JP2011127244A - Polyarylene sulfide porous membrane and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an oriented polyarylene sulfide porous membrane exhibiting excellent heat resistance, chemical resistance, flame retardancy or the like, and having a thin and fine porous shape, to provide the thin polyarylene sulfide porous membrane, especially when used as a battery separator, not only exhibiting excellent chemical resistance, but also having the high melting point (285°C) and the heat resistance, and providing a reduced internal resistance, and to provide a production method thereof. <P>SOLUTION: The oriented polyarylene sulfide porous membrane is produced by subjecting an unoriented thermoplastic resin film and a nonwoven fabric comprising an undrawn polyarylene sulfide fiber to thermal compression, subjecting the bonded sheet to biaxial orientation, and separating the nonwoven fabric comprising the polyarylene sulfide fiber from the polyester film after the biaxial orientation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyarylene sulfide porous membrane suitable for battery separators, electrical insulating materials, filters, papermaking canvases and the like.

Polyarylene sulfide fibers typified by polyphenylene sulfide fibers are excellent in heat resistance, chemical resistance, flame retardancy, etc., and are used for various filters, electrical insulation materials, paper making canvas, battery separators, etc. using this feature. Is expected to be used. For example, the battery separator needs to have micropores that prevent ions from being short-circuited between the electrodes and can move ions in the electrolyte, and wet nonwoven fabrics made of short fibers are used. Since the nonwoven fabric of this battery separator is used by being immersed in an electrolytic solution such as a strong alkaline aqueous solution or an organic solution, the short fiber material constituting the nonwoven fabric is resistant to being decomposed into a strong alkaline aqueous solution or an organic solution. Chemical properties are required. Polyethylene, polypropylene, etc. are known to be used for battery separators as materials with high chemical resistance, but their melting point is low, continuous use at temperatures around 80 ° C is difficult, and they can withstand discharge at high temperatures. Such a further improvement in heat resistance cannot be met. On the other hand, it is known that polyarylene sulfide is excellent in chemical resistance, has a high melting point (285 ° C.), and can be suitably applied to battery separators and the like (see Patent Documents 1, 2, and 3). However, in recent years, there has been a demand for further improvement of battery performance, for example, improvement of heat resistance and reduction of internal resistance. Although it is not possible to reduce the internal resistance by thinning the nonwoven fabric, it is extremely difficult to produce a thin nonwoven fabric of 100 μm or less because the manufacturing process is limited and the mechanical strength of the nonwoven fabric cannot be secured. In addition, such non-woven fabrics have too large pore diameters and cannot be used for battery separators.

JP-A-1-272899 JP-A-9-67786 JP-A-10-64502

  The present invention provides a polyarylene sulfide porous membrane that solves the problems as described above, has excellent heat resistance, chemical resistance, flame retardancy, etc., and has a pore size suitable for battery separator applications. Objective.

  That is, the gist of the present invention is a polyarylene sulfide porous membrane formed by forming a network structure in which fibers form fusion points and are fused to each other, and all or one of the fusion points. The polyarylene sulfide porous membrane is characterized in that a film having a thickness smaller than the fiber diameter of the fiber forming the fusion point is formed so as to straddle the fiber forming the fusion point in the portion The glass transition temperature (Tg) is from [the glass transition temperature (Tg) of polyarylene sulfide constituting the polyarylene sulfide non-woven fabric to be thermocompressed−10 ° C.]] to constitute the polyarylene sulfide non-woven fabric to be thermocompression bonded. Polyarylene sulfide glass transition temperature (Tg) + 30 ° C] thermoplastic resin (thermoplastic resin A) unstretched resin film and polyarylene A polyarylene sulfide porous membrane comprising a step of thermocompression bonding with a nonwoven fabric made of luffed fibers, a step of biaxially stretching the thermocompression-bonded laminate, and a step of peeling the film made of the thermoplastic resin A after biaxial stretching. It is a manufacturing method.

According to the present invention, a method for producing a polyarylene sulfide porous membrane excellent in heat resistance, chemical resistance, flame retardancy, and the like can be provided.

It is a surface photograph of one mode of a nonwoven fabric consisting of polyarylene sulfide fibers. It is a surface photograph of one mode of a polyarylene sulfide porous membrane of the present invention.

