JP4122007B2 - Composite fiber and non-woven fabric for battery separator comprising the same - Google Patents

Description

  The present invention relates to a composite fiber containing a specific semi-aromatic polyamide as a component, and also relates to a nonwoven fabric suitable as a separator for a battery using an alkaline solution.

  Alkaline batteries have excellent charge / discharge characteristics and overcharge / overdischarge characteristics, and can be used repeatedly with a long life, so that they are widely used in electronic devices that are significantly reduced in size and weight. The characteristics of such an alkaline battery greatly depend on the characteristics of the alkaline battery separator nonwoven fabric.

  As such a non-woven fabric, a polyamide fiber non-woven fabric is used as a non-woven fabric for an alkaline battery separator, which is easily wetted by an electrolytic solution, has a large liquid retention amount, and has a low electric resistance in a state containing the electrolytic solution. Polyolefin fiber nonwoven fabrics are used as nonwoven fabrics for alkaline battery separators in alkaline batteries that require durability at relatively high temperatures. However, the polyamide fiber constituting the polyamide fiber nonwoven fabric is an aliphatic polyamide fiber, which has excellent alkali resistance, high hydrophilicity and excellent electrolyte retention, but lacks chemical stability. There is a drawback that it is oxidized and decomposed in the liquid. Accordingly, in an alkaline battery using a nonwoven fabric composed of such aliphatic polyamide fibers as a separator, the self-discharge is increased due to the decomposition of the separator, and in the secondary battery that is repeatedly charged and discharged at a high temperature, the cycle life is increased. There was a problem of shortening.

  On the other hand, a battery separator made of a polyolefin fiber nonwoven fabric is excellent in alkali resistance and oxidative deterioration resistance, but has a drawback that it is difficult to get wet with the electrolyte because it is hydrophobic, and its liquid retention amount is small. Therefore, various means for improving the electrolytic solution retention of the polyolefin fiber nonwoven fabric have been proposed. For example, there is a method of applying a surfactant treatment to a polyolefin fiber nonwoven fabric. However, the surfactant has a problem in the deterioration resistance against the electrolytic solution, and when the cycle is used, the surfactant is not passed after a certain period. Since it is liberated, it has not been able to sufficiently improve the liquid absorption and liquid retention of the electrolyte.

  A battery separator that combines a polyamide fiber and a polyolefin fiber has also been proposed. For example, a fiber made by mixing and spinning polyamide and polyolefin is made into a non-woven fabric to form a battery separator, and after the polyamide is deteriorated, the polyolefin is maintained as the main fiber (Japanese Patent Laid-Open No. 52-3120, Japanese Patent Laid-Open No. Sho 55-25921, JP 55-66864, JP 3-93154), polyamide fibers and polyethylene-polypropylene composite fibers mixed to form a non-woven fabric, polyamide / polypropylene A composite fiber that maintains its form as a main fiber even after deterioration of the polyamide, such as a non-woven fabric obtained by mixing a composite spun fiber and a polyethylene-polypropylene composite fiber (JP 50-154745 A, JP Japanese Laid-Open Patent Publication No. 59-101663, Japanese Laid-Open Patent Publication No. 59-196556, Japanese Laid-Open Patent Publication No. 5 -201365, JP-see JP-A-59-201366) have been proposed. These non-woven fabrics for battery separators have the problem that the battery performance deteriorates because the polyamide itself deteriorates, and the main fibers that maintain the strength that can maintain the form after the polyamide deteriorates are required. There is also a problem that it is impossible to cope with downsizing of the battery, that is, reduction in thickness of the battery separator.

  In order to solve the above-mentioned problems, a woven fabric and a non-woven fabric using an aromatic polyamide fiber are used for a battery separator (see JP-A-53-58636 and JP-A-5-283054). It has been proposed to use a non-woven fabric made of an aromatic polyamide fiber and a non-woven fabric made of nylon 6 and nylon 66 for a battery separator (see Japanese Patent Application Laid-Open No. 58-147958).

  However, non-woven fabrics made of aromatic polyamide fibers have excellent hydrophilicity and excellent electrolyte retention, but some have poor alkali resistance and oxidation degradation resistance, and are hot meltable. Therefore, there may be cases where an adhesive for making a nonwoven fabric is required separately, and there are problems with the electrolytic solution resistance of the adhesive, problems with adhesion when using binder fibers as the adhesive, and problems with mixed cotton spots. Arise. Further, when a non-woven fabric made of nylon 6 fiber or nylon 66 fiber is used as a binder, the nylon 6 fiber or nylon 66 fiber deteriorates, resulting in insufficient battery separator performance. Although it is conceivable to use wholly aromatic polyamide fiber as the polyamide fiber, it is expensive and has problems in alkali resistance and oxidation deterioration resistance at high temperatures, and has not been put into practical use.

