JP7077503B2 - Heat-resistant non-woven fabric thin film, its manufacturing method and its use - Google Patents

Description

The present invention relates to a heat-resistant nonwoven fabric thin film, a method for producing the heat-resistant nonwoven fabric thin film, and applications of the heat-resistant nonwoven fabric thin film. More specifically, the present invention relates to a nonwoven fabric manufactured by a melt blow method using a heat-resistant resin as a raw material (hereinafter, "melt blow"). It may be referred to as "nonwoven fabric".) It relates to a heat-resistant melt-blown non-woven fabric thin film made by thinning a raw fabric, a method for producing the same, and its use.
In particular, the present invention provides a separator for an electric double layer capacitor (EDLC) and a separator for a lithium ion secondary battery such as a lithium ion secondary battery and a lithium ion polymer secondary battery for use in a heat-resistant melt blow non-woven thin film. Is.

Regarding the conventional use of non-woven fabrics for battery separators, non-woven fabrics have a high void ratio, so that they have high electrolyte retention performance, easy to generate electric capacity, and good electrolyte absorption performance, and batteries. It has been used by paying attention to its merits such as high productivity and low price. However, it is difficult to manufacture a non-woven fabric with a low basis weight because the melt-blown non-woven fabric lacks tensile strength, and only a non-woven fabric having a certain size of weight can be manufactured, and as a result, the thickness is also increased. Since it is relatively large, it has been considered unsuitable for use as a thin film separator for batteries.

Therefore, under such circumstances, it has been attempted to adjust the thickness of the melt-blown nonwoven fabric by a calendering process using a thermal roll press. According to the calendering treatment of the non-woven fabric raw fabric, it is possible to manufacture a separator made of a melt-blown non-woven fabric thin film or a separator having a certain thickness by thinning the fabric, and it is possible to contribute to the miniaturization of the battery, but it is desired. It has been pointed out that the pressure treatment required to obtain a separator having the same thickness causes the fibers constituting the non-woven fabric to be crushed, resulting in a problem that the air permeability is lowered. Therefore, as the thickness of the melt-blown nonwoven fabric is reduced, the overlapping portion and the lump portion of the constituent fibers of the nonwoven fabric are partially formed into a film, so that the internal resistance increases, and the liquid absorption performance and the liquid retention performance of the electrolytic solution are also improved. It has been pointed out that the battery performance is inferior, and that the film formation leads to the formation of transparent spots, which significantly reduces the commercial value in appearance.

Further, a laminated body composed of two or more non-woven fabric layers having different physical characteristics also has a problem of curling, a lack of stacking adhesion, which affects battery productivity and lacks safety. On the other hand, it is a material different from the melt blown non-woven fabric made of synthetic resin, and even with the paper separators that have been used conventionally, the air permeability and the liquid retention performance of the electrolytic solution are not sufficient, the internal resistance is high, and the long-term cycle characteristics. There is a drawback that it lacks.

For the above reasons, there is a limit to the thinning of the melt-blown non-woven fabric by the calendar processing treatment, and the thin film can only be thinned to about 40 μm without the formation of transparent spots by filming.
Therefore, it is extremely difficult to provide a separator for a lithium ion battery whose thickness is limited to about 5 to 30 μm and a separator for an electric double layer capacitor (EDLC) whose thickness is limited to about 40 μm by using a melt blown nonwoven fabric. I was in a difficult situation.
Further, in recent years, a battery is required to have heat resistance as a separator, and a battery having low shrinkage is particularly required at a high temperature. Further, a step of drying the separator at a high temperature before manufacturing the battery is also adopted, and a battery having a low high temperature shrinkage rate is required.
From the above viewpoints, as a battery separator made of a melt-blown non-woven fabric, a thin-film separator having a low shrinkage rate at a high temperature has been desired.

Under such circumstances, the present applicant has developed a nonwoven fabric using a heat-resistant resin as a battery separator, and Polybutylene terephthalate is described in JP-A-2002-50335 (hereinafter referred to as "Patent Document 1"). A heat-resistant separator made of melt-blown non-woven fabric has been proposed. According to the same publication, the maximum value of impedance at a frequency of 10 KHz from 100 ° C to 180 ° C is 100 times or less of the real impedance at room temperature, and the absolute value is 2000 Ωcm ² or less. A low resistance heat resistant separator that does not melt and does not short-circuit the electrodes is described. However, there is no disclosure about a melt-blown nonwoven fabric having a thickness of 0.01 to 1.0 mm and having a thin film of 40 μm or less.

Further, Japanese Patent Application Laid-Open No. 2002-170540 (hereinafter referred to as "Patent Document 2") describes a heat-resistant separator made of a laminate of melt-blown nonwoven fabrics made of two or more kinds of resins having different melting points. According to Patent Document 2, a function of blocking permeability at a low temperature is also described, but there is no disclosure of a thin-film separator having a thickness of 40 μm or less.

Further, Japanese Patent Application Laid-Open No. 2014-222706 (hereinafter referred to as "Patent Document 3") describes a separator for an aluminum electrolytic capacitor made of α-cellulose fiber. Aluminum electrolytic capacitors shall be manufactured by interposing electrolytic paper as a separator between the anode aluminum foil and the cathode aluminum foil to create a capacitor element, impregnating this capacitor element with an electrolytic solution, and sealing it. Is described. Further, it is described that the thickness of the separator is 25 to 100 μm.
Under such circumstances, a heat-resistant melt-blown non-woven fabric thin film that is a thin-film non-woven fabric and can be used as a separator for lithium batteries and a separator for electric double layer capacitors, which has excellent breathability and stability under high temperature conditions. Development has been coveted.

Japanese Unexamined Patent Publication No. 2002-50335 Japanese Unexamined Patent Publication No. 2002-170540 Japanese Unexamined Patent Publication No. 2014-222706

Therefore, an object of the present invention is firstly to provide a heat-resistant melt-blown non-woven fabric thin film which maintains a high porosity and is excellent in stability under a specific Garley air permeability and high temperature conditions.
Another object of the present invention is to provide a heat-resistant melt-blow nonwoven fabric thin film that is applicable to a separator for a lithium secondary battery or an electric double layer capacitor (EDLC).
Further, thirdly, to provide a method for producing a heat-resistant melt-blown nonwoven fabric thin film in which the crushing of the fibers constituting the nonwoven fabric thin film is suppressed even if the thin film is thinned by the calendering treatment, and the formation of transparent spots due to the film formation is suppressed. It is in.

Therefore, the present inventor has made extensive studies in order to solve the above-mentioned problems of the present invention.
A heat-resistant melt-blown non-woven fabric thin film made of a heat-resistant resin, having a thickness of 50 μm or less, having high air permeability by maintaining a high opening degree, and having a high air permeability (meaning the air permeability by the JIS P8117 Garley method). The same applies hereinafter.) Is specified in the range of 1 to 40 s / φ10 / 300 cc, and the heat-resistant melt-blown non-woven fabric thin film capable of maintaining high-temperature stability with a low heat shrinkage rate can solve the above-mentioned problems. In addition, the heat-resistant melt-blow non-woven fabric thin film having such physical properties uses a heat-resistant resin as the raw material resin for the melt-blow non-woven fabric raw material, and is provided with a calendering process for the melt-blow non-woven fabric raw material, a high-temperature calendering process using a metal roll, and an elastic roll. By performing the special calendar processing in two stages with different processing conditions, thinning can be achieved, the morphology of the constituent fibers of the non-woven fabric raw fabric is maintained as it is, and the entangled parts and lump parts of the fibers are maintained. Focusing on the fact that the formation of transparent spots due to film formation can be suppressed, the above-mentioned problems can be solved based on such findings, and the present invention has been completed.