  The polyarylene sulfide porous membrane of the present invention has a network structure in which fibers are fused to each other by forming fusion points. The fusion point is formed at the entanglement point or contact point of the fiber. Here, the term “fused” means that the fibers are bonded to each other without using an adhesive. In addition, the network structure is a state in which the bonded fibers have a two-dimensional or three-dimensional spread, and there are voids in the space surrounded by the fibers (note that some medium is filled with the voids). It is not excluded that the present invention is used. All or part of the voids are preferably continuous from the front surface to the back surface of the porous membrane.

  In addition, the polyarylene sulfide porous membrane of the present invention has a thin membrane (also referred to as a membrane having a thin fusion point for convenience) over the fibers forming the fusion point in all or part of the fusion point. is doing. In the fibers constituting the porous membrane, the fibers have a fusion point where the thin membrane is formed, so that the strength of the porous membrane is stabilized and a uniform aperture state with a small pore diameter can be realized.

The thin film of the fusion point is a so-called “duck foot scooping” shape, “claw foot scooping” shape, or “please” shape, which is usually formed across two or more fibers. The thickness is thinner than the average diameter of the fibers forming the fusion point where the thin film is formed. Further, the area per film having a thin fusion point is not particularly limited, but is preferably 1 μm ² or more, and more preferably 5 μm ² or more. Although there is no particular limitation on the upper limit, if it is too large, sufficient performance as a separator or a filter may not be exhibited, and is usually 500 μm ² or less.

  Here, the area of the membrane with a thin fusion point is calculated by subtracting the “area of the fiber portion” from the “area of the fusion portion formed over two or more fibers” from the SEM photograph of the porous membrane. You can ask for it. For the measurement of the area, for example, general image analysis software such as a microanalyzer can be used.

  The fineness of the fibers constituting the polyarylene sulfide porous membrane of the present invention, that is, the average thickness of the fibers in the portion where the membrane thinner than the fiber diameter is not formed is preferably 1 μm to 500 μm, more preferably 1 μm to 300 μm. It is. If the average thickness of the fiber is 1 μm to 500 μm, the pore diameter is small and the porous body becomes thin.

The basis weight of the polyarylene sulfide porous membrane of the present invention is preferably ^{2 to} 25 g / m ² , more preferably ² to 15 g / m ² . When the basis weight is ² to 25 g / m ² , a thin porous film having excellent mechanical properties is obtained.

  The thickness of the polyarylene sulfide porous membrane of the present invention is preferably 1 to 50 μm, more preferably 1 to 30 μm. If it is 1-50 micrometers in thickness, when used as a separator, it will become a porous with reduced internal resistance.

  Next, the method for producing the polyarylene sulfide porous membrane of the present invention will be described with examples.

  The polyarylene sulfide used in the present invention is a homopolymer or copolymer having a repeating unit of-(Ar-S)-. Ar includes structural units represented by the following formulas (A) to (K).

(R1 and R2 are substituents selected from hydrogen, an alkyl group, an alkoxy group, and a halogen group, and R1 and R2 may be the same or different.)
The polyarylene sulfide repeating unit used in the present invention is preferably a structural formula represented by the above formula (A), and representative examples thereof include polyarylene sulfide, polyarylene sulfide sulfone, polyarylene sulfide ketone. , These random copolymers, block copolymers, and mixtures thereof. Particularly preferred polyarylene sulfide is preferably polyphenylene sulfide (hereinafter sometimes referred to as PPS) from the viewpoint of film properties and economy, and p-phenylene represented by the following structural formula as the main structural unit of the polymer. The resin preferably contains 80 mol% or more of sulfide units, more preferably 90 mol% or more, and still more preferably 95 mol% or more. When the p-phenylene sulfide component is less than 80 mol%, the crystallinity and heat transition temperature of the polymer are low, and the heat resistance, dimensional stability, mechanical properties, dielectric properties and the like, which are the characteristics of PPS, may be impaired.

Examples of the repeating unit other than p-phenylene sulfide include m-phenylene sulfide units, but other phenylene sulfide units may be copolymerized.
Moreover, within the range which does not inhibit the objective of this invention, the polyarylene sulfide used for this invention may be mixed with other aromatic sulfides and other polymers.

