JP7370510B2 - Separator for electric double layer capacitor and its manufacturing method - Google Patents

Description

The present invention relates to a separator for electric double layer capacitors (hereinafter sometimes referred to as "separator") and a method for manufacturing the same, and more specifically relates to a nonwoven fabric (hereinafter referred to as "separator") manufactured by a melt blow method using a heat-resistant resin as a raw material. The present invention relates to a separator for an electric double layer capacitor composed of a thin film laminate of a melt-blown non-woven fabric formed by bonding a plurality of sheets together to form a thin film (also referred to as "melt-blown non-woven fabric"), and a method for manufacturing the separator.

In recent years, with the miniaturization and diversification of electronic devices, there has been a demand for thin and high-performance power storage devices. In particular, with the expansion of applications in electric vehicles and the like, electric double layer capacitors are required to have a larger capacity and a longer life, and there is a strong desire for the development of further improved electric double layer capacitors that can be rapidly charged and discharged.
Such an electric double layer capacitor has a basic structure including an electrode pair consisting of a positive electrode and a negative electrode, a separator placed between the two electrodes, and an electrolyte that impregnates the separator, and the performance of the separator is Since separators have a large effect on the performance of capacitors, many proposals have been made regarding separators. For example, Patent Document 1 discloses a separator for an electric double layer capacitor that includes a fiber layer containing ultrafine fibers with a fiber diameter of 4 μm or less and thick fibers with a fiber diameter of 7 μm or more. According to such a separator, even if high pressure is applied, the separator can be prevented from breaking due to the presence of thick fibers, and a certain amount of voids can be secured, and it also contains ultra-fine fibers. There is a description that the retention of ionic solutions can be ensured by this method.
Further, Patent Document 2 discloses a separator for an electric double layer capacitor made of a nonwoven fabric having a two-layer structure of a glass fiber-containing layer and a cellulose fiber layer.

However, according to the prior art as described above, there is still no sufficient disclosure regarding the control of the dispersion state of fibers and pores in the three-dimensional space in the thickness direction of the separator. Cellulose fibers and glass fibers have been used as such, but the use of ultrafine fibers alone cannot effectively control the pore distribution in three-dimensional space, resulting in poor electrolyte retention. It has been pointed out that the problem is that the resistance is low and the internal resistance is also high. Furthermore, these materials also have the disadvantage of low mechanical strength.

In addition, separators made by laminating nonwoven fabrics manufactured using different manufacturing methods, such as SMS (spunbond/melt blow/spunbond), have been proposed, but bulky nonwoven fabrics are calendered at high temperatures in order to reduce the thickness and improve interlayer adhesion. If this is done, even if the pore distribution on the surface can be controlled to some extent, excessively crushed portions will occur, making it impossible to realize a three-dimensional structure that is effective as a separator. Therefore, there was a problem in that a separator with low air permeability and high internal resistance was formed. In addition, such a nonwoven fabric laminate has the disadvantage that the shrinkage rate is large at high temperatures because nonwoven fabrics manufactured by different manufacturing methods are simultaneously pressure-bonded. Furthermore, due to the nature of nonwoven fabrics, shading occurs in the arrangement structure of the constituent fibers and the physical properties of the base material become non-uniform, so it has been desired to reduce the shading.

Japanese Patent Application Publication No. 2003-45752 Japanese Patent Application Publication No. 2017-168743

Therefore, an object of the present invention is to overcome the contradictory characteristics of having electrical insulation properties and preventing short circuits between the positive and negative electrodes, and at the same time having excellent wettability with electrolyte and excellent electrolyte retention. To provide a separator for an electric double layer capacitor made of a melt-blown nonwoven fabric laminate that can achieve both of these properties, reduce shading that occurs in the arrangement structure of constituent fibers, and have uniform characteristics, and a method for producing the separator. be.

Therefore, in order to solve the problems of the above-mentioned invention, the present inventors have made extensive studies and found that the dispersion of fibers and pores in a three-dimensional space in the surface and thickness direction of a separator made of a melt-blown nonwoven fabric laminate. We focused on the fact that the above-mentioned problems of the present invention can be solved if fibers and pores of appropriate size can be arranged in a well-balanced manner, and based on this knowledge, we have come up with the idea of completing the present invention.
In other words, in view of solving the problem, as mentioned above, in order to achieve a well-balanced arrangement of fibers of appropriate size and pores, we created at least two layers of melt-blown nonwoven fabric thin films manufactured using heat-resistant resin as the raw material resin. A laminate with a basis weight adjusted to 50 g/m2 or less, a thickness of 50 μm or less, an average fiber diameter controlled to 0.5 to 15 μm, and a pore size distribution set to a specific range as shown below. By doing so, the above-mentioned contradictory characteristics can be made compatible. A melt-blown nonwoven thin film laminate that can have both of these properties can be obtained by a two-step calendering process: a first calendering process under high-temperature conditions using metal rolls and a second calendering process using elastic rolls. I discovered that it can be done. In particular, by using a nonwoven fabric thin film laminate made only of nonwoven fabrics produced by the melt blowing method, it is possible to maintain a stable pore size distribution and to stabilize the above-mentioned properties, resulting in lower yields in the production process. In some cases, it is possible to carry out low-cost production, and the value of industrial use is extremely large.

Thus, the gist of the present invention is as shown in the following (1) to (14).
In this specification, the inventions according to (1) to (6) are referred to as the first invention, the inventions according to (7) to (13) are referred to as the second invention, and the invention according to (14) is referred to as the third invention. There is a thing.

(1) A separator for an electric double layer capacitor composed of a melt-blown non-woven fabric thin film laminate formed by laminating at least two layers of melt-blown non-woven fabric thin films, the separator comprising:
The average fiber diameter of the fibers constituting the melt-blown nonwoven thin film laminate is 0.5 to 15 μm, the Gurley air permeability is 1 to 40 s/φ10/300 cc, and the heat shrinkage rate is 1 hour at 150° C. After heat treatment under these conditions, the shrinkage change in shape in either the MD direction or the CD direction, expressed as a dimensional change rate, is 1.2% or less, and the electrolyte retention rate is 260% or more. A separator for electric double layer capacitors featuring:

(2) The electric double layer capacitor according to (1) above, wherein the average fiber diameters of the constituent fibers of each layer of the at least two melt-blown non-woven fabric thin films constituting the melt-blown non-woven fabric thin film laminate are substantially the same or different from each other. separator.

(3) The melt-blown nonwoven fabric thin film laminate is an interlayer adhesion processed body formed by partial thermal fusion of fibers present at the interface between each layer of at least two layers of melt-blown nonwoven fabric thin films constituting this ( 1) The separator for electric double layer capacitors according to item 1).

(4) The separator for an electric double layer capacitor according to (1) above, wherein the ratio of pores having a pore diameter in the range of 3 to 7 μm out of all the pores in the melt-blown nonwoven thin film laminate is 50% or more.

(5) The separator for an electric double layer capacitor according to (1) above, wherein the melt-blown nonwoven fabric thin film laminate has a pore size distribution that satisfies the following 1 to 5.
1. Maximum pore diameter: 15 μm or less2. Minimum pore diameter: 3μm or less3. Average pore diameter: 8 μm or less4. Maximum pore diameter/average pore diameter: less than 2.005. Maximum pore diameter/minimum pore diameter: 5.00 or more

(6) The separator for an electric double layer capacitor according to (1) above, wherein the constituent material of the melt-blown nonwoven fabric thin film laminate is a heat-resistant resin.

(7) A method for producing a separator for an electric double layer capacitor comprising a melt-blown non-woven fabric thin film laminate formed by laminating at least two layers of melt-blown non-woven fabric thin films, the method comprising:
(a) At least two raw melt-blown nonwoven fabrics are stacked one on top of the other, and a calender mechanism having metal rolls suppresses processing temperature conditions higher than the glass transition point of the raw material resin and crushing of the constituent fibers of the raw melt-blown nonwoven fabric. , and a first calendering process in which calendering is performed under pressurized conditions that are adjusted to conditions that allow thinning.
(b) The calendering intermediate obtained in the first calendering step is subjected to effective processing temperature conditions and the crushing of the constituent fibers of the nonwoven fabric is suppressed by a calender mechanism having at least one elastic roll. , and a second calendering step in which calendering is performed under pressurized conditions adjusted to conditions that allow thinning. A method for producing a separator for an electric double layer capacitor composed of a nonwoven thin film laminate.

(8) The method for producing a separator for an electric double layer capacitor according to ( 7 ) above, wherein in the first calender processing step, the processing temperature condition above the glass transition point is a temperature of 130° C. or above.

(9) In the first calendering process, the linear pressure of the metal roll is 200 N/mm or less among the pressurizing conditions adjusted so as to suppress the collapse of the constituent fibers of the melt-blown nonwoven fabric material. The method for producing a separator for an electric double layer capacitor according to (7).

(10) In the second calender processing step, the calender mechanism includes a combination of at least one pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and a metal roll. 7) The method for manufacturing a separator for an electric double layer capacitor according to item 7).

(11) In the second calender processing step, the calender mechanism includes a combination of at least one pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and an elastic roll. 7) The method for manufacturing a separator for an electric double layer capacitor according to item 7).

(12) The method for producing a separator for an electric double layer capacitor according to (7) above, wherein in the second calendar processing step, an effective processing temperature condition is a temperature of 130° C. or lower.

