JP2018048228A - Polyacetal-based resin oriented porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal-based resin oriented porous body using a polyacetal-based resin which has excellent air permeability, heat resistance and dimensional stability, has high liquid permeability when used as a separator for electronic member, and can be produced under high productivity.SOLUTION: A polyacetal-based resin oriented porous body is an oriented porous body having at least one porous layer formed of a resin composition which contains a polyacetal-based resin (A) as a main component and a styrenic thermoplastic elastomer (B) and a compatibilizer (C), where a mixed composition ratio of the polyacetal-based resin (A), the styrenic thermoplastic elastomer (B) and the compatibilizer (C) is a predetermined mixed composition ratio, and the compatibilizer (C) is a thermoplastic resin having a segment (x) having affinity with the polyacetal-based resin (A) and a segment (y) having affinity with the styrenic thermoplastic elastomer (B) in a molecular skeleton.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a porous body using a polyacetal resin. More specifically, for packaging, hygiene, livestock, agriculture, construction, medical, separation membrane, water treatment membrane, light diffusion plate, heat insulating material, buffer material, foam material for electronic member, separator for electronic member In particular, a foam material for printed circuit boards of electronic members such as tablet devices and smartphones, separators for electronic members such as batteries and capacitors, and polyacetals that can be suitably used for electronic members using the separators for electronic members The present invention relates to a porous body using a resin. The present invention also relates to an electronic member using this porous body.

  The polymer porous body having a large number of fine communication holes is a separation membrane used for production of ultrapure water, purification of chemicals, water treatment, etc., a waterproof and moisture permeable film used for clothing and sanitary materials, or an alkaline battery, It is used in various fields such as batteries used for nickel metal hydride batteries, lithium batteries, lithium ion secondary batteries, and separators used for electronic members such as electrolytic capacitors, electric double layer capacitors, and capacitors such as lithium ion capacitors.

  Among them, the secondary battery is widely used as a power source for portable devices such as OA, FA, household electric appliances, and communication devices. Portable equipment using lithium ion secondary batteries, which are a type of non-aqueous electrolyte secondary battery, is increasing because of its volumetric efficiency, especially when equipped in equipment, leading to smaller and lighter equipment. In recent years, research and development has been promoted in many fields related to energy / environmental problems, including road leveling, UPS, and electric vehicles, and the large size, high output, high voltage, and long-term storage stability make it large. Applications of lithium ion secondary batteries are also expanding.

  Capacitors such as electric double layer capacitors and lithium ion capacitors are smaller in charge capacity per time than secondary batteries, but have excellent instantaneous charge / discharge characteristics and no deterioration in charge / discharge characteristics. It is applied to auxiliary power supplies and storage of regenerative energy, and has become widespread in applications such as backup power supplies for electronically controlled brakes and idling stop backup applications in automobiles.

  An electric double layer capacitor is manufactured by sandwiching a separator between a pair of electrodes carrying activated carbon, carbon black or the like and impregnating them with an electrolyte. As an electrolytic solution used for the electric double layer capacitor, generally, an organic solvent such as propylene carbonate in which tetraethylammonium tetrafluoroborate, tetraethylphosphonium tetrafluoroborate or the like is dissolved is used.

  In a lithium ion capacitor or a lithium ion secondary battery, a nonaqueous electrolytic solution using an organic solvent is used as an electrolytic solution that can withstand a high voltage. As the solvent for the non-aqueous electrolyte, a high dielectric constant organic solvent capable of causing more lithium ions to be present is used, and as the high dielectric constant organic solvent, organic carbonate compounds such as propylene carbonate and ethylene carbonate are mainly used. Is used. As the supporting electrolyte serving as a lithium ion source in the solvent, a highly reactive electrolyte such as lithium hexafluorophosphate is used.

  In these electronic members, a separator is interposed between the positive electrode and the negative electrode from the viewpoint of preventing an internal short circuit. Of course, the separator is required to have insulating properties due to its role. Further, in recent electronic members, for example, lithium ion secondary batteries, the importance for safety is increasing as the capacity increases. In particular, when the electronic member is abnormally heated, there is a risk of causing further heat generation due to the film breakage of the separator or short-circuiting of both electrodes due to thermal contraction of the separator. Dimensional stability is one of the important required characteristics, and further improvement is required.

  Moreover, in these electronic members, since ions must move inside the separator and be able to move from one pole side to the other pole side, the inside must be filled with an electrolyte solution. It is. Therefore, the separator is required to have an affinity (immersion property) for the electrolytic solution. Furthermore, from the viewpoint of improving the productivity and quality of the electronic member, it is desired that the rate of penetration of the electrolyte into the separator is high.

  On the other hand, examples of a method for producing a polymer porous body having a large number of fine communication holes include a wet method and a dry method. As a wet method, for example, a polymer that does not dissolve a polymer material but dissolves a pore former in a solvent in which a sheet-like molded body obtained by mixing and dispersing a pore former and a polymer modifier in a polymer material is dissolved. A method for producing a porous sheet (Patent Document 1), or a porous hollow fiber in which a resin composition comprising a resin different from a polyacetal resin and a polyacetal resin is immersed in an alkaline aqueous solution to remove part or all of the resin different from the polyacetal resin A film manufacturing method (Patent Document 2) has been proposed.

  Examples of the dry method include a method for producing a microporous membrane obtained by biaxially stretching a non-porous precursor (Patent Document 3), and a fibrous shape obtained by stretching a film containing a semicrystalline polymer component and a void initiation component. A method for producing a film having a surface (Patent Document 4), and further a porous film (Patent Document 5) obtained by stretching a resin composition comprising a thermoplastic resin such as a polyolefin resin and a diene copolymer. Proposed.

  Further, in Patent Document 6, it was found that a stretched porous body made of a resin composition containing a polyacetal resin as a main component and containing a thermoplastic elastomer having a specific weight average molecular weight has a high affinity for an electrolytic solution. Has been.

JP 2004-277633 A JP 2013-39530 A JP 2009-527633 A Special Table 2002-544310 JP 2005-145998 A JP-A-2006-132740

  However, in the wet porosification methods such as Patent Documents 1 and 2, a large amount of a cleaning solvent is used and a process for removing other components is included. Therefore, equipment for recovering the cleaning solvent and additives is required. Reduce productivity significantly.

  In addition, the method for producing a microporous membrane as in Patent Document 3 includes a step of extruding a non-porous precursor and a step of biaxially stretching the non-porous precursor, and substantially both steps. During this period, a heat treatment step is required, and if the non-porous precursor is not sufficiently crystallized, porosity cannot be achieved, and a pre-process in stretching and porosification occurs, resulting in a significant reduction in productivity. Moreover, although polyacetal is mentioned as an example of the polymer used for the microporous membrane obtained by the said manufacturing method, there is no reference to the specific technical thought about it, or description of embodiment.

  Furthermore, in the porous method as in Patent Document 4, unless an appropriate void initiating component is selected, not only a poor appearance occurs in the porous film, but also stress due to stretching deformation is generated at the interface between the void initiating component and the base resin. It is difficult to transmit, or in the first place, depending on the resin, cracks do not occur at the interface, making it difficult to make the entire film uniformly porous. Moreover, although polyoxymethylene is mentioned as an example of a semi-crystalline polymer, there is no reference to a specific technical idea or description of the embodiment. Also, in the porous film described in Patent Document 5, a thermoplastic resin such as a polyolefin resin is used, but no illustration or mention is made regarding a polyacetal resin.

  In Patent Document 6, it has been found that it has excellent air permeability characteristics and high affinity for an electrolyte solution, but with the recent enhancement of productivity and quality requirements of electronic members, There is a demand for further improvement in the rate of penetration of the electrolytic solution into the separator and formation of a uniform porous structure.

  The present invention has been made in view of the above problems, has excellent air permeability and heat resistance, has high liquid immersion properties when used as a separator for electronic members, and is manufactured under high productivity. An object of the present invention is to provide a stretched porous body using a polyacetal-based resin that can be used, and an electronic member using the stretched porous body.

  As a result of intensive studies in view of the above problems, the present inventor has at least one porous layer made of a resin composition containing a polyacetal resin as a main component, a styrene thermoplastic elastomer, and a compatibilizer. And it discovered that the extending | stretching porous body which the said compatibilizing agent has a specific segment in molecular skeleton can solve said subject, and came to complete this invention.

That is, the gist of the present invention is as follows.
[1] Stretched porous body having at least one porous layer comprising a resin composition containing a polyacetal resin (A) as a main component and containing a styrene thermoplastic elastomer (B) and a compatibilizer (C). The mixed composition ratio of the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizer (C) is (A) / (B) / (C) = 45 mass% to 98 mass% / 1 mass% -45 mass% / 1 mass% -45 mass% (however, the total mass% of (A), (B) and (C) is 100 mass%), and the compatibilization The thermoplastic (C) has a segment (x) having an affinity for the polyacetal resin (A) and a segment (y) having an affinity for the styrene thermoplastic elastomer (B) in the molecular skeleton. Characterized by being a resin Polyacetal resin stretched porous body.
[2] The polyacetal resin according to [1], wherein the segment (y) contains at least one unit selected from the group consisting of polyolefin units, polystyrene units, and polyphenylene ether units. Stretched porous body.
[3] In the above [1] or [2], the segment (x) contains at least one unit selected from the group consisting of polyurethane-based units, polylactic acid-based units, and polyether-based units. The polyacetal resin stretched porous body according to the description.
[4] The crystal melting enthalpy (ΔHm) derived from the polyacetal resin (A) in differential scanning calorimetry (DSC) is from 10 J / g to 160 J / g [1] to [3 ] The polyacetal-type resin stretched porous body in any one of.
[5] The polyacetal resin stretched porous body according to any one of [1] to [4], wherein the styrene thermoplastic elastomer (B) has a weight average molecular weight (Mw) of 150,000 or more. .
[6] The melt flow rate (MFR) at a temperature of 230 ° C. and a load of 2.16 kg of the styrene-based thermoplastic elastomer (B) is 30 g / 10 min or less, according to [1] to [5] The polyacetal resin stretched porous body according to any one of the above.
[7] The polyacetal resin according to any one of [1] to [6], wherein the styrene thermoplastic elastomer (B) has a styrene content of 1% by mass to 55% by mass. Stretched porous body.
[8] An electronic member comprising the polyacetal resin stretched porous material according to any one of [1] to [7].

  According to the present invention, a stretched porous body using a polyacetal-based resin having a uniform porous structure, excellent air permeability, and heat resistance, particularly having high liquid immersion properties when used as a separator for an electronic member. Can be provided with high productivity.