  The weight average molecular weight of the polyarylene sulfide used in the present invention is preferably 30,000 to 70,000, more preferably 40,000 to 60,000. By setting the weight average molecular weight to 30,000 or more, yarn breakage can be suppressed in the spinning process, and the spinning tension can be set higher, whereby stable spinnability can be obtained. Accordingly, PPS fibers having excellent mechanical properties can also be obtained. Further, by setting the weight average molecular weight to 70,000 or less, it is possible to suppress the melt viscosity of polyarylene sulfide in the melt spinning process, it is not necessary to set the spinning equipment to a special high pressure resistance specification, and the manufacturing equipment cost can be reduced.

  The nonwoven fabric made of polyarylene sulfide fibers used in the present invention can be produced by a known production method such as forming a web made of crimped polyarylene sulfide short fibers and entangled with a needle punch or the like. It is easy to manufacture by.

  In the melt blow method, when the melted polyarylene sulfide is discharged from the die, hot air is blown from the periphery of the die, and the fiber diameter of the polyarylene sulfide discharged by the hot air is reduced and blown, and then a net conveyor arranged at an appropriate position. It is manufactured by spraying on top and collecting to form a web. Since the web is sucked together with hot air by a suction device provided on the net conveyor, the individual fibers are collected before they are completely solidified. That is, the fibers of the web are collected in a state where they are lightly temporarily fixed to each other. By appropriately setting the collection distance between the base and the net conveyor, the degree of fiber fixation can be adjusted. Further, by appropriately adjusting the polymer discharge amount, hot air temperature, hot air flow rate, conveyor moving speed, etc., the fiber orientation, fiber diameter, and polyarylene sulfide nonwoven fabric weight can be arbitrarily set. A fiber that is made into a thin fiber diameter by the pressure of hot air and solidified in a non-oriented or low-oriented state is particularly preferably used. The fibers constituting the polyarylene sulfide nonwoven fabric are preferably substantially continuous. Further, the fiber is preferably solidified in a state of near crystallinity and low crystallinity by quenching from a molten state to a room temperature atmosphere.

  The fineness of the fibers constituting the polyarylene sulfide nonwoven fabric used in the present invention is preferably 2 to 1000 μm, more preferably 2 to 500 μm. If the fineness is 2 to 1000 μm, the pore diameter after stretching can be reduced, and a thinner porous membrane can be obtained.

The fiber basis weight of the polyarylene sulfide nonwoven fabric used in the present invention is preferably 20 to 250 g / m ² , more preferably 20 to 150 g / m ² . When the fiber basis weight is 20 to 250 g / m ² , a thin porous film having excellent mechanical properties after stretching can be obtained.

  The polyarylene sulfide non-woven fabric is once wound up or continuously thermocompression bonded to an unstretched film made of the thermoplastic resin A described below, and then biaxially stretched. For reference, a surface photograph of an example of a nonwoven fabric made of polyarylene sulfide fibers is shown in FIG.

  The unstretched film used in the present invention has a glass transition temperature (Tg) of polyarylene sulfide constituting the nonwoven fabric composed of the polyarylene sulfide fibers of -10 ° C to a glass transition temperature of polyarylene sulfide (Tg) + 30 ° C. It is preferable to use a resin having a temperature from the viewpoint of co-stretchability, and when using a nonwoven fabric made of PPS fibers, the glass transition temperature (Tg) of the thermoplastic resin A constituting the unstretched film is 80 ° C to 120 ° C. A thermoplastic resin is used. The glass transition temperature is more preferably 80 ° C to 100 ° C. By setting the glass transition temperature (Tg) to 80 ° C. or higher, stable biaxial stretching with a nonwoven fabric composed of polyarylene sulfide fibers becomes possible. In addition, by setting the glass transition temperature (Tg) to 120 ° C. or less, crystallization of the nonwoven fabric made of unstretched polyarylene sulfide fibers is suppressed, and it is easy to peel in the peeling process after biaxial stretching and large pores are formed in the final product. Without any defects, it can be made defect-free when used as a separator.

  The thermoplastic resin A is not particularly limited as long as it is a resin that can be co-stretched with polyarylene sulfide, and a preferable resin is, for example, a polyester resin. In order to set the glass transition temperature within the range specified in the present invention, it is possible to select the type of monomer to be used, the selection of another resin to be mixed, and the like. In general, if a monomer having a high proportion of aromatic rings is used, the glass transition temperature tends to increase. As a resin to be mixed, an imide having an aromatic ring itself has a high glass transition temperature and is compatible with polyester. If the resin to be used is used, the glass transition temperature tends to increase.