(13) The method for producing a separator for an electric double layer capacitor according to (7) or (12), wherein in the second calendering step, the elastic material of the elastic roll is a synthetic resin.

(14) Next step:
(a) At least two raw melt-blown nonwoven fabrics are superimposed, and a metal roll suppresses processing temperature conditions higher than the glass transition point of the raw material resin and crushing of the constituent fibers of the raw melt-blown nonwoven fabric, and forms a thin film. a first calendering process in which calendering is performed under pressurized conditions adjusted to allow for
(b) The calendering intermediate obtained in the first calendering step is subjected to effective processing temperature conditions and the crushing of the constituent fibers of the nonwoven fabric is suppressed by a calender mechanism having at least one elastic roll. A separator for an electric double layer capacitor manufactured by a method comprising: and a second calender processing step in which the separator is subjected to calender processing under pressurized conditions adjusted to conditions that allow thinning.

The present invention has the above-mentioned configuration, and according to the first invention, a separator for an electric double layer capacitor composed of a melt-blown nonwoven fabric thin film laminate has a specific pore size distribution. Despite its small thickness, significant deformation of the constituent fibers of the nonwoven fabric is suppressed, there is no formation of transparent spots due to the formation of a film at intertwined parts, and the Gurley air permeability is within a good range, making it resistant to heat at high temperatures. It also has the effect of having a low shrinkage rate.
In addition, by laminating and combining nonwoven fabric layers having fibers with the same or different average fiber diameters, a specific pore size distribution can be obtained, and in particular, the liquid absorption and liquid retention properties of the electrolyte can be improved. By using a melt-blown nonwoven fabric thin film laminate having such characteristics as a separator, we have successfully applied it to electric double layer capacitors (EDLC), thereby realizing stable performance and improving safety of electric double layer capacitors. Therefore, it is possible to improve productivity.
According to the second invention, there is provided a calendering process that is a combination of two steps, a first calendering process and a second calendering process. As shown in the Examples and Comparative Examples described later, by subjecting it to the calendering process, a melt-blown nonwoven thin film laminate having the above-mentioned performance obtained by the first invention and the second invention can be obtained for the first time. It is possible to achieve remarkable effects such as being able to provide a separator for an electric double layer capacitor that is suitable for use in electric double layer capacitors.
Furthermore, according to the third invention, effects equivalent to those of the first invention and the second invention can be achieved.

1 is a graph showing the pore size distribution of a PBT melt-blown nonwoven thin film two-layer laminate produced in Example 1. 2 is a graph showing the pore size distribution of a PBT melt-blown nonwoven thin film three-layer laminate produced in Example 2. 1 is a graph showing the pore size distribution of a PBT nonwoven fabric thin film monolayer a (monolayer comparative product (a)) produced by the method of Comparative Example 1. 3 is a graph showing the pore size distribution of a PBT nonwoven fabric thin film single layer body d (single layer comparative product (d)) manufactured by the method of Comparative Example 4. 3 is a graph showing the pore size distribution of a PP nonwoven fabric thin film monolayer e (monolayer comparative product (e)) produced by the method of Comparative Example 5. 2 is a graph showing a pressure-permeation flow rate curve for determining the average pore diameter, maximum pore diameter, and minimum pore diameter by the bubble point method.

The present invention will be explained in detail below.
A. First invention
1. Electric double layer capacitor separator composed of melt-blown nonwoven thin film laminate:
According to a first aspect of the invention, there is provided a separator for an electric double layer capacitor that is composed of a melt-blown nonwoven fabric thin film laminate whose constituent material is a heat-resistant resin. Such a melt-blown nonwoven thin film laminate has at least the following physical properties.
That is,
・The thickness is 50 μm or less,
・The basis weight is 5 to 100 g/m2,
・The average fiber diameter is 0.5 to 15 μm,
・Gurley air permeability is 1 to 40s/φ10/300cc,
・Even after heat treatment under heating conditions of 150°C for 1 hour, the heat shrinkage rate is 1.2% or less, expressed as a dimensional change rate in either the MD direction or the CD direction. .
Furthermore, as mentioned above, even though the film thickness was reduced to 50 μm or less, it had excellent electrolyte absorption performance and electrolyte retention performance. As shown, it is possible to achieve an electrolyte absorption rate of 15 seconds or less and an electrolyte retention rate of 280% or more.
Furthermore, the degree of porosity of the melt-blown nonwoven fabric thin film constituting the electric double layer capacitor according to the present invention was sufficiently maintained due to the presence of pores existing in the gaps between the fibers constituting the melt-blown nonwoven fabric thin film laminate observed by SEM. It is something.

2. Structure of melt-blown nonwoven thin film laminate:
(1) Characteristics The melt-blown nonwoven thin film laminate according to the present invention is a nonwoven fabric laminate formed by laminating and bonding at least two nonwoven fabric layers. In particular, it is preferable to employ a laminated nonwoven fabric formed by laminating and bonding at least two or more nonwoven fabric layers, depending on the application, since it has the following distinctive effects compared to a single layer. Such melt-blown nonwoven fabric thin film laminates include (A) one in which nonwoven fabric layers having the same physical properties are bonded together, and (B) a nonwoven fabric layer in which physical properties include fibers having at least different average fiber diameters bonded together. I can list things.

As described later, the above-mentioned "nonwoven fabric laminated body" is formed by bonding the nonwoven fabric layers to each other by, for example, a first calendering treatment under high temperature conditions and a second calendering treatment under special conditions. This includes processed products obtained by. By pressure bonding, an interlayer adhesion processed body is formed in which some of the fibers constituting the nonwoven fabric layer are bonded to each other by heat fusion. The heat-fused portion may account for 50% or less of the fibers present at each interface of the nonwoven fabric layer, and can be appropriately selected from the viewpoint of maintaining the formation of the nonwoven fabric thin film laminate.
(A) A nonwoven fabric laminate formed by laminating nonwoven fabric layers with the same physical properties is one in which the average fiber diameter of the constituent fibers of each nonwoven fabric layer of at least two layers is substantially the same, and other physical properties are Values, for example, at least two or more physical property values such as basis weight, tensile strength, and tensile elongation may be substantially the same. According to such a configuration, for example, when the average fiber diameter is the same, by bonding a laminate of fine fibers together, variations in physical property values are made more uniform compared to a single layer, and the separator for electric double layer capacitors can be used. When used, short circuits can be prevented, and tensile strength and electrolyte retention properties can be improved.

On the other hand, according to (B) lamination of at least two nonwoven fabric layers having fibers with different average fiber diameters, the resulting melt-blown nonwoven fabric thin film laminate has excellent tensile strength and Gurley air permeability as shown in Examples. In addition, the liquid absorption performance and liquid retention performance of the electrolytic solution can be improved. In particular, a bonded nonwoven fabric laminate obtained by combining nonwoven fabric layers each having fine fibers and thick fibers can improve tensile strength, Gurley air permeability, electrolyte absorption performance, and liquid retention performance.

Specifically, the fine fibers have an average fiber diameter of 0.5 to 10 μm, preferably 1 to 5 μm, and more preferably 1.5 to 4 μm, while the thick fibers include is a nonwoven fabric layer having an average fiber diameter of 1 to 15 μm, preferably 1.5 to 10 μm, more preferably 2 to 5 μm, and having fine fibers and thick fibers whose average fiber diameters do not overlap with each other. A combination is preferred.

(2) Pore structure of melt-blown non-woven fabric thin film laminate The melt-blown non-woven fabric thin-film laminate constituting the electric double layer capacitor separator according to the present invention has a group of fibers arranged in a three-dimensional space in the surface and thickness direction; The pores are formed in the gaps due to the arrangement of the fiber groups. Since the melt-blown nonwoven thin film laminate is made of synthetic resin, it has electrical insulation properties, and its pore structure allows it to retain contradictory properties, such as electrolyte retention. The material has uniform physical properties, and has a pore size distribution controlled in at least the following two points, as described below.

a. The first point is that in the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention, pores with a pore diameter in the range of 3 to 7 μm account for 50% or more of the total pores. be.
The proportion of pores having a pore diameter in the range of 3 to 7 μm is preferably 60% or more, more preferably 70% or more, and the uniformity of the pore diameter is extremely high.
Figures 1 and 2 below show the pore size distributions of two-layer and three-layer PBT melt-blown nonwoven thin film laminates according to Example 1 and Example 2, respectively. According to the invention, the size of the pores is extremely controlled, and as a result, the formation of uneven appearance is controlled, air permeability is maintained, and the electrolyte retaining property is excellent.
On the other hand, when the pore size is below the range of 3 to 7 μm, the variation in properties is reduced but the air permeability decreases, whereas when the pore size is above the range of 3 to 7 μm, the air permeability is improved. However, variations in properties become large, causing problems such as instability in appearance and other physical properties.
In addition, FIGS. 3, 4, and 5 show the pore size distributions of the nonwoven fabric monolayers produced in Comparative Example 1, Comparative Example 4, and Comparative Example 5, respectively. As shown in FIG. The pore diameter of the PBT melt-blown nonwoven fabric monolayer according to Comparative Example 1 showed wide variation, indicating that the uniformity of the pore diameter was significantly lower than that of the melt-blown nonwoven fabric laminate of Examples 1 and 2.
Further, as shown in FIG. 4, the pore size distribution of the melt-blown nonwoven fabric monolayer according to Comparative Example 4 also has a peak range of 3 to 7 μm that the melt-blown nonwoven fabric thin film laminate according to the present invention has, as shown in FIGS. 1 and 2. It is a deviation.

stomach. The second point is that the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention has the following pore size distribution (1) to (5):
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter/average pore diameter: Less than 2.00 (5) Maximum pore diameter/minimum Pore diameter: 5.00 or more is satisfied, especially (4) "maximum pore diameter/average pore diameter" is less than 2.00, and (5) "maximum pore diameter" /minimum pore diameter" is 5.00 or more.