JP-A-52-3120 Japanese Patent Laid-Open No. 55-25921 JP 55-68664 A Japanese Patent Laid-Open No. 3-93154 Japanese Patent Laid-Open No. 50-154745 JP 59-101863 A JP 59-196556 A JP 59-201365 A JP 59-201366 A JP-A-53-58636 Japanese Patent Application Laid-Open No. H5-283054 Japanese Patent Laid-Open No. 58-147756

  Development of a nonwoven fabric for battery separators that can be made thin so that it is excellent in alkali resistance, oxidative degradation resistance, hydrophilicity, electrolyte retention, and can follow the downsizing of alkaline batteries. As a result, development of fibers forming the nonwoven fabric is eagerly desired.

  As a result of intensive studies to achieve the above object, the present inventors have found that a non-woven fabric comprising a composite fiber containing a semi-aromatic polyamide containing an aromatic dicarboxylic acid and a specific aliphatic alkylenediamine as a component is an alkaline battery separator. -It has been found that it has various excellent physical properties, and the present invention has been completed.

  That is, the present invention relates to a dicarboxylic acid component in which 60 mol% or more of the dicarboxylic acid component is an aromatic dicarboxylic acid, and 60 mol% or more of the diamine component is 1,9-nonanediamine or 1,9-nonanediamine and 2-methyl- A non-woven fabric comprising a polyamide composed of a diamine component which is a combined product of 1,8-octanediamine and a composite fiber composed of a thermoplastic polymer incompatible with the polyamide, and a fiber obtained by fibrillating the composite fiber, or A nonwoven fabric containing a composite fiber using a heat-fusible component as a thermoplastic polymer is provided as a nonwoven fabric for an alkaline battery separator. Hereinafter, the present invention will be described in detail.

Since the composite fiber of the present invention contains semi-aromatic polyamide as one component, it is excellent in alkali resistance, oxidation deterioration resistance, electrolyte solution retention, etc., and is combined with a heat-adhesive component or made into a fibrillated fiber. As a result, the electrolyte solution retention and the strength of the nonwoven fabric are improved, so that it has an effective performance as a battery separator and can be used for various battery applications for a long period of time.

  The polyamide constituting the conjugate fiber of the present invention comprises a dicarboxylic acid component and a diamine component, wherein 60 mol% or more of the dicarboxylic acid component is an aromatic dicarboxylic acid, and 60 mol% or more of the diamine component is 1,9. -It is characterized by being nonanediamine or a combination of 1,9-nonanediamine and 2-methyl-1,8-octanediamine.

  As the aromatic dicarboxylic acid, terephthalic acid is preferable from the viewpoint of the alkali resistance and oxidation resistance of the battery separator. Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4- Naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, diphenic acid, dibenzoic acid, 4,4′-oxydibenzoic acid, diphenylmethane-4,4′-dicarboxylic acid, One or more aromatic dicarboxylic acids such as diphenylsulfone-4,4′-dicarboxylic acid and 4,4′-biphenyldicarboxylic acid can be used in combination. The content of the aromatic dicarboxylic acid is 60 mol% or more of the dicarboxylic acid component, preferably 75 mol% or more, particularly preferably 90 mol% or more. When the aromatic dicarboxylic acid is less than 60 mol%, alkali resistance and oxidation deterioration resistance when used for a battery separator are lowered.

  Examples of dicarboxylic acids other than the aromatic dicarboxylic acids include malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, and trimethyl. Aliphatic dicarboxylic acids such as adipic acid, pimelic acid, azelaic acid, sebacic acid and suberic acid; and alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, These acids can be used alone or in combination of two or more. In particular, the dicarboxylic acid component is preferably 100% aromatic dicarboxylic acid in terms of the strength, chemical resistance, oxidation degradation resistance, heat resistance, etc. of the nonwoven fabric. Furthermore, a polyvalent carboxylic acid such as trimellitic acid, trimesic acid, and pyromellitic acid can be contained within a range where fiberization and non-woven fabric can be easily formed.

  In addition, 60 mol% or more of the diamine component is composed of 1,9-nonanediamine or 1,9-nonanediamine and 2-methyl-1,8-octanediamine in terms of heat resistance, hydrolysis resistance, chemical resistance, and the like. It is a combination product. The content of the aliphatic alkylene diamine is 60 mol% or more of the diamine component, but 75 mol% or more, particularly 90 mol% or more is preferable from the viewpoint of liquid electrolyte retention.

