JP2015137302A - Porous film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous film mainly containing a biodegradable resin, excellent in moisture vapor permeability, uniformity of moisture vapor transmission rate, water resistance and thin film formation property, and a manufacturing method therefor.SOLUTION: There is provided a porous film containing a biodegradable resin and a filler (C) with the content of the filler (C) of 1 to 400 pts.mass based on 100 pts.mass of the content of the biodegradable resin and satisfying a condition 1. Condition 1: 1≤30(Ta-Tb)/T≤5, where Ta: maximum thickness when thicknesses at 100 points per 10 mm interval are measured in a length direction, Tb: minimum thickness when thicknesses at 100 points per 10 mm interval are measured in a length direction and T: average thickness when thicknesses at 100 points per 10 mm interval are measured in a length direction.

Description

  The present invention relates to a porous film mainly composed of a biodegradable resin excellent in moisture permeability, moisture permeability uniformity, water resistance, and thin film formation, and a method for producing the same.

  There is known a porous film obtained by blending inorganic particles into a polyolefin resin typified by polyethylene and the like, melt-forming it, and then drawing it. Such a porous film is used as an agricultural material such as a multi-film, a sanitary material such as a waterproof film for paper diapers, and various packaging materials, and is generally discarded immediately after use. In recent years, with the increasing awareness of the environment, soil contamination problems due to the disposal of plastic products have attracted attention. However, the polyolefin resin hardly decomposes in the natural environment and remains in the soil semipermanently. There is.

  On the other hand, biodegradable resins that decompose in a natural environment have attracted attention. In the field of porous films, for example, Patent Document 1 discloses a porous sheet formed by stretching at least uniaxially a sheet containing a polylactic acid resin that is a biodegradable resin, a filler, and a general polyester plasticizer. It is disclosed. Patent Document 2 discloses that in addition to a polylactic acid polymer, an aliphatic aromatic copolymer polyester, and a fine powder filler, an aliphatic polycarboxylic acid ester, an aliphatic polyhydric alcohol ester, and an aliphatic polyhydric alcohol. A porous film containing a general plasticizer selected from ether and oxyacid ester and having pores formed by interfacial peeling between a fine powder filler and a resin component is disclosed. Furthermore, Patent Document 3 discloses a porous film including a polylactic acid resin, a thermoplastic resin other than polylactic acid, and a filler and having a certain porosity.

JP 2007-112867 A JP 2004-149679 A WO2009 / 084518 pamphlet

  In the above-mentioned Patent Document 1, there is a description that the thickness of the porous sheet can be about 4 to 90 μm, but in actuality, it is only an example in which the final thickness is about 30 μm, and a thin film having a thickness of less than 20 μm is formed. In addition, the uniformity of moisture permeability was insufficient. Here, the uniformity of moisture permeability means that there is no unevenness in the value of moisture permeability at each location in the film plane, and is an important performance required for improving quality after various products. In the above-mentioned Patent Document 2, there is a description that the thickness of the porous film is generally about 10 to 100 μm. However, in actuality, only the final thickness is 30 μm, and the moisture permeability is uniform. This point was also insufficient. In the above-mentioned Patent Document 3, it is described that the thickness of the film is preferably 5 to 200 μm. However, in actuality, only the final thickness is 20 μm, and the uniformity of moisture permeability is not satisfactory. It was enough.

  In view of the background of such prior art, the present invention provides a porous film mainly composed of a biodegradable resin excellent in moisture permeability, uniformity of moisture permeability, water resistance, and thin film formation, and a method for producing the same. To do.

The present invention includes a biodegradable resin and a filler (C), and the content of the filler (C) when the content of the biodegradable resin is 100 parts by mass is 1 to 400 parts by mass,
A porous film characterized by satisfying Condition 1.

Condition 1: 1 ≦ 30 (Ta−Tb) / T ≦ 5
However,
Ta: the maximum thickness when measuring 100 thicknesses at intervals of 10 mm in the length direction (hereinafter, Ta is referred to as the maximum thickness)
Tb: the minimum thickness when measuring the thickness at 100 points at intervals of 10 mm in the length direction (hereinafter, Tb is referred to as the minimum thickness)
T: Average thickness when 100 thicknesses are measured at intervals of 10 mm in the length direction (hereinafter, T is referred to as average thickness)
Another aspect of the present invention is a process for producing a film by extruding a resin composition melted by an extruder from a die (hereinafter referred to as an extrusion process), and using the difference in peripheral speed between rolls in the longitudinal direction of the film. A step (hereinafter referred to as a stretching step) and a step of heat-setting the stretched film (hereinafter referred to as a heat-setting step) in this order,
In the extrusion process, the average temperature (° C.) of the die is S-5 to S-50, where S is the maximum value of the cylinder temperature (° C.) of the extruder. Manufacturing method.

  The present invention provides a porous film mainly made of a biodegradable resin and excellent in moisture permeability, uniformity of moisture permeability, water resistance, and thin film formation, and a method for producing the same. The porous film of the present invention can be preferably used for applications requiring moisture permeability, uniformity of moisture permeability, water resistance, and thin film formation. Specifically, clothing materials, bed sheets, mats that have moisture and dust resistance required for sportswear, rainy clothing, gloves, etc., and moisture and dust resistance required for protective clothing, etc. Pillowcases and other bedding, medical and sanitary materials that are required for absorbent articles such as disposable diapers and sanitary goods, garbage bags, compost bags, food bags, bags for various industrial products, etc. It can be preferably used for packaging materials, industrial materials such as filters and separators for separating various substances.

  As a result of earnestly examining the above-mentioned problems, that is, a porous film made of a biodegradable resin excellent in moisture permeability, uniformity of moisture permeability, water resistance, and thin film formation, and a method for producing the same, a specific composition was obtained. And the relationship between the maximum thickness, the minimum thickness and the average thickness of the film is kept within a certain range, and the maximum temperature of the cylinder and the average temperature of the die in the extrusion process during film production. This is the first successful solution to this problem by a manufacturing method that keeps the above relationship within certain conditions.

  That is, the present invention includes a biodegradable resin and a filler (C), and the content of the filler (C) is 1 to 400 parts by mass when the content of the biodegradable resin is 100 parts by mass. A porous film characterized by satisfying condition 1.

Condition 1: 1 ≦ 30 (Ta−Tb) / T ≦ 5
However,
Ta: Maximum thickness Tb: Minimum thickness T: Average thickness Further, the present invention has an extrusion process, a stretching process, and a heat setting process in this order,
In the extrusion process, the average temperature (° C.) of the die is S-5 to S-50, where S is the maximum value of the cylinder temperature (° C.) of the extruder. Manufacturing method.

  Hereinafter, the porous film of the present invention and the production method thereof will be described.

(Biodegradable resin)
It is important that the porous film of the present invention contains a biodegradable resin. Since the biodegradable resin has a property of degrading in a natural environment, for example, even if it is discarded in the soil, the problem of remaining in the soil semipermanently does not occur. The biodegradable resin referred to in the present invention is JIS K6950 (2000), JIS K6951 (2000), JIS K6953-1 (2011), JIS K6953-2 (2010), JIS K6955 (2006), Chemical Substances Control Law. A resin having a degree of biodegradation of 60% or more when tested in any of the biodegradability tests (MITI method).