The maximum pore diameter of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is preferably 15 μm or less. When the maximum pore diameter is 15 μm or less, the pore diameter has excellent uniformity, ensuring electrical insulation and controlling the possibility of short circuits. In addition, the electrolytic solution retention property can be improved, and from that point of view, the thickness is more preferably 13 μm or less, and particularly preferably 11 μm or less.

The minimum pore diameter of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is preferably 3 μm or less. When the minimum pore diameter is 3 μm or less, the electrolyte retention property can be maintained and the possibility of short circuit can be reduced. The lower limit of the minimum pore diameter is not particularly limited, but from the viewpoint of electrolyte retention, it is 1 μm or more, preferably 1.5 μm or more.

The average pore diameter of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is preferably 8 μm or less. When the average pore diameter is 8 μm or less, the possibility of short circuiting is reduced. Further, when the thickness is 8 μm or less, the electrolyte retention property is also excellent.

The ratio of the maximum pore diameter to the average pore diameter (maximum pore diameter/average pore diameter) of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is less than 2.00, preferably 1 .50 or more. When the maximum pore size/average pore size is less than 2.00 and 1.50 or more, the pore size distribution becomes uniform within a specific pore size range, and the electrolyte retention property is unexpectedly improved significantly. was found from the results of numerous experiments. From the viewpoint of electrolyte retention, it is preferably 1.90 or less, more preferably 1.85 or less, particularly preferably 1.75 or less, and in the range of 1.50 or more.
The ratio of the maximum pore diameter to the minimum pore diameter (maximum pore diameter/minimum pore diameter) of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 5.00 or more. When the maximum pore size/minimum pore size is 5.00 or more, the pore size distribution becomes uniform within a specific pore size range, and the electrolyte retention property is unexpectedly improved significantly. From the viewpoint of electrolyte retention, it is preferably 5.30 or more, more preferably 5.50 or more, particularly preferably 5.70 or more. On the other hand, the upper limit is 7.00, preferably 6.00 or less.

3. Constituent material of melt-blown nonwoven fabric thin film laminate The constituent material of the melt-blown nonwoven fabric thin film laminate according to the present invention is a component containing a heat-resistant resin, and may be a mixture of two or more heat-resistant resins. Derived from the opposite component. A specific example is as follows.

As the raw material resin for the melt-blown nonwoven fabric according to the present invention, a heat-resistant resin is selected from the viewpoint of maintaining high temperature stability.
As the heat-resistant resin, thermoplastic synthetic resins with a melting point of 200°C or higher are suitable, and specific examples include polyester, polyamide, polyimide, polyacrylonitrile, polyarylene sulfide, polycarbonate, polyphthalamide, polyolefin, etc. can.

Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate (hereinafter sometimes abbreviated as PBT), polybutylene isophthalate, polybutylene adipate, poly(1,6-hexamethylene terephthalate, poly(ethylene-2,6- naphthalate), poly(1,4-cyclohexylene methylene terephthalate), etc.These may be homopolymers, copolymers, or mixtures thereof.Among these polyesters, polybutylene Terephthalate, a mixture of polybutylene terephthalate and polybutylene isophthalate, etc. are preferable as raw material resins for the melt-blown nonwoven fabric thin film laminate related to the present invention. By using these, melt-blown spinnability is improved and the tensile strength of the melt-blown nonwoven fabric thin film laminate is improved. In addition, polybutylene terephthalate preferably has a number average molecular weight of 5,000 to 20,000.Furthermore, one having an IV value of 0.6 to 0.9 is preferable.

Examples of the polyamide (hereinafter sometimes abbreviated as PA) include nylon 6, nylon 66, nylon 6-66 copolymer, nylon 12, nylon 6-12 copolymer, nylon 46, and the like. For melt-blown nonwoven fabrics, those with as low a molecular weight as possible are preferable because they have good spinnability and thin fibers can be obtained. For example, PA with a number average molecular weight of 10,000 to 25,000 is preferable.

The polyarylene sulfide is a resin with excellent heat resistance and chemical resistance, and includes a polymer in which 90 mol% or more of the structural units are [C6H4S], and in particular, a polymer with a melt viscosity (V6) of 200 to 200. 500 poise polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) is preferred.

Polyphthalamides are not particularly limited, but include those containing terephthalamide units and isophthalamide units, such as hexamethylene terephthalamide-isophthalamide-adipamide terpolymer (mole ratio 65: 25:10), etc. Examples of the raw material resin for the melt-blown nonwoven thin film laminate include those having a melt viscosity of 100 to 1000 Pas.
Further, examples of the polyolefin include polymethylpentene, cyclic olefin polymer, and the like.

4. Physical Properties of Meltblown Nonwoven Fabric Thin Film Laminate Next, physical property values that the meltblown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention should have will be explained.
In addition, when the melt-blown nonwoven fabric thin film laminate is composed of two or more nonwoven fabric thin film layers having different physical property values, these physical property values are the average values of all such nonwoven fabric thin film layers.

(1) Average fiber diameter The average fiber diameter of the fibers in each nonwoven fabric layer of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 0.5 to 15 μm, preferably 1.0 to 10 μm, More preferably, it is 1.5 to 8 μm. If the average fiber diameter is less than 0.5 μm, not only the tensile strength becomes weak, but also the internal resistance of the electric double layer capacitor becomes too large to be used as a separator. On the other hand, if the average fiber diameter exceeds 15 μm, there is a risk that the separator may have an increased risk of internal short circuit.

(2) Fabric weight The melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention has a fabric weight of 5 to 100 g/m2, preferably 7 to 50 g/m2, and more preferably 10 to 40 g/m2. . If the basis weight is less than 5 g/m2, the tensile strength will be insufficient, resulting in lower reliability in battery assembly, and this is not preferred as a separator because short circuits are likely to occur. On the other hand, if the basis weight exceeds 100 g/m2, the internal resistance of the separator may increase.

(3) Thickness The thickness of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 50 μm or less, preferably 1 to 45 μm as the electric double layer capacitor separator and lithium secondary battery separator. , particularly preferably from 5 to 40 μm, more preferably from 10 to 35 μm. When the thickness exceeds 1 μm, the risk of internal short circuit is suppressed as a separator, while when it exceeds 50 μm, there is a risk that the battery capacity will decrease.

(4) Gurley air permeability The Gurley air permeability of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 1 to 40 s/φ10/300 cc, preferably 5 to 30 s/φ10/300 cc. be. If the Gurley air permeability is less than 1 s/φ10/300 cc, the risk of internal short circuit as a separator increases, while if it exceeds 40 s/φ10/300 cc, a problem arises in that the internal resistance increases as a separator.
In addition, "Gurley air permeability" is determined by a measurement method according to JIS P8117 (2009) "Paper and paperboard - Air permeability and air resistance test method" (intermediate area) - Gurley method, as described below. It means the result obtained.

(5) Tensile strength The tensile strength of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 2 to 50 N/25 mm width, preferably 5 to 40 N/25 mm width. If the tensile strength is less than 2N/25mm width, breakage is likely to occur during battery assembly. On the other hand, when the tensile strength exceeds 50 N/25 mm width, the elongation is extremely reduced, and there is a possibility that problems may easily occur due to the reduced degree of freedom during assembly.

(6) Tensile elongation The tensile elongation of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 1 to 100%, preferably 5 to 80%. If the tensile elongation is less than 1%, breakage is likely to occur during assembly. On the other hand, if the tensile elongation is 100% or more, necking is likely to occur and there is a possibility that stable assembly may be difficult.

(7) Heat shrinkage rate The heat shrinkage rate at high temperatures of the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention is 1.0% or less in a heating environment at 120°C for 1 hour; Preferably it is 0.5% or less, and in a heating environment at 150° C. for 1 hour, it is 1.2% or less, preferably 1.0% or less. It is desirable that this value satisfy at least one of the MD direction or the CD direction, and more preferably both. If the thermal shrinkage rate is high, the separator at the end will shrink due to the internal temperature rising when an abnormality occurs in the electric double layer capacitor in a high-temperature environment, and problems such as internal short circuits may occur due to contact between the positive and negative electrodes. .