  Examples of diamines other than the above aliphatic alkylene diamines include ethylene diamine, propylene diamine, 1,4-butane diamine, 1,6-hexane diamine, 1,8-octane diamine, 1,10-decane diamine, and 1,11-undecane. Diamine, 1,12-dodecanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4, Aliphatic diamine having a straight chain or a side chain such as 4-trimethyl-1,6-hexanediamine, 5-methyl-1,9-nonanediamine; cyclohexanediamine, methylcyclohexanediamine, isophoronediamine, norbornanedimethyldiamine, tricyclodecane Alicyclic diamines such as dimethyldiamine; Aromatic diamines such as nylenediamine, m-phenylenediamine, xylylenediamine, xylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether, or these A mixture can be mentioned, These can use not only one type but 2 or more types.

  When 1,9-nonanediamine and 2-methyl-1,8-octanediamine are used in combination as the aliphatic alkylenediamine, 60 to 100 mol% of the diamine component is 1,9-nonanediamine and 2-methyl-1,8-. It consists of octanediamine, and the molar ratio is preferably the former: the latter = 40: 60 to 99: 1, particularly the former: the latter = 70: 30 to 95: 5.

  The aliphatic alkylene diamine in the above polyamide may have a side chain, but the aliphatic alkylene diamine having a side chain is an aliphatic alkylene in terms of alkali resistance, oxidation deterioration resistance, spinnability and the like. It is preferable that it is 60 mol% or less in diamine.

  The intrinsic viscosity (value measured at 30 ° C. in concentrated sulfuric acid) of the above polyamide is preferably 0.6 to 2.0 dl / g, particularly 0.6 to 1.8 dl / g, 0.7 to 1. 6 dl / g is preferred. The polyamide within the range of the intrinsic viscosity has good melt viscosity characteristics when it is made into a fiber and a non-woven fabric, and further, the strength, alkali resistance, oxidation deterioration resistance, and the like of the obtained separator are excellent.

Furthermore, in the above-mentioned polyamide, it is preferable that 10% or more of the terminal groups of the molecular chain are sealed with an end-capping agent, 40% or more of the terminals, and 70% or more of the terminals are sealed. Is preferred. By sealing the end of the molecular chain, the strength, alkali resistance, oxidation deterioration resistance, and the like of the obtained separator are excellent. The end capping agent is not particularly limited as long as it is a monofunctional compound having reactivity with the amino group or carboxyl group at the end of the polyamide, but monocarboxylic acid from the viewpoint of reactivity and stability of the capping end. Monoamine is preferred. Monocarboxylic acids are preferred from the standpoints of ease of handling, reactivity, stability of the sealing ends, and price. Examples of the monocarboxylic acid include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, and benzoic acid. The terminal sealing rate can be determined from the integral value of the characteristic signal corresponding to each terminal group by ¹ H-NMR.

  The method for producing the polyamide according to the present invention is not particularly limited, and any known method for producing a crystalline polyamide can be used. For example, it can be produced by a solution polymerization method or an interfacial polymerization method using acid chloride and diamine as raw materials, a melt polymerization method using dicarboxylic acid or an alkyl ester of dicarboxylic acid and diamine as raw materials, or a solid phase polymerization method.

  For example, after the end-capping agent, catalyst, diamine component and dicarboxylic acid component are reacted together to produce a nylon salt, the intrinsic viscosity is 0.15 to 0.30 dl / The polymer can be easily produced by solid-phase polymerization with a prepolymer of g or polymerization using a melt extruder. When the final stage of the polymerization is carried out by solid phase polymerization, it is preferably carried out under reduced pressure or under an inert gas flow. If the polymerization temperature is in the range of 200 to 250 ° C., the polymerization rate is high, the productivity is excellent, and coloring And gelling can be effectively suppressed. When the final stage of the polymerization is carried out by a melt extruder, it is preferable that the polymerization temperature is 370 ° C. or lower because the polyamide is hardly decomposed and a polyamide having no deterioration is obtained.

  Examples of the polymerization catalyst include phosphoric acid, phosphorous acid, hypophosphorous acid or ammonium salts thereof, metal salts thereof, esters thereof, and among them, sodium hypophosphite is easily available, It is preferable in terms of handleability. If necessary, stabilizers such as copper compounds, colorants, UV absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, plasticizers, lubricants, crystallization rate retarders, etc. are polycondensed. It can be added during or after the reaction. Especially when an organic stabilizer such as hindered phenol, a copper halide compound such as copper iodide, or an alkali metal halide compound such as potassium iodide is added as a heat stabilizer, the melt retention stability during fiberization Is preferable.

