JP2016125150A - Polyphthalamide-based melt-blown nonwoven fabric, manufacturing method thereof and separator for heat resistant battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melt-blown nonwoven fabric with well-balanced tension strength, air permeability or thermal shrinkage rate, which has a high heat resistance, a low heat shrinkage rate and a fast liquid-absorbing speed, a manufacturing method thereof and a separator for battery made of the melt-blown nonwoven fabric.SOLUTION: A melt-blown nonwoven fabric is made from polyphthalamide resin and has an average fiber diameter of 1 to 30 μm, a basis weight of 5 to 300 g/m, permeability of 0.1 to 200 cc/cm/sec, thickness of 10 to 1000 μm, tension strength of 1 to 50 N/25 mm width, and tension elongation of 1 to 100%. The melt-blown nonwoven fabric can be provided as a separator for battery with further improved thermal shrinkage rate, tension strength, tension elongation and electrolyte absorbing speed obtained by press forming. The thermal shrinkage rate of the melt-blown nonwoven fabric in either horizontal direction or vertical direction is 1.5% or less after a heating treatment at 200°C. The electrolyte propylene carbonate absorbing speed of the melt-blown nonwoven fabric is 10 seconds or less.SELECTED DRAWING: None

Description

  The present invention relates to a meltblown nonwoven fabric made of polyphthalamide (hereinafter sometimes referred to as “PPA”), a method for producing the meltblown nonwoven fabric, and a separator for a heat-resistant battery. The present invention relates to a melt blown nonwoven fabric that can be used as a separation membrane for air filters and the like, and can provide a battery separator that is particularly excellent in heat resistance and shrinkage resistance, and also has excellent electrolyte retention and liquid absorption speed. It is.

  In recent years, non-woven fabrics have been used for a wide variety of applications, and their applications have been further expanded significantly. Conventionally, it has been widely used for various separation membranes such as liquid filters and air filters taking advantage of its characteristics, but after that, sanitary materials such as paper diapers and sanitary products, heat insulating materials, clothing materials, medical materials, etc. In addition, with the development of batteries, electrochemical substrates such as primary batteries, secondary batteries, electrolytic capacitors, and electric double capacitors (hereinafter sometimes referred to as “batteries”). It has been used as a separator which is a component. In particular, lithium batteries are frequently used as separators that are insoluble in organic solvents and are stable for electrolytes and electrode active materials.

  The separator as a battery component is required to have functions such as separation of the positive electrode material and negative electrode material, prevention of short circuit, passage of electrolyte or ions, and maintenance of close contact between the electrolyte and the electrode by absorbing and holding the electrolyte. It has been.

  However, when a short circuit occurs inside and outside the battery, a large current is discharged, which causes Joule heat or chemical reaction heat to cause thermal contraction of the separator between the positive and negative electrodes facing each other, or the separator heat melts. As a result of the short circuit between the positive and negative electrodes, the internal short circuit expands, and a large amount of heat is released to the surroundings, and a large amount of gas is ejected. Conventional separators made of polyolefin nonwoven fabrics such as polyethylene and polypropylene have a melting point of polyethylene of about 125 to 140 ° C and a melting point of polypropylene of about 160 to 180 ° C. There was a problem that short circuiting due to dissolution of the separator was likely to occur. In order to solve such problems, it is desired to have a shutdown function, which is a function of blocking current by blocking the passage of ions, and a function in which the separator itself does not contract or melt. It was.

  Melt blown nonwoven fabrics using heat-resistant resins have been developed as battery separators that solve these problems. For example, Japanese Unexamined Patent Application Publication No. 2004-47280 (hereinafter referred to as “Patent Document 1”) describes a melt blown nonwoven fabric separator using polyphenylene sulfide (PPS) having a melting point of about 280 ° C., which is a heat resistant resin, as a raw material resin. ing. Japanese Patent Application Publication No. 2011-503880 (hereinafter referred to as “Patent Document 2”) describes a separator including a porous layer of polyamide nanofibers as a component of a capacitor.

  However, conventionally proposed battery separators using a heat-resistant resin have a drawback that the thermal shrinkage rate is still large, and even if the thermal shrinkage rate is low, the electrolyte absorbability is insufficient. Therefore, there is a problem that battery productivity is not good. In addition, the nanofiber with a small fiber diameter shown in Patent Document 2 has a problem that the strength as a battery separator is insufficient, and safety and battery productivity are not sufficient.

  Under such circumstances, it has been desired to develop a melt blown nonwoven fabric that can provide a battery separator having a lower thermal shrinkage rate and a faster electrolyte absorption rate.

JP 2004-47280 A Special table 2011-503880 gazette

  Accordingly, the first object of the present invention is a battery separator having an excellent balance of tensile strength, air permeability, and heat shrinkage ratio, excellent heat resistance, low heat shrinkage ratio, and high electrolyte solution absorption speed. An object is to provide a melt-blown nonwoven fabric that can be provided, a method for producing the melt-blown nonwoven fabric, and a battery separator that is made of the melt-blown nonwoven fabric and has excellent heat resistance.