(8) Electrolyte absorption rate The electrolyte absorption property of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is determined by the pore structure of the electrolyte liquid absorption rate, which allows the separator to smoothly absorb the electrolyte solution, for example, propylene carbonate. According to the present invention, it is possible to provide an electrolyte absorbing rate of 20 seconds or less, further 10 seconds or less, as determined by the measurement method described below. .
(9) Electrolyte retention rate The melt-blown nonwoven thin film laminate constituting the separator for electric double layer capacitors according to the present invention can be used as a separator after absorbing electrolyte due to the dispersion state of its constituent fibers and the specificity of its pore structure. It has excellent liquid retention properties, and it shows 260% or more by the measurement method described below, and can provide 360% or more, and even about 380%.
(10) Static electricity The amount of static electricity of the melt-blown nonwoven fabric thin film laminate that constitutes the electric double layer capacitor according to the present invention is small as shown in Table 1, which reduces sticking on the production line and contributes to improving battery productivity. be able to.
As explained above, the melt-blown nonwoven fabric laminate constituting the electric double layer capacitor separator according to the first invention is a laminate formed by laminating at least two or more layers of melt-blown nonwoven fabric made of heat-resistant resin, and comprising:
The proportion of pores with a pore diameter in the range of 3 to 7 μm among all pores is 50% or more, preferably 60% or more,
And the following (1) to (5):
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter/average pore diameter: Less than 2.00 (5) Maximum pore diameter/minimum Pore size: It has a pore size distribution satisfying 5.00 or more,
At least the following physical properties;
・Thickness is 50μm or less,
・Weight is 5-100g/m2,
・Average fiber diameter is 0.5 to 15 μm,
・Gurley air permeability is 1~40s/φ10/300cc,
・The heat shrinkage rate is 1.2% or less, expressed as a dimensional change rate in either the MD direction or the CD direction, even after heat treatment under heating conditions of 150°C for 1 hour. .
As one method, such a melt-blown nonwoven thin film laminate can be manufactured through the following calendering process.
That is, (a) a laminate obtained by laminating melt-blown nonwoven fabrics is processed using a metal roll at a temperature higher than the glass transition point of the heat-resistant resin, and crushing of the constituent fibers of the melt-blown nonwoven fabrics is suppressed. A first calender processing step in which calender processing is performed under pressurized conditions adjusted as follows;
(b) The calendering intermediate obtained in the first calendering step is processed using an elastic roll under effective processing temperature conditions and under pressure conditions adjusted to suppress collapse of the constituent fibers of the nonwoven fabric. A melt-blown nonwoven fabric laminate having at least the above-mentioned physical properties can be obtained by calendering, which includes a second calendering treatment step below.

B. Second invention According to the second invention, there is provided a method for manufacturing a separator for an electric double layer capacitor comprised of a melt-blown nonwoven fabric thin film laminate.
That is, a method for producing a separator for an electric double layer capacitor comprising a melt-blown non-woven fabric thin film laminate in which raw melt-blown non-woven fabrics produced using a heat-resistant resin as a raw material resin are laminated and thinned.
There is provided a method for producing a melt-blown nonwoven fabric laminate, characterized in that the melt-blown nonwoven fabrics are laminated and subjected to at least (a) a first calendering process and (b) a second calendering process.
Here, the term "melt-blown nonwoven fabric" refers to a nonwoven fabric manufactured by a melt-blowing method, which is to be thinned into a nonwoven fabric thin film laminate.

1. Melt-blown non-woven fabric The following describes the physical properties of the melt-blown non-woven fabric used as a base material for the production of the melt-blown non-woven fabric laminate constituting the electric double layer capacitor separator according to the present invention, and the method for producing the melt-blown non-woven fabric having such physical properties. Explain.
The melt-blown nonwoven fabric material constituting the electric double layer capacitor separator according to the present invention is produced by a melt-blowing method using a heat-resistant resin as a raw material resin.
The heat-resistant resin is as described above, and can be appropriately selected and used from such heat-resistant resins. However, for the purpose of the present invention, polybutylene terephthalate is suitable as described above, and the melt-blown resin described below is suitable. The manufacturing conditions for the raw nonwoven fabric are based on the case where polybutylene terephthalate is used as the heat-resistant resin.

The melt-blown nonwoven fabric material is an important element for producing the melt-blown nonwoven fabric thin film laminate according to the present invention, and preferably has at least the following physical properties.
(1) Fabric weight The fabric weight of the melt-blown nonwoven fabric according to the present invention is 4 to 80 g/m2, preferably 5 to 50 g/m2, and more preferably 6 to 40 g/m2. If the basis weight does not reach 4 g/m2, the tensile strength of the melt-blown nonwoven thin film laminate obtained after calendering treatment will be insufficient. On the other hand, if the basis weight exceeds 80 g/m2, fluff will increase and the nonwoven thin film laminate will not be stable. Problems such as difficulty in manufacturing the body may arise.
(2) Thickness The thickness of the melt-blown nonwoven fabric according to the present invention varies depending on the type of raw material resin, manufacturing conditions, etc., but is 50 to 800 μm, preferably 60 to 400 μm, more preferably 70 to 300 μm, and especially As the separator for an electric double layer capacitor according to the present invention, a melt-blown nonwoven fabric original fabric adjusted to a thickness of 300 μm or less, particularly preferably 250 μm or less is preferable.
(3) Air permeability The permeability of the raw melt-blown nonwoven fabric according to the present invention is 10 to 400 cc/cm2/s, preferably 20 to 300 cc/cm2/s. When the air permeability is less than 10 cc/cm2/s, the Gurley air permeability of the melt-blown nonwoven thin film laminate obtained after the first calendering treatment becomes high and exceeds 40 s/φ10/300 cc; If it exceeds cm2/s, the Gurley air permeability of the melt-blown non-woven thin film laminate decreases to less than 1 s/φ10/300 cc. A problem arises in that there is a greater possibility that the product cannot be manufactured.
(4) Tensile strength The tensile strength of the melt-blown nonwoven fabric according to the present invention is at least 1N/25mm width or more so that a meltblown nonwoven fabric thin film laminate having a tensile strength of 2 to 50N/25mm width is provided, Preferably, the width is 3N/25mm or more. If the tensile strength of the original melt-blown nonwoven fabric does not reach 1 N/25 mm width, a problem arises in that it is not possible to obtain a melt-blown nonwoven fabric thin film laminate having sufficient tensile strength.
(5) Tensile elongation The tensile elongation of the melt-blown nonwoven fabric according to the present invention is 1 to 150%, preferably 10 to 100%.
(6) Average fiber diameter The average fiber diameter of the fibers constituting the melt-blown nonwoven fabric according to the present invention is 0.5 to 15 μm, preferably 1 to 10 μm, and more preferably 1.3 to 5 μm. be.

2. Melt blowing method The melt blowing method for producing the melt blown nonwoven fabric material according to the present invention is not particularly limited, and for example, the method described in U.S. Pat. No. 3,650,866 and U.S. Pat. No. 3,978,185 (ExxonMobil). It is preferable to use these, and the melt blowing method described below can be adopted as a method similar to these.
In the melt blowing method, molten raw material resin is discharged as a molten polymer from multiple nozzle holes arranged in a row, and high-temperature, high-velocity air is injected from an injection gas port installed adjacent to an orifice die to blow the molten polymer. A method is adopted in which the polymer is made into fine fibers and the fiber flow is collected. Specifically, the following method is adopted.

After the raw resin is melted at an extruder temperature of 210 to 380°C, it is fed into a die set at 250 to 380°C and discharged from the die nozzle, and simultaneously stretched and made into fine fibers by high-temperature air blow gas of 260 to 380°C. , collected in a collector located away from the nozzle.

In the melt blowing device die, the nozzle hole diameter is preferably 0.1 to 1 mmφ, more preferably 0.2 to 0.8 mmφ. The number of nozzles is preferably 5 to 20/cm, more preferably 10 to 15/cm. If the nozzle hole diameter is less than 0.1 mmφ, the discharge resin pressure will be high, while if the nozzle hole diameter exceeds 1 mmφ, the fibers cannot be made thin. Also, if the number of nozzles is less than 5/cm, the discharge pressure of the raw resin will be high, while if the number of nozzles exceeds 20/cm, the fibers will be too fused together and the nonwoven fabric will lose its uniformity. becomes.

In addition, as for the production conditions of the melt blow method, in the production of melt blown nonwoven fabric using a heat resistant resin, for example, polybutylene terephthalate resin as a raw material, the extrusion temperature is 210 to 350 °C, preferably 230 to 330 °C, and the die The temperature is 250-350°C, preferably 280-330°C, and the high velocity air temperature is 260-380°C, preferably 300-350°C. If the extruder/die and air temperatures are below the above range, the discharge resin pressure will be high and fine fibers will not be obtained. On the other hand, if it exceeds the above range, gelation of the resin will be promoted and it will deteriorate. In addition, it not only damages the conveyor net, but also has poor peelability of the resulting nonwoven fabric from the conveyor net, making it difficult to produce stably. The resin discharge rate is 0.05 to 3 g/min/hole, preferably 0.1 to 1 g/min/hole. If the resin discharge amount is small, the discharge resin pressure will be lower than the above range and a uniform nonwoven fabric will not be obtained.On the other hand, if the resin discharge amount exceeds the above range, the discharge resin pressure will be high and thin fibers will not be obtained. do not have.

3. Calendar Processing The melt-blown nonwoven fabric thin film laminate according to the present invention is manufactured by the following two-step calender processing process. The physical properties of such a melt-blown nonwoven fabric thin film can be adjusted by selecting the processing temperature conditions, processing pressure conditions (including roll linear pressure and clearance between rolls), and processing speed conditions for each processing step as described below. .

(a) First calender processing step The first calender processing step utilizes a calender mechanism consisting of a combination of at least two metal rolls, and specifically uses a melt blow method using heat-resistant resin as a raw material. The manufactured melt-blown nonwoven fabrics are laminated, and a pressure is adjusted using a metal roll to suppress the temperature condition above the glass transition point of the heat-resistant resin and the crushing of the constituent fibers of the nonwoven fabric laminate. Calendered under certain conditions. As the metal calender roll, commonly used ones can be employed, but those made of steel and alloy materials equivalent to steel are particularly preferred. As the calendar format and roll arrangement, an inverted L shape, Z shape, two upright shapes, etc. (Practical Plastic Terminology Dictionary, page 151 (Published by Plastics Age Co., Ltd.)) may also be adopted.