It is the surface observation photograph of the porous film produced in Example 2 by the scanning electron microscope. It is the surface observation photograph of the porous film produced in Example 4 by the scanning electron microscope. It is the surface observation photograph of the porous film produced in Example 6 by the scanning electron microscope. It is a surface observation photograph of the porous film produced in the comparative example 2 by the scanning electron microscope.

  Hereinafter, a polyacetal resin stretched porous body (hereinafter also referred to as “the present porous body”) as an example of an embodiment of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiments described below. Here, the stretched porous body is a porous body that has been made porous by stretching in at least a uniaxial direction.

  Below, each component which comprises this porous body is demonstrated.

<Polyacetal resin (A)>
It is important that the resin composition constituting the porous body is mainly composed of the polyacetal resin (A). Here, the main component means a component occupying the largest mass ratio in the resin composition constituting the porous body, preferably 45% by mass or more, more preferably 50% by mass or more, and 55% by mass or more. Further preferred.
In the mixed resin of the polyacetal resin (A), a styrene thermoplastic elastomer (B) described later, and a compatibilizer (C) described later, the (A), the (B), and the (C )) Is 100 mass%, it is important that the composition ratio of the polyacetal resin (A) in the mixed resin is 45 mass% to 98 mass%.

  The polyacetal resin (A) used in the present invention is a resin having an oxymethylene unit as a main repeating unit. Here, a main repeating unit means the repeating unit contained in the ratio of 50 mol% or more among all the repeating units which comprise the said polyacetal type-resin (A). The upper limit of the ratio of the oxymethylene unit is not particularly limited, but the oxymethylene unit is preferably 99 mol% or less from the viewpoint of improving moldability and toughness, and from the viewpoint of improving the film strength due to high crystallinity. The methylene unit is preferably 70 mol% or more. Two or more kinds of polyacetal resins may be blended, and a soft component such as a polyurethane resin may be added to impart flexibility. Furthermore, a modified product of a polyacetal resin modified with a functional group such as an acid anhydride can also be used.

  The polyacetal resin (A) used in the present invention may be a homopolymer obtained by a polymerization reaction using formaldehyde or trioxane as a main raw material, and a copolymer composed of oxymethylene units and structural units other than oxymethylene units, That is, any of a block copolymer, a terpolymer, a graft polymer, and a crosslinked polymer may be used. Examples of structural units other than oxymethylene units include oxyalkylene units having 2 or more carbon atoms.

  The oxyalkylene group having 2 or more carbon atoms only needs to have 2 or more carbon atoms. Examples of such oxyalkylene groups having 2 or more carbon atoms include oxyethylene groups, oxypropylene groups, oxybutylene groups, oxy Examples thereof include a pentene group, an oxyhexene group, an oxyheptene group, and an oxyoctene group. Among these, an oxyethylene group having 2 carbon atoms is preferable in order to balance thermal stability and strength.

  There is no restriction | limiting in particular in the manufacturing method of the said polyacetal type resin (A) used for this invention, It can manufacture by a well-known method. As an example of a typical method for producing a polyacetal homopolymer, high-purity formaldehyde is introduced into an organic solvent containing a basic polymerization catalyst such as an organic amine, an organic or inorganic tin compound, or a metal hydroxide. Examples of the method include polymerizing and filtering the polymer, followed by heating in acetic anhydride in the presence of sodium acetate to acetylate the polymer terminal.

  In addition, as a preferable example of another production method, a high purity trioxane and a copolymer component such as cyclic formal or cyclic ether are introduced into an organic solvent such as cyclohexane, and a boron trifluoride diethyl ether complex or the like is introduced. After cationic polymerization using a Lewis acid catalyst, trioxane, a copolymer component, a production method by deactivating the catalyst and stabilizing the end group, or without using any solvent, And a method in which the catalyst is introduced and bulk polymerization is performed, and then the unstable terminal is further decomposed and removed. Specific examples of the cyclic formal used as a copolymerization component include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, 1, Specific examples of the cyclic ether include, for example, ethylene oxide, propylene oxide, butylene oxide, 1,3-dioxabicyclo [3,4,0] nonane, epichlorohydrin, styrene oxide, oxytane, 3 , 3-bis (chloromethyl) oxetane, tetrahydrofuran, oxepane and the like.

The melt flow rate (MFR) of the polyacetal resin (A) is not particularly limited, but it is usually preferable that the MFR at a temperature of 190 ° C. and a load of 2.16 kg is 0.03 to 60 g / 10 min. More preferably, it is 0.3-30 g / 10min. If the MFR is in the above range, the back pressure of the extruder does not become too high during the molding process and the productivity is excellent.
The MFR of the polyacetal resin (A) is measured based on JIS K7210-1 (2014).

  The melting point of the polyacetal-based resin (A) can be determined according to the monomer ratio to be constituted, but the viewpoint of heat resistance required when the porous body is used as a separator for electronic members. Therefore, 140 ° C. or higher is preferable, 150 ° C. or higher is more preferable, and 160 ° C. or higher is more preferable.

  Examples of the polyacetal resin (A) include “Iupital” (registered trademark) (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), “Duracon” (registered trademark) (manufactured by Polyplastics Co., Ltd.), “Tenac” ( (Registered trademark) (manufactured by Asahi Kasei Corporation), "Ecotar" (registered trademark) (manufactured by Intertec Corporation), "Derlin" (registered trademark) (manufactured by DuPont), "KOCETAL" (registered trademark) (Toray International Corporation) Commercially available products such as a company) can be used.

<Styrenic thermoplastic elastomer (B)>
The present porous body is composed of a resin composition containing a polyacetal resin (A) as a main component and a styrene thermoplastic elastomer (B) and a compatibilizer (C), and the polyacetal resin (A ), The styrene-based thermoplastic elastomer (B), and the compatibilizer (C) described later, the total mass% of the (A), the (B), and the (C) is 100 mass. %, The composition ratio of the styrenic thermoplastic elastomer (B) in the mixed resin is important to be 1% by mass to 45% by mass.

Moreover, it is preferable that the weight average molecular weight (Mw) of the said styrene-type thermoplastic elastomer (B) is 150,000 or more. The weight average molecular weight (Mw) of the styrenic thermoplastic elastomer (B) is more preferably 160,000 or more and 1,000,000 or less, further preferably 170,000 or more and 800,000 or less, and 180,000 or more. 600,000 or less is particularly preferable.
The ratio (molecular weight distribution) Mw / Mn of the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the styrenic thermoplastic elastomer (B) is preferably 1.00 or more and 1.50 or less. 00 or more and 1.30 or less are more preferable, and 1.00 or more and 1.10 or less are more preferable.

  The reason why the weight average molecular weight (Mw) of the styrenic thermoplastic elastomer (B) is preferably 150,000 or more is that the polyacetal resin (A) is a main component and the styrenic thermoplastic elastomer. (B) and the polyacetal-based resin (A) in the resin composition before stretching when the layer composed of a resin composition containing the compatibilizer (C) described below is at least uniaxially stretched to be porous. The styrenic thermoplastic elastomer (B) is likely to be present in the form of particles with respect to the matrix mainly composed of, so that a good porous body can be obtained.

Generally, when a resin composition having a matrix / domain sea-island structure is melt-extruded and cooled and solidified, the resin composition that is extruded from a shaping equipment such as a die or a nozzle is flown into a cast roll (cooling roll) or air-cooled, Cool and solidify with cooling and solidification equipment such as water cooling. At that time, since the resin composition melts and extends in a gap between the shaping equipment and the cooling and solidification equipment, the domain flows when the weight average molecular weight Mw of the styrene thermoplastic elastomer (B) as the domain is small. It is easy to obtain a resin composition elongated in the direction (extrusion direction).
When stretching a resin composition in which this domain extends in the flow direction (extrusion direction), the stress imparted by deformation is easily applied uniformly to the entire resin composition, preventing stress concentration at the matrix / domain interface. Cheap. This is because the cross-sectional area of the interface that receives the stress is small because the domain has been previously extended.

  On the other hand, when the weight average molecular weight Mw of the domain is large, the domain is not easily affected by the melt elongation, and the domain in the resin composition before stretching obtained is easily maintained in the form of particles. Therefore, when the obtained resin composition is stretched, stress applied by deformation tends to concentrate on the interface of the matrix / domain, and the cross-sectional area of the interface that receives the stress also increases, so that interface peeling is likely to occur. As a result, it becomes easy to form a uniform porous structure.

  Further, when the weight average molecular weight Mw of the styrene-based thermoplastic elastomer (B) is smaller than 150,000, the styrene-based thermoplastic elastomer (B) is likely to bleed out from the resulting porous body, and as a result, deterioration with time is caused. Easy to be promoted.

  Further, when the ratio (molecular weight distribution) Mw / Mn of the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the styrene-based thermoplastic elastomer (B) is within the above preferred range, the dispersed diameter of the formed domain is uniform. Since it is easy to become, it is preferable.

  In the present invention, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the styrenic thermoplastic elastomer (B) are based on JIS K7252-1 (2008), and gel permeation chromatography (GPC). The value in terms of polystyrene measured using is specifically, measured and calculated by the method described in the Examples section below.

  Further, the melt flow rate (MFR) at a temperature of 230 ° C. and a load of 2.16 kg of the styrenic thermoplastic elastomer (B) is preferably 30 g / 10 min or less, more preferably 10 g / 10 min or less, and 5 g / 10 min. The following is more preferable, 1 g / 10 min or less is further preferable, and it is most preferable not to flow.

As described above, at least a uniaxial layer composed of the resin composition containing the polyacetal resin (A) as a main component and containing the styrene thermoplastic elastomer (B) and a compatibilizer (C) described later. It is uniform that the styrene-based thermoplastic elastomer (B) existing as a domain is present in the form of particles with respect to the matrix mainly composed of the polyacetal-based resin (A) when stretched in the direction and made porous. It is preferable for obtaining a porous body having a porous structure and excellent air permeability.
Therefore, when the MFR at a temperature of 230 ° C. and a load of 2.16 kg of the styrene-based thermoplastic elastomer (B) is 30 g / 10 minutes or less, the styrene-based thermoplastic elastomer (B) as a domain flows in the flow direction (extrusion direction). It is preferable that the domain in the resin composition before being stretched is easy to maintain a particle shape.
The MFR of the styrenic thermoplastic elastomer (B) is measured based on JIS K7210-1 (2014).

The styrene content of the styrenic thermoplastic elastomer (B) is preferably 1% by mass or more and 55% by mass or less. The styrene content of the styrenic thermoplastic elastomer (B) is more preferably 2% by mass to 50% by mass, further preferably 3% by mass to 45% by mass, and most preferably 5% by mass to 40% by mass. .
In addition, the styrene content of the styrene-based thermoplastic elastomer (B) is a structural unit derived from styrene in all the structural units (structural units derived from all raw material monomers) constituting the styrene-based thermoplastic elastomer (B). It is a ratio and is determined by composition analysis using a nuclear magnetic resonance apparatus (NMR).