Thus, the gist of the present invention is as shown in the following (1) to (15).
In the present 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 inventions according to (15) to (16) are referred to as the first invention. It may be called a third invention.
(1) A heat-resistant melt-blown non-woven fabric thin film made of a heat-resistant resin.
The thickness is 50 μm or less,
The basis weight is 5 to 100 g / m ² ,
The average fiber diameter is 0.5 to 15 μm,
Garley air permeability is 1-40s / φ10 / 300cc,
Even after heat treatment under heating conditions with a heat shrinkage rate of 150 ° C. for 1 hour (may be abbreviated as “150 ° C. × 1 Hr environment” in the present specification), the MD direction (length direction; hereinafter, hereinafter, The same.) And the CD direction (width direction; hereinafter the same) are expressed by the dimensional change rate, and either of them is 1.2% or less, which is a heat-resistant melt blow non-woven fabric thin film.

(2) The heat-resistant melt-blown nonwoven fabric thin film according to 1 above, wherein the heat-resistant resin is a thermoplastic resin having a melting point of 200 ° C. or higher.

(3) The heat-resistant melt-blow non-woven fabric thin film according to (1) above, wherein the heat-resistant melt-blow non-woven fabric thin film is a non-woven fabric processed product obtained by laminating and laminating at least two non-woven fabric layers.

(4) The heat-resistant melt blow according to (1) above, wherein the heat-resistant melt blow nonwoven fabric thin film is a nonwoven fabric processed product obtained by laminating and laminating at least two nonwoven fabric layers having fibers having fibers having different average fiber diameters. Non-woven thin film.

(5) The heat-resistant melt-blown nonwoven fabric thin film according to (1), wherein the thickness is 1 to 45 μm.

(6) The heat-resistant melt-blown non-woven fabric thin film according to (1) above, wherein the Garley air permeability is 5 to 30 s / φ10 / 300 cc.

(7) The heat shrinkage rate is 1.2% or less in both the MD direction and the CD direction in terms of dimensional change rates after heat treatment under heating conditions at 150 ° C. for 1 hour. Heat-resistant melt blown non-woven fabric thin film according to.

(8) Melt-blow non-woven fabric made of heat-resistant resin A method for producing a heat-resistant melt-blow non-woven fabric thin film obtained by thinning a raw fabric.
1. 1. The melt-blown nonwoven fabric is sandwiched between at least two metal rolls to suppress the processing temperature conditions above the glass transition point of the heat-resistant resin and the crushing of the constituent fibers of the nonwoven fabric, and to reduce the thickness. A high-temperature calendering process to be subjected to calendering under pressurized conditions adjusted to possible conditions, and a high-temperature calendering process.
2. 2. The processing intermediate obtained by the high-temperature calendar processing step is subjected to a special calendar processing treatment including at least two rolls in which at least one roll is an elastic roll, and the processing temperature condition is 130 ° C. or lower and the nonwoven fabric. It includes a special calendering process that is adjusted so as to prevent the constituent fibers of the raw fabric from being crushed and that is subjected to the calendering under pressure conditions adjusted to the conditions that can be thinned. A method for manufacturing a heat-resistant melt-blown non-woven fabric thin film.

(9) The method for producing a heat-resistant melt-blow nonwoven fabric thin film according to (8) above, wherein the melt-blow nonwoven fabric raw fabric is a laminated body composed of at least two layers of nonwoven fabric.

(10) The method for producing a heat-resistant melt-blow nonwoven fabric thin film according to (8) above, wherein the melt-blown nonwoven fabric raw fabric is a laminate composed of at least two nonwoven fabric layers having fibers having fibers having different average fiber diameters. ..

(11) The method for producing a heat-resistant melt-blown nonwoven fabric thin film according to (8) above, wherein the processing temperature condition of the glass transition point or higher is 130 ° C. or higher.

(12) Among the pressurizing conditions adjusted so as to suppress the crushing of the constituent fibers of the nonwoven fabric raw fabric in the high temperature calendering process, the linear pressure of the roll is 200 N / mm or less in the above (8). The method for producing a heat-resistant melt-blown non-woven fabric thin film according to the above method.

(13) The method for producing a heat-resistant melt-blow non-woven fabric thin film according to (8) above, wherein the special calendar processing step includes a calendar device composed of at least one elastic roll and at least one metal roll.

(14) The method for producing a heat-resistant melt-blown nonwoven fabric thin film according to the above (8) or (13), wherein the elastic material of the elastic roll is a synthetic resin in the special calendar processing step.

(15) An electric double layer capacitor (EDLC) separator made of the heat-resistant melt-blown non-woven fabric thin film according to any one of (1) to (7) above.

(16) A separator for a lithium ion secondary battery made of the heat-resistant melt-blown non-woven fabric thin film according to any one of (1) to (7) above.

The present invention has the above-mentioned structure, and the heat-resistant melt-blown nonwoven fabric thin film according to the present invention has a small thickness, but the constituent fibers of the nonwoven fabric are less deformed, and the entangled portion is formed into a film. There is no formation of transparent plaques, the garley permeability is in a good range, and the heat shrinkage rate at high temperatures is small. Further, by laminating the melt-blown non-woven fabric raw fabric on at least two non-woven fabric layers and laminating them by high-temperature calendering treatment, the obtained non-woven fabric thin film can improve the tensile strength and the appearance unevenness peculiar to the non-woven fabric. can.
Furthermore, high air permeability can be maintained by laminating and combining non-woven fabric layers having fibers having different average fiber diameters, and the liquid absorption performance and liquid retention performance of the electrolytic solution can be improved. By using a heat-resistant melt-blow non-woven thin film having such characteristics as a separator, it has been successfully applied to lithium secondary batteries and electric double layer capacitors (EDLC), thereby exhibiting stable battery characteristics and ensuring safety. It can be secured and the productivity of the battery can be improved.

Hereinafter, the present invention will be described in detail.
A. First invention
1. 1. The first invention of the heat-resistant melt-blow non-woven fabric thin film provides a heat-resistant melt-blow non-woven fabric thin film made of a heat-resistant resin, and the heat-resistant melt-blow non-woven fabric thin film has at least the following physical property values.
That is,
-Thickness is 50 μm or less
・ The basis weight is 5 to 100 g / m ² .
-The average fiber diameter is 0.5 to 15 μm,
・ Garley air permeability is 1-40s / φ10 / 300cc.
-Even after heat treatment under heating conditions at 150 ° C. for 1 hour, the heat shrinkage rate is 1.2% or less in either the MD direction or the CD direction in terms of dimensional change rates.
Further, as described above, although the thickness is reduced to 50 μm or less, the electrolytic solution absorption performance and the electrolytic solution retention performance are excellent, and more specifically, they are shown in Examples and Table 1 described later. As you can see, it is possible to manufacture a product having an electrolytic solution absorption rate of 15 seconds or less and an electrolytic solution retention rate of 250% or more.
Further, the degree of opening of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention is sufficiently maintained by the presence of gaps between the fibers constituting the nonwoven fabric observed by SEM.

2. 2. Components of the Heat-Resistant Melt-Blow Nonwoven Fabric Thin Film The components of the heat-resistant melt-blow non-woven fabric thin film according to the present invention are components containing a heat-resistant resin, and may be a mixture of two or more types of heat-resistant resins. Derived from the anti-component. Specific examples are as follows.

As the raw material resin for the heat-resistant 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, a thermoplastic synthetic resin having a melting point of 200 ° C. or higher is suitable, and specific examples thereof include polyester, polyamide, polyimide, polyacrylonitrile, polyarylene sulfide, polycarbonate, polyphthalamide, and polyolefin. can.

Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate (hereinafter, may be abbreviated as PBT), polybutylene isophthalate, polybutylene adipate, and poly (1,6-hexamethylene terephthalate, poly (ethylene-2,6-). Naphthalate), poly (1,4-cyclohexylene methylene terephthalate) and the like. These may be homopolymers, copolymers, or mixtures thereof. Among these polyesters, polybutylene in particular. Telephthalate, a mixture of polybutylene terephthalate and polybutylene isophthalate, etc. are preferable as the raw material resin for the heat-resistant melt-blow non-woven polyester thin film according to the present invention, and by using these, the melt-blow spinnability is improved and the tensile strength of the non-woven fabric is increased. Further, the number average molecular weight of polybutylene terephthalate is preferably 5,000 to 20,000, and more preferably an IV value of 0.6 to 0.9.