  A second object of the present invention is to provide a melt-blown nonwoven fabric with a low environmental load and a battery separator using the melt-blown nonwoven fabric.

  Therefore, as a result of intensive studies in order to solve the above-described problems of the present invention, the present inventors have determined that the raw material resin for manufacturing the nonwoven fabric is a key factor, and used polyphthalamide resin as the raw material resin. By using it, it was possible to realize a heat-resistant melt-blown nonwoven fabric, thereby paying attention to the fact that the above-mentioned problems could be solved, and the present invention was conceived based on such knowledge.

  Also, paying attention to plant-derived polyphthalamide resin with a high degree of biomass, and using this as a raw material resin, while maintaining the same level of performance as conventional petroleum-based plastic nonwoven fabrics, Thus, it was possible to obtain knowledge that a non-woven fabric having stable properties even under high temperature use environment can be provided, and the present invention has been achieved based on such knowledge.

 Thus, according to the first invention of the present invention, there is provided a melt blown nonwoven fabric made of polyphthalamide resin.

  According to a second invention of the present invention, in the first invention, the polyphthalamide resin has a melt flow rate measured at a load of 5.0 kg and a temperature of 300 ° C. in accordance with JIS K7210. There is provided a melt blown nonwoven fabric having a content of 10 to 1000 g / 10 minutes and a terephthalamide unit content of 50 mol% or more.

According to the third invention of the present invention, in the first or second invention, the average fiber diameter is 1 to 30 μm, the basis weight is 5 to 300 g / m ² , and the air permeability is 0.1 to 200 cc / cm ^2. / Sec, a thickness of 10 to 1000 μm, a tensile strength of 1 to 50 N / 25 mm width, and a melt blown nonwoven fabric having a tensile elongation of 1 to 100% are provided.

  According to the fourth invention of the present invention, in any of the first to third inventions, the heat shrinkage rate, the tensile strength, the tensile elongation, and the electrolyte solution absorption speed are further improved by the press molding process. A melt-blown nonwoven fabric that can be provided as a battery separator is provided.

  According to a fifth aspect of the present invention, in the fourth aspect, the heat shrinkage ratio is 1.5% or less in either the horizontal direction or the vertical direction after the heat treatment at 200 ° C. And the melt blown nonwoven fabric whose liquid absorption rate of the said electrolyte solution propylene carbonate is 310 seconds or less is provided.

  According to a sixth aspect of the present invention, there is provided the melt blown nonwoven fabric according to the fourth aspect, wherein the press molding process is a calendering process at a temperature not lower than the glass transition temperature and not higher than the melting point. .

  According to a seventh aspect of the present invention, in the sixth aspect, the calendering treatment is a means for sandwiching and pressurizing the meltblown nonwoven fabric between calender rolls having two pairs of roll materials. There is provided a melt blown nonwoven fabric in which a roll material is metal / metal or metal / elastic body.

  Further, according to the eighth invention of the present invention, after the polyphthalamide resin is melted at an extruder temperature of 260 to 380 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle, There is provided a method for producing a melt blown nonwoven fabric, which comprises drawing into a fine fiber by high-temperature air blow gas at 260 to 380 ° C. and collecting the fine fiber at a collector installed at a position away from the nozzle.

According to the ninth aspect of the present invention, after the polyphthalamide resin is melted at an extruder temperature of 260 to 380 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle. Stretched with a high-temperature air blow gas of 260 to 380 ° C. to form fine fibers, collected in a collector installed at a position away from the nozzle, and the obtained melt blown nonwoven fabric is at a temperature not lower than the glass transition temperature and not higher than the melting point. A method for producing a melt blown nonwoven fabric comprising subjecting to a calendering treatment is provided.
A method is provided.

  According to a tenth aspect of the present invention, in the eighth or ninth aspect, the die has a nozzle hole diameter of 0.1 to 1 mmφ and a number of nozzles of 5 to 15 / cm. A method for producing a melt blown nonwoven fabric in which the amount of the polyphthalamide resin discharged from is 0.05 to 3 g / min / hole is provided.

  Moreover, according to the eleventh aspect of the present invention, there is provided a battery separator comprising the melt blown nonwoven fabric according to any one of the first to seventh aspects.

  According to the present invention, by using a polyphthalamide resin as a raw material resin for producing a meltblown nonwoven fabric, it is possible to obtain a meltblown nonwoven fabric having specific heat resistance and excellent air permeability, and having a glass transition temperature or higher. By subjecting it to a pressure molding treatment at a temperature, a melt blown nonwoven fabric having a low thermal shrinkage rate and a high electrolyte solution absorption rate can be provided, and can be suitably used as a separator for heat-resistant batteries. Such heat-resistant separators can prevent explosive runaway such as melt rupture (meltdown) during heat generation such as short circuit, and are excellent in safety, and used as separators for high energy density batteries can do. In addition, by using plant-derived polyphthalamide resin with a high degree of biomass as a raw material resin, the environmental impact is lower than that of petroleum-derived raw materials, and no harmful gases are generated during combustion. Remarkably effective.