The reason why the styrene content of the styrenic thermoplastic elastomer (B) is preferably 1% by mass or more and 55% by mass or less is that the polyacetal resin (A) is a main component and the styrenic heat When the layer made of the resin composition containing the plastic elastomer (B) and the compatibilizer (C) to be described later is stretched at least in a uniaxial direction to make it porous, the polyacetal-based resin in the resin composition before stretching ( This is because when the difference in elastic modulus between A) and the styrene-based thermoplastic elastomer (B) is increased, a porous body having a uniform porous structure and excellent air permeability can be obtained.
Specifically, after the resin composition having a sea-island structure in which the styrene-based thermoplastic elastomer (B) is a domain is melt-extruded to the matrix mainly composed of the polyacetal-based resin (A), and cooled and solidified, When a porous structure is formed by stretching in at least one direction, stress is concentrated on the matrix / domain interface to cause dissociation at the matrix / domain interface, which becomes the starting point of the porosity. However, when the elastic modulus of the domain is high, the difference in elastic modulus between the matrix / domain becomes small, so that the stress applied by the deformation is easily applied to the entire composition, and the stress concentration at the interface of the matrix / domain is reduced. Hinder. Since the styrene content contained in the styrene thermoplastic elastomer (B) which is a domain greatly contributes to the elastic modulus of the styrene thermoplastic elastomer (B), the styrene content of the styrene thermoplastic elastomer (B) is 1. In the case of mass% or more and 55 mass% or less, when the obtained resin composition is stretched, the stress imparted by the deformation is easily concentrated on the interface of the matrix / domain, and interface peeling is likely to occur, and uniform. It is preferable because a porous structure can be formed.

  Examples of the styrenic thermoplastic elastomer (B) include styrene-butadiene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, and styrene-ethylene-propylene copolymer. Polymer, styrene-isoprene-styrene copolymer, styrene-ethylene- (ethylene-propylene) -styrene copolymer, styrene-isobutylene-styrene copolymer, and modified products thereof, hydrogenated products, and side chains A graft copolymer having a styrene structure, a core-shell type multilayer rubber having a styrene structure in the shell, and the like can be suitably used, and two or more kinds of blends may be used. Of these, styrene-ethylene-butylene-styrene copolymers, styrene-ethylene-propylene-styrene copolymers, styrene-ethylene- (ethylene-propylene) -styrene copolymers, and the like are preferable.

  In the resin composition which comprises this porous body, only 1 type of said styrene-type thermoplastic elastomer (B) may be contained, and 2 or more types may be contained.

<Compatibilizer (C)>
This porous body is composed of a resin composition containing a polyacetal resin (A) as a main component and also containing a styrene thermoplastic elastomer (B) and a compatibilizer (C), and the compatibilizer (C ) Is a thermoplastic resin having a segment (x) having affinity for the polyacetal resin (A) and a segment (y) having affinity for the styrene thermoplastic elastomer (B) in the molecular skeleton. This is very important.
In the mixed resin of the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizer (C), the (A), the (B), and the (C) It is important that the composition ratio of the compatibilizing agent (C) in the mixed resin is 1% by mass to 45% by mass when the total mass% is 100% by mass.

  It is the most important point in the present invention that the composition and content of the compatibilizer (C) are selected within the range defined by the present invention. This is because the compatibilizer (C) has a role of improving the compatibility between the polyacetal resin (A) and the styrene thermoplastic elastomer (B).

As described above, a resin composition having a sea-island structure formed from a domain composed of the styrene-based thermoplastic elastomer (B) is melt-extruded to a matrix mainly composed of the polyacetal-based resin (A), and then cooled and solidified. Then, when forming a porous structure by stretching in at least one direction, stress is concentrated on the matrix / domain interface to cause dissociation at the matrix / domain interface, which becomes the starting point of the porosity.
At this time, by applying the composition and content of the compatibilizing agent (C) within the range defined by the present invention, the domain styrene-based thermoplastic elastomer (B) can be uniformly dispersed and refined. It becomes.
This is because the compatibilizer (C) is composed of a segment (x) having affinity for the polyacetal resin (A) and a segment (y) having affinity for the styrene thermoplastic elastomer (B). This is because the compatibilizer (C) promotes the affinity between the polyacetal resin (A) and the styrene thermoplastic elastomer (B) because it is contained in the skeleton.
Therefore, it is important to apply the composition and content of the compatibilizer (C) within the range defined by the present invention.

  The compatibilizer (C) has a molecular skeleton comprising a segment (x) having affinity for the polyacetal resin (A) and a segment (y) having affinity for the styrene thermoplastic elastomer (B). The phase between the polyacetal resin (A) and the styrenic thermoplastic elastomer (B) is a random copolymer or / and a block copolymer or / and a graft copolymer. It is preferable from the viewpoint of improving the solubility.

In the compatibilizer (C), the mass ratio of the segment (x) having an affinity for the polyacetal resin (A) and the segment (y) having an affinity for the styrene thermoplastic elastomer (B) is as follows: (X) :( y) = 3: 97 to 97: 3 is preferable, (x) :( y) = 5: 95 to 95: 5 is more preferable, and (x) : (Y) = 10: 90 to 90:10 is particularly preferable.
(X): (y) = 3: 97 to 97: 3, so that the compatibilizer (C) is compatible with the polyacetal resin (A) and the styrene thermoplastic elastomer (B). To improve.

  In the compatibilizer (C), the segment (x) having an affinity for the polyacetal resin (A) is at least one selected from the group consisting of polyurethane units, polylactic acid units, and polyether units. It is preferable to contain a known thermoplastic resin unit that is compatible with the unit and the polyacetal resin. Especially, since it has a high affinity for the polyacetal resin (A), it may contain at least one unit selected from the group consisting of polyurethane units, polylactic acid units, and polyether units. preferable.

  The polyurethane unit is a polymer unit in which an isocyanate and a polyol are bonded by a urethane bond. Moreover, the copolymer unit which uses as a repeating unit the hard segment which the isocyanate and the chain extension agent couple | bonded by the urethane bond, and the soft segment which the isocyanate and polyol couple | bonded by the urethane bond is mentioned. These polymer units can be used alone or in combination of two or more.

  Examples of the isocyanate component constituting the polyurethane unit include 1,6-hexamethylene diisocyanate (HDI) 2,2,4-trimethylenehexamethylene diisocyanate, lysine methyl ester diisocyanate, methylene diisocyanate, isopropylene diisocyanate, and lysine diisocyanate. Aliphatic isocyanates such as 1,5-octylene diisocyanate and dimer acid diisocyanate; 4,4′-dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicthexyl Alicyclic isocyanates such as -4,4'-diisocyanate; 2,4- or 2,6-tri Diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), xylene diisocyanate (XDI), triphenylmethane triisocyanate, tris (4-phenylisocyanate) thiophosphate, Examples include aromatic isocyanates such as tolidine diisocyanate, p-phenylene diisocyanate, diphenyl ether diisocyanate, and diphenylsulfone diisocyanate.

  Examples of the polyol component constituting the polyurethane unit include polyester polyol, polyester ether polyol, polyether polyol, and polycarbonate polyol.

  Examples of the polyester polyol include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid, aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, hexahydrophthalic acid, hexa Examples thereof include alicyclic dicarboxylic acids such as hydroterephthalic acid and hexahydroisophthalic acid. Examples thereof also include ester compounds of dicarboxylic acids or polyester polyols obtained by condensation reaction between acid anhydrides and diols, and polylactone diols obtained by ring-opening polymerization of lactone monomers such as ε-caprolactone. Examples of the diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl- 1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,4-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8 -Octanediol, 1,9-nonanediol, 2,2-dimethylolheptane and the like may be mentioned, and these may be used in combination of two or more.

  In addition, as the polyester ether-based polyol, the aliphatic dicarboxylic acid, the aromatic dicarboxylic acid, the aliphatic dicarboxylic acid, and an ester compound thereof, or an acid anhydride, glycols such as diethylene glycol, propylene oxide adduct, etc. Or the condensation reaction material with these mixtures, etc. are mentioned.

  Examples of the polyether-based polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymerized polyethers thereof obtained by polymerizing cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran. .

  Polycarbonate polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl- 1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,4-pentanediol, neopentyl glycol, 1,3-octanediol, 1,9 -Polycarbonate polyols obtained by reacting one or more polyhydric alcohols such as nonanediol, 2,2-dimethylolheptane, diethylene glycol and the like with ethylene carbonate, diethyl carbonate and the like. Further, it may be a copolymer of polycaprolactone polyol and polyhexamethylene carbonate.

  Further, as the chain extender component constituting the polyurethane unit, a low molecular weight polyol is used. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1, 4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,4-pentane Aliphatic acids such as diol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, 2,2-dimethylolheptane, diethylene glycol, 1,4-cyclohexanedimethanol, glycerol Polyol; 1,4-dimethylolbenzene, bisphenol A, bisphenol A Aromatic glycol such as Chi alkylene oxide adducts or propylene oxide adducts.

  The polylactic acid unit is a homopolymer unit of D-lactic acid or L-lactic acid, or a copolymer unit thereof, specifically, poly (D-lactic acid) whose structural unit is D-lactic acid, There are poly (L-lactic acid) whose structural unit is L-lactic acid, and poly (DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid. The polymer unit of the said several copolymer from which copolymerization ratio differs can use single or 2 types or more.

  Examples of the polyether unit include polymer units obtained by polymerization reaction using formaldehyde or trioxane as a main raw material, and polymer units obtained by polymerizing cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran. Specific examples of the structural unit include polyalkyl oxides such as polyacetal, polyethylene oxide, polypropylene oxide, and polytetramethylene glycol, and copolymerized polyethers thereof. These polymer units can be used alone or in combination of two or more.

  In the compatibilizer (C), the segment (y) having an affinity for the styrenic thermoplastic elastomer (B) is at least one selected from the group consisting of polyolefin units, polystyrene units, and polyphenylene ether units. And a known thermoplastic resin unit that is compatible with the styrene-based thermoplastic elastomer. Especially, since it has a high affinity for the styrene-based thermoplastic elastomer (B), it contains at least one unit selected from the group consisting of polyolefin-based units, polystyrene-based units, and polyphenylene ether-based units. Is preferred.

  Examples of the polyolefin-based unit include α- such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene. Examples include olefin polymer units. Among these, from the viewpoint of compatibility with the styrenic thermoplastic elastomer (B), polymer units of ethylene and propylene are preferable. These polymer units can be used alone or in combination of two or more.