  Specific examples of the biodegradable resin include, for example, polylactic acid, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), and poly (3-hydroxybutyrate). 3-hydroxyhexanoate), polycaprolactone, polyethylene succinate, polybutylene succinate, polybutylene succinate, aliphatic polyesters represented by adipate, polyethylene succinate terephthalate, polybutylene succinate terephthalate, poly Use is made of aliphatic aromatic polyesters such as butylene adipate and terephthalate, thermoplastic starch, polyester resins containing starches such as Novamont's biodegradable resin “Matterby (registered trademark)”, and cellulose esters. It can be.

(Polylactic acid resin (A))
The porous film of the present invention preferably uses a polylactic acid resin (A) as a biodegradable resin. The polylactic acid-based resin is preferable in that it is made of a plant-derived raw material that does not give a new carbon dioxide load to the atmosphere even when incinerated, and is relatively advantageous in terms of cost.

  The polylactic acid resin (A) referred to in the present invention means a resin containing 10% by mass to 100% by mass of lactic acid units in 100% by mass of the polymer. The content of the lactic acid unit in the polylactic acid resin (A) is preferably 20% by mass or more and 100% by mass or less.

  Hereinafter, the polylactic acid resin (A) referred to in the present invention will be described separately for the polylactic acid resin of the first aspect and the polylactic acid resin of the second aspect.

  The polylactic acid-based resin according to the first aspect of the present invention refers to a resin containing 70 to 100% by mass of lactic acid units in 100% by mass of a polymer. It is preferable that the mass ratio of a lactic acid unit is 80-100 mass% in 100 mass% of polymers.

  The polylactic acid resin of the first aspect referred to in the present invention is preferably polylactic acid. And polylactic acid as used in the field of this invention means the general term of poly L-lactic acid and poly D-lactic acid. Furthermore, the poly-L-lactic acid referred to in the present invention is the polylactic acid-based resin of the first aspect, and further contains L-lactic acid units in 100 mol% of all lactic acid units in the polymer (polylactic acid-based resin). The ratio is over 50 mol% and 100 mol% or less. On the other hand, the poly-D-lactic acid referred to in the present invention is the polylactic acid-based resin of the first aspect, and further, in 100 mol% of all lactic acid units in the polymer (polylactic acid-based resin), The content ratio is more than 50 mol% and 100 mol% or less.

  In poly L-lactic acid, the crystallinity of the resin itself varies depending on the content ratio of the D-lactic acid unit. That is, if the content ratio of the D-lactic acid unit in the poly L-lactic acid increases, the crystallinity of the poly L-lactic acid decreases and approaches amorphous. Conversely, when the content ratio of the D-lactic acid unit in the poly L-lactic acid decreases, the crystallinity of the poly L-lactic acid increases. Similarly, in poly D-lactic acid, the crystallinity of the resin itself changes depending on the content ratio of the L-lactic acid unit. That is, when the content ratio of the L-lactic acid unit in the poly-D-lactic acid increases, the crystallinity of the poly-D-lactic acid decreases and approaches amorphous. Conversely, if the content ratio of the L-lactic acid unit in the poly-D-lactic acid decreases, the crystallinity of the poly-D-lactic acid increases.

  The content ratio of the L-lactic acid unit in the poly L-lactic acid or the content ratio of the D-lactic acid unit in the poly D-lactic acid is 80 in 100 mol% of all lactic acid units from the viewpoint of maintaining the mechanical strength of the resin composition. -100 mol% is preferable, More preferably, it is 85-100 mol%.

  The polylactic acid resin according to the first aspect of the present invention may be copolymerized with other monomer units other than the lactic acid unit. Examples of other monomers include glycol compounds such as ethylene glycol, dicarboxylic acids such as succinic acid and sebacic acid, hydroxycarboxylic acids such as glycolic acid, and lactones such as caprolactone. The copolymerization amount of the other monomer units is preferably 0 to 30 mol% and more preferably 0 to 10 mol% in 100 mol% of the whole monomer units in the polymer. In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

  Moreover, when using the polylactic acid-type resin of 1st aspect as a polylactic acid-type resin (A), it is also a preferable aspect to form a stereocomplex crystal | crystallization using poly L-lactic acid and poly D-lactic acid together. It is. Since the stereocomplex crystal has a higher melting point than the normal polylactic acid crystal, the heat resistance of the film can be improved.

  The mass average molecular weight of the polylactic acid resin of the first aspect referred to in the present invention, particularly the mass average molecular weight when the polylactic acid resin of the first aspect is polylactic acid, is practical in addition to water resistance and thin film formability. In order to maintain mechanical properties, it is preferably 100,000 to 300,000, more preferably 150,000 to 250,000.

  As the method for producing the polylactic acid resin of the first aspect referred to in the present invention, a known polymerization method can be used. Specific examples include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

  The polylactic acid resin according to the second aspect of the present invention refers to a resin containing 10% by mass or more and less than 70% by mass of a lactic acid unit in 100% by mass of a polymer. The mass ratio of the lactic acid unit is preferably 20 to 50 mass%, more preferably 25 to 45 mass%, in 100 mass% of the polymer.

  As the polylactic acid resin of the second aspect referred to in the present invention, a block copolymer having a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, and the like are preferably used. Here, the polyester segment means a segment made of polyester other than polylactic acid. These polylactic acid resins of the second aspect have at least the ability to plasticize the polylactic acid resin of the first aspect. Therefore, hereinafter, a block copolymer having a polyether segment and a polylactic acid segment and a block copolymer having a polyester segment and a polylactic acid segment are collectively referred to as a “block copolymer plasticizer”. These block copolymer plasticizers will be described below.

  The mass ratio of the polylactic acid segment contained in the block copolymer plasticizer is preferably 50% by mass or less of the entire block copolymer plasticizer, since it can impart desired flexibility with a smaller amount of addition, It is preferable from the point of bleed-out suppression that it is more than mass%. Preferably, in 100 mass% of the block copolymer plasticizer, the mass proportion of the polylactic acid segment is 25 to 45 mass%, and the mass proportion of the polyether segment or the polyester segment is 55 to 75 mass%.