Examples of the polyamide (hereinafter, may be abbreviated as PA) include nylon 6, nylon 66, nylon 6-66 copolymer, nylon 12, nylon 6-12 copolymer, nylon 46 and the like. The melt-blown nonwoven fabric having a molecular weight as low as possible is preferable because it has good spinnability and fine fibers can be obtained. For example, PA having a number average molecular weight of 10,000 to 25,000 is preferable.

Examples of the polyarylene sulfide include polymers having excellent heat resistance and chemical resistance, and 90 mol% or more of the constituent units are composed of [C5 _H4 S], and in particular, melt viscosity ( _V ). ₆ ) is preferably a polyphenylene sulfide having a poise of 200 to 500 (hereinafter, may be abbreviated as PPS).

The polyphthalamide is not particularly limited, but contains a terephthalamide unit, an isophthalamide unit, and the like, and is, for example, a hexamethylene terephthalamide-isophthalamide-adipoamide terpolymer (molar ratio 65:25). : 10) and the like can be exemplified. Examples of the raw material resin for the heat-resistant melt-blown non-woven fabric thin film include those having a melt viscosity of 100 to 1000 Pas.
Examples of the polyolefin include polymethylpentene and cyclic olefin polymers.

3. 3. Structure of Heat-Resistant Melt-Blow Nonwoven Fabric Thin Film The heat-resistant melt-blow non-woven fabric thin film according to the present invention is a non-woven fabric processed product composed of a single non-woven fabric layer or a non-woven fabric processed product obtained by laminating and laminating at least two non-woven fabric layers. In particular, it is preferable to adopt a non-woven fabric processed product in which at least two or more non-woven fabric layers are laminated and laminated, depending on the application, because it has the following characteristics as compared with a single layer. The heat-resistant melt-blown non-woven fabric thin film includes (A) a laminated non-woven fabric layer having the same physical characteristics and (B) a non-woven fabric layer having at least fibers having different fiber diameters among the physical properties. Can be mentioned.

As described later, the above-mentioned "woven fabric processed body made of bonded material" includes, for example, a processed product obtained by pressure-bonding the nonwoven fabric layers to each other by a high-temperature calendering process and a special calendering process. be.
(A) The non-woven fabric processed product in which the non-woven fabric layers having the same physical characteristics are bonded is a case where the values of the average fiber diameters of the constituent fibers of the non-woven fabric layers of at least two layers are substantially the same, and other physical property values. For example, at least two or more kinds of physical property values such as texture, tensile strength, and tensile elongation may be substantially the same. According to this configuration, for example, when the average fiber diameter is the same, the variation in physical properties is made uniform as compared with a single layer, especially by laminating a laminate of fine fibers, and when used in a battery, a short circuit occurs. It can be prevented, and at the same time, it is possible to improve the tensile strength and the electrolyte liquid absorption rate.

On the other hand, according to (B) laminated bonding of at least two layers of a non-woven fabric having fibers having different average fiber diameters, the obtained heat-resistant melt-blown non-woven fabric thin film has tensile strength and garley permeability as shown in Examples. The air quality can be improved, and the liquid absorption performance and the liquid retention performance of the electrolytic solution can also be improved. In particular, a laminated non-woven fabric obtained by combining a non-woven fabric layer having fine fibers and thick fibers can improve tensile strength, garley air permeability, electrolyte liquid absorption performance and liquid retention performance.

The fine fibers are specifically those having 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 are specifically. Is an average fiber diameter of 1 to 15 μm, preferably 1.5 to 10 μm, more preferably 2 to 5 μm, and is a nonwoven fabric layer having fine fibers and thick fibers in which these average fiber diameters do not overlap with each other. The combination is preferred.

4. Physical Properties of Heat-Resistant Melt-Blow Nonwoven Fabric Thin Film Next, the physical property values that the heat-resistant melt-blow non-woven fabric thin film according to the present invention should have will be described.
When the heat-resistant melt-blown nonwoven fabric thin film is composed of two or more layers of nonwoven fabrics having different physical properties, the physical property values are average values of all the nonwoven fabric layers.

(1) Average Fiber Diameter The average fiber diameter of the fibers of the nonwoven fabric layer constituting the heat-resistant melt-blown nonwoven fabric thin film according to the present invention is 0.5 to 15 μm, preferably 1.0 to 10 μm, and more preferably 1.5 to 8 μm. Is. If the average fiber diameter is less than 0.5 μm, not only the tensile strength is weakened, but also the internal resistance of the battery becomes too large when used as a battery separator. On the other hand, if the average fiber diameter exceeds 15 μm, the risk of internal short circuit may increase when used as a battery separator.

(2) Metsuke The basis weight of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention is 5 to 100 g / m ² , preferably 7 to 50 g / m ² , and more preferably 10 to 40 g / m ² . If the basis weight is less than 5 g / m ² , the tensile strength is insufficient, so that the reliability in the battery assembly is lowered, and the battery separator is not preferable because shorts are likely to occur. On the other hand, if the basis weight exceeds 100 g / m ² , the internal resistance may increase when used as a battery separator.

(3) Thickness The thickness of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention is 50 μm or less, preferably 1 to 45 μm, particularly preferably 1 to 45 μm in view of its use as a separator for an electric double layer capacitor and a separator for a lithium secondary battery. It is 5 to 40 μm, more preferably 10 to 35 μm. If the thickness exceeds 1 μm, the risk of internal short circuit is suppressed when used as a battery separator, while if it exceeds 50 μm, the battery capacity may decrease.

(4) Garley permeability The garley permeability of the melt-blown nonwoven fabric thin film according to the present invention is 1 to 40 s / φ10 / 300 cc, preferably 5 to 30 s / φ10 / 300 cc. If the garley air permeability is less than 1 s / φ10 / 300 cc, the risk of an internal short circuit increases as a battery separator, while if it exceeds 40 s / φ10 / 300 cc, the internal resistance of the battery separator increases.
As will be described later, "Garley air permeability" is measured by a measurement method based on JIS P8117 (2009) "Paper and paperboard one air permeability and air permeability resistance test method" (intermediate region) one Garley method. It means the result obtained.

(5) Tensile strength The tensile strength of the heat-resistant melt-blown nonwoven fabric thin film 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, it is likely to break during battery assembly. On the other hand, if the tensile strength exceeds 50 N / 25 mm width, the elongation is extremely lowered, and there is a possibility that a defect is likely to occur due to a decrease in the degree of freedom during assembly.

(6) Tensile Elongation The tensile elongation of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention is 1 to 100%, preferably 5 to 80%. If the tensile elongation is less than 1%, it is likely to break during assembly. On the other hand, if the tensile elongation is 100% or more, necking is likely to occur, and stable assembly may be difficult.

(7) Heat Shrinkage Rate The heat shrinkage rate of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention under high temperature is 1.0% or less, preferably 0.5% or less under a heating environment at 120 ° C. for 1 hour. , 1.2% or less, preferably 1.0% or less under a heating environment at 150 ° C. for 1 hour. It is desirable that this value satisfies at least one of the MD direction and the CD direction, more preferably both. If the heat shrinkage rate is high, the separator at the end of the battery shrinks due to the temperature rise inside the battery due to the occurrence of an abnormality in the battery in a high temperature environment, and the contact between the positive electrode and the negative electrode may cause a problem such as an internal short circuit.

As described above, the heat-resistant melt-blow non-woven fabric thin film according to the first invention is a heat-resistant melt-blow non-woven fabric thin film made of a heat-resistant resin.
At least the following physical characteristics;
・ Thickness is 50 μm or less,
・ Metsuke is 5-100g / m ² ,
・ Average fiber diameter is 0.5 to 15 μm,
・ Garley air permeability is 1-40s / φ10 / 300cc,
A heat-resistant melt-blown non-woven fabric thin film having a heat shrinkage rate of 1.2% or less in the MD direction and the CD direction, respectively, even after heat treatment under heating conditions of 150 ° C. for 1 hour. can be,
The heat-resistant melt-blown nonwoven fabric thin film can be produced through the following calendar processing step as one method.
That is, (1) the melt-blown nonwoven fabric raw fabric is sandwiched between at least two metal rolls, and the processing temperature conditions above the glass transition point of the heat-resistant resin and the crushing of the constituent fibers of the melt-blown nonwoven fabric raw fabric are suppressed. The high temperature calendering process to be subjected to the calendering under the pressurized conditions adjusted so as to
(2) The calendering process intermediate obtained by the high temperature calendering process is subjected to a special calendering process including at least two rolls in which at least one roll is an elastic roll, and the processing temperature condition is 130 ° C. or lower. The heat-resistant melt-blown non-woven fabric thin film having at least the above-mentioned physical properties is subjected to the calendar processing including the special calendar processing step of performing the calendar processing under the pressure condition adjusted so as to suppress the crushing of the constituent fibers of the nonwoven fabric raw fabric. Can be obtained.