  Specifically, for example, the polyester is composed of a polymer having an acid component or a diol component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid as a structural unit (polymerization unit). What is done is common. Of course, a hydroxycarboxylic acid may be used as long as the object of the present invention is not impaired.

  Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like can be used. Among them, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. . As the alicyclic dicarboxylic acid component, for example, cyclohexane dicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2'-bis (4'- β-hydroxyethoxyphenyl) propane and the like can be used, and among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be preferably used, and ethylene glycol is particularly preferable. etc It can be used. These diol components may be used alone or in combination of two or more.

  The polyester may be copolymerized with a monofunctional compound such as lauryl alcohol or phenyl isocyanate, or a trifunctional compound such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, or 2,4-dioxybenzoic acid. A compound or the like may be copolymerized within a range in which the polymer is substantially linear without excessive branching or crosslinking. In addition to the acid component and diol component, the present invention includes aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 2,6-hydroxynaphthoic acid, p-aminophenol, and p-aminobenzoic acid. As long as the effect is not impaired, the copolymerization can be further carried out. These polyesters may be composed of one type of repeating unit or may be composed of two or more types of repeating units. In this case, the polyester may be a random copolymer or a block copolymer. . Moreover, what mixed 2 or more types of polyester may be sufficient.

Most preferred polyesters include polyethylene terephthalate, polycyclohexane terephthalate, and polyethylene naphthalate.
Moreover, when it is set as a polymer alloy, since the control of a glass transition temperature is easy by the mixing ratio, the polymer alloy of the said polyester resin and a polyimide-type resin can be employ | adopted preferably. In addition, when setting it as a polymer alloy, the mixing ratio of each resin can be confirmed using NMR method (nuclear magnetic resonance method) and microscopic FT-IR method (Fourier transform microinfrared spectroscopy).

  As a polyimide-type resin, what contains a structural unit as shown by the following general formula, for example is preferable.

Here, R ¹ in the formula is

Represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. R ² in the formula is

Represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group.

  From the viewpoints of melt moldability and affinity with polyester, a polyetherimide containing an ether bond in the polyimide component as shown by the following general formula is particularly preferred.

(Wherein R ³ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ⁴ is a divalent aromatic residue having 6 to 30 carbon atoms, From the group consisting of alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-terminated with alkylene groups having 2 to 8 carbon atoms Selected divalent organic group.)
As said R < ³ >, R < ⁴ >, the aromatic residue shown by the following formula group can be mentioned, for example.

  In the present invention, 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine from the viewpoint of affinity with polyester, cost, melt moldability, and the like, or A polymer having a repeating unit represented by the following formula, which is a condensate with p-phenylenediamine, is preferable.

Or

(N is an integer of 2 or more, preferably an integer of 20 to 50)
This polyetherimide is available from Subic Innovative Plastics under the trade name “Ultem” (registered trademark).

  In order to facilitate the peeling process after stretching, the thermoplastic resin A preferably contains a release agent such as a wax compound, a silicone compound, or paraffin, and particularly preferably contains a wax compound. Here, as the release agent, for example, straight silicone such as dimethyl silicone, methyl phenyl silicone, methyl hydrogen silicone, amino group, epoxy group, carboxyl group, carbinol group, alkyl group at the side chain and / or terminal, Silicone compounds such as modified silicones that have introduced organic groups such as polyether groups, natural waxes such as whale wax, beeswax, lanolin, carnauba wax, canderia wax, montan wax, rice wax, stearyl stearate, paraffin wax, micro Wax compounds such as crystalline wax, oxidized wax, ester wax, synthetic wax such as low molecular weight polyethylene, polytetrafluoroethylene, tetrafluoroethylene / perfluoroalkoxy Fluorine-based compounds such as len copolymer, tetrafluoroethylene / ethylene copolymer, etc. Among them, carnauba wax, or handleability, economy, heat resistance, repellency, etc. in terms of handleability and releasability can be mentioned. From the viewpoint of the water effect, a silicone compound is preferably used. As content of a mold release agent, it is preferable that it is 0.2-2 weight% with respect to the whole quantity of the thermoplastic resin A, It is desirable to contain 0.3-2 weight% more preferably. As a method of incorporating a release agent, when the thermoplastic resin A is a condensation polymer such as polyester, a method of adding it during the polymerization, or a method of kneading and mixing generally in a biaxial melt extruder Etc. are preferably used.