  The number average molecular weight of the polylactic acid segment in one molecule of the block copolymer plasticizer is preferably 1,200 to 10,000. If the number average molecular weight of the polylactic acid segment of the block copolymer plasticizer is 1,200 or more, sufficient affinity between the block copolymer plasticizer and the polylactic acid resin of the first embodiment Occurs. In addition, a part of the polylactic acid segment is taken into the crystal formed from the polylactic acid-based resin of the first aspect and forms a so-called eutectic so that the block copolymer plasticizer becomes the first aspect. The polylactic acid-based resin of the present invention has an effect of anchoring, and exerts a great effect on the bleed-out suppression of the block copolymer plasticizer. The block copolymer plasticizer has excellent affinity with the polylactic acid resin of the first aspect and excellent bleed-out resistance, enabling uniform dispersion in the film and stability over time. I have to. As a result, the thin film formability when producing the porous film and the uniformity of moisture permeability of the porous film are further improved. These effects are not observed with a plasticizer that does not form a eutectic with the polylactic acid resin of the first embodiment. When the plasticizer is dispersed non-uniformly, the formation of pores during the production of the porous film is biased and the moisture permeability becomes non-uniform, or the film becomes uneven and the formation of a thin film becomes impossible. Plasticizer bleed-out also causes film thickness spots. The number average molecular weight of the polylactic acid segment in the block copolymer plasticizer is more preferably 1,500 to 6,000, and further preferably 2,000 to 5,000. In addition, in the polylactic acid segment of the block copolymer plasticizer, the L-lactic acid unit is 95 to 100% by mass, or the D-lactic acid unit is 95 to 100% by mass. Therefore, it is preferable.

  When the block copolymer plasticizer has a polyether segment, it is more preferable to have a segment made of polyalkylene ether as the polyether segment. Specific examples of the polyether segment include segments made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, and the like. In particular, the segment made of polyethylene glycol is excellent in modification efficiency because of its high affinity with the polylactic acid resin of the first aspect, and can impart desired flexibility with the addition of a small amount of plasticizer. The formability is also excellent. Addition of a large amount of plasticizer causes a decrease in the melt tension of the resin composition constituting the film, causing thickness unevenness or film tearing during thin film formation.

  When the block copolymer plasticizer has a polyester segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), poly (3-hydroxybutyrate · 3-hydroxyhexanoate), polycaprolactone, or a segment composed of an aliphatic diol such as ethylene glycol, propanediol, or butanediol, and a polyester composed of an aliphatic dicarboxylic acid such as succinic acid, sebacic acid, or adipic acid. It is suitably used as a polyester segment.

  In addition, the block copolymer plasticizer may contain both components of the polyether segment and the polyester segment in one molecule, or may contain only one of the components. For reasons of plasticizer productivity, cost, etc., when either component is used, it is preferable to use a polyether segment from the viewpoint that desired flexibility can be imparted by adding a smaller amount of the plasticizer. That is, a preferred embodiment as a block copolymer plasticizer is a block copolymer of a polyether segment and a polylactic acid segment.

  Furthermore, the number average molecular weight of the polyether segment or the polyester segment in one molecule of the block copolymer plasticizer is preferably 7,000 to 20,000. By setting the amount within the above range, the resin composition constituting the porous film has sufficient flexibility, and the melt viscosity of the resin composition constituting the film is set to an appropriate level. Film processability can be stabilized.

  There is no particular limitation on the order configuration of each segment block of the polyether segment and / or the polyester segment and the polylactic acid segment, but at least one block of polylactic acid segment is a block common from the viewpoint of more effectively suppressing bleed out. It is preferably at the end of the polymer plasticizer molecule. Most preferably, the block of polylactic acid segment is at both ends of the block copolymer plasticizer molecule.

  The porous film of the present invention has a total biodegradable resin content of 100% by mass, that is, the total of the polylactic acid resin (A) and the biodegradable resin (B) other than the polylactic acid resin. When it is 100 mass%, it is preferable to contain 40-95 mass% of polylactic acid-type resin (A). In a total of 100% by mass of the polylactic acid resin (A) and the biodegradable resin (B), by setting the content of the polylactic acid resin (A) to 40% by mass or more, moisture permeability and heat resistance are good. Thus, when the content of the polylactic acid resin (A) is 95% by mass or less, moisture permeability and flexibility are improved. The content of the polylactic acid resin (A) is more preferably 45 to 90% by mass in a total of 100% by mass of the polylactic acid resin (A) and the biodegradable resin (B), and 50 to 85%. It is more preferable that it is mass%, it is still more preferable that it is 55-80 mass%, and it is especially preferable that it is 60-80 mass%.

  The porous film of the present invention preferably contains both the polylactic acid resin of the first aspect and the polylactic acid resin of the second aspect as the polylactic acid resin (A). Further, in the porous film of the present invention, the polylactic acid resin (A) contains polylactic acid, and the polylactic acid resin (A) further has a block copolymer having a polyether segment and a polylactic acid segment, and / or Alternatively, it is more preferable to include a block copolymer having a polyester segment and a polylactic acid segment.

  In the polylactic acid resin (A) contained in the porous film of the present invention, when the total of the polylactic acid resin of the first aspect and the polylactic acid resin of the second aspect is 100% by mass, the second It is preferable that content of the polylactic acid-type resin of this aspect is 30-70 mass%. When the total of the polylactic acid resin of the first aspect and the polylactic acid resin of the second aspect is 100% by mass, the content of the polylactic acid resin of the second aspect is 30% by mass or more. The flexibility and moisture permeability become good, and the moisture permeability uniformity, thin film formability, and water resistance become good when the content of the polylactic acid resin of the second aspect is 70% by mass or less. The content of the polylactic acid resin of the second aspect is 35 to 65% by mass when the total of the polylactic acid resin of the first aspect and the polylactic acid resin of the second aspect is 100% by mass. It is more preferable, it is more preferable that it is 40-60 mass%, and it is especially preferable that it is 45-55 mass%.

  Moreover, it is preferable that content of the polylactic acid-type resin (A) when the whole porous film of this invention is 100 mass% is 20-65 mass%, and it is 25-60 mass%. More preferably, it is 30-55 mass%, More preferably, it is 35-50 mass%.

(Biodegradable resin other than polylactic acid resin (B))
The porous film of the present invention contains a polylactic acid resin (A) and a biodegradable resin (B) other than the polylactic acid resin as a biodegradable resin in order to improve flexibility and moisture permeability. Is preferred. The biodegradable resin (B) other than the polylactic acid resin referred to in the present invention refers to a biodegradable resin that does not correspond to the polylactic acid resin.

  Specific examples of the biodegradable resin (B) include polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), poly (3-hydroxybutyrate-3 -Hydroxyhexanoate), polycaprolactone, polyethylene succinate, polybutylene succinate, aliphatic polyesters represented by polybutylene succinate adipate, polyethylene succinate terephthalate, polybutylene succinate terephthalate, polybutylene adipate -Aliphatic aromatic polyester typified by terephthalate, thermoplastic starch, polyester resin containing starch typified by Novamont's biodegradable resin "Matterby (registered trademark)", cellulose ester, polyvinyl alcohol , And the like can be used. These biodegradable resins (B) may contain only 1 type and may contain it in combination of 2 or more type.

  Among these, since the compatibility or dispersibility in the polylactic acid-based resin (A) is relatively good, and the moisture permeability is uniform when formed into a porous film and the thin film formability is excellent, a biodegradable resin ( B) preferably contains an aliphatic polyester-based resin and / or an aliphatic aromatic polyester-based resin.