According to the present invention, as described above, it is a melt blown nonwoven fabric made of polyphthalamide resin, having an average fiber diameter of 1 to 30 μm, a basis weight of 5 to 300 g / m ² , and an air permeability of 0.1 to 200 cc / m ^2. / Sec, the thickness is 10 to 1000 μm, the tensile strength is 1 to 50 N / 25 mm width, the tensile elongation is 1 to 100%, and the thermal shrinkage at a temperature of 200 ° C. is 5 in either the longitudinal direction or the transverse direction. %, And a melt blown nonwoven fabric having physical properties of an electrolyte solution propylene carbonate absorption rate of 10 seconds or less is provided, and by press molding treatment, tensile strength, air permeability, heat shrinkage rate and electrolyte solution absorption rate are provided. A melt blown nonwoven fabric is provided which is further improved.

  Further, according to the present invention, after the polyphthalamide resin is melted by an extruder at 260 to 380 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle, and at the same time, a high-temperature air blow at 260 to 380 ° C. There is provided a method for producing a melt blown nonwoven fabric, which comprises drawing into a fine fiber by gas and collecting it in a collector installed at a position away from a nozzle.

  Further, according to the present invention, after the polyphthalamide resin is melted by an extruder at 260 to 380 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle, and at the same time, a high-temperature air blow at 260 to 380 ° C. A method for producing a melt blown nonwoven fabric comprising drawing a gas into a fine fiber, collecting it in a collector installed at a position away from the nozzle, and subjecting the obtained melt blown nonwoven fabric to a calendering treatment at a temperature higher than the glass transition temperature Is provided.

  The melt blown nonwoven fabric according to the present invention can be used for various applications. Specifically, liquid filters made of the melt blown nonwoven fabric, for example, industrial filters, beverage filters, and fuel filters are provided. Further, as the air filter, for example, a medium performance filter, an air purifier filter, an automobile cabin filter, and the like are provided. In addition, medical and sanitary materials such as masks can be provided. In particular, according to the present invention, there is provided a battery separator having excellent heat resistance made of a melt blown nonwoven fabric that has undergone the calendar processing.

を５０モル％以上含有することが融点を制御する観点から好ましい。 式（ｉ）中、Ｒは炭素数１−１４の直鎖状または分岐状の脂肪族炭化水素基であり、置換または非置換脂肪族基を含む。脂肪族炭化水素基の具体例として、テトラメチレン、ヘキサメチレン、ドデカメチレン等およびこれらのアルキル置換類似体、例えば、２−メチルペンタメチレン、２．４−ジメチルヘキサメチレン、２．２．４−トリメチルヘキサメチレン等が挙げられる。特に好ましい脂肪族炭化水素基は、ヘキサメチレン基である。また、ポリフタルアミド樹脂には、式（ｉ）で表されるテレフタルアミド単位のほかに、次の式（ii）で表されるイソフタルアミド単位も含有する。 Hereinafter, the present invention will be described in detail.
1. Polyphthalamide resin
The polyphthalamide resin used as the raw material resin for producing the melt blown nonwoven fabric according to the present invention preferably has a melt flow rate of 10 to 1000 g / 10 min measured at a load of 5.0 kg and 300 ° C. in accordance with JISK7210. . Moreover, as melt viscosity, what is 100-1000 Pa.s is preferable. Such polyphthalamide resin is a terephthalamide unit represented by the following structural formula:
(I)

Is preferably contained in an amount of 50 mol% or more from the viewpoint of controlling the melting point. In formula (i), R is a linear or branched aliphatic hydrocarbon group having 1 to 14 carbon atoms, and includes a substituted or unsubstituted aliphatic group. Specific examples of the aliphatic hydrocarbon group include tetramethylene, hexamethylene, dodecamethylene, and the like, and alkyl-substituted analogs thereof such as 2-methylpentamethylene, 2.4-dimethylhexamethylene, 2.2.4-trimethyl. Hexamethylene and the like can be mentioned. A particularly preferred aliphatic hydrocarbon group is a hexamethylene group. In addition to the terephthalamide unit represented by the formula (i), the polyphthalamide resin also contains an isophthalamide unit represented by the following formula (ii).

かかるポリフタルアミド樹脂は、テレフタルアミド単位（ｉ）およびイソフタルアミド単位（ii）等を含有するものであり、例えば、ヘキサメチレンテレフタルアミド−イソフタルアミド−アジポアミドターポリマー（モル比６５；２５；１０）を例示することができる。市販品としてアルケマ社製リルサン（登録商標）ＨＴを入手することができ、融点２５５〜２６０℃（ＤＳＣによる。）、ガラス転移温度（Ｔｇ）９０℃（ＤＳＣによる。）を有するものである。また、アモコケミカル社製Ａｍｏｄｅｌポリフタルアミドを入手することもできる。 (Ii)

Such polyphthalamide resins contain terephthalamide units (i), isophthalamide units (ii) and the like, for example, hexamethylene terephthalamide-isophthalamide-adipamide terpolymer (molar ratio 65; 25; 10) can be exemplified. Rilsan (registered trademark) HT manufactured by Arkema Co., Ltd. can be obtained as a commercial product, and has a melting point of 255 to 260 ° C. (according to DSC) and a glass transition temperature (Tg) of 90 ° C. (according to DSC). Amoco Chemical's Amodel polyphthalamide can also be obtained.

