JP2012057004A - Porous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous film comprising mainly a polylactic acid-based resin which is excellent in moisture permeability and suppresses odor.SOLUTION: This porous film is a porous film comprising a composition containing 100 pts.mass of a thermoplastic resin comprising mainly a polylactic acid-based resin (A) and 0.1 to 200 pts.mass of a deodorant (B), and having a porosity of 10 to 80%.

Description

  The present invention relates to a porous film mainly composed of a polylactic acid-based resin in which the generation of odor is suppressed, and further relates to a porous film excellent in flexibility, moisture permeability, heat resistance and excellent deodorizing effect.

  In recent years, with increasing environmental awareness, attention has been focused on soil pollution problems caused by the disposal of plastic products and global warming problems caused by increased carbon dioxide caused by incineration. As a measure against the former, various biodegradable resins, and as a measure against the latter, a resin made of biomass (plant-derived raw material) that does not give a new carbon dioxide load to the atmosphere even if it is incinerated has been extensively researched and developed. ing. Attention has been focused on polylactic acid that satisfies both requirements and is relatively advantageous in terms of cost. When polylactic acid is applied to soft film applications typified by polyolefins such as polyethylene, it lacks flexibility and impact resistance. Therefore, various attempts have been made to improve these properties and put them into practical use.

  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, a filler, and a general polyester plasticizer. Patent Document 2 discloses a polylactic acid polymer, an aliphatic aromatic copolymer polyester, an aliphatic polycarboxylic acid ester, an aliphatic polyhydric alcohol ester, an aliphatic polyhydric alcohol ether, and an oxyester. A porous film is disclosed in which fine powder fillers are blended with general plasticizers selected to form pores.

  On the other hand, since a molded product made of a polylactic acid-based resin has a peculiar odor, there is a problem that the range of use is limited particularly in applications that hate odor, such as food packaging materials and sanitary materials.

Regarding the odor problem of polylactic acid, a method is disclosed in which residual lactide and odor components are devolatilized by heating under reduced pressure or at the end of polymerization reaction (Patent Document 3). Other,
A technique (Patent Document 4) in which a volatile component generated by heating is not more than a specific amount and a technique (Patent Document 5) in which a molded product containing a biodegradable resin contains an odorous substance adsorbent are disclosed.
However, the above-described method is an insufficient technique for suppressing the odor generated in the melt molding of polylactic acid resin and the subsequent processing.

JP 2007-112867 A JP 2004-149679 A JP-A-7-173266 JP 2005-146274 A JP 2003-128798 A

  The techniques described in the above-mentioned patent documents have a certain moisture permeability but are not sufficient, and the suppression of odor is insufficient. In other words, porous films that have been biodegraded and have a high degree of biomass have been studied so far, but their moisture permeability is not sufficient, and the invention of a film having excellent performance in which odor is sufficiently suppressed. Has not yet been achieved.

  Therefore, in view of the background of such conventional technology, the present invention is intended to provide a porous film mainly composed of a polylactic acid-based resin having excellent moisture permeability and suppressing odor.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following, and have reached the present invention.
1) It consists of a composition containing 0.1 to 200 parts by mass of deodorant (B) with respect to 100 parts by mass of thermoplastic resin mainly composed of polylactic acid resin (A), and the porosity is 10 to 80%. A porous film, characterized in that
2) The porous film according to 1), wherein the deodorant (B) is made of zeolite.
3) The porous film according to 1) or 2), wherein the composition contains 10 to 200 parts by mass of a filler (C) with respect to 100 parts by mass of the thermoplastic resin.
4) The thermoplastic resin contains a resin (D) other than the polylactic acid resin (A), and the polylactic acid resin (A) is 50 in a total of 100% by mass of the polylactic acid resin (A) and the resin (D). The porous film according to any one of 1) to 3), wherein the content is -95% by mass and the resin (D) is 5-50% by mass.
5) Resin (D) is a block copolymer having a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, an aliphatic polyester resin, and an aliphatic aromatic The porous film as described in 4), which is at least one resin selected from the group consisting of polyester resins.
6) The porous film according to any one of 1) to 5), wherein the tensile elastic modulus is 100 to 1,500 MPa.

  ADVANTAGE OF THE INVENTION According to this invention, the porous film which consists of polylactic acid-type resin mainly which was excellent in moisture permeability and the odor was suppressed is provided. The porous film of the present invention is a medical / hygienic material such as bed sheets, pillow covers, sanitary napkins, back sheets of absorbent articles such as paper diapers, etc., which are mainly required to be moisture permeable and dislike odor. It can be preferably used for clothing materials such as gloves, garbage bags and compost bags, food bags such as vegetables and fruits, and packaging materials such as bags for various industrial products.

  The present invention has a composition comprising a specific resin and a deodorant as a result of intensive studies on the above-mentioned problem, that is, a porous film mainly composed of a polylactic acid-based resin having excellent moisture permeability and suppressing odor. Furthermore, the solution of this problem has been successful for the first time by keeping the porosity of the film within a certain condition. That is, this invention consists of a composition which contains 0.1-200 mass parts of deodorizers (B) with respect to 100 mass parts of thermoplastic resins which have polylactic acid resin (A) as a main component, and the porosity is 10 It is a porous film characterized by being -80%.

Hereinafter, the porous film of the present invention will be described.
(Polylactic acid resin (A))
It is important that the porous film of the present invention is made of a thermoplastic resin mainly composed of the polylactic acid resin (A). Here, the thermoplastic resin mainly composed of the polylactic acid resin (A) means an aspect in which the polylactic acid resin (A) is 50% by mass or more and 100% by mass or less in 100% by mass of the thermoplastic resin. The polylactic acid-based resin is a polymer having an L-lactic acid unit and / or a D-lactic acid unit as main constituent components. Here, the main component means that the mass ratio of the lactic acid unit is the maximum in 100% by mass of the polymer. The mass ratio of the lactic acid unit is preferably 70% by mass to 100% by mass of the lactic acid unit in 100% by mass of the polymer.

  The term “poly L-lactic acid” as used in the present invention means that the content of L-lactic acid units is more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polylactic acid polymer. On the other hand, the poly-D-lactic acid referred to in the present invention refers to those having a D-lactic acid unit content of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polylactic acid polymer.

  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 becomes lower and becomes closer to an amorphous state, and conversely, the content ratio of the D-lactic acid unit in the poly-L-lactic acid. As the amount decreases, the crystallinity of 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, if the content ratio of the L-lactic acid unit in the poly-D-lactic acid increases, the crystallinity of the poly-D-lactic acid becomes low and approaches an amorphous state. Conversely, the content ratio of the L-lactic acid unit in the poly-D-lactic acid. As the amount decreases, the crystallinity of poly-D-lactic acid increases.