  The content of the biodegradable resin (B) contained in the porous film of the present invention is 5 to 60% by mass in a total of 100% by mass of the polylactic acid resin (A) and the biodegradable resin (B). It is preferable that Moisture permeability and flexibility are good by making the content of the biodegradable resin (B) 5% by mass or more in the total 100% by mass of the polylactic acid resin (A) and the biodegradable resin (B). Thus, by setting the content of the biodegradable resin (B) to 60% by mass or less, moisture permeability uniformity and heat resistance are improved. The content of the biodegradable resin (B) is more preferably 10 to 55% by mass in a total of 100% by mass of the polylactic acid resin (A) and the biodegradable resin (B). It is more preferable that it is mass%, and it is especially preferable that it is 20-45 mass%.

(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
Of the polylactic acid resin (A) contained in the porous film of the present invention, the polylactic acid resin of the first aspect is a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. Is preferred. This is because, by using a mixture, the advantages of both crystalline and amorphous polylactic acid resins can be achieved.

  The crystalline polylactic acid-based resin is polylactic acid when the polylactic acid-based resin is sufficiently crystallized under heating and then measured with a differential scanning calorimeter (DSC) in an appropriate temperature range. This refers to a polylactic acid resin in which a melting point derived from a component is observed. On the other hand, an amorphous polylactic acid-based resin refers to a polylactic acid-based resin that does not exhibit a clear melting point when the same measurement is performed.

  Inclusion of a crystalline polylactic acid resin as the polylactic acid resin of the first aspect is suitable for improving the heat resistance and blocking resistance of the film. Further, when the above-mentioned block copolymer plasticizer is used as the polylactic acid-based resin of the second aspect, the crystalline polylactic acid-based resin forms a eutectic with the polylactic acid segment of the block copolymer plasticizer. Great effect on bleed-out resistance.

  On the other hand, the inclusion of an amorphous polylactic acid resin as the polylactic acid resin of the first aspect is suitable for improving the uniformity of moisture permeability of the film and the bleed-out resistance of the plasticizer. This has an influence that the plasticizer is easily dispersed in the amorphous part of the amorphous polylactic acid resin in the film.

  From the viewpoint of improving heat resistance and blocking resistance, the crystalline polylactic acid-based resin has a content ratio of L-lactic acid units in poly L-lactic acid or a content ratio of D-lactic acid units in poly D-lactic acid. 96-100 mol% is preferable in 100 mol% of all lactic acid units, More preferably, it is 98-100 mol%.

  When a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin is used as the polylactic acid resin of the first aspect, the total of the crystalline polylactic acid resin and the amorphous polylactic acid resin is 100 mass. %, The content of the crystalline polylactic acid resin is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and further preferably 20 to 40% by mass.

(Filler (C))
The porous film of the present invention contains a filler (C), and it is important that the content of the filler (C) is 1 to 400 parts by mass when the content of the biodegradable resin is 100 parts by mass. It is. When content of a filler (C) is less than 1 mass part, it will be inferior to moisture permeability. Moreover, when content of a filler (C) exceeds 400 mass parts, the drawability at the time of film manufacture will deteriorate, and it will be inferior to moisture permeability uniformity, thin film formation property, and also water resistance. . The content of the filler (C) is preferably 10 to 400 parts by mass, more preferably 20 to 300 parts by mass, and further preferably 30 to 200 parts by mass with respect to 100 parts by mass of the biodegradable resin. Preferably, it is still more preferably 40 to 150 parts by mass, and particularly preferably 60 to 120 parts by mass.

  The filler refers to a substance added as a base material for improving various properties, or an inert substance added for the purpose of increasing the amount, increasing the volume, reducing the cost of the product, or the like. As the filler (C), an inorganic filler and / or an organic filler can be used.

  Examples of inorganic fillers include carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate; sulfates such as magnesium sulfate, barium sulfate, and calcium sulfate; zinc oxide, silicon oxide (silica), zirconium oxide, magnesium oxide, and oxide. Metal oxides such as calcium, titanium oxide, magnesium oxide, iron oxide, and alumina; hydroxides such as aluminum hydroxide; composites such as silicate minerals, hydroxyapatite, mica, talc, kaolin, clay, montmorillonite, zeolite, and zepiolite Oxides; phosphates such as lithium phosphate, calcium phosphate, and magnesium phosphate; metal salts such as lithium chloride and lithium fluoride can be used.

  Examples of organic fillers include oxalates such as calcium oxalate; terephthalates such as calcium terephthalate, barium terephthalate, zinc terephthalate, manganese terephthalate, magnesium terephthalate; divinylbenzene, styrene, acrylic acid, Fine particles made of vinyl monomers such as methacrylic acid or copolymers; organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, thermosetting phenol resin Cellulosic powder such as wood powder and pulp powder; Chips such as rice husk, wood chips, okara, waste paper ground material, clothing ground material; paper sludge; cotton fiber, hemp fiber, bamboo fiber, wood fiber, kenaf Plant fiber such as fiber, jute fiber, banana fiber, coconut fiber Silk, wool, angora, cashmere, animal fibers camel like; polyester fibers, nylon fibers, etc. can be used synthetic fibers such as acrylic fibers.

  Among these fillers, calcium carbonate, barium carbonate, barium sulfate, calcium sulfate, silicon oxide (silica), titanium oxide, mica, talc from the viewpoint of uniformity of moisture permeability of the film, thin film formation, and water resistance. , Kaolin, clay, montmorillonite and zeolite are preferred.

  Although the average particle diameter of the filler (C) used for the porous film of this invention is not specifically limited, 0.01-10 micrometers is preferable. In addition, the average particle diameter here means the particle diameter (D50 described later) at which the integrated mass from the minimum particle diameter side becomes 50% in the particle size distribution of the filler (C). When the average particle diameter (D50) is 0.01 μm or more, the film can be highly filled with the filler. When the average particle size (D50) is 10 μm or less, the stretchability of the film becomes good, and as a result, the film has excellent moisture permeability uniformity, thin film formability, and water resistance. The average particle diameter (D50) is more preferably 0.1 to 8 μm, still more preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. The filler (C) used in the porous film of the present invention preferably satisfies the following condition 3.

Condition 3: 1 ≦ (D100−D50) / D50 ≦ 5
However,
D50: the particle size distribution of the filler (C), the cumulative mass from the minimum particle size side becomes 50% D100: the particle size distribution of the filler (C), the cumulative mass from the minimum particle size side is 100% Here, the particle size distribution is measured by a laser diffraction method.

  In this invention, it discovered that the uniformity of moisture permeability became favorable because (D100-D50) / D50 was 1 or more. This is because the particle size of the filler has a certain difference, and the resin is filled without gaps, and when producing a porous film by stretching, voids are not formed in the film surface direction or thickness direction. It is thought that it is formed. Moreover, in this invention, it discovered that the uniformity of moisture permeability, thin film formation property, and water resistance became favorable because (D100-D50) / D50 is 5 or less. This is because, when extremely large particles are present with respect to the average particle diameter (D50) of the filler, when the porous film is stretched to produce pores, This may be due to tearing or pinholes.

  The filler (C) used in the porous film of the present invention preferably satisfies 1.5 ≦ (D100−D50) /D50≦4.0, and 1.5 ≦ (D100−D50) / More preferably, D50 ≦ 3.0 is satisfied.