B. Second Invention According to the second invention, there is provided a method for producing a heat resistant melt blown nonwoven fabric thin film.
That is, it is a method for manufacturing a heat-resistant melt-blow non-woven fabric thin film obtained by thinning a melt-blow non-woven fabric raw fabric made of a heat-resistant resin.
Provided is a method for producing a heat-resistant melt-blown nonwoven fabric thin film, which comprises subjecting the melt-blown nonwoven fabric raw fabric to at least (1) a high-temperature calendering treatment step and (2) a special calendering treatment step.
Here, the "melt-blow non-woven fabric raw fabric" means a non-woven fabric manufactured by the melt-blow method and is a target non-woven fabric to be thinned into a non-woven fabric thin film.

1. 1. Melt-blow non-woven fabric Raw fabric Non-woven fabric is made from a fiber aggregate directly into a cloth without going through the thread stage, unlike the one made by weaving and knitting threads like conventional cloth.
The physical properties and manufacturing method of the melt-blown nonwoven fabric, which is a raw material for producing the heat-resistant melt-blown nonwoven fabric thin film according to the present invention, will be described below.
The melt-blown nonwoven fabric according to the present invention is manufactured by a melt-blow method using a heat-resistant resin as a raw material resin.
The heat-resistant resin is as described above, and can be appropriately selected from such heat-resistant resins and used. However, polybutylene terephthalate is suitable for the purpose of the present invention, and the melt blow described below is preferable. The manufacturing conditions for the non-woven fabric raw fabric are based on the case where polybutylene terephthalate is used as the heat-resistant resin.

The melt-blow non-woven fabric raw fabric is an important element for the production of the heat-resistant melt-blow non-woven fabric thin film according to the present invention, and preferably has at least the following physical properties.
(1) Metsuke The basis weight of the melt-blown nonwoven fabric according to the present invention is 5 to 100 g / m ² , preferably 7 to 50 g / m ² , and more preferably 10 to 40 g / m ² . If the basis weight does not reach 5 g / m ² , the tensile strength of the heat-resistant melt-blown non-woven fabric thin film obtained after the calendering process is insufficient, while if the basis weight exceeds 100 g / m ² , fluffing increases and the non-woven fabric is stable. Problems such as difficulty in manufacturing a thin film may occur.
(2) Air permeability The air permeability of the melt-blown nonwoven fabric according to the present invention is 10 to 200 cc / cm ² / s, preferably 20 to 150 cc / cm ² / s. When the air permeability is less than 10 cc / cm ² / s, the garley air permeability of the heat-resistant melt-blown non-woven fabric thin film obtained after the high-temperature calendar processing becomes high, exceeding 40 s / φ10 / 300 cc, while the air permeability is 200 cc / s. If it exceeds cm ² / s, the garley permeability of the heat-resistant melt-blow non-woven fabric thin film decreases to less than 1 s / φ10 / 300 cc. There is a problem that the risk of not being able to manufacture the product increases.
(3) Tensile Strength The tensile strength of the melt-blown nonwoven fabric according to the present invention is at least 1 N / 25 mm or more so as to provide a heat-resistant melt-blow nonwoven fabric thin film having a tensile strength of 2 to 50 N / 25 mm. It is preferably 3N / 25 mm width or more. If the tensile strength does not reach 1 N / 25 mm width, there arises a problem that a heat-resistant melt-blown nonwoven fabric thin film having sufficient tensile strength cannot be obtained.
(4) Tension elongation The tensile elongation of the melt-blown nonwoven fabric according to the present invention is 1 to 150%, preferably 10 to 100%.
(5) 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 in both the single layer and the two or more layers of the nonwoven fabric, preferably 1. It is ~ 10 μm.

2. 2. Melt-blow method The melt-blow method for producing the melt-blow nonwoven fabric according to the present invention is not particularly limited, and is, for example, the method described in US Pat. No. 3,650866 and US Pat. No. 3,978185 (ExxonMobil). Is preferable, and the melt blow method described below can be adopted as a method similar to these.
As a melt blow method, a molten raw material resin is discharged as a molten polymer from a plurality of nozzle holes arranged in a row, and a high-temperature high-speed air is injected from an injection gas port installed adjacent to an orifice die to discharge the molten polymer. A method is adopted in which the fiber is made into fine fibers and the fiber flow is collected. Specifically, the following method is adopted.

After melting the raw material resin at an extruder temperature of 260 to 380 ° C, it is sent to a die set at 300 to 380 ° C and discharged from a die nozzle, and at the same time, it is stretched by a high temperature air blow gas of 260 to 380 ° C to form fine fibers. Collect in a collector installed at a position away from the nozzle.

In the melt blow device die, the nozzle hole 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 becomes high, while if the nozzle hole diameter exceeds 1 mmφ, the fibers cannot be thinned. Further, when the number of nozzles is less than 5 / cm, the discharge pressure of the raw material resin becomes high, while when the number of nozzles exceeds 20 / cm, the fibers are fused too much and the uniformity of the nonwoven fabric is lost. Will be.

Further, as the production conditions of the melt blow method, in the production of a melt blow nonwoven fabric using a heat resistant resin, for example, a polybutylene terephthalate resin as a raw material, the extrusion temperature is 260 to 380 ° C, preferably 300 to 350 ° C, and the die. The temperature is 300 to 380 ° C., preferably 320 to 350 ° C., and the high-speed air temperature is 260 ° C. to 380 ° C., preferably 300 to 350 ° C. If the extruder / die and air temperature are below the above range, the discharge resin pressure becomes high and fine fibers cannot be obtained. On the other hand, if it exceeds the above range, gelation of the resin is promoted and deteriorates. In addition to damaging the conveyor net, the resulting non-woven fabric has poor peelability from the conveyor net, making stable production difficult. The resin discharge amount is 0.05 to 3 g / min / hole, preferably 0.1 to 1 g / min / hole. When the resin discharge amount is small, the discharge resin pressure falls below the above range and a uniform non-woven fabric cannot be obtained. On the other hand, when the resin discharge amount exceeds the above range, the discharge resin pressure increases and fine fibers are obtained. do not have.

3. 3. Calendar processing The heat-resistant melt-blown nonwoven fabric thin film according to the present invention is manufactured by a calendar processing process consisting of the following two steps. The physical characteristics of the heat-resistant melt-blown non-woven fabric thin film shall be adjusted by selecting the processing temperature conditions, processing pressure conditions (including roll linear pressure and inter-roll clearance) and processing speed conditions of each processing process as described below. Can be done.