The temperature above the glass transition point of the heat-resistant resin depends on the type of the heat-resistant resin, but for polyester resins, a temperature of 130°C or above, preferably 140°C or above is adopted. The temperature conditions are adjusted by setting the respective heating temperatures of the two metal rolls to be combined.
The upper limit of the processing temperature in the first calender processing is a temperature below the melting point of the heat-resistant resin, and specifically, it is preferable to adopt a temperature 30 to 100° C. lower than the melting point. It is presumed that the first calender treatment alleviates residual strain during the production of the nonwoven fabric material and promotes crystallization of the raw material resin. As a result, high temperature stability is improved and high temperature shrinkability can be improved. Quantitative measurements of crystallization are difficult and even impractical to measure. In addition to the linear pressure of the rolls, the pressure conditions also include the clearance provided between the rolls as factors that affect thinning. The size of the clearance is set so that the thickness of the calendered intermediate after the first calendering process is at a predetermined level, and also so that crushing or deformation of the fibers in the melt-blown nonwoven fabric can be suppressed. It has been adjusted. The linear pressure of the roll is preferably 200 N/mm or less, preferably 30 to 170 N/mm, and more preferably 50 to 150 N/mm.
Under these calendering conditions, it is possible to obtain a melt-blown nonwoven thin film laminate that has a low shrinkage rate under high-temperature conditions, a low Gurley air permeability, and a low internal resistance. The clearance between the rolls can be selected within the range necessary to ensure close contact between at least two melt-blown nonwoven fabric layers and to transmit a temperature capable of promoting crystallization.

Further, the processing speed condition is 1 to 50 m/min, preferably 2 to 30 m/min, and more preferably 3 to 20 m/min. If the speed is less than 1 m/min, productivity will be low, while if it exceeds 50 m/min, there will be a problem that heat for relaxing strain and promoting crystallization will not be sufficiently transmitted.

(b) Second calender processing step In the second calender processing step, which is one element of the manufacturing process of the melt-blown nonwoven fabric thin film laminate according to the present invention, an elastic roll is used as the calender mechanism, and 1 The combination of the pair of processing rolls can be selected from a combination of two elastic rolls, an elastic roll and an elastic roll, or a combination of an elastic roll and a metal roll. Among these combinations of processing rolls, those using a combination of metal rolls and elastic rolls are particularly preferred. As for the combination of processing rolls and processing rolls, in addition to a pair of two rolls, multiple combinations of four to six rolls can also be used. Regarding the format of the calender and the arrangement of the rolls, the same format as that usable in the first calender processing process can be adopted, and the arrangement of the metal rolls can be made by appropriately combining metal rolls and elastic rolls. good. The metal roll can be the same as that used in the first calendering step, and is preferably made of steel or an alloy material equivalent to steel. The material of the elastic roll to be combined with the metal roll is preferably a material with a high coefficient of friction and made of hard synthetic resin. For example, synthetic rubber can be used. The hardness of such a roll is 60 or more Shore D hardness, preferably 70 to 90, for the purpose of adjusting the thickness and smoothness of the melt-blown nonwoven fabric thin film laminate of the present invention.

In the second calendering process, the calendering intermediate obtained in the first calendering process is held between the metal roll and the elastic roll, and the temperature is 130°C or lower, preferably 120°C or lower, and Preferably, the processing is carried out under processing temperature conditions of 110° C. or less and pressurization conditions that allow control of collapse of the fibers in the intermediate. In the second calender processing step, the lower limit of the processing temperature is at least the glass transition point, and although it depends on the type of raw material resin, it is preferably 60°C or higher, more preferably 80°C or higher. It's temperature.

The pressurizing conditions include the linear pressure of the processing rolls as well as the clearance between the processing rolls, but in the second calendering process, the thickness of the melt-blown nonwoven fabric thin film laminate to be formed is adjusted. It is preferable that the processing rolls are pinched together. The linear pressure of the processing roll is 15 to 130 N/mm, preferably 20 to 100 N/mm, and more preferably 30 to 70 N/mm.

Furthermore, the machining speed conditions may be the same as the machining speed conditions in the first processing step. Specifically, the speed is 1 to 50 m/min, preferably 2 to 30 m/min, and more preferably 3 to 20 m/min.

In the second calender processing process according to the present invention, each processing roll in a pair of processing rolls is usually heated, but in the case of a combination of a metal roll and an elastic roll, heating is performed on the metal roll. A combination processing of a cold elastic roll and a heated metal roll is provided. In addition to heating the metal roll, the elastic roll can also be heated if necessary. When heating both the metal roll and the elastic roll, the temperature is 40 to 130°C for the metal roll, preferably 60 to 120°C, more preferably 80 to 110°C, and 40 to 200°C for the elastic roll, preferably 50 to 120°C. A temperature condition of 150°C, more preferably 80 to 120°C can be appropriately employed.
Special calender processing using such an elastic roll can not only adjust the thickness of the melt-blown nonwoven thin film laminate, but also improve thickness uniformity and surface smoothness.
The melt-blown nonwoven fabric thin film laminate obtained through the first calendering process and the second calendering process can maintain a high degree of porosity and be ultra-thin, and can withstand high temperature conditions. Heat shrinkage can also be improved, Gurley air permeability is low, and tensile strength is also improved.

The calendering process as a method for manufacturing the melt-blown nonwoven fabric thin film laminate according to the present invention is performed by setting the first calendering process as the first stage and the second calendering process as the second stage, as described above. If the second calendering process is the first stage and the first calendaring process is the second stage, the thickness of the nonwoven thin film laminate will be set at the first processing stage, and the thickness of the nonwoven fabric thin film laminate will be set at the first stage. In processing where there is a gap between metal rolls, the object to be processed is too thin and comes into loose contact with the processing rolls, making it impossible to sufficiently promote crystallization due to high-temperature heat, and causing residual strain. Since relaxation is also performed at a later stage, there is a problem that the nonwoven fabric thin film laminate, which is a processed product, relaxes and shrinks in the width direction, making it impossible to use it as a product due to shape problems. It is not possible to obtain quality melt-blown nonwoven thin film laminates.

C. Third invention According to the third invention, there is provided a separator for an electric double layer capacitor manufactured by a method comprising at least the first processing step and the second processing step according to the second invention. be done.
In this product-by-process invention, the first processing step relieves the residual strain generated during the production of the original melt-blown nonwoven fabric, and at the same time forms a melt-blown nonwoven fabric thin film laminate in which the raw resin component has progressed to crystallization. However, it is technically impossible to measure and quantify such residual strain relaxation and crystallization, and even if it were possible, implementing them would be difficult in terms of labor and time. Therefore, it should be protected as a product-by-process invention.
Although the melt-blown nonwoven fabric thin film laminate constituting the electric double layer capacitor separator according to the present invention has the above-mentioned characteristics, no data has been obtained to prove the specific relationship between the relaxation of residual strain and crystallization. There is a reason that there is no such thing.
From this perspective, it has been pointed out that the third invention, a product-by-process invention, should be recognized.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples.
The physical property values of the melt-blown nonwoven fabric and the melt-blown nonwoven fabric thin film laminate described in the Examples and Comparative Examples were determined by measurement using the methods described below.
1.Methods for measuring various physical properties

(1) Fabric weight: A 100 mm x 100 mm test piece was taken from the longitudinal direction of the sample, and its weight in a moisture equilibrium state was measured, and the weight was calculated by converting it to the weight per square meter.

(2) Thickness: A 100 mm x 100 mm test piece was taken from the length direction of the sample and measured using a dial thickness gauge.

(3) Air permeability: Take a 100 mm x 100 mm test piece from the length direction of the sample, and use a Frazier type tester in accordance with the "Air permeability method A (Fragile type method)" of JIS L1096 "General textile testing methods". Measured using

(4) Gurley air permeability: Measured in accordance with JIS P8117 (2009)+. A Gurley densometer (manufactured by Toyo Seiki Co., Ltd.) is used as a measuring device, and a sample piece is tightened into a circular hole with a diameter of 10 mm and an area of 78.5 mm2. The inner cylinder mass of 567 g allows the air inside the cylinder to pass from the test cylindrical part to the outside of the cylinder. The time taken for 300 cc of air to pass was measured and defined as the Gurley value.

(5) Tensile strength and tensile elongation: Measured in accordance with JIS L1085 "Tensile strength and elongation rate" of "Nonwoven fabric test method" at a sample width of 25 mm, grip interval of 100 mm, and tensile speed of 300 mm/min.

(6) Average fiber diameter: Take 5 photographs of 5 arbitrary locations on the test piece using an electron microscope, measure the diameter of 20 fibers for each photograph, measure the diameter of these 5 photographs, and calculate the total The average diameter of 100 fibers was determined.

(7) Heat shrinkage rate: Draw a 100 mm line in the MD direction (length direction) and CD direction (width direction) at the center and edge of a 200 mm square sample, and place it in an oven set at 120 °C and 150 °C, respectively. After heating for a period of time, the wire length was measured and the dimensional change rate was determined.

(8) Electrolyte absorption property: In accordance with JIS L1907 "Water absorption test method for textile products", one drop of PC (propylene carbonate) was picked from a height of 10 mm onto the test piece, and the droplet was placed on the test piece. The time from when the specular reflection of the droplet was completely eliminated was measured with a stopwatch, and the measured value was taken as the liquid absorption rate of the electrolyte.