  As the filler, a surface-treated filler can also be used. Surface treatment agents for surface treatment include fatty acids, phosphate ester compounds, surfactants, fats and oils, waxes, carboxylic acid coupling agents, silane coupling agents, titanate coupling agents, and polymer surface treatments. An agent or the like can be used. The surface treatment is effective in improving the affinity with the matrix resin, suppressing the aggregation of the filler, and improving the dispersibility, and can be uniformly dispersed in the resin composition. As a result, it becomes possible to obtain a resin composition having excellent film forming properties such as uniformity of moisture permeability and stretchability for expressing thin film forming properties.

  Moreover, in order to improve the dispersibility in the resin composition of a filler (C), it is also preferable to add dispersing agents, such as a fatty acid.

(Other resins)
Other resins other than the above-described biodegradable resin can be blended in the porous film of the present invention. Other resins include polyacetal, polyethylene, polypropylene, polyamide, poly (meth) acrylate, polyphenylene sulfide, polyether ether ketone, polyester, polyurethane, polyisoprene, polysulfone, polyphenylene oxide, polyimide, polyetherimide, ethylene / glycidyl methacrylate. Examples thereof include copolymers, ethylene / vinyl alcohol copolymers, polyester elastomers, polyamide elastomers, polyolefin elastomers, ethylene / propylene terpolymers, and ethylene / butene-1 copolymers.

(Film thickness)
It is important that the porous film of the present invention satisfies the following condition 1.

Condition 1: 1 ≦ 30 (Ta−Tb) / T ≦ 5
However,
Ta: Maximum thickness Tb: Minimum thickness T: Average thickness When 30 (Ta-Tb) / T is less than 1, thin film formability is poor. The main defect is that, after film formation, blocking occurs when winding into a roll shape, and the roll cross section does not become a uniform circle. On the other hand, when 30 (Ta-Tb) / T exceeds 5, the uniformity of moisture permeability becomes poor. This is considered to be caused by a difference in thickness depending on an arbitrary position in the film plane.

  The thickness of the porous film of the present invention preferably satisfies 1 ≦ 30 (Ta—Tb) / T ≦ 4, more preferably satisfies 1 ≦ 30 (Ta—Tb) / T ≦ 3. More preferably, ≦ 30 (Ta−Tb) / T ≦ 2 is satisfied.

  Means for achieving the thickness of the porous film of the present invention satisfying the condition 1 is not particularly limited. For example, a method using a filler satisfying the condition 3 as the filler (C), an average temperature of the die during film production In the method of S-5 to S-50 (S is the maximum temperature of the cylinder of the extruder), the method of providing a step of cooling the film between the stretching step and the heat setting step, the heat setting step, And a method of relaxing at a relaxation rate of 1 to 10% in the longitudinal direction of the film.

  The thin film as used in the field of this invention means the thickness below 20 micrometers. In addition, thickness here means the average thickness (the above-mentioned average thickness (T)) at the time of measuring the thickness of 100 points | pieces at intervals of 10 mm in the length direction. By being a thin film, the moisture permeability becomes good and the basis weight becomes low. Low weight per unit area is preferable in terms of weight reduction when the porous film is incorporated into a product and in terms of suppressing material costs.

  In addition, the criteria for determining good thin film formability in the present invention is that a film having an average thickness (T) of less than 20 μm can be formed without being broken, and blocking occurs when winding into a roll shape. Without, the cross section of the roll becomes a uniform circle.

  The porous film of the present invention is preferably a thin film, and the average thickness (T) of the film is preferably 5 to 18 μm. By setting the average thickness (T) of the film to 5 μm or more, the water resistance becomes good, the stiffness of the film becomes strong, and the handleability becomes excellent. The average thickness (T) of the film is more preferably 6 to 15 μm, further preferably 6 to 12 μm, and particularly preferably 6 to 10 μm.

(Porosity)
The porous film referred to in the present invention has an average porosity (average porosity (V) described later) of 1 to 80% when the porosity at 20 points is measured at intervals of 50 mm in the length direction. Refers to the film. The average porosity (V) of the porous film of the present invention is preferably 5 to 70%, more preferably 10 to 65%, still more preferably 15 to 60%, and further preferably 20 to 50%. % Is particularly preferred.

  Means for achieving the average porosity (V) of 1 to 80% are not particularly limited, but a method of using the biodegradable resin with the filler (C) as described above, and a preferred draw ratio described below. And a method for producing a porous film.

  The porous film of the present invention preferably satisfies the following condition 2.

Condition 2: (Va−Vb) /V≦0.25
However,
Va: the maximum porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction (hereinafter, Va is referred to as the maximum porosity)
Vb: the minimum porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction (hereinafter, Vb is referred to as the minimum porosity)
V: Average porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction (hereinafter, V is referred to as average porosity)
When (Va−Vb) / V is 0.25 or less, the uniformity of moisture permeability is improved.

  Means for achieving Condition 2 is not particularly limited. For example, the process of cooling the film between the stretching process and the heat setting process at the time of producing the porous film (hereinafter, referred to as satisfying Condition 3 described above, or as described later) Having a cooling step).

  The porous film of the present invention preferably satisfies (Va−Vb) /V≦0.20, more preferably satisfies (Va−Vb) /V≦0.15, and (Va−Vb). ) /V≦0.10 is particularly preferable. The lower limit of (Va−Vb) / V is preferably closer to 0, but is practically about 0.001.

(Melt tension of biodegradable resin (B))
In the porous film of the present invention, the melt tension of the biodegradable resin (B) at a temperature of 160 ° C. and a take-up speed of 10 m / min is represented by MS _B , and the melt tension of the entire resin composition constituting the porous film is represented by MS. When the moisture permeability is uniform, the melt tension ratio (MS _B / MS) is preferably 0.5 to 2.0. Here, each melt tension is measured at the stage of the raw material constituting the porous film. The melt tension ratio (MS _B / MS) is more preferably 0.7 to 1.6, and still more preferably 0.9 to 1.2.

Here, when the porous film contains a plurality of resins as the biodegradable resin (B), the melt tension MS _B of the biodegradable resin (B) is a value obtained by weighted averaging the individual melt tensions. To do. The weighted average here means an average in consideration of the resin-based content ratio. For example, the mass _{w 1,} a resin 1 of melt tension MS _1, mass _{w 2,} when containing resin 2 melt viscosity MS _2, the melt _{tension, (MS 1 × w 1 +} MS 2 × w 2) / ( w ₁ + w ₂ ).

(Tensile modulus)
The porous film of the present invention preferably has a tensile elastic modulus of 100 to 1,200 MPa in the length direction and the width direction in order to impart sufficient flexibility. The tensile modulus is more preferably 150 to 1,000 MPa, further preferably 200 to 800 MPa, and particularly preferably 250 to 600 MPa.

  As a method for setting the tensile modulus of elasticity in the length direction and the width direction to 100 to 1,200 MPa, types and blends of the polylactic acid resin (A) and the biodegradable resin (B) other than the polylactic acid resin The method which makes the amount the preferable aspect mentioned above, respectively is mentioned.