2. Polyphthalamide resin melt blown nonwoven fabric The polyphthalamide resin nonwoven fabric according to the present invention is a melt blown nonwoven fabric produced by a melt blow method.

  As a melt-blowing method, molten polyphthalamide resin was discharged as a molten polymer from a plurality of nozzle holes arranged in a row, and was discharged by injecting high-temperature high-speed air from an injection gas port installed adjacent to the orifice die. A method is adopted in which the molten polymer is made into fine fibers and the fiber stream is collected. However, since the raw material polyphthalamide has a high melting point and is close to the decomposition temperature, the production conditions must be controlled. Yes, the following method is adopted.

  After the polyphthalamide resin is melted at an extruder temperature of 260 to 380 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle, and at the same time, the polyphthalamide resin is stretched by a high-temperature air blow gas of 260 to 380 ° C. More preferably, the melt blown non-woven fabric is collected in a collector that is fiberized and installed at a position away from the nozzle, and is subjected to a calendering treatment at a temperature equal to or higher than the glass transition temperature.

  In the melt blow device die, the nozzle hole is preferably 0.1 to 1 mmφ, and more preferably 0.2 to 0.8 mmφ. The number of nozzles is preferably 5 to 20 / cm, and more preferably 10 to 15 / cm. When the nozzle hole diameter is less than 0.1 mmφ, the discharge resin pressure is increased. On the other hand, when the nozzle hole diameter exceeds 1 mmφ, the fibers cannot be thinned. Also, when the number of nozzles is less than 5 / cm, the discharge pressure of the polyphthalamide resin increases, whereas when the number of nozzles exceeds 20 / cm, the fibers are excessively fused, and the uniformity of the nonwoven fabric is increased. You will lose.

  Moreover, as manufacturing conditions of the melt-blowing method, in the production of melt-blown nonwoven fabric using PPA resin as a raw material, the extrusion temperature is 260 to 380 ° C, preferably 300 to 350 ° C, and the die temperature is 300 to 380 ° C, Preferably it is 320-350 degreeC, Furthermore, high-speed air temperature is 260-380 degreeC, Preferably it is 300-350 degreeC. When the extruder / die and the air temperature are below the above ranges, the discharge resin pressure becomes high and fine fibers cannot be obtained. On the other hand, when the above range is exceeded, gelation of the resin is promoted and deteriorates. Moreover, not only does the conveyor net be damaged, but the peelability of the resulting nonwoven fabric from the conveyor net is poor, 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. When the resin discharge amount is small, the discharge resin pressure falls below the above range and a uniform nonwoven fabric cannot be obtained. On the other hand, when the resin discharge amount exceeds the above range, the discharge resin pressure becomes high and fine fibers are obtained. Absent.

  Moreover, it is preferable that the melt blown nonwoven fabric which consists of polyphthalamide resin which concerns on this invention has the following physical property.

(1) Average fiber diameter The average fiber diameter of the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention is 1 to 30 µm, preferably 1.5 to 20 µm, and more preferably 2 to 8 µm. When the average fiber diameter is less than 1 μm, not only is the strength weakened, but when used in a battery separator, the internal resistance of the battery becomes too large. On the other hand, when the average fiber diameter exceeds 30 μm, the risk of an internal short circuit increases when used for a battery separator.

(2) Fabric weight The fabric weight of the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention is 5 to 300 g / m ² , preferably 7 to 80 g / m ² , more preferably 10 to 50 g / m ² . When the basis weight is less than 5 g / m ² , the strength is insufficient, the reliability in the assembly is lowered, and when used for a battery separator, a short circuit is likely to occur, which is not preferable. On the other hand, if the basis weight exceeds 300 g / m ² , it becomes easy to cause flaking during the production of the nonwoven fabric, making it difficult to produce stably. Moreover, when it uses for a battery separator, there exists a possibility that internal resistance may rise.

(3) Air permeability The air permeability of the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention is 0.1 to 200 cc / cm ² / sec, preferably 0.3 to 150 cc / cm ² / sec, and is calendered. More preferably, it is 1-50 cc / cm < ² > / sec by a process. When the air permeability is less than 0.1 cc / cm ² / sec, the internal resistance is large when used for a battery separator. On the other hand, when the air permeability exceeds 200 cc / cm ² / sec, Increased risk of short circuit.

(4) Thickness The thickness of the meltblown nonwoven fabric made of the polyphthalamide resin according to the present invention is 1-1000 μm, preferably 5-150 μm, more preferably 10-40 μm. When the thickness is less than 1 μm, the risk of an internal short circuit increases when used for a battery separator, while when it exceeds 500 μm, the battery capacity may decrease.

(5) Tensile strength The tensile strength of the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention is 2 to 50 N / 25 mm width, and preferably 10 to 40 N / 25 mm width. If the tensile strength is less than 2 N / 25 mm width, breakage is likely to occur during assembly. On the other hand, if the tensile strength exceeds 50 N / 25 mm width, the elongation is extremely lowered, and a problem is likely to occur due to a decrease in the degree of freedom during assembly.