  The content ratio of the L-lactic acid unit in the poly L-lactic acid used in the present invention or the content ratio of the D-lactic acid unit in the poly D-lactic acid used in the present invention is a viewpoint for maintaining the mechanical strength of the composition. From 100 to 100 mol% of all lactic acid units, 80 to 100 mol% is preferable, and 85 to 100 mol% is more preferable.

  The crystalline polylactic acid resin referred to in the present invention is a case where the polylactic acid 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 the heat of crystal melting derived from the polylactic acid component is observed.

  On the other hand, the amorphous polylactic acid-based resin referred to in the present invention refers to a polylactic acid-based resin that does not exhibit a clear melting point when measured in the same manner.

  The polylactic acid resin used in the present invention may copolymerize other monomer units other than lactic acid. Other monomers include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentane. Glycol compounds such as erythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid , Isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, -Dicarboxylic acids such as sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, caprolactone, valerolactone, Examples include lactones such as propiolactone, undecalactone, and 1,5-oxepan-2-one. The copolymerization amount of the other monomer units is preferably 0 to 30 mol%, based on 100 mol% of the whole monomer units in the polymer of the polylactic acid resin, and 0 to 10 mol%. More preferably. In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

  Moreover, about the polylactic acid-type resin used by this invention, when a main component is poly L-lactic acid, poly D-lactic acid is mixed, when a main component is poly D-lactic acid, poly L-lactic acid is mixed a little. It is also preferable. This is because the stereocomplex crystal formed thereby has a higher melting point than a normal polylactic acid crystal (α crystal), so that the heat resistance of the film is improved.

  The mass average molecular weight of the polylactic acid resin used in the present invention is preferably 50,000 to 500,000, more preferably 80,000 to 400,000, in order to satisfy practical mechanical properties. More preferably, it is ˜300,000. The mass average molecular weight as used herein refers to a molecular weight calculated by a polymethyl methacrylate conversion method after measurement with a chloroform solvent by gel permeation chromatography (GPC).

  The production method of the polylactic acid-based resin will be described later in detail, but a known polymerization method can be used, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

Further, the content of the polylactic acid resin (A) in the whole composition constituting the porous film of the present invention is preferably 5 to 80% by mass, more preferably 15 to 70% by mass, More preferably, it is 25-60 mass%, and it is especially preferable that it is 35-50 mass%.
(Deodorant (B))
It is important that the porous film of the present invention comprises a composition containing a deodorant (B). Here, the deodorant (B) is not particularly limited as long as it has a deodorizing effect. However, the deodorant (B) has an effect of reducing the odor by incorporating or wrapping the odor component, or the odor component is subjected to an oxidation reaction or a medium. Examples thereof include those having an effect of changing to a chemically less odorous substance by a sum reaction. Examples of those having an effect of reducing odor components include porous adsorbents having adsorption ability such as charcoal, activated carbon, diatomaceous earth, silica gel, zeolite, activated alumina, and inclusion ability typified by cyclodextrin. Compounds. Examples of those having an effect by chemical reaction include compounds having reactivity with odor components such as sodium bicarbonate, citric acid and polyphenol, metals such as copper, silver, titanium, and zinc, or metal oxides, Examples thereof include compounds that promote the decomposition reaction of odor components and odor-causing substances by catalytic effects such as salts thereof. These may be used alone or in combination.

  Among these deodorants (B), for example, charcoal, activated carbon, diatomaceous earth, silica gel, zeolite from the viewpoint of thermal stability in the film production process without impairing the performance of the polylactic acid resin used in the present invention. A porous adsorbent having an adsorbing ability such as activated alumina is preferably used, and zeolite is particularly preferred from the viewpoint of adsorbing ability of odor components.

  Zeolite is generally composed of aluminum, silicon, oxygen, alkali metal or alkaline earth metal, etc., and has a three-dimensional crystal structure and structural cavities (pores). Either zeolite or synthetic zeolite can be used. In addition, zeolite has a structure in which the alkali metal or alkaline earth metal constituting it is supported by ion exchange with a metal such as copper, silver, or zinc, in addition to adsorption capacity, decomposition of odor components and odor-causing substances. This is preferable because it has an effect of promoting the reaction.

  Moreover, the film of this invention is comprised from the composition which contains 0.1-200 mass parts of deodorizers (B) with respect to 100 mass parts of thermoplastic resins which have polylactic acid-type resin (A) as a main component. It's important to. When the amount is less than 0.1 parts by mass, the deodorizing effect is insufficient. When the amount exceeds 200 parts by mass, the tensile strength and tensile elongation of the film are insufficient. It gets worse. The content of the deodorant (B) in the composition constituting the film is 0.3 to 150 parts by mass with respect to 100 parts by mass of the thermoplastic resin mainly composed of the polylactic acid resin (A). Preferably, it is 0.5-100 mass parts, More preferably, it is 1-80 mass parts.

  The deodorant (B) is preferably blended uniformly in the thermoplastic resin, and is preferably in a granular form from the viewpoint of dispersibility in the resin or handleability during production, and can be handled in the form of powder or slurry. preferable.

  The particle size of the deodorant (B) is not particularly limited, but an average particle size of 0.01 to 10 μm is preferable. By setting the average particle size to 0.01 μm or more, the deodorant (B) can be easily dispersed uniformly in the film, and can be further filled with high density. As a result, the contact opportunity with an odor substance can be increased and the deodorizing effect can be made remarkable. In addition, when the average particle size is 10 μm or less, the stretchability of the film is improved, and as a result, the film has high potential in terms of making the film porous and improving moisture permeability. The average particle diameter is more preferably 0.1 to 8 μm, further preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. Here, the average particle diameter is a 50% cumulative distribution average particle diameter measured by a laser diffraction scattering method.

As the deodorant (B) is uniformly dispersed in the porous film of the present invention, the deodorant component exposed on the film surface and the surface of the voids (holes) in the film increases, and the odor substance It is preferable in terms of increasing the chance of contact with and making the deodorizing effect remarkable. Furthermore, when a particulate deodorant is used, the thermoplastic resin covering the deodorant is reduced by forming voids in the film by highly filling and stretching the particulate deodorant. In addition, it is particularly preferable because the deodorizing effect is remarkable.
(Filler (C))
The composition constituting the porous film of the present invention can be a composition containing a filler (C) in order to improve moisture permeability. As the filler (C), an inorganic filler and / or an organic filler can be used.

  The filler (C) 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.