(Additive)
The porous film of the present invention may contain additives other than those described above as long as the effects of the present invention are not impaired. For example, known plasticizers, organic lubricants, antioxidants, crystal nucleating agents, endblockers, chain extenders, UV stabilizers, anti-coloring agents, matting agents, antibacterial agents, deodorants, flame retardants, weather resistance Agents, antistatic agents, antioxidants, ion exchange agents, tackifiers, antifoaming agents, color pigments, dyes, and the like can be used.

(Production method)
Next, the method for producing the porous film of the present invention will be specifically described, but the present invention is not limited thereto.

  In obtaining a resin composition that constitutes the porous film of the present invention, that is, a resin composition containing a biodegradable resin, a filler (C), and other additives as required, etc. It is possible to produce a resin composition by uniformly mixing a solution in which each component is dissolved in a solvent, and then removing the solvent. However, a method for producing a resin composition by melt-kneading each component is a solvent. It is preferable because steps such as dissolution of the raw material in the solvent and solvent removal are unnecessary. The melt kneading method is not particularly limited, and a known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity and dispersibility of the filler (C) in the resin, it is preferable to use a twin screw extruder. From the viewpoint of removing volatiles such as moisture and low molecular weight substances, it is more preferable to use a twin screw extruder with a vent hole.

  The temperature at the time of melt kneading is preferably in the range of 150 ° C. to 240 ° C., and more preferably in the range of 180 ° C. to 200 ° C. from the viewpoint of preventing deterioration of the biodegradable resin.

  When the resin composition obtained by the above-mentioned method is once pelletized, melt-kneaded again, and extruded and formed into a film, the pellets are dried at 60 to 100 ° C. for 6 hours or more, and the water content is 200 ppm. It is preferable to use a resin composition having a mass basis or less.

The method for producing a porous film of the present invention includes, for example, a step of producing a film by extruding a resin composition melted by an extruder from a die using the resin composition obtained by the above-described method (hereinafter referred to as an extrusion step). ), A step of stretching the film in the longitudinal direction of the film using a difference in peripheral speed between rolls (hereinafter referred to as a stretching step), and a step of heat-setting the stretched film (hereinafter referred to as a heat-setting step) in this order. In the extrusion step, when the maximum value of the cylinder temperature (° C.) of the extruder is S, the average temperature (° C.) of the die is preferably S-5 to S-50.

  Here, the highest value of the temperature of the cylinder of the extruder is the highest value among the actual temperatures of each section of the cylinder. The average die temperature is an average value of the actual temperatures when the heater section including the lip portion of the die is divided into a plurality of sections in the width direction of the film.

  By setting the average temperature of the die to S-5 to S-50, the uniformity of moisture permeability and thin film formability of the resulting porous film are improved. The reason for this is considered to be that the viscosity of the film extruded from the die is increased, and fluctuations in the thickness of the film are suppressed. In particular, biodegradable resins have a large change in melt viscosity with respect to temperature, and the above effect is considered to be very large. The average temperature (° C.) of the die is more preferably S-15 to S-50, further preferably S-25 to S-50, and particularly preferably S-35 to S-50. preferable.

  The die lip interval is preferably adjusted so that the draft ratio (draw ratio) of the film is 5-20. By adjusting the draft ratio within the above range, the moisture permeability uniformity and the thin film formability are improved. This is thought to be due to suppression of uneven thickness of the film. The draft ratio (draw ratio) is more preferably from 5 to 15, and further preferably from 5 to 10.

For the extrusion step of the porous film of the present invention, an existing method such as a known inflation method or T-die casting method can be adopted, but the T-die casting method is preferable from the viewpoint of uniformity of moisture permeability.

  When the T-die casting method is employed as the extrusion process, for example, the following method is used. The resin composition produced and dried by the above-described method is melt-extruded with a single-screw or twin-screw extruder set so that the temperature of the cylinder and the temperature of the die are in the ranges described above, so that the draft ratio described above is obtained. It is discharged from a slit-shaped die with the lip interval adjusted to the surface, and is electrostatically applied to a metal cooling casting drum set to a surface temperature of 0 to 40 ° C. by using a wire-like electrode having a diameter of 0.5 mm. A film before stretching is obtained.

  When the film before stretching obtained in the extrusion process is stretched in the longitudinal direction in the stretching process, for example, the following method is used. By heating the film before stretching on a heating roll, the temperature is raised to a temperature at which stretching in the longitudinal direction is performed. An auxiliary heating means such as an infrared heater may be used in combination for raising the temperature. The preferable range of the temperature of the film in the stretching step is 40 to 80 ° C, more preferably 45 to 75 ° C, and still more preferably 50 to 70 ° C. Thus, the film before extending | stretching heated up is extended | stretched by the multistage of 1 step | paragraph or 2 steps | paragraphs or more in a film longitudinal direction using the peripheral speed difference between heating rolls. The total draw ratio is preferably 1.5 to 5.5 times, more preferably 2 to 5 times, and even more preferably 2.5 to 4.5 times.

  Subsequently, the process proceeds to the heat setting step. From the viewpoint of uniformity of moisture permeability, the porous film of the present invention is a step of cooling the film between the stretching step and the heat setting step (hereinafter referred to as the cooling step). It is preferable to have. The reason why it is preferable to have the cooling step at this position is considered to be that the shape of the holes formed in the stretching step is once fixed before the heat fixing step. Here, means for cooling the film in the cooling step is not particularly limited, but means for conveying the film onto the cooled roll is preferable. 5-35 degreeC is preferable and, as for the temperature of the film in a cooling process, 10-30 degreeC is more preferable.

  In the heat setting step, for example, a method of transporting the film on a heating roll is used. 60-100 degreeC is preferable and, as for the temperature of the film in a heat setting process, 70-90 degreeC is more preferable. The heat setting time is preferably 0.2 to 30 seconds, but is not particularly limited. The porous film of the present invention is preferably relaxed in the longitudinal direction of the film in the heat setting step from the viewpoint of uniformity of moisture permeability, and the relaxation rate at that time is preferably 1 to 10%. This is considered to be effective by suppressing the change in the pore shape due to the shrinkage of the film over time by relaxing. The relaxation rate in the longitudinal direction of the film in the heat setting step is more preferably 5 to 10%.

  The porous film of the present invention may be a film uniaxially stretched only in the longitudinal direction as described above, or may be a film uniaxially stretched only in the width direction. A film uniaxially stretched in the longitudinal direction may be further stretched in the width direction. A known tenter method or the like is used for stretching in the width direction. The heat setting at the time of stretching in the width direction is preferably performed in a tenter.

  The film which passed through the extending process and the heat setting process as described above can be cooled and wound to obtain the intended porous film.