(6) Tensile elongation The tensile elongation of the meltblown nonwoven fabric made of the polyphthalamide resin according to the present invention is 1 to 100%, preferably 5 to 80%, and more preferably 10 to 10% by calendering treatment. 50%. 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 it becomes difficult to assemble stably.

(7) Heat Shrinkage The heat shrinkage at 150 ° C. of the meltblown nonwoven fabric made of the polyphthalamide resin according to the present invention is preferably 3% or less, preferably 1% in both directions, preferably in both directions. Hereinafter, it is more preferably 0.5% or less.
The thermal shrinkage at 200 ° C. is preferably 1.5% or less, preferably 1.0% or less, more preferably 0.5% or less in at least one of the horizontal direction and the vertical direction in both directions.
The melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention preferably satisfies the heat shrinkage rate after heat treatment at both 150 ° C. and 200 ° C.

(8) Electrolyte liquid absorption speed
The melt absorption rate of the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention is 10 seconds or less, preferably 3 seconds or less, and more preferably 1 second or less. When the electrolyte solution absorption speed of the separator is fast, the production efficiency at the time of battery production becomes good.

(9) Physical property evaluation after heating test When the temperature in the battery suddenly rises for some reason, if the separator deteriorates, there is a risk of short-circuiting again even if the temperature in the battery subsequently decreases. Therefore, it is preferable to keep the physical properties after heating for a certain time at 200 ° C. at 80% or more before heating.

3. In the present invention, it is preferable to perform a calendering treatment as a press molding treatment of a meltblown nonwoven fabric made of the polyphthalamide resin obtained by the meltblowing method.

  The battery separator according to the present invention uses a heat-shrinkable, electrolytic solution-absorbing solution by using a polyphthalamide melt-blown nonwoven fabric (hereinafter also referred to as a calendar-treated product) obtained by the above-described melt-blown method. There is an effect that breakage resistance and the like are imparted by improving speed and tensile strength. In particular, a battery separator having excellent heat resistance, shrinkage resistance, and electrolyte solution absorption speed can be obtained by calendering treatment.

  The apparatus used for the calendering method of the melt blown nonwoven fabric according to the present invention is a combination of 2 to 4 pairs of heat rolls, in particular 2 pairs of heat rolls, and is preferably an upright two-pair type. Is not limited. The temperature and pressure of the calendering process are adjusted according to the temperature of the heat roll and the sense of mutual arrangement of the heat roll.

  As the calendering treatment of the meltblown nonwoven fabric according to the present invention, after the meltblown nonwoven fabric is formed, the heating temperature is usually a glass transition temperature or higher, for example, 100 to 250 ° C, preferably 120 to 200 ° C. As a specific method, there is a method in which a melt-blown nonwoven fabric is processed by pressurizing between two pairs of rolls heated to a predetermined temperature.

  Two rolls having a metal surface may be used, but the contact surface of the pair of rolls may be an elastic body such as a resin roll, and a roll having a metal surface may be combined. When the contact surface of the two pairs of rolls is a metal surface, uniformity of thickness can be mentioned as an effect. However, when processing into a certain thinness, film formation occurs on the surface of the base material, resulting in large variations in physical properties. And the appearance is also non-uniform. On the other hand, when the contact surface of the roll is an elastic body, it is possible to obtain a battery separator that is thin with low resistance and uniform physical properties and appearance. A preferable thickness for the thin film separator is 10 to 40 μm, and more preferably 15 to 35 μm.

[Processing with elastic roll]
As a heat-resistant separator, a battery separator made of a melt blown nonwoven fabric made of PPS resin has been proposed. However, since the elongation after crystallization of PPS resin is remarkably reduced, processing with a roll contact surface made of an elastic body. However, there is a problem of cracking, and conventionally, it has been difficult to obtain a battery separator having heat resistance and a reduced thickness. This time, by using PPA resin, the melt-blown nonwoven fabric has excellent strength even when it is thinned, has a low thermal shrinkage rate, has a high rate of liquid absorption, and has little deterioration in physical properties in a high-temperature environment. In order to maintain a sufficient mechanical strength, attention was paid to the fact that it can be suitably used as a heat-resistant battery separator.

4). Battery separator Since the melt-blown nonwoven fabric made of the polyphthalamide resin according to the present invention is heat resistant, it can be suitably used for a battery separator that requires heat resistance. In particular, the calendered product has high tensile strength and low thermal shrinkage, so it has excellent safety to prevent explosive thermal runaway such as melt rupture (meltdown), and as a battery separator that requires heat resistance, preferable.

  As a battery separator, thickness is 10-40 micrometers, Preferably it is 15-35 micrometers, More preferably, it is 20-30 micrometers. Further, the heat shrinkage rate at 150 ° C. is preferably 1.5% or less, preferably 1% or less, more preferably 0.5% or less in both the horizontal direction and the vertical direction.