(9) Electrolyte retention property: A test piece of 100 mm x 100 mm is taken and immersed in PC (propylene carbonate) for 60 minutes, then taken out and left hanging for 10 minutes. The weight of the liquid-retained test piece was measured using a balance, and the liquid retention rate was calculated using the following formula.
Liquid retention rate calculation formula: (B) - (A) / (A) x 100 = liquid retention rate (%)
(However, in the formula, (A): sample weight (B): sample weight after immersion)

(10) Appearance:
The presence or absence of film formation was determined by the presence or absence of transparent spots with a diameter of 0.5 mm or more in a 100 cm 2 sample piece.
(11) Method for measuring maximum pore diameter, minimum pore diameter, and average pore diameter The average pore diameter and maximum pore diameter were measured by the bubble point method (ASTM F316-86, JIS K3832) shown below. First, a dried melt-blown nonwoven fabric test piece with a diameter of 25 mm was set in an automatic pore size distribution measuring device (model "CFP-1200AX", manufactured by Porous Materials), and the air pressure applied to one side was gradually increased. The pressure P1 at which air began to permeate through the dry test piece was determined, a dry flow rate curve shown in FIG. 3 was created, and a half dry flow rate curve was created by setting the permeation flow rate to 1/2. Similarly, the air pressure applied to one side of a 25 mm diameter melt-blown nonwoven fabric specimen whose pores were filled with a solvent with a surface tension of 16 dyne/cm (trade name "POREWICK", manufactured by Porous Materials) was gradually increased. The pressure P2 at which air began to pass through the wet test piece was determined, and the wet flow rate curve shown in FIG. 6 was created.
The average pore diameter Dav was determined from the pressure Pcross at the intersection of the half-dry flow rate curve and the wet flow rate curve using the following formula.
Dav = 4γcosα / (Pcross-P1)
[However, γ is the surface tension of the solvent, and α is the contact angle of the solvent with respect to polybutylene terephthalate. ]
The maximum pore diameter Dmax was determined by the following formula.
Dmax = 4γcosα / (P2 - P1)
The minimum pore diameter Dmin was determined by substituting the pressure value when the wet flow rate curve and the dry flow rate curve matched into the formula P2 expressing the above Dmax.
(12) Method for creating a pore size distribution graph In order to investigate the pore size distribution, the data obtained by measuring the pore size was divided into sections of 0.5 μm, the frequencies of each section were totaled, and a histogram was created. .
(13) Static electricity is measured by applying Statylon DZ4 manufactured by Shishido Static Electric Co., Ltd. at a distance of 30 mm at a right angle to the electrostatic test piece, focusing the red LED, and checking the polarity value when focused.

2. Raw material resin for manufacturing raw melt-blown nonwoven fabric The following resins were used as raw material resins for manufacturing raw melt-blown nonwoven fabric.
・Polybutylene terephthalate (PBT); melting point 225°C (manufactured by Polyplastics)
・Polypropylene (PP); melting point 165°C (manufactured by Nippon Polypro Co., Ltd.)
・Polymethylpentene (PMP); melting point 232°C (manufactured by Mitsui Chemicals)

Example 1
By the melt-blowing method described in paragraph [0042] of the present specification, using the polybutylene terephthalate (hereinafter sometimes referred to as "PBT") as a raw material resin, PBT melt-blown nonwoven fabrics (A) and (B) are produced. manufactured respectively. Specifically, the raw resin is melted at an extruder temperature of 290°C, fed into a die set at 300°C, and discharged from the die nozzle. At the same time, it is stretched with high-temperature air blow gas at 310°C to form fine fibers, and then released from the nozzle. It was collected by a collector installed at a remote location. The nozzle diameter, discharge amount, etc., as well as the melting temperature and die temperature, were appropriately selected so that the desired nonwoven fabric material could be obtained.
Two types of raw PBT melt-blown nonwoven fabric (A) having fibers with an average fiber diameter of 1.8 μm and PBT melt-blown nonwoven fabric raw fabric (B) having fibers with an average fiber diameter of 1.8 μm manufactured by the above manufacturing method are as follows. A raw melt-blown nonwoven fabric was prepared.

PBT melt-blown nonwoven fabric (A)
Weight (g/m2): 8
Thickness (μm): 86
Air permeability (cc/cm2/s): 113.4
Tensile strength (N/25mm width): 4.7
Tensile elongation (%): 32.8
Average fiber diameter (μm): 1.8

PBT melt-blown nonwoven fabric (B)
Weight (g/m2): 12
Thickness (μm): 103
Air permeability (cc/cm2/s): 70.6
Tensile strength (N/25mm width): 5.5
Tensile elongation (%): 37.3
Average fiber diameter (μm): 1.8

The melt-blown nonwoven fabric (A) and the melt-blown nonwoven fabric (B) were stacked and sandwiched between two metal rolls heated to 150°C, respectively, and under pressure conditions. The first calender processing was performed under a pressure condition of 130 N/mm with the roll pressure as the linear pressure of the roll. A clearance was provided between the metal rolls, which was adjusted so that the thickness of the calendered intermediate after the first calendering treatment was at a level of about 50 to 70 μm. Steel was used as the material for the metal roll.

A calendar having two adhesion layers obtained by thermally fusing some of the fibers present at the interface of each layer of the raw nonwoven fabric (A) and the raw nonwoven fabric (B) by the first calendering treatment. The processing intermediate is sandwiched between an elastic roll and a metal roll heated to 100 ° C., and further subjected to a second calender processing under a pressure condition of 30 N/mm with the roll pressure as the linear pressure of the roll, A melt-blown nonwoven fabric thin film laminate was obtained, which was a laminate consisting of two types of thin films of a nonwoven fabric (A) and a nonwoven fabric (B).
As the elastic roll, one made of polyamide synthetic resin having a Shore D hardness of 80 was used. The physical properties of the obtained PBT melt-blown nonwoven fabric thin film laminate (two-layer product (1)) are as follows.

PBT/PBT melt-blown nonwoven thin film two-layer laminate (two-layer product 1)
Weight (g/m2): 20
Thickness (μm): 33
Gurley air permeability (s/φ10/300cc): 13.6
Air permeability T (cc/cm2/s): 5.10
Tensile strength (N/25mm width): 13.8
Tensile elongation (%): 22.5
Average fiber diameter (μm): 2.6
Appearance (film formation due to formation of transparent spots): None Electrolyte absorption rate (seconds): 9.72
Electrolyte retention rate (%): 365
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 1.2
CD: 0.5
Pore size distribution
(1) Maximum pore diameter (μm) 12.27
(2) Minimum pore diameter (μm) 2.285
(3) Average pore diameter (μm) 6.673
(4) Maximum pore diameter/average pore diameter 1.84
(5) Maximum pore diameter/minimum pore diameter 5.37
(6) Percentage of pores with a pore diameter range of 3 to 7 μm (%): 70

As shown in the above results, by laminating and bonding two layers of nonwoven fabric with the same average fiber diameter of the constituent fibers, the Gurley air permeability was 13.6 s/φ10/300 cc even though it was a thin film with a thickness of 33 μm. It was possible to maintain a high degree of porosity, suppress the collapse of the fibers, and suppress the formation of transparent spots on the film. In addition, regarding the thermal shrinkage rate under high temperature conditions, after heating in an oven set at 120°C for 1 hour, the dimensional change rate was 0.5% in both MD and CD directions, and after heating in an oven set at 150°C for 1 hour. The dimensional change rate was 1.2% in the MD direction and 0.5% in the CD direction, and good results were obtained. Furthermore, the electrolyte absorption rate was 9 seconds and 72 seconds, and the electrolyte retention rate was also 365%, which was a remarkable effect, demonstrating extremely high superiority as a separator for electric double layer capacitors.
As shown in the graph of FIG. 1, the pore size distribution of the nonwoven fabric laminate that achieved such characteristics was shown to be significantly controlled.

Example 2
Melt-blown nonwoven fabric (C) having the following fibers with an average fiber diameter of 1.8 μm manufactured by the melt-blowing method using the PBT as a raw material resin:

PBT melt-blown nonwoven fabric (C)
Weight (g/m2): 7
Thickness (μm): 84
Air permeability (cc/cm2/s): 121.5
Tensile strength (N/25mm width): 4.3
Tensile elongation (%): 41.8
Average fiber diameter (μm): 1.8

Three sheets were piled up and sandwiched between two metal rolls/metal rolls heated to 150°C, and under pressure conditions of 130 N/mm with the roll pressure as the linear pressure of the processing roll. The sample was subjected to the first calendering process. A clearance was provided between the two metal rolls, which was adjusted so that the thickness of the calendered intermediate was approximately 50 to 70 μm. Steel was used as the material for the metal roll.

The calendering intermediate body consisting of three adhesive layers obtained by the first calendering treatment is sandwiched between an elastic roll and a metal roll heated to 100°C, and the roll pressure is applied to the processing roll. This was further subjected to a second calender treatment under a linear pressure of 30 N/mm to obtain a melt-blown nonwoven thin film laminate consisting of three layers of nonwoven fabric. As the elastic roll, one made of polyamide synthetic resin having the hardness described above (Shore D hardness 80) was used. The physical properties of the obtained PBT melt-blown nonwoven thin film three-layer laminate (three-layer product (1)) are as follows.