  Examples of inorganic fillers include various carbonates such as calcium carbonate, magnesium carbonate and barium carbonate, various sulfates such as magnesium sulfate, barium sulfate and calcium sulfate, zinc oxide, silicon oxide (silica), zirconium oxide and magnesium oxide. , Calcium oxide, titanium oxide, magnesium oxide, iron oxide, alumina and other oxides, other hydroxides such as aluminum hydroxide, silicate minerals, hydroxyapatite, mica, talc, kaolin, clay, montmorillonite, zeolite, etc. These various composite oxides, various phosphates such as lithium phosphate, calcium phosphate and magnesium phosphate, and various 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, barium, zinc, manganese and magnesium, vinyl monomers such as divinylbenzene, styrene, acrylic acid and methacrylic acid alone or Copolymer fine particles, polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, thermosetting phenol resin and other organic fine particles, wood powder and pulp powder Plants such as powder, rice husk, wood chip, okara, waste paper ground material, clothing ground material, cotton fiber, hemp fiber, bamboo fiber, wood fiber, kenaf fiber, jute fiber, banana fiber, coconut fiber, etc. Fiber, silk, wool, angora, cashmere, camel and other animal fibers, polyester fiber, nylon Wei, or the like can be used synthetic fibers such as acrylic fibers.

  Among these fillers (C), calcium carbonate, barium carbonate, barium sulfate, calcium sulfate, silicon oxide (silica) are used from the viewpoints of improving the moisture permeability of the film, maintaining mechanical properties such as strength and elongation, and reducing costs. ), Titanium oxide, mica, talc, kaolin, clay and montmorillonite are preferred.

  The average particle diameter of the inorganic filler and the organic filler is not particularly limited, but is preferably 0.01 to 10 μm. By setting the average particle size to 0.01 μm or more, it becomes possible to fill the film with a high amount of a filler. As a result, the film has a high potential for increasing the porosity and moisture permeability of the film, and the average particle size is 10 μm. By setting it as the following, the drawability of a film becomes favorable, As a result, it becomes a film with the high potential of the porosity of a film and moisture permeability improvement. The average particle diameter is more preferably 0.1 to 8 μm, further preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. Here, the average particle diameter is a 50% cumulative distribution average particle diameter measured by a laser diffraction scattering method.

  The filler (C) of the present invention contains at least one functional group selected from a hydroxyl group, amino group, amide group, carboxyl group, glycidyl group, acid anhydride group, carbodiimide group, and oxazoline group as necessary. Can be surface treated. By the surface treatment, the affinity with the matrix resin is improved, and the filler (C) is effective in suppressing aggregation and dispersibility, and can be uniformly dispersed in the resin composition.

  Moreover, in order to improve the dispersibility in the resin composition of the filler (C) of this invention, it is preferable to add a dispersing agent further.

Moreover, it is preferable that the composition which comprises the film of this invention contains 10-200 mass parts of fillers (C) with respect to 100 mass parts of thermoplastic resins. When the amount is less than 10 parts by mass, the moisture permeability is insufficient. When the amount exceeds 200 parts by mass, the tensile strength and tensile elongation of the film are insufficient, or the melt processability and extensibility when producing the film are deteriorated. There is a case. The content of the filler (C) in the composition constituting the film is preferably 20 to 150 parts by mass, more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the thermoplastic resin. More preferably, it is 40-80 mass parts. The blending amount of the filler (C) is preferably adjusted according to the blending amount of the deodorant (B). When the particulate deodorant is used, the deodorant (B) and the filler (C) The total amount is preferably 10 to 200 parts by mass.
(Resin (D) (thermoplastic resin other than polylactic acid resin))
The porous film of the present invention can be composed of a composition containing the resin (D) in order to improve flexibility and moisture permeability. Here, the resin (D) is a thermoplastic resin other than the polylactic acid resin. The thermoplastic resin includes polyacetal, polyethylene, polypropylene, polyamide, poly (meth) acrylate, polyphenylene sulfide, polyether ether ketone, polyester, polyurethane, polyisoprene, polysulfone, polyphenylene oxide, polyimide, polyetherimide, ethylene / glycidyl. Methacrylate copolymers, polyester elastomers, polyamide elastomers, ethylene / propylene terpolymers, ethylene / butene-1 copolymers, polymers containing starch, various resin plasticizers, and the like can be used.

  Specific examples of polyesters include aromatic polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, poly (ethylene succinate terephthalate), poly (butylene succinate terephthalate), poly (butylene adipate terephthalate), etc. Aliphatic aromatic polyester resins, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), polycaprolactone, polybutylene succinate, poly (butylene succinate) Aliphatic polyester resins such as adipate) can be used. Among these, aliphatic aromatic polyester resins and aliphatic polyester resins are preferable from the viewpoints of flexibility, moisture permeability, and biodegradability.

  As a specific example of the polymer containing starch, Novamont's biodegradable resin “Matterby” and the like can be used.

  Specific examples of various resin plasticizers include polyesters such as polypropylene glycol sebacate, polyalkylene ethers, ether esters, and acrylate plasticizers.

In particular, in order to suppress bleed out and increase plasticization efficiency, the solubility parameter of the resin plasticizer, which is the resin (D) contained in the composition constituting the porous film: SP is (16-23) ) ^1/2 MJ / m ³ is preferable, and (17-21) ^1/2 MJ / m ³ is more preferable. The method for calculating the solubility parameter is described in P.A. Small, J.M. Appl. Chem. 3, 71 (1953). Among such plasticizers, from the viewpoint of maintaining the biodegradability of the entire film, the resin-based plasticizer as the resin (D) is preferably a biodegradable plasticizer.

  In addition, in the case of suitability for food packaging applications and agricultural and forestry applications, considering the possibility of residual undegraded products remaining in compost / farmland, as a resin plasticizer as resin (D) It is preferably a plasticizer approved by the US Food and Sanitation Administration (FDA), the Sanitation Council for Polyolefins, and the like. Examples of the plasticizer include glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, bis (alkyldiglycol) adipate, and polyethylene glycol.

  Furthermore, from the viewpoint of the bleed-out resistance of the plasticizer, the heat resistance of the film, and the blocking resistance, the resin plasticizer as the resin (D) used in the present invention is, for example, a number average molecular weight of 1,000 or more. Polyethylene glycol or the like is preferably solid at room temperature (20 ° C. ± 15 ° C.), that is, the melting point exceeds 35 ° C. Moreover, 150 degreeC is an upper limit at the point which matches melt processing temperature with thermoplastic resins other than polylactic acid-type resin and polylactic acid-type resin.

  From the same viewpoint, the resin plasticizer as the resin (D) used in the present invention is a block copolymer having a polyether segment and a polylactic acid segment, or a polyester segment and a polylactic acid segment. More preferably, it is a block copolymer having: Here, the plasticizing component is a polyether segment or a polyester segment. Furthermore, a polyester-type segment means the segment which consists of polyesters other than polylactic acid. These block copolymers (hereinafter referred to as 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 “block copolymer”. The "polymer plasticizer" will be described below.