  The method of thermocompression bonding between the film made of the thermoplastic resin A and the unstretched polyarylene sulfide non-woven fabric is not particularly limited, but thermocompression bonding with a heating roll is particularly preferable from the viewpoint of processability. The thermocompression bonding temperature is preferably between the glass transition temperature (Tg) of the thermoplastic resin A and the cold crystallization temperature (Tcc), particularly preferably Tg to Tg + 50 ° C.

  In the present invention, it is important that the film made of the thermoplastic resin A and the unstretched polyarylene sulfide nonwoven fabric be co-stretched in a thermocompression-bonded state. By co-stretching in a thermocompression-bonded state, the film and the nonwoven fabric can be suitably stretched without being integrally peeled off. Also, by co-stretching both together, the film serves as a reinforcing body, and a porous membrane having a uniform fineness and fiber basis weight can be obtained without breaking the nonwoven fabric made of polyarylene sulfide fibers.

The stretching method is not particularly limited, but biaxial stretching is preferred from the viewpoint of thinning the polyarylene sulfide porous membrane, reducing the pore diameter, and mechanical properties. Biaxial stretching may be either a sequential biaxial stretching method or a simultaneous biaxial stretching method. In the case of the sequential biaxial stretching method, stretching is generally performed in the order of the longitudinal direction and the transverse direction, but the stretching may be performed in reverse. The stretching temperature is preferably between the glass transition temperature (Tg) and the cold crystallization temperature (Tcc) of the unstretched thermoplastic resin A film. The draw ratio is not particularly limited, and is appropriately determined depending on the required thickness, pore size, etc. of the obtained stretched polyarylene sulfide porous membrane, but usually about 2 to 5 times in length and width are appropriate. . Further, after biaxial stretching, it may be re-stretched vertically or horizontally, or vertically and horizontally.
Furthermore, it is preferable to heat-treat after biaxial stretching. The heat treatment temperature is not particularly limited,
It is preferably between the cold crystallization temperature (Tcc) and the melting point (Tm) of the resin constituting the polyarylene sulfide nonwoven fabric. The heat treatment time is suitably about 0.5 to 60 seconds.

  The polyarylene sulfide porous membrane of the present invention can be obtained by peeling from a film made of the thermoplastic resin A stretched after the biaxial stretching. The method of peeling is not particularly limited, but a method of peeling continuously in a winder process after biaxial stretching, a method of peeling after winding with a film made of the stretched thermoplastic resin A, and the like are particularly preferable. For reference, a surface photograph of the polyarylene sulfide porous membrane of the present invention is shown in FIG. As is apparent from comparison with FIG. 1, it can be seen that a large number of films whose thickness is thinner than the fiber diameter of the fibers forming the fusion point are formed so as to extend between the fused fibers.

  The polyarylene sulfide porous membrane of the present invention can be applied to applications in which the porous membrane can be generally used. For example, the polyarylene sulfide porous membrane is impregnated with an electrolytic solution and used as it is as a battery separator or impregnated with insulating oil or varnish. It is particularly preferably used as an insulating material or for applications such as filters and paper canvas.

The present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not construed as being limited to the embodiments. Even when a non-woven fabric made of polyarylene sulfide other than PPS is used, the present invention can be applied by applying the following examples and the like if conditions such as thermocompression bonding and stretching temperature are set with reference to the description of the present specification. A porous membrane can be obtained.