  Examples of the polystyrene unit include styrene, α-methylstyrene, 1-vinylnaphthalene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4- Examples thereof include polymer units such as (phenylbutyl) styrene and halogenated styrene. Among these, from the viewpoint of compatibility with the styrenic thermoplastic elastomer (B), polymer units of styrene and α-methylstyrene are preferable. These polymer units can be used alone or in combination of two or more.

  Examples of the polyphenylene ether unit include poly (2,6-dimethyl-1,4-phenylene) ether, poly (2-methyl-6-ethyl-1,4-phenylene) ether, poly (2,6-diethyl- 1,4-phenylene) ether, poly (2-ethyl-6-npropyl-1,4-phenylene) ether, poly (2,6-di-npropyl-1,4-phenylene) ether, poly (2- Methyl-6-nbutyl-1,4-phenylene) ether, poly (2-ethyl-6-isopropyl-1,4-phenylene) ether, poly (2-methyl-6-chloro-1,4-phenylene) ether , Poly (2-methyl-6-hydroxyethyl-1,4-phenylene) ether, poly (2-methyl-6-chloroethyl-1,4-phenylene) ether, etc. Body, or copolymers thereof. These polymer units can be used alone or in combination of two or more.

As the compatibilizing agent (C), a copolymer of a polyurethane-based unit-containing segment and a polystyrene-based unit-containing segment, or a copolymer of a polyether-based unit-containing segment and a polyolefin-based unit-containing segment can be suitably used.
Examples of the copolymer of the polyurethane-based unit-containing segment and the polystyrene-based unit-containing segment include a copolymer of a urethane-based thermoplastic elastomer and a styrene-based thermoplastic elastomer. As the copolymer of the urethane-based thermoplastic elastomer and the styrene-based thermoplastic elastomer, for example, a commercially available product such as a trade name “Cramiron” (registered trademark) (manufactured by Kuraray Co., Ltd.) can be used.
Examples of the copolymer of the polyether-based unit-containing segment and the polyolefin-based unit-containing segment include a polyether-polyolefin copolymer. Commercially available products such as trade names “Pelestat” (registered trademark) “Peletron” (registered trademark) (manufactured by Sanyo Chemical Industries, Ltd.) can be used as the copolymer of polyether and polyolefin.

  The compatibilizer (C) has a segment (x) having affinity for the polyacetal resin (A) and a segment (y) having affinity for the styrene thermoplastic elastomer (B). And a segment other than the segment (x) and the segment (y) may be included as a component of the copolymer.

In the present invention, the mixed resin composition ratio (A) / (B) / (C) of the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizer (C) is 45% by mass. It is important that it is -98 mass% / 1 mass% -45 mass% / 1 mass% -45 mass% (however, the total mass% of (A), (B), and (C) is 100 mass%). It is.
In general, since the density of the polyacetal resin is as large as 1.4 g / cm ³ or more, when the mixed resin composition ratio of the styrene thermoplastic elastomer (B) in the mixed resin exceeds 45% by mass, The volume of the styrene thermoplastic elastomer (B) is larger than the volume of the polyacetal resin (A), and the matrix of the resin composition to be formed becomes a styrene thermoplastic elastomer, making it difficult to form a porous structure. At the same time, the heat resistance may be significantly reduced.
Further, when the mixed resin composition ratio of the styrene thermoplastic elastomer (B) in the mixed resin is less than 1% by mass, at the interface between the polyacetal resin (A) and the styrene thermoplastic elastomer (B). There is a possibility that porosity is difficult to form.
Further, when the mixed resin composition ratio of the compatibilizing agent (C) in the mixed resin exceeds 45% by mass, the compatibilizing agent (C) tends to be a main component of the domain of the resin composition to be formed, There is a possibility that the formation of porosity at the interface between the polyacetal resin (A) and the styrene thermoplastic elastomer (B) is difficult to form.
Further, when the mixed resin composition ratio of the compatibilizer (C) in the mixed resin is less than 1% by mass, the compatibility between the polyacetal resin (A) and the styrene thermoplastic elastomer (B) is improved. There is a risk that it will not be able to exert its full effect.
Therefore, the mixed resin composition ratio (A) / (B) / (C) of the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizer (C) is 50% by mass to 92%. It is preferable that the mass% is 5% by mass to 40% by mass / 3% by mass to 40% by mass (provided that the total mass% of (A), (B), and (C) is 100% by mass). ) / (B) / (C) is 55 mass% to 85 mass% / 10 mass% to 40 mass% / 5 mass% to 35 mass% (however, the total mass of (A), (B) and (C) % Is 100% by mass).

<Other ingredients>
In the resin composition constituting the porous body, the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizing agent (C) other than the above-described polyacetal resin (A) are within the range not impairing the effects of the present invention. It can be allowed to contain other components other than the above components (A), (B), and (C).
Other resins include polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, polyamide resins, fluorine resins, polymethylpentene resins, polyvinyl alcohol resins. , Cyclic olefin resin, polylactic acid resin, polybutylene succinate resin, polyacrylonitrile resin, polyether resin, cellulose resin, polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, Polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide bismaleimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, polyester Polyether ketone resin, polyether sulfone resin, polyketone resin, polysulfone resin, aramid-based resin and the like.
Further, a thermoplastic elastomer other than the styrene-based thermoplastic elastomer (B) may be contained. Examples of other thermoplastic elastomers that may be contained include amide-based thermoplastic elastomers, ester-based thermoplastic elastomers, and olefin-based materials. Thermoplastic elastomer, urethane thermoplastic elastomer, dynamic vulcanized thermoplastic elastomer, vinyl chloride thermoplastic elastomer, acrylic thermoplastic elastomer, lactic acid thermoplastic elastomer, fluorine thermoplastic elastomer, silicone thermoplastic elastomer , Ionomers, and blends, alloys, modified products, dynamically crosslinked products, block copolymers, graft copolymers, random copolymers, core-shell multilayer rubbers, and the like thereof.

  In addition to the components described above, additives generally blended in the resin composition can be appropriately added to the resin composition as long as the effects of the present invention are not significantly impaired. Examples of the additive include recycled resin generated from trimming loss of ears and the like, silica, talc, kaolin, carbonic acid, which are added for the purpose of improving / adjusting molding processability, productivity and various physical properties of the porous body. Inorganic particles such as calcium, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents , Antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, slip agents, colorants and the like.

<This porous body>
This porous body has at least one porous layer made of a resin composition containing a polyacetal resin (A) as a main component and containing a styrene thermoplastic elastomer (B) and a compatibilizer (C). The porous layer is a polyacetal-based resin stretched porous body that has been made porous by stretching in at least a uniaxial direction.

  Although there is no restriction | limiting in particular as a shape of this porous body, The 1 type of molded object chosen from the group which consists of a sheet-like thing, a fibrous thing, and a hollow thing is mentioned. “Sheet” includes from thick (mm order) plates to thin (μm order) films, and “fibrous” includes from thick rods to thin threads, and “hollow” The term “thick pipe” means “thin tube”, “hollow fiber”, “inflation film” and the like. Of course, the sheet-like thing which cut the inflation film is also included.

This porous body should just have at least one porous layer which consists of the said resin composition. That is, the present porous body may be formed only by a porous layer made of the resin composition, or may be formed by laminating with another porous layer as long as the characteristics of the present porous body are not impaired.
Further, when the porous body is a sheet-like material, a laminated sheet-like porous body laminated in the thickness direction of the sheet-like material may be used, and when the porous material is a fibrous material, a so-called core-sheath structure-like porous body may be used. In this case, a porous body laminated in the radial direction of the hollow body may be used.
In particular, when the porous body is used as an electronic member separator, a sheet-like material is preferable. Further, the porous layer may be formed by laminating a porous layer made of the resin composition with a polyolefin resin porous film generally used as a separator. In that case, a porous layer made of the resin composition may be formed. The layer is preferably disposed on the outermost layer of the porous body.

  Furthermore, it is important that the porous layer made of the resin composition in the porous body is stretched at least in a uniaxial direction. The porous layer made of the resin composition is stretched at least in a uniaxial direction, preferably in a biaxial direction, so that the layer becomes porous and the porous body has excellent air permeability.

When using this porous body as a separator for electronic members, the thickness of the porous body as a sheet-like material is preferably 1 μm to 200 μm, and more preferably 5 μm to 170 μm. When used as a separator for an electronic member, if the thickness is 1 μm or more, substantially necessary electrical insulation can be obtained. For example, even when a large voltage is applied, short-circuiting is difficult and excellent safety is achieved.
Further, when the thickness is 200 μm or less, preferably 170 μm or less, the resistance of the separator can be reduced, so that the performance of electronic members such as batteries and capacitors can be sufficiently ensured.

The air permeability of the porous body is preferably 1 second / 100 mL to 100 seconds / 100 mL, more preferably 1 second / 100 mL to 50 seconds / 100 mL. If the air permeability is 1 second / 100 mL or more and 100 seconds / 100 mL or less, it indicates that the porous body has connectivity and can exhibit excellent air permeability characteristics, which is also preferable for improving the penetration rate of the electrolyte. Become superior.
The air permeability represents the difficulty in passing through the air in the thickness direction, and is specifically expressed in seconds required for 100 mL of air to pass through the porous body. Therefore, it means that the smaller the numerical value is, the easier it is to pass through, and the higher numerical value is, the more difficult it is to pass. That is, the smaller the value means the better in the thickness direction, and the larger the value means the less in the thickness direction. Communication is the connection of holes in the thickness direction. If the air permeability of the porous body is low, it can be used for various purposes. For example, when used as a separator for an electronic member such as a lithium ion secondary battery or an electric double layer capacitor, a low air permeability means that ions can be easily moved, and a battery or a capacitor using the separator. Such an electronic member is preferable because it is excellent in performance.
In addition, the measuring method is described in the term of the below-mentioned Example of air permeability.

  The porous body preferably has an air permeability per 1 μm thickness of 0.001 (second / 100 mL) / μm or more and 1 (second / 100 mL) / μm or less. As described above, the air permeability indicates the difficulty of air passage in the thickness direction, and therefore the air permeability is lowered by reducing the thickness of the porous body. Therefore, the air permeability per 1 μm thickness is an index indicating the superiority or inferiority of the air permeability characteristics as a porous film at any thickness. Therefore, if the air permeability per 1 μm thickness is 0.001 (second / 100 mL) / μm or more and 1 (second / 100 mL) / μm or less, excellent air permeability characteristics can be exhibited at any thickness. Preferably, it is also superior in improving the penetration rate of the electrolytic solution.