[Advantages of PPA resin in battery separator applications]
As shown in the examples described later, the melt blown nonwoven fabric made of nylon as a raw material resin has appropriate heat resistance and hydrophilicity, but can be obtained in battery characteristics but is decomposed in a long-term alkaline solution and has a liquid retaining property. Battery life is short due to the occurrence of a drop or short circuit. As an alternative, PP non-woven fabric is also excellent in chemical resistance and oxidation resistance and is used. However, since PP is hydrophobic, it needs to be subjected to hydrophilic treatment and requires secondary processing. In contrast, melt blown non-woven fabrics made from PPA resin have long-term chemical resistance and wettability with electrolytes, and can be used as separators for long-life batteries that do not require secondary processing. I can expect.

  In addition, the melt-blown nonwoven fabric made of the polyphthalamide resin according to the present invention or the battery separator according to the present invention can improve the lyophilicity of the nonwoven fabric surface by applying a surfactant or the like depending on the purpose. it can.

The present invention will be specifically described by the following examples and comparative examples. However, the present invention is not limited to these examples.
In addition, each physical-property value in an Example and a comparative example is each calculated | required and measured by the following method.

(1) Weight per unit area: A 100 × 100 mm test piece was collected from the nonwoven fabric sample length direction, the weight in a moisture equilibrium state was measured, and the weight per unit area was calculated by converting to a unit weight per 1 m ² .
(2) Thickness: A test piece of 100 × 100 mm was taken from the nonwoven fabric sample length direction and measured with a dial thickness gauge.
(3) Air permeability: 100 x 100 mm non-woven fabric test specimens were collected from the length direction of the non-woven fabric sample, and fragile type in accordance with "Breathability A method (Fragile shape method)" of JIS L1096 "General fabric test method" Measurement was performed using a testing machine.
(4) Tensile strength and tensile elongation: Measured at a sample width of 25 mm, a grip 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”.
(5) Fiber diameter: Take 5 photographs with an electron microscope at any 5 locations on the nonwoven fabric test piece, measure the diameter of 20 fibers per photograph, and perform these 5 photographs. 100 fiber diameters were averaged.
(6) Thermal contraction rate: A line of about 10 cm is drawn in the MD direction (length direction) and CD angle direction (width direction) at the center and end of a 20 cm square nonwoven fabric sample, and set to 120 ° C, 150 ° C, and 200 ° C. After heating for 24 hours in the oven, the line length was measured and the rate of change was determined.
(7) Electrolyte solution absorption rate Electrolyte solution absorption rate: Predetermined height on a water tank containing a solution in which PC (propylene carbonate) and DME (1,2-dimethoxyethane) are mixed at a weight ratio of 1: 1. A non-woven fabric test piece (20 mm × 200 mm) is pinned to the horizontal bar, and then the horizontal bar is lowered to immerse the end of the sample piece in the above mixed solution by 5 mm. The height (mm) at which the mixed solution rose in a minute due to capillary action was measured, and the measured value was taken as the liquid absorption rate of the electrolytic solution.
(8) Physical property evaluation after heating test Heating test method;
The nonwoven fabric trial was held at the same temperature for one week in an oven set at 200 ° C.
Evaluation of the physical properties;
About the nonwoven fabric trial after the said heat processing, tensile strength, elongation, and air permeability were measured by the said method as heat resistance evaluation items.

Example 1
A polyphthalamide resin (Rilsan (registered trademark) HT melting point 255 ° C. manufactured by Arkema Co., Ltd.) was melt-kneaded at an extruder temperature of 350 ° C., and melt blown at a discharge rate of 2 g / min / hol using a 0.4 mm nozzle. Polyphthalamide melt blown nonwoven fabric (hereinafter referred to as “polyphthalamide”) having an average fiber diameter of 5.5 μm, basis weight of 15 g / m ² , thickness of 130 μm, air permeability of 150 cc / cm ² / sec, tensile strength of 10 N / 25 mm width, and tensile elongation of 52.1%. "Prototype 1"). Propylene carbonate liquid absorption speed of prototype 1 was 0 second 66. The thermal shrinkage after heating and holding at 150 ° C. for 24 hours was MD 0.5% and CD 0%, and the thermal shrinkage under the condition of holding at 200 ° C. for 24 hours was MD 1.0% and CD 1.0%.
Moreover, when the prototype 1 was subjected to a heating test for one week in an environment of 200 ° C., and the physical properties were evaluated, the following results were obtained.
Tensile strength: 10.2 N / 25 mm width Tensile elongation: 46.5%
Air permeability: 130cc / cm ² / sec

Example 2
The melt blown nonwoven fabric obtained by the method of Example 1 was subjected to calendering treatment at 150 ° C. with a metal / metal roll. The obtained calendered product (hereinafter referred to as “Prototype 2”), basis weight 15 g / m ² , thickness 38 μm, air permeability 37.5 cc / cm ² / sec, tensile strength 12.1 N / 25 mm width, tensile The elongation was 45.5%, and the propylene carbonate liquid absorption rate was 0 second 88. The thermal shrinkage after heating and holding at 150 ° C. for 24 hours was MD 0% and CD 0%, and the thermal shrinkage after heating and holding at 200 ° C. for 24 hours was MD 0.5% and CD 0.5%. Furthermore, when the calendered product was subjected to a heating test under a heating and holding condition for 1 week in a 200 ° C. environment, the tensile strength was 11.8 N / 25 mm width, the tensile elongation was 43.0%, and the air permeability was 11.5 cc / A result of cm ² / sec was obtained.