  The other component constituting the composite fiber of the present invention, which is a thermoplastic polymer incompatible with the above-mentioned polyamide, is an aliphatic polyamide such as nylon 6, nylon 66, nylon 10, etc .; polyethylene, polypropylene, ionomer, etc. Examples thereof include polyolefins such as the following copolymers; ethylene-vinyl alcohol copolymers; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polycyclohexane terephthalate. When an aliphatic polyamide is used as the thermoplastic polymer, the liquid retaining property of the electrolytic solution can be further enhanced because the liquid retaining property as a battery separator is excellent. Moreover, since melting | fusing point is lower than the above-mentioned polyamide, it also functions as a heat-fusible component. When polyolefin is used as the thermoplastic polymer, it is excellent in oxidation deterioration resistance as a battery separator, and since the polyolefin has a lower melting point than polyamide, it acts as a heat-fusible component and functions as a binder. Thus, a non-woven fabric for a battery separator that can maintain strong adhesiveness for a long period of time is obtained.

  When the melting point of the thermoplastic polymer is lower than the melting point of the polyamide, particularly when the difference in melting point is 20 ° C. or more, the thermoplastic polymer becomes a heat-adhesive component, and a nonwoven fabric made of a composite fiber containing the component is prepared. In this case, the nonwoven fabric can be easily bonded by thermocompression bonding. The bonding method can be appropriately selected from a hot calendar method, a hot air air method, an ultrasonic bonding method, and the like.

  In the composite fiber of the present invention, the composite form can be appropriately set such as a core-sheath type, a sea-island type, a laminated type, a combination thereof, a composite form using a static mixer, etc. When the melting point is low, the thermoplastic polymer functions as a heat-fusible component, and therefore a composite form capable of performing such a function is preferable. Even if the thermoplastic polymer is a composite fiber that does not constitute a fiber surface, the composite fiber is crushed at the time of thermocompression bonding when producing a nonwoven fabric using the composite fiber, and the thermoplastic polymer inside the fiber If it is a composite form which exudes to the fiber surface and becomes an adhesive component, it falls within the scope of the present invention. For example, in the core-sheath type composite fiber, it is preferable that the core component is the thermoplastic polymer, and the core is arranged near the fiber surface so that the core can be easily arranged.

  The fineness of the composite fiber may be appropriately set depending on various uses, and is not particularly limited. However, when used as a nonwoven material for battery separator, the electrolyte retainability, the positive electrode and the negative electrode are constituted. It is preferably 0.1 to 5 denier in order to prevent metal precipitation and to prevent short circuit due to movement of the electrode active material. The fiber cross section may be a circular cross section or an irregular cross section. In the case of an irregular cross section, the fiber diameter is a value converted to a circular cross section. Further, the fiber length is not particularly limited, but can be appropriately set depending on the method of forming the nonwoven fabric. For example, when forming a nonwoven fabric by a wet method, it is preferable that it is 1-30 mm, and when forming a nonwoven fabric by dry methods, such as a card method and an air method, it is preferable that it is 10-70 mm.

  In the present invention, a nonwoven fabric can be prepared using the above-described composite fiber as a main fiber, and can be used as a battery separator. The composite fiber is preferably 50% by weight or more in the nonwoven fabric, and particularly preferably 70% by weight or more so that the electrolyte solution of the battery separator is excellent in liquid retention.

  The fibers other than the above-mentioned composite fibers include general-purpose aliphatic polyamides such as nylon 6 and nylon 66; ethylene-vinyl alcohol copolymers, polypropylene, polyethylene, polybutene, polymethylpentene, ethylene-propylene copolymers. , Polyolefin resin such as ethylene-butene copolymer alone or a composite fiber composed of these two types; cellulose fiber obtained by merging natural cellulose fiber; Can be mentioned.

  The nonwoven fabric concerning this invention can be obtained with arbitrary manufacturing methods. First, a fiber web (before entanglement or bonding of the nonwoven fabric) is formed, and a nonwoven fabric can be produced by bonding or entanglement of the composite fibers in the fiber web. The obtained nonwoven fabric may be used as it is or may be used as a laminate of a plurality of sheets. At this time, the composite fiber may be fibrillated to form a nonwoven fabric, or the nonwoven fabric may be fibrillated after the nonwoven fabric. By making the composite fiber into a fibril fiber, liquid retention as a battery separator can be remarkably improved by capillary action, and the strength of the battery separator (nonwoven fabric) can be remarkably improved by entanglement of the fibril fibers with each other. .

  Examples of the fibrillation include a method of fibrillating fibers by water flow or air flow, a method of fibrillating fibers by friction, a method of using a beating machine, a method of extracting and removing a thermoplastic polymer with a solvent, and the like. Among these, the method of fibrillation with a water stream or an air stream can be performed even after the nonwoven fabric is formed, and at the same time, the fibers can be entangled.