  The mass ratio of the polylactic acid-based segment contained in the block copolymer plasticizer is preferably 50% by mass or less of the entire block copolymer plasticizer, because a desired flexibility can be imparted with a smaller amount of addition. It is preferable from the point of bleed-out suppression that it is more than 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. When the block copolymer plasticizer which is the resin (D) has 1,200 or more, the block copolymer plasticizer which is the resin (D) and the resin (A) (polylactic acid resin) ), And a part of the polylactic acid-based segment is incorporated into a crystal formed from the resin (A) (polylactic acid-based resin) to form a so-called eutectic crystal. Thus, the block copolymer plasticizer, which is the resin (D), is bonded to the resin (A), and the block copolymer plasticizer has a great effect in suppressing the bleed out. As a result, the blocking resistance of the film is also excellent. Further, this block copolymer plasticizer is greatly superior in moisture permeability as compared with a plasticizer that is liquid at room temperature and a plasticizer that does not form a eutectic even when in solid form at room temperature. This is because the eutectic formed improves the hole formation efficiency by stretching described later. The number average molecular weight of the polylactic acid-based segment in the block copolymer plasticizer is more preferably 1,500 to 6,000, and further preferably 2,000 to 5,000. In addition, the lactic acid segment of the block copolymer plasticizer is such that L-lactic acid is 95 to 100% by mass or D-lactic acid is 95 to 100% by mass. Therefore, it is preferable.

  As described above, the resin (A) is a polylactic acid-based resin, and the polylactic acid-based resin is a polymer mainly composed of an L-lactic acid unit and / or a D-lactic acid unit. Is a resin in which the mass proportion of lactic acid units is the maximum in 100% by mass of the polymer. Therefore, at least the mass ratio of the lactic acid unit in the block copolymer plasticizer that is the resin (D) is the second mass ratio of the lactic acid unit in 100 mass% of the block copolymer plasticizer that is the resin (D). It means that the mass ratio of the polyether segment or the polyester segment is maximum. Preferably, in 100% by mass of the block copolymer plasticizer as the resin (D), the mass ratio of the lactic acid unit is 5% by mass to 45% by mass, and the mass ratio of the polyether segment or the polyester segment is 55%. It is mass%-95 mass%.

  In addition, the plasticizing component of the block copolymer plasticizer which is the resin (D) is a polyether segment or a polyester segment. The polyether segment is more flexible with a small amount of addition. It is preferable from a viewpoint which can provide. Furthermore, from the same viewpoint, it is more preferable to have a segment made of polyalkylene ether as the polyether segment. Specifically, examples of the polyether-based segment include a segment made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, and the like. In particular, a segment made of polyethylene glycol is a resin (A ) (Polylactic acid resin) has high affinity and is excellent in reforming efficiency, and is particularly preferable because desired flexibility can be imparted by adding a small amount of plasticizer.

  In addition, when the block copolymer plasticizer has a segment composed of a polyalkylene ether, the polyalkylene ether segment tends to be easily oxidized or thermally decomposed when heated at the time of molding, etc. It is preferable to use a hindered amine-based antioxidant or a phosphorus-based heat stabilizer in combination.

  When the block copolymer plasticizer has a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), polycaprolactone, or ethylene glycol, Polyesters composed of aliphatic diols such as propanediol and butanediol and aliphatic dicarboxylic acids such as succinic acid, sebacic acid and adipic acid are preferably used as the polyester-based segment.

  The block copolymer plasticizer may contain both components of the polyether segment and the polyester segment in one molecule, or may be either one of the components. From the viewpoint of plasticizer productivity, cost, and the like, when using any one component, it is preferable to use a polyether-based 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 it as the above range, the composition constituting the porous film has sufficient flexibility, and the melt viscosity is appropriate when the composition containing the resin (A) (polylactic acid resin) is used. The film forming processability such as the inflation film forming method can be stabilized.

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

  Next, the case where polyethylene glycol having a hydroxyl terminal at both ends (hereinafter, polyethylene glycol is referred to as PEG) is employed as the polyether segment will be specifically described.

The number average molecular weight of PEG having hydroxyl ends at both ends (hereinafter, the number average molecular weight of _PEG is referred to as _MPEG ) is usually calculated from the hydroxyl value determined by a neutralization method or the like in the case of a commercially available product. In a system in which lactide w _L parts by mass are added to w _E parts by mass of PEG having hydroxyl groups at both ends, lactide is subjected to ring-opening addition polymerization at both hydroxyl groups of PEG and sufficiently reacted, so that PLA is substantially obtained. A block copolymer of the -PEG-PLA type can be obtained (PLA here indicates polylactic acid). This reaction is performed in the presence of a catalyst such as tin octylate as necessary. The number average molecular weight of one polylactic acid segment of this block copolymer plasticizer can be substantially determined as (1/2) × (w _L / w _E ) × M _PEG . The mass percentage of the total block copolymer plasticizer of the polylactic acid segment component can be substantially determined as _{100 × w L / (w L} + w E)%. Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire block copolymer plasticizer can be determined to be substantially 100 × w _E / (w _L + w _E )%.
The purpose other than the flexibility and moisture permeability containing the resin (D) depends on the type of the resin, for example, by improving the melt viscosity and the melt tension, especially by stabilizing the bubble formation in the inflation film formation method, Improvement of high-temperature rigidity of porous film by containing (meth) acrylate, impact resistance and toughness of porous film by containing polyester, biodegradability of porous film by containing polymer containing starch For example, promotion.

  Regarding the content of the resin (D) contained in the porous film of the present invention, the polylactic acid resin (A) is 50 to 95 mass% in the total 100 mass% of the polylactic acid resin (A) and the resin (D). The resin (D) is preferably 5 to 50% by mass. When the resin (D) is less than 5% by mass, the flexibility is insufficient, and when the resin (D) exceeds 50% by mass, the heat resistance and bleed-out resistance are insufficient. The content of the resin (D) is preferably 10 to 45 mass%, more preferably 15 to 40 mass%, more preferably 20 to 20 mass%, in the total 100 mass% of the resin (A) and the resin (D). It is especially preferable that it is 35 mass%.

It is preferable that content of the polylactic acid-type resin (A) contained in the porous film of this invention is 50-95 mass% in the total 100 mass% of resin (A) and resin (D) mentioned later. When the total amount of the resin (A) and the resin (D) is 100% by mass, if the resin (A) is less than 50% by mass, the heat resistance and bleed-out resistance are insufficient, and if it exceeds 95% by mass, the flexibility is insufficient. . The content of the resin (A) is preferably 55 to 90% by mass, more preferably 60 to 85% by mass in a total of 100% by mass of the resin (A) and the resin (D) described later. It is particularly preferably 65 to 80% by mass.
(Combination of resin (D))
The porous film of the present invention may contain only one kind of these resins (D) or a combination of two or more kinds. There is no restriction | limiting in particular in resin to combine, Thermoplastic resin groups other than the polylactic acid-type resin mentioned above as resin (D) can be combined, respectively. Among them, a combination of various resin-based plasticizers and a thermoplastic resin other than the resin-based plasticizer is preferable from the viewpoint of achieving both flexibility and moisture permeability. In particular, in the present invention, it has been found that when resin (D) is combined with various resin plasticizers and a thermoplastic resin other than the resin plasticizer, the moisture permeability is remarkably improved.