(1) High-temperature non-woven fabric processing process In the high-temperature non-woven fabric processing process, a non-woven fabric mechanism consisting of a combination of at least two metal rolls is used, and specifically, it is manufactured by a melt blow method using a heat-resistant resin as a raw material. The melt-blown non-woven fabric raw fabric is sandwiched between two metal rolls, and the temperature conditions are equal to or higher than the glass transition point of the heat-resistant resin and the pressure conditions are adjusted so as to suppress the crushing of the constituent fibers of the non-woven fabric. Is calendered in. As the metal calendar roll, those usually used can be adopted, but steel and an alloy material equivalent to steel are particularly preferable. As the calendar type and roll arrangement, an inverted L type, a Z type, an upright double type, etc. (Practical Plastics Glossary, page 151 (published by Plastics Age Co., Ltd.)) can 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 the polyester resin, a temperature of 130 ° C. or higher, preferably 140 ° C. or higher is adopted. The temperature conditions are adjusted by setting the heating temperatures of both of the two metal rolls to be combined.
The upper limit of the processing temperature in the high-temperature calendar processing treatment is a temperature equal to or lower than 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 high-temperature calendering treatment alleviates the residual strain during the production of the non-woven fabric and promotes the crystallization of the raw material resin. As a result, high temperature stability is improved and high temperature shrinkage can be improved. Quantitative measurement of crystallization is difficult and impractical. Further, as the pressurizing condition, in addition to the roll linear pressure, the clearance provided between the rolls is also included as an element affecting the thinning. The clearance size is set so that the thickness of the calendaring intermediate after the high-temperature calendaring treatment reaches a predetermined level, and the fiber crushing or deformation in the melt-blown non-woven fabric raw fabric can be suppressed. It was done. As the linear pressure of the roll, it is preferable to adopt a processing pressure of 200 N / mm or less, preferably 30 to 170 N / mm, and more preferably 50 to 150 N / mm.
Under such calendering conditions, a heat-resistant melt-blow nonwoven fabric thin film having a small shrinkage rate under high-temperature conditions, a small garley air permeability, and a small internal resistance can be obtained. The clearance between the rolls can be selected within a range necessary for thinning the single-layer melt-blow non-woven fabric raw fabric and transmitting at least two layers of the melt-blow non-woven fabric raw fabric to adhere to each other and transfer the temperature at which crystallization can be promoted.

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 it is less than 1 m / min, the productivity is low, while if it exceeds 50 m / min, there arises a problem that heat for relaxing strain and promoting crystallization is not sufficiently transferred.

(2) Special calendar processing process In the special calendar processing process, which is one of the elements of the heat-resistant melt-blown nonwoven fabric thin film manufacturing process according to the present invention, a combination of a metal roll and an elastic roll is used as the calendar mechanism. Is. As for the combination of the metal roll and the elastic roll, in addition to the pair combination, a plurality of combinations of 4 to 6 can be used. As for the format of the calendar and the arrangement of the rolls, the same format as the format that can be used in the high temperature calendar processing step can be adopted, and the metal roll and the elastic roll may be appropriately combined. As the metal roll, the same one used in the above-mentioned high-temperature calendar processing step can be used, and steel and an alloy material equivalent to steel are preferable. As the elastic roll to be combined with the metal roll, one made of a hard synthetic resin is preferable. The hardness of the roll is a shore D hardness of 60 or more, preferably 70 to 90, for the purpose of adjusting the thickness of the melt-blown nonwoven fabric of the present invention and smoothness.

In the special calendar processing step, the calendar processing intermediate obtained in the high temperature calendar processing step is sandwiched between the metal roll and the elastic roll, and the temperature is 130 ° C. or lower, preferably 120 ° C. or lower, more preferably 120 ° C. or lower. Processing is performed under 110 ° C. or lower processing, temperature conditions, and pressure conditions that can control the crushing of fibers in the intermediate. In the special calendar processing step, the lower limit of the processing temperature is at least the glass transition point and depends on the raw material resin, but for example, a temperature of 60 ° C. or higher is preferable, and a temperature of 80 ° C. or higher is more preferable.

The pressurizing conditions include not only the linear pressure of the rolls but also the clearance between the rolls, but in the special calendering process, the rolls were pinched so as to adjust the thickness of the non-woven fabric thin film to be formed. It is preferable to keep it in a state. The linear pressure of the roll is 15 to 130 N / mm, preferably 20 to 100 N / mm, and more preferably 30 to 70 N / mm.

Further, as the processing speed condition, the same conditions as the processing speed condition in the high temperature processing process can be adopted. Specifically, it is 1 to 50 m / min, preferably 2 to 30 m / min, and more preferably 3 to 20 m / min.

In the special calendar processing step according to the present invention, heating is applied to the metal roll, and a combination processing process of the elastic roll at room temperature and the heated metal roll is provided.
By special calendar processing using such an elastic roll, the thickness of the melt-blown nonwoven fabric thin film can be adjusted, and the effects of thickness uniformity and surface smoothness can be obtained.
The heat-resistant melt-blown non-woven fabric thin film obtained through the above-mentioned high-temperature calendering process and special calendering process can maintain a high degree of pore opening and can be ultra-thin, and is heat-shrinkable under high-temperature conditions. It can also be improved and the air permeability of the garley becomes low, and it has an excellent effect on the tensile strength.

The calendering process as a method for producing the heat-resistant melt-blown non-woven fabric thin film according to the present invention has the above-mentioned effect by setting the high-temperature calendering process as the first stage and the special calendering process as the second stage as described above. If the special calendering process is the first stage and the high temperature calendering process is the second stage, the thickness of the non-woven fabric thin film will be set at the first processing stage, and there will be gaps between the metal rolls in the subsequent stage. In a certain processing, the object to be processed is too thin and the contact with the roll becomes loose, crystallization due to high temperature heat cannot be sufficiently promoted, and residual strain is alleviated at a later stage. Therefore, there is a problem that the non-woven fabric thin film, which is a processed product, relaxes and shrinks in the width direction, and there is a problem that it cannot be used as a product due to a problem of shape, and a heat-resistant melt-blow non-woven fabric thin film of the quality required by the present invention can be obtained. I can't.

C. Third Invention According to the third invention, a separator for an electric double layer capacitor and a separator for a lithium ion secondary battery of the heat-resistant melt blow nonwoven fabric thin film are provided.
The electric double layer capacitor in which the heat-resistant melt-blown nonwoven fabric thin film according to the present invention can be used as a separator may have the structure of a conventional electric double layer capacitor, but in particular, it has a thin structure and has a thickness. Other than requiring a small separator and using the heat-resistant melt-blown non-woven fabric thin film according to the present invention as a component, other components are not particularly limited.
The lithium ion secondary battery in which the heat-resistant melt-blow non-woven thin film according to the present invention can be used as a separator is not particularly limited, and is a conventional lithium secondary battery, in which the thickness of the separator is small and it is on the thin film. The heat-resistant melt-blow non-woven thin film according to the present invention can sufficiently cope with a lithium secondary battery that requires the above.
The heat-resistant melt-blown non-woven fabric thin film according to the present invention is used as a separator for an electric double layer capacitor and a separator for a lithium secondary battery, as well as a member for a liquid filter, a member for an air filter, a member for a mask, a member for miscellaneous goods, and the like. It is not particularly limited as long as it can utilize the physical properties of the heat-resistant melt-blown nonwoven fabric thin film according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples and the like.
In addition, each physical property value described in an Example and a comparative example was measured and obtained by the following method, respectively.
1. Various physical property value measurement methods

(1) Metsuke: A test piece of 100 mm × 100 mm was collected from the sample length direction, the weight in the water equilibrium state was measured, and the weight was converted into the basis weight per 1 m.

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

(3) Air permeability: A 100 mm × 100 mm test piece is collected from the sample length direction, and conforms to the “breathability A method (Frazil type method)” of JIS L1096 “General woven fabric test method”, and is a Frazier type tester. Was measured using.

(4) Garley air permeability: Measured according to JIS P8117 (2009) +. A Garley Denso meter (manufactured by Toyo Seiki Co., Ltd.) is used as a measuring device, and the sample piece is tightened into a circular hole having a diameter of 10 mm and an area of 78.5 mm ² . With an inner cylinder mass of 567 g, the air inside the cylinder is passed from the test cylinder portion to the outside of the cylinder. The time through which 300 cc of air passed was measured and used as the Garley value.

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

(6) Average fiber diameter: Take 5 photographs with an electron microscope at any 5 points of the test piece, measure the diameter of 20 fibers per photograph, and take a total of these 5 photographs. The diameter of 100 fibers was averaged and determined.

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

(8) Electrolyte liquid absorption performance: In accordance with JIS L1907 "Water absorption test method for textile products", one drop of PC (propylene carbonate) was removed from a height of 10 mm on the test piece, and the droplet became the test piece. The time from the arrival to the complete elimination of the mirror reflection of the droplet was measured with a stopwatch, and the measured value was taken as the absorption rate of the electrolytic solution.