  Examples of fiber web forming methods include dry methods such as card method and air array method, wet methods such as paper making method, spunbond method, and melt blow method. Among these, the wet method and melt blow method can be used. The resulting fiber web has a dense and uniform surface state, and when used as a separator for a battery, it is possible to prevent metal deposition and migration of the electrode active material, which is a preferred method for forming a fiber web. Further, the fiber webs formed by the above methods can be combined and used.

  Each method will be specifically described. The fiber web can be formed by a dry method using a roller card, a random card, a weber, or the like. The web can be formed into a parallel web, a cross web, or a cross cloth depending on the direction of the fiber. Although it is classified into a web, a semi-random web, and a random web, in the composite fiber according to the present invention, when the fiber itself has thermal adhesiveness, a binder fiber is not required, and therefore there is no worry about unevenness at the time of blending. .

  Examples of a method for forming a nonwoven fabric from such a fiber web include, for example, a method in which a fiber web is entangled by the action of a water stream or a needle, a method in which the fiber web is bonded, and a method in which the web is sewn in a vertical mesh shape with sewing threads. These methods can be used alone or in combination. Among them, the method of entanglement by the action of water flow or needle is preferable because the composite fiber can be fibrillated during the entanglement.

  A paper web method is generally used to form a fiber web by a wet method, but such a method has a higher production speed than other methods, and fibers of different diameters and multiple types of fibers can be used at an arbitrary ratio in the same apparatus. There is an advantage that can be mixed. In other words, the fiber form has a wide range of choices such as staple and pulp, and the usable fiber diameter can be used from ultra-fine fibers to thick fibers, so that a web with good formation can be obtained. It is done. In this method, first, the fiber obtained by melt spinning is cut and dispersed in water to form a uniform papermaking slurry under gentle stirring. Paper making using a paper machine having at least one of the wires. Further, the wet paper obtained in this way or the paper after drying may be entangled by applying a water stream to a single sheet or a laminated sheet. The cut fiber may be made into a papermaking slurry after being beaten with a beater or a refiner, and a sticking agent, a splitting agent or the like may be added during papermaking. In this case, paper is made after the fibers are fibrillated, which is suitable as a nonwoven fabric for battery separators.

  In the case of forming a non-woven fabric that does not contain 100% of the above-mentioned composite fiber and substantially does not contain an adhesive or other fibers, a high-temperature air stream is ejected from the surroundings while melt spinning, and the fibers are fibrillated. The meltblowing method that accumulates in the substrate is preferred. In addition, a spunbond method in which a thinning-stretching-web forming process is directly connected while cooling the spun fiber can be used. The stretching method may be air jet or roller. It can be performed by a forced charging method, a collision diffusion method, an airflow diffusion method, or the like.

  The surface of the nonwoven fabric formed by such a method is subjected to thermal calendering on the entire nonwoven fabric surface or partially to improve surface smoothness, adjust the thickness of the nonwoven fabric, develop strength, increase density, etc. It is preferable.

  In the melt blow method, the polyamide and the thermoplastic polymer constituting the above-mentioned composite fiber can be blown from a die of an extruder onto an integrated screen with a high-speed air flow and entangled to form a web. At the time of collection, when a polyolefin that is a heat-adhesive component is used as a thermoplastic polymer, it is bonded, but it must also be calendered to provide web strength and surface smoothness. Is preferred.

  In addition to the above, it is also possible to form a non-woven fabric by using a fiber film method with a split film method or a foam film method.

  Although the conjugate fiber of the present invention can be applied to various uses, it can be used as a nonwoven fabric for battery separators. This battery may be an open type or a sealed type, and the shape may be cylindrical, flat, or square. More specifically, alkaline manganese batteries, mercury batteries, silver oxide batteries, lead storage batteries, primary batteries such as air batteries, nickel-cadmium batteries, silver-zinc batteries, silver-cadmium batteries, nickel-zinc batteries, nickel-hydrogen batteries. It can be suitably used as a nonwoven fabric for separators of secondary batteries such as lithium ion secondary batteries. In addition to non-woven fabric for battery separators, it is also useful as an air filter or liquid filter.

EXAMPLES Hereinafter, although an Example explains this invention in full detail, this invention is not limited at all by these Examples. In addition, each measured value in an Example is a value measured with the following method.
(1) Basis weight of nonwoven fabric (g / m ² )
In accordance with JIS P 8124, the nonwoven fabric was cut into a 10 cm square, and its weight W was measured with an electronic balance (AE 160 type, manufactured by METRA), and calculated by W / 0.01.
(2) Non-woven fabric strength / breaking length (km)
In accordance with JIS P 8113, the strength (kg / 15 mm) was measured using a test piece obtained by cutting a nonwoven fabric into 15 mm × 250 mm, and the breaking length was calculated.
(3) Air permeability (cc / m ² / sec)
In accordance with JIS L 1096, the nonwoven fabric was cut into a 20 cm square to obtain a test piece, and the amount of air passing through the test piece was determined using a fragile type tester.