  Among various resin-based plasticizers, from the viewpoint of heat resistance, moisture permeability, blocking resistance, and bleed-out resistance, the above-mentioned block copolymer plasticizer, that is, has a polyether segment and a polylactic acid segment. A block copolymer or a block copolymer having a polyester-based segment and a polylactic acid segment is preferable. More preferably, it is a block copolymer having a polyether segment and a polylactic acid segment.

  Among thermoplastic resins other than resin-based plasticizers, aliphatic polyester resins and aliphatic aromatic polyester resins are preferable from the viewpoint of biodegradability. Examples of aliphatic polyester resins include polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), polycaprolactone, polybutylene succinate, poly (butylene succinate, Adipate) is more preferable, and poly (ethylene succinate terephthalate), poly (butylene succinate terephthalate), and poly (butylene adipate terephthalate) are more preferable as the aliphatic aromatic polyester resin. Among these, from the viewpoint of flexibility, polycaprolactone, poly (butylene succinate adipate), and poly (butylene adipate terephthalate) are more preferable.

  That is, in the present invention, the resin (D) is a block copolymer having a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, an aliphatic polyester resin, and It is preferably at least one resin selected from the group consisting of aliphatic aromatic polyester resins, but a block copolymer having a polyether segment and a polylactic acid segment, and a polyester segment and a polylactic acid segment, And at least one resin (resin-based plasticizer) selected from the group consisting of block copolymers having at least one resin (resin-based plasticizer) selected from aliphatic polyester-based resins and aliphatic aromatic polyester-based resins. From combinations with other thermoplastics) Rukoto is more preferable.

When the resin (D) contained in the porous film of the present invention combines various resin plasticizers and a thermoplastic resin other than the resin plasticizer, the blending mass ratio is (various resin plastics). The thermoplastic resin other than the agent / resin-based plasticizer) = (5/95) to (95/5), more preferably (10/90) to (80/20), More preferably, it is 20/80) to (60/40).
(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
The resin (A) (polylactic acid resin) contained in the composition constituting the porous film of the present invention is preferably a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. This is because, by using a mixture, the advantages of both crystalline and amorphous polylactic acid resins can be achieved.

  As described above, the crystalline polylactic acid resin was measured with a differential scanning calorimeter (DSC) in an appropriate temperature range after the polylactic acid resin was sufficiently crystallized under heating. In this case, it refers to a polylactic acid resin in which a melting point derived from a polylactic acid 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.

  That is, the inclusion of the crystalline polylactic acid resin is suitable for improving the heat resistance and blocking resistance of the film. In addition, when a block copolymer plasticizer is used as the above-mentioned various plasticizers, the crystalline polylactic acid-based resin forms a eutectic with the polylactic acid segment of the block copolymer plasticizer, thereby improving the bleed-out resistance. Demonstrate great effect.

  On the other hand, the inclusion of an amorphous polylactic acid resin is suitable for improving the flexibility and bleed-out resistance of the film. This has an effect of providing an amorphous part in which the plasticizer can be dispersed.

  From the viewpoint of improving heat resistance and blocking resistance, the crystalline polylactic acid-based resin used for the porous film of the present invention contains the L-lactic acid unit content in poly L-lactic acid, or in poly D-lactic acid. The content ratio of D-lactic acid units is preferably 96 to 100 mol%, more preferably 98 to 100 mol%, in 100 mol% of all lactic acid units.

When the amount of the resin (A) in the composition constituting the porous film of the present invention is 100% by mass (when the total of the crystalline polylactic acid resin and the amorphous polylactic acid resin is 100% by mass) ), The proportion of the crystalline polylactic acid-based resin is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 40% by mass.
(Crystal nucleating agent)
The porous film of the present invention may contain a crystal nucleating agent in order to improve the heat resistance and tear resistance of the film.

  As the organic crystal nucleating agent, aliphatic amide compounds, melamine compounds, phenylphosphonic acid metal salts, benzenecarboxamide derivatives, aliphatic / aromatic carboxylic acid hydrazides, sorbitol compounds, amino acids, polypeptides, etc. are preferably used. be able to.

  As the inorganic crystal nucleating agent, carbon black or the like can be preferably used.

The content of the crystal nucleating agent is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass in total of the resin (A) and the resin (D).
(Elongation)
In the porous film of the present invention, the elongation in the length direction and the width direction (direction perpendicular to the length direction) is preferably 50 to 500%. When the elongation is 50% or more, the workability is good, and when the elongation is 500% or less, it is difficult for tarmi and wrinkles to occur during film-to-roll running and winding, and roll winding shape and unwinding property. Becomes better. The elongation in the length direction and the width direction is more preferably from 75% to 450%, and even more preferably from 100% to 400%.

As a method for adjusting the elongation in the length direction and the width direction to 50 to 500%, the blending amount of the polylactic acid resin, the thermoplastic resin other than the polylactic acid resin, and the particles is preferably the above-described preferred range. The method to do is mentioned.
(Elastic modulus)
The porous film of the present invention preferably has a tensile elastic modulus in the length direction and the width direction of 100 to 1,500 MPa in order to impart sufficient flexibility. The tensile elastic modulus is more preferably 150 to 1,200 MPa, and further preferably 200 to 1,000 MPa.

As a method for setting the tensile modulus of elasticity in the length direction and the width direction to 100 to 1,500 MPa, the blending amount of the polylactic acid resin, the thermoplastic resin other than the polylactic acid resin, and the filler is described above, respectively. The method of making it into a preferable range is mentioned.
(Porosity)
It is important that the porous film of the present invention has a porosity of 10 to 80%. When the porosity is less than 10%, moisture permeability is insufficient, and when the porosity exceeds 80%, the tensile strength and tensile elongation of the film are insufficient. The porosity is more preferably 20 to 75%, further preferably 30 to 70%, and particularly preferably 40 to 65%.