PBT/PBT/PBT melt-blown nonwoven thin film three-layer laminate (three-layer product 1)
Weight (g/m2): 21
Thickness (μm): 31
Gurley air permeability (s/φ10/300cc): 26.1
Air permeability T (cc/cm2/s): 2.78
Tensile strength (N/25mm width): 11.1
Tensile elongation (%): 42.5
Average fiber diameter (μm): 2.9
Appearance (film formation due to formation of transparent spots): None Electrolyte absorption rate (seconds): 9.97
Electrolyte retention rate (%): 380
Heat shrinkage rate (%):
(In the oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 1.2
CD: 0.5
Pore size distribution
(1) Maximum pore diameter (μm) 10.75
(2) Minimum pore diameter (μm) 1.865
(3) Average pore diameter (μm) 6.145
(4) Maximum pore diameter/average pore diameter 1.75
(5) Maximum pore diameter/minimum pore diameter 5.76
(6) Percentage of pores occupying the pore diameter range of 3 to 7 μm (%): 85

As shown in the above results, the nonwoven thin film laminate consisting of three layers with the same average fiber diameter of the constituent fibers has a Gurley air permeability of 26.1 s/φ10/300 cc and a high pore size even though the thickness is 31 μm. It was possible to maintain the strength of the film, suppress the collapse of the fibers, and suppress the formation of transparent spots on the film. In addition, regarding the thermal shrinkage rate under high temperature conditions, after heating in an oven set at 120°C for 1 hour, the dimensional change rate was 0.5% for both MD and CD, and even after heating in an oven set at 150°C for 1 hour. The dimensional change rate was 1.2% in the MD direction and 0.5% in the CD direction, and good results were obtained. Furthermore, the electrolyte absorption rate was 9 seconds and 97 seconds, and the electrolyte retention rate was also 380%, which was a remarkable effect, demonstrating extremely high superiority as a separator for electric double layer capacitors.
The nonwoven fabric thin film laminate that achieves these characteristics has pore size distributions (1) to (6), and as shown in the graph of FIG. 2, the pore size distribution is significantly controlled as described above. It has been shown.

Example 3
PBT melt-blown nonwoven fabric (C) having fibers with an average fiber diameter of 1.8 μm used in Example 2, and PMP melt-blown nonwoven fabric fabric (D) having fibers with an average fiber diameter of 2.9 μm shown below:
PMP melt-blown nonwoven fabric (D):
Weight (g/m2): 8
Thickness (μm): 208
Air permeability (cc/cm2/s): 273
Tensile strength (N/25mm width): 2.7
Tensile elongation (%): 29.8
Average fiber diameter (μm): 2.9

Using the same conditions and operations as in Example 2, the PBT melt-blown non-woven fabric (C) / PMP melt-blown non-woven fabric (D) / PBT melt-blown non-woven fabric (C) were stacked to form three layers. , a first calender treatment and a second calender treatment to obtain a three-layer laminate (three-layer product 2) of PBT melt-blown nonwoven fabric thin film/PMP melt-blown nonwoven fabric thin film/PBT melt-blown nonwoven fabric thin film shown below.

PBT melt-blown non-woven fabric thin film/PMP melt-blown non-woven fabric thin film/PBT melt-blown non-woven fabric thin film three-layer laminate (three-layer product 2)
Weight (g): 22
Thickness (μm): 40
Gurley air permeability (s/φ10/300cc): 22.1
Air permeability T (cc/cm2/s): 3.17
Tensile strength (N/25mm width): 12.7
Tensile elongation (%): 27.6
Average fiber diameter: 2.4
Appearance (film formation due to formation of transparent spots): None Electrolyte absorption rate (seconds): 18.72
Electrolyte retention rate (%): 280
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 0
CD: 0
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
Pore size distribution
(1) Maximum pore diameter: 14.58
(2) Minimum pore diameter: 2.885
(3) Average pore diameter: 7.964
(4) Maximum pore diameter/average pore diameter: 1.83
(5) Maximum pore diameter/minimum pore diameter: 5.05

As mentioned above, by forming the three-layer structure of PBT/PMP/PBT, the maximum It shows a unique pore size distribution with a pore size/average pore size of less than 2.00 and a maximum pore size/minimum pore size of 5.00 or more, and also has high Gurley air permeability, especially heat shrinkage. was small, and excellent high-temperature stability was obtained.

Comparative example 1
PBT melt-blown nonwoven fabric ( E ) having fibers with an average fiber diameter of 1.8 μm shown below:

PBT melt-blown nonwoven fabric (E):
Weight (g/m2): 15
Thickness (μm): 154
Air permeability (cc/cm2/s): 29.6
Tensile strength (N/25mm width): 8.1
Tensile elongation (%): 14.7
Average fiber diameter (μm): 1.8

was subjected to the first calendering treatment and the second calendering treatment under the same conditions and operations as in Example 1 to obtain a PBT melt-blown nonwoven fabric thin film monolayer (single-layer comparative product (a)). The physical properties of the obtained PBT melt-blown nonwoven thin film single layer body (single layer comparative product (a)) were as follows, and the electrolyte retention rate and thermal shrinkage rate were outside the scope of the present invention.

PBT melt-blown nonwoven fabric thin film single layer a (single layer comparison product (a))
Weight (g/m2): 15
Thickness (μm): 28
Gurley air permeability (s/φ10/300cc): 8.7
Air permeability T (cc/cm2/s): 5.24
Tensile strength (N/25mm width): 10.2
Tensile elongation (%): 22.6
Average fiber diameter (μm): 2.3
Appearance (filming due to formation of transparent spots): None Electrolyte absorption rate (seconds): 8.95
Electrolyte retention rate (%): 250
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 1.0
CD: 0.5
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 1.5
CD: 1.0
Further, the pore size distribution of the melt-blown nonwoven thin film monolayer a (single-layer comparative product (a)) is as shown in the following (1) to (6).
Pore size distribution
(1) Maximum pore diameter (μm) 18.14
(2) Minimum pore diameter (μm) 4.552
(3) Average pore diameter (μm) 8.766
(4) Maximum pore diameter/average pore diameter 2.07
(5) Maximum pore diameter/minimum pore diameter 3.99
(6) Percentage of pores occupying the pore diameter range of 3 to 7 μm (%): 33

As shown in the pore size distribution, (1) maximum pore size, (2) minimum pore size, (3) average pore size, (4) maximum pore size/average pore size, and (5) maximum pore size/minimum pore size. All of the pore sizes were outside the scope of the present invention, and sufficient effects were not obtained in terms of high temperature stability and electrolyte retention.

Comparative example 2
The melt-blown nonwoven fabrics (A) and (B) used in Example 1 were not subjected to the first calendering treatment, but were subjected only to the second calendering treatment. The conditions and operations of the second calender processing were the same as those of the second calender processing of Example 1.
By the above calender treatment, a PBT melt-blown nonwoven thin film two-layer laminate b (two-layer comparative product (b)) having the following physical properties was obtained.

PBT melt-blown nonwoven thin film two-layer laminate b (two-layer comparison product (b))
Weight (g/m2): 20
Thickness (μm): 45
Gurley air permeability (cc/cm2/s): 3.5
Air permeability (cc/cm2/s): 13.47
Tensile strength (N/25mm width): 9.3
Tensile elongation (%): 38.8
Average fiber diameter (μm): 3.0
Appearance (filming due to formation of transparent spots): None Electrolyte absorption rate (seconds): 9.39
Electrolyte retention rate (%): 390
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 2.0
CD: 1.5
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 4.5
CD: 3.0
Pore size distribution
(1) Maximum pore diameter (μm) 19.35
(2) Minimum pore diameter (μm) 5.217
(3) Average pore diameter (μm) 13.38
(4) Maximum pore diameter/average pore diameter 1.45
(5) Maximum pore diameter/minimum pore diameter 3.71

As described above, the PBT melt-blown nonwoven fabric two-layer laminate b (two-layer comparative product (b)) obtained in Comparative Example 2 is the PBT melt-blown nonwoven fabric thin film two-layer laminate of Example 1, but is not subjected to the first calendering treatment. As a result of omitting pore size distributions (1) to (3) and (5), the pore size distributions (1) to (3) and (5) deviated from the scope of the present invention, had a high thermal shrinkage rate, and lacked high temperature stability.

Comparative example 3
PBT melt-blown nonwoven fabric (F) having the following physical properties:

PBT melt-blown nonwoven fabric (F)
Weight (g/m2): 20
Thickness (μm): 175
Air permeability (cc/cm2/s): 38.7
Tensile strength (N/25mm width): 9.6
Tensile elongation (%): 15.8
Average fiber diameter (μm): 1.8

was subjected to only the second calendering treatment without being subjected to the first calendering treatment under the same conditions and operations as those of Comparative Example 2 except that the temperature of the second treatment was set at 180 ° C. .
The obtained PBT melt-blown nonwoven fabric thin film monolayer c (monolayer comparative product (c)) has the following physical properties.