The porosity of the porous body is preferably 30% or more, and more preferably 35% or more. When the porosity is 40% or more, it is possible to obtain a porous film that secures communication and has excellent air permeability, and is advantageous in improving the penetration rate of the electrolytic solution.
On the other hand, the upper limit of the porosity is preferably 80% or less, more preferably 75% or less, and still more preferably 70% or less. If the porosity is 80% or less, there is no problem that the fine pores are excessively increased and the strength of the porous body is lowered, which is preferable from the viewpoint of handling.
In addition, the measuring method is described in the term of the below-mentioned Example for the porosity.

In the present porous body, it is preferable that the heat shrinkage rate in the flow direction (MD) of the stretched porous body after standing for 1 hour in an atmosphere of 105 ° C. is 0% or more and 5% or less. More preferably, they are 0% or more and 4% or less, More preferably, they are 0% or more and 3% or less. If the thermal contraction rate in the flow direction after being left in a 105 ° C atmosphere for 1 hour exceeds 5%, when used as a separator for an electronic member, when the separator is dried in a wound state, tightening and wrinkles occur. There is a fear. In addition, even when wound together with the electrode, the end of the electrode is strongly pressed against the separator, so that the separator is easily cracked and short-circuited easily.
If it is less than 0%, it means that it is left in an atmosphere at 105 ° C. for 1 hour and then expands in the flow direction. When the separator is dried in a roll, wrinkles and sagging may occur. Further, even when wound together with the electrode, the adhesion with the electrode may be hindered and the performance of the electronic member may be deteriorated. When the thermal contraction rate in the flow direction after being left in an atmosphere at 105 ° C. for 1 hour is in the above range, it is excellent in dimensional stability and contributes to stable performance of the electronic member and improvement in safety.

  Further, in this porous body, the heat shrinkage rate in the flow direction (MD) of the stretched porous body after standing for 1 hour in an atmosphere at 130 ° C. is preferably 0% or more and 10% or less, and preferably 0% or more and 9%. % Or less, more preferably 0% or more and 8% or less. As the importance of safety increases with the recent increase in capacity of electronic components, the dimensional stability of the separator in a higher temperature region is also required. Therefore, for the same reason as described above, in the state of being wound together with the electrode, the end of the electrode is strongly pressed against the separator, and in view of maintaining the adhesion with the electrode, after being left in a 130 ° C. atmosphere for 1 hour, When the thermal contraction rate in the flow direction (MD) of the stretched porous body is in the above range, it is preferable because safety can be ensured even in a state exposed to higher temperatures.

Further, in the case of a sheet-like material having a suitable shape when the porous body is used as a separator for an electronic member, the thermal contraction rate in the width direction (TD) of the sheet-like material after being left in an atmosphere at 105 ° C. for 1 hour. Is preferably from 0% to 6%, more preferably from 0% to 5%, and even more preferably from 0% to 4%. In the separator for electronic members, the electronic member is often configured by being wound in the flow direction together with the electrode or being folded into a ninety-nine shape. For this reason, the flow direction of the separator is in a state having a certain restraining force due to the structure of the electronic member, but the restraining force is small in the width direction. For this reason, when the separator is thermally contracted, the electrodes interposed on both sides of the separator come into contact with each other, causing a short circuit. Therefore, if the thermal contraction rate in the width direction after being left in an atmosphere of 105 ° C. for 1 hour exceeds 6%, there is a risk of causing a short circuit when used as a separator for electronic members.
Moreover, if it is less than 0%, it means that it expands in the width direction, which may impair adhesion with the electrode and reduce the performance of the electronic member. When the thermal contraction rate in the width direction after being left in a 105 ° C. atmosphere for 1 hour is in the above range, the dimensional stability is excellent, contributing to the stable performance of the electronic member and the improvement of safety.

  Further, in the case of a sheet-like material having a suitable shape when the porous body is used as a separator for an electronic member, the thermal contraction rate in the width direction (TD) of the sheet-like material after being left in a 130 ° C. atmosphere for 1 hour. However, it is preferably 0% or more and 12% or less, more preferably 0% or more and 11% or less, and further preferably 0% or more and 10% or less. As described above, as the importance of safety increases with the recent increase in capacity of electronic members, the dimensional stability of the separator in a higher temperature region is also required. Therefore, for the same reason as described above, the width of the sheet-like material after being left in a 130 ° C. atmosphere for 1 hour in terms of preventing a short circuit due to contact between electrodes on both sides of the separator and maintaining adhesion with the electrodes. When the thermal contraction rate in the direction (TD) is in the above-described range, it is preferable because safety can be ensured even in a state exposed to a higher temperature.

  This porous body has a crystal melting enthalpy (ΔHm) derived from the polyacetal resin (A) in differential scanning calorimetry (DSC) of a porous layer made of the resin composition of 10 J / g or more and 160 J / g or less. It is preferable. ΔHm in DSC of the porous layer is preferably 20 J / g or more and 150 J / g or less, and more preferably 30 J / g or more and 140 J / g or less.

The reason why ΔHm derived from the polyacetal resin (A) in the DSC of the porous layer is preferably in the above range is that the polyacetal resin (A) is a main component and a styrene thermoplastic elastomer (B ) And a layer made of the resin composition containing the compatibilizing agent (C) is stretched at least in a uniaxial direction to make the layer porous, the elastic modulus of the polyacetal resin (A) in the resin composition before stretching is This is because dissociation easily occurs at the matrix / domain interface due to the increase in size, and a porous body having a uniform porous structure and excellent air permeability can be obtained.
If ΔHm derived from the polyacetal resin (A) of the porous layer made of the resin composition is 10 J / g or more, the elastic modulus of the matrix is improved by the crystal component of the polyacetal resin (A) as the matrix. When the obtained resin composition is stretched, the stress imparted by deformation tends to concentrate on the matrix / domain interface, and interfacial delamination tends to occur, thereby forming a uniform porous structure. Further, if ΔHm derived from the polyacetal resin (A) of the porous layer made of the resin composition is 160 J / g or less, the yield stress of the resin composition does not become too large in the low-temperature stretching step described later, Since a large amount of energy is not required to cause matrix / domain interfacial delamination, deformation easily follows the stretching, and the possibility of breakage is reduced.

ΔHm of the porous layer is based on JIS K7141-2 (2006), and the porous body is heated from 30 ° C. to a high temperature holding temperature at a heating rate of 10 ° C./min with a differential scanning calorimeter and held for 1 minute. Then, the temperature was lowered from the high temperature holding temperature to 30 ° C. at a cooling rate of 10 ° C./min, and then held for 1 minute, and when the temperature was raised again from 30 ° C. to the high temperature holding temperature at a heating rate of 10 ° C./min, The crystal melting enthalpy (ΔHm) is calculated from the crystal melting peak area derived from the polyacetal resin (A). At this time, the high temperature holding temperature can be arbitrarily selected in the range of Tm + 20 ° C. or more and Tm + 100 ° C. or less with respect to the crystal melting peak temperature Tm of the polyacetal resin (A) to be used.
Note that ΔHm defined in the present invention is the ΔHm calculated from the crystal melting peak generated in the re-heating process even in the case where cold crystallization as seen in the semi-crystalline resin occurs in the re-heating process. Apply. That is, the crystallization enthalpy (ΔHc) calculated from the exothermic peak area in cold crystallization that occurs in the reheating process is not subtracted from ΔHm obtained in the reheating process. Furthermore, the present invention only needs to have at least one porous layer made of the resin composition. When the porous body is laminated with another layer, the polyacetal system is obtained by performing DSC measurement on the laminated body as it is. There is a possibility that ΔHm derived from the resin (A) is estimated to be low. Therefore, when this porous body is a laminate, the porous layer of the present invention can be peeled off and ΔHm can be measured for this porous layer. When peeling is difficult, ΔSm derived from the polyacetal-based resin (A) in the entire laminate is calculated by DSC measurement, and the lamination ratio of the porous layer in the entire laminate is calculated. ΔHm defined by the present invention can be calculated. The calculation of the lamination ratio is not particularly limited, but is preferably calculated by cross-sectional observation using an optical microscope, an electron microscope, or the like.
ΔHm (J / g) of the porous body = ΔHm (J / g) derived from the polyacetal resin (A) in the entire laminate / laminate ratio of the porous layer in the entire laminate (%) / 100 (%)

In this porous body, the tensile strength _{E MD} is preferably from 5MPa or more 100MPa flow direction (MD), more preferably at least 95MPa or less 8 MPa, more preferably not more than more than 10 MPa 90 MPa. When the _EMD is 5 MPa or more and 100 MPa or less, it has a supple texture and excellent handling properties.
When the porous body is a sheet-like material, the tensile strength E _{TD in} the width direction (TD) of the sheet-like material is preferably 5 MPa to 100 MPa, more preferably 8 MPa to 95 MPa, and further preferably 10 MPa to 90 MPa. . It _is preferable that the ratio of _{E MD} and _{E TD (E MD / E TD} ) is 0.5 to 5, more preferably 0.8 or more and 4 or less, more preferably 1.0 to 3. By adjusting the E _MD / E _TD within the above range, the porous structure has a structure close to isotropic and can exhibit excellent air permeability. Further, by having an isotropic porous structure, the electrolytic solution can penetrate uniformly, which is advantageous in improving the penetration rate of the electrolytic solution.

  When the porous body is a sheet-like material, the puncture strength of the porous body is preferably 0.88N or more, more preferably 1.18N or more, and further preferably 1.47N or more. When the piercing strength is less than 0.88 N, the mechanical strength in the plane direction of the porous body is insufficient and is easily broken, which is not preferable. The upper limit of the piercing strength is not particularly limited, and it is preferable that the piercing strength is higher.However, when the piercing strength is increased, the porosity is lowered, and the contradictory property that the air permeability property of the porous body is inhibited. Have.