Means for achieving a porosity of 10 to 80% are polylactic acid resin (A), deodorant (B), resin (D) (thermoplastic resin other than polylactic acid resin), filler ( C) is a porous film obtained by the production method described later using the above-described blending amount. In addition, as described above, in particular, the resin (D) can achieve the porosity range more efficiently by combining various plasticizers and thermoplastic resins other than the plasticizer in a preferable type and blending ratio. .
(Thickness)
The porous film of the present invention preferably has a film thickness of 5 to 200 μm. By setting the film thickness to 5 μm or more, the firmness of the film becomes strong, the handleability is excellent, and the roll winding shape and unwinding property are good. When the film thickness is 200 μm or less, the film is excellent in flexibility and moisture permeability, and in particular, in the inflation film forming method, bubbles do not become unstable due to their own weight. The film thickness is more preferably 7 to 150 μm, further preferably 10 to 100 μm, and still more preferably 12 to 50 μm.
(Heat shrinkage)
When the porous film of the present invention is treated at 65 ° C. for 30 minutes, the thermal shrinkage in the length direction and the width direction is preferably −5 to 5%. By making it 5% or less, it is possible to suppress deterioration of the winding shape due to shrinkage with time of the film after winding, so-called winding tightening. Furthermore, the occurrence of blocking due to excessively high winding hardness can be suppressed. Moreover, by setting it as -5% or more, the deterioration of a winding form by the film after winding up loosening to a length direction with time can be suppressed. Here, when the heat shrinkage rate is a negative value less than 0, it means that the film is stretched.
(Organic lubricant)
It is preferable that the composition which comprises the porous film of this invention contains 0.1-5 mass% of organic lubricants in 100 mass% of the whole composition. In this case, blocking of the film after winding can be favorably suppressed. Fatty acid amide-based organic lubricants that are easy to obtain effects in a small amount due to their moderate compatibility with polylactic acid are preferred. Among them, ethylene bis-stearic acid amide and ethylene bis-oleic acid amide are preferred in terms of expressing better blocking resistance. Organic lubricants having a relatively high melting point such as ethylene bislauric acid amide are preferred.
(Additive)
The composition constituting 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, antioxidants, UV stabilizers, anti-coloring agents, matting agents, antibacterial agents, flame retardants, weathering agents, antistatic agents, antioxidants, ion exchange agents, tackifiers, Antifoaming agents, coloring pigments, dyes and the like can be contained.

  Plasticizers include acetyl citrate ester, phthalate ester, aliphatic dibasic acid ester, phosphate ester, hydroxy polycarboxylic acid ester, fatty acid ester, polyhydric alcohol ester, epoxy, Polyester, polyalkylene ether, ether ester and acrylate plasticizers can be used.

Examples of the antioxidant include hindered phenols and hindered amines.
(Carboxyl terminal)
The porous film of the present invention suppresses a decrease in strength due to hydrolysis of polylactic acid resin, especially in applications where biodegradability is not required, such as packaging for various industrial products, or where storage durability is preferred. From the viewpoint of imparting good durability, the carboxyl group terminal concentration of the film is preferably 30 equivalents / 10 ³ kg or less, more preferably 20 equivalents / 10 ³ kg or less, and even more preferably 10 equivalents / 10 ³ kg or less. When the carboxyl group terminal concentration of the film is 30 equivalents / 10 ³ kg or less, the carboxyl group terminal concentration that also serves as a hydrolysis autocatalyst is sufficiently low. There are many cases where this is possible.

Examples of a method for setting the carboxyl group terminal concentration of the film to 30 equivalents / 10 ³ kg or less include, for example, a method of controlling by a catalyst and a thermal history during the synthesis of a polylactic acid resin, a lowering of the extrusion temperature during film formation, or Examples thereof include a method of reducing the heat history such as shortening the residence time, a method of blocking the carboxyl group terminal using a reactive compound, and the like.

In the method of blocking the carboxyl group terminal using a reactive compound, it is preferable that at least a part of the carboxyl group terminal in the film is blocked, and it is more preferable that the whole amount is blocked. Examples of reactive compounds include condensation reactive compounds such as aliphatic alcohols and amide compounds, and addition reactive compounds such as carbodiimide compounds, epoxy compounds, and oxazoline compounds, but extra by-products are generated during the reaction. An addition reaction type compound is preferable in terms of difficulty, and among them, a carbodiimide compound and an epoxy compound are preferable from the viewpoint of reaction efficiency.
(Lactic acid oligomer component amount)
In the porous film of the present invention, the amount of the lactic acid oligomer component contained in the film is preferably 0.3% by mass or less. More preferably, it is 0.2 mass% or less, More preferably, it is 0.1 mass% or less. By controlling the amount of the lactic acid oligomer component contained in the film to 0.3% by mass or less, the deterioration of the handling property when the lactic acid oligomer component remaining in the film is precipitated as a powder or liquid, The progress of hydrolysis of the polylactic acid resin can be suppressed to prevent deterioration of the film over time, and furthermore, the odor peculiar to polylactic acid can be suppressed. The term “lactic acid oligomer component” as used herein refers to lactic acid, a linear oligomer of lactic acid, a cyclic oligomer of lactic acid, etc., which is quantitatively representative among lactic acid and lactic acid cyclic dimer (lactide). Lactide and DD-lactide, DL (meso) -lactide. A method for setting the amount of the lactic acid oligomer component to 0.3% by mass or less will be described later.
(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.

  The polylactic acid resin (A) in the present invention can be obtained, for example, by the following method. As a raw material, a lactic acid component of L-lactic acid or D-lactic acid is mainly used, and a hydroxycarboxylic acid other than the lactic acid component described above can be used in combination. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide, glycolide, etc. can be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.

  The polylactic acid resin can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

  Composition constituting the porous film of the present invention, that is, polylactic acid resin (A), deodorant (B), resin (D) (thermoplastic resin other than polylactic acid resin), filler (C) Alternatively, in obtaining a composition containing other components such as an organic lubricant, it is possible to produce a composition by uniformly mixing a solution in which each component is dissolved in a solvent, and then removing the solvent. It is preferable to employ a melt-kneading method for producing a composition by melt-kneading each component, which is a practical production method that does not require steps such as dissolution of the raw material in the solvent and solvent removal. The melt kneading method is not particularly limited, and a commonly used 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, it is preferable to use a single screw or twin screw extruder.

  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 190 ° C. to 210 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

  The porous film of the present invention can be obtained, for example, by a known film production method such as a known inflation method, a tubular method, or a T-die cast method using the composition obtained by the above-described method.

  In producing the porous film of the present invention, for example, when the composition obtained by the above-described method is once pelletized, melt-kneaded again, and extruded and formed into a film, the pellet is heated at 60 to 100 ° C. It is preferable to use a composition containing a polylactic acid resin or the like having a moisture content of 500 ppm or less by drying for more than an hour. Furthermore, it is preferable to reduce the lactide content in the composition containing the polylactic acid resin or the like by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. By reducing the water content of the composition containing the polylactic acid resin and the like to 500 ppm or less and the lactide content, hydrolysis during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. This is also preferable because the melt viscosity can be adjusted to an appropriate level and the film forming process can be stabilized. From the same point of view, when pelletizing or melt-extrusion / film formation, a twin-screw extruder with a vent hole is used and melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances. It is preferable.

  When the porous film of the present invention is produced by the inflation method, for example, the following method is used. The composition prepared by the method as described above is melt-extruded by a twin-screw extruder with a vent hole, led to an annular die, extruded from the annular die, and supplied with dry air to form balloons (bubbles). Furthermore, after air-cooling and solidifying uniformly with an air ring, taking it at a predetermined take-up speed while folding it flat with a nip roll, if necessary, it cuts both ends or one end and winds it up, so that the intended porous film Can be obtained.

  In addition, the extrusion temperature of the composition constituting the porous film of the present invention is usually in the range of 150 to 240 ° C., but the temperature of the annular die is important in order to develop good moisture permeability. The temperature is preferably in the range of 150 to 190 ° C, more preferably 155 to 185 ° C.