Example 3
The melt blown nonwoven fabric obtained by the method of Example 1 was subjected to a calendering treatment with a metal / elastic roll at 150 ° C. The obtained calendered product has a basis weight of 15 g / m ² , a thickness of 25 μm, an air permeability of 29.8 cc / cm ² / sec, a tensile strength of 17.5 N / 25 mm width, and a tensile elongation of 27.5%. Propylene carbonate The liquid absorption speed was 0 seconds 94. Moreover, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours is MD 0.5% and CD 0.5%, and the thermal shrinkage rate after holding for 24 hours at 200 ° C. is MD 0.5% and CD 0.5%. Met. Furthermore, Table 1 shows the results of physical property evaluation after a heating test under a heating and holding condition for one week in a 200 ° C. environment.

Example 4
A melt blown nonwoven fabric obtained by processing under the same conditions as in Example 1 except that a 0.3 mmφ nozzle was used instead of a 0.4 mmφ nozzle was calendered with a metal / elastic roll at 150 ° C. The product was subjected to processing to obtain a calendar processed product. The obtained calendered product has a basis weight of 20 g / m ² , a thickness of 33 μm, an air permeability of 8.5 cc / cm ² / sec, a tensile strength of 15 N / 25 mm width, and a tensile elongation of 30.5%. The speed was 0 seconds 83. Moreover, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours was MD 0% and CD 0%, and the thermal shrinkage rate after being held at 200 ° C. for 24 hours was MD 0.5% and CD 0.5%. Furthermore, it shows in Table 1 about the result of the physical-property evaluation after the heating test on 200 degreeC environment on a 1-week heating holding condition.

Comparative Example 1
A melt blown nonwoven fabric was produced under the same conditions as in Example 1 except that a polypropylene (PP) resin (MFR1550 g / 10 min) was melt-kneaded at an extruder temperature of 240 ° C. instead of the polyphthalamide resin. The obtained meltblown nonwoven fabric was subjected to a calendering treatment at 110 ° C. with a metal / elastic roll. The obtained calendered product has a basis weight of 14 g / m ² , a thickness of 27 μm, an air permeability of 0.3 cc / cm ² / sec, a tensile strength of 17.2 N / 25 mm width, and a tensile elongation of 16%. The liquid shrinkage rate is 100 seconds or more, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours is MD 6.0%, and CD 5.5%. there were. In addition, physical property evaluation after a heating test under a heating and holding condition for one week in a 200 ° C. environment could not be evaluated because it could not be measured due to melting.

Comparative Example 2
Except that polybutylene terephthalate (PBT) resin was used in place of the polyphthalamide resin, all were melt blown under the same conditions as in Example 1, and the resulting melt blown nonwoven fabric was subjected to the same conditions as in Example 3. It used for the calendar process. A calendered product obtained by calendering has a basis weight of 20 g / m ² , a thickness of 30 μm, an air permeability of 7 cc / cm ² / sec, a tensile strength of 28.4 N / 25 mm, and a tensile elongation of 11.9%. The liquid absorption rate of the propylene carbonate liquid is 11 seconds 75, and the heat shrinkage ratio after heating and holding at 150 ° C. for 24 hours is MD1.5%, CD 1.0%, and heat shrinkage after holding for 24 hours at 200 ° C. The rates were MD 3.0% and CD 3.0%. Moreover, it shows in Table 1 about the result of the physical-property evaluation after the heat test of the environment hold | maintained for one week in a 200 degreeC environment.

Comparative Example 3
A melt blown nonwoven fabric was obtained by melt blowing under the same conditions as in Example 1 except that nylon 6 resin was used instead of the polyphthalamide resin. The obtained melt blown nonwoven fabric was subjected to calendering treatment under the same conditions as in Example 3. The calendered product has a basis weight of 20 g / m ² , a thickness of 30 μm, an air permeability of ^2.5 cc / cm ² / sec, a tensile strength of 72 N / 25 mm width, a tensile elongation of 45.3%, and a polypropylene liquid absorption speed of 3 seconds. 88. Moreover, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours is MD 0.5% and CD 0.5%, and the thermal shrinkage rate after holding for 24 hours at 200 ° C. is MD 1.5% and CD 1.5%. Met. Furthermore, it shows in Table 1 about the result of the physical-property evaluation after the heating test on the heating conditions for one week in 200 degreeC environment.