It is preferable that propylene carbonate having a droplet amount of 1 μL permeates the porous body within 60 seconds. By penetrating, it is meant that the droplets are encapsulated in the porous body and do not remain in a flowable state outside the porous body. Therefore, the surface is wet and spread (the state where the liquid droplet remains in a state where it can flow outside the contact object with the liquid droplet) and the state where the liquid droplet penetrates (the liquid droplet is in contact with the liquid droplet. A state in which the liquid droplets are contained and no liquid droplets remain outside the contact object with the liquid droplets is distinguished.
The permeation rate of propylene carbonate widely used as an electrolyte solution for electronic members is an index that is regarded as important from the viewpoint of productivity of electronic members, and that propylene carbonate having a droplet volume of 1 μL permeates within 60 seconds. In the production process of the electronic member, it means that the process time for injecting the electrolyte can be shortened.
Moreover, the electronic member has the subject that the phenomenon called liquid erosion generate | occur | produces by internal degradation or generation | occurrence | production of gas with continuous use, and the performance of an electronic member falls. When the lyophilicity of the electrolytic solution and the separator for the electronic member is low, liquid withering is promoted and it is difficult to maintain the performance of the electronic member for a long time. On the other hand, the electronic member separator in which propylene carbonate having a droplet volume of 1 μL permeates within 60 seconds has a high lyophilicity with the electrolyte solution, and thus acts predominately in suppressing liquid drainage.
Therefore, the permeation rate of propylene carbonate having a droplet volume of 1 μL is preferably within 60 seconds, more preferably within 45 seconds, even more preferably within 35 seconds, and most preferably within 25 seconds.
The polarity of the resin composition constituting the electronic member separator contributes to such an effect. A polyolefin resin generally used as a separator for an electronic member does not have a polar group in the molecule and is considered to have a low affinity with an electrolytic solution.
On the other hand, in this porous body, since it has an oxygen atom in the polyacetal resin (A), it becomes possible to improve the affinity with a polar solvent such as an electrolytic solution, and to improve the penetration rate and retention of the electrolytic solution. Greatly contributes.
In addition, as a method for measuring the permeation time of propylene carbonate having a droplet volume of 1 μL, when the porous body is a sheet-like material, the liquid is applied to the porous body by the contact angle measurement described in the section of Examples below. It is preferable to measure the time for which the droplets penetrate into the porous body while measuring the contact angle of the dropped propylene carbonate while dropping 1 μL of propylene carbonate. It doesn't matter.
In addition, when the porous body is a fibrous material or a hollow fiber-like material and it is difficult to drop propylene carbonate having a droplet amount of 1 μL onto the porous body, the propylene carbonate does not dissolve or swell, and does not penetrate or wet. Drop propylene carbonate with a droplet volume of 1 μL on a flat plate that is unlikely to spread, and contact a fibrous porous body or hollow fiber porous body with the droplet, and measure the penetration time into the porous body. May be.

<Method for producing the porous body>
Next, the manufacturing method of this porous body is demonstrated. As described above, in the present porous body, a layer composed of a resin composition containing the polyacetal resin (A) as a main component and containing the styrene thermoplastic elastomer (B) and the compatibilizer (C). It is important that the material is made porous by stretching in at least a uniaxial direction.
More specifically, the porous body is selected from the group consisting of (a) melt-extruding the resin composition, and a sheet-like material, a fibrous material, and a hollow material having at least one layer made of the resin composition. A step of cooling and solidifying into one kind of molded product, (b) a step of stretching the molded product molded in the step (a) at a temperature of −20 ° C. or higher and 90 ° C. or lower, and (c) the above The molded product stretched in the step (b) is preferably produced via a step of stretching at a temperature of 100 ° C. or higher and 160 ° C. or lower.

[Step (a)]
The resin composition is melt-extruded, and a molded product selected from the group consisting of a sheet-like material, a fibrous material, and a hollow material having at least one substantially non-porous layer made of the resin composition, The method for cooling and solidifying is not particularly limited, and a known method may be used. For example, the resin composition is melt-extruded using an extruder, and a T die, a round die, a nozzle, a hollow nozzle, or the like is shaped. Examples of the method include extruding from equipment, and cooling and solidifying with equipment such as cast roll (cooling roll), air cooling, and water cooling. Moreover, the method of cutting open the film-like thing manufactured by the inflation method and the tubular method, and making it planar can also be applied.
The “substantially non-porous layer” means that in the step of melt-extruding the resin composition, cooling and solidifying, and forming the void intentionally in the layer, It means that it includes the case where a fine pinhole is unintentionally generated due to an unexpected factor.

In the melt extrusion of the resin composition, the extrusion processing temperature is appropriately adjusted depending on the flow characteristics and moldability of the resin composition, but in view of the thermal decomposition temperature of the polyacetal resin (A), it is generally 180 to 260 ° C. Is preferable, 190-250 degreeC is more preferable, and 200-240 degreeC is still more preferable. When the extrusion temperature is equal to or higher than the above lower limit, it is preferable because the viscosity of the molten resin is sufficiently low and the moldability is excellent and the productivity is improved. On the other hand, by making the extrusion processing temperature below the above upper limit, deterioration of the resin composition, thermal decomposition, and reduction in mechanical strength of the resulting porous body can be suppressed.
Moreover, the cooling solidification temperature, for example, the cooling solidification temperature of the cast roll is preferably 20 to 160 ° C, more preferably 40 to 140 ° C, and still more preferably 50 to 130 ° C. By setting the cooling and solidification temperature to the above lower limit or more, crystallization of the polyacetal resin (A) is promoted, and a difference in elastic modulus from the thermoplastic elastomer (B) is likely to occur, and a porous body is formed during stretching. It is preferable because it is easy. Moreover, it is preferable to make the extruded resin below the above upper limit because troubles such as the extruded molten resin sticking to and wrapping around the cast roll are unlikely to occur, and the molding can be efficiently performed.

[Step (b)]
In the step (b), the molded product obtained in the step (a) is stretched at a temperature of −20 ° C. or higher and 90 ° C. or lower (hereinafter, this step (b) may be referred to as “low-temperature stretching step”). ). Examples of the stretching method in the step (b) include methods such as a roll stretching method, a rolling method, a tenter stretching method, and a simultaneous biaxial stretching method, and these may be performed alone or in combination of two or more. Among these, from the viewpoint of productivity, stretching in the flow direction in the step (a) (that is, the extrusion direction or the take-off direction, hereinafter may be referred to as “longitudinal direction” or “MD”) is preferable, and the resin composition From the viewpoint of concentration of stress on the styrene-based thermoplastic elastomer (B), a roll stretching method that facilitates increasing the stretching speed is preferred.

  Here, by stretching at a temperature of −20 ° C. or higher, a special facility for making the stretching atmosphere at a temperature lower than −20 ° C. is unnecessary, which is preferable in production. Further, the elastic modulus of the polyacetal-based resin (A) in the stretching atmosphere does not become too high, deformation can follow the stretching, and the possibility of breakage is small. On the other hand, by stretching at a temperature of 90 ° C. or less, the elastic modulus of the polyacetal resin (A) does not become too low, and stress concentration on the styrene thermoplastic elastomer (B) is moderately expressed, and the resin composition The layer consisting of can be easily made porous. The temperature in the low temperature stretching step is particularly preferably 0 ° C. or higher and 70 ° C. or lower.

  The draw ratio in this low temperature drawing step is not particularly limited, but is preferably 1.15 times or more and 4.00 times or less, particularly preferably 1.25 times or more and 3.00 times or less. When the draw ratio is not less than the above lower limit, stress concentrates at the interface of the matrix / domain, and it is easy to form a porous structure by peeling of the interface accompanying deformation, and when the draw ratio is not more than the above upper limit, the formed porous structure is excessive. This is preferable because it is not blocked by the deformation of

[Step (c)]
In the step (c), the molded product stretched in the step (b) is further stretched at a temperature of 100 ° C. or higher and 160 ° C. or lower (hereinafter, this step (c) may be referred to as a “high temperature stretching step”). ). About the extending | stretching method in a process (c), although the same method as the above-mentioned process (b) can be employ | adopted, a roll extending | stretching method and a tenter extending | stretching method are preferable especially, and it forms by the process (b). From the viewpoint of expanding the pores, it is preferable to further stretch in the flow direction (longitudinal direction) by a roll stretching method.
Here, by extending | stretching at the temperature of 100 degreeC or more, the hole formed at the process (b) can be expanded | stretched and a hole diameter can be expanded. On the other hand, by stretching at a temperature of 160 ° C. or lower, the blockage of the holes formed in the step (b) can be suppressed. The temperature in the high temperature stretching step is particularly preferably 110 ° C. or higher and 150 ° C. or lower.

  Further, the draw ratio in this high temperature drawing step is not particularly limited, but is preferably 1.25 times or more and 6.00 times or less, particularly 1.40 times or more and 5.00 times or less. Furthermore, the stretching ratio of the low temperature stretching step and the high temperature stretching step is preferably 1.40 times or more and 24.0 times or less, particularly 1.75 times or more and 15.0 times or less. When the draw ratio is not less than the above lower limit, it is easy to expand the pore diameter and maintain the porous structure, and when it is not more than the above upper limit, blockage of the pores can be suppressed, which is preferable.

  In the method for producing a porous body, the steps are continuous in the order of (a), (b), and (c), and in particular, by performing step (c) after step (b), the styrene The layer made of the resin composition can be easily made porous without the thermoplastic elastomer (B) being stretched too much during stretching. If the process sequence is performed in the order of (a), (c), and (b), the styrenic thermoplastic elastomer (B) is stretched by the process (c) and stress is applied. Since the cross-sectional area of the interface to be received is small, it is not preferable because it becomes difficult to make it porous. This is the same as the state in which the domain extends in the flow direction in the step (a) described above. In addition, the manufacturing method of this porous body should just perform each process in order of (a), (b), (c), and other than that between each process of (a), (b), (c) A process may be included. Moreover, you may include a process other than that after a process (c).

  Specifically, it is preferable to perform heat treatment after the step (c) from the viewpoint of improving dimensional stability. Further, for the purpose of further expanding the pores, after step (c), the film is stretched in the direction (hereinafter sometimes referred to as “lateral direction” or “TD”) perpendicular to the longitudinal direction by a tenter stretching method or the like (transverse direction). It is also preferable to stretch). Furthermore, it is also preferable to perform heat treatment from the viewpoint of improving dimensional stability after transverse stretching by a tenter stretching method or the like. In addition, from the viewpoint of further dimensional stability, the obtained porous body may be cross-linked by electron beam cross-linking or the like, or a viewpoint of improving adhesion when laminated with other porous layers or the like as described later, From the viewpoint of further improving the immersion property with respect to the electrolytic solution, the obtained porous body may be subjected to a surface treatment by performing a corona discharge treatment, a plasma treatment or the like.

In the case where the transverse stretching is performed after the step (c), the temperature in the transverse stretching step is preferably 100 ° C. or more and 160 ° C. or less in view of further expansion of the pore diameter and suppression of blockage of the pores. In addition, the draw ratio at that time should be 1.25 times or more and 6.00 times or less, particularly 1.40 times or more and 5.00 times or less in terms of further expansion of the pore diameter and suppression of blockage of the pores. preferable.
Moreover, when performing heat processing after a process (c), it is preferable in the point of dimensional stability that the temperature in a heat processing process is 120 to 200 degreeC.