(9) Electrolyte retention performance: A 100 mm × 100 mm test piece is collected, immersed in PC (propylene carbonate) for 60 minutes, then the test piece is taken out and left to hang for 10 minutes. The liquid-retaining test piece was weighed with a balance, and the liquid-retaining rate was calculated by 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 based on the presence or absence of transparent spots having a diameter of 0.5 mm or more in the sample piece 100 cm ² .

2. 2. Raw Material Resin for Manufacturing Melt Blow Nonwoven Fabric The following materials were used as the raw material resin for manufacturing Melt Blow Nonwoven Fabric.
-Polybutylene terephthalate (PBT); melting point 225 ° C (manufactured by Polyplastics) -polystyrene (PS); melting point 270 ° C (manufactured by Idemitsu Kosan)
-Polypropylene (PP); melting point 165 ° C (manufactured by Japan Polypropylene Corporation)
-Polymethylpentene (PMP); melting point 232 ° C (manufactured by Mitsui Chemicals, Inc.)
・ Cellulose; (manufactured by Nippon Kodoshi Paper Industry Co., Ltd.)

Example 1
A melt-blow non-woven fabric raw material single-layer product manufactured by the melt-blow method using the polybutylene terephthalate (PBT) as a raw material resin and having the following physical properties.

PBT melt blow non-woven fabric original fabric (single layer product)

Metsuke (g / m ² ): 20
Thickness (μm): 175
Air permeability (cc / cm ² / s): 38.7
Tensile strength (N / 25mm width): 9.6
Tensile elongation (%): 15.8
Average fiber diameter (μm): 1.8

Is sandwiched between metal rolls / metal rolls (type: upright double type) heated to a calendar processing temperature of 150 ° C., and the pressurization condition is set to 130 N / mm with the roll pressure as the linear pressure of the roll. Was subjected to high temperature calendar processing. A clearance was provided between the metal rolls so that the thickness of the non-woven fabric thin film intermediate after the high-temperature calendar processing was adjusted to a level of about 50 to 70 μm.

As described above, the melt-blown non-woven fabric thin film intermediate obtained by high-temperature calendering with a metal roll / metal roll is in a state where the rolls are pinched between the elastic roll and the metal roll heated to the calendering temperature of 100 ° C. A PBT heat-resistant melt-blown non-woven fabric thin film (single-layer product) having the following physical properties was obtained by being subjected to a special calendering process in which the roll pressure was set to 30 N / mm as the linear pressure under the pressurizing conditions.

PBT melt blow non-woven fabric thin film (single layer product)
Eyes (g / m ² ): 20
Thickness (μm): 35
Garley air permeability (s / φ10 / 300cc): 12.4
Tensile strength (N / 25mm width): 11.3
Tensile elongation (%): 22.9
Appearance (film formation due to formation of transparent spots): None Electrolyte absorption rate (seconds): 11.15
Electrolyte retention rate (%): 286
Heat shrinkage rate (%): Dimensional change rate after heating in an oven at 120 ° C for 1 hour MD: 0.5
CD: 0.5
Dimensional change rate after heating in an oven at 150 ° C for 1 hour MD: 1.0
CD: 0.5

Although the heat-resistant melt-blown nonwoven fabric thin film obtained by the above-mentioned two-step calendar processing was thinned to a thickness of 35 μm, the crushing of the fibers in the nonwoven fabric thin film was suppressed. In addition, it was observed that no transparent plaque was formed in 100 cm ² due to the film formation of the entangled part of the fiber. A heat-resistant melt-blown non-woven fabric thin film having a small garley air permeability of 12.4 s / φ10 / 300 cc as shown below and having a high porosity as shown by SEM was obtained. In addition, the strength was as high as 11.3 N / 25 mm width), and a sufficient result with a tensile elongation of 22.9% was obtained. Further, the heat shrinkage rate was 1.0% or less in both the MD direction and the CD direction under each heating condition of 120 ° C. × 1 Hr and 150 ° C. × 1 Hr.

Example 2
A melt-blow non-woven fabric raw fabric (A) having fibers having an average fiber diameter of 1.8 μm and a melt-blow non-woven fabric raw fabric having an average fiber diameter of 2.6 μm produced by a melt blow method using the polybutylene terephthalate (PBT) as a raw material (A). The two types of melt-blown non-woven fabrics of B) were laminated on the two-layered body.
The physical properties of the melt-blow non-woven fabric raw fabric (A) and the melt-blow non-woven fabric raw fabric (B) used for laminating the two layers are as follows.

T Melt Blow Nonwoven Fabric Original Fabric (A) PBT Melt Blow Nonwoven Fabric Original Fabric (B) Metsuke (g / m ² ): 10 10
Thickness (μm): 95 145
Air permeability (cc / cm ² / s): 83.1 131.2
Tensile strength (N / 25mm width): 5.3 4.9
Tensile elongation (%): 34.8 49.6
Average fiber diameter (μm): 1.8 2.6

The two-layer product is sandwiched between two types of metal rolls / metal rolls heated to 150 ° C., and among the pressurizing conditions, the roll pressure is the linear pressure of the roll and the temperature is high at 130 N / mm. It was subjected to calendar processing. A clearance was provided between the metal rolls as in Example 1.

The calendar processing intermediate composed of the two adhesive layers obtained by the above-mentioned high-temperature calendar processing is sandwiched between the elastic roll and the metal roll heated to 100 ° C., and the roll pressure is the linear pressure of the roll. Under the pressure condition of 30 N / mm, it is further subjected to special calendar processing.
A heat-resistant melt-blown non-woven fabric thin film of a laminated product composed of two types of non-woven fabric raw fabric was obtained. As the elastic roll, one made of a polyamide-based synthetic resin having the above-mentioned hardness (shore D hardness 80) was used. The physical characteristics of the obtained PBT heat-resistant melt-blown non-woven fabric thin film (two-layer product (1)) are as follows.

PBT heat resistant melt blow non-woven fabric thin film (double layer product (1))

Metsuke (g / m ² ): 20
Thickness (μm): 35
Garley air permeability (s / φ10 / 300cc): 6.5
Tensile strength (N / 25mm width): 9.3
Tensile elongation (%): 21.7
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 9.80
Electrolyte retention rate (%): 340
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 0.5
CD: 0.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 1.2
CD: 0.5

As shown in the above results, by laminating and laminating two layers of nonwoven fabrics having different average fiber diameters of the constituent fibers, the thin film has a thickness of 35 μm. The garley air permeability is 6.5 s / φ10 / 300 cc, it can maintain high porosity, suppress fiber crushing, suppress the formation of transparent spots on the film, and heat shrinkage under high temperature conditions. After heating in an oven set at 120 ° C for 1 hour, both MD and CD have a dimensional change rate of 0.5%, and even after heating in an oven set at 150 ° C for 1 hour, the dimensional change rate is 1.2 in the MD direction. %, 0.5% in the CD direction, and good results were obtained. Further, the electrolytic solution absorption rate was 9 seconds and 80 seconds, and the electrolytic solution retention rate was 340%, which was a remarkable effect, showing an extremely high superiority as a separator for a lithium secondary battery.

Example 3
Instead of the PBT melt-blow non-woven fabric raw fabric (B) having an average fiber diameter of 2.6 μm used in Example 2, the PBT melt-blow non-woven fabric raw fabric (A) having the following fibers having an average fiber diameter of 1.8 μm is shown below.

PBT Melt Blow Nonwoven Fabric Original Fabric (A)
Metsuke (g / m ² ): 10
Average fiber diameter (μm): 1.8
Thickness (μm): 95
Air permeability (cc / c / s): 83.1
Tensile strength (N / 25mm width): 5.3
Tensile elongation (%): 34.8

High-temperature calendar processing and special calendar under the same conditions and operations as in Example 2 except that the obtained two-layer product (2) was laminated by laminating two layers of the PBT melt blow nonwoven fabric raw fabric (A). It was subjected to processing to obtain a PBT heat-resistant melt-blown non-woven fabric thin film (two-layer product (2)). The physical characteristics of the obtained PBT heat-resistant melt-blown non-woven fabric thin film (two-layer product (2)) are as follows.