  The annular die is preferably a spiral type in terms of thickness accuracy and uniformity.

  After forming into a film, various surface treatments may be applied for the purpose of improving printability, laminate suitability, coating suitability, and the like. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and any method can be used, but continuous treatment is possible, and equipment for existing film forming equipment is used. Corona discharge treatment can be exemplified as the most preferable because of its easy installation and simple processing.

  Since the porous film of the present invention is excellent in bleed resistance and blocking resistance, when the film is unwound from the film roll after being wound, it can be smoothly unwound.

When the porous film of the present invention is produced by an inflation method in order to achieve a porosity of 10 to 80%, it is important to adjust the blow ratio and the draw ratio within preferable ranges. Here, the blow ratio is a ratio R _L / R _O of the final radius R _{L of the} bubble and the radius R _O of the annular die, and the draw ratio is the winding speed V _L of the molded film and melted from the die lip. The ratio V _L / V _O of the speed V _{O at which} the resin is discharged. A preferable range of the blow ratio for achieving a porosity of 10 to 80% is 1.5 to 5.0, more preferably 2.0 to 4.5, and still more preferably 2.5 to 5.0. 4.0, and the preferable range of the draw ratio is 2 to 100, more preferably 5 to 80, still more preferably 10 to 60, and particularly preferably 20 to 40.

  When the porous film of the present invention is produced by the T die casting method, for example, the following method is used. The composition prepared by the method as described above was melt-extruded by a twin-screw extruder with a vent hole, discharged from a slit-shaped die having a lip interval of 0.5 to 3 mm, and set to a surface temperature of 0 to 40 ° C. A non-oriented cast film is obtained on a metal cooling casting drum by electrostatic application using a wire-like electrode having a diameter of 0.5 mm to make it adhere.

  The unoriented film obtained in this way is heated up to the temperature which performs longitudinal stretching by conveying on a heating roll. An auxiliary heating means such as an infrared heater may be used in combination for raising the temperature. The preferable range of the stretching temperature is 50 to 90 ° C, more preferably 55 to 85 ° C, and further preferably 60 to 80 ° C. The non-oriented film heated in this way is stretched in one stage, or two or more stages in the longitudinal direction of the film using a difference in peripheral speed between heating rolls. The total draw ratio is preferably 1.5 to 5 times, more preferably 2 to 4 times.

  After the film uniaxially stretched in this way is once cooled, both ends of the film are held with clips and guided to a tenter, and stretched in the width direction. The stretching temperature is preferably 55 to 95 ° C, more preferably 60 to 90 ° C, still more preferably 65 to 85 ° C. The draw ratio is preferably 1.5 to 5 times, more preferably 2 to 4 times.

  Next, this stretched film is heat-set under tension or while relaxing in the width direction. A preferable heat treatment temperature is 90 to 150 ° C, more preferably 100 to 140 ° C, and still more preferably 110 to 130 ° C. When it is desired to reduce the thermal shrinkage rate of the film, the heat treatment temperature is preferably increased. The heat treatment time is preferably in the range of 0.2 to 30 seconds, but is not particularly limited. The relaxation rate is preferably 1 to 10%, more preferably 3 to 5%, from the viewpoint of reducing the thermal contraction rate in the width direction. More preferably, the film is once cooled before the heat setting treatment. Furthermore, the film can be cooled and rolled up while relaxing the film in the longitudinal and width directions as needed to room temperature, and the intended porous film can be obtained.

  When the porous film of the present invention is produced by the T-die casting method in order to achieve a porosity of 10 to 80%, it is important to stretch at the above-mentioned preferable temperature and magnification. Stretching may be longitudinal or lateral uniaxial stretching, or longitudinal and lateral biaxial stretching. Moreover, you may perform re-longitudinal stretching and / or re-lateral stretching as needed.

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) Tensile modulus (MPa)
Tensile elastic modulus was measured using TENSILON UCT-100 manufactured by Orientec Co., Ltd. in an atmosphere at a room temperature of 23 ° C. and a relative humidity of 65%.

  Specifically, a sample is cut out in a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and according to the method defined in JIS K-7127 (1999) at an initial tensile chuck distance of 50 mm and a tensile speed of 200 mm / min. The measurement was performed 10 times for each of the length direction and the width direction, and the average value was taken as the tensile modulus.

(2) Tensile elongation (%)
Tensile elongation was measured using TENSILON UCT-100 manufactured by Orientec Co., Ltd. in an atmosphere having a room temperature of 23 ° C. and a relative humidity of 65%.

  Specifically, a sample is cut out in a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and according to the method defined in JIS K-7127 (1999) at an initial tensile chuck distance of 50 mm and a tensile speed of 200 mm / min. The measurement was performed 10 times for each of the length direction and the width direction, and the average value was taken as the tensile elongation.

(3) Porosity (%)
The film was cut into a size of 30 mm × 40 mm and used as a sample. Using an electronic hydrometer (SD-120L manufactured by Mirage Trading Co., Ltd.), the specific gravity was measured in an atmosphere at a room temperature of 23 ° C. and a relative humidity of 65%. The measurement was performed three times, and the average value was defined as the specific gravity ρ of the film.

  Next, the measured film was hot-pressed at 280 ° C. and 5 MPa, and then quenched with water at 25 ° C. to prepare a sheet. The specific gravity of this sheet was measured in the same manner as described above, and the average value 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
(4) Moisture permeability The moisture permeability (g / (m ² · day)) was measured according to the method defined in JIS Z0208 (1976) with a constant temperature and humidity device set at 25 ° C. and 90% RH.
Using the value of moisture permeability, the evaluation was made according to the following criteria.
A: 1500 g / (m ² · day) or more ○: 1000 g / (m ² · day) or more and less than 1500 g / (m ² · day) Δ: 200 g / (m ² · day) or more 1000 g / (m ² · day) Less than x: Less than 200 g / (m ² · day).

(5) Odor during heating Place 2 g of the film sample on a hot plate at 120 ° C., immediately cover it with a glass petri dish facing down, leave it for 1 minute, and then check for odor immediately after removing the covered petri dish Was evaluated according to the following criteria.
A: Randomly extracted 9 out of 10 people do not feel odor.
○: 7 to 8 out of 10 randomly selected people do not feel odor.
Δ: 5 to 6 out of 10 randomly selected people do not feel odor.
X: Other than the above.