The measurement method of each characteristic or physical property value and the evaluation method of the effect are as follows.
(1) Glass transition temperature (Tg), melting temperature (Tm), and melt crystallization temperature (Tmc)
The measurement was performed according to JIS K7121-1987. Using a differential scanning calorimeter DSC (RDC220) manufactured by Seiko Instruments Inc. and a disk station (SSC / 5200) manufactured by Seiko Instruments Inc. as a data analyzer, 5 mg of the sample was melted and held at 350 ° C. for 5 minutes on an aluminum tray, and then rapidly solidified. The temperature was raised from room temperature at a heating rate of 20 ° C./min. At that time, the peak temperature of the endothermic peak of melting observed was defined as the melting temperature (Tm). The glass transition temperature (Tg) was calculated by the following formula.
Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
Further, 5 mg of a sample was heated from room temperature to 350 ° C. at a heating rate of 20 ° C./min on an aluminum tray, melted and held at 35 ° C. for 5 minutes, and cooled from 350 ° C. to room temperature at 20 ° C./min. The peak temperature of the exothermic peak observed at that time was taken as the melt crystallization temperature (Tmc).

(2) Fineness (average fiber thickness)
Ten images of 10 non-woven fabrics were taken with a scanning electron microscope at a magnification of 2000 times, and the diameter of any 15 fibers per image (however, spanning the fibers forming the fusion point) The portion where the film whose thickness is thinner than the fiber diameter of the fiber forming the fusion point is not measured) is measured for 10 images, and the average of 150 measurement results is obtained. The fiber diameter (fineness) was measured.

(3) Weight per unit area (g / m ² )
A non-woven fabric or porous membrane was cut into a size of 20 cm × 20 cm, and the weight was measured and converted into a weight per 1 m ² .

(4) Peel strength (g / cm), peelability It measured by the 180 degree peel test method based on JIS-K-6854.
○: 0 or more and less than 50 g / cm Δ: 50 or more and less than 100 g / cm x: 100 g / cm or more, or breakage is observed in the non-woven fabric-derived part.

(5) Measurement of wax concentration The wax concentration contained in the film was quantified by Fourier transform infrared absorption spectroscopy-total reflection method. The measurement was performed by reflection once at an incident angle of 60 ° using FTS-60A / 896 (FTIR manufactured by GIGILAB) as a spectroscope, ZnSE as IRE. At that time, the resolution was 4 cm ⁻¹ and the number of integrations was 256. In quantification, the intensity ratio of the peak near the C—H stretching vibration band 2850 cm ⁻¹ derived from the wax and the peak near 3050 cm ⁻¹ derived from the benzene ring in the polyester was determined. The quantification was performed by preparing a calibration curve in advance.

(6) Presence / absence of a film having a thin fusion point The surface of a porous film 5 cm × 5 cm is observed using a stereomicroscope or an electron microscope, and the thickness of the porous film extends over the fibers forming the fusion point. The presence or absence of a film thinner than the fiber diameter of the fiber forming the fusing point, that is, a film having a thin fusing point was confirmed and evaluated as follows.
○: A film having one or more thin fusion points is observed. ×: A film having a thin fusion point is not formed.

[Reference Example 1] Production of PPS non-woven fabric (unstretched) Polyarylene sulfide pellets were rotated by vacuum using a device equipped with a melt blow injection device having 7 orifices per 1 cm of the base width and a gas injection slit gap of 0.3 mm. Vacuum-dried at 180 ° C. for 3 hours in a dryer, melted at 315 ° C., extruded from an orifice, and ejected heated air at 330 ° C. to a gas injection slit to pull the fibers having the fiber diameters shown in Table 2 from a melt blow jet device. It collected on the porous belt distribute | arranged 14 cm apart, and obtained the PPS nonwoven fabric of the fabric weight of Table 2.

Examples 1 and 2
Polyethylene terephthalate pellets (50 parts by weight) and polyetherimide pellets (“Ultem” 1010 (registered trademark of Subic Innovative Plastics)) (50 parts by weight) were heated to 280 ° C. with a vent type 2 The mixture was supplied to a shaft kneading extruder and melt-extruded at a shear rate of 100 sec ⁻¹ and a residence time of 1 minute to obtain a polyetherimide-containing chip (I) containing 50% by weight of polyetherimide.

  The resulting polyetherimide-containing chip (I) and polyethylene terephthalate (inherent viscosity 0.62) containing 0.625% by weight of carnauba wax were dry blended at a ratio of 20:80 to obtain thermoplastic resin A. Obtained.