PBT heat resistant melt blow non-woven fabric thin film (double layer product (2)
Metsuke (g): 20
Thickness (μm): 35
Garley air permeability (s / φ10 / 300cc): 11.5
Tensile strength (N / 25mm width): 12.8
Tensile elongation (%): 21.1
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 9.72
Electrolyte retention rate (%): 365
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 0.5
CD: 0.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 1.2 CD: 0.5

As shown in the above results, the heat-resistant melt-blown nonwoven fabric thin film (two-layer product (2)) obtained by laminating two layers of the melt-blown nonwoven fabric raw fabric (A) having the same average fiber diameter is different. Compared with the heat-resistant melt-blown non-woven fabric thin-layer product (1) consisting of two non-woven fabric layers having fibers with an average fiber diameter, the tensile strength was improved to 12.8 N / 25 mm width even though the thin film had a thickness of 35 μm. .. Regarding the heat shrinkage rate, the rate of change was 1.2% in the MD direction and 0.5% in the CD direction even after heating in an oven set at 150 ° C. for 1 hour, and similarly good results were obtained. In addition, the electrolyte absorption rate was improved to 9.72 seconds, and the electrolyte retention rate was 365%, which was a remarkable effect.

Example 4
All of them were subjected to the high temperature calendar processing and the special calendar processing under the same conditions as in Example 1 except that the PS melt blow nonwoven fabric raw material single layer produced by the melt blow method using polystyrene (PS) as a raw material was used. The PS melt blown non-woven fabric had an average fiber diameter of 3.8 μm, and other physical properties were as follows. The properties of the obtained PS heat-resistant melt-blown non-woven fabric thin film are shown in Table 1 and Table 1 below.
Although the thickness was reduced to 35 μm, the Garley air permeability was as low as 15.5 s / φ10 / 300 cc, the tensile strength and tensile elongation were excellent, and the heat shrinkage rate was reduced, and the following results were obtained. In addition, there was no fiber crushing and no transparent spots were formed due to film formation.

PS Melt Blow Nonwoven Fabric Original

Metsuke (g / m ² ): 20
Average fiber diameter (μm): 3.8
Thickness (μm): 184
Air permeability (cc / c / cc): 32.2
Tensile strength (N / 25mm width): 12.2
Tensile elongation (%): 11.7

PS heat resistant melt blow non-woven fabric thin film (single layer product )

Metsuke (g): 20
Thickness (μm): 35
Garley air permeability (s / φ10 / 300cc): 15.5
Tensile strength (N / 25mm width): 11.8
Tensile elongation (%): 16.9
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 13.22
Electrolyte retention rate (%): 264
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 0
CD: 0
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 0
CD: 0

Example 5
A two-layer product made of a melt-blow non-woven fabric raw fabric (a) and (b) manufactured by a melt-blow method using polymethylpentene (PMP) as a raw material resin and having the following physical characteristics was used.

PMP Melt Blow Nonwoven Fabric Original Fabric (a) PMP Melt Blow Nonwoven Fabric Original Fabric (b)

Metsuke (g / m ² ): 15 15
Thickness (μm): 207 207
Fiber diameter (μm): 3.5 3.5
Air permeability (cc // s): 86.6 86.6
Tensile strength (N / 25mm width): 6.9 6.9
Tensile elongation (%): 14.2 14.2
The laminates of the PMP melt-blown non-woven fabric raw fabrics (a) and (b) were subjected to high-temperature calendering treatment with a metal roll / metal roll and special calendering treatment with an elastic roll / metal roll under the same conditions as in Example 1. A PMP heat-resistant melt-blown non-woven fabric thin film having the following physical properties was obtained.

PMP heat resistant melt blow non-woven fabric thin film (double layer product)
Metsuke (g / m ² ): 30
Thickness (μm): 45
Garley air permeability (s / φ10 / 300cc): 28.6
Tensile strength (N / 25mm width): 14.5
Tensile elongation (%): 19.8
Appearance (film formation due to the formation of transparent spots): None
Electrolyte absorption rate (seconds): 30
Electrolyte retention rate (%): 57
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 0
CD: 0
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 0
CD: 0

Comparative Example 1
The same PBT melt-blow non-woven fabric single-layer product as the polybutylene terephthalate (PBT) PBT melt-blow non-woven fabric single-layer product used in Example 1 was subjected to the calendering treatment with the conditions and operations of the high-temperature calendering treatment of Example 1. Only high-temperature calendering treatment with metal rolls / metal rolls under the same conditions and operations was performed, and no special calendering treatment was performed. As a result, a melt-blown non-woven fabric thin film (single-layer comparative product (1)) having the following physical property values was obtained. rice field.

PBT Melt Blow Nonwoven Fabric Thin Film (Single Layer Comparative Product (1) )
Metsuke (g / m ² ): 20
Thickness (μm): 55
Garley air permeability (s / φ10 / 300cc): 0.8
Tensile strength (N / 25mm width): 16.7
Tensile elongation (%): 26.6
Appearance (film formation due to the formation of transparent spots): None
Electrolyte absorption rate (seconds): 12.05
Electrolyte retention rate (%): 275
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 1.0
CD: 0.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 1.5
CD: 1.0

The thickness of the PBT melt blow non-woven fabric thin film (single-layer comparative product (1)) after the high-temperature calendar processing was 55 μm, which could not reach 50 μm or less, making it difficult to apply to lithium secondary batteries, electric double layer capacitors, etc. Become. Further, the garley air permeability was 0.8 s / φ10 / 300 cc, which deviated from the lower limit of the garley air permeability that the heat-resistant melt-blown nonwoven fabric thin film according to the present invention should have. The electrolytic solution absorption rate was 12 seconds 05, and the electrolytic solution retention rate was 275%. Further, the heat shrinkage rate is as described above, and a non-woven fabric thin film having high high temperature stability could not be obtained even though it was subjected to the high temperature calendar processing treatment.

Comparative Example 2
Using the same polybutylene terephthalate melt-blown non-woven fabric single-layer product as in Comparative Example 1, the roll linear pressure was 130 N / N among the pressure conditions in the high-temperature calendar processing process using two metal rolls heated to 150 ° C. When the thickness was set to mm and the clearance between the rolls was changed to adjust the thickness of the thin film after the calendering process to 35 μm, the garley air permeability of the obtained thin film increased significantly to 98 s / φ10 / 300 cc. However, as a result of the decrease in air permeability, the internal resistance of the separator increased. In addition, a transparent group was formed by forming a film of the confounding part. It was observed as if a hole was formed in the separator by the transparent group, which significantly reduced the commercial value. The heat shrinkage rate was not different from the result of Comparative Example 1, but the electrolyte liquid absorption performance and the electrolyte liquid retention performance were deteriorated.

PBT melt blow non-woven fabric thin film (single layer comparative product (2))
Metsuke (g / m): 20
Thickness (μm): 35
Garley air permeability (s / φ10 / 300cc): 98
Tensile strength (N / 25mm width): 24.5
Tensile elongation (%): 12.7
Appearance (film formation due to the formation of transparent spots): Yes
Electrolyte absorption rate (seconds): 14.50
Electrolyte retention rate (%): 150
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 1.0
CD: 0.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 1.5
CD: 1.0

Comparative Example 3
An elastic roll / metal of a melt-blow non-woven fabric raw fabric single-layer product manufactured by the melt blow method using the polybutylene terephthalate of Comparative Example 1 as a raw material, and an elastic roll and a metal roll heated to 100 ° C. When the roll pressure was set to 65 N / mm as the linear pressure of the roll to obtain a non-woven fabric thin film having a thickness of 40 μm, the thermal shrinkage rate increased remarkably as shown below. No film formation occurred.