(6) 10 g of the deodorant film sample was put in a Tedlar bag, 3 liters of ammonia / air mixed gas adjusted to about 50 ppm was sealed, allowed to stand at room temperature for 5 hours, and then the gas concentration in the bag was measured with a detector tube.
A: Gas concentration is less than 10 ppm.
○: Gas concentration is 10 ppm or more and less than 20 ppm.
Δ: Gas concentration is 20 ppm or more and less than 30 ppm.
X: Gas concentration is 30 ppm or more.
[Polylactic acid resin (A)]
(A1)
Polylactic acid resin, mass average molecular weight = 200,000, D-form content = 1.4%, melting point = 166 ° C.
(A2)
Polylactic acid resin, mass average molecular weight = 200,000, D-form content = 5.0%, melting point = 150 ° C.
(A3)
Polylactic acid resin, mass average molecular weight = 200,000, D-form content = 12.0%, melting point = none The above-mentioned mass average molecular weight uses Warters 2690 manufactured by Japan Warters Co., Ltd., with polymethyl methacrylate as a standard. Measurement was performed using a column temperature of 40 ° C. and a chloroform solvent.

The above melting point was determined by heating the 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. Was determined as the peak temperature of the crystal melting peak when the temperature was raised to 250 ° C. at a heating rate of 20 ° C./min.
[Deodorant (B)]
(B1)
Silver ion-supported zeolite (product name “Zeomic AW10D”, average particle size 2.5 μm, manufactured by Sinanen Zeomic Co., Ltd.)
[Filler (C)]
(C1)
Calcium carbonate (manufactured by Maruo Calcium Co., Ltd., trade name “Caltex R”, average particle size 2.8 μm)
(C2)
Talc (Nippon Talc Co., Ltd., trade name “SG-95”, average particle size 2.5 μm)
[Resin (D)]
(D1)
Polybutylene adipate terephthalate resin (trade name “Ecoflex” FBX7011 manufactured by BASF)
(D2)
62 parts by mass of polyethylene glycol having a number average molecular weight 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 block copolymer plasticizer D2 having a polylactic acid segment having a number average molecular weight of 2,500 at both ends of polyethylene glycol having a number average molecular weight of 8,000 was obtained.
[Creation of porous film]
Example 1
A mixture of 100 parts by mass of polylactic acid resin (A1), 0.5 parts by mass of deodorant (B1), and 60 parts by mass of filler (C1) was added to a twin screw extruder equipped with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm. The mixture was melt-kneaded while degassing the vacuum vent part, homogenized, and pelletized to obtain a composition.

  The pellets of this composition were vacuum-dried at a temperature of 120 ° C. for 5 hours using a rotary drum type vacuum dryer.

Pellets of this composition were supplied to a single screw extruder having a cylinder temperature of 220 ° C., extruded into a film at a T die die temperature of 220 ° C., and cast on a drum cooled to 20 ° C. to produce a non-oriented film. This non-oriented film was stretched twice in the longitudinal direction at a temperature of 85 ° C. by a roll type stretching machine. After this uniaxially oriented film was once cooled on a cooling roll, both ends were held with clips and guided into a tenter, and stretched twice at a temperature of 75 ° C. in the width direction. Subsequently, after a heat treatment at a temperature of 120 ° C. for 10 seconds under a constant length, a relaxation treatment of 5% in the width direction was performed to obtain a porous film having a thickness of 20 μm. Table 1 shows the physical properties of the obtained film.
(Example 2)
A mixture of 100 parts by mass of polylactic acid resin (A2) and 60 parts by mass of deodorant (B1) was subjected to a twin screw extruder with a vacuum vent of 44 mm and a cylinder temperature of 220 ° C. and a vacuum vent, and melted while degassing the vacuum vent. The mixture was kneaded, homogenized and then pelletized to obtain a composition.

A porous film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that pellets of this composition were used. Table 1 shows the physical properties of the obtained film.
Example 3
15 parts by mass of polylactic acid resin (A1), 45 parts by mass of polylactic acid resin (A3), 5 parts by mass of deodorant (B1), 20 parts by mass of polybutylene adipate / terephthalate resin (D1), block copolymer plasticizer ( D2) A mixture of 20 parts by mass and 70 parts by mass of filler (C1) was subjected to a twin screw extruder with a vacuum vent of 44 mm and a cylinder temperature of 190 ° C., melt-kneaded while degassing the vacuum vent and homogenized. And then pelletized to obtain a composition. The pellets of this composition were vacuum-dried at a temperature of 60 ° C. for 12 hours using a rotary drum type vacuum dryer.

Pellets of this composition were supplied to a single screw extruder having a cylinder temperature of 190 ° C., extruded into a film at a T die die temperature of 190 ° C., and cast on a drum cooled to 20 ° C. to produce an unoriented film. This non-oriented film was stretched 3 times in a longitudinal direction at a temperature of 70 ° C. by a roll type stretching machine. After this uniaxially oriented film was once cooled on a cooling roll, both ends were held with clips and guided into a tenter, and stretched three times at a temperature of 70 ° C. in the width direction. Subsequently, after a heat treatment at a temperature of 120 ° C. for 10 seconds under a constant length, a relaxation treatment of 5% in the width direction was performed to obtain a porous film having a thickness of 20 μm. Table 1 shows the physical properties of the obtained film.
(Example 4, Comparative Examples 1-3)
A film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that the composition and production conditions of the film were changed as shown in Table 1. Table 1 shows the physical properties of the obtained film.

  In the table, “mass%” of the resin (A) and the resin (D) is a value (mass%) at a total of 100 mass% of the resin (A) and the resin (D), and the deodorant (B) and The “parts by mass” of the filler (C) is a value (parts by mass) when resin (A) + resin (D) = 100 parts by mass.

  The porous film of the present invention provides a porous film mainly composed of a polylactic acid-based resin having excellent moisture permeability and suppressing odor. The porous film of the present invention is a medical / hygienic material such as bed sheets, pillow covers, sanitary napkins, back sheets of absorbent articles such as paper diapers, etc., which are mainly required to be moisture permeable and dislike odor. It can be used for clothing materials such as gloves, garbage bags and compost bags, food bags such as vegetables and fruits, and packaging materials such as bags for various industrial products.

Claims (6)

  It consists of a composition containing 0.1 to 200 parts by mass of deodorant (B) with respect to 100 parts by mass of thermoplastic resin mainly composed of polylactic acid resin (A), and the porosity is 10 to 80%. A porous film characterized by that.   The porous film according to claim 1, wherein the deodorant (B) is made of zeolite.   The porous film according to claim 1, wherein the composition contains 10 to 200 parts by mass of the filler (C) with respect to 100 parts by mass of the thermoplastic resin.   The thermoplastic resin contains a resin (D) other than the polylactic acid resin (A), and the polylactic acid resin (A) is 50 to 95 in a total of 100% by mass of the polylactic acid resin (A) and the resin (D). The porous film according to any one of claims 1 to 3, wherein the mass% and the resin (D) are 5 to 50 mass%.   Resin (D) is a block copolymer having a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, an aliphatic polyester resin, and an aliphatic aromatic polyester The porous film according to claim 4, wherein the porous film is at least one resin selected from the group consisting of resins.   The porous elastic film according to any one of claims 1 to 5, wherein a tensile elastic modulus is 100 to 1,500 MPa.