  After forming into a film, various surface treatments may be applied to the porous film of the present invention for the purpose of improving printability, laminate suitability, coating suitability, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Film thickness (μm)
Using the upright dial gauge R1-A (measuring element 10 mmφ, measuring load 50 g) manufactured by Ozaki Mfg. Co., Ltd., the thickness of 100 points is measured in the width direction of the film roll with a measurement center interval of 10 mm. At the center position, measurement was performed continuously in the longitudinal direction to determine Ta, Tb, T, and 30 (Ta-Tb) / T.
Ta: Maximum thickness when measuring 100 points at 10 mm intervals in the length direction Tb: Minimum thickness when measuring 100 points at 10 mm intervals in the length direction T: 10 mm intervals in the length direction (2) Porosity (%)
The center position in the width direction of the film roll was continuously cut from an arbitrary place in the longitudinal direction, and 20 films were cut into a square of 50 mm (longitudinal direction) × 30 mm (width direction) as a sample. Using an electronic hydrometer (SD-120L manufactured by Mirage Trading Co., Ltd.), the specific gravity (ρ) was measured in an atmosphere having a room temperature of 23 ° C. and a relative humidity of 65%.

Next, the film roll was cut out from an arbitrary place and subjected to hot pressing at 280 ° C. and 5 MPa, and then rapidly cooled with water at 25 ° C. to prepare a sheet from which voids were completely erased. At this time, if necessary, several sheets of film were stacked and hot-pressed so that the sheet thickness after hot-pressing was about 50 to 100 μm to create a sheet. The specific gravity of this sheet was measured in the same manner as described above, and the average specific gravity of the three hot-pressed sheets was defined as the specific gravity (d) of the resin. From the specific gravity of the film and the specific gravity of the resin, the porosity was calculated by the following formula.
Porosity (%) = [(d−ρ) / d] × 100
The porosity was calculated for each sample (20 pieces), Va, Vb, and V were determined, and (Va−Vb) / V was determined.

(3) Melt tension The melt tension of the resin pellets dried until the water content became 200 ppm or less was measured under the following conditions using the load measurement mode of the melt tension test of Capillograph 1D manufactured by Toyo Seiki.
Capillary: 1mm diameter, 10mm length
Measurement temperature: 160 ° C
Preheating time: 5 min
Extrusion speed: 10mm / min
Take-off speed: 10 m / min
Extrusion before measurement: 2 min
(4) Uniformity of moisture permeability Ten films in a square of 100 mm (longitudinal direction) × 100 mm (width direction) continuously from the center in the longitudinal direction at the center in the width direction of the film roll. A cut sample was obtained. The moisture permeability (g / (m ² · day)) of 10 samples was measured according to the method specified in JIS Z0208 (1976) with a constant temperature and humidity device set at 25 ° C. and 90% RH, and the maximum Using the value of (Pa-Pb) / P where Pa is the moisture permeability, Pb is the minimum moisture permeability, and P is the average moisture permeability, the following criteria were used for evaluation.

A: Less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.20 D: 0.20 or more.

(5) Moisture permeability Using the average moisture permeability P value measured in (4), the following criteria were used for evaluation.
A: 1500 g / (m ² · day) or more B: 1000 g / (m ² · day) or more and less than 1500 g / (m ² · day) C: 500 g / (m ² · day) or more 1000 g / (m ² · day) Less than D: Less than 500 g / (m ² · day).

(6) Water resistance The center position in the width direction of the film roll is continuously cut from an arbitrary place in the longitudinal direction, and six films are cut into a square having a size of 160 mm (longitudinal direction) × 160 mm (width direction). did. According to the method specified in JIS L 1092 (2009), the water resistance (mm) of 6 samples was measured. At this time, the water level rising speed of the measuring device was 600 mm / min ± 30 mm / min. In addition, to prevent large deformation of the film sample during measurement, a wire mesh (plain weave type, mesh approximately 4 mm, wire mesh wire diameter approximately 1 mm) is installed on the top surface of the film sample. did. Rubber packing was put on the upper and lower surfaces of the wire mesh. Evaluation was made based on the following criteria using the minimum water resistance value among the water resistance values of the six samples.

A: 1000 mm or more B: 400 mm or more and less than 1000 mm C: 100 mm or more and less than 400 mm D: Less than 100 mm.

  Below, the material used in the Example is demonstrated.

[Polylactic acid resin (A) of the first embodiment]
(A1)
Crystalline poly L-lactic acid resin, mass average molecular weight = 200,000, D-form content = 1.4 mol%, melting point = 166 ° C.

(A2)
Amorphous poly L-lactic acid resin, mass average molecular weight = 200,000, D-form content = 12.0 mol%, melting point = none.

  The above melting point is obtained by heating a polylactic acid resin in a hot air oven at 100 ° C. for 24 hours, and then using a differential scanning calorimeter RDC220 manufactured by Seiko Instruments Inc. It calculated | required as a peak temperature of the crystal melting peak at the time of heating up to 250 degreeC with the temperature increase rate of 20 degree-C / min.

[Polylactic acid resin (A) of the second embodiment]
(A3)
62 parts by mass of polyethylene glycol having a number average molecular weight Mn of 8,000, 38 parts by mass of L-lactide and 0.05 parts by mass of tin octylate are mixed and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 3 hours in a nitrogen atmosphere. Thus, a polylactic acid resin A3 having polylactic acid segments having a number average molecular weight Mn of 2,500 at both ends of polyethylene glycol having a number average molecular weight Mn of 8,000 was obtained.

[Biodegradable resin (B)]
(B1)
Polybutylene succinate resin (trade name “GSPla (registered trademark)” AZ91TN, manufactured by Mitsubishi Chemical Corporation), MS _B = 5 mN.

(B2)
Polybutylene succinate resin (trade name “GSPla (registered trademark)” FZ91PN, manufactured by Mitsubishi Chemical Corporation), MS _B = 10 mN.

[Filler (C)]
(C2)
Calcium carbonate (Ajinomoto Fine Techno Co., Ltd., trade name “Top Flow H200”, average particle diameter (D50): 2.1 μm, surface treatment agent: phosphate ester compound, ratio of surface treatment agent: 3% by mass or less, (D100-D50) /D50=3.6)
(C1)
Calcium carbonate (“Sankyo Seimitsu Co., Ltd., trade name“ ESCALON # 2300 ”, average particle size: 1.8 μm” was subjected to the same kind and the same amount of surface treatment as C2, (D100−D50) / D50 = 2.7)
(C3)
Calcium carbonate (manufactured by Maruo Calcium Co., Ltd., trade name “Caltex R”, average particle size: 2.8 μm, surface treatment agent: stearic acid, ratio of surface treatment agent: 3% by mass or less, (D100−D50) / D50 = 4 .7)
(C4)
Calcium carbonate (“Sankyo Seimitsu Co., Ltd., trade name“ Escalon # 1500 ”, average particle size: 2.8 μm” was subjected to the same type and the same amount of surface treatment as C2, (D100−D50) / D50 = 5.6)
(C5)
Calcium carbonate (average particle size: 2.6 μm, (D100−D50) /D50=0.5)
In addition, the particle size distribution for calculating | requiring D50 and D100 was measured using the laser diffraction type particle size distribution measuring machine (Nikkiso Co., Ltd. Microtrac MT3000-II).

