in the present invention, the glass fibers constituting the separator are bonded to each other by heat fusion, so that the strength and hardness thereof are significantly improved.

Moreover, during this heat fusion, the main glass fibers are not melted, and only the low softening point glass fibers are softened, the heating temperature and the heating time for melting can be selected from a wide range, and therefore the storage battery separator of the present invention. Can be easily produced without requiring strict control of conditions.

[Examples] Examples and comparative examples will be described below.

Examples 1 to 3 and Comparative Examples 1 to 4 The constituent fibers having the formulations shown in Table 2 were put into water and stirred by a water-flow type disperser to disperse, and sulfuric acid was further added to the water.
The pH was adjusted to 2.7 and kept for about 10 minutes. Then papermaking is performed 150
After heating at 0 ° C. and drying, the glass fibers were heat-fused by heating at high temperature under the conditions shown in Table 2 except for Comparative Example 1 to manufacture a mat-shaped storage battery separator.

Table 2 shows the results of measuring the loss on ignition, liquid absorption rate, tensile strength, buckling strength, and liquid retention under pressure of this separator.

The following is clear from Table 2.

That is, in the case where the separator made of only the glass fiber A is used when the heating temperature of the heat fusion treatment is as low as 630 ° C. (Comparative Example 2) as in the case where the heat fusion treatment by high temperature heating is not performed (Comparative Example 1). , Cannot obtain sufficient strength. Further, when the heating temperature in the heat fusion treatment is as high as 670 ° C., the strength is improved but the liquid absorbing property is lowered. Among the separators composed only of glass fiber A, the ones that give good results are only those that have been subjected to heat fusion treatment at a heating temperature of 650 ° C. (Comparative Example 3), and the range of suitable treatment conditions is extremely narrow, and condition control Finds it difficult.

On the other hand, mainly the glass fiber A according to the present invention,
In the case of using the low softening point glass of the glass fiber B in combination, 560 ° C. (Example 1), 580 ° C. (Example 2), 600 ° C.
Even with the heat fusion treatment at a wide range of heating temperatures as in (Example 3), excellent liquid absorbing properties and liquid retaining properties can always be obtained, and good results can also be obtained regarding its tensile strength and buckling strength. .

 The fibers * 1 to * 2 in Table 2 are as follows.

* 1 Glass fiber A: Composition = A in Table 1 average diameter = 0.8 µm * 2 Glass fiber B: Composition = B in Table 1 Average diameter = 0.8 µm Further, the measuring methods of various characteristic values in Examples and Comparative Examples. Is as follows.

Thickness (mm) Measure the sample while pressing it in the thickness direction with a load of 20 kg / dm ² . (JISC-2202) Unit weight (g / cm ³ ) A value obtained by dividing the sample weight by the sample area.

Density (g / cm ³ ) Sample (weight W) Area (S) of 10 cm × 10 cm (S) When the load of 20 kg is applied to the thickness of the sample, the formula: W / (S ×
It is represented by the value given by T) (g / cm ³ ).

Loss on ignition (%) The sample is heated in air to 600 ° C until a constant weight is reached, and the loss is divided by the original sample weight.

Liquid absorption speed (mm / 5 minutes) The liquid absorption rate is determined by making the sample vertical and immersing the lower part in a dilute sulfuric acid solution having a specific gravity of 1.3, and measuring the liquid level that rises with time after 5 minutes.

Tensile strength (g / 15mm width) Pull both ends of a sample with a width of 15mm, find the value of the external force when it cuts, divide by the thickness, and display with width 15mm, value per 1mm of thickness (g) To do.

Buckling strength (g / 10mm width) Prepare a sample with a width of 50mm and a length of 100mm, 50mm above the length
Hold the sample with a holder, hold it so that the lower 50 mm is protruding, make the lower tip of the sample contact the scale, and gently lower the holder to press the sample against the scale, and load when buckling (g ). Then, the value is converted into a value per width 10 mm and thickness 1 mm and displayed.

Liquid retentivity under pressure (g / cc) 20kg / dm ² A sample with a thickness of 1mm and dimensions of 10cm × 10cm was made to contain water, and a weight of 20kg was applied in the thickness direction. The water content (g) was determined and is shown by the value divided by the volume (cc) of the sample.

[Effects of the Invention] As described in detail above, the storage battery separator of the present invention is
Consisting essentially of glass fibers,
A glass is made by mixing 3 to 20% by weight of all glass fibers with a low softening point glass fiber having a softening point of 50 to 400 ° C. lower than the softening point of the main glass fiber, and glass fibers are heat-sealed together. Since it is composed of only fibers, it has good liquid absorption and liquid retention properties, and particularly excellent liquid retention properties under pressure. Also,
Excellent in oxidation resistance.

Since the glass fibers are stably bonded by heat fusion, high strength and hardness can be obtained.

And so on.

Moreover, in its production, according to the method of the present invention, it is possible to easily and efficiently produce an extremely high-performance separator without requiring strict control of the heat fusion treatment conditions.

According to such a separator of the present invention, a high-performance storage battery can be manufactured with excellent workability, and its industrial utility is extremely high.

Claims (6)

(57) [Claims] 1. A storage battery separator comprising substantially only glass fibers, wherein the low softening point glass fiber having a softening point lower than that of the main glass fiber by 50 to 400 ° C. is all glass fibers. A storage battery separator, characterized in that it is mixed in an amount of 3 to 20% by weight, and glass fibers are fused together. 2. Glass fibers having an average diameter of 10 to 30 μm, 0 to 35% by weight, glass fibers having an average diameter of more than 2 μm and less than 10 μm 0
The storage battery separator according to claim 1, wherein the storage battery separator is composed of glass fibers having a balance of -30% by weight and a balance average diameter of 2 μm or less. 3. The storage battery separator according to claim 1, which has a density of 0.16 ± 0.03 g / cm ³ . 4. The storage battery separator according to any one of claims 1 to 3, which has a tensile strength of 400 g / 15 mm width × 1 mm thickness or more. 5. The storage battery separator according to claim 1, which has a buckling strength of 30 g / 10 mm width × 1 mm thickness or more. 6. A method for producing a storage battery separator consisting essentially of glass fibers, which comprises glass fibers as a main component and a softening point of 50 to 40 higher than the softening point of the main glass fibers.
A low softening point glass fiber having a low softening point of 0 ° C. is mixed so that the ratio of the low softening point glass fiber is 3 to 20% by weight of all the glass fibers, and the softening point and the low softening point glass of the main glass fiber are mixed. A method for manufacturing a separator for a storage battery, comprising heating the glass fibers by heating at a temperature midway between the softening point of the fibers and the glass fibers.