  Moreover, when this porous body has other porous layers other than the layer which consists of the said resin composition, in the said process (a), it has the said polyacetal type-resin (A) as a main component, and the said styrene-type thermoplasticity The elastomer (B) and a layer composed of a resin composition containing the compatibilizer (C) and a layer of a composition constituting another porous layer are laminated by a coextrusion method or a laminating method, After producing a substantially non-porous laminate, the porous body may be produced by stretching in step (b) and step (c) to make the porous body, and the polyacetal resin (A) A layer comprising a resin composition containing the styrene-based thermoplastic elastomer (B) and the compatibilizer (C) as a main component was made porous through the steps (a) to (c). After that, other porous layers and lamination methods and co Laminated such as by plating method, it may be produced this porous body.

<Electronic member using this porous body>
Another embodiment of the present invention is an electronic member using the porous body. Electronic members that can preferably use the porous body include batteries such as alkaline batteries, nickel metal hydride batteries, lithium batteries, lithium ion secondary batteries, and electronic members such as electrolytic capacitors, electric double layer capacitors, capacitors such as lithium ion capacitors. Is mentioned.
The electronic member of the present invention is not particularly limited as long as the porous body is used as a separator for an electronic member, and a conventionally known electrode or electrolyte is used for the electronic member. Can be configured.

  Next, although an Example and a comparative example are shown and this porous body is demonstrated in detail, this invention is not limited to these. In addition, as an embodiment of the present porous body, it was shaped into a sheet. Hereinafter, this porous body is called a porous film. Moreover, the take-up (flow) direction of a porous film is described as "MD" direction, and the perpendicular direction is described as "TD" direction.

(1) Molecular weight, molecular weight distribution After dissolving the styrenic thermoplastic elastomer used in Examples and Comparative Examples in chloroform, based on JIS K7252-1 (2008), weight average molecular weight Mw, number average molecular weight using GPC Mn and molecular weight distribution Mw / Mn were measured and calculated. The molecular weight was calculated using the molecular weight of a polystyrene standard sample as a calibration curve.

(2) MFR
Regarding the raw materials used in the examples and comparative examples, based on JIS K7210-1 (2014), the polyacetal resin is at a temperature of 190 ° C. and the load is 2.16 kg, and the styrene thermoplastic elastomer is at a temperature of 230 ° C. The MFR was measured under a load of 2.16 kg.

(3) Styrene content, oxymethylene unit content, compatibilizer segment ratio The styrene thermoplastic elastomers used in Examples and Comparative Examples were subjected to composition analysis using NMR, and the styrene content was calculated. Moreover, about the polyacetal type resin used by the Example and the comparative example, the composition analysis was conducted using NMR and oxymethylene unit content was computed. Furthermore, regarding the compatibilizing agent used in Examples and Comparative Examples, composition analysis was performed using NMR to calculate a segment ratio.

(4) Thickness The surface of the obtained porous film was measured unspecified in five places with a 1/1000 mm dial gauge, and the average was taken as the thickness.

(5) Air permeability The sample was cut out from the obtained porous film with a diameter of 40 mm, and the air permeability (seconds / 100 mL) was measured according to JIS P8117 (2009). Further, the air permeability was divided by the thickness obtained by the above measurement, and the air permeability per 1 μm thickness was calculated.

(6) Porosity was measured substantial amount W ₁ of the resulting porous film, to calculate the mass W ₀ if the density and the thickness porosity of 0% of the resin composition, the following formulas these values Calculated based on
Porosity (%) = {(W ₀ −W ₁ ) / W ₀ } × 100

(7) Evaluation of heat shrinkage rate The porous film was cut into a size of 150 mm in the measurement direction and 15 mm in the direction perpendicular to the measurement direction, and marked lines were drawn at intervals of 100 mm along the measurement direction. The sample was hung in a baking test apparatus (DK-1M, manufactured by Daiei Kagaku Seisakusho Co., Ltd.) preheated to 130 ° C. After 1 hour, the sample was taken out and allowed to cool to room temperature, then the marked line interval L (mm) of the sample was measured with a metal scale, and the shrinkage rate in the flow direction (MD) and width direction (TD) was calculated using the following formula. Each was calculated.
Shrinkage rate (%) = {(100 (mm) -L (mm)) / 100 (mm)} × 100 (%)

(8) Crystal melting peak temperature, crystal melting enthalpy (ΔHm)
Based on JIS K7141-2 (2006), the obtained porous film was subjected to DSC measurement. The temperature was raised from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min and held for 1 minute, then the temperature was lowered from 250 ° C. to 30 ° C. at a cooling rate of 10 ° C./min, held for 1 minute, and further from 30 ° C. to 250 ° C. The temperature was raised again to 10 ° C. at a heating rate of 10 ° C./min. At this time, the crystal melting enthalpy (ΔHm) was calculated from the crystal melting peak temperature derived from the polyacetal resin in the reheating process and the crystal melting peak area. As a result, in the case of the same composition, the same numerical value was obtained. Therefore, in Tables 1 and 2, the crystal melting peak temperature and ΔHm in the same composition are collectively shown.

(9) Immersion evaluation Static contact of the porous film obtained using propylene carbonate (Nacalai Tesque Kogyo Co., Ltd., content 98.0% or more) widely used as an electrolyte for electric double layer capacitors Angular measurements were taken. For the contact angle measurement, a contact angle measuring device DropMaster 500 (manufactured by Kyowa Interface Science Co., Ltd.) and evaluation analysis software FAMAS (manufactured by Kyowa Interface Science Co., Ltd.) were used. The porous films obtained in the examples and comparative examples were cut out with MD5 cm × TD5 cm, and fixed on the stage on the DropMaster 500 with tape so that the cut porous film was flat. Thereafter, propylene carbonate having a droplet amount of 1 μL was dropped onto the porous film from a syringe having a diameter of 1.8 mm, and the contact angle after 3 seconds was measured after dropping. Further, contact angles were measured at intervals of 10 seconds, 13 seconds, 23 seconds, 33 seconds, 43 seconds, 53 seconds after dropping, and finally 60 seconds after dropping. The contact angle was calculated by the θ / 2 method. At this time, the state in which the liquid droplet permeated the porous film and the contact angle could not be calculated was described as “penetration”.

(10) Scanning Electron Microscope (SEM) Observation of Porous Film Surface The film surfaces of the porous films obtained in Example 2, Example 4, Example 6, and Comparative Example 2 were obtained with a scanning electron microscope. Observed. They are shown in FIGS.

  The raw materials used in Examples and Comparative Examples are as follows.

(Polyacetal resin)
A-1; polyacetal resin, grade name: Iupital F20-01 (registered trademark), manufactured by Mitsubishi Engineering Plastics Co., Ltd., oxymethylene unit content: 98.4 mol%, MFR; 7.8 g / 10 min. Melting point: 166 ° C

(Styrenic thermoplastic elastomer)
B-1: Styrene-ethylene-propylene-styrene copolymer, grade name: SEPTON 2006 (registered trademark), manufactured by Kuraray Co., Ltd., styrene content: 35 mass%, MFR: non-flowing, weight average molecular weight Mw: 271 1,000, molecular weight distribution Mw / Mn; 1.09

(Compatibilizer)
C-1; copolymer of urethane-based thermoplastic elastomer and styrene-based thermoplastic elastomer, grade name: Kuramylon TU-S5265 (registered trademark), manufactured by Kuraray Co., Ltd., segment ratio; urethane-based thermoplastic elastomer segment (polyurethane-based) Unit-containing) / styrene-based thermoplastic elastomer segment (polystyrene-based unit and polyolefin-based unit included) = 55% by mass / 45% by mass)

Example 1
A polyacetal resin (A-1), a styrene thermoplastic elastomer (B-1), and a compatibilizer (C-1) were blended in the blending ratios shown in Table 1, and a twin-screw extruder (screw diameter: 25 mmφ) , Melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, and then cooled and solidified with a cast roll set at 120 ° C. to obtain an unstretched sheet with a thickness of 150 μm. . Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., an unstretched sheet-like material obtained under the above-mentioned conditions has a draw ratio of 50% (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 1 is multiplied by 50% (stretching ratio: 1.50 times), and high-temperature stretching is performed, and MD stretching is performed. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 2)
The MD stretched porous film obtained in Example 1 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 3)
A polyacetal resin (A-1), a styrene thermoplastic elastomer (B-1), and a compatibilizer (C-1) were blended in the blending ratios shown in Table 1, and a twin-screw extruder (screw diameter: 25 mmφ) , Melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, and then cooled and solidified with a cast roll set at 120 ° C. to obtain an unstretched sheet with a thickness of 150 μm. . Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., an unstretched sheet-like material obtained under the above-mentioned conditions has a draw ratio of 50% (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 1 is multiplied by 50% (stretching ratio: 1.50 times), and high-temperature stretching is performed, and MD stretching is performed. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 1.

Example 4
The MD stretched porous film obtained in Example 3 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 5)
A polyacetal resin (A-1), a styrene thermoplastic elastomer (B-1), and a compatibilizer (C-1) were blended in the blending ratios shown in Table 1, and a twin-screw extruder (screw diameter: 25 mmφ) , Melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, and then cooled and solidified with a cast roll set at 120 ° C. to obtain an unstretched sheet-like material with a thickness of 180 μm. . Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., an unstretched sheet-like material obtained under the above-mentioned conditions has a draw ratio of 50% (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 1 is multiplied by 50% (stretching ratio: 1.50 times), and high-temperature stretching is performed, and MD stretching is performed. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 6)
The MD stretched porous film obtained in Example 5 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 7)
A polyacetal resin (A-1), a styrene thermoplastic elastomer (B-1), and a compatibilizer (C-1) were blended in the blending ratios shown in Table 1, and a twin-screw extruder (screw diameter: 25 mmφ) , Melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 120 ° C., and an unstretched sheet having a thickness of 190 μm was obtained. . Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., an unstretched sheet-like material obtained under the above-mentioned conditions has a draw ratio of 50% (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 1 is multiplied by 50% (stretching ratio: 1.50 times), and high-temperature stretching is performed, and MD stretching is performed. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 8)
The MD stretched porous film obtained in Example 7 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 1.

Example 9
A polyacetal resin (A-1), a styrene thermoplastic elastomer (B-1), and a compatibilizer (C-1) were blended in the blending ratios shown in Table 1, and a twin-screw extruder (screw diameter: 25 mmφ) , Melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, and then cooled and solidified with a cast roll set at 120 ° C. to obtain an unstretched sheet-like material with a thickness of 160 μm. . Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., an unstretched sheet-like material obtained under the above-mentioned conditions has a draw ratio of 50% (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 1 is multiplied by 50% (stretching ratio: 1.50 times), and high-temperature stretching is performed, and MD stretching is performed. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 1.

(Example 10)
The MD stretched porous film obtained in Example 9 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 1.