(4) Alkali resistance According to JIS P8113, the test piece of the nonwoven fabric was immersed in a 10% aqueous sodium hydroxide solution at 70 ° C. for 60 hours. The strength (kg / 15 mm) of the test piece before and after the treatment was measured and expressed by its strength retention.
(5) Resistance to oxidation deterioration According to JIS P 8113, a nonwoven fabric test piece was immersed in a mixed solution of 5% KMnO ₄ and 30% potassium hydroxide (the former / the latter = 250/50 cc, 50 ° C.) for 1 hour. . The strength (kg / 15 mm) of the test piece before and after the treatment was measured and expressed by its strength retention.
(6) Electrolyte solution retention property A test piece obtained by cutting a nonwoven fabric into 5 cm squares was immersed in a 30% potassium hydroxide solution at 20 ° C. for 30 minutes, and liquid was removed by natural dropping in air for 30 seconds. The weight of the test piece before treatment was W ₀ , the weight of the test piece after treatment was W ₁ , and the weight ratio (W ₁ / W ₀ ) was calculated as the total liquid absorption (g / g).
(7) Acid resistance According to JIS P8113, the nonwoven fabric test piece was immersed in a 10% sulfuric acid aqueous solution at 70 ° C. for 100 hours. The strength (kg / 15 mm) of the test piece before and after the treatment was measured and expressed by its strength retention.

Reference Examples 1 to 7 In the amounts shown in Table 1, terephthalic acid, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, benzoic acid, sodium hypophosphite-hydrate (0. 1 wt%) and 2.2 liters of distilled water were added to an autoclave having an internal volume of 20 liters to perform nitrogen substitution. Subsequently, the mixture was stirred at 100 ° C. for 30 minutes, and the internal temperature was raised to 210 ° C. over 2 hours. At this time, the autoclave was pressurized to 22 kg / cm ² . The reaction was continued for 1 hour, then the temperature was raised to 230 ° C., and then maintained at 230 ° C. for 2 hours. The reaction was continued while gradually removing water vapor and maintaining the pressure at 22 kg / cm ² . Next, the pressure was reduced to 10 kg / cm ² over 30 minutes, and the reaction was continued for another hour to obtain a prepolymer. The prepolymer was dried at 100 ° C. under reduced pressure for 12 hours and pulverized to a size of 2 mm or less. The pulverized product was subjected to solid phase polymerization at 230 ° C. and 0.1 mmHg for 10 hours to obtain a polymer. Table 1 shows the intrinsic viscosity of the obtained polymer.

Examples 1-7
Spinning temperature and discharge amount ratio shown in Table 2 for the polyamides and polypropylenes (Ube Industries, Ltd .: UBE Polypro) obtained in Reference Examples 1 to 7 using two extruders. Polyamide: polypropylene = 1: 1 (weight ratio) ) And discharged from a 0.3 mmφ × 200 hole composite nozzle to obtain a side-by-side type composite fiber. Subsequently, a one-stage stretching / shrinking treatment was performed using a water bath of 85 ° C. for one bath and 95 ° C. for two baths to obtain a tow of about 300 denier / 100 filaments. The draw ratio was 0.8 times the maximum draw ratio. The obtained tow was crimped to a number of crimps of 10 pieces / inch and cut into a length of 51 mm to form a cotton. A non-woven fabric in which this cotton is made into a web shape using a roller card and embossed by an embossing calendering apparatus set at a roll temperature of 150 ° C. and a crimping area of 15%, and a part of the fibers are bonded. Obtained. Battery separators were prepared from these nonwoven fabrics, and these separators (nonwoven fabrics) were evaluated. The results are shown in Table 2.

Examples 8-14
The polyamides obtained in Reference Examples 1 to 7 and polypropylene (Ube Industries, Ltd .: UBE Polypro) were mixed at a weight ratio of 7: 3 and melt-kneaded using an extruder. It was discharged from a 3 mmφ × 100 hole composite nozzle to obtain 900 denier / 100 filament sea-island type composite fiber. The composite form was a composite form in which polypropylene islands existed in the sea component of polyamide. The obtained spinning yarn was stretched at a magnification of 3 times in a 90 ° C. water bath to obtain a 300 denier / 100 filament tow. The tow was crimped with a number of crimps of 10 pieces / inch, cut into 51 mm, and formed into cotton. The cotton was made into a web using a roller card, fibrillated and hydroentangled with a water flow having a pressure of 80 kg / cm ² , and then calendered at a roll temperature of 150 ° C. to obtain a nonwoven fabric. Battery separators were prepared from these nonwoven fabrics, and these separators (nonwoven fabrics) were evaluated. The results are shown in Table 3.

Example 15
In Example 11, a non-woven fabric was obtained in the same manner as in Example 11 except that nylon 6 (manufactured by Ube Industries, Ltd .: UBE nylon 1013BK) was used instead of polypropylene, and the calendar temperature was changed to 180 ° C. A battery separator was prepared. This separator was evaluated and the results are shown in Table 4.

Example 16
In Example 11, a non-woven fabric was used in the same manner except that polyethylene [manufactured by Diapolymer Co., Ltd .: Mitsubishi Polyethylene HD HJ490] was used instead of polypropylene and heat bonding was performed with a hot air dryer at 140 ° C. instead of calendering. A battery separator was prepared. This separator was evaluated and the results are shown in Table 4.

Example 17
The polyamide obtained in Reference Example 4 and polypropylene were mixed at a ratio of 6: 4 (weight ratio), melted and kneaded with an extruder, and led to the sheath side of the spinning head. On the other hand, the polyamide obtained in Reference Example 4 was separated. Was led to the core side of the spinning head and discharged simultaneously from the die to obtain a core-sheath type composite fiber. The cross-sectional form of the composite fiber was a cross-sectional form composed of a sheath part having a sea-island structure in which island-like polypropylene is present in the sea-like polyamide and a core part of the polyamide. A nonwoven fabric was prepared from this composite fiber in the same manner as in Example 11 to obtain a battery separator. This separator was evaluated and the results are shown in Table 4.

Examples 18-19
In Example 11, the polyamide and polypropylene were melt-kneaded with separate melt extruders and led to a spinning head, and these polymers were simultaneously spun using a specially-shaped spinneret to form a radial laminating die (Example 18). A multilayer laminated type (Example 19) composite fiber was obtained. Using these conjugate fibers, a nonwoven fabric was obtained in the same manner as in Example 11 to prepare a battery separator. These separators were evaluated and the results are shown in Table 4.

Example 20
A composite fiber and a non-woven fabric were obtained in the same manner as in Example 18 except that a random composite form using a static mixing element was used as the composite form, and a battery separator was prepared. This separator was evaluated and the results are shown in Table 4.

Example 21
The tow obtained in the same manner as in Example 11 was cut into 5 mm, and the composite fiber was fibrillated using a single disc refiner to obtain a pulp-like product. On the other hand, the polyamide obtained in Reference Example 4 was spun at 310 ° C., and stretched 3 times in a 90 ° C. water bath to obtain 300 denier / 100 filament fibers. This fiber was cut into 5 mm to obtain a cut fiber. The above pulp-like material 70% by weight and cut fiber 30% by weight were disaggregated with a standard disaggregator, and a handsheet having a basis weight of 70 g / m ² was obtained with a test paper machine. This sheet was put into a 190 ° C. hot air dryer and the heat-fusible component polypropylene was melted and subjected to an adhesion treatment to prepare a nonwoven fabric. A battery separator was prepared using this nonwoven fabric and evaluated. The results are shown in Table 4.

Example 22
In Example 11, polyamide and polypropylene were mixed at a weight ratio of 7: 3, put into an extruder, melt-kneaded, and using a 0.45 × 300H rectangular nozzle, a nozzle temperature of 330 ° C., an air temperature of 350 ° C., A nonwoven fabric was prepared by the melt blow method at an air pressure of 2.7 kg / cm ² . The nonwoven fabric was fibrillated with a water flow having a pressure of 80 kg / cm ² and then calendered at 150 ° C. A battery separator was prepared from the treated non-woven fabric and evaluated. The results are shown in Table 4.

Comparative Example 1
A composite fiber and a nonwoven fabric were prepared in the same manner as in Example 1 except that nylon 6 (Ube Industries, Ltd .: UBE nylon 6) obtained by ring-opening polymerization of caprolactam was used as polyamide. A battery separator was prepared from the nonwoven fabric, and the separator was evaluated. The results are shown in Table 5. As is apparent from the results in Table 5, although the alkali resistance and the electrolyte solution retention were excellent, the oxidation degradation resistance was low.

Comparative Example 2
A composite fiber and a non-woven fabric were prepared in the same manner as in Example 11 except that nylon 6 (Ube Industries, Ltd .: UBE nylon 6) obtained by ring-opening polymerization of caprolactam was used as polyamide. A battery separator was prepared from this nonwoven fabric, and the separator was evaluated. The results are shown in Table 5. As is apparent from the results in Table 5, although the alkali resistance and the electrolyte solution retention were excellent, the oxidation degradation resistance was low.

Comparative Example 3
In the same manner as in Example 1 except that nylon 66 composed of hexamethylenediamine (aliphatic diamine) and adipic acid (aliphatic dicarboxylic acid) was used as polyamide (UBE Nylon 66: UBE nylon 66), A non-woven fabric was created. A battery separator was prepared from the nonwoven fabric, the separator was evaluated, and the results are shown in Table 5. As is apparent from the results in Table 5, although the alkali resistance and the electrolyte solution retention were excellent, the oxidation degradation resistance was low.

Comparative Example 4
In the same manner as in Example 11, except that nylon 66 composed of hexamethylenediamine (aliphatic diamine) and adipic acid (aliphatic dicarboxylic acid) was used as the polyamide, UBE nylon 66 was used. A non-woven fabric was created. A battery separator was prepared from the nonwoven fabric, the separator was evaluated, and the results are shown in Table 5. As is apparent from the results in Table 5, although the alkali resistance and the electrolyte solution retention were excellent, the oxidation degradation resistance was low.

Comparative Example 5
A composite fiber was obtained in the same manner as in Example 1 except that a polyamide (metabolized by Mitsubishi Gas Chemical Co., Inc .: MX nylon 6007) composed of metaxylylenediamine (aromatic diamine) and adipic acid (aliphatic dicarboxylic acid) was used as the polyamide.・ Nonwoven fabric was created. A battery separator was prepared using this nonwoven fabric, and the separator was evaluated. The results are shown in Table 5. Polyamide is composed of aliphatic dicarboxylic acid, so the amide bond is structurally weak and the crystallinity is low, but in the oxidation resistance deterioration test, the polyamide is significantly oxidized and deteriorated in the test solution. Only a few pieces remained.

Comparative Example 6
A composite fiber was obtained in the same manner as in Example 11 except that a polyamide (metabolized by Mitsubishi Gas Chemical Co., Inc .: MX nylon 6007) composed of metaxylylenediamine (aromatic diamine) and adipic acid (aliphatic dicarboxylic acid) was used as the polyamide.・ Nonwoven fabric was created. A battery separator was prepared using this nonwoven fabric, and the separator was evaluated. The results are shown in Table 5. Polyamide is composed of aliphatic dicarboxylic acid, so the amide bond is structurally weak and the crystallinity is low, but in the oxidation resistance deterioration test, the polyamide is significantly oxidized and deteriorated in the test solution. Only a few pieces remained.

Comparative Example 7
Polypropylene (Ube Industries, Ltd .: UBE Polypro) was spun at a spinning head temperature of 200 ° C. and stretched 4 times at a water bath temperature of 80 ° C. to obtain 250 denier / 100 filament fibers. Using this fiber, a nonwoven fabric was obtained in the same manner as in Example 8 to prepare a battery separator. This separator was evaluated and the results are shown in Table 5. As is clear from the results in Table 5, the electrolytic solution retention was very low, although the alkali resistance and oxidation deterioration resistance were excellent.

Comparative Example 8
Nylon 6 (manufactured by Ube Industries Ltd .: UBE nylon 6) was spun at a spinning head temperature of 250 ° C. and stretched 4 times at a water bath temperature of 85 ° C. to obtain a fiber of 200 denier / 100 filament. Using this fiber, a nonwoven fabric was obtained in the same manner as in Example 8 to prepare a battery separator. This separator was evaluated and the results are shown in Table 5. As is apparent from the results in Table 5, although the alkali resistance and electrolyte solution retention were excellent, the oxidation degradation resistance was very low.

Claims (4)

  Dicarboxylic acid component in which 60 mol% or more of dicarboxylic acid component is aromatic dicarboxylic acid, and 60 mol% or more of diamine component is 1,9-nonanediamine or 1,9-nonanediamine and 2-methyl-1,8-octanediamine A composite fiber comprising a polyamide comprising a diamine component which is a combination of the above and a thermoplastic polymer incompatible with the polyamide.   2. The composite fiber according to claim 1, wherein the thermoplastic polymer is a heat-fusible component.   A non-woven fabric for a battery separator using at least 50% by weight of the conjugate fiber according to claim 2. Dicarboxylic acid component in which 60 mol% or more of dicarboxylic acid component is aromatic dicarboxylic acid, and 60 mol% or more of diamine component is 1,9-nonanediamine or 1,9-nonanediamine and 2-methyl-1,8-octanediamine A non-woven fabric for a battery separator using at least 50% by weight of a fibrillated fiber comprising a polyamide composed of a diamine component and a polyamide polymer incompatible with the polyamide.