The thermoplastic resin A was vacuum-dried at 180 ° C. for 3 hours and then charged into an extruder, melt-extruded at a set temperature of 285 ° C. and a residence time of 300 seconds, and a shear rate of 10 in a fiber sintered stainless steel filter (10 μm cut). After passing in seconds ⁻¹ , the sheet was discharged from a T die. Further, this sheet was closely adhered on a cooling drum having a surface temperature of 25 ° C. at a speed of 3 m / min to be cooled and solidified to obtain a substantially non-oriented film.

  The obtained film and the PPS nonwoven fabric were bonded together and biaxially stretched under the conditions shown in Table 1. That is, first, spray glue is sprayed on the tip of the unstretched PPS nonwoven fabric produced by the method described in Reference Example 1 on the cast substantially non-oriented film, and lightly adhered to the film at the entrance of the longitudinal stretching. Then, using a longitudinal stretching machine in which several rolls of hard chrome or ceramic material are arranged, after the preheating, use the difference in the peripheral speed of the roll to perform thermal bonding and longitudinal direction. Stretching was performed, followed by transverse stretching and heat treatment using a stenter. After cooling to room temperature, the edge of the composite was removed and wound.

  Subsequently, the PPS nonwoven fabric was peeled from the wound composite to obtain a stretched PPS porous membrane. The peelability was good, and the resulting stretched PPS porous membrane had the fineness, average basis weight, thickness, and shape of the membrane with a thin fusion point as shown in Table 2. A film having a thin fusion point could be confirmed, and the evaluation of the shape was as shown in Table 1.

  The stretched polyphenylene sulfide porous membranes obtained in Examples 1 and 2 are excellent in heat resistance, chemical resistance, flame retardancy, etc., and have favorable air permeability. Various filters, electrical insulating materials, papermaking canvases And can be preferably used for applications such as battery separators.

Examples 3-12
Examples 3 to 9 are dry blends of the polyetherimide-containing chip (I) and polyethylene terephthalate (inherent viscosity 0.62) containing 0.72% by weight of carnauba wax in a ratio of 30:70 in Example 1. In Example 10, polyetherimide-containing chip (I) and polyethylene terephthalate (inherent viscosity 0.62) were dry blended in a ratio of 30:70 in Example 1,
Examples 11 and 12 are the same as in Example 1, except that polyetherimide-containing chips (I) and polyethylene terephthalate (inherent viscosity 0.62) containing 1.43% by weight of carnauba wax were dry blended at a ratio of 30:70. Example 1 except that the addition amount of polyetherimide was changed, and a film composed of the unstretched PPS nonwoven fabric and the thermoplastic resin A shown in Table 2 was bonded and stretched under the conditions shown in Table 1. The film was formed in the same manner as above and wound up. The PPS nonwoven fabric was peeled from the wound film / PPS nonwoven composite to obtain a stretched PPS porous membrane. The peelability was good, and the fineness, average basis weight, and thickness of the obtained stretched PPS porous membrane were as shown in Table 2.

  The stretched polyphenylene sulfide porous membranes obtained in Examples 3 to 9 are excellent in heat resistance, chemical resistance, flame retardancy, and the like, and have favorable air permeability. Various filters, electrical insulation materials, papermaking canvases And could be used for applications such as battery separators.

Examples 13 and 14
In Example 1, the thermoplastic resin A was changed to an ethylene terephthalate (80 mol%) / ethylene 2,6-naphthalenedicarboxylate (20 mol%) copolymerized polyester containing 0.5% by weight of carnauba wax. The nonwoven fabric-film composite was wound up in the same manner as in Example 1 except that it was superposed on the unstretched PPS nonwoven fabric shown in Table 2 and bonded and stretched under the conditions shown in Table 1. The PPS nonwoven fabric was peeled off from the wound film / PPS nonwoven composite to obtain a stretched PPS porous membrane. The peelability was good, and the fineness, average basis weight, and thickness of the obtained stretched PPS porous membrane were as shown in Table 2.

  The stretched polyphenylene sulfide porous membranes obtained in Examples 13 and 14 are excellent in heat resistance, chemical resistance, flame retardancy, and the like, and have favorable air permeability. Various filters, electrical insulating materials, papermaking canvases And could be used for applications such as battery separators.