PBT melt-blown nonwoven thin film single layer c (single layer comparison product (c))
Weight (g/m2): 20
Thickness (μm): 30
Gurley air permeability (cc/φ10/300cc): 210
Air permeability T (cc/cm2/s): 1.17
Tensile strength (N/25mm width): 14.8
Tensile elongation (%): 19.4
Average fiber diameter (μm): 3.0
Appearance (film formation due to formation of transparent spots): Yes Electrolyte absorption rate (seconds): 11.2
Electrolyte retention rate (%): 245
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 0
CD: 0
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 1.0
CD: 0.5
Pore size distribution
(1) Maximum pore diameter (μm) 12.13
(2) Minimum pore diameter (μm) 2.84
(3) Average pore diameter (μm) 6.007
(4) Maximum pore diameter/average pore diameter 2.02
(5) Maximum pore diameter/minimum pore diameter 4.27

As mentioned above, the first calendering treatment is omitted and only the second calendering treatment is performed.Moreover, the high temperature treatment causes film formation due to transparent spots and decreases air permeability, so it is not sufficient to be used as a separator. A nonwoven thin film with such characteristics could not be obtained.

Comparative example 4
Same as Comparative Example 1 except that the same PBT melt-blown nonwoven fabric (F) used in Comparative Example 3 was subjected to only the first calendering treatment without being subjected to the second calendering treatment. A PBT melt-blown nonwoven fabric thin film monolayer d (single-layer comparison product (d)) having the following physical properties was obtained by calendering under the following conditions and operations.

PBT melt-blown nonwoven thin film single layer d (single layer comparison product (d))
Weight (g/m2): 20
Thickness (μm): 42
Gurley air permeability (s/φ10/300cc): 87
Air permeability (cc/cm2/s): 4.42
Tensile strength (N/25mm width): 20.5
Tensile elongation (%): 12.9
Average fiber diameter (μm): 3.6
Appearance (filming due to formation of transparent spots): Yes Electrolyte absorption rate (seconds): 14.18
Electrolyte retention rate (%): 155
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 1.5
CD: 1.0
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 2.5
CD: 1.5
Pore size distribution
(1) Maximum pore diameter (μm): 14.65
(2) Minimum pore diameter (μm): 5.355
(3) Average pore diameter (μm): 9.982
(4) Maximum pore diameter/average pore diameter: 1.47
(5) Maximum pore diameter/minimum pore diameter: 2.74
(6) Percentage of pores occupying the range of pore diameters from 3 to 7 μm (%): 1

As mentioned above, when only the first calendering treatment was performed, film formation occurred due to the formation of transparent spots, and the necessary properties as a separator, such as a decrease in air permeability and an increase in heat shrinkage rate, could not be obtained.

Comparative example 5
The following PP melt-blown nonwoven fabric (G) manufactured by the melt-blowing method using the polypropylene as a raw material resin:

PP melt-blown nonwoven fabric (G)
Weight (g/m2): 7
Thickness (μm): 111
Air permeability (cc/cm2/s): 103
Tensile strength (N/25mm width): 2.7
Tensile elongation (%): 42.7
Average fiber diameter (μm): 3.2

A PP melt-blown nonwoven fabric thin film monolayer having the following physical properties was prepared using the same calendering conditions and operations as those of Comparative Example 2, except that it was subjected to only the second calendering treatment at a processing temperature of 65°C. A layered body e (single-layer comparative product (e)) was obtained.

PP melt-blown nonwoven thin film single layer e (single layer comparison product (e))
Weight (g/m2): 7
Thickness (μm): 20
Gurley air permeability (s/φ10/300cc): 8.8
Air permeability (cc/cm2/s): 6.7
Tensile strength (N/25mm width): 3.8
Tensile elongation (%): 23.5
Average fiber diameter (μm): 3.6
Appearance (film formation due to formation of transparent spots): None Electrolyte absorption rate (seconds): 30 or more Electrolyte retention rate (%): 65
Heat shrinkage rate (%):
(In oven at 120℃
Dimensional change rate after heating for 1 hour) MD: 5.5
CD: 5.0
(In oven at 150℃
Dimensional change rate after heating for 1 hour) MD: 12.5
CD: 10.0
Pore distribution
(1) Maximum pore diameter (μm): 13.33
(2) Minimum pore diameter (μm): 1.566
(3) Average pore diameter (μm): 4.568
(4) Maximum pore diameter/average pore diameter: 2.92
(5) Maximum pore diameter/minimum pore diameter: 8.51
(6) Percentage of pores with a pore diameter range of 3 to 7 μm (%): 70

As mentioned above, the melt-blown nonwoven thin film monolayer made from polypropylene obtained only by the second calender processing does not satisfy all of the requirements (1) to (6) in terms of pore distribution and has a low heat shrinkage rate. was extremely high, had low electrolyte retention, and lacked the properties required as a separator.

The contents of the above Examples and Comparative Examples are summarized in Table 1.
From the results of Examples and Comparative Examples, it has been found that a melt-blown non-woven fabric thin film laminate of two or more layers of melt-blown non-woven fabric thin films manufactured using heat-resistant resin as a raw material resin has a unique pore size distribution as described above, and is capable of retaining electrolyte. It was found that it has excellent liquid properties and high temperature stability, was realized by the first calendering treatment and the second calendering treatment, and has extremely high performance as a separator for electric double layer capacitors.

Claims (14)

A separator for an electric double layer capacitor composed of a melt-blown non-woven fabric thin film laminate formed by laminating at least two layers of melt-blown non-woven fabric thin films, the separator comprising:
The average fiber diameter of the fibers constituting the melt-blown nonwoven thin film laminate is 0.5 to 15 μm, the Gurley air permeability is 1 to 40 s/φ10/300 cc, and the heat shrinkage rate is 1 hour at 150° C. After heat treatment under these conditions, the shrinkage change in shape in either the MD direction or the CD direction, expressed as a dimensional change rate, is 1.2% or less, and the electrolyte retention rate is 260% or more. A separator for electric double layer capacitors featuring:
2. The separator for an electric double layer capacitor according to claim 1, wherein the average fiber diameters of the constituent fibers of each layer of the at least two melt-blown non-woven fabric thin films constituting the melt-blown non-woven fabric thin film laminate are substantially the same or different.
2. The melt-blown nonwoven fabric thin film laminate is an interlayer adhesion product formed by partial thermal fusion of fibers present at the interface between each layer of the at least two layers of melt-blown nonwoven fabric thin films constituting the melt-blown nonwoven fabric thin film laminate. separator for electric double layer capacitors.
The separator for an electric double layer capacitor according to claim 1, wherein the ratio of pores having a pore diameter in the range of 3 to 7 μm out of all the pores in the melt-blown nonwoven thin film laminate is 50% or more.
The separator for an electric double layer capacitor according to claim 1, wherein the melt-blown nonwoven fabric thin film laminate has a pore size distribution that satisfies the following (1) to (5).
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter/average pore diameter: Less than 2.00 (5) Maximum pore diameter/minimum Pore diameter: 5.00 or more
The separator for an electric double layer capacitor according to claim 1, wherein the constituent material of the melt-blown nonwoven thin film laminate is a heat-resistant resin.
A method for producing a separator for an electric double layer capacitor comprising at least two layers of a melt-blown nonwoven fabric thin film laminate, the method comprising:
(a) At least two raw melt-blown nonwoven fabrics are stacked one on top of the other, and a calender mechanism having metal rolls suppresses processing temperature conditions higher than the glass transition point of the raw material resin and crushing of the constituent fibers of the raw melt-blown nonwoven fabric. , and a first calendering process in which calendering is performed under pressurized conditions that are adjusted to conditions that allow thinning.
(b) The calendering intermediate obtained in the first calendering step is subjected to effective processing temperature conditions and the crushing of the constituent fibers of the nonwoven fabric is suppressed by a calender mechanism having at least one elastic roll. , and a second calendering step in which calendering is performed under pressurized conditions adjusted to conditions that allow thinning. A method for producing a separator for an electric double layer capacitor composed of a nonwoven thin film laminate.
8. The method of manufacturing a separator for an electric double layer capacitor according to claim 7 , wherein in the first calender processing step, the processing temperature condition equal to or higher than the glass transition point is a temperature of 130° C. or higher.
According to claim 7, in the first calender processing step, among the pressurizing conditions adjusted so that collapse of the constituent fibers of the melt-blown nonwoven fabric is suppressed, the linear pressure of the metal roll is 200 N/mm or less. A method of manufacturing the separator for an electric double layer capacitor as described above.
8. In the second calender processing step, the calender mechanism includes a combination of at least one pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and a metal roll. A method for manufacturing a separator for an electric double layer capacitor.
8. In the second calender processing step, the calender mechanism includes a combination of at least one pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and an elastic roll. A method for manufacturing a separator for an electric double layer capacitor.
8. The method of manufacturing a separator for an electric double layer capacitor according to claim 7, wherein in the second calender processing step, an effective processing temperature condition is a temperature of 130° C. or lower.
13. The method of manufacturing a separator for an electric double layer capacitor according to claim 7 or 12, wherein in the second calendering step, the elastic material of the elastic roll is a synthetic resin.
Next step:
(a) At least two raw melt-blown nonwoven fabrics are superimposed, and a metal roll suppresses processing temperature conditions higher than the glass transition point of the raw material resin and crushing of the constituent fibers of the raw melt-blown nonwoven fabric, and forms a thin film. a first calendering process in which calendering is performed under pressurized conditions adjusted to allow for
(b) the calendering intermediate obtained in the first calendering step is subjected to effective processing temperature conditions and the collapse of the constituent fibers of the nonwoven fabric is suppressed by a calender mechanism having elastic rolls, and A separator for an electric double layer capacitor manufactured by a method comprising a second calendering treatment step in which the separator is subjected to calendering under pressurized conditions adjusted to allow thinning.