[Production of porous film]
Example 1
15 parts by mass of polylactic acid resin (A1), 35 parts by mass of polylactic acid resin (A2), 20 parts by mass of polylactic acid resin (A3), 30 parts by mass of polybutylene succinate resin (B1), and filler (C1 ) 70 parts by mass of the mixture was subjected to a twin screw extruder with a cylinder diameter of 190 ° C and a screw diameter of 44 mm with a vacuum vent, melt kneaded while degassing the vacuum vent, homogenized, and then pelletized to obtain a resin composition It was. The pellet of the resin composition was vacuum-dried at a temperature of 60 ° C. for 12 hours using a rotary drum type vacuum dryer.

  The dried pellets are fed into a single screw extruder having a maximum cylinder temperature value S of 190 ° C. and extruded into a film form from a T die having a lip spacing of 0.4 mm and an average die temperature of 150 ° C. A film before stretching was prepared by casting on the top of a drum cooled to 20 ° C. at a lip-drum distance of 30 mm. This unstretched film was guided to a heating roll, and stretched 3.5 times at a temperature of 60 ° C. in the longitudinal direction due to a difference in peripheral speed between the heating rolls. The film was once cooled to 20 ° C. with a cooling roll and then guided again to the heating roll, and heat-fixed at a temperature of 70 ° C. for 3 seconds while relaxing at a relaxation rate of 5% in the longitudinal direction of the film. Thereafter, the film was cooled to 20 ° C. with a cooling roll, and then wound up to obtain a porous film having a thickness of 14 μm. The physical properties of the obtained film are shown in the table.

(Examples 2-4, 6-10, Comparative Examples 1-3)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the composition of the film was changed as shown in Tables 1 and 2. The physical properties of the obtained film are shown in the table.

(Example 5)
A film having a thickness of 18 μm was obtained in the same manner as in Example 1 except that the composition of the film was changed as shown in Table 1. The physical properties of the obtained film are shown in the table.

(Examples 11 to 13)
The composition of the film was changed as shown in Table 2 except that the maximum temperature S of the cylinder of the single screw extruder was changed to 200 ° C., the average temperature of the T die was changed to 160 ° C., and the stretching temperature was changed to 70 ° C. A film having a thickness of 14 μm was obtained in the same manner as in Example 1. The physical properties of the obtained film are shown in the table.

(Example 14)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the average temperature of the T-die was changed to 160 ° C. The physical properties of the obtained film are shown in the table.

(Example 15)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the average temperature of the T-die was changed to 170 ° C. The physical properties of the obtained film are shown in the table.

(Example 16)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the average temperature of the T-die was changed to 180 ° C. The physical properties of the obtained film are shown in the table.

(Comparative Example 4)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the average temperature of the T-die was changed to 190 ° C. The physical properties of the obtained film are shown in the table.

(Example 17)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the cooling step after stretching was eliminated. The physical properties of the obtained film are shown in the table.

(Example 18)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that the relaxation rate in the heat setting step was changed to 10%. The physical properties of the obtained film are shown in the table.

(Example 19)
A film having a thickness of 14 μm was obtained in the same manner as in Example 1 except that relaxation was not performed in the heat setting step. The physical properties of the obtained film are shown in the table.

The thin film formability was good except for Comparative Examples 1 and 2.
As for the ratio of the melt tension _(MS B / MS), Example 1,6,7,14～19, Comparative Example 3 1.0 Example 9 was 1.7. Other examples are not measured.

  In the table, “mass%” of the polylactic acid resin (A) and the thermoplastic resin (B) is a value in a total of 100 mass% of (A) and (B), and “ “Mass part” is a value when (A) + (B) = 100 parts by mass.

  The present invention is a porous film mainly composed of a biodegradable resin, excellent in moisture permeability uniformity, water resistance, and thin film formation, and a method for producing the same. The porous film of the present invention is a clothing material having moisture permeability / water resistance required for sportswear, clothes for rainy weather, gloves, etc., moisture permeability / dust resistance required for protective clothing, etc., bed sheets , Mattresses, pillowcases and other beddings, medical and sanitary materials with moisture permeability and waterproofness required for absorbent articles such as disposable diapers and sanitary products, garbage bags, compost bags, food bags, and various industrial products It can be preferably used for packaging materials such as bags, industrial materials such as filters and separators for separating various substances.

Claims (10)

The content of the filler (C) is 1 to 400 parts by mass when the content of the biodegradable resin is 100 parts by mass, including the biodegradable resin and the filler (C),
A porous film characterized by satisfying condition 1.
Condition 1: 1 ≦ 30 (Ta−Tb) / T ≦ 5
However,
Ta: Maximum thickness when measuring 100 points at 10 mm intervals in the length direction Tb: Minimum thickness when measuring 100 points at 10 mm intervals in the length direction T: 10 mm intervals in the length direction The average thickness when measuring the thickness of 100 points The porous film according to claim 1, wherein Condition 2 is satisfied.
Condition 2: (Va−Vb) /V≦0.25
However,
Va: Maximum porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction Vb: Minimum porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction V: Average porosity when measuring the porosity of 20 points at intervals of 50 mm in the length direction The porous film according to claim 1, wherein Condition 3 is satisfied.
Condition 3: 1 ≦ (D100−D50) / D50 ≦ 5
However,
D50: the particle size distribution of the filler (C), the cumulative mass from the minimum particle size side becomes 50% D100: the particle size distribution of the filler (C), the cumulative mass from the minimum particle size side is 100% Particle size   The porous film according to any one of claims 1 to 3, wherein the biodegradable resin includes a polylactic acid resin (A) and a biodegradable resin (B) other than the polylactic acid resin. . The polylactic acid resin (A) contains polylactic acid,
Furthermore, the polylactic acid-based resin (A) includes a block copolymer having a polyether segment and a polylactic acid segment, and / or a block copolymer having a polyester segment and a polylactic acid segment, The porous film according to claim 4.   The porous film according to claim 4 or 5, wherein the biodegradable resin (B) contains an aliphatic polyester-based resin and / or an aliphatic aromatic polyester-based resin. A process of producing an extruded film from a die melted resin composition by an extruder (hereinafter referred to as an extrusion process), a process of stretching the film in the longitudinal direction of the film using a difference in peripheral speed between rolls (hereinafter referred to as stretching) Process), and a step of heat-setting the stretched film (hereinafter referred to as heat-setting step) in this order,
In the extrusion process, the average temperature (° C.) of the die is S-5 to S-50, where S is the maximum value of the cylinder temperature (° C.) of the extruder. Manufacturing method.   The method for producing a porous film according to claim 7, further comprising a step of cooling the film between the stretching step and the heat setting step.   The method for producing a porous film according to claim 7 or 8, wherein in the heat setting step, the film relaxes in the longitudinal direction of the film, and the relaxation rate at that time is 1 to 10%.   The resin composition contains a biodegradable resin and a filler (C), and the content of the filler (C) is 1 to 400 parts by mass when the content of the biodegradable resin is 100 parts by mass. It exists, The manufacturing method of the porous film in any one of Claims 7-9 characterized by the above-mentioned.