PBT melt blow non-woven fabric thin film (single layer comparative product (3))
Metsuke (g / m ² ): 20
Thickness (μm): 40
Garley air permeability (s / φ10 / 300cc): 9.3
Tensile strength (N / 25mm width): 12.5
Tensile elongation (%): 28.8
Appearance (film formation due to the formation of transparent spots): None
Electrolyte absorption rate (seconds): 12
Electrolyte retention rate (%): 268
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 2.5
CD: 1.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 5.8
CD: 4.0

Comparative Example 4
In the special calendar processing using the combination with the metal roll / elastic roll, the metal roll heated to the processing temperature of 150 ° C. is used, and the calendar processing is performed under the same conditions and operations as in Comparative Example 3 except for the setting. As shown below, the heat shrinkage rate was significantly improved, but the Garley air permeability increased significantly to 84 s / φ10 / 300 cc, the air permeability decreased, and the internal resistance of the battery separator increased. It became a thing.

PBT melt blow non-woven fabric thin film (single layer comparative product (4))
Metsuke (g / m ² ): 20
Thickness (μm): 30
Garley air permeability (s / φ10 / 300cc): 84
Tensile strength (N / 25mm width): 20.5
Tensile elongation (%): 235
Appearance (film formation due to the formation of transparent spots): None
Electrolyte absorption rate (seconds): 12.18
Electrolyte retention rate (%): 243
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 1.0
CD: 0.5
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 1.5
CD: 0.5

Comparative Example 5
The melt-blow non-woven fabric raw fabric produced by the melt-blow method using polypropylene as a raw material was subjected only to a high-temperature calendar processing step using a metal roll / metal roll combination at a processing temperature of 110 ° C., and was not subjected to a special calendar processing. By the above processing, a thin film separator having a thickness of 40 μm was obtained, but transparent spots were formed as shown below, and film formation occurred.

PP melt blow non-woven fabric thin film (single layer comparative product (5))
Metsuke (g / m ² ): 14
Thickness (μm): 40
Garley air permeability (s / φ10 / 300cc): 6.5
Tensile strength (N / 25mm width): 6.9
Tensile elongation (%): 15.4
Appearance (film formation due to the formation of transparent spots): None
Electrolyte absorption rate (seconds): 30.00
Electrolyte retention rate (%): 70
Heat shrinkage rate (%): (Dimensional change rate after heating in an oven at 120 ° C for 1 hour) MD: 7.5
CD: 6.0
(Dimensional change rate after heating in an oven at 150 ° C for 1 hour) MD: 14.0
CD: 11.2
Comparative Example 6
When cellulose having a thickness of 40 μm was evaluated as a separator, it was shown that the garley air permeability was remarkably large, the air permeability was lacking, and the internal resistance was high as a battery separator as shown in Table 1. In addition, it is water-soluble, and the liquid retention performance of the electrolytic solution is not sufficient.

From the results of the above Examples and Comparative Examples, the thickness of the heat-resistant melt-blown non-woven fabric thin film cannot be reduced to 50 μm or less only by the high-temperature calendar processing step, and the thickness can be increased to 35 μm by changing the pressurizing conditions. Film formation occurs when the film is thinned, while the heat shrinkage rate increases significantly only in the special calendar processing process, and when the processing temperature in the special calendar processing process is raised, the heat shrinkage rate decreases, but Garley see-through. There is a drawback that the air temperature increases and the internal resistance increases due to the decrease in air permeability.
From the above results, it is possible to thin the film while maintaining high air permeability by providing two types of processes, a high-temperature calendar processing process and a special calendar processing process, and the heat shrinkage rate under high-temperature conditions is also improved. It was clarified that it can be done.
Table 1 summarizes the evaluation results of the examples and comparative examples.
In the table, the "first stage processing" in the "calendar processing condition" column is "high temperature calendar processing", and the "second stage processing" is "special calendar processing".

Claims (16)

A heat-resistant melt-blown non-woven fabric thin film made of heat-resistant resin.
The heat-resistant resin is a thermoplastic resin (excluding polyphthalamide resin) having a melting point of 200 ° C. or higher.
The thickness is 50 μm or less,
The basis weight is 5 to 100 g / m ² ,
The average fiber diameter is 0.5 to 15 μm,
Garley air permeability is 1-40s / φ10 / 300cc,
After the heat treatment under the heating condition of 150 ° C. for 1 hour, the heat shrinkage rate is 1.2% or less in either the MD direction or the CD direction in terms of dimensional change rate.
A heat-resistant melt-blown non-woven fabric thin film characterized in that the liquid-retaining performance is 57 to 365% in terms of the electrolytic solution-retaining ratio . The heat-resistant melt-blow non-woven fabric thin film according to claim 1, wherein the heat-resistant melt-blow non-woven fabric thin film is a non-woven fabric processed product obtained by laminating and laminating at least two non-woven fabric layers. The heat-resistant melt-blow non-woven fabric thin film according to claim 1, wherein the heat-resistant melt-blow non-woven fabric thin film is a non-woven fabric processed product obtained by laminating and laminating at least two non-woven fabric layers having fibers having fibers having different average fiber diameters. The heat-resistant melt-blown non-woven fabric thin film according to claim 1, wherein the thickness is 1 to 45 μm. The heat-resistant melt-blown non-woven fabric thin film according to claim 1, wherein the Garley air permeability is 5 to 30 s / φ10 / 300 cc. The first aspect of claim 1, wherein the heat shrinkage rate is 1.2% or less in terms of dimensional change rates in the MD direction and the CD direction after heat treatment under heating conditions at 150 ° C. for 1 hour. Heat resistant melt blow non-woven fabric thin film. The heat-resistant melt-blow non-woven fabric thin film according to claim 1, wherein the heat-resistant melt-blow non-woven fabric thin film suppresses the formation of transparent spots due to film formation. Melt-blow non-woven fabric made of heat-resistant resin This is a method for manufacturing a heat-resistant melt-blow non-woven fabric thin film made by thinning the raw fabric.
The heat-resistant resin is a thermoplastic resin having a melting point of 200 ° C. or higher.
Next step:
(1) The melt-blow non-woven fabric raw fabric is sandwiched between at least two metal rolls, and the processing temperature conditions above the glass transition point of the heat-resistant resin and the crushing of the constituent fibers of the melt-blow non-woven fabric raw fabric are suppressed. A high-temperature non-woven fabric processing step to be subjected to calendering under pressurized conditions adjusted to the conditions that can be thinned, and
(2) The calendering processing intermediate obtained by the high temperature calendering processing step is subjected to a processing temperature condition of 130 ° C. or lower by a special calendering process including at least two rolls in which at least one roll is an elastic roll. And, it is characterized by containing at least a special calendering process for performing calendering under pressure conditions adjusted to a condition in which the constituent fibers of the non-woven fabric raw fabric are suppressed from being crushed and thinned. A method for manufacturing a heat-resistant melt-blown non-woven fabric thin film. The method for producing a heat-resistant melt-blow non-woven fabric thin film according to claim 8, wherein the melt-blow non-woven fabric raw fabric is a laminated body composed of at least two non-woven fabric layers. The method for producing a heat-resistant melt-blow non-woven fabric thin film according to claim 8, wherein the melt-blow non-woven fabric raw fabric is a laminate composed of at least two non-woven fabric layers having fibers having fibers having different average fiber diameters. The method for producing a heat-resistant melt-blown nonwoven fabric thin film according to claim 8, wherein the processing temperature condition of the glass transition point or higher is 130 ° C. or higher. The eighth aspect of the present invention, wherein the linear pressure of the metal roll is 200 N / mm or less among the pressurizing conditions adjusted so as to suppress the crushing of the constituent fibers of the melt-blown nonwoven fabric in the high-temperature calendering process. A method for manufacturing a heat-resistant melt-blown non-woven fabric thin film. The method for producing a heat-resistant melt-blown non-woven fabric thin film according to claim 8, wherein the special calendar processing step includes a calendar device composed of at least one elastic roll and at least one metal roll. The method for producing a heat-resistant melt-blown non-woven fabric thin film according to claim 8 or 13, wherein the elastic material of the elastic roll is a synthetic resin in the special calendar processing step. The separator for an electric double layer capacitor (EDLC) made of the heat-resistant melt-blown non-woven fabric thin film according to any one of claims 1 to 7. A separator for a lithium ion secondary battery made of the heat-resistant melt-blown non-woven fabric thin film according to any one of claims 1 to 7.