Examples 15 and 16
In Example 1, the thermoplastic resin A was changed to an ethylene terephthalate (70 mol%) / ethylene 2,6-naphthalenedicarboxylate (30 mol%) copolymerized polyester containing 0.5% by weight of carnauba wax. The nonwoven fabric-film composite was wound up in the same manner as in Example 1 except that it was superposed on the unstretched PPS nonwoven fabric shown in Table 2 and bonded and stretched under the conditions shown in Table 1. The PPS nonwoven fabric was peeled from the wound film / PPS nonwoven composite to obtain a stretched PPS porous membrane. The peelability was good, and the fineness, average basis weight, and thickness of the obtained stretched PPS porous membrane were as shown in Table 2.

  The stretched polyphenylene sulfide porous membranes obtained in Examples 15 and 16 are excellent in heat resistance, chemical resistance, flame retardancy, etc., and have favorable air permeability. Various filters, electrical insulation materials, papermaking canvases And could be used for applications such as battery separators.

Comparative Examples 1-6
The unstretched PPS nonwoven fabric shown in Table 2 was biaxially stretched under the conditions described in Table 1 using a longitudinal stretching machine and a stenter that were used in Example 1. Any of the PPS nonwoven fabrics could be stretched in the longitudinal direction, but it was not obtained as a product because tearing occurred frequently due to transverse stretching with a stenter.

Comparative Example 7
When the unstretched PPS nonwoven fabric shown in Table 2 was introduced into a group of rolls heated to the temperature conditions shown in Table 1 and subjected to hot pressing, the fibers were fused to form a porous film. The obtained heat-sealed PPS porous film was as thick as 70 μm, but a film with a thin fusion point was not formed, and it was difficult to use it for applications such as a battery separator.

Claims (10)

A polyarylene sulfide porous membrane formed by forming a network structure in which fibers form a fusion point and are fused to each other, and the fusion point is formed in all or a part of the fusion point. A polyarylene sulfide porous membrane characterized in that a membrane having a thickness smaller than the fiber diameter of the fibers forming the fusion point is formed so as to straddle the fibers. The average thickness of fibers in a portion where a membrane thinner than the fiber diameter is not formed is 1 µm to 500 µm, the basis weight of the porous membrane is ² to 25 g / m ² , and the thickness is 1 to 50 µm. 2. The polyarylene sulfide porous membrane according to 1. From a glass transition temperature (Tg) of [a glass transition temperature (Tg) of polyarylene sulfide constituting a non-woven fabric made of polyarylene sulfide fiber to be thermocompression-bonded −10 ° C.]] [a non-woven fabric made of polyarylene sulfide fiber to be thermocompression-bonded] A step of thermocompression bonding of an unstretched resin film made of a thermoplastic resin (thermoplastic resin A) having a glass transition temperature (Tg) + 30 ° C. of the polyarylene sulfide constituting and a non-woven fabric made of polyarylene sulfide fiber; A method for producing a polyarylene sulfide porous membrane comprising a step of biaxially stretching the laminated body and a step of peeling the film made of the thermoplastic resin A after biaxial stretching. The method for producing a polyarylene sulfide porous membrane according to claim 3, wherein the nonwoven fabric made of the polyarylene sulfide fiber is made of polyphenylene sulfide, and the glass transition temperature of the thermoplastic resin A is 80 to 120 ° C. The non-woven fabric made of the polyarylene sulfide fiber is a non-woven fabric made of fibers having an average thickness of 2 µm to 1000 µm, and has a fiber basis weight of 20 to 250 g / m ^2. A method for producing a polyarylene sulfide porous membrane. The method for producing a stretched polyarylene sulfide porous membrane according to any one of claims 3 to 5, wherein the thermoplastic resin A contains 0.2 to 2 wt% of a release agent. A battery separator using the polyarylene sulfide porous membrane according to claim 1 or 2, or the polyarylene sulfide porous membrane obtained by the production method according to any one of claims 3 to 6. An electrical insulating material comprising the polyarylene sulfide porous membrane according to claim 1 or 2, or the polyarylene sulfide porous membrane obtained by the production method according to any one of claims 3 to 6. A filter comprising the polyarylene sulfide porous membrane according to claim 1 or 2, or the polyarylene sulfide porous membrane obtained by the production method according to any one of claims 3 to 6. A paper making canvas using the polyarylene sulfide porous membrane according to claim 1 or 2, or the polyarylene sulfide porous membrane obtained by the production method according to any one of claims 3 to 6.