(Comparative Example 1)
Polyacetal resin (A-1) and styrene thermoplastic elastomer (B-1) were blended at the blending ratios shown in Table 2 and charged into a twin screw extruder (screw diameter 25 mmφ) at a set temperature of 200 ° C. After melt-kneading and shaping into a sheet with a T-die, cooling and solidification was performed with a cast roll set at 120 ° C. to obtain an unstretched sheet having a thickness of 140 μm. Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., the draw ratio 50% shown in Table 2 (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 2 is multiplied by 50% (stretching ratio: 1.50 times) to perform high-temperature stretching, and MD stretching. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 2.

(Comparative Example 2)
The MD stretched porous film obtained in Comparative Example 1 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd. and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 2.

(Comparative Example 3)
Polyacetal resin (A-1) and compatibilizing agent (C-1) are blended in the blending ratios shown in Table 2, charged into a twin screw extruder (screw diameter 25 mmφ), and melt kneaded at a set temperature of 200 ° C. Then, after forming into a sheet with a T-die, cooling and solidification was performed with a cast roll set at 120 ° C. to obtain an unstretched sheet with a thickness of 140 μm. Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., the draw ratio 50% shown in Table 2 (stretch ratio 1. The film was stretched at a low temperature. Next, between the roll (P) set to 120 ° C. and the roll (Q) set to 120 ° C., a draw ratio shown in Table 2 is multiplied by 50% (stretching ratio: 1.50 times) to perform high-temperature stretching, and MD stretching. A porous film was obtained. The evaluation results of the obtained porous film are summarized in Table 2.

(Comparative Example 4)
The MD stretched porous film obtained in Comparative Example 3 was preheated at a preheating temperature of 145 ° C. in a film tenter facility manufactured by Kyoto Machine Co., Ltd. and then stretched 2.00 times in the transverse direction at a stretching temperature of 145 ° C. A biaxially stretched porous film was obtained by performing a heat treatment at 0 ° C. The evaluation results of the obtained porous film are summarized in Table 2.

(Comparative Example 5)
As shown in Table 2, the polyacetal resin (A-1) is 38% by mass, the styrene thermoplastic elastomer (B-1) is 24% by mass, and the compatibilizer (C-1) is 38% by mass. Blended and put into a twin screw extruder (screw diameter 25 mmφ), melted and kneaded at a set temperature of 200 ° C., shaped into a sheet with a T-die, and then cooled and solidified with a cast roll set at 120 ° C. And an unstretched sheet having a thickness of 160 μm was obtained. Between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., the draw ratio 50% shown in Table 2 (stretch ratio 1. The film was broken between the roll (X) and the roll (Y) as described in Table 2 when the film was stretched at a low temperature.

(Comparative Example 6)
As shown in Table 2, the polyacetal resin (A-1) is 40% by mass, the styrene thermoplastic elastomer (B-1) is 50% by mass, and the compatibilizing agent (C-1) is 10% by mass. Compounded, put into a twin screw extruder (screw diameter 25 mmφ), melt kneaded at a set temperature of 200 ° C., and then tried to shape it into a sheet with a T die, but the molten resin discharged from the T die hardly flowed When the sheet was taken up by a cast roll, the sheet was torn off, and as shown in Table 2, an unstretched sheet-like product was not obtained.

(Comparative Example 7)
As shown in Table 2, the polyacetal resin (A-1) alone was put into a twin-screw extruder (screw diameter 25 mmφ), melted and kneaded at a set temperature of 200 ° C., and shaped into a sheet with a T-die Then, it was cooled and solidified with a cast roll set at 120 ° C. to obtain an unstretched sheet-like material having a thickness of 200 μm. Thereafter, between the roll (X) set to 20 ° C. and the roll (Y) set to 40 ° C., the obtained unstretched sheet-like material has a draw ratio of 50% shown in Table 2 (stretch ratio: 1.50 times). Was subjected to low-temperature stretching. Next, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., when the draw ratio shown in Table 2 was multiplied by 50% (stretch ratio 1.50 times), high-temperature stretching was performed. As described in Table 2, the film broke between the roll (P) and the roll (Q).

From Table 1, it can be seen that the stretched polyacetal resin obtained in Examples 1 to 10 has excellent air permeability and high porosity. Further, from Table 2 in which the compatibilizing agent defined by the present invention is not used, in Comparative Examples 1 and 2, a porous film having very excellent air permeability and high porosity is obtained.
However, when the penetration rates of propylene carbonate in the MD stretched porous films of Examples 1, 3, 5, 7, and 9 and the MD stretched porous film of Comparative Example 1 were compared, the MD stretched porous film of Comparative Example 1 Then, although the behavior in which the contact angle after the propylene carbonate was dropped decreased with time, it did not penetrate within 60 seconds, whereas the MD stretching of Examples 1, 3, 5, 7, and 9 In the porous film, penetration within 60 seconds was confirmed, and an improvement in the penetration rate of the electrolytic solution was confirmed.
Similarly, even when the penetration rates of propylene carbonate in the biaxially stretched porous films of Examples 2, 4, 6, 8, and 10 and the biaxially stretched porous film of Comparative Example 2 were compared, The biaxially stretched porous film penetrates after 33 seconds, whereas the biaxially stretched porous films of Examples 2, 4, 6, 8, and 10 penetrate after 13 seconds. Also in the porous film, it was confirmed that the penetration rate of the electrolytic solution was improved.

Moreover, the surface observation photograph (FIGS. 1, 2, and 3) of the porous film obtained in Examples 2, 4, and 6 and the porosity obtained in Comparative Example 2 using a scanning electron microscope (SEM). Comparing the surface observation photograph of the film (FIG. 4), in FIG. 4, the styrene-based elastomer that is the starting point for forming the porous structure is aggregated to confirm the location where large domains are formed, and the matrix around the pores The trunk structure seen in the part is observed thick. That is, it means that the gap between the holes to be formed is wide.
On the other hand, in FIGS. 1, 2, and 3, the styrene-based elastomer domain that is the starting point for forming the porous structure is smaller than the styrene-based elastomer domain confirmed in FIG. 4. It is considered that this is because the compatibility between the polyacetal resin and the styrene elastomer is improved by using the compatibilizer defined by the present invention, and the styrene elastomer is refined.
Also, in the trunk structure found in the matrix portion around the hole, it is confirmed that the trunk structure is thinner in FIGS. 1, 2, and 3 than in FIG. That is, due to the refinement of the styrene-based elastomer that is the domain, the gap between the formed holes is narrowed, and a uniform porous structure is formed throughout the matrix.
That is, the stretched porous body of the polyacetal resin of the present invention is a porous film having excellent air permeability, heat resistance, a dense porous structure, and high immersion in the electrolyte. I can say.

On the other hand, in Comparative Examples 3 and 4 in which the styrenic thermoplastic elastomer defined by the present invention is not used, both the MD stretched porous film and the biaxially stretched porous film are more air permeable and the electrolytic solution than in Examples 1 to 10. The permeability was poor.
Further, in Comparative Example 5 in which the mixed resin composition ratio of the polyacetal resin specified by the present invention deviates from the mixed resin composition ratio of the polyacetal resin, the styrene thermoplastic elastomer, and the compatibilizer, the film was broken and porous. A film was not obtained. This is presumably because the mixed resin composition ratio of the polyacetal resin is insufficient when the polyacetal resin constructs the matrix of the resin composition forming the unstretched sheet.
Further, in Comparative Example 6 in which the mixed resin composition ratio of the polyacetal resin and the styrene thermoplastic elastomer defined in the present invention deviates in the mixed resin composition ratio of the polyacetal resin, the styrene thermoplastic elastomer, and the compatibilizer, A stretched sheet was not obtained. This is presumably because the styrene-based thermoplastic elastomer is formed as a matrix having a sea-island structure because the weight ratio of the styrene-based thermoplastic elastomer exceeds 45% by mass.
And in the comparative example 7 which consists of a polyacetal type resin single-piece | unit, the film fractured | ruptured immediately after drawing by high temperature stretching, and the porous film was not obtained. This is probably because the thermoplastic elastomer and the compatibilizing agent specified in the present invention are not contained, so that the elastic modulus at the time of stretching increases and the material is broken.

  The porous body of the present invention can be applied to various uses that require air permeability. Specifically, separators for electronic components; foam materials for printed circuit boards of electronic components such as tablet devices and smartphones; sanitary materials such as disposable paper diapers and pads for absorbing bodily fluids such as sanitary items; bed sheets; Medical materials such as base materials; clothing materials such as jumpers, sportswear or rainwear; hollow fiber membranes for water treatment; building materials such as wallpaper, roof waterproofing materials, heat insulating materials, and sound absorbing materials; desiccants; An oxygen scavenger; a disposable body warmer; can be used very suitably as a material for packaging materials such as freshness-keeping packaging or food packaging, and is particularly useful as a foam material for electronic members and a separator for electronic members.

Claims (8)

  A stretched porous body comprising at least one porous layer comprising a resin composition comprising a polyacetal resin (A) as a main component and comprising a styrene thermoplastic elastomer (B) and a compatibilizer (C). The mixing composition ratio of the polyacetal resin (A), the styrene thermoplastic elastomer (B), and the compatibilizer (C) is (A) / (B) / (C) = 45 mass% to 98 mass%. / 1 mass% to 45 mass% / 1 mass% to 45 mass% (provided that the total mass% of (A), (B), and (C) is 100 mass%), and the compatibilizer (C ) Is a thermoplastic resin having a segment (x) having affinity for the polyacetal resin (A) and a segment (y) having affinity for the styrene thermoplastic elastomer (B) in the molecular skeleton. It is characterized by Acetal resin stretched porous.   The stretched polyacetal resin according to claim 1, wherein the segment (y) contains at least one unit selected from the group consisting of polyolefin units, polystyrene units, and polyphenylene ether units. .   The polyacetal resin according to claim 1 or 2, wherein the segment (x) contains at least one unit selected from the group consisting of polyurethane units, polylactic acid units, and polyether units. Stretched porous body.   4. The crystal melting enthalpy (ΔHm) derived from the polyacetal resin (A) in differential scanning calorimetry (DSC) is 10 J / g or more and 160 J / g or less. The polyacetal-based resin stretched porous body according to Item.   The polyacetal resin stretched porous body according to any one of claims 1 to 4, wherein the styrene thermoplastic elastomer (B) has a weight average molecular weight (Mw) of 150,000 or more.   The melt flow rate (MFR) at a temperature of 230 ° C and a load of 2.16 kg of the styrenic thermoplastic elastomer (B) is 30 g / 10 min or less, according to any one of claims 1 to 5. The polyacetal resin stretched porous body according to the description.   The stretched polyacetal-based resin according to any one of claims 1 to 6, wherein the styrene-based thermoplastic elastomer (B) has a styrene content of 1% by mass to 55% by mass. .   The electronic member formed using the polyacetal-type resin stretched porous body of any one of Claims 1-7.

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