Comparative Example 4
Except for using a polyphenylene sulfide (PPS) resin instead of the polyphthalamide resin, all were melt blown under the same conditions as in Example 1 to obtain a melt blown nonwoven fabric. The obtained melt blown nonwoven fabric has a basis weight of 25 g / m ² , a thickness of 230 μm, an air permeability of 60 cc / cm ² / sec, a tensile strength of 17 N / 25 mm width, a tensile elongation of 25%, a fiber diameter of 6 μm, and a propylene carbonate liquid absorption rate. It was 0 seconds 91. Moreover, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours is MD 5.0% and CD 4.5%, and the thermal shrinkage rate after holding for 24 hours at 200 ° C. is MD 9.0% and CD 7.5%. Met. Furthermore, physical property evaluation after a heating test under a heating and holding condition for one week in an environment of 200 ° C. could not be measured due to melting.

Comparative Example 5
The melt blown nonwoven fabric obtained in Example 4 was subjected to a calendering process under the same conditions as in Example 2 to obtain a calendered product. The calendered product has a basis weight of 25 g / m ² , a thickness of 250 μm, an air permeability of 13.0 cc / cm ² / sec, a tensile strength of 41.1 N / 25 mm width, a tensile elongation of 3.8%, and a propylene carbonate liquid absorption rate. Was 8 per second. Moreover, the thermal shrinkage rate after heating and holding at 150 ° C. for 24 hours was MD 0% and CD 0%, and the thermal shrinkage rate after heating and holding at 200 ° C. for 24 hours was MD 2.0% and CD 0.5%. Furthermore, it shows in Table 1 about the result of the physical-property evaluation after the heating test on 200 degreeC environment on the heating conditions for one week.

Comparative Example 6
The melt blown nonwoven fabric obtained in Example 4 was subjected to calendering treatment under the same conditions as in Example 3. However, cracking occurred in the calendered product, making evaluation impossible.

  As is clear from Table 1, the melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention has a markedly superior heat shrinkage rate according to the above test method, compared to the melt blown nonwoven fabric obtained by using other conventional raw material resins. Even in severe physical property evaluation after a severe heat test, excellent results can be obtained.

  The melt blown nonwoven fabric made of the polyphthalamide resin according to the present invention can be suitably used as a battery separator having excellent heat resistance and electrolyte solution absorption speed, and can be applied to various battery manufacturing applications. In particular, because of its excellent heat resistance and tensile strength, it is suitable for other uses such as separators for electric double layer capacitors, heat resistant liquid filters, heat resistant air filters, and other industrial materials that require heat resistance. Can be used.

Claims (11)

  Melt blown nonwoven fabric made of polyphthalamide resin.   According to JIS K7210, the polyphthalamide resin has a melt flow rate of 10 to 1000 g / 10 min measured at a load of 5.0 kg and a temperature of 300 ° C., and a terephthalamide unit content of 50 mol. The melt blown nonwoven fabric according to claim 1, which is at least%. Average fiber diameter is 1 to 30 μm, basis weight is 5 to 300 gm ² , air permeability is 0.1 to 200 cc / cm ² / sec, thickness is 1 to 1000 μm, tensile strength is 1 to 50 N / 25 mm width, and tensile elongation is 1 The melt blown nonwoven fabric according to claim 1 or 2, which is -100%.   The melt blown nonwoven fabric according to any one of claims 1 to 3, wherein the melt blown nonwoven fabric according to any one of claims 1 to 3 can be provided as a battery separator having further improved heat shrinkage rate, tensile strength, tensile elongation, and electrolyte solution absorption speed by pressing. .   The heat shrinkage ratio is 1.5% or less in at least one of the horizontal direction and the vertical direction after heat treatment at 200 ° C., and the liquid absorption rate of the electrolytic solution propylene carbonate is 10 seconds or less. The melt blown nonwoven fabric according to claim 4.   The melt blown nonwoven fabric according to claim 4, wherein the pressing process is a calendering process at a temperature not lower than the glass transition temperature and not higher than the melting point.   7. The calendering process is means for sandwiching and pressurizing the melt-blown nonwoven fabric between calender rolls having two pairs of roll materials, wherein the roll material is metal / metal or metal / elastic body. The melt blown nonwoven fabric described.   After the polyphthalamide resin is melted at an extruder temperature of 260 to 300 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from the die nozzle, and at the same time, the polyphthalamide resin is stretched with a high-temperature air blow gas of 260 to 300 ° C. A method for producing a melt blown nonwoven fabric, characterized in that the fiber blown fibers are collected in a collector installed at a position away from the nozzle.   After the polyphthalamide resin is melted at an extruder temperature of 260 to 300 ° C., it is fed into a die set at 300 to 380 ° C. and discharged from a die nozzle, and at the same time, it is drawn by a high-temperature air blow gas of 260 to 300 ° C. The melt-blown nonwoven fabric is collected in a collector installed at a position away from the nozzle, and the obtained melt-blown nonwoven fabric is subjected to a calendering treatment at a temperature not lower than the glass transition temperature and not higher than the melting point. .   The die has a nozzle hole diameter of 0.1 to 1 mmφ, a nozzle number of 5 to 15 / cm, and an amount of polyphthalamide resin discharged from the nozzle of 0.05 to 3 g / min / hole. The method for producing a melt blown nonwoven fabric according to 8 or 9.   The battery separator which consists of a melt blown nonwoven fabric of any one of